KR20130034152A - Back light unit - Google Patents

Abstract

PURPOSE: A backlight unit is provided to improve color uniformity by uniformly spraying a wavelength conversion material on a groove formed on a diffusion plate. CONSTITUTION: The LED(Light Emitting Diode)(110) of a light emitting module(117) or a part of the upper and the lateral surface of the light emitting device is inserted into a groove(145). A reflection sheet(120) delivers the light of the light emitting device to the upper part of a backlight unit. A first prism sheet, a second prism sheet, and a protection sheet are arranged in the upper part of a diffusion sheet(140). A wavelength conversion sheet(150) is arranged in one side of the groove.

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 a plurality of light emitting elements disposed on the substrate; A diffusion plate disposed on the light emitting module and having a plurality of grooves formed in a direction facing the light emitting device; And a wavelength conversion sheet disposed on at least one surface of the groove.

A plurality of grooves may be formed to correspond to the plurality of light emitting devices, respectively.

At least a portion of the upper surface and the side surface of the light emitting device may be inserted into the groove.

At least a portion of an upper surface and a side surface of the light emitting device may be disposed to horizontally overlap the wavelength conversion sheet.

The vertical cross-sectional shape of the groove may be hemispherical, semi-elliptic, or polygonal.

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

Two or more light emitting devices may be correspondingly disposed in one groove formed in the diffusion plate.

The diffusion plate may include a first diffusion plate and a second diffusion plate, and a second diffusion plate having a through hole may be attached to the first diffusion plate to form the groove.

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

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

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

According to the backlight unit according to the embodiment, color uniformity can be improved by applying a uniform wavelength converter to at least one surface of the groove formed in the diffusion plate without using a lens, and the thickness of the backlight unit can be reduced.

1 to 3 are cross-sectional side views of a backlight unit of a direct type according to one embodiment;
4 is a side sectional view showing a backlight unit of a direct type according to another embodiment;
5 and 6 are a plan view showing a grooved diffusion plate,
7 and 8 are views showing a top view of the light emitting device disposed corresponding to the groove of the diffusion plate,
9 to 12 are views illustrating a manufacturing process of a backlight unit of a direct type according to an embodiment.

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 an "on or under" of each component, the (up) or down (below) ( on or under includes both two components directly contacting each other or one or more other components are formed indirectly between the two components (on or under). In addition, when expressed as “on” or “under”, it may include the meaning of the downward direction as well as the upward direction based on one component.

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

A direct light backlight unit according to an embodiment includes a plurality of light sources emitting light, and a chip on board (COB) type light source that directly mounts the plurality of light emitting devices 110 to the substrate 115 in a chip form. This can be used.

As shown in FIG. 1, the direct-type backlight unit according to the embodiment includes a substrate 115 having a circuit pattern formed thereon and a light emitting module 117 including a plurality of light emitting elements 110 disposed on the substrate 115. ), A diffusion plate 140 disposed on the light emitting module 117 and having a plurality of grooves 145 formed in a direction facing the light emitting device 110, and disposed on at least one surface of the groove 145. The wavelength conversion sheet 150 is included.

A plurality of grooves 145 may be formed to correspond to the plurality of light emitting devices 110, respectively.

1 illustrates a light source module 117 including only three light emitting devices 110 for convenience, but four or more light emitting devices 110 may be used.

A circuit pattern is formed on the substrate 115 to supply current 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 117.

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.

The light emitting device 110 of the light emitting module 117 may be disposed such that the entire light emitting device is inserted into the groove 145, and at least a portion of an upper surface and a side surface of the light emitting device is inserted into the groove 145. Although the bottom surface of the diffusion plate 140 is shown in direct contact with the substrate 115 in FIG. 1, this is only an example and may be spaced apart from the substrate 115 at a predetermined interval. .

When the diffusion plate 140 is spaced apart from the substrate 115 by a predetermined distance, the side wall 132 of the bottom cover 130 may have separate supporting portions supporting both ends of the diffusion plate 140. In this case, the light emitting device 110 may not be entirely inserted into the groove 145 formed in the diffusion plate 140, but at least a portion of the upper surface and the side surface of the light emitting device 110 may be inserted into the groove 145. For example, the 140 may be made of polyester and polycarbonate-based materials, and may widen the light projection angle through refraction and scattering of 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.

The wavelength conversion sheet 150 may be disposed on at least one surface of the groove 145 formed in the diffusion plate 140.

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 formed by evenly distributing the phosphor may be disposed on one surface of the groove 145 formed in the diffusion plate 140 without using a light emitting device package including the phosphor integrally.

The wavelength conversion sheet 150 may be disposed to face the upper surface of the light emitting device 110 disposed on the substrate 115, and may be spaced apart from the light emitting device 110.

The wavelength conversion sheet 150 may be disposed only on the bottom surface of the groove 145 of the diffusion plate 140 as shown in FIG. 1, and the bottom and side surfaces of the groove 145 as shown in FIG. 2. It may be arranged in part.

In particular, in the case of the horizontal light emitting device, since the amount of light emitted in the horizontal direction is larger than that of the vertical light emitting device, the wavelength conversion sheet 150 is disposed on a portion of the bottom and side surfaces of the groove 145 as shown in FIG. 2. Can be configured to

Alternatively, the wavelength conversion sheet 150 may be disposed to cover all surfaces of the groove 145.

1 to 3, the vertical cross-sectional shape of the groove 145 of the diffusion plate 140 viewed based on the axis Y-Y ′ in the vertical direction may be polygonal as shown in FIGS. 1 and 2. It may be hemispherical or semi-elliptic as shown in FIG.

In addition, at least a portion of an upper surface and a side surface of the light emitting device 110 may be disposed to overlap the wavelength conversion sheet 150.

That is, as shown in FIG. 1, when the wavelength conversion sheet 150 is disposed only on the bottom surface of the groove 145 of the diffusion plate 140, the upper surface of the light emitting device 110 may be formed of the wavelength conversion sheet 150. 2, the wavelength conversion sheet 150 may be disposed on a portion of the bottom and side surfaces of the groove 145, or the groove 145 may be disposed as illustrated in FIG. 3. If the vertical cross-sectional shape of the hemispherical shape is at least a portion of the upper surface and the side surface of the light emitting device 110 may be disposed overlapping with the wavelength conversion sheet 150.

4 is a side cross-sectional view of a backlight unit of a direct type according to another embodiment.

In another embodiment, the diffusion plate 140 may include a first diffusion plate 140a and a second diffusion plate 140b.

As shown in FIG. 4, no groove is formed in the first diffusion plate 140a, and a plurality of through holes 147 are formed in the second diffusion plate 140b.

Accordingly, the groove 145 may be formed by attaching the second diffusion plate 140b having the through hole 147 to the first diffusion plate 140a.

In the backlight unit illustrated in FIG. 4, the wavelength diffusion sheet 150 having phosphors evenly distributed on the first diffusion plate 140a is applied by patterning using a mask, and thereafter, a second diffusion in which the through hole 147 is formed. It may be manufactured by attaching the plate 140b.

The materials of the first diffusion plate 140a and the second diffusion plate 140b are the same as those of the embodiment described above with reference to FIGS. 1 to 3, and include the light emitting device 110, the substrate 115, and the reflective sheet 120. , And the arrangement relationship between the light emitting element 110 and the wavelength conversion sheet 150 are the same as described above and will not be described again.

5 and 6 illustrate a plan view of a diffusion plate having grooves formed therein.

5 and 6, the horizontal cross-sectional shape of the groove 145 of the diffusion plate 140 viewed from the horizontal axis X-X ′ in FIGS. 1 to 3 may be circular, elliptical, or polygonal. Can be.

5 illustrates a diffusion plate 140 having a groove 145 having a square horizontal cross sectional shape, and FIG. 6 illustrates a diffusion plate 140 having a groove 145 having a circular horizontal cross sectional shape.

If necessary, a diffusion plate 140 formed by mixing a groove 145 having a horizontal cross-sectional shape of a circular, elliptical, or polygonal shape may be used, and the number of the grooves 145 formed in the diffusion plate 140 is limited. Do not put

7 and 8 are views showing a top view of the light emitting device disposed corresponding to the groove of the diffusion plate.

As shown in FIG. 7, only one light emitting device 110 may be disposed corresponding to each groove 145 of the diffusion plate 140, and as shown in FIG. 8, two or more light emitting devices 110 may correspond to each other. It may be arranged.

When the plurality of light emitting devices 110 are correspondingly disposed in the grooves 145 of the diffusion plate 140, the light emitting elements 110 disposed in one groove 145 form one unit to be local dimmed. Dimming) region can be formed.

When the plurality of light emitting devices 110 are disposed in the grooves 145 of the diffusion plate 140 as shown in FIG. 8, one light emitting device 110 is disposed in the grooves 145 of the diffusion plate 140 as shown in FIG. 7. ), The number of grooves 145 formed in the diffusion plate 140 may be reduced, and the size of one groove 145 may be larger than in the case where only) is disposed.

9 to 12 are views illustrating a manufacturing process of a backlight unit of a direct type according to an embodiment. Hereinafter, a method of manufacturing the backlight unit of the direct method according to the embodiment will be described with reference to FIGS. 9 to 12.

First, as shown in FIG. 9, the groove 145 is formed in the diffusion plate 140. The groove 145 may be formed through mechanical processing.

When the groove 145 is formed in the diffusion plate 140, the wavelength conversion sheet 150 is disposed on at least one surface of the groove 145 as shown in FIG. 10. As described above, the wavelength conversion sheet 150 may be disposed only on one surface of the groove 145, or the wavelength conversion sheet 150 may be disposed to cover all surfaces of the groove 145.

11, the bottom cover 130 is prepared, a substrate 115 having a circuit pattern formed thereon is disposed on the bottom cover 130, and the reflective sheet 120 is disposed on the substrate 115. Place it.

The reflective sheet 120 forms an open region W at a position where the light emitting element 110 is to be subsequently disposed, and may not be disposed in the region a where the diffusion plate 140 and the substrate 115 are to be contacted later. .

Thereafter, as illustrated in FIG. 12, the light emitting device 110 is disposed to contact the substrate 115 in the open area W of the reflective sheet 120.

In addition, the diffusion plate 140 illustrated in FIG. 10 is assembled into the bottom cover 130 such that the groove 145 and the light emitting device 110 face each other.

A panel (not shown) may be disposed in the backlight unit 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 converting member to at least one surface of a groove formed in the diffusion plate without using a lens on the light emitting device, color uniformity is eliminated to improve color uniformity, and the backlight unit is improved. The thickness of can be reduced.

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: light emitting device 115: substrate
117: light emitting module 120: reflective sheet
130: bottom cover 140: diffusion plate
145: home

Claims (11)

A light emitting module including a substrate having a circuit pattern formed thereon and a plurality of light emitting elements disposed on the substrate;
A diffusion plate disposed on the light emitting module and having a plurality of grooves formed in a direction facing the light emitting device; And
And a wavelength conversion sheet disposed on at least one surface of the groove. The method of claim 1,
And a plurality of grooves formed in correspondence with the plurality of light emitting elements, respectively. The method of claim 1,
At least a portion of the upper surface and the side surface of the light emitting device is inserted into the groove is disposed. The method of claim 1,
And at least a portion of an upper surface and a side surface of the light emitting device overlapping the wavelength conversion sheet. The method of claim 1,
And a vertical cross-sectional shape of the groove is hemispherical, semi-elliptic, or polygonal. The method of claim 1,
And a horizontal cross-sectional shape of the groove is circular, elliptical, or polygonal. The method of claim 1,
Two or more light emitting elements correspondingly disposed in one groove formed in the diffusion plate. The method of claim 1,
The diffusion plate may include a first diffusion plate and a second diffusion plate, and the second diffusion plate having a through hole is attached to the first diffusion plate to form the groove. The method of claim 1,
And a reflective sheet disposed on the substrate. The method of claim 1,
And a heat dissipation pad attached to a rear surface of the light emitting module. The method of claim 1,
The light emitting device is a backlight unit disposed to be spaced apart from the wavelength conversion sheet.

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