KR20060117060A - Liquid crystal display - Google Patents

Abstract

There is provided a liquid crystal display device that can improve image quality, improve luminance uniformity, and can be manufactured in a light and simple manner. The liquid crystal display includes a color filter substrate and a thin film transistor substrate formed on both sides of the liquid crystal layer, a polarizer attached to the upper portion of the color filter substrate, and a plurality of smaller size than the subpixels of the color filter substrate. A transparent substrate on which the LED is formed, a reflector formed surrounding the LED to reflect the light emitted from the LED toward the color filter substrate, and a reflective member formed between the liquid crystal layer and the thin film transistor substrate and reflecting the light emitted from the LED upwards. Include.

Description

Liquid crystal display {Apparatus for liquid crystal display}

1 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 2A is a schematic diagram illustrating the flow of light when the voltage is turned OFF in the liquid crystal display of FIG. 1.

FIG. 2B is a schematic diagram illustrating the flow of light when the voltage is turned ON in the liquid crystal display of FIG. 1.

3 is a cross-sectional view of the front light substrate of the liquid crystal display of FIG. 1.

4A is a cross-sectional view of a liquid crystal display according to another exemplary embodiment of the present invention.

4B is a cross-sectional view of the polarizer of the liquid crystal display of FIG. 4A.

(Explanation of symbols for the main parts of the drawing)

100 liquid crystal panel 110 thin film transistor substrate

120: color filter substrate 130: liquid crystal layer

160: reflecting plate 200: polarizing plate

210: polarizing film 220: protective film

250: phase difference plate 300: front light substrate

320: LED 322: first electrode

324: Compound semiconductor layer 328: Second electrode

330: reflector 340: protective layer

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 in which image quality is improved, luminance uniformity is improved, and light and simple production is possible.

The liquid crystal display is a transmissive type LCD using a back light, a reflective liquid crystal display using an external light source or a front light according to a method of using a light source. type LCD), and a transflective liquid crystal display (trans-reflective type LCD) in which a transmissive liquid crystal display and a reflective liquid crystal display are mixed.

A reflective liquid crystal display device using the front light is a liquid crystal display device in which a light supply device for supplying light to the liquid crystal panel is disposed on the front surface of the liquid crystal display device. The light source of the light supply device of the front light is generally located at one side end of the front surface of the liquid crystal display. The light emitted from the light supply device is scattered and reflected by the light guide plate and is incident to the liquid crystal panel side. This light is reflected back from the reflector located at the rear of the liquid crystal panel and emitted to the front of the liquid crystal display to reach our eyes.

At this time, a considerable amount of light emitted from the light source is not incident in the liquid crystal panel direction and leaks through the other side end where the light source is not located. Therefore, the light utilization efficiency is lowered, the power consumption is increased, and the luminance is lowered.

On the other hand, since such a light supply device uses a light guide plate, a reflecting plate, or the like, a certain space is required, thus increasing the volume of the liquid crystal display device.

In addition, optical interference occurs between the lattice pattern of the light guide plate and the pixels of the liquid crystal display to generate a moire phenomenon. Moiré phenomenon refers to a wave-like noise phenomenon that appears on the screen. In order to eliminate this, there is a method of arranging the lattice of the light guide plate and the arrangement of pixels to form an angle of about 22.5 degrees, but in this case, the light efficiency is significantly lowered and the moiré phenomenon is not completely removed. Another way to eliminate moiré is to match the height of the light guide plate grid with the pixels of the liquid crystal panel. In this case, the height of the light guide plate should be changed as the pixel height of the liquid crystal display device changes. If the size is small, the lattice formation of the light guide plate itself becomes difficult. In addition, when the arrangement of the liquid crystal panel and the pixel is distorted, the moiré phenomenon occurs, and the light efficiency decreases because a lot of light leaks to the opposite side of the light guide plate.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a liquid crystal display device in which image quality is improved, luminance uniformity is improved, and light and simple production is possible.

The technical problem of the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, a liquid crystal display device includes a color filter substrate and a thin film transistor substrate formed on both surfaces of a liquid crystal layer, and a polarizing plate attached to an upper portion of the color filter substrate. And a transparent substrate having a plurality of LEDs attached to an upper portion of the polarizing plate and having a smaller size than a sub pixel of the color filter substrate, and surrounding the LEDs to reflect light emitted from the LEDs toward the color filter substrate. And a reflector and a reflective member formed between the liquid crystal layer and the thin film transistor substrate to reflect light emitted from the LED upwardly.

According to another exemplary embodiment of the present invention, a liquid crystal display device includes a color filter substrate and a thin film transistor substrate formed on both surfaces of a liquid crystal layer, and are attached to an upper portion of the color filter substrate and have a size larger than a subpixel of the color filter substrate. A polarizing plate having a plurality of small LEDs formed thereon, a reflector formed surrounding the LEDs to reflect light emitted from the LEDs toward the color filter substrate, and formed between the liquid crystal layer and the thin film transistor substrate and exiting the LEDs It includes a reflection member for reflecting the light to the upper side.

Other specific details of the invention are included in the detailed description and 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 implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and the general knowledge in the technical field to which the present invention belongs. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

1 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the liquid crystal display includes a liquid crystal panel 100, a polarizer 200, and a front light substrate 300.

The liquid crystal panel 100 includes a thin film transistor substrate 110, a color filter substrate 120, and a liquid crystal layer 130, and includes an alignment layer 140 and a reflective plate between the thin film transistor substrate 110 and the liquid crystal layer 130. 160 is formed, and an alignment layer 150 is formed between the color filter substrate 120 and the liquid crystal layer 130.

The thin film transistor substrate 110 is a transparent glass substrate in which a thin film transistor (TFT) (not shown), which is a switching element, is formed in a matrix form. Data and gate lines are respectively connected to the source and gate terminals of the thin film transistors, and a pixel electrode made of indium tin oxide (ITO), which is a transparent conductive material, is formed at the drain terminal.

The color filter substrate 120 is positioned to face the thin film transistor substrate 110, and a plurality of RGB subpixels are formed in a mosaic shape on a supporting substrate such as glass. In addition, a transparent electrode is coated on the RGB subpixels by, for example, sputtering. As the transparent electrode, a transparent material such as ITO or indium zinc oxide (IZO) is used.

The liquid crystal layer 130 is a layer in which liquid crystal molecules are injected between the thin film transistor substrate 110 and the color filter substrate 120. The liquid crystal molecules have a twist structure that is twisted 90 degrees from the top to the bottom of the liquid crystal layer 130. Can have When a voltage is applied between the pixel electrode of the thin film transistor substrate 110 and the transparent electrode of the color filter substrate 120, the arrangement of the liquid crystal molecules changes according to the strength of the voltage. Therefore, the amount of light passing through the liquid crystal layer 130 may vary according to the voltage. The liquid crystal layer 130 has optical anisotropy for converting the vibration direction of polarized light passing through the liquid crystal layer 130 and dielectric anisotropy moving according to the intensity of the voltage applied to the liquid crystal.

The alignment layers 140 and 150 are formed between the liquid crystal layer 130, the thin film transistor substrate 110, and the liquid crystal layer 130 and the color filter substrate 120, respectively. The liquid crystal molecules of the liquid crystal layer 130 are twisted 90 degrees from the first alignment layer 140 formed on the thin film transistor substrate 110 side to the second alignment layer 150 formed on the color filter substrate 120 side. Has a twisted structure.

In addition, a reflective plate 160 is formed between the alignment layer 140 and the thin film transistor substrate 110. The reflector 160 serves to reflect light incident from the liquid crystal layer 130 back to the liquid crystal layer 130. The reflective plate 160 may be formed of metal. For example, metals such as Al, Ag, and Au may be deposited on the thin film transistor substrate 110 by a method such as metal organic chemical vapor deposition (MOCVD).

The polarizer 200 is formed on the color filter substrate 120. The polarizing plate 200 changes the vibration direction of the light incident on the polarizing plate 200 and serves to linearly polarize the light. The polarizing plate 200 includes a polarizing film 210 and a protective film 220. The polarizing film 210 may be obtained by stretching a polyvinyl alcohol (hereinafter referred to as PVA) film to which iodine and a coloring dye are applied in a specific direction. The protective film 220 is formed on one or both surfaces of the polarizing film 210 to provide a function such as surface hardness improvement or antistatic and to protect the polarizing film 210. For example, a cellulose ester film may be used as the protective film 220, and in particular, a triacetyl cellulose (hereinafter referred to as TAC) film is widely used because it can easily prepare a film having excellent transparency and low anisotropy of refractive index. do. When the TAC film is used as the protective film 220, the polarizing plate 200 may be manufactured by sequentially stacking TAC, PVA, and TAC.

A phase difference plate 250 may be formed between the polarizer 200 and the color filter substrate 110 to compensate for the phase difference by delaying the phase of light. The retardation plate 250 is made by stretching the polymer film uniaxially, and may have a specific retardation. For example, when the retardation plate 250 is composed of a λ / 4 phase retardation film, the λ / 4 phase retardation film circularly polarizes incident linearly polarized light. As the retardation plate 250, for example, polycarbonate may be used.

Although the case where the retardation plate 250 is disposed between the polarizing plate 200 and the color filter substrate 120 has been described, the position of the retardation plate 250 is not limited thereto, and the inside of the liquid crystal panel and the polarizing plate 200 may be described. And may be formed between the front light substrate 110 and the like, and may be formed integrally with the polarizer 200.

The front light substrate 300 is attached to the upper portion of the polarizer 200. A plurality of light emitting diodes (LEDs) 320 smaller than the size of a subpixel are formed on the front light substrate 300. Details of the front light substrate 300 will be described later.

FIG. 2A is a schematic diagram illustrating the flow of light when the voltage is turned OFF in the liquid crystal display of FIG. 1, and FIG. 2B is a schematic diagram illustrating the flow of light when the voltage is turned ON in the liquid crystal display of FIG. 1.

2A and 2B, a path through which light moves in the liquid crystal display according to the exemplary embodiment of the present invention will be described. First, when the voltage is turned off, light is emitted from the LED (320 of FIG. 1) of the front light substrate 300 of FIG. 1 toward the liquid crystal layer (130 of FIG. 1). The light emitted from the LED 320 is linearly polarized while passing through the polarizer 200, and the linearly polarized light is circularly polarized while passing through the λ / 4 retardation plate 250. In this case, the circularly polarized light may be left circularly polarized light or right circularly polarized light. When the voltage is OFF, the liquid crystal molecules of the liquid crystal layer 130 are twisted by 90 degrees. When circularly polarized light passes therethrough, the light is linearly polarized again by the optical anisotropy of the liquid crystal molecules. The linearly polarized light passing through the liquid crystal layer 130 is reflected by the reflector 160 to the liquid crystal layer 130, and is then circularly polarized by the optical anisotropy of the liquid crystal molecules. The light is linearly polarized in the same direction as the first incident light while passing through the retardation plate 250. The linearly polarized light passes through the polarizer 200 to display WHITE.

Looking at the case that the voltage is turned on, the light is emitted from the LED 320 of the front light substrate 300 toward the liquid crystal layer 130. The light emitted from the LED 320 is linearly polarized while passing through the polarizer 200, and the linearly polarized light is circularly polarized while passing through the λ / 4 retardation plate 250. In this case, the circularly polarized light may be left circularly polarized light or right circularly polarized light. When the voltage is turned on, the liquid crystal molecules are vertically arranged by an electric field applied to the liquid crystal layer 130. Therefore, circularly polarized light emitted from the retardation plate 250 is passed through as it is. The circularly polarized light is reflected by the reflector 160, and the left circularly polarized light is changed into the right circularly polarized light, and the right circularly polarized light is changed into the left circularly polarized light. The circularly polarized light passes through the liquid crystal layer 130 as it is, and then changes to linearly polarized light while passing through the retardation plate 250. The linearly polarized light is changed from the first incident light. Therefore, this light cannot pass through the polarizing plate and BLACK is displayed.

3 is a cross-sectional view of the front light substrate of the liquid crystal display of FIG. 1.

Referring to FIG. 3, the front light substrate 300 will be described in detail. The front light substrate 300 includes a transparent substrate 310, an LED 320, a reflector 330, and a protective layer 340.

The transparent substrate 310 is directly attached to the lower polarizing plate (200 of FIG. 1) to serve as a support on which the LED 320 is formed. As the transparent substrate 310, a transparent material such as plastic, glass, or film may be used.

The LED 320 includes a first electrode 322, a compound semiconductor layer 324, an insulating layer 326, and a second electrode 328, and a plurality of LEDs 320 are disposed on the front light substrate 300. It is arranged in a mosaic shape. In this case, each of the plurality of LEDs 320 may be formed to have a smaller size than the sub pixels, and may correspond to one sub pixel of the color filter substrate 120 disposed below.

The first electrode 322 is formed on the transparent substrate 310. The first electrode 322 may be formed of a transparent material such as ITO, IZO, or the like, and may be deposited on the transparent substrate 310 by sputtering.

The compound semiconductor layer 324 including the III-V group, the II-IV group, and the V-V group is formed on the first electrode 322. For example, GaAs, GaP, InP, or the like may be used. The compound semiconductor layer 324 is formed by sequentially stacking a P-type doped compound semiconductor and an N-type doped compound semiconductor. In the present specification, the compound semiconductor layer 324 is formed by sequentially stacking a P-type doped compound semiconductor and an N-type doped compound semiconductor, but the present disclosure is not limited thereto and may be modified in various ways.

The compound semiconductor layer 324 may be formed by a method such as plasma enhanced chemical vapor deposition (PECVD). In order to form the LED 320 smaller than the size of the subpixel, the compound semiconductor layer is stacked, and then the compound semiconductor layer 324 is formed using the photoresist pattern formed on the compound semiconductor as an etching mask. For example, when the length of the long axis of the subpixel is about 140 μm to 250 μm and the length of the short axis is about 40 μm to 50 μm, the length of the long axis or short axis of the LED 320 may be about 3 μm to 5 μm.

The insulating layer 326 is formed on the compound semiconductor layer 324. The insulating layer 326 may be formed of SiO ₂ , SiNx, or the like, and a method such as chemical vapor deposition may be used. In order to connect the compound semiconductor layer 324 and the second electrode 328, a contact hole may be formed on the insulating layer 326.

The second electrode 328 is formed on the insulating layer 326. As in the first electrode 322, a transparent material such as ITO or IZO is used, and is deposited on the transparent substrate 310 by sputtering or the like. The second electrode 328 may be connected to the compound semiconductor layer 324 through a contact hole formed on the insulating layer 326.

As described above, since the LED 320 is smaller than the sub pixel, one LED 320 may be disposed to correspond to each sub pixel. In this case, since light can be emitted evenly to all surfaces of the liquid crystal display, the uniformity of luminance is improved.

In addition, since the LED 320 is sufficiently smaller than the color filter substrate (120 in FIG. 1), the area occupied by the LED 320 can be manufactured to about 1% or less of the front light substrate 300, so that the aperture ratio is good. Lose.

Meanwhile, as shown in FIG. 3, the reflector 330 may be formed in a shape surrounding the LED 320 on the transparent substrate 310. The reflector 330 reflects the light emitted to the upper side of the LED 320 toward the color filter substrate 120. The reflector 330 may be formed by, for example, depositing a metal such as Al, Ag, Au, or the like by using a method such as metal organic chemical vapor deposition (MOCVD).

In addition, the reflector 330 may be formed in a holographic pattern. The holographic pattern refers to an interference fringe formed by two laser beams having coherence, and may be manufactured to reflect or transmit light. The holographic pattern is manufactured to reflect the incident light by injecting an object beam and a reference beam into the recording plate to form an interference fringe. For example, the holographic reflector may be made by injecting a laser beam directly onto the second electrode 328 to form a holographic pattern. In addition, the holographic film on which the holographic pattern is formed may be formed by patterning the holographic film on the front light substrate 300 by patterning the holographic film. This holographic film may be attached, for example, on the second electrode 328 of the front light substrate 300 or on the protective layer 340.

Since the reflector 330 is formed, light emitted in a direction other than the color filter substrate 120 among the light emitted from the LED 320 hits the reflector 330 and is incident to the color filter substrate 120 again. The amount of light leaking is less. Therefore, the light utilization efficiency is increased, the power consumption is reduced, and the brightness is improved.

In addition, when the holographic reflector is used as the reflector 330, the holographic pattern may be directly formed on the LED 320, thereby simplifying the process and reducing the cost. Even when the holographic film is used, it is not necessary to go through a complicated process simply by attaching it.

The protective layer 340 is formed on the second electrode 328 and serves to protect the LED 320 formed on the transparent substrate. The protective layer 340 may be made of a metal oxide, a metal emulsion, or the like. It may also be composed of a transparent plastic or the like.

The height of the front light substrate 300 as described above may be manufactured to 50 μm or less including the transparent substrate 310. The height of the light supply device using the light guide plate is about several hundred μm. Therefore, by forming the LED 320 on the front light substrate 300, the volume of the liquid crystal display device is reduced, making it possible to manufacture a thin and simple liquid crystal display device.

In addition, since the light guide plate disappears, moiré patterns generated by optical interference between the lattice pattern of the light guide plate and the pixels of the liquid crystal display do not occur. Therefore, the image quality is improved.

Hereinafter, another embodiment of the present invention will be described with reference to FIGS. 4A and 4B. For convenience of description, members having the same functions as the members shown in the drawings of the above embodiment are denoted by the same reference numerals, and thus description thereof is omitted. 4A is a cross-sectional view of a liquid crystal display according to another exemplary embodiment. FIG. 4B is a cross-sectional view of a polarizer of the liquid crystal display of FIG. 4A.

In the present embodiment, as shown in FIGS. 4A and 4B, the transparent substrate (310 of FIG. 3) to which the LED 320 is attached does not exist on the front light substrate 301, and the LED 320 is a polarizer 200. Is formed directly on Referring to this, first, the first electrode 322 is stacked on the protective film 220 on the polarizer 200, and then the compound semiconductor layer 324 is formed. Next, the insulating layer 326 and the second electrode 328 may be stacked, and the LED 320 may be formed on the polarizer 200 by covering the protective layer 340.

As described above, when the LED is directly formed on the polarizer 200, it is not necessary to use the transparent substrate 310 separately, thereby reducing costs and increasing productivity.

In addition, since the polarizer 200 and the front light substrate 300 separately manufactured are floated without being accurately contacted or air is injected, it may prevent the path of light or the luminance uniformity from deteriorating.

According to the liquid crystal display as described above has one or more of the following effects.

First, since there is no light guide plate, moiré does not occur, and thus the image quality may be improved.

Second, since light may be evenly emitted to all surfaces of the liquid crystal display, uniformity of luminance may be improved.

Third, the volume of the front light substrate is reduced, so that the liquid crystal display device can be made thinner and simpler.

Claims (6)

A color filter substrate and a thin film transistor substrate respectively formed on both surfaces of the liquid crystal layer; A polarizer attached to an upper portion of the color filter substrate; A transparent substrate attached to an upper portion of the polarizer and having a plurality of LEDs smaller in size than the subpixels of the color filter substrate; A reflector formed surrounding the LED to reflect light emitted from the LED toward the color filter substrate; And And a reflective member formed between the liquid crystal layer and the thin film transistor substrate and reflecting light emitted from the LED upward. The method of claim 1, And the LEDs are disposed so as to correspond to each subpixel. The method of claim 1, The LED includes a liquid crystal display device comprising a compound semiconductor. The method of claim 1, And the reflector is formed of a metal. The method of claim 1, The reflector is a liquid crystal display device having a transparent holographic pattern is formed. A color filter substrate and a thin film transistor substrate respectively formed on both surfaces of the liquid crystal layer; A polarizer attached to an upper portion of the color filter substrate and having a plurality of LEDs smaller in size than the subpixels of the color filter substrate; A reflector formed surrounding the LED to reflect light emitted from the LED toward the color filter substrate; And And a reflective member formed between the liquid crystal layer and the thin film transistor substrate and reflecting light emitted from the LED upward.

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