KR102050433B1

KR102050433B1 - Liquid crystal display device

Info

Publication number: KR102050433B1
Application number: KR1020110142659A
Authority: KR
Inventors: 공현식
Original assignee: 엘지디스플레이 주식회사
Priority date: 2011-12-26
Filing date: 2011-12-26
Publication date: 2019-11-29
Also published as: KR20130074552A

Abstract

The liquid crystal display of the present invention forms a chamfer at the lower edge of the light guide plate for guiding the backlight light to induce light scattered in the light guide plate to be totally reflected by the chamfer to improve the darkness of the edge of the screen. The liquid crystal panel for outputting an image; A backlight disposed on a rear surface of the liquid crystal panel to emit light to the liquid crystal panel; And a guide panel configured to receive and fix the liquid crystal panel and the backlight, wherein the light guide plate constituting the backlight has a chamfer formed at a lower edge thereof so that light scattered in the light guide plate is totally reflected by the chamfer.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having an edge type backlight having a lamp disposed on a side of a liquid crystal panel.

BACKGROUND ART In general, a liquid crystal display device is a display device in which data signals according to image information are individually supplied to pixels arranged in a matrix, and a desired image is displayed by adjusting light transmittance of the pixels.

Accordingly, the liquid crystal display includes a liquid crystal panel in which pixels are arranged in a matrix and a driving unit for driving the pixels.

The liquid crystal panel is formed in a thin film transistor array substrate, a color filter substrate, and a cell gap between the array substrate and the color filter substrate, which are bonded to face each other to maintain a uniform cell gap. It consists of a liquid crystal layer.

In this case, a common electrode and a pixel electrode are formed in the liquid crystal panel where the array substrate and the color filter substrate are bonded to apply an electric field to the liquid crystal layer.

Therefore, when the voltage of the data signal applied to the pixel electrode is controlled while the voltage is applied to the common electrode, the liquid crystal of the liquid crystal layer rotates by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode. Characters or images are displayed by transmitting or blocking light for each pixel.

In this case, since the liquid crystal display does not emit light by itself and is a light-receiving element that displays an image by controlling the transmittance of light coming from the outside, a separate device for illuminating the liquid crystal panel, that is, a backlight is required. .

The backlight is an edge (lamp) is disposed on one side or both sides of the liquid crystal panel so that light is reflected, diffused and focused through the light guide plate, reflector and optical sheets (transmission) through the front of the liquid crystal panel type) and a lamp are disposed on the rear surface of the liquid crystal panel so that light is directly transmitted to the front surface of the liquid crystal panel.

1 is a cross-sectional view schematically illustrating a part of a general liquid crystal display device, and schematically illustrates a part of a configuration of a liquid crystal display device having an edge type backlight.

As shown in the drawing, a general liquid crystal display device includes a liquid crystal panel 10 for large-scale liquid crystal injection between the color filter substrate 6 and the array substrate 5 to output an image, and a rear surface of the liquid crystal panel 10. It is provided with a backlight for emitting light over the entire surface of the liquid crystal panel 10 and a guide panel 45 for storing and fixing the liquid crystal panel 10 and the backlight.

In this case, upper and lower polarizers 1 and 11 are attached to the outer side of the color filter substrate 6 and the array substrate 5, respectively, and the lower polarizer 11 polarizes light passing through the backlight. The upper polarizing plate 1 polarizes light passing through the liquid crystal panel 10.

In detail, the backlight is provided with an LED assembly (not shown) for generating light on one side of the light guide plate 42, and a reflecting plate 41 is provided on the rear surface of the light guide plate 42.

Although not shown in the drawings, the LED assembly includes an LED array, an LED printed circuit board (PCB) for driving the LED array, and a heat dissipation pad for dissipating heat generated from the LED array.

The light emitted from the LED array is incident on the side of the light guide plate 42 of a transparent material, and the reflective plate 41 disposed on the rear surface of the light guide plate 42 transmits light transmitted to the rear surface of the light guide plate 42. (42) It is reflected toward the optical sheets 43 on the upper surface to reduce the loss of light and improve the uniformity.

The liquid crystal panel 10 including the color filter substrate 6 and the array substrate 5 is seated on the upper portion of the backlight configured through the guide panel 45, and the liquid crystal panel 10 and the guide panel 45 are mounted thereon. In addition, the backlight is coupled to each other by a cover bottom 50 and a case top 60 at the top to form a liquid crystal display.

In this case, a predetermined pattern (not shown) is formed below the light guide plate 42 to uniformly diffuse light, and the pattern is used to improve the brightness of the active area AA. It is formed to have a predetermined interval from the end of.

The region in which the pattern is not formed has a lower luminance than the region in which the pattern is formed, so that an observer feels darker than the surroundings when observing the edge of the screen AA.

In addition, when the distance between the screen AA and the guide panel 45 is narrow, light passing through the light guide plate 42 hits the guide panel 45 and does not come out of the screen AA. You will feel dark.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and an object of the present invention is to provide a liquid crystal display device for improving the darkness of the screen edge.

Other objects and features of the present invention will be described in the configuration and claims of the invention described below.

In order to achieve the above object, the liquid crystal display device of the present invention comprises a liquid crystal panel for outputting an image; A backlight disposed on a rear surface of the liquid crystal panel to emit light to the liquid crystal panel; And a guide panel configured to receive and fix the liquid crystal panel and the backlight, wherein a light guide plate constituting the backlight has a chamfer formed at a lower edge thereof, so that light scattered in the light guide plate is totally reflected by the chamfer. It characterized in that).

In this case, the backlight may include a light guide plate disposed on a rear surface of the liquid crystal panel; A light source disposed on at least one side of the light guide plate to generate light; And a reflector disposed on a rear surface of the light guide plate.

In this case, when the light guide plate is formed of polymethyl methacrylate (PMMA), the light introduced into the air from the light guide plate is totally reflected at an incident angle of 48 degrees or more.

The chamfer is formed on the lower edge of the light guide plate to leave the side of the light guide plate.

At this time, the angle between the left side of the light guide plate and the chamfer is characterized by exceeding 90 degrees.

When the light source is disposed on one side of the light guide plate, the chamfer may be formed at three lower edges of the light guide plate on which the light source is not disposed.

When the light source is disposed on both sides of the light guide plate, the chamfer is formed at two lower edges of the light guide plate on which the light source is not disposed.

The liquid crystal panel may further include a lower cover bottom and an upper case top which couple the guide panel and the backlight to each other.

As described above, the liquid crystal display according to the present invention provides an effect of improving the darkness of the edge of the screen by forming a chamfer at the lower edge of the light guide plate to induce the light scattered in the light guide plate to be totally reflected by the chamfer. .

1 is a cross-sectional view schematically showing a part of a general liquid crystal display device.
2 is an exploded perspective view schematically illustrating a structure of a liquid crystal display according to an exemplary embodiment of the present invention.
3 is a schematic cross-sectional view of a portion of a liquid crystal display according to an exemplary embodiment of the present invention.
4 is a view for explaining a phenomenon in which total reflection occurs.
FIG. 5 is a cross-sectional view illustrating a state in which total reflection occurs through a chamfer formed at a lower edge of a light guide plate in the liquid crystal display according to the exemplary embodiment of the present invention illustrated in FIG. 3.

Hereinafter, exemplary embodiments of a liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

2 is an exploded perspective view schematically illustrating a structure of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a cross-sectional view schematically showing a part of a liquid crystal display device according to an exemplary embodiment of the present invention, and schematically shows a part of a configuration of a liquid crystal display device having an edge type backlight. However, the present invention is not limited thereto, and the present invention can be applied to a liquid crystal display device having a direct type backlight.

As shown in the figure, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal panel 110 in which pixels are arranged in a matrix form to output an image, drivers 115 and 116 for driving the pixels, and the liquid crystal. It is provided on the rear of the panel 110 is composed of a backlight for emitting light over the front of the liquid crystal panel 110 and a guide panel 145 for receiving and fixing the liquid crystal panel 110 and the backlight.

The liquid crystal panel 110 is a liquid crystal formed in the cell gap between the color filter substrate 106 and the array substrate 105 and the color filter substrate 106 and the array substrate 105 bonded to each other to maintain a uniform cell gap facing each other. It consists of layers (not shown).

In this case, although not shown in detail, a common electrode and a pixel electrode are formed in the liquid crystal panel 110 to which the color filter substrate 106 and the array substrate 105 are bonded to apply an electric field to the liquid crystal layer. When the voltage of the data signal applied to the pixel electrode is controlled while the voltage is applied to the electrode, the liquid crystal of the liquid crystal layer rotates by the dielectric anisotropy according to the electric field between the common electrode and the pixel electrode to emit light for each pixel. It transmits or blocks to display characters or images.

In order to control the voltage of the data signal applied to the pixel electrode for each pixel, a switching element such as a thin film transistor (TFT) is individually provided in the pixels.

Upper and lower polarizers 101 and 111 are attached to the outside of the liquid crystal panel 110 configured as described above, and the lower polarizer 111 polarizes light passing through the backlight, and the upper polarizer 101 Polarizes the light passing through the liquid crystal panel 110.

In detail, the backlight is provided with a light source such as an LED assembly 130 generating light on one side of the light guide plate 142, and a reflecting plate 141 is provided on a rear surface of the light guide plate 142. However, the present invention is not limited to a light source such as the LED assembly 130, and a light source to which a Cold Cathode Fluorescence Lamp (CCFL) is applied may be used.

In this case, the LED assembly 130 heats the LED array 131, the LED printed circuit board (PCB) 132 driving the LED array 131, and the heat generated from the LED array 131. It may be made of a heat radiation pad (not shown) for emitting.

The light emitted from the LED array 131 is incident to the side of the light guide plate 142 of a transparent material, and the reflective plate 141 disposed on the rear surface of the light guide plate 142 is transmitted to the rear surface of the light guide plate 142. The light is reflected toward the optical sheets 143 on the upper surface of the light guide plate 142 to reduce light loss and improve uniformity.

The liquid crystal panel 110 including the color filter substrate 106 and the array substrate 105 is seated on the upper portion of the backlight configured as described above through the guide panel 145, and the liquid crystal panel 110 and the guide panel 145 are mounted thereon. The backlight is coupled to each other by the lower cover bottom 150 and the upper case top 160 to form a liquid crystal display.

In this case, in the conventional case, darkening may occur at the edge of the screen in the process of designing a structure in which darkening occurs at the edge of the screen in order to satisfy the outer specification required by the customer or improving the brightness of the entire screen. there was.

In the liquid crystal display according to the exemplary embodiment of the present invention, a chamfer 142-1 is formed at a lower edge of the light guide plate 142 so that light scattered in the light guide plate 142 is chamfered. It is characterized by improving the darkness of the edge of the screen by inducing total reflection by.

That is, the total reflection theory is applied to the region of the light guide plate 142 where the dark occurs to increase the reflected amount more than the amount through which light is transmitted. This will be described in detail with reference to the accompanying drawings.

4 is a diagram for describing a phenomenon in which total reflection occurs.

Referring to FIG. 4, the light incident from the light guide plate into the air may be incident from the dense medium into the small medium, and the refractive angle θr becomes larger than the incident angle θi.

At this time, as the incident angle θi increases, the refractive angle θr also increases. The incident angle θi when the refractive angle θr becomes 90 degrees is referred to as a critical angle.

In this way, if the incident angle θi is gradually increased, total reflection occurs when the angle reaches a specific angle, that is, a critical angle or more. Using this principle, the darkness of the edge of the screen can be improved.

Referring to Equation 1 below, the light incident to the air from the light guide plate is totally reflected at an incident angle of 48 degrees or more.

In this case, n and n1 are the refractive indices of the light guide plate and air, respectively, and n1 corresponds to 1.55 when the light guide plate is formed of polymethyl methacrylate (PMMA).

5 is a cross-sectional view illustrating a state in which total reflection occurs through a chamfer formed at a lower edge of a light guide plate in the liquid crystal display according to the exemplary embodiment of the present invention illustrated in FIG. 3.

Referring to FIG. 5, by forming a chamfer 142-1 at the lower edge of the light guide plate 142 to increase the incident angle of light reaching the chamfer 142-1, total reflection occurs without refracting toward the air. . As a result, it is possible to improve the darkness of the edge of the screen.

As such, by forming the chamfer 142-1 at the lower edge of the light guide plate 142, the darkness of the edge of the screen can be improved by changing the light reflection path.

The chamfer 142-1 may be formed at a lower edge of the light guide plate 142, but may be formed to leave some side surfaces 142-2 of the light guide plate 142, and the left side of the light guide plate 142 ( As the angle θ formed between the 142-2 and the chamfer 142-1 increases, total reflection occurs better.

In this case, when the light source is disposed only on one side of the light guide plate 142, the chamfer 142-1 may be formed at three lower corners of the light guide plate 142 in which the light source is not disposed. However, the present invention is not limited thereto, and the chamfer 142-1 may be formed at one or two corners of the lower side of the light guide plate 142 in which the light source is not disposed.

In addition, when the light source is disposed at both sides of the light guide plate 142, the chamfer 142-1 may be formed at two lower edges of the light guide plate 142 in which the light source is not disposed. However, the present invention is not limited thereto, and the chamfer 142-1 may be formed at one corner of the lower side of the light guide plate 142 in which the light source is not disposed.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

101,111 polarizer 105 array substrate
106: color filter substrate 110: liquid crystal panel
141: reflector 142: light guide plate
142-1: Chamfer 143: Optical sheet
145: guide panel 150: cover bottom
160: case top

Claims

A liquid crystal panel for outputting an image;
At least one optical sheet disposed on a rear surface of the liquid crystal panel;
A light source having at least one LED array, an LED printed circuit board driving the LED array, and a heat dissipation pad for dissipating heat generated by the LED array, and a light guide plate reflecting light emitted from the light source toward the optical sheet. And a backlight disposed on a rear surface of the optical sheet, including a reflective plate provided on a rear surface and a side surface of the light guide plate;
A cover bottom for storing the backlight and the optical sheet therein;
A guide panel configured to receive and fix the liquid crystal panel and the backlight and surround the outer side of the cover bottom; And
A case top disposed to surround an upper edge of the liquid crystal panel and an outer side surface of the guide panel;
In the light guide plate, a chamfer is formed at at least two lower edges at which the light source is not disposed, so that light scattered in the light guide plate is totally reflected by the chamfer, and an upper side of the light guide plate is disposed above the chamfer. A vertical side extending from the corner vertex in the chamfer direction,
The angle between the vertical side of the light guide plate and the inclined surface of the chamfer is greater than 90 degrees,
The reflecting plate extends from the rear surface of the light guide plate so that the light guide plate and the cover bottom face each other, and the extended side of the reflecting plate is arranged to contact the inner surface of the cover bottom and at the same time the vertical side of the light guide plate and the side of the optical sheets. Contact with,
The guide panel extends between each corner side surface of the liquid crystal panel and an inner side surface of the case top to contact the upper rear surface of the case top, and is disposed below the first guide portion and is disposed outside the cover bottom. A second guide part disposed between a side surface and the case top and a third guide part extending between the liquid crystal panel and the optical sheet between the first guide part and the second guide part,
The third guide part includes a first projection part in contact with a lower polarizing plate provided on a lower surface of the liquid crystal panel at an end thereof, and a second projection part in contact with an upper surface of the optical sheet,
And an upper portion of the side surface of the reflective plate and the cover bottom is disposed higher than the optical sheet by the height of the second protrusion.

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The liquid crystal display of claim 1, wherein when the light guide plate is formed of polymethyl methacrylate (PMMA), light incident on the light guide plate into the air is totally reflected at an incident angle of 48 degrees or more.

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The liquid crystal display of claim 1, wherein when the light source is disposed on one side of the light guide plate, the chamfer is formed at three lower edges of the light guide plate on which the light source is not disposed.

The liquid crystal display of claim 1, wherein when the light source is disposed at both sides of the light guide plate, the chamfer is formed at two lower edges of the light guide plate where the light source is not disposed.

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