Patent Description:
Liquid crystal displays (LCDs) which are one type of displays are used in a variety of monitors for televisions, notebook computers and desktops as well as cellular phones.

Such an LCD does not self-emit light, thus requiring a light-emitting device to light a liquid crystal panel so as to display image information.

A light emitting device of LCDs is bonded to a rear surface of a liquid crystal panel and is thus referred to as a backlight unit. This backlight unit forms a uniform surface light source and supplies light to a liquid crystal panel.

A light emitting diode (LED) has a structure in which an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer are stacked in a substrate and an electrode is formed on the p-type semiconductor layer and the n-type semiconductor layer. Regarding a principle of light generation by the light emitting diode, light of the light-emitting layer generated upon recombination between holes and electrons injected from respective semiconductor layers is discharged to the outside.

Such a light emitting diode constitutes a light emitting diode package which is used as a light source of a backlight unit (BLU).

Such a backlight unit provides a planar light source toward the liquid crystal panel, which is thus considered to be an example of a planar lighting device. The planar lighting device is considered to be a light source which uniformly emits light through a flat surface and has a relatively small thickness.

The planar lighting device improves luminous efficacy of a display device and accomplishes structural slimness thereof.

For instance, <CIT> relates to a display device having a backlight unit including a circuit board layer, a plurality of light sources mounted on the circuit board layer, a reflection layer formed on the top surface of the circuit board layer, a patterned metal reflection layer separated from the reflection layer, and a diffusion layer positioned on a top of the patterned metal reflection layer.

When the light emitting diode is used as a light source of a planar lighting device, the light emitting diode may be a side type in which light is diffused to a side direction or a direct type in which light is emitted in a front direction. A method for uniformly diffusing light emitted from the light emitting diode is required.

Accordingly, the present invention is directed to a planar lighting device that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a direct-type planar lighting device which improves an edge luminance uniformity of the planar lighting device.

These objects and other advantages are achieved by a display device according to independent claim <NUM>. For instance, a display device comprises, amongst others, a plurality of light sources arranged on a first surface of a circuit substrate, and a light regulator disposed in an edge of the first surface, the light regulator regulating luminance difference caused by difference in distance between light sources close to the edge.

The light regulator may include one or more reflectors for reflecting light emitted from the light sources to an inside or an upper part of an area defined by the first surface.

The reflector may include a reflection layer disposed along the edge, and a plurality of through holes provided in the reflection layer.

The through holes may change in size according to positions relative to the light sources.

The light regulator may be formed by bending the reflection layer.

Meanwhile, the light regulator may be provided at least one side of four edges of the first surface.

The accompanying drawings provide further understanding of the disclosure and together with the description serve to explain the principle of the disclosure. In the drawings:.

Reference will now be made in detail to the specific embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

However, the present invention allows various modifications and variations and specific embodiments thereof will be exemplified with reference to drawings and be described in detail.

It will be understood that when an element such as a layer, area or substrate is referred to as being "on" another element, it can be directly on the element, or one or more intervening elements may also be present therebetween.

In addition, it will be understood that although terms such as "first" and "second" may be used herein to describe elements, components, areas, layers and/or regions, the elements, components, areas, layers and/or regions should not be limited by these terms.

<FIG> is a sectional view illustrating an example of a planar lighting device.

The planar lighting device <NUM> may be disposed on a lower cover <NUM> and a liquid crystal panel (not shown) may be disposed on the planar lighting device <NUM>.

The planar lighting device <NUM> includes a plurality of light sources <NUM> mounted respectively on a plurality of circuit substrates <NUM> disposed in an upper part of the lower cover <NUM>. Each light source <NUM> is mounted by surface-mounting a light emitting diode (LED) package on the circuit substrate <NUM>.

The light source <NUM> including the light emitting diode (LED) package includes a pair of electrodes <NUM> passing through a sub-mount substrate <NUM>, an LED <NUM> connected to and mounted on the electrode <NUM>, and a phosphor layer <NUM> containing a silicone resin mixture disposed outside the LED <NUM>.

The phosphor layer <NUM> may have a planarized upper surface and the phosphor layer <NUM> may be provided on the upper surface with an optical layer <NUM> having optical property such as reflectivity or transmittance.

The optical layer <NUM> may be formed of a material prepared by mixing a resin with phenyl propanol amine (PPA), epoxy molding compound (EMC), microcell polyethylene terephthalate (MCPET), silver (Ag) and aluminum (Al) having reflectivity, and a bead of Ti, Al, Ag, SiO<NUM> or the like, exhibiting reflectivity, transmittance or refraction.

Light emitted upward from the LED <NUM> through the optical layer <NUM> is reflected in a side direction of the phosphor layer <NUM>. The LED <NUM> is a blue LED and the phosphor material constituting the phosphor layer <NUM> is a yellow phosphor, thus rendering white light to be emitted from the light source <NUM>.

The circuit substrate <NUM> on which the light source <NUM> is mounted may be disposed on a mount groove <NUM> disposed on the upper surface of the lower cover <NUM>. In addition, a plurality of mount grooves <NUM> including the mount groove <NUM> may be spaced from one another by a predetermined distance and circuit substrates <NUM> including the circuit substrate <NUM> disposed respectively in the mount grooves <NUM> may be also spaced from one another by a predetermined distance. Accordingly, the light sources <NUM> may be spaced from one another by a predetermined distance on the lower cover <NUM>.

The light sources <NUM> may be disposed in one line or a zigzag form.

A reflection layer <NUM> is disposed in a gap between the light sources <NUM> disposed on the circuit substrates <NUM>. Accordingly, the light sources <NUM> protrude from an upper surface of the reflection layer <NUM>.

In addition, a transmission regulation layer <NUM> having a pattern of holes <NUM> transmitting light, which is spaced from the reflection layer <NUM> by a predetermined distance, may be disposed on the reflection layer <NUM>.

The transmission regulation layer <NUM> may utilize a reflective sheet which transmits some of light emitted from the light source <NUM> and reflects the remaining light again.

The transmission regulation layer <NUM> is a hole patterned reflective sheet having a plurality of holes <NUM> on an upper surface thereof. That is, light discharged from the light source <NUM> through the holes <NUM> or reflected by the reflection layer <NUM> passes through the holes <NUM>, and light travelling in other regions is reflected to the reflection layer <NUM> again or is refracted or reflected by a spacer <NUM>.

In addition, radiuses of the holes <NUM> increase with increasing distance from a center of the light source <NUM>, thus passing more light than is reflected with increasing distance from the light source <NUM>.

That is, the holes <NUM> are disposed such that the size of the holes <NUM> is the smallest in the closest position to the light source <NUM> and is the largest in the middle between two adjacent light sources <NUM>.

In addition, the holes <NUM> are disposed such that sizes of the holes <NUM> gradually increase from the closest position to the light source <NUM> to the middle position between two adjacent light sources <NUM> and decrease from the middle position between the two adjacent light sources <NUM> to the closest position to the light source <NUM>.

The reason for this is that intensity of light increases as the light source becomes closer to the light source <NUM> and decreases as the light source becomes farther from the light source <NUM>. Preferably, light transmission increases as a distance from the light source <NUM> increases and decreases as the distance from the light source <NUM> decreases so that luminance of light is uniformly maintained throughout the entire surface of a display using such a planar lighting device.

Light emitted from the light source <NUM> is diffused in a side direction through the gap between the reflection layer <NUM> and the transmission regulation layer <NUM>. The diffused light is emitted in an upper direction through the pattern of the holes <NUM>. As such, the area between the reflection layer <NUM> and the transmission regulation layer <NUM> is defined by a light-guide layer <NUM>.

The light-guide layer <NUM> may be formed by a spacer <NUM> enabling a predetermined gap between the reflection layer <NUM> and the transmission regulation layer <NUM> to be maintained.

That is, the spacer <NUM> functions to maintain the distance between the transmission regulation layer <NUM> and the light source <NUM> and extends to a height corresponding to a designed height of the light-guide layer <NUM> and a length corresponding to a length of the reflection layer <NUM>.

The spacer <NUM> is formed of a material such as polycarbonate (PC), polymethyl methacrylate (PMMA), glass, a resin, phenyl propanol amine (PPA) or aluminum (Al) and thus exhibits light transmission, refraction or reflection.

In addition, the spacer <NUM> may be mounted by applying an adhesive to the upper and lower surfaces of the spacer <NUM> and performing UV curing or thermal curing.

In addition, optical sheets such as a diffusion layer <NUM>, a lower polarizing plate <NUM>, a color filter substrate <NUM> and an upper polarizing plate <NUM> may be disposed on the transmission regulation layer <NUM>.

Meanwhile, the circuit substrate <NUM> may be fixed to the mount groove <NUM> of the lower cover <NUM> by applying an adhesive <NUM> to a lower surface of the circuit substrate <NUM> and a lower surface of the reflection layer <NUM>. In addition, the reflection layer <NUM> may be fixed to the circuit substrate <NUM>.

<FIG> and <FIG> are schematic views illustrating distribution of luminance at an edge of a reflection surface according to position of light sources.

As described above, in a direct-type planar lighting device, a combination of light emitted from the light sources <NUM> is emitted in the center of the surface on which the light sources <NUM> are distributed. Accordingly, luminance of the planar lighting device can be uniformized using the optical sheets <NUM>, <NUM>, <NUM> and <NUM> described above.

The surface on which the light sources <NUM> are distributed is a surface of the circuit substrate <NUM> or an upper surface of the reflection layer <NUM> disposed on the circuit substrate <NUM>. Hereinafter, the following description is provided under the assumption that the surface on which the light sources <NUM> are distributed is the upper surface (reflection surface) of the reflection layer <NUM>.

Meanwhile, difference in luminance between areas close to the light source <NUM> and areas far from the light source <NUM> may be generated at an edge <NUM> in which distribution of the light source <NUM> is completed.

For example, as can be seen from <FIG> and <FIG>, as the disposition of the light source <NUM> is changed, luminance difference may be generated according to the distance from the light source <NUM> at the edge <NUM> of the light source <NUM>.

That is, in a direct-type lighting device, luminance is high at the position close to the light source <NUM> and luminance is low at the position far from the light source <NUM> at an edge <NUM> of the upper surface of the reflection layer <NUM>.

As shown in <FIG> provided to better understand the present disclosure, but not covered by the claimed invention, a light regulator <NUM> for regulating luminance difference caused by distance difference between the light source <NUM> and the edge <NUM> may be provided.

The light regulator <NUM> regulates luminance difference which may occur between the reflection layer <NUM> and the edge <NUM>. That is, uniformity of luminance can be improved at the edge <NUM>.

Accordingly, when such a light regulator <NUM> is provided, light emitted from the light sources <NUM> may be more uniform. More preferably, more uniform lighting can be implemented with the transmission regulation layer <NUM> having the pattern of holes <NUM> and the optical sheets <NUM>, <NUM>, <NUM> and <NUM> disposed on the reflection layer <NUM> and the light source <NUM>.

As an example, the light regulator <NUM> may include a plurality of reflectors <NUM> for reflecting light emitted from the light sources <NUM> to an inside of an area formed by the reflection layer <NUM>, disposed at the edge <NUM> of the reflection layer <NUM>.

For example, the reflectors <NUM> are disposed in portions of the edge <NUM> farther from the light sources <NUM> so that the reflectors <NUM> reflect light travelling toward the edge <NUM> and thus focus surrounding light upon relatively dark regions, thereby regulating luminance uniformity.

As shown in <FIG>, the reflectors <NUM> may be discontinuously disposed at the edge <NUM> in the positions relatively far from the light sources <NUM>. That is, the reflectors <NUM> with a predetermined width may be discontinuously disposed along the edge <NUM> in the positions farther from the light sources <NUM>.

In addition, from another point of view, the reflectors <NUM> may be discontinuously disposed in portions of the edge corresponding to areas between adjacent light sources <NUM> close to the edge <NUM>. That is, the reflectors <NUM> with a predetermined width may be disposed in portions of the edge corresponding to areas between two light sources <NUM> close to the edge <NUM>.

<FIG> shows traveling of light seen from the cross-section taken along the line A-A of <FIG>, and <FIG> shows traveling of light seen from the cross-section taken along the line B-B of <FIG>. In addition, <FIG> is a schematic view illustrating an example of luminance regulation by the reflector <NUM>.

As shown in <FIG>, the reflector <NUM> is disposed in a portion of the edge <NUM> in the position farther from the light source <NUM> so that light emitted from the light source <NUM> is reflected through the reflector <NUM> and brightness of area which may be dark due to great distance from the light source <NUM> are thus reinforced.

In a portion of the edge <NUM> in the position closer to the light source <NUM>, light travels without being reflected in the portion of the edge <NUM> to prevent the area from becoming brighter and thereby regulate luminance, as shown in <FIG>.

In addition, as shown in <FIG>, light emitted from the light source <NUM> close to the edge <NUM> is also reflected by the reflector <NUM> and travels toward areas farther from the light source <NUM>. Accordingly, such a reflector <NUM> uniformizes luminance of the light sources <NUM> close to the edge <NUM> and of the light sources <NUM> far from the edge <NUM>.

As shown in <FIG> provided to better understand the present disclosure, but not covered by the claimed invention, the light regulator <NUM> can include a plurality of absorbers <NUM> for absorbing light emitted from the light source <NUM>. The absorbers <NUM> may be disposed at the edge <NUM> in positions corresponding to the light sources <NUM> close to the edge <NUM>.

Such an absorber <NUM> is close to the light source <NUM> and absorbs light of areas brighter than neighboring areas to darken the brighter areas and thereby regulate luminance uniformity.

As shown in <FIG>, the absorbers <NUM> may be discontinuously disposed close to the light sources <NUM> at the edge <NUM>. That is, the absorbers <NUM> with a predetermined width may be discontinuously disposed along the edge <NUM> in positions relatively close to the light sources <NUM>.

<FIG> shows traveling of light seen from the cross-section taken along the line C-C of <FIG>, and <FIG> shows traveling of light seen from the cross-section taken along the line D-D of <FIG>. In addition, <FIG> is a schematic view illustrating an example of luminance regulation by the absorber <NUM>.

As shown in <FIG>, in a portion of the edge <NUM> in the position farther from the light source <NUM>, light travels without being reflected in the portion of the edge <NUM>, thereby regulating luminance.

As shown in <FIG>, the absorber <NUM> can be disposed along the edge in the position of the edge <NUM> close to the light source <NUM> so that light emitted from the light source <NUM> is absorbed in the absorber <NUM> without being reflected or passing through the absorber and brightness of areas which may be relatively bright due to small distance from the light source <NUM> are thus reduced.

In addition, as shown in <FIG>, as described above, light emitted from the light source <NUM> close to the edge <NUM> is absorbed in the absorber <NUM> and light emitted from the light source <NUM> far from the edge <NUM> passes through the absorber <NUM> without being absorbing therein. Accordingly, the absorber <NUM> contributes to luminance uniformity of the light sources <NUM> close to the edge <NUM> and of the light sources <NUM> far from the edge <NUM>.

As shown in <FIG> provided to better understand the present disclosure, but not covered by the claimed invention, the light regulator <NUM> can include a plurality of reflectors <NUM> and a plurality of absorbers <NUM> which are alternately disposed, as another example of the light regulator <NUM>.

That is, the light regulator <NUM> may include the reflectors <NUM> for reflecting light emitted from the light sources <NUM> to an inside of the reflection layer <NUM> and absorbers <NUM> being disposed between the reflectors <NUM> and absorbing light emitted from the light sources <NUM>.

As such, the reflectors <NUM> and the absorbers <NUM> alternate with each other and the light regulator <NUM> may be continuously disposed along an edge <NUM> of at least one side of the reflection layer <NUM>.

Although <FIG> illustrates an example in which the reflectors <NUM> and the absorbers <NUM> are provided in edges of upper and lower sides of a transmission regulation layer <NUM> for convenience, the reflectors <NUM> and the absorbers <NUM> may be provided in edges of left and right sides thereof.

As shown in the drawing, the reflectors <NUM> having a predetermined width may be disposed along the edge <NUM> in positions of portions of the edge <NUM> far from the light sources <NUM> and the absorbers <NUM> having a predetermined width may be disposed along the edge <NUM> in positions of portions of the edge <NUM> close to the light source <NUM>.

Each reflector <NUM> and each absorber <NUM> may have the same width. However, in some cases, the width of the reflector <NUM> may be greater than that of the absorber <NUM> and vice versa.

<FIG> shows traveling of light seen from the cross-section taken along the line E-E of <FIG>, and <FIG> shows traveling of light seen from the cross-section taken along the line F-F of <FIG>. In addition, <FIG> is a schematic view illustrating an example of luminance regulation by the reflector <NUM> and the absorber <NUM>.

As shown in <FIG>, the reflector <NUM> can be disposed along the edge in the position of a portion of the edge <NUM> far from the light source <NUM> so that light emitted from the light source <NUM> is reflected by the reflector <NUM> and brightness of areas which may be relatively dark due to great distance from the light source <NUM> is thus reinforced.

The absorber <NUM> can be disposed in a portion of the edge <NUM> close to the light source <NUM>, as shown in <FIG>, so that light emitted from the close light source <NUM> is absorbed in the absorber <NUM> and luminance of areas which may be relatively bright is thus regulated.

In addition, as shown in <FIG>, light emitted from the light source <NUM> close to the edge <NUM> may be absorbed in the absorber <NUM> and light emitted from the light source <NUM> far from the edge <NUM> is reflected by the reflector <NUM>. Light emitted from the light source <NUM> close to the edge <NUM> is reflected by the reflector <NUM> and luminance of areas which may be relatively dark is thus regulated.

That is, the reflector <NUM> and the absorber <NUM> regulate light emitted from the light sources <NUM> close to the edge <NUM> and light emitted from the light sources <NUM> far from the edge <NUM>, thus contributing to luminance uniformity.

As shown in <FIG>, according to the present invention, the light regulator <NUM> includes a reflection layer <NUM> disposed along the edge <NUM> and a plurality of through holes <NUM> provided in the reflection layer <NUM>.

Although <FIG> illustrates an example in which the reflection layer <NUM> and the through holes <NUM> are provided in edges of upper and lower sides of the transmission regulation layer <NUM> for convenience, the reflection layer <NUM> and the through holes <NUM> may be provided in edges of left and right sides thereof.

As shown in <FIG>, the through holes <NUM> may change in size according to position relative to the light source <NUM>.

That is, larger through holes <NUM> are disposed in areas closer to the light source <NUM> and small through holes are disposed in areas far from the light source <NUM>.

In addition, the size of the through holes <NUM> may be gradually changed. That is, the largest through hole <NUM> is disposed in an area relatively close to the light source <NUM>, through holes <NUM> gradually decrease in size, with increasing the distance from the largest through hole and the smallest through hole <NUM> is disposed in the position farthest from the light source <NUM>.

<FIG> shows traveling of light seen from the cross-section taken along the line G-G of <FIG>, and <FIG> shows traveling of light seen from the cross-section taken along the line H-H of <FIG>. In addition, <FIG> is a schematic view illustrating an example of luminance regulation by the reflection layer <NUM>.

As shown in <FIG>, the reflection layer <NUM> having small through holes <NUM> is disposed in a portion of the edge <NUM> relatively far from the light source <NUM> so that a small amount of light emitted from the light source <NUM> passes through the through holes <NUM>, most thereof is reflected, and brightness of an area which may be relatively dark due to great distance from the light source <NUM> is thus reinforced.

In addition, a reflection layer <NUM> having large through holes <NUM> is disposed in a portion of the edge <NUM> close to the light source <NUM>, as shown in <FIG>, so that a great amount of light emitted from the light source <NUM> passes through the through holes <NUM> and brightness of an area which may be relatively bright is thus regulated.

<FIG> is a schematic view illustrating travelling of light by the reflection layer <NUM> having through holes <NUM> with various sizes.

That is, some of light emitted from the light source <NUM> close to the edge <NUM> passes through large through holes <NUM> and the remaining thereof is reflected by a portion of the reflection layer <NUM> in which small through holes <NUM> are disposed, thereby regulating luminance of areas which may be relatively dark.

In addition, as most of light emitted from light source <NUM> far from the edge <NUM> is reflected by the reflection layer <NUM>, luminance of areas, which may be relatively dark, is regulated and luminance uniformity can be thus improved.

Meanwhile, the reflector <NUM> or the reflection layer <NUM> described above is shown as a form such as thin wall, but may be provided with a reflection plate <NUM> whose cross-section has an inclined surface having a polygonal shape, as shown in <FIG>.

That is, as shown in <FIG> provided to better understand the present disclosure, a reflection plate <NUM> whose cross-section has an inclined surface having a right-angled triangle shape is formed so that light emitted from the light source <NUM> travels upward.

In addition, regarding the shape for reflection, a reflection plate <NUM> whose cross-section has a curved surface having a semi-spherical or circular arc shape may be formed, as shown in <FIG> also provided to better understand the present disclosure. In some cases, the reflection plate <NUM> may have an oval curved surface.

That is, a reflection plate <NUM> whose cross-section has an inclined surface having a triangle shape may be formed, as shown in <FIG> provided to better understand the present disclosure, and a reflection plate <NUM> whose cross-section has an inclined surface having a trapezoidal shape may be formed, as shown in <FIG> provided to better understand the present disclosure.

The reflection plate <NUM> reflects at least part of light emitted from the light source <NUM> toward the upper surface of the reflection layer <NUM> and reflects the remaining light into an inside of an area formed by the reflection layer <NUM>.

The reflection plates <NUM>, <NUM>, <NUM> and <NUM> having various shapes may be applied to the shape of the reflector <NUM> or the reflection layer <NUM> described above.

Meanwhile, the absorption layer <NUM> described above may be also formed as one of shapes that are the same as the reflection plates <NUM>, <NUM>, <NUM> and <NUM>.

As shown in <FIG> provided to better understand the present disclosure, in a portion of the edge <NUM> in the position far from the light source <NUM>, a reflection structure <NUM> for reducing the distance between the edge and the light source <NUM> may be provided.

That is, in the portion of the edge <NUM> far from the light source <NUM>, the distance between the edge and the light source <NUM> is reduced using the reflection structure <NUM> and surrounding light is transferred to dark areas and luminance uniformity can thus be regulated.

The reflection structure <NUM> may be formed of a highly reflective material. <FIG> shows the reflection structure <NUM> having an oval portion, but the shape of the reflection structure <NUM> may be selected from a variety of shapes such as curved shapes including circular or circular arc shapes, and triangular or trapezoidal shapes.

Regarding the light regulator <NUM> including the reflector <NUM> that is provided for explaining the present disclosure, but does not fall under the claimed invention, the absorber <NUM> and the reflection plate <NUM> described above, another light regulator <NUM> newly produced is bonded to the edge <NUM> of the light regulator <NUM>, as shown in <FIG>.

For example, as shown in <FIG>, reflectors <NUM> and absorbers <NUM> which alternate with each other are produced as separate structures and are then bonded to the edge <NUM>.

In addition, as shown in <FIG>, a surface of the reflection layer <NUM> can be bent in an inside direction to constitute the reflector <NUM>, in accordance with an embodiment of the present invention.

Claim 1:
A display device comprising:
a lighting device (<NUM>) including:
a lower cover (<NUM>);
a circuit substrate (<NUM>) disposed on the lower cover (<NUM>);
a plurality of light sources (<NUM>) disposed on a surface of the circuit substrate (<NUM>);
a reflection layer (<NUM>, <NUM>) disposed on the surface of the circuit substrate (<NUM>), the reflection layer (<NUM>) comprising:
a first region (<NUM>) having a plurality of openings where the respective light sources (<NUM>) are located,
a second region (<NUM>) connected to the first region (<NUM>), wherein the second region (<NUM>) is located at an edge (<NUM>) of the first region (<NUM>) wherein the second region (<NUM>) has an inclination with respect to the first region (<NUM>), and
a hole pattern having a plurality of through holes (<NUM>) provided in the second region (<NUM>) of the reflection layer (<NUM>, <NUM>), wherein at least two through holes (<NUM>) of the hole pattern are different in size, and wherein a largest through hole (<NUM>) is disposed in a location close to a corresponding light source (<NUM>);
an optical sheet (<NUM>) disposed on the light sources (<NUM>); and
a liquid crystal panel on the lighting device (<NUM>).