Light emitting diode and lens for the same

A lens has a refractive index of n, and includes a base, a first curved circumferential surface extending from the base, a curved center-edge surface extending from the first curved circumferential surface, and a curved centermost surface extending from the curved center-edge surface. The base includes a groove for receiving a light emitting chip. A distance from a center of the base to a point of the curved center-edge surface is shorter than the radius of curvature for the point of the curved center-edge surface. The curved centermost surface has a concave shape with respect to the base. The lens satisfies A1+A2<90+sin−1(1/n), where A1 an obtuse angle between a main axis and a tangent line of the curved centermost surface, and A2 is an acute angle between a straight line linking the center of the base to the point of the curved centermost surface and the main axis.

BACKGROUND OF THE INVENTION

(a) Technical Field

The present disclosure relates to a light source for a display device.

(b) Discussion of the Related Art

Display devices used for image display such as in a television receiver or computer monitor are classified into a self-luminescence display and a light-receiving display requiring a separate light source. Light emitting diode (LED), electroluminescence (EL), vacuum fluorescent display (VFD), field emission display (FED), and plasma display panel (PDP) devices, etc., are included in the self-luminescence display device, while liquid crystal displays (LCDs), etc., are included in the light-receiving display devices.

The LCD includes, for example, a pair of panels individually having electrodes on their inner surfaces, and a dielectric anisotropy liquid crystal layer interposed between the panels. In the LCD, a variation of the voltage difference between the field generating electrodes, i.e., the variation in the strength of an electric field generated by the electrodes, changes the transmittance of the light passing through the LCD, and thus desired images are obtained by controlling the voltage difference between the electrodes.

In the LCD, a light may be a natural light or an artificial light emitted from a light source unit separately employed in the LCD.

A backlight device is a representative artificial light source device for the LCD. The backlight device utilizes light emitting diodes (LEDs) or fluorescent lamps such as cold cathode fluorescent lamps (CCFLs), external electrode fluorescent lamps (EEFLs), etc., as the light source.

The LED is eco-friendly since it does not use mercury (Hg) and it has stable characteristics. For these reasons, the LED is a preferred light source.

However, some problems may arise when the LED is used as a surface light source device. This is because the light rays emitted from the LED tend to condense to a narrow region.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is provided a lens comprising: a base; a first curved circumferential surface upwardly extending from the base; and a first curved central surface extending from the first curved circumferential surface, wherein a distance from the center of the base to a point of the first curved central surface is shorter than the radius of curvature for the corresponding point of the first curved central surface.

The lens further comprises a central hollow portion upwardly formed from the base. The central hollow portion is comprised of a second curved circumferential surface and a second curved central surface extending from the second curved circumferential surface, which are inner surfaces of the lens. In this lens, it is preferable that a distance from the center of the base to a point of the second curved central surface is longer than the radius of curvature for the corresponding point of the second curved central surface.

A boundary region of the second curved central surface and the second curved circumferential surface is preferably placed within about 20 degrees to about 50 degrees with respect to the center of the base. Also, a boundary region of the first curved central surface and the first curved circumferential surface is placed within 20 degrees to 50 degrees with respect to the center of the base.

In this lens, the base includes a groove for receiving a light emitting chip therein, and a distance from the center of the base to a point of the first curved circumferential surface is shorter than the radius of curvature for the corresponding point of the first curved circumferential surface.

According to another embodiment of the present invention, there is provided a lens which is formed with a material having a refractive index of n, and which comprises: a base; a first curved circumferential surface upwardly extending from the base; a curved center-edge surface extending from the first curved circumferential surface; and a curved centermost surface extending from the curved center-edge surface.

Here, it is preferable that a distance from a center of the base to a point of the curved center-edge surface is always shorter than the radius of curvature for the corresponding point of the curved center-edge surface.

The curved centermost surface has a concave shape with respect to the base.

Here, it is preferable that the lens is constructed to satisfy the following equation:
A1+A2<90+sin−1(1/n),

wherein A1 is an obtuse angle formed between a main axis of the lens and a tangent line of a point of the curved centermost surface, and A2 is an acute angle formed between a straight line linking the center of the base to the corresponding point of the curved centermost surface and the main axis of the lens.

The lens further comprises a central hollow portion upwardly formed from the base of the lens. The central hollow portion includes a second curved circumferential surface and a curved central surface extending from the second curved circumferential surface, which are inner surfaces of the lens.

Here, it is preferable that a distance from the center of the base to a point of the curved central surface is longer than the radius of curvature for the corresponding point of the curved central surface. When the main axis of the lens is intersected with a tangent line of a boundary point of the curved center-edge surface and the curved centermost surface, they are intersected at an angle of 90 degrees.

It is also preferable that a boundary region of the curved center-edge surface and the first curved circumferential surface may be placed within about 20 degrees to about 50 degrees with respect to the center of the base. The curved centermost surface may be a cone-shaped groove.

According to another embodiment of the present invention, there is provided an LED comprising: a first lens including a base, a first curved circumferential surface upwardly extending from the base, and a first curved central surface; and a light emitting chip provided under the first lens.

Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the first curved central surface is shorter than the radius of curvature for the corresponding point of the first curved central surface.

The LED further comprises a central hollow portion upwardly formed from the base of the first lens. The central hollow portion includes a second curved circumferential surface and a second curved central surface extending from the second curved circumferential surface, which are inner surfaces of the first lens. Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the second curved central surface is longer than the radius of curvature for the corresponding point of the second curved central surface.

The LED further comprises a second lens which is provided in the central hollow portion of the first lens to cover the light emitting chip. The second lens includes a base, a third curved circumferential surface upwardly extending from the base, and a third curved central curved extending from the third curved circumferential surface. In this lens, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the third curved central surface is shorter than the radius of curvature for a corresponding point of the third curved central surface.

The LED further comprises a central hollow portion upwardly formed from the base of the second lens. The central hollow portion includes a fourth curved circumferential surface and a fourth curved central surface extending from the fourth curved circumferential surface, which are inner surfaces of the lens. In the second lens, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the fourth curved central surface is longer than the radius of curvature for the corresponding point of the fourth curved central surface.

The second lens is formed with a material having a refractive index of n, and it includes a base, a fifth curved circumferential surface upwardly extending from the base, a curved center-edge surface extending from the fifth curved circumferential surface, and a curved centermost surface extending from the curved center-edge surface. A groove is formed at the center of the base for receiving the light emitting chip therein.

In the second lens, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the curved center-edge surface is shorter than the radius of curvature for the corresponding point of the curved center-edge surface, and the curved centermost surface has a concave shape when viewed from the light emitting chip.

The LED further comprises a central hollow portion upwardly formed from the base of the second lens. The central hollow includes a sixth curved circumferential surface and a sixth curved central surface extending from the sixth curved circumferential surface, which are inner surfaces of the second lens. Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the sixth curved central surface is longer than the radius of curvature for the corresponding point of the sixth curved central surface.

The LED further comprises a supporting unit which is attached to the base of the first lens for supporting the light emitting chip thereon.

According to another embodiment of the present invention, there is provided an LED comprised of: a first lens which is formed with a material having a refractive index of n, and the lens includes a base, a first curved circumferential surface upwardly extending from the base, a first curved center-edge surface extending from the first curved circumferential surface, and a first curved centermost surface extending from the first curved center-edge surface; and a light emitting chip which is provided under the first lens.

In this LED, a distance from a point of an upper surface of the light emitting chip to a point of the first curved center-edge surface is shorter than the radius of curvature for the corresponding point of the first curved center-edge surface. The first curved centermost surface has a concave shape when viewed from the light emitting chip.

Here, it is preferable that the LED is constructed to satisfy the following equation:
A1+A2<90+sin−1(1/n),

wherein A1 is an obtuse angle formed between the main axis of the first lens and a tangent line of a point of the first curved centermost surface, and A2 is an acute angle formed between a straight line linking the center of the base to the corresponding point of the first curved centermost surface and the main axis of the first lens.

The LED further comprises a central hollow portion upwardly formed from the base of the first lens. The central hollow portion includes a second curved circumferential surface and a first curved central surface extending from the second curved circumferential surface, which are inner surfaces of the first lens. Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the first curved central surface is longer than the radius of curvature for the corresponding point of the first curved central surface.

The LED further comprises a second lens which is provided in the central hollow portion of the first lens to cover the light emitting chip. The second lens includes a base, a third curved circumferential surface upwardly extending from the base, and a second curved central surface extending from the third curved circumferential surface.

Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the second curved central surface is shorter than the radius of curvature for the corresponding point of the second curved central surface.

The LED further comprises a central hollow portion upwardly formed from the base of the second lens. The central hollow portion includes a fourth curved circumferential surface and a third curved central surface extending from the fourth curved circumferential surface, which are inner surfaces of the second lens.

Here, it is also preferable that a distance from a point of an upper surface of the light emitting chip to a point of the third curved central surface is longer than the radius of curvature for the corresponding point of the third curved central surface.

The second lens is formed with a material having a refractive index of n, and the second lens includes a base, a fifth curved circumferential surface upwardly extending from the base, a second curved center-edge surface extending from the fifth curved circumferential surface, and a second curved centermost surface extending from the second curved center-edge surface.

Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the second curved center-edge surface is shorter than the radius of curvature for the corresponding point of the second curved center-edge surface, and the second curved centermost surface has a concave shape when viewed from the light emitting chip.

The LED further comprises a central hollow portion upwardly formed from the base of the second lens. The central hollow portion is comprised of a sixth curved circumferential surface and a fourth curved central surface extending from the sixth curved circumferential surface, which are inner surfaces of the second lens.

Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the fourth curved central surface is longer than the radius of curvature for the corresponding point of the fourth curved central surface.

The LED further comprises a supporting unit which is attached to the base of the first lens for supporting the light emitting chip thereon.

In this LED, the first curved centermost surface is a cone-shaped groove.

According to another embodiment of the present invention, there is provided an LED which comprises: a lens including a base, a first curved circumferential surface upwardly extending from the base, and a first curved central surface; and a light emitting chip provided under the lens.

In this LED, at least a partial area of the first curved central surface and the first curved circumferential surface includes an uneven pattern. Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of an outline of the first curved central surface is shorter than the radius of curvature for the corresponding point of the outline surface of the first curved central surface.

The LED further comprises a central hollow portion upwardly formed from the base of the lens. The central hollow portion includes a second curved circumferential surface and a second curved central surface extending from the second curved circumferential surface, which are inner surfaces of the lens. Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the second curved central surface is longer than the radius of curvature for the corresponding point of the second curved central surface.

The LED further comprises an inner lens which is provided in the central hollow portion of the lens to cover the light emitting chip. The inner lens includes a base, a curved circumferential surface upwardly extending from the base, and a curved central surface extending from the curved circumferential surface.

Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the curved central surface is shorter than the radius of curvature for the corresponding point of the curved central surface.

In the LED, the uneven pattern is formed at the boundary area of the first curved central surface and the first curved circumferential surface.

According to another embodiment of the present invention, there is provided an LED which comprises: a lens which is formed with a material having a refractive index of n, and it includes a base, a first curved circumferential surface upwardly extending from the base, a curved central-edge surface extending from the first curved circumferential surface, and a curved centermost surface extending from the curved central-edge surface; and a light emitting chip which is provided under the lens.

In the LED, at least a partial area of the curved centermost surface, the curved central-edge surface and the first curved circumferential surface includes an uneven pattern. Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the curved central-edge surface is shorter than the radius of curvature for the corresponding point of an outline surface of the curved central-edge surface, and the curved centermost surface has a concave shape when viewed from the light emitting chip.

Here, it is preferable that the LED is constructed to satisfy the following equation:
A1+A2<90+sin−1(1/n),

wherein A1 is an obtuse angle formed between the main axis of the lens and a tangent line of a point of the curved centermost surface, and A2 is an acute angle formed between a straight line linking the center of the base to the corresponding point of the curved centermost surface and the main axis of the lens.

The LED further comprises a central hollow portion upwardly formed from the base of the lens. The central hollow portion includes a second curved circumferential surface and a curved central surface upwardly extending from the second curved circumferential surface, which are inner surfaces of the lens.

Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the curved central surface is longer than the radius of curvature for the corresponding point of the curved central surface.

The LED further comprises an inner lens which is provided in the central hollow portion of the lens to cover the light emitting chip. The inner lens includes a base, a curved circumferential surface upwardly extending from the base, and a curved central surface extending from the curved circumferential surface. Here, it is preferable that a distance from a point of an upper surface of the light emitting chip to a point of the curved central surface is shorter than the radius of curvature for the corresponding point of the curved central surface.

In the LED, the uneven pattern may be formed at the boundary area of the curved centermost surface and the curved center-edge surface and the boundary area of the curved center-edge surface and the first curved circumferential surface. The curved centermost surface may be a cone-shaped groove.

According to another embodiment of the present invention, there is provided an LED which comprises a lens including a base, a first curved circumferential surface upwardly extending from the base, and a first curved central surface.

In this LED, an acute angle formed between a straight line linking the center of the base to a point of the first curved central surface and the main axis of the lens is larger than an acute angle formed between the normal for the corresponding point of the first curved surface and the main axis of the lens.

The LED further comprises a central hollow portion upwardly formed from the base of the lens. The central hollow portion is comprised of a second curved circumferential surface and a second curved central surface extending from the second curved circumferential surface, which are inner surfaces of the lens.

Here, it is preferable that an acute angle formed between a straight line linking the center of the base to a point of the second curved central surface and the main axis of the lens is smaller than an acute angle formed between the normal for the corresponding point of the second curved central surface and the main axis of the lens.

According to another embodiment of the present invention, there is provided a lens for an LED, which is formed with a material having a refractive index of n, and is comprised of: a base; a first curved circumferential surface upwardly extending from the base; a curved center-edge surface extending from the first curved circumferential surface; and a curved centermost surface extending from the curved central-edge surface.

Here, it is preferable that an acute angle formed between a straight line linking the center of the base to a point of the curved center-edge surface and the main axis of the lens is larger than an acute angle formed between the normal for the corresponding point of the curved center-edge surface and the main axis of the lens, and the curved centermost surface has a concave shape when viewed from the base.

Here, it is preferable that the lens is constructed to satisfy the following equation:
A1+A2<90+sin−1(1/n),

wherein A1 is an obtuse angle formed between the main axis of the lens and a tangent line of a point of the curved centermost surface, and A2 is an acute angle formed between a straight line linking the center of the base to the corresponding point of the curved centermost surface and the main axis of the lens.

The lens further comprises a central hollow portion upwardly formed from the base of the lens. The central hollow portion is comprised of a second curved circumferential surface and a curved central surface extending from the second curved circumferential surface, which are inner surfaces of the lens.

Here, it is preferable that an acute angle formed between a straight line linking the center of the base to a point of the curved central surface and the main axis of the lens is smaller than an acute angle formed between the normal for the corresponding point of the curved central surface and the main axis of the lens.

According to another embodiment of the present invention, a lens for a light emitting diode comprises a base, a first curved surface extending from the base, and a second curved surface extending from the first curved surface, wherein a distance from a center of the base to a point of the second curved surface is shorter than a radius of curvature for the point of the first curved central surface.

The lens may include a hollow portion formed from the base,

wherein the hollow portion is comprised of a third curved surface and a fourth curved surface extending from the third curved surface, and wherein a distance from the center of the base to a point of the fourth curved surface is longer than the radius of curvature for the point of the fourth curved surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, the thickness of the layers, films, and regions are exaggerated for clarity. Like numerals refer to like elements throughout. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present.

Hereinafter, a light source device for a display device according to preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1is a block diagram of an LCD according to an embodiment of the present invention,FIG. 2is an exploded perspective view schematically illustrating an LCD according to an embodiment of the present invention, andFIG. 3is an equivalent circuit view of pixel unit of an LCD according to an embodiment of the present invention.

Referring toFIG. 1, an LCD according to an embodiment of the present invention comprises an LC panel assembly300, a gate driver400and a data driver500which are connected to the LC panel assembly300, a gray voltage generator800connected to the data driver400, a light source section910for supplying light to the LC panel assembly300, a light source driver920for controlling the light source section910, and a signal controller600for controlling the above elements.

Referring toFIG. 2, the LCD configuration according to an embodiment of the present invention comprises an LC module350including a display unit330and a back light340, a front housing361and a rear housing362for receiving and supporting the LC module350, and mold frames363and364.

The display unit330includes the LC panel assembly300, a gate tape carrier package (TCP)410and a data TCP510which are attached to the LC panel assembly300, and a gate printed circuit board (PCB)450and a data PCB550which are individually attached to the corresponding TCPs410and510.

In a structural view shown inFIG. 2andFIG. 3, the LC panel assembly300includes a lower panel100and an upper panel200facing each other, and an LC layer3interposed therebetween. In an equivalent circuit shown inFIG. 1andFIG. 3, the LC panel assembly300includes a plurality of display signal lines G1-Gnand D1-Dmand a plurality of pixels connected thereto and arranged substantially in a matrix.

The display signal lines G1-Gnand D1-Dmare provided on the lower panel100and include a plurality of gate lines G1-Gnfor transmitting gate signals (also referred to as “scanning signals”), and a plurality of data lines D1-Dmfor transmitting data signals. The gate lines G1-Gnextend substantially in a row direction and substantially parallel to each other, while the data lines D1-Dmextend substantially in a column direction and substantially parallel to each other.

Each pixel includes a switching element Q which are connected to the display signal lines G1-Gnand D1-Dm, and an LC capacitor CLCand a storage capacitor CSTwhich are connected to the switching element Q. The storage capacitor CSTmay be omitted.

The switching element Q such as a thin film transistor (TFT) is provided on the lower panel100and has three terminals: a control terminal connected to one of the gate lines G1-Gn; an input terminal connected to one of the data lines D1-Dm; and an output terminal connected to both of the LC capacitor CLCand the storage capacitor CST.

The LC capacitor CLCincludes a pixel electrode190provided on the lower panel100and a common electrode270provided on the upper panel200as two terminals. The LC layer3interposed between the two electrodes190and270functions as a dielectric for the LC capacitor CLC. The pixel electrode190is connected to the switching element Q, and the common electrode270is supplied with a common voltage Vcomand covers the entire surface of the upper panel200. Alternatively, the common electrode270may be provided on the lower panel100. At least one of the pixel electrode190and the common electrode270may be shaped as a bar or a stripe.

The storage capacitor CSTis an auxiliary capacitor for the LC capacitor CLC. When the pixel electrode190and a separate signal line (not shown) which is provided on the lower panel100are overlapped with each other, interposing an insulator therebetween, the overlapped portion becomes the storage capacitor CST. The separate signal line is supplied with a predetermined voltage such as the common voltage Vcom. Alternatively, the storage capacitor CSTmay be formed by overlapping of the separate signal line with a pixel electrode of the previous gate line which is placed directly before the pixel electrode190, and interposing an insulator therebetween.

For color display, each pixel uniquely exhibits one of three primary colors (i.e., spatial division), or sequentially exhibits three primary colors in turn depending on time (i.e., temporal division), so that a spatial or temporal sum of the primary colors are recognized as a desired color.FIG. 3shows an example of the spatial division in which each pixel includes a color filter230for exhibiting one of the primary colors in an area of the upper panel200corresponding to the pixel electrode190. Alternatively, the color filter230may be provided on or under the pixel electrode190of the lower panel100.

Referring toFIG. 2, the backlight340is mounted under the LC panel assembly300. The backlight340comprises a light source unit349including a printed circuit board (PCB)345and a plurality of light emitting diodes (LEDs)344mounted thereon, and a light guiding plate342and a plurality of optical sheets343which are provided between the LC panel assembly300and the LEDs344for dispersing the light from the LEDs344to the LC panel assembly300. The backlight340further comprises a reflecting plate341which is provided on the PCB345for reflecting the light from the LEDs344toward the LC panel assembly300, and includes a plurality of holes where light emitting chips of the LEDs344are protruded therethrough. The backlight340further comprises a mold frame364which is provided between the reflecting plate341and the light guiding plate342for maintaining a regular interval between the light source unit349and the light guiding plate342and for supporting the light guiding plate342and the optical sheets343.

The LEDs344as the light source may be white light emitting diodes or a combination of red, green, and blue light emitting diodes. The red light emitting diode, etc. can be used as an auxiliary diode for the white light emitting diode. The LEDs344are arranged on the PCB345in a predetermined form, thereby forming the light source unit349.

FIG. 2shows three light source units349, but the number of the light source units349can be varied depending on required brightness, screen size of the LCD, etc.

Polarizers (not shown) are provided on the outer surfaces of the two panels100and200for polarizing the light emitted from the light source units349.

Referring toFIG. 1andFIG. 2, the gray voltage generator800is included in the data PCB550and generates two sets of a plurality of gray voltages related to the transmittance of the pixels. The gray voltages in one set have a positive polarity with respect to the common voltage Vcom, while those of the other set have a negative polarity with respect to the common voltage Vcom.

The gate drivers400are individually mounted on each gate TCP410, having the shapes of an integrated circuit (IC) chip, and are individually connected to the gate lines G1-Gnof the LC panel assembly300for transmitting the gate signals consisting of combinations of the gate-on voltage Vonand the gate-off voltage Voffinput from an external device to the gate signal lines G1-Gn.

The data drivers500are individually mounted on each data TCP510, having the shapes of IC chips, and are individually connected to the data lines D1-Dmof the LC panel assembly300for transmitting the data voltages which are selected from the gray voltages supplied from the gray voltage generator800to the data signal lines D1-Dm.

In another embodiment of the present invention, the gate driver400or the data driver500is directly mounted on the lower panel100, having the shape of an IC chip, and in still another embodiment of the present invention, the gate driver400or the data driver500is integrated into the lower panel100along with other elements. In the above cases, the gate PCB450or the gate TCP410can be omitted.

The signal controller600is included in the data PCB550or the gate PCB450for controlling the operation of the gate driver400or the data driver500.

Hereinafter, the operation of the above-mentioned LCD will be described.

The signal controller600receives input image signals R, G, and B and input control signals for controlling the display thereof such as a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, a main clock MCLK, a data enable signal DE, etc. from an external graphic controller (not shown). In response to the input image signals R, G, and B and the input control signals, the signal controller600processes the image signals R, G, and B suitably for the operation of the LC panel assembly300and generates gate control signals CONT1and data control signals CONT2, and then outputs the gate control signals CONT1and the data control signals CONT2to the gate driver400and the data driver500, respectively.

The gate control signals CONT1include a vertical synchronizing start signal SW for indicating the beginning of a frame, a gate clock signal CPV for controlling the output time of the gate-on voltage Von, and an output enable signal OE for defining the duration of the gate-on voltage Von.

The data control signals CONT2include a horizontal synchronizing start signal STH for indicating the beginning of data transmission, a load signal LOAD for instructing to apply the data voltages to the data lines D1-Dm, a reverse signal RVS for reversing the polarity of the data voltages with respect to the common voltage Vcom, and a data clock signal HCLK.

Responsive to the data control signals CONT2from the signal controller600, the data driver500successively receives the image data DAT for a row of the pixels from the signal controller600, shifts them, converts the image data DAT into analog data voltages selected from the gray voltages from the gray voltage generator800, and then applies the data voltages to data lines D1-Dm.

The gate driver400applies the gate-on voltage Von to the gate lines G1-Gnin response to the gate control signals CONT1from the signal controller600, and thereby turns on the switching elements Q connected thereto. The data voltages applied to the data lines D1-Dmare applied to the corresponding pixel through the activated switching elements Q.

The difference between the data voltage applied to the pixel and the common voltage Vcomis represented as a voltage across the LC capacitor CLC, namely, a pixel voltage. The LC molecules in the LC capacitor CLChave orientations depending on the magnitude of the pixel voltage.

The light source driver920controls current applied to the light source section910for switching the LED344of the light source section910, and also controls the brightness of the light from the LED344.

When the light emitted from the LED344passes through the LC layer3, the polarization of the light is varied according to the orientations of the LC molecules. The polarizer converts the difference of the light polarization into a difference of the light transmittance.

By repeating this procedure by a unit of the horizontal period (which is denoted by “1H” and is equal to one period of the horizontal synchronizing signal Hsync, the data enable signal DE, and the gate clock CPV), all gate lines G1-Gnare sequentially supplied with the gate-on voltage Vonduring a frame, thereby applying the data voltages to all pixels. When the next frame starts after finishing one frame, the reverse control signal RVS applied to the data driver500is controlled such that the polarity of the data voltages is reversed with respect to that of the previous frame (which is referred to as “frame inversion”). The reverse control signal RVS may be also controlled such that the polarity of the data voltages flowing in a data line in one frame are reversed (for example, line inversion and dot inversion), or the polarity of the data voltages in one packet are reversed (for example, column inversion and dot inversion).

Hereinafter, an LED for a backlight device according to an embodiment of the present invention will be described with reference toFIG. 4,FIG. 5, andFIG. 6.

FIG. 4is a perspective view of an LED according to an embodiment of the present invention.FIG. 5is a cross-sectional view of the LED ofFIG. 4.FIG. 6is a reference view for illustrating the refraction of light at the surface of a lens of the LED ofFIG. 4.

Referring toFIG. 4andFIG. 5, an LED344comprises a light emitting chip4and a lens. The lens is made of a transparent dielectric material and includes a base31, a curved circumferential surface2which extends from the base31, and a curved central surface1which extends from the curved circumferential surface2. The base31has a groove for receiving the light emitting chip4therein.

It is preferable that the curved central surface1of the lens has a convex shape when viewed from the light emitting chip4, and is symmetrical with respect to a lens axis which vertically extends from the center of the light emitting chip4. In the lens shown inFIGS. 4 and 5, a distance from a point of the light ray emitting surface of the light emitting chip4to a point of the curved central surface1is always shorter than the radius of curvature for the corresponding point of the curved central surface1. This condition is hereinafter referred to as “the first condition of the radius of curvature” and results in uniform dispersion of the light ray emitted from the light emitting chip4to a wider area.

While only considering the lens, it is preferable that a distance from the center of the base31to a point of the curved central surface1is always shorter than the radius of curvature for the corresponding point of the curved central surface1. This condition is hereinafter referred to as “the modified first condition of the radius of curvature”. Otherwise, it is preferable to construct a lens so that an acute angle formed between a line linking the center of the base31to a point of the curved central surface1and the main axis of the lens is always larger than an acute angle formed between a normal for the corresponding point of the curved central surface1and the main axis of the lens. This condition is hereinafter referred to as “the first condition of light dispersion”.

The shape of the curved circumferential surface2results by steeply cutting the side of the lens, so that the size of the lens is reduced and incident light which excessively slants toward the side of the lens is redirected to the upper direction of the lens. However, if necessary, the lens may be constructed so that the curved circumferential surface2satisfies the first condition of the radius of curvature or the first condition of light dispersion. That is, the lens may be constructed in such a way that the curved central surface1extends to the base31, omitting the curved circumferential surface2.

The radius of curvature is more abruptly changed at the boundary area of the curved central surface1and the curved circumferential surface2as compared with at the curved central surface1or at the curved circumferential surface2, and therefore it may be discontinuous. A discontinuous radius of curvature brings a discontinuous light distribution. Therefore, it is preferable to trim the boundary corner for a continuous variation of the radius of curvature. It is also preferable that the position of the boundary of the curved central surface1and the curved circumferential surface2is controlled depending on the light emitting distribution. For example, the boundary of the curved central surface1and the curved circumferential surface2is placed at an angle between about 20 degrees and about 50 degrees from the center of the groove for receiving the light emitting chip4. That is, since the light ray emitted from the light emitting chip4is condensed within an angle between about 20 degrees and about 50 degrees from the center of the groove and is rarely distributed beyond that range, it is enough that the lens is formed in order that the curved central surface1covers the light condensed region.

In a lens satisfying the first condition of the radius of curvature or the first condition of light dispersion, the light ray emitted from the light emitting chip4is always refracted in a receding direction from the main axis of the lens. This will be described with reference toFIG. 6.

If the lens satisfies the first condition of the radius of curvature or the first condition of light dispersion, when the wave plane of the light meets the curved central surface1as shown inFIG. 6, the wave plane near the main axis of the lens first enters into the air before passing through the lens. As a result, the incident light is refracted in the receding direction from the main axis of the lens due to the difference of the speed of the light in air and in the lens.

FIG. 7is a perspective view of an LED according to an embodiment of the present invention, andFIG. 8is a cross-sectional view of the LED ofFIG. 7.

As compared to that of the embodiment described in connection withFIGS. 4-6, this LED further comprises a central hollow portion upwardly formed from a base31, and a supporting unit7provided on the base31for supporting a light emitting chip4thereon.

The central hollow portion comprises a curved central surface5and a curved circumferential surface6which are the inner surface of the lens. It is preferable that the curved central surface5of the central hollow portion has a convex shape when viewed from the light emitting chip4and is symmetrical with respect to the main axis of the lens, which vertically extends from the center of the light emitting chip4. In this lens, a distance from a point of the light emitting surface of the light emitting chip4to a point of the curved central surface5is always longer than the radius of curvature for the corresponding point of the curved central surface5. This condition is hereinafter referred to as “the second condition of the radius of curvature” and results in uniform dispersion of the light ray emitted from the light emitting chip4to a wider region.

While only considering the lens, it is preferable that a distance from the center of the base31to a point of the curved central surface5of the central hollow portion is always longer than the radius of curvature for the corresponding point of the curved central surface5of the central hollow portion. This condition is hereinafter referred to as “the modified second condition of the radius of curvature”. Otherwise, it is preferable to construct the lens so that an acute angle formed between a straight line linking the center of the base31to a point of the curved central surface5of the central hollow portion and the main axis of the lens is always smaller than an acute angle formed between the normal for the corresponding point of the curved central surface5of the central hollow portion and the main axis of the lens. This condition is hereinafter referred to as “the second condition of light dispersion”.

The supporting unit7is attached to the base31for receiving the light emitting chip4therein. It is preferable that the supporting unit7is attached to the base31so as to not close the bottom opening of the central hollow portion. If the bottom opening were closed, the air in the central hollow portion would expand by the heat generated when the light emitting chip4is operating, causing the supporting unit7to be separated from the lens.

When the curved central surface5of the central hollow portion is formed to satisfy the second condition of the radius of curvature or the second condition of light dispersion, the light ray emitted from the light emitting chip4is always refracted in the receding direction from the main axis of the lens.

In accordance with the above, since the light ray emitted from the light emitting chip4enters the lens passing through the air of the central hollow portion, the curved central surface5of the central hollow portion should satisfy the condition of the radius of curvature or the condition of light dispersion opposite to those for the curved central surface1of the lens for satisfactory light dispersion.

FIG. 9is a cross-sectional view of an LED according to an embodiment of the present invention.

As compared to the embodiment shown inFIG. 4andFIG. 5, this LED further comprises an uneven pattern8, which is formed at the curved central surface1and the partial curved circumferential surface2of the lens. The uneven pattern8can be configured as a minute pattern. The uneven pattern8causes the light ray to disperse more uniformly. It can be formed at the entire curved central surface1and the entire curved circumferential surface2, or only at the boundary of the curved central surface1and the curved circumferential surface2.

FIG. 10is a cross-sectional view of an LED according to an embodiment of the present invention.

As compared to that of the embodiment shown inFIG. 7andFIG. 8, this LED further comprises an uneven pattern8which is formed at the boundary of the curved central surface1and the curved circumferential surface2. The uneven pattern8causes the light ray to disperse more uniformly. It can be formed at the entire curved central surface1and the entire curved circumferential surface2, or only at specific areas of the curved central surface1and the curved circumferential surface2.

In the embodiments shown inFIG. 9andFIG. 10, although the uneven pattern8is provided at the curved central surface1and the curved circumferential surface2, an outline surface resulting by linking top points of the prominences of the uneven pattern8satisfies the first condition of the radius of curvature or the modified first condition of the radius of curvature or the first condition of light dispersion.

FIG. 11is a perspective view of an LED according to an embodiment of the present invention,FIG. 12is a cross-sectional view of the LED ofFIG. 11, andFIG. 13is a reference view for illustrating the light reflection at the surface of the lens for the LED ofFIG. 11.

Referring toFIG. 11andFIG. 12, an LED comprises a light emitting chip15and a lens. The lens is formed with a transparent dielectric and includes a base14, a curved circumferential surface13which extends from the base14, a curved center-edge surface12which extends from the curved circumferential surface13, and a curved centermost surface11which extends from the curved center-edge surface12. The base14has a groove for receiving a light emitting chip15.

It is preferable that the curved center-edge surface12of the lens has a convex shape when viewed from the light emitting chip15, and is symmetrical with respect to the main axis of the lens which vertically extends from the center of the light emitting chip15. In this lens, a distance from a point of the light emitting surface of the light emitting chip15to a point of the curved center-edge surface12is always shorter than the radius of curvature for the corresponding point of the curved center-edge surface12of the lens (i.e., the first condition of the radius of curvature). This is to uniformly disperse the light ray emitted from the light emitting chip15to a wider region.

While only considering the lens, it is preferable that a distance from the center of the base14to a point of the curved center-edge surface12of the lens is always shorter than the radius of curvature for the corresponding point of the curved center-edge surface12(i.e., the modified first condition of the radius of curvature). Otherwise, it is preferable to construct the lens so that an acute angle formed between a straight line linking the center of the base14to a point of the curved center-edge surface12of the central hollow and the main axis of the lens is always larger than an acute angle formed between the normal for the corresponding point of the curved center-edge surface12and the main axis of the lens (i.e., the first condition of light dispersion).

It is preferable that the curved centermost surface11of the lens has a concave shape when viewed from the light emitting chip15and is symmetrical with respect to the main axis of the lens which vertically extends from the center of the light emitting chip15. Also, the curved centermost surface11is formed to satisfy the following equation:
A1+A2<90+sin−1(1/n)  (Equation 1)

where n is a refraction index, A1 is an obtuse angle formed between the main axis of the lens and a tangent line of a point on the curved centermost surface11, and A2 is an acute angle formed between a line linking the center of the light emitting chip15to the corresponding point of the curved centermost surface11and the main axis of the lens.

When the curved centermost surface11satisfies the above equation, the light ray emitted from the light emitting chip15is refracted at the curved centermost surface11and then is dispersed without total internal reflection. In other words, most of the light ray from the light emitting chip15is upwardly dispersed passing through the curved centermost surface11and the curved center-edge surface12.

In this manner, since most of the light ray is directly dispersed upward without the reflection, the light ray from the light emitting diode can be efficiently used.

Hereinafter, the derivation of Equation 1 will be described with reference toFIG. 13.

InFIG. 13, Ai is the angle of incidence measured when the light ray emitted from the light emitting chip15is directed toward a point of the curved centermost surface11, Ar is the angle of refraction, and n is the index of refraction. With these elements, Snell's Law is expressed by the following equation:
SinAr/SinAi=n/1  (Equation 2)

If a total internal reflection occurs, Ar is 90 degrees. Accordingly, the critical angle of incidence Ai is derived by the following equations:
SinAi=1/n(Equation 3)
Ai=Sin−1(1/n)  (Equation 4)

Therefore, the condition that the total internal reflection does not occur is expressed by the following equation:
Ai<Sin−1(1/n)  (Equation 5)

InFIG. 13, since the sum of the internal angles of a triangle is 180 degrees, the following equation is given:
A1+A2+A3=180 degrees  (Equation 6)

From the equations 5, 6, and 7, Equation 1 is derived. That is, Equation 1 means the condition that the total reflection of the light from the light emitting chip15does not occur at the curved centermost surface11.

The shape of the circumferential curved surface13results from steeply cutting the side of the lens, so that the size of the lens is reduced and the incident light which excessively slants toward the side of the lens is redirected to the upper direction of the lens. If necessary, the lens may be constructed so that a distance from a point of the light emitting surface of the light emitting chip15to a point of the curved circumferential surface13is always shorter than the radius of curvature for the corresponding point of the curved circumferential surface13of the lens. That is, the lens may be constructed in such a way that the curved center-edge surface12extends until it reaches to the base14, omitting the formation of the curved circumferential surface13.

The radius of curvature is more abruptly changed at the boundary of the curved centermost surface11and the curved center-edge surface12and at the boundary of the curved center-edge surface12and the curved circumferential surface13as compared to at the curved centermost surface11, the curved center-edge surface12, or the curved circumferential surface13. The abrupt change in the radius of curvature results in a discontinuous radius of curvature, which causes a discontinuous light distribution. Therefore, it is preferable to trim the boundary corners for a continuous variation of the radius of curvature.

It is also preferable that the position of the boundary of the curved centermost surface11and the curved center-edge surface12and the position of the boundary of the curved center-edge surface12and the curved circumferential surface13are controlled depending on the light emitting distribution. For example, the boundary of the curved center-edge surface12and the curved circumferential surface13is positioned at an angle between about 20 degrees and about 50 degrees with respect to the center of the groove. That is, since the light ray emitted from the light emitting chip15is condensed within an angle between about 20 degrees and about 50 degrees to the center of the groove and is rarely distributed beyond that range, it is enough that the lens is formed in order that the curved centermost surface11and the curved center-edge surface12cover the light condensed region.

When the first curved centermost surface11satisfies Equation 1 and the curved center-edge surface12satisfies the first condition of the radius of curvature, the light ray emitted from the light emitting chip15is always refracted at the curved centermost surface11and the curved center-edge surface12in the receding direction from the main axis of the lens.

FIG. 14is a cross-sectional view of a light emitting diode according to an embodiment of the present invention.

As compared to that of the embodiment shown inFIG. 11andFIG. 12, this light emitting diode further comprises a central hollow portion upwardly formed from a base14, and a supporting unit7is attached to the base14for supporting a light emitting chip15thereon.

The central hollow portion comprises a curved circumferential surface17and a curved central surface16, which form an inner surface of the lens. It is preferable that the curved central surface16of the central hollow portion has a convex shape when viewed from the light emitting chip15, and is symmetrical with respect to the main axis of the lens which vertically extends from the center of the light emitting chip15. In this lens, a distance from a point of the light emitting surface of the light emitting chip15to a point of the curved central surface16of the central hollow portion is always longer than the radius of curvature for the corresponding point of the curved central surface16(i.e., the second condition of the radius of curvature). This is to uniformly disperse the light ray emitted from the light emitting chip15to a wider region.

While only considering the lens, it is preferable that a distance from the center of the base14to a point of the curved central surface16of the central hollow portion is always longer than the radius of curvature for the corresponding point of the curved central surface16(i.e., the modified second condition of the radius of curvature). Otherwise, it is preferable to construct the lens so that an acute angle formed between a straight line linking the center of the base14to a point of the curved central surface16of the central hollow portion and the main axis of the lens is always smaller than an acute angle formed between the normal for the corresponding point of the curved central surface16and the main axis of the lens (i.e., the second condition of light dispersion).

A supporting unit18is attached to the base14for receiving the light emitting chip15therein. Here, it is preferable that the supporting unit18is attached to the base14not so as to close a bottom opening of the central hollow portion. If the opening were closed, the air in the central hollow portion would expand by the heat generated when the light emitting chip15is operating, causing the supporting unit18to separate from the lens.

If the central hollow portion is formed to satisfy the above-mentioned conditions, the light ray emitted from the light emitting chip15is always refracted at the curved central surface16of the central hollow portion in the receding direction from the main axis of the lens.

FIG. 15is a cross-sectional view of an LED according to an embodiment of the present invention.

As compared to that of the embodiment shown inFIG. 11andFIG. 12, this LED further comprises an uneven pattern19which is formed at the entire curved centermost surface11, the entire curved center-edge surface12, and the partial curved circumferential surface13of the lens. The uneven pattern19as a minute pattern. The uneven pattern19causes more uniform dispersion of the light ray and can be formed at the entire curved centermost surface11, the entire curved center-edge surface12, and the entire curved circumferential surface13, or only at the boundary of the second central curved surface12and the curved circumferential surface13.

FIG. 16is a cross-sectional view of an LED according to an embodiment of the present invention.

As compared to that of the embodiment shown inFIG. 14, this LED further comprises uneven patterns19and20which are individually formed at the boundary of the curved centermost surface11and the curved center-edge surface12and at the boundary of the curved center-edge surface12and the circumferential curved surface13. The uneven patterns19and20cause more uniform dispersion of the light ray and can be configured as minute patterns. The uneven patterns19and20can be formed entirely over the first central curved surface11, the second central curved surface12, and the circumferential curved surface13, or only at the specific areas of the first central curved surface11, the second central curved surface12, and the circumferential curved surface13.

In the embodiments shown inFIG. 15andFIG. 16, although the uneven patterns19and20are provided at the curved centermost surface11, the curved center-edge surface12, and the curved circumferential surface13, an outline surface of the curved center-edge surface12(created by linking top points of the prominences of the uneven patterns) satisfies the first condition of the radius of curvature or the modified first condition of the radius of curvature or the first condition of light dispersion, and an outline surface of the curved centermost surface11satisfies Equation 1.

FIG. 17is a cross-sectional view of an LED according to an embodiment of the present invention.

As compared to that of the embodiment shown inFIG. 7andFIG. 8, this LED further comprises an inner lens200which covers a light emitting chip4in a central hollow portion. The inner lens200has the same shape as the lens of light emitting diode shown inFIG. 4andFIG. 5. That is, the inner lens200comprises a base, a curved circumferential surface that extends from the base, a curved central surface which extends from the curved circumferential surface, and a groove which is provided in the base for receiving the light emitting chip4therein. The curved central surface of the inner lens200satisfies the first condition of the radius of curvature or the first condition of light dispersion. Also, the inner lens200may be formed in such a way that the curved central surface extends to the base, omitting the curved circumferential surface.

In the LED shown inFIG. 17, since the refraction is generated at the outer surface of the inner lens, the inner surface of outer lens, and the outer surface of the outer lens, the light ray is dispersed to a wider region.

FIG. 18is a cross-sectional view of an LED according to an embodiment of the present invention.

As compared to that of the embodiment shown inFIG. 14, this LED further comprises an inner lens200which covers a light emitting chip15in a central hollow portion. The inner lens200has the same shape as the lens of light emitting diode shown inFIG. 4andFIG. 5. That is, the inner lens200comprises a base, a curved circumferential surface that extends from the base, a curved central surface which extends from the curved circumferential surface, and a groove which is provided in the base of the inner lens200for receiving the light emitting chip15therein. The curved central surface of the inner lens200satisfies the first condition of the radius of curvature or the first condition of light dispersion. Also, the inner lens200may be formed in such a way that the curved central surface extends to the base, omitting the curved circumferential surface.

In the LED shown inFIG. 18, since the refraction is generated at the outer surface of the inner lens, the inner surface of the outer lens, and the outer surface of the outer lens, the light ray is dispersed to a wider region.

In the embodiments shown inFIG. 17andFIG. 18, the inner lens has the same shape as the lens of the light emitting diode shown inFIG. 4andFIG. 5, but the shape of the inner lens can be varied. Hereinafter, such variations will be described.

Referring toFIG. 19, an LED includes an outer lens101and an inner lens401. The outer lens101has the same shape as the lens of the LED ofFIG. 7andFIG. 8. The inner lens401is provided in the central hollow portion of the outer lens101and has a central hollow portion9therein. A light emitting chip4is provided in the central hollow portion9of the inner lens401. The inner lens401has the same shape as the lens of the LED shown inFIG. 7andFIG. 8. That is, the inner lens401comprises an outer surface, an inner surface defining the central hollow portion9, and a base. The outer surface of the inner lens401comprises a curved circumferential surface and a curved central surface which satisfies the first condition of the radius of curvature or the first condition of light dispersion, and the inner surface comprises a curved circumferential surface and a curved central surface which satisfies the second condition of the radius of curvature or the second condition of light dispersion.

In the LED shown inFIG. 19, since the refraction is generated at the inner and outer surfaces of the inner lens, and at the inner and outer surfaces of the outer lens, the light ray is dispersed to a wider region.

Referring toFIG. 20, an LED includes an outer lens301and an inner lens401. The outer lens301has the same shape as the lens of the LED ofFIG. 14. The inner lens401is provided in the central hollow portion of the outer lens301and has a central hollow portion9therein. A light emitting chip15is provided in the central hollow portion9of the inner lens401. The inner lens401has the same shape as the lens of the LED shown inFIG. 7andFIG. 8. That is, the inner lens401comprises an outer surface, an inner surface defining the central hollow portion9, and a base. The outer surface of the inner lens401comprises a curved circumferential surface and a curved central surface that satisfies the first condition of the radius of curvature or the first condition of light dispersion. The inner surface of the inner lens401comprises a curved circumferential surface and a curved central surface that satisfies the second condition of the radius of curvature or the second condition of light dispersion.

In the LED shown inFIG. 20, since the refraction is generated at the inner and outer surfaces of the inner lens, and at the inner and outer surfaces of outer lens, the light ray is dispersed to a wider region.

Referring toFIG. 21, an LED includes an outer lens101and an inner lens601. The outer lens101has the same shape as the lens of the LED ofFIG. 7andFIG. 8. The inner lens601is provided in the central hollow portion of the outer lens101and covers a light emitting chip4. The inner lens601has the same shape as the lens of the light emitting diode shown inFIG. 11andFIG. 12. That is, the inner lens601made of a transparent dielectric comprises a base, a curved circumferential surface which extends from the base, a curved center-edge surface which extends from the curved circumferential surface, and a curved centermost surface which extends from the curved center-edge surface. A groove is provided in the base of the inner lens601for receiving the light emitting chip4therein. The curved center-edge surface of the inner lens601satisfies the first condition of the radius of curvature or the first condition of light dispersion, and the curved centermost surface satisfies Equation 1 relating to the condition that no total refraction is generated.

In the LED shown inFIG. 21, since the refraction is generated at the outer surface of the inner lens, and at the inner and outer surfaces of the outer lens, the light ray is dispersed to a wider region.

Referring toFIG. 22, an LED includes an outer lens301and an inner lens601. The outer lens301has the same shape as the lens of the LED shown inFIG. 14. The inner lens601is provided in the central hollow portion of the outer lens301and covers a light emitting chip15. The inner lens601has the same shape as the lens of the LED shown inFIG. 11andFIG. 12. That is, the inner lens601made of a transparent dielectric comprises a base, a curved circumferential surface that extends from the base, a curved center-edge surface that extends from the curved circumferential surface, and a curved centermost surface which extends from the curved center-edge surface. A groove is provided in the base of the inner lens601for receiving the light emitting chip15therein. The curved center-edge surface of the inner lens601satisfies the first condition of the radius of curvature or the first condition of light dispersion, and the curved centermost surface satisfies Equation 1 relating to the condition that no total refraction is generated.

In the LED shown inFIG. 22, since the refraction is generated at the outer surface of the inner lens, and at the inner and outer surfaces of outer lens, the light ray is dispersed to a wider region.

Referring toFIG. 23, an LED includes an outer lens101and an inner lens801. The outer lens101has the same shape as the lens of the LED shown inFIG. 7andFIG. 8. The inner lens801is provided in the central hollow portion of the outer lens101and has a central hollow portion22therein. A light emitting chip4is provided in the central hollow portion22of the inner lens801. The inner lens801has the same shape as the lens of the LED shown inFIG. 14. That is, the inner lens801comprises an outer surface, an inner surface defining the central hollow portion22, and a base. The outer surface of the inner lens801comprises a curved circumferential surface, a curved center-edge surface which satisfies the first condition of the radius of curvature or the first condition of light dispersion, and a curved centermost surface which satisfies Equation 1 relating to the condition that no total refraction is generated, and the inner surface of the inner lens801comprises a curved circumferential surface and a curved central surface which satisfies the second condition of the radius of curvature or the second condition of light dispersion.

In the LED shown inFIG. 23, since the refraction is generated at the inner and outer surfaces of the inner lens, and at the inner and outer surfaces of the outer lens, the light ray is dispersed to a wider region.

Referring toFIG. 24, an LED includes an outer lens301and an inner lens801. The outer lens301has the same shape as the lens of the LED shown inFIG. 14. The inner lens801is provided in the central hollow portion of the outer lens301and has a central hollow portion22therein. A light emitting chip15is provided in the central hollow portion22of the inner lens801. The inner lens801has the same shape as the lens of the LED shown inFIG. 14. That is, the inner lens801comprises an outer surface, an inner surface defining the central hollow portion22, and a base. The outer surface of the inner lens801comprises a curved circumferential surface, a curved center-edge surface that satisfies the first condition of the radius of curvature or the first condition of light dispersion, and a curved centermost surface that satisfies Equation 1 relating to the condition that no total refraction is generated. The inner surface of the inner lens801comprises a curved circumferential surface and a curved central surface that satisfies the second condition of the radius of curvature or the second condition of light dispersion.

In the LED shown inFIG. 24, since the refraction is generated at the inner and outer surfaces of the inner lens, and at the inner and outer surfaces of the outer lens, the light ray is dispersed to a wider region.

The above-mentioned embodiments of the LED are examples, and more variations can be given. For example, the formation of the uneven pattern can be further varied.

FIG. 25is a graph showing the flux to the incident angle of the light ray from the LEDs according to embodiments of the present invention.

InFIG. 25, curve C0is the flux to the incident angle of the light ray emitted from the LED shown inFIG. 4andFIG. 5, curve C1is the flux to the incident angle of the light ray emitted from the LED shown inFIG. 7andFIG. 8, curve C2is the flux to the incident angle of the light ray emitted from the LED shown inFIG. 11andFIG. 12, and curve C3is the flux to the incident angle of the light ray emitted from the LED shown inFIG. 4andFIG. 5. The flux is measured at 20 mm above the LED.

As shown inFIG. 25, the dispersion of the light ray is enlarged in the order of the embodiment shown inFIG. 4andFIG. 5, the embodiment shown inFIG. 7andFIG. 8, the embodiment shown inFIG. 11andFIG. 12, and the embodiment shown inFIG. 14.

As the incident angle of the light ray emitted from the LED increases, the RGB mixing section for producing the white light and the uniform dispersion section for producing the uniform surface light can be minimized.

Accordingly, an LED according to embodiments of the present invention can widen the three-dimensional incident angle, and thus the RGB mixing section for producing the white light and the uniform dispersion section for emitting the uniform surface light can be minimized. Such a property results in construction of a compact, slim, and light LCD.

Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one of ordinary skill in the related art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims.