KR102232058B1 - backlight unit and liquid crystal display module including the same - Google Patents

Abstract

The backlight unit of the present invention includes a light emitting diode assembly including a plurality of light emitting diode packages positioned on a light emitting diode printed circuit board; A diffusion plate positioned above the LED assembly and having a plurality of conical grooves respectively corresponding to the plurality of LED packages on a lower surface thereof; And a plurality of optical sheets positioned on the diffusion plate.

Description

Backlight unit and liquid crystal display module including the same

The present invention relates to a liquid crystal display device, and more particularly, to a backlight unit and a liquid crystal display module including the same.

A liquid crystal display (LCD) device includes two substrates and a liquid crystal layer formed between the two substrates, and displays an image by transmitting light by adjusting the arrangement of liquid crystal molecules of the liquid crystal layer.

In general, a liquid crystal display device includes a plurality of pixels arranged in a matrix form, and each pixel includes a thin film transistor, a pixel electrode, and a common electrode. By applying a voltage to the pixel electrode and the common electrode of each pixel, an electric field is generated between the pixel electrode and the common electrode, and the liquid crystal molecules in the liquid crystal layer are rearranged by the generated electric field, thereby changing the transmittance of the liquid crystal layer. Accordingly, by controlling the voltage applied to the pixel electrode and the common electrode of the liquid crystal display, the transmittance of the liquid crystal layer of each pixel can be adjusted to have a value corresponding to the image signal, and as a result, the liquid crystal display displays an image.

Since such a liquid crystal display device is not a self-luminous device, light must be separately supplied. Accordingly, the liquid crystal display device includes a liquid crystal panel that displays an image and a backlight unit that supplies light to the liquid crystal panel.

The backlight unit includes a light source, and a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) has been used as a light source of the backlight unit.

The backlight unit may be divided into a direct type and an edge type according to a path of light emitted from the lamp. The direct type backlight unit is a method of directly supplying light emitted from the lamp to the liquid crystal panel by arranging a plurality of lamps under the liquid crystal panel. In the side type backlight unit, a light guide plate is disposed under the liquid crystal panel and the lamp is disposed on at least one side of the light guide plate, so that light emitted from the lamp is indirectly supplied to the liquid crystal panel by using refraction and reflection from the light guide plate.

Recently, a liquid crystal display device has been widely applied to a display device having a large screen such as a television, but a direct type backlight unit is more suitable for a large area liquid crystal display device than a side type backlight unit and thus is widely used.

Meanwhile, a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) has been used as a light source for the backlight unit. Light-emitting diode (LED) lamps, which have advantages in power consumption, weight, and brightness, as well as light sources of backlight units, are replacing fluorescent lamps.

1 is a schematic cross-sectional view of a liquid crystal display module including a conventional direct type backlight unit.

As shown in FIG. 1, a conventional liquid crystal display module includes a liquid crystal panel 10 that displays an image and a backlight unit 20 that supplies light.

The liquid crystal panel 10 includes a lower substrate 12 and an upper substrate 14, and a liquid crystal layer (not shown) is positioned between the two substrates 12 and 14.

A backlight unit 20 is positioned under the liquid crystal panel 10, and the backlight unit 20 includes a reflective sheet 22, a plurality of LED lamps 24, and a plurality of optical sheets 26 sequentially arranged from the bottom. ).

The liquid crystal panel 10 and the backlight unit 20 are modularized through the support main 30, the top cover 40, and the bottom cover 50. More specifically, the support main 30 surrounds the side surfaces of the liquid crystal panel 10 and the backlight unit 20, and the top cover 40 at the front of the liquid crystal panel 10 and the bottom cover at the rear of the backlight unit 20 (50) is combined and integrated through the support main (30).

Therefore, the light emitted from each LED lamp 24 passes through the optical sheets 26 and is transmitted to the liquid crystal panel 10 in the form of a surface light source, and the liquid crystal panel 10 changes the arrangement of liquid crystal molecules. An image is displayed by selectively transmitting light.

However, in such a conventional direct type backlight unit, a hot spot may occur due to the light emitting diode lamp 24, and accordingly, a lamp mura in which spots are recognized on the display screen appears. In order to prevent hot spots, a certain distance D must be maintained between the light emitting diode lamp 24 and the optical sheets 26, and this distance D is referred to as an optical gap. Since the optical gap D affects the thickness of the liquid crystal display module, it is desirable to reduce the thickness of the liquid crystal display module by reducing the optical gap D.

On the other hand, the LED lamp includes a LED package, and the LED package mounts a LED chip, which is an individual element, and connects a lead to the LED chip to provide a printed circuit. It is manufactured to be attachable to the substrate.

However, such a light emitting diode package has optical characteristics different from that of a fluorescent lamp. More specifically, the fluorescent lamp has a Batwing light distribution shape that spreads to the side, while the light emitting diode package has a round shape Lambertian light distribution shape.

Therefore, a method of making a flat light source by diffusing a light source by installing an optical component such as a lens in a light emitting diode package having a Lambertian light distribution type has been proposed.

2A and 2B are diagrams schematically showing the structure of a light emitting diode lamp including a conventional lens.

As shown in FIG. 2A, a lens 64 is formed on the LED package 62 having a lead 66 on one side, or, as shown in FIG. 2B, the LED package 72 is formed on the reflector 76. And a structure in which a separate lens 74 is aligned with the LED package 72 is used.

These lenses 64 and 74 improve the uniformity of the screen by making the beam angle of light emitted from the LED packages 62 and 72 wider.

However, in the case of the structure of FIG. 2A, the directivity angle cannot be increased by 140 degrees or more, and a lens forming process is added to increase the working time and raw materials used, thereby increasing the manufacturing cost of the LED lamp.

On the other hand, in the case of the structure of FIG. 2B, the process of aligning the lens in the process after the LED package and materials such as a lens and a reflector are added, requiring installation of additional equipment, increasing the manufacturing cost of the LED lamp, and emitting light. Since the size of the lens is determined according to the size of the diode package, there is a disadvantage that the size of the LED package cannot be changed.

In order to solve the above-mentioned conventional problems, an object of the present invention is to provide a thin backlight unit and a liquid crystal display module including the same with improved mura and reduced cost.

In order to achieve the above object, the backlight unit of the present invention includes a light emitting diode assembly including a plurality of light emitting diode packages positioned on a light emitting diode printed circuit board; A diffusion plate positioned above the LED assembly and having a plurality of conical grooves respectively corresponding to the plurality of LED packages on a lower surface thereof; And a plurality of optical sheets positioned on the diffusion plate.

The lower surface of the diffusion plate is in contact with the upper surface of the LED printed circuit board.

The plurality of LED packages are respectively located in the plurality of conical grooves.

Each of the plurality of conical grooves has a vertex angle of 90 degrees to 140 degrees.

The liquid crystal display module of the present invention corresponds to a light-emitting diode assembly including a plurality of light-emitting diode packages disposed on a light-emitting diode printed circuit board, and a light-emitting diode assembly disposed on the light-emitting diode assembly, and to the plurality of light-emitting diode packages on a lower surface thereof. A backlight unit including a diffusion plate having a plurality of conical grooves and a plurality of optical sheets positioned on the diffusion plate; A liquid crystal panel positioned above the backlight unit and displaying an image; A support main surrounding the side surfaces of the liquid crystal panel and the backlight unit; A top cover on the front of the liquid crystal panel; And it includes a bottom cover on the back of the backlight unit.

In the present invention, by forming a conical groove on the lower surface of the diffusion plate so that the LED package is located in the groove and the lower surface of the diffusion plate is in contact with the LED printed circuit board, the light of the LED package is scattered without a lens to generate hot spots and Mura can be prevented and costs can be reduced.

In addition, the groove of the diffusion plate can be applied to a light emitting diode package of various sizes, and an optical gap can be reduced to provide a thin display device.

1 is a schematic cross-sectional view of a liquid crystal display module including a conventional direct type backlight unit.
2A and 2B are diagrams schematically showing the structure of a light emitting diode lamp including a conventional lens.
3 is an exploded perspective view schematically illustrating a liquid crystal display module according to an embodiment of the present invention.
4A is a rear perspective view of a diffusion plate according to an exemplary embodiment of the present invention, and FIG. 4B is an enlarged view of area A1 of FIG. 4A.
5A is a cross-sectional view illustrating a modularized LED assembly and a diffusion plate according to an exemplary embodiment of the present invention, and FIG. 5B is an enlarged view illustrating an area A2 of FIG. 5A.
6A and 6B are diagrams showing simulation results of a backlight unit according to Comparative Example 1 of the present invention.
7A and 7B are diagrams showing simulation results of a backlight unit according to Comparative Example 2 of the present invention.
8A and 8B are diagrams showing simulation results of a backlight unit according to an exemplary embodiment of the present invention.
9A and 9B are diagrams showing simulation results of a backlight unit according to Comparative Example 3 of the present invention.
10A and 10B are diagrams showing simulation results of a backlight unit according to Comparative Example 4 of the present invention.

Hereinafter, a liquid crystal display module according to the present invention will be described in detail with reference to the accompanying drawings.

3 is an exploded perspective view schematically illustrating a liquid crystal display module according to an embodiment of the present invention.

3, the liquid crystal display module of the present invention includes a liquid crystal panel 110, a backlight unit 120, a support main 130, a top cover 140, and a bottom cover 150.

The liquid crystal panel 110 includes a lower first substrate 110a and an upper second substrate 110b, and a liquid crystal layer (not shown) is positioned between the two substrates 110a and 110b.

Although not shown, the first substrate 110a includes a plurality of gates and data lines on its inner surface, and the gates and data lines cross each other to define a plurality of pixel regions. In each pixel region, a thin film transistor and a pixel electrode connected to the gate and data lines are positioned. This first substrate 110a is referred to as an array substrate.

Further, although not shown, the second substrate 110b includes a black matrix, a color filter layer, and a common electrode on an inner surface. The black matrix has openings corresponding to the pixel regions, and red, green, and blue color filter patterns of the color filter layer are sequentially positioned corresponding to the openings of the black matrix. The common electrode covers the black matrix and the color filter layer, and the common electrode forms a liquid crystal capacitor together with the pixel electrode. This second substrate 110b is referred to as a color filter substrate.

Meanwhile, the common electrode may be formed in the pixel region of the first substrate 110a together with the pixel electrode, and in this case, the common electrode and the pixel electrode may be patterned in a bar shape and alternately positioned.

Here, since the area of the second substrate 110b is smaller than that of the first substrate 110a, two adjacent edges of the first substrate 110a are partially exposed.

A driving integrated circuit 114 is located on the exposed first board 110a, and the driving integrated circuit 114 is connected to a printed circuit board (PCB) 116 through a connecting member such as a flexible circuit board. .

A first polarizing plate (not shown) and a second polarizing plate (not shown) are attached to the outer side of the liquid crystal panel 110, that is, a lower portion of the first substrate 110a and an upper portion of the second substrate 110b. . The first polarizing plate and the second polarizing plate transmit only linearly polarized light parallel to each light transmission axis, and the light transmission axis of the first polarizing plate and the light transmission axis of the second polarizing plate are disposed perpendicular to each other.

A backlight unit 120 is positioned under the liquid crystal panel 110 to supply light to the liquid crystal panel 110. The backlight unit 120 includes a light emitting diode (LED) assembly 122, a diffusion plate 124 and optical sheets 126.

The LED assembly 122 includes a plurality of LED printed circuit boards 122a and a plurality of LED packages 122b. A plurality of LED printed circuit boards 122a are placed side by side on the bottom cover 150, and a plurality of LED packages 122b are mounted on the upper surface of each LED printed circuit board 122a. It is located at regular intervals along the length direction of ). Here, a structure in which the LED package 122b is arranged in a row on one LED printed circuit board 122a is presented, but the LED package 122b may be arranged in two rows on one LED printed circuit board 122a, All the LED packages 122b may be arranged in several rows on one LED printed circuit board 122a.

A diffusion plate 124 is positioned on the LED assembly 122. The diffusion plate 124 has a conical groove 124a corresponding to each of the LED packages 122b on its lower surface.

A plurality of optical sheets 126 are positioned on the diffusion plate 124, and the optical sheets 126 may include first to third optical sheets. Here, the first to third optical sheets diffuse or condensate light from the diffusion plate 124, the first optical sheet is a sheet having a light diffusion function, and the second and third optical sheets are sheets having a condensing function. Can be The first optical sheet may be omitted.

Subsequently, the side surface of the backlight unit 120 is surrounded by a support main 130 having a rectangular frame, and an edge of the liquid crystal panel 110 is placed on the support main 130.

The top cover 140 has a'b' shape in cross section including the front and side surfaces, and has an opening in the center of the front, covering the front edge and side surfaces of the liquid crystal panel 110.

The bottom cover 150 is located on the rear surface of the backlight unit 120 and is combined with the top cover 140 via the support main 130 to form a liquid crystal display module.

Here, the top cover 140 is sometimes referred to as a case top, a top case, or a top frame, and the support main 130 is also referred to as a main support or a main frame, and the bottom cover 150 is a cover bottom, a bottom case, or a bottom It is also referred to as a frame.

The diffuser plate of the present invention will be described in more detail with reference to the drawings.

4A is a rear perspective view of a diffusion plate according to an exemplary embodiment of the present invention, and FIG. 4B is an enlarged view of area A1 of FIG. 4A.

4A and 4B, the diffusion plate 124 has a plurality of grooves 124a on its lower surface, and each groove 124a has a conical shape whose diameter decreases from the lower surface to the upper surface. The lower surface diameter of the groove 124a is larger than the width of the LED package (122b in FIG. 3), and when modularized, the LED package (122b in FIG. 3) is located in the groove 124a.

This will be described with reference to FIGS. 5A and 5B.

5A is a cross-sectional view illustrating a modularized LED assembly and a diffusion plate according to an exemplary embodiment of the present invention, and FIG. 5B is an enlarged view illustrating an area A2 of FIG. 5A.

5A and 5B, the LED assembly 122 includes a plurality of LED packages 122b mounted on the LED printed circuit board 122a, and the LED package 122b is located on the LED assembly 122. ), a diffusion plate 124 having a plurality of grooves 124a is positioned.

The LED package 122b is located in each groove 124a, and the lower surface of the diffusion plate 124 contacts the upper surface of the LED printed circuit board 122a.

At this time, it is preferable that the apex angle θ of the groove 124a has an angle ranging from about 90 degrees to about 140 degrees. In addition, as shown, the lower surface diameter of the groove 124a is larger than the height, and the distance between the corresponding LED package 122b and the vertex of the groove 124a is larger than the thickness of the LED package 122b.

Here, the diffusion plate 124 may be made of polymethyl methacrylate (PMMA), and is processed to have a haze characteristic to scatter the total reflected light.

6A and 6B are views showing simulation results of the backlight unit according to Comparative Example 1 of the present invention, and FIGS. 7A and 7B are views showing simulation results of the backlight unit according to Comparative Example 2 of the present invention. 8A and 8B are diagrams showing simulation results of a backlight unit according to an embodiment of the present invention, and are results measured at a position 25mm above the LED assembly. Here, FIGS. 6A, 7A, and 8A show thermal irradiance in the X-axis and Y-axis directions, and FIGS. 6B, 7B, and 8B are graphs of light intensity in the Y-axis direction.

Comparative Example 1 corresponds to a case with an optical gap of 25 mm, and there is no diffusion plate or optical sheet within a distance of 25 mm from the LED assembly, and Comparative Example 2 is a case in which a diffusion plate without grooves is disposed within a distance of 25 mm from the LED assembly. In some cases, the diffuser plate is located directly above the LED assembly.

6A and 6B, in Comparative Example 1, a hot spot is generated corresponding to the LED package, and according to FIG. 6B, which is a light intensity graph in the Y-axis direction, a light peak is generated in the area where the hot spot is generated. It can be seen that the bright and dark repeating mura occurs.

In addition, as shown in Figs. 7A and 7B, even if the diffusion plate is disposed on the upper part of the LED assembly in Comparative Example 2, the result is similar to that of Comparative Example 1, and a hot spot still occurs corresponding to the LED package. It can be seen that there is no improvement.

On the other hand, as shown in Figs. 8A and 8B, in the embodiment of the present invention, by using a diffuser plate having a conical groove on the lower surface, it is found that the hot spot is removed, thereby improving the light uniformity and improving the mura. I can.

Meanwhile, FIGS. 9A and 9B are views showing simulation results of a backlight unit according to Comparative Example 3 of the present invention, and FIGS. 10A and 10B are views showing simulation results of a backlight unit according to Comparative Example 4 of the present invention. 9A and 10A show thermal irradiance in the X-axis and Y-axis directions, and FIGS. 9B and 10B are light intensity graphs in the Y-axis direction. Here, Comparative Example 3 of FIGS. 9A and 9B includes a square pillar-shaped groove on the lower surface of the diffusion plate, and the cross section is a quadrangular shape. It includes a shaped groove, and its cross section forms a semicircle.

As shown in FIGS. 9A and 9B, it can be seen that in the case of Comparative Example 3, a hot spot is generated corresponding to the LED package and thus there is no effect of dispersing light.

In addition, as shown in FIGS. 10A and 10B, in the case of Comparative Example 4, although it is better than that of Comparative Example 3, it can be seen that the hot spot is still generated and the effect of dispersing light is insufficient.

As described above, in the present invention, by using a diffuser plate having a conical groove on the lower surface thereof, the light of the LED package can be scattered without a lens to prevent hot spots and mura, and cost can be reduced. In this case, the groove of the diffusion plate can be applied to LED packages of various sizes, and an optical gap can be reduced to provide a thin display device.

On the other hand, by arranging a reflector or a reflective sheet between the LED assembly and the diffusion plate to reflect light directed toward the bottom cover toward the liquid crystal panel, the efficiency of light may be further increased.

The present invention is not limited to the above-described embodiments, and various changes and modifications are possible without departing from the spirit of the present invention.

110: liquid crystal panel 110a: first substrate
110b: second substrate 112a: first polarizing plate
112b: second polarizing plate 114: driving integrated circuit
116: printed circuit board 120: backlight unit
122: LED assembly 122a: LED printed circuit board
122b: LED package 124: diffuser plate
124a: groove 126: optical sheet
130: support main 140: top cover
150: bottom cover

Claims (6)

A light emitting diode assembly including a plurality of light emitting diode packages positioned on a light emitting diode printed circuit board;
A diffusion plate positioned above the LED assembly and having a plurality of conical grooves respectively corresponding to the plurality of LED packages on a lower surface thereof;
A plurality of optical sheets positioned on the diffusion plate
Including,
Each of the plurality of conical grooves has a vertex angle greater than 90 degrees and less than 140 degrees,
Each of the plurality of conical grooves has a lower surface diameter greater than a height, and a distance between a corresponding LED package and a vertex of the groove is greater than a thickness of the LED package.
The method of claim 1,
A backlight unit, wherein a lower surface of the diffusion plate is in contact with an upper surface of the LED printed circuit board.
The method of claim 2,
The plurality of LED packages are respectively located in the plurality of conical grooves.
delete A backlight unit according to any one of claims 1 to 3;
A liquid crystal panel positioned above the backlight unit and displaying an image;
A support main surrounding the side surfaces of the liquid crystal panel and the backlight unit;
A top cover on the front of the liquid crystal panel; And
Bottom cover on the back of the backlight unit
Liquid crystal display module comprising a.
delete

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