KR19990000032A - Method of orienting liquid crystal cell - Google Patents

Abstract

According to the method of orienting a liquid crystal cell of the present invention, the azimuth angle of the light irradiated to the liquid crystal cell forms an angle of? With the extending direction of the light shielding layer for blocking the misorientation region occurring in the domain, . As a result, the width of the light shielding layer blocking the misoriented region is reduced, and the aperture ratio characteristic of the liquid crystal cell is greatly improved.

Description

Method of orienting liquid crystal cell

The present invention relates to a liquid crystal cell, and more particularly, to a method of aligning a liquid crystal cell in which an aperture ratio is improved by inclining an irradiation angle of light with a light shielding layer in a light alignment treatment.

TN (Twisted Nematic) LCD, which is mainly used as a large-area, high-quality liquid crystal display device, has a problem in viewing angle characteristics. In order to solve such a problem, a multi-domain (multi-domain) multi-domain such as a TDDN (Two Domain TN, IDRC 91 DIGEST, P.68 (1991)) LCD, DDTN (Domain Divided TN, SID 92 DIGEST, -domain TNLCD is proposed. The manufacturing process of such multi-domain TNLCDs can be characterized by photoliphography and rubbing. That is, two photo printing processes and a rubbing process are required to form domains having opposite orientation directions or different orientation directions within each pixel.

By the rubbing process, uniform microgrooves are formed in the alignment layer. The fine grooves align liquid crystal molecules parallel to the fine grooves so as to minimize the elastic disformation energy. However, in the above-described rubbing process, the shape of fine grooves formed in the alignment film is changed according to the rubbing strength between the rubbing film and the orientation film, so that the arrangement of the liquid crystal molecules becomes uneven, causing phase distortion and light scattering This phase distortion and light scattering can have a significant impact on the performance of the LCD. Particularly, dust and static electricity generated in the substrate during the rubbing process cause the substrate to be damaged, which is a major factor for lowering the yield of the LCD.

In order to solve the above-described problem of rubbing, the proposed alignment treatment method is a photo alignment treatment method, and alignment of liquid crystal molecules is caused by photopolymerization of the alignment layer by irradiation of light. The aforementioned photo-alignment method is disclosed in Korean Patent Application Nos. 96-44455, 96-52665, 97-4280 filed by SID 95 DIGEST, page 877 (Kobayashi et al), the present applicant.

Figs. 1 to 4 each show the above-described photo alignment method. Fig. 1 shows a photo-alignment method proposed by Kobayashi, and Figs. 2 to 4 show photo-alignment methods filed by the present applicant. The difference between the two optical alignment methods described above is that the optical alignment method of Kobayashi determines the alignment direction by irradiating ultraviolet rays twice, while the present applicant's optical alignment method determines the alignment direction by obliquely irradiating ultraviolet light only once.

Hereinafter, the two alignment methods will be described in detail with reference to the drawings.

1 is a photoalignment method proposed by Kobayashi et al. In this optical alignment method, a pretilt direction of the surface of the alignment layer is determined by vertically and obliquely irradiating ultraviolet rays on the alignment layer using a photo alignment layer of polyvinylcinnamate (PVCN) polymer as an alignment layer. That is, as shown in Fig. 1 (a), if the alignment film is vertically irradiated with ultraviolet rays whose polarization direction is parallel to the y-axis, the side chains of the y-axis of the polymer are dimerized to form only the side chains of the xz plane It remains. At this time, the arrows in the dotted line in Fig. 1 (a) indicate the direction of the polymerisation reaction and the arrows in the solid line indicate the direction of the side chains remaining in the ultraviolet irradiation. As shown in the figure, the optical constant of the x-z plane shows anisotropy by vertical irradiation of the ultraviolet ray, but the optical constant of the y-z plane is directed to the z-axis. Then, as shown in Fig. 1 (b), when the substrate is irradiated with the ultraviolet rays whose polarization direction is in the xz plane, the side chains in the direction coinciding with the above- Only. The remaining side chains interact with the liquid crystal molecules to give alignment directions to the liquid crystal molecules. At this time, the pretilt angle on the surface of the alignment film is determined by changing the irradiation angle of the alignment film and ultraviolet ray. For example, when the angle at which the ultraviolet rays are irradiated on the surface of the alignment film in the irradiation of the second ultraviolet ray is changed by 30 °, 45 °, and 60 °, the generated pretilt angles are about 0.15 °, 0.26 °, and 0.30 °.

FIGS. 2 to 4 are views showing the photo-alignment method applied by the present applicant, wherein a photo-reactive material such as a polysiloxane based material or PVCN-F (polyvinylfluorocinnamate) is used as the alignment layer 10 . The following formulas represent polysiloxane-based materials and PVCN-F, respectively: (Formula 1) represents PVCN-F, and Formula 2 and Formula 3 are examples of the polysiloxane substance, polysiloxane cinnamate I ) And polysiloxane cinnamate II.

[Chemical Formula 1]

n = 300-6000

(2)

(3)

Z = OH, CH ₃ or CH ₃ OH and the mixture,

m = 10 to 100,

l = 1 to 11,

K = 0 or 1,

L = 0 or 1,

(N = 1 to 10), X ₁ , X ₂ , Y = H, F, Cl, CN, CF ₃ , C _n H _{2n + 1} or OC _n H _{2n +}

First, FIG. 2 shows the alignment treatment process of the alignment film 10 by irradiation with polarized ultraviolet rays once. As shown in the figure, when the polarized ultraviolet light is obliquely irradiated onto the alignment film 10, the actual polarization direction in three dimensions is as indicated by a dotted line in the drawing. As the ultraviolet light is irradiated, the side chains of the polymer parallel to the polarization direction of the ultraviolet ray are subjected to the coupling reaction (solid arrows), leaving only side chains (dotted arrows) substantially parallel to the traveling direction of the ultraviolet rays. Accordingly, the side chains of the polymer and the liquid crystal molecules react with each other and the liquid crystal molecules are arranged in a certain direction, that is, in the traveling direction of ultraviolet rays. At this time,? Is the pretilt angle of the side chain relative to the surface of the alignment film 10, and becomes the tilt angle between the liquid crystal molecules and the alignment film 10 when the alignment film 10 reacts with the liquid crystal molecules.

Fig. 3 shows a photo-alignment treatment process when the unpolarized ultraviolet ray is irradiated once on the alignment film 10. Fig. 3 (b), unpolarized ultraviolet rays having electric fields in all directions except for the direction of the incident ultraviolet rays are applied to the alignment film 10 made of the advertising molecules in the isotropic state of Fig. 3 (a) (10) at an angle. Advertising molecules having side chains in all directions parallel to the electric field form cycloaddition due to the photoreaction so that the anisotropy in the direction parallel to the electric field disappears. However, since there is no electric field in the direction of the incident ultraviolet ray, The anisotropy of the advertising molecule having the side chain in the traveling direction remains. Accordingly, the liquid crystal molecules are arranged along the direction of the anisotropy of the advertising molecule.

Fig. 4 is a view showing a photo-alignment treatment process by irradiation of ultraviolet ray partially polarized once. First, the alignment film 10 coated on the substrate 1 is irradiated with partially polarized ultraviolet rays having a polarization degree of 0.67. At this time, if the direction in which the ultraviolet light is irradiated is obliquely irradiated at a certain angle (?) With the normal line of the substrate 1, the P wave component (⊙) of the partially polarized ultraviolet ray is directed in the direction perpendicular to the polarization direction of the P wave The direction of the alignment axis of the liquid crystal is selected and the S wave component (?) Is incident in the oblique direction, so that the pretilt angular direction in the direction in which the ultraviolet ray is incident is selected.

Fig. 5 is a diagram showing the irradiation direction of light at the time of light irradiation in a rectangular coordinate system. As shown in the figure, the light is irradiated to the alignment film 10 at an angle of polar angle &thetas; and an azimuth angle ϕ = 90 DEG. At this time, although not shown in the drawing, the alignment film 10 lies in the xy plane of the coordinate system described above.

In general, when a multi-domain is implemented in a photo-alignment, a mask for blocking another region is required in order to align a certain region. 6 is a diagram showing a problem that arises when a certain region is photo-aligned using a mask. A gap is generated between the alignment film 10 and the mask 15 when aligning the alignment film 10 and the mask 15 as shown in Fig. This gap is caused by an error in alignment between the alignment film 10 and the mask 15, a limitation in the accuracy of the alignment film 10 and the surface of the mask 15, and the like. 6 (b), the light is irradiated to the inside of the mask 15 to about .DELTA.x, and an misorientation region is generated in the alignment film 10. Practically, as shown in FIG. 6 (a), the alignment film 10 is irradiated with light on both sides of the mask 15, so that a misorientation region of 2 DELTA x occurs.

7 is a view showing a multi-domain liquid crystal cell composed of four domains whose orientation directions are determined by a photo alignment method. In the figure, the light indicated by an arrow indicates a projection onto the surface of an alignment film, in which case the azimuth angle of light is φ = 90 °. Further, the liquid crystal cell is formed so that each side is parallel to the x-axis and the y-axis in the x-y plane. Therefore, light is irradiated to the side of the liquid crystal cell such that its projection is vertical. In order to determine the alignment direction in each domain of the 4-domain liquid crystal cell, light must be irradiated to each domain in different directions using a mask. Therefore, when irradiating light to each of the domains, a misorientation area of? X is generated due to the gap between the alignment film and the mask as shown in Fig. 7 (a). In the figure, a solid line indicates a desired domain region, and a dotted line indicates an actual domain region generated by light irradiation. The two domains adjacent to each other in the 4-domain liquid crystal cell cause a 2? X misorientation region at the boundary between the domains. Since the misorientation region occurring at the boundary between these domains is a serious problem for the image quality of the liquid crystal display device, this region must be blocked. 7 (b) shows a black matrix 17 which is a light-shielding layer formed on the liquid crystal cell for blocking the above-mentioned area. At this time, in order to completely cover the misoriented area, the width of the black matrix 17 must be 2Δx + α to completely cover the error area, and thus the aperture ratio characteristic of the liquid crystal display device is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide a method of orienting a liquid crystal cell in which the aperture ratio is further improved by reducing the width of a black matrix between domains by obliquely irradiating light with respect to the extending direction of the black matrix do.

According to an aspect of the present invention, there is provided a method of aligning a liquid crystal cell, comprising: forming a light shielding layer at a boundary between domains of an alignment film divided into a plurality of domains; And irradiating the light with an azimuth angle? With respect to the light shielding layer.

In the first embodiment of the present invention, the liquid crystal cell is formed in a quadrangle on the x-y plane and each side is parallel to the x-axis and the y-axis and the light-shielding layer is also arranged in parallel with the x- and y-axes. Since the light is irradiated at angles of the polar angle &thetas; and the azimuth angle ϕ to reduce the misoriented regions generated in the domains, the width of the black matrix for blocking the misoriented regions is also reduced.

In the second embodiment of the present invention, the liquid crystal cell is formed in a diamond shape in the xy plane, and the angle forms an angle between the x-axis and phi, and the light shielding layer has the x- and y- Lt; / RTI > The light is irradiated to the liquid crystal cell at an angle of the polar angle &thetas; and an azimuthal angle [phi] = 90 DEG.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a photo-alignment method by light irradiation twice. Fig.

Fig. 2 is a view showing a photo-alignment method by a single oblique irradiation of polarized light. Fig.

Fig. 3 is a view showing a photo-alignment method by a single oblique irradiation of unpolarized light; Fig.

4 is a view showing a photo-alignment method by one-time oblique irradiation of partially polarized light.

5 is a view showing a conventional irradiation direction of light at the time of light focusing.

6A is a view showing a misorientation region generated by a gap between an alignment film and a mask at the time of conventional light distribution.

Fig. 6B is an enlarged view of a portion A in Fig. 6A. Fig.

7 is a view showing a conventional photo-aligned 4-domain liquid crystal cell;

8 is a view showing the irradiation direction of light according to the present invention.

Figure 9 shows a 4-domain liquid crystal cell that has been subjected to an orientation treatment according to the present invention.

10 is a view showing a first embodiment of the present invention.

11 is a view showing a second embodiment of the present invention.

Hereinafter, a method of processing an alignment treatment of a liquid crystal cell of the present invention will be described in detail with reference to the accompanying drawings.

As described in the related art, there are various methods for the photo alignment treatment. However, in the present invention, only the photo alignment treatment by irradiation of the polarized ultraviolet ray will be described for convenience of explanation. However, the general optical alignment treatment, particularly all the optical alignment methods by the inclined irradiation of light, will also fall within the scope of the present invention.

8 is a view showing the irradiation direction of light according to the present invention. As shown in the figure, the light is irradiated on the alignment film at an angle of a polar angle? And an azimuth angle?. Further, although not shown in the figure, the liquid crystal cell is formed on the x-y plane. Accordingly, the azimuth angle? Means projection onto the xy plane of light, that is, projection to the liquid crystal cell.

FIG. 9 is a view showing a 4-domain liquid crystal cell that has been subjected to alignment treatment by irradiating the light. As shown in Fig. 9 (a), the liquid crystal cell is formed on the x-y plane with a rectangle whose sides are parallel to the x-axis and the y-axis. When light is irradiated at an angle of the polar angle &thetas; and the azimuth angle & phi in a state where another domain of the domain is blocked by the mask for orienting the first domain (I), a gap ), An misorientation area of? X sin? Is generated. At this time, considering the influence of the adjacent domains, an error region of 2 DELTA x sin ϕ occurs at the boundaries of each domain, which is very small compared with the misorientation region of 2 DELTA x that occurs in the conventional optical alignment method. Therefore, in the case of forming the black matrix 17 as shown in Fig. 6 (b) for blocking the above-mentioned misorientation region, when the width of the black matrix 17 is set to 2? Xsin? +? , The aperture ratio characteristic is greatly improved.

Although the boundary of the liquid crystal cell is parallel to the reference line and the light is irradiated at an angle of phi with respect to the reference line, the boundary surface of the liquid crystal cell is formed at an angle of phi with respect to the reference line, The same effect can be obtained.

Hereinafter, the method of controlling the alignment direction of the multi-domain liquid crystal cell according to the present invention will be described in detail for each embodiment.

Fig. 10 shows a first embodiment according to the present invention. In this embodiment, a 4-domain liquid crystal cell will be described. 10 (a), a black matrix 17 made of Cr or CrOx or a black resin is formed on the boundary surface of each domain on the first substrate (upper plate), and a polysiloxane-based material or PVCN-F And then light is irradiated in a state where the remaining domains except for the first domain are blocked with the mask 15. Light is irradiated at an angle of the polar angle &thetas; and azimuthal angle ϕ, and the liquid crystal cell is also formed on the x-y plane so that each side is parallel to the x- and y-axes. At this time, the polar angle? = 0 to 60 degrees, and the azimuth angle? = 0 to 90 degrees. The extending direction of the black matrix 17 is also arranged parallel to the x-axis and the y-axis. By the irradiation of the light described above, the alignment direction is determined in the first domain toward the irradiation direction of the light. Thereafter, as shown in Figs. 10 (b) to 10 (d), light is irradiated while changing the irradiation direction at an azimuth angle? While changing the mask 15 having another opening or rotating the mask And determines the orientation direction in each of the second to fourth domains. Then, the above process is repeated to determine the alignment direction in each domain of the second substrate (lower plate) as shown in Figs. 10 (e) to 10 (h).

Then, the first substrate and the second substrate are attached to each other, and liquid crystal is injected between both substrates to complete the liquid crystal cell. 10 (i) is a view showing the liquid crystal cell completed as described above. Arrows in solid lines in each domain indicate the alignment direction of the first substrate, arrows in the dotted line indicate the alignment direction of the second substrate, and points between the arrows indicate the main viewing angle direction in each domain. Since the directions of the main viewing angles of the adjacent domains, particularly the directions of the main viewing angles of the vertically adjacent domains are opposite to each other, the viewing angle characteristics in the up and down directions, which are particularly problematic in the viewing angle characteristics of the liquid crystal display device, are greatly improved.

11 is a view showing a second embodiment of the present invention. The most significant feature of this embodiment is that the shape of the liquid crystal cell is rhombic, and one side forms an angle between the x-axis and phi. The extending direction of the black matrix 17 also forms an angle of? With the x-axis and the y-axis, and the direction of light irradiation is the polar angle? And the azimuth angle? = 90 degrees. As a result, the irradiation angle of the projection of the light to the sides of the liquid crystal cell becomes?, And the same result as in the first embodiment is obtained. The orientation method of each domain of the liquid crystal cell is the same as the first embodiment. First, the black matrix 17 is formed at the boundary of each domain of the first substrate (upper plate), and then the orientation is determined for each domain as shown in Figs. 11 (a) to 11 (d) 11 (e) to 11 (h), the orientation direction is determined for each domain of the second substrate (lower plate). The resultant liquid crystal cell is shown in Fig. 11 (i). As shown in the figure, the main viewing angle direction of each domain of the liquid crystal cell is also opposite to the main viewing angle direction of the adjacent domain, thereby improving viewing angle characteristics.

As described above, by irradiating the azimuth angle of the light irradiated on the liquid crystal cell with the angle of the extending direction of the light shielding layer and the angle?, The light shielding layer for reducing the misorientation region generated in the domain and blocking the misoriented region Thereby reducing the width. Therefore, the aperture ratio characteristic is significantly improved as compared with the prior art.

Claims (26)

Applying an alignment film divided into at least one domain onto a substrate; Forming a light-shielding layer at a boundary of the domain; And a step of irradiating the above alignment film with a polar angle &thetas; and an azimuth ϕ with the light-shielding layer using a mask to determine the alignment direction. The method according to claim 1, wherein the alignment film is a photoreactive material. The method according to claim 2, wherein the photoreactive material is selected from the group consisting of a polysiloxane-based material and polyvinylfluorocinnamate (PVCN-F). The method according to claim 1, wherein the light-shielding layer is a black matrix. The method according to claim 1, wherein the light is irradiated once or twice. The method according to claim 1, wherein the light is ultraviolet light. The method according to claim 1, wherein θ = 0 ° to 60 °. The method of orienting a liquid crystal cell according to claim 1, wherein? = 0 ° to 90 °. Applying on the substrate an alignment film divided on a x-y plane into a plurality of domains each parallel to the x-axis and the y-axis; Forming a light shielding layer arranged in parallel with the x-axis and the y-axis at the boundary of each of the domains described above; And determining the alignment direction by irradiating each of the domains with light having a polar angle &thetas; and an azimuth angle ϕ. The method according to claim 9, wherein the alignment film is a photoreactive material. The method of claim 10, wherein the photoreactive material is selected from the group consisting of a polysiloxane-based material and polyvinylfluorocinnamate (PVCN-F). The method of processing an alignment of a liquid crystal cell according to claim 9, wherein the light-shielding layer is a black matrix. 10. The method according to claim 9, wherein the light is irradiated once or twice. 10. The method of orienting a liquid crystal cell according to claim 9, wherein the light is ultraviolet light. 10. The method according to claim 9, wherein? = 0 ° to 60 °. The method of orienting a liquid crystal cell according to claim 9, wherein φ = 0 ° to 90 °. 10. The method according to claim 9, wherein the step of determining the alignment direction in each of the domains comprises the step of irradiating light in a state where another domain is blocked with a mask. Applying an orientation film on the substrate, the orientation film being divided into a plurality of domains on the x-y plane that each angle forms an angle with the x-axis and the y-axis; Forming a light-shielding layer at an angle between the x-axis and the y-axis at the boundary of each of the domains described above; And determining the alignment direction by irradiating each of the above-mentioned domains with light having a polar angle &thetas; and an azimuth angle of 90 DEG. The method according to claim 18, wherein the orientation film is a photoreactive substance. 20. The method of claim 19, wherein the photoreactive material is selected from the group consisting of a polysiloxane-based material and polyvinylfluorocinnamate (PVCN-F). The method according to claim 18, wherein the light-shielding layer is a black matrix. The method according to claim 18, wherein the light is irradiated once or twice. The method according to claim 18, wherein the light is ultraviolet light. The method according to claim 18, wherein? = 0 ° to 60 °. The method according to claim 18, wherein φ = 0 ° to 90 °. The method of claim 18, wherein the step of determining an alignment direction for each of the domains comprises irradiating light in a state where another domain is blocked with a mask.