JP2002250820A - Structure of light guide plate and electronic equipment having the plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a light guide plate in which illuminance is made uniform by increasing light irradiation to the outside of the irradiation region of a point light source and design and manufacturing of the waveguide. SOLUTION: The light guide plate 2 has slanted walls C having an apex in the vicinity of a light source 1 and a light diffusing hole 3. The walls C have a light reflecting function. The hole 3 is made of a through-hole or a recessed hole. The plane shape of the hole 3 is made of a polygon such as an isosceles triangle or the like and one of the apexes is directed toward a light source direction. Oblique sides F that sandwich the apex of the hole 3 totally reflect incident light beams in accordance with the critical angle, the reflected light beams are again reflected by the walls C, sections A and B are irradiated and the luminance is increased and made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display unit such as a liquid crystal using a light source having irradiation directivity such as an LED (Light Emitting Diode) as a backlight light source. The present invention relates to a structure of a light guide plate for improving the efficiency of an electronic device and an electronic device including the structure.

[0002]

2. Description of the Related Art Conventionally, a display section of a digital automobile instrument, a car navigation system, a television, a personal computer display,
Liquid crystal display units are widely used for facsimile display units and the like, and all use a backlight. In addition, liquid crystal display units are mainly used for display units in portable electronic devices such as mobile phones and PHSs, which have rapidly spread in recent years. Many of the liquid crystal display units are provided with a backlight so that they can be used in a dark place and illuminate the display from behind.

As a backlight of such a liquid crystal display unit, there are a linear light source using a cold cathode tube, a planar light source using electroluminescence, and a point light source using LEDs or the like. Although all the light sources have advantages and disadvantages, point light sources using LEDs that are easy to drive, are advantageous for miniaturization and thinning, and have good impact resistance are being promoted. In particular, since electronic devices such as mobile phones are premised on the use of a storage battery or the like as a power source, they are required to have high light conversion efficiency and not require a complicated driver circuit. It is necessary to make the display unit smaller and thinner, and in particular, it is strongly required to make it thinner. To achieve this priority, it is important to make the backlight smaller and thinner. Has become.

Therefore, point light sources using LEDs are being used. However, in order to display clear information even under sunlight, a backlight is required to have sufficient illuminance and uniform display. It is necessary to eliminate the disadvantage of the point light source that it is difficult to irradiate light uniformly widely.
In order to eliminate this disadvantage, it has been practiced to drive a large number of LED elements at the same time. However, LEDs have a low conversion efficiency into light energy, require a large current and generate heat. It was a bad thing to aim for electricity.

For this reason, it has been studied to irradiate light widely and uniformly by improving the light directivity of a single LED without using a large number of LEDs.
A surface illumination device disclosed in Japanese Patent Publication No. 35 is proposed. As shown in FIG. 11, the surface illumination device has a light guide plate 12 provided in front of a point light source 11 made of an LED in an irradiation direction and provided with a light diffusion hole 13 having a circular plane shape formed of a through hole or a concave hole. . The light diffusing holes 13 transmit the light from the point light source 11 whose incident angle is equal to or less than the critical angle, totally reflect the light exceeding the critical angle, and are outside the irradiation area of the point light source 11. Light is diffused to achieve uniform display illuminance.

[0006]

However, the above-mentioned prior art has the following problems. That is, the light diffusion hole 1 composed of a combination of circular or circular arcs
In the case of 3, light reflected at the outer peripheral portion of the light diffusion hole 13 is radially diffused, but the degree of diffusion of the reflection angle becomes extremely large, and the reflected light cannot sufficiently irradiate the A portion and the B portion. There was a problem.

Referring to FIG. 12, the critical angle i for determining whether light is transmitted or reflected through the light diffusion hole 13 is a fixed numerical value (acrylic) determined by the material of the light guide plate 12. In the case of the same light guide plate, the reflection and diffusion of light are determined by the shape of the surface on which the light hits and the angle of incidence of the light. The light reflected on the circumference is reflected at the same angle in the normal direction along the curvature of the circle according to the law of reflection, so that the light from the point light source 11 reflects the reflected light c, The light is reflected like d and e, respectively.
The reflected lights c, d, and e are largely dispersed in proportion to the curvature of the light diffusion hole 13, and only a small amount of reflected light is applied to the narrow areas A and B, thereby reducing the brightness. It did not reach homogeneity.

Here, if the circular radius of the light diffusion hole 13 is reduced, the reflected lights c, d, and e deviate from the portion A and converge on the central portion, so that the light cannot be diffused. Further, when the light diffusion hole 13 is brought closer to the point light source 11, the area of the portion B increases, and a new problem occurs. For this reason, it has been proposed to form the light diffusion hole 13 by combining two large arcs or to combine two or more large and small light diffusion holes. However, regarding these combinations, it is necessary to perform an extremely complicated analysis in order to obtain optimum conditions for the shape, position, number, and the like of the curved surface. In particular, the directional characteristics of the LED for light irradiation are shown in FIG.
As shown in (2), generally, the irradiation energy becomes maximum in the front direction of the optical axis, gradually attenuates as it deviates from the optical axis, and rapidly attenuates beyond a certain radiation angle. Therefore, the irradiation light that is distributed and enhanced in the region where the light irradiation amount is insufficient is not constant, and it is difficult to achieve uniform luminance unless the analysis can be performed more easily.

Further, if the theoretical analysis is complicated and difficult,
The trial production and data acquisition from the trial production are repeated, but this requires enormous design cost and production time. In particular, in recent years, electronic devices such as mobile phones have their designs and functions changed in a short period of time. Therefore, it is necessary to conduct a theoretical analysis quickly and easily to produce prototypes. Shortening was a major problem.

Further, it is pointed out that there is a possibility that the shape of the light diffusing hole is made a polygon such as a triangle or a rectangular parallelepiped to obtain the same effect as in the case of a circular shape. No suggestions were made. In particular, there is no suggestion as to what can solve the problem in the circular light diffusion hole as described above.

The present invention has been made in view of the above-mentioned problems of the prior art, and increases the irradiation of light to the outside of the irradiation area of a point light source to make the illuminance uniform and efficiently irradiate, thereby suppressing power consumption. An object of the present invention is to provide a structure of a light guide plate that facilitates analysis on light distribution and enables quick design and manufacture.

[0012]

According to a first aspect of the present invention, there is provided a light guide plate having a point light source having irradiation directivity as a light source, and a tilt function having a reflection function of tilting with the vicinity of the light source as a vertex. In the structure of a light guide plate provided with a wall and provided with a light diffusion hole near the light source to irradiate light outside an irradiation region generated by the irradiation directivity of the light source, the light diffusion hole has a large planar shape. It has a rectangular shape, and one of its vertices is formed so as to face the light source direction. The light diffusing hole in the structure of the light guide plate has a triangular planar shape, a vertex thereof faces the light source direction, and a base is orthogonal to an optical axis center line of the light source. Formed at the location. Further, the light diffusing hole in the structure of the light guide plate has a square planar shape, one of the vertices faces the light source direction, and the vertex opposed to the vertex has a rectangular shape. It is located on the optical axis of the light source. The light diffusing hole in the structure of the light guide plate comprises a through hole or a concave hole. Further, in the light diffusion hole formed by the concave hole, the concave hole is formed by providing a spot facing portion from the display unit side of the light guide plate. Further, as set forth in claim 6, the inner wall surface of the light diffusing hole has a substantially mirror surface state.

Further, the light guide plate has a structure in which a side sandwiching an apex of the light diffusion hole facing the light source is formed in a concave arc shape, and the light from the light source is reflected. The light is focused.

Further, the inner wall surface of the light diffusing hole in the structure of the light guide plate is smaller than the critical angle at a critical angle which is uniquely determined by the refractive index of the light guide plate material. The incident light having an incident angle is transmitted through the inside of the light diffusion hole, and the incident light exceeding the critical angle is totally reflected and irradiated outside the irradiation area.

In the light guide plate, when the light diffusing hole is formed as a concave hole, the depth of the spot facing with respect to the thickness of the light guide plate may be adjusted to provide the light source. The ratio between the straight light coming from the light and the light reflected by the light diffusing holes can be adjusted.

The structure of the light guide plate may be such that the light diffusing hole is formed on the basis of an optical optimum condition for the purpose of making the reflected light out of the irradiation range uniform and the diffused light uniform. The inclination of the side sandwiching the vertex facing the light source direction and the inclination of the inclined wall of the light guide plate are set. The light diffusing holes in the structure of the light guide plate form a prism made of air, as described in claim 11, for the purpose of reflecting the light outside the irradiation area and making the diffused light uniform. An inclination of the oblique side of the prism and an inclination of the inclined wall of the light guide plate are set based on optical optimum conditions.

According to a twelfth aspect of the present invention, there is provided a light guide plate, wherein a point light source having irradiation directivity is used as a light source, and an inclined wall having a reflecting function of inclining with a vertex near the light source is provided. In order to irradiate light to the outside of the irradiation area generated by the irradiation directivity of the light source, in the structure of the light guide plate provided with the light diffusion holes near the light source, the light diffusion holes have a single arc portion in plan view. It has an arc shape, the arc portion of which faces the light source direction, and the arc portion has a reflective portion. The light diffusing hole in the structure of the light guide plate comprises a through hole or a concave hole. Further, the inner wall surface of the light diffusion hole has a substantially mirror surface state.

In the present invention, the reflective portion is formed by applying a white or reflective coating to the inner wall surface of the light diffusion hole on the light source side. According to a sixteenth aspect of the present invention, a reflection member is formed in the light diffusion hole by inserting a reflection member adapted to the inner wall surface on the light source side. In this case, as shown in claim 17, the reflective member is a film having light reflectivity,
It consists of a metal strip or sheet. Further, as described in claim 18, the light diffusion hole is filled with a filler having light reflectivity to form a reflection portion. According to a nineteenth aspect, a reflecting member having a concave shape with respect to the inner wall surface on the light source side is inserted into the light diffusion hole to form a reflecting portion. Here, when the light diffusion hole is a through hole, as shown in claim 20, the reflection portion is formed in a part of the inner wall surface on the light source side in a depth direction, and another portion of the inner wall surface is formed. To form a transmission part. At this time, by adjusting the ratio of the reflection part and the transmission part of the light diffusion hole, the ratio of the straight light from the light source and the reflection light from the light diffusion hole can be adjusted. And

Further, an electronic apparatus according to the present invention is provided with the structure of the light guide plate according to any one of claims 1 to 21 described above.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a light guide plate according to the present invention is, as shown in FIG.
The light diffusing hole 3 is provided in the light guide plate 2 provided with. The inclined wall C has a reflecting function in a plane direction. The light diffusion holes 3 are provided in the direction in which the light source 1 near the light source 1 emits light. The light diffusion hole 3 is formed of a through hole or a concave hole, and has a planar shape formed of a polygon such as an isosceles triangle or a regular tetrahedron, and is formed such that one of its vertices faces the light source direction. It has become.
The light diffusing hole 3 in FIG. 1 has a planar shape of an isosceles triangular shape, a vertex of which faces the light source direction, and a base formed at a position orthogonal to the optical axis center line of the light source. The inner wall of the oblique side sandwiching the apex of the light diffusion hole 3 has a mirror surface, and totally reflects incident light according to the critical angle.

In the case of this light guide plate structure, the light source 1 has directivity for light irradiation, and the original irradiation area is
Is set in the range of the angle θ centered at. The portion A outside the irradiation area angle θ is outside the irradiation area where the light from the light source 1 is not irradiated. Further, since the light diffusion holes 3 are provided even in this irradiation region, the light is totally reflected there and the portion B near the boundary of the irradiation region where the light from the light source 1 is no longer irradiated is also outside the irradiation region. I have.

In the structure of the light guide plate of the present invention, the light source 1
A part of the light from the light diffuser 3 is reflected by the light diffusing hole 3 and the reflected light is further reflected by the inclined wall C of the light guide plate 2 to widen the irradiation area, thereby increasing the brightness of the A portion and the B portion and making them uniform. It is something to do. That is, the inclined side sandwiching the apex of the light diffusion hole 3 in the present invention is a slope parallel or inclined to the inclined wall C of the light guide plate 2 and faces the inclined wall C of the light guide plate 2. Has become. The inclined side of the light diffusion hole 3 is
The light from the light source 1 is transmitted or reflected according to the critical angle based on the material of the light guide plate 2. The light reflected here is radiated to the inclined wall C by setting the reflection angle, and is further reflected by the inclined wall C and irradiated in the directions of the portions A and B.

In the case of the structure of the light guide plate, since the inclined wall C of the light guide plate 2 and the inclined side of the light diffusing hole 3 are flat, the efficiency and uniformity of light reflection to the portions A and B outside the irradiation area are uniform. It is extremely easy to determine the optimum conditions. In particular, by setting the planar shape of the light diffusing hole 3 to a symmetrical shape such as an isosceles triangle and arranging its apexes on the optical axis in the direction of the light source 1, the light trace of the reflected light can be easily analyzed. Thus, the angle and the positional relationship between the inclined wall C and the inclined side of the light diffusion hole 3 can be easily determined.

Further, by providing the light diffusing hole 3 with a reflecting portion for reflecting light and a transmitting portion for transmitting light, it is possible to easily set the reflecting direction or the transmitting direction. The reflecting portion of the light diffusion hole 3 is formed by applying a white or reflective coating to the inner wall surface of the light diffusion hole 3 on the light source side, or is adapted to the inner wall surface of the light diffusion hole 3 on the light source side. Or by filling the light diffusion hole 3 with a filler having light reflectivity,
The light diffusion hole 3 is formed by inserting a reflecting member having a concave shape with respect to the inner wall surface on the light source side. By adjusting the ratio between the reflection part and the transmission part of the light diffusion hole, it is also possible to adjust the ratio between the straight light from the light source and the light reflected by the light diffusion hole.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a light guide plate according to one embodiment of the present invention will be described below. FIG. 2 is a plan view showing the structure of the light guide plate according to the first embodiment of the present invention, FIG. 3 is a sectional view of a liquid crystal display unit incorporating the light guide plate, and FIG. 4 is a portion of the light guide plate shown in FIG. It is an enlarged view.

In the center of the left end surface of the light guide plate 2 in the drawing, an LED is provided.
A light source 1 composed of a point light source is installed. Light guide plate 2
The left end face in the drawing of FIG.
An inclined wall C is provided so as to be substantially evenly inclined with respect to the optical axis center line of the light source 1 so as to satisfy (α <180 °). The inclined wall C is a plane perpendicular to the plane 2a of the light guide plate 2, and is mirror-finished to have a light reflecting action. Therefore, the light reflected by the inclined wall C travels in the light guide plate 2 in the plane direction (horizontal direction). Further, if necessary, the side wall D of the light guide plate 2 is also mirror-finished to have a reflecting effect. Also,
In order to further improve the light reflection state, a metal band, a reflection sheet, or the like may be attached from the outside of the inclined wall C or the side wall D.

The value of the angle α is set to an appropriate value according to the radiation directivity characteristics of the light source 1, the size of the light guide plate 2, and the vertical and horizontal dimensional ratios. For example, the angle α is such that the light guide plate 2 is formed of a material such as transparent acrylic or polycarbonate, and the light guide plate 2 is made of a mobile phone or FA.
Assuming that it is set to the size of the display part of X,
It is preferable to set the angle to approximately 120 ° to 140 °. In this embodiment, the angle α is set to about 130 °.

On the other hand, the light diffusing hole 3 in this embodiment has a planar shape of an isosceles triangle, and is formed in a through hole formed in the thickness direction of the light guide plate 2 or on the display side as shown in FIG. It is composed of a concave hole formed from. The light diffusing hole 3 in this embodiment is a concave hole. This light diffusion hole 3
Is formed as a concave hole, the spot facing portion is
It has been confirmed by experiments that the provision of the light emitting element on the side of the display unit is more efficient in making the luminance uniform. This is considered to be due to the following operation. That is, around the light diffusing hole 3 formed by the spot facing, light reflection and refraction occur mainly in the plane direction of the light guide plate, while in the part without the spot facing, the light follows the directional characteristics of the light source 1. It travels substantially uniformly radially in the light guide plate. In the liquid crystal display device with a backlight, as described later, a reflection plate is provided on the lower surface side of the normal light guide plate 2 in order to increase the efficiency of irradiation toward the display unit. It is considered that it is more advantageous for such a reflector to apply light traveling straight from a light source than to light that has already been reflected and refracted, in terms of reflection efficiency and brightness uniformity. It is provided on the display unit side, and the part without the spot facing is located on the reflection plate side. The vertex 3 a of the light diffusion hole 3 faces the direction of the light source 1 and is located on the optical axis center line 1 a of the light source 1. Further, the bottom 3b of the light diffusion hole 3 is located at the optical axis center line 1.
It is positioned so as to be orthogonal to a.

The oblique side F sandwiching the vertex 3a of the light diffusion hole 3
Is formed so that the inner wall thereof is as close as possible to a mirror surface state, and is formed so as to reduce energy loss and efficiently guide light when reflecting and transmitting light. In this embodiment, the bottom 3b of the light diffusion hole 3 is used.
Also, the inner wall is finished so as to have a substantially mirror surface state. By making the bottom 3b substantially mirror-surfaced as well, the light passing through the bottom 3b is transmitted without being diffused, so that the light trace can be easily analyzed. Further, the apex angle of the light diffusion hole 3, that is, the angle β which is the opening angle of the hypotenuse F is larger than (or equal to) the above-mentioned angle α.
Is set to be approximately 15 in this embodiment.
It is set to 0 °. The reason for setting α ≦ β is that the light emitted from the light source 1 to the oblique side F of the light diffusing hole 3 is totally reflected beyond the critical angle and hits the inclined wall C again. In order to efficiently collect the reflected light at the portions A and B outside the irradiation area, the setting is made in this way. If it is set so that α <β, the reflected light from the inclined wall C spreads outside the A portion and the B portion, and the reflected light cannot be collected at the A portion and the B portion.

The state of reflection by the oblique side F and the inclined wall C as described above will be described with reference to FIG. As described above, the reflection of light by the light diffusion holes 3 is determined by whether or not the incident angle exceeds the critical angle i determined by the material of the light guide plate 2. This critical angle i is about 42 ° when the light guide plate 2 is made of acrylic, polycarbonate or the like. Therefore, the rays a, a '
As described above, a light ray incident on the hypotenuse F at an angle within the critical angle i passes through the light diffusion hole 3 while being refracted without being reflected. The light ray b is a light ray at a critical angle and does not reflect or transmit. Light rays H at an incident angle exceeding the critical angle i are totally reflected by the hypotenuse F and radiated in the direction of the inclined wall C. Then, the light is further reflected by the inclined wall C having a reflection function, and is irradiated toward the portions A and B outside the irradiation region.
Here, by making the side wall D also have a reflection function, the light beam is further reflected and diffused by the side wall D, and the portion A,
The light is irradiated to the portion B, and the irradiation efficiency can be increased.
In addition, the light ray which goes out of the light diffusion hole 3 goes straight as it is,
The light beam at this angle has a weak energy and travels straight without being reflected by the light diffusion holes 3.

In this embodiment, the opening angle α of the inclined portion C is
In contrast, the opening angle β of the oblique side F of the light diffusion hole 3 is set to be larger by about 20 °. Thereby, it is possible to prevent the reflection angle at the inclined portion C from unnecessarily increasing, and to efficiently irradiate the portion A and the portion B with light. When the side wall D has a reflection function and is actively used, α ≧ β
In some cases, it is possible to efficiently irradiate the part A and the part B even if the setting is made such that

The distance L from the light source 1 to the light diffusion hole 3
By adjusting the length L2 of the base 1 and the bottom side 3b of the light diffusion hole 3, it is possible to further change the light reflection direction and efficiently irradiate the portions A and B. That is, the reflection angle increases when the light diffusion hole 3 is brought closer to the light source 1 with the distance L1 reduced, and the reflection angle decreases when the distance L1 is increased and moved away. Further, the length L2 of the base 3b is long, and the light diffusion holes 3
Is large, the reflection area due to the hypotenuse F is widened, but the straight light from the light source 1 is blocked. For this reason, the area of the part B outside the irradiation area is expanded, and further,
When the light diffusion hole 3 is hidden so as not to be seen from the outside, a device is required. For this reason, it is preferable not only to set the angles α and β but also to minimize the size of the light diffusion hole 3 and to arrange the light diffusion hole 3 at a position close to the light source 1.
This makes it possible to irradiate light efficiently and uniformly, and to further reduce the size of the entire display device.

The light guide plate 2 and the light source 1 having the above structures are
As shown in FIG. 3, a housing 4 in which a reflecting plate 5 is arranged at the bottom.
The liquid crystal display unit includes a diffusion plate 6 for diffusing light and a liquid crystal cell 7 on its surface side.

In the structure of the light guide plate of the first embodiment, it is possible to relatively easily derive a light trace or a light distribution state drawn by straight and reflected light in the plane direction of the light guide plate. This makes it possible to confirm the optimum conditions for uniforming the brightness of the display unit and for saving power through a simple simulation, and to significantly reduce the cost and time required for the design. In this embodiment, the plane shape of the light diffusing hole 3 is set to be an isosceles triangle in order to facilitate the analysis of the light trace. Can be changed according to the position of the light guide plate and the shape of the light guide plate.

FIG. 5 is a plan view showing the structure of a light guide plate according to a second embodiment of the present invention. In the first embodiment, the planar shape of the light diffusing hole 3 is an isosceles triangle, but in the second embodiment, a regular four-sided surface formed by providing a congruent shape that is line-symmetric with respect to the base 3b as a center line. The shape is set. Thus, even when the planar shape of the light diffusion hole 3 is set to a regular tetrahedron, the same operation and effect as in the first embodiment can be obtained.

In the case of the regular tetrahedral light diffusing hole 3, air is used as a material adjacent to the light axis of the light diffusing hole 3.
It can be regarded as one prism and can be analyzed by applying the general principle of the prism. Accordingly, it is possible to relatively easily obtain the light trace of the transmitted light transmitted through the light diffusion hole 3, and it is extremely effective when the transmitted light is further expanded and distributed. Further, even if the plane shape of the light diffusion hole 3 is set to a square other than the regular tetrahedron, the analysis can be sufficiently performed.
It can be changed according to the position of the light source and the like.

FIG. 6 is a partial plan view showing the structure of the light guide plate according to the third embodiment in which the hypotenuse F of the light diffusion hole shown in FIG. 2 is a concave arcuate curved surface. Since the hypotenuse F of the light diffusion hole 3 in this embodiment is a concave arcuate curved surface, the light from the light source 1 is reflected and condensed and radiated on the inclined wall C. In the present embodiment, since the transmitted light that passes through the light diffusion hole 3 is not generated by the incident angle within the critical angle in principle, the B portion region where the light is shielded by the light diffusion hole 3 is widened as illustrated. . For this reason, in order to obtain straight light, it is preferable that the light diffusion hole 3 is formed as a concave hole, and the straight portion passes below the light diffusion hole 3 to irradiate the portion B.
Further, even when the light diffusion holes 3 are formed by through holes,
Obtaining straight light passing through the light diffusion holes 3 by forming a part (for example, upper half) in the depth direction of the hypotenuse F as a concave arc curved surface and making the other part (for example, lower half) a flat surface. Can be.

FIG. 7 is a plan view showing the structure of a light guide plate according to a fourth embodiment in which the oblique side F of the light diffusion hole shown in FIG. 2 has a reflection function. In this embodiment, a light reflecting function is provided by applying or coating a white or reflective paint or the like or applying a reflective film or sheet to the hypotenuse F of the light diffusion hole 3. I'm making it.

As described in the first embodiment, the light diffusion holes 3
Light is transmitted through the light guide plate, air, and light guide plate, and is refracted. When a simulation is performed to check the distribution of light in the planar direction in the light guide plate 2,
As described above, if there is no light beam with refraction, it can be performed more easily. In the present embodiment, by providing the oblique side F of the light diffusion hole 3 with a reflection function, light transmitted through the light diffusion hole 3 can be removed, and the distribution state of the light can be grasped without considering refraction. I have to. Also in this case, since the transmitted light passing through the light diffusion hole 3 is not generated, the area of the portion B where the light is blocked by the light diffusion hole 3 is widened. For this reason, it is preferable that the light diffusing hole 3 is formed as a concave hole, and the section B is irradiated so that straight light passes under the light diffusing hole 3. Further, even when the light diffusion hole 3 is formed by a through hole, the reflection part for reflecting the light is formed in a part in the depth direction or the like (for example, the upper half, or the light source side half in the length direction of the oblique side F). By making the other part (for example, the lower half or the irradiation side half in the length direction of the oblique side F) a transmissive part that transmits light, it is possible to obtain straight light that passes through the light diffusion hole 3.

The oblique side F may have a reflecting function by filling the light diffusion holes 3 with a filler such as a resin having white or light reflectivity, instead of the paint or the film.

FIG. 8 shows a fifth embodiment in which the light diffusing hole has a reflecting function.
FIG. 4 is a partial plan view showing the structure of the light guide plate according to the example. The light diffusing hole 3 has an arcuate planar shape, and the arc wall G has a reflecting function instead of the hypotenuse F in the above-described embodiment. In this embodiment, in order to facilitate manufacture and assembly, the reflecting member 8 that fits the arc wall G is fitted without using painting, coating, filling, or the like. That is, the reflection member 8 is made of a metal material having a spring property (for example, phosphor bronze, beryllium copper, a stainless steel strip for a spring, or the like), and the arc wall G of the light diffusion hole 3 is formed.
It is adapted along. In addition, as this metal material, discoloration, rust, etc. are hardly generated so that the reflection function is not deteriorated, and it can be easily deformed and inserted while having a spring property, and is about 0.1 to 0.3 mm. It is appropriate to use a stainless steel strip for a spring, which has a good surface finish and excellent reflectivity. Also in this case, since light transmitted through the light diffusion hole 3 is not generated, the light diffusion hole 3 is formed as a concave hole, and straight light is transmitted through the light diffusion hole 3.
It is preferable to irradiate a part (part B) where light is shielded by the light diffusion holes 3 so as to pass under the light diffusion hole 3. Further, even when the light diffusion hole 3 is formed by a through hole, a reflection part for reflecting the light is formed in a part (for example, an upper half or a half in a circumferential direction of the arc wall G) in a depth direction or the like. (For example, the lower half or the remaining half in the circumferential direction of the circular arc wall G) is a light transmitting part, so that straight light passing through the light diffusion hole 3 can be obtained.

In order to eliminate uneven brightness by maximizing the reflection effect of the light diffusing hole 3 as described above, the planar shape of the light diffusing hole 3 should be triangular as in the first embodiment. Is optimal. However, it is expected that it is difficult to fit the reflecting member 8 having a spring property into the light diffusing hole 3 and to make it close to the oblique side. Therefore, in the present embodiment, the light diffusing hole 3 is formed in an arc shape, and the reflecting member 8 is configured to adhere to the arc wall G thereof. Further, in this case, the reflection member 8 can be fixed in close contact with the arc wall G by using the spring property of the reflection member 8 without using an adhesive or the like.

When the inner wall of the light diffusion hole 3 is formed in an arc shape,
Since the light is largely dispersed and reflected, it is disadvantageous in that all the reflected light is effectively used. However, by setting the curvature of the arc wall G as large as possible, it is possible to minimize this disadvantage. Can be.

FIGS. 9 and 10 are partial plan views showing the structure of a light guide plate according to a sixth embodiment in which a reflecting member is fitted into a light diffusing hole to have a reflecting function. Basically, this embodiment is similar to the above-described fifth embodiment in that the light diffusing hole 3 formed of a concave hole is formed.
A reflection member 10 such as a leaf spring is fitted therein.
However, as shown in FIGS. 9 and 10, the reflecting member 10 has a concave arc shape with respect to the direction of incidence and reflection of light. In order to form the reflecting member 10 into a concave arc shape, the inner wall of the oblique side F of the light diffusion hole 3 has a concave shape as in the third embodiment described above.
The reflection member 10 which has been press-deformed into a U-shape is fitted to fit the inner wall of the light diffusion hole 3 (FIG. 9), or the first member described above is used.
In the light diffusion hole 3 having an isosceles triangular shape as in the embodiment,
The concave member is bent by fitting a substantially “heavy” shaped reflecting member 10 that is about 5 to 10% longer than the hypotenuse F (FIG. 1).
0).

Here, the leaf spring used as the reflection member 10 is not easily discolored or rusted, so that the reflection function is not deteriorated. Deformable and insertable, 0.1-0.3
It is appropriate to use a stainless steel strip for a spring having a thickness of about mm, a good surface finish and excellent reflectivity.

The operation and effects of this embodiment are the same as those of the third embodiment. In the structure shown in FIG. 10, a gap is formed between the hypotenuse F and the reflection member 10,
The spacing is small and practically negligible.

Further, the inner wall surface corresponding to the light reflecting portion of the light diffusing hole 3 in each of the above-described embodiments is preferably finished to a substantially mirror-finished state in order to minimize the loss of the reflected light.

Further, in each of the above-described embodiments, regardless of whether the light diffusion hole 3 is formed as a through hole or a concave hole, the reflected light is determined by the ratio of forming the reflection part and the transmission part of the light diffusion hole 3. The ratio between the reflected light and the straight light can be adjusted, and the direction of the reflected light and the straight light can be set depending on the position where the light is formed. For example, the reflection part can be formed in a part of the light diffusion hole 3 in the depth direction, or can be formed in a part of the length direction of the oblique side F, and the reflection part and the transmission part are alternately formed. The ratio and direction of the reflected light and the straight light can be adjusted according to the size and shape of the light guide plate.

[0049]

According to the present invention, the light guide plate is provided with a light diffusion hole such as an isosceles triangle or a polygon such as a regular tetrahedron, and the light reflected by the light diffusion hole is reflected by the inclined wall of the light guide plate. Thereby, the illuminance can be made uniform by irradiating the light from the light source to the outside of the irradiation area. This makes it possible to efficiently irradiate the entire light guide plate, and it is only necessary to provide a minimum number of light sources, so that power consumption can be suppressed.

Since reflection / diffusion between flat surfaces, reflection / diffusion between flat surfaces and concave surfaces, and reflection / diffusion between flat surfaces and an arc-shaped surface having a large curvature are used, the light reflected by the light diffusion holes is reduced. Light trace analysis is easy and can be designed and manufactured quickly.

Further, since the analysis on the light distribution is easy, the optimum condition can be determined and the irradiation can be performed most efficiently in accordance with the condition.

[Brief description of the drawings]

FIG. 1 is a plan view showing a structure of a light guide plate of the present invention.

FIG. 2 is a plan view showing the structure of the light guide plate according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a liquid crystal display unit incorporating the light guide plate shown in FIG.

FIG. 4 is a partially enlarged view of the light guide plate shown in FIG.

FIG. 5 is a plan view illustrating a structure of a light guide plate according to a second embodiment of the present invention.

FIG. 6 is a partial plan view showing the structure of a light guide plate according to a third embodiment in which the hypotenuse of the light diffusion hole shown in FIG. 2 is a concave arc-shaped curved surface.

FIG. 7 is a plan view showing the structure of a light guide plate according to a fourth embodiment in which the oblique side of the light diffusion hole shown in FIG. 2 has a reflection function.

FIG. 8 is a partial plan view showing the structure of a light guide plate according to a fifth embodiment in which a light diffusing hole has a reflecting function.

FIG. 9 is a partial plan view showing a structure of a light guide plate according to a sixth embodiment in which a reflection member is fitted into a light diffusion hole to have a reflection function.

FIG. 10 is a partial plan view showing another mode of the structure of the light guide plate according to the sixth embodiment in which a reflection member is fitted into a light diffusion hole to have a reflection function.

FIG. 11 is a plan view showing a structure of a conventional light guide plate.

FIG. 12 is a partial plan view of the structure of the conventional light guide plate shown in FIG.

FIG. 13 is a graph showing light emission characteristics of an LED.

[Explanation of symbols]

 Reference Signs List 1 light source 2 light guide plate 3 light diffusion hole 3a apex angle 3b bottom 4 housing 5 reflection plate 6 diffusion plate 7 liquid crystal cell 8, 10 reflection member A, B outside irradiation area C inclined wall D side wall F oblique side G arc wall

Claims (22)

[Claims] 1. A point light source having irradiation directivity is used as a light source,
A light guide plate provided with a light diffusing hole near the light source, in order to provide an inclined wall having a reflection function to be inclined with the vicinity of the light source as an apex, and to irradiate light outside an irradiation region generated by the irradiation directivity of the light source. The structure of the light guide plate, wherein the light diffusing hole has a polygonal planar shape, and one of its vertices is directed toward the light source. 2. The light diffusing hole is characterized in that its planar shape is triangular, its apex faces the light source direction, and its base is formed at a position orthogonal to the optical axis center line of the light source. The structure of the light guide plate according to claim 1. 3. The light-diffusing hole has a quadrangular planar shape, one of its vertices facing the light source direction, and a vertex opposed to the vertex is located on the optical axis of the light source. The structure of the light guide plate according to claim 1. 4. The structure of the light guide plate according to claim 1, wherein the light diffusion holes are formed as through holes or concave holes. 5. The light diffusion hole formed by the concave hole, wherein the concave hole is formed by providing a spot facing portion from the display portion side of the light guide plate.
The structure of the light guide plate described. 6. The light guide plate structure according to claim 1, wherein an inner wall surface of the light diffusion hole has a substantially mirror surface state. 7. The light diffusion hole according to claim 1, wherein a side sandwiching a vertex facing the light source is formed in a concave arc shape, and light from the light source is reflected and collected. Structure of the light guide plate of any one of the above. 8. An inner wall surface of the light diffusing hole transmits an incident light having an incident angle smaller than the critical angle into the light diffusing hole at a critical angle uniquely determined by a refractive index of a light guide plate material. The structure of the light guide plate according to claim 6, wherein incident light exceeding the critical angle is totally reflected and irradiated outside the irradiation region. 9. When the light diffusing hole is a concave hole, by adjusting a counterbore depth with respect to the thickness of the light guide plate, the straight light from the light source and the reflected light from the light diffusing hole can be adjusted. The structure of the light guide plate according to claim 4, wherein the ratio can be adjusted. 10. A method according to claim 1, wherein the inclination of a side of the light diffusion hole sandwiching a vertex facing the light source is determined based on an optical optimum condition for the purpose of equalizing reflection and diffused light outside the irradiation range. The structure of the light guide plate according to claim 2, wherein an inclination of the inclined wall of the light plate is set. 11. The light diffusion hole forms a prism made of air, and the hypotenuse of the prism is determined based on optical optimum conditions for the purpose of reflecting the light outside the irradiation area and making the diffused light uniform. The structure of the light guide plate according to any one of claims 2 to 6, wherein the inclination of the inclined wall of the light guide plate is set. 12. A point light source having an irradiation directivity is used as a light source, an inclined wall having a reflection function is provided to incline with the vicinity of the light source as an apex, and light is radiated out of an irradiation area generated by the irradiation directivity of the light source. Therefore, in the structure of the light guide plate provided with a light diffusion hole near the light source, the light diffusion hole has an arcuate shape having a single arc portion in plan view, the arc portion faces the light source direction, A light guide plate structure having a reflective portion in an arc portion. 13. The structure of the light guide plate according to claim 12, wherein the light diffusion holes are formed as through holes or concave holes. 14. The structure of the light guide plate according to claim 12, wherein an inner wall surface of the light diffusing hole has a substantially mirror surface state. 15. The light guide plate according to claim 1, wherein a reflecting portion is formed by applying white or reflective coating to an inner wall surface of the light diffusion hole on the light source side. Structure. 16. The light guide plate according to claim 1, wherein a reflection member is formed in the light diffusion hole by inserting a reflection member adapted to the inner wall surface on the light source side. Construction. 17. The light guide plate structure according to claim 16, wherein the reflection member is made of a film, a metal band or a sheet having light reflectivity. 18. The structure of the light guide plate according to claim 1, wherein the light diffusion hole is filled with a filler having light reflectivity to form a reflection portion. 19. The reflection part according to claim 1, wherein a reflection member having a concave shape with respect to the inner wall surface on the light source side is inserted into the light diffusion hole to form a reflection part. Light guide plate structure. 20. When the light diffusion hole is a through hole, the reflection portion is formed on a part of the inner wall surface on the light source side in the depth direction, and the transmission portion is formed on another portion of the inner wall surface. 20. The structure of the light guide plate according to claim 15, wherein 21. The apparatus according to claim 21, wherein the ratio of the straight light from the light source to the light reflected by the light diffusion hole can be adjusted by adjusting the ratio of the reflection part and the transmission part of the light diffusion hole. The structure of the light guide plate according to claim 20. 22. An electronic apparatus, comprising: a display unit having the structure of the light guide plate according to claim 1.