JP2006164625A - Luminaire and display device provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and light luminaire with no frame by realizing a downlight type using an LED light source. <P>SOLUTION: In this luminaire, a plurality of LED light sources are arranged on a back surface of a transparent light guide plate arranged on a matrix, a light incident prism having the top-most vertex on right above the light emission center of the LED light sources is formed at the light irradiation surface of the light guide plate, fine prisms split into a plurality of pieces are formed on the reflecting surface of the light incident prism, a plurality of fine prisms are formed on a back surface of the light incident prism, and a light diffusion plate is arranged on a light irradiation surface side of the light guide plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lighting device used in a liquid crystal display device used in a timepiece, a mobile phone, an audio, an electronic device, and the like.

  In recent years, liquid crystal display devices having a thin and light feature have been widely used for portable devices and information devices. However, since the liquid crystal display device is a light-receiving type, an illuminating device is often installed on the front or back surface of the liquid crystal display element for the purpose of displaying a bright and high-definition image.

In order to realize the thin and light nature inherent in the liquid crystal display device, a sidelight type illumination device in which an LED element is arranged as a light source on the side surface of the light guide plate is often used. However, in the sidelight type lighting device, since the light source is arranged on the side surface of the light guide plate, a frame region which is a non-display region at the periphery of the liquid crystal display device becomes wide. In order to eliminate this frame region, a direct type illumination device in which a light source is arranged on the back surface of the light guide plate has been proposed (see, for example, Patent Document 1).
JP-A-8-271886 (3rd term, FIG. 2)

  However, in the conventional direct type illumination device, in order to perform uniform illumination, a light source such as a cold cathode tube capable of isotropic illumination must be used as the light source, and an LED having high directivity of emitted light The device could not be used even with high luminous efficiency and high luminance. Therefore, it has been impossible to realize a thin direct type illumination device using an LED element.

  The illumination device of the present invention includes a light irradiation surface for irradiating illumination light, a light guide plate having a back surface facing the light irradiation surface, a point light source provided so that the light emission surface faces the back surface of the light guide plate, light Formed on the irradiation surface, with its apex directly above the light emission center of the point light source, with a convex light incident prism on the inner side of the light guide plate, and a plurality formed on the surface constituting the light incident prism, on the outer side And a convex prism body. With such a structure, a direct illumination type illumination device can be realized using a point light source such as an LED light source. As a result, it was possible to realize a lighting device that is thin and lightweight and that can eliminate the frame that is a non-display portion of the display device.

  According to the present invention, it is possible to provide a thin and light liquid crystal display device without a frame using an LED light source. Therefore, there is an effect that further thinning and light weight of information equipment using these liquid crystal display devices can be realized.

  In addition, since the lighting device can be configured regardless of the position and number of the LED light sources by arranging the LED light source on the back surface of the light guide plate, illumination for large liquid crystal display devices such as personal computers and liquid crystal televisions. The apparatus can be easily realized.

  The illumination device of the present invention includes a light irradiation surface for irradiating illumination light, a light guide plate having a back surface facing the light irradiation surface, a point light source provided so that the light emission surface faces the back surface of the light guide plate, light Formed on the irradiation surface, with its apex directly above the light emission center of the point light source, with a convex light incident prism on the inner side of the light guide plate, and a plurality formed on the surface constituting the light incident prism, on the outer side And a convex prism body. Furthermore, the angle formed between the component surface of the light incident prism and the perpendicular line formed on the light irradiation surface of the light guide plate is configured to be larger than the critical angle of light guided in the light guide plate.

  Further, as the prism body, a triangular prism having a ridge line substantially parallel to the light irradiation surface of the light guide plate and an apex angle of approximately 90 degrees is used, and an inclined surface adjacent to the vertex angle of the triangular prism and positioned on the light irradiation surface side of the light guide plate. The angle formed with the constituent surface of the light incident prism was approximately 90 to 135 degrees.

  Further, the prism bodies are distributed and arranged along the hyperbola on the light incident prism constituting surface. The prism body is configured to include a transmission surface that transmits the light emitted from the point light source toward the light irradiation surface, and the total area of the transmission surfaces per unit area corresponds to the light intensity irradiated from the point light source. Form in inverse proportion. Thereby, the intensity of light emitted from the light incident prism to the irradiated object can be made constant.

  Further, a plurality of light guide plates are provided. Specifically, a lighting device having a large irradiation area can be easily realized by arranging a plurality of light guide plates adjacent to each other in a planar shape or a matrix shape. That is, since each small light guide plate can be accurately manufactured by applying a semiconductor process, a large illuminating device can also be manufactured with a highly accurate luminance distribution. As a result, the light utilization efficiency can be remarkably improved, and a thin illuminating device having a large irradiation area with high luminance and uniform luminance distribution can be realized.

  In addition, on the back surface of the light guide plate, there are provided a light incident portion into which the light from the point light source is incident and a reflection portion provided to guide the inside of the light guide plate. A reflecting prism is suitable as the reflecting means provided in the reflecting portion. By providing the reflecting prism on a concentric circle with the point light source as the center, uniform illumination is possible.

  Furthermore, the display device of the present invention includes the illumination device having any one of the above-described configurations and a non-self-luminous display element that is irradiated with illumination light of the illumination device. With such a configuration, even a display device with a large display area can realize a thin display device with high brightness and uniform brightness.

  Embodiments of the illumination device of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a plan view of the illumination device of this embodiment. As shown in the drawing, in this embodiment, a plurality of light guide plates 2a, 2b, 2c, and 2d are arranged in a matrix inside the housing 5. Here, for the sake of simplicity, the case of a 2 × 2 matrix arrangement is shown, but more light guide plates may be arranged in a matrix. LED light sources 1a, 1b, 1c, and 1d are disposed as point light sources on the back surfaces of these light guide plates. Immediately above each LED light source, light incident prisms 3a, 3b, 3c, and 3d are formed. In this embodiment, these light incident prisms 3 have a reflecting surface composed of four inclined surfaces. These reflecting surfaces cross over the LED light source 1. That is, the reflecting surface of the light incident prism 3 is divided into four inclined surfaces, and the reflecting surface of the light incident prism 3 forms a quadrangular pyramid. The LED light source 1 is arranged so that its light emission center comes to the position of the apex of this quadrangular pyramid. In addition to the four divisions shown in FIG. 1, the light incident prism 3 may be divided into a larger number such as two divisions, six divisions or eight divisions.

  On the other hand, reflection prisms 4a, 4b, 4c, and 4d are formed on the back surface of each light guide plate opposite to the light irradiation surface. These reflecting prisms are arranged along concentric circles centering on each LED light source. Each light guide plate is made of a transparent polymer material. Specifically, it is formed of a polymer material such as an acrylic resin, a polycarbonate resin, or a cycloolefin resin. The light guide plate 2 can be easily manufactured by injection molding these materials. The light guide plates arranged in a matrix are supported by the housing 5. The housing 5 is formed of a normal polymer structural material. Further, between each light guide plate facing the housing 5 and the housing 5, a reflecting plate 6 is disposed as a light reflecting means.

  FIG. 2 shows a partial cross section of the illumination device of this embodiment. As shown in FIG. 2, the fine prism 4 formed on the back surface of the light guide plate 2 is formed in a convex shape inside the light guide plate 2. In this embodiment, the reflecting prism 4 is a triangular prism. The ridge line of the triangular prism faces the tangential direction of the concentric circle shown in FIG. The angle formed by the slope on the center side of the triangular prism and the perpendicular line standing on the back surface of the light guide plate 2 is 45 to 70 degrees, the slope facing the outside of the concentric circle and the perpendicular line on the back surface of the light guide plate 2 The angle formed by is 0 to 20 degrees.

  A reflection plate 7 is disposed on the back surface of the light guide plate 2, and an opening is provided at a position corresponding to the LED light source 1 of the reflection plate 7. Supply of current to the LED light source 1 is performed by a circuit line wired to the substrate 10. Further, on the reflecting surface of the light incident prism 3, prism bodies 8 having a convex shape on the outside are formed in a dispersed manner.

  FIG. 5 shows the prism body 8 formed on the reflection surface of the light incident prism 3. The LED light source 1 is disposed on the lower right side of the paper. This prism body is composed of two surfaces 8b and 8c sandwiching the ridgeline and its side surface 8a. As shown in this figure, the prism bodies 8 are arranged in a distributed manner, and are not necessarily arranged in a row. These prism bodies 8 are arranged such that when the area of the inclined surface 8b on the light irradiation surface side of the light guide plate 2 is summed per unit area, the total area is inversely proportional to the light intensity from the LED light source 1 irradiated to that portion. Is formed. As an example of the dimensions for these prism bodies 8, the height is 1 to 20 μm and the length is 5 to 50 μm. Of course, other dimensions may be used as long as the above conditions are satisfied. However, if the prism height is too high, a bright spot is generated, which is not preferable and attention is required. In the present embodiment, the prism body 8 is a triangular prism having an apex angle of approximately 90 degrees, and the inclined surface located adjacent to the apex angle of the triangular prism and located on the light irradiation surface side of the light guide plate 2 is the light incident prism 3. The angle formed with the reflecting surface is approximately 90 to 135 degrees. By setting the angle of the slope within this range, the light irradiated from the region of the light incident prism 3 can be made substantially perpendicular to the light irradiation surface of the light guide plate 2. Such a prism can be easily processed by using an injection mold processed by applying a semiconductor process.

  FIG. 3 shows a state in which the prism bodies 8 are arranged on the reflecting surface of the light incident prism 3. The prism bodies 8 are arranged along a hyperbola on the reflection surface of the light incident prism 3 as shown in FIG. However, the arrangement is not necessarily strictly aligned in a hyperbola, and it is preferable that the arrangement is slightly deviated from the hyperbola and dispersed as shown in FIG. Of the light emitted from the LED light source 1, the intensity of light having the same emission angle is equal. Further, when a portion where light having the same emission angle intersects the reflecting surface of the light incident prism 3 is plotted, a hyperbola is obtained. Therefore, the light intensities incident on the prism bodies 8 arranged on the same hyperbola on the reflecting surface of the light incident prism 3 are equal. In general, the LED light source 1 has a light intensity distribution depending on its light emission angle. Therefore, by arranging these prism bodies 8 so that the area density of the slopes of the prism bodies 8 on the hyperbola facing the irradiated body is inversely proportional to the emission intensity distribution of the LED light source 1, a uniform intensity distribution is obtained. Can be extracted to the upper surface of the light incident prism 3.

  FIG. 4 shows a cross section along the broken line BB ′ in FIG. However, only one prism body 8 formed on the reflection surface of the light incident prism 3 is drawn for easy viewing of the drawing. One example of light emitted from the LED light source 1 is indicated by an optical path 20 in FIG. The light path 20 is refracted and incident on the light guide plate 2 and then directly enters the light irradiation surface of the light guide plate 2. The incident angle to the light irradiation surface of the light guide plate 2 is assumed to be χ. On the other hand, an angle formed by the light incident prism 3 and a perpendicular line standing on the light irradiation surface of the light guide plate 2 is defined as θ. At this time, when θ is larger than the critical angle satisfying the total reflection condition for the light from the LED light source 1, the light guide plate 2 directly from the LED light source 1 as shown by the optical path 20 in FIG. All the light incident on the light irradiation surface has an incident angle larger than the critical angle, and is totally reflected by the light irradiation surface, and is repeatedly reflected inside the light guide plate 2 to be guided. The critical angle depends on the refractive index of the material forming the light guide plate 2 and the wavelength of light used, but is about 43 degrees. Further, the light 21 incident on the reflecting surface other than the prism body 8 of the light incident prism 3 is totally reflected and guided to the inside of the light guide plate 2 in order to enter the reflecting surface at an incident angle greater than the critical angle. To do.

  On the other hand, among the slopes constituting the prism body 8, the light 22 incident on the slope on the light irradiation surface side of the light guide plate 2 is transmitted through the slope because the incident angle is equal to or less than the critical angle. Will be irradiated. Thus, the intensity of the light transmitted through the prism body 8 is proportional to the area of the slope of the prism body 8 facing the light irradiation surface side. Therefore, in order to make the intensity of light irradiated to the irradiated object from the light incident prism 3 constant, the area of the inclined surface facing the light irradiation surface side of the light guide plate 2 in the prism body 8 is reduced from the LED light source 1. Must be inversely proportional to the light intensity incident on the.

  FIG. 6 shows an example of an optical path inside the light guide plate of the illumination device of the present invention. First, the case of the optical path 23 will be described. The light emitted from the LED light source 1 enters the light guide plate 2, is totally reflected by the reflecting surface of the light incident prism 3, and then totally reflected again by the light irradiation surface of the light guide plate 2, and is formed on the back surface of the light guide plate 2. Is incident on the reflecting prism 4. The reflecting prism 4 reflects incident light to the light irradiation surface side of the light guide plate 2. Since the reflected light is deflected by the reflecting prism, it enters the light irradiation surface of the light guide plate 2 as light having a critical angle or less, and is emitted from the surface toward the irradiated body.

  Next, the case of the optical path 25 will be described. In this case, after the light emitted from the LED light source 1 enters the light guide plate 2, it passes through the slope facing the light irradiation surface side of the fine prism 8 formed on the reflection surface of the light incident prism 3 and is directly covered. It is emitted toward the irradiation body.

  On the other hand, in the case of the optical path 24, the light emitted from the LED light source 1 is directly incident on the light emitting surface of the light guide plate 2 and totally reflected, and enters the reflecting prism 4 formed on the back surface of the light guide plate 2. The reflecting prism 4 reflects incident light to the light irradiation surface side of the light guide plate 2. Since the reflected light is deflected by the reflecting prism, it enters the light irradiation surface of the light guide plate 2 as light having a critical angle or less, and is emitted from the surface toward the irradiated body.

  Further, as shown in FIG. 1, since the light guide plates are arranged in a matrix in the illumination device of the present embodiment, there is also light incident from an adjacent light guide plate as indicated by the optical path 26. Thus, since the light from another light guide plate is guided over a plurality of light guide plates, the luminance distribution of the entire lighting device is improved. Since the light is deflected many times each time multiple reflection is repeated inside the light guide plate 2, a lot of light escapes from the back and side surfaces of the light guide plate 2. In order to reuse these lights, light reflecting plates 6 and 7 are disposed on the back and side surfaces of the light guide plate 2, and these lights are reflected and returned to the inside of the light guide plate 2 again.

  Further, the reflecting prism 4 formed on the back surface of the light guide plate 2 is arranged so that the area density of the reflecting surface increases as it goes outside the concentric circle with the LED light source 1 as the center. Specifically, the height, length, or both of the reflecting prisms 4 are formed so as to increase sequentially. Or although the dimension of each reflective prism 4 is constant, it forms so that arrangement density may become large sequentially. By doing in this way, the emitted light intensity from the light irradiation surface of the light guide plate 2 becomes uniform. Further, the diffusion plate 9 is disposed for the purpose of making the irradiation light from the light guide plate 2 more uniform. By disposing the diffusing plate 9, it is possible to reduce the influence of bright spots generated on the outer periphery and apex of the light incident prism 3. Moreover, it turns out that the unnecessary part (what is called a frame) of the periphery of an illuminating device required in order to arrange | position an LED light source with the conventional sidelight type illuminating device becomes unnecessary except a housing part.

Specific examples of the present invention will be described below.
(Concrete example)
The lighting device shown in FIG. 1 was produced as follows. A light incident prism having a reflective surface divided into four with an angle of 50 degrees between the light guide plate arranged in a matrix and having a dimension of 35 mm × 43 mm × 0.6 mm and a perpendicular to the light emitting portion of the light guide plate at the center. Formed. The light incident prism has a vertical angle of 0.5 mm and a white LED light source with two chips in one package. The light incident prism is placed in close contact with the back surface of the light guide plate at the vertical angle of the light incident prism. did. All the prism bodies 8 formed on the reflecting surface of the light incident prism have the same shape. That is, the prism body has an apex angle of 90 degrees, an angle formed by the inclined surface on the light irradiation surface side of the light guide plate with the reflecting surface of the light incident prism is 100 degrees, the height is 5 μm, and the length in the ridge line direction is 10 μm. These prism bodies are arranged in the vicinity of the hyperbola of the reflecting surface of the light incident prism by adjusting the number so as to be inversely proportional to the light irradiation intensity from the LED light source.

  In addition, on the back surface of the light guide plate, reflecting prisms were arranged concentrically with the LED light source as the center. The shapes of these reflecting prisms are all the same, the height is 60 μm, the angle formed by the vertical line standing on the back surface of the light guide plate and the surface on the center side of the concentric circle is 70 degrees, and the other surface is set on the back surface of the light guide plate. The angle formed with the perpendicular was 10 degrees. The length of the reflecting prism in the ridgeline direction was 20 μm. The pitch of concentric circles was 50 μm. The number of the reflecting prisms was arranged so as to be proportional to the fourth power of the number of concentric circles as the distance from the center of the circle increased. Such light guide plates are arranged in a matrix of 10 × 10 sheets to provide an illuminating device for an 18-inch liquid crystal display device. A bead diffusion sheet having a haze value of 90% was used as the diffusion plate.

  With the above configuration, a bright illumination device having a maximum brightness of 3000 Cd / m 2 and a good and uniform brightness distribution of 75% over the entire illumination surface was obtained.

It is a top view which shows typically the illuminating device by this invention. It is sectional drawing which shows typically the illuminating device by this invention. It is a schematic diagram which shows the arrangement | sequence of the prism body provided in the light-incidence prism of the illuminating device by this invention. It is sectional drawing which shows typically the optical path in a light-guide plate. It is a perspective view which shows the structural example of a prism body typically. It is sectional drawing which shows typically the optical path in the illuminating device by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED light source 2 Light guide plate 3 Light incident prism 4 Reflection prism 5 Housing 6, 7 Light reflection layer 8 Prism body 9 Diffusion plate

Claims (9)

A light irradiating surface for irradiating illumination light, and a light guide plate having a back surface facing the light irradiating surface;
A point light source provided such that a light exit surface faces the back surface of the light guide plate;
The light irradiation surface is formed and has its apex directly above the light emission center of the point light source, and a light incident prism having a convex shape inside the light guide plate,
An illuminating device comprising: a plurality of prism bodies that are formed on the surface of the light incident prism and are convex outward.   2. The angle formed between a surface of the light incident prism and a perpendicular formed on a light irradiation surface of the light guide plate is larger than a critical angle of light guided in the light guide plate. The lighting device described. The prism body is a triangular prism having a ridge line substantially parallel to the light irradiation surface of the light guide plate and an apex angle of about 90 degrees,
3. The illumination according to claim 1, wherein an angle formed by an inclined surface adjacent to the apex angle of the triangular prism and located on the light irradiation surface side of the light guide plate with a constituent surface of the light incident prism is approximately 90 to 135 degrees. apparatus.   The illumination device according to any one of claims 1 to 3, wherein the prism bodies are arranged in a distributed manner along a hyperbola on the light incident prism constituting surface. The prism body includes a transmission surface that transmits light emitted from the point light source toward the light irradiation surface,
The lighting device according to any one of claims 1 to 3, wherein the total area of the transmission surfaces per unit area is formed in inverse proportion to the light intensity emitted from the point light source. .   The illuminating device according to claim 1, comprising a plurality of the light guide plates.   The light incident part into which the light of the said point light source injects, and the reflection part provided in order to guide the inside of the said light-guide plate were provided in the said back surface. Lighting equipment.   The lighting device according to claim 7, wherein the reflecting portion is provided with a reflecting prism.   A display device comprising: the illumination device according to claim 1; and a non-self-luminous display element that is irradiated with illumination light of the illumination device.

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