KR20110037730A - Liquid crystal display - Google Patents

Abstract

PURPOSE: A liquid crystal display is provided to embody local diming by using edge type backlight including a light guiding plate which a regular lens array is formed and embody scanning backlight operation by using an edge type backlight unit. CONSTITUTION: A liquid crystal display includes a liquid crystal display panel. The liquid crystal display includes a light guiding plate which is arranged under the liquid display panel(17). The display includes a plurality of light sources(16) facing the side part of the light guiding plate. The display has a buffer material(20) which is arranged between the light sources and the light guiding plate. The buffer material has at least one between an acrylic copolymer and silicone resin and has a higher refractive index than the air.

Description

Liquid Crystal Display {LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystal display device including an edge type backlight unit.

BACKGROUND ART Liquid crystal display devices have tended to be gradually widened due to their light weight, thinness, and low power consumption. The liquid crystal display device is used as a portable computer such as a notebook PC, office automation equipment, audio / video equipment, indoor and outdoor advertising display devices, and the like. The transmissive liquid crystal display device, which occupies most of the liquid crystal display device, displays an image by controlling an electric field applied to the liquid crystal layer to modulate the light incident from the backlight unit.

The backlight unit is roughly divided into a direct type and an edge type. The edge type backlight unit has a structure in which the light source 1 is disposed to face the side surface of the light guide plate 2 and a plurality of optical sheets are disposed between the liquid crystal display panel and the light guide plate as shown in FIG. 1. The edge type backlight unit may be implemented to have a thickness thinner than that of the direct type backlight unit. The direct type backlight unit has a structure in which a plurality of optical sheets and a diffusion plate are stacked below the liquid crystal display panel and a plurality of light sources are disposed below the diffusion plate.

The light guide plate 2 of the edge type backlight unit is easily expanded due to heat from the light source 1 because the distance from the light source 1 is short. The size of the light guide plate 2 increases as the display screen of the liquid crystal display device increases, and the size change due to thermal expansion also increases. In order to reduce mechanical interference between the light source 1 and the light guide plate 2 due to thermal expansion of the light guide plate 2, the light source 1 and the light guide plate 2 have a predetermined gap d as shown in FIG. 1. Are assembled. However, the light loss occurs between the light source 1 and the light guide plate 2 due to the gap d between the light source 1 and the light guide plate 2.

Referring to FIG. 1, when using a light emitting diode (LED) package as a light source 1, the light emitted from the LED passes vertically through a silicon dome of the LED package. It passes vertically through the side of the light guide plate 2 via air. Reflection loss occurs between the light source 1 and the light guide plate 2. When light passes through two media vertically, the surface reflection loss R reflected at the interface between the media may be defined as Equation 1 below. The actual light loss between the LED package and the light guide plate 2 is about 8% which adds about 4% between the LED package and the air layer and about 4% between the air layer and the light guide plate 2.

Here, n1 is the refractive index of the light-receiving medium, and n2 means the refractive index of the light-emitting medium, respectively. The refractive index of silicon is 1.4-1.5, and the refractive index of air is approximately 1. The refractive index of the light guide plate medium is about 1.49.

Accordingly, an object of the present invention is to solve the problems of the prior art as a liquid crystal display to reduce the mechanical interference between the light source and the light guide plate during thermal expansion of the light guide plate of the edge type backlight unit and to minimize the light loss between the light source and the light guide plate. To provide a device.

In order to achieve the above object, the liquid crystal display device of the present invention comprises a liquid crystal display panel; A light guide plate disposed under the liquid crystal display panel; A plurality of light sources facing the side of the light guide plate; And a buffer disposed between the light sources and the light guide plate. The buffer material includes a colorless transparent polymer material of any one of an acrylic copolymer and a silicone resin, and its refractive index is higher than that of air.

According to the present invention, local dimming may be implemented using an edge type backlight including a light guide plate on which a lenticular lens array in a short axis direction is formed, and further, scanning backlight driving may be implemented using the edge type backlight unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like numbers refer to like elements throughout. In the following description, when it is determined that a detailed description of known functions or configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Other objects and features of the present invention in addition to the above objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 2 through 11B.

2 to 6, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 10, a source driver 12 for driving data lines 14 of the liquid crystal display panel 10, The gate driver 13 for driving the gate lines 15 of the liquid crystal display panel 10, the timing controller 11 for controlling the source driver 12 and the gate driver 13, and the liquid crystal display panel 10. And a backlight unit for irradiating light and a light source driver 18.

In the liquid crystal display panel 10, a liquid crystal layer is formed between two glass substrates. A plurality of data lines 14 and a plurality of gate lines 15 intersect the lower glass substrate of the liquid crystal display panel 10. The liquid crystal cells Clc are arranged in a matrix in the pixel array due to the cross structure of the data lines 14 and the gate lines 15. The lower glass substrate of the liquid crystal display panel 10 includes a liquid crystal cell connected to the data lines 14, the gate lines 15, the thin film transistors TFT, T1, and T2, and the thin film transistors TFT, T1, and T2. Clc) pixel electrodes, storage capacitors, and the like are formed. The pixel array may be implemented in various forms as shown in FIGS. 3 to 5. The liquid crystal cells Clc are connected to the TFT and driven by an electric field between the pixel electrodes 1 and the common electrode. A black matrix, a color filter, and the like are formed on the upper glass substrate of the liquid crystal display panel 10. A polarizing plate is attached to each of the upper glass substrate and the lower glass substrate of the liquid crystal display panel 10, and an alignment layer for setting the pre-tilt angle of the liquid crystal is formed.

A black matrix, a color filter, and a common electrode are formed on the upper glass substrate of the liquid crystal display panel 10. The common electrode is formed on the upper glass substrate in a vertical electric field driving method such as twisted nematic (TN) mode and vertical alignment (VA) mode, and a horizontal electric field such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode. The driving method is formed on the lower glass substrate together with the pixel electrode. A polarizing plate is attached to each of the upper glass substrate and the lower glass substrate of the liquid crystal display panel 10, and an alignment layer for setting a pretilt angle of the liquid crystal is formed on an inner surface of the liquid crystal display panel 10 in contact with the liquid crystal.

3 to 5 are equivalent circuits showing various examples of pixel arrays.

The pixel array of FIG. 3 is a pixel array applied to most liquid crystal displays, and the data lines D1 to D6 and the gate lines G1 to G4 cross each other. In this pixel array, each of the red subpixel R, the green subpixel G, and the blue subpixel B is disposed along the column direction. Each of the TFTs includes a pixel electrode of a liquid crystal cell in which data voltages from the data lines D1 to D6 are disposed on the left side (or right side) of the data lines D1 to D6 in response to gate pulses from the gate lines G1 to G4. To feed. In the pixel array illustrated in FIG. 3, one pixel includes neighboring red subpixels R, green subpixels G, and blue subpixels B along a row direction (or a line direction) orthogonal to the column direction. . When the resolution of the pixel array shown in FIG. 3 is m × n, m × 3 (where 3 is RGB) data lines and n gate lines are required. Gate pulses of one horizontal period synchronized with the data voltage are sequentially supplied to each of the gate lines of the pixel array.

The pixel array shown in FIG. 4 can reduce the number of data lines required at the same resolution by one half and the number of necessary source drive ICs can be reduced by one half as compared with the pixel array shown in FIG. 3. In this pixel array, each of the red subpixel R, the green subpixel G, and the blue subpixel B are disposed along the column direction. In the pixel array illustrated in FIG. 4, one pixel includes neighboring red subpixels R, green subpixels G, and blue subpixels G along a line direction perpendicular to the column direction. In the pixel array shown in FIG. 4, the liquid crystal cells adjacent to the left and right share the same data line and continuously charge the data voltage supplied in a time division manner through the data line. The liquid crystal cell and the TFT disposed on the left side of the data lines D1 to D4 are defined as the first liquid crystal cell and the first TFT T1, respectively, and the liquid crystal cell and the TFT disposed on the right side of the data line D1 to D4 are defined. The connection relationship between the TFTs is defined as the second liquid crystal cell and the second TFT (T2), respectively. The first TFT T1 supplies the data voltage from the data lines D1 to D4 to the pixel electrode of the first liquid crystal cell in response to the gate pulses from the odd gate lines G1, G3, G5, and G7. The gate electrode of the first TFT T1 is connected to the odd gate lines G1, G3, G5, and G7, and the drain electrode is connected to the data lines D1 to D4. The source electrode of the first TFT T1 is connected to the pixel electrode of the first liquid crystal cell. The second TFT T2 supplies the data voltage from the data lines D1 to D4 to the pixel electrode of the second liquid crystal cell in response to the gate pulses from the even gate lines G2, G4, G6, and G8. The gate electrode of the second TFT T2 is connected to the even gate lines G2, G4, G6, and G8, and the drain electrode is connected to the data lines D1 to D4. The source electrode of the second TFT T2 is connected to the pixel electrode of the second liquid crystal cell. When the resolution of the pixel array shown in FIG. 4 is m × n, {m × 3 (where 3 is RGB)} / 2 data lines and 2n gate lines are required. Each of the gate lines of the pixel array PA is sequentially supplied with gate pulses of 1/2 horizontal period synchronized with the data voltage.

The pixel array shown in FIG. 5 can reduce the number of data lines required by the same resolution to one third and the number of source drive ICs required to one third as compared to the pixel array shown in FIG. 3. In this pixel array, each of the red subpixel R, the green subpixel G, and the blue subpixel B are disposed along the line direction. In the pixel array illustrated in FIG. 5, one pixel includes neighboring red subpixels R, green subpixels G, and blue subpixels G in a column direction. Each of the TFTs includes a pixel electrode of a liquid crystal cell in which data voltages from the data lines D1 to D6 are disposed on the left side (or right side) of the data lines D1 to D6 in response to gate pulses from the gate lines G1 to G6. To feed. When the resolution of the pixel array PA illustrated in FIG. 5 is m × n, m data lines and 3n gate lines are required. Gate pulses of one-third horizontal period in synchronization with the data voltage are sequentially supplied to each of the gate lines of the pixel array PA.

The source driver 12 includes a plurality of source drive ICs. The source driver 12 latches the digital video data RGB under the control of the timing controller 11. The source driver 12 converts the digital video data RGB into a positive / negative analog data voltage using the positive / negative gamma compensation voltage and supplies the converted data to the data lines 14.

The gate driver 13 includes a plurality of gate drive ICs. The gate driver 13 includes a shift register, a level shifter for converting an output signal of the shift register into a swing width suitable for driving a TFT of a liquid crystal cell, an output buffer, and the like. The gate driver 13 is composed of a plurality of gate drive integrated circuits and sequentially outputs gate pulses (or scan pulses) having a pulse width of approximately one horizontal period and supplies them to the gate lines 15.

The light source driver 18 generates driving power of the light sources 16 and adjusts the light source driving power in response to the dimming signal DIM input from the timing controller 11 or the external system board.

The timing controller 11 receives digital video data RGB and timing signals Vsync, Hsync, DE, and DCLK input from an external system board on which a video source is mounted. The timing signals Vsync, Hsync, DE, and DCLK include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, a dot clock signal DCLK, and the like. The timing controller 11 may include timing control signals DDC, for controlling an operation timing of the source driver 12 and the gate driver 13 based on timing signals Vsync, Hsync, DE, and DCLK from the system board. GDC). The timing controller 11 inserts an interpolation frame between the frames of the input video signal input at a frame frequency of 60 Hz, multiplies the source timing control signal DDC and the gate timing control signal GDC, and 60 × N The operation of the source driver 12 and the gate driver 13 may be controlled at a frame frequency of two or more positive integers Hz.

As illustrated in FIG. 6, the backlight unit includes a light guide plate 17, light sources 16 for irradiating light to the side surfaces of the light guide plate 17, and a buffer material 20 disposed between the light sources 16 and the light guide plate 17. do. The light guide plate 17 may be made of a flat plate or a wedge plate. The backlight unit supports the plurality of optical sheets 26 stacked between the light guide plate 17 and the liquid crystal display panel 10, the reflective sheet 25 disposed below the light guide plate 17, and the liquid crystal display panel 10. The guide panel 22, the support main 21 fixing the guide panel 22 and the backlight unit below the guide panel 22, a case top 23 surrounding the guide panel 22, and a bottom surface of the backlight unit. It further includes a cover bottom 24 surrounding the cover. The optical sheets 26 include at least one prism sheet and at least one diffusion sheet to diffuse light incident from the diffuser plate and to guide the light path at an angle substantially perpendicular to the light incident surface of the liquid crystal display panel. Refraction The optical sheets 26 may comprise a dual brightness enhancement film (DBEF).

Each of the light sources 16 may be selected as an LED package as shown in FIG. 7, and faces the side of the light guide plate 17 with the buffer material 20 therebetween. The LED packages are mounted on a FR4 Printed Circuit Board (hereinafter referred to as "PCB") or a metal PCB (Metal PCB). The LED package is mounted on the PCB 76 as shown in FIG. 7, and includes a mold frame 71 made of plastic such as polypatraamide (PPA), an LED chip 72 mounted on an upper recess of the mold frame 71, an anode, and the like. The cathode lead terminals 74 and 75 and the silicon dome 73 covering the LED chip 72 are provided. On the other hand, it is to be noted that the LED applied in the present invention is not limited to the LED package shown in FIG.

The buffer material 20 reduces surface light loss between the light source 16 and the light guide plate 17 and absorbs the amount of thermal expansion during thermal expansion of the light guide plate medium to prevent mechanical interference between the light source 16 and the light guide plate 17. Play a role. To this end, the buffer material 20 is a colorless transparent polymer material of any one of an acrylic copolymer and a silicone resin, and includes a urethane group having excellent adhesion and elasticity, and has a visible light transmittance of 95% or more. The refractive index of the buffer material 20 is higher than the refractive index of air and is similar to the refractive index of the light emitting medium medium and the light guide plate medium of the light source. Considering the refractive index of the above-mentioned buffer material, the refractive index of the buffer material 20 may be selected in the range of 1.3 to 1.6. The shock absorbing material 20 is in contact with the light exit portion of the light source 16 and the side surface of the light guide plate 17 even when the light guide plate 17 is not thermally expanded. The cushioning material 20 is adhered to the light incident portion of the light source 16 and the light incident plate 17 by its adhesive force without a separate adhesive.

The amount of deformation due to thermal expansion of the light guide plate 20 may be represented by a linear expansion coefficient (cm / ° C.) in a measurement standard such as ASTM D696, and may not exceed 300 μm / ° C. for a general plastic resin used as the light guide plate material. According to the present invention, the gap between the light source 16 and the light guide plate 17 may vary depending on the set size of the liquid crystal display module and the design specification of the backlight unit. Assume up to ℃. The buffer range of the buffer material 20 should be larger than the maximum heat deformation amount of 500 탆 / 占 폚 of the light guide plate. On the other hand, if the buffering range of the buffer member is smaller than the thermal deformation amount of the light guide plate, mechanical interference between the light source 16 and the light guide plate 17 occurs during thermal expansion of the light guide plate 17. For example, when assembling the light source 16 and the light guide plate 17 with a gap of 1 mm, and filling the buffer material having a buffering effect of 10% between the light source 16 and the light guide plate 17 to 100 μm / ° C or more. The light guide plate 17 is in contact with the light source 16 when the light guide plate 17 is thermally expanded.

According to the present invention, there is little difference in refractive index between the light source 16 and the light guide plate 17 and a high elastic buffer material 20 is disposed to minimize light loss between the light source 16 and the light guide plate 17 as shown in FIG. It is possible to absorb thermal expansion of the light guide plate 17 and to prevent mechanical interference between the light guide plate 17 and the light source 16.

9A to 9E are views showing various arrangements of the buffer material 20 and the light source 16.

9A to 9E, the light source 16 may be disposed to face one or more of four sides including the top, bottom, left and right sides of the light guide plate 17. The buffer member 20 adheres to the light exit portion of the light source 16 and the light incident portion of the light guide plate 17 between the light source 16 and the side surface of the light guide plate 17, and the light guide plate 17 on which the light source 16 is not disposed. It can stick only to the sides. Thus, the buffer 20 may include one or more buffers and may adhere to one or more of the four sides of the light guide plate 17.

10A to 10D are views illustrating various structural modifications of the cushioning material 20.

10A to 10D, the shock absorbing material 20 has a cross section of a quadrangle, a trapezoid, a trumpet shape, etc., with curved edges close to the light source. The buffer material 20 may be thicker from the light exit portion of the light source 16 to the light incident portion of the light guide plate 17.

11A and 11B are diagrams showing examples of independent arrangement and common arrangement of the cushioning material 20.

11A and 11B, the shock absorbing material 20 may be commonly adhered to a single unit between the plurality of light sources 16 and the light guide plate 17, and may be adhered 1: 1 with the light sources 16. .

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a view showing a gap between a light source and a light guide plate in an edge type light guide plate.

2 is a block diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

3 to 5 illustrate various pixel array examples of the liquid crystal display panel illustrated in FIG. 2.

6 is a cross-sectional view illustrating an assembly state of an edge type backlight unit and a liquid crystal display panel according to an exemplary embodiment of the present invention.

7 is a cross-sectional view showing an example of the LED package.

8 is a view comparing light loss of the edge-type backlight unit in the prior art and the present invention.

9A to 9E are views illustrating various arrangements of the buffer material and the light source.

10A to 10D are views illustrating various structural modification examples of the cushioning material.

11A and 11B are diagrams showing an independent arrangement and a common arrangement example of a cushioning material.

<Description of Symbols for Main Parts of Drawings>

201: Light guide plate 201a: Lenticular lens array

202: light source array

Claims (6)

A liquid crystal display panel; A light guide plate disposed under the liquid crystal display panel; A plurality of light sources facing the side of the light guide plate; And A buffer member disposed between the light sources and the light guide plate, The buffer member comprises a colorless transparent polymer material of any one of an acrylic copolymer and a silicone resin, and a refractive index thereof is higher than air. The method of claim 1, The buffer member comprises a urethane group. The method of claim 1, And the buffer material has a visible light transmittance of 95% or more. The method of claim 1, The refractive index of the buffer member has a refractive index of 1.3 to 1.6, characterized in that the liquid crystal display device. The method of claim 1, And the buffer member is adhered to the light exit portion of the light source and the side surface of the light guide plate. The method of claim 1, The buffer range of the buffer member comprises a heat deformation range of the light guide plate.

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