KR20070037108A - Back light unit and liquid crystal display including the same - Google Patents

Abstract

A backlight unit and a liquid crystal display device having the same are provided. According to an embodiment of the present invention, a backlight unit includes a lamp and a reflector having a coating layer formed on the lower surface of the light emitted from the lamp and reflecting the light from the lamp and reflecting the light from the lamp and the reflector. And an optical sheet for improving the luminance of the emitted light.

Back light unit, LCD, Reflector, Coating, High reflectivity material

Description

Back light unit and liquid crystal display including the same {Back light unit and liquid crystal display including the same}

1 is an explanatory diagram schematically showing a reflecting plate provided in a conventional backlight unit.

2 is an explanatory view schematically showing a reflecting plate provided in the backlight unit according to an exemplary embodiment of the present invention.

3A and 3B are exploded explanatory diagrams schematically illustrating a backlight unit provided with the reflector of FIG. 2.

4 is an explanatory diagram illustrating a liquid crystal display including the backlight unit provided with the reflector of FIG. 2.

<Explanation of symbols on main parts of the drawings>

110, 210, 320, 440: reflector plates 215, 325: coating layer

310, 430: lamp 330: diffusion sheet

340: prism sheet 350: light guide plate

410 thin film transistor substrate 420 color filter substrate

450: optical sheet 460: mold frame

470 chassis

The present invention relates to a backlight unit and a liquid crystal display device having the same, and more particularly, to a backlight unit and a liquid crystal display device including the same, which are improved to improve overall luminance by improving reflection efficiency of a reflector. will be.

In recent years, liquid crystal displays are spotlighted as display means.

The liquid crystal display performs display functions using the electrical and optical properties of the liquid crystal injected into the panel, and is widely applied to various fields such as computer monitors and mobile communication terminals due to the advantages of small size, light weight, and low power consumption. There is a trend.

The liquid crystal display device has an active matrix display method using a switching element and a twisted nematic liquid crystal and a passive matrix display method using a super-twisted nematic liquid crystal according to a difference in driving method. It can be divided into

The biggest difference between the two display methods is that the active matrix display method uses a thin film transistor (TFT) as a switch to drive the LCD, whereas the passive matrix display method does not use a transistor, and thus requires a complicated circuit. It is not to be. However, the liquid crystal display of the active matrix display method, which is technically superior in terms of image quality, is widely used.

Since the liquid crystal display device is not a self-luminous display device but a light receiving type display device, a separate light source such as a back light unit equipped with a lamp is required. That is, by selectively transmitting the light applied from the backlight unit through the liquid crystal display panel, desired image information can be displayed.

The backlight unit may be classified into a light guide plate type and a light guide plate type according to the presence or absence of the light guide plate, and include a plurality of components such as a lamp, an optical sheet, and a reflector plate separately from the presence or absence of the light guide plate. .

1 is an explanatory diagram schematically showing a reflecting plate provided in a conventional backlight unit.

Referring to FIG. 1, when the lower leakage light a generated from a lamp or the like is incident on the reflective plate 110 provided in the conventional backlight unit, most of the reflective plate 110 may be disposed on a reflective surface such as an upper surface of the reflective plate 110. b) is reflected, but part (c) is transmitted, again part (d) of transmitted light (c) is reflected from the lower surface or the like of the reflecting plate (110) and the rest (e) is transmitted and extinguished.

However, at this time, since the transmitted light c is much weaker than the reflected light b, the re-reflected light d is further weaker than the reflected light b. Therefore, the luminance of the liquid crystal display device by the reflected light d is thus weak. The improvement is almost unanticipated.

Accordingly, a method for increasing the re-reflected light (d) by preventing the reflection of the light (e) transmitted and extinguished under the reflecting plate 110 and reflecting the light (e), thereby increasing the luminance of the liquid crystal display device. It is required.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an improved backlight unit and a liquid crystal display including the same to improve overall luminance by improving reflection efficiency of a reflector.

The objects of the present invention are not limited to the above-mentioned objects, and other objects which are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the backlight unit according to the embodiment of the present invention, the reflecting plate and the reflecting plate having a coating layer formed by a high reflectivity material on the lower surface reflecting the light leakage of the light emitted from the lamp and irradiated from the lamp And an optical sheet for improving the luminance of the light reflected by the light and the reflecting plate.

Here, the coating layer may be formed on the outer lower surface of the reflecting plate by a high reflectance material such as silver (Ag), aluminum (Al) or an alloy material including them, and the thickness thereof may be 100 micrometers (μm) or less.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various forms, and the present embodiments are merely provided to make the disclosure of the present invention complete and to provide a general knowledge of the present invention. It is provided to fully inform the person having the scope of the invention, the invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

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

2 is an explanatory view schematically showing a reflecting plate provided in the backlight unit according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the reflective plate 210 provided in the backlight unit according to the exemplary embodiment of the present invention is provided with a coating layer 220 on a lower surface thereof. In this case, the coating layer 220 may be formed on the outer bottom surface of the reflecting plate 210 by a high reflectance material such as silver (Ag), aluminum (Al), or an alloy material including them.

Accordingly, the downward leakage light (a ') generated from the lamp or the like can be reflected back (d') almost 100% of the reflected light (b ') and the transmitted light (c') generated by the incident light (b ') As a result, the reflection efficiency of the reflector 210 may be increased, and thus, the brightness of the liquid crystal display may be improved.

Here, the reflector 210 may be made of a foamed synthetic resin (MC PET) material and may have a thickness of about 1 millimeter (mm), but is not limited thereto.

The coating layer 220 is preferably formed to have a thickness of less than 100 micrometers (㎛).

3A and 3B are exploded explanatory diagrams schematically illustrating a backlight unit provided with the reflector of FIG. 2.

That is, FIGS. 3A and 3B are cross-sectional views illustrating a backlight unit according to an embodiment of the present invention, and FIG. 3A illustrates a non-light guide plate type direct backlight unit, and FIG. 3B illustrates a light guide plate type. An edge type backlight unit is shown. Accordingly, FIGS. 3A and 3B are different in the presence or absence of the light guide plate, and the functions and operations of the other components are almost similar. Therefore, the same reference numerals will be used to collectively describe the same.

As shown in FIGS. 3A and 3B, the backlight unit according to one or more embodiments of the present invention may include a lamp 310, a reflector plate 320, a diffusion sheet 330, a prism sheet 340, and the like. It is configured to include.

The lamp 310 serves as a light source and applies a light to a liquid crystal display panel (not shown). In this case, in the case of the direct type as shown in FIG. 3A, the lamp 310 directly irradiates light to the liquid crystal display panel. However, in the case of the edge type as shown in FIG. 3B, the lamp 310 is the light guide plate 350. The light can be irradiated to the liquid crystal display panel through Here, the light guide plate 350 guides the light incident from the lamp 310 on the side toward the upper liquid crystal display panel. As shown in FIG. 3B, only the light guide plate 350 is disposed on one side of the light guide plate 350. 310 may be provided, but lamps 310 may be provided at both sides of the light guide plate 350, and a wedge type light guide plate may be used in addition to the flat light guide plate.

As the lamp 310, a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), an LED lamp, or the like may be used, but is not limited thereto.

The reflector 320 performs a function of increasing light efficiency by reflecting light leaking downward from the light emitted from the lamp 310 upward.

In this case, the coating layer 325 may be provided on the bottom surface of the reflecting plate 320 provided in the backlight unit according to the exemplary embodiment of the present invention. Accordingly, by allowing the transmitted light not reflected from the reflecting surface of the reflecting plate 320 to be reflected back by the coating layer 325, the reflecting efficiency of the reflecting plate 320 may be increased to eventually improve the brightness of the liquid crystal display device. To make it possible.

The coating layer 325 may be formed on the outer bottom surface of the reflecting plate 320 by a high reflectance material such as silver (Ag), aluminum (Al), or an alloy material including the same, and has a thickness of 100 micrometers (μm) or less. It is preferred that it is formed to have a reference to the drawings and the description of FIG.

The diffusion sheet 330 performs a function of improving the upward luminance of the light emitted from the lamp 310, and may be constituted by a plurality of sheets performing different functions, and may not be provided in some cases. .

The prism sheet 340 is provided on the diffusion sheet 330. The prism sheet 340 collects light incident from below and improves brightness, and may include a horizontal prism sheet, a vertical prism sheet, and the like.

The backlight unit is fastened / supported by respective components by a support frame such as a mold frame (not shown), which is provided separately, thereby forming the appearance of the backlight unit.

4 is an explanatory diagram illustrating a liquid crystal display including the backlight unit provided with the reflector of FIG. 2.

As shown in FIG. 4, the LCD including the backlight unit according to the exemplary embodiment of the present invention generally includes a lower substrate 410, which is a thin film transistor (TFT) substrate, and an upper substrate 420, which is a color filter substrate. And a backlight unit and a chassis 470 formed of a lamp 430, a reflector 440, an optical sheet 450, a mold frame 460, and the like.

Each component is described as follows.

First, the liquid crystal display panel includes a lower substrate 410 and an upper substrate 420, and a liquid crystal, a gate driving circuit, a data driving circuit, and the like filled therebetween.

In general, a common electrode and a color filter are formed on the upper substrate 420 facing the lower substrate 410 on which the thin film transistor is formed, and a liquid crystal display panel is formed by encapsulating liquid crystal between the two substrates.

The color filter substrate 420 is configured by sequentially stacking a black matrix, a color filter, an electrode, and the like on an insulating substrate. That is, a color filter composed of R (Red), G (Green), and B (Blue) is provided on the insulating substrate, and a black matrix is formed at a position opposite to the thin film transistor array of the thin film transistor substrate 410. The common electrode is stacked on the uniform thickness.

An alignment film is formed on the common electrode.

The thin film transistor substrate 410 is a substrate having a plurality of gate lines, data lines, a plurality of thin film transistors connected thereto, and a plurality of pixel electrodes connected thereto.

The thin film transistor is formed of a gate electrode, a source / drain electrode, or the like formed on an insulating substrate. The gate electrode and the source / drain electrode may be formed of a conductive film such as aluminum (Al), chromium (Cr), or molybdenum tungsten (MoW). Can be used.

An insulating layer having a contact hole for exposing the drain electrode is formed on the thin film transistor.

On the insulating layer, pixel electrodes electrically contacting the drain electrodes through the contact holes are stacked to have a uniform thickness. The pixel electrode may be made of indium tin oxide (ITO) or indium zinc oxide (IZO), which is a transparent conductive material.

The liquid crystal is filled and formed by a method such as injection into the space between the color filter substrate 420 and the thin film transistor substrate 410.

The liquid crystal molecules of the liquid crystal formed by a method such as injection into the space between the color filter substrate 420 and the thin film transistor substrate 410 are the electrodes (common electrode) of the color filter substrate 420 and the thin film transistor substrate 410. And pixel electrodes) at an angle designated by the alignment film.

The operation and function of each of the above-mentioned components are briefly described as follows.

Although not shown in detail, the thin film transistor formed on the lower substrate 410 includes a gate electrode, a source electrode, a drain electrode, an active layer, and an ohmic contact layer, and the drain electrode is connected to the pixel electrode to form a unit pixel. When the gate signal is applied to the gate electrode through the gate line, the thin film transistor having such a structure operates by transferring the data signal applied to the data line from the source electrode to the drain electrode through the ohmic contact layer and the active layer.

That is, when a data signal is applied to the source electrode, a voltage corresponding thereto is applied to the pixel electrode connected to the source electrode, which causes a voltage difference between the pixel electrode and the common electrode. In addition, due to the voltage difference between the pixel electrode and the common electrode, the molecular arrangement of the liquid crystal interposed therebetween changes, and the change in the molecular arrangement of the liquid crystal changes the amount of transmission for the light applied from the backlight unit of each pixel. As a result, the color difference of the pixel is generated according to the difference of the data signal applied to each pixel. By using the color difference, the screen of the LCD may be controlled.

Next, the backlight unit includes a lamp 430, a reflecting plate 440, an optical sheet 450, a mold frame 460, and the like.

The lamp 430 performs a function as a light source.

The reflector 440 reflects the leakage light downward of the lamp 440 to maximize the light efficiency of the backlight unit. In this case, since a coating layer made of a high reflectance material is formed on the bottom surface of the reflector 440, leakage light of the reflector 440 may be greatly reduced, and thus the reflection efficiency of the reflector 440 may be further increased.

The coating layer may be formed on the outer lower surface of the reflecting plate 440 by a high reflectance material such as silver (Ag), aluminum (Al) or an alloy material including the same, and have a thickness of 100 micrometers (μm) or less. It is good to be.

The optical sheet 450 finally condenses the light irradiated from the lamp 430 to increase the luminance of the light incident on the liquid crystal display panel as much as possible.

Here, the optical sheet 450 may be configured of a diffusion sheet for primarily increasing the brightness of the light incident from the lamp 430 and a prism sheet for condensing the light incident from the diffusion sheet to increase the brightness again. have. The diffusion sheet and the prism sheet may each be constituted by a plurality of sheets.

The mold frame 460 combines and fixes the respective components of the backlight unit.

Here, the mold frame 460 may have a structure in which openings are formed by opening portions other than a portion on which an outer portion of the reflective plate 440 and the optical sheet 450 is seated. In addition, the mold frame 460 may be formed by casting, for example, injection molding, or the like, in which a material such as a plastic, such as a thermoplastic resin, is melted and put into a mold.

In this case, in FIG. 4, only the liquid crystal display device having the direct type backlight unit of the non-light guide plate type is illustrated, but the present invention is not limited thereto.

The chassis 470 supports and protects components such as a backlight unit and a liquid crystal display panel supported by the mold frame 460. As a constituent material of the chassis 470, a light and hard metal, for example, a metal such as stainless, may be used.

That is, the backlight unit is fastened / supported by the mold frame 460, and the liquid crystal display panel and the backlight unit are fixedly coupled by the chassis 470, and are coupled to the mold frame 460 and the chassis 470. As a result, the external shape of the liquid crystal display device is formed. Here, all known corresponding coupling methods such as hook coupling and screw coupling may be applied between the mold frame 460 and the chassis 470.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive.

According to the backlight unit of the present invention and the liquid crystal display device having the same as described above, by forming a coating layer of a high reflectance material on the lower surface of the reflecting plate it is possible to maximize the reflection efficiency of the reflecting plate.

Accordingly, there is an advantage that the luminance of the liquid crystal display device can be improved without a significant increase in cost and process.

Claims (5)

lamp; A reflecting plate reflecting downward leakage light emitted from the lamp and having a coating layer formed on a lower surface thereof by a high reflectance material; And And an optical sheet for improving the luminance of the light irradiated from the lamp and the light reflected by the reflector. The method of claim 1, The high reflectance material forming the coating layer is a back light unit, characterized in that the silver (Ag), aluminum (Al) or an alloy material containing them. The method of claim 2, The coating layer is a backlight unit, characterized in that formed on the outer lower surface of the reflecting plate. The method of claim 3, wherein The thickness of the coating layer is a backlight unit, characterized in that less than 100 micrometers (㎛). A liquid crystal display device comprising the backlight unit according to any one of claims 1 to 4.

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