JP2008311091A - Lighting system and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, in a conventional configuration, a diffusion film or a prism sheet is provided on the emitting-face side of a light-guide plate, consequently, it prevents thinning, cost reduction, and higher luminance, and also, in a configuration that forms a microprism in a light-guide body, it is difficult to achieve an increase in size. <P>SOLUTION: An emitting face of a light-guide body is formed on a mirror plane. Each prism with an angle of 40-50 degrees with respect to the emitting face is provided on a face opposite to the emitting face. By this, emitting of light with a vertical component to the emitting face is significantly increased. Consequently, it is possible to achieve higher luminance even without using a prism sheet, and also, it allows die manufacture by a conventional machining technique. Further, it is possible to achieve an increase in size by mounting a plurality of light-emitting diodes on the same substrate so as to make it as a light source almost similar to a linear light source. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lighting device and a display device used for an electronic device. In particular, the present invention relates to a liquid crystal display device used for a portable information device, a mobile phone, a liquid crystal television, and the like, and a lighting device such as a front light and a backlight for illuminating a non-self-luminous display element. The present invention also relates to equipment lighting equipment for residences and offices.

  2. Description of the Related Art Conventionally, an edge light type illumination device is known in which light from a light source is incident from a side surface of a light guide and is emitted from an upper surface (hereinafter referred to as an emission surface) of the light guide. A point light source such as a light emitting diode (LED) is used as the light source, and a large number of grooves and dot patterns are formed on a surface opposite to the light exit surface of the light guide (hereinafter referred to as an opposing surface). In addition, a diffusion pattern having an effect of diffusing light is often formed on the exit surface. A prism is formed on a light incident surface of the light guide (that is, a surface on which light from the light source is incident facing the light source), and has a function of diffusing a point light source into a surface light source. A transparent resin such as polycarbonate (PC) or acrylic (PMMA) having a refractive index higher than that of air is used as the material of the light guide. In addition, a configuration in which a diffusion sheet and a prism sheet are arranged on the light exit surface side of the light guide is the mainstream. Further, a reflection sheet is disposed below the light guide.

In addition, an edge light type illumination device that uses a line light source such as a cold cathode tube instead of a point light source is also known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-292531 (FIGS. 1 and 2)

  In the conventional illumination device, in order to uniformly disperse the light emitted from the exit surface, an optical design is performed so that the inside of the light guide is repeatedly reflected and refracted. However, when the number of reflections and refractions increases, the amount of light lost increases accordingly, resulting in a problem that the light use efficiency decreases.

  In particular, when a point light source such as an LED (light emitting diode) is used, it is often diffused once by a prism or a diffusion layer when entering the light guide. Therefore, like the inside of the light guide, extra reflection and refraction increase, which also leads to a decrease in light utilization efficiency.

  In addition, in order to increase the number of reflections and increase the in-plane uniformity, a diffusion film or a prism sheet is often provided on the light guide. The presence of these films causes the problem of increased thickness and cost of the lighting device.

  In addition, a lighting device that combines a point light source and a light guide subjected to micro-prism processing and has high light utilization efficiency is disclosed, but there is a problem that it is difficult to increase the size of the light guide plate.

  In view of the above, an object of the present invention is to realize an illumination device and a display device that have high light use efficiency and can be reduced in thickness and size.

  In order to solve the above-described problems, an illumination device according to the present invention includes a light source, a light incident surface on which light from the light source is incident, an emission surface that emits illumination light, and a facing surface opposite to the emission surface. In the illumination device including the body, the light exit surface of the light guide is a mirror surface, and a plurality of prisms having an angle of 40 ° to 50 ° with respect to the light exit surface are provided on the opposing surface. Furthermore, a light emitting diode as a point light source was mounted adjacently on the same substrate, and it was as close as possible to a linear light source.

  According to the present invention, the light exit surface is a mirror surface, and the prism is provided on the opposite surface at an angle of 40 to 50 degrees with respect to the light exit surface. Increasing the brightness without using a prism sheet. With the structure of the present invention, a lighting device and a display device that are high-intensity, inexpensive, thin, and can be enlarged can be realized.

  The light guide which guides the light radiate | emitted from the light source is arrange | positioned at the illuminating device of this invention. The light guide has a surface that emits light (this surface is referred to as an exit surface) and a surface that faces the exit surface (this surface is referred to as an opposing surface). A large number of concave reflecting structures that refract and reflect light are formed on the facing surface. The prism is formed at an angle of 40 to 50 degrees with respect to the opposing surface. That is, since the prism is a recess formed on the opposing surface of the light guide plate, it is composed of at least two surfaces. Of these two surfaces, the surface close to the light source is the reflecting surface. The angle formed by the reflecting surface and the emitting surface is 40 to 50 degrees. Further, the exit surface is not provided with a pattern, and has a mirror finish. As a result, the emission of light having a component perpendicular to the emission surface is greatly increased, and high brightness can be achieved without using a prism sheet.

  The prism is a prism having a linear shape when viewed from above. If the prism height is increased as the distance from the light source increases, the brightness on the exit surface can be made uniform. Alternatively, when the prism is composed of a prism having a linear shape when viewed from the top, and the prism addresses are assigned in order from the light source, the relationship between the linear prism pitch and the address is a quadratic function. Alternatively, the pitch of the linear prisms is wider as it is closer to the light source, and becomes narrower as the distance from the light source is increased. The pitch near the light source is designed to be about 100 μm, and the farthest distance is about 40 μm. The top view of the prism is a straight line.

  Further, by using a linear light source as the light source, it is possible to easily realize an increase in the size of a lighting device with high light use efficiency. A point light source with a configuration in which a plurality of light emitting diode (LED) elements are mounted on a single substrate, a transparent sealant in which phosphors and diffusing particles are dispersed is potted, and a reflective frame is provided between the LED elements. A certain LED can be used as if it were a line light source.

  The top view shape of the linear prism may be a corrugated shape so as to correspond to the brightness and the positional relationship of such a linear light source. Or you may arrange | position a fragment | piece prism so that it may respond | correspond only to the dark part of a linear light source.

  In the display device of the present invention, the lighting device having any one of the above structures is used as a non-self-luminous display element.

  A first embodiment of the present invention will be described with reference to FIGS. 1, 4, 5, 8, and 9. FIG. FIG. 1 schematically shows a cross-sectional configuration of the illumination device of the present embodiment. As shown in the drawing, a light guide 2 that guides light emitted from the light source 1 is disposed on the side of the light source 1 that emits light. The light guide 2 has a surface that emits light (this surface is referred to as an emission surface 2a) and a surface that faces the emission surface (this surface is referred to as an opposing surface 2b). A large number of concave reflecting structures 3 that refract and reflect light are formed on the facing surface 2b. The prism 3 includes a reflecting surface that refracts or reflects light. The exit surface 2a has no pattern or the like and has a mirror finish. The light guide 2 is a molded product of transparent resin, and as a material, polycarbonate or acrylic resin is often used. The reflection sheet 4 is disposed so as to face the facing surface 2b of the light guide 2. In the present embodiment, the reflection sheet 4 is configured to cover the light source 1, and has an effect of preventing light leakage and improving light utilization efficiency. Instead of such a reflection sheet 4, for example, a frame having a reflection function or a double-sided sheet can be used. In this embodiment, the reflective sheet 4 is disposed on the facing surface 2b side. However, the reflective sheet 4 may be disposed on the light exit surface 2a side. In this case, the light emitted from the light exit surface 2a is reflected by the reflection sheet 4, returns to the light guide 2 again, and exits from the facing surface 2b. And by using what has a diffusion function as a reflective sheet, the dispersibility of light improves, uniformity improves, and it becomes difficult to see a nonuniformity. On the other hand, there is a demerit that luminance efficiency is slightly reduced.

  FIG. 5 shows an enlarged cross-sectional configuration of the light source 1 of the present embodiment. The light source 1 includes a plurality of LED elements 8 and a reflection frame 9 provided between the LED elements 8. The plurality of LED elements 8 mounted on the substrate are potted with a transparent sealing agent 7 in which phosphors and diffusion particles are dispersed. If the LED element 8 that emits blue light and the phosphor that emits yellow light when excited by blue light are used, the light source 1 emits white light that is a mixture of blue light and yellow light. In the case of a conventional LED package, there is a large difference in luminous intensity near and far from the LED element, and there is a tendency that uneven brightness called an eyeball tends to occur in front of the LED element. However, in the case of the present embodiment, a plurality of LED elements 8 are mounted on one substrate adjacent to each other. Further, the reflective frame 9 efficiently disperses the light emitted from the LED element 8, or the diffusing agent is dispersed in the transparent encapsulant 7, and the sealing shape is devised, so that an LED as a point light source can be obtained. It is designed to be used like a line light source.

  FIG. 4 shows an enlarged cross-sectional view of the reflecting structure provided on the facing surface 2b. Here, the opposing surface 2b is configured in parallel to the emission surface 2a. A prism is formed on the facing surface 2b at a prism angle 5 of 40 to 50 ° with respect to the facing surface. The optimum angle of the prism angle 5 varies slightly depending on parameters such as the size, thickness, and material of the light guide, but in most cases, the optimum angle exists in the range of 40 to 50 °. When light hits the prism at an angle substantially parallel to the facing surface 2b, many components are reflected in a direction perpendicular to the facing surface 2b. The reflected light collides perpendicularly with the exit surface 2a, but exits from the exit surface without reflecting most components. Since the exit surface 2a has a mirror finish, light components other than those perpendicular to the exit surface are reflected and returned to the inside of the light guide when they hit the exit surface. In the conventional light guide design, a diffusion pattern or a prism pattern is often provided on the exit surface. However, in the present invention, since the exit surface 2a is a mirror surface, the light output rate of the light component perpendicular to the surface increases. Become. Therefore, it becomes a light guide with very high directivity.

FIG. 8 schematically shows a front view of the illumination apparatus of the present embodiment. The prism 3 is arranged in parallel to the light source 1. In this embodiment, the pitch of the prisms 3 is wider as it is closer to the light source 1 and becomes narrower as it gets farther from the light source. The design is 100 μm near the light source and 40 μm farthest away. The top view shape of the prism is a straight line. At this time, if an address is assigned to the prism and the address closest to the light source is set to 1, the relationship between the address and the optimum prism pitch is a quadratic function. This quadratic function can be expressed as “optimum pitch = a × address ² + b”. Here, a and b are coefficients that vary depending on the refractive index and size of the light guide, the radiation characteristics of the light source, and the like. In this example, optimization was possible with a coefficient a = 1.2 × 10 ⁻⁴ and a coefficient b = 10 ⁻⁷ .

  The optimum pitch varies depending on the prism height 6. The prism height in this embodiment was designed to be 10 μm. However, the prism height can be changed in the range of 1 to 50 μm. Basically, when the height is lowered, the uniformity of light is increased and the display quality is improved when used as a backlight, but the cost and lead time for mold production are increased. Increasing the height can reduce the number of prisms. However, if the height is decreased too much, it may cause a line defect such that the prism lines can be seen through the LCD.

  FIG. 9 is a cross-sectional view of a display device provided with the illumination device of this embodiment. The light from the light source 1 enters the light guide 2 and is emitted from the light exit surface by the prism provided on the light guide to illuminate the liquid crystal panel 11. By covering the light guide with the frame 10, a liquid crystal display with extremely high luminance can be realized.

  FIG. 6 schematically shows a top view of the illumination device of this example. The difference from the first embodiment is the front shape of the prism 3 of the light guide 2. In Example 1, the prism shape was a straight line. This is based on the premise that the light source 1 is infinitely close to a linear light source and there is no luminance unevenness in the front. However, it is difficult to completely eliminate the luminance unevenness only by the structure of the light source 1, and in fact, the LED element tends to be bright where there is an LED element and dark where there is no LED element. Therefore, in this embodiment, the top view shape of the prism 3 is a wave shape. Since light is emitted radially from each of the plurality of LED elements of the light source 1, a prism was formed so as to draw an arc from a position close to the LED element. Thereby, luminance unevenness can be reduced. Also in the present invention, since a plurality of LED elements are mounted on the substrate, a pattern is formed in which arcs corresponding to the respective LED elements are connected, resulting in a wave shape.

  FIG. 7 schematically shows a top view of the illumination device of this example. The difference from the first and second embodiments is the top view shape of the prism 3 of the light guide 2. In each of the above-described embodiments, the prisms are continuously connected. However, in this embodiment, the prisms are arranged in pieces. As described in Example 2, the area far from the LED element tends to be dark. Therefore, not only the continuous linear prisms as in the first embodiment but also the fragmentary short-side prisms 13 are arranged in the area without the LED elements. This makes it possible to brighten areas that were previously dark. On the other hand, there is a problem that fragmentary prisms can be seen through the liquid crystal panel. However, the shape of the fragmentary prisms can be lowered, or the center can be made higher and the edges can be made lower. Can be prevented by doing.

  A cross-sectional configuration of the illumination device of the present embodiment is schematically shown in FIG. The difference from the first embodiment is the height and pitch of the prisms 3 arranged on the facing surface 2b. In the first embodiment, the prism 3 is designed so that the pitch of the prisms 3 decreases as the distance from the light source increases. In the present embodiment, the height is changed at equal intervals. The prism 3 is designed to be lower as it is closer to the light source and higher as it is farther away. As in the first embodiment, when the prism pitch is changed, there may be a prism pitch that easily interferes with the inter-dot pitch of the liquid crystal panel. If the pitch is constant as in this embodiment, there is an advantage that it is easy to avoid interference with the liquid crystal panel. However, since there is a demerit that it is difficult to accurately process the light guide mold as in this embodiment, whether the prism height or the pitch is variable depends on the TPO. It is necessary to select together.

  A cross-sectional configuration of the illumination device of the present embodiment is schematically shown in FIG. In the case of the first and fourth embodiments, the mold for molding the light guide plate 2 has a convex shape. In that case, there is a problem that it is difficult to create a metal mold because the area to be sharpened is greatly increased compared to the concave shape. Although there is a method in which a concave shape is first created and electroformed, there is a production lead time and cost. Therefore, in this embodiment, the cross-sectional shape of the prism is changed. As shown in FIG. 4, the light incident on the light guide plate 2 from the light source 1 is large if the prism angle (angle formed by the reflecting surface of the prism and the light exit surface of the light guide plate) is in the range of 40 to 50 degrees. Is reflected by the reflecting surface of the prism in the direction perpendicular to the exit surface of the light guide plate. The prism is a recess formed on the surface of the light guide plate, and is composed of at least two surfaces. Of these two surfaces, the surface close to the light source is the reflecting surface. If the surface far from the light source is referred to as an inclined surface, the inclined surface does not contribute much to the light emitted from the light guide plate. Therefore, in this embodiment, the manufacturing of the mold is emphasized, the angle between the inclined surface of the prism and the light exit surface of the light guide plate is made smooth, and the bottom of the reflecting surface and the bottom of the inclined surface are in contact with each other. By adopting such a prism shape, the mold is neither convex nor concave and is easy to manufacture. Further, the mold can be manufactured by a conventional machining technique, and the size can be easily increased.

  The illumination device and the display device according to the present invention can be applied to display devices such as a mobile phone, a PDA, a car navigation system, and a television. It can also be applied to equipment lighting equipment such as a residence or office.

It is sectional drawing which shows the structure of the illuminating device of this invention typically. It is sectional drawing which shows the structure of the illuminating device of this invention typically. It is sectional drawing which shows the structure of the illuminating device of this invention typically. It is an expanded sectional view which shows a part of structure of the illuminating device of this invention typically. It is sectional drawing which shows the structure of the light source of this invention typically. It is an upper view which shows typically the structure of the illuminating device of this invention. It is an upper view which shows typically the structure of the illuminating device of this invention. It is an upper view which shows typically the structure of the illuminating device of this invention. It is an upper view which shows typically the structure of the display apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide 2a Outgoing surface 2b Opposite surface 3 Prism 4 Reflective sheet 5 Prism angle 6 Prism height 7 Transparent sealing resin 8 LED element 9 Reflective frame 10 Frame 11 Liquid crystal panel

Claims (11)

A light source;
In an illuminating device comprising a light guide having an incident surface on which light from the light source is incident, an exit surface that emits illumination light, and a facing surface opposite to the exit surface,
An illuminating device characterized in that the exit surface of the light guide is a mirror surface, and a plurality of prisms of 40 ° to 50 ° are provided on the facing surface with respect to the exit surface.   The lighting device according to claim 1, wherein the prism is a linear prism, and the height of the prism increases as the distance from the light source increases.   2. The prism according to claim 1, wherein the prism is a linear prism, and the relationship between the linear prism pitch and the address is a quadratic function when the prism addresses are assigned in the order from the light source. Or the illuminating device of 2.   The lighting device according to claim 1, wherein the light source is a linear light source.   The lighting device according to claim 4, wherein the linear light source includes a plurality of light emitting diodes mounted on a substrate and a reflection frame provided between the light emitting diodes.   6. The lighting device according to claim 5, wherein a transparent resin in which a diffusing agent or a phosphor is dispersed is potted on the light emitting diode.   The illuminating device according to any one of claims 4 to 6, wherein a top-view shape of the prism is a wave shape corresponding to light and darkness and a positional relationship of the linear light source.   The illumination device according to any one of claims 4 to 6, wherein a fragment prism is disposed so as to correspond only to a dark portion of the linear light source.   The prism includes a reflective surface close to the light source and an inclined surface far from the light source, and the bottom of the reflective surface of the prism is in contact with the bottom of the inclined surface of the prism adjacent to the prism. The lighting device according to any one of claims 4 to 7.   The lighting device according to claim 1, wherein a reflection sheet is disposed so as to face the emission surface.   A display device comprising: the illuminating device having the configuration described in any one of claims 1 to 10; and a non-self-luminous display element provided on an emission surface side of the illuminating device.

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