KR100770475B1 - Liquid crystal display - Google Patents

Abstract

The present invention discloses a liquid crystal display device.

A thin film transistor liquid crystal display device comprising a light guide plate having a reflector plate formed at a lower portion thereof and spreading and outputting light incident from a backlight, and a panel in which the amount of light transmitted from the light guide plate is controlled by a polarizing plate and a liquid crystal. In the present invention, the light guide plate is formed by combining the upper light guide plate and the lower light guide plate having different refractive indices, and the junction angle of the top light guide plate and the lower light guide plate satisfies the Brester angle (tanθ = n 1 / n 2).

 Therefore, the present invention has the advantage of improving the brightness by increasing the amount of light without increasing the thickness.

Description

Liquid crystal display

1 is a structural diagram of a liquid crystal display device according to the prior art.

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

3 is a structural diagram of a thin film transistor liquid crystal display according to another exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

21: down light guide plate 23: top light guide plate

25: light guide plate 27: reflecting plate

29 panel 30 liquid crystal

31: polarizer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display that can improve brightness by forming a light guide plate by combining a plurality of light guide plates having different refractive indices.

Thin-film transistor liquid crystal display devices (hereinafter TFT-LCDs) have characteristics such as light weight, thinness, and low power consumption, and thus have been used in terminals or video devices of various information devices instead of CRTs. With high quality, large size, and colorization, it is getting a lot of attention in the notebook PC and monitor market, and it is expected to erode the TV market in the future.

Such a TFT-LCD has a structure in which a liquid crystal layer is interposed between an array substrate and a color filter substrate, and each pixel is individually driven to display a predetermined image.

The light transmittance can be increased by changing or recycling the light path using a polarizer, a back light, a film, or the like of a TFT-LCD, thereby improving luminance. In the above, the light transmittance may be improved by using a polarizing plate, a backlight and a film together.

1 is a structural diagram of a liquid crystal display according to the prior art.

The liquid crystal display according to the related art includes a light guide plate 11 and a panel 15.

In the above, the light guide plate 11 includes a reflecting plate 13 to spread the light incident from a backlight (not shown) to the panel 15. The light incident on the light guide plate 11 from the backlight is unpolarized light, and the light output from the light guide plate 11 is also unpolarized light.

The panel 15 is filled with a liquid crystal 16 in the space, and adjusts the amount of light transmitted by driving the liquid crystal 16. The panel 15 is formed with a polarizing plate 17 that polarizes unpolarized light output from the light guide plate 11. The polarizing plate 17 absorbs light of a component perpendicular to the transmission axis among the unpolarized light input from the light guide plate 11 and transmits only light of parallel components. Therefore, the panel 15 outputs only 50% of the reflected light by the polarizing plate 17.

As described above, the liquid crystal display according to the related art polarizes the unpolarized light reflected by the reflector through the light guide plate by the polarizer, so that the light output from the panel is at most 50%.

However, in order to increase the amount of light output from the panel, a separate layer or film is required to change the light path, thereby increasing the thickness.

Accordingly, an object of the present invention is to provide a thin film transistor liquid crystal display device which can improve brightness by increasing the amount of light without increasing the thickness without adding a separate layer or film.

In order to achieve the above object, a thin film transistor including a light guide plate having a reflecting plate formed at the bottom and spreading the light incident from the backlight evenly, and a panel in which the amount of light transmitted from the light guide plate is controlled by the polarizing plate and the liquid crystal. In the liquid crystal display device, in the present invention, the light guide plate is formed by combining the upper light guide plate and the lower light guide plate having different refractive indices, and the junction angle of the top light guide plate and the lower light guide plate satisfies the Brester angle (tanθ = n 1 / n 2). It features.

The upper light guide plate and the lower light guide plate are bonded to each other and have one of a triangular shape and a circular shape.

The lower light guide plate is coupled to the upper light guide plate based on the reflecting plate, and the refractive index of the lower light guide plate is larger than that of the upper light guide plate.

At least one light guide plate is further added between the top light guide plate and the bottom light guide plate.

A thin film transistor liquid crystal display device comprising a light guide plate having a reflecting plate formed at a lower portion of the light guide plate to spread the light incident from the backlight evenly, and a panel in which the amount of light transmitted from the light guide plate is controlled by the polarizing plate and the liquid crystal. In the present invention, the light guide plate is formed by combining two or more light guide plates having different refractive indices, and the junction angles of the light guide plates satisfy the Brester angle.

The cross section to which the light guide plates are bonded may have any one of a triangular shape and a circular shape.

The refractive indexes of the light guide plates coupled to each other increase as the distance from the reflecting plate increases.

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

2 is a structural diagram of a thin film transistor liquid crystal display according to an exemplary embodiment of the present invention.

In the TFT-LCD according to the exemplary embodiment of the present invention, as illustrated in FIG. 2, a light guide plate 25 is formed to spread the light incident from a backlight (not shown) and a reflecting plate 31 is formed on the lower portion 25. ) And a panel 29 in which the amount of light transmitted from the light guide plate 25 is controlled by the polarizing plate 31 and the liquid crystal 30.

The light guide plate 25 is an upper light guide plate 23 and a lower light guide plate 21 coupled to each other, and the upper light guide plate 23 and the lower light guide plate 21 have a triangular or circular cross-section of any one of a plurality of surfaces. Cross-sections having these shapes have shapes joined to each other.

The reflecting plate 27 is disposed on the lower surface of the light guide plate 23. In this case, the light guide plate 21 is coupled to the top light guide plate 23 based on the reflector plate 27.

On the other hand, the panel 29 is filled with a liquid crystal 30 in the space, the polarizer 31 is formed below.

The lower light guide plate 21 and the upper light guide plate 23 have different refractive indices, and for the sake of convenience, the refractive index of the lower light guide plate 21 is defined as n1, and the refractive index of the upper light guide plate 23 is defined as n2.

The lower light guide plate 21 and the upper light guide plate 23 have an angle θ of the junction to satisfy the Brester angle, so that the light efficiency is maximized, and the angle θ of the junction is combined. And a correlation between the refractive index ratio of the light guide plate and the angle of light emitted from the backlight.

In addition, the refractive index n1 of the lower light guide plate 21 should be smaller than the refractive index n2 of the upper light guide plate 23. That is, the condition of n1> n2 must be satisfied. The Brester angle θ means an angle at which the polarization direction of the transmitted light and the polarization direction of the reflected light are perpendicular to each other, and satisfy Equation 1 below.

Brester Angle (θ) = tanθ = n1 / n2

Here, n1 means the refractive index of the light guide plate, and means the refractive index of the incident material. In addition, n2 means the refractive index of the light guide plate, and means the refractive index of the bonding material.

The light guide plate 25 is refracted without polarization with light b that is polarized and reflected by only a component perpendicular to the incident angle θ1 of the incident light a at a portion where the lower light guide plate 21 and the upper light guide plate 23 are bonded to each other. And separated into unpolarized light c passing through. In FIG. 2, θ1 represents a refraction angle. At this time, the direction of the reflected light b is polarized only in the direction perpendicular to the incident angle. That is, the light guide plate 25 outputs the light of the non-polarization component and the polarization component together, and the direction of the polarized and reflected light is polarized only in the direction perpendicular to the incident angle.

When the unpolarized non-polarized light c is reflected by the reflecting plate 27 and reaches the polarizing plate 31, only a component of light parallel to the transmission axis of the polarizing plate 31 is transmitted, and a perpendicular component is absorbed by the polarizing plate. . On the other hand, when the light passes through the polarizing plate 31, only the light passing through the transmission axis is exited, so that the amount of light is reduced by half than the initial.

The polarizing plate 31 polarizes the light output from the light guide plate 25. The polarizing plate 31 transmits all of the light reflected therefrom and transmits only a portion α of the light, which is a polarization component. Therefore, the panel 29 outputs light incident on the light guide plate 25 by 50% + α. In addition, when the transmission axis of the polarizing plate 31 matches the light of the polarization component output from the light guide plate 25, the incident light incident on the light guide plate 25 may be transmitted without loss.

Since the light guide plate 25 may reflect a part of the incident light to the reflector 27 of the backlight to be reused, the light output from the panel 29 may be controlled to be greater than 50% + α.

According to the exemplary embodiment of the present invention, when the light b direction polarized and reflected by only the component perpendicular to the incident angle matches the transmission axis of the polarizing plate 31 attached to the panel 29, the light may be used without loss of light. If the transmission axis of the polarizer 31 and the polarization component do not coincide with each other, the transmittance may be lowered than before, and the luminance may be reduced.

In addition, the light output from the panel 29 corresponds to 50% + alpha by reflecting part of the incident light by the light guide plate 25 to the reflector 27 of the backlight.

On the other hand, although the coupling surface of the upper and lower light guide plate has been described as an example of a triangular shape or a circular shape, it can also be produced in a sawtooth shape.

FIG. 3 is a structural diagram of a thin film transistor liquid crystal display according to another exemplary embodiment of the present invention.

In the TFT-LCD according to another embodiment of the present invention, the light guide plate 36 is, as shown in Fig. 3, the first, second,... Sixth light guide plate 30 (31); (35) are combined with each other, and these first, second,... N-th light guide plate 30 (31). 35 has a shape in which any one of a plurality of cross sections has a triangular or circular shape, and the cross sections having these shapes are joined to each other.

The reflective plate 37 is disposed on the lower surface of the first light guide plate 30 among the light guide plates 36 having the above-described configuration.

Meanwhile, the first, second,... Sixth light guide plate 30 (31); Each of the light guide plates 35 may have different refractive indices, and in the sixth light guide plate 35, the first light guide plate 30 may have different refractive indices, but the refractive indices of these light guide plates are the same. Further, these first, second,... Sixth light guide plate 30 (31); The angle θ of the junction at 35 satisfies the Brester angle so that the light efficiency is maximized.

Therefore, the light guide plate according to another embodiment of the present invention combines the light guide plates having different refractive indices, thereby increasing the amount of light that is polarized and reflected.

In this case, in another embodiment of the present invention, a total of six light guide plates has been described as an example, but the number of light guide plates may be combined to six or more.

In addition, although the coupling surface of the light guide plates has been described as an example of a triangular shape or a circular shape, it may be manufactured in a sawtooth shape.

Accordingly, the present invention eliminates the need for a separate layer or film to increase the amount of light output from the panel by combining the plurality of light guide plates having different refractive indices and making the junction angles of these light guide plates satisfy the Brester angle. There is an advantage in that the brightness can be improved by increasing the amount of light without increasing the thickness of the device.

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (7)

A thin film transistor liquid crystal display device comprising: a light guide plate having a reflector plate formed at a lower portion thereof, and spreading and outputting light incident from a backlight; and a panel in which the amount of light transmitted from the light guide plate is controlled by a polarizing plate and a liquid crystal. The light guide plate is formed by combining a light guide plate and a lower light guide plate having different refractive indices, and the junction angle of the top light guide plate and the light guide plate satisfies the following Brester angle. (Brester angle = tanθ = n1 / n2, n1 is the refractive index of the light guide plate, n2 is the refractive index of the light guide plate) The liquid crystal display device of claim 1, wherein a cross section of the top light guide plate and the bottom light guide plate is one of a triangular shape and a circular shape. The liquid crystal display of claim 1, wherein the light guide plate is coupled to the top light guide plate based on the reflective plate, and the refractive index of the light guide plate is larger than that of the top light guide plate. The liquid crystal display device of claim 1, wherein at least one light guide plate is further added between the top light guide plate and the bottom light guide plate. A liquid crystal display device of a thin film transistor comprising: a light guide plate having a reflector plate formed at a lower portion thereof to spread and output light incident from a backlight; and a panel in which a transmittance of light output from the light guide plate is controlled by a polarizing plate and a liquid crystal. The light guide plate is formed by combining two or more light guide plates having different refractive indices, and an angle of each junction of the two or more light guide plates satisfies the following Brester angle. (Brester angle = tanθ = n1 / n2, where n1 is the refractive index of the light guide plate on which light is incident based on each junction, and n2 is the refractive index of the light guide plate bonded to the light guide plate on which the light is incident based on each junction.) The method according to claim 5, A cross-section of each junction of the two or more light guide plates is one of a triangular shape and a circular shape, wherein the liquid crystal display device of the thin film transistor. The method according to claim 5, The refractive index of the two or more light guide plates of the different thin film transistors, characterized in that the greater the distance away from the reflecting plate.

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