KR20070060922A - Led back light unit - Google Patents

Abstract

An LED(Light Emitting Diode) back light unit is provided to install an R(Red)-G(Green)-B(Blue) LED package to an LED cell at the lower portion of a light guide panel, thereby forming the white light. A light guide panel(108) has a plate shape. Plural LED cells(100) are arranged at the lower portion of the light guide panel and include plural LED packages having LED chips for generating the light of RGB. Plural LED cells are electrically connected with a metal PCB(Printed Circuit Board)(104). The PCB is installed at a substrate chassis(102). Total reflection members(120) are formed at the upper portion of the light guide panel and correspond to the LED chips of LED cells. The total reflection member is an inverted and conical shape member by a coating layer. The light guide panel include PMMA(Poly Methyl Meta Acrylate) or PC(Poly Carbonate).

Description

LED backlight unit {LED back light unit}

1 is a vertical cross-sectional view showing a state in which a unit LED package constituting a conventional backlight unit is installed.

2 is a partially exploded perspective view of an LED backlight unit having an LED package according to an embodiment of the present invention.

3 is a front view of the LED package of FIG.

4 is a partial vertical cross-sectional view taken along line IV-IV of FIGS. 2 and 3.

5 is a partial vertical cross-sectional view showing a modification of FIG. 4.

FIG. 6 is a partially enlarged cross-sectional view of the unit LED package of FIG. 5.

<Description of the symbols for the main parts of the drawings>

100: LED cell 102: substrate chassis

104: metal PCB 106: reflective sheet

108: light guide plate 110: LED package

120: total reflection portion 150: diffusion plate

152: diffusion sheet 154: BEF sheet

156: DBEF-D Sheet

The present invention relates to a back light unit using an LED light source, and more particularly, a red-green-blue (RGB) LED package is located under a light guide plate, mounted on an LED cell, and emitted from each LED package. It is a backlight unit using an LED light source mixed in this light guide plate to make white light.

In general, a flat panel display is classified into a light emitting type and a light receiving type, and the light emitting type includes a cathode ray tube (CRT), an electroluminescent (EL) element, and a plasma display panel (PDP). And the light-receiving type include Liquid Crystal Display (LCD).

Since the LCD itself is a light-receiving element which emits light and does not form an image, but receives light from the outside to form an image, a separate light source, for example, a so-called backlight, is installed to observe the image.

These backlights for LCD are classified into direct type and edge type according to the installation position of the light source.In the method of generating white light using the LED as a light source, white light is mixed by optically mixing red and green (RGB) LEDs. There is an RGB LED method for generating a light emitting diode, a method for mixing an ultraviolet LED and a red cyan phosphor, and a binary complimentary method for mixing a blue LED and a yellow phosphor. The LED light source has an advantage that it is not only fast response time compared to the CCFL used as a conventional light source, but also eco-friendly because it does not contain heavy metals such as mercury and is a solid solid element. In particular, the RGB LED system has excellent color expression capability compared to the CCFL and other LED methods that have been used as a light source in the prior art, it was adopted in the LED backlight for high-quality LCD TV.

1 is a cross-sectional view illustrating an installation of a unit LED package in a direct backlight unit. Referring to FIG. 1, a metal printed circuit board (PCB) 20 is installed under a light emitting LED package 16, and the assembly of the LED package 16 and the metal PBC 20 is a substrate chassis. It is installed on 44.

Here, on the light traveling path (upward direction in FIG. 1) of the LED chip (not shown) mounted inside the frame 21, the lens means is installed to adjust the light traveling path, the heat generated from the LED chip In order to discharge, a heat sink slug 22 is installed below the frame 21 and connected to the metal PCB.

Meanwhile, a polymethyl methacrylate (PMMA) plate 28 is disposed on an oval dot 50 of the LED package 16, and a diffusion plate 36 is disposed thereon, and optically thereon. The diffusion sheet 38, the BEF sheet 40, and the DBED-D sheet 42, which are sheets, are stacked to correct luminance of light generated from the LED package.

However, in the case of a backlight unit employing such an LED package having a vertical cross-sectional structure, the heat sink slug 22, the frame 21 and the lens means 18 on the components of the LED package, for example, the metal PCB 20. ) Is stacked and assembled, so that the distance (hm) of the white light mixing section becomes far, and thus the overall thickness (ht) of the backlight unit is thickened, and finally, a product such as a TV set using such a backlight unit. There was a disadvantage that the thickness of the increased.

In addition, in the case of a backlight unit employing an existing LED package, one LED package includes only the LED chip emitting one color, so that the local brightness of the white light of the entire backlight unit can be controlled by controlling the individual LED packages. There was a problem that could not be.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to introduce a light guide plate structure in a backlight unit having an LED package, the thickness of which is structurally reduced, and a backlight unit capable of local dimming. To provide.

LED package for backlight according to the present invention for achieving the above object,

Plate-shaped light guide plate,

A plurality of LED cells disposed below the light guide plate and including a plurality of LED packages having LED chips for generating red, green, and blue (R, G, B) light;

A PCB to which the plurality of LED cells are electrically connected;

A substrate chassis on which the PCB is installed; Include,

The total reflection part is formed in the upper side of the light guide plate of the position corresponding to each LED chip in each LED cell.

Here, it is preferable that the total reflection part is an inverted conical part.

In particular, the conical portion is formed by forming a coating layer in the inverted conical grooves.

In addition, the light guide plate preferably includes PMMA (poly methyl methacrylate) or PC (poly carbonate).

The plurality of LED packages are four LED packages, each of which includes one red and blue light emitting LED package, each of two green light emitting LED packages located opposite each other.

On the other hand, it is preferable that the optical pattern is formed in the lower surface of the said light guide plate.

Here, the optical pattern is preferably formed to avoid the portion corresponding to the LED package.

Optionally, it is preferable that an optical pattern is formed on the exit surface of the light guide plate.

Here, it is preferable that the said optical pattern is formed avoiding a total reflection part.

The LED package is positioned on the lower side of the light guide plate.

On the other hand, the coating layer preferably comprises the coating bonding layer, Ag and a protective layer.

In particular, the coating layer is preferably formed on the inner front of the groove.

Optionally, the coating layer may be formed on the inner half surface of the groove.

On the other hand, the plurality of LED cells is preferably arranged in a matrix shape.

The backlight unit according to another embodiment of the present invention,

Plate-shaped light guide plate,

A plurality of LED cells disposed below the light guide plate and including a plurality of LED packages having LED chips for generating red, green, and blue (R, G, B) light;

A PCB to which the plurality of LED cells are electrically connected;

A substrate chassis on which the PCB is installed; Include,

The total reflection assembly including an inverted conical portion and a cover placed above is formed on an upper side of the light guide plate at a position corresponding to each LED chip in each LED cell.

Here, the conical portion is formed by forming a coating layer in the inverted conical grooves.

On the other hand, the total reflection assembly is preferably formed at the same height as the exit surface of the light guide plate.

The plurality of LED packages are four LED packages, and each of the two green light emitting LED packages positioned opposite to each other preferably includes one red and blue light emitting LED package.

Hereinafter, a direct type backlight unit according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a partially exploded perspective view of a backlight unit in which an LED cell 100 is installed according to an embodiment of the present invention. Although only four LED cells 100 are shown in FIG. 2 by way of example, the actual backlight unit may have more LED cells than that.

In particular, the LED cells 100 mounted in the backlight unit according to the present invention are arranged in a matrix shape. That is, the LED cells 100 are continuously arranged in the horizontal direction and the vertical direction.

Referring to FIG. 2, in the case of a backlight unit according to a preferred embodiment of the present invention, a substrate chassis 102 is provided and a metal PCB 104 is disposed thereon. On the metal PCB 104, a plurality of LED cells 100 of the same shape are mounted adjacent to each other in a matrix shape.

In addition, the white light generated in the LED cell 100 mounted on the substrate chassis 102 passes through the optical element disposed thereon and is finally emitted from the backlight unit.

The diffusion plate 150 is disposed on the LED cell 100 to diffuse light primarily to uniformly maintain the brightness of the white light generated in the unit LED cell. The diffusion sheet 152 is disposed, and on top of that, a BEF sheet 154 and a DBEF-D sheet 156 are disposed.

Hereinafter, in describing the structure of the LED package, the structure thereof will be described based on one unit LED cell 100.

Referring to FIG. 2, the LED cell 100 is disposed between a light guide plate 108 for mixing and mixing light, and a red, green, blue (R, G, B) disposed between the reflective sheet 106 under the light guide plate. A plurality of LED packages 110 for generating colored light. Here, the LED package has a structure that is fitted to the lower surface of the light guide plate 108 through the reflective sheet 106.

On the other hand, the total reflection portion 120 is formed at a position corresponding to the LED package on the emission surface corresponding to the upper surface of the light guide plate.

3 is a front view of the plurality of LED cells 100 in FIG. 2 from above.

In FIG. 3, the symbol R represents a red light emitting LED package, G represents a green light emitting LED package, and B represents a blue light emitting LED package.

Referring to FIG. 3, one unit LED cell 100 includes four LED packages 110, in particular two green light emitting LED packages G and one red and blue light emitting LED packages R and B, respectively. ). Thus, R: G: B is 1: 2: 1 in one LED cell. The green light emitting LED packages are positioned opposite each other. The LED packages are placed in a lozenge in the order of G-B-G-R clockwise.

4 is a cross section taken along line IV-IV of FIGS. 2 and 3. In FIG. 4, there is shown a diffusion plate 150, a diffusion sheet 152, a BEF sheet 154 and a DBEF-D sheet 156, which are optical elements located above the LED cell 100.

In particular, in FIG. 4 the shape of the direct cross section is shown by the solid line and the back shape of the cross section is shown by the broken line.

A plate-shaped metal PCB 104 is positioned on the plate-shaped chassis substrate 102, and a plurality of LED cells 100 are disposed thereon. Each LED cell 100 is arranged with the R, G, B LED package 110 in the arrangement as described above. Meanwhile, the LED package 110 is electrically connected to the metal PCB 104 by the lead 114.

The plurality of LED packages 110 are spaced apart at predetermined intervals, the reflective sheet 106 is located in the space between the spaced apart LED package 110.

The plate-shaped light guide plate 108 is positioned on the plurality of LED packages 110 and the reflective sheet 106, and the LED package is positioned at a predetermined position on a lower side of the light guide plate 108. Here, the light guide plate preferably contains PMMA (poly methyl methacrylate) or PC (poly carbonate).

On the other hand, the total reflection portion 120 is formed on the emission surface that is the upper surface of the light guide plate 108 to correspond to the LED package 110. Therefore, the LED package 110 and the total reflection portion 120 is aligned.

Here, the total reflection portion 120 is a conical portion in the shape of an inverted cone. The conical part is formed with a coating layer 116 in the inverted conical groove 118, the curvature of the groove 118 is determined in consideration of the path of the light to be reflected.

Meanwhile, a separate optical pattern may be formed on the light guide plate in order to make the brightness of the light constant and increase the light efficiency in the process of mixing the light inside the light guide plate and emitting the light. For example, an optical pattern 130 may be formed on the lower surface 186 of the light guide plate 108. The optical pattern 130 may be formed to avoid portions corresponding to the LED package 110. .

Optionally, an optical pattern 125 may be formed on the exit surface 188 of the light guide plate 108. Here, it is preferable that the said optical pattern is formed avoiding a total reflection part.

The method for forming the optical pattern uses a conventional light guide plate pattern forming method such as sand blasting, stamper injection molding, etching. As described above, the method of printing a pattern on an extruded light guide plate has a disadvantage of high manufacturing cost and difficulty in high efficiency, and in the case of injecting a pattern using a stamper, the cost of manufacturing the light guide plate is low, but the cost of manufacturing a mold And time has a significant disadvantage. In the case of processing the prism pattern on the mold core and injection molding the light guide plate using the same, the manufacturing cost and time required for the mold are significant, but the manufacturing cost of the light guide plate is low and the luminance of the generated light is improved. When the optical pattern having the V-shaped cross section is formed on the lower side, the brightness of the light exiting the light guide plate is increased by about 10 to 15%, and when the optical pattern having the V-shaped cross section is formed on the exit surface, about 5 to 10. A luminance increase of% occurs.

On the other hand, the LED package 110 is preferably located on the lower side of the light guide plate 108, the reason is, if there is a space between the LED package 110 and the light guide plate 108, the LED package and the final optical sheet This is because the light mixing distance Hm becomes long, so that the overall thickness Ht of the backlight unit becomes thick. Such a structure can reduce the distance from the LED package to the optical sheet from about 40 mm to about 26 mm compared to the prior art. To this end, the lower side of the light guide plate is provided with a groove having a suitable size to fit the LED package.

On the other hand, the coating layer 116 of the total reflection portion 120 formed on the exit surface of the light guide plate 108 includes the coating bonding layer, Ag and the protective layer in the order close to the groove 118, although not shown in detail. Since Ag has a total reflection property, the light generated in the LED package 110 is totally reflected regardless of the incident angle at the total reflection part, so that the light proceeds laterally in the light guide plate.

Here, as shown in FIG. 4, the coating layer 116 may be formed on the entire inner surface of the groove, but may be formed only on about half surface (based on height) of the inside of the groove.

The LED cells 100 having such a structure are arranged in a matrix shape on the substrate chassis 102. Since each LED cell 100 has all of its own R, G, and B LED packages, it produces white light. The luminance control can be performed respectively. In this case, the luminance of the necessary section can be controlled, so that local dimming is possible.

FIG. 5 is a partial vertical cross-sectional view illustrating a modification of FIG. 4, and FIG. 6 is a partially enlarged assembled cross-sectional view of the unit LED package of FIG. 5.

Compared with the case of FIGS. 2 to 4, the same components will be described using the same reference numerals.

In FIG. 5, a diffusion plate 150, a diffusion sheet 152, a BEF sheet 154, and a DBEF-D sheet 156, which are optical elements located above the LED cell 100, are shown for reference.

In particular, in Figure 5 the shape of the direct cross section is shown by the solid line and the shape behind the cross section is shown by the broken line.

A plate-shaped metal PCB 104 is positioned on the plate-shaped chassis substrate 102, and a plurality of LED cells 100 are disposed thereon. Each LED cell 100 is arranged with the R, G, B LED package 110 in the arrangement as described above. Meanwhile, the LED package 110 is electrically connected to the metal PCB 104 by the lead 114.

The plurality of LED packages 110 are spaced apart at predetermined intervals, the reflective sheet 106 is located in the space between the spaced apart LED package 110.

The plate-shaped light guide plate 108 is positioned on the plurality of LED packages 110 and the reflective sheet 106, and the LED package is positioned at a predetermined position on a lower side of the light guide plate 108. Here, the light guide plate preferably contains PMMA (poly methyl methacrylate) or PC (poly carbonate).

On the other hand, the total reflection assembly 130 is formed to correspond to the LED package 110 on the emission surface that is the upper surface of the light guide plate (108). Thus, the LED package 110 and the total reflection assembly 130 are aligned.

On the other hand, in the process of forming a total reflection coating layer on the total reflection assembly is a task that takes a lot of effort to precisely coating the coating layer is formed. Therefore, in the embodiment illustrated in FIG. 5, the total reflection assembly 130 is improved by darkening due to the coating layer 116 on the upper side of the light guide plate at a position corresponding to each LED package 110 in each LED cell 100. It includes an auxiliary light guide plate 135 for the purpose.

The conical portion is formed by forming a coating layer 116 in the inverted conical groove 118.

In particular, referring to FIG. 6, unlike the case of FIG. 4, the conical groove 118 having the coating layer 116 forms sidewalls 134 having a predetermined depth on the exit surface of the light guide plate 108. A flat support 132 is formed between the sidewalls 134 to form the coating layer 116 inside the groove 118 and then cover the auxiliary light guide plate 135 to form the total reflection assembly 130.

Here, the total reflection assembly is formed at the same height as the exit surface of the light guide plate by making the depth of the side wall 134 and the thickness of the auxiliary light guide plate 135 the same. The curvature of the groove 118 is determined in consideration of the path of the light to be reflected.

Meanwhile, a separate optical pattern may be formed on the light guide plate in order to make the brightness of the light constant and increase the light efficiency in the process of mixing the light inside the light guide plate and emitting the light. For example, an optical pattern may be formed on the lower side of the light guide plate 108, and the optical pattern is preferably formed to avoid a portion corresponding to the LED package 110.

Optionally, an optical pattern may also be formed on the exit surface of the auxiliary LGP 135. Here, it is preferable that the said optical pattern is formed avoiding a total reflection part.

Since the method of forming such an optical pattern is the same as the method described above, overlapping description is omitted. When the optical pattern having the V-shaped cross section is formed on the lower side, the brightness of the light exiting the light guide plate is increased by about 10 to 15%, and when the optical pattern having the V-shaped cross section is formed on the exit surface, about 5 to 10. A luminance increase of% occurs.

On the other hand, the LED package 110 is preferably placed in the insertion hole 148 (see Fig. 6) formed on the lower side of the light guide plate 108, the reason is between the LED package 110 and the light guide plate 108. If there is space, it is difficult for the light emitted from the LED package to be incident on the light guide plate 108 without light loss.

On the other hand, the coating layer 116 of the total reflection assembly 130 formed on the exit surface of the light guide plate 108 includes the coating bonding layer, Ag and the protective layer from the order close to the groove 118, although not shown in detail in the figure. Since Ag has a total reflection property, the light generated in the LED package 110 is totally reflected regardless of the incident angle at the total reflection part, so that the light proceeds laterally in the light guide plate.

The LED cells 100 having such a structure are arranged in a matrix shape on the substrate chassis 102. Since each LED cell 100 has all of its own R, G, and B LED packages, it produces white light. The luminance control can be performed respectively. In this case, the luminance of the necessary section can be controlled, so that local dimming is possible.

As described above, according to the direct type backlight unit of the structure according to the present invention, the following effects can be achieved.

First, the structure of the LED package is not mixed with space, but the light guide plate is placed on the LED package to mix the light in the light guide plate to generate white light. Therefore, the distance from which the light generated from the LED package is mixed is shortened. There is an advantage that the thickness of the backlight unit is reduced.

Second, all of the RGB LED packages are mounted on one LED cell, and the light efficiency is maximized by entering the light guide plate.

Third, since white light can be generated from each LED cell itself, it is possible to control to display a separate brightness for each LED package, which enables local dimming.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (18)

Plate-shaped light guide plate, A plurality of LED cells disposed under the light guide plate and including a plurality of LED packages having LED chips for generating red, green, and blue (R, G, B) light; A PCB to which the plurality of LED cells are electrically connected; A substrate chassis on which the PCB is installed; An LED backlight unit having a total reflection portion formed on an upper side of the light guide plate at a position corresponding to each LED chip in each LED cell. The method of claim 1, The total reflection part is an inverted cone-shaped LED backlight unit, characterized in that. The method of claim 2, The cone-shaped LED backlight unit, characterized in that the coating layer is formed in the inverted conical grooves. The method of claim 1, The light guide plate comprises a PMMA (poly methyl methacrylate) or PC (poly carbonate) LED backlight unit, characterized in that. The method of claim 1, The plurality of LED package is a four LED package, the LED backlight unit, characterized in that it comprises one red and blue light emitting LED package each of the two green light emitting LED packages located opposite each other. The method of claim 1, LED backlight unit, characterized in that the optical pattern is formed on the lower side of the light guide plate. The method of claim 6, And the optical pattern is formed to avoid a portion corresponding to the LED package. The method of claim 1, The LED backlight unit, characterized in that the optical pattern is formed on the exit surface of the light guide plate. The method of claim 8, And the optical pattern is formed to avoid the total reflection part. The method of claim 1, The LED package unit, characterized in that positioned on the lower side of the light guide plate. The method of claim 3, wherein The coating layer LED backlight unit, characterized in that comprising the coating layer, Ag and a protective layer. The method of claim 11, LED coating unit, characterized in that the coating layer is formed on the inner front of the groove. The method of claim 11, The coating layer is LED backlight unit, characterized in that formed on the inner half of the groove. The method of claim 1, And said plurality of LED cells are arranged in a matrix. Plate-shaped light guide plate, A plurality of LED cells disposed under the light guide plate and including a plurality of LED packages having LED chips for generating red, green, and blue (R, G, B) light; A PCB to which the plurality of LED cells are electrically connected; A substrate chassis on which the PCB is installed; And a total reflection assembly including an inverted conical portion and a cover overlying the light guide plate at a position corresponding to each LED package in each LED cell. The method of claim 15, The cone-shaped LED backlight unit, characterized in that the coating layer is formed in the inverted conical grooves. The method of claim 16, The total reflection assembly is LED backlight unit, characterized in that formed with the same height as the exit surface of the light guide plate. The method of claim 15, The plurality of LED package is a four LED package, the LED backlight unit, characterized in that it comprises one red and blue light emitting LED package each of the two green light emitting LED packages located opposite each other.

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