KR20120058340A - Backlight unit and lcd module - Google Patents

Abstract

PURPOSE: A backlight unit and an LCD module with the same are provided to place a diffraction member between a light source and a light guide plate, thereby reducing a color sense difference which occurs according to a location of the light source. CONSTITUTION: A backlight unit(150) comprises the following units. A plurality of light sources(151) are arranged on a lower side of a liquid crystal panel(100). The light sources emit light. The light sources are bonded on a lamp substrate(152). The lamp substrate is mounted on an inner side of a lamp housing(153). A light guide plate(154) is arranged in a lower part of the liquid crystal panel. The light guide plate supplies light emitted from the light sources to the liquid crystal panel.

Description

BACKLIGHT UNIT AND LCD MODULE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit, and more particularly to a backlight unit for minimizing color difference occurring on a screen according to a distance from a light source in a large-area liquid crystal display device including a photometric type backlight unit having a light source at a side thereof, and the same. The present invention relates to a liquid crystal display module.

Recently, various portable devices such as mobile phones and laptop computers, and information electronic devices that implement high resolution and high quality images such as HDTVs have been developed. The demand for display devices is gradually increasing. Such flat panel displays include liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and organic light emitting diodes (OLEDs), but mass production technologies, ease of driving, Liquid crystal displays (LCDs) are in the spotlight nowadays for reasons of implementation and realization of large area screens.

The above-described liquid crystal display device uses a passive transmissive display element, and displays the desired gray level on the screen by adjusting the amount of light passing through the liquid crystal layer by refractive index anisotropy of the liquid crystal molecules. Accordingly, a liquid crystal display (LCD) includes a backlight unit (back light) for providing light passing through the liquid crystal layer for displaying an image. Typically, the backlight unit may be classified into two types according to the structure of the light source.

One is a direct type, the lamp is a light source is located on the back of the liquid crystal panel to direct light from the bottom to the panel direction, the other is an edge type, the lamp is a type of liquid crystal panel It is located on the side to provide the light direction by changing the direction of the panel through the optical sheet.

The above-described direct type method is mainly applied to manufacturing a liquid crystal panel for a large-screen TV because the light emitted from the lamp is directly supplied to the liquid crystal panel, and can be applied to a large area panel.

On the other hand, the side type system is installed on the side of the liquid crystal panel to supply light to the liquid crystal panel through the optical sheet, the reflector plate and the light guide plate. Since light is supplied, it is difficult to obtain high brightness. However, there is an advantage that the thickness of the liquid crystal display module can be made thin because the backlight unit is located at the side. Therefore, the lateral type is mainly applied to a backlight unit of a liquid crystal display device provided in a portable device or the like requiring a thin display device.

Conventionally, as a light source of such a backlight unit, fluorescent lamps such as Cold Cathode Fluorescent Lamps (CCFLs) and External Electrode Fluoresecent Lamps (EEFLs) are mainly used. Light Emitting Device, LED) is used a lot. Since the light emitting diode emits RGB monochromatic light, there is an advantage that the color reproducibility is good and the driving power can be reduced when applied to the backlight.

1 is an exploded perspective view illustrating a structure of a side-type backlight unit having a conventional LED.

As shown in FIG. 1, the side type backlight unit 50 includes an LED lamp 51 positioned at one end of the liquid crystal display panel to provide light, a lamp substrate 52 to which the LED lamp 51 is bonded, The lamp substrate 52 is mounted inward to face the side of the lamp housing 53 and the opening of the lamp housing 53 to guide the light emitted from the LED lamp 51 to supply light to the top. The light guide plate 54 and the diffusion sheet 56 provided at the upper portion of the light guide plate 54 to diffuse the light guided by the light guide plate 54 and to uniformly supply the entire area of the upper portion, and to the upper portion of the diffusion sheet 56. One or more prism sheets 57 provided to increase the brightness of the front surface, and a reflector 58 disposed under the light guide plate 54 to reflect light directed to the lower part of the light guide plate 54 to the light guide plate 54. Include.

The backlight unit 50 having such a structure is located at the rear of the liquid crystal panel (not shown) to supply light, and the LED lamp 51 is disposed at the side of the light guide plate 54. Although not shown, a wire (not shown) electrically connected to the power supply unit may be attached to one end of the lamp substrate 52 to which the LED lamp 51 is bonded. The lamp substrate 52 is disposed inside the lamp housing 53, and the inner surface of the lamp housing 53 has a reflecting surface to reflect the light incident plate 54 from the LED lamp 51 toward the incident surface. The reflecting plate 58 serves to reduce the loss of light by reflecting light incident to itself through the back surface of the light guide plate 53 toward the light guide plate 53.

In the case where the backlight unit having such a structure is particularly used in a large area liquid crystal display device, a method of increasing light emission efficiency by adding a diffusion agent to the light guide plate in order to have high luminance even with a small light source has been proposed. This has the advantage of greatly increasing the brightness of the light emitted from the backlight unit at low cost.

However, the method of increasing the light output efficiency of the light guide plate using the above-described diffusion agent has a problem that color difference occurs in the image according to the distance between the LED lamp and the screen.

2A and 2B are diagrams for explaining color difference occurring in a liquid crystal display device having a light metering backlight unit, and as illustrated, a lamp substrate on which a plurality of LED lamps 51 of the light metering backlight unit are mounted. 52 is provided on at least one side of the liquid crystal display, and the light guide plate 54 is disposed to face the liquid crystal display.

As shown in FIG. 2A, when the LED lamp 51 emits light in the two-meter type backlight unit, white should be evenly distributed over the entire area of the screen, but the observer may be at the position of the LED lamp 51. Both ends of the near screen receive a blue feeling (B), and the center of the screen away from the position of the LED lamp receives a red feeling (R).

In addition, when the lamp is emitted in the 1-metered backlight unit shown in FIG. 2B, the observer receives a blue feeling (B) at the side of the screen where the LED lamp 51 is located, and at the center, green or green. It feels yellow, and it gets red more and more towards the other side.

This is due to the characteristic that the light guided by the light guide plate has a different refractive index for each band of the wavelength, and the light has a characteristic that the angle of refraction of the long wavelength is small and the angle of refraction toward the short wavelength is large. Accordingly, as shown in FIG. 3, the light guide plate 54 guides the light emitted from the LED lamp 51 to advance to the end of the light guide plate 54, that is, as far as possible D, and emit light upward. In the driving of the lamp, the short wavelength light sw is refracted by the diffusing agent 54a included in the light guide plate 54 and proceeds up to a distance d1 close to the LED lamp 51 so that the light guide plate 54 may be moved. The amount of light emitted to the upper part is large, and the long wavelength light (lw) has a small refraction angle, so it travels farther than the short wavelength light, so that the light emitted to the upper part of the light guide plate 54 at a distance d2 from the LED lamp 51 is increased. Large amounts (d1 << d2).

Thus, for example, in a liquid crystal display device having a light guide plate having a length of 1 m, color differences of blue, green, yellow, and red occur for each third point away from the light source 51.

This color difference makes it difficult to implement a uniform surface light source and causes a drop in image quality of the liquid crystal display device.

The present invention has been made to solve the above-described problems, the backlight unit for improving the color difference caused by the position of the light source is disposed in the liquid crystal display device having a light source having one or two side shape and the liquid crystal display comprising the same The purpose is to provide a device module.

In order to achieve the above object, a backlight unit according to a preferred embodiment of the present invention, a light source; A light guide plate having one or more side surfaces facing the light source and configured to guide incident light to one surface; And a diffraction member interposed between the light source and the light guide plate and diffracting the light emitted from the light source to enter the light guide plate.

The diffractive member is characterized by having a multi-slit structure including a plurality of openings and blocking portions.

The diffraction member is characterized in that the thickness is 100㎛ ~ 400㎛.

The opening is characterized in that the width is 1㎛ ~ 10㎛.

The blocking unit is characterized in that the width is 1nm ~ 10nm.

The diffraction member may further include an adhesive pad bonded to one end of the light guide plate.

The light source may be a plurality of light emitting diode (LED) lamps.

In order to achieve the above object, the liquid crystal display device module including the backlight unit includes: a liquid crystal panel disposed on one surface of the backlight unit; A support main on which the liquid crystal panel is seated; A top case positioned on the other surface of the liquid crystal panel to surround the liquid crystal panel and be fastened to the support main; And a cover bottom on which the liquid crystal panel and the backlight unit are seated, disposed on one surface of the backlight unit, and fastened to the top case.

According to a preferred embodiment of the present invention, the backlight unit of the present invention further comprises a diffraction member for increasing the diffraction amount of long wavelength light between the light source and the light guide plate, thereby reducing the color difference caused by the position of the light source on the screen of the liquid crystal display device. There is an effect that can be removed.

1 is an exploded perspective view illustrating a structure of a side-type backlight unit having a conventional LED.
2A and 2B are views for explaining color difference occurring in a liquid crystal display device having a photometric backlight unit.
3 is a diagram illustrating a path of light for each wavelength in the light guide plate.
4 is an exploded perspective view illustrating a structure of a backlight unit and a liquid crystal display including the same according to an exemplary embodiment of the present invention.
5 is a view illustrating a portion of a backlight unit according to an embodiment of the present invention.
6 is a view for explaining the path of light of the backlight unit according to an embodiment of the present invention.
7 is an enlarged view of a diffraction member according to an embodiment of the present invention.
8 is a graph showing luminance at a predetermined angle for each color of light passing through the diffraction member according to the exemplary embodiment of the present invention.

Hereinafter, a backlight unit and a liquid crystal display including the same according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

In addition, the drawings referred to for the embodiments of the present specification are not intended to limit the shape and position of the components to the illustrated form, in particular, in order to help the understanding of the structure and shape that are technical features of the present invention, Some components are exaggerated or reduced in scale.

4 is an exploded perspective view illustrating a structure of a backlight unit and a liquid crystal display including the same according to an exemplary embodiment of the present invention.

As shown, the liquid crystal display device of the present invention includes a liquid crystal panel 100 and a backlight unit 150, and is coupled and modularized by various mechanism parts 130, 140, and 160.

The liquid crystal panel 100 is formed of a liquid crystal layer interposed between the first substrate and the second substrate by a predetermined distance, and is implemented to implement an image as a signal is applied from the driver substrate 120. In addition to the thin film transistor, various wirings and pixel electrodes are formed on the first substrate. The second substrate is a color filter substrate for displaying RGB color, and a color filter layer and a black matrix BM are formed. The driver substrate 120 includes a scan driver IC providing a scan signal for driving the above-described thin film transistor and a data driver IC providing a data signal to the pixel electrode.

The liquid crystal panel 100 will be described in more detail. A plurality of scan lines and data lines are formed on the first substrate to be arranged horizontally and horizontally to define a plurality of pixel regions, and each pixel region is a thin film as a switching element. Transistors are formed. In addition, the thin film transistor includes a gate electrode connected to a gate line, a semiconductor layer formed by stacking amorphous silicon, etc. on the gate electrode, a source electrode and a drain electrode formed on the semiconductor layer and electrically connected to the data line and the pixel electrode. Is done.

The second substrate is a color filter composed of a plurality of sub-color filters that implements the colors of red (R), green (G), and blue (B), and separates each sub-color filter and blocks light transmitted through the liquid crystal layer. It is composed of Black Matrix (BM).

The first and second substrates configured as described above are joined to face each other by sealants formed on the outer side of the image display area to form a liquid crystal panel, and the first and second substrates described above respectively include a first polarizing plate and a first substrate. 2 is attached to the polarizing plate to polarize the light incident and output to the liquid crystal panel 100 to implement an image.

The liquid crystal panel 100 is seated on the inner side of the support main 130, and the case top 140 is coupled and supported and fixed to the upper side.

In addition, the backlight unit 150 includes a plurality of light sources 151 disposed on the lower side of the liquid crystal panel 100 to emit light, a lamp substrate 152 to which the light sources 151 are bonded, and a lamp inwardly. A lamp housing 153 for mounting the substrate 152, a light guide plate 154 disposed under the liquid crystal panel 100 to guide light emitted from the light source 151 to the liquid crystal panel 100, and a light guide plate. A diffraction member 155 attached to one end of the light source 151 to diffract the light emitted from the light source 151, and provided between the liquid crystal panel 100 and the light guide plate 154 to receive light incident from the light guide plate 154. The diffusion sheet 156 to diffuse, the prism sheet 157 for condensing the light diffused on the diffusion sheet 156 to the liquid crystal panel 100, and the light disposed under the light guide plate 154. The reflection plate 158 reflects the light back to the light guide plate.

Here, as a light source, a set of three RGB LEDs emitting monochromatic light of red (R), green (G), and blue (B) is used, or a plurality of light emitting diodes emitting white light are used. Although not limited thereto, a fluorescent lamp such as a Cold Cathode Flourscent Lamp (CCFL) or an External Electrode Flourscent Lanm (EEFL) may be used. In the embodiment of the present invention will be described the technical spirit of the present invention as an example using a plurality of LED lamps 151 as a light source.

The above-described light source LED lamp 151 is bonded to the lamp substrate 152 which is a conventional printed circuit board (PCB), the lamp substrate 152 is disposed along the side of the light guide plate 154 to face the lamp housing It is mounted at 153. The lamp housing 153 may be made of a metal material so that the light emitted from the LED lamp 151 can be efficiently incident on the light guide plate 154, and thus the LED lamp 151 bonded to the lamp substrate 151. The light source directly acts on the side of the light guide plate 154 or provides light to the light guide plate 154 reflected by the lamp housing 153.

The light guide plate 540 guides the light incident from the LED lamp 151 upwardly to spread the light evenly over the entire area of the liquid crystal panel 100. In detail, the light emitted from the LED lamp 151 is incident from the side of the light guide plate 154 and proceeds to the other side, and is reflected and refracted in the light guide plate 154 to uniformly light to the rear surface of the upper diffusion sheet. To provide.

The diffraction member 155 is provided between the LED lamp 151, which is a light source, and the light guide plate 154, and diffracts the light incident from the LED lamp to emit light to the light guide plate 154. In detail, the diffraction member 155 is attached to one side of the light guide plate 154 through a separate adhesive pad, and diffracts the light emitted from the LED lamp 151 by the formed slit pattern, corresponding to the long wavelength red color. Increases the probability that the light will travel in a different direction than the front direction. Accordingly, the long wavelength light is emitted near the position where the LED lamp 151 is disposed on the light guide plate 154 to compensate for the color difference by corresponding to the short wavelength light. A more detailed description of the structure of the diffraction member 155 will be described later.

The diffusion sheet 156 serves to diffuse the light provided from the light guide plate 154 to be uniformly provided to the entire area of the liquid crystal panel 100. The diffusion sheet 156 is a bead for diffusion of light and a base film made of PET. It consists of.

The prism sheet 157 is provided above the light guide plate 154 to concentrate the diffused light emitted from the diffusion sheet 156 toward the liquid crystal panel 100 to increase luminance. To this end, the prism sheet 157 may be provided in plural so as to be able to refract light in the x-axis and y-axis directions, respectively.

The reflector 158 is provided under the light guide plate 154 to reflect the light exiting in the lower direction of the light guide plate 154 toward the upper direction of the light guide plate 154. Do it.

In the liquid crystal display device having such a structure, the light guide plate 154, the diffusion sheet 156, and the prism sheet 157 of the backlight unit 150 are sequentially received in the cover bottom 160, and the cover bottom 160 and the support main are provided. The module 130 is modularized as the 130 and the case top 140 are fastened. Hereinafter, a structure of a backlight unit and a diffraction member included therein according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

5 is a view illustrating a portion of a backlight unit according to an embodiment of the present invention.

As shown, the backlight unit of the present invention is located under the liquid crystal panel 100 supported by the support main 130 and the case top 140.

The LED lamp 151 of the backlight unit is bonded to the lamp substrate 152 and disposed on the inner side of the lamp housing 153, and one side of the light guide plate 154 is disposed to face the LED lamp 151 described above. Although not shown, the LED lamp 151 and the lamp housing 153 described above may be further provided on the other side of the light guide plate 154 in the case of the two-meter type backlight unit.

In addition, an optical sheet 157 and a reflecting plate 158 are disposed on upper and lower portions of the light guide plate 154, and the light guide plate 154 and the lamp housing 153 are seated inside the cover bottom 160, and the cover bottom ( 160 is fastened to the case top 140.

In the above-described structure, a diffraction member 155 is diffracted between the light guide plate 154 and the LED lamp 151 to diffract the light emitted from the LED lamp 151. The diffraction member 155 includes a blocking portion 155a for blocking incident light, and an opening 155b through which light passes between the blocking portions 155a. Here, the opening 155b generates light diffraction, and thus the probability that the light having a long wavelength corresponding to red reaches the light guide plate in the region close to the LED lamp 151 is higher than that of the conventional blue light. White light is emitted from the same area. The diffraction member 155 may be attached to the light guide plate 154 through an adhesive pad 155c on one side of the light guide plate 154 and fixed to one side end.

According to this structure, the backlight unit of the present invention includes a diffraction member between the light source and the light guide plate to diffract the light emitted from the light source, thereby removing the color difference due to the difference in the light travel distance according to the wavelength in the light guide plate. have.

Hereinafter, a light path by a diffraction member included in the backlight unit of the present invention will be described with reference to the drawings.

6 is a view for explaining the path of light of the backlight unit according to an embodiment of the present invention.

As shown, the backlight unit of the present invention, when the light emitted from the LED lamp 151 reaches the diffraction member 155, a part is reflected or refracted by the blocking portion, and a part passes through the opening.

The light passing through the opening is refracted by the diffusion agent 154a in the light guide plate 154 to be emitted to the upper portion of the light guide plate 154. Among these lights, the short wavelength light (sw) is hardly diffracted. Therefore, the light is emitted to the upper portion of the light guide plate 154 after advancing to a distance d1 close to the lamp along the same path as in the prior art (d1). However, among the light passing through the opening 155a, the long-wavelength light lw is actively diffracted to increase the probability that the light propagates in a wider range, and thus, the light lw is advanced to a distance d2 close to the lamp. The amount of light emitted to the upper portion of the light guide plate 154 is increased. As a result, the short-wavelength light sw and the long-wavelength light lw have a similar distance traveling inside the light guide plate (d1 ≦ d2).

This phenomenon occurs when the light passes through a barrier having a narrow gap, and as the wavelength increases, the larger the angle incident on the gap, the amount of light diffracted increases, so that the light emitted above the light guide plate 154 adjacent to the lamp is increased. Because the amount will increase.

As an example, in the case of a light guide plate having a length of about 1 m, the probability that light emitted from the lamp and incident on the diffraction member of the present invention is incident to the side of the light guide plate through the diffraction member with the angles θ and θ. If P (θ) and the ratio of light emitted to the top of the light guide plate within a range of approximately 10 cm of the position where light is incident on the light guide plate is F (θ), the light emission ratio of light having an incident angle of θ in the lamp Table 1 is as follows.

Incident angle (θ) P (θ) F (θ) 5 ° 0.045 0.129 10 ° 0.06 0.31 15 ° 0.076 0.504 20 ° 0.09 0.678 25 ° 0.105 0.831 30 ° 0.12 0.912 35 ° 0.135 0.959 40 ° 0.15 0.989

Referring to Table 1, 4.5% of light incident on the diffraction member at a 5 ° angle is incident on the light guide plate, and 12.9% of the light is emitted within a 10 cm range from the side surface of the light guide plate. In addition, 15% of the light incident on the diffraction member at a 40 ° angle is incident on the light guide plate, and 98.9% of the light is emitted within a 10 cm range from the side surface of the light guide plate. That is, almost all the light is emitted.

8 is an enlarged view of a diffraction member according to an exemplary embodiment of the present invention.

As shown, the diffraction member of the present invention has a plurality of openings 155a and blocking portions 155b formed in a slit shape, and is attached to the side of the light guide plate perpendicular to the longitudinal direction.

The width of the diffraction member is the same as the side width of the light guide plate, and the thickness (w) is preferably formed to be approximately 100 μm to 400 μm. The opening 155a has a width g of approximately 1 μm to 10 μm. Further, the width t of the blocking portion 155b is formed to be at least smaller than the width g of the opening 155a (t <g), and is preferably formed to be approximately 1 nm to 10 nm.

The diffraction member may further include adhesive means 155c protruding a predetermined distance in the direction of the light guide plate so as to be easily attached to the light guide plate at both ends of the upper and lower parts.

9 is a graph showing the luminosity at a predetermined angle for each color of light passing through the diffraction member according to the embodiment of the present invention.

As shown, among the light diffracted through the diffraction member of the present invention, the light of the red wavelength band is 0.05: 0.11 when comparing the amount of light at the position where the angle difference of 0.20 radians or more in the traveling direction is compared with the light of the blue wavelength band. It's about twice as big. Specifically, the intensity of red light is about 0.7 candela (cd) and the intensity of blue light is about 0.5 candela (cd) at a position having an angle difference of about 0.2 radians ([pi]) in the advancing direction. In addition, the light intensity of the red wavelength band is 0.25 candela (cd) at the position having an angle difference of 0.37 radians (π) in the advancing direction, but the light intensity of the blue wavelength band is about 0.05 candela (cd).

Therefore, the diffraction member according to the embodiment of the present invention can remove the color difference in the adjacent portion of the light source by having a light amount of longer wavelength than the light of the shorter wavelength as the angle difference increases in the advancing direction.

Although the above detailed description has been described with reference to a preferred embodiment of the present invention, those skilled in the art may variously modify or modify the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. It can be modified.

150: backlight unit 151: LED lamp
152: lamp substrate 153: lamp housing
154 light guide plate 155 diffractive member
156: diffusion sheet 157: prism sheet
158: reflector

Claims (8)

Light source;
A light guide plate having one or more side surfaces facing the light source and configured to guide incident light to one surface; And,
A diffraction member interposed between the light source and the light guide plate and diffracting the light emitted from the light source to enter the light guide plate
Backlight unit comprising a. The method of claim 1,
The diffraction member,
A backlight unit, characterized in that the multi-slit (slit) structure comprising a plurality of openings and blocking. The method of claim 2,
The diffraction member is a backlight unit, characterized in that the thickness of 100㎛ ~ 400㎛. The method of claim 2,
The opening is a backlight unit, characterized in that the width 1㎛ ~ 10㎛. The method of claim 2,
The blocking unit is a backlight unit, characterized in that the width of 1nm ~ 10nm. The method of claim 1,
The diffraction member further comprises an adhesive pad bonded to one end of the light guide plate. The method of claim 1,
The light source is a backlight unit, characterized in that a plurality of light emitting diode (LED) lamp. A liquid crystal display module comprising the backlight unit according to claim 1,
A liquid crystal panel disposed on one surface of the backlight unit;
A support main on which the liquid crystal panel is seated;
A top case positioned on the other surface of the liquid crystal panel to surround the liquid crystal panel and be fastened to the support main; And,
The cover bottom is mounted on the liquid crystal panel and the backlight unit and is disposed on one surface of the backlight unit to be coupled to the top case.
Liquid crystal display module comprising a.

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