JP2015115128A - Reflection plate for backlight of flat display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection plate for a backlight of a flat display device using a lateral radiation light source capable of obtaining even illuminance over the whole surface even when a distance with a display surface is small.SOLUTION: A plurality of sets of flat surface parts P1 to P5 and difference parts D1 to D4 which surround lateral radiation light sources 51 and adjoin each other inward and outward are provided on respective unit reflection plates 52 constituting a flat surface display device such that angles of respective difference parts D1 to D4 have such a round shape or an oblique shape as to reflect light radiated to lateral side from the light source 51 upward. Further, a plurality of protrusions 54 are preferably disposed on respective flat plane parts P1 to P5. Accordingly, light radiated from the lateral side of the light source 51 is reflected upward and the even illuminance can be obtained on the whole surface of a display surface.

Description

  The present invention relates to a reflector for backlight of a flat display device such as a liquid crystal television.

  In flat display devices such as liquid crystal televisions, it is necessary to irradiate the display surface with light from the back of a surface on which a large number of display elements are arranged in a two-dimensional manner (hereinafter referred to as “display surface”). From the viewpoint of uniformity of illuminance on the entire display surface, the direct type that arranges multiple light sources evenly on the back side is often used instead of the conventional side type that arranges multiple light sources (LED light sources) on the side. It is becoming.

  In the direct type light source, in order to irradiate the display surface with light from discretely arranged light sources as evenly as possible, as shown in FIG. 1, a diffusion plate is disposed between the light source 11 and the display surface 12 arranged in a two-dimensional manner. 13 is arranged. However, in order to make the illuminance as uniform as possible on the entire display surface 12, the distance between the light source 11 and the display surface 12 (diffusion plate 13) is increased due to the fundamental problem that the light sources 11 exist only discretely. Alternatively, a method of increasing the arrangement density by increasing the number of light sources 11 must be adopted. However, the former method increases the thickness of the flat display device, and the latter method increases the cost.

  Therefore, as shown in FIG. 2, by devising the lens of the LED light source 21, the light from the light source is emitted from the side surface instead of the front surface, and the light emitted from the side surface is curved. A method of reflecting the light toward the front by the reflecting plate 22 has been devised.

JP 2008-270144 A

  In the reflection plate 22 described in Patent Document 1, the shape of the reflection plate 22 is such that light emitted from the LED light source 21 to the side is reflected as evenly as possible as a whole (upward in FIG. 2A). In the vicinity of the light source 21, the slope is small and is set to be a continuous curve in which the slope increases as the distance from the light source 21 increases. However, if the distance between the LED light source 21 and the display surface (diffusion plate 23) is reduced, the difference in illuminance between the portion directly above the LED light source 21 and the portion away from it will inevitably occur, making it difficult to uniformly illuminate the entire surface. It was.

  The present invention has been made in view of the above points, and an object of the present invention is to use a side-emitting light source that can obtain uniform illuminance over the entire surface even if the distance to the display surface is small. An object of the present invention is to provide a backlight reflector for a flat display device.

  In order to solve the above-described problems, the backlight reflector of the flat display device using the side emission light source according to the present invention is a set of a planar portion and a step portion adjacent to each other inside and outside the light source. And the corner of each stepped portion has a shape that reflects upward the light emitted from the light source to the side.

  Here, “upward” refers to the direction of the display surface as viewed from the side radiant light source, and “side” of the “side radiant light source” refers to a direction substantially perpendicular thereto. It is independent of the direction of gravity. An LED is typically used as the light source in the present invention, but other light sources such as a light bulb, a fluorescent lamp, or a cold cathode tube may be used.

  In the backlight reflector according to the present invention, it is desirable that a plurality of protrusions be provided on the flat portion. The plurality of protrusions allow light to be reflected upward from the flat portion.

  As described above, according to the present invention, when a side-emitting light source is used, the difference in illuminance between the portion directly above the light source and the portion away from the light source can be reduced. Even if the distance is small, uniform illuminance can be obtained over almost the entire display surface.

The schematic block diagram of the cross section of the conventional reflector for direct type | mold backlights. It is a schematic block diagram of a conventional reflector for a backlight using a side-emitting LED light source, and is a cross-sectional view of a unit reflector (a), an overall plan view (b), a cc cross-sectional view (c) and dd Sectional view (d). 1 is an overall plan view of a reflector for backlight that is an embodiment of the present invention. The top view (a), center sectional view (b), enlarged sectional view (c) of one side of the unit reflecting plate of the reflective plate for backlight of the same embodiment, and enlarged sectional view (d) of one side of the modified example. The top view (a) of the unit reflecting plate of the reflecting plate for backlights which is another Example of this invention, and the enlarged view of a part of the cross section (c). The top view (a) of a square unit reflecting plate which is another Example of this invention, and the top view (b) of a rectangular unit reflecting plate.

  Hereinafter, a direct-type illumination flat display device using a reflector for backlight according to the present invention will be described with reference to the drawings. FIG. 3 is a plan view showing a state in which the display surface of the flat display device 30 of this embodiment is removed. As shown in FIG. 3, the flat display device 30 is provided with 6 × 3 = 18 LED light sources 31 as light sources. The LED light source 31 of the flat display device 30 of the present embodiment is a side emission type. A unit reflector 32 is provided for each LED light source 31, and a backlight reflector is formed by the 6 × 3 unit reflector 32 as a whole of the flat display device 30.

  A plan view of one LED light source and its unit reflector 32 is shown in FIG. 4 (a), and a central sectional view thereof is shown in FIG. 4 (b). As shown in FIG. 4 (a), the unit reflector 32 of this embodiment surrounds the central LED light source 31, and gradually increases from the center toward the periphery (closer to the display surface). It consists of P1 to P5 and quadruple step portions D1 to D4 at the boundary between the five flat portions P1 to P5. As shown in FIG. 4C, which is an enlarged cross-sectional view, the step size of each stepped portion D1 to D4 (the difference in height between the flat portions P on both sides of each stepped portion D) is determined from the light source 31. It gets bigger with increasing distance. In addition, each stepped portion D1 to D4 is provided with a round shape (rounded to a quarter arc), and the size of the rounded portion (arc radius) increases according to the size of the stepped portion D. Yes. These are for compensating that the intensity of light decreases as the distance from the light source 31 increases. In addition, instead of changing the step size of each of the step portions D1 to D4, or at the same time, the distance in the radial direction from the LED light source 31 of each flat portion P1 to P5 decreases as the distance from the LED light source 31 increases. It may be made to become. In any case, the overall inclination becomes steeper as the distance from the light source increases.

In the reflector for backlight according to the present embodiment, the light emitted from the side of the light source 31 is reflected upward at each of the step portions D1 to D4. Is reflected. Further, since the rounds (circular arc surfaces) of the stepped portions D1 to D4 are reflected at a wide angle when reflected upward, further upward irradiation is possible. A diffusing plate may be disposed as usual between the backlight reflecting plate and the display surface of the present embodiment, or the display surface may be disposed directly above the reflecting plate 32 without the diffusing plate.
In this embodiment, the number of flat portions is five (the number of steps is four), but in order to perform more uniform illumination, it is preferable to increase the number of steps.

  A modification of this embodiment is shown in FIG. In the unit reflecting plate 42 of this modification, slopes are provided in place of the rounds at the step portions D1 to D4. In this unit reflecting plate 42, the same effect as that of the unit reflecting plate 32 in the above example is obtained in terms of upward reflection at each of the step portions D1 to D4, but the spread of the reflected light is slightly smaller than in the above example. However, there is an advantage that the manufacturing cost can be reduced. As described above, when the number of plane portions P (or stepped portions D) is increased, the merit of this modification is increased.

  Another embodiment of the reflector for backlight according to the present invention will be described with reference to FIG. The plan view of the entire flat display device using this is the same as FIG. Further, the overall shape (planar shape and cross-sectional shape) of the unit reflection plate 52 is the same as the example shown in FIGS. However, as shown in FIGS. 5A and 5B, the unit reflector 52 of the present embodiment is characterized in that a large number of substantially hemispherical protrusions 54 are provided on the plane portions P1 to P5. . As a result, the light emitted from the side of the LED light source 51 is reflected not only at the step portions D1 to D4 but also at the flat portions P1 to P5, so that the illumination on the display surface is uniform. Sexuality increases.

  As shown in FIG. 5 (b), the size of the protrusion 54 increases as the step D becomes higher (as the outer plane portion P increases). This is to compensate for a decrease in light intensity as the distance from the light source 51 increases, as described above. Note that the number of the protrusions 54 may be increased as the distance from the light source 51 is not changed or simultaneously with the change of the size of the protrusions 54.

  Also in this embodiment, slopes can be provided in place of the rounds in the step portions D1 to D4.

  Still another embodiment of the reflector for backlight according to the present invention is shown in FIGS. 6A, the unit reflector 62 is square, and in FIG. 6B, the unit reflector 72 is rectangular. In any of the unit reflecting plates 62 and 72, the unit reflecting plate has a plurality of sets of a plane portion P and a step portion D surrounding the light source, and each step portion D is provided with a rounded portion or an inclined portion. In addition, each planar portion P can be provided with a protrusion.

DESCRIPTION OF SYMBOLS 11, 21, 31, 41, 51 ... Light source 12 ... Display surface 13, 23 ... Diffusing plate 22, 32, 42, 52, 62, 72 ... Unit reflecting plate 30 ... Flat display device 54 ... Projection
D, D1-D4 ... Step
P, P1 to P5 ... Planar part

Claims (8)

  A reflector for a backlight of a flat display device using a side radiation light source, wherein the light reflector surrounds the light source, and has a plurality of sets of flat portions and step portions adjacent to each other inside and outside, and the corner of each step portion is the light source A reflector for backlight characterized by having a shape that reflects light emitted from the side to the side upward.   The backlight reflector according to claim 1, wherein the difference in height between the flat portions on both sides of the stepped portion increases as the distance from the light source increases.   3. The backlight reflector according to claim 1, wherein a distance in a radial direction from the light source of the flat portion decreases as the distance from the light source increases.   4. The backlight reflector according to claim 1, wherein each of the step portions is provided with a radius.   The reflector for backlight according to any one of claims 1 to 3, wherein each of the step portions is provided with a slope.   6. The backlight reflecting plate according to claim 1, wherein a plurality of protrusions are provided on each of the flat portions.   The backlight reflector according to claim 6, wherein the protrusion is larger at a flat portion far from the light source.   8. The backlight reflector according to claim 6, wherein the number of the protrusions is larger in a plane portion far from the light source. 9.

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