KR100462380B1 - Rubbing method of vertical alignment mode liquid crystal display - Google Patents

Abstract

The present invention discloses a rubbing method of a vertical alignment mode liquid crystal display.

In the disclosed invention, in the vertical alignment film formed on the opposing surfaces of the upper and lower substrates, only the portions corresponding to the diagonal directions are rubbed so as to have a predetermined pretilt angle. Accordingly, since the liquid crystal molecules are tilted in a symmetrical direction, double domains are formed.

Description

Rubbing method of vertical alignment mode liquid crystal display

The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly, to a rubbing method for a liquid crystal display device in a vertical alignment mode.

In general, the liquid crystal display of the vertical alignment mode has an advantage of excellent response speed characteristics, and includes a vertical substrate disposed opposite to each other with the liquid crystal layer interposed therebetween, and a vertical alignment layer formed on the surface of the opposite surface of the vertical substrate.

In the liquid crystal display of the vertical alignment mode, the molecules in the liquid crystal layer are arranged perpendicular to the substrate before the electric field is formed, and when the electric field is formed, the liquid crystal molecules are arranged perpendicular to the electric field. At this time, when the electric field is formed, the liquid crystal molecules are all twisted in the same direction to be perpendicular to the electric field. Then, the viewing angle of the liquid crystal molecules is reduced by refractive index anisotropy.

In more detail, since the liquid crystal molecules are rod-shaped, the refractive indexes and dielectric constants of the major and minor axes 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 and short axes of the liquid crystal molecules.

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 layer by several rubbing steps, and a problem occurs in the pretilt angle of the liquid crystal molecules.

Accordingly, an object of the present invention is to provide a rubbing method for a vertical alignment mode liquid crystal display device capable of forming a double domain in a simple process.

In addition, another object of the present invention is to provide a rubbing method of a vertical alignment mode liquid crystal display device which can reduce the loss of the alignment layer.

In order to achieve the above object of the present invention, according to one aspect of the present invention, the rubbing method of the liquid crystal display device of the present invention, the upper and lower substrates each provided with a vertical alignment film in which the first and second domain predetermined region is defined Providing a; Rubbing the vertical alignment layer of the lower substrate corresponding to the first domain predetermined region in a first direction; Rubbing the vertical alignment layer of the upper substrate corresponding to the second domain predetermined region in a second direction; And after bonding the upper and lower substrates, characterized in that it comprises a step of injecting a liquid crystal.

In addition, according to another aspect of the invention, the step of providing a top and bottom substrate each having a vertical alignment film is defined the first and second domain predetermined region; Rubbing the vertical alignment layer of the upper substrate corresponding to the second domain predetermined region in a second direction; And rubbing the vertical alignment layer of the lower substrate corresponding to the first domain predetermined region in a first direction. After bonding the upper and lower substrates, characterized in that it comprises the step of injecting a liquid crystal.

According to the present invention, a double domain is formed by one rubbing process per substrate. Therefore, since the double domain is formed by rubbing twice for each substrate to form the double domain by single rubbing, the process is simplified, and the problem of alignment layer damage caused by multiple rubbing is solved.

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

2 and 3 are cross-sectional views illustrating a liquid crystal display device in a vertical alignment mode according to the present invention.

First, in the present invention, only the portions that are symmetrical with respect to the alignment layer are rubbed onto the lower substrate alignment layer and the upper substrate where the first and second domain regions are defined.

That is, as shown in FIG. 2, the lower substrate 11 having the alignment layer 12 is prepared. Although not shown in the drawing, the lower substrate 11 includes a liquid crystal driving electrode, and the alignment layer 12 is a vertical alignment layer. At this time, the first domain predetermined region X1 and the second domain predetermined region X2 are defined in the alignment layer 12.

Subsequently, the following process is performed to form a double domain region in which the liquid crystal molecules may be arranged in different directions in the alignment layer 12.

First, a photoresist film (not shown) is formed on the second domain region X2 so that only the first domain region X1 of the lower alignment layer 12 is exposed, and then the liquid crystal molecules have a predetermined pretilt angle. 1st rubbing process is performed in the rubbing direction R1 of FIG. 4A so that it may have (theta) and it may be tilt-oriented to the board | substrate side. At this time, the rubbing process is performed by rubbing the surface of the rubbing oriented film or by optical alignment using a mask. Then, the photoresist film is removed. In addition, in the rubbing process, it is preferable to make the rubbing strength stronger than before.

Thereafter, the same process is performed for the alignment layer of the upper substrate, but rubbing is performed only in the opposite direction, that is, the second domain predetermined region. That is, the upper substrate 21 provided with the alignment layer 22 is prepared. At this time, the upper substrate 21 is also provided with a driving electrode for driving the liquid crystal, and the alignment layer 22 is also a vertical alignment layer. The upper alignment layer 22 also has the first and second domains of the lower substrate 11. In order to correspond to the regions X1 and X2, the first and second domain predetermined regions Y1 and Y2 are defined. That is, the first domain region X1 of the lower alignment layer 12 corresponds to the first domain region Y1 of the upper alignment layer 22, and the first domain region X2 of the lower alignment layer 12 corresponds to the upper alignment layer ( 22 corresponds to the second domain region Y2.

In the upper alignment layer 22, unlike rubbing of the lower alignment layer 12, a photoresist layer (not shown) is formed on the first domain region Y1 so that the second domain region Y2 is exposed. . Thereafter, the exposed second domain predetermined region Y2 is formed in a direction crossing the rubbing direction R1 of the first domain predetermined region X1 of the lower alignment layer 12, that is, the R2 direction of FIG. 4B. 2 Carry out a rubbing process. Thereafter, the photoresist film is removed. The second rubbing process may also be accomplished by rubbing with a rubbing cloth, or may also be accomplished in a known light orientation manner. In addition, it is preferable that the strength of the second rubbing be stronger than the conventional one like the first rubbing.

The upper and lower substrates 21 and 11 are opposed to each other, and then the liquid crystal 30 is preferably injected therebetween.

Then, before the electric field is formed between the upper and lower substrates 11 and 21, the long axes of the liquid crystal molecules 30a in the liquid crystal 30 stand perpendicular to the substrate under the influence of the vertical alignment layers 12 and 22. At this time, the liquid crystal molecules 30a in the first domain predetermined region X1 subjected to the first rubbing in the lower vertical alignment layer 12 face the substrate by a predetermined pretilt angle θ by the first rubbing process. Is tilted. In addition, the liquid crystal molecules 30a in the second domain predetermined region Y2 rubbed in the upper vertical alignment layer 22 are also tilted toward the substrate by a predetermined pretilt angle θ by the second rubbing process. .

Therefore, when the left and right of the upper and lower substrates 21 and 11 are used as a reference, as shown in FIG. 2, the shapes are symmetrical to each other in a diagonal direction. In addition, the liquid crystal molecules 30a of the middle layer of the liquid crystal 30 are also tilted by a predetermined angle under the influence of the strongly rubbed lower and upper alignment layers 12 and 22. Accordingly, only one rubbing for each substrate 11 and 21 forms a double domain.

Then, as shown in FIG. 3, when an electric field is formed between the upper and lower substrates 11 and 21, an electric field perpendicular to the upper and lower substrates is formed, and the liquid crystal molecules 30a having negative dielectric anisotropy are twisted perpendicularly to the electric field. Lose. At this time, the liquid crystal molecules present on the surfaces of the alignment layers 12 and 21 maintain the previous unfielded state. The liquid crystal molecules 30a in the first domain predetermined regions X1 and Y1 are distorted to the right due to the first rubbing process, and the liquid crystal molecules 30a in the second domain predetermined regions X2 and Y2 are shifted to the right. It is arranged to be distorted to the left under the influence of the second rubbing process. Then, light leaks by the angle difference between the polarization axis of a polarizing plate (not shown), and a liquid crystal molecule.

As such, since the liquid crystal molecules are symmetrically arranged up and down diagonally, optical anisotropy of the liquid crystal molecules is compensated. That is, when looking at the screen in the portion Z1 of FIG. 3, the liquid crystal molecules on the upper substrate side show long axes, but the liquid crystal molecules on the lower substrate show short axes, thereby compensating for anisotropy of the liquid crystal molecules.

In addition, when looking at the screen from the Z2 portion of FIG. 3, the liquid crystal molecules appear to be arranged perpendicularly to the substrate on the upper and lower substrate surfaces, but the liquid crystal molecules are arranged with a predetermined tilt because the liquid crystal molecules present in the intermediate layer are arranged with a predetermined tilt. Anisotropy of 30a) is compensated.

In this embodiment, the lower alignment layer is first rubbed, and then the upper alignment layer is rubbed.

As described in detail above, according to the present invention, a double domain is formed by one rubbing process for each substrate.

Therefore, since the double domain is formed by rubbing twice for each substrate to form the double domain by single rubbing, the process is simplified, and the problem of alignment layer damage caused by multiple rubbing is solved.

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

1A to 1C are process drawings for explaining a rubbing method for forming a conventional double domain.

2 and 3 are cross-sectional views of a vertical alignment mode liquid crystal display device according to the present invention.

4A is a view showing an alignment direction of a lower alignment layer according to the present invention.

Figure 4b is a view showing the alignment direction of the upper alignment film according to the present invention.

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

11-bottom substrate 12-bottom vertical alignment layer

21-top substrate 22- top vertical alignment layer

30-Liquid Crystal Layer 30a-Liquid Crystal Molecules

Claims (5)

Providing a top and bottom substrate each having a vertical alignment layer defining first and second domain predetermined regions; Rubbing the vertical alignment layer of the lower substrate corresponding to the first domain predetermined region in a first direction; Rubbing the vertical alignment layer of the upper substrate corresponding to the second domain predetermined region in a second direction; And And then injecting a liquid crystal after the upper and lower substrates are bonded to each other. The rubbing method of claim 1, wherein the first direction and the second direction cross each other. The rubbing method of claim 1, wherein the rubbing step is performed by rubbing the alignment layer with a rubbing cloth or by a photo alignment method. The rubbing method of a vertical alignment mode liquid crystal display device according to claim 1, wherein the liquid crystal is a liquid crystal having a dielectric anisotropy being negative. Providing a top and bottom substrate each having a vertical alignment layer defining first and second domain predetermined regions; Rubbing the vertical alignment layer of the upper substrate corresponding to the second domain predetermined region in a second direction; And Rubbing the vertical alignment layer of the lower substrate corresponding to the first domain predetermined region in a first direction; And then injecting a liquid crystal after the upper and lower substrates are bonded to each other.

Images