JP2007234385A - Backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device with a low-profile size, high optical utilization efficiency, and less variations in luminance. <P>SOLUTION: The numeral 11 denotes a light emitting diode (hereinafter referred to as "LED"). The numeral 12 denotes a reflector having a parabolic mirror. The parabolic mirror on the reflector 12 is in the shape of a topside paraboloid formed when the paraboloid in all directions is cut by a plane crossing the paraboloid's axis line horizontally (such a one-side paraboloid separated by a plane crossing the axis line is hereinafter referred to as "half-paraboloid"). The numeral 13 denotes a half-round cover, to which the opening side edge of the reflector 12 touches internally. Further, a light emitting point of the LED 11 is positioned at a focal point of the parabolic mirror on the reflector 12. Most of the lights outgoing from the LED are collected at the reflector 12 to be fed into a light guide plate 40 as parallel lights. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technology of a backlight device.

In non-light-emitting display devices such as liquid crystal panels that have been widely used in recent years, EL (Electro Luminescence) lamps, cathode fluorescent lamps (CFL: Cathode Fluorescent Lamps), and the like are used as backlight light sources (for example, Patent Document 1).
There are two types of backlight devices for such non-light emitting display devices, one using a direct method and the one using an edge light method. Here, the backlight devices of the direct type and the edge light type will be described below with reference to FIG. 13 and FIG.
FIGS. 13A and 13B are a top view and a side view of the backlight device 2 of the direct type, respectively, and FIG. 13C is a diagram of light rays emitted from the light source 211 of the backlight device 2. It is the figure which showed direction roughly. As shown in FIG. 13B, the direct-type backlight device has a plurality of light sources 211 such as CFLs arranged in a plane in a direction parallel to the surface direction of the light guide plate 240. In addition, the arrow shown in FIG.13 (c) shows the direction of the light ray of the light from the light source 211 roughly.
Next, FIG. 14 is a diagram for explaining the configuration of the backlight device 3 based on the edge light system. As shown in FIG. 14, the edge light type backlight device 3 is configured by arranging one or a plurality of light sources 311 such as CFLs in a direction parallel to the end face of the light guide plate 340. The arrow shown in FIG. 14 schematically shows the direction of the light beam from the light source 311. The light emitted from the light source 311 is reflected by the reflective dots 341 of the light guide plate 340 and emitted from the surface of the light guide plate 340, as shown in the figure, and these lights are diffused sheet P1, prism sheet P2, and prism sheet P3. Through the liquid crystal panel. In this way, light is diffused and scattered in the light guide plate 340 to realize a light source on the surface, thereby realizing a reduction in thickness and power consumption.
JP-A-2005-347062

Incidentally, in the case of a direct-type backlight device, as shown in FIG. 13C, the light emitted in the P1 direction is emitted from the surface of the light guide plate 240 and reaches the viewer's eyes, but in the P2 and P3 directions. The light emitted to the viewer does not reach the viewer's eyes, or even if it reaches, the light is attenuated or has poor controllability.
Also in the case of the edge light method, as shown in FIG. 14, there are light rays that pass directly from the light guide plate 340 to the display surface side, and light rays that exit from the display surface while being reflected and attenuated many times. is there. Thus, the directions and intensities of the light beams emitted from the light guide plate 340 are different from each other, and messy light having no regularity is emitted from the light guide plate 340. In particular, when a large light source such as CFL is used, the range of the light emission source is widened, so that the light reflected by the reflector 312 becomes cluttered, so that the light emitted from the light guide plate 340 is It becomes even more cluttered.

As described above, in the conventional backlight device, the light emitted from the light guide plate becomes messy with no regularity, and thus the amount of light emitted from the surface of the light guide plate may be uneven. . For this reason, it is difficult to maintain the uniformity (brightness uniformity of the display surface) of the liquid crystal panel.
In order to avoid this problem, it is necessary to provide a large number of reflective dots on the light guide plate. However, if a large number of reflective dots are provided, there is a problem that the mold cost increases.
Also, in the edge light type backlight device, when the distance between the light source and the end face of the light guide plate is large, a lot of light that does not enter the end face of the light guide plate is generated. The amount will also decrease.

  In particular, when CFL is used as the light source, the light source 311 is larger than the reflector 312 as shown in FIG. There is also a problem that usage efficiency is low.

  The present invention has been made in view of the above-described background, and an object thereof is to provide a backlight device that is thin, has high light utilization efficiency, and has little unevenness.

A backlight device according to a preferred aspect of the present invention is a flat three-dimensional object comprising a plurality of light sources, a substrate on which the light sources are provided, an upper surface and a lower surface that are arranged to face each other, and a side surface that connects edges of the upper surface and the lower surface. And a part of the side surface is an incident end surface on which light is incident, and the light incident from the incident end surface is reflected by the lower surface, whereby the light guide plate emitted from the upper surface and each of the light sources A curved surface having a focal point and an axis passing through the focal point, and at least a part of a surface on one side separated by a plane passing through the axis is a reflective surface, and each light source is the reflective surface And a plurality of reflecting plates that are open from one side along the axis and serve as exits for the reflected light of the light source, and the light source is located at the focal point. Emanating from the light source Wherein the light emitted from the light and the reflection plate is said light source to be incident on the incident end face, the positional relationship between the reflection plate and the light guide plate is set.
In this aspect, a filling material that fills a space formed between the light source, the substrate, and the reflecting plate may be provided.
In addition, the end surface of the filler that is located at the exit of the reflected light in the reflection plate may be a curved surface.
Or you may make it provide the lens provided so that the end surface of the said filling material might be covered in the position of the exit of the reflected light in the said reflecting plate.
In the above-described aspect, the curved surface may be formed by a surface on one side separated by a plane passing through the axis with respect to a parabolic surface, a hyperbolic surface, or an elliptical surface.
Alternatively, the lower surface of the light guide plate may be formed so as to approach the upper surface as the distance from the incident end surface in the light entering direction increases.
In addition, a plurality of reflective dots that protrude toward the inside of the light guide plate and reflect light from the light source may be formed on the lower surface of the light guide plate.
Alternatively, a plurality of dimples that are concave with respect to the inside of the light guide plate and reflect light from the light source may be formed on the lower surface of the light guide plate.

  According to the present invention, it is possible to provide a backlight device that is thin, has high light utilization efficiency, and has little unevenness.

<A: First Embodiment>
FIG. 1 is a perspective view showing an appearance of a backlight device 1 according to the first embodiment of the present invention. 2 and 3 are a top view and a side view of the backlight device 1 shown in FIG. 1, respectively. In FIG. 1, 10 is a light source device provided with a light source. As shown in the figure, the backlight device 1 is provided with a plurality of light source devices 10. Reference numeral 30 denotes a substrate on which a plurality of light source devices 10 are provided.

Here, the configuration of the light source device 10 will be described below with reference to FIGS. 5 to 7.
FIG. 5 is a perspective view showing an overview of the light source device 10. In the figure, 11 is a light emitting diode (hereinafter referred to as “LED”). Reference numeral 12 denotes a reflector having a parabolic mirror. The parabolic mirror of the reflector 12 has an upper paraboloid when cut along a plane that horizontally crosses its axis with respect to an omnidirectional paraboloid (hereinafter, one side separated by a plane that crosses the axis in this way). The paraboloid is called “semi-paraboloid”. Reference numeral 13 denotes a semi-cylindrical cover, and the opening edge of the reflector 12 is inscribed in the cover 13. The light emitting point of the LED 11 is located at the focal point of the parabolic mirror of the reflector 12.

  Next, FIG. 6 is a top view of the light source device 10 shown in FIG. FIG. 7 is a front view of the light source device 10. FIG. 8 is a cross-sectional view taken along line A-A ′ shown in FIG. 6. The illumination light emitted from the LED 11 is emitted as a substantially parallel light beam by the reflector 12, as indicated by arrows in FIGS.

As shown in FIGS. 7 and 8, the LED 11 is attached to the base portion 15a, and the lower end of the base portion 15a is attached to the heat sink 15b. Thereby, the heat emitted from the LED 11 is radiated through the heat sink 15b. A resin mold 15c covers the LED 11, the base portion 15a, and the heat sink 15b. Electrodes 15d and 15d extend from the mold 15c, and the anode and cathode of the LED 11 are bonded to the electrodes 15d and 15d. The electrodes 15d and 15d are joined to the wiring pattern of the substrate 30 by soldering or the like. A drive circuit for controlling the light emission of the LED 11 is attached via this wiring pattern (not shown). Further, the drive circuit is attached to another substrate different from the substrate 30. The substrate 30 to which the LEDs 11 are attached is provided so as to be parallel to the parallel rays emitted from the reflector 12.
Further, as shown in FIGS. 1 to 3, each reflector 12 of the light source device 10 is arranged such that its emission port faces the same direction.
The size of the light source device 10 is very small and has a shape of about 2 mm × 2 mm × 2 mm. However, it is possible to apply even those having a size of about 50 mm × 50 mm × 50 mm or more. In order to make the backlight device 1 thin, a size of about 2 mm × 2 mm × 2 mm is preferable.

Returning to the description of FIGS. In the figure, reference numeral 20 denotes an electric cable, which is connected to a drive circuit that controls the light emission of the LED 11. In this case, the drive current output from the drive circuit is supplied to each LED 11 via the electric cable 20 so that the light emission of each LED 11 is controlled. Reference numeral 40 denotes a light guide plate that reflects light emitted from the light source device 10. In the backlight device 1 according to the present embodiment, the positional relationship between the LED 11, the reflector 12, and the light guide plate 40 is such that the light emitted from the LED 11 and the light emitted from the reflector 12 enter the end surface 40 a of the light guide plate 40. Is set. The light guide plate 40 is made of, for example, acrylic, and has a flat plate shape as shown in the drawing. In addition, as shown in FIG. 4, the light guide plate 40 is formed so that its lower surface gets closer to the upper surface as it moves away in the light entering direction. For this reason, the thickness of the end surface 40a on which the light emitted from the LED is incident is thinner than the thickness of the opposing end surface 40b.
As shown in FIG. 3, a display device 5 such as a liquid crystal panel is installed on the light source device 10. Light emitted from the light source device 10 is reflected by the lower surface of the light guide plate 40 and emitted from the upper surface. Then, the light enters the display device 5. In this way, when the light from the backlight device 1 is incident on the display device 5, an image displayed on the display device 5 is brightened.

  Reference numeral 50 denotes a reflective dot provided on the lower surface of the light guide plate 40 so as to protrude toward the inside of the light guide plate 40. The outline of the reflective dot 50 is substantially elliptical. As shown in FIG. 4, a plurality of reflective dots 50 are provided in a matrix on the entire lower surface of the light guide plate 40. The reflective dots 50 are shaped such that light emitted from the light source device 10 as parallel light can reach the display device 5 with maximum brightness and good uniformity.

  Under the configuration described above, when light is emitted from the light source device 10 of the backlight device 1, the emitted light is reflected by the reflector 12 and enters the end face 40 a of the light guide plate 40 as a substantially parallel light beam. To do. The light incident on the end surface 40 a travels in the light guide plate 40 as parallel rays, and is emitted from the surface of the light guide plate 40 while being diffused and condensed by the reflective dots 50 provided on the light guide plate 40. The light emitted from the backlight device 1 in this way illuminates the display device 5, and thereby an image or the like is displayed on the display device 5.

At this time, since the light incident on the end surface 40a of the light guide plate 40 is converted into parallel light by the reflector 12, most of the light rays from the LED 11 are in a regular state, that is, in a controlled state as parallel light. 40 is incident on the end face 40a. In addition, since the reflective dot 50 is designed in advance to reflect parallel rays with maximum brightness and good uniformity, the light incident on the end surface 40a of the light guide plate 40 is reflected by the reflective dot 50. Reflected as light controlled by 50.
As described above, in the present embodiment, the light emitted from the LED 11 can be incident on the end surface 40a of the light guide plate 40 in a state (parallel light beam) controlled by the reflector 12, and further, the light incident on the end surface 40a. Therefore, the light can be efficiently emitted from the surface of the light guide plate 40.

  Furthermore, in this embodiment, the output light from LED11 can be efficiently collected by using the semiparabolic reflector 12.

Moreover, since the light emitted from the reflector 12 is parallel light, the light can be delivered to a place away from the light source device 10. This is similar to the principle that light from a lighthouse, for example, reaches far away.
Furthermore, since the light guide plate 40 of the present embodiment is formed so that its thickness decreases from the end surface 40a to the end surface 40b, the light emitted from the LEDs 11 is emitted almost uniformly from the end surface 40a to the end surface 40b of the light guide plate 40. Can be reached. As a result, light that is uniform over the entire surface 40c of the light guide plate 40 is emitted, so that unevenness can be reduced and uniformity can be maintained.

  In addition, since the light incident on the end surface 40a of the light guide plate 40 is a substantially parallel light beam, the intensity of the incident light is substantially the same in each of the reflective dots 50. Therefore, the reflective dots 50 are designed uniformly. However, the light beam as designed can be supplied to the display device 5.

In the conventional edge light type backlight device, the light incident on the light guide plate is messy with no regularity. In other words, since the angle and intensity of light incident on the light guide plate varied, it was difficult to design a reflective dot so that light could be emitted with the maximum brightness and good uniformity. It was.
On the other hand, in the present embodiment, the light incident on the end face 40a of the light guide plate 40 is not a messy and irregular regular light, but is an orderly parallel light beam, and the intensity of the incident light is a reflective dot. 50 is substantially the same, it is possible to easily design the reflective dot 50.

<B: Second Embodiment>
Next explained is the second embodiment of the invention.
The backlight device according to this embodiment is different from the backlight device 1 shown in the first embodiment described above in that the configuration of the light source device 10 is different, and other components are shown in the first embodiment. It is similar to that. Therefore, in the following description, the same code | symbol is provided about the component similar to the backlight apparatus 1 shown in 1st Embodiment, and the description is abbreviate | omitted suitably.

  FIG. 9 is a top view of the light source device 10A used in the backlight device of this embodiment, and corresponds to the top view shown in FIG. 6 in the first embodiment described above. This light source device 10A is different from the light source device 10 in the first embodiment described above in that a space formed by the substrate 30 and the inner surface of the reflector 12 is filled with a filler 60 such as silicon. is there. The filler 60 may be any material that has good light extraction efficiency and can fix the reflector 12, the LED 11, and the substrate 30. Further, an end surface 60a that is an end surface of the filler 60 and is located at the reflected light exit of the reflector 12 has a convex curved surface as shown in FIG. 9, and this curved surface has the same function as the convex lens. is doing. The filling 60 has a function of fixing each component of the light source device 10A, and the light source device 10A is formed as an integral type.

In this embodiment, since the lens is integrally formed with a filler such as silicon, the utilization efficiency of light emitted from the light source can be further increased.
In addition, since the end surface 60 a of the filling 60 has a curved surface and has the same function as the convex lens, the output light from the LED 11 is collected in the filling 60. Therefore, by arranging a reflective member and a reflective shape suitable for the light condensing position on the lower surface of the light guide plate 40, the same effects as those of the above-described embodiment can be obtained.

<C: Modification>
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with another various form. An example is shown below.
(1) In the second embodiment described above, the convex lens is formed by making the end surface of the filler 60 a curved surface. Thus, the lens formed by the filler is not limited to a convex lens. For example, as shown in FIG. 10, a concave lens may be formed by making the end surface of the filler 60B a curved surface. If the light source device 10B having a concave lens as shown in FIG. 10 is used, the output light from the LED 11 can be efficiently diffused.
In the second embodiment described above, the convex lens is formed by the filler 60. However, the filler and the lens (convex lens or concave lens) do not have to be integrated, for example, as shown in FIG. In addition, a lens (convex lens or concave lens) 61 may be provided at the position of the reflected light exit of the reflector 12 so as to cover the end face of the filler 60C. Even in this configuration, similarly to the second embodiment described above, it is possible to efficiently collect (or diffuse) the output light from the LED.
The space formed between the LED, the substrate and the reflecting plate may be simply filled without forming the lens with the filler.

(2) In each of the above-described embodiments, the parabolic mirror of the reflector has a semi-parabolic surface (one parabolic surface separated from the omnidirectional parabolic surface by a plane crossing its axis). However, the shape of the reflector is not limited to this, and may be a shape in which a part of the semi-parabolic surface is a reflecting surface, for example. Alternatively, the reflection curved surface may be formed by using at least a part of a surface on one side separated from a hyperbolic surface or an elliptical surface by a plane passing through its axis, not limited to a parabolic surface. FIG. 12 shows an example of a light source device 10D using a reflector 12D having a reflection curved surface on one side separated from the elliptical plane by a plane passing through its axis.

(3) The light guide plate 40 is not limited to the shape used in the above-described embodiment. Any shape may be used as long as it has an incident end face on which light is incident, a lower surface that reflects light incident from the incident end face, and an upper surface that emits light reflected by the lower surface. In this case, in order to uniformly irradiate light on the flat display device from behind, the light guide plate is formed in a flat plate shape, and the upper surface and the lower surface must have a shape and an area corresponding to the size of the display device. is there.
That is, the light guide plate has a flat three-dimensional shape composed of an upper surface and a lower surface arranged opposite to each other and a side surface connecting edges of the upper surface and the lower surface, and a part of the side surface becomes an incident end surface on which light is incident, The light incident from the incident end face may be formed so as to be emitted from the upper surface by being reflected by the lower surface.

(4) In the embodiment described above, the reflection dot 50 is provided on the light guide plate 40 so that the light is diffused and collected by the reflection dot 50. However, instead of the reflection dot, the reflection dot 50 is provided inside the light guide plate. On the other hand, a plurality of dimples having a concave shape and reflecting light from the light source may be formed. Light may be uniformly output from the upper surface of the light guide plate by appropriately diffusing or condensing the light with the dimples.

It is a perspective view which shows the external appearance of a backlight apparatus. It is a top view of a backlight device. It is a side view of a backlight device. It is a figure which shows schematically the structure of the reflective dot of a light-guide plate. It is a perspective view which shows the external appearance of a light source device. It is a top view of a light source device. It is a front view of a light source device. FIG. 7 is a cross-sectional view taken along line A-A ′ of FIG. 6. It is a top view of the light source device which has a convex lens. It is a top view of the light source device which has a concave lens. It is a top view of the light source device which has a concave lens. It is a top view of the light source device which has the reflector of an ellipsoidal mirror. It is a figure which shows the structure of the backlight apparatus of the conventional direct type. It is a figure which shows the structure of the backlight apparatus of the conventional edge light system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Backlight apparatus, 5 ... Display device, 10 ... Light source apparatus, 11 ... LED, 12 ... Reflector, 13 ... Cover, 20 ... Electric cable, 30 ... Substrate, 40 ... Light guide plate, 40a ... End face, 50 ... Reflection dot 60 ... filler, 60a ... end face.

Claims (8)

Multiple light sources;
A substrate provided with the light source;
It has a flat three-dimensional shape consisting of an upper surface and a lower surface arranged opposite to each other and a side surface connecting the edges of the upper surface and the lower surface, and a part of the side surface becomes an incident end surface on which light is incident, and is incident from the incident end surface A light guide plate that is emitted from the upper surface by reflecting light on the lower surface;
A curved surface provided for each of the light sources and having a focal point and an axis passing through the focal point, and at least a part of a surface on one side separated by a plane passing through the axis is a reflective surface, A plurality of reflecting plates that are covered from the side facing the substrate by the reflecting surface and that are open on one side along the axis and serve as an exit of reflected light of the light source;
The light source is located at the focal point, and the positional relationship between the light source, the reflecting plate, and the light guide plate is such that light emitted from the light source and light emitted from the reflecting plate are incident on the incident end surface. A backlight device characterized by being set.   The backlight device according to claim 1, further comprising a filler that fills a space formed between the light source, the substrate, and the reflector. 3. The backlight device according to claim 2, wherein an end surface of the filler which is an end surface located at an exit of reflected light in the reflection plate is a curved surface. The backlight device according to claim 2, further comprising: a lens provided at a position of an exit of the reflected light in the reflecting plate so as to cover an end surface of the filler.   5. The backlight device according to claim 1, wherein the curved surface is formed by a surface on one side separated by a plane passing through an axis with respect to a parabolic surface, a hyperbolic surface, or an elliptical surface. . The backlight device according to any one of claims 1 to 5, wherein the lower surface of the light guide plate is formed so as to approach the upper surface as the distance from the incident end surface increases in the light entering direction. The reflective surface which protrudes toward the inside of the said light-guide plate, and reflects the light from the said light source is formed in the said lower surface of the said light-guide plate. Backlight device. The back according to any one of claims 1 to 6, wherein a plurality of dimples that are concave with respect to the inside of the light guide plate and reflect light from the light source are formed on the lower surface of the light guide plate. Light equipment.

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