Backlight assembly and display device having the same

Provided are a backlight assembly and a display device having the same. The backlight assembly includes a light source unit which generates light; and a light guide plate which comprises an incident light surface through which the light from the light source unit enters the light guide plate, an upper surface joined to the incident light surface and that includes a prism pattern, and a lower surface opposing the upper surface and formed with a plurality of concave portions. A diffusing pattern is formed on one of the upper surface and the lower surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2008-0038276 filed on Apr. 24, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a backlight assembly and a display device having the same, and more particularly, to a backlight assembly and a display device having the same, in which the generation of dark areas and bright areas is prevented such that light is uniformly supplied.

2. Description of the Related Art

In recent years, there has been an increasing demand for flat panel display devices such as plasma display panel (PDP) devices, plasma-addressed liquid crystal (PALC) display panel devices, liquid crystal display (LCD) devices and organic light-emitting diode (OLED) devices, since conventional cathode ray tube (CRT) devices cannot meet the demand for thin and large-scale display devices.

As the most popular flat panel display (FPD), the LCD includes a pair of substrates formed with electrodes and a liquid crystal layer interposed between the substrates. The liquid crystal molecules of the liquid crystal layer are realigned when a voltage is applied to the electrodes to thereby control the amount of light transmission and display a desired image.

Since the LCD is a non-emissive device, a backlight assembly that includes a light source must be included in the LCD in order to display images. The backlight assembly irradiates light from the rear of a liquid crystal panel, and functions as a surface light source that emits light over the entire area of the liquid crystal panel. Depending on the location of the light source, the backlight assembly is referred to as being either of the direct type or edge type. In the direct-type backlight assembly, the light source is positioned directly below the liquid crystal panel, while in the edge-type backlight assembly, the light source is positioned to the side of the liquid crystal panel and a light guide plate is used to transmit light over the entire area of the liquid crystal panel.

In order to enhance the quality of display devices, there is a need for a backlight assembly that is capable of uniformly supplying light to the display panel.

SUMMARY OF THE INVENTION

Aspects of the present invention provide a backlight assembly which prevents the generation of dark areas and bright areas to thereby uniformly supply light.

Aspects of the present invention also provide a display device having a backlight assembly that prevents the generation of dark areas and bright areas to thereby uniformly supply light.

However, the aspects of the present invention are not restricted to the aspects set forth herein. The above and other aspects of the present invention will become more apparent to one of skill in the art to which the present invention pertains by referencing a detailed description of the present invention given below.

According to an aspect of the present invention, there is provided a backlight assembly including: a light source unit which generates light; and a light guide plate which includes an incident light surface through which the light from the light source unit enters the light guide plate, an upper surface joined to the incident light surface and that includes a prism pattern, and a lower surface opposing the upper surface and including a plurality of concave portions. A diffusing pattern is formed on one of the upper surface and the lower surface.

According to another aspect of the present invention, there is provided a backlight assembly including: a light source unit which generates light; a light guide plate which includes an incident light surface through which the light from the light source unit enters the light guide plate, an upper surface joined to the incident light surface and that has a prism pattern, and a lower surface opposing the upper surface and including a plurality of concave portions; and an optical sheet disposed above the light guide plate and that comprises a first surface and a second surface opposing the first surface. A diffusing pattern is formed on one of the first surface and the second surface.

According to another aspect of the present invention, there is provided a display device including: a display panel which displays an image; and a backlight assembly which includes a light source unit that supplies light to the display panel, a light guide plate which includes an incident light surface through which the light from the light source unit enters the light guide plate, an upper surface joined to the incident light surface and that has a prism pattern, and a lower surface opposing the upper surface and including a plurality of concave portions, and an optical sheet disposed above the light guide plate. A diffusing pattern is formed on one of the light guide plate and the optical sheet.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Furthermore, relative terms such as “below,” “beneath,” or “lower,” “above,” and “upper” may be used herein to describe one element's relationship to another element as illustrated in the accompanying drawings. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the accompanying drawings. For example, if the device in the accompanying drawings is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” and “beneath” can, therefore, encompass both an orientation of above and below.

A liquid crystal display according to a first embodiment of the present invention will hereinafter be described with reference toFIGS. 1 through 3.FIG. 1is an exploded perspective view of a display device according to a first embodiment of the present invention,FIG. 2is a partial perspective view of a light guide plate ofFIG. 1, andFIG. 3is a bottom perspective view of the light guide plate ofFIG. 1.

Referring first toFIG. 1, a liquid crystal display10according to an embodiment of the present invention includes a liquid crystal panel assembly20, a backlight assembly100, an intermediate frame120, an upper holder110, and a lower holder170.

The liquid crystal panel assembly20includes a liquid crystal panel30, a liquid crystal layer (not shown), a gate driver IC (integrated circuit)21, a data chip film package22, and a printed circuit board23.

The liquid crystal panel30includes a lower display panel31on which are formed gate lines (not shown), data lines (not shown), a thin-film transistor array, and pixel electrodes, and an upper display panel36, disposed opposite the lower display panel31, and on which are formed a color filter, a black matrix, and common electrodes. Alternatively, the color filter and the common electrodes may be formed on the lower display panel31.

The gate driver IC21is integrated directly on the lower display panel31and is connected to each gate line (not shown) formed on the lower display panel31. The data chip film package22is connected to each data line (not shown) formed on the lower display panel31. The data chip film package22is a semiconductor chip that includes a wiring pattern formed on a base film and a TAB (Tape Automated Bonding) tape which is bonded using the TAB technique. As an example, a tape carrier package (TCP) or a chip on film (COP) may be used for the data chip film package22. However, these are merely examples and the present invention is not limited in this regard.

The printed circuit board23has mounted thereon various driving elements capable of processing gate drive signals and data drive signals, such that gate drive signals may be input to the gate driver IC21and data drive signals may be input to the data chip film package22.

Further, the backlight assembly100includes an optical sheet130, a light guide plate140, a light source unit150, and a reflective sheet160.

The light guide plate140guides light supplied from the light source unit150to the liquid crystal panel assembly20, and is made of a panel formed of a plastic-based transparent material such as an acrylic material. The light guide plate140functions so that light emitted from the light source unit150is directed to the liquid crystal panel30which is disposed above the light guide plate140.

The backlight assembly100is of the edge type in this embodiment. Hence, the light source unit150is provided in an edge-type configuration in which the light source unit150is disposed to one side of the light guide plate140. The light source unit150includes a light source151.

With additional reference toFIGS. 2 and 3, the light guide plate140includes a light incident surface141, an upper surface143, a lower surface142, concave portions145, and a prism pattern144. The light incident surface141is formed on one side surface of the light guide plate140and is adjacent to the light source151so that light passes into the light guide plate140through the light incident surface141. The upper surface143is perpendicular to the light incident surface141and includes the prism pattern144. The lower surface142opposes the upper surface143and includes a plurality of the concave portions145.

The light guide plate140includes various patterns such that light entering into the light guide plate140through the light incident surface141is directed toward the liquid crystal panel30. Such patterns may include the concave portions145formed in the lower surface142.

The concave portions145are formed in the lower surface142in a channel-shaped configuration and extend along the same direction as the light incident surface141. The concave portions145include inclined surfaces that reflect light such that a predetermined amount of the light supplied through the light incident surface141is reflected to thereby change the path of the light upwardly toward the liquid crystal panel30. To allow the concave portions145to effectively change the light path in this manner, each of the concave portions145includes a first inclined surface145aand a second inclined surface145bthat are able to reflect light. The first inclined surface145aand the second inclined surface145bof each concave portion145respectively form an oblique angle with the lower surface142and meet at a line to be inclined to the upper surface143. At least one of the first inclined surface145aand the second inclined surface145bof each concave portion145is directed toward the light incident surface141. Therefore, a predetermined amount of the light supplied through the light incident surface141is reflected by the first inclined surface145aand supplied to the liquid crystal panel30. The inclining angle of the first inclined surface145aof each concave portion145may be varied as needed.

The concave portions145may be formed such that the spacing between adjacent concave portions145is varied as the distance from the light incident surface141is increased. Areas, hereinafter called flat surfaces, of the lower surface142between the concave portions145may be formed parallel to the upper surface143, or may be angled to form a positive slope or a negative slope with respect to the upper surface143.

The lower surface142cooperates with the upper surface143to reflect the light supplied through the light incident surface141such that light reaches areas distant from the light incident surface141. The lower surface142may be formed parallel to the upper surface143. Alternatively, the distance between the lower surface142and the upper surface143may be tapered in a manner that decreases as the distance from the light incident surface141is increased, thereby increasing the distance that the light travels before reflection by a first inclined surface145aby an amount that is greater than if the lower surface142were formed at a predetermined angle. Therefore, light passing through the light incident surface141may be more effectively transferred to a greater distance from the light incident surface141such that the required amount of light is reflected from the first inclined surfaces145aof the concave portions145and transmitted to the liquid crystal panel30.

The depths of the concave portions145may be varied as needed. The light supplied from the light source151is extremely strong near the light incident surface141, while the light weakens as the distance from the light incident surface141is increased. Accordingly, in order to uniformly supply light to the entire area of the liquid crystal panel30, the fractional amount of light reflected by the concave portions145at areas near the light incident surface141is made small, while the fractional amount of light reflected by the concave portions145is increased in proportion to the distance from the light incident surface141.

In order to vary the light reflected by the concave portions145in this manner, the depths of the concave portions145may be varied. Alternatively, the concave portions145may be made to the same size (i.e., the same depth) and the density with respect to the number of the concave portions145formed within a predetermined area may be increased to thereby make the amount of light that is reflected uniform.

The upper surface143of the light guide plate140is formed with the prism pattern144as described above. The prism pattern144focuses the light emitted from the light guide plate140such that the light passed through the light guide plate140is vertically directed onto the liquid crystal panel30.

The prism pattern144may be formed in an elongated configuration from one side of the light guide plate140to the opposite side of the light guide plate140, and may be formed with a plurality of continuous pattern elements or with a plurality of pattern elements that are spaced apart at a predetermined interval. The cross section of the prism pattern144may include elements that are triangular, semicircular, or semielliptical. “Semicircular” as used herein encompasses a shape resembling a part of circle and not necessarily an exact half of a circle, and “semielliptical” as used herein encompasses a shape resembling is a part of an ellipse and not necessarily an exact half of an ellipse.

The cross-sectional shape and area of the prism pattern144may be varied as needed. For example, the cross-sectional shape of the prism pattern144may be such that semicircular or triangular elements are provided between semielliptical elements, and the cross-sectional area thereof may be such that adjacent elements have different areas.

The lower surface142of the light guide plate140includes a diffusing pattern146afor scattering light and preventing the generation of bright dots or areas and dark dots or areas. The diffusing pattern146amay be formed on the surfaces of the concave portions145and on the flat surfaces between the concave portions145. The diffusing pattern146ascatters light passing through the inside of the light guide plate140to prevent the light from reflecting through the entire inner portion of the light guide plate140by multiple reflections and instead allowing the light to exit through the upper surface143. The diffusing pattern146ais formed on the lower surface142of the light guide plate140to perform compensation with respect to locations where bright areas and dark areas form due to the accumulation of light or due to the failure of light to reach certain locations. That is, the diffusing pattern146acauses variances in the paths of light which, in turn, prevents the generation of dark areas and bright areas due to the resulting light interference.

The diffusing pattern146ais formed on the lower surface142of the light guide plate140, and may be formed in a concentrated manner near the light incident surface141. The light guide plate140includes the concave portions145formed in the lower surface142and the prism pattern144formed on the upper surface143, such that the interference of light occurs and bright areas and dark areas are formed near the light incident surface141. By forming the diffusing pattern146anear the light incident surface141, light is uniformly emitted from the entire area of the light guide plate140. The diffusing pattern146amay be formed over an area that may extend to about 70 mm from the light incident surface141.

The diffusing pattern146amay be formed by treating the lower surface with a sand blaster, or may be formed by depositing a coating that scatters light. The diffusing pattern146amay be formed over the entire lower surface142of the light guide plate140or only over an area of the lower surface142in the vicinity of the light incident surface141.

The light source151of the light source unit150supplies light to the liquid crystal panel30. One or more light sources151may be included in the backlight assembly100, the light sources151being spaced apart in a row along the length of the light source unit150with spaces between the light sources151. A point light source such as a light-emitting diode (LED), or a line light source such as a cold cathode fluorescent lamp (CCFL) or a hot cathode fluorescent lamp (HCFL) may be used for the light sources151.

The reflective sheet160is disposed under the light guide plate140and reflects light that is downwardly directed from the light guide plate140back in an upward direction. The reflective sheet160reflects light that is not internally reflected by the lower surface142of the light guide plate140and by the concave portions145formed therein, and that passes out of the light guide plate140, such that this light re-enters the light guide plate140and possibly passes completely therethrough to the liquid crystal panel30. Hence, the reflective sheet160reduces loss of the light emitted from the light sources151and further enhances the uniformity of the light supplied to the liquid crystal panel30.

The optical sheet130is disposed above the light guide plate140such that light transmitted through the light guide plate140is diffused and focused. The optical sheet130may include one or more of the following: a diffusion sheet (not shown), a prism sheet (not shown), and a protection sheet (not shown). The diffusion sheet disperses light received from the light guide plate140to prevent the light from being concentrated in some areas. The prism sheet is formed with triangular prisms formed in a predetermined arrangement on an upper surface thereof, such that the light diffused by the diffusion sheet is focused vertically on the liquid crystal panel30. Accordingly, most of the light passing through the prism sheet travels vertically such that the luminance distribution on the protection sheet is uniform. Further, the protection sheet protects the surface of the prism sheet, and further disperses light to enhance light distribution uniformity.

The liquid crystal display10according to an embodiment of the present invention includes the prism pattern144such that a single prism sheet or a single protection sheet on the single prism sheet may be used as the optical sheet130. Further, when a sufficient focusing effect is obtained through the prism pattern144, a separate prism sheet is unneeded and it is possible to use only the protection sheet.

As described above, the prism pattern144is formed on the light guide plate140, and hence, it is possible to avoid in some cases the use of an additional prism sheet or diffusion sheet.

With reference toFIGS. 1 to 3, the reflective sheet160, the light source unit150, the light guide plate140, and the optical sheet130are received, in this order, in the lower holder170. The lower holder170is made of a metal material, and constructed as a chassis, that provides sufficient protection against external shocks and that may be used for grounding purposes.

The intermediate frame120includes four side walls that are formed into a rectangular frame configuration. The intermediate frame120is lowered downwardly to be mounted surrounding the side walls of the lower holder170.

The liquid crystal panel30is mounted above the protection sheet and is placed within the intermediate frame120. To prevent damage to the elements secured by the intermediate frame120, the intermediate frame120may be formed as a mold frame of a plastic material.

The upper holder110is lowered downwardly to cover the upper surface of the liquid crystal panel30, which is received in the intermediate frame120, and attached to the lower holder170. A window is formed in the upper holder110that exposes the liquid crystal panel30. As in the case of the lower holder170, the upper holder110is made of a metal material, and constructed as a chassis, that provides sufficient protection against external shocks and that may be used for grounding purposes. The upper holder110may be attached to the lower holder170through a hook connection. Further, the printed circuit board23of the liquid crystal panel assembly20may extend past and may be bent along the outer side surfaces of the intermediate frame120to rest against the side surfaces or bottom surface of the lower holder170.

A liquid crystal display according to a second embodiment of the present invention will hereinafter be described with reference toFIGS. 4 and 5.FIG. 4is a partial perspective view of a light guide plate included in a display device according to a second embodiment of the present invention, andFIG. 5is a bottom perspective view of the light guide plate ofFIG. 4. The same reference numerals are used for elements of the second embodiment that are identical in operation and structure as the elements of the first embodiment, and a description of these elements will not be repeated.

In the light guide plate140_1included in the liquid crystal display according to the second embodiment of the present invention, the density distribution of the diffusing pattern146bformed on the lower surface142may be adjusted.

The diffusing pattern146bmay be formed mainly near the light incident surface141of the light guide plate140_1. For example, the density of the diffusing pattern146bin the area adjacent to the light incident surface141may be lowered, while the density of the diffusing pattern146bin an area at a predetermined distance that is further from the light incident surface141may be increased. As another example, the density of the diffusing pattern146bin the area adjacent to the light source151may be lowered, while the density of the diffusing pattern146bin an area at a predetermined distance that is further from the light source151may be increased.

The light guide plate140_1includes the prism pattern144and the concave portions145formed respectively on the upper surface143and in the lower surface142such that the light paths are made complex and random. As a result, bright areas and dark areas may be formed in some areas of the light guide plate140_1. By forming the diffusing pattern146bin such a manner that the density of the diffusing pattern146bat locations where the bright areas are formed is increased, while the density of the diffusing pattern146bat locations where the dark areas are formed is lowered, the light at the bright areas is scattered by the diffusing pattern146band moves to the dark areas. Hence, the uniformity of light over the entire light guide plate140_1is increased.

Such a phenomenon (of the formation of bright and dark areas) is caused by reflection and interference of light. Other factors affecting the position, size, and formation of a pattern of bright and dark areas include the thickness of the light guide plate140_1, and the formations of the prism pattern144and the concave portions145. The density distribution of the diffusing pattern146bmay be varied depending on the location of such bright and dark areas. For example, bright areas may be formed at locations adjacent to the light sources151(assuming a plurality of the light sources151), and dark areas may be formed at locations between the light sources151. In this case, the density of the diffusing pattern146bmay be increased at the locations adjacent to the light sources151and decreased at the locations between the light sources151.

As shown inFIGS. 4 and 5, the lower surface142may include an area147athat is adjacent to and extends along the length of the light source unit150and an area147bthat is adjacent to the area147aand is separated from the light source unit150by the area147a. The area147aincludes a first row of areas of high density148aof the diffusing pattern146band areas of low density148bof the diffusing pattern146b. The first row is adjacent to and parallel to the row of light sources in the light source unit. In the area147a, the areas of high density148amay be located opposite light sources151and the areas of low density148bare located between the areas of high density148aand may be opposite the spaces in the light source unit150, the areas of high density148athus alternating with areas of low density148balong the length of the area147a, or equivalently along the length of the light source unit150.

Area147bincludes a second row of areas of high density148aalternating with areas of low density148b. The areas of high density148ain area147bare disposed opposite areas of low density148bin area147a, and areas of low density148bin area147bare disposed opposite areas of high density148ain area147a.

The first and second rows may be regarded as rows in a rectangular matrix. The matrix pattern may include additional rows formed in areas similar to areas147aand147bwith each such additional area including areas of high density of the diffusing pattern146balternating with areas of low density of the diffusing pattern146b.

In an alternative arrangement, in the first row, the areas of low density diffusing pattern may be located opposite lights sources151and the areas of high density diffusing pattern146bmay be located opposite spaces in the light source unit150, and in the second row the pattern is reversed.

The variation in density of the diffusing pattern146baccording to the bright and dark areas is not limited to a matrix pattern, and the diffusing pattern146bmay be radially formed in a manner centered about each of the light sources151or may be irregularly formed.

Furthermore, it is not necessary that the diffusing pattern146bbe formed only within an area that is at a predetermined distance from the light incident surface141, and the diffusing pattern146bmay be formed partly at an area(s) that is at a distance from the light incident surface141and partly at an area(s) that is close to the light incident surface141.

A liquid crystal display according to a third embodiment of the present invention will hereinafter be described with reference toFIGS. 6 through 8.FIG. 6is a partial perspective view of a light guide plate included in a display device according to a third embodiment of the present invention,FIG. 7is a sectional view taken along line VII-VII′ ofFIG. 6, andFIG. 8shows a modified embodiment of the light guide plate ofFIG. 6. The same reference numerals will be used for elements of the third embodiment that are identical in operation and structure to the elements of the first embodiment, and a description of these elements will not be repeated.

In the liquid crystal display according to the third embodiment of the present invention, the diffusing pattern246aof the light guide plate140_2is formed on the prism pattern144.

The prism pattern144is formed on the upper surface143of the light guide plate140_2and has a cross section that is semielliptical in shape. The diffusing pattern246ais formed on the surface of the prism pattern144. As in the previous embodiments, due to light interference resulting from the formation of the concave portions145in the lower surface142of the light guide plate140_2and the prism pattern144on the upper surface143, bright areas and dark areas may be formed in the area near the light incident surface141of the light guide plate140_2. By forming the diffusing pattern246aon the prism pattern144which, in turn, is formed on the upper surface143of the light guide plate140_2, the formation of the bright areas and the dark areas may be prevented.

The cross section of the prism pattern144may include elements that are triangular, semicircular, or semielliptical. (As described above, “semicircular” encompasses a shape resembling a part of circle and not necessarily an exact half of a circle, and “semielliptical” encompasses a shape resembling is a part of an ellipse and not necessarily an exact half of an ellipse.) The cross-sectional shape of the prism pattern144may also be such that elements with different shapes are alternatingly provided in the prism pattern144. The cross-sectional area of the prism pattern144may also be varied as needed.

The diffusing pattern246amay be formed over only a predetermined portion of the prism pattern144. That is, the light paths vary depending on the cross-sectional shape of the prism pattern144, and the diffusing pattern246amay be formed in areas corresponding to the paths that the light takes. For example, when the prism pattern144is formed of elements that are semicircular in cross section, the diffusing pattern246amay be formed at only the areas in the vicinity of the apexes of the semicircular elements of the prism pattern144, or may be concentrated at the apexes of the semicircular elements of the prism pattern144. Alternatively, the diffusing pattern246amay be omitted at the areas of the apexes of the semicircular elements of the prism pattern144, or may be formed to a low density at the areas of the apexes of the semicircular elements of the prism pattern144. As yet another alternative, the diffusing pattern246amay be formed only in and around the troughs between the elements of the prism pattern144, or may be formed to a high density in these areas.

Referring toFIG. 8, in the light guide plate140_3of this modified embodiment, the density of the diffusing pattern246bformed on the prism pattern144is varied according to position. That is, the density of the diffusing pattern246bmay be changed in a variety of ways depending on the proximity to the light sources151(assuming a plurality of the light sources151). Hence, the diffusing pattern246bmay be formed differently depending on the location of the light sources151, and may be varied also depending on the formation, size, and positioning of the prism pattern144and the concave portions145.

The matrix pattern described in connection with the second exemplary embodiment of the invention may be applied to the prism pattern144.

A backlight assembly according to a fourth embodiment of the present invention will hereinafter be described with reference toFIGS. 9 through 12.FIG. 9is an exploded perspective view of a backlight assembly according to a fourth embodiment of the present invention,FIG. 10is a sectional view taken along line X-X′ ofFIG. 9,FIG. 11is a rear view of a prism sheet of the backlight assembly ofFIG. 9, andFIG. 12shows a modified embodiment of the backlight assembly ofFIG. 10.

The backlight assembly100′ according to the fourth embodiment of the present invention includes a prism sheet130a, the light guide plate140′, the light source unit150having light sources151, and the reflective sheet160.

The light guide plate140′ guides the light supplied by the light sources151to the liquid crystal panel assembly20(seeFIG. 1), and is made of a panel formed of a plastic-based transparent material such as an acrylic material. The light guide plate140′ functions such that light emitted from the light sources151is directed to the liquid crystal panel30(seeFIG. 1) which is disposed above the light guide plate140′.

The light guide plate140′ includes the light incident surface141, the upper surface143, the lower surface142, the concave portions145, and the prism pattern144. The light incident surface141is formed on one side surface of the light guide plate140′ and is adjacent to the light sources151so that light passes into the light guide plate140′ through the light incident surface141. The upper surface143is perpendicular to the light incident surface141and includes the prism pattern144. The lower surface142opposes the upper surface143and includes a plurality of the concave portions145.

The light guide plate140′ includes various patterns such that light entering into the light guide plate140′ through the light incident surface141is directed toward the liquid crystal panel30(seeFIG. 1). Such patterns may include the concave portions145that are formed with inclined surfaces.

The prism sheet130ais disposed above the light guide plate140′ and focuses the light transmitted through the light guide plate140′. The prism sheet130ais formed with triangular prisms in a predetermined arrangement in an upper surface thereof such that light supplied from the light guide plate140′ is focused vertically onto the liquid crystal panel30(seeFIG. 1). Accordingly, most of the light passing through the prism sheet130atravels vertically such that the luminance distribution on the protection sheet (not shown) is uniform. The prism sheet130aincludes a first surface131a, and a second surface131bopposing the first surface131aand on which the prism pattern is formed. A diffusing pattern346amay be formed on the first surface131a.

The diffusing pattern346aadjusts the light supplied from the light guide plate140′ that may be non-uniform so that the light becomes uniform. The diffusing pattern346amay be formed only in an area proximate to the light incident surface141of the light guide plate140′. Further, the density of the diffusing pattern346amay be varied depending on the positioning of the light sources151(assuming a plurality of the same), the distance from the light sources151, and the thickness of the light guide plate140′.

The reflective sheet160is disposed under the light guide plate140′ to reflect light that is downwardly directed from the light guide plate140′ back in an upward direction. The reflective sheet160reflects light that is not reflected by the lower surface142of the light guide plate140and by the concave portions145formed therein, and that passes through light guide plate140′, such that this light re-enters the light guide plate140′ and possibly passes completely therethrough to the liquid crystal panel30(seeFIG. 1). Hence, the reflective sheet160reduces loss of the light emitted from the light source151and further enhances the uniformity of the light supplied to the liquid crystal panel30(seeFIG. 1).

FIG. 11is a rear view of the prism sheet of the backlight assembly ofFIG. 9. The diffusing pattern346aas shown inFIG. 11includes areas of high density and areas of low density arranged in the matrix pattern described with reference to the second exemplary embodiment of the invention. The matrix pattern may, alternatively be form on the upper surface131bof the prism sheet130a.

Referring toFIG. 12, in the modified embodiment of the backlight assembly100′ of the fourth embodiment, the prism sheet130a′ includes the first surface131a, and the second surface131bopposing the first surface131aand which includes the prism pattern. Further, in this modified embodiment, the diffusing pattern346bis formed on the second surface131b, i.e., the diffusing pattern346bis formed on the prism pattern of the second surface131b.

A backlight assembly according to a fifth embodiment of the present invention will hereinafter be described with reference toFIGS. 13 through 15.FIG. 13is an exploded perspective view of a backlight assembly according to a fifth embodiment of the present invention,FIG. 14is a sectional view taken along line XIV-XIV′ ofFIG. 13, andFIG. 15is a rear view of a diffusion sheet of the backlight assembly ofFIG. 13.

The backlight assembly100″ according to the fifth embodiment of the present invention includes the prism sheet130a, a diffusion sheet130b, the light guide plate140′, the light source unit150having the light sources151, and the reflective sheet160.

The light guide plate140′ guides the light supplied by the light sources151to the liquid crystal panel assembly20(seeFIG. 1), and is made of a panel formed of a plastic-based transparent material such as an acrylic material. The light guide plate140′ functions so that light emitted from the light source151is directed to the liquid crystal panel30(seeFIG. 1) which is disposed above the light guide plate140′. The light sources151may be a single light source.

The light guide plate140′ includes the light incident surface141, the upper surface143, the lower surface142, the concave portions145, and the prism pattern144. The light incident surface141is formed on one side surface of the light guide plate140′ and is adjacent to the light sources151so that light passes into the light guide plate140′ through the light incident surface141. The upper surface143is perpendicular to the light incident surface141and includes the prism pattern144. The lower surface142opposes the upper surface143and includes a plurality of the concave portions145.

The light guide plate140′ includes various patterns such that light entering into the light guide plate140′ through the light incident surface141is directed toward the liquid crystal panel30(seeFIG. 1). Such patterns may include the concave portions145that are formed with inclined surfaces.

The diffusion sheet130band the prism sheet130aare disposed above the light guide plate140′ such that light transmitted through the light guide plate140′ is diffused and focused. The diffusion sheet130bdiffuses the light irradiated from the light guide plate140′ to prevent the concentration of light in some areas. The prism sheet130ais formed with triangular prisms in a predetermined arrangement on an upper surface thereof such that light which is dispersed by the diffusion sheet130bis focused vertically onto the liquid crystal panel30(seeFIG. 1). Accordingly, most of the light passing through the prism sheet130atravels vertically such that the luminance distribution on a protection sheet (not shown) is uniform. The protection sheet protects the surface of the prism sheet130a, and further disperses light to enhance light distribution uniformity.

The diffusion sheet130bincludes a diffusing pattern446. The diffusing pattern446adjusts the light supplied from the light guide plate140′ that may be non-uniform so that the light becomes uniform. The diffusing pattern446may be formed only in an area proximate to the light incident surface141of the light guide plate140′. Further, the density of the diffusing pattern446may be varied depending on the positioning of the light sources151(assuming a plurality of the same), the distance from the light sources151, and the thickness of the light guide plate140′.

InFIG. 14, the diffusing pattern446is shown on the lower surface of the diffusion sheet130b. Alternatively the diffusing pattern may be formed on the upper surface of the diffusion sheet130b.

The reflective sheet160is disposed under the light guide plate140′ to reflect light that is downwardly directed from the light guide plate140′ back in an upward direction. The reflective sheet160reflects light that is not internally reflected by the lower surface142of the light guide plate140and by the concave portions145formed therein, and that passes through light guide plate140′, such that this light re-enters the light guide plate140′ and possibly passes completely therethrough to the liquid crystal panel30(seeFIG. 1). Hence, the reflective sheet160reduces loss of the light emitted from the light source151and further enhances the uniformity of the light supplied to the liquid crystal panel30(seeFIG. 1).

FIG. 15shows a rear view of a diffusion sheet of the backlight assembly ofFIG. 13. InFIG. 15, a matrix pattern on the lower surface of the diffusion sheet130bis shown. The matrix pattern is described in connection with the second exemplary embodiment of the invention. The matrix pattern may alternatively be formed on the upper surface of the diffusion film.

While the present disclosure of invention has been particularly provided with reference to exemplary embodiments, it will be understood in light of the disclosure and by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present teachings.