Patent Application
20090237596
This application claims priority to Korean Patent application No. 10-2008-0025534, filed on Mar. 19, 2008, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference.
1. Field of the Invention
The present invention relates to a backlight unit and a liquid crystal display (“LCD”) having the same, and more particularly to a backlight unit and an LCD having the same, provided with a mold frame having a projection formed thereon.
2. Description of the Prior Art
Recently, flat panel displays, such as a liquid crystal displays (“LCDs”), plasma display panels (“PDPs”), or the like, have been rapidly developed in place of a cathode ray tube (“CRT”).
LCDs, which are a kind of flat panel display, have been used in computers, notebook computers, personal digital (data) assistants (“PDAs”), portable phones, televisions (“TVs”), audio/video appliances, and the like, due to their characteristics, such as light weight, thin type, low-power consumption, full color, high resolution, and other beneficial properties, and its application range has been expanded to commercial display fields. However, unlike the PDP, the LCD is not a self-illuminating device, and light sources are required. Various types of light sources are provided in the LCD in accordance with a display method of the LDC. For example, a backlight unit having light sources may be arranged on a rear surface of a liquid crystal display panel to form an LCD.
A backlight unit of a conventional LCD for use in a medium or small-sized portable device, such as a portable phone, a personal portable information terminal, and the like, is provided with a flat tetragonal light guide plate and a plurality of light emitting diodes (“LEDs”) positioned on the rear surface of the light guide plate. In such a conventional LCD, the plurality of LEDs are mounted at predetermined intervals on a substrate having a specified size, and an LED unit, in which the LEDs and the substrate are combined, is positioned on the side surface, e.g., a light input part, of the light guide plate. Also, in order to keep the luminance of the backlight unit uniform, it is important to make the light emitted from the LEDs uniformly incident to the light guide plate without light loss or leakage.
However, according to the conventional backlight unit having the above-described structure, when the LEDs are mounted on the substrate, the respective LED may have an error in mounting position. Although it is difficult to recognize such an error with human eyes, a gap is produced between the light output part of the LED and the light input part of the light guide plate due to the error in mounting position of the LED when the LED unit is positioned on a light-incident surface of the light guide plate. In addition to the error in mounting position, an assembly error may occur when the backlight unit is assembled. For example, in the case of the backlight unit using four LEDs, the light output part of only one LED may be in close contact with the light input part of the light guide plate while the light output parts of the three remaining LEDs may be separated from the light input parts of the light guide plate. In a display having such an assembly error, the backlight unit cannot achieve 100% light efficiency because all of the light from the LEDs is not input into the backlight unit.
Ad described above, according to the conventional backlight unit, a part of the light emitted from the LED cannot be incident to the light guide plate due to the gap between the light output part of the light emitting diode and the light input part of the light guide plate, and thus the light emitting efficiency of the backlight unit is deteriorated.
Accordingly, the present invention alleviates the above-mentioned problems occurring in the prior art, and an aspect of the present invention is to provide a backlight unit and a liquid crystal display (“LCD”) having the same, which can maximize the light emitting efficiency by positioning a light output part of a light emitting diode and a light input part of a light guide plate in close contact with each other.
Additional advantages, aspects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
An exemplary embodiment of a backlight unit according to the present invention includes: a light emitting diode including a light output part, a light guide plate having a light input part positioned substantially opposite to the light output part of the light emitting diode, a mold frame configured to receive and fix the light emitting diode and the light guide plate thereto, and a projection part disposed on the mold frame in a position corresponding to the light emitting diode and the light input part of the light guide plate, wherein a distance between the projection part and the light input part of the light guide plate is shorter than a distance between one side of the light output part of the light emitting diode and a rear surface of the other side of the light emitting diode.
In one exemplary embodiment, the mold frame may include a sidewall configured to fix the light guide plate thereto, and the projection part may be disposed on the sidewall. However, features of the mold frame and the projection part are not limited thereto. In one exemplary embodiment, the mold frame may include a flat part extending from the sidewall of the mold frame to an inner side thereof, and wherein the projection part may be disposed on the flat part. In one exemplary embodiment, the mold frame may include a recess part disposed on the flat part of the mold frame, the recess part being configured to receive the light emitting diode therein, and wherein the projection part may be disposed on the recess part. In one exemplary embodiment, the light guide plate may include a flat base plate, a plurality of guide parts projected from a side of the base plate, and a light input part disposed between adjacent guide parts of the plurality of guide parts. In one exemplary embodiment, the light guide plate is supported by the flat part of the mold frame. In another exemplary embodiment the projection part has a rounded edge in a direction corresponding to a direction from which the light emitting diode is mounted.
In one exemplary embodiment, the projection part contacts the rear surface of the light emitting diode. In one exemplary embodiment, the light emitting diode may include a concave part and convex parts disposed on the rear surface thereof, wherein the convex parts may be disposed on substantially opposite sides of the rear surface of the light emitting diode, and the concave part may be disposed between the convex parts. In one exemplary embodiment, a width of the concave part on the rear surface of the light emitting diode corresponds to a width of the projection part. However, the widths of the concave part and the projection part are not limited thereto. In one exemplary embodiment, the projection part may be formed to be in contact with the concave part and the convex part of the light emitting diode, and in this exemplary embodiment, a width of the rear surface of the light emitting diode and the width of the projection may correspond to each other.
In addition, in one exemplary embodiment, the projection part may include an elastic member, and the elastic member may be at least one of a plate spring, rubber and sponge. In one exemplary embodiment, the plate spring extends from the mold frame to a rear surface of the light emitting diode, and is bent in one of an upward and downward direction.
In addition, in one exemplary embodiment, the projection part and the mold frame may be a single, indivisible unitary body. In another exemplary embodiment, the projection part and the mold frame may be separately prepared and then attached to the mold frame.
In another exemplary embodiment of the present invention, there is provided a liquid crystal display, which includes; a liquid crystal display panel, and a backlight unit configured to supply light to the liquid crystal display panel, and including; a light emitting diode including a light output part, a light guide plate having a light input part positioned substantially opposite to the light output part of the light emitting diode, a mold frame configured to receive and fix the light emitting diode and the light guide plate therein, and a projection part disposed on the mold frame in a position corresponding to the light emitting diode and the light input part of the light guide plate, wherein a distance between the projection part and the light input part of the light guide plate is shorter than a distance between one side of the light output part of the light emitting diode and a rear surface of the other side of the light emitting diode.
In one exemplary embodiment, the projection part is in contact with a rear surface of the light emitting diode. In one exemplary embodiment, the light emitting diode may include a concave part and convex parts disposed on the rear surface thereof, wherein the convex parts may be disposed on opposing sides of the rear surface of the light emitting diode, and the concave part may be disposed between the convex parts. In one exemplary embodiment, a width of the concave part on the rear surface of the light emitting diode corresponds to a width of the projection part. The widths of the concave part and the projection part are not limited thereto, and, in one exemplary embodiment, a width of the rear surface of the light emitting diode and the width of the projection may correspond to each other.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:
The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.
It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element's relationship to another elements as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures 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. The exemplary term “lower”, can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. 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” or “beneath” can, therefore, encompass both an orientation of above and below.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Exemplary embodiments of the present invention are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments of the present invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present invention.
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
The first exemplary embodiment of a backlight unit according to the present invention, as illustrated in
The light guide plate 400 converts light emitted from the LED unit 300 from a point light source into a surface light source, and includes a base plate 400a converting the light emitted from a LED 300a into the surface light source by scattering the light, a plurality of guide parts 400b facilitating the mounting of the LED 300a, and a light scattering pattern 400c formed on a light input part between the guide parts 400b. In this case, the guide parts 400b project a specified distance from one side of the base plate 400a, and in one exemplary embodiment of the present invention, a plurality of tetragonal guide parts 400b are projected from the side of the base plate 400a.
In one exemplary embodiment, the light guide plate 400 is made of a transparent material having a specified refraction ratio, such as polyolefin, polycarbonate, or other materials having similar characteristics. In one exemplary embodiment, the light guide plate 400 is made from a typical acrylic resin, e.g., poly methyl methacrylate (“PMMA”). The LED unit 300 is positioned on a side surface of the light guide plate 400. The side surface of the light guide plate 400 may also be referred to as a light input part. The light scattering pattern 400c may then be disposed on the light input part. In the current exemplary embodiment, the light emitted from the LED unit 300 is incident through the light scattering pattern 400c, and then supplied upward through the base plate 400a. Alternative exemplary embodiments include configurations wherein the guide part 400b and the light scattering pattern 400c may be omitted.
The LED unit 300 is a main light source of the backlight unit, and includes LEDs 300a, and a board 300b for packaging the LEDs 300a. In the current exemplary embodiment, a side-emitting LED having a side surface, on which the light output part is positioned when the LED 300a is mounted on the board 300b, is used as the LED 300a. In such an exemplary embodiment, a flexible printed circuit board (“PCB”) having a high degree of flexibility may be used as the board 300b. The flexible PCB includes a circuit formed thereon, and an external power is supplied to the LED 300a through the circuit. Also, in one exemplary embodiment the LED unit 300 may be attached to the side surface of the light guide plate 400 by using an adhesive member (not illustrated) such as a double-sided adhesive tape. Alternative exemplary embodiments include configurations wherein the LEDs 300a may be affixed to the light guide plate 400 and powered using other means as would be apparent to one of ordinary skill in the art.
The optical sheets 500 are arranged on the upper part and the lower part of the light guide plate 400 to make the luminance distribution of the emitted light uniform, and, in the present exemplary embodiment, includes a diffusion sheet 520, a prism sheet 510, and a reflection sheet 530. The diffusion sheet 520 directs the light incident from the LED unit 300 toward a rear surface of the liquid crystal panel, diffuses the light so that it has a uniform distribution in a wide range of viewing angles, and then irradiates the light onto the liquid crystal display (“LCD”) panel. The prism sheet 510 refracts the inclined light at right angles among the lights incident to the prism sheet 510. The reflection sheet 530 reflects the light output to the lower surface of the light guide plate 400, so that the reflected light is re-incident into the light guide plate 400. In one exemplary embodiment, the reflection sheet 530 may be positioned on the lower surface of the light guide plate 400.
The mold frame 200 receives and fixes the light guide plate 400, the LED unit 300, and the optical sheets 500 thereto, and, in the present exemplary embodiment, is in the form of a tetragon. The mold frame 200 includes a sidewall 200a, a flat part 200b bent in a direction substantially perpendicular to the sidewall 200a, a recess part 200c concavely formed on the flat part 200b, and a projection part 200d formed on the recess part 200c.
In one exemplary embodiment, the sidewall 200a is prepared in a shape corresponding to the light guide plate 400 and the optical sheets 500 so that the sidewall receives and protects the light guide plate 400 and the optical sheet 500. In the current embodiment of the present invention, the light guide plate 400 and the optical sheets 500 are in the form of a tetragon, and thus the sidewall 200a of the mold frame 200 includes first to fourth sidewalls in the form of a tetragon. However, the feature of the sidewall is not limited thereto, and the shape of the sidewall 200a of the mold frame 200 may differ in accordance with the shape of the light guide plate 400 and the optical sheets 500 as would be apparent to one of ordinary skill in the art.
The flat part 200b supports the light guide plate 400, and includes a flat part 200b extending from the sidewall 200a to the inside of the mold frame 200. In the current exemplary embodiment, the flat part 200b includes first to fourth flat parts extending from the first to fourth sidewalls, respectively. The respective flat parts are bent at specified angles from the first to fourth sidewalls, respectively, and extend to support the light guide plate 400 and the optical sheets 500. In order to support the light guide plate 400 and the optical sheets 500, the first to fourth flat parts are bent from the first to fourth sidewalls in directions substantially perpendicular to the first to fourth sidewalls, respectively. Also, on one of the flat parts extending from the first to fourth sidewalls, i.e., on the flat part on which the LED 300a is mounted, a recess part 200c is formed in a direction substantially parallel to the sidewall. In this case, the flat part on which the recess part 200c is formed may not support the light guide plate 400 and the optical sheets 500 in order to secure a space in which the LED may be positioned.
The recess part 200c provides a space in which the LED 300a may be positioned, and is formed on one of the first to fourth flat parts, on which the LED 300a is to be mounted, e.g., on the first flat part 200b. In one exemplary embodiment, the recess part 200c is formed to correspond to the shape of the LED 300a, and the number of the recess parts 200c corresponds to the number of LEDs 300a. That is, in one exemplary embodiment of the present invention, three LEDs 300a are used, and thus the recess part 200c includes first to third recess parts 200c. Exemplary embodiments also include configurations wherein a portion of the flat part 200b may be concavely formed to correspond to the shape of the LED 300a, for example, in the form of a tetragon. Also, since the LED 300a is positioned apart from the light input part of the light guide plate 400 by a specified distance, the recess part 200c is also spaced a specified distance apart from the end of the flat part 200b to correspond to the position of the LED 300a. Alternative exemplary embodiments include configurations wherein the recess part 200c may be omitted.
The projection part 200d positions the light output part of the LED 300a in close contact with the light input part of the light guide plate 400, and is formed on the recess part 200c. In one exemplary embodiment, the projection part 200d may be made of substantially the same material as the mold frame 200. Alternative exemplary embodiments include configurations wherein the projection part 200d may be made from a material different from the mold frame 200. Also, exemplary embodiments include configurations wherein the projection part 200d may be manufactured as a single, unitary and indivisible body with the mold frame 200 and exemplary embodiments wherein the projection part 200d may be separately manufactured and then attached to the mold frame 200. If the projection part 200d is made of a material different from the mold frame 200, the projection part 200d may be separately manufactured and then attached to the mold frame 200, while if the projection part 200d is made of the same material as the mold frame 200, the projection part 200d may be manufactured in a body with the mold frame 200 to save manufacturing costs.
In one exemplary embodiment, the number of the projection parts 200d is substantially the same as the number of the LEDs 300a. In the current exemplary embodiment of the present invention, three LEDs, e.g., the first to third LEDs, are provided, and thus first to third projection parts may be formed on the first to third recess parts in order to position the first to third LEDs in close contact with the light guide plate 400. Alternative exemplary embodiments include configurations wherein the number of projection parts 200d may be increased or decreased in accordance with the number of LEDs 200a.
In one exemplary embodiment the projection part 200d is formed on the recess part 200c that is positioned on the opposite surface of the light out put part of the LED 300a, and pushes the LED 300a with pressure outward against the light guide plate 400, so that the LED 300a becomes in close contact with the light guide plate 400. That is, in one exemplary embodiment, the mold frame 200 projects from the recess part 200c toward the LED 300a. In such an exemplary embodiment, if the recess part is omitted, the projection part 200d may be formed on the flat part 200b corresponding to the position where the LED 300a is mounted. In the exemplary embodiment where the recess part 200c is omitted, the flat part 200b, on which the recess part 200c is to be formed, can also be omitted, and in such an exemplary embodiment the projection part 200d may be formed on the sidewall 200a corresponding to the position where the LED 300a is mounted.
The projection part 200d, as illustrated in
According to an exemplary embodiment of the backlight unit according to the present invention, as illustrated in
The width P1 of the projection part 200d corresponds to the width D1 of the concave part of the LED 300a, and in one exemplary embodiment, the width P1 of the projection part 200d is set to be equal to or smaller than the width D1 of the concave part of the LED 300a. If the width P1 of the projection part 200d is equal to the with D1 of the concave part of the LED 300a, the movement of the LED 300a left and right is prevented by the projection part 200d, e.g., the ends of the concave part act as end-stops for the projection part 200d thereby fixing the LED 300a in a longitudinal direction in addition to a lateral direction, and thus the misalignment between the light scattering pattern 400c of the light guide plate 400 and the light output part of the LED is prevented. On the other hand, the thickness P2 of the projection part 200d is defined as a length projected from the sidewall 200a, and the width P1 of the projection part 200d is defined as a length of a surface that is substantially parallel to the flat part 200b on which the projection part 200d is formed.
In the assembled backlight unit, the side surfaces of the projected guide parts 400b of the light guide plate 400 and the flat parts 200b are in contact with each other, and a space S for mounting the LED is formed by the projected guide parts of the light guide plate 400 and the recess part 200c. In such an exemplary embodiment, the space S for mounting the LED, which is formed by the guide parts 400b and the recess part 200c, is formed to correspond to the shape and the size of the LED 300a. In the exemplary embodiment illustrated in
As shown in
Also, even if the LED having the concave part and the convex parts formed on the rear surface thereof is used according to the embodiment of the present invention, as shown in
In one exemplary embodiment, the first length G1 of the space S for mounting the LED is substantially equal to the sum of the thickness P2 of the projection part 200d, the thickness D2 between the light output part of the LED 300a and the rear surface of the concave part thereof, and a distance D3 between the concave part of the LED 300a and the convex part (i.e., G1=P2+D2+D3). That is, the present invention can be applied to any structure in which the projection part 200d is formed on the mold frame 200, and wherein the projection part 200d ensures close contact between the light output part of the LED and the light input part of the light guide plate 400.
As described above, in the first exemplary embodiment of the present invention, the projection parts 200d formed on the recess parts 200c can position the respective light output parts of the LEDs 300a in close contact with the light input parts of the light guide plate 400, respectively. Also, in the case where the light output parts of the LEDs 300a are in close contact with the light input parts of the light guide plate 400, a luminance difference between the LEDs 300a is prevented, and thus the luminance of the entire backlight unit becomes uniform. Also, since the light input part of the light guide plate 400 is in close contact with the light output part of the LED 300a, most light emitted from the LED 300a is incident to the light guide plate 400, and thus the luminance deterioration due to a gap between the LED 300a and the light guide plate 400 can be prevented.
Hereinafter, a second exemplary embodiment of a backlight unit according to the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, duplicate explanation of the backlight unit which is substantially similar to the description of the first exemplary embodiment of a backlight unit of the present invention will be omitted or will only be briefly stated.
As illustrated in
The light guide plate 400 converts light emitted from the LED 300a from a point light source into a surface light source. In substantially the same manner as the first exemplary embodiment of the present invention, the light guide plate 400 includes a base plate 400a converting the light emitted from an LED 300a into the surface light source by scattering the light, a plurality of guide parts 400b facilitating the mounting of the LED 300a, and a light scattering pattern 400c formed on a light input part between the guide parts 400b. As discussed above, alternative exemplary embodiments include configurations wherein the guide part 400b and the light scattering pattern 400c may be omitted.
The LED unit 300 is a main light source of the backlight unit 1000, and includes LEDs 300a, and a board 300b for packaging the LEDs 300a. In the same manner as the first exemplary embodiment of the present invention, a side-emitting LED having a side surface, on which the light output part is positioned when the LED 300a is mounted on the board 300b, is used as the LED 300a.
The mold frame 200 receives and fixes the light guide plate 400, the LED unit 300, and the optical sheets 500 thereto, and, in the present exemplary embodiment, is in the form of a tetragon. The mold frame 200 includes a sidewall 200a, a flat part 200b bent in a direction crossing the sidewall 200a, a recess part 200c formed on the flat part 200b, and a projection part 200d formed on the recess part 200c. Alternative exemplary embodiments include configurations wherein the mold frame 200 is formed in shapes other than a tetragon.
The projection part 200d according to the second exemplary embodiment of the present invention, unlike the projection part according to the first exemplary embodiment of the present invention, is in the form of a plate spring. That is, as illustrated in
In one exemplary embodiment, the projection part 200d is made of a material having specified strength and elasticity to prevent the projection part 200d from being damaged even if pressure is applied to the projection part 200d when the LED 300a is mounted. After the LED 300a is mounted, the projection part 200d pushes the LED 300a with the restoring force thereof and positions the LED 300a in close contact with the light input part of the light guide plate 400.
In the embodiment shown in
In the second exemplary embodiment of a backlight unit according to the present invention, as illustrated in
In the second exemplary embodiment of the present invention, a tetragonal space S for mounting the tetragonal LED is formed. The area of the space S is represented by a first length G1 and a second length G2 that is longer than the first length G1. In this case, the first length G1 corresponds to the distance between the light input part, on which the light scattering pattern 400c of the light guide plate 400 is formed, and the recess part 200c. In the first exemplary embodiment of the present invention as described above, the sum of the thickness P2 of the projection part 200d and the thickness D2 between the light output part of the LED 300a and a rear surface thereof, which is in contact with the projection part 200d, is set to be equal to the first length G1 of the space S for mounting the LED in order to position the light input part of the light guide plate 400 in close contact with the light output part of the LED 300a.
However, in the second exemplary embodiment of the present invention, the projection part 200d may have substantial elasticity, and thus it is not necessary that the sum of the thickness P2 of the projection part 200d and the thickness D2 between the light output part of the LED 300a and the rear surface, which is in contact with the projection part 200d, be substantially equal to the first length G1 of the space S for mounting the LED. That is, when the LED 300a is mounted, the thickness P2 of the projection part 200d may be reduced by the pressure applied during mounting of the LED, and thus the sum of the thickness P2 of the projection part 200d and the thickness D2 between the light output part of the LED 300a and the rear surface thereof, which is in contact with the projection part 200d, is set to be larger than the first length G1 of the space S for mounting the LED (e.g., G1<P2+D2). In such an exemplary embodiment, the space S may be suitably arranged for mounting the LED 300a therein. After the LED 300a is mounted, the first length G1 of the space S for mounting the LED becomes substantially equal to the sum of the thickness P2 of the projection part 200d and the thickness D2 between the light output part of the LED 300a and the rear surface that is in contact with the projection part 200d.
In the same manner as the first exemplary embodiment of the present invention, an LED having an even rear surface may be used. As illustrated in
As described above, in the second exemplary embodiment of the present invention, the elastic projection parts 200d formed on the recess parts 200c can position the respective light output part of the LEDs 300a in close contact with the light input parts of the light guide plate 400, irrespective of the thickness error and assembly error of the LED 300a. Also, in the case of forming the projection part 200d having the elasticity, the LEDs 300a can be in close contact with the light input parts of the light guide plate, respectively, even if the LEDs have different thicknesses, and thus the luminance of the backlight unit becomes uniform on the whole.
Hereinafter, an exemplary embodiment of an LCD according to the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, duplicate explanation of the backlight unit according to the first and second embodiments of the present invention will be omitted or will be briefly made.
The exemplary embodiment of an LCD according to the present invention, as illustrated in
The LCD panel 600 is configured to display an image, and includes a thin film transistor substrate 600b, a color filter substrate 600a corresponding to the thin film transistor substrate 600b, and a liquid crystal layer (not illustrated) interposed between the thin film transistor substrate 600b and the color filter substrate 600a. The LCD panel 600 may further include a polarizing plate (not illustrated) formed to correspond to the upper part of the color filter substrate 600a and the lower part of the thin film transistor substrate 600b.
In one exemplary embodiment, the thin film transistor substrate 600b is a transparent glass substrate on which thin film transistors and pixel electrodes are formed in the form of a matrix. In such an exemplary embodiment, data lines may be connected to source terminals of the thin film transistors, and gate lines may be connected to gate terminals thereof Also, the pixel electrodes (not illustrated) composed of transparent electrode made of a transparent conductive material are connected to drain terminals thereof. When electric signals are applied to the data lines and the gate lines, the respective thin film transistors are turned on/off, and electric signals required to form images are applied to the drain electrodes thereof
In one exemplary embodiment, the color filter substrate 600a may be a substrate on which color filters of red (R), green (G), and blue (B) that produce specified colors as light passes through the color filter substrate are formed. In one exemplary embodiment a common electrode (not illustrated), made of a transparent conductor, exemplary embodiments of which include indium tin oxide (“ITO”) or indium zinc oxide (“IZO”), is formed on substantially the entire surface of the color filter substrate 600a. The LCD panel 600 receives the signals from an LCD panel driving part (not illustrated) and displays the image in accordance with the received signals.
The backlight unit 1000 includes a light guide plate 400, an LED unit 300 arranged on a side surface of the light guide plate 400 and provided with LEDs 300a and a substrate 300b on which the LEDs are mounted, and a mold frame 200 receiving and fixing thereto the light guide plate 400 and the LED unit 300. In one exemplary embodiment, the backlight unit 1000 further includes optical sheets 500 positioned on upper and lower parts of the light guide plate 400.
The light guide plate 400 converts light emitted from the LED 300a from a point light source into a surface light source, and includes a base plate 400a converting the light emitted from an LED 300a into the surface light source by scattering the light, a plurality of guide parts 400b facilitating the mounting of the LED 300a, and a light scattering pattern 400c formed on the light input part between the guide parts 400b.
The mold frame 200 receives and fixes the light guide plate 400, the LED unit 300, and the optical sheets 500 thereto, and, in the present exemplary embodiment, is in the form of a tetragon. The mold frame 200 includes a sidewall 200a, a flat part 200b bent in a direction crossing the sidewall 200a, a recess part 200c formed on the flat part 200b on which the LED 300a is positioned, and a projection part 200d formed on the recess part 200c. Alternative exemplary embodiments include configurations wherein the recess part 200c and the flat part 200b on which the recess part 200c is formed are omitted.
In the first and second exemplary embodiments of the present invention as described above, the mold frame 200 is provided with the projection part 200d, and the projection part 200d positions the light output part of the LED 300a, which is provided between the mold frame 200 and the light input part of the light guide plate 400, in close contact with the light input part of the light guide plate 400 by applying force to the LED. In one exemplary embodiment, the projection part 200d may be made of substantially the same material as the mold frame 200, or may be separately prepared using a material different from the mold frame 200 and subsequently attached to the mold frame 200. Exemplary embodiments of the projection part 200d may be made of the same resin as the mold frame 200, rubber, or sponge. Also, in the exemplary embodiment wherein the projection part 200d is made of resin, it may be in the form of a plate spring having elasticity.
On the other hand, the receiving member 800 is configured to receive and protect the LCD panel 600 and the backlight unit 1000, and includes an upper receiving member provided on the upper part of the LCD panel 600 and a lower receiving member 100 provided on the lower part of the backlight unit 1000.
As described above, according to the LCD of the present invention, since the light output part of the LED 300a is in close contact with the light input part of the light guide plate 400, the light emitting efficiency of the backlight unit is increased, and thus the luminance of the LCD 600, which receives light from the backlight unit 1000, is improved in comparison to the conventional liquid crystal display.
According to the backlight unit and the LCD having the same according to the present invention, the mold frame is provided with the projection part formed thereon to position the light output part of the LED in close contact with the light input part of the light guide plate, and thus the light efficiency is maximized.
Also, the mold frame is provided with the projection part having elasticity to position the light output part of the LED in close contact with the light input part of the light guide plate, irrespective of the size error of the LED, and thus the light efficiency is maximized.
Also, the light emitting efficiency of the backlight unit is increased, and thus the display quality of the LCD is improved.
Although preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0025534 | Mar 2008 | KR | national |
