JP2013171767A - Led backlight module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of reducing a white color floating phenomenon generated on a boundary between a lighting LED substrate and non-lighting LED substrate in an LED backlight module.SOLUTION: As for an LED substrate A14a, total twelve sets of LED packages 11 are arranged in four columns and three rows on a rectangular substrate surface 18 at designated intervals. Then, LEDs 12 are arranged on the substrate surface 18 of the LED substrate A14a, and lenses 13 being circular in a top plane view and hemispheric in a side plane view are formed to cover respective LEDs 12 so as to seal the LEDs 12. Outer LED packages 11b, 11c arranged along an outer edge of the substrate surface 18 are cut (deleted) at outer parts. The cut face 15 of the LED package is formed of a plane.

Description

  The present invention relates to an LED backlight module, and more particularly to a direct type LED backlight module.

  In a liquid crystal television, a backlight module is used, but in recent years, a direct type LED backlight module in which a plurality of LEDs are arranged directly below a liquid crystal panel module has been used particularly in a model that appeals high image quality.

  In a liquid crystal television having a direct type LED backlight module, so-called local dimming, a technology for controlling the brightness of the backlight for each divided area is possible, and image quality is improved.

  FIG. 1 shows a general direct type LED backlight module 9, an LED substrate 4, and an LED package 1. As shown in FIG. 1A, a backlight is configured by arranging a plurality of LED substrates 4 having a rectangular shape, a square shape, or other shapes side by side. Here, four LED substrates 4 (LED substrates A to D4a to 4d) are arranged. As shown in FIG. 1B, a total of twelve LED packages 1 are arranged at predetermined intervals on a single LED substrate 4 (here, LED substrate A4a) in 3 × 4 directions. The arrangement of the LED package 1 viewed from the side shown in FIG. 1C and the side structure of one LED package 1 shown in FIG. 1D (the LED package 1 in the region X1 in FIG. 1B). The LED 2 is disposed on the substrate surface 8 of the LED substrate 4 (4a), and a lens 3 that is circular in a top view and substantially hemispherical in a side view is formed so as to cover the LED 2. By adopting these structures, light is emitted radially from the LED 2 as a planar light source.

  On the other hand, various technologies have been proposed because higher quality as a backlight is required than ever.

  For example, there is a technique for providing a planar light source device having a partition wall between adjacent light sources as a structure in which luminance unevenness hardly occurs between adjacent planar light source units (see, for example, Patent Document 1 and Patent Document 2). . In addition, with regard to a light-emitting diode light source, without changing the mounting angle with respect to the printed circuit board, light is generally irradiated to one side where the illumination direction is required from the normal direction of the printed circuit board to the normal line, and light is emitted to the opposite side. There is also a technique for preventing the irradiation of the light (see, for example, Patent Document 3). Furthermore, a technique for reducing leakage of light to adjacent light emitting areas for a plurality of LEDs has been proposed (see, for example, Patent Document 4).

JP 2007-324047 A JP 2009-36872 A JP 2010-171612 A JP 2011-60706 A

  By the way, in a liquid crystal television provided with a direct type LED backlight, when local dimming is performed, white floating (unwanted light leakage) occurs at the boundary between the backlight lighting part and the non-lighting part. This is because, in the LED package 1 arranged near the outer edge of the LED substrate 4 shown in FIG. 1, for example, the radiated light in the portion indicated by the region X2 affects the adjacent LED substrate 4 (LED substrate B4b or LED substrate C4c). This occurred especially when one was lit and the other was not lit. If there is white floating, there is a problem that it becomes difficult to realize a high-contrast and high-definition image. Even in the above-described Patent Documents 1 to 4, there are similar problems, and another technique has been demanded.

  This invention is made | formed in view of the above situations, Comprising: It aims at providing the technique which solves the said subject.

The present invention is an LED backlight module including a plurality of LED substrates in which a plurality of LED packages are spaced apart from each other, wherein the LED package is formed by covering an LED light source disposed on the substrate and the LED light source. The lens of the LED package disposed on the outer edge of the substrate includes a cut surface from which an outer portion is removed, unlike an inner portion.
The cut surface may be non-transparent processed.
Moreover, the area | region where the said non-transmissive process is given may be an area | region where the incident angle to the said cut surface of the emitted light of the said LED light source is smaller than a critical angle.
The cut surface may be formed outside the LED light source, and the non-transparent processing may be performed on a region outside the LED light source on the upper surface of the lens.

  ADVANTAGE OF THE INVENTION According to this invention, in an LED backlight module, the white floating phenomenon which generate | occur | produces in the boundary of the LED board to light and a non-lighting LED board can be reduced.

It is a figure which shows the general direct type | mold LED backlight module, LED board, and LED package based on a prior art. It is a figure which shows the LED board and LED package of a direct type LED backlight module which concern on embodiment. It is a figure which shows the upper surface of the lens of the LED package based on embodiment by a simple convex-shaped curved surface. It is a figure explaining reflection and refraction in the boundary of a different medium based on embodiment. It is a figure which shows the structure of the LED backlight module and LED package 1 which concern on the 1st modification of embodiment. It is a figure which shows the structure of the LED package based on the 2nd modification of embodiment.

  Next, modes for carrying out the present invention (hereinafter, simply referred to as “embodiments”) will be specifically described with reference to the drawings.

  FIG. 2 shows the LED substrate 14 and the LED package 11 arranged in a general direct type LED backlight module. The arrangement of the LED substrate 14 in the LED backlight module is the same as in FIG. FIGS. 2A and 2B show a configuration corresponding to one LED board 14 (LED board A14a), in particular, the LED board A4a shown in FIG. FIG. 2C shows the side surface of the LED package 11 c arranged at the corner of the substrate surface 18.

  The difference from the structure shown in FIG. 1 resides in the LED package 11, mainly the differences will be described, and the description of the same configuration will be omitted as appropriate.

  In the LED substrate A14a, a total of 12 LED packages 11 are arranged on the rectangular substrate surface 18 in a vertical and horizontal direction 3 × 4 at a predetermined interval. And as the structure of the LED package 11 seen from the side surface of FIG. 2 (b) or FIG. 2 (c), the LED 12 is arranged on the substrate surface 18 of the LED substrate A 14a and is circular in top view so as to cover it. A substantially hemispherical lens 13 is formed in a side view and seals the LED 12.

  In addition, the LED package 11a arrange | positioned inside LED package 11 is a conventional shape as shown in FIG. On the other hand, the outer LED packages 11b and 11c arranged along the outer edge of the substrate surface 18 have the outer portions cut (deleted). For example, in the LED package 11 c arranged at the corner of FIG. 2C, a part A <b> 1 of the lens 13 on the right side of the drawing, more specifically, on the right side of the LED 12 is cut by the cut surface 15. Here, the cut surface 15 is formed as a flat surface.

  The lens 13 has a curved shape with a slightly concave central portion, but is not limited to this shape, and may be a simple convex curved surface as shown in FIG. Moreover, as a material of the lens 13, there is an acrylic resin, for example.

  Here, the optical path of the radiated light of LED12 is demonstrated with reference to FIG.3 and FIG.4. FIG. 4 is a diagram for explaining reflection and refraction at the boundary between different media.

First, the reflection and refraction at the cut surface 15 of the lens 13 will be described with reference to FIG. As shown in FIG. 4A, generally, when the relative refractive index of the medium B with respect to the medium A is n _AB ,
n _AB = sin θ _A / sin θ _B
Is satisfied.

When the absolute refractive index of the medium A is n _A and the absolute refractive index of the medium B is n _B ,
n _AB = sin θ _A / sin θ _B
= N _B / n _A
n _A × sin θ _A = n _B × sin θ _B
It becomes.
From this point, assuming that the critical angle is θm, the conditions for total reflection are as follows.
θ _B = 90 °, θm = θ _A
n _A × sin θ _m = n _B × sin 90 °
sin θ _m = n _B / n _A

Here, when the material of the lens 13 is an acrylic resin, the absolute refractive index of the acrylic resin is 1.49, and the absolute refractive index of the air layer is 1.00. Therefore, as shown in FIG. 4B, the incident angle (critical angle θ _m ) for total reflection when the emitted light of the LED 2 enters the air layer (medium B) from the acrylic layer (medium A) is It becomes as follows.
sin θm = 1.00 / 1.49
θm = 42.2 °

Here, with reference to FIG. 3, the reflection and refraction of the radiated light on the cut surface 15 will be described. As described above, when the critical angle .theta.m = 42.2 °, it is desirable in many cases the emitted light angle of incidence greater than the critical angle theta _m along the cut surface 15. Therefore, as shown in the drawing, the cut surface 15 is formed in the vicinity of the LED 12. As a result, in the drawing, the radiated light L1 (solid line in the figure) emitted right above the LED 12 and in the left oblique direction is refracted at the upper surface of the lens 13 but is emitted to the outside without being reflected by the cut surface 15.

LED12 of radiation emitting in the right oblique direction than shown, the angle of incidence is the critical angle theta _m or more of the emitted light L2 (dashed line in the figure), if originally transmitted light L3 (the broken line in the drawing) However, it is reflected by the cut surface 15 and does not transmit to the right side of the cut surface 15. However, the incident angle is critical angle theta _m smaller than the emitted light L4 (dashed double-dotted in the figure) is transmitted while being refracted the cut surface 15, can be realized sufficient reduction of the transmitted light as a whole.

In the cut surface 15, the portion below the position where the incident angle becomes the critical angle θ _m (the substrate surface 18 side portion) is made non-transparent processing such as mirror processing or light-absorbing coating, thereby transmitting from the cut surface 15. Can be substantially completely prevented. As the non-transmission process, a known technique such as a film formation process by vapor deposition or a predetermined paste can be used. In addition, when the cut surface 15 is entirely non-transparent processed, it is not necessary to consider the critical angle.

  As described above, according to the present embodiment, white floating between the LED substrates 4 is reduced, and the contrast feeling can be improved in the liquid crystal display device that includes the LED backlight module having such a structure and performs local dimming. Moreover, since light is not leaked to an unnecessary area, the luminance of a desired lighting area can be increased efficiently.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to combinations of the respective components and the like, and such modifications are within the scope of the present invention.

  FIG. 5 shows an LED substrate 104 (LED substrate A 104a) according to a first modification. In this modification, the inner LED package 101 a is not changed, and the arrangement of the outer LED packages 101 b and 101 c is made to coincide with the outer edge of the substrate surface 108. In other words. The cut surfaces 105 of the LED packages 101b and 101c coincide with the substrate end surface 118. By adopting such a configuration, it is possible to reduce a decrease in luminance at the boundary surface of the LED substrate 104.

  FIG. 6 shows the shape of the LED package 201 according to the second modification. In this LED package 201, as shown by a bold line in the figure, the cut surface 205 is mirror-finished from the substrate surface 208 side to the lens 203. Further, the upper surface portion of the lens 203 is rounded so that a region (round processing surface 206) that is on the substrate outer side (B2 side in the drawing) than the LED 202 constitutes a surface continuous with the cut surface 205. Further, the round processed surface 206 is mirror-finished in the same manner as the cut surface 205.

  By adopting such a configuration, it is possible to prevent light leakage outside a desired area when performing local dimming. Then, by adjusting the mirror processing position (the boundary between B1 and B2 in the figure), it is possible to control the region where the emitted light of the LED 202 is to be transmitted actively and the region where it is desired to be non-transmitted.

11, 11a, 11b, 11c LED package 101a, 101b, 101c, 201 LED package 12, 202 LED (LED light source)
13, 203 Lens 14, 104 LED board 14a, 104a LED board A
15, 105, 205 Cut surface 18, 108, 208 Substrate surface 118 Substrate end surface 206 Round processing surface

Claims (4)

An LED backlight module including a plurality of LED substrates in which a plurality of LED packages are spaced apart from each other,
The LED package includes an LED light source disposed on a substrate, and a lens formed to cover the LED light source,
The LED backlight module, wherein the lens of the LED package disposed on the outer edge of the substrate includes a cut surface from which an outer portion is deleted, unlike an inner portion.   The LED backlight module according to claim 1, wherein the cut surface is non-transparent processed.   3. The LED backlight according to claim 2, wherein the non-transparent region is a region where an incident angle of the emitted light of the LED light source to the cut surface is smaller than a critical angle. module.   The said cut surface is formed outside the said LED light source, and the said non-transparent process is given to the area | region outside the said LED light source of the upper surface of the said lens. The LED backlight module in any one.

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