KR20110071642A - Liquid crystal display device excepting light polarizer - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to improve the efficiency of a backlight by removing a light polarizing plate. CONSTITUTION: A liquid crystal display device comprises a first substrate which has a pixel region which is divided into 3 parts, a first black matrix(BM1) which is formed on a first area or a third area of the pixel region, a color filter(CF) which is formed on a second area of the first black matrix, an over coat layer(OC) which is sprayed on the first black matrix and the color filter area, a second black matrix which is formed on the over coat layer, and a common electrode(COM) which is sprayed on the over coat layer and the second black matrix. A liquid crystal layer placed between the color filter substrate and the TFT substrate.

Description

Liquid crystal display without polarizer {LIQUID CRYSTAL DISPLAY DEVICE EXCEPTING LIGHT POLARIZER}

The present invention relates to a liquid crystal display device. In particular, the present invention relates to a liquid crystal display device using the light amount of the backlight to the maximum by removing the polarizing plate on both sides of the panel.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Such flat panel displays include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and electroluminescence devices.

In particular, an active matrix liquid crystal display device displays an image using a thin film transistor (TFT) as a switching element. The liquid crystal display device can be miniaturized compared to the cathode ray tube, which is applied to a display device in portable information equipment, office equipment, computer, etc., and is also rapidly applied to a television to replace the cathode ray tube.

1 is a plan view illustrating a pixel area of a liquid crystal display device. FIG. 2 is a cross-sectional view illustrating the structure of a liquid crystal display device taken along the line II ′ of FIG. 1. As shown in FIG. 1 and FIG. 2, the liquid crystal display device has a form in which a liquid crystal is interposed between two glass substrates. The structure of the liquid crystal display will be described in detail with reference to FIGS. 1 and 2 as follows.

The thin film transistor TFT including the gate electrode G, the gate insulating layer GI, the semiconductor layer ACT, the source electrode S, and the drain electrode D is formed on the lower glass substrate SUBL. The thin film transistor TFT is covered with a passivation layer PASI, and the pixel electrode PXL is formed on the passivation layer PASI. The lower alignment layer ALGL is formed on the uppermost surface of the lower substrate SUBL. Since the thin film transistor TFT is formed, it is called a thin film transistor substrate TFTS.

On the upper glass substrate SUBU, a black matrix BM defining a pixel area is formed in a matrix array. The color filter CF is formed between the black matrices BM. The common electrode COM is entirely formed on the color filter CF and the black matrix BM. An upper alignment layer ALGU is formed on the uppermost surface of the upper substrate SUBU. Since the color filter CF is formed, it is called a color filter substrate CFS.

The thin film transistor substrate TFTS and the color filter substrate CFS are bonded to each other with the liquid crystal layer LC interposed therebetween. The lower polarizer POLL is attached to the outside of the thin film transistor substrate TFTS, and the upper polarizer POLU is attached to the outside of the color filter substrate CFS. In particular, the lower polarizer POLL and the upper polarizer POLU are disposed such that the optical axes are perpendicular to each other. Therefore, in the non-operation state, light does not pass through the liquid crystal display device, thereby showing a perfect black gradation.

In this state, when an electric field is formed between the pixel electrode PXL and the common electrode COM, the liquid crystal layer LC changes the alignment, thereby changing the polarization state of the light polarized through the lower polarizing plate POLL. , It becomes a state which can pass through the upper polarizing plate POLU. At this time, by adjusting the amount of light that can pass through the upper polarizing plate (POLU) by the amount of the electric field applied to the liquid crystal, it is possible to implement a variety of color tones.

Since the liquid crystal display uses the polarizing plate as described above, an image is realized by only 50% of the amount of light emitted from the backlight. The light is used only as much as the ratio of the area corresponding to the area of the pixel electrode PXL in the pixel area PA shown in FIG. That is, the portion covered by the black matrix BM does not pass light, and only the region where the liquid crystal is driven by the pixel electrode PXL contributes to the brightness of the light.

The area ratio occupied by the pixel electrode PXL in the area of the pixel area PA is called an aperture ratio, and is used as one of criteria for evaluating the brightness of the liquid crystal display. Usually, the opening ratio is about 90%. Therefore, only 50% of the light amount of the backlight is used by the lower polarizing plate POLL, and the amount of light used by the aperture ratio 90% is about 45% of the amount of backlight light.

As described above, the liquid crystal display implements black gray using a polarizing plate, which results in using only 50% of the backlight. Therefore, there is a problem that the light use efficiency is much lower than that of other flat panel displays.

An object of the present invention is to provide a liquid crystal display device that does not employ a polarizing plate. Another object of the present invention is to provide a liquid crystal display device capable of switching a black mode and a white mode without adopting a polarizing plate. Still another object of the present invention is to provide a liquid crystal display device by removing the polarizing plate and increasing the light efficiency of the backlight.

In order to achieve the above object, a liquid crystal display according to an embodiment of the present invention, the first substrate having a pixel region divided into three zones; First black matrices formed in zones 1 and 3 of the pixel region; A color filter formed in two regions between the first black matrix; An overcoat layer applied over the first black matrix and the color filter area; A second black matrix formed in said two zones above said overcoat layer; A color filter substrate having a common electrode coated on the overcoat layer and the second black matrix; A thin film transistor substrate; It includes a liquid crystal layer interposed between the color filter substrate and the thin film transistor substrate.

The pixel electrode and the common electrode selectively form a first electric field for making the liquid crystal layer interposed therebetween and a second electric field for making the microlens array.

The pixel electrode and the common electrode may selectively form a first electric field which makes the liquid crystal layer interposed therebetween in a vertical arrangement state, and a second electric field which makes the microlens form arrangement.

The pixel electrode may include a plurality of divided pixel electrodes formed in the first zone and the third zone.

A voltage that increases or decreases sequentially is applied to the plurality of divided pixel electrodes.

The area ratio of the first zone, the second zone, and the third zone is 1: 1: 1.

The area ratio of the first zone, the second zone, and the third zone is 35:30:35.

The area ratio of the two zones is 25% to 40%, and the first and third zones are divided into two areas.

The refractive index of the overcoat layer is 1.5; The refractive index of the liquid crystal layer is characterized in that the refractive index when the liquid crystal layer has a micro lens shape has a range of 2.5 ~ 3.0.

The thickness of the overcoat layer has a value in the range of 4 to 8 μm; The liquid crystal layer has a thickness of 5.0 μm.

The liquid crystal display device according to the present invention does not require a polarizing plate. Therefore, the structure of the display device is simplified, the manufacturing process is simple, and the price of the product is low. Further, the liquid crystal display according to the present invention can obtain a brighter display device than the liquid crystal display according to the prior art even if the area of the color filter is about 30% of the pixel area. Therefore, the same brightness can be obtained with low backlight power consumption, or a brighter screen can be obtained with the same power consumption.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. 3 is an enlarged view of a pixel portion of a liquid crystal display according to the present invention. 4 is a cross-sectional view illustrating a state in which a black tint is implemented in a liquid crystal display according to an exemplary embodiment of the present invention. 5 is a cross-sectional view illustrating a state in which a white tint is implemented in a liquid crystal display according to an exemplary embodiment of the present invention. 4 and 5 are cross-sectional views taken along the line II-II ′ of FIG. 3.

First, referring to FIG. 3, the structure of a pixel area of a liquid crystal display according to the present invention will be described as follows. The liquid crystal display device according to the present invention does not attach a polarizing plate. In order to realize complete black gradation, the following configuration is obtained. The pixel area PA is divided into three parts into the left area PAL, the center area PAC, and the right area PAR, and the first black matrix BM1 is formed in the left area PAL and the right area PAR. The second black matrix BM2 is formed in the central area PAC. On the plane, the first black matrix BM1 and the second black matrix BM2 cover the entire pixel area PA without overlapping regions. Therefore, when viewed from the front, in the one-line vertical alignment state in which the liquid crystal is in the initial alignment state, all black gradations are realized.

However, when the first black matrix BM1 and the second black matrix BM2 are viewed in cross section, the first black matrix BM1 and the second black matrix BM2 are spaced apart by a predetermined distance due to the overcoat layer OC formed of a transparent material. Therefore, when the liquid crystal is arranged in the form of a lens by applying an electric field to the liquid crystal, white gray may be realized since the light blocked by the first black matrix BM1 is refracted to guide the color filter CF. In this case, gray levels are implemented by adjusting the amount of light refracted by the color filter CF by adjusting an electric field applied to the liquid crystal.

3 to 5, the structure of the liquid crystal display according to the present invention will be described. The liquid crystal display according to the present invention includes a thin film transistor substrate TFTS and a color filter substrate CFS bonded together with the liquid crystal layer LC therebetween.

The thin film transistor substrate TFTS has the same structure as the thin film transistor substrate TFTS used in a general liquid crystal display device. That is, a thin film transistor including a gate electrode, a semiconductor layer, a source electrode, and a drain electrode is formed on the lower glass substrate SUBL. Since the thin film transistor of the present invention is the same as the conventional one, it is not shown in the drawings in FIG. 3. The thin film transistor TFT is covered with a passivation layer PASI, and the pixel electrode PXL is formed on the passivation layer PASI.

The color filter substrate CFS includes a color filter CF formed between the first black matrix BM1 and the first black matrix BM1 on the upper glass substrate SUBU. An overcoat layer OC is formed of a transparent material on the first black matrix BM1 and the color filter CF. The overcoat OC may have a sufficient distance so that the light blocked by going straight to the first black matrix BM1 may be collected by the color filter CF when the light blocked is refracted. The second black matrix BM2 is formed on the overcoat layer OC. In this case, the second black matrix BM2 is formed to completely overlap the color filter CF region. That is, when viewed from the front of the liquid crystal display device, it is preferable that the color filter CF and the second black matrix BM2 have a shape that completely matches. In order to planarize the surface of the substrate, a transparent dummy layer DUM may be further formed between the second black matrices BM2. The common electrode COM is formed on the second black matrix BM2 and the overcoat layer OC.

The thin film transistor substrate TFTS and the color filter substrate CFS are bonded to each other via the liquid crystal layer LLC. The backlight BL is mounted under the bonded substrate. The arrangement of the liquid crystal layer LLC is controlled by adjusting an electric field between the pixel electrode PXL formed on the thin film transistor substrate TFTS and the common electrode COM formed on the color filter substrate CFS. For example, as shown in FIG. 4, when the liquid crystal molecules of the liquid crystal layer LLC are aligned in the vertical direction, black gray is implemented by allowing the light emitted from the backlight BL to go straight to the substrate. In addition, as shown in FIG. 5, the liquid crystal molecules are arranged in the shape of a micro lens, and the light blocked by the first black matrix BM1 is refracted by the backlight to condense to the color filter CF region, thereby providing white gradation. Implement

In such a structure, it is important to arrange the liquid crystal in the form of a micro lens in order to condense the light when realizing the white gradation. It is desirable to consider further. For example, when the liquid crystal layer (LLC) has a micro lens shape, a liquid crystal material having a refractive index of about 2.5 to 3.0 is used, and the transparent material constituting the overcoat layer (OC) is 1.5, which is similar to the refractive index of glass. desirable. In addition, the thickness of the overcoat layer OC may also be an important factor in inducing light into the color filter CF region when condensing. When the thickness of the liquid crystal layer LLC is about 5.0 µm, the thickness of the overcoat layer LC is preferably about 4 to 8 µm.

When an electric field is applied between the pixel electrode PXL and the common electrode COM, the electric field is differently formed in one pixel area PA in order to arrange the liquid crystal molecules of the liquid crystal layer LLC to have a micro lens shape. To this end, the common electrode COM or the pixel electrode PXL may be divided into multiple electrodes so that a different electric field may be applied to each region.

For example, as illustrated in FIG. 6, divided pixel electrodes PPXL divided into three equal parts may be formed in the left and right regions where the first black matrix BM2 is formed, based on the portion where the second black matrix BM2 is formed. Can be. 6 is a diagram illustrating an example of divided pixel electrodes of a liquid crystal display according to the present invention. When the black gray scale is to be realized, the same voltage may be applied to each of the divided pixel electrodes PPXL to arrange all of the liquid crystal molecules vertically. Then, as shown in FIG. 4, the light incident on the microlens liquid crystal layer LLC from the backlight BL is blocked by both the first black matrix BM1 and the second black matrix BM2 to realize black gradation. . On the other hand, by sequentially increasing or decreasing voltage to each of the divided pixel electrodes PPXL, the arrangement of the microlens liquid crystal layer LLC may have a microlens shape. Then, as shown in FIG. 5, the light traveling to the first black matrix BM2 among the light incident from the backlight BL to the liquid crystal layer LLC is collected by the lens to the color filter CF.

In the liquid crystal display according to the exemplary embodiment of the present invention, the polarizing plate is not provided. Therefore, the amount of light irradiated from the backlight BL can be used 100%. Referring to FIG. 3 again, the first black matrix BM1 formed in the left region PAL, the second black matrix BM2 formed in the central region PAC, and the first black matrix BM1 formed in the right region PAR ), The area of the first black matrix BM1 may define the aperture ratio.

For example, when the left area PAL, the center area PAC, and the right area PAR are partitioned with the pixel area PA in an equal ratio (1: 1: 1), the pixel area PA is divided into the pixel areas PA. Although the area ratio of the color filter CF is 33.3%, the area ratio of 66.6% of the left area PAL and the right area PAR is the actual aperture ratio. As another example, when the center area PAC is allocated at 30% and the left area PAL and right area PAR are allocated at 35%, respectively, the area of the color filter CF with respect to the pixel area PA is limited. Although the ratio is 30%, the light emitting area ratio, that is, the actual aperture ratio is 70%. The area ratio of the center area PAC or the color filter CF with respect to the pixel area PA may be selectively set between 25% and 40%. Accordingly, the area ratio of the left area PAL and the right area PAR is set between 75% and 60%, but it is preferable to equally distribute the left area PAL and the right area PAR. That is, the area ratio of the left area PAL, the center area PAC, and the right area PAR can be selectively selected from 30:40:30 to 37.5: 25: 37.5.

The liquid crystal display device according to the present invention having such a structure does not require a polarizing plate. Therefore, the structure of the display device is simplified, the manufacturing process is simple, and the price of the product is low. Further, the liquid crystal display according to the present invention can obtain a brighter display device than the liquid crystal display according to the prior art even if the area of the color filter is about 30% of the pixel area. Therefore, the same brightness can be obtained with low backlight power consumption, or a brighter screen can be obtained with the same power consumption.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a plan view showing a pixel area of a liquid crystal display device;

FIG. 2 is a cross-sectional view illustrating a structure of a liquid crystal display device taken along the line II ′ of FIG. 1.

3 is an enlarged view of a pixel portion of a liquid crystal display according to the present invention;

4 is a cross-sectional view illustrating a state in which a black tint is implemented in a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a cross-sectional view illustrating a state in which a white tint is implemented in a liquid crystal display according to an exemplary embodiment of the present invention.

6 is a view showing an example of divided pixel electrodes of a liquid crystal display device according to the present invention;

<Description of the symbols for the main parts of the drawings>

DL: data line GL: gate line

PA: pixel region PXL: pixel electrode

TFT: thin film transistor G: gate electrode

S: source electrode D: drain electrode

SUBL: lower transparent substrate ACT: semiconductor layer

GI: gate insulating film PASI: protective film

ALGL: lower alignment layer LC: liquid crystal layer

SUBU: top transparent substrate BM: black matrix

CF: color filter COM: common electrode

ALGU: Upper alignment layer LLC: (microlens) liquid crystal layer

TFTS: thin film transistor substrate CFS: color filter substrate

POLL: Lower Polarizer POLU: Upper Polarizer

BM1: first black matrix BM2: second black matrix

PAL: (pixel) left area PAC: (pixel) center area

PAR: (pixel) right area OC: overcoat layer

DUM: Transparent dummy layer PPXL: Split pixel electrode

BL: backlight

Claims (10)

A first substrate having a pixel region partitioned into three zones; First black matrices formed in zones 1 and 3 of the pixel region; A color filter formed in two regions between the first black matrix; An overcoat layer applied over the first black matrix and the color filter area; A second black matrix formed in said two zones above said overcoat layer; A color filter substrate having a common electrode coated on the overcoat layer and the second black matrix; A thin film transistor substrate; And a liquid crystal layer interposed between the color filter substrate and the thin film transistor substrate. The method of claim 1, The thin film transistor substrate, A second substrate; A gate line and a data line arranged to cross each other around the pixel area; A thin film transistor formed at an intersection of the gate line and the data line; And a pixel electrode connected to the thin film transistor and formed in the pixel area. The method of claim 2, And the pixel electrode and the common electrode selectively form a first electric field for vertically arranging the liquid crystal layer interposed therebetween, and a second electric field for making a micro lens array. The method of claim 2, And the pixel electrode includes a plurality of divided pixel electrodes formed in the first zone and the third zone. The method of claim 4, wherein And increasing or decreasing voltages are sequentially applied to the plurality of divided pixel electrodes. The method of claim 1, And the area ratio of the first zone, the second zone, and the third zone is 1: 1: 1. The method of claim 1, And the area ratio of the first zone, the second zone, and the third zone is 35:30:35. The method of claim 1, The area ratio of the two zones is 25% to 40%, And the first zone and the third zone divide the remaining area ratio into two. The method of claim 1, The refractive index of the overcoat layer is 1.5; The refractive index of the liquid crystal layer is a liquid crystal display device characterized in that the refractive index when the liquid crystal layer has a micro lens shape has a range of 2.5 ~ 3.0. The method of claim 1, The thickness of the overcoat layer has a value in the range of 4 to 8 μm; The liquid crystal display device, characterized in that the thickness of the liquid crystal layer is 5.0㎛.

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