JP2002358811A - Light transmission device, backlight unit, and liquid crystal displaying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light transmission device which can heighten the brightness of a light guide plane, and to provide a backlight unit and a liquid crystal displaying device equipped with such a light transmission device. SOLUTION: The light transmission device 2 of the backlight unit 1 comprises a light guide plate 22 with a plurality of convex parts 25, and a light transmission plate 23 comprising concave parts 28 corresponding to respective convex parts 25, and a plurality of projected parts 29 totally reflecting the light guided from the concave parts 28. Concave parts 28 of the light transmission plate 23 are fitted to the convex parts 25 of the light guide plate 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light transmitting device for guiding introduced light from a specific direction, a backlight unit, and a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, portable telephones and car navigation systems have been reduced in weight and thickness. Along with this, reduction in weight and thickness of a backlight unit used as a light source of a liquid crystal panel has become an important issue.
As one of means for solving this problem, a sidelight type backlight unit in which a light source is disposed on a side surface of a light guide plate has attracted attention.

[0003] The above-described sidelight type backlight unit emits light from a light source, introduces light from a side surface of a light guide plate, and emits light from an exit surface that is perpendicular to the side surface. I have.

[0004]

However, in such a sidelight type backlight unit, since light is totally reflected in the light guide, it is difficult for light to be emitted from the exit surface. For this reason, white dot printing is provided on the back surface of the light guide plate, and V-groove-shaped irregularities are also provided on the back surface of the light guide plate. To cope with such a problem, at present, a lens sheet is provided on the light guide plate to improve the brightness of the light guide surface of the light guide plate.

[0005] However, there is a problem that even higher luminance is required for some applications, and even when a lens sheet is provided, it is difficult to increase the luminance to a value satisfying this requirement.

The present invention has been made to solve the above-mentioned conventional problems. That is, an object of the present invention is to provide a light transmission device that can increase the luminance of the output surface. Further, it is another object of the present invention to provide a backlight unit including such a light transmission device and a liquid crystal display device.

[0007]

According to a first aspect of the present invention, there is provided a light transmitting device, comprising: an introduction surface for introducing light therein; a plurality of uneven portions for guiding light introduced from the introduction surface; A light guide plate provided with a flat portion that totally reflects light introduced from the introduction surface; and a convex and concave portion fitted to each of the concave and convex portions for introducing light derived from the concave and convex portions. A plurality of projections that totally reflect the light introduced from the part, an air layer formed when the projections and depressions of the light guide plate are fitted into the projections and depressions of the projections, and light totally reflected by the projections to the outside. And a light-transmitting plate having a leading surface for leading out.

[0008] In the invention described in claim 1 and each of the inventions described below, the definitions of terms and their technical meanings are as follows unless otherwise limited.

(Light Guide Plate) The light guide plate has an introduction surface, a flat portion, and a plurality of uneven portions. The light guide plate is
It is formed of a light-transmitting material that transmits light in a substantially plate shape. The light transmitting material forming the light guide plate may be any material as long as it can transmit light. Examples of such a light-transmitting material include light-transmitting synthetic resins such as acrylic resin, polycarbonate, and polystyrene, and glass. In addition, examples of the overall shape of the light guide plate include, but are not particularly limited to, a substantially square plate and a substantially circular plate.

The introduction surface may be formed on the side surface, the back surface of the light guide plate, or the inner surface existing inside the light guide plate.

[0011] The uneven portion is formed on one side of the light guide plate. In addition, the concave and convex portions are constituted by at least one of a concave portion formed in a concave shape and a convex portion formed in a convex shape. Further, each concave / convex portion may have any shape as long as light can be led out. Examples of the shape of each of the concavo-convex portions include, for example, a substantially prism, a substantially pyramid, a substantially cylinder, a substantially cone, a cut sphere obtained by cutting a substantially sphere in a plane, or a shape obtained by cutting a column in a plane, that is, a so-called substantially kamaboko shape. Can be Here, when the shape of the concave and convex portions is a substantially prismatic or substantially semicylindrical shape, the axis of the substantially rectangular prism or substantially semicylindrical shape is substantially parallel to the surface provided with the concave and convex portions. Further, when the shape of the concave and convex portions is a substantially cylindrical shape, the axis of the substantially cylindrical shape is substantially perpendicular to the surface provided with the concave and convex portions. Furthermore, the truncated pyramids and the truncated cones include truncated pyramids and truncated cones whose tops are cut off. In addition, the light guide plate provided with such an uneven part can be easily formed with a metal mold, for example.
Further, light is totally reflected on the surface, the back surface, and the side surface of the light guide plate provided with the uneven portion without the uneven portion.

(Transparent plate) The translucent plate has a projection, an air layer, and a lead-out surface. The light-transmitting plate is formed of a plate formed of a light-transmitting material that transmits light. The light-transmitting material forming the light-transmitting plate may be any material as long as it can transmit light. As such a translucent material, for example, acrylic resin, polycarbonate, or translucent synthetic resin such as polystyrene,
Alternatively, glass or the like can be used. Here, as the light transmitting material forming the light transmitting plate, it is preferable to use a material having a thermal expansion coefficient equivalent to that of the light transmitting material forming the light guiding plate. The translucent plate and the light guide plate undergo thermal expansion during use or storage, but if the thermal expansion coefficients of the translucent plate and the light guide plate are equivalent, the translucent plate and the light transmissive plate may be used even when the thermal expansion occurs. This is because the fitting with the light guide plate is reliably maintained. Further, from such a viewpoint, it is most preferable that the light transmitting material forming the light transmitting plate is the same as the light transmitting material forming the light guiding plate.

The projection is formed on one surface of the light transmitting plate. Further, the protruding portion has a concave and convex portion fitted to each of the concave and convex portions for introducing the light derived from the concave and convex portion. The shape of the protrusion may be any shape as long as the protrusion has a concave and convex portion and can totally reflect light introduced into the concave and convex portion. As the shape of such a projection, for example, a substantially prismatic,
A substantially pyramid, a substantially cone, a substantially cut sphere, or a substantially semicylindrical shape may be used. Here, when the shape of the protruding portion is a substantially prismatic or substantially semicylindrical shape, the axis of the substantially prismatic or substantially semicylindrical shape is substantially parallel to the surface provided with the protruding portion. Among these shapes, a substantially prism, a substantially pyramid, a substantially cut sphere, or a substantially semicircular shape is preferable. These shapes are preferred because a large amount of light can be totally reflected. That is, when the protrusions are formed in these shapes, the roots of the protrusions are formed in a rectangular shape, so that the distance between the protrusions can be reduced. As a result, the surface area of the entire protrusion can be increased, so that much light can be totally reflected.

The convex and concave portions are composed of at least one of a convex portion formed in a convex shape and a concave portion formed in a concave shape. The projections and depressions are formed so as to correspond to the projections and depressions. Here, the protrusions and recesses may be formed so that the height is higher or lower than the height of the protrusions. For example, when the height of the projection is about 1.0 mm, the height of the projections and depressions can be about 0.5 mm. The convex and concave portions are fitted with the concave and convex portions. Here, it is assumed that no adhesive is interposed between the concave and convex portions and the concave and convex portions. The light-transmitting plate provided with such convex and concave portions can be easily formed by, for example, a mold.

The air layer is formed when the projections and depressions of the light guide plate are fitted into the projections and depressions of the projections. By providing such an air layer, total reflection can be performed at the flat portion and the protrusion. Note that, instead of the air layer, a low-refractive-index substance having a lower refractive index than the light-transmitting material forming the light guide plate and the light-transmitting plate can also be used. Low refractive index materials
Any material may be used as long as it has a lower refractive index than the translucent material forming the light guide plate and the translucent plate.

The deriving surface may be a flat surface or a curved surface as long as the light totally reflected by the projection can be derived. When the derivation surface is formed as a curved surface, a convex curved surface is preferable. By forming the derived surface as a convex curved surface,
The light can be led out in the normal direction of the lead-out surface. Also,
The light transmission device of the present invention can be used by being incorporated in, for example, a backlight of a mobile phone and a car navigation system.

According to the first aspect of the present invention, there is provided a light transmitting device, wherein an introduction surface for introducing light into the inside, a plurality of uneven portions for guiding the light introduced from the introduction surface, and an introduction surface formed between the uneven portions. A light guide plate having a flat portion that totally reflects light introduced from the surface; and a light guide having projections and depressions fitted into each of the projections and depressions for introducing light derived from the projections and depressions. A plurality of projections that totally reflect the light, an air layer formed when the projections and depressions of the light guide plate are fitted into the projections and depressions of the projections, and an output surface that guides the light totally reflected by the projections to the outside. And a light-transmitting plate provided with the light-transmitting plate; Further, since the light guide plate and the light transmitting plate are separated, it can be easily manufactured.

According to a second aspect of the present invention, in the light transmission device, at least one surface forming the concave and convex portions forms an angle of 30 ° to 60 ° with respect to the surface having the concave and convex portions. I do. The reason why the angle is defined is that, when the angle is less than 30 °, the light totally reflected on at least one surface constituting the uneven portion becomes too large, and the luminance of the derived surface can be effectively improved. Because it becomes difficult. On the other hand, if the angle exceeds 60 °, the height of the uneven portion becomes too high, and it is difficult to reduce the thickness of the light transmitting device. In the light transmission device of the invention according to claim 2,
Since at least one surface constituting the uneven portion forms an angle of 30 ° to 60 ° with respect to the surface provided with the uneven portion,
It is possible to effectively improve the brightness of the lead-out surface and to reduce the thickness of the light transmission device.

According to a third aspect of the present invention, there is provided the light transmitting device according to the first or second aspect, wherein at least one side surface of the projection is provided with respect to a surface provided with an uneven portion. At an angle of 40 ° to 70 °. The reason for defining the angle is that, when the angle is less than 40 °, the amount of light totally reflected on at least one side surface of the protrusion is too small, and the brightness of the derived surface can be effectively improved. Because it becomes difficult. On the other hand, if the angle exceeds 70 °, the height of the projections becomes too high, and it is difficult to reduce the thickness of the light transmitting device. In the light transmitting device according to the third aspect of the present invention,
Since at least one side surface forming the projection forms an angle of 40 ° to 70 ° with respect to the surface having the unevenness, the brightness of the output surface can be effectively improved and the light transmission device can be used. The thickness can be reduced.

According to a fourth aspect of the present invention, there is provided the light transmitting device according to any one of the first to third aspects, wherein the light transmitting plate is guided by pressing an edge of the light transmitting plate. It is characterized by further comprising a fixing member for fixing to the light plate. The fixing member may be any member as long as it can fix the light transmitting plate to the light guide plate. However, the adhesive is excluded. As such a fixing member, for example, a case,
Examples include a frame, and a screw member such as a screw and a nut. Although the fixing member presses the edge of the light transmitting plate, it may press the entire or a part of the edge of the light transmitting plate.
Here, comparing the case where the fixing member presses the entire edge of the light transmitting plate and the case where the fixing member presses a part thereof, the case where the entire edge is pressed is more preferable. This is because the fixing member presses the entire edge of the light-transmitting plate, so that it becomes more difficult for dust and air to enter between the concave and convex portions and the concave and convex portions. Note that if dust or air enters between the concave and convex portions and the concave and convex portions, there is a possibility that total reflection will occur on the surface of the concave and convex portion. The light transmitting device according to the fourth aspect of the present invention further includes a fixing member that presses the edge of the light transmitting plate and fixes the light transmitting plate to the light guide plate, so that the light can be reliably extracted from the uneven portion. it can.

According to a fifth aspect of the present invention, there is provided a light transmitting device, wherein the light introduced into the inside, which is a boundary surface between the introduction surface through which light is introduced and at least one or more holes formed inside, is totally removed. The light guide plate includes: a total reflection surface that reflects light; a guide surface that guides light totally reflected by the total reflection surface to the outside; and an air layer existing in the hole.

The light guide plate has an entrance surface, a total reflection surface, an exit surface, and an air layer. The light guide plate of the present invention is integrally formed of a light transmitting material. The light transmitting material forming the light guide plate is the same as the light transmitting material forming the light guide plate according to the light transmission device of claim 1 described above. The position of the introduction surface or the shape of the derivation surface is the same as the introduction surface or the derivation surface according to the first aspect of the light transmitting device.

The total reflection surface is a boundary surface of at least one or more holes formed inside the light guide. The shape of the hole may be any shape as long as the light introduced into the light guide can be totally reflected. Examples of such a shape of the hole include a space between the projections when a flat plate and a flat plate having a plurality of projections formed on one surface are fitted such that the projections are on the inside. Examples of the protruding portion include a substantially prism, a substantially pyramid, a substantially cone, a substantially cut sphere, and a substantially semicylindrical shape. Also, such holes are
For example, it can be formed by drilling a light guide plate with a drill or a high-pressure gas. Alternatively, it can also be formed by forming a shape corresponding to the hole portion in advance with a substance soluble in an acid and then dissolving the substance after molding the light guide plate.

The air layer is present in the hole, and by providing such an air layer, light can be totally reflected by the total reflection surface. Instead of the air layer, a low-refractive-index substance having a lower refractive index than the light-transmitting material forming the light guide plate can be used. The low-refractive-index substance may be any substance as long as it has a lower refractive index than the translucent material constituting the light guide plate. As such a low refractive index material, for example, air can be mentioned.

According to a fifth aspect of the present invention, there is provided a light transmitting device, wherein the light introduced inside, which is a boundary surface between an introduction surface for introducing light inside and at least one or more holes formed inside, is totally removed. Includes a light guide plate including a total reflection surface that reflects, a light guide surface that guides light totally reflected by the total reflection surface to the outside, and an air layer that is present in the hole, so that the brightness of the light guide surface is increased. be able to.

According to a sixth aspect of the present invention, there is provided a light transmitting device according to any one of the first to fifth aspects, wherein the lead-out surface is formed in a convex curved shape. I do. In the light transmission device according to the sixth aspect of the present invention, since the outgoing surface is formed in a convex curved shape, light can be guided in the normal direction of the outgoing surface. As a result, a higher luminance value can be obtained.

According to a seventh aspect of the present invention, there is provided a backlight unit according to any one of the first to sixth aspects, and a light source which emits light and is disposed near an introduction surface of the light transmitting apparatus. And a reflector disposed on the back of the light source to reflect the light emitted from the light source and guide the reflected light to the introduction surface of the light transmitting device.

The light source may be any one that emits light. Such light sources include, for example, fluorescent lamps such as hot-cathode fluorescent lamps and cold-cathode fluorescent lamps, electric bulbs, light-emitting diodes, or high-intensity discharge lamps. The light source is preferably a linear light source rather than a point light source. This is because the light emitted from the light emitting surface of the linear light source is more uniform than that of the point light source. Further, a plurality of light sources can be provided.

If the reflector can reflect the light emitted from the light source and guide the reflected light to the introduction surface of the light transmitting device,
Anything may be used. Examples of such a reflector include a metal such as noble aluminum, or a synthetic resin such as polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyester, polyvinyl chloride, and polystyrene on which silver or aluminum is deposited.

Further, it is preferable that a reflection tape is adhered to one of the side surfaces of the light guide or the light transmitting plate. This is because the reflection of the light from the side surface can be prevented by attaching the reflective tape to the end surface. As such a reflective tape, a synthetic resin such as polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyester, polyvinyl chloride, or polystyrene, on which silver or aluminum is deposited, can be used.

According to a seventh aspect of the present invention, since the backlight unit includes the light transmitting device according to any one of the first to sixth aspects, it is possible to increase the brightness of the outgoing surface.

[0032] A liquid crystal display device according to an eighth aspect of the present invention is a backlight unit according to the seventh aspect, and a liquid crystal panel disposed on the lead-out surface side of the backlight unit;
It is characterized by having. In the liquid crystal display device according to the eighth aspect of the present invention, since the backlight unit according to the seventh aspect is provided, it is possible to improve the luminance of the surface from which the backlight is derived, and to provide a brighter liquid crystal display device.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a backlight unit according to a first embodiment of the present invention will be described. Here, the present embodiment will be described on the assumption that the backlight unit is used in the air.
1 and 2 are a vertical sectional view and a plan view schematically showing a backlight unit according to the present embodiment, and FIG. 3 is a plan view schematically showing a light guide plate according to the present embodiment. . FIG. 4 is a vertical cross-sectional view schematically showing the light transmitting plate according to the present embodiment, and FIG. 5 schematically shows the state of light when light is introduced into the light guide plate according to the present embodiment. FIG.

As shown in FIGS. 1 to 4, the backlight unit 1 of the present embodiment is a backlight unit of a sidelight system, and mainly includes a light transmitting device 2 and a light transmitting device 2 which will be described later. The fluorescent lamp 3 includes a fluorescent lamp 3 as a light source that emits light to be introduced into the light guide plate 22, and a reflector 4 that reflects light emitted from the fluorescent lamp 3 and guides reflected light to the light transmission device 2.

The light transmitting device 2 has a case 21 as a fixing member having an opening formed on the upper surface. Case 21
Inside, a light guide plate 22 and a light transmitting plate 23 are accommodated.
By housing the light guide plate 22 and the light transmission plate 23 in the case 21, the light transmission plate 23 can be fixed to the light guide plate 22. That is, the lower surface of the case 21 presses the lower surface of the light guide plate 22, and the edge of the upper surface of the case 21 is
By pressing the upper surface of the light guide plate 22
Fixed to By fixing the translucent plate 23 to the light guide plate 22 in such a case 21, light can be surely led out from the convex portion 25 described later. The case 21 also accommodates the fluorescent lamp 3 and the reflector 4.

A lighting circuit (not shown) for lighting the fluorescent lamp 3 is electrically connected to the fluorescent lamp 3 so as to light the fluorescent lamp 3. Reflector 4
Are formed of noble aluminum and are arranged on the back side of the fluorescent lamp 3. By disposing the reflector 4, the light emitted from the fluorescent lamp 3 can be efficiently guided to the light guide plate 22.

On a side surface of the light guide plate 22 other than an introduction surface 24, which will be described later, and on all side surfaces of the light transmission plate 23, a reflective tape 5 made of, for example, polyethylene terephthalate on which silver is deposited.
Is adhered to prevent light introduced into the light guide plate 22 and the light transmission plate 23 from being transmitted from the side surface.

Next, the light guide plate 22 and the light transmitting plate 23 will be described in detail. The light guide plate 22 is made of an acrylic resin and is formed in a substantially rectangular shape. One side surface of the light guide plate 22 is close to the fluorescent lamp 3,
Light is introduced into the light guide plate 22 from this side. Here, in the present embodiment, the side surface of the light guide plate 23 close to the fluorescent lamp 3 is referred to as an introduction surface 24.

On one surface of the light guide plate 22, a plurality of projections 25 are formed at predetermined intervals as substantially triangular prism-shaped projections and depressions in the longitudinal direction. By forming the projection 25, the introduction surface 2
The light introduced from 4 is guided out of the longitudinal side surface 26 of the convex portion 25 without being totally reflected. On the other hand, light is totally reflected on all surfaces other than the side surface 26, and is hardly emitted. The angle α between the flat surface 27 and the side surface 26 as a flat portion existing between the convex portions 25 is 30 ° to 30 °.
It is formed to be 60 °. By forming the protrusions 25 at such an angle, it is possible to effectively improve the brightness of the lead-out surface 31 described later and to reduce the thickness of the backlight unit.

The light-transmitting plate 23 is made of an acrylic resin and is formed so as to be substantially the same in size as the light guide plate 22. On one surface of the light transmitting plate 23, a plurality of substantially truncated triangular prism-shaped protrusions 29 each having a concave portion 28 as a convex and concave portion at the end are formed in the longitudinal direction. By forming the protrusion 29 in a substantially truncated triangular prism shape, much light can be totally reflected. Further, the protrusion 29 is formed on the flat surface 2.
7 and the longitudinal sides 30 are each 40
° to 70 °. By forming the protrusions 29 at such an angle, a large amount of light can be totally reflected.

The recess 28 of the projection 29 is formed in a shape corresponding to the projection 25 of the light guide plate 22. That is, the recess 2
8 is formed in a substantially triangular prism shape. Further, these concave portions 28 are fitted to the convex portions 25. By this fitting, the light led out from the side surface 26 of the convex portion 25 is introduced into the concave portion 28. Further, this fitting forms a space sandwiched between the side surface 30 and the flat surface 27 of the projection 29. Here, in the present embodiment, it is assumed that the device is used in the air, so that the air exists in this space during use.
Due to the presence of air in this space, light is
And at the side surface 30.

The surface of the light-transmitting plate 23 facing the surface provided with the projections 29 is formed in a convex curved shape. Here, in the present embodiment, this surface is referred to as an outgoing surface 31. By forming the derivation surface 31 in a convex curved shape, the derivation surface 31 is formed.
Can be derived in the direction of the normal line, and a higher luminance value can be obtained.

Since the backlight unit according to the present embodiment includes the light transmission device 2, the brightness of the lead-out surface 31 can be increased. That is, the backlight unit 1
When light is emitted from the fluorescent lamp 3, the light is
Of the light guide plate 22, and travels through the light guide plate 22. Here, when light traveling inside the light guide plate 22 is incident on surfaces other than the side surfaces 26 of the light guide plate 22, most of the light is totally reflected on these surfaces as shown in FIG. Proceed inside 22. On the other hand, when light traveling inside the light guide plate 22 enters the side surface 26, most of the light exits from the side surface 26 of the convex portion 25 because the side surface 26 has an angle with respect to the flat surface 27. I do. The light emitted from the side surface 26 of the projection 25 enters the recess 28 of the light transmitting plate 23 fitted with the projection 25 and travels inside the projection 29. Here, the light traveling inside the protrusion 29 is reflected by the protrusion 29.
Most of the light is totally reflected by the side surface 30 of the protrusion 29, and the traveling direction of the light changes. Since the light whose traveling direction has been changed is incident on the exit surface 31 at an angle nearly perpendicular to the exit surface 31, even if the light enters the exit surface 31, most of the light exits from the exit surface 31 without being totally reflected. Therefore, by providing such a light transmission device 2, it can be said that a large amount of light can be extracted from the extraction surface 31 and the luminance of the extraction surface 31 can be increased.

Further, Japanese Patent Publication No. Hei 10-511803 discloses an illumination system similar to the backlight unit 1 of the present embodiment. In this illumination system, an adhesive layer for bonding the waveguide and the microprism is provided between the waveguide corresponding to the light guide plate 22 of the present embodiment and the microprism corresponding to the protrusion 29 of the present embodiment. It is interposed. When such an adhesive layer is provided, a large amount of stress is applied due to a difference in thermal expansion between the waveguide and the microprism and the adhesive during use, so that the adhesive may be peeled off during use. When the adhesive is peeled off, almost no light is incident on the microprisms existing in the part where the adhesive has been peeled off. Therefore, there is a possibility that the brightness will be reduced as it is used. On the other hand, in the backlight unit 1 of the present embodiment, since the light guide plate 22 and the light transmitting plate 23 are fitted without using an adhesive, even if used,
Light can be reliably introduced from the convex portion 25 of the light guide plate 22 to the concave portion 28 of the light transmitting plate 23, and high luminance can be maintained. Further, in the present embodiment, since the light guide plate 22 and the light transmissive plate 23 are formed of the same material, even if they are thermally expanded during use, the fitting is reliably maintained,
Light can be reliably introduced from the convex portion 25 of the light guide plate 22 to the concave portion 28 of the light transmitting plate 23. Further, in this embodiment, since the light guide plate 22 and the light transmissive plate 23 are separated, the light guide plate 22 and the light transmissive plate 23 can be easily manufactured.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described.
An embodiment will be described. In the following description, among the embodiments after this embodiment, description of contents which are the same as those of the preceding embodiment will be omitted. In the present embodiment,
The light guide plate having the hole was used. In addition,
When the light guide plate of the present embodiment is used, it is not necessary to use the light transmitting plate 23 described in the first embodiment.

FIG. 6 is a vertical sectional view schematically showing the backlight unit 1 according to this embodiment, and FIG. 7 shows a state of light when light is introduced into the light guide plate according to this embodiment. FIG. 4 is a state diagram schematically shown. As shown in FIG. 6, the backlight unit 1 of the present embodiment includes a light guide plate 41.

In the light guide plate 41, a plurality of substantially triangular prism-shaped holes 42 are formed in the longitudinal direction at predetermined intervals. Each hole 42 has three surfaces 43, 4 inside the light guide plate 41.
It is surrounded by four. Each hole 42 has a surface 43 that is an introduction surface 45.
And the angles γ between the surface 43 and the surface 44 are each set to 40 ° to 70 °. Here, in the present embodiment, since it is assumed that the device is used in air, air is present in each hole 42 during use. Due to the presence of air in each hole 42, light is totally reflected by the surfaces 43 and 44.

Further, the light guide plate 41 of the present embodiment has a lead-out surface 46 formed in a convex curved shape. Further, the light guide plate 41 is formed integrally. In order to integrally mold the light guide plate 41, an acrylic resin is poured into a mold to form a light guide plate having no hole 42, and then the light guide plate is excavated by a drill. Further, the fluorescent lamp 3 of the present embodiment is provided at a position lower than the surface 43.

Since the backlight unit according to the present embodiment includes the light transmission device 2 having the light guide plate 41, the brightness of the lead-out surface 46 can be increased. That is, when light is emitted from the fluorescent lamp 3 of the backlight unit 1, the light is introduced from the introduction surface 45 of the light guide plate 41 and travels inside the light guide plate 41. Here, as shown in FIG.
When light traveling inside the light guide plate 41 is incident on the side surface, the lower surface, and the surface 43 of the light guide plate 41, most of the light is totally reflected on these surfaces, and travels inside the light guide plate 41 again. Also, most of the light is totally reflected on the surface 44,
Since the light totally reflected by these surfaces 44 enters the exit surface 46 at an angle close to perpendicular, even if the light enters the exit surface 46, most of the light exits from the exit surface 46 without being totally reflected. I do. Therefore, by providing such a light transmission device 2, it can be said that a large amount of light can be extracted from the extraction surface 46, and the luminance of the extraction surface 46 can be increased.

In this embodiment, since the light guide plate 41 having the hole 42 and integrally formed is used,
More light can be extracted from the extraction surface 46, and the luminance of the extraction surface 46 can be further increased. That is, the first
In this embodiment, since the light guide plate 22 and the light transmitting plate 23 are separately formed, a small amount of light may be totally reflected on the side surface 26 of the projection 25. On the other hand, in the present embodiment, since no convex portion 25 is provided, such total reflection is eliminated. As a result, the light incident on the surface 44 becomes larger than the light incident on the side surface 30 of the protrusion 29, and thus the light emitted from the emission surface 46 is reduced to the emission surface 31 of the first embodiment.
From the light derived from

(Third Embodiment) Hereinafter, a third embodiment of the present invention will be described.
An embodiment will be described. In the present embodiment, the backlight unit 1 of the first embodiment is provided in a liquid crystal display device.

FIG. 8 is a schematic diagram schematically showing the liquid crystal display device according to the present embodiment. As shown in FIG. 8, a liquid crystal display device 51 according to the present embodiment includes the backlight unit 1 described in the first embodiment. A transmissive liquid crystal panel 52 is provided on the outgoing surface 31 side of the backlight unit 1 so that light derived from the outgoing surface 31 of the backlight 1 is irradiated from the back side of the liquid crystal panel 52. It has become. In the present embodiment, since the liquid crystal panel 52 is irradiated with light using the backlight unit 1, a brighter liquid crystal display device 51 can be provided.

The present invention is not limited to the description of the above embodiment, and the structure, material, arrangement of each member and the like can be appropriately changed without departing from the gist of the present invention. FIG. 9 is a vertical sectional view schematically showing a modified example of the backlight unit 1 according to the first embodiment. FIGS. 10A and 10B are a vertical sectional view and a plan view schematically showing a modified example of the light guide plate 22 according to the first embodiment, and FIGS. FIG. 11B is a vertical sectional view and a plan view schematically showing a modified example of the light transmitting plate 23 according to the first embodiment.

In the first embodiment, the backlight unit 1 includes the light guide plate 22 having the projection 25 formed thereon and the light transmitting plate 23 having the projection 29 formed with the recess 28. As shown in FIG. 9, a light guide plate 22 having a substantially triangular prism-shaped concave portion 61 formed thereon and a light transmitting plate 23 having a substantially triangular prism-shaped convex portion 62 fitted to the concave portion 61 formed on the projection 29 may be provided. It is possible.

In the first embodiment, the projection 25 of the light guide plate 22 is formed in a substantially triangular prism shape.
As shown in FIG. 10A and FIG. 10B, the projection 25 of the light guide plate 22 may be formed in a truncated quadrangular pyramid shape. In this case, as shown in FIGS. 11A and 11B, the concave portion 28 of the light transmitting plate 23 is also formed in a truncated quadrangular pyramid shape. Further, as shown in these figures, it is also possible to form the projection 29 in a substantially truncated quadrangular pyramid shape.

Further, in the second embodiment, the hole 42 is formed in a substantially triangular prism shape. However, the hole 42 is formed with the light guide plate 22 and the truncated quadrangular pyramid or truncated cone projection 29. It is also possible to form such a shape as a gap formed by fitting the light-transmitting plates 23 each having a. To form the hole 42 into such a shape, the hole 42 may be drilled using a drill as described above, or an acid may be used. When the hole 42 is formed using an acid, first, a shape corresponding to the hole 42 is formed in advance with a substance soluble in an acid.
Next, this substance is disposed in a mold, and an acrylic resin is poured into the mold. Thereafter, an acid is poured to dissolve substances that dissolve in the acid. Through such steps, the hole 42 having a shape like the above-mentioned gap can be formed.

[0057]

As described in detail above, according to the light transmitting device of the first aspect of the present invention, the brightness of the outgoing surface can be increased. According to the light transmission device of the second and third aspects of the present invention, it is possible to effectively improve the brightness of the lead-out surface and to reduce the thickness of the light transmission device. Claim 4
According to the light transmission device of the invention, light can be surely led out from the concave and convex portions. According to the light transmission device of the fifth aspect of the invention, it is possible to increase the brightness of the outgoing surface. According to the light transmitting device of the sixth aspect, a higher luminance value can be obtained. According to the backlight unit of the invention of claim 7, it is possible to provide a backlight unit having a high luminance on the lead-out surface. According to the liquid crystal display device of the eighth aspect, a brighter liquid crystal display device can be provided.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view schematically showing a backlight unit according to a first embodiment.

FIG. 2 is a plan view schematically showing a backlight unit according to the first embodiment.

FIG. 3 is a plan view schematically showing the light guide plate according to the first embodiment.

FIG. 4 is a plan view schematically showing the light transmitting plate according to the first embodiment.

FIG. 5 is a state diagram schematically showing a state of light when light is introduced into the light guide plate according to the first embodiment.

FIG. 6 is a vertical sectional view schematically showing a backlight unit according to a second embodiment.

FIG. 7 is a state diagram schematically showing a state of light when light is introduced into the light guide plate according to the second embodiment.

FIG. 8 is a schematic diagram schematically showing a liquid crystal display device according to a third embodiment.

FIG. 9 is a vertical sectional view schematically showing a modified example of the backlight unit according to the first embodiment.

FIG. 10A is a vertical sectional view schematically showing a modification of the light guide plate according to the first embodiment. FIG. 10B is a plan view schematically showing a modification of the light guide plate according to the first embodiment.

FIG. 11A is a vertical sectional view schematically showing a modified example of the light transmitting plate according to the first embodiment. FIG. 11B is a plan view schematically showing a modified example of the light transmitting plate according to the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Backlight unit 2 ... Light transmission device 22 ... Light guide plate 23 ... Light transmission plate 24 ... Introducing surface 25 ... Convex part 27 ... Flat surface 28 ... Concave part 29 ... Projection part 31 ... Outgoing surface

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) // F21Y 103: 00 F21Y 103: 00

Claims (8)

[Claims] 1. An introduction surface for introducing light into the inside, a plurality of uneven portions for deriving the light introduced from the introduction surface, and a light introduced from the introduction surface formed between the uneven portions. A light guide plate having a flat portion that totally reflects the light; a light guide plate having projections and depressions fitted into the respective projections and depressions for introducing light derived from the projections and depressions, and totally reflects light introduced from the projections and depressions. A plurality of projections, an air layer formed when the projections and depressions of the light guide plate are fitted into the projections and depressions of the projections, and a derivation surface that guides light totally reflected by the projections to the outside. A light transmitting plate comprising: a light transmitting device; 2. The light transmitting device according to claim 1, wherein at least one surface constituting the concave and convex portion forms an angle of 30 ° to 60 ° with respect to the surface provided with the concave and convex portion. A light transmitting device characterized by the above-mentioned. 3. The light transmitting device according to claim 1, wherein at least one side surface of the projection has an angle of 40 ° to 70 ° with respect to the surface having the uneven portion. A light transmitting device, comprising: 4. The light transmitting device according to claim 1, wherein an edge of the light transmitting plate is pressed,
The light transmitting device further comprises a fixing member for fixing the light transmitting plate to the light guide plate. 5. A boundary surface between an introduction surface for introducing light into the inside and at least one or more holes formed in the inside.
A total reflection surface that totally reflects the light introduced into the inside, and a derivation surface that guides light totally reflected by the total reflection surface to the outside,
A light transmission device, comprising: a light guide plate including an air layer existing in the hole. 6. The light transmitting device according to claim 1, wherein said lead-out surface is formed in a convex curved shape. 7. The light transmitting device according to claim 1, a light emitting device disposed near an introduction surface of the light transmitting device, and a light transmitting device disposed on a back surface of the light source. A reflector that reflects light emitted from the light source and guides the reflected light to the introduction surface of the light transmitting device. 8. A liquid crystal display device comprising: the backlight unit according to claim 7; and a liquid crystal panel disposed on the lead-out surface side of the backlight unit.