KR100245052B1 - Liquid crystal display alignment layer and method of processing alignment - Google Patents

Abstract

The alignment method of the alignment layer of the liquid crystal display device according to the present invention comprises the steps of providing a substrate, applying a polymer film such as polyimide (PI) to the substrate, and rubbing the substrate to form a rubbing in which an alignment direction is formed. Completing an alignment layer, applying a photoalignment material of a polyvinyl cinnamate (PVCN) -based material or a polysiloxane cinnamate (PSCN) -based material to the rubbing alignment film, and curing the photoalignment material to the photoalignment film And forming a tilt direction by irradiating the optical alignment layer with light.

Description

Alignment film and alignment treatment method of liquid crystal display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to an alignment film and an alignment processing method of a liquid crystal display device in which the alignment force of the alignment film is enhanced and the process is simplified.

In general, the liquid crystal alignment film of TN (Twisted Nematic) -LCD, which is mainly used as a large-area, high-definition liquid crystal display device, is disposed inside the transparent electrode to directly contact the liquid crystal molecules. At the interface of the liquid crystal alignment film and the liquid crystal molecules, the alignment of the liquid crystal molecules is expressed by the uniaxial alignment of the liquid crystal molecules by the uniaxial stretching method of the liquid crystal alignment film and the angle (pretilted angle) between the liquid crystal alignment film and the liquid crystal molecules. It is possible.

The conventional rubbing method used as a means for performing a uniaxial stretching process on a liquid crystal aligning film is a simple method of rubbing a substrate coated with a polymer with a cloth, and is a method widely used industrially because of its large area and high speed processing.

1 is a view illustrating a method of rubbing orientation of a substrate using a conventional roller. The conventional rubbing method first provides a substrate 1 to which a color filter, TFT, or the like is attached, and then forms an alignment film 10 by applying a polymer film such as PI or polyvinyl alcohol (PVA) to the substrate. The roller 20 winds and attaches the oriented cloth 23 made of fiber, such as nylon and polyester, to the cylindrical roll 21. As shown in FIG. A method of mechanically rubbing the substrate surface in an arbitrary direction by placing the substrate 1 in a substrate transfer device (not shown) to move in the substrate advancing direction 40 and rotating the roller 20. to be.

When the substrate is rubbed by the above-described method, the liquid crystal molecules are oriented in the stretching direction of the PI chain by Van der Waals force between the liquid crystal alignment layer and the liquid crystal molecules, and the excluded volume effect As a result, the liquid crystal molecules are arranged in accordance with the PI chain changed on the liquid crystal alignment film so as to minimize its exclusion volume. From this, the liquid crystal molecules exhibit orientation along the rubbing direction, and the pretilt angle of the liquid crystal molecules is generated in the rubbing direction.

In addition, when the substrate is rubbed by the above method, uniform micro grooves are formed in the alignment layer. The microgrooves arrange liquid crystal molecules in parallel with the microgrooves so as to minimize the elastic deformation energy. However, in the above rubbing process, since the shape of the microgrooves formed in the alignment layer varies according to the frictional strength of the alignment cloth and the alignment layer, the arrangement of liquid crystal molecules becomes nonuniform, resulting in phase distortion and light scattering. This phase distortion and light scattering can have a significant impact on the performance of the LCD.

Therefore, in this rubbing method, the value of the pretilt angle fluctuates slightly depending on the film forming conditions or the rubbing conditions, and therefore sufficient consideration is required in the realization thereof. In addition, since the polymer film is rubbed with an alignment cloth, there is a problem of generation of fine dust or generation of electrostatic discharge (ESD) by high pressure static electricity. Dust is a major obstacle in the process of forming a thin film transistor (TFT) by repeating a high definition pixel electrode, film formation, exposure and etching. Local discharge may cause damage to the alignment film itself, or cause disconnection or electrostatic destruction of the transparent electrode or TFT. In addition, the TFT alignment film is also required to have a property of having a high voltage storage rate, which can maintain charge charge for a long time.

In addition, in the operation method, there is a problem in that an orientation nonuniformity due to a step generated when a color filter or a TFT substrate is formed, and an orientation scratch occurs to generate an unaligned portion.

Particularly, in TN-LCD, light transmittance is distributed symmetrically with respect to the viewing angle in the left and right directions, but light transmittance is distributed asymmetrically with respect to the up and down directions. There is also a narrowing problem.

In order to compensate for the anisotropy of such liquid crystals, multi-domain TN-LCDs such as two domain TN-LCDs and domain-divided TN-LCDs have been proposed. The manufacturing process of such a multi-domain TN-LCD can be characterized by photolithography and rubbing. In other words, two photolithography and rubbing processes are required in order to form domains having opposite or different alignment directions in each pixel, and a four-domain TN-LCD further developed.

However, the two-domain TN-LCD has only a vertical viewing angle of ± 25 ° with a contrast ratio higher than 10, and the four-domain TN-LCD has only a vertical viewing angle of only ± 40 °. And crucially, there are disadvantages in that the manufacturing process is complicated. In addition, problems such as reliability of the liquid crystal cell itself and instability of the tilt angle still remain.

The alignment treatment method proposed to solve the problems of the rubbing method as described above is a photo-alignment treatment method, and the alignment of liquid crystal molecules is caused by photopolymerization of the alignment film by irradiation of light. The conventional photo-alignment method is to irradiate ultraviolet rays twice to determine the orientation direction.

In this photo-alignment method, the pretilt direction of the alignment film surface is determined by irradiating the alignment film vertically and obliquely using an optical alignment film of PVCN polymer as the alignment film. At this time, the irradiation angles of the alignment film and the ultraviolet light are changed to determine the pretilt angle of the alignment film surface.

However, this photo-alignment method is characterized by weak anisotropy in the photo-alignment film and consequently weak anchoring energy, disclination due to liquid crystal orientation unevenness and action of the liquid crystal, and a flow appearing during liquid crystal injection. The traces remain a challenge. In addition, four irradiations are essential for forming one domain by performing two irradiations on one substrate (upper and lower substrates). Therefore, the number of irradiations for one pixel increases in order to form a multi-domain structure. This complicated problem arises.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide an alignment film and an alignment treatment method for a liquid crystal display device which strengthen the alignment force of the alignment film and simplify the process.

In order to achieve the above object, the alignment treatment method of the alignment film of the liquid crystal display device according to the present invention comprises the steps of providing a substrate, applying a polymer film such as PI to the substrate, and rubbing the substrate Comprising: forming a rubbing alignment film having an orientation direction, applying a photoalignment material of PVCN-based material or PSCN-based material on the rubbing alignment film, and curing the optical alignment material to form a photoalignment film; And determining the tilt direction by irradiating the optical alignment layer with light.

In addition, another alignment treatment method of the alignment film of the liquid crystal display device according to the present invention comprises the steps of providing a substrate, applying a polymer film such as PI to the substrate, and stamping the substrate to form an orientation stamping Comprising the step of completing the alignment layer, the step of applying a photo-alignment material of PVCN-based material or PSCN-based material on the stamping alignment film, the step of curing the photo-alignment material to form a photo-alignment film, the photo-alignment film And irradiating light to determine the tilt direction.

1 is a cross-sectional view showing a conventional rubbing orientation method.

Fig. 2 is a diagram showing a first embodiment of the present invention.

3 shows a second embodiment of the present invention;

Explanation of symbols on the main parts of the drawings

1: substrate 3: rubbing alignment film

5, 9: photo-alignment layer 7: stamping alignment layer

10: alignment film 20: roller

21: roll 23: alignment cloth

40: traveling direction of the substrate 70: rotation direction of the roller

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the alignment film and the alignment treatment method of the liquid crystal display device of the present invention.

2 is a diagram showing a first embodiment of the present invention. As shown in the same drawing, the alignment treatment method of the alignment film of the present invention comprises the steps of providing a substrate (1) to which a color filter or TFT is attached, and applying a polymer film such as PI to the substrate, Completing the rubbing alignment layer 3 by rubbing the substrate to form an alignment direction, applying a UV alignment substance to the rubbing alignment layer, and curing the UV alignment substance to form an optical alignment layer 5 And forming a tilt direction by irradiating the optical alignment layer with light.

In forming the rubbing alignment film 3 of the first embodiment, the rubbing method uses a conventional method, and by the rubbing method described above, microgrooves are formed in the polymer film coated on the substrate, and the rubbing alignment film exhibits anisotropy because of this microgroove. In addition, the UV alignment material may be a PVCN material or a PSCN material. In the curing of the material, an appropriate temperature is applied for a suitable time depending on the nature of the UV alignment material used.

By curing the photo-alignment film 5, anisotropy is induced in the same direction as the above-mentioned rubbing alignment film under the influence of the already formed rubbing alignment film. In addition, polarized or unpolarized light is irradiated to break the degenerate pretilt degeneracy of the cured UV alignment material, thereby completing the photo alignment layer.

In the alignment processing method of the alignment film of the liquid crystal display element of this invention, 2nd Example is shown in FIG. The second embodiment is the same as the first embodiment except for forming a stamping alignment film 7 which is stamped instead of a rubbing alignment film using a rubbing method.

In detail, the steps of providing a substrate 1 to which a color filter or TFT is attached, coating a polymer film such as PI to the substrate, and stamping the substrate to form an orientation direction are stamped. Completing the alignment layer (7), applying a UV alignment material to the stamping alignment layer, curing the UV alignment material (curing) to form a photo alignment layer (9), the photo alignment layer And irradiating light to determine the tilt direction.

As in the first embodiment described above, in forming the stamping alignment film 7, the stamping alignment film exhibits anisotropy by stamping the polymer film applied to the substrate. The UV alignment material may be a PVCN material or a PSCN material. In the curing of the material, a proper temperature is applied for a proper time depending on the nature of the UV alignment material used.

By curing the photo-alignment film 9, anisotropy is induced in the same direction as the above-mentioned stamping alignment film under the influence of the already formed stamping alignment film. In addition, polarized or unpolarized light is irradiated to break the degenerate pretilt of the cured UV alignment material, thereby completing the photo alignment layer.

As described above, the present invention eliminates problems such as generation of static electricity and damage of TFT when only the rubbing alignment layer is formed, and improves the anisotropy of the photoalignment layer by reducing defects such as weak alignment when forming only the alignment layer. Improve.

In addition, when the multi-domain is implemented to achieve stability of the tilt angle, it also increases the reliability of the liquid crystal cell itself.

In addition, by shortening the process of irradiating the photo-alignment film, it is possible to simplify the process and reduce the cost by forming the multi-domain.

Claims (16)

Substrate, A rubbing alignment film composed of a polymer film on the substrate and rubbing to form an orientation direction; An alignment film of a liquid crystal display device comprising a photo alignment material on the rubbing alignment film, wherein the photo alignment material is cured and irradiated with light to form a tilt direction. The alignment film of a liquid crystal display device according to claim 1, wherein the polymer film constituting the rubbing alignment film is made of polyimide (PI). The alignment layer of the liquid crystal display device according to claim 1, wherein the optical alignment material constituting the optical alignment layer is selected from a group consisting of a polyvinyl cinnamate (PVCN) -based material or a polysiloxane cinnamate (PSCN) -based material. The alignment film of a liquid crystal display device according to claim 1, wherein the light used to irradiate the optical alignment film is polarized light or unpolarized light. Substrate, A stamping alignment film composed of a polymer film on the substrate and stamped to form an orientation direction, An alignment film of a liquid crystal display device comprising a photo alignment material on the stamping alignment film, wherein the photo alignment material is cured and irradiated with light to determine a tilt direction. 6. The alignment film of a liquid crystal display device according to claim 5, wherein the polymer film constituting the stamping alignment film is made of polyimide (PI). The alignment layer of the liquid crystal display device according to claim 5, wherein the optical alignment material constituting the optical alignment layer is selected from a group consisting of a polyvinyl cinnamate (PVCN) -based material or a polysiloxane cinnamate (PSCN) -based material. 6. The alignment film of a liquid crystal display device according to claim 5, wherein the light used for irradiating the optical alignment film is polarized light or unpolarized light. Providing a substrate, Applying a polymer film to the substrate; Rubbing the substrate to complete a rubbing alignment film in which an alignment direction is formed; Applying an optical alignment material on the rubbing alignment layer; Curing the photo-alignment material to form a photo-alignment layer; And irradiating the optical alignment layer with light to determine the tilt direction. The method of claim 9, wherein the polymer film is made of polyimide (PI). The method of claim 9, wherein the optical alignment material is selected from a group consisting of a polyvinyl cinnamate (PVCN) -based material and a polysiloxane cinnamate (PSCN) -based material. 10. The liquid crystal display element alignment processing method according to claim 9, wherein the light used for light irradiation is polarized or unpolarized light. Providing a substrate, Applying a polymer film to the substrate; Stamping the substrate to complete a stamping alignment film having an orientation direction formed thereon; Coating an optical alignment material on the stamping alignment layer; Curing the photo-alignment material to form a photo-alignment layer; And irradiating the optical alignment layer with light to determine the tilt direction. The liquid crystal display device according to claim 13, wherein the polymer film is made of polyimide (PI). The method of claim 13, wherein the photo-alignment material is selected from a group consisting of a polyvinyl cinnamate (PVCN) -based material and a polysiloxane cinnamate (PSCN) -based material. The liquid crystal display element alignment processing method according to claim 13, wherein the light used for light irradiation is polarized or unpolarized light.

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