KR20110024270A - Backlight unit and liquid crystal display device having the same - Google Patents

Abstract

PURPOSE: A backlight unit and a liquid crystal display device having the same are provided to reduce the thickness of the backlight unit by excluding the use of a lamp housing in a liquid crystal display device. CONSTITUTION: A backlight unit comprises: plural LEDs(Light Emitting Diodes)(150) which are a light source; a light guide panel which is parallel to the LEDs; a first diffusion sheet which is placed on an upper portion of the light guide panel; a white pattern which is prepared on a rear plane of the first diffusion sheet and reflects the light of the LEDs to project the reflected light to a light reception unit of the light guide panel.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME}

The present invention relates to a backlight unit and a liquid crystal display device having the same.

Cathode ray tube (CRT), one of the widely used display devices, is mainly used for monitors such as TVs, measuring devices, and information terminal devices, but the size and weight of electronic products are reduced due to the weight and size of CRT itself. Could not actively respond to the response.

Therefore, in the trend of miniaturization and weight reduction of various electronic products, CRT has a certain limit in weight and size, and is expected to replace the liquid crystal display (LCD) and gas discharge using electro-optic effects. Plasma Display Panel (PDP) and Electro Luminescence Display (ELD) using the electroluminescent effect, and the like, among them, researches on liquid crystal displays are being actively conducted.

BACKGROUND ART Liquid crystal display devices have tended to be gradually widened due to their light weight, thinness, and low power consumption. Accordingly, in order to meet the needs of users, liquid crystal display devices are progressing in the direction of large area, thinning, and low power consumption.

BACKGROUND ART A liquid crystal display device is a display device that displays an image by controlling an amount of light passing through a liquid crystal, and is widely used for advantages such as thinning and low power consumption.

Unlike the CRT, the liquid crystal display is not a display device that emits light by itself, and thus, a back light unit including a separate light source is provided on the rear surface of the liquid crystal display panel to provide light for visually representing an image. .

The backlight unit is classified into an edge method and a direct method according to the position of the light source.

The edge type backlight unit is mainly applied to a relatively small liquid crystal display device such as a laptop computer and a desktop computer monitor, and has good light uniformity, long life, and an advantage in thinning the liquid crystal display device. .

The direct type backlight unit is mainly developed as the size of the liquid crystal display device is increased to 20 inches or more, and a plurality of light sources are disposed on the lower surface of the diffuser plate to direct light directly to the front of the liquid crystal display panel. will be. Such a direct type backlight unit is mainly used for a large screen liquid crystal display device requiring high luminance because the light utilization efficiency is higher than that of the edge method.

The backlight unit uses a plasma light source such as a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent tube (HCFL), an external electrode fluorescent tube (EEFL), and an external & internal electrode fluorescent tube (EIFL). Or white light emitting diodes (LEDs).

Among them, light emitting diodes (LEDs) are widely used for their advantages of long life, low power, small size, and high durability.

An edge type backlight unit using a light emitting diode (LED) as a light source is provided with optical sheets that serve as light diffusion and condensing light in a lower portion of the liquid crystal panel, and a light guide plate is positioned below the optical sheets. A light emitting diode, which is a light source, is disposed on one side of the light emitting diode, and a lamp housing surrounding the light emitting diode is disposed on one side of the light guide plate.

At this time, the light emitted from the light source is mostly incident on the light incident part of the light guide plate, but the light not reflected is reflected on the lamp housing having good reflectance and is incident on the light incident part of the light guide plate.

As a result, the lamp housing reflects all light except the light incident toward the light guide plate to the light incident surface of the light guide plate, thereby satisfying high reflectance and low absorption rate.

Since the lamp housing provided in the backlight unit having such a structure needs to be assembled with a light guide plate, an optical sheet, etc. in order to increase the light efficiency of the light source when assembling the backlight unit, assembly time is required. There is a problem that appearance defects may occur.

In addition, the lamp housing surrounds the light emitting diode and at the same time surrounds the one end is located above the optical sheet, and the other end is located below the light guide plate to surround the light emitting diode, thereby increasing the overall thickness of the backlight unit.

An object of the present invention for solving the above problems is to provide a backlight unit omitting a lamp housing and a liquid crystal display device having the same.

In addition, an object of the present invention for solving the above problems is to provide a backlight unit having a reduced overall thickness and a liquid crystal display device having the same.

The backlight unit according to the present invention includes a plurality of light emitting diodes as light sources, a light guide plate disposed in parallel with the light emitting diodes, a first diffusion sheet disposed on the light guide plate, and a rear surface of the first diffusion sheet, It includes a white pattern reflecting the light of the diode and incident to the light incident portion of the light guide plate.

The white pattern is positioned on an upper surface between a portion where light of the light emitting diode is emitted and the light guide plate.

The first diffusion sheet provided with the white pattern is formed by applying a white paint to the mother diffusion sheet and cutting it.

A prism sheet positioned above the first diffusion sheet, and configured to adjust a traveling direction of light passing through the first diffusion sheet, and a second diffusion sheet including light passing through the prism sheet.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes a liquid crystal display panel, a light emitting diode that is a light source for providing light to the liquid crystal display panel, a light guide plate disposed in parallel with the light emitting diode, a first diffusion sheet disposed on the light guide plate; It is provided on the back of the first diffusion sheet, and includes a white pattern for reflecting the light of the light emitting diode and incident to the light incident portion of the light guide plate.

The white pattern is positioned on an upper surface between a portion where light of the light emitting diode is emitted and the light guide plate.

The first diffusion sheet provided with the white pattern is formed by applying a white paint to the mother diffusion sheet and cutting it.

A prism sheet positioned above the first diffusion sheet, and configured to adjust a traveling direction of light passing through the first diffusion sheet, and a second diffusion sheet including light passing through the prism sheet.

The backlight unit and the liquid crystal display device having the same include a white pattern 200 of the first diffusion sheet 133 that reflects the light of the light source and serves as an existing lamp housing that enters the light incident portion of the light guide plate. By providing the rear surface, it is possible to omit the lamp housing provided in the existing backlight unit, it is possible to reduce the assembly time required when assembling the backlight unit, and to prevent appearance defects caused by the position or wrinkle of the lamp housing There is an effect that can be done.

The backlight unit and the liquid crystal display having the same according to the present invention can omit the existing lamp housing, thereby reducing the overall thickness of the backlight unit.

Hereinafter, a manufacturing method of a liquid crystal display device according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

1 is an exploded perspective view illustrating a liquid crystal display device according to an exemplary embodiment of the present invention, and FIG. 2 is a cross-sectional view of the liquid crystal display device taken along the line II ′ of FIG. 1.

1 and 2, the liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 110 displaying an image and a support main 115 supporting an edge of the liquid crystal display panel 110. And a backlight unit 120 provided on the rear surface of the liquid crystal display panel 110 to provide light.

The liquid crystal display panel 110 includes a color filter substrate and a thin film transistor substrate bonded together to maintain a uniform cell gap facing each other, and a liquid crystal layer interposed between the two substrates. Although not shown in detail in the drawings, the color filter substrate and the thin film transistor substrate will be described in detail. In the thin film transistor substrate, a plurality of gate lines and data lines cross each other to define pixels, and thin film transistors (TFTs) are formed at respective crossing regions. A thin flim transistor) is provided and connected in a one-to-one correspondence with the pixel electrode mounted on each pixel. The color filter substrate includes a color filter of R, G, and B colors corresponding to each pixel, a black matrix bordering each of them, and covering a gate line, a data line, a thin film transistor, and the like, and a common electrode covering all of them.

On the side of the liquid crystal display panel 110, a gate driver (not shown) connected to the gate line and the data line of the liquid crystal display panel 110 to supply a scan signal to the gate line, and data to supply a data signal to the data line, respectively. A driver (not shown) is provided.

The gate and data driver are electrically connected to each other by a tap formed of a tape carrier package (TCP).

The gate and the data driver are electrically connected to the liquid crystal display panel 110 to supply scan signals and data signals to a plurality of gate lines and data lines formed in the liquid crystal display panel 110, thereby providing a liquid crystal display panel 110 of the liquid crystal display panel 110. Drive the pixels.

The backlight unit 120 disposed below the liquid crystal display panel 110 may include a rectangular box shape bottom cover 180 having an upper surface, a metal PCB 160 disposed inside one side of the bottom cover 180, and And a plurality of light emitting diodes 150 mounted on the metal PCB 160.

The backlight unit 120 is disposed in parallel with the light emitting diodes 150 to convert point light into surface light, and the light is disposed below the light guide plate 140 to travel below the light guide plate 140. It further includes a reflective sheet 170 for reflecting in the (110) direction, and optical sheets 130 disposed on the light guide plate 140 to diffuse and focus the light irradiated from the light guide plate 140.

The light emitting diode 150 may be formed of a light emitting diode emitting white light or a combination of light emitting diodes emitting red, green, and blue light or a combination of light emitting diodes emitting white, red, green, and blue light.

The plurality of light emitting diodes 150 are driven to the first and second channels for stable driving. The first and second channels are connected in parallel with each other. Here, the plurality of light emitting diodes 150 are divided into first and second channels and connected in parallel to supply the same driving signal to all of the light emitting diodes 150. As the number of channels increases, the stability of the light emitting diodes 150 is increased. Driving can be implemented.

The metal PCB 160 is formed with a plurality of pad portions (not shown) on which the plurality of light emitting diodes 150 connected to the first channel are mounted at regular intervals, and the plurality of light emitting diodes connected to the second channel. A plurality of second pad portions (not shown) to be mounted are formed at regular intervals.

The optical sheets 130 may include a first diffusion sheet 133 that diffuses light, a prism sheet 132 that adjusts a traveling direction of light through the first diffusion sheet, and light through the prism sheet 132. It includes a second diffusion sheet 131 for diffusing.

In this case, the rear surface of the first diffusion sheet 133 is further provided with a white pattern 200 for reflecting the light of the light source to enter the light incident portion of the light guide plate. The white pattern 200 is disposed on the rear surface of the first diffusion sheet 133 on the upper surface between the light emitting portion of the light emitting diode 150 and the light guide plate 140.

That is, as shown in FIG. 3A, only the diffusion sheet without the white pattern 200 is formed on the front surface of the first diffusion sheet 133, and as illustrated in FIG. 3B on the rear surface of the first diffusion sheet 133. As described above, a diffusion sheet having a white pattern 200 disposed at one end thereof is formed. One end of the first diffusion sheet 133 on which the white pattern 200 is formed is disposed between the light emitting portion of the light emitting diode 150 and the light guide plate 140.

Next, a method of forming the white pattern 200 on the first diffusion sheet 133 will be described with reference to FIGS. 4A to 4C.

First, as shown in FIG. 4A, a mother diffusion sheet 201 divided into a unit area by a plurality of first cutting lines L1 is provided.

In the embodiment of the present invention, the mother diffusion sheet 201 is divided into a first region a, a second region b, and a third region c through two first cutting lines L1.

Subsequently, as shown in FIG. 4B, a white paint is applied along the first cutting line L1 of the mother diffusion sheet 201 through a printing process such as screen printing or offset printing to form a white pattern 202. do.

At this time, a white paint is applied to coincide with the boundary of the white pattern 202 and the first cutting line L1. As a result, a white pattern 202 is formed at the lower ends of the first region a, the second region b, and the third region c.

Next, as shown in FIG. 4C, the plurality of agents are formed by cutting the mother diffusion sheet 201 having the white pattern 202 along the first cutting line L1 and the second cutting line L2, which is a vertical cutting line. 1 is separated into a diffusion sheet 133. In the present embodiment, nine first diffusion sheets 133 are separated from the mother diffusion sheet 201. As a result, the first diffusion sheet 133 having the white pattern 200 formed thereon is formed.

At this time, the white pattern 202 is not cut by cutting along the first cutting line L1 which matches the boundary of the white pattern 202.

As such, the white pattern 200, which serves as an existing lamp housing that reflects light of the light source and enters the light incident part of the light guide plate, is provided on the rear surface of the first diffusion sheet 133, and thus, is provided in the existing backlight unit. Since the lamp housing can be omitted, it is possible to reduce the assembly time required during assembly of the backlight unit, and to prevent appearance defects caused by the position or wrinkle of the lamp housing.

In addition, the existing lamp housing can be omitted, thereby reducing the overall thickness of the backlight unit.

In addition, by having a white pattern serving as a conventional lamp housing on the back of the first diffusion sheet, the light evenly proceeds to the light incident part of the light guide plate, which will be described with reference to the drawings.

The light propagation path to the conventional light guide plate and the light propagation path to the light guide plate of the present invention are shown in Figs. 5A and 5B, respectively.

Referring to FIG. 5A, light emitted from the light emitting diodes 150 is incident to the light guide plate 140 through the lamp housing 15 surrounding the light emitting diodes, and the light is incident on the light incident part of the light guide plate. The path is very distracting, and as shown in FIG. 5B, the light emitted from the light emitting diodes 150 is incident on the light guide plate through a white pattern (not shown) positioned on the rear surface of the first diffusion sheet 133. However, the path of light propagation to the light incident part of the light guide plate is very constant. Therefore, the backlight unit according to the present invention has a white pattern on the rear surface of the first diffusion sheet, so that the path of light propagation to the light incident part of the light guide plate is very constant.

In the prior art, although the luminance uniformity of the backlight unit is improved through the lamp housing, the luminance unit of the present invention is improved due to the light incident on the light guide plate incident part through the white pattern despite the absence of the lamp housing.

Therefore, as in the present invention, even if the lamp unit is not provided with the lamp housing, the luminance uniformity is similar to that of the backlight unit provided with the lamp housing.

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

FIG. 2 is a cross-sectional view of the liquid crystal display taken along the line II ′ of FIG. 1.

3A and 3B illustrate a diffusion sheet according to the present invention.

4A to 4C illustrate a method of forming a white pattern on the diffusion sheet of the present invention.

5A and 5B show a light traveling path to a conventional light guide plate and a light traveling path to a light guide plate according to the present invention, respectively.

Claims (8)

A plurality of light emitting diodes as light sources, A light guide plate disposed side by side with the light emitting diode; A first diffusion sheet disposed on the light guide plate; And a white pattern provided on a rear surface of the first diffusion sheet and reflecting the light of the light emitting diode to enter the light incident part of the light guide plate. The method of claim 1, wherein the white pattern is And a light emitting device positioned on an upper surface of the light emitting plate. The method of claim 1, wherein the first diffusion sheet is provided with a white pattern The backlight unit is formed by applying a white paint to the mother diffusion sheet and then cut. According to claim 1, A prism sheet positioned above the first diffusion sheet and configured to adjust a traveling direction of light passing through the first diffusion sheet; And a second diffusion sheet of light passing through the prism sheet. A liquid crystal display panel, A light emitting diode which is a light source for providing light to the liquid crystal display panel; A light guide plate disposed side by side with the light emitting diode; A first diffusion sheet disposed on the light guide plate; And a white pattern provided on a rear surface of the first diffusion sheet and reflecting the light of the light emitting diode to be incident on the light incident part of the light guide plate. The method of claim 5, wherein the white pattern is And an upper surface between the portion where the light of the light emitting diode is emitted and the light guide plate. The method of claim 5, wherein the first diffusion sheet is provided with a white pattern The liquid crystal display device is formed by applying a white paint to the mother diffusion sheet and then cut. 6. The method of claim 5, A prism sheet positioned above the first diffusion sheet and configured to adjust a traveling direction of light passing through the first diffusion sheet; And a second diffusion sheet for the light passing through the prism sheet.

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