KR20120045479A - Liquid crystal display device excepting light polarizer - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to use all light of a backlight unit by omitting a polarization plate. CONSTITUTION: A pixel area is divided into an opening area and a non opening area. A first panel includes a transparent pixel electrode which is formed on the non opening area on a first transparent substrate(SBL). A second panel includes a black matrix(BM), an overcoat layer(OC), and an opaque common electrode on a second transparent substrate(SBU). The non opening area is filled with the black matrix. The overcoat layer is formed on the black matrix. The opening area is filled with the opaque common electrode on the overcoat layer.

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.

2. Description of the Related Art Recently, various flat panel display devices capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), have been developed. 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.

The liquid crystal display device developed so far includes an upper glass substrate and a lower glass substrate bonded together with a liquid crystal layer interposed therebetween, and a top polarizing plate and a bottom polarizing plate attached to the front and rear surfaces of the bonded glass substrate, respectively. Include. The upper and lower plates are formed with elements that can be applied to the liquid crystal layer by adjusting an electric field. The polarizing plates attached to the front and back surfaces of the bonded glass substrates are arranged with their light transmission axes perpendicular to each other. The liquid crystal display device includes a backlight unit installed on the rear surface of the liquid crystal display panel.

Light emitted from the backlight unit of the liquid crystal display device is linearly polarized while passing through the polarizer. When an electric field is formed between the liquid crystal display panels, the arrangement of the liquid crystal layers is changed, and the polarization state of the polarized light is changed. The light whose polarization state is changed becomes a state which can pass through an upper polarizing plate. At this time, by adjusting the amount of light that can pass through the upper polarizing plate by the amount of the electric field applied to the liquid crystal layer, 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 unit. Therefore, there is a problem that the light use efficiency is much lower than that of other flat panel displays that do not use a polarizing plate.

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 pixel region divided into an opening area and a non-opening area; A first panel including a transparent pixel electrode formed in the non-opening region on a first transparent substrate; And a second panel on the second transparent substrate, the second panel including a black matrix filling the non-opening area, an overcoat layer formed on the black matrix, and an opaque common electrode filling the opening area on the overcoat layer.

The first panel may include: a gate line running in a horizontal direction defining the pixel region and a data line running in a vertical direction; And a thin film transistor connected to the gate wiring, the data wiring, and the pixel electrode.

The second panel further comprises a color filter filling the opening region between the black matrices.

It further comprises a liquid crystal layer interposed between the first panel and the second panel.

And a backlight unit installed on a rear surface of the first panel to irradiate the backlight in the front direction of the second panel.

In a state in which no electric field is applied between the opaque common electrode and the transparent pixel electrode, the backlight emitted from the backlight unit is blocked by the black matrix of the second panel and the opaque common electrode so that the second panel is blocked. Black gradation is implemented in the front of the.

In a state where an electric field is applied between the opaque common electrode and the transparent pixel electrode, the backlight emitted from the backlight unit is refracted by the liquid crystal layer and transmitted to the opening region of the second panel. .

The opening region is defined in a rod shape having a first width in the pixel region; The transparent pixel electrode has a plurality of rod shapes arranged around the opening regions of the non-opening region with a second width; The opaque common electrode is completely overlapped with the opening region in the same size and shape as the opening region.

The aperture region is defined circularly within the pixel region; The transparent pixel electrode has a circular ring shape having a predetermined width surrounding the opening area in the non-opening area; The opaque common electrode is completely overlapped with the opening region in the same size and shape as the opening region.

The liquid crystal display device according to the present invention does not require a polarizing plate. Therefore, all (100%) of the light quantity of a backlight unit can be used as it is. In addition, the structure of the display device is simplified, the manufacturing process is simple, and the price of the product is low. The liquid crystal display device according to the present invention can obtain a high transmittance display device which is brighter than the liquid crystal display device according to the prior art even if the opening area occupied by the color filter is 40% or less than 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.

1 is an enlarged view of a pixel portion of a liquid crystal display according to the present invention.
FIG. 2 is a cross-sectional view illustrating a structure of a liquid crystal display according to the present invention, taken along the line II ′ of FIG. 1.
3 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.
4 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.
5 is a plan view illustrating a case in which the pixel electrode and the common electrode are formed in a circular shape.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. 1 is an enlarged view of a pixel portion of a liquid crystal display according to the present invention. FIG. 2 is a cross-sectional view illustrating a structure of a liquid crystal display according to the present invention, taken along the line II ′ of FIG. 1.

1 and 2, a liquid crystal display according to the present invention will be described. First, referring to FIG. 2, in the liquid crystal display according to the present invention, a thin film transistor substrate TFTS, a color filter substrate CFS, and a rear surface of the thin film transistor substrate TFTS bonded together with the liquid crystal layer LC interposed therebetween. It includes a backlight unit (BLU) located in.

The thin film transistor substrate TFTS includes a thin film transistor including a gate electrode G, a gate insulating film GI, a semiconductor layer A, a source electrode S, and a drain electrode D formed on the lower glass substrate SBL. T). The thin film transistor T is covered with the passivation layer PAS, and the pixel electrode PXL is formed on the passivation layer PAS. A lower alignment layer (not shown) may be further formed on an uppermost surface of the lower substrate SBL. Since the thin film transistor T is formed, it is called a thin film transistor substrate TFTS.

The color filter substrate CFS includes a color filter CF formed between the black matrix BM and the black matrix BM formed on the upper glass substrate SBU. An overcoat layer OC is formed of a transparent material on the black matrix BM and the color filter CF. The overcoat layer OC preferably has a sufficient distance so that the light blocked by going straight toward the black matrix BM can be collected by the color filter CF when the light is refracted by the change of the arrangement of the liquid crystal. The common electrode COM is formed on the overcoat layer OC. In particular, the common electrode COM has a size corresponding to the opening area OA between the black matrices BM and is formed to completely overlap the opening area OA. The color filter CF is formed between the black matrices BM. An upper alignment layer (not shown) may be further formed on the uppermost surface of the upper substrate SBU. Since the color filter CF is formed, it is called a color filter substrate CFS.

Referring to FIG. 1, which is an enlarged plan view of a pixel region, features of the liquid crystal display according to the present invention will be described in more detail. As described above, the rectangular pixel area PA is defined by crossing the gate line GL and the data line DL. The pixel area PA is divided into an opening area OA and a non-open area CA. Within the pixel area, the color filter CF corresponds to the opening area OA for implementing the image data. The color filter CF may be divided into a plurality of bar shapes in one pixel area. The non-opening area CA is filled with the black matrix BM. That is, a black matrix BM is formed between the color filters CF. The common electrode COM is formed to overlap the region where the color filter CF is formed. In particular, the common electrode COM may be formed of an opaque metal material such as cobalt (Co), molybdenum (Mo), chromium (Cr), or aluminum (Al).

On the other hand, the pixel electrode PXL formed on the thin film transistor substrate TFTS is formed so as to be limited only in the non-opening area PA, which is a region where the black matrix BM formed on the color filter substrate CFS is formed. In particular, since the pixel electrode PXL must transmit as much light as possible from the backlight unit BLU to the thin film transistor substrate TFTS, a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) may be used. It is preferable to form with a material.

In FIG. 1, the pixel electrode PXL and the black matrix BM have a shape in which a plurality of simple bar shapes having a predetermined width are arranged at regular intervals. However, it is not limited to this form. Although not shown in the drawings, in the pixel area, if necessary, a plurality of bar shapes having a predetermined width and formed in a zigzag shape may be arranged at regular intervals. Due to the shape of the pixel electrode PXL and the black matrix BM, the shape of the color filter CF may have a corresponding shape. That is, the color filter CF may have a shape in which a plurality of simple bar shapes having a predetermined width are arranged at regular intervals in the pixel region, or a plurality of bar shapes having a predetermined width and formed in a zigzag shape may have a predetermined interval. It can be arranged as.

Hereinafter, a method of implementing an image in the liquid crystal display according to the present invention shown in FIGS. 1 and 2 will be described with reference to FIGS. 3 and 4. 3 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. 4 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.

In the liquid crystal display device according to the present invention, when viewed in plan view, the black matrix BM and the opaque common electrode COM have a shape in which the pixel area PA is tightly filled. Therefore, in the normal state in which the liquid crystal is not driven, the light emitted from the backlight unit BLU cannot be observed from the front of the liquid crystal display panel. That is, as shown in FIG. 3, the black gray scale is implemented. The liquid crystal display according to the present invention operates in a normally black mode that realizes a full black gray level in a normal state in which no electric field is applied. The liquid crystal layer LC in FIG. 3 maintains an initial arrangement state in which an electric field is not applied. In FIG. 3, the initial arrangement state of the liquid crystal layer LC is arranged in a vertical state between the upper substrate SBU and the lower substrate SBL, but is not limited thereto. If necessary, it can be arranged parallel to the substrate.

In addition, the pixel electrode PXL and the common electrode COM are alternately arranged on the upper substrate SBU and the lower substrate SBL. Therefore, the electric field formed between the pixel electrode PXL and the common electrode COM is formed in the inclined line direction, not the vertical line direction, between the upper substrate SBU and the lower substrate SBL. In particular, since the electromotive force is inversely proportional to the distance, the electromotive force is formed in a hemispherical or parabola shape which is curved between the pixel electrode PXL and the common electrode COM. That is, as shown in FIG. 4, when an electric field is formed between the pixel electrode PXL and the common electrode COM, the liquid crystal molecules of the liquid crystal layer LC are arranged along the direction of the electric field line. As a result, the liquid crystal layer LC is rearranged in the shape of a convex lens as shown in FIG. 4.

In this state, the light emitted from the backlight unit BLU, especially the light occupying the black matrix BM region, passes through the liquid crystal layer LC and is a space between the black matrix BM and the opaque common electrode COM. Is refracted by. As a result, light may be recognized from the front surface of the liquid crystal display panel through the color filter CF region. That is, as shown in FIG. 4, the white gray scale is implemented. In particular, the refractive index may be changed by varying the shape of the lens from the non-lens shape to the convex lens shape according to the intensity of the electric field formed between the common electrode COM and the pixel electrode PXL. Due to the shape change of the liquid crystal layer LC and the change in the refractive index, the degree of concentration toward the color filter CF of the light emitted from the backlight unit BLU may be adjusted.

The shape of the opening region OA, the non-opening region CA, the common electrode COM, and the pixel electrode PXL may be variously modified as necessary. 5 is a plan view illustrating a case in which the pixel electrode and the common electrode are formed in a circular shape. In FIG. 5, the upper figure is a plan view, and the lower figure is a sectional view corresponding to the top view. Since the pixel area PA is defined by the gate line and the data line, the pixel area PA may have a general rectangular shape. The opening area OA may be formed in a circular shape substantially located at the center of the pixel area PA. In this case, the pixel electrode preferably has a circular annular shape that surrounds the opening region OA within the non-opening region CA.

5, 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 thin film transistor substrate TFTS includes a pixel electrode PXL including a gate insulating layer GI and a transparent conductive material formed on the passivation layer PAS. In addition, a lower alignment layer AGL is formed on the pixel electrode PXL. On the other hand, in the color filter substrate CFS, a black matrix BM having the same size and shape as the non-opening area CA, and a circular color filter CF formed at the center of the black matrix BM are formed on the same layer. It is. An overcoat layer OC is formed on the black matrix BM and the color filter CF. On the overcoat layer OC, the common electrode COM containing the opaque conductive material is formed at the same size and position as the opening region OA. An upper alignment layer AGU is formed on the common electrode COM.

In the liquid crystal display device according to the present invention, it is important to arrange the liquid crystal in the form of a micro lens in order to condense the light when implementing the white gradation, but in order to increase the light collection efficiency, the liquid crystal layer LC and the overcoat layer OC It is further desirable to take advantage of the difference in refractive index of For example, when the liquid crystal layer LC has a microlens 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 is also an important factor in inducing light to the color filter CF region when condensing. When the thickness of liquid crystal layer LC is about 5.0 micrometers, it is preferable that the thickness of overcoat layer LC is about 4-8 micrometers.

The liquid crystal display device according to the present invention does not include a polarizing plate. Therefore, 100% of the light emitted from the backlight unit BLU can be used. Referring back to FIG. 1, the total area occupied by the color filter CF, which is an opening region, may define the opening ratio and the light transmittance. In the pixel area of the liquid crystal display according to the present invention, the opening area OA has a smaller area ratio than the non-open area CA by design. For example, the ratio of the open area OA and the non-open area CA may be formed at 40% to 60%. In this case, the aperture ratio on the area is 40%, but when the liquid crystal layer LC is rearranged in the form of a lens and the light emitted from the backlight unit BLU is refracted, the light in the non-opening area CA, which has occupied 60%, is occupied. It is led to this opening area OA. As a result, the actual light transmittance is 60%.

In this way, the area ratio of the opening area OA can be selectively set between 25% and 40%. Accordingly, the area ratio of the non-opening area CA is set between 75% and 60%. As a result, the light transmittance at the time of actually operating the liquid crystal display device can secure 75% to 60% of the area ratio of the non-opening area CA. This reduces the amount of light of the backlight unit (BLU) by 50%, thereby achieving an effect of increasing the light transmittance by at least 30% or more than the liquid crystal display using the polarizing plate having an actual light transmittance of 40% or less.

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.

PA: pixel area OA: aperture area
CA: non-opening area TFTS: thin film transistor substrate
CFS: color filter substrate LC: liquid crystal layer
T: thin film transistor G: gate electrode
S: source electrode D: drain electrode
GL: gate wiring DL: data electrode
GI: gate insulating film PAS: protective film
BM: Black Matrix CF: Color Filter
OC: overcoat layer COM: common electrode
SBU: Upper Glass Substrate SBL: Lower Glass Substrate
AGL: lower alignment layer AGU: upper alignment layer
BLU: Backlight Unit

Claims (9)

A pixel region divided into an opening region and a non-opening region;
A first panel including a transparent pixel electrode formed in the non-opening region on a first transparent substrate; And
And a second panel on a second transparent substrate, the second panel including a black matrix filling the non-opening region, an overcoat layer formed on the black matrix, and an opaque common electrode filling the opening region over the overcoat layer. A liquid crystal display device.
The method of claim 1, wherein the first panel,
A gate wiring running in a horizontal direction defining the pixel region and a data wiring running in a vertical direction; And
And a thin film transistor connected to the gate line, the data line, and the pixel electrode.
The method of claim 1,
And the second panel further comprises a color filter filling the opening region between the black matrices.
The method of claim 1,
And a liquid crystal layer interposed between the first panel and the second panel.
The method of claim 4, wherein
And a backlight unit disposed on a rear surface of the first panel to irradiate the backlight in a direction toward the front surface of the second panel.
The method of claim 5, wherein
In a state in which no electric field is applied between the opaque common electrode and the transparent pixel electrode, the backlight emitted from the backlight unit is blocked by the black matrix of the second panel and the opaque common electrode so that the second panel is blocked. Liquid crystal display, characterized in that the black gray is implemented in the front of the.
The method of claim 5, wherein
In the state where an electric field is applied between the opaque common electrode and the transparent pixel electrode, the backlight emitted from the backlight unit is refracted by the liquid crystal layer and transmitted to the opening region of the second panel. LCD display device.
The method of claim 1,
The opening region is defined in a rod shape having a first width in the pixel region;
The transparent pixel electrode has a plurality of rod shapes arranged around the opening regions of the non-opening region with a second width;
And the opaque common electrode completely overlaps the opening region in the same size and shape as the opening region.
The method of claim 1,
The aperture region is defined circularly within the pixel region;
The transparent pixel electrode has a circular ring shape having a predetermined width surrounding the opening area in the non-opening area;
And the opaque common electrode has the same size and shape as the opening area and completely overlaps the opening area.

Images