JP2007042479A - Backlight - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight which can make a good use of light reflected repeatedly in a light guide plate. <P>SOLUTION: A backlight has a light source 2 facing a incident surface 1c of one end of a light guide plate of which one of the surfaces is an outgoing surface 1a and the other is a reflecting surface 1b, and the reflecting surface 1b of the light guide plate 1 is making an inclined surface from the side of the incident surface 1c toward the end of the rear side drawing near the outgoing surface 1a. On the whole of the reflecting surface 1b are provided with light reflecting recess parts with a flat inclined surface connected with a curved inclined surface of a partially circular arc. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a backlight.

  FIG. 12 is a side view showing a configuration of a conventional backlight. 13 is an enlarged view of the light guide plate 41. FIG. 13 (a) is a cross-sectional view, and FIG. 13 (b) is a plan view from the bottom side of the recess 44. FIG. 41 is a light guide plate, 41a is an exit surface, 41b is a reflection surface, 41c is a light entrance surface, 41d is a light exit surface, 42 is a light source, 43 is a substrate, 44 is a recess, 44a is a flat slope of the recess 44, 44b is a recess 44 , 45a represents incident light, and 45b represents reflected light. As shown in FIG. 12, a light source 42 is disposed on one end surface of the light guide plate 41, and light enters from the light incident surface 41 c of the light guide plate 41. The incident light 45a travels by being totally reflected in the light guide plate 41, and its angle can be changed by the recess 44 provided in the reflecting surface 41b, and is incident on the emitting surface 41a at an angle less than the critical angle as indicated by an arrow 45b. The light exits from the exit surface 41a to the outside as exit light 46.

  The concave portion 44 provided in the reflecting surface 41b has a structure as shown in FIG. 13, and the light incident surface side is a flat slope 44a, and the opposite side of the light incident surface is a curved surface 44b. FIG. 14 shows an optical path of incident light 45a incident on the light guide plate 41 from the light incident surface 41c side of the end surface. When the incident light 45a enters the flat inclined surface 44a almost in parallel, the reflected light 45b is directed to the upper surface and is incident on the emission surface 41a shown in FIG. The light is emitted as light 46. The flat slope 44a is set to an angle at which light incident in parallel toward the slope is efficiently reflected and emitted from the light guide plate 41.

  FIG. 15 shows an optical path when light is incident from the light incident surface 41d shown in FIG. When the incident light 45a enters the curved surface 44b, it does not enter the curved surface 44b in the normal direction. Therefore, the reflected light 45b varies depending on the incident angle, and is a critical angle with respect to the output surface 41a of the light guide plate 41. The incidence rate is reduced below. That is, the light incident from the light incident surface 41c repeats total reflection in the light guide plate 41, reaches the anti-light incident surface 41d, and the reflected light cannot be used effectively.

In addition, when LEDs are used as a light source in a conventional edge light type backlight, it is necessary to reduce the number of LEDs to be used in order to emit light uniformly and efficiently as cheaply as possible. In the above conventional method, even if the power consumption and the cost are reduced by reducing the number of LEDs used, the light source plate and the light guide plate are structurally close to each other, so that the light guide plate near the LED In the region, the reflection of the reflection sheet portion disposed on the lower surface of the light guide plate becomes stronger, and the portion near the LED on the light emitting surface of the light guide plate becomes brighter than the other regions. This has been a problem to be solved in realizing a backlight that emits light uniformly using a bright point light source.
JP-A-8-271891

  The present invention has been made in view of the above-described problems of the prior art, and effectively uses light that has been repeatedly reflected in the light guide plate, and is capable of bright and uniform surface light emission. The purpose is to provide.

  The invention according to claim 1 is a backlight in which a light source is disposed opposite to an incident surface at one end of a light guide plate having one surface on the front and back sides as an emission surface and the other surface as a reflection surface. A light reflecting recess having an inclined surface that is closer to the exit surface from the incident surface side to the opposite end surface, and has a flat inclined surface and a partially arcuate curved inclined surface connected to the entire reflecting surface. Is formed.

  According to a second aspect of the present invention, in the backlight according to the first aspect, the light guide plate has a shape in which the emission surface and the reflection surface intersect at an acute angle at an end opposite to the light incident surface. It is characterized by.

  The invention according to claim 3 is a backlight in which a light source is disposed opposite to an incident surface of one end of a light guide plate having one side of the front and back as an emission surface and the other surface as a reflection surface. A light diffusion reflection surface is formed by performing a light diffusion process on a region near the light source.

  According to the present invention, it is possible to provide a backlight that can efficiently emit light that has been repeatedly reflected in the light guide plate from the exit surface and can illuminate the liquid crystal surface brightly.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  (First Embodiment) FIG. 1 is a sectional view of a backlight according to a first embodiment of the present invention, and FIG. 2 is a perspective view. 1 and 2, reference numeral 1 denotes a light guide plate, 1a denotes an emission surface, 1b denotes a reflection surface, 1c denotes a light incident surface, 1d denotes a light incident surface, 2 denotes a light source, and 3 denotes a substrate. In the present embodiment, the light guide plate 1 is a flat plate whose other surface is inclined with respect to one side of the front and back surfaces, the exit surface 1a is perpendicular to the light incident surface 1c at one end, and the reflecting surface 1b is an inclined surface. As the distance from the light surface 1c increases, the thickness of the light guide plate 1 is reduced, and the anti-light-incident surface 1d becomes smaller than the light incident surface 1c. A number of recesses 44 are formed in the inclined reflecting surface 1b as in the prior art.

  The light source 2 is composed of a plurality of LEDs arranged on the substrate 3 at appropriate intervals. Light from the light source 2 enters the light incident surface 1 c of the light guide plate 1. The light incident from the light incident surface 1c travels while totally reflecting the inside of the light guide plate 1, but since the reflective surface 1b is inclined, the light reflected by the reflective surface 1b has a critical angle with respect to the output surface 1a. It becomes easy to enter at the following angles. In addition, since the thickness of the light guide plate 1 is reduced as it approaches the anti-light-incident surface 1d, it is easy for light to hit the reflective surfaces 44a of the many concave portions 44, and before reaching the anti-light-incident surface 1d, Can be efficiently emitted from the exit surface 1a.

  It is also possible to use a directional point light source for the light source 2. By using a directional point light source for the light source 2, there is a high possibility that the light enters the flat reflecting surface 44 a of each recess 44 at an angle of approximately 45 °, and light can be efficiently extracted from the exit surface. Become.

  As for the shape of the light guide plate 1, the light guide plate 1 having a wedge-shaped cross section with an acute angle on the anti-incident surface 1 d side having a reduced thickness in the first embodiment can be employed. And in that case, the whole apparatus can be made compact by disposing the lighting drive circuit on the lower surface on the tip end side, which is an empty space.

  (Second Embodiment) FIG. 3 is a sectional view of a backlight according to a second embodiment of the present invention, and FIG. 4 is a top view thereof. 3 and 4, 21 is a point light source, 22 is a substrate, 23 is a light guide plate, 23a is a light incident surface, 23b is a reflection surface, 23c is a light emission surface, 24 is a reflection sheet, 25a and 25b are optical films, 26 Denotes a backlight case, 27 denotes a fixing adhesive, 28 denotes a grooved portion, and 29 denotes a light diffusive reflective paint.

  In the present embodiment, a light diffusive reflective coating 29 is formed in the vicinity of the light source on the reflective surface 23b of the light guide plate 23, and a groove 28 is formed at a location sufficiently away from the point light source 21. It is characterized by that. This will be described in detail below.

  A plurality of point light sources 21 are arranged in the vicinity of the light incident surface 23 a which is one end surface of the light guide plate 23. In the configuration of the present embodiment, the point light source 21 uses an LED. The point light source 21 may be other field emission devices or discharge lamps in addition to LEDs, or may be disposed on the substrate 22 as shown in FIG. Further, the point light sources 21 may be arranged in the major axis direction and the minor axis direction of the light guide plate 23, or may be arranged at both ends in the major axis direction and both ends in the minor axis direction.

  Optical films 25 a and 25 b are disposed on the light output surface 23 c of the light guide plate 23. At least one optical film 25a, 25b is arranged, and a plurality of optical films 25a, 25b are used depending on required light distribution characteristics.

  On the reflection surface 23b of the light guide plate 23, a light diffusive reflective coating 29 is disposed in the vicinity where the point light source 21 is disposed by a method such as screen printing. A grooved portion 28 is formed in a portion of the reflecting surface 23b away from the point light source 21 by an appropriate processing method such as moon cutting or embossing.

  Light that enters the light guide plate 23 from the point light source 21 proceeds while being totally reflected inside the light guide plate 23. When light is incident on the surface of the light diffusive reflective coating 29, it is diffusely reflected on the ink surface and reenters the light guide plate 23. Part of the re-entered light is incident on the light exit surface 23c at an angle less than the critical angle and exits from the light exit surface 23c. As a result, the light exits with a certain extent on the light exit surface 23c, so that a bright line is hardly generated. In addition, the light diffusive reflective paint 29 uses the point light source 21 by changing the size, pitch, and density of the coated surface so as to reduce unevenness of the light exit surface 23c in the vicinity of the light incident portion 23a. It is possible to improve unevenness of light in the vicinity of the light incident portion, which sometimes becomes a problem.

  As described above, part of the light incident on the light diffusive and reflective paint surface 29 is diffused and emitted from the light exit surface 23c, and part of the light reaches the reflection sheet 24 through the ink surface. . The light reflected by the reflection sheet 24 tries to enter the light guide plate 23 again, but is reflected again by the ink surface, and the light cannot be used effectively. Therefore, the groove processing portion 28 is formed except in the vicinity of the light incident portion. A part of the light incident on the groove processing portion 28 is reflected on the light exit surface side of the light guide plate and exits from the light exit surface. A part of the light is transmitted to the reflection sheet 24 side, but the light reflected by the reflection sheet 24 reenters the light guide plate 23 and can be used efficiently, and as a result, uniform surface light emission is possible. To.

  (Third Embodiment) FIG. 5 is a longitudinal sectional view of a lamp of a backlight according to a third embodiment of the present invention. In FIG. 5, reference numeral 30 denotes a surface diffusion processing section that has been subjected to surface diffusion processing by sandblasting. In FIG. 5, the same elements as those in FIGS. 3 and 4 are denoted by the same reference numerals.

  In the present embodiment, a surface diffusion processing unit 30 by sandblasting is provided in the vicinity of the light source 21 with respect to the reflecting surface 23b of the light guide plate 23, and a groove processing unit 28 is formed in a portion sufficiently away from the light source 21. It is.

  By forming the surface diffusion processing unit 30 by sandblasting on the reflection surface 23b in the vicinity of the light incident surface 23a of the light guide plate 23, unevenness in the vicinity of the light source 21 can be reduced, and a reflection surface other than the vicinity of the light incident surface 23a. By forming the groove processing part 28 in 23b, light can be used efficiently.

  (Fourth Embodiment) FIG. 6 is a sectional view of a backlight according to a fourth embodiment of the present invention. In FIG. 6, reference numeral 31 denotes a light diffuse reflection surface. In FIG. 6, the same elements as those in FIGS. 3 to 5 are denoted by the same reference numerals.

  In the present embodiment, the groove processing portion 28 is formed on the reflection surface 23 b of the light guide plate 23, and the light diffusion reflection surface 31 is formed near the light source by groove processing different from the groove processing portion 28. It is characterized by. The shape of the groove formed on the light diffusing and reflecting surface 31 is a curved surface so that the light from the light source 21 incident from the edge of the light guide plate 23 can diffuse as shown in any of FIGS. . 7 illustrates a conical groove 31a, FIG. 8 illustrates a frustoconical groove 31b, and FIG. 9 illustrates a cylindrical groove 31c.

  It is possible to reduce unevenness in the vicinity of the light source by forming the groove processing portion 28 in a portion other than the vicinity of the light incident surface 23a of the reflection surface 23b and forming the light diffusion reflection surface 31 in the vicinity of the light incident surface 23a. it can. In addition, light can be efficiently used by not using the light diffusing reflection surface 31 except in the vicinity of the light incident surface 23a.

  In the light diffusion treatment, a light diffuse reflection paint may be applied or the surface may be subjected to light diffusion reflection treatment.

  In addition, as in the second to fourth embodiments of the present invention, a backlight in which a light source is arranged opposite to an incident surface at one end of a light guide plate having one surface on the front and back sides as an emission surface and the other surface as a reflection surface. In the case of forming a light diffusion reflection surface on the reflection surface of the light guide plate in the vicinity of the light source, the thickness of the light guide plate is reduced to the end face on the judgment side from the light source. It is also possible to employ a uniform thickness.

  (Fifth Embodiment) FIG. 10 is a view showing the structure of an end portion of a backlight according to a fifth embodiment of the present invention. In FIG. 10, 11 is an LED as a light source, 12 is an aluminum substrate, 13 is a frame, 14 is a metal plate, and 15 is a light guide plate. An aluminum substrate 12 having a plate thickness of 0.3 to 0.5 mm on which a plurality of LEDs 11 are mounted is disposed on the side of one end face of the light guide plate 15. The light source 11 may be a discharge lamp in addition to a single item or a plurality of bullet-type or surface-mount type LEDs. When the light source 11 is a discharge lamp, it may be arranged in the major axis direction or in the minor axis direction. A metal plate 14 made of a material having high thermal conductivity such as aluminum is installed so as to be inscribed inside the frame 13, and a light guide plate 15 is arranged inside the metal plate 14. As the light source 11, an LED assembly is provided between the metal plate 14 and the light guide plate 15 so as to be arranged in the vertical direction with respect to the light guide plate light incident portion.

  According to the present embodiment, when the aluminum substrate 12 and the metal plate 14 are in close contact with each other, the heat generated when the light source 11 is turned on can be diffused and the local high temperature can be reduced.

  (Sixth Embodiment) FIG. 11 is a view showing the structure of the end of a backlight according to a sixth embodiment of the present invention. In FIG. 11, the same elements as those in FIG. 10 are denoted by the same reference numerals. In the present embodiment, a metal plate 14 made of a material having high thermal conductivity such as aluminum is installed so as to be inscribed inside the frame 13, and a light guide plate 15 is arranged on the inside thereof. The metal plate 14 and the light guide plate 15, an LED assembly as the light source 11 is provided so as to be perpendicular to the light guide plate light incident portion. Further, a member 16 having high thermal conductivity such as aluminum bent in an L shape is sandwiched between the aluminum substrate 12 and the metal plate 14 and fixed so that the light source 11 as a heat source is sandwiched between the upper direction and the bottom direction. I am letting.

  According to the present embodiment, the member 16 can be thermally diffused to relieve the local high temperature, and the light leaking upward can be guided to the inside of the light guide plate 15 to be reused.

Sectional drawing of the backlight of the 1st Embodiment of this invention. The perspective view of the backlight of the 1st Embodiment of this invention. Sectional drawing of the backlight of the 2nd Embodiment of this invention. The top view of the backlight of the 2nd Embodiment of this invention. Sectional drawing of the backlight of the 3rd Embodiment of this invention. Sectional drawing of the backlight of the 4th Embodiment of this invention. FIG. 6A is a cross-sectional view and an enlarged perspective view of an example of a groove formed on the light diffusion reflection surface in the above embodiment, and FIG. FIG. 4A is a cross-sectional view and an enlarged perspective view of another example of a groove formed on the light diffusion reflection surface in the above embodiment, and FIG. FIG. 6A is a cross-sectional view and an enlarged perspective view of still another example of a groove formed on the light diffusion reflection surface in the above embodiment, and FIG. The figure which shows the structure of the edge part of the backlight of the 5th Embodiment of this invention. The figure which shows the structure of the edge part of the backlight of the 6th Embodiment of this invention. Sectional drawing of the lamp | ramp of the conventional backlight. The expanded sectional view of the conventional backlight. Action explanatory drawing 1 of the recessed part of the conventional backlight. Action explanatory drawing 2 of the recessed part of the conventional backlight.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide plate 1a Outgoing surface 1b Reflecting surface 1c Light incident surface 1d Anti-light incident surface 2 Light source 3 Substrate 4 Recess 11 Light source 21 Point light source (LED)
22 Substrate 23 Light guide plate 23a Light incident surface 23b Reflective surface 23c Light exit surface 24 Reflective sheet 28 Grooved portion 29 Light diffuse reflective paint 31 Light diffuse reflective surface 31a-31c Groove 44a Reflective surface 44b Curved surface

Claims (3)

In the backlight in which the light source is arranged opposite to the incident surface at one end of the light guide plate with one side of the front and back as the emission surface and the other surface as the reflection surface,
The reflective surface of the light guide plate is an inclined surface that is closer to the exit surface as it reaches the opposite end surface from the incident surface side,
A backlight characterized in that a large number of light reflecting recesses having a flat inclined surface and a partially arcuate curved inclined surface connected to the flat inclined surface are formed on the entire reflective surface.   2. The backlight according to claim 1, wherein the light guide plate has a shape in which the emission surface and the reflection surface intersect at an acute angle at an end opposite to the light incident surface. In the backlight in which the light source is arranged opposite to the incident surface at one end of the light guide plate with one side of the front and back as the emission surface and the other surface as the reflection surface,
A light diffusion reflection surface is formed on the reflection surface of the light guide plate by performing light diffusion processing on a region near the light source.

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