KR20050000803A - Backlight for liquid crystal display device - Google Patents

Abstract

PURPOSE: A back light unit of an LCD(Liquid Crystal Display) is provided to enhance brightness of the LCD by arranging LEDs(Light Emitting diodes) in the back light unit in addition to lamps located at the sides of a light guide plate. CONSTITUTION: A back light unit of an LCD includes a light guide plate(124), linear lamps(120a,120b) located at the side of the light guide plate, and a PCB(Printed Circuit Board)(130) in which a plurality of LEDs(133) are arranged. The PCB is located under the light guide plate. The back light unit further includes a diffusion sheet(118) and a dual brightness enhancement film(112), located on the light guide plate. The light guide plate includes lamp housings(122a,122b) that respectively surround the lamps and reflect light emitted from the lamps to the light guide plate.

Description

Backlight for liquid crystal display device

The present invention relates to a backlight for a liquid crystal display device, and more particularly to a structure of a side type backlight for a liquid crystal display device.

Recently, with the rapid development of the information society, there is a need for a flat panel display having excellent characteristics such as thinning, light weight, and low power consumption. A liquid crystal display has a resolution and color. It is excellent in display and image quality, and is actively applied to notebooks and desktop monitors.

In general, a liquid crystal display device is formed by arranging two substrates on which electric field generating electrodes are formed so that the surfaces on which two electrodes are formed face each other, injecting a liquid crystal material between the two substrates, and then applying voltage to the two electrodes. By moving the liquid crystal molecules by an electric field, the device expresses an image by the transmittance of light that varies accordingly.

However, the liquid crystal display does not emit light by itself and merely controls a light transmittance, and thus requires a separate light source.

Accordingly, a backlight is disposed below the liquid crystal panel and light emitted from the backlight is incident on the liquid crystal panel to display an image by adjusting the amount of light according to the arrangement of liquid crystals.

Such backlight is divided into a direct method of directly dimming the front surface of the substrate by placing a lamp, which is a light source, on the bottom of the liquid crystal panel, and a side method of reflecting and diffusing light by a light guide plate and a reflecting plate by placing the lamp on one side or both sides of the liquid crystal panel. Lose. The direct method does not require a light guide plate because the light emitted from the lamp is directly emitted to the front of the liquid crystal panel, whereas the side method requires a light guide plate that emits the light emitted from the side lamp to the front of the backlight. In general, the backlight used in the notebook computer adopts a side method with low luminance unevenness, a thin film type, and low power consumption. The direct type backlight also has high light utilization, simple handling, and limited display size. It is widely used in a large liquid crystal display device because it is not present.

1 and 2 are plan views and cross-sectional views of a general side type backlight structure, in which lamps are provided at both sides of the light guide plate.

As shown in FIG. 1, although not shown in the drawing, there are several sheets that serve as light diffusion, condensing, etc., and a light guide plate 24 is positioned below the sheets. Linear lamps 20a and 20b serving as light sources are formed on both side surfaces of the light guide plate 24.

As shown in FIG. 2, which is a cross-sectional view of FIG. 1, in a general side type backlight, lamps 20a and 20b which are linear light sources and lamp housings 22a and 22b which surround the lamps 20a and 20b are The light guide plate 24 is disposed on both side surfaces thereof. The light guide plate 24 serves to change the light emitted from the lamps 20a and 20b on the side surface to a surface light source. Although not shown at the bottom of the light guide plate 24, the light guide plate 24 diffuses the light to create a uniform surface light source. A dot pattern made through a method such as printing is formed.

In addition, a diffusion sheet 18, a prism sheet 14, and a dual brightness enhancement film (DBEF) sheet 12 are sequentially disposed on the light guide plate 24 to secure a desired viewing angle.

Next, a reflector 26 is disposed under the light guide plate 24 to prevent light leakage and reflect light emitted from the light guide plate 24 toward the upper liquid crystal panel (not shown). It is.

Although not shown, a lower plate (not shown) is disposed above the DBEF sheet 12 below the panel guide (not shown _ and the reflecting plate 26).

Each component forming the above-described side type backlight will be described in more detail.

The linear lamps 20a and 20b are light sources that generate visible light by applying a high voltage, and include two types of cold cathode lamps or hot cathode fluorescent lamps. It emits electrons from the cathode and irradiates the phosphor to produce visible light. Cold cathode lamps are mainly used. In addition, the lamp housings 22a and 22b surrounding the lamps 20a and 20b reflect the light sources emitted from the lamps 20a and 20b and enter the light guide plate 24.

Next, the light guide plate 24 serves to transmit the light emitted from the linear lamps 20a and 20b and the lamp housings 22a and 22b to the front surface of the backlight using the total reflection principle. Although not shown, a dot pattern (not shown) is formed on the bottom surface of the light guide plate 24, and the dot pattern serves to make total reflection diffused to emit light toward the entire back light.

Next, the diffusion sheet 18 forms a spherical shape with an acrylic resin on a polyester (PET) substrate, and uniformly diffuses and condenses the light source from the light guide plate 24 to uniform the luminance.

The prism sheet 14 mainly forms a prism shape with an acrylic resin on a polyester (PET) substrate and serves to condense light.

In addition, the DBEF sheet 12 is a polarizer having a structure in which thin films are laminated as a kind of prism sheet, and serves to increase luminance by reflecting and recycling light that does not transmit.

The reflecting plate 26 positioned below the light guide plate 24 mainly serves to reflect light emitted from the lower part of the light guide plate 24 back to the polyester substrate.

Although not shown, the guide panel and the lower plate serve as an outer case of the backlight, and in particular, the lower plate serves to dissipate heat from the light source and the backlight inner heat.

Recently, a liquid crystal display including the above-described backlight is used for a TV, and a laptop computer has a tendency to express a lot of movies such as movies.

However, in a TV or notebook computer using a liquid crystal display device having a backlight as a light source, the brightness of the backlight light source is partially limited, such as an image having an explosion scene because the brightness itself is not limited. When a high image signal is input, it is difficult to realize a vivid image such as a CRT TV with the above-described backlight structure.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a plurality of individual or partially on / off in addition to lamps located on one or both sides of the light guide plate in the backlight. It is an object of the present invention to provide a liquid crystal display device that can be more vividly and effectively expressed in scenes requiring high brightness such as explosion scenes by providing an adjustable LED in the backlight and partially adjusting luminance.

1 is a plan view of a side type backlight for a conventional liquid crystal display device.

FIG. 2 is a cross-sectional view of a side-side backlight for a conventional liquid crystal display device cut according to A-A of FIG.

3 is a plan view of a side type backlight for a liquid crystal display according to a first embodiment of the present invention;

4 is a cross-sectional view of a side type backlight for a liquid crystal display device according to a first embodiment of the present invention taken along line B-B of FIG.

5 is a plan view of a side type backlight for a liquid crystal display according to a second embodiment of the present invention;

FIG. 6 is a cross-sectional view of a side type backlight for a liquid crystal display according to a second exemplary embodiment of the present invention taken along the line C-C of FIG. 5.

7 and 8 are perspective views showing only a PCB and a reflector including a light guide plate and an LED in the first and second embodiments of the present invention.

9 and 10 are perspective views showing only a PCB including a light guide plate and an LED as a modification of the first and second embodiments;

11 is a block diagram illustrating a signal flow for driving a backlight having an LED according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

112: DBEF sheet 114: prism sheet

118: diffusion sheet 120a, 120b: linear lamp

122a, 122b: lamp housing 124: light guide plate

128: reflector 130: PCB

133: LED

According to an aspect of the present invention, there is provided a side type backlight for a liquid crystal display device comprising: a light guide plate; A linear lamp provided on the side of the light guide plate; It is formed under the light guide plate and includes a printed circuit board (PCB) having a plurality of light emitting diodes (LEDs).

Another side type backlight for a liquid crystal display according to the present invention includes a light guide plate; A linear lamp provided on the side of the light guide plate; A PCB having a plurality of light emitting diodes (LEDs) arranged at predetermined intervals under the light guide plate, and having a region between the arranged LEDs removed; And a reflector formed under the PCB from which the region between the arranged LEDs is removed.

The light guide plate further includes a diffusion sheet, a prism sheet, and a dual brightness enhancement film (DBEF) sheet, wherein the light guide plate surrounds a linear lamp positioned at a side thereof and reflects light generated from the lamp to the light guide plate. It further comprises a housing.

In addition, the PCB is preferably a reflective layer is formed by coating a reflective material over the entire area except the portion covered by the LED.

In addition, the LED is a surface mount device (SMD) LED, which is one of chip type LEDs, and is characterized by generating white light when it is turned on.

In addition, the LED is characterized in that the LED controller is connected to the PCB is turned on and off in individual or group units.

The linear lamp is composed of one on one side of the light guide plate or two on both sides of the light guide plate.

Hereinafter, a structure of a backlight according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

LED refers to a light emitting diode, which is a type of semiconductor used to send and receive signals by converting electrical signals into infrared or light using the characteristics of compound semiconductors. Since the LED has high light conversion efficiency, it consumes less power, can be miniaturized, thinner, and lighter, and has a relatively long lifespan and is not thermally or discharging. Since a pulse operation can be performed, the liquid crystal display can serve as a backlight, and thus, a small liquid crystal display using a light emitting diode (LED) as a light source has been studied.

However, since the LED is small in size, in order to use it as a light source of a large-area liquid crystal display device, it is necessary to use tens to hundreds of LEDs. Therefore, even if the power consumption of one LED is small, when the tens to hundreds of LEDs are all kept on, the power consumption is much larger than that of the current cold cathode lamp.

In the liquid crystal display device having a backlight according to the present invention, when a linear lamp and light from a light guide plate are used as a main light source, and a video screen requiring an especially bright brightness is displayed, for example, an explosion scene, Partially lit LEDs are located to enhance the brightness of a specific area to create a more vibrant image.

3 is a plan view of a backlight according to a first exemplary embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along the line B-B of FIG. 3.

As illustrated, the backlight 100 has transparent light guide plates 124 having linear lamps 120a and 120b formed on both sides thereof, and the diffusion sheet 118 and the prism sheet 114 are disposed on the light guide plates 124. Dual Brightness Enhancement Film (DBEF) sheets 112 are sequentially formed. In addition, lamp housings 122a and 122b for allowing light from the lamps 120a and 120b to enter the light guide plate 124 are disposed around the linear lamps 120a and 120b provided at both sides of the light guide plate 124. It is formed surrounding the 120a and 120b.

Next, a printed circuit board (130) having a plurality of LEDs (Light Emitting Diodes) 133 is formed under the light guide plate 124, and a reflecting plate below the PCB 130 provided with the LEDs 133. 128 is formed.

5 and 6 are plan views of the backlight according to the second exemplary embodiment of the present invention, and sectional views taken along the cutting line C-C of FIG.

As shown, in the backlight 200 according to the second embodiment of the present invention, a linear lamp 220 is formed on one side of the light guide plate 224, wherein the light guide plate 220 is linear on both sides. Unlike the backlight (100 in FIG. 4) with the lamp (124 in FIG. 4), the thickness of the light guide plate 224 on one side where the lamp 220 is provided is thinner than the thickness of the light guide plate 224 without the lamp 220. It is characterized by being formed. As described above, the reason for configuring the light guide plate 224 is that the role of the light guide plate 224 is to change the light emitted from the lamp 220 on the side to the surface light source and irradiate the light to the upper liquid crystal panel. This is to have the brightness and to irradiate the light emitted from the side upwards.

Next, a plurality of LEDs 233 are arranged on the lower portion of the light guide plate 224 and the PCB 230 is arranged to have a predetermined interval, and the reflecting plate 228 is formed on the lower portion of the PCB 130.

In the structure of the backlight type 100 and 200 according to the first and second embodiments described above, the sheets positioned on the light guide plates 124 and 224 and serving as the respective roles are formed in both the first and second embodiments. Since the sheets have the same structure, each sheet will be briefly described with reference to FIGS. 3 to 6.

First, the diffusion sheets 118 and 218 positioned on the light guide plates 124 and 224 diffuse and condense the light emitted from the lower light guide plates 124 and 224 uniformly onto the entire liquid crystal panel (not shown). It plays a role of constant. In this case, the diffusion sheets 118 and 218 are formed by applying a spherical acrylic resin to the base film made of polyester (PET).

Next, the prism sheets 114 and 214 positioned on the diffusion sheets 118 and 218 are made of an acrylic resin on a polyester (PET) substrate made of the same material as the diffusion sheets 118 and 218. The difference from 118 and 218 is to condense light by regularly forming a prism shape with an acrylic resin.

Next, the DBEF sheets 112 and 212 positioned on the prism sheets 114 and 214 are polarizers having a structure in which a thin film is laminated as a kind of prism sheet, and do not penetrate upward from the inside thereof. By reflecting back light that does not recycle, it increases the brightness.

Next, a printed circuit board (PCB) having LEDs positioned below the light guide plates of the first and second embodiments will be described with reference to FIGS. 7 and 8, which are perspective views showing only the light guide plate, the PCB, and the reflecting plate.

As shown, a plurality of LEDs 133, 233 are arranged on the PCB (130, 230) at regular intervals. In this case, the interval between the LEDs 133 and 233 is adjusted in consideration of the size, brightness, and power consumption of the liquid crystal panel (not shown).

First, the LEDs 133 and 233 arranged on the PCB 130 and 230 will be briefly described. The LEDs 133 arranged on the PCB 130 are a type of chip type LED. It consists of Surface Mount Device Light Emitting Diode (SDM LED), which is a small chip type LED. At this time, the size of the SMD LED (133, 233) has a length and width of approximately 0.5mm to 5mm, the height has a size smaller than the length or width, and a variety of colors including red, green, blue Light may be generated, and in the present invention, SMD LEDs 133 and 233 which generate white light are used.

Next, the PCBs 130 and 230 fixing the LEDs 133 and 233 are formed of an opaque material. In order to fix the LEDs 133 and 233 to the PCBs 130 and 230, a solder is applied to the lower surfaces of the PCBs 130 and 230, and a conductive material such as copper is deposited / etched to signal the LEDs 133 and 233. A wiring (not shown) for applying the same is formed. Therefore, the material constituting the PCB (130, 230) is heat resistant and is formed of a material that is not deformed by the etching solution, the material is typically opaque, so the PCB (130, 230) is not opaque light It is made of one material.

However, the light from the lamps 120a, 120b, and 220 positioned on one or both sides of the light guide plates 124 and 224 is converted into a surface light source through the light guide plates 124 and 224, and most of the light is directed toward the upper liquid crystal panel (not shown). As the light is emitted, but some of the light proceeds to the bottom, it is necessary to form the reflecting plates 128 and 228, which serve to reflect the light directed downward to the top again. In the conventional backlight, the reflector (28 in FIG. 2) is disposed below the light guide plate (24 in FIG. 2). However, in the present invention, the circuits for driving the LEDs 133 and 233 and the LEDs 133 and 233 are not shown. PCB (130, 230) made of an opaque material having a) is formed below the light guide plate (124, 224). Therefore, in the PCB (130, 230), if there is a predetermined interval to remove the area between the array of the arrayed LED (133, 233) to form a transmission area (TA) through which light can pass. Accordingly, the efficiency of the backlight is increased by partially emitting the light toward the bottom through the reflecting plates 128 and 228 exposed to the transmission area TA from which some of the PCBs 130 and 230 are removed.

9 and 10 show modifications of the first and second embodiments (FIGS. 7 and 8).

Reflectivity is excellent in the exposed part of the PCB 131 and 233 with the LEDs 133 and 233 without exposing a reflecting plate, except for the portion where the LEDs 133 and 233 are formed. The material is coated to form the reflective layers 136 and 236 to replace the reflective plate.

The linear lamps 120a, 120b, 220 and the lamp housings 122a, 122b, 222 may have one side (see FIG. 10, a variant of the second embodiment) or both sides (see FIG. 9, a variant of the first embodiment). Transparent light guide plates 124 and 224 and LEDs 133 and 233 are provided below the light guide plates 124 and 224, and the reflective layer is coated by coating a material having excellent reflectance in an area excluding the LEDs 124 and 224. PCBs 131 and 231 having 136 and 236 are formed, and although not shown, diffusion sheets, prism sheets, and DBEF sheets are sequentially formed on the light guide plates 124 and 224.

Although not shown in the drawings, the backlight structure according to another modification includes a plurality of LEDs under a light guide plate having a linear lamp on one side or both sides, and forms a reflective layer by coating a reflective material on a portion other than the LEDs. A PCB is formed, wherein a portion of a predetermined interval between the arrangement and the arrangement of the LEDs in the PCB is removed to expose a lower portion thereof, and a reflector is formed on the lower portion of the PCB from which the LEDs and the reflective layer and a portion of the region are removed. As in the other embodiments, the light guide plate has a structure in which several sheets including a diffusion sheet are sequentially provided.

In the above-described modified example, light recycling from the light guide plate to the lower portion of the light guide plate may be more efficiently reflected by the reflective layer formed on the reflective plate and the PCB.

Next, a brief description will be given of screen driving of a liquid crystal display using a backlight having LEDs according to the first and second embodiments and modifications of the present invention including LED lighting.

11 is a block diagram showing signal processing for displaying an image in a liquid crystal display device.

First, an image signal input from a graphics card embedded in a computer main body is input to an interface located between the graphics card and the liquid crystal panel.

Next, the interface converts an image signal transmitted from the graphic card into a signal for input to the liquid crystal panel. As an example of the processing of the interface, an image signal transferred from a graphics card in an analog form is converted into a digital image signal by the interface device.

Next, the image signal converted in the interface is input to a data processing apparatus for analyzing the converted image signal. The data processing apparatus extracts an image signal requiring high brightness, such as an explosion scene, from the signal converted by the interface, and selects the location of the explosion image from the extracted information.

Next, a general image signal passed through the data processing apparatus is input to a lamp inverter driving a backlight, and a signal having high brightness and a signal having physical position information on the screen of the image is input to an LED controller. .

Next, each image signal passed through the lamp inverter and the LED controller is input to the liquid crystal panel. At this time, when a video such as an explosion scene should be displayed on a display screen by an image and a position signal received from the LED controller, one or more LEDs corresponding to the position of the explosion screen on the display screen are turned on to emit a light source by a cathode ray lamp. By partially providing a light source generated by the LED, a high brightness, more vibrant image can be expressed.

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

The side type backlight for a liquid crystal display according to the present invention forms a PCB with LEDs that can be turned on and off in individual or group units below the light guide plate, so that only a cathode ray lamp is used as a light source for the display of a general screen. When displaying and displaying an image which requires a high brightness partly, such as an explosion scene, the liquid crystal display device which can express a high brightness vivid image by partially lighting the LED can be provided.

Claims (10)

A light guide plate; A linear lamp provided on the side of the light guide plate; A printed circuit board (PCB) formed under the light guide plate and provided with a plurality of light emitting diodes (LEDs). Backlight for a liquid crystal display device comprising a. A light guide plate; A linear lamp provided on the side of the light guide plate; A PCB having a plurality of light emitting diodes (LEDs) arranged at predetermined intervals under the light guide plate, and having a region between the arranged LEDs removed; Reflector plate formed under the PCB where the region between the arranged LED is removed Backlight for a liquid crystal display device comprising a. The method according to any one of claims 1 and 2, And a diffusion sheet, a prism sheet, and a dual brightness enhancement film (DBEF) sheet on the light guide plate. The method according to any one of claims 1 and 2, The PCB is a backlight for a liquid crystal display device in which a reflective layer is formed by coating a reflective material over the entire area except for the portion covered by the LED. The method according to any one of claims 1 and 2, The LED is a backlight for a liquid crystal display device is a surface mount device (SMD) LED, which is one of chip type LEDs. The method of claim 5, wherein The SMD LED is a backlight for a liquid crystal display device that generates white light when turned on. The method according to any one of claims 1 and 2, The LED is a backlight for a liquid crystal display device that is turned on and off by the LED controller connected to the PCB in individual or group units. The method according to any one of claims 1 and 2, And one linear lamp on one side of the light guide plate. The method according to any one of claims 1 and 2, And two linear lamps on both sides of the light guide plate. The method according to any one of claims 1 and 2, The light guide plate further includes a lamp housing surrounding a linear lamp positioned at a side thereof and reflecting light generated from the lamp to the light guide plate.