KR20060133821A - Backlight assembly and liquid crystal display comprising the same - Google Patents

Abstract

A backlight assembly and an LCD comprising the same are provided to reduce the leakage of light at a coupling region between a mold frame and an optical sheet, by forming a guide protrusion on the optical sheet and forming a guide groove in the mold frame. A light guiding plate(20) upwardly guides the light, which is emitted from a light source(10). An optical sheet part(40) is disposed above the light guiding plate, and has one or more optical sheets(41,42). Each of the optical sheets has a guide protrusion formed at an edge thereof. A mold frame(50) contains the optical sheets, and has a guide groove(50a) for containing the guide protrusion of each optical sheet. The guide protrusion has a square shape.

Description

Backlight assembly and liquid crystal display including the same

1 is a schematic exploded perspective view of a backlight assembly according to an embodiment of the present invention.

FIG. 2A is a schematic plan view illustrating a state in which a light guide plate and an optical sheet which are applied to a backlight assembly according to an exemplary embodiment of the present invention are overlapped.

FIG. 2B is a cross-sectional view taken along the line BB ′ of FIG. 2A.

FIG. 2C is a cross-sectional view taken along the line BB ′ of FIG. 2A.

3 and 4 are perspective views of a modification of the optical sheet applied to the backlight assembly according to an embodiment of the present invention.

FIG. 5A is a schematic plan view illustrating a light propagation path in a backlight assembly according to an exemplary embodiment of the present invention. FIG.

FIG. 5B is a schematic cross-sectional view taken along the line BB ′ of FIG. 5A.

6 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

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

10: point light source 20: light guide plate

20a: guide protrusion 30: reflective sheet

40: optical sheet layer 41, 42: optical sheet

41a, 42a: guide protrusion 50: mold frame

50a: guide groove 100: backlight assembly

300: liquid crystal panel assembly 500: liquid crystal display device

The present invention relates to a backlight assembly and a liquid crystal display including the same, and more particularly, to a backlight assembly and a liquid crystal display including the same to minimize the light leakage phenomenon.

A liquid crystal display (LCD) is a device that displays an image by injecting a liquid crystal between two glass plates and applying power to the upper and lower glass plate electrodes to change the liquid crystal molecular array in each pixel. Unlike a cathode ray tube (CRT), a plasma display panel (PDP), and the like, a display by a liquid crystal display is not light-emitting because it is non-luminous in itself. To compensate for these disadvantages, a backlight assembly that is uniformly irradiated on the information display surface is mounted for the purpose of enabling use in a dark place.

The backlight assembly used in the conventional liquid crystal display device is largely divided into two types. The first is an edge type backlight assembly that provides light from the side of the liquid crystal display, and the second type is a direct backlight assembly that provides light directly from the back of the liquid crystal display. This classification is determined by the position of the light source that provides the light. In general, the edge type backlight assembly is used in the liquid crystal of notebook PCs, mobile phones, etc. because of the good light uniformity, long durability, and thin film.

The edge type backlight assembly places a light source on the side of the backlight assembly and reflects the light emitted from the bottom surface of the light guide plate to irradiate the light toward the upper side of the backlight assembly. Provide uniform light to the panel. The optical sheet has a guide protrusion on the side, and the guide protrusion is received in the guide groove of the mold frame to form the guide protrusion / guide groove coupling portion.

As described above, in the guide protrusion / guide groove coupling portion, the guide protrusion and the guide groove are not completely in contact with each other, and there is a slight gap. A light leakage phenomenon occurs in which light passing through the light guide plate from the light source partially flows between the gaps. In recent years, the light leakage phenomenon becomes more prominent as the light guide area through which light is transmitted increases instead of decreasing the space occupied by the mold frame. When viewed from the outside, it appears to be partially brighter than the periphery, which is not good in appearance, and causes a deterioration in image quality.

It is an object of the present invention to provide a backlight assembly that minimizes light leakage.

Another object of the present invention is to provide a liquid crystal display device including the backlight assembly as described above.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a backlight assembly including a light source, a light guide plate for guiding light emitted from the light source to an upper side, and a top of the light guide plate, and having a step in at least one corner area. And an optical sheet layer including at least one optical sheet having a guide protrusion formed to protrude from the mold, and a mold frame accommodating the optical sheet and having a guide groove for receiving the guide protrusion.

According to another aspect of the present invention, there is provided a liquid crystal display device including a liquid crystal panel including a liquid crystal configured to determine whether light is transmitted by receiving an electrical signal, and positioned at a rear surface of the liquid crystal panel. Providing a backlight assembly as described above.

Specific details of other embodiments are included in the detailed description and drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, only the embodiments are to make the disclosure of the present invention complete, and the general knowledge in the art to which the present invention belongs It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, a backlight assembly according to an embodiment of the present invention will be described with reference to FIG. 1. 1 is a schematic exploded perspective view of a backlight assembly according to an embodiment of the present invention.

The backlight assembly 100 according to an embodiment of the present invention includes a point light source 10, a light guide plate 20, a reflective sheet 30, an optical sheet 40, and a mold frame 50.

The point light source 10 is disposed on one side of the light guide plate 20 to serve to provide light to the light guide plate 20. The point light source 10 is, for example, a light emitting diode (LED). LEDs are semiconductor diodes that emit light when a direct current flows and can convert electrical signals into lights of various colors such as red, green, and blue. In addition, the LED can be preferably used as the point light source 10 of the present embodiment because of excellent processing speed, power consumption, lifespan, cost and the like.

The point light source 10 may be disposed in a shape accommodated in the light source cover 11 that is accommodated in the mold frame 50. The light source cover 11 serves to receive and support the point light source 10. The light source cover 11 may surround the point light source 10, and may have a shape in which a side opposite to the light guide plate 20 is opened so that light emitted from the point light source 10 is emitted to the light guide plate 20. In addition, the inner surface of the light source cover 11 may be provided with a reflective surface for reflecting the light emitted from the point light source 10 to be emitted to the light guide plate 20.

In addition, although not shown in the drawing, the point light source may be mounted on a flexible printed circuit board and folded to the inside of the mold frame to be positioned to face one side of the light guide plate. In this case, the mold frame may include a receiving part (not shown) having a step to accommodate the point light source.

The light guide plate 20 serves to guide the light emitted from the point light source 10 toward the upper side of the backlight assembly 100. The light guide plate 20 is made of a material having good refractive index and transmittance, for example, polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene (PE), or the like. A scattering pattern for scattering light is formed on the bottom of the light guide plate 20 to guide light incident from the side surface of the light guide plate 20 to the upper side. The scattering pattern may be formed by applying a scattering material to the bottom surface of the light guide plate 20 and patterning the scattering material, and by applying a predetermined bending to the bottom surface of the light guide plate 20, but is not limited thereto. Guide protrusions 20a may be formed in at least one edge area of the light guide plate 20. The guide protrusion 20a of the light guide plate 20 will be described later.

The reflective sheet 30 is disposed under the light guide plate 20. The reflective sheet 30 passes through the bottom of the light guide plate 20 and reflects the light emitted from the lower portion of the light guide plate 20 to the upper side of the light guide plate 20 to increase the luminance of the backlight assembly 100, and thus the light guide plate 20 Make sure the light is emitted uniformly above As the reflective sheet 30, a material having good elasticity, excellent light reflection, and which can be used to form a thin backlight assembly 100 may be used. For example, polyethylene terephthalate (PET) having a thickness of 0.01 mm to 5 mm may be used, but is not limited thereto. In addition, if necessary, a thin film having good elasticity may be used by coating a reflective film to increase light reflection.

The optical sheet layer 40 is disposed on the light guide plate 20. The optical sheet layer 40 allows the light guided by the light guide plate 20 to be uniformly irradiated onto the upper side of the backlight assembly 100, and may include, for example, an optical sheet 41 such as one or more diffusion sheets, prism sheets, or protective sheets. , 42) are selectively stacked. In addition, the optical sheet layer 40 may consist of only one optical sheet, or may include a plurality of identical optical sheets. In addition, the stacking order of the optical sheets 41 and 42 may be variously modified in a range of increasing the uniformity of light. Such optical sheets 41 and 42 can be molded using a transparent resin such as an acrylic resin, a polyurethane resin, a silicone resin, or the like.

Guide protrusions 41a and 42a are formed in at least one corner region of the optical sheets 41 and 42. Detailed description of the guide protrusions 41a and 42a will be described later.

The mold frame 50 stores and supports the point light source 10, the light guide plate 20, the reflective sheet 30, and the optical sheet layer 40, and is formed in, for example, a rectangular shape. On the inner side surface of the corner region of the mold frame 50 is formed a guide groove 50a for receiving the guide protrusion 20a of the light guide plate 20 and / or the guide protrusions 41a and 42a of the optical sheets 41 and 42. It is. The guide groove 50a of the mold frame 50 is mentioned later.

In addition, although not shown in the figure, a bottom chassis for enhancing strength may be disposed under the mold frame 50. At this time, the mold frame 50 is provided with a fastening portion is coupled to the bottom chassis, for example hook coupling.

Hereinafter, the guide protrusions 20a, 41a and 42a of the light guide plate 20 and the optical sheets 41 and 42 and the guide groove 50a of the mold frame 50 will be described with reference to FIGS. 1 and 2A to 4. do.

As illustrated in FIG. 1, the light guide plate 20 and the optical sheets 41 and 42 having a generally rectangular shape include guide protrusions 20a, 41a, and 42a which protrude in stepped form at least one corner area. In response to the guide protrusions 20a, 41a, and 42a, a guide groove 50a is formed in the mold frame 50 to accommodate the guide protrusions 20a, 41a, and 42a. The light guide plate 20 and the optical sheets 41 and 42 are fixed to the mold frame 50 by the guide protrusions 20a, 41a, and 42a and the guide grooves 50a, and may be aligned with each other.

The guide protrusions 20a, 41a, and 42a may be formed at at least one of four corners of the light guide plate 20 and the optical sheets 41 and 42, and preferably considering a fixing force with the mold frame 50. It can be formed at two or more corners. In addition, for example, in the case of the prism sheet among the optical sheets 41 and 42, it is required to be firmly fixed without flowing inside the mold frame 50 because the prism sheet determines the direction of refraction of light. It is preferable that 41a and 42a be formed.

In addition, the shape of the guide protrusions 20a, 41a, 42a may be any shape that can be accommodated in the guide groove 50a of the mold frame 50. It may preferably be a polygonal shape, for example a rectangular shape.

FIG. 2A is a schematic plan view illustrating a state in which a light guide plate and an optical sheet which are applied to a backlight assembly according to an exemplary embodiment of the present invention are overlapped. FIG. 2B is a cross-sectional view taken along the line BB ′ of FIG. 2A. FIG. 2C is a cross-sectional view taken along the line BB ′ of FIG. 2A. 2A to 2C, when the light guide plate 20 and the optical sheets 41 and 42 are overlapped with each other, the guide protrusions 20a, 41a and 42a are formed to overlap each other, and the lower guide protrusions are formed. It may have a shape larger than the guide protrusion overlapping the upper portion.

3 and 4 are perspective views of a modification of the optical sheet applied to the backlight assembly according to an embodiment of the present invention. 3 and 4, the guide protrusion is not necessarily limited to one formed over two sides while including an edge. That is, as shown in Figure 3 may be formed in only one side adjacent to the corner, as shown in Figure 4 except for the corner may be formed in the area adjacent to the corner of the two sides connected to the corner. 3 and 4 illustrate an example of the optical sheet 41 and the guide protrusion 41a provided therein, but the light guide plate 20 may be similarly applied.

Referring back to FIG. 1, the guide protrusions 20a, 41a, 42a as described above are not necessarily provided in the light guide plate 20 and all the optical sheets 41, 42, and may be selectively omitted as necessary. Can be. That is, for example, since the light guide plate 20 is thicker than other optical sheets 41 and 42, the shape of the mold frame 50 may be fixed and aligned to the mold frame 50 even without the guide protrusion 20a. have. Therefore, for example, the light guide plate 20 is used without the guide protrusion 20a, and the first optical sheet 41 such as the diffusion sheet has two guide protrusions 41a, and the second like the prism sheet. The optical sheet 42 can use the thing provided with four guide protrusions 42a.

The guide groove 50a of the mold frame 50 is configured to accommodate the guide protrusions 20a, 41a, 42a when the light guide plate 20 and the optical sheets 41, 42 are disposed on the mold frame 50. It is formed corresponding to the position where the 20a, 41a, 42a are formed. Since the number of the guide grooves 50a should accommodate both the light guide plate 20 and the optical sheets 41 and 42 when overlapping, the guide protrusions 20a, 41a and 42a should be accommodated at least. It is preferable to form the number 20 and the optical sheet layer 40 in a superimposed manner, and then form the same number of superimposed or single guide protrusion groups as viewed from above. For example, two guide protrusions 20a and 41a are formed in the first optical sheet 41 such as the light guide plate 20 and the diffusion sheet, respectively, and four guides in the second optical sheet 42 such as the prism sheet. When the projections 42a are formed, and the guide projections 41a of the double light guide plate 20 and the first optical sheet 41 and the two guide projections 42a of the second optical sheet 42 overlap, Two guide protrusion groups are superimposed and two are independent guide protrusion groups. Therefore, the total number of guide protrusions is four, and correspondingly, four or more guide grooves 50a of the mold frame 50 may be formed.

The size of the guide groove 50a is equal to or larger than the size of the corresponding guide protrusions 20a, 41a, 42a. If the size of the guide groove 50a is too large, light may leak into the space formed between the guide protrusions 20a, 41a, and 42a and the guide groove 50a. In addition, if the size of the guide groove (50a) is exactly the same as the size of the guide projections (20a, 41a, 42a) can minimize the light leakage phenomenon, but difficult to assemble the workability. Thus, it may be possible to make it easy to assemble with a little extra. For example, an excess of about 0.05 to 0.5 mm can be left.

The guide protrusions 20a, 41a, 42a and the guide groove 50a as described above are combined with each other to form a guide protrusion / guide groove coupling portion. Since the guide protrusion / guide groove coupling part is located at a corner of a square shape, light leakage can be reduced. Also, in order to further minimize light leakage, the guide protrusion / guide groove coupling part may be disposed at a relatively far corner from the point light source 10.

5A and 5B, the principle of light leakage improvement by the guide protrusion / guide groove coupling unit formed in the corner region of the rectangular shape as described above will be described. FIG. 5A is a schematic plan view illustrating a light propagation path in a backlight assembly according to an exemplary embodiment of the present invention, and FIG. 5B is a schematic cross-sectional view taken along the line BB ′ of FIG. 5A.

First, as shown in FIGS. 5A and 5B, light emitted from the point light source 10 is obliquely incident on the light guide plate 20. After the light reaching the upper surface of the light guide plate 20, which is the interface between the light guide plate 20 and the air layer, is reflected or refracted, the light reaches the upper side, and the light that reaches the bottom surface of the light guide plate 20 is reflected or refracted downward and passes therethrough. Reflected by the reflective sheet 30 disposed below the light guide plate 20, the light is moved upward. At this time, when the light incident on the light guide plate 20 is formed at the angle formed by the normal to the top or bottom surface of the light guide plate 20, that is, the square of the mouth is larger than the critical angle of the total reflection, the light is not transmitted to the outside of the light guide plate 20 and is totally reflected. Continue to the opposite side of the point light source (10). When the light collides with the scattering pattern formed on the bottom surface of the light guide plate 20, light scattering occurs and proceeds directly to the upper side of the light guide plate 20 or is reflected by the reflective sheet 30 disposed below the upper side. Will proceed.

When the light which continues to the opposite side of the point light source 10 reaches the guide protrusion / guide groove coupling part, the light leaks through the gap between the guide protrusions 20a, 41a, 42a and the guide groove 50a to be recognized. Light leakage phenomenon occurs. In addition, as the leaked light collides with the upper guide protrusions 20a, 41a, and 42a, reflection and scattering of light occur, thereby causing light leakage phenomenon in a wide range as well as directly above the guide protrusion / guide groove coupling part. Appearance defects in which leakage light is observed. In order to improve this, in the backlight assembly 100 according to the exemplary embodiment of the present invention, the light guide plate 20, the optical sheets 41 and 42 and the guide protrusion / guide groove coupling portion may be disposed on the side of the rectangular shape. The structure arrange | positioned at the edge area | region of the mold frame 50 is employ | adopted, and accordingly, the range in which leaking light is observed becomes narrow. In addition, since the guide protrusion / guide groove coupling portion is located at a corner portion relatively far from the point light source 10, the amount of light reaching this is relatively small, and the leakage light is also small, thereby minimizing light leakage.

Although the case where the point light source 10 is disposed on one side of the light guide plate 20 has been described above, the point light source 10 may be disposed on one side of the light guide plate 20 and its opposite surface, and the light guide plate 20 may be disposed on the light guide plate 20. It may be disposed on one side and the other side connected thereto, but is not limited thereto, and may be applied in the same manner except that only one side is applied. In addition, although the example of the point light source 10 has been described as a light source, a line light source such as a cold cathode light source (CCFL) or a hot cathode light source (HCFL) may be used. It is not limited.

Next, a liquid crystal display including the backlight assembly as described above will be described with reference to FIG. 6. 6 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention. Since the backlight assembly used in the liquid crystal display according to the exemplary embodiment of the present invention is the same as described above, a redundant description thereof is omitted.

The liquid crystal display 500 according to the exemplary embodiment of the present invention includes a liquid crystal panel assembly 300 and a backlight assembly 100, among which the liquid crystal panel assembly 300 includes a first substrate 210 and a second substrate. 220, a liquid crystal layer (not shown), a first polarizer 231, and a second polarizer 232.

The first substrate 210 includes a transparent substrate and an array layer on which a thin film transistor (TFT), which is a switching element, is formed in a matrix form on the transparent substrate. The array layer is connected to a pixel electrode and a data line and a gate line made of a conductive oxide film such as indium tin oxide (ITO) and a data line and a gate line for applying a data signal and a gate signal to apply a signal voltage to the pixel electrode. And TFT to cut off. On the source side of the first substrate 210, a Tape Carrier Package (TCP) 211 mounted with a driving element for applying a data side driving signal to a data line is attached, and a gate of the first substrate 210 is attached. On the side is a gate side TCP 212 mounted with a drive element for applying a gate side drive signal to the gate line.

The data side and gate side TCPs 211 and 212 are electrically connected to the printed circuit board 213. The printed circuit board 213 generates driving signals and timing signals and applies them to the plurality of data side and gate side TCPs 211 and 212, respectively.

The second substrate 220 surrounds the color filter and the color filter including a plurality of color pixels formed on the transparent substrate, the plurality of color pixels formed on the transparent substrate, and displaying an image by expressing light provided from the backlight assembly 100 in a predetermined color. Includes a black matrix.

The plurality of color pixels includes red, green, and blue color pixels (RGB color pixels), and one color pixel among RGB color pixels is positioned in a pixel area that is a basic unit for displaying an image. RGB color pixels are produced using photoresist with pigments or dyes of red, green and blue.

The black matrix is disposed to correspond to the TFT formed on the first substrate so that the TFT is not recognized from the outside of the liquid crystal display device.

Meanwhile, in the liquid crystal layer (not shown) interposed between the first substrate 210 and the second substrate 220, the arrangement direction of the liquid crystal molecules is continuously 90 relative to the first substrate 210 and the second substrate 220. ° Twisted Nematic (TN) liquid crystal can be formed. The sealant is interposed between the first substrate 210 and the second substrate 220 to encapsulate the liquid crystal layer between the first substrate 210 and the second substrate 220. The first polarizing plate 231 and the second polarizing plate 232 are disposed on the outer surfaces of the first substrate 210 and the second substrate 220, respectively, and the vibration direction of the light transmitted from the backlight assembly 100 is transmitted. Adjust

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

As described above, the present invention provides a light guide plate and an optical sheet with a guide protrusion in a corner region of a rectangular shape and a mold frame having a guide groove at a corresponding position thereof, Light leakage can be reduced. In addition, by forming the guide protrusion / guide groove coupling portion at a corner far from the light source, the amount of light reaching is reduced, thereby minimizing light leakage. In addition, the liquid crystal display including the backlight assembly may suppress deterioration of image quality due to light leakage.

Claims (8)

Light source; A light guide plate for guiding light emitted from the light source to an upper side; An optical sheet layer disposed on the light guide plate, the optical sheet layer including at least one optical sheet having a guide protrusion formed to protrude in a stepped manner in at least one corner region; And And a mold frame accommodating the optical sheet and having a guide groove for receiving the guide protrusion. According to claim 1, The light source is disposed on one side of the light guide plate, and the guide protrusion is disposed in the opposite corner region of the region where the light source is disposed. According to claim 1, And the optical sheet layer includes two or more optical sheets including the guide protrusions, and the guide protrusions of the two or more optical sheets overlap each other to form a guide protrusion group. According to claim 1, And the guide protrusion is formed over two sides while including an edge of the optical sheet. According to claim 1, The guide protrusion has a square shape. According to claim 1, And the light source includes a plurality of LEDs. According to claim 1, The light guide plate protrudes and forms a step in at least one corner area, and includes a guide protrusion received in the guide groove of the mold frame. A liquid crystal panel assembly including a liquid crystal configured to receive an electrical signal and determine whether light is transmitted; And A liquid crystal display device comprising a backlight assembly according to any one of claims 1 to 7 positioned below the liquid crystal panel and providing the light.

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