JP2003156632A - Light transmission plate, surface light emitting body and liquid crystal display device using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device which provides sufficient visibility with little power consumption and reduces uneven brightness by reducing light transmission loss of a light transmission plate 10 in a surface light emitting body 40 having the light transmission plate 10 and a rod-like light transmission body 20. SOLUTION: A counter side face 3 opposed to an incident side face 1 of the light transmission plate 10 is made into an inclined surface with an internal angle θ of <90 deg. so that at least a part of light projected from the direction of a light entering side face 1 is reflected not in parallel with a light emitting surface 2.

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, a surface light emitter and a liquid crystal display device, and more particularly to a light guide plate having high brightness and little unevenness in brightness when used as an illuminating means of a reflection type liquid crystal display device. The present invention relates to a high-luminance surface-emitting body that is included as a component, and a liquid crystal display device that uses this surface-emitting body and has excellent visibility.

[0002]

2. Description of the Related Art Reflective liquid crystal display devices, which are often used in mobile phones, portable display terminals, game consoles, etc., generally rely on external light for illumination of the display screen. In that case, the image contrast is lowered and the visibility of the displayed image is extremely lowered. In order to solve this problem, a "front light" is displayed on the display surface of the reflective LCD unit.
2. Description of the Related Art A liquid crystal display device in which a so-called surface light emitter is mounted as a lighting device is used. This surface-emitting body is transparent in itself, and the liquid crystal display device equipped with the surface-emitting body is a liquid crystal display device that is exposed to external light in a daytime environment such as outdoors or in a bright room where ambient light is sufficiently emitted. The display screen is illuminated, and in a dark environment, the surface light-emitting body is caused to emit light to illuminate the entire liquid crystal display screen to obtain clear visibility.

FIG. 13 shows an example of a conventionally used liquid crystal display device with a front light. In FIG. 13, this liquid crystal display device is roughly composed of a surface light emitter 140 and a liquid crystal display unit 50. Of these, the surface light emitter 14
Reference numeral 0 denotes the light sources 30a and 30b, the rod-shaped light guide 20, and the light guide plate 11
It consists of 0. The rod-shaped light guide 20 and the light guide plate 110 are made of transparent synthetic resin. The liquid crystal display unit 50 is generally composed of a liquid crystal display plate 60 and a reflection plate 70. The operation of the surface light emitter 140, which is a front light, will be described. The light emitted from each of the light sources 30a and 30b (represented by a beam Bo) is transmitted from one end face (hereinafter referred to as “light receiving end face”) 21 of the rod-shaped light guide 20 formed of a light-transmitting rod-shaped body to the inside of the rod-shaped light guide 20. Is reflected in a substantially perpendicular direction inside, and is emitted as a band-shaped light beam L1 from one side surface (hereinafter referred to as “emission side surface”) 22 in the longitudinal direction. The emitted light enters a transparent rectangular plate-shaped light guide plate 110 from one side surface (light incident side surface) 101 thereof. The band-shaped light flux L1 that has entered the light guide plate 110 is internally reflected in a substantially right-angled direction and is emitted from the lower surface (light emitting surface) 102 of the light guide plate 110 as a planar light flux that spreads over the entire surface, and the entire display surface 51 of the liquid crystal display unit 50. To evenly illuminate. At this time, when the pixel 52 of the liquid crystal display plate 60 is in the translucent mode by the liquid crystal drive circuit, the light projected from the light guide plate 110 passes through this pixel 52 and is reflected by the reflection plate 70 disposed below the pixel 52. The reflected light (beam Bm) is transmitted through the pixel 52 again, and further transmitted through the light guide plate 110 that is a transparent body, and is visually recognized as a light spot by an observer.

FIG. 14 shows a conventional light guide plate 1
10 shows the configuration of 10. In FIG. 14, the light guide plate 11
0 is a plate surface (hereinafter referred to as “reflection surface”) 104 facing the light emitting surface 102, and a large number of prism portions 105 each having a ridge line 106 extending in the length direction of the light incident side surface 101 and inclined surfaces 107 a and 107 b sandwiching the ridge line 106. ... is formed. In these prism parts 105, the distance between the ridge lines 106, the height of the inclined surface, and the inclination angle are adjusted. As a result, the light incident side surface 101 is emitted from the light sources 30a and 30b.
The light of the band-shaped light flux introduced from the inside into the light guide plate 110 is projected on the inner walls of the light emitting surface 102 and the reflecting surface 104 of the light guide plate 110, as represented by the beam Bn, and repeats complicated inner surface reflection, and finally. Most of the light is reflected in the direction of the light emitting surface 102, and the liquid crystal display panel 6 is formed as a planar light beam from the light emitting surface 102.
It is ejected toward 0.

[0005]

Since the conventional liquid crystal display device having the above-described structure is used in a small portable device in many cases, the light source 30 is used for illumination by the surface light emitter 140.
It is required to reduce the power consumption as much as possible along with miniaturization of a and 30b, and to obtain sufficient illuminance and illumination uniformity. From this viewpoint, the efficiency of the light source is improved and the rod-shaped light guide 2
0 and a technique for reducing the light guide loss in the light guide plate 110 as much as possible are required. Therefore, when the light guide loss in the light guide plate 110 is carefully examined, about 2% of the light incident from the light receiving end face 101 is typified by the beam Bw in FIG.
It was found that 0% was diffused from the opposite end face (opposing end face) 103 to the outside of the system, resulting in a light guide loss. Also,
When the brightness distribution of the planar light flux emitted from the light guide plate 110 is measured, the brightness is large in the part close to the rod-shaped light guide 20 and the brightness is low in the part close to the facing end face 103. It was found that the illumination light emitted from the light plate 110 has uneven brightness. The present invention has been made to solve the above problems, and therefore an object thereof is to prevent light from being diffused from opposite end surfaces of a light guide plate,
Accordingly, it is intended to obtain a liquid crystal display device capable of reducing the light guide loss of the surface light emitter, improving the uneven brightness, and obtaining good visibility with low power consumption.

[0006]

In order to solve the above-mentioned problems, the present invention comprises a translucent plate-shaped body, and at least a strip-shaped light beam incident from one side surface (light incident side surface) of this plate-shaped body. A light guide plate that emits as a planar light beam from one plate surface (light emitting surface), and the side surface (opposing side surface) facing the light incident side surface is
Provided is a light guide plate formed to reflect at least a part of light projected from a direction of the light incident side surface non-parallel to the light emitting surface.

In the light guide plate of the present invention, the light projected on the opposite end face is reflected toward the inside of the light guide plate non-parallel to the light emitting surface, so that the non-parallel reflected light is projected on the light emitting surface. Or the light is projected on a plate surface (reflection surface) facing the light emitting surface, and at least a part of the surface is repeatedly reflected on the inside of the light guide plate and finally reflected in the direction of the light emitting surface to form a planar surface. It transmits through the light emitting surface as a part of the light flux and contributes to the increase in the brightness of the planar light flux.

In the above, it is preferable that the facing side surfaces are inclined surfaces having an interior angle with respect to the light emitting surface of less than 90 ° or more than 90 °. In particular, the interior angle is more preferably within the range of 30 ° to 60 °. As a means for reflecting the light projected on the opposite side surface non-parallel to the light emitting surface, it is preferable to incline the opposite side surface with respect to the light emitting surface.
In particular, if the interior angle with respect to the light emitting surface is within the range of 30 ° to 60 °, the amount of light directly projected onto the light emitting surface out of the reflected light from the opposite side surface can be increased, so that the output luminance can be further improved and within the above range. By adjusting the interior angle, it is possible to reduce the uneven brightness of the plane light flux emitted.

It is preferable that the opposed side surfaces are composed of two or more inclined surfaces that reflect the light projected from the direction of the light incident side surface non-parallel to the light emitting surface. Alternatively, the facing side surfaces may be curved. When the opposite side surface is composed of one flat surface inclined with respect to the light emitting surface, the reflected light is projected onto a limited portion of the light emitting surface, which may cause uneven brightness in the planar light flux. If the opposite side surfaces are composed of two or more inclined surfaces, the reflected light can be appropriately dispersed inside the light guide plate, and the uneven brightness due to the reflected light being concentrated on a limited part of the light emitting surface. It can be prevented. Even when the opposite side surfaces are curved surfaces, the reflected light can be continuously dispersed inside the light guide plate, and uneven brightness due to the reflected light being concentrated on a limited portion of the light emitting surface can be prevented. This curved surface is a quadric surface that is convex toward the inside of the light guide plate, and the tangent line at any point on the curved surface has an interior angle within the range of 30 ° to 60 ° with respect to the light emitting surface. More preferable.

A reflective layer is preferably formed on the opposite side surfaces. The light projected on the inclined opposite side faces is partially reflected toward the inside of the light guide plate according to the inclination angle, but part of it is still transmitted and radiated outside the system, resulting in a light guide loss. is there. By providing a reflection layer for internally reflecting light on the opposite side surface, it is possible to prevent light guide loss due to this transmission and improve the brightness of the planar light flux. The reflective layer can be formed by forming an aluminum thin film on the surface of the opposite side surface or by mounting a mirror plate on the opposite side surface.

The opposite side surfaces may be diffusely reflective. If the opposite side surface is irregularly reflected, the reflected light from the opposite side surface can be diffused in a wide area inside the light guide plate, and uneven brightness due to the reflected light being concentrated on a limited part of the light emitting surface can be prevented. It is further preferable that a reflective layer is formed on the diffused opposing side surfaces. The diffuse reflection of the opposite side is
It can be realized by a method such as attaching a diffuse reflection film to the opposite side surface, forming fine unevenness on the opposite side surface itself, or mounting a reflective layer having fine unevenness.

In the light guide plate of the present invention, the light incident from the light incident side surface and the light reflected by the opposite side surface are both directed to the light emitting surface on the plate surface (reflection surface) facing the light emitting surface. Reflecting means for reflecting may be provided. In the light guide plate of the present invention, the light internally reflected from the opposite side surface generally diffuses not only in the direction of the light emitting surface but also in part in the direction of the reflecting surface. At this time, if the reflecting surface is formed so as to reflect not only the light incident from the light incident side surface but also the light reflected from the opposite side surface toward the light emitting surface, the reflection diffused in the direction of the reflecting surface. The light is also reflected toward the light emitting surface, which contributes to an increase in the output of the planar light flux. As a means for reflecting both the light incident from the light incident side surface and the light reflected from the opposite side surface toward the light emitting surface, the reflection surface is designed to reflect the light incident from the light incident side surface in the light emitting surface direction. It is preferable to form a complex prism surface having both inclined surfaces and inclined surfaces designed to reflect the light reflected from the opposite side surface toward the light emitting surface.

The present invention also includes any one of the above light guide plates,
It consists of a light-transmissive rod-shaped body that receives the light emitted by the light source from one end face (light receiving end face) of the light source, and the longitudinal side face (exit side face).
To provide a surface light-emitting body having a rod-shaped light guide that is emitted as a strip-shaped light flux to the light incident side surface of the light guide plate. It is preferable that the light guide plate be translucent in the plate thickness direction, and that the light guide plate be provided with a reflection unit that emits the planar light flux from one plate surface (light emitting surface).

In the surface light emitter of the present invention, since the output brightness of the light guide plate of the present invention is higher than that of the conventional light guide plate, even if the rod-shaped light guide member is the same as the conventional light guide plate, the surface light emitter is The brightness of the planar light beam emitted from the light emitting surface is improved as a whole body. If the light guide plate is transmissive in the plate thickness direction and provided with a reflecting means for emitting a planar light beam from one plate surface (light emitting surface), this surface light emitter is a display surface of a reflection type liquid crystal display device. It becomes possible to illuminate this display surface by mounting on top of it, and it becomes possible to emit the light reflected from the reflective layer of the reflective liquid crystal display device upward through the light guide plate, and as a front light of the reflective liquid crystal display device. It will be applicable. The reflecting means of the light guide plate is a surface (reflection surface) facing the light emitting surface.
It is preferable that the ridge line is formed of a plurality of prismatic inclined surfaces extending parallel to the length direction of the light receiving end surface.

The present invention further provides a liquid crystal display device comprising the above-mentioned surface light emitter and a liquid crystal display unit. Since the liquid crystal display device of the present invention uses the surface light emitter of the present invention for illuminating the liquid crystal display surface, a bright and good visibility screen can be obtained while using a small power-saving light source. The stacking order of the surface light emitter and the liquid crystal display unit is not limited.
For example, when a surface light emitter of the type in which the light guide plate is light-transmissive in the plate thickness direction and which radiates a planar light beam from one light emitting surface is arranged in the upper layer of the reflection type liquid crystal display unit, the surface light emitter of the present invention can be obtained. A reflective liquid crystal display device as a front light can be obtained. Further, if a translucent liquid crystal display panel having no reflective layer is arranged in the upper layer, and a surface light-emitting body having a light-reflecting reflection surface of the light guide plate is arranged below the light-emitting surface, the light-emitting surface faces upward, A reflective liquid crystal display device using a surface light emitter as a backlight can be obtained.
Furthermore, by arranging a translucent liquid crystal display panel without a reflective layer on both sides of a surface light emitter of a type in which a planar light beam is emitted from both plate surfaces of the light guide plate at the same time, it is possible to arrange the light beams in the front and back phase directions. A liquid crystal display device capable of displaying the same or different images is obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to specific examples, but these specific examples do not limit the present invention in any way. Further, the attached drawings are for explaining the idea of the present invention, and the elements unnecessary for the explanation of the present invention are omitted, and the shapes, dimensional ratios, the numbers, etc. of the illustrated elements are not necessarily the actual ones. It does not match.

(Embodiment 1) FIGS. 1 and 2 are side views showing a light guide plate according to an embodiment of the present invention.
1 and 2, the light guide plate 10 is made of a transparent acrylic resin and has a rectangular plate shape. As shown in FIG. 1, the light guide plate 10 is combined with a light source (not shown) and a rod-shaped light guide 20 to form a surface light emitter 40 as a whole.

One end surface of the light guide plate 10 has a light incident side surface 1,
One plate surface adjacent to the light incident side surface 1 is a light emitting surface 2, a side surface facing the light incident side surface 1 is a facing side surface 3, and a plate surface facing the light emitting surface 2 is a reflecting surface 4. The light incident side surface 1 is the light guide plate 1
It is a plane perpendicular to the plate surface of 0 and receives the band-shaped light flux emitted from the emission side surface 22 of the rod-shaped light guide 20. The light emitting surface 2 is a flat surface, and the light received by the light incident side surface 1 is converted into a planar light flux from the entire plate surface, and the liquid crystal display plate 60 of the liquid crystal display unit 50 is displayed.
Shoot towards. The reflecting surface 4 facing the light emitting surface 2
Is formed by a large number of prism parts 5 ... Consisting of ridge lines 6 extending in the lengthwise direction of the light incident side surface 1 and inclined surfaces 7a, 7b sandwiching the ridge lines 6, and the light projected onto the inclined surfaces 7a, 7b. The shape, the arrangement interval, etc. of the prism parts 5 are appropriately adjusted so that the beam Bn is reflected in the direction of the light emitting surface 2.

In the present embodiment, the facing side surface 3 has an interior angle θ with respect to the light emitting surface 2 of less than 90 °, particularly within a range of 30 ° to 60 °, as shown in FIGS. 2 or 9 as shown in Example 4 of FIG. 2 and Table 1.
It is composed of an inclined surface that exceeds 0 °, and in any case, it is formed so as to reflect the light projected from the direction of the light incident side surface 1 (represented by the beam Bo) non-parallel to the light emitting surface 2. .

The light guide plate 10 of the above embodiment operates as follows. When the light of the band-shaped light flux is emitted from the emission side surface 22 of the rod-shaped light guide 20, the light is emitted from the light incident side surface 1 to the light guide plate 1.
0, is diffused in the light guide plate 10, and generally, as shown by the beam Bn in FIG. 1, complex inner surface reflection is repeated by the inner surface of the light emitting surface 2 and the prism portion 5 of the reflecting surface 4, and finally, Most of the incident light is reflected by the prism portions 5 of the reflecting surface 4 and is emitted from the light emitting surface 2 as a planar light beam spreading over the entire plate surface. Since the light is totally diffused inside the light guide plate 10, the brightness of the emitted planar light flux is relatively uniform as a whole.

On the other hand, of the light incident on the light guide plate 10,
The light that travels substantially straight is projected on the facing side surface 3 as shown by a representative example of the beam Bo. Since the facing side surface 3 is inclined with respect to the light emitting surface 2, the projection light is reflected as reflected light (beam Br) that is not parallel to the light emitting surface 2. As shown in FIG. 1, when the internal angle θ of the facing side surface 3 is less than 90 °, the reflected light (beam Br) is directly reflected in the direction of the light emitting surface 2 and emitted from the light emitting surface 2 as a part of the planar light flux. To be done. Further, as shown in FIG. 2, when the internal angle θ of the facing side surface 3 exceeds 90 °, the reflected light (beam Br) is projected and reflected on the inclined surface 7 a formed on the prism portion 5 of the reflecting surface 4. After all, the light is emitted from the light emitting surface 2 as a part of the planar light flux. Therefore, in the light guide plate 10 of the present embodiment, the light guide loss is less than that of the conventional light guide plate and the brightness of the planar light flux is improved regardless of whether the internal angle is less than 90 ° or more than 90 °.

In the above embodiment, the internal angles θ of the side surface 3 facing the light emitting surface 2 are 30 °, 45 ° and 60 °, respectively.
Prototype of light guide plate with different angles of 90 ° and 120 °, internal angle θ = 9
A conventional light guide plate having an angle of 0 ° was compared with the average brightness and brightness unevenness of the planar light flux. To measure the average brightness, the light emitting surface 2 is equally divided into 25 sections in a grid pattern, and a measurement point is provided at the center of each section. At each measurement point, as shown in FIG.
The measurement visual field was shaken within the range of 20 ° to measure the luminance, and the average value was used as the luminance at each measurement point, and the average value of the luminances at the 25 measurement points was determined and used as the average luminance. The measurement result is
The evaluation was made by the ratio when the average brightness of the conventional light guide plate (Comparative Example 1) with θ = 90 ° is 1. In addition, the brightness unevenness is the minimum value (min) and the maximum value (m
The ratio (min / max) with respect to ax) was obtained, and it was determined that the larger this value was, the less uneven brightness was. The results are shown in Table 1.

[0023]

[Table 1]

From the results of Table 1, Examples 1 to 3 are
The interior angle of the facing side surface 3 with respect to the light emitting surface 2 is less than 90 °, and the light projected onto the facing side surface 3 is reflected in the direction of the light emitting surface 2 and is emitted from the light emitting surface 2 to improve the average brightness of the planar light flux. did. In Example 4, the interior angle exceeds 90 °, but in this case, the reflected light from the opposite side surface 3 is projected onto the reflecting surface 4, is further reflected in the direction of the light emitting surface 2, and is emitted from the light emitting surface 2 to form a surface. The average brightness of the light beam is improved. In any case, the improvement of the average luminance was achieved by the fact that the opposed side surface 3 was configured to reflect the light projected from the direction of the light incident side surface 1 non-parallel to the light emitting surface 2.

(Second Embodiment) FIG. 4 is a side view showing a light guide plate of a second embodiment. In FIG. 4, the light guide plate 11 is substantially the same as that of the first embodiment except that the configuration of the opposite side surface 3 is different. The facing side surface 3 in this embodiment is composed of two inclined surfaces 3a and 3b, and these inclined surfaces 3a and 3b.
Respectively reflect light projected from the direction of the light incident side surface 1 non-parallel to the light emitting surface 2. Of the inclined surfaces 3a and 3b, the internal angle θa of the inclined surface 3a adjacent to the reflective surface 4 with respect to the light emitting surface 2 is 60 °, and the inclined surface 3 adjacent to the light emitting surface 2 is
The internal angle θb of b is 45 °. A reflective layer 8 made of an aluminum film is formed on the facing side surface 3.

The light guide plate 11 of this embodiment is composed of two inclined surfaces 3a and 3b whose opposite side surfaces 3 have different inclination angles.
Since the inclined surface 3a has a relatively steep inclination of 60 °, the light (beam Bo) projected from the direction of the light incident side surface 1 is reflected by the light emitting surface 2 near the light incident side surface 1 as shown by the beam Boa, and the inclined surface 3b becomes Since the inclination is gentle, the light is reflected by the light emitting surface 2 near the facing side surface 3 as indicated by the beam Bob. As a result, the light reflected by the facing side surface 3 is dispersed relatively uniformly over the entire surface light flux, and a high quality surface light flux with less uneven brightness can be obtained. Further, since the opposing side surface 3 is provided with the reflection layer 8, the reflectance of the surface is high and the brightness of the planar light flux is further improved.

The average brightness and uneven brightness of the planar light beam on the light guide plate 11 were measured. The respective measurement methods and evaluation methods are the same as those described in the first embodiment. The light guide plate sample of the present embodiment is referred to as Example 5, and the first embodiment is used for comparison.
The measurement results are shown in Tables 2 and 3 together with the conventional light guide plate (Comparative Example 1) in which θ = 90 °.

[0028]

[Table 2]

From the results in Table 2, it is clear that the average luminance of Example 5 is higher than that of Comparative Example 1, but the higher average luminance than that of Examples 2 and 3 is that the reflective layer 8 is formed on the opposite side surface 3. Is provided. In the fifth embodiment, the opposite side surface 3 is
Due to the two inclined surfaces having different inclination angles, the luminance unevenness is significantly improved as compared with the second and third embodiments and the first comparative example.

(Third Embodiment) FIG. 5 is a side view showing a light guide plate according to a third embodiment. In FIG. 5, the light guide plate 12 is substantially the same as that of the second embodiment except that the configuration of the opposite side surface 3 is different. The facing side surface 3 in this embodiment is a quadric surface that is convex toward the inside of the light guide plate, and the facing side surface 3 is provided with a reflective layer 8 made of an aluminum film. The tangent line of the opposing side surface 3 adjacent to the reflecting surface 4 and the light emitting surface 2
The interior angle formed by and is 80 °, and the interior angle formed by the tangent of the opposing side surface 3 adjacent to the light emitting surface 2 and the light emitting surface 2 is 30 °.

In the light guide plate 12 of this embodiment, since the facing side surface 3 is a quadric surface that continuously changes the interior angle from 80 ° to 30 °, the light projected from the direction of the light incident side surface 1 is emitted from the light emitting surface. The light is reflected almost uniformly over the entire surface of No. 2 to obtain a good-quality planar light flux with less uneven brightness. Further, since the opposing side surface 3 is provided with the reflection layer 8, the reflectance on this surface is high and the brightness of the planar light flux is further improved.

The light guide plate sample of this embodiment is referred to as Example 6,
The average brightness and brightness unevenness of the emitted planar light beam were measured in the same manner as in the second embodiment. The results are shown in Table 2. From the results shown in Table 2, since the facing side surface 3 in Example 6 is a quadric surface that reflects light almost uniformly over the entire surface of the light emitting surface 2, compared with Examples 2, 3 and Comparative Example 1. The uneven brightness is greatly improved. Needless to say, the average brightness of Example 6 is higher than that of Comparative Example 1, but the reason why it is higher than that of Examples 2 and 3 is that the reflective layer 8 is provided on the facing side surface 3. .

(Fourth Embodiment) FIG. 6 is a side view showing a part of a light guide plate according to a fourth embodiment. In FIG. 6, the light guide plate 13
Is substantially the same as that of the first embodiment shown in FIG. 1 except that the configuration of the facing side surface 3 is different. The facing side surface 3 in the present embodiment is an inclined surface having an interior angle of 60 ° with respect to the light emitting surface 2, and fine irregularities 9 ... With irregular reflection are formed on the entire surface of the facing side surface 3. A reflective layer 8 made of an aluminum film is formed on the facing side surface 3.

Since the facing side surface 3 of this embodiment is inclined in the direction of the light emitting surface 2, fine irregularities 9 ... Are formed with diffused reflection, and the reflecting layer 8 is provided, from the direction of the light incident side surface 1. The light (beam Bo) projected on the facing side surface 3 is diffused mainly in the direction of the light emitting surface 2 substantially uniformly, and a part of the diffused reflected light represented by the beam Br is projected on the reflecting surface 4 and is eventually emitted. Is reflected in the direction of. As a result, the opposite side surface 3
The light reflected by is relatively evenly dispersed over the entire surface of the sheet-like light flux, and a sheet-like light flux with little brightness unevenness and high brightness can be obtained.

Example 7 is a sample of the light guide plate 13 of this embodiment.
Then, the average luminance and the luminance unevenness of the emitted planar light flux were measured in the same manner as in the second embodiment. The results are shown in Table 2.
From the results of Table 2, the average luminance of Example 7 is Comparative Example 1 (1.
Needless to say, it is higher than that of Example 00), but it is higher than that of Example 3 in which the inclination angle of the facing side surface is 60 ° because the reflective layer 8 is provided on the facing side surface 3. Further, the uneven brightness was further improved as compared with Example 5 in which the inner side angle was set to two levels because the opposite side surface 3 was made to be diffusely reflective.

(Fifth Embodiment) FIG. 7 is a side view showing a part of a light guide plate according to a fifth embodiment. In FIG. 7, the light guide plate 14
Is provided with reflecting means for reflecting both the light (beam Bn) incident from the light incident side surface 1 and the light (beam Br) reflected by the opposite side surface 3 toward the light emitting surface 2. This reflecting means is composed of a large number of prism parts 55 ... Arranged on the reflecting surface 4. The prism portion 55 is composed of a ridge line 6 extending in the length direction of the light incident side surface 1 and inclined surfaces 7 a, 7 b, and 7 c sandwiching the ridge line 6. Among these, the inclination angle αb of the inclined surface 7b arranged in the direction of the opposite side surface 3 from the ridge line 6 with respect to the light emitting surface 2 is the light projected from the light incident side surface 1 direction (beam Bn) at the position where the prism portion is arranged. Is set to reflect in the direction of the light emitting surface 2. In addition, the inclination angle αc of the inclined surface 7c arranged in the direction of the light incident side surface 1 from the ridge 6 with respect to the light emitting surface 2 indicates that the light (beam Br) reflected by the opposed side surface 3 at the position where the prism portion is arranged. It is set to reflect in the direction of the light emitting surface 2. Therefore, the width, height, and inclination angles αb, αc of the arrayed prism parts 55 are determined by the position where the prism parts are arranged, the directivity of light incident from the light incident side surface 1, and the configuration of the opposite side surface 3. Considering the directivity of the reflected light, etc., they are individually designed and shaped so that the largest amount of light is reflected in the direction of the light emitting surface 2 as a whole.

Since the light guide plate 14 of this embodiment is provided with the prism portions 55 ... Which reflect both the light incident from the light incident side surface 1 and the light reflected by the opposite side surface 3 toward the light emitting surface 2, Of the light incident from the light side surface 1 and the light reflected from the opposite side surface 3, the light directed in the direction of the reflecting surface 4 is effectively used for improving the brightness of the planar light flux, and the brightness unevenness is also improved.

In the light guide plate 14 of this embodiment, the shape of the opposite side surface 3 is formed so as to reflect at least a part of the light projected from the direction of the light incident side surface 1 non-parallel to the light emitting surface 2. It is not particularly limited as long as it is present, but, for example, as shown in FIG. 2, it has an inclined surface with an internal angle θ of more than 90 °, or as shown in FIG. Is especially useful for. When the opposite side surface 3 is diffusely reflective, as shown in FIG. 8, the opposite side surface 3 is perpendicular to the light emitting surface 2 (θ = 90).
°). Also in this case, at least a part of the reflected light (beam Br) from the opposite side surface 3 travels non-parallel to the light emitting surface 2, and a part of the reflected light (beam Br) is inclined surface 7c of the reflecting surface 4.
It is possible to contribute to the improvement of the brightness of the planar light flux because it is projected onto the light emitting surface 2 and reflected on the light emitting surface 2 side.

In each of the above-described embodiments, each surface of the light guide plate except the light incident side surface 1, the light emitting surface 2 and the reflection surface 4 is made to have an inner surface reflectivity in order to reduce the light guide loss due to the transmission and diffusion of the incident light. Preferably. The inner surface reflectivity can be provided by vapor deposition or sticking of a silver surface material such as aluminum.

(Embodiment 6) FIG. 9 is a perspective view showing a surface light emitter which is an embodiment of the present invention. In FIG. 9, the surface light emitter 40 includes the light sources 30a and 30b and the rod-shaped light guide 2
0 and the light guide plate 10. Light sources 30a, 30b
Each of them comprises a lamp house containing a light emitting diode (LED), and irradiates light (represented by a beam Bo) toward the light receiving end surface 21 of the rod-shaped light guide 20 from an irradiation window provided on one surface thereof. Are arranged as follows. The rod-shaped light guide 20 in the present embodiment is made of a transparent acrylic resin and is made of a substantially prismatic elongated rod-shaped body. In this rod-shaped light guide 20, both end faces are light receiving end faces 21 and 21, one side face adjacent to the light receiving end faces is an emission side face 22, and a side face facing the emission side face 22 is a reflection side face 24. The light receiving end faces 21 and 21 are planes perpendicular to the longitudinal direction of the rod-shaped light guide 20 and receive the light emitted from the light sources 30a and 30b. The emission side surface 22 is a plane along the longitudinal direction of the rod-shaped light guide 20, and the light received by the light-receiving end surface 21 is converted into a band-shaped light flux L.
The light is emitted toward the light guide plate 10 as 1. This ejection side 2
The reflecting side surface 24 facing 2 is formed by a large number of prism portions 25, which are each composed of a ridge line extending in the width (short side) direction and an inclined surface that sandwiches the ridge line, and the light (beam Bo that is projected on the inclined surface of the prism portion 25. The shape of the prism portions, the arrangement interval, and the like are appropriately adjusted so as to reflect the light beam in the direction of the exit side surface 22.

The light guide plate 10 is as shown in FIG. 1 and described as Example 3 of the first embodiment, and has a configuration in which the interior angle θ of the facing side surface 3 with respect to the light emitting surface 2 is 60 °. Any other light guide plate to which it belongs can be replaced with this, and any of them is effective. In FIG. 9, the light guide plate 10 is arranged such that the light incident side surface 1 faces the exit side surface 22 of the rod-shaped light guide 20, and the band-shaped light flux L emitted from the rod-shaped light guide 20.
1 is received.

The downward plate surface of the light guide plate 10 is the light emitting surface 2 and is arranged so as to face the display surface 51 of the liquid crystal display unit 50. The upwardly facing plate surface of the light guide plate 10 facing the light emitting surface 2 is the reflecting surface 4. A large number of prism parts 5 are arranged on the reflecting surface 4 at predetermined intervals. Each prism portion 5 is composed of a ridge line 6 extending in a direction parallel to the light incident side surface 1 and inclined surfaces 7a and 7b sandwiching the ridge line 6, and the angle and height of the inclined surfaces 7a and 7b are different from each other at that position. It is adjusted so that the light (beam Bi) incident on the light plate 10 is projected on the inclined surface 7b and is most efficiently reflected in the direction of the light emitting surface 2.

The light guide plate 10 is the exit side surface 2 of the rod-shaped light guide 20.
When the band-shaped light flux L1 emitted from the light receiving side surface 1 is received, the light (beam Bi) incident on the light guide plate 10 is diffused inside the light guide plate 10, and the prism portions 5 of the light emitting surface 2 and the reflecting surface 4 are ...
And repeats complicated internal reflection, and finally the light (beam B
Most of i) is reflected by the prism portions 5 ... And is emitted from the light emitting surface 2 as a planar light flux L2 that spreads over the entire display surface of the liquid crystal display unit 50 and illuminates the display surface 51 of the liquid crystal display unit 50. And the display surface 5 of the liquid crystal display unit
The light (beam Bs) of the light that illuminates 1 is transmitted through the pixel 52, which is made transparent by the alignment of the liquid crystal, is reflected by the reflection plate 70, which will be described in detail below.
And the light-transmitting light guide plate 10 is also transmitted and emitted from the reflecting surface 4 as monitor light (beam Bm) to be visually recognized by an observer.

In the surface light-emitting body 40 of this embodiment, the structure of the rod-shaped light guide 20 is the same as the rod-shaped light guide in the conventionally used surface light-emitting body, and the brightness of the band-shaped light beam L1 is the same as that of the conventional one. However, since the light guide plate 10 emits light having a higher brightness and less uneven brightness than the conventional one, the light guide plate 10 is inclined so that the light emitting surface 2 is reduced.
The planar light beam L2 emitted from the device has high brightness and less brightness unevenness, and as a result, the monitor light (beam Bm) visually recognized.
Is bright, the contrast between the transmissive pixel and the non-transmissive pixel is high, and an image with good visibility in which uneven brightness is eliminated can be obtained.

In the above light guide plate 10, side surfaces other than the light incident side surface 1 and upper and lower plate surfaces are reflected in order to prevent haze and glare due to extra reflection or scattering of external light or incident light and to enhance image contrast. A preventive film may be applied.

(Embodiment 7) FIG. 10 is a perspective view showing a liquid crystal display device according to an embodiment of the present invention. In FIG. 10, the liquid crystal display device generally includes a surface light emitter 40 and a liquid crystal display unit 50. Of these, the surface-emitting body 40 is the same as that shown in the sixth embodiment, and therefore detailed description thereof is omitted. The liquid crystal display unit 50 is generally composed of a liquid crystal display plate 60 and a reflection plate 70.

As shown in FIG. 11, the liquid crystal display panel 60 has a light control layer 61 including a protective film, a retardation film, a polarizing film and the like, and an upper transparent electrode layer 6 in order from the display surface 51 side downward.
2, a liquid crystal layer 63, and a lower transparent electrode layer 64, and these layers form a matrix of pixels 52 ... Which are driven and controlled independently in the plane of the display surface 51. The layer structure and driving method of the illustrated liquid crystal display panel 60 are examples, and are not particularly limited. For example, the layer structure may include a color filter layer and the like, and the driving method may be any of a simple matrix method and an active matrix method. In each pixel 52, the liquid crystal molecules in the corresponding portions of the liquid crystal layer 63 change the alignment mode due to the potential change between the corresponding upper transparent electrode layer 62 and the lower transparent electrode layer 64, whereby light transmission / shielding is performed. Realize mode conversion.

As shown in FIG. 12, an example of the reflector 70 is a synthetic resin substrate 71, on the surface of which a large number of concave portions 72 ... A reflective film 73 is formed on the entire upper surface including the concave portions 72 ... The reflector 70 diffusely reflects the light (beam Bs) projected from above from the concave portion 72 and diffuses and emits it as a monitor light (beam Bm) in a wide range. When the reflection plate 70 is attached to the lower surface of the liquid crystal display plate 60 as shown in FIG. 10, the light emitted from the light emitting surface 2 of the light guide plate 10 and transmitted through the pixels 52 in the light transmission mode in the liquid crystal display plate 60 ( The beam Bs) is diffusely reflected by the reflection plate 70, passes through the pixel 52 and the light guide plate 10 and is diffused in a wide range, so that the viewing angle at which an image can be clearly observed becomes wide.

The liquid crystal display device according to the present embodiment includes the surface light emitter 4
When the light (beam Bs) emitted as the planar light flux L2 from the light emitting surface 2 of 0 irradiates the display surface 51 of the liquid crystal display unit 50, the emitted light (beam Bs) is emitted at the portion of the pixel 52 which is set to the transmissive mode by the liquid crystal drive circuit. The beam Bs) is the liquid crystal display panel 60
And is diffusely reflected by the reflection plate 70, and the reflected light (beam Bm) again passes through the liquid crystal display plate 60 and is further guided by the light guide plate 1.
0 is also transmitted, and becomes visible as a monitor light Bm from the reflecting surface 4 to the observer with a wide viewing angle.

In this liquid crystal display device, the light guide plate 10 of the surface light emitter 40 emits a planar light beam having higher brightness and reduced brightness unevenness as compared with the conventional one, so that the monitor light Bm visually recognized as a result. It is possible to obtain an image that is bright, has little unevenness in the brightness of the screen, has a high contrast between transparent pixels and non-transparent pixels, and has good visibility.

[0051]

In the light guide plate of the present invention, the opposite side surfaces are formed so as to reflect at least a part of the light projected from the direction of the light incident side surface non-parallel to the light emitting surface. The light projected on the side surface is effectively used, and the brightness of the light emitted from the light emitting surface is increased and the uneven brightness is reduced. Since the surface light emitter of the present invention has the above-mentioned light guide plate having high output brightness, the surface light emitter has higher illumination brightness and less uneven brightness as compared with the conventional surface light emitter. Since the liquid crystal display device of the present invention has the surface light emitter and the liquid crystal display unit, it has a higher image contrast, less brightness unevenness, and good visibility as compared with the conventional liquid crystal display device of the same kind. .

[Brief description of drawings]

FIG. 1 is a side view showing a light guide plate according to an embodiment of the present invention.

FIG. 2 is a side view showing a light guide plate according to another embodiment of the present invention.

FIG. 3 is a side view showing a method for measuring the output brightness of the light guide plate.

FIG. 4 is a side view showing a light guide plate according to another embodiment of the present invention.

FIG. 5 is a side view showing a light guide plate according to still another embodiment of the present invention.

FIG. 6 is a side view showing a part of a light guide plate according to still another embodiment of the present invention.

FIG. 7 is a side view showing a part of a light guide plate according to still another embodiment of the present invention.

8 is a side view showing a modification of the embodiment of FIG. 7. FIG.

FIG. 9 is a perspective view showing a surface light emitter that is an embodiment of the present invention.

FIG. 10 is a perspective view showing a liquid crystal display device according to an embodiment of the present invention.

11 is a perspective view showing a liquid crystal display panel in the embodiment of FIG.

FIG. 12 is a perspective view showing a reflection plate in the embodiment of FIG.

FIG. 13 is a perspective view showing a conventional example of a liquid crystal display device with a front light.

FIG. 14 is a side view showing a light guide plate in the conventional example of FIG.

[Explanation of symbols]

1 ... Light-incident side surface, 2 ... Light-emitting surface, 3 ... Opposing side surface, 4 ... Reflective surface. 5 ... Prism part, 6 ... Ridge line, 7a, 7b ... Inclined surface.
10 ... Light guide plate, 20 ... Rod-shaped light guide, 30a, 30b ... Light source, 40 ... Surface light emitter. 50 ... Liquid crystal display unit, 60 ...
Liquid crystal display plate, 70 ... Reflector.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // F21Y 101: 02 F21Y 101: 02 (72) Inventor Mitsuru Shikano 1-7 Otsuka-cho, Yutani, Ota-ku, Tokyo No. Alps Electric Co., Ltd. (72) Inventor Hiroyasu Miyata No. 1-7 Yukiya Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) No. 7 Ryumaro Yamashita Otaku-ku, Ota-ku, Tokyo 1-7 No. Alps Electric Co., Ltd. F-term (reference) 2H038 AA52 AA55 BA06 2H091 FA14X FA23X FA41X FD06 FD12 LA18

Claims (11)

[Claims] 1. A light guide which is made of a light-transmissive plate-like member, and emits a band-shaped light beam incident from one side surface (light-incident side surface) of the plate-shaped member as a planar light beam from at least one plate surface (light-emitting surface). In the light plate, a side surface (opposing side surface) facing the light incident side surface is formed so as to reflect at least a part of the light projected from the direction of the light incident side surface non-parallel to the light emitting surface. A light guide plate characterized by that. 2. The light guide plate according to claim 1, wherein the facing side surfaces are inclined surfaces having an interior angle with respect to the light emitting surface of less than 90 ° or more than 90 °. 3. The light guide plate according to claim 2, wherein the interior angle is in the range of 30 ° to 60 °. 4. The opposing side surface is composed of two or more inclined surfaces that reflect light projected from the direction of the light incident side surface non-parallel to the light emitting surface. Item 4. The light guide plate according to any one of items 3. 5. The light guide plate according to claim 1, wherein the opposite side surfaces are curved surfaces. 6. The light guide plate according to claim 1, wherein a reflective layer is formed on the opposite side surfaces. 7. The light guide plate according to claim 1, wherein the opposite side surfaces are irregularly reflective. 8. A plate surface (reflection surface) facing the light emitting surface.
8. A reflecting means for reflecting both the light incident from the light incident side surface and the light reflected by the facing side surface toward the light emitting surface is provided in any one of claims 1 to 7. The light guide plate described in. 9. The light guide plate according to any one of claims 1 to 8 and a light-transmissive rod-shaped body that receives light emitted by a light source from one end surface (light receiving end surface) thereof, A surface light emitter, comprising: a rod-shaped light guide that is emitted from the side surface (emission side surface) as a band-shaped light beam to the light incident side surface of the light guide plate. 10. The light guide plate is translucent in the plate thickness direction, and a reflecting means for emitting the planar light flux from one plate surface (light emitting surface) is provided. The surface light-emitting device according to. 11. A liquid crystal display device comprising the surface light emitter according to claim 9 or claim 10 and a liquid crystal display unit.