Backlight unit and display apparatus having the same

An exemplary embodiment of the present invention discloses a backlight unit with a plurality of light-emitting blocks and a light source driving section. The plurality of light-emitting blocks are arranged in a matrix shape along first and second directions different from each other. Each of the light-emitting blocks includes a light source unit having at least one light-emitting chip to emit light, and a light guiding unit to guide the light. The light source driving section controls the light source unit of the light-emitting blocks to drive the light source unit. Therefore, a thickness of the backlight unit may be reduced.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean Patent Application No. 10-2008-0095400, filed on Sep. 29, 2008, and Korean Patent Application No. 10-2008-0135446, filed on Dec. 29, 2008, which are hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Exemplary embodiments of the present invention relate to a backlight unit and a display apparatus having the backlight assembly and, more particularly, exemplary embodiments of the present invention relate to a backlight unit providing a liquid crystal display (LCD) apparatus with light and an LCD apparatus having the backlight assembly.

2. Discussion of the Background

In general, an LCD apparatus includes an LCD panel to display an image and a backlight unit disposed under the LCD panel to provide the LCD panel with light.

The LCD panel includes a first substrate having a thin film transistor (TFT) and a pixel electrode electrically connected to the TFT, a second substrate having a color filter corresponding to the pixel electrode and a common electrode, and a liquid crystal layer disposed between the first substrate and the second substrate.

The backlight unit includes a receiving container, a plurality of lamps disposed in parallel in the receiving container, and an optical member disposed over the lamps to improve optical characteristics of the light generated by the lamps. The optical member includes a light-diffusing plate diffusing the light to improve luminance uniformity.

The optical member is in general spaced apart from the lamps to improve diffusion of light. As a result, the thickness of the backlight unit increases.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a backlight unit with a reduced thickness.

Exemplary embodiments of the present invention also provide a display apparatus having the backlight unit.

An exemplary embodiment of the present invention discloses a backlight unit, comprising a plurality of light-emitting blocks arranged in a matrix shape along a first direction and a second direction, wherein the first direction and the second direction are different from each other, each of the light-emitting blocks comprising a light source unit, wherein each light source unit comprises a light-emitting chip to emit light and a light guiding unit to guide the light; and a light source driving section to control the light source unit of each of the light-emitting blocks and to drive the light source unit.

An exemplary embodiment of the present invention also discloses a backlight unit, comprising a light guiding unit comprising a light guiding body portion, an upper extending portion extended from an upper portion of a first side surface of the light guiding body portion, and a lower extending portion extended from a lower portion of a second side surface of the light guiding body portion, wherein the first side surface is opposite the second side surface; a first light source unit disposed under the upper extending portion to provide the upper extending portion with a first light; a second light source unit disposed adjacent to the lower extending portion to provide the lower extending portion with a second light; and a transmit-reflecting sheet disposed between the upper extending portion and the first light source unit to transmit the first light.

An exemplary embodiment of the present invention also discloses a display device, comprising a backlight unit to generate light; and a display unit to display an image with the light generated by the backlight unit, wherein the backlight unit, comprises a plurality of light-emitting blocks arranged in a matrix shape along a first direction and a second direction, wherein the first direction and the second direction are different from each other, each of light-emitting blocks comprising a light source unit, wherein each light source unit comprises at least one light-emitting chip to emit light and a light guiding unit to guide the light; and a light source driving section to control the light source unit of the light-emitting blocks and to drive the light source unit.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1is a block diagram illustrating a display apparatus according to an exemplary embodiment of the present invention.

Referring toFIG. 1, a display apparatus according to an exemplary embodiment of the present invention includes a signal processing unit100, a display unit200, and a backlight unit300.

The signal processing unit100receives an external image signal10including image data and image control signal. The signal processing unit100outputs a display control signal20for driving the display unit200, and a backlight control signal30for driving the backlight unit300in response to the external image signal10.

The display unit200receives the display control signal20from the signal processing unit100to display an image in response to the display control signal20. For example, the display unit200may include a panel driving section210and a display panel220.

The panel driving section210outputs a panel driving signal40for driving the display panel220in response to the display control signal20. The display panel220receives the panel driving signal40from the panel driving section210, and displays an image in response to the panel driving signal40. For example, the display panel220may be a liquid crystal display (LCD) panel that displays an image by using the light generated by the backlight unit300.

The LCD panel includes a first substrate (not shown), a second substrate (not shown) opposite to the first substrate and a liquid crystal layer (not shown) disposed between the first substrate and the second substrate. The first substrate may include signal lines, thin film transistors (TFTs) electrically connected to the signal lines, and pixel electrodes electrically connected to the TFTs. The second substrate may include a common electrode and color filters. The color filters may be disposed corresponding to the pixel electrodes. The liquid crystal layer adjusts light transmissivity when electric fields are generated between the pixel electrode and the common electrode.

The backlight unit300receives the backlight control signal30from the signal processing unit100, and provides the display panel220with light in response to the backlight control signal30. For example, the backlight unit300includes a light source driving section310and a plurality of light-emitting blocks320.

The light source driving section310outputs light source driving signals50for individually controlling the plurality of light-emitting blocks320in response to the backlight control signal30. The plurality of light-emitting blocks320individually emit light in response to the light source driving signals50. In other words, the plurality of light-emitting blocks320emit light in a local dimming method.

FIG. 2is a block diagram illustrating a backlight unit inFIG. 1.

Referring toFIG. 1andFIG. 2, the plurality of light-emitting blocks320are arranged in a matrix shape along a first direction DI1and a second direction DI2that is different from the first direction DI1. InFIG. 1andFIG. 2, the plurality of light-emitting blocks320are arranged in, for example, 4×4 matrix shape.

The light source driving section310may include, for example, a driving section controller312and at least one LED driving section314.

The driving section controller312receives the backlight control signal30from the signal processing unit100, and outputs driving section control signals60for controlling the LED driving section314in response to the backlight control signal30.

The LED driving section314receives the driving section control signal60from the driving section controller312, and provides the plurality of light-emitting blocks320with the light source driving signals50in response to the driving section control signal60.

For example, the number of the LED driving sections314may be four. That is, each of the LED driving sections314may control four light-emitting blocks320disposed in a line. Alternatively, the number of the LED driving sections314may be the same as the number of the light-emitting blocks320. Alternatively, one LED driving section314may control all of the plurality of light-emitting blocks320.

FIG. 3is a cross-sectional view taken along a line I-I′ inFIG. 2, andFIG. 4is a plain view illustrating a light-emitting block inFIG. 3.

Referring toFIG. 2,FIG. 3andFIG. 4, each of the plurality of light-emitting blocks320includes a light guiding unit322, a light source unit324and a reflection sheet326.

The light guiding unit322includes a light guiding body portion322aand an upper extending portion322b. The light guiding unit322may further include a lower extending portion322c.

The light guiding body portion322amay have a rectangular plate shape of which two sides extend in the first direction DI1and the second direction DI2. The light guiding body portion322ahas a pair of side surfaces extending respectively in the first direction DI1or the second direction DI2. The pair of side surfaces is an incident surface and an opposite surface. The incident surface is a surface through which light enters the light guiding body portion322a, and the opposite surface is disposed opposite to the incident surface. InFIG. 2andFIG. 3, for example, the incident surface and the opposite surface are disposed such that a normal line thereof is extended along the first direction DI1.

The upper extending portion322bextends outwardly from a first side of the light guiding body portion322a. That is, the upper extending portion322bextends outwardly from the incident surface. The upper extending portion322bis thinner than the light guiding body portion322a. Therefore, a receiving space70may be defined under the upper extending portion322b.

The lower extending portion322cextends outwardly from a second side of the light guiding body portion322a, which is opposite to the first side. That is, the lower extending portion322cextends outwardly from the opposite surface. In this case, the lower extending portion322cextends to be disposed in a receiving space70under an upper extending portion322bof an adjacent light guiding unit322to support the upper extending portion322bof the adjacent light guiding unit322.

The lower extending portion322cis shorter than the upper extending portion322bto define a space in the receiving space70, which receives the light source unit324. For example, a summation of a thickness of the lower extending portion322cand a thickness of the upper extending portion322bmay be substantially the same as a thickness of the light guiding body portion322a.

The light source unit324is disposed such that the light source unit324faces the incident surface of the light guiding body portion322a. The light source unit324generates light toward the incident surface in response to the light source driving signal50from the LED driving section314. The light generated by the light source unit324enters the light guiding body portion322athrough the incident surface, and is guided by the light guiding body portion322atoward an upper surface of the light guiding body portion322a.

A lower surface of the light guiding body portion322a, which is opposite to the upper surface, may have a plurality of reflection dots DOT. The reflection dots DOT adjust light paths by refracting, diffusing, and reflecting the light that enters the light guiding body portion322athrough the incident surface. The reflection dots DOT are formed such that a density of the reflection dots DOT increases along a direction from the incident surface to the opposite surface.

The light source unit324may include at least one light-emitting chip324aand a driver substrate324b.

The driver substrate324bmay extend along the incident surface of the light guiding body portion322a. The driver substrate324bis electrically connected to the LED driving section314to receive the light source driving signal50.

The light-emitting chip324ais disposed on the driver substrate324b, and emits light in response to the light source driving signal50. That is, the light-emitting chip324areceives electric power through the driver substrate324bto generate light. For example, a plurality of the light-emitting chips324amay be arranged in at least one line along a longitudinal direction of the driver substrate324b. In this case, the plurality of light-emitting chips324amay be controlled by the light source driving signal50to generate light of the same luminance. Alternatively, the plurality of light-emitting chips324amay be individually controlled by a plurality of different light source driving signals50.

The light-emitting chip324amay include white light emitting diode (LED) emitting white light. Alternatively, the light-emitting chip324amay include a red LED emitting red light, a green LED emitting green light, and a blue LED emitting blue light.

The reflection sheet326is disposed on the lower surface of the light guiding body portion322a. The reflection sheet326reflects light exiting the light guiding body portion322atoward the light guiding body portion322ato enter the light guiding body portion322a, so that light-using efficiency may be improved.

FIG. 5is a cross-sectional view illustrating a portion of a light-emitting block according to another exemplary embodiment of the present invention.

The display apparatus according to the present exemplary embodiment is substantially the similar to the display apparatus of the previous exemplary embodiment illustrated inFIG. 1andFIG. 2except for the shape of the light guiding unit. Thus, same reference numerals will be used to refer the same elements, and any further explanation will be omitted.

Referring toFIG. 2andFIG. 5, a light guiding body portion322aof the light guiding unit322has a wedge shape having a decreasing thickness in a direction from the first side to the second side. That is, the thickness of the light guiding body portion322adecreases along a direction from the incident surface to the opposite surface that is opposite to the incident surface.

In the present embodiment, the light guiding unit322has only the upper extending portion322b. However, the light guiding unit322may have both of the upper extending portion322band the lower extending portion322cas shown in the previous embodiment andFIG. 3. A light guiding unit supporter328is disposed under the light guiding body portion322ato support the light guiding body portion322a. In this case, the light guiding unit supporter328is disposed adjacent to the opposite surface of the light guiding body portion322a.

According to the present invention, the plurality of light-emitting blocks320are arranged in a matrix shape, and each of the light-emitting blocks320includes the light guiding unit322and the light-emitting chip324adisposed adjacent to the light guiding unit322, backlight unit300to reduce the thickness of the backlight unit300in comparison with a backlight unit of direct illumination type.

Furthermore, the plurality of light-emitting blocks320are individually controlled by the light source driving section310. In other words, the plurality of light-emitting blocks320emit light in a local dimming method. Therefore, power consumption for driving the plurality of light-emitting blocks320may be reduced. Additionally, when the plurality of light-emitting blocks320is controlled in the local dimming method, contrast ratio and visibility of images displayed by the display apparatus may be improved.

FIG. 6is a cross-sectional view illustrating a display apparatus according to another exemplary embodiment of the present invention, andFIG. 7is a cross-sectional view illustrating a portion of a backlight unit inFIG. 6according to still another exemplary embodiment of the present invention.

Referring toFIG. 6andFIG. 7, a display apparatus according to another exemplary embodiment of the present invention includes a backlight unit300to generate light and a display panel220to display an image by using the light generated by the backlight unit300.

The backlight unit300includes a plurality of light-emitting blocks320, a plurality of reflection sheets326, a plurality of optical sheets400, a plurality of border region diffusion sheets500, an optical member600, and at least one optical member supporter650. Each of the light-emitting blocks320includes a light source unit324and a light guiding unit322.

The plurality of light-emitting blocks320may be arranged in a matrix shape in a receiving container (not shown). Each light guiding unit322includes a light guiding body portion322a, a lower extending portion322c, and an upper extending portion322b.

The light guiding body portion322amay have a rectangular plate shape. The light guiding body portion322ahas an upper surface through which light exits the light guiding body portion322a, a lower surface that is opposite to the upper surface, and four side surfaces connecting the upper surface and the lower surface. The four side surfaces include an incident surface through which light enters the light guiding body portion322aand an opposite surface that is disposed opposite to the incident surface.

The lower extending portion322cextends from the incident surface of the light guiding body portion322ain the first direction D1. The lower extending portion322cmay have a rectangular plate shape. The lower extending portion322cextends from a lower portion of the incident surface of the light guiding body portion322asuch that the lower surfaces of the light guiding body portion322aand the lower extending portion322care connected to each other. Furthermore, the lower extending portion322cis thinner than the light guiding body portion322a.

The upper extending portion322bextends from the opposite surface of the light guiding body portion322ain the second direction D2that is opposite to the first direction D1. The upper extending portion322bmay have a rectangular plate shape. The upper extending portion322bextends from an upper portion of the opposite surface of the light guiding body portion322asuch that the upper surfaces of the light guiding body portion322aand the upper extending portion322bare connected to each other. Furthermore, the upper extending portion322bis thinner than the light guiding body portion322a.

The lower surfaces of the light guiding body portion322aand the lower extending portion322cmay have a main light-guiding pattern140for adjusting a light path, and the lower surface of the upper extending portion322bmay have a sub light-guiding pattern150for adjusting a light path. For example, the main light-guiding pattern140and the sub light-guiding pattern150may have dot patterns for diffused refraction and diffusion.

The light source units324are disposed adjacent to a side surface of the lower extending portion322cof the light guiding units322, respectively. Furthermore, a light source unit324is disposed under the upper extending portion322bof an outermost region of each of the light guiding units322in the second direction D2. That is, the light source units324are disposed between the light guiding units322, respectively. In other words, the light source units324are alternately disposed along with the light guiding units322.

Each light source unit324may include a driver substrate324band at least one light-emitting chip324a. The light-emitting chip324ais mounted on the driver substrate324b, and generates light when the light-emitting chip324areceives electric power from the driver substrate324b. The light-emitting chip324aincludes a light emitting diode (LED). For example, light-emitting chip324amay include a white LED, a blue LED, etc. The light source units324may be individually controlled in a local dimming method.

The reflection sheets326are disposed under the light guiding units322, respectively. For example, the reflection sheets326may be disposed on lower surfaces of the light guiding body portion322a, the lower extending portion322c, and the upper extending portion322b, respectively. Furthermore, the reflection sheets326also may be disposed on a side surface of the light guiding body portion322a, which connects the lower surface of the light guiding body portion322awith the lower surface of the lower extending portion322c. Alternatively, one reflection sheet326may be bent to cover the lower surfaces of the light guiding body portion322a, the lower extending portion322c, and the upper extending portion322b.

The plurality of optical sheets400are disposed between the light source units324and the upper extending portions322bof the light guiding units322. For example, the plurality of optical sheets400may be attached to the lower surface of the upper extending portions322b. The plurality of optical sheets400transmits light generated by the light source units324to provide the upper extending portions322bwith light.

The plurality of optical sheets400may include a transmit-reflecting sheet410and a diffusion sheet420. For example, the transmit-reflecting sheet410may be disposed on a lower surface of the upper extending portions322b, and the diffusion sheet420may be disposed on a lower surface of the transmit-reflecting sheet410. Alternatively, the diffusion sheet420may be disposed on a lower surface of the upper extending portions322b, and the transmit-reflecting sheet410may be disposed on a lower surface of the diffusion sheet420.

The transmit-reflecting sheet410may transmit light generated by the light source unit324to provide the upper extending portion322bwith the light, and may reflect light, which advances toward the lower surface of the upper extending portion322b, toward the upper surface of the upper extending portion322b.

Alternatively, the transmit-reflecting sheet410may transmit a portion of light generated by the light source unit324and reflect a remaining portion of the light. For example, a white paper sheet may be employed as the transmit-reflecting sheet410.

The plurality of border region diffusion sheets500is disposed at a border region between the light guiding units322. The plurality of border region diffusion sheets500diffuses light emitted through the border region between the light guiding units322to improve luminance uniformity at the border region.

In detail, each border region diffusion sheet500may be disposed between the upper surface of the light guiding body portion322aof a first light guiding unit of the light guiding units322and the upper surface of the upper extending portion322bof a second light guiding unit of the light guiding units322adjacent to the first light guiding unit. In this case, the upper surface of the light guiding body portion322aof the first light guiding unit and the upper surface of the upper extending portion322bof the second light guiding unit may be connected to each other.

The optical member600is disposed over the light guiding units322to improve optical characteristics of light generated by the light guiding units322. For example, the optical member600may include a light-diffusing plate610disposed over the light guiding units322, a diffusion sheet620disposed on the light-diffusing plate610, a prism sheet630disposed on the diffusion sheet620, and a reflection-polarization sheet640disposed on the prism sheet630.

The optical member supporter650is disposed between the light guiding units322and the optical member600, so that the optical member600is spaced apart from the light guiding units322. A plurality of the optical member supporters650may be arranged along edges of the light guiding units322and the optical member600. When the plurality of optical member supporters650includes optically transparent material, the plurality of optical member supporters650may be disposed at the center portion of the light guiding units322and the optical member600. In the present embodiment, the lower extending portion322cof the first light guiding unit may overlap with the upper extending portion322bof the second light guiding unit adjacent to the first light guiding unit, so that the lower extending portion322cof the first light guiding unit may support the upper extending portion322bof the second light guiding unit. That is, the lower extending portion322cof the first light guiding unit may make contact with the optical sheets400on the lower surface of the upper extending portion322bof the second light guiding unit to support the upper extending portion322b.

As shown inFIG. 1, the display panel220is disposed over the backlight unit300, and displays an image by using light generated by the backlight unit300. The display panel220may be, for example, a liquid crystal display (LCD) panel.

With respect toFIG. 6, the LCD panel includes a first substrate710, a second substrate720facing the first substrate710, a liquid crystal layer730disposed between the first substrate710and the second substrate720, and a seal line740disposed along edges of the first substrate710and the second substrate720to confine the liquid crystal layer430.

The first substrate710includes signal lines, TFTs electrically connected to the signal lines, and pixel electrodes electrically connected to the TFTs. The second substrate720includes color filters respectively corresponding to the pixel electrodes and a common electrode. When electric fields are generated between the pixel electrode and the common electrode, an arrangement of liquid crystal molecules of the liquid crystal layer730is changed to alter the optical transmissivity of the liquid crystal layer730.

Hereinafter, a path of light generated by the light source units324will be explained referring toFIG. 7. For convenience, a light source unit facing the lower extending portion322cof a light guiding unit322, which is disposed at right side of the light guiding unit322, is referred to as a first light source unit324c, and a light source unit disposed under the upper extending portion322bof the light guiding unit322, which is disposed at a left side of the light guiding unit322, is referred to as a second light source unit324d.

A portion of a first light generated by the first light source unit324centers the light guiding unit322through a side surface of the lower extending portion322c, advances in the light guiding body portion322aand exits from the light guiding unit322through the upper surface of the light guiding body portion322a. In this case, the first light may be diffused, refracted or diffusedly reflected by the main light-guiding pattern140formed at the lower surfaces of the light guiding body portion322aand the lower extending portion322c, so that light path of the first light may be changed. Furthermore, a portion of the first light, which exits the light guiding unit322, may be reflected by the reflection sheet326of the lower surfaces of the lower extending portion322cand the and side surface of the light guiding body portion322ato re-enter the light guiding unit322.

On the other hand, a portion10of the first light, which advances toward the upper surface of the upper extending portion322bby the lower extending portion322cand the light guiding body portion322a, may exit from the light guiding unit322through the upper extending portion322b.

The portion10of the first light may be diffused, refracted, or diffusedly reflected by the sub light-guiding pattern150formed at the lower surface of the upper extending portion322b, so that light path of the first light may be changed. Furthermore, a portion of the portion10of the first light, which exits from the upper extending portion322b, may be reflected by the transmit-reflecting sheet410to re-enter the upper extending portion322b.

A portion of a first light generated by the first light source unit324centers the light guiding unit322through a side surface of the lower extending portion322c, advances in the light guiding body portion322aand exits from the light guiding unit322through the upper surface of the light guiding body portion322a. In this case, the first light may be diffused, refracted or diffusedly reflected by the main light-guiding pattern140formed at the lower surfaces of the light guiding body portion322aand the lower extending portion322c, so that light path of the first light may be changed. Furthermore, a portion of the first light, which exits the light guiding unit322, may be reflected by the reflection sheet326of the lower surfaces of the lower extending portion322cand the side surface of the light guiding body portion322ato re-enter the light guiding unit322.

For example, the transmit-reflecting sheet410in the present invention reflects the portion10of the first light and transmits the portion20of the second light in the upper extending portion322b. Alternatively, the transmit-reflecting sheet410may transmit a portion of light and reflect a remaining portion of the light.

According to the present exemplary embodiment, the portion10of the first light generated by the first light source unit324a, passes through the lower extending portion322cand the light guiding body portion322aand exits the light guiding unit322through the upper surface of the upper extending portion322b. Furthermore, the portion20of the second light generated by the second light source unit324denters the upper extending portion322bthrough the lower surface of the upper extending portion322band exits the upper extending portion322bthrough the upper surface of the upper extending portion322b.

As a result, the portion10of the first light and the portion20of the second light exit from the upper extending portion322b, so that a luminance over the upper extending portion322bmay be improved. Therefore, a dark line, which may be displayed over the upper extending portion322b, may be reduced.

Furthermore, according to the conventional backlight unit, an optical member600should be spaced apart from the light guiding unit322in order to reduce the dark line. However, according to the present embodiment, there is no need to increase the distance between the light guiding unit322and the optical member600, so that the thickness of the backlight unit300may be reduced.