KR101197762B1 - Back light unit and liquid crystal display including the same - Google Patents

Abstract

A backlight unit and a liquid crystal display device having the backlight unit are provided. According to an embodiment of the present invention, a backlight unit includes a lamp assembly that provides light, a reflector that reflects downward leakage light of light provided from the lamp assembly, and has a different transmittance between the central part and the peripheral part, And a diffuser plate for improving the upward luminance of the light reflected by the provided light and the reflecting plate.

Luminance Control, Diffusion Plate, Transmittance, Center, Peripheral, Middle

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME

1 is a conceptual diagram illustrating a luminance distribution of a conventional liquid crystal display device.

2A to 2C are conceptual views illustrating a light transmittance distribution of a diffuser plate included in a backlight unit according to one or more embodiments of the present invention.

3 is an exploded perspective view illustrating an example of a liquid crystal display device including the backlight unit of FIGS. 2A to 2C.

DESCRIPTION OF THE REFERENCE NUMERALS

300: liquid crystal display panel 310: lower substrate

320: upper substrate 350: backlight unit

351 optical sheet 352 diffuser plate

353: mold frame 354: lamp

355: Reflector 360: Top Chassis

370: bottom 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 improved to have a more uniform luminance distribution and a liquid crystal display device having the same.

In recent years, a liquid crystal display device has attracted attention as a display means.

The liquid crystal display device performs a display function by utilizing the electrical and optical properties of the liquid crystal injected into the panel. The liquid crystal display device is widely applied to various fields such as a computer monitor and a mobile communication terminal due to its 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, it is possible to display desired image information.

However, since the image information is displayed by using light applied from an external light source, the LCD has a problem in that the luminance distribution is not uniform throughout the screen.

1 is a conceptual diagram illustrating a luminance distribution of a conventional liquid crystal display device.

As shown in FIG. 1, a conventional liquid crystal display is divided into a central portion C and peripheral portions E1 to E4, and luminance is measured for each of the regions in the 255 gray (full white) mode. Are summarized in the following <Table 1>.

C E1 E2 E3 E4 Nit 570 465 460 420 425

As shown in Table 1, the luminance of the liquid crystal display device was measured to show a large difference of about 100 to 150 nits in the respective peripheral portions from the center portion in the same gray mode. Such a problem of luminance non-uniformity is a problem that is common to all liquid crystal display devices although there is a degree of difference depending on the size of the panel, etc., and it appears that the problem becomes larger as the liquid crystal display device becomes larger.

Therefore, there is a demand for a method for allowing a liquid crystal display device to have a more uniform luminance distribution over the entire surface of the panel.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a backlight unit improved to have a more uniform luminance distribution and a liquid crystal display device having the same.

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

In order to achieve the above object, a backlight unit according to an embodiment of the present invention, a lamp assembly for providing light, a reflecting plate for reflecting the light leaking down from the light provided from the lamp assembly and between the center and the peripheral portion And a diffuser plate having different transmittances and improving the upward luminance of the light reflected by the reflecting plate and the light provided from the lamp assembly.

At this time, the diffusion plate is preferably formed so that the transmittance of the periphery is higher than the transmittance of the central portion, this periphery may be divided into a plurality of areas having a slightly different transmittance each other again.

Here, one or more intermediate portions may be formed between the periphery of the diffuser plate and the central portion having a transmittance lower than that of the peripheral portion and having a transmittance higher than that of the central portion. When there are a plurality of intermediate portions, the transmittance of the intermediate portion adjacent to the peripheral portion is adjacent to the central portion. It is better to be higher than the transmittance of the intermediate part.

In addition, the present invention provides a liquid crystal display device having the above backlight unit.

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

Advantages and features of the present invention, and methods of achieving the same will become apparent with reference to the embodiments described below in detail in conjunction 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 the general knowledge in the art to which the present invention belongs. 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, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A to 2C are conceptual views illustrating a light transmittance distribution of a diffuser plate included in a backlight unit according to one or more embodiments of the present invention.

First, FIGS. 2A and 2B illustrate a diffusion plate provided in a backlight unit according to an embodiment of the present invention, which is a conceptual diagram of a diffusion plate having different transmittances between a central portion and a peripheral portion. Diffusion plate having a single peripheral portion (E) having a light transmittance higher than that of (C) and the central portion (C) is shown. Diffusion plates having peripheral portions E1 to E4 are shown.

That is, although the image information displayed through the liquid crystal display panel is slightly different depending on the conditions such as the size of the panel, the fact that the luminance is different in the central portion C and the peripheral portions E1 to E4. And <Table 1> and their descriptions have been discussed.

Accordingly, in order to overcome such a problem, in one embodiment and another embodiment of the present invention as shown in FIGS. 2A and 2B, the diffusion plate is divided into a central portion and a peripheral portion so as to correspond to luminance information of a previously measured liquid crystal display panel. By varying the light transmittance of each division region, it is possible to display image information having a more uniform luminance distribution.

In other words, the light transmittance of the diffuser plate of the central portion C having a relatively high brightness is set low according to the luminance information previously measured for the central portion C and the peripheral portions E, E1 to E4, and the peripheral portion having a relatively low luminance. By increasing the light transmittance of the light, the overall luminance distribution of the light passing through the liquid crystal display panel is evenly displayed. In this case, as shown in FIG. 2A, the diffuser plate may be configured such that all of the peripheral portion E regions except for the central portion C have the same transmittance, but each of the peripheral portions E1 to E4 that are slightly different as shown in FIG. The diffusion plate may be configured to have slightly different transmittances between the peripheral parts E1 to E4 according to the luminance characteristic.

Next, referring to FIG. 2C, the diffusion plate provided in the backlight unit according to another embodiment of the present invention may further include one or more intermediate parts M1 to M3 between the central part C and the one or more peripheral parts E1 to E4. It can be seen that is formed.

That is, according to the embodiment of FIG. 2C, a liquid crystal display having a more detailed and naturally uniform luminance distribution can be prevented due to a sudden change in luminance due to a sudden change in transmittance between the central portion C and the peripheral portions E1 to E4. It is possible to provide a device.

Therefore, the luminance distribution of the liquid crystal display device may be more precise and natural as the middle portions M1 to M3 of more stages exist. As illustrated, if the middle portions M1 to M3 of three stages exist, as shown in FIG. If so, it is preferable that the transmittance of the middle portion M1 adjacent to the central portion C is relatively lower than the transmittance of the middle portion M3 adjacent to the peripheral portions E1 to E4.

Here, it will be apparent to those skilled in the art that the division of the central portion C, the middle portions M1 to M3 and the peripheral portions E1 to E4 can be made by various methods other than those shown in FIGS. 2A to 2C.

3 is an exploded perspective view illustrating an example of a liquid crystal display device including the backlight unit of FIGS. 2A to 2C.

Referring to FIG. 3, the LCD including the backlight unit according to the exemplary embodiments of the present invention generally includes the LCD panel 300, the backlight unit 350, and the chassis 360 and 370. Can be configured.

The liquid crystal display panel 300 includes a lower substrate 310, an upper substrate 320, a liquid crystal (not shown), a gate tape carrier package (TCP), a gate printed circuit board (PCB), 335, data TCP 340, data PCB 345, and the like.

The lower substrate 310 may include a gate line, a data line, a thin film transistor, a pixel electrode, and the like, and the upper substrate 320 may be positioned to face the upper substrate 310 and include a color filter and a common electrode. Although not shown in detail.

The gate TCP 330 is connected to each gate line formed on the lower substrate 310, and the data TCP 340 is connected to each data line formed on the lower substrate 310.

Meanwhile, the gate PCB 335 and the data PCB 345 can process both the gate driving signal and the data driving signal so that the gate driving signal can be input to the gate TCP 330 and the data driving signal can be input to the data TCP 340. Many circuit components can be mounted.

The configuration and operation of these components will be described below.

A color filter, a black matrix, a common electrode, and the like may be formed on the upper substrate 320. In addition, a plurality of gate lines and data lines may be formed in a matrix form on the lower substrate 310 formed to face the lower substrate 310. Thin film transistors are formed at intersections of the plurality of gate lines and data lines.

The liquid crystal is injected between the upper substrate 320 and the lower substrate 310 and sealed by a sealant to form a liquid crystal display panel.

Although not shown in detail, the thin film transistor formed on the lower substrate 310 includes a gate electrode, a source electrode, a drain electrode, an active layer, and an ohmic contact layer, and the drain electrode is electrically connected to the pixel electrode to form a unit pixel. Achieve. 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 light transmittance of the pixel changes due to the change in the molecular arrangement of the liquid crystal, thereby causing the data signal applied to each pixel. The color difference of the pixel is generated according to the difference. The color difference may be used to control the screen of the liquid crystal display.

The backlight unit 350 includes an optical sheet 351, a diffuser plate 352, a mold frame 353, a lamp assembly 354, a reflector plate 355, and the like.

That is, the lamp assembly 354 irradiates light, and the reflector 355 is installed under the lamp assembly 354 to emit light emitted to the lower part of the lamp assembly 354. And reflects toward the diffusion plate 352.

The light irradiated from the lamp assembly 354 and the light reflected by the reflecting plate 355 are diffused by the diffuser plate 352 to have a uniform brightness to a certain degree, and then focused by an optical sheet 351 such as a prism.

Here, the diffusion plate 352 may be configured to have a different light transmittance between the central portion and the peripheral portion, in particular, the transmittance of the peripheral portion is preferably higher than the transmittance of the central portion. Accordingly, the light transmitted by different transmittances between the central portion and the peripheral portion of the diffusion plate 352 is irradiated onto the liquid crystal display panel 300 having different luminance characteristics between the central portion and the peripheral portion. It can be recognized as having a uniform luminance distribution.

Therefore, the transmittance of each of the central portion and the peripheral portion of the diffusion plate 352 is preferably set to maintain the luminance of the light passing through the liquid crystal display panel 300 uniformly within a predetermined error range.

In this case, the periphery may be divided into a plurality of periphery parts having a higher transmittance than the central part and having different transmittances. Also, the periphery may have a higher transmittance than the permeability of the center and a lower permeability than the periphery of the periphery. One or more intermediate parts may be provided.

In the internal space defined by the combination of the mold frame 353 and the bottom chassis 370, the components of the backlight unit 350 described above are accommodated, and the bottom chassis 370 is coupled to the top chassis 360 again. Thus, the entire frame of the liquid crystal display device is formed.

In the liquid crystal display according to the exemplary embodiment of the present invention described with reference to FIG. 3, the backlight unit 350 is illustrated as a direct type. However, this is only an example and may be applied to the liquid crystal display of the present invention. Naturally, various methods such as a direct type, an edge type, or a wedge type may be applied to the backlight unit 350.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand. Therefore, the embodiments described above are to be understood in all respects as illustrative and not restrictive.

According to the backlight unit and the liquid crystal display device according to the embodiment of the present invention as described above, it is possible to provide a backlight unit for providing light having a more uniform luminance distribution as a whole and a liquid crystal display device having the same. There is such an advantage.

Claims (6)

A lamp assembly that provides light; A reflector reflecting light leaking downward of the light provided from the lamp assembly; And A diffuser plate having a different transmittance between the center portion and the periphery, the diffuser plate for improving the upward luminance of the light provided by the lamp assembly and the light reflected by the reflecting plate, the transmittance of the periphery between the periphery and the center portion being lower than And at least one intermediate portion having a transmittance higher than that of the central portion is formed. The method of claim 1, The diffusion plate is a backlight unit, characterized in that the transmittance of the peripheral portion is higher than the transmittance of the central portion. The method of claim 2, The diffuser plate has a higher transmittance than the central portion and the transmittance of the central portion, wherein the backlight unit, characterized in that composed of a plurality of peripheral portions having different transmittances. delete The method of claim 1, And a plurality of the intermediate portions are present, wherein the transmittance of the intermediate portion adjacent to the peripheral portion is higher than that of the intermediate portion adjacent to the central portion. A liquid crystal display device comprising the backlight unit according to any one of claims 1 to 3.

Images