JP4599215B2 - Light guide plate device and display device - Google Patents

Description

  The present invention relates to a light guide plate device used in a device utilizing surface light emission such as a liquid crystal display device and a lighting device, and a display device using the light guide plate device.

Compared with displays such as cathode ray tubes, thin displays such as liquid crystal display devices have the advantage that they can be made thinner and lighter. A device for emitting light having a luminance surface distribution so as to pass through the liquid crystal portion of the liquid crystal display device is required, and a backlight device portion is usually disposed on the back side of the liquid crystal portion of the liquid crystal display device. The

In general, the backlight unit includes a light source, but in order to make the display thin, an LED (light emitting diode), a cold cathode tube, or the like is arranged on the side. Light emitted from such LEDs and cold cathode tubes is converted into a surface light source by using a transparent substrate that guides light introduced from a side surface called a light guide plate to the main surface side, and the liquid crystal portion of the liquid crystal display device is used. Go through. Usually, a reflector or the like is disposed on the back side of the light guide plate, which is the opposite side of the liquid crystal unit, and the light emission surface of the light guide plate is spaced from the liquid crystal unit so as to provide a surface-distributed light source that maintains uniformity. In addition, a diffusion sheet, a prism sheet, and the like are disposed.

A light guide plate having a configuration in which a reflection dot for scattering light is provided on a light reflection surface on the back side of the light guide plate is known (see, for example, Patent Document 1), and such a light guide plate is used. Thus, it is possible to increase the reflectance at the light reflecting surface and to reduce the non-uniformity in the surface. As another example of the light guide plate, there is also known an example in which a plurality of square pyramid-shaped reflection regions called brightness enhancement recesses are formed on the reflection surface (see, for example, Patent Document 2).

JP 2003-215351 A JP 2003-43265 A

However, with the technology of providing a light guide plate or providing a plurality of reflective dots and brightness enhancement recesses on a part of the light guide plate, it is possible to improve brightness in a narrow range around the reflection dots and brightness enhancement recesses. However, there is a problem that the amount of light emitted from the light exit surface is insufficient as a whole because it is not sufficient to create in-plane brightness uniformity in a wider area.

In addition, the reflective dots and the brightness enhancement recesses are formed by processing a transparent resin substrate such as an acrylic resin plate, but in order to form dots and recesses with higher definition on the reflective surface side of the light guide plate, Manufacturing limitations have occurred.

Therefore, in view of the above technical problems, the present invention provides a light guide plate device that realizes surface light emission capable of achieving uniform brightness over a wide area and that can easily realize high-definition processing in manufacturing. The purpose is to do.

The light guide plate device of the present invention is a light guide plate device in which a plurality of light guide plates capable of extracting light incident from at least one side surface as light of a surface light source distribution from a light exit surface facing the reflection surface are provided . The first light guide plate in which a plurality of recesses are formed only in the peripheral part of the reflection surface, and the recesses smaller than the recesses in the first light guide plate only in the center part of the reflection surface than the recesses of the first light guide plate A plurality of densely formed second light guide plates, the first light guide plate and the second light guide plate are adjacent to each other, and the peripheral portion of the first light guide plate and the second light guide plate The light guide plate is arranged so as not to overlap the central portion .

According to the light guide plate device of the present invention, surface light emission is not performed by a single light guide plate, but light can be extracted from the light exit surface by a combination of the first and second light guide plates. It is possible to efficiently reflect the light incident from. By changing the density of the recesses of the two light guide plates, for example, the first light guide plate having a low density has a role of increasing the transmission component in the surface direction, and the surface direction is determined by the second light guide plate having a high density. It is possible to have a role of increasing the reflection component in the light. By using these simultaneously, light can be reflected efficiently.

By using multiple light guide plates, it is possible to efficiently reflect the light incident from the side surface, and the brightness of the light emitted from the light guide plate device can be increased, which is used for liquid crystal display devices. In this case, a bright display screen can be created. Further, by arranging the two light guide plates so as to overlap each other, when viewed from the light exit surface side, the concave portion of the first light guide plate and the concave portion of the second light guide plate exist in the same region. Thus, there is an advantage that the density of the recesses is increased. This is because when the processing for disposing the recesses in a required region is considered, the space between the recesses can be widened, and the light guide plate can be processed with a margin.

A preferred embodiment of the light guide plate device of the present invention will be described with reference to the drawings. FIG. 1 shows an example of the light guide plate device of the present embodiment. The light guide plate device of the present embodiment is a light guide plate device capable of extracting light that is a surface light source distribution from the light exit surface, and the first light guide plate 11 having a plurality of recesses 17 formed on the light reflecting surface 11b. And the second light guide plate 12 in which a plurality of recesses 16 are formed more densely than the recesses 17 of the first light guide plate on the light reflecting surface 12b, and these first and second light guide plates 11, 12 are provided. Are emitted from the light exit surface 11f.

The light guide plate device of the present embodiment has a structure that is used as a backlight device of a liquid crystal display device that includes a liquid crystal unit 15, and includes reflective recesses 17 that are arranged at a relatively coarse density as reflecting surfaces 11b. And the second light guide plate 12 having the reflection concave portions 16 arranged at a relatively dense density on the reflection surface 12b. Each light guide plate 11 and 12 is a transparent rectangular resin plate. For example, polyester resin, amorphous polyester resin, acrylic resin such as polymethyl methacrylate (PMMA), polycarbonate resin, polystyrene resin (PS), styrene Acrylonitrile resin (SAN), urethane resin, cycloolefin resin, alicyclic polyolefin resin, cyclic polyolefin resin, alicyclic acrylic resin, amorphous fluorine resin, epoxy resin, polyimide resin, polyamide resin, vinyl ester resin, etc. Various kinds of transparent polymer materials can be used, and a combination of these modified materials and a plurality of resin materials may be used.

The bottom surfaces of the light guide plates 11 and 12 are reflection surfaces 11b and 12b, and concave portions are formed in a substantially quadrangular pyramid shape from the surfaces of the reflection surfaces 11b and 12b. The shape of the recess may be another pyramid shape such as a cone, a triangular pyramid, or a hexagonal pyramid. On the back surface side of the light guide plate 12, a reflection plate 13 whose surface is a light reflection surface is formed, and light leaking from the light guide plates 11 and 12 to the reflection surface side is reflected by the surface of the reflection plate 13. Head to the exit side.

The LED array 14 is disposed so as to face the side surfaces 11i and 12i of the respective light guide plates 11 and 12. The LED array 14 is a device in which a plurality of white light emitting diodes are arranged, and is connected to a power supply line (not shown) to emit light to the side surfaces 11i and 12i of the light guide plates 11 and 12.

The liquid crystal unit 15 is a device that is supplied with a required electrical signal and drives a liquid crystal cell for each pixel, and is a device that selectively transmits light from the light guide plate device of the present embodiment and displays an image or monochromatic light. is there. A diffuser plate, a prism sheet, a diffuser sheet, or the like can be arranged between the liquid crystal unit 15 and the first light guide plate 11, but when uniform light is obtained with a sufficient amount of light, these An optical member may not be provided.

The light emitted from the LED array 14 is incident on the side surfaces 11i and 12i of the respective light guide plates 11 and 12, and is mainly transmitted through the second light guide plate 12 having the concave portions 16 arranged in a relatively dense density on the reflection surface 12b. In addition, the light that travels in the horizontal direction inside the first light guide plate 11 is also reflected by the concave portion 17 of the first light guide plate 11, and the reflection efficiency is high. That is, since the concave portions 17 of the first light guide plate 11 positioned on the upper side are arranged with a relatively coarse density, the light having a surface distribution from the second light guide plate 12 incident from the bottom surface side thereof is The light is transmitted through the first light guide plate 11 between the concave portions 17 arranged at a rough density, and is added to the light reflected by the concave portion 17 of the first light guide plate 11 to be emitted.

When the light guide plate device is configured by the combination of the two light guide plates 11 and 12, the light guide plates 11 and 12 can be independently created and combined, and manufactured relatively easily. In particular, since the recesses can be arranged in the stacking direction, the reflectance per unit area can be sufficiently increased.

As a method for forming the recesses, the first light guide plate 11 and the second light guide plate can be used in common, and hot press processing generally used widely in plastic processing can be used. This hot pressing can be performed by a heat processing plate or roll having protrusions corresponding to the recesses. By using a plate or roll for heat processing, the structure of the processing apparatus becomes relatively simple and suitable for mass production. Further, as another method for processing the concave portion of the light guide plate, high frequency processing or ultrasonic processing can be used.

The light reflecting surface of each light guide plate may be subjected to light scattering processing together with the concave portion. For example, the surrounding light reflecting surface provided with the concave portion may be finely textured or matted. . Further, the peripheral portion of the concave portion of each light guide plate can be configured to have a peripheral ridge formed so as to protrude from the reflective surface in the back direction opposite to the concave portion. By providing the part, it is possible to reflect the light emitted from the reflecting surface at a minute angle toward the liquid crystal part 15 side.

Next, an example of a combination of the second light guide plate 21 and the first light guide plate 22 will be described with reference to FIG. FIG. 2 is a top view of the second light guide plate 21 and the first light guide plate 22, and quadrangular pyramid-shaped concave portions 23 and 24 are formed on the bottom surface portion that can be seen through. The second light guide plate 21 has small size recesses 23 arranged in a matrix, and the first light guide plate 22 has recesses 24 larger in size than the recesses 23 of the second light guide plate 21 in a matrix. It is formed. Further, the first light guide plate 22 is overlapped on the second light guide plate 21, and the interval between the recesses 24 is set relatively wide in the first light guide plate 22. The light reflected from the recess 23 of the second light guide plate 21 is configured to pass through the gap between the two.

By using the second light guide plate 21 and the first light guide plate 22 having such a configuration, not only the first light guide plate 22 but also the second light guide plate 21 contributes to the emission of light having a surface distribution. Thus, the light reflection efficiency of the light guide plate device can be increased.

FIG. 3 shows different combinations of the second light guide plate 31 and the first light guide plate 32. The second light guide plate 31 has quadrangular pyramid-shaped concave portions 33r and 33d having a relatively small size, and a plurality of concave portions 33d that are densely arranged are formed on the center side, and relatively relatively on the peripheral side. A plurality of recesses 33r that are roughly arranged are formed. The second light guide plate 31 has relatively large sized quadrangular pyramid-shaped recesses 34r and 34d, and similarly to the first light guide plate 31, the recesses are densely arranged on the center side. A plurality of 34d are formed, and a plurality of recesses 34r that are disposed relatively coarsely on the peripheral side are formed.

Since the central portion of the light guide plate is far from the light source such as the LED array, it tends to be darker than the peripheral portion. By using the light guide plate device having such a configuration, a concave portion is formed near the center of the light guide plate. Since 33d and 34d exist densely, the light reflection efficiency at the central portion can be increased, and it is also possible to uniformly irradiate light having a surface distribution as a whole.

FIG. 4 is an enlarged sectional view showing an example of the recess. A plurality of recesses 42 are formed on the bottom surface of the acrylic resin plate 40. Each recess 42 is a hole for reflecting light incident from the end face of the acrylic resin plate 40 to the surface side of the acrylic resin plate 40. In the present embodiment, each recess 42 is a hole having a substantially square pyramid shape. The A peripheral ridge 41 formed so as to protrude from the back surface of the acrylic resin plate 40 is provided in the periphery of each recess 42.

The peripheral protrusion 41 is a portion that is raised when a pyramid-shaped protrusion formed on the surface of the heat roll or the heat plate is pressed against the back surface of the acrylic resin plate 40 when the recess 42 is formed. There is a portion that is once melted by heat and cooled at the time of pressurization and solidified at the periphery of each recess 42. The peripheral protrusion 41 diffuses the light traveling in the in-plane direction on the back surface of the acrylic resin plate 40, improving the light extraction efficiency around the recess 42. Since each concave portion 42 has a required inclined surface, light incident from the end surface of the acrylic resin plate 40 is efficiently reflected to the surface side of the acrylic resin plate 40, but incident light from the end surface At the same time, the light traveling in the in-plane direction on the back surface of the acrylic resin plate 40 due to irregular reflection in the concave portion 42 is also effectively reflected by the peripheral protrusion 41 to the surface side of the acrylic resin plate 40.

FIG. 5 shows an example in which a light guide plate device is constituted by three light guide plates. As shown in FIG. 5, three rectangular transparent resin plates 51, 52, and 53 are stacked. The transparent resin plates 51, 52, 53 are each formed with a plurality of quadrangular pyramid-shaped recesses 54, 55, 56 on the back side, which is the reflective surface side. By using the three resin plates 51 to 53, light that is diffused in the stacking direction can be effectively reflected to the surface side, and the concave portions are formed at a higher density than when two light guide plates are used. And the luminance of light supplied to the liquid crystal portion can be improved.

FIG. 6 shows an example of a light guide plate device using two light guide plates. The first light guide plate 62 is laminated on the display side of the second light guide plate 61. The second light guide plate 61 is formed with a plurality of concave portions 63 so as to be concentrated near the center, and the first light guide plate 62 is not formed with a concave portion near the center, and a plurality of concave portions 63 are concentrated only at the peripheral portion. A recess 64 is formed. Even in such a combination, it is possible to concentrate lightly on the central part and form small-sized concave parts densely, and to form large-sized concave parts roughly on the peripheral part to emit light with a uniform surface distribution as a whole. It is.

In the case where such two light guide plates 61 and 62 are used, the depth and size of the recesses 63 and 64 in each light guide plate are substantially the same for each light guide plate. In the case of processing, since the depth of each recess is uniform, the processing can be performed relatively easily.

It is a disassembled perspective view which shows an example of the light-guide plate apparatus concerning one Embodiment of this invention. It is a top view which shows an example of the 1st, 2nd light guide plate used for the light guide plate apparatus concerning other embodiment of this invention. It is a top view which shows an example of the 1st, 2nd light guide plate used for the light guide plate apparatus concerning further another embodiment of this invention. It is a principal part expanded sectional view of an example of the light-guide plate of this invention. It is a figure which shows an example of the light-guide plate apparatus concerning further another embodiment of this invention, Comprising: (A) is an exploded view, (B) is the side view which shows the place laminated | stacked. It is a top view which shows an example of the 1st, 2nd light guide plate used for the light guide plate apparatus concerning further another embodiment of this invention.

Explanation of symbols

11, 22, 32, 62 First light guide plate 12, 21, 31, 61 Second light guide plate 13 Reflecting plate 14 LED array 16, 17, 23, 24, 33r, 33d, 34r, 34d, 63, 64 Recess

Claims (5)

In the light guide plate device provided with a plurality of light guide plates capable of extracting light incident from at least one of the side surfaces as light of a surface light source distribution from a light exit surface facing the reflection surface ,
A first light guide plate in which a plurality of recesses are formed only in the periphery of the reflecting surface ;
A second light guide plate in which a plurality of recesses smaller than the recesses of the first light guide plate are formed more densely than the recesses of the first light guide plate only at the center of the reflective surface ;
The first light guide plate and the second light guide plate are adjacent to each other;
The light guide plate device is arranged so that the peripheral portion of the first light guide plate and the central portion of the second light guide plate do not overlap . 2. The light guide plate device according to claim 1 , wherein a light scattering process is applied to the reflection surface of the first light guide plate and the reflection surface of the second light guide plate together with the concave portion. The protrusion part which protruded from the said reflective surface is formed in the surroundings of the said recessed part in the reflective surface of the said 1st light-guide plate, and the reflective surface of the said 2nd light-guide plate . Light guide plate device. The light guide plate device according to claim 1, wherein the first light guide plate surface and the second light guide plate are formed of a transparent resin material that can be processed by a thermal processing device or a high-frequency processing device. . A light guide plate device according to claim 1 ;
A light source that is provided adjacent to at least one of the side surfaces of the light guide plate device, and that makes light incident on the side surface of the first light guide plate and the side surface of the second light guide plate;
A display unit provided adjacent to an upper surface of the light guide plate device and performing a required display using light emitted from a light emission surface of the first light guide plate and a light emission surface of the second light guide plate ; A display device comprising: