KR20000040123A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to form a multi domain without adopting rubbing operation. CONSTITUTION: A liquid crystal display device includes an upper and a lower substrates(10,20), liquid crystal layer(30), a first slant material(14a), and a second slant material(14b). The upper and the lower substrates(10,20) are facing each other and confine unit cells. The liquid crystal layer(30) includes plurality of liquid crystal molecules applied between the upper and the lower substrates. The first slant material(14a) is formed for each unit cell on the upper substrate. The surface of the substrate and the first slant material defines a first angle between them. The second slant material(14b) is formed for each unit cell on the upper substrate, and is implemented with a predetermined spacing from the first slant material such that the first and second slant materials are symmetrical.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a triple domain.

In general, a vertical alignment liquid crystal display device has liquid crystals having negative dielectric anisotropy between the upper and lower substrates, a vertical alignment layer is provided on opposite surfaces of the upper and lower substrates, and a polarizing plate on each of the rear surfaces of the upper and lower substrates. It has a structure to which it is attached. At this time, each of the opposing surfaces of the upper and lower substrates is provided with a liquid crystal driving electrode, and the polarization axes of the upper and lower polarizing plates are attached to cross each other.

In the vertical alignment mode liquid crystal display, the liquid crystal molecules are vertically arranged on the substrate under the influence of the vertical alignment layer before the electric field is formed. At this time, the screen becomes dark because the vertical polarizers cross vertically. On the other hand, when an electric field is formed between the driving electrodes of the upper and lower substrates, the liquid crystal molecules are distorted to be perpendicular to the shape of the electric field according to the liquid crystal property of negative dielectric anisotropy. Accordingly, light leaks through the twisted liquid crystal molecules, and the screen becomes white.

At this time, since the liquid crystal molecules are rod-shaped, the refractive index and the dielectric constant of the long axis and the short axis are different from each other. Accordingly, the refractive index is different depending on the direction in which the liquid crystal molecules are viewed, resulting in a difference in viewing angle between the front and the side views of the screen. Therefore, in order to solve this problem, conventionally, even in one unit pixel, the initial arrangement of the liquid crystal molecules are different, thereby forming a double domain. That is, when the electric field is formed between the pixel electrode and the common electrode, the direction in which the liquid crystal molecules are distorted is changed to compensate for the anisotropy of the long axis and the short axis of the liquid crystal molecule.

Here, conventionally forming a double domain in one pixel is achieved by rubbing the alignment film.

That is, as shown in FIG. 1A, the alignment layer 3 of the lower substrate (not shown) is rubbed in the r1 direction as a whole. At this time, rubbing is a step of rubbing the surface of the alignment film with a material such as a roller in a predetermined direction as is known. In the drawing, reference numeral A1 denotes a first domain predetermined region, and A2 denotes a second domain predetermined region.

Then, as shown in FIG. 1B, the photoresist film 4 is coated on the alignment film 3, and then exposed and developed so as to expose the second domain predetermined region A2. Thereafter, the exposed second domain predetermined region A2 is rubbed in the r2 direction, which is a direction crossing with r1.

Thereafter, as shown in FIG. 1C, the photoresist film 4 is removed to form two domains A1 and A2 in the unit pixel space. Thereafter, the alignment film on the upper substrate is also rubbed in the same process as above to form a double domain.

However, in order to form the above-mentioned double domain, two rubbing steps must be performed on the alignment film of the lower substrate, and then two rubbing steps must be performed on the alignment film of the upper substrate, which is cumbersome.

In addition, damage is caused to the alignment film by several rubbing steps.

In addition, even if a worker rubs so as to be symmetrical correctly up, down, left, and right, the rubbing angles of the top, bottom, left, and right sides are difficult to be exactly symmetrical after rubbing.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of forming multiple domains without a separate rubbing process.

1A to 1C are diagrams for explaining a conventional double domain forming method.

2 is a cross-sectional view of a liquid crystal display device according to the present invention.

3 is a cross-sectional view showing a phase correction plate according to the present invention.

4 is a graph showing the transmittance according to the viewing angle.

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

10-lower substrate 12-pixel electrode

14a-first slope 14b-second slope

16,26-alignment layer 18,32-polarizer

20-Top Board 22-Color Filter

24 Common electrode 30 Liquid crystal layer

34-phase correction plate

In order to achieve the above object of the present invention, according to one aspect of the present invention, the liquid crystal layer comprising a plurality of liquid crystal molecules interposed between the upper and lower substrates, the unit cell is limited, and interposed between the upper and lower substrates, A first inclination formed on each of the upper unit cells in the lower substrate, the first inclination forming a first angle with the surface of the substrate, formed in each unit cell on the lower substrate, and spaced apart from the first inclination by a predetermined distance; And a second slope arranged in a symmetrical form with the first slope.

In addition, the present invention is a liquid crystal layer comprising a plurality of liquid crystal molecules interposed between the upper and lower substrates, the upper and lower substrates are limited to each other, the upper and lower substrates, a pixel electrode formed for each unit cell on the surface of the lower substrate, A first inclination formed in each unit cell above the pixel electrode, the first inclination forming a first angle with the substrate surface, and formed in each unit cell in the upper portion of the pixel electrode, and spaced apart from the first inclination by a predetermined distance; A second slope disposed in a symmetrical form with the first slope, a common electrode disposed on an inner surface of the upper substrate, and forming an electric field together with the pixel electrode, and liquid crystal molecules disposed outside the upper substrate. The liquid crystal molecules in the liquid crystal layer include a phase correction plate, and the hypotenuse of the inclined object and the long axis of the liquid crystal molecules are orthogonal at the portion where the inclined object is disposed before the electric field is formed. In the locked portion, the long axis of the liquid crystal molecules is arranged to be orthogonal to the surface of the substrate, and the liquid crystal molecules in the phase correction plate are aligned with the long axis of the liquid crystal molecules in the corresponding liquid crystal layer before the electric field is formed. It is characterized in that the short axis of is arranged to be parallel to each other.

According to the present invention, the inclined structure having a symmetrical shape in the unit cell is disposed at a predetermined distance, thereby forming a triple domain in the unit cell.

Accordingly, triple domains can be formed without a separate rubbing process, and accurate symmetry can be achieved by using a symmetrical inclined structure.

(Example)

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

2 is a cross-sectional view of a liquid crystal display device according to the present invention, FIG. 3 is a cross-sectional view showing a phase correction plate according to the present invention, and FIG. 4 is a graph showing transmittance according to a viewing angle.

2 is a cross-sectional view of a vertical alignment mode liquid crystal display according to the present invention. This figure shows only a cross section of one unit cell in the vertical alignment mode liquid crystal display device.

Referring to FIG. 2, the lower substrate 10 and the upper substrates 10 and 20 are disposed to face each other with the liquid crystal layer 30 interposed therebetween. In this case, the liquid crystal layer 30 is composed of liquid crystal molecules having negative dielectric anisotropy.

The pixel electrode 12 is disposed on the inner side surface of the lower substrate 10. Above the pixel electrode 12, the first slope 14a forming the first angle θ1 with the surface of the pixel electrode 12, and the normal axis of the surface of the first slope 14a and the pixel electrode 12. A second inclined member 14b disposed symmetrically with respect to (a) and spaced apart from the first inclined member 14a by a predetermined distance x is formed. The first slope 14a and the second slope 14b preferably have the same size and the same shape, for example, formed in a right triangle shape.

In this case, the distance x between the first inclined member 14a and the second inclined member 14b may be, for example, about one third of the long width or short width of the unit cell. The bottom sides of the two slopes 14a and 14b may also be formed to about one third of the long width and short width X of the unit cell.

A first vertical alignment layer 16 is formed on the hypotenuse surface of the first inclined member 14a and the second inclined member 14b and the upper surface of the pixel electrode 12.

The color filter 22 is disposed on an inner surface of the upper substrate 20 facing the lower substrate 10, and the common electrode 24 forming an electric field together with the pixel electrode 12 on the surface of the color filter 22. The second vertical alignment layer 26 is formed on the surface of the common electrode 24.

The first polarizing plate 18 for polarizing the light incident from the bottom surface of the lower substrate 10 is disposed on the outer surface of the lower substrate 10, and the light passing through the liquid crystal layer 30 on the outer surface of the upper substrate 20. The second polarizing plate 32 for selectively transmitting and blocking the light is disposed.

Here, a phase correction plate 34 is included between the second polarizing plate 32 and the upper substrate 20 to compensate for the refractive anisotropy of the vertically aligned liquid crystal molecules in the dark to obtain a complete dark screen.

At this time, the phase correction plate 34 is composed of liquid crystal molecules 34a having negative refractive index anisotropy, and the liquid crystal molecules 34a in the phase correction plate 34 are as shown in FIG. 3. In the part where 14b is not disposed, the long axis of the liquid crystal molecules 34a and the surface of the substrate 10 are arranged in parallel, and in the part where the inclined objects 14a and 14b are disposed, the long axis of the liquid crystal molecules 34a is a slope ( And parallel to the hypotenuse of 14a, 14b).

The liquid crystal display of the vertical alignment mode having such a configuration operates as follows.

When no electric field is applied, the liquid crystal molecules 30a are arranged such that their long axes are perpendicular to the surface of the substrate resulting from the influence of the vertical alignment layers 16 and 26 formed on the inner surfaces of the lower substrates 10 and 20. At this time, the liquid crystal molecules on the inclined objects 14a and 14b are arranged to form a normal with the hypotenuse of the inclined objects 14a and 14b, thereby naturally forming a triple domain.

Here, the liquid crystal molecules 34a of the phase correction plate 34 are arranged such that their short axis and the long axis of the liquid crystal molecules 30a in the liquid crystal layer 30 are parallel, so that refractive index anisotropy is compensated. Thus, a complete dark screen can be obtained.

Further, when an electric field is formed between the pixel electrode 12 and the common electrode 24, the liquid crystal molecules 30a are twisted so that their electric fields and their short axes are parallel. At this time, the arrangement of the first and second inclined objects (14a, 14b), the electric field also perpendicular to the surface of the lower substrate 10, the electric field orthogonal to the hypotenuse of the first inclined object (14a), and 2 An electric field perpendicular to the hypotenuse of the inclined object 14a is formed. Accordingly, the liquid crystal molecules are arranged in three domains within the unit pixel.

4 is a graph of transmittance of a viewing angle according to a spaced distance between the inclined objects 14a and 14b according to the present invention. According to the drawing, the space between the first inclined material 14a and the second inclined material 14b is shown. It can be seen that the greater the distance (x1x2x3), the greater the transmittance with respect to the viewing angle. Accordingly, in order to obtain high transmittance at a wide viewing angle, it is preferable to form a distance between the first inclined material 14a and the second inclined material 14b in a range capable of forming a triple domain.

In addition, in the present invention, the larger the dielectric constant value of the liquid crystal molecules, for example, in the range of the absolute value of the dielectric constant of about 5 to 15, the liquid crystal molecules are easily driven to obtain the maximum transmittance.

In addition, the present invention is not necessarily applied to the vertical alignment mode.

For example, the present invention may be applied to an IPS mode in which a pixel electrode and a common electrode are formed on one substrate.

As described in detail above, according to the present invention, by arranging the inclined structure of the symmetrical form in the unit cell spaced a predetermined distance, to form a triple domain in the unit cell.

Accordingly, triple domains can be formed without a separate rubbing process, and accurate symmetry can be achieved by using a symmetrical inclined structure.

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

Claims (9)

Upper and lower substrates disposed opposite to each other and in which unit cells are defined; A liquid crystal layer comprising several liquid crystal molecules interposed between the upper and lower substrates; A first slope formed on each of the upper unit cells in the lower substrate and forming a first angle with a surface of the substrate; And a second inclination formed in each unit cell above the lower substrate, spaced apart from the first inclination by a predetermined distance, and arranged in a symmetrical form with the first inclination. The liquid crystal display of claim 1, wherein the first inclined object and the second inclined object have the same shape. The liquid crystal display of claim 2, wherein the first and second inclined objects have a right triangle shape in cross section. Upper and lower substrates disposed opposite to each other and in which unit cells are defined; A liquid crystal layer comprising several liquid crystal molecules interposed between the upper and lower substrates; A pixel electrode formed in each unit cell on the lower substrate surface; A first slope formed at each unit cell above the pixel electrode, the first inclined portion having a first angle with a surface of the substrate; A second slope formed at each unit cell above the pixel electrode, spaced apart from the first slope by a predetermined distance, and disposed to be symmetrical with the first slope; A common electrode disposed on an inner surface of the upper substrate and forming an electric field together with the pixel electrode; And A phase correction plate disposed outside the upper substrate and including liquid crystal molecules; Before the electric field is formed, the liquid crystal molecules in the liquid crystal layer are arranged such that the oblique side of the slope and the long axis of the liquid crystal molecules are orthogonal to each other before the electric field is formed. Arranged to be orthogonal to And the liquid crystal molecules in the phase correction plate are arranged such that the major axis and the minor axis of the liquid crystal molecules in the corresponding liquid crystal layer are parallel to each other before the electric field is formed. The liquid crystal display of claim 4, wherein the first inclined object and the second inclined object have the same shape. 6. The liquid crystal display of claim 5, wherein the first and second inclined objects have a right triangle shape in cross section. The liquid crystal display device according to claim 4, wherein the liquid crystal molecules in the liquid crystal layer are formed of a material having negative dielectric anisotropy. The liquid crystal display device according to claim 4 or 7, wherein an absolute value of the dielectric constant of the liquid crystal molecules in the liquid crystal layer is about 5 to about 15. The liquid crystal display device according to claim 4, wherein the liquid crystal molecules constituting the phase correction plate have negative refractive index anisotropy.