KR20130036447A - Back light unit - Google Patents

Abstract

PURPOSE: A backlight unit is provided to improve color uniformity by coating a wavelength conversion material on the lower surface of a diffusion plate. CONSTITUTION: A reflection sheet(120) is arranged on the upper surface of a substrate(115) including a light emitting device(110). A bottom cover(130) supports the lower surface of the substrate. A diffusion plate(140) is separated from the upper part of the light emitting device. A wavelength conversion sheet(150) is arranged on the lower surface of the diffusion plate. The wavelength conversion sheet faces the light emitting device.

Description

Backlight unit {BACK LIGHT UNIT}

An embodiment relates to a backlight unit.

Typically, typical large-sized display devices include a liquid crystal display (LCD), a plasma display panel (PDP), and the like.

Unlike the self-luminous PDP, an LCD requires a separate backlight unit due to the absence of its own light emitting device.

The backlight unit used in LCD is classified into an edge type backlight unit and a direct type backlight unit according to the position of the light source. As a light source of an existing edge type or direct type backlight unit, CCFL (Cold Cathode Fluorescent Lamp) Was used.

However, since the CCFL-based backlight unit is always powered by the CCFL, a considerable amount of power is consumed, and the problems of environmental pollution due to the addition of about 70% color reproduction rate and mercury are pointed out as disadvantages.

As a substitute for solving the above problems, research on a backlight unit using an LED (Light Emitting Diode) has been actively conducted.

When the LED is used as a backlight unit, the LED array can be partially turned on and off, which can drastically reduce the power consumption. For the RGB LED, it exceeds 100% of the NTSC (National Television System Committee) color reproduction range specification. To provide consumers with more vivid picture quality.

In addition, the LED produced by the semiconductor process is characterized by harmless to the environment.

LCD products employing LEDs with the above advantages are being released one after another. However, since the driving mechanism is different from the existing CCFL light source, driving drivers and PCB substrates are expensive. Therefore, the LED backlight unit is still applied only to expensive LCD products.

The edge type backlight unit arranges light sources on the left and right sides or top and bottom sides of the LCD panel and evenly distributes the light to the front surface using a light guide plate, so that the light uniformity is excellent and the panel thickness can be made ultra thin.

The direct-type backlight unit is a technology generally used for a display of 20 inches or more. Since a plurality of light sources are disposed under the panel, the backlight unit is mainly used for a large display requiring high brightness because it has an advantage of superior light efficiency compared to an edge method.

A light emitting device package commonly used in a direct-type backlight unit uses a lens to adjust a directing angle, and a yellow ring is used for each angle due to the nonuniformity of the wavelength converter used in the light emitting device package and the use of a lens. A phenomenon such as mura occurs and there is a problem that the color uniformity is lowered.

Embodiments seek to improve color uniformity of the backlight unit.

According to an embodiment, a backlight unit may include: a light emitting module including a substrate on which a circuit pattern is formed and at least one light emitting element disposed on the substrate; A diffusion plate disposed on the light emitting module; It includes a wavelength conversion sheet disposed on the lower surface of the diffusion plate to face the upper surface of the light emitting device.

The wavelength conversion sheet may be formed by being divided into a plurality of regions corresponding to each light emitting device.

The light emitting device may further include a reflector disposed on the substrate and surrounding the light emitting device.

The reflector may have at least one cavity with an open bottom.

The horizontal cross-sectional shape of the cavity of the reflector may be circular, elliptical, or polygonal.

The side wall of the cavity of the reflector may be formed of an inclined surface that forms an obtuse angle with the substrate on which the light emitting device is disposed.

The side wall of the cavity of the reflector may be formed of an inclined surface having a predetermined curvature.

The side wall of the cavity of the reflector may consist of at least two inclined surfaces having at least one inflection point.

Two or more light emitting devices may be disposed in one cavity of the reflector.

The reflector may be made of tempered glass or PET.

The horizontal cross-sectional shape of the wavelength conversion sheet may be circular, elliptical, or polygonal.

The reflector may be integrally formed by connecting the upper sidewalls of adjacent cavities to each other.

It may further include a reflective sheet disposed on the substrate.

The light emitting device may be spaced apart from the wavelength conversion sheet.

The light emitting module may further include a heat radiating pad attached to a rear surface of the light emitting module.

According to the backlight unit according to the embodiment, color uniformity can be improved by applying a uniform wavelength converter on the lower surface of the diffusion plate without using a lens, and thickness of the backlight unit can be reduced.

1 and 2 are side cross-sectional views of a backlight unit of a direct type according to one embodiment;
3 to 6 are cross-sectional side views of a backlight unit of a direct type according to another embodiment;
7 and 8 are plan views showing the top view of the diffusion plate and the wavelength conversion sheet in the backlight unit of the direct type according to the embodiment,
9 to 10 is a plan view showing a top view of the reflector according to the embodiment,
11 and 12 are views showing the state of the light emitting device disposed in the cavity of the reflector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

In the description of the embodiment according to the present invention, when described as being formed on the "on or under" of each element, the (up) or down (on) or under) includes both two elements being directly contacted with each other or one or more other elements are formed indirectly between the two elements. Also, when expressed as "on or under", it may include not only an upward direction but also a downward direction with respect to one element.

The thickness and size of each layer in the drawings are exaggerated, omitted, or schematically shown for convenience and clarity of explanation. In addition, the size of each component does not necessarily reflect the actual size.

1 and 2 are side cross-sectional views of a backlight unit of a direct type according to one embodiment.

A direct light backlight unit 100 according to an embodiment includes a plurality of light sources for emitting light, and a chip on board (COB) for mounting the plurality of light emitting devices 110 directly on the substrate 115 in a chip form. Type light sources can be used.

As shown in FIG. 1, the backlight unit 100 according to the embodiment includes a light emitting module including a substrate 115 having a circuit pattern formed thereon and at least one light emitting device 110 disposed on the substrate 115. 117, a diffusion plate 140 disposed on the upper portion of the light emitting module 117, and a wavelength conversion sheet disposed on the lower surface of the diffusion plate 140 to face the upper surface of the light emitting device 110. And 150.

1 illustrates a light emitting module 117 including only three light emitting devices 110 for convenience, but four or more light emitting devices 110 may be used. Of course, a circuit pattern is formed on the substrate 115. Thereby, the current can be supplied to the light emitting device 110.

The light emitting device 110 is disposed in an area on the substrate 115 on which the first electrode pattern is formed, and is directly energized with the first electrode pattern. It may be connected to receive a current, or may be connected to both the first and second electrode patterns using a wire to receive a current.

The reflective sheet 120 may be disposed on the upper surface of the substrate 115 on which the light emitting device 110 is disposed to transmit the light emitted from the light emitting device 110 to the upper direction of the backlight unit 100.

The reflective sheet 120 may use a material having high reflectance and capable of ultra-thin thickness.

The reflective sheet 120 is disposed on the substrate 115 in a state where an open area is formed at a portion where the light emitting device 110 is to be positioned, and the light emitting device 110 and the substrate 115 contact each other in the open area. The current may be supplied to the light emitting device 110.

The bottom cover 130 is disposed below the substrate 115 to support the bottom surface of the substrate 115.

A heat dissipation pad (not shown) may be disposed between the bottom cover 130 and the light emitting module 117 to dissipate heat generated from the light emitting device 110 to the outside.

That is, the heat radiating pad may be disposed on the rear surface of the substrate 115 of the light emitting module 11.

Heat generated from the light emitting device 110 is discharged to the outside through the bottom cover 130 through the heat radiating pad to ensure the reliability of the backlight unit.

A diffusion plate 140 may be disposed to be spaced apart from the upper portion of the light emitting device 110, and both edges of the diffusion plate may be supported at the edge of the bottom cover 130.

The diffusion plate 140 may have a predetermined strength so that the diffusion plate 140 may maintain a flat shape without bending toward the light emitting device 110.

The diffusion plate 140 may be made of polyester and polycarbonate-based materials, and may widen the light projection angle by refracting and scattering light incident from the light emitting device 110.

The first prism sheet, the second prism sheet, and the protective sheet (not shown) may be disposed on the diffusion plate 140, and the arrangement order of these sheets may be changed.

The first prism sheet is formed of a translucent and elastic polymer material on one surface of the support film, and the polymer may have a prism layer in which a plurality of three-dimensional structures are repeatedly formed. In the first prism sheet, the floor and the valley may be repeatedly provided in a stripe type to form a pattern.

The direction of the floor and the valleys in the second prism sheet is disposed perpendicular to the direction of the floor and the valleys on one surface of the support film in the first prism sheet to panel the light transmitted from the light emitting element 110 and the reflective sheet 120. Evenly distributed in all directions.

On the lower surface of the diffusion plate 140, the wavelength conversion sheet 150 may be disposed to face the light emitting elements 110.

The light emitting device 110 may be spaced apart from the wavelength conversion sheet 150.

The wavelength conversion sheet 150 may include a garnet-based phosphor, a silicate-based phosphor, a nitride-based phosphor, or an oxynitride-based phosphor.

For example, the garnet-base phosphor is _{YAG (Y 3 Al 5 O 12} : Ce 3 +) or TAG: may be a _{(Tb 3 Al 5 O 12 Ce} 3 +), wherein the silicate-based phosphor is (Sr, Ba, _{Mg, Ca) 2 SiO 4:} Eu 2 + one can, the nitride-based fluorescent material is CaAlSiN ₃ containing SiN: Eu ^{2 +} one can, Si ₆ of the oxynitride-based fluorescent material includes SiON _{- x} Al _x O _x N _{8 -x} : Eu ^{2 +} (0 <x <6).

In the exemplary embodiment, the wavelength conversion sheet 150 having the wavelength converter evenly distributed on the lower surface of the diffusion plate 140 may be disposed without using the light emitting device package in which the wavelength converter is integrally formed.

As shown in FIG. 1, the wavelength conversion sheet 150 may be disposed to cover the entire lower surface of the diffusion plate 140. As illustrated in FIG. 2, the wavelength conversion sheet 150 may correspond to each of the light emitting elements 110. It may be arranged divided into a plurality of areas.

3 to 6 are cross-sectional side views of a backlight unit of a direct type according to another embodiment.

The backlight unit 200 according to another embodiment includes a light emitting module 217 including a substrate 215 on which a circuit pattern is formed and at least one light emitting device 210 disposed on the substrate 215, and the light emitting module. 217 may include a diffusion plate 240 disposed on the upper portion and a wavelength conversion sheet 250 disposed on the lower surface of the diffusion plate 240 so as to face the upper surface of the light emitting device 210.

The bottom cover 230, the substrate 215, the light emitting device 210, the diffusion plate 240, and the arrangement relationship between the wavelength conversion sheet 250 and the light emitting device 210 are the same as described in the above-described embodiment. Therefore, it will not be described again.

The difference between the present embodiment and the above-described embodiment is that it further includes a reflector 260 disposed on the substrate 215 while surrounding the light emitting device 210.

The reflector 260 may use a material having a high reflectance and being extremely thin, and for example, tempered glass or polyethylene terephtalate (PET) may be used.

As shown in FIG. 3, the reflector 260 may be formed with a plurality of cavities 263 having a lower opening. That is, the reflector 260 may be formed of only the sidewall 265 surrounding each of the light emitting devices 210 without the bottom surface.

The reflector 260 may serve as a light guide that reflects the light emitted from the light emitting device 210 and transmits the light toward the upper direction, that is, in the direction of the wavelength conversion sheet 250 and the diffusion plate 240.

The reflective sheet 220 may be disposed in an area on the substrate 215 exposed through the cavity 263 having an open bottom. Since the reflector 260 reflects the light emitted from the light emitting device 210 and guides the light toward the upper direction, a separate reflective sheet 220 may not be disposed on the substrate 215. If the 220 is disposed can be expected to improve the light extraction efficiency more.

Alternatively, although not shown, the lower portion of the sidewall 265 of the cavity 263 of the reflector 260 is formed to extend to a part of the area on the substrate 215 to form a bottom surface. You can also reflect light.

The wavelength conversion sheet 250 may be disposed to cover the entire lower surface of the diffusion plate 240 as shown in FIG. 3, and as illustrated in FIG. 4A, a plurality of wavelength conversion sheets 250 may correspond to each of the light emitting elements 210. It may be arranged divided into regions.

Hereinafter, a description will be given on the assumption that the wavelength conversion sheet 250 is divided into a plurality of regions.

The sidewall 265 of the cavity 263 of the reflector 260 may be formed of a straight inclined surface as shown in FIG. 4A, or may be formed of an inclined surface having a predetermined curvature as shown in FIG. 5A, and FIG. As shown in 6a, it may consist of two inclined surfaces having at least one inflection point.

4B to 6B are enlarged views of portions of the light emitting device, the substrate, and the reflector shown in FIGS. 4A to 6A. An arrangement relationship between the light emitting device 210, the substrate 215, and the reflector 260 will be described in detail with reference to FIGS. 4B to 6B.

As shown in FIG. 4B, the sidewall 265 of the cavity 263 of the reflector 260 may be formed of a straight inclined surface that forms an obtuse angle θ ₁ with the substrate 215 on which the light emitting device 210 is disposed. .

An angle θ ₂ formed between the height h of the reflector 260 and the area on the substrate 215 covered with the reflector 260 and the light emitting device 210 is not disposed and the sidewall 265 of the cavity 263 is defined as a light emitting device ( The orientation angle of 210 may be adjusted to 120 degrees.

Alternatively, as shown in FIG. 5B, the sidewall 265 of the cavity 263 of the reflector 260 may be formed of an inclined surface having a predetermined curvature R. If the curvature R is too small, the light emitted from the light emitting device 210 may be concentrated only in an area of the upper portion, and dark portions may occur according to the distance between the light emitting devices, so that the R value may be determined so that the light may be evenly distributed and distributed. have.

An angle θ ₃ formed between the height h of the reflector 260, the area on the substrate 215 covered with the reflector 260, on which the light emitting element 210 is not disposed, and the sidewall 265 of the cavity 263 is defined as a light emitting element ( The orientation angle of 210 may be adjusted to 120 degrees.

In FIG. 5B, since the sidewall 265 of the cavity 263 is an inclined surface having a curvature, θ ₃ is an angle between the tangent contacting the inclined surface and the substrate 215 at the point where the sidewall 265 meets the substrate 215. Means.

Alternatively, as shown in FIG. 6B, the sidewall 265 of the cavity 623 of the reflector 260 may be formed of at least two inclined surfaces having at least one inflection point P. FIG.

In FIG. 6B, as an example, a reflector 260 having a sidewall 265 composed of two inclined surfaces having one inflection point P is shown.

The two inclined surfaces may have curvatures of R ₁ and R ₂ , respectively, and R ₁ and R ₂ may be the same or different. The curvatures R ₁ and R ₂ may be determined so that light may be evenly distributed and distributed without dark parts depending on the distance between the light emitting devices.

An angle θ ₄ of the height h of the reflector 260 and the sidewall 265 of the cavity 263 having the curvature R ₂ and the virtual horizontal line S may be adjusted such that the orientation angle of the light emitting device 210 is 120 degrees. .

Since θ ₄ is an inclined surface having a curvature of the side wall 265, the angle between the tangent line and the horizontal line S contacting the inclined surface at the point where the side wall 265 of the cavity 263 having the curvature R ₂ meets the virtual horizontal line S is determined. it means.

7 and 8 are plan views illustrating a top view of the diffusion plate and the wavelength conversion sheet in the backlight unit of the direct type according to the embodiment.

The horizontal cross-sectional shape of the wavelength conversion sheet 250 may be circular, elliptical, or polygonal. FIG. 7 illustrates a wavelength conversion sheet 250 having a square cross-sectional shape, and FIG. 8 illustrates a wavelength conversion sheet 250 having a circular cross-sectional shape.

If necessary, the wavelength conversion sheets 250 having a circular, elliptical, or polygonal cross-sectional shape may be mixed and included in one backlight unit.

9 to 10 is a plan view showing a top view of the reflector according to the embodiment.

As described above, the reflector 260 may be formed with a plurality of cavities 263 having a lower opening.

The horizontal cross-sectional shape of the cavity 263 may be circular, elliptical, or polygonal. In FIG. 9, a reflector 260 having a square cross-sectional shape of the cavity 263 is illustrated as an example, and a reflector 260 having a circular cross-sectional shape of the cavity 263 is illustrated in FIG. 10.

If necessary, the cross-sectional shape of the plurality of cavities formed in one reflector may be formed by mixing circular, elliptical, or polygonal shapes.

11 and 12 are views showing the state of the light emitting device disposed in the cavity of the reflector.

In one embodiment, as described above, a reflector 260 having a cavity 263 having an open bottom is disposed on the substrate 215, and the light emitting device 210 is disposed on the substrate 215 in the cavity 263. Can be deployed.

As shown in FIG. 11, only one light emitting device 210 may be disposed per cavity 263 of the reflector 260, and two or more light emitting devices 210 may be disposed as shown in FIG. 12. .

When the plurality of light emitting elements 210 are disposed in the cavity 263 of the reflector 260, the local dimming area is formed by the light emitting elements 210 disposed in one cavity 263 as one unit. Can be achieved.

12, when the plurality of light emitting devices 210 are disposed in the cavity 263 of the reflector 260, one light emitting device 210 is disposed in the cavity 263 of the reflector 260 as shown in FIG. 11. The number of cavities 263 formed in the reflector 260 may be reduced and the size of one cavity 263 may be larger than when only the bays are disposed.

A panel (not shown) may be disposed in the backlight units 100 and 200 according to the above embodiments to form an image display device. A liquid crystal display panel may be disposed as the panel. In addition to the liquid crystal display panel, other types of display devices requiring a light source may be provided.

The panel is in a state in which a liquid crystal is positioned between a pair of transparent substrates and a polarizing plate is placed on each transparent substrate in order to use polarization of light. Here, the liquid crystal has an intermediate property between a liquid and a solid, and liquid crystals, which are organic molecules having fluidity like a liquid, are regularly arranged like crystals. The liquid crystal has a structure in which the molecular arrangement is changed by an external electric field And displays an image.

A liquid crystal display panel used in a display device is an active matrix type, and a transistor is used as a switch for controlling a voltage supplied to each pixel.

A color filter is provided on the front of the panel, so that the light projected by the panel transmits only red, green, and blue light for each pixel, thereby representing an image.

According to the embodiments described above, by applying a uniform wavelength converter to the lower portion of the light emitting device without using a lens, the color uniformity is improved by eliminating color deviation or mura, and the thickness of the backlight unit is reduced. Can be.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible.

For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

110 and 210: light emitting elements 115 and 215: substrate
117 and 217: light emitting modules 120 and 220: reflective sheets
130, 230: bottom cover 140, 240: diffusion plate

Claims (15)

A light emitting module including a substrate having a circuit pattern formed thereon and at least one light emitting device disposed on the substrate;
A diffusion plate disposed on the light emitting module;
And a wavelength conversion sheet disposed on a lower surface of the diffusion plate so as to face an upper surface of the light emitting device. The method of claim 1,
The wavelength conversion sheet is divided into a plurality of areas corresponding to each of the light emitting elements formed in the backlight unit. The method of claim 1,
And a reflector disposed on the substrate and surrounding the light emitting element. The method of claim 3, wherein
The reflector is a backlight unit is formed with at least one cavity of the lower opening. The method of claim 4, wherein
And a horizontal cross-sectional shape of the cavity of the reflector is circular, elliptical, or polygonal. The method of claim 4, wherein
And a sidewall of the cavity of the reflector having an inclined surface that forms an obtuse angle with a substrate on which the light emitting element is disposed. The method of claim 4, wherein
And a sidewall of the cavity of the reflector is an inclined surface having a predetermined curvature. The method of claim 7, wherein
And at least two inclined surfaces having sidewalls of the cavity of the reflector having at least one inflection point. The method of claim 4, wherein
And at least two light emitting elements in one cavity of the reflector. The method of claim 3, wherein
The reflector is a backlight unit made of tempered glass or PET. The method of claim 2,
And a horizontal cross-sectional shape of the wavelength conversion sheet is circular, elliptical, or polygonal. The method of claim 4, wherein
The reflector is a unit of the backlight unit is formed integrally with the upper sidewalls of adjacent cavities. The method of claim 1,
And a reflective sheet disposed on the substrate. The method of claim 1,
The light emitting device is a backlight unit disposed to be spaced apart from the wavelength conversion sheet. The method of claim 1,
And a heat dissipation pad attached to a rear surface of the light emitting module.

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