Backlight assembly and display apparatus having the same

A backlight assembly includes a receiving container, a light guide plate, a light source unit, an optical member and a panel-guiding member. The receiving container includes a bottom plate and a sidewall extended from an edge portion of the bottom plate. The light source unit includes a light source generating light and disposed at side face of the light guide plate, and a light reflecting cover that covers the light source to reflect the light generated from the light source toward the side face. The optical member is disposed over the light guide plate. The panel-guiding member has a first plate combined with the sidewall of the receiving container, and a second plate extended from the first plate such that the second plate covers a portion of the optical member and is spaced apart from an upper face of the optical member. Therefore, warpage and cleavage of the optical member are prevented.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No. 2004-62140 filed on Aug. 6, 2004 and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which are herein incorporated 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 apparatus having the backlight assembly. More particularly, the present invention relates to a backlight assembly preventing warpage of an optical member and a display apparatus having the backlight assembly.

2. Description of the Related Art

A display apparatus converts electric signals processed by an information processing apparatus into images. The display apparatus is characterized either into an active display apparatus that generates light or a passive display apparatus that uses external light to display the image.

Examples of the active display apparatus are a cathode ray tube (“CRT”) display apparatus, an organic light emitting display (“OLED”) apparatus, etc., and an example of the passive display apparatus is a liquid crystal display (“LCD”) apparatus.

The LCD apparatus corresponding to the passive display apparatus does not generate light but uses light in order to display images. Therefore, most LCD apparatuses require a backlight assembly that generates light.

The backlight assembly includes a light source that generates light and an optical member that enhances optical properties of the light generated from the light source. The optical member includes a light guide plate, a light diffusing plate, etc.

The backlight assembly further includes a panel-guiding member. The panel-guiding member fixes the optical member. When the optical member is heated, the optical member is expanded or shrunk resulting in damage to the optical member. The optical member is, for example, warped which deteriorates display quality.

SUMMARY OF THE INVENTION

The present invention provides a backlight assembly preventing warpage and cleavage of an optical member.

The present invention also provides a display apparatus having the above-mentioned backlight assembly.

In an exemplary backlight assembly, the backlight assembly includes a receiving container, a light guide plate, a light source unit, an optical member and a panel-guiding member. The receiving container includes a bottom plate and a sidewall extended from an edge portion of the bottom plate. The receiving container receives the light guide plate. The receiving container receives the light source unit. The light source unit includes a light source that generates light and is disposed at side face of the light guide plate, and a light reflecting cover that covers the light source to reflect the light generated from the light source toward the side face of the light guide plate. The optical member is disposed over the light guide plate. The panel guiding member has a first plate combined with the sidewall of the receiving container, and a second plate extended from the first plate such that the second plate covers a portion of the optical member and spaced apart from an upper face of the optical member.

In an exemplary display apparatus, the display apparatus includes a receiving container, a light guide plate, a light source unit, an optical member, a panel-guiding member and a display panel. The receiving container includes a bottom plate and a sidewall extended from an edge portion of the bottom plate. The receiving container receives the light guide plate. The receiving container receives the light source unit. The light source unit includes a light source that generates light and is disposed at side face of the light guide plate, and a light reflecting cover that covers the light source to reflect the light generated from the light source toward the side face of the light guide plate. The optical member is disposed over the light guide plate. The panel-guiding member has a first plate combined with the sidewall of the receiving container, and a second plate extended from the first plate such that the second plate covers a portion of the optical member and spaced apart from an upper face of the optical member. The display panel is supported by the panel-guiding member, and converts the light into an image.

The optical member in the embodiments disclosed herein is separated from the panel-guiding member. Therefore, warpage and cleavage of the optical member caused by expansion or shrinkage are prevented. Therefore, a display quality is maintained.

In an embodiment described herein, a backlight assembly for preventing warpage and cleavage of an optical member includes an optical member having at least one of a diffusion sheet, a prism sheet, and a brightness enhancing film, wherein the optical member is susceptible to expansion or shrinkage during temperature changes within the backlight assembly and a panel-guiding member for maintaining the optical member within the backlight assembly, wherein the panel-guiding member is spaced from the optical member by a distance that allows the optical member to expand within the backlight assembly without resulting in warpage or cleavage of the optical member.

A method for preventing warpage and cleavage within an optical member of a backlight assembly includes providing an optical member upon a light exiting face of a light guide plate, the optical member provided for enhancing optical properties of light exiting the light guide plate, providing a panel-guiding member within the backlight assembly for fixing the optical member within the backlight member, and, spacing the panel-guiding member from the optical member by a distance sufficient for allowing expansion of the optical member within the backlight assembly without causing warpage or cleavage of the optical member.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanied drawings. In the drawings, the thickness of layers, films, and regions are exaggerated for clarity. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present.

FIG. 1is a cross-sectional view illustrating a backlight assembly according to an exemplary embodiment of the present invention, andFIG. 2is an enlarged view illustrating portion ‘A’ inFIG. 1.

Referring toFIGS. 1 and 2, a backlight assembly according to one embodiment includes a receiving container100, a light source unit200, a light guide plate300, an optical member400and a panel-guiding member500.

The receiving container100includes a bottom plate110and a sidewall120. The receiving container100may be made of, for example, metal. The bottom plate110can have a rectangular plate shape. The sidewall120is extended from edge portions of the bottom plate110to define a receiving space therein.

The light source unit200is disposed in the receiving space of the receiving container100. The light source unit200is disposed within a side portion of the receiving container100. Two light source units200may be disposed within both side portions of the receiving container100such that the light source units200face each other with the light guide plate300interposed therebetween as shown inFIG. 1. Although two light source units200are illustrated, it would be within the scope of this embodiment to utilize more or less light source units200within the receiving container100.

The light source unit200includes a light source210and a light reflecting cover220. The light source210may employ a cold cathode fluorescent lamp (“CCFL”) having a cylindrical shape. Alternatively, the light source210may employ an external electrode fluorescent lamp (“EEFL”) of which electrodes are formed on an external surface of end portions of a lamp body. The EEFL has merits such as low power consumption and a quality of easily performing parallel driving. Although two particular light sources210are described for use within the light source unit200, other suitable light sources210may also be employed within the light source unit200.

The light reflecting cover220covers the light source210such that the light reflecting cover220reflects light generated from the light source210and advances the light from the light reflecting cover220towards the light guide plate300. The light reflecting cover220includes material that has high optical reflectivity and radiates heat well. The light reflecting cover220may include metal, such as, but not limited to, brass.

The light guide plate300changes a path of light from a horizontal direction, substantially parallel to the bottom plate110of the receiving container100, to a vertical direction, substantially parallel to a sidewall120of the receiving container100, to enhance luminance uniformity.

The light guide plate300includes side faces, a light reflecting face320and a light exiting face330. The side faces include light incident faces310facing the light source210. The light reflecting face320faces the bottom plate110of the receiving container100. The light exiting face330is opposite the light reflecting face320.

Light generated from the light source unit200enters the light guide plate300through the light incident faces310. A first portion of the light may exit the light guide plate300through the light exiting face330according to Snell's law. The relationship between the angles of incidence and refraction and the indices of refraction of two medium is known as Snell's law. The relationship may be written as: ni*sin(θi)=nr*sin(θr) where θiis the angle of incidence, θris the angle of refraction, niis the index of refraction of the incident medium, and nris the index of refraction of the refractive medium.

A second portion of the light may exit the light guide plate300through the light reflecting face320. Therefore, a light reflecting material may be coated on the light reflecting face320of the light guide plate300. Alternatively, a light reflecting plate350may be interposed between the bottom plate110of the receiving container100and the light reflecting face320, or the bottom plate110may reflect the second portion of the light, such as by forming the bottom plate110from a reflective material or by applying a reflective coating to the bottom plate110.

The first portion of the light exits the light guide plate300such that a path of the first portion of light forms an acute angle with respect to the light exiting face330. Therefore, the optical member400that changes the path of the first portion of the light forms a right angle with respect to the light incident face310and is disposed over the light exiting face330of the light guide plate300.

The optical member400also enhances luminance uniformity.

The optical member400has a sheet shape with a thin thickness. The optical member400includes, for example, a diffusion sheet, a prism sheet, a brightness enhancing film (“BEF”), etc.

The diffusion sheet diffuses light that exits the light guide plate300through the light exiting face330to enhance luminance uniformity. The prism sheet changes a path of light such that a light-exiting angle approaches a right angle. The BEF also enhances luminance.

The panel-guiding member500extends from the sidewall120of the receiving container100. The panel-guiding member500includes first and second plates510and520.

The first plate510of the panel-guiding member500has a plate shape. The first plate510can be combined with the sidewall120of the receiving container100by using a mechanical connection, such as, but not limited to, a hook combination.

The second plate520of the panel-guiding member500extends from the first plate510such that the second plate520is substantially parallel with the light exiting face330of the light guide plate300. The second plate520covers an upper portion of the light reflecting cover220. A portion of the second plate520overlaps both the light guide plate300and the optical member400disposed over the light guide plate300. The portion of the second plate520, which overlaps the optical member400, is spaced apart from the optical member400. By overlapping the optical member400, the second plate520fixes the optical member400within the backlight assembly, that is, the optical member400is maintained within the backlight assembly.

The second plate520may include a stepped portion525that spaces the second plate520apart from the optical member400.

Therefore, in the event the optical member400experiences shrinkage or expansion, warpage and cleavage of the optical member400may be prevented.

If the second plate520of the panel-guiding member500is compressed towards the light guide plate300, the second plate520may make contact with the optical member400.

In order to prevent such contact between the second plate520and the optical member400, the first plate510of the panel guiding member500is fixed to the sidewall120of the receiving container100such that the second plate520is spaced apart from an upper portion of the light reflecting cover220to form a first gap G1and the second plate520is spaced apart from an upper portion of the optical member400to form a second gap G2that is greater than the first gap G1. As shown inFIGS. 1 and 2, it is the stepped portion525of the second plate520that is spaced from the optical member400by the second gap G2. The stepped portion525can be a reduced portion of the second plate520, that is, as illustrated, the second plate520has a reduced thickness in the area of the stepped portion525, as compared to a portion of the second plate520that is adjacent to the stepped portion525. The portion of the second plate520that is adjacent to the stepped portion525overlies the light reflecting cover220. Any space formed between the light reflecting cover220and the light incident face310may be covered by the stepped portion525of the second plate520. While the stepped portion525is illustrated as having a reduced thickness, it would also be within the scope of this invention for the portion adjacent the stepped portion to have a similar thickness, i.e. via a cutaway portion on the top of the second plate520. The stepped portion525includes a surface facing the optical member400, wherein this surface is spaced from the optical member400by a gap G2, the portion of the second plate adjacent the stepped portion525includes a surface facing the light reflecting cover220, wherein this surface is spaced from the light reflecting cover220by a gap G1, and an intermediate wall is formed between the spaced surfaces. The intermediate wall faces an edge of the optical member400.

The first gap G1is, for example, in a range from about 0.05 mm to about 0.1 mm, and the second gap G2is, for example, in a range from about 0.05 mm to about 0.3 mm. While exemplary ranges are described, it should be understood that a backlight assembly having varying dimensions may require gaps having smaller or larger dimensions than the described ranges.

In order to prevent the optical member400from drifting from the second plate520, the optical member400has substantially the same shape and area as that of the light guide plate300.

Additionally, a side portion, which may be substantially parallel with light incident face310, of the optical member400is spaced apart from the intermediate wall between the stepped portion525of the second plate520and the portion adjacent the stepped portion525by a first distance D1. Therefore, the side portion of the optical member400does not make contact with the second plate520even if the optical member400is expanded. The width of the gap G2and the distance D1may be no less than what is necessary to prevent warpage or cleavage of the optical member400if expanded. If an amount of maximum expansion potential of the optical member400is determined, then the gap G2and the distance D1may be set to be equal to or greater than such an amount. For example, if it is known that the optical member400is capable of expanding 0.1 mm in width and 0.2 mm in length, then the gap G2can be greater than or equal to 0.1 mm and the distance D1can be greater than or equal to 0.2 mm. It is also possible that the gap G2and the distance D1could be slightly less than the amount of maximum expansion potential, so long as the optical member400does not experience warpage or cleavage during expansion. Referring toFIG. 2, light may be leaked through gaps formed between the optical member400and the second plate520of the panel-guiding member500, even though warpage and cleavage may be prevented by the gaps.

In order to prevent leakage of light, a light absorbing film527is disposed on an inner face of the second plate520of the panel-guiding member500, such as on the surface of the stepped portion525that faces the optical member400. The light absorbing film527absorbs light to reduce the leakage of light.

FIG. 3is a cross-sectional view illustrating a backlight assembly according to another exemplary embodiment of the present invention, andFIG. 4is an enlarged view illustrating portion ‘B’ inFIG. 3. The backlight assembly of this embodiment is the same as shown inFIGS. 1 and 2except for a panel-guiding member. Thus, the same reference numerals will be used to refer to the same or like parts as those described with respect toFIGS. 1 and 2and any further explanation will be omitted.

Referring toFIGS. 3 and 4, a spacer529is interposed between the second plate520of the panel-guiding member500and the optical member400. The spacer529prevents contact between the second plate520and the optical member400.

The spacer529has sufficient thickness T1for preventing the contact between the second plate520and the optical member400. The thickness T1can be chosen such that the size of the second gap G2is maintained. The spacer529may include flexible material, such as, but not limited to, rubber.

The spacer529may be attached to an inner surface of the second plate520. Alternatively, the spacer529may be attached to an upper surface of the light reflecting cover220.

Thus, the spacer529eliminates the need to form a stepped portion525into the second plate520as in the embodiment shown inFIG. 1. Similar to portion of the second plate520adjacent the stepped portion525and the intermediate wall of the prior embodiment, the spacer529includes a wall that faces the edge of the optical member400, and includes a surface that faces the light reflecting cover220. An edge of the upper portion of the light reflecting cover220may still be spaced from the optical member400by a first distance D1for preventing the optical member400from making contact with the light reflecting cover220if the optical member400expands. The spacer529does not enter the space (shown as first distance D1) between the optical member400and the light reflecting cover220so that the optical member400also does not make contact with the spacer529during expansion.

FIG. 5is a cross-sectional view illustrating a display apparatus according to an exemplary embodiment of the present invention, andFIG. 6is an enlarged view illustrating portion ‘C’ inFIG. 5. The display apparatus employs a backlight assembly that is the same as in either of the embodiments shown inFIGS. 1 and 2, and inFIGS. 3 and 4. Thus, the same reference numerals will be used to refer to the same or like parts as those described inFIGS. 1-4and any further explanation will be omitted.

Referring toFIGS. 5 and 6, a display panel600is disposed on the second plate520of the panel-guiding member500. The display panel600includes a thin film transistor (“TFT”) substrate610, a color filter substrate620and a liquid crystal (“LC”) layer630interposed between the TFT substrate610and the color filter substrate620.

A display apparatus further includes a first light polarizing plate615disposed on a surface of the TFT substrate610opposite the surface of the TFT substrate610that faces the color filter substrate620, and a second light polarizing plate625disposed on a surface of the color filter substrate620opposite the surface of the color filter substrate620that faces the TFT substrate610.

The display apparatus further includes a top chassis700that prevents the display panel600from drifting from the panel-guiding member500. The top chassis700includes a first chassis portion710that surrounds edge portions of the display panel600, and a second chassis portion720extended from an edge portion of the first chassis portion710such that the second chassis portion720is substantially parallel with the sidewall120of the receiving container100.

The second chassis portion720may be combined with the sidewall120of the receiving container120through any known mechanical or other connection, such as, but not limited to, a hook combination.

According to the embodiment disclosed herein, the optical member400is separated from the panel-guiding member500. Therefore, warpage and cleavage of the optical member400caused by expansion or shrinkage are prevented. Therefore, display quality is maintained.

In view of the above-described embodiments, a method for preventing warpage and cleavage within an optical member of a backlight assembly is made possible and includes, in part, providing an optical member upon a light exiting face of a light guide plate, the optical member provided for enhancing optical properties of light exiting the light guide plate, providing a panel-guiding member within the backlight assembly for fixing the optical member within the backlight member, and spacing the panel-guiding member from the optical member by a distance sufficient for allowing the expansion of the optical member within the backlight assembly without causing warpage or cleavage of the optical member. Having described the exemplary embodiments of the present invention and its advantages, it is noted that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation or quantity, but rather denote the presence of at least one o the referenced item.