KR20080012511A - Led unit, backlight unit using the same and display device having the same - Google Patents

Abstract

An LED(Light Emitting Diode) unit, a backlight unit using the same, and a display device having the same are provided to increase the size of a conductive pad by separately forming conductive pads of an FPCB(Flexible Printed Circuit Board) in at least two or more layers, thereby reducing resistance of the conductive pads as much as the size, and accordingly further reducing heat generated from an LED. An FPCB(Flexible Printed Circuit Board)(32) comprises plural first and second conductive pads(322,323) separately formed in at least two or more different layers. In plural LEDs(Light Emitting Diodes)(31), first and second terminals are respectively connected to the first and second conductive pads of the FPCB. The LED is a lateral emitting LED. The FPCB further comprises first and second protection films(324,325) each formed in upper parts of the first and second conductive pads.

Description

LED unit, backlight unit using same, and display device having same {LED unit, backlight unit using the same and display device having the same}

1 is an exploded perspective view of a display device using an LED unit as a light source of a backlight unit according to an exemplary embodiment.

2 is a cross-sectional view of a flexible circuit board included in the LED unit according to an embodiment of the present invention taken along the line II of FIG.

3 is a plan view illustrating a wiring structure of a flexible circuit board on which an LED is mounted according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: liquid crystal panel 200: backlight unit

10 color filter substrate 20 thin film transistor substrate

30: LED unit 40: light guide plate

50: optical sheet

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting diode (LED) unit, a backlight unit including the same, and a display device having the same. In particular, a flexible printed circuit includes heat generated from an LED. The present invention relates to an LED unit that can be reduced on a board (FPCB), a backlight unit using the same, and a display device having the same.

In general, a liquid crystal display (LCD), which is a type of light receiving type flat panel display, itself does not emit light to form an image, and light is incident from the outside to form an image. To this end, a backlight unit is installed on the back of the liquid crystal display to irradiate light. The backlight unit is classified into a direct light type and an edge light type according to the arrangement of the light sources. The dual side emission type is a method in which light is irradiated from a light source installed at a side edge of a light guide panel disposed below the liquid crystal display panel, and the irradiated light is transmitted to the liquid crystal display panel through the light guide plate.

The side-emitting backlight unit may use a line light source and a point light source as a light source. Representative line light source is a cold cathode fluorescent lamp (CCFL) in which the electrode is installed in the tube. The point light source includes a light emitting diode (LED). CCFLs have the advantage of being able to emit strong white light, high brightness and high uniformity, and large area design. However, the CCFL has the disadvantage of being operated by a high frequency alternating signal and having a narrow operating temperature range. In comparison, LEDs have a lower performance than CCFLs in terms of brightness and uniformity, but have the advantage of being operated by a DC signal, having a long lifetime, a wide operating temperature range, and being thinner. Therefore, research to use LED as a light source has been actively conducted. In particular, an LED unit in which an LED is mounted on a flexible printed circuit board is used as a light source of a backlight unit for light weight and thinness.

The backlight unit using the LED unit as a light source includes a light guide plate and an LED unit for irradiating light to the light guide plate. Here, the LED unit includes an LED and a flexible printed circuit board on which the LED is mounted. In addition, the flexible printed circuit board mainly uses a structure in which a plurality of conductive pads are formed on the base film and a protective film is formed on the base film. And a part of protective film is removed and LED is mounted on the exposed metal pad.

However, in accordance with the trend of ultra-thin LCD modules such as mobile display devices, LEDs are also being used in a thinner size, especially in thickness. This thin LED is mounted on the flexible printed circuit board and used as a light source. As the LED becomes smaller, high heat is generated in the LED because the resistance of the conductive pattern to which the LED is connected is large. Therefore, problems such as shortening the life of the LED occur.

It is an object of the present invention to provide an LED unit, a backlight unit using the same, and a display device having the same, which can reduce heat generated from an LED on a flexible printed circuit board.

Another object of the present invention is to provide an LED unit, a backlight unit using the same, and a display device having the same, which can reduce the heat generated from the LED by reducing the resistance by making the size of the conductive pad of the flexible printed circuit board larger than before. have.

Another object of the present invention is to form a conductive pad of the flexible printed circuit board in a multi-layer structure to increase the size of the conductive pad than conventional LED unit to reduce the heat generated from the LED by reducing the resistance, the backlight unit using the same And a display device having the same.

According to an embodiment of the present invention, an LED unit may include: a flexible printed circuit board including a plurality of first and second conductive pads formed separately on at least two different layers; And a plurality of LEDs each having a first terminal and a second terminal connected to the first and second conductive pads of the flexible printed circuit board.

The LED is a side-emitting LED, the flexible printed circuit board further comprises a first and a second protective film formed on the first and second conductive pads, respectively, the white film formed on the flexible printed circuit board and It further comprises an adhesive member.

First metal wires for connecting the first conductive pads to each other; And a second metal wire for connecting the second conductive pads to each other.

According to another embodiment of the present invention, a backlight unit using an LED may include a flexible printed circuit board having a plurality of first and second conductive pads formed separately on at least two different layers, and the first printed circuit board. An LED unit including a plurality of LEDs to which first and second terminals are respectively connected to the first and second conductive pads; And a light guide plate coupled to the LED unit.

The LED unit further includes an adhesive member adhered to an upper portion of the flexible printed circuit board, and the adhesive member is adhered to the upper surface of the light guide plate.

A reflector disposed under the light guide plate; And a plurality of optical sheets provided on the light guide plate.

According to still another aspect of the present invention, there is provided a display device including a flexible printed circuit board including a plurality of first and second conductive pads formed separately on at least two different layers, and the first and second portions of the flexible printed circuit board. A backlight unit including a LED unit including a plurality of LEDs connected to a second conductive pad and having a first terminal and a second terminal, respectively, and a light guide plate coupled to the LED unit; And a liquid crystal display panel displaying an image using light supplied from the backlight unit.

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

1 is an exploded perspective view of a display device using an LED unit as a light source of a backlight unit according to an exemplary embodiment.

Referring to FIG. 1, a display device according to an exemplary embodiment includes a liquid crystal panel 100 for displaying an image and a backlight unit 200 for irradiating light to the liquid crystal panel 100.

The liquid crystal panel 100 includes a color filter substrate 10, a thin firm transistor (TFT) substrate 20, and a liquid crystal layer (not shown) injected therebetween.

Here, the color filter substrate 10 is a substrate in which an RGB color filter, which is a color filter in which a predetermined color is expressed while light passes, is formed by a thin film process. A common electrode made of a transparent conductor such as indium tin oxide (ITO) or indium zinc oxide (IZO) is coated on the front surface of the color filter substrate 10.

The thin film transistor substrate 20 is a transparent glass substrate on which a thin film transistor in matrix form is formed. The data line is connected to the source terminal of the thin film transistors, and the gate line is connected to the gate terminal. In addition, a pixel electrode made of a transparent electrode made of a transparent conductive material is formed in the drain terminal. When the electrical signals are input to the data lines and the gate lines, the respective thin film transistors are turned on or turned off to apply electrical signals necessary for forming the pixel of the drain terminal. When the thin film transistor is turned on by applying power to the gate terminal and the source terminal of the thin film transistor substrate 20, an electric field is formed between the pixel electrode and the common electrode of the color filter substrate 10, and thus, the thin film transistor substrate 20 The arrangement of the liquid crystal layer injected between and the color filter substrate 10 is changed, and the light transmittance is changed according to the changed arrangement to obtain a desired image.

Meanwhile, the backlight unit 200 includes an LED unit 30, a light guide plate 40 coupled to one side of the LED unit 30, and a plurality of optical sheets 50 installed on the light guide plate 40.

The LED unit 30 includes an LED 31, a flexible printed circuit board 32 on which the LED 31 is mounted, a white film 33 and an adhesive member 34 provided in a predetermined area on the flexible printed circuit board 32. ). Here, the flexible circuit board 32 has a structure in which a plurality of conductive pads are formed on at least two different layers, respectively, and a protective film for protecting the conductive pads is formed.

For example, the LED 31 uses an LED that emits white light, and preferably uses an LED that emits side light. In this case, the white light is coupled to the light emitting chip emitting R, G, B inside the white LED 31 to emit white light, or the light emitting chip emitting any one of R, G, B light and a corresponding phosphor. Can emit white light. In addition, it is preferable that a region other than the region where white light is emitted for side emission is provided as a shielding region. In the present embodiment, four LEDs 31 are used as shown in the figure. The four LEDs 31 may be spaced at uniform intervals to supply light uniformly to the light guide plate 40. However, the present embodiment is not limited to this number, it is preferable to use at least one LED (31).

The flexible printed circuit board 32 includes a first extension extending in one direction as shown and a second extension extending in a direction perpendicular thereto. A plurality of LEDs 31 are mounted on the first extension part, and a white film 33 and an adhesive member 34 are provided on the first extension part, and the flexible printed circuit board on which the light guide plate 40 and the LEDs 31 are mounted. 32 is adhesively bonded. In this case, the first and second extensions may be manufactured integrally, and may be separately manufactured and then combined.

On the other hand, the white film 33 and the adhesive member 34 attached to a predetermined region of the flexible printed circuit board 32 may be used in one configuration using a white double-sided tape or a white adhesive. The white film 33 and the adhesive member 34 are preferably attached above the LED 31 of the first extension part in which the LED 31 of the flexible circuit board 32 is mounted. By applying such a white film 33, it is possible to prevent the phenomenon that the light irradiated and refracted in the direction of the flexible circuit board 32 becomes yellow. That is, the light irradiated in the direction of the flexible circuit board 32 may be reflected by the white film 33 provided on the surface thereof and may be irradiated onto the light guide plate 40 without changing the color of the light. Meanwhile, the adhesive member 34 is bonded to the upper surface of the light guide plate 40 so that the flexible circuit board 32 on which the LED 31 is mounted and the light guide plate 40 are coupled.

The light guide plate 40 is coupled to the LED unit 30 and converts light having an optical distribution in the form of a line light source generated from the plurality of LEDs 31 into light having an optical distribution in the form of a surface light source. As the light guide plate 40, a wedge type plate or a parallel flat plate may be used. In addition, the light guide plate 40 is generally formed of polymethylmethacrylate (PMMA) having high strength and not easily being deformed or broken and having good transmittance. In addition, a reflecting plate (not shown) is provided under the light guide plate 40. At this time, by using a plate having a high light reflectance as a reflecting plate to reduce the light loss by re-reflecting the light incident to itself through the back of the light guide plate 40 toward the light guide plate 40.

The plurality of optical sheets 50 include a diffusion sheet, a polarizing sheet, and a brightness enhancing sheet, which are disposed above the light guide plate 40 to uniform the luminance distribution of the light emitted from the light guide plate 40. The diffusion sheet directs the light incident from the light guide plate toward the front of the liquid crystal panel, and diffuses the light to have a uniform distribution in a wide range so that the liquid crystal panel is irradiated. As the diffusion sheet, it is preferable to use a film composed of a transparent resin coated with a predetermined light diffusion member on both surfaces. The polarizing sheet serves to change the light incident obliquely among the light incident on the polarizing sheet to be emitted vertically. This is because the light efficiency increases when the light incident on the liquid crystal panel is perpendicular to the liquid crystal panel. Therefore, at least one polarizing sheet may be disposed under the liquid crystal panel in order to vertically convert the light emitted from the polarizing sheet. Meanwhile, two polarizing sheets may be used, wherein the first polarizing sheet polarizes the light of the diffusion sheet in one direction, and the second polarizing sheet polarizes the light in the direction perpendicular to the first polarizing sheet. The brightness enhancing sheet transmits light parallel to its transmission axis and reflects light perpendicular to the transmission axis. It is preferable that the transmission axis of such a brightness improving sheet is the same as the polarization axis and direction of a polarizing sheet in order to raise transmission efficiency.

FIG. 2 is a cross-sectional view of the flexible circuit board with the LED unit of FIG. 1 taken along the line II. FIG.

The flexible circuit board 32 having the LED 31 mounted thereon is flexible and has a base film 321 that is easily bent, and a plurality of first conductive patterns patterned on the upper surface of the base film 321 to transmit electrical signals. The conductive pads 322 and the conductive material are patterned on the rear surface of the base film 321, and are formed on the upper and lower surfaces of the upper and lower surfaces of the second conductive pad 323 and the base film 321. First and second protective films 324 and 325 protecting the first conductive pad 322 and the second conductive pad 323. In addition, the first conductive layer 328 and the first conductive pad embedded in the first via hole 326 exposing the predetermined region of the first conductive pad 323 by removing the predetermined region of the first protective film 324. The first buried film 324 between the first protective film 324 and the lower portion of the base film 321 is removed, buried in the second via hole 327 exposing a predetermined area of the second conductive pad 323 2 conductive layers 329 are included.

The first terminal of the LED 31 is connected to the first conductive pad 322 through the first conductive layer 328 buried in the first via hole 326, and the first buried in the second via hole 327. The second terminal of the LED 31 is connected with the second conductive pad 323 through the second conductive layer 329. The first terminal may be an anode terminal and the second terminal may be a cathode terminal. In contrast, the first terminal may be a cathode terminal and the second terminal may be a cathode terminal.

Meanwhile, as shown in FIG. 1, the base film 321 is manufactured in an L shape having a first extension part and a second extension part, and a plurality of first and second conductive pads 322 and 323 are formed thereon. May be patterned.

In addition, although four first and second conductive pads 322 and 323 are illustrated in FIG. 2, the present invention is not limited thereto, and the first and second conductive pads 322 and 323 may be formed according to the number of LEDs 31 mounted thereon. It is preferable to form by adjusting the number. In FIG. 2, the first and second conductive pads 322 and 323 formed on the upper surface and the rear surface of the base film 331 are illustrated, but the present invention is not limited thereto, and a conductive pad having a multilayer structure of at least two layers may be formed. .

As described above, the flexible printed circuit board 32 has a plurality of first and second conductive pads 322 and 323 formed on an upper surface and a rear surface of the base film 321. That is, although the conventional flexible printed circuit board forms conductive pads only on the base film, the conductive pads are divided and formed on the upper and rear surfaces of the base film. For example, to mount four LEDs, eight conductive pads are required because one LED requires two conductive pads. If it is formed only on one side, the conductive pads should not be in contact with each other, so the size of the conductive pads is inevitably limited. However, when the conductive pads are formed by dividing the conductive pads on at least two surfaces or more, the size of the conductive pads can be further increased as compared with the conventional method of forming only one surface. Accordingly, when the conductive pads are divided and formed on two or more surfaces, the size of the conductive pads can be increased by the size of the conductive pads, and thus the resistance is lowered, thereby further reducing the heat generated from the LED.

3 is a plan view of a flexible printed circuit board for explaining a wiring structure of a flexible printed circuit board on which an LED unit is mounted according to an exemplary embodiment. As shown in FIG. 3, the plurality of first conductive pads 322 as described above are connected to each other by a first metal wire 331, and the plurality of second conductive pads 323 are second metal wires 332. Are connected to each other by When the first terminal of the LED 31 connected to the first conductive pad 322 is an anode terminal, the first metal wiring 331 is a voltage wiring for applying power, and is connected to the second conductive pad 323. When the second terminal of the LED 31 is a cathode terminal, the second metal wire 332 is a ground wire for grounding. On the contrary, when the first terminal of the LED 31 connected to the first conductive pad 322 is a cathode terminal, the first metal wire 331 is a ground wire for grounding and is connected to the second conductive pad 323. When the second terminal of the LED 31 is an anode terminal, the second metal wire 332 is a power wire for applying power.

On the other hand, the first metal wiring 331 is formed above the flexible printed circuit board 32 on the basis of the LED 31 mounted on the flexible printed circuit board 32 when viewed in plan view, and the second metal wiring 331 is formed. Although 332 is formed downward, the first and second metal wires 331 and 332 are formed on different layers, so that they may be formed above or below the flexible printed circuit board 32 so as to overlap each other when viewed in plan view. have. In addition, since the first and second metal wires 331 and 332 are formed in different layers, the thickness and size of these wires can also be larger than in the prior art, so that the resistance can be further reduced.

In addition, in FIGS. 2 and 3, the first and second conductive pads 322 and 323 are formed so as not to overlap each other when viewed in a cross section and a plane, so that the size of the first and second conductive pads 322 and 323 is considerably limited. The first conductive pad 322 may be formed in the remaining space except the space where the second via hole 327 is formed between the first conductive pad 322 and the second conductive pad 323. Since it is formed in a layer different from the 322, it can be formed to overlap each other when viewed in the cross section and the plane can be made larger in size. Meanwhile, as described above, the conductive pad may be formed in a multilayer structure of at least two layers.

As described above, according to the present invention, the conductive pad of the flexible printed circuit board to which the anode terminal and the cathode terminal of the LED lamp are connected is formed by dividing the conductive pad into at least two layers, thereby increasing the size of the conductive pad compared to the conventional method of forming the conductive pad only on one side. Since the resistance of the conductive pad can be reduced by that, the heat generated from the LED can be further reduced. In addition, by reducing the heat generation and heat concentration of the LED can extend the life of the LED unit, it is possible to improve the reliability of the product.

Claims (9)

A flexible printed circuit board having a plurality of first and second conductive pads formed separately on at least two layers different from each other; And And a plurality of LEDs each having a first terminal and a second terminal connected to the first and second conductive pads of the flexible printed circuit board. The LED unit of claim 1, wherein the LED is a side emitting LED. The LED unit of claim 1, wherein the flexible printed circuit board further comprises first and second protective films formed on the first and second conductive pads, respectively. The LED unit of claim 1, further comprising a white film and an adhesive member formed on the flexible printed circuit board. The semiconductor device of claim 1, further comprising: first metal wires for connecting the first conductive pads to each other; And And a second metal wire for connecting the second conductive pads to each other. A flexible printed circuit board comprising a plurality of first and second conductive pads formed separately on at least two different layers, respectively, and a first terminal and a second terminal on the first and second conductive pads of the flexible printed circuit board. An LED unit comprising a plurality of LEDs to which each is connected; And And a light guide plate coupled to the LED unit. The backlight unit of claim 6, wherein the LED unit further comprises an adhesive member adhered to an upper portion of the flexible printed circuit board, and the adhesive member adheres to an upper surface of the light guide plate. The display apparatus of claim 6, further comprising: a reflector disposed below the light guide plate; And And a plurality of optical sheets provided on the light guide plate. A flexible printed circuit board comprising a plurality of first and second conductive pads formed separately on at least two different layers, respectively, and a first terminal and a second terminal on the first and second conductive pads of the flexible printed circuit board. A backlight unit including a LED unit including a plurality of LEDs to which each is connected, and a light guide plate coupled to the LED unit; And a liquid crystal display panel configured to display an image using light supplied from the backlight unit.

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