JP6486608B2 - Illumination device and display device - Google Patents

Description

  The present invention relates to an illuminating device, and more specifically, an illuminating device in which light leaking from a curved portion of an optical fiber propagates through the inside of the light guide plate and then is emitted to the outside of the light guide plate, and a display including the illuminating device. Relates to the device.

  A liquid crystal display (LCD) includes a liquid crystal display panel and a backlight unit disposed on the back of the liquid crystal display panel. The liquid crystal display panel transmits light from the backlight unit. An image is displayed on the front surface of the liquid crystal display panel by adjusting the rate (transmission amount).

  Conventional technologies and problems in the LCD field can be classified into the following three categories. First, there is a problem that the manufacturing cost of the backlight used in the LCD is high. Secondly, there is a problem related to a planar illumination device that can switch between a light source state and a see-through state. That is, the conventional display device has a problem that the light use efficiency in the light source mode is low and the image in the see-through mode is not clear. Third, there is a problem related to a display device that can obtain good visibility in both a bright place and a dark place. That is, the conventional transflective LCD has a problem that the light use efficiency is low both in a bright place and in a dark place. These three prior arts and their problems will be described in order below with reference to references.

First issue (manufacturing cost)
A backlight is essential for transmissive LCDs and transflective LCDs. Currently, light emitting diodes (LEDs) are the mainstream, but in order to improve the color reproducibility of LCDs, laser diodes (LDs) are used as the light source. Is reasonable. In any case, since both LED and LD are point light sources, optical technology to make a planar light source is necessary. There are two technologies, a direct type backlight and an edge lighting type backlight. In the former, a point light source is arranged on a two-dimensional plane, and a diffusion plate is arranged above the point light source to make the light output uniform. The latter is a configuration in which a point light source is disposed at the end of the transparent substrate and light is uniformly extracted from the transparent substrate using an optical means called an output coupler. In particular, the latter is advantageous for reducing the thickness of the backlight. The latter is advantageous in terms of manufacturing cost because the number of light source elements may be small. In the past few years, the edge-lit backlights have been made thinner and lower in cost by integrating the functions of the components to reduce the number of parts. Two specific examples will be described below.

  The first conventional technique is the configuration reported in Reference Document 1 shown as Non-Patent Document 1. FIG. 1 is a diagram of Reference 1 according to the prior art showing a configuration example for converting a point light source into a uniform planar light source. (A) is a perspective view which shows the structure of a light-guide plate, (b) is sectional drawing of a light-guide plate containing a fine structure.

  In the first prior art, as shown in FIG. 1A, a fine structure such as a plurality of prisms is formed on one surface of a transparent substrate. A transparent substrate including these fine structures is generally called a light guide plate. When an LED is installed on the side surface of the lower left corner of the light guide plate and light enters, the light repeats total reflection and propagates inside the light guide plate. When light enters the fine structure, as shown in FIG. 1B, the light is totally reflected on the inclined surface of the fine structure, and the light is extracted to the outside. Such a structure is called an output coupler or output coupler.

  The second prior art is the configuration reported in Reference Document 2 shown as Non-Patent Document 2. FIG. 2 is a diagram of Reference 2 according to the prior art showing a configuration example for converting a point light source into a uniform planar light source.

  In the second prior art, as shown in FIG. 2, an optically-patterned film (OPF) is bonded to a light guide that is a transparent substrate. Light propagating through the transparent substrate enters the OPF from the optical window, which is a contact portion with the OPF, and is extracted in the direction of the liquid crystal panel disposed above. That is, the OPF portion that contacts the transparent substrate functions as an output coupler.

  In both the configurations of FIGS. 1 and 2, in order to extract light uniformly from the light guide plate, it is necessary to increase the density of the output coupler as the distance from the light source increases. The shape and distribution of the light source, light guide plate, and output coupler are generally determined by computer simulation using a ray tracing technique. The input parameters of this analysis include the shape and thickness of the light guide plate as well as the shape and density of the output coupler, and the angular distribution of light emitted from the light source. Since many input parameters are required for the analysis, designing an edge-lit backlight requires a great deal of labor. Further, the shape of the backlight is often rectangular, but a design with a high degree of freedom is desired. In the conventional edge-lit backlight technology, for example, it is not always obvious to design a flat light source having a heart shape. In order to efficiently design a uniform surface light source having an arbitrary shape, some device is required.

  FIG. 3 is a diagram of Reference 2 according to the prior art showing a method of manufacturing an output coupler by an embossing process. A fine structure such as an output coupler is generally manufactured by an embossing process as shown in FIG. That is, a photocurable resin is applied to one side of a transparent substrate, and ultraviolet rays are irradiated in a state where the photocurable resin is pressed against a mold. Although the roll manufacturing method shown in FIG. 3 is excellent in productivity, initial capital investment is required. In addition, a new mold is required each time the backlight design is changed in response to a change in the display device specifications.

  As described above, the design and manufacture of the conventional backlight requires a great deal of labor and initial and continuous capital investment, so that the manufacturing cost is high, and it is difficult to manufacture the light emitting part in a free shape and at a low cost. There is a problem of being.

Second issue (see-through)
By making the display see-through, it is possible to display related information superimposed on an image of the real world. For example, applications such as displaying navigation information on the windshield of a car and displaying office entrance guidance and business hours on a portable terminal can be applied. Glasses-type terminals provide these functions using a projection display and a semi-transparent screen that are configured by combining a small liquid crystal light valve or MEMS element with the light source. Since an image projection requires a certain distance to the screen, there is a problem that it is difficult to reduce the size of the apparatus. If a direct-view thin display is made see-through, the problem of downsizing can be solved.

  As a direct-view type thin display, the potential of an organic EL display (Organic Light Emitting Diode, hereinafter referred to as OLED) has been attracting attention since the 1980s. If the two electrodes of the light-emitting element are made transparent, the OLED becomes see-through. However, half of the light is emitted to the opposite side of the observer and cannot be used for display purposes. Despite over 30 years of research and development, OLEDs still have manufacturing cost and reliability issues.

  As a direct-view thin display, LCD is a much more mature technology and has been commercially successful. An LCD without a backlight is generally called a liquid crystal panel. If the orientation of the polarizing plate and liquid crystal molecules of the liquid crystal panel is devised, the liquid crystal panel becomes see-through. When this is used as a part of a show window, it becomes possible to display information such as price and specifications on an actual product. Since the show window is provided with a light source for illuminating the product, a person can see an object in the show window. However, other applications have the problem of how to provide a light source.

  Therefore, it is desirable to make the LCD including the backlight see-through. FIG. 4 is a diagram showing an embodiment of a liquid crystal display device according to the prior art. In the liquid crystal display device of this embodiment, a backlight that emits ultraviolet light (corresponding to the light guide plate / diffuser plate in the figure) and a liquid crystal panel that switches between transmission and non-transmission of ultraviolet light (the LCD panel in the figure and the both sides thereof are arranged) A structure corresponding to a polarizing plate (generally including a polarizing plate is called a liquid crystal panel) and fluorescent glass that absorbs ultraviolet rays to emit light are laminated. Fluorescent glass is made by dispersing metal components that emit light in three colors of R, G, and B corresponding to the pixel pattern of the liquid crystal panel, and is said to have high transparency.

  Consider the configuration of FIG. The element composed of the UV light source and the light guide plate / diffusion plate is obtained by replacing the light source of the conventional edge-lit backlight with a UV light source, but there is no detailed description regarding the transparency of this component. Actually, the light propagating from the lower side to the upper side of the light guide plate / diffusion plate in FIG. 4 should be diffused by the diffusion plate. Therefore, it is considered that the image seen through this component loses its clarity. In an image viewed through a frosted glass, it is difficult to apply as described above, as assumed in the present invention. That is, the configuration of FIG. 4 has a problem that the sharpness is insufficient and a clear see-through image cannot be obtained.

  The edge-lit backlight of the configuration shown in FIGS. 1 and 2 is intended to be thinned without the need for a diffuser plate or other components, and is not intended for see-through. Actually, in order to extract light uniformly from the light guide plate, the density of the output coupler must be increased, and there is a problem similar to that of the diffusion plate of FIG. That is, since the light transmitted from the lower side to the upper side in the configuration of FIGS. 1 and 2 is diffused by the output coupler, a clear see-through image cannot be obtained. Since the light source is placed at the end of the light guide plate, the density of the output coupler may be low in a region near the light source. However, in the region away from the light source, the amount of light propagating through the light guide plate is reduced, so the density of the output coupler can only be increased. Therefore, it is still difficult to make the entire surface of the edge lighting type backlight see-through.

Third issue (Both visibility in the light and image quality in the dark)
A transmissive LCD or OLED has a problem of poor visibility in bright places such as outdoors. On the other hand, the reflective LCD uses outside light, and thus has the advantages of excellent visibility in the outdoors and low power consumption. However, the image quality is inferior compared to OLED and transmissive LCD indoors.

  In application to small devices such as mobile phones and smartphones, power consumption is important in addition to visibility in a bright place and image quality in a dark place. For this reason, transflective LCDs are widely used for these small devices. In the transflective LCD, the pixel electrode is formed of a translucent material or divided into a transparent region and a reflective region. Since the transmittance of the pixel electrode is set in consideration of the balance of use in a bright place and a dark place, the light use efficiency is low in any scene. In other words, the transflective LCD is a compromise product, and its image quality is inferior to a reflective LCD in a bright place and inferior to a transmissive LCD or OLED in a dark place.

Shigeru Aoyama, Akihiro Funamoto, and Koichi Imanaka, “Hybrid normal-reverse prism coupler for light-emitting diode backlight systems,” Applied Optics 45, 7273-7278, 2006. A. Nagasawa and K. Fujisawa, “An ultra slim backlight system using optical-patterned film,” Digest of Technical Papers, Society for Information Display 36, 570-573, 2005.

  The present invention has been made to solve the above-described problems, and a first object is to facilitate the design of a planar lighting device having an arbitrary shape and to reduce the manufacturing cost thereof. .

  The second object is to realize an illumination device that has two functions of a planar light source mode and a see-through and clear image viewing mode and has high light use efficiency in the light source mode.

  A third object is to realize a display device that has good visibility in both bright and dark places and low power consumption in bright places.

  The inventor has been diligently studying in order to achieve the above object. As a result, the first problem (manufacturing cost) and the second problem (by the configuration in which light is leaked from the curved portion of the optical fiber to the light guide plate) We found that we could solve see-through). In general, an optical fiber is used as a transmission path for transmitting light to a distant place. In such an application, it is required to further reduce the transmission loss of light. In this invention, it is set as the structure which leaks light intentionally by providing a curved part in an optical fiber, Such a structure is not assumed by the use of the conventional optical fiber.

  Furthermore, the third problem (coexistence of visibility in a bright place and image quality in a dark place) is solved by laminating a liquid crystal panel and a see-through backlight on the reflecting member in this order. I found out that I can do it.

  That is, the present invention includes the following aspects.

  A first illumination device according to the present invention includes a light source, an optical fiber having a curved portion, and a light guide plate, light from the light source is incident on one end of the optical fiber, and the light guide plate includes the light guide plate. An illuminating device in which an optical fiber is disposed and light leaking from the curved portion of the optical fiber propagates through the light guide plate and is emitted to the outside of the light guide plate.

  In the first lighting device, the second lighting device further includes a diffusion plate on one surface side of the light guide plate.

  In the second illumination device, the third illumination device further includes a reflection plate on the other surface side of the light guide plate.

  In the fourth illumination device, in any one of the first to third illumination devices, the plurality of light guide plates are connected by the optical fiber.

  In the fifth illumination device, in the first illumination device, an output coupler for extracting light to the outside of the light guide plate is disposed on the surface of the light guide plate.

  In the fifth illumination device, in the fifth illumination device, a light absorber or refractor is disposed in a region corresponding to the output coupler, and limits the amount of external light incident on the output coupler.

  The seventh lighting device is the fifth lighting device, wherein the refractive index of the light guide plate is substantially the same as the refractive index of the core of the optical fiber.

  In an eighth illumination device according to any one of the fifth to seventh illumination devices, a plurality of the light guide plates are connected by the optical fiber, and each of the light guide plates has a curvature radius of the curved portion of the optical fiber. Is different.

  A first display device according to the present invention is a display device including any one of first to eighth lighting devices and a liquid crystal panel arranged on one surface side of the lighting device.

  A second display device according to the present invention includes any of the fifth to eighth lighting devices and a liquid crystal panel disposed on one surface side of the lighting device, and the liquid crystal panel includes the lighting device. Is a display device that uses light from the illumination device as a light source for image display when the illumination device is in an off state, and uses external light as a light source for image display when the illumination device is in an off state.

  The third display device is arranged on the other surface side of the illumination device in the second display device, and the state of transmitting light and the state of diffusing light by applying a voltage are independent for each of a plurality of regions. The illuminating device can be switched between an on state and an off state independently for each of a plurality of regions corresponding to the plurality of regions of the transmissive diffusion panel.

  In the illumination device according to the first embodiment of the present invention, since the optical fiber having a curved portion is arranged inside the light guide plate, the layout of the optical fiber has a high degree of freedom and the light emitting region is uniform. Is easy to design. Further, since fine processing is not necessary, manufacturing is also easy. Furthermore, it is also possible to apply an adaptive dimming technique by arranging unit elements periodically.

  In the illumination device according to the second embodiment of the present invention, the density of the output coupler formed on the light guide plate can be reduced by arranging the curved portion of the optical fiber as an equivalent light source in the center of the light guide plate. Since external light is not scattered by the output coupler, it becomes see-through. A clear see-through image can be obtained by placing a light absorbing or refracting material in the vicinity of the output coupler. In addition, a uniform lighting device having a large area and various shapes can be realized by using a modularization technique.

  In the display device according to the third embodiment of the present invention, by using the illumination device according to the second embodiment, the light use efficiency is improved as compared with the conventional transflective LCD. Compared with conventional OLEDs and transmissive LCDs, the visibility in an environment with strong external light is excellent, and the power consumption is significantly reduced. Image quality equivalent to that of conventional OLEDs and transmissive LCDs can be obtained even in environments with low ambient light.

  Furthermore, when a laser diode is used as the light source of the illumination device of the present invention, the color reproduction region of the display device is expanded as compared with a transmissive LCD or OLED using a conventional light source, and a more realistic image can be displayed.

It is a figure of the reference literature 1 which shows the example of a structure for converting a point light source into a uniform plane light source. It is the figure of the reference literature 2 which shows the example of a structure for converting a point light source into a uniform plane light source. It is a figure of the reference literature 2 which shows the manufacturing method of the output coupler by an embossing process which concerns on a prior art. It is a figure which shows the one aspect | mode of the liquid crystal display device based on a prior art. It is a schematic diagram which shows the structure of the illuminating device which concerns on 1st embodiment of this invention. It is a photograph during operation of the components of the lighting device and the lighting device. This is a picture of the lighting device in operation with the POF layout changed. It is a schematic diagram which shows the structure which arranges a some cell in parallel and controls each light output independently. It is a schematic diagram which shows the structure of the illuminating device which concerns on 2nd embodiment of this invention. It is a schematic diagram showing a configuration for preventing scattering of external light by the output coupler It is a schematic diagram which shows the structure which puts together the illuminating device which concerns on 2nd embodiment of this invention, and enlarges an area. It is a schematic diagram for explaining a phenomenon in which the amount of light extracted from the curved portion changes depending on the curvature radius of POF. It is a graph which shows an example of the design example of the light extraction efficiency of each cell, and the light quantity which propagates POF in each cell. It is a schematic diagram which shows an example of the illuminating device of various shapes. It is a disassembled perspective view which shows the structure of a liquid crystal display device provided with the illuminating device of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same reference numerals indicate the same or similar components, and thus descriptions of the same or similar components are omitted.

  The illuminating device of this invention is equipped with the optical fiber which has a curved part at least. In the embodiment described below, the optical fiber is made of plastic because of its resistance to bending.

First Embodiment FIG. 5 is a schematic diagram showing a configuration of a lighting device according to a first embodiment of the present invention. (A) is a top view, (b) is sectional drawing. A groove 2 is formed on the surface of the transparent substrate 1 functioning as a light guide plate, and a plastic optical fiber 3 (hereinafter, POF) is disposed therein. In this example, air exists in the gap between the POF 3 and the groove 2. Since the groove 2 is curved as shown in FIG. 5A, the POF 3 also has a curved portion 3a. Here, the curvature radius of the POF 3 is appropriately set so that the light leaks from the curved portion 3 a and the leaked light propagates inside the transparent substrate 1. The light leaking from the curved portion 3a is indicated by an arrow in the figure. The side surface of the end portion of the transparent substrate 1 is covered with the reflective material 4 except for the region of the groove 2 for passing the POF 3. A reflective plate 5 is disposed on the bottom surface of the transparent substrate 1. A diffusion plate 7 is disposed above the transparent substrate 1.

  Next, the operation of the configuration shown in FIG. 5 will be described. The light from the light source 6 propagates through the POF 3 and reaches the bending portion 3a. Light leaks from the curved portion 3a at a constant rate and enters the transparent substrate 1. This light propagates inside the transparent substrate 1 as shown in FIG. The light that reaches the end of the transparent substrate 1 is reflected by the reflecting material 4 and propagates inside the transparent substrate 1. The light reaching the bottom surface of the transparent substrate 1 is also reflected by the reflecting plate 5 and propagates inside the transparent substrate 1. Through such a process, the amount of light propagating through the transparent substrate 1 becomes uniform regardless of the location of the transparent substrate. A part of this light is refracted and reflected at the interface between the POF 3 and the groove 2 and the air to change the course, and is emitted to the outside of the transparent substrate 1. That is, the structure composed of the POF / groove / gap air layer functions as an output coupler. If the light absorption by the transparent material or the reflective material is ignored, all the light emitted from the light source finally enters the diffusion plate 7, and the uniformized light propagates upward in the figure. In the present embodiment, the diffusion plate 7 is disposed above the light guide plate 1 in the drawing with a space between the light guide plate 1 and the light guide plate 1.

  Hereinafter, embodiments will be described in more detail with numerical examples. FIG. 6 is a photograph of the components of the lighting device and the operation of the lighting device. The components are shown in FIG. An acrylic plate (refractive index: 1.49) having a size of 10 cm × 10 cm × 3 mm was used as a light guide plate (transparent substrate 1), and a groove 2 having a rectangular cross section was formed on the surface thereof in a wave shape. Hereinafter, the light guide plate processed in this way is referred to as a POF holder 1h. POF 3 having a diameter of 500 μm and core and clad refractive indexes of 1.49 and 1.40, respectively. Light leaks when the radius of curvature is less than 12.5 mm. Here, the curvature radius of POF3 was all set to 9.5 mm. For the reflecting plate 5 and the diffusing plate 7, general members used for the configuration of the backlight were used. In FIG. 5A, the light source 6 is arranged corresponding to one POF pattern. However, in the embodiment of FIG. 6, one POF 3 is laid out in a manner of one-stroke writing, and one light source 6 is also provided. Only used. FIGS. 6B and 6C show photographs when the laser beam is incident on the POF 3 with the distance d between the POF holder 1h and the diffusion plate 7 set to 0.2 cm or 2.0 cm, respectively. In the example of FIG. 6B in which the diffusion plate 7 is arranged at a position 0.2 cm from the POF holder 1h, the light is not sufficiently diffused and the light source is not uniform, but the example of FIG. 6C. When the diffusion plate 7 is placed at a position 2.0 cm from the POF holder 1h, it can be confirmed that the light is sufficiently diffused. Further, the POF pattern in FIG. 6B has almost the same intensity. This indicates that the structure of the POF 3 and the groove 2 functions as an output coupler, and that the amount of light propagating through the acrylic plate is almost constant regardless of the location.

  FIG. 7 is a photograph of the lighting device in operation with the POF layout changed. The example in which the POF 3 is laid out in a wave shape has been described above, but the layout pattern of the POF 3 is not limited to the wave shape, and various patterns are possible as shown in FIG. 7 as long as the POF 3 has the curved portion 3a. . The only difference from the example of FIG. 6 is the pattern of the groove 2 of the POF holder 1h. The radius of curvature is 8.5 mm in FIGS. 7A and 7B and 10.5 mm in FIGS. 7C and 7D. When the distance d between the POF holder 1h and the diffusion plate 7 is set to 2.0 cm, light is sufficiently diffused in any of the three layout patterns of the POF 3 shown so far, and thus the surface shape A light source can be realized.

  Thus, in the illuminating device of this invention, the optical fiber 3 which has the curved part 3a is arrange | positioned inside the light-guide plate 1. FIG. The layout of the optical fiber has a high degree of freedom, and it is easy to design an illumination device with a uniform light emitting area. Further, since fine processing is not necessary, manufacturing is also easy.

  Furthermore, when a laser diode is used for the light source 6, a known technique relating to the optical fiber can be applied to the coupling between the light source 6 and the optical fiber 3, so that the loss of light can be further reduced. . That is, the loss when light leaks from the curved portion 3a to the light guide plate 1 is almost zero. Therefore, the light utilization efficiency is high. Further, since the laser has a single wavelength, the color reproduction range when a display device is configured in combination with a liquid crystal panel is widened. Of course, in the present invention, the type of the light source is not limited to the laser, and various light sources such as an LED, a fluorescent lamp, or an incandescent bulb can be used as the light source as long as the light can pass through the optical fiber.

Modification (configuration without groove)
In the configuration described above, the groove 2 is formed on the surface of the light guide plate 1 and the POF 3 is arranged. This is because the curved portion is provided in the POF arranged inside the light guide plate to leak light to the outside of the POF. It is an object. The configuration for achieving this object is not limited to the groove 2 on the surface of the light guide plate 1. For example, you may utilize the phenomenon by which the shape at the time of a heating is memorize | stored when POF is heated and cooled. That is, first, POF is placed in a mold having a curved groove, heated and then cooled. Next, the curved POF is taken out from the mold, placed on the surface of the transparent substrate, and fixed with an adhesive. Finally, cover the other transparent substrate from the top and fix it. Through the above steps, the POF having a curved portion is arranged inside the light guide plate, and light can be leaked into the space around the curved portion. The surrounding space is specifically air in this case, but may be filled with a material having a lower refractive index than the POF core. Alternatively, a protrusion having a curved portion is formed on the surface of one transparent substrate, and a certain tension is applied to the POF along the side surface of the protrusion, and another transparent substrate is bonded from above. Through these steps, a POF having a curved portion inside can be disposed in the light guide plate, and light can be leaked from the curved portion into the light guide plate.

Modification (unit element)
In the configuration described above, one POF 3 is arranged in one POF holder 1h. However, by arranging this configuration as a unit element (cell) periodically in a planar shape, a large-area lighting device can be easily formed. Can be realized. FIG. 8 is a schematic diagram showing a configuration in which a plurality of cells are juxtaposed to control each light output independently. (A) is a top view, (b) is a figure explaining the time division | segmentation branch of an optical output. (A) shows an example in which twelve POF holders are arranged in three rows and four columns as unit elements (cells). Similar to the configuration described above, one POF is laid out in a single-stroke manner on one POF holder 1h. At this time, by providing independent light sources 6 ^{# 1 to # 12} for each POF, it is possible to apply a technique called “adaptive dimming” (adaptive dimming) that is generally realized by a direct type backlight. it can. That is, the output of the light source can be adjusted in accordance with the brightness of the image to be displayed. Specifically, the output of the light source corresponding to the dark area of the display image is decreased, and the output of the light source corresponding to the bright area is increased. As a result, the amount of light absorbed in the liquid crystal panel is reduced, so that the power consumption of the display device is reduced. When it is desired to reduce the number of light sources, as shown in FIG. 8B, the light from one light source 6 may be input to a plurality of POFs in a time division manner using an optical switch 6s. As such an optical switch 6s, various integrated optical elements (for example, directional couplers) cultivated in the optical communication field can be used.

Second embodiment (see-through)
FIG. 9 is a schematic diagram showing the configuration of the illumination device according to the second embodiment of the present invention. (A) is a top view, (b) is sectional drawing. The curved portion 3a is included in the layout of the POF 3 in common with the first embodiment. As shown in FIG. 9A, in the second embodiment, the curved portion 3 a is disposed at the substantially center of the plane of the transparent substrate 1. In the example of FIG. 9A, the bending portion 3a has an arc shape, and the plurality of bending portions 3a are continuously circular, but the shape of the bending portion 3a is not limited to the arc shape, It may be corrugated. Furthermore, in this embodiment, it is important to fill the gap between the groove 2 and the POF 3 with the contact liquid 8. The refractive index of the contact liquid 8 is preferably substantially the same as the refractive index of the core of the transparent substrate 1 or the POF 3 (for example, a refractive index of 1.49). Although the refractive index of the cladding of POF 3 is slightly different, this configuration makes POF 3 almost impossible to visually confirm. A plurality of fine structures 9 (output couplers) are arranged on the surface of the transparent substrate 1. Further, a reflective material 4 is disposed on the side surface of the transparent substrate 1 except for the region of the groove 2 for passing the POF 3. The output coupler 9 has a structure for extracting light propagating through the transparent substrate 1 to the outside, and has been conventionally used for edge-lit backlights. For example, the structure of Reference Document 1 or 2 may be adopted for the output coupler 9. In order to achieve see-through, in the second embodiment, the lighting device does not include the reflecting plate 5 on the bottom surface of the transparent substrate 1. The diffusion plate 7 is not provided above the transparent substrate 1.

  In the configuration described above, the groove 2 is formed on the surface of the light guide plate 1 and the POF 3 is arranged, and the gap is filled with the contact liquid 8. This is intended to prevent the POF 3 from being visually confirmed. . In order to achieve this object, the refractive index of the POF core and the light guide need only be substantially the same. For example, the following method may be used. The curved portion is memorized in the POF by the method described in the first embodiment, and this is sandwiched between two transparent substrates, and the periphery of the POF is made of a thermosetting resin or an ultraviolet curable resin whose refractive index is almost the same as that of the POF core. Fill the space and solidify the resin by heating or UV irradiation. As a result, POF cannot be confirmed visually.

  Next, the operation of the configuration shown in FIG. 9 will be described. The light emitted from the light source 6 propagates through the POF 3 to reach the curved portion 3 a and enters the transparent substrate 1. Since light absorption by the transparent material is negligible, there is no loss of light in this process. The light leaking into the transparent substrate 1 is extracted to the outside by the output coupler 9. This light extraction process is the same as that of the conventional edge-lit backlight, and almost all light is emitted above the transparent substrate 1. However, in FIG. 9, since the curved portion 3 a of the POF 3 is equivalent to a light source, the light source is placed at the center of the transparent substrate 1. As described above, since the light source can be equivalently disposed in the center of the transparent substrate 1 functioning as the light guide plate, the density of the output coupler 9 can be reduced as compared with the conventional edge-lit backlight. become. In the state where the light source 6 is turned off and no light is incident on the POF 3, the gap between the POF 3 and the groove 2 is filled with the contact liquid 8 as described above, so that the POF 3 and the groove 2 become almost invisible. Since the area occupied by the output coupler 9 is small in the plane of the transparent substrate 1, the configuration of FIG. 9 is almost see-through in a state where light is not incident on the POF 3. From the above, the configuration of FIG. 9 is neither a conventional edge lighting type nor a direct type, but, in other words, is a compromise type backlight of both.

  However, in the configuration of FIG. 9, a part of the external light Lex that penetrates the transparent substrate 1 is incident on the output coupler 9 although it is slight. Since the external light Lex incident on the output coupler 9 is scattered in various directions, the transparent substrate 1 becomes slightly white under white illumination, and the contrast of the see-through image is deteriorated. In order to prevent this phenomenon, the configuration of FIG. 10 may be employed. FIG. 10 is a schematic diagram showing a configuration for preventing scattering of external light by the output coupler. (A) shows a configuration using an absorbing material, and (b) shows a configuration using refraction. In the example shown in FIG. 10A, the light absorbing material 10a is disposed on the surface side of the output coupler 9 where the external light Lex is incident to prevent scattering of the external light Lex. In the example shown in FIG. 10B, a plurality of transparent bodies 10b having parallel inclined surfaces are arranged on the surface side of the output coupler 9 where the external light Lex is incident. The transparent body 10b is provided with a slope, and the pair of slopes of the transparent body 10b are arranged substantially in parallel, so that the external light Lex slightly deflects in the traveling direction and passes through the side of the output coupler 9 to be transparent. Released to the outside of the substrate 1. Thus, by arranging the light absorbing material 10a or the component 10b that refracts light in the vicinity of the output coupler 9, the external light Lex is incident on the output coupler, and the contrast of the image can be prevented from being lowered.

  Next, problems and solutions for increasing the area of the configuration described above will be described. FIG. 11 is a schematic diagram illustrating a configuration in which the lighting devices according to the second embodiment of the present invention are arranged to increase the area. If the area of the transparent substrate 1 is increased as it is in the configuration of FIG. 9, the distance through which the light leaked from the curved portion 3a of the POF 3 propagates increases. Therefore, as in the case of the conventional edge lighting type backlight, the density of the output coupler 9 must be increased in the peripheral portion of the transparent substrate 1. If the configuration of FIG. 10 is adopted, scattering of the external light Lex by the output coupler 9 can be prevented, but there is a problem that the transmittance of the external light deteriorates in the peripheral portion of the transparent substrate 1 or the see-through image is distorted in the peripheral portion. To do. In order to solve these problems and increase the area of the see-through lighting device, a modularization technique is employed in this embodiment. That is, as shown in FIG. 11, the configurations of FIG. 9 (hereinafter referred to as cells) are arranged and connected by POF3. Here, the area of each cell is the same and optically independent, and the same amount of light is extracted from all the cells. A method for realizing this will be described in detail below.

Before describing the operation of the configuration shown in FIG. 11, a preliminary experiment for realizing a see-through lighting device having a uniform and large area will be described. That is, the phenomenon in which the amount of light extracted from the curved portion 3a of the POF 3 depends on the radius of curvature is quantified. The method of this experiment is shown in FIG. FIG. 12 is a schematic diagram for explaining a phenomenon in which the amount of light extracted from the curved portion changes depending on the curvature radius of the POF. (A) is a top view which shows the setup of experiment, (b) is the graph which plotted the experimental data of the light extraction efficiency of two types of POF. As shown in FIG. 12A, a plurality of grooves 2 having different radii of curvature are formed in an arc shape on an acrylic substrate 1 to form a POF holder 1 h, and a POF 3 is disposed in one of the grooves 2. In this state, a certain amount of light is incident from one end of the POF 3 and the amount of light emitted from the other end is measured by the power meter 21. If the input and output are respectively P _in and Pout, the light extraction efficiency is defined by the following equation as a function of the radius of curvature r.

The result of repeating this measurement for two types of POFs having diameters of 500 μm and 250 μm is shown in the graph of FIG. The vertical axis of the graph is the light extraction efficiency, and the horizontal axis is the radius of curvature r of the curved portion 3a. From the graph of the measurement result, it can be seen that the light extraction efficiency can be accurately set in the range from about 0 to about 0.5 by appropriately selecting the curvature radius r. It should be noted that the light extraction efficiency shown in FIG. 12B corresponds to a quarter partial circle. Further, the gap between the groove 2 and the POF 3 is filled with a contact liquid having the same refractive index of 1.49 as that of the acrylic plate, and the detection unit of the power meter 21 is placed in a region D surrounded by a dotted line in FIG. When the parts 3a attempted to measure the light leaking in the direction perpendicular to the surface of the acrylic substrate, result to 1mW of P _in was below the detection limit (0.1nW). Therefore, the light leaking from the curved portion 3a of the POF 3 propagates through the acrylic substrate 1 almost completely. That is, it is determined that there is no loss in the process of leaking light from the curved portion 3a of the POF 3 to the transparent substrate 1.

Next, the principle of realizing a uniform and large-area lighting device will be described with reference to FIG. The light intensity and light extraction efficiency input to the nth cell are I _n and η _n , respectively, the total number of cells is N, and the light intensity input to the first cell is I ₀ . As described above, if the area of each cell is the same and optically independent, and the same amount of light is extracted from all the cells, the following equation is established.

From these, I _n and η _n are obtained as follows.

FIG. 13 is a graph showing an example of a design example of the light extraction efficiency of each cell and the amount of light that propagates POF in each cell. As a numerical example, I _n and η _n when N = 25 and I ₀ = 100 are shown in the graph of FIG. When the light extraction efficiency of each cell is set in this way, the same amount of light can be extracted from all cells. The light extraction efficiency of each cell is set by selecting the curvature radius of the POF as illustrated in FIG. As described above, a uniform illumination device with a large area is realized.

  FIG. 14 is a schematic diagram illustrating an example of a lighting device having various shapes. In the above-described embodiment, the light emitting areas are all rectangular, but as shown in FIG. 14, a plurality of rectangular cells can be arranged to lay out POF 3 in the manner of one stroke. Preferably, the reflecting material 4 is not provided on the outer side surface of the cell arranged on the outermost side, and the reflecting material 4 is provided on the outer side surface of the shape 22 of the lighting device to be actually realized. Furthermore, by setting the curvature radius of the curved portion of the POF 3 of the cell arranged on the outer periphery to be slightly smaller, it becomes an illumination device that uniformly emits light to every region. Thereby, it is possible to easily and inexpensively realize variously shaped lighting devices. In FIG. 14, the curved portion of the POF 3 on the arc inside each cell is not drawn, but this is for the purpose of simplification for emphasizing the main points. Actually, as in FIG. There is a curved portion 3a of the POF 3 inside.

  As described above, in the second embodiment, the density of the output coupler 9 formed on the light guide plate 1 can be reduced by arranging the curved portion 3a of the optical fiber 3 as an equivalent light source in the center of the plane of the light guide plate 1. . Since the outside light Lex is not scattered by the output coupler 9, it becomes see-through. By arranging the light absorbing material 10a or the material 10b that refracts light in the vicinity of the output coupler 9, a clear see-through image can be obtained. In addition, a uniform lighting device having a large area and various shapes can be realized by using a modularization technique.

Third embodiment (display device)
If the display device is configured using the illumination device of the second embodiment, both visibility in a bright place and image quality in a dark place can be achieved. Furthermore, the power consumption of the display device can be significantly reduced by using external light without turning on the lighting device in a bright place. The configuration and operation of the third embodiment will be described below.

  FIG. 15 is an exploded perspective view showing a configuration of a liquid crystal display device including the illumination device of the present invention. The display device 30 includes a liquid crystal panel 31, a lighting device 32 according to a second embodiment of the present invention, and a polymer-dispersed liquid crystal (hereinafter referred to as PDLC) panel 33 laminated. Configured. The liquid crystal panel 31 has a known configuration, and generally a TFT substrate 311 provided with a thin film transistor (hereinafter referred to as TFT) functioning as a switching element for each pixel, and a counter substrate 312 provided with a color filter, a transparent electrode, and the like. And a liquid crystal layer (not shown) positioned therebetween, and two polarizing plates 313 and 314 sandwiching these components from above and below. Furthermore, the liquid crystal panel 31 may be provided with a component that realizes a touch detection function for inputting with a finger or a pen. The illumination device 32 has the configuration described in the second embodiment of the present invention, and may be a single cell or a configuration in which a plurality of cells are connected by POF. In the example of FIG. 15, the light emitting area of the illumination device 32 is divided into two areas, an area A <b> 2 and an area B <b> 2, and lighting ON / OFF is controlled independently for each area. The PDLC panel 33 is arranged in the lowest layer. The PDLC panel 33 is obtained by sandwiching a PDLC between two transparent substrates having transparent electrodes. By applying a voltage to the transparent electrodes, the PDLC panel 33 is transparent (a state that transmits light) and light is transmitted. It can be switched to the state of spreading. In this embodiment, corresponding to the area A2 and the area B2 of the illumination device 32, the PDLC panel 33 is also divided into the area A1 and the area B1, and the state of transparency / diffusion is switched independently for each area. be able to.

  Next, the operation of the configuration shown in FIG. 15 will be described. In the configuration of the liquid crystal display device 30 shown in the example of FIG. 15, the next display operation is performed by performing ON / OFF control of the illumination device 32 and switching between transmission and diffusion of the PDLC panel 33 independently for each of a plurality of regions. Is possible.

  First, in an environment where the outside light is not strong, such as indoors, for example, when the region A1 of the PDLC panel 33 is in a diffusion state and the illumination of the region A2 of the illumination device 32 corresponding to this region A1 is turned ON, the corresponding liquid crystal panel 31 An image is displayed in a region (hereinafter referred to as region A). Further, for example, when the region B1 of the PDLC panel 33 is set in the transmission state and the illumination of the region B2 of the illumination device 32 corresponding to the region B1 is turned off, the corresponding region of the liquid crystal panel 31 (hereinafter referred to as region B) is see-through. become. That is, related information can be displayed in the area A while observing a see-through image in the area B. The operation described above is realized by dividing both the see-through mode and the image display mode into regions.

  On the other hand, in an environment with strong external light such as outdoors, if the illumination device 32 is turned off on the entire surface and the PDLC panel 33 is in a diffused state on the entire surface, it functions as a general reflective liquid crystal display device. In this state, if the PDLC panel 33 is in a transmissive state on the entire surface, the display device 30 becomes see-through. If a part of the region of the PDLC panel 33 is in a diffusion state, display using outside light is realized in this region, and the other regions are see-through. In these operations, the power consumed by the lighting device 32 and the PDLC panel 33 is only the standby power of the electronic circuit necessary for controlling the respective components.

  If such a display device 30 is installed in a portable terminal device, for example, if the see-through image in the region B is a product, the specification and price of the product, and if it is a sentence written in a foreign language, the translation, etc. Can be displayed side by side in the adjacent area A. In this state, when both the illumination of the areas A2 and B2 of the illumination device 32 are turned off, the entire surface of the display device 30 becomes see-through. Further, in this state, when both the areas A2 and B2 are turned on, an image can be displayed on the entire surface of the display device 30. When such a display device 30 capable of switching between the see-through mode and the image display mode for each region is attached to, for example, a windshield of a car, a conventional projector-type head-up display can be greatly reduced in size.

  For applications that do not require the see-through function, the diffusion plate 7 may be used instead of the PDLC panel 33. Also in this case, a display device with good visibility in both bright and dark places and low power consumption in bright places can be realized.

  As described above, in the display device 30 using the illumination device 32 of the present invention, the external light or the output light of the illumination device 32 can be selected and used in the entire area of each pixel of the liquid crystal panel. Therefore, the display device 30 of the present invention has higher light utilization efficiency than the conventional transflective LCD. In addition, the display device 30 of the present invention has excellent visibility in an environment with strong external light and significantly lower power consumption than conventional OLEDs and transmissive LCDs. Image quality equivalent to that of conventional OLEDs and transmissive LCDs can be obtained even in environments with low ambient light. Furthermore, the optical fiber is characterized by good compatibility with the laser. That is, if a laser diode is used as the light source 6 of the illumination device 32 of the present invention, the color reproduction area of the display device is expanded as compared with a transmissive LCD or OLED using a conventional light source, and a more realistic image is displayed. it can.

  As described above, in the illumination device according to the first embodiment of the present invention, since the optical fiber having the curved portion is arranged inside the light guide plate, the layout of the optical fiber is highly flexible and the light emitting region is uniform. The design of the lighting device is easy. Further, since fine processing is not necessary, manufacturing is also easy. Furthermore, it is also possible to apply an adaptive dimming technique by arranging unit elements periodically.

  In the illumination device according to the second embodiment of the present invention, the density of the output coupler formed on the light guide plate can be reduced by arranging the curved portion of the optical fiber as an equivalent light source in the center of the light guide plate. Since external light is not scattered by the output coupler, it becomes see-through. A clear see-through image can be obtained by placing a light absorbing or refracting material in the vicinity of the output coupler. In addition, a uniform lighting device having a large area and various shapes can be realized by using a modularization technique.

  In addition, the display device according to the third embodiment of the present invention includes the illumination device according to the second embodiment, so that the light use efficiency is improved as compared with the conventional transflective LCD. Compared with conventional OLEDs and transmissive LCDs, the visibility in an environment with strong external light is excellent, and the power consumption is significantly reduced. Image quality equivalent to that of conventional OLEDs and transmissive LCDs can be obtained even in environments with low ambient light.

  Furthermore, when a laser diode is used as the light source of the illumination device of the present invention, the color reproduction region of the display device is expanded as compared with a transmissive LCD or OLED using a conventional light source, and a more realistic image can be displayed.

  As mentioned above, although this invention was demonstrated by specific embodiment, this invention is not limited to above-described embodiment.

  In the above embodiment, the optical fiber is made of plastic, but an optical fiber formed of other materials such as glass may be used as long as light can be leaked from the curved portion using bending loss. .

  In the first embodiment, the POF 3 is laid out in a wave shape. However, the layout pattern of the POF 3 is not limited to the wave shape. As long as the POF 3 has the curved portion 3a, the POF 3 has various layout patterns. Is possible.

  In the first embodiment, the diffusion plate 7 is disposed with a space between the light guide plate 1, but the diffusion plate 7 may be disposed on the surface of the light guide plate 1. .

  In the first embodiment, the light guide plate 1 is provided with the diffusion plate 7 on one side, the other side is provided with the reflection plate 5, and emits light only from one side of the light guide plate 1. However, instead of the reflecting plate 5, a diffusion plate similar to the diffusion plate 7 may be arranged to emit light from both the upper and lower surfaces of the light guide plate 1.

  Moreover, in the said embodiment, although the illuminating device is enlarged by arranging the several illuminating device made into the unit element (cell) in planar shape, arrangement | positioning of an illuminating device is not restricted to planar shape, light As long as the bending strength of the fiber 3 and the light guide plate 1 is allowed, it may be curved. This makes it possible to provide Head-Up Display lighting devices for curved surfaces with relatively strong curvature, such as helmet visors and aircraft canopies, as well as generally flat surfaces such as car windshields. Become.

  In the above embodiment, the type of the light source 6 is not particularly limited. However, as long as the POF 3 can pass, the light source 6 includes a light emitting diode (LED), an electroluminescence panel (ELP), a cold cathode tube. Various light sources such as (CCFL), fluorescent lamps, incandescent bulbs, discharge tubes, laser diodes (LD) can be used.

  Moreover, in said 2nd embodiment, although the curved part 3a of POF3 is circular arc shape, and the some curved part 3a is circular continuously, the shape of the curved part 3a is not restricted to circular arc shape, It may be a partial circle or a wave shape.

  In the third embodiment, the display device is configured using the see-through lighting device of the second embodiment. However, in applications where the see-through is unnecessary, the first embodiment is used. The display device may be configured by using the illumination device. In this case, the display device includes the illumination device of the first embodiment that functions as a backlight, and the liquid crystal panel 31.

  In the third embodiment, the PDLC panel 33 is used. Instead, a polymer network liquid crystal (hereinafter referred to as PNLC) panel may be used. In other words, the PNLC panel may be arranged in the lowermost layer of the display device 30, and the transparency / diffusion state of the PNLC panel may be switched independently for each region. In addition to this, various liquid crystal driving methods can be used as long as the transparent and diffusing states of the panel can be switched independently for each region.

  The present invention provides an illuminating device and a display device including the illuminating device, and in particular, improves the visibility and power consumption of the display device of a portable device by using the illuminating device as a backlight of a liquid crystal display device. Furthermore, a see-through display function is added. Currently, the transflective LCD is dominant in the market of smartphones and tablet terminals, but the transflective LCD can be replaced by the display device of the present invention having superior image quality and power consumption. Furthermore, the market of these portable devices can be further expanded by a newly provided see-through function.

  Currently, projector-type display devices that display navigation information and the like on the windshield of a car are beginning to become widespread. Since the display device of the present invention has the advantage of being thin, the market can be expanded even in such applications.

1 Transparent substrate (light guide plate)
1h POF holder 2 Groove 3 Plastic optical fiber (POF)
3a Curved part 4 Reflector 5 Reflector 6 Light source 6s Optical switch 7 Diffuser 8 Contact liquid 9 Output coupler 10a Light absorber 10b Transparent body 21 Power meter 30 Display device 31 Liquid crystal panel 32 Illumination device of the present invention 33 PDLC panel Lex Outside light obs observer

Claims (11)

A light source;
An optical fiber having a curved portion;
A light guide plate,
The light from the light source is incident on one end of the optical fiber, the optical fiber is disposed inside the light guide plate,
The illuminating device, wherein light leaking from only the curved portion of the optical fiber propagates through the inside of the light guide plate and is emitted to the outside of the light guide plate.   The lighting device according to claim 1, further comprising a diffusion plate on one surface side of the light guide plate.   The lighting device according to claim 2, further comprising a reflecting plate on the other surface side of the light guide plate.   The lighting device according to claim 1, wherein a plurality of the light guide plates are connected by the optical fiber.   The lighting device according to claim 1, wherein an output coupler for extracting light to the outside of the light guide plate is disposed on a surface of the light guide plate.   6. The illumination device according to claim 5, wherein a light absorber or refractor is disposed in a region corresponding to the output coupler to limit the amount of external light incident on the output coupler.   The lighting device according to claim 5, wherein the refractive index of the light guide plate is substantially the same as the refractive index of the core of the optical fiber.   The lighting device according to claim 5, wherein a plurality of the light guide plates are connected by the optical fiber, and the curvature radius of the curved portion of the optical fiber is different in each of the light guide plates.   A display device comprising: the lighting device according to claim 1; and a liquid crystal panel disposed on one surface side of the lighting device. A lighting device according to any one of claims 5 to 8, and a liquid crystal panel disposed on one surface side of the lighting device,
The liquid crystal panel is
When the lighting device is in an on state, the light from the lighting device is used as a light source for image display,
A display device that uses external light as a light source for image display when the illumination device is in an off state. The illuminating device is further provided with a transmissive diffusion panel that is arranged on the other surface side of the lighting device and can switch between a state of transmitting light and a state of diffusing light by applying a voltage independently for each of a plurality of regions,
The display device according to claim 10, wherein the lighting device can be switched between an on state and an off state independently for each of a plurality of regions corresponding to the plurality of regions of the transmission diffusion panel.