KR20120057726A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to increase the directional angle and brightness of light emitted from an LED, thereby preventing LED mura phenomena. CONSTITUTION: A cover layer(127d) with reflecting efficiency is formed on a PCB(127). A plurality of LEDs(200) are separated on the cover layer. A light diffusing lens(300) covers the LEDs respectively. The light diffusing lens is made of an inner surface and an outer surface. The light diffusing lens passes through penetration holes(123). The light diffusing lens are formed on a reflecting plate(122). A plurality of optical sheets are mounted on the light diffusing lens.

Description

[0001] Liquid crystal display device [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a backlight unit having an improved directivity angle of light emitted from an LED.

Recently, with the development of information technology and mobile communication technology, the development of a display device that can visually display information has been made, and the display device displays an image by a self-luminous display having a large emission characteristic and other external factors. It is classified as non-light-emitting display which can do it.

A non-light emitting display may be, for example, a liquid crystal display (LCD).

Here, since the LCD does not have a light emitting element, it requires a separate light source. Accordingly, a backlight unit having a light source on the back is provided to irradiate light toward the front of the LCD, thereby realizing an identifiable image.

The backlight unit uses a Cold Cathode Fluorescent Lamp (CCFL), an External Electrode Fluorescent Lamp, and a Light Emitting Diode (LED) as a light source.

Among them, LEDs are particularly widely used as light sources for displays with features such as small size, low power consumption, and high reliability.

Meanwhile, a general backlight unit is classified into a side light type and a direct light type according to the arrangement of lamps. In the side light type, one or a pair of lamps is disposed at one side of the light guide plate. It has a structure, or two or two pairs of lamps are arranged on each side of the light guide plate, and the direct-light type has a structure in which several lamps are arranged under the optical sheet.

In recent years, in the state of active research of large-area liquid crystal display devices at the request of consumers, the direct-light type is more suitable for the large-area liquid crystal display device than the side light type.

1 is a cross-sectional view of a direct-light type liquid crystal display device using a general LED as a light source, and FIG. 2 is a view schematically illustrating an emission angle at which light is emitted from the LED of FIG. 1.

As shown in FIG. 1, a general liquid crystal display device includes a liquid crystal panel 10 including first and second substrates 12 and 14 and a backlight unit 20 behind the liquid crystal panel 10.

Here, the backlight unit 20 includes a reflector plate 21, and a plurality of LEDs 23 are arranged side by side on the upper surface thereof, and a plurality of optical sheets 25 are positioned on the LEDs 23.

In this case, light emitted from two or three LEDs 23 adjacent to each other overlaps and is mixed with each other, and then enters the liquid crystal panel 10 to provide a surface light source.

The backlight unit 20 and the liquid crystal panel 10 are modularized through the top cover 40, the support main 30, and the cover bottom 50. That is, the edges of the liquid crystal panel 10 and the backlight unit 20 are formed. The top cover 40 covering the front edge of the liquid crystal panel 10 and the cover bottom 50 covering the back surface of the backlight unit 20 in the state in which the support frame 30 having the rectangular frame shape are coupled are supported in front and rear, respectively. 30) is integrated through the medium.

On the other hand, the liquid crystal display device has recently been increasingly used as a portable computer, a desktop computer monitor and a wall-mounted television, and has been actively studied for a thin liquid crystal display device having a large display area.

Accordingly, attempts have been made to provide a thin liquid crystal display device by reducing the distance A between the LEDs 23 of the backlight unit 20 and the plurality of optical sheets 25.

However, in order to supply the high-quality surface light source, which is the most important role of the backlight unit 20, to the liquid crystal panel 10, various optical designs for this are considered, and one of them is an LED 23 and a plurality of optical sheets ( Maintaining the proper distance (A) between 25 is an important factor.

In particular, in the case of the LED 23 having a certain directivity angle, since light emitted from two or three LEDs 23 adjacent to each other overlaps and is mixed with each other, it is incident on the liquid crystal panel 10 to provide a surface light source. As shown in FIG. 2, when the distance A between the LEDs 23 and the plurality of optical sheets 25 is small, hot spots are generated in an area corresponding to the LEDs 23, and the LEDs 23. Between the adjacent LED 23 and the light emitted from the LED 23 generates a dark portion (B) does not overlap and mix with each other.

As a result, an LED mura phenomenon occurs, and furthermore, a problem of deterioration of display quality of the liquid crystal display device due to luminance unevenness is caused.

Therefore, one attempts to solve this problem by reducing the distance between the LED 23 and the adjacent LED 23, which causes a cost increase problem and heat dissipation problem according to the increase in the number of the LED 23, Furthermore, it is a factor that increases the power consumption.

In addition, it is not possible to implement a lightweight liquid crystal display device.

The present invention has been made to solve the above problems, and a first object of the present invention is to provide an LED having an improved orientation angle.

In addition, the second object of the present invention is to provide a light weight and thin liquid crystal display device, and to solve a defect such as LED mura, and to prevent a problem of deterioration of display quality due to uneven brightness of the liquid crystal display device. It is for the third purpose.

In order to achieve the object as described above, the present invention is a PCB with a cover layer having a reflection efficiency; A plurality of LEDs mounted on the cover layer at regular intervals; Covering each of the plurality of LEDs, the inner surface and the outer surface, the inner surface includes an elliptical cross-section concave toward the outer surface, the outer surface is concave toward the inner surface, the light emission of the LED A light diffusing lens comprising a center portion facing the center of the surface, a total reflection portion formed around the center portion, and a side portion extending below the total reflection portion; A reflection plate including a plurality of through holes through which the light diffusion lens passes; A plurality of optical sheets mounted on the light diffusing lens; And a liquid crystal panel mounted on the plurality of optical sheets, wherein the thickness of the light diffusing lens is the thinnest the central portion of the outer surface, the space between the inner surface and the PCB is filled with air, and the reflecting plate The present invention provides a liquid crystal display device covering the entire PCB except for the light diffusion lens in a state where the light diffusion lens is provided to cover the LED on the PCB.

At this time, the plurality of LED and each of the heat radiation slug; An LED chip mounted on the heat dissipation slug; A case disposed on the heat dissipation slug, and having a sidewall protruding upwardly from an edge of the LED chip; Located on the LED chip and filled in the sidewall, and includes a transparent resin containing a phosphor, the cover layer is made of white PSR ink (Photo solder resist ink).

The light diffusing lens is adhered to the PCB through an ultraviolet curing adhesive, and the center portion of the light diffusing lens passes light incident through the inner surface as it is, and the total reflection part is light incident through the inner surface. Total reflection and the side portion refracts light incident through the inner surface according to the angle of incidence to diffuse.

As described above, according to the present invention, a light diffusing lens is further provided on the LED, and a white insulating ink layer having a high reflection efficiency is formed on the PCB on which the LED is mounted, thereby improving the direction angle and brightness of the light emitted from the LED. It can be effected.

Therefore, the LED mura phenomenon can be prevented from occurring and the thickness of the backlight unit can be reduced.

1 is a cross-sectional view of a direct-light type liquid crystal display device using a general LED as a light source.
FIG. 2 is a view schematically illustrating an exit angle at which light is emitted from the LED of FIG. 1. FIG.
3 is an exploded perspective view showing a liquid crystal display device according to an embodiment of the present invention.
4 is a partial cross-sectional view of a backlight unit including an LED according to the present invention.
5 is a perspective view of the LED of FIG. 3;
6A and 6B are enlarged perspective views and cross-sectional views of an LED and a light diffusing lens according to an exemplary embodiment of the present invention.
7a to 7b are views showing the directing angle of light varied by the presence or absence of a light diffusing lens on the LED.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

3 is an exploded perspective view illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

As illustrated, the liquid crystal display device 100 includes a liquid crystal panel 110, a backlight unit 120, a support main 130, a cover bottom 150, and a top cover 140.

First, the liquid crystal panel 110 plays a key role in image expression, and includes the first and second substrates 112 and 114 bonded to each other with the liquid crystal layer interposed therebetween.

At this time, although not clearly shown in the drawings under the premise of an active matrix method, a plurality of gate lines and data lines intersect on the inner surface of the first substrate 112, which is commonly referred to as a lower substrate or an array substrate, thereby defining pixels. Thin film transistors (TFTs) are provided at each intersection to be connected one-to-one with the transparent pixel electrodes formed in each pixel.

An inner surface of the second substrate 114, called an upper substrate or a color filter substrate, may correspond to each pixel, for example, a color filter of red (R), green (G), and blue (B) color, and these. A black matrix is provided around each other to cover non-display elements such as gate lines, data lines, and thin film transistors. In addition, a transparent common electrode covering them is provided.

The printed circuit boards 118a and 118b are connected to each other along at least one edge of the liquid crystal panel 110 via a connecting member 116 such as a flexible circuit board. 150) It is flipped to the back and adhered.

Although not clearly shown in the drawings, upper and lower alignment layers (not shown) for determining the initial molecular alignment direction of the liquid crystal are interposed between the two substrates 112 and 114 of the liquid crystal panel 110 and the liquid crystal layer. In order to prevent leakage of the liquid crystal layer filled therebetween, a seal pattern is formed along edges of both substrates 112 and 114.

In this case, upper and lower polarizers (not shown) are attached to outer surfaces of the first and second substrates 112 and 114, respectively.

The backlight unit 120 for supplying light is provided on a rear surface of the liquid crystal panel 110 such that a difference in transmittance of the liquid crystal panel 110 is expressed to the outside.

The backlight unit 120 includes an LED assembly 128 and a plurality of optical sheets 126 interposed on the LED assembly 128.

The aforementioned LED assembly 128 includes a PCB 127 formed along the inner surface of the cover bottom 150 and a plurality of LEDs 200 mounted on each of them.

In particular, the backlight unit 120 of the present invention is characterized in that the light diffusion lens 300 is provided on each LED 200.

In addition, the backlight unit 120 includes a plurality of through-holes 123 through which each light diffusing lens 300 can pass, so that the inner surface of the PCB 127 and the cover bottom 150 except the light diffusing lens 300 are formed. White or silver reflector plate 122 covering the entirety.

A diffuser plate 124 and a plurality of optical sheets 126 are disposed on the light diffusion lens 300 exposed through the through hole 123 of the reflector plate 122 for uniformity of luminance.

Here, light emitted from the plurality of LEDs 200 of the present invention implements a uniform surface light source through color mixing and is irradiated toward the liquid crystal panel 110.

In this case, the light diffusing lens 300 serves to improve the directing angle of the light emitted from the plurality of LEDs (200).

Accordingly, a result of substantially increasing the color mixing space in the backlight unit 120 may be obtained, and the color mixed light together with the light reflected by the reflecting plate 122 may include the optical sheet 126 including the diffuser plate 124. In the process of passing through is supplied to the liquid crystal panel 110 in the form of a more uniform surface light source.

In addition, since the directivity angle of the light emitted from the LED 200 is widened, even when the separation distance between the diffusion plate 124 and the LED 200 is minimized, the occurrence of the LED mura phenomenon can be prevented.

We will discuss this in more detail later.

In addition, the plurality of optical sheets 126 may include a diffusion sheet, at least one light collecting sheet, and the like, and may include various functional sheets such as a reflective polarizing film called a dual brightness enhancement film (DBEF).

The liquid crystal panel 110 and the backlight unit 120 are modularized through the top cover 140, the support main 130, and the cover bottom 150. The top cover 140 is the top and side surfaces of the liquid crystal panel 110. A rectangular frame having a cross section bent in a shape so as to cover an edge thereof is configured to open an entire surface of the top cover 140 to display an image implemented in the liquid crystal panel 110.

In addition, the cover bottom 150, which is the basis for assembling the entire structure of the liquid crystal display device 100 by mounting the liquid crystal panel 110 and the backlight unit 120, has a rectangular plate shape and covers the cover bottom 150 with each other. It includes a pair of bar-shaped side support 129 coupled to opposite opposite edges, except that the remaining two edges of the cover bottom 150 bent obliquely to be the same height and the inside thereof The low backlight unit 120 forms a predetermined space on which to be seated.

A support main 130 having a rectangular frame shape seated on the cover bottom 150 and surrounding the edges of the liquid crystal panel 110 and the backlight unit 120 is combined with the top cover 140 and the cover bottom 150.

Meanwhile, the top cover 140 may be referred to as a case top or a top case, the support main 130 may be referred to as a guide panel or a main support, and a mold frame, and the cover bottom 150 may be referred to as a bottom cover.

As described above, the liquid crystal display device 100 of the present invention includes a light diffusing lens 300 on the upper portion of each LED 200, thereby improving the directing angle of the light emitted from each LED 200. Can be.

Accordingly, a result of substantially increasing the color mixing space in the backlight unit 120 may be obtained, and the color mixed light together with the light reflected by the reflecting plate 122 may include the optical sheet 126 including the diffuser plate 124. In the process of passing through is supplied to the liquid crystal panel 110 in the form of a more uniform surface light source.

In addition, since the directivity angle of the light emitted from the LED 200 is widened, even when the separation distance between the diffusion plate 124 and the LED 200 is minimized, the occurrence of the LED mura phenomenon can be prevented.

That is, FIG. 4 is a partial cross-sectional view of the backlight unit 120 including the light diffusing lens 300 according to the present invention, the cross section of the liquid crystal panel 110 and in particular cut along the longitudinal direction of the PCB 127. It is part.

In addition, for convenience of explanation, the emission light for each of the LEDs 200 is displayed together, and the light emitted from the LEDs 200 of the present invention is diffused laterally by the light diffusing lens 300 so that only the LEDs 200 are emitted. Compared with the directing angle emitted, the directing angle of light is substantially increased.

Therefore, the liquid crystal display (100 in FIG. 3) of the present invention corresponds to the LED 200 even when the distance A between the LED 200 and the plurality of optical sheets 126 is reduced for light weight and thinness. It is possible to prevent the occurrence of hot spots in the light, and the light emitted from the LED 200 between the LED 200 and the adjacent LED 200 is not overlapped and mixed with each other (B in Fig. 2) Can be prevented from occurring.

For this reason, LED mura phenomenon is prevented from occurring.

5 is a perspective view of the LED of FIG. 3.

As shown, the LED 200 is mounted on the heat dissipation slug 215, the LED chip 211 that emits light, the heat dissipation slug 215 is a high temperature heat accompanying the light emission of the LED chip 211 It is made of metal as a conductive discharge part to the outside.

The heat dissipation slug 215 is surrounded by a case 213 serving as a housing, and a pair of positive / cathode electrode leads electrically connected to the case 213 through an LED chip 211 and a wire 218. 217a and 217b are provided and exposed outside the case 213.

 At this time, a current supply means (not shown) for supplying a power (+) and a ground power (-) for light emission of the LED chip 211 is provided outside, and is electrically connected to the anode and cathode leads 217a and 217b. .

In addition, the case 213 is configured to have sidewalls 220a, 220b, 220c, and 220d protruding highly upward along the side surface of the heat dissipation slug 215, and the inner surface of the sidewalls 220a, 220b, 220c and 220d is half. Amnesty

The side walls 220a, 220b, 220c, and 220d serve to block or reflect light emitted from the LED chip 211 to the side and form a region filled with the transparent resin 219 therein. .

That is, the storage space is defined above the LED chip 211 by the first to fourth sidewalls 220a, 220b, 220c, and 220d formed to surround the LED chip 211, and the transparent resin ( 219 is filled to control the angle of the main outgoing light of the LED (200).

In this case, the transparent resin 219 may include a phosphor (not shown), and a mixture of the phosphor (not shown) with a transparent epoxy resin (not shown) or a silicone resin (not shown) in a predetermined ratio may be used.

The phosphor (not shown) is a yellow phosphor when the LED chip 211 is a blue LED chip, and the yellow phosphor is a yttrium (Y) aluminum (Al) garnet doped with cerium (Ce) having a wavelength of 530 to 570 nm. It is preferable to use YAG: Ce (T3Al5O12: Ce) series phosphor which is phosphorus.

In addition, when the LED chip 211 is a UV LED chip, the phosphor (not shown) is composed of three color phosphors of red (R), green (G), and blue (B), and red (R), green (G), and blue. The luminescent color can be selected by adjusting the compounding ratio of the phosphor (B) (B).

In this case, the red phosphor is a YOX (Y 2 O 3: EU) -based phosphor made of yttrium oxide (Y 2 O 3) and europium (EU) compound having a 611 nm wavelength, and the green (G) phosphor is a 544 nm wavelength. Is a LAP (LaPo4: Ce, Tb) -based phosphor which is a compound of phosphoric acid (Po4), lanthanum (La), and terbium (Tb), and the blue (B) phosphor has a barium wavelength of 450 nm. It is preferable to use BAM blue (BaMgAl 10 O 17: EU) -based phosphor, which is a compound of Ba), magnesium (Mg), aluminum oxide-based material, and europium (EU).

Here, the dominant wavelength is referred to as the wavelength of the phosphor that generates the highest luminance in each of red (R), green (G), and blue (B).

Therefore, when the power supply (+) and ground power supply (-) are supplied to the LED chip 211 through the pair of lead frames 217a and 217b, the LED chip 211 emits light, and thus the LED chip 211 A portion of the emitted light excites the phosphor (not shown) of the transparent resin 219 and is mixed with the light emitted by the phosphor (not shown) to emit white light, and the white light is emitted to the outside of the LED 200. .

At this time, the present invention is further provided with a light diffusion lens (300 of FIG. 4) on the LED (200).

6A and 6B are enlarged perspective views and cross-sectional views of an LED and a light diffusing lens according to an exemplary embodiment of the present invention.

As shown, the plurality of LEDs 200 are mounted on the PCB 127 by surface mount technology (SMT) at regular intervals.

Here, the PCB 127 is composed of a power wiring layer 127c, a cover layer 127d, an insulating layer 127b, and a PCB base 127a on which a metal wiring (not shown) is formed, and the PCB base 127a is a power wiring layer. 127c, the cover layer 127d, the insulating layer 127b, and other components are mounted on and supported by the upper layer, and serve to release heat generated from the plurality of LEDs 200 to the bottom side.

The PCB base 127a may be formed of a metal having high thermal conductivity such as aluminum (Al) or copper (Cu), or may be coated with a heat transfer material to improve a heat dissipation function.

A power wiring layer 127c including a plurality of metal wirings (not shown) formed by patterning a conductive material is formed on the PCB base 127a, and is insulated between the PCB base 127a and the power wiring layer 127c. The layer 127b is positioned to electrically insulate the PCB base 127a from the metal wiring (not shown) of the power supply layer 127c.

The cover layer 127d is formed on the power wiring layer 127c, and the cover layer 127d serves to protect the metal wiring (not shown) of the power wiring layer 127c.

Here, the cover layer 127d is made of PSR ink (Photo solder resist ink), in particular, the cover layer 127d of the present invention is white with a high reflection efficiency to serve as a brightness reflector (Reflector) of the LED 200 It is preferable that it consists of PSR ink.

Therefore, the light emitted from the LED 200 is reflected toward the front to improve the brightness.

In particular, the present invention is characterized in that the light diffusion lens 300 is positioned in correspondence with each LED 200 above the LED (200).

Here, the light diffusion lens 300 may be a transparent plastic lens made of polymethylmethacrylate (PMMA) or polycarbonate.

The refractive index of the light diffusing lens 300 made of PMMA (Polymethylmethacrylate) or polycarbonate is 1.49.

The light diffusing lens 300 is an inner surface that is a space between an outer surface 311 of the lens, an inner surface 313 of the lens, a bottom surface 315 of the lens, and an inner surface 313 and the bottom surface 315 of the lens. It consists of the space part 317.

Looking at this in more detail, the outer surface 311 of the lens is concave toward the inner surface 313 from the bottom of the total reflection portion 311b, the total reflection portion 311b convexly formed around the center portion 311a It is divided into the side portion 311c leading to.

At this time, the center portion 311a faces the center of the light emitting surface of the LED 200.

The center portion 311a proceeds without refracting the light incident through the inner surface 313 of the lens, and is emitted toward the front of the light diffusion lens 300.

The total reflection part 311b totally reflects light incident through the inner surface 313 of the lens. The light totally reflected by the total reflection part 311b travels toward the bottom surface 315 of the lens, and is reflected by the cover layer 127d of the PCB 127 and is emitted toward the front.

The side portion 311c refracts and diffuses light incident through the inner surface 313 of the lens according to the incident angle thereof.

Therefore, the light emitted from the LED 200 is widely spread.

That is, among the light emitted from the LED 200, the light concentrated at the center of the light diffusion lens 300 is dispersed by the recesses, so that the left and right luminances are increased and have a wide direction angle.

The light diffusing lens 300 has an aspherical surface, and the shape of the light diffusing lens 300 may be defined by Equation (1) below.

?? Equation (1)

In Equation (1), r is the radius of the bottom surface of the light diffusing lens 300, c is the curvature of the curved surface, k is the conic constant, A is the aspherical coefficient of the fourth order term, B is the sixth term Aspheric coefficient, C is aspherical coefficient of 8th order and D is aspheric coefficient of 10th order. The curvature of the curved surface means the curvature of the groove of the light diffusing lens 300.

In Equation (1), the radius of the bottom surface of the light diffusion lens 300 is greater than 0.25 and has a value less than or equal to 5, and the koenic constant k is greater than -12 and has a value less than or equal to 0. . In addition, aspheric coefficient A has a value greater than -0.01 and equal to or less than 0, aspheric coefficient B has a value greater than 0 and equal to or less than 0.0001, and aspheric coefficient C is greater than -0.000001 and less than or equal to 0. Aspheric coefficient D has a value greater than 0 and less than or equal to 0.000000001.

Further, in order to make the aspherical surface of the light diffusing lens 300 more precise, a higher order term having aspherical coefficients other than A, B, C, and D may be added.

In this case, the inner surface 313 of the lens has an elliptical cross-section concave toward the outer surface 311, and thus, the thickness of the light diffusing lens 300 is the thinnest at the center portion 311a of the outer surface 311.

The inner space 317 is a space between the inner surface 313 and the bottom surface 315 of the lens, and the LED 200 is located at the center of the inner space 317. The remaining space after storing the LED 200 in the internal space 317 may be filled with an air layer.

The light diffusing lens 300 is bonded to the PCB 127 through the bottom surface 315. The light diffusing lens 300 is bonded to the PCB 127 by applying the ultraviolet curing adhesive 500 to the PCB 127. Thereafter, the light diffusing lens 300 is positioned on the PCB 127, and the UV light is applied to harden the adhesive 500.

At this time, the light diffusing lens 300 is formed in a form corresponding to the light emitting surface of the LED 200, that is, the ratio of the length, width and length of the LED 200 is not 1: 1 as shown in FIG. When the light emitting surface from which the light is emitted from the LED 200 is formed in the shape of a rectangle, the light diffusing lens 300 is formed to form an elliptic hemisphere corresponding to the length of the LED 200.

Therefore, the light emitted from the LED 200 can be uniformly diffused in a circular shape. As a result, it is possible to design the light diffusion lens 300 optimized for the light emitting surface of the rectangular shape of the LED (200).

As described above, the present invention includes the light diffusing lens 300 optimized on the light emitting surface of the LED 200 on the LED 200, thereby improving the directing angle of the light emitted from each LED 200. .

As a result, the color mixing space in the backlight unit 120 (in FIG. 4) may be substantially increased, and the mixed color light may diffuse the diffusion plate (124 in FIG. 3) together with the light reflected by the reflecting plate 122. In the process of passing through the optical sheet (126 of FIG. 4), it is supplied to the liquid crystal panel (110 of FIG. 3) in the form of a more uniform surface light source.

In addition, by widening the directing angle of the light emitted from the LED 200, even if the distance between the diffusion plate (124 of FIG. 3) and the LED 200 is minimized, it is possible to prevent the occurrence of the LED mura phenomenon. .

As such, after the light diffusing lenses 300 corresponding to the respective LEDs 200 are bonded to the PCB 127, the reflecting plate is provided with a plurality of through holes 123 through which the light diffusing lenses 300 can pass. 122, the entire inner surface of the PCB 127 and the cover bottom (150 of FIG. 3) except for the light diffusion lens 300 are covered.

At this time, the light diffusing lens 300 is fixed on the PCB 127 and then the reflecting plate 122 is interposed therebetween, thereby reflecting the reflecting plate by ultraviolet rays applied in the process of fixing the light diffusing lens 300 on the PCB 127. It is possible to prevent the occurrence of the rim in 122).

As described above, the present invention forms a cover layer 127d having a high reflection efficiency on the PCB 127 and includes a light diffusing lens 300 on each LED 200, thereby providing an LED 200. By reflecting the light emitted from the front toward the front to improve the brightness while improving the directivity angle of the light emitted from each LED (200).

7A to 7B are diagrams showing the directing angles of light varied by the presence or absence of a light diffusing lens on the LED.

As shown in FIG. 7A, when there is no light diffusing lens 300 above the LED 200, the light emitted from the LED 200 is directly emitted to the air. On the contrary, as shown in FIG. 7B, when the light diffusion lens 300 is provided on the LED 200, the inner surface 313 of the lens is formed by the center portion 311a of the light diffusion lens 300. The incident light proceeds as it is without refraction and exits to the front of the light diffusion lens 300, and totally reflects the light incident through the inner surface 313 of the lens by the total reflection part 311b.

The light totally reflected by the total reflection part 311b proceeds toward the bottom surface 315 of the lens, is reflected by the cover layer 127d of the PCB 127 and is emitted toward the front, and the side part 311c is Light incident through the inner surface 313 is refracted and diffused according to its incident angle.

Therefore, the light diffusion lens 300 is provided on the LED 200, the light emitted from the LED 200 has a wider angle of view.

As described above, in the backlight unit according to the present invention, since the light emitted from the LED 200 has a wider beam directivity than the light emitted from the conventional LED (23 of FIG. 2), the backlight unit (FIG. 4). Color space within 120) may be increased.

Therefore, even when the distance (A in FIG. 4) between the LED 200 and the plurality of optical sheets (126 in FIG. 4) is reduced, hot spots may be prevented from occurring in an area corresponding to the LED 200. In addition, the light emitted from the LED 200 between the LED 200 and the LED 200 adjacent thereto may prevent the dark portion (B of FIG. 2) from not overlapping and mixing with each other.

As a result, the LED mura phenomenon can be prevented from occurring and the thickness of the backlight unit 120 of FIG. 4 can be reduced.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

122: reflector, 123: through hole
127: PCB (127a: PCB base, 127b: insulating layer, 127c: power wiring layer, 127d: cover layer)
200: LED, 300: light diffusion lens
311: lens outer surface (311a: center portion, 311b: total reflection portion, 311c: side portion)
313: lens inner surface, 315: bottom surface, 317: internal space portion

Claims (6)

A PCB having a cover layer having a reflection efficiency;
A plurality of LEDs mounted on the cover layer at regular intervals;
Covering each of the plurality of LEDs, the inner surface and the outer surface, the inner surface includes an elliptical cross-section concave toward the outer surface, the outer surface is concave toward the inner surface, the light emission of the LED A light diffusing lens comprising a center portion facing the center of the surface, a total reflection portion formed around the center portion, and a side portion extending below the total reflection portion;
A reflection plate including a plurality of through holes through which the light diffusion lens passes;
A plurality of optical sheets mounted on the light diffusing lens;
Liquid crystal panel mounted on the plurality of optical sheets
Wherein the thickness of the light diffusing lens is the thinnest the central portion of the outer surface, the space between the inner surface and the PCB is filled with air, and the reflector plate covers the LED on the PCB. A liquid crystal display device covering the entire PCB except for the light diffusion lens in a state where the diffusion lens is provided.
The method of claim 1,
Each of the plurality of LEDs and the heat radiation slug; An LED chip mounted on the heat dissipation slug; A case disposed on the heat dissipation slug, and having a sidewall protruding upwardly from an edge of the LED chip; And a transparent resin disposed on the LED chip and filled in the sidewalls, the transparent resin including a phosphor.
The method of claim 1,
The cover layer is a liquid crystal display device made of white PSR ink (Photo solder resist ink).
The method of claim 1,
The light diffusion lens is bonded to the PCB through the ultraviolet curing adhesive.
The method of claim 1,
The center portion of the light diffusion lens passes light incident through the inner surface as it is, the total reflection portion totally reflects light incident through the inner surface, and the side portion transmits light incident through the inner surface at an incident angle. A liquid crystal display device is refracted and diffused accordingly.
The method of claim 5, wherein
And the light diffusion lens has a shape corresponding to a light emitting surface of the LED.

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