Method of forming an alignment layer, and apparatus for forming the alignment layer

A method of forming an alignment layer includes; providing a substrate having a base substrate and a photosensitive polymer layer disposed on the base substrate, the base substrate including a plurality of unit pixel areas, each of which is divided into a plurality of sub-pixel areas, photoaligning the photosensitive polymer layer by irradiating first light to a first exposure area of a first unit pixel area, the first light being inclined at a first angle with respect to the substrate in a first direction, and substantially simultaneously photoaligning the photosensitive polymer layer by irradiating second light to a second exposure area of a second unit pixel area at substantially the same time as the first light is irradiated to the first exposure area, the second light being inclined at a second angle with respect to the substrate in a second direction.

This application claims priority to Korean patent application No. 2008-76899, filed on Aug. 6, 2008, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Exemplary embodiments of the present invention relate to a method of forming an alignment layer, and an apparatus for forming the alignment layer. More particularly, exemplary embodiments of the present invention relate to a method of forming an alignment layer capable of reducing the number of steps of a photoalignment process for forming a multi-domain structure, and an apparatus for forming the alignment layer.

2. Description of the Related Art

A liquid crystal display (“LCD”) apparatus is one of the most widely used types of flat panel display apparatuses. The LCD apparatus includes two display substrates, a liquid crystal layer interposed between the two display substrates and a polarization member disposed on the outside of the display substrates. Each of the display substrates includes an electric field generating electrode such as a pixel electrode, a common electrode, etc.

The LCD apparatus may have a problem of a narrow viewing angle. In order to increase the viewing angle of the LCD apparatus, a multi-domain liquid crystal cell has been developed. Main viewing angles of pixels in the multi-domain liquid crystal cell are different from each other in order to increase the viewing angle.

In order to form the multi-domain liquid crystal cell, a method of forming a slit in the electric field generating electrode or a method of forming a protrusion on the electric field generating electrode has been devised.

However, the slit or the protrusion formed in/on the electric field generating electrode may reduce the optical transmissivity of the pixel. Therefore, in order to form the multi-domain liquid crystal cell without the slit or the protrusion, a method of forming an alignment layer having multiple alignment directions has been developed. For example, an alignment layer including polyimide is coated on a substrate, and a mono-domain structure is formed on the substrate by rubbing the entire substrate. Then, a first domain is rubbed in the opposite direction while a second domain is blocked with photoresist, so that a multi-domain structure is formed having a first domain with an alignment orientation corresponding to the rubbing in the opposite direction and a second domain retaining the alignment orientation corresponding to the original mono-domain structure.

However, there is a problem with the liquid crystal cell manufactured by the above-mentioned method in that dust or static electricity generated during the rubbing process may damage the liquid crystal cell, and thus a manufacturing yield may be reduced.

In order to solve the problem of the rubbing process, a method of photoalignment using an ultraviolet light instead of the rubbing process has been proposed. In the method of the photoalignment, a mask having a transmission portion and a blocking portion in a predetermined pattern is disposed over a substrate and an ultraviolet light is irradiated onto the substrate to form a pretilt at an alignment layer.

When four domains are formed by a conventional photoalignment method, at least four processes for the photoalignment are required. When the combination of an upper substrate and a lower substrate, each having a multi-domain alignment layer, is considered, at least eight processes for the photoalignment are required. When the steps of the photoalignment process are increased, it is necessary to additionally readjust a gap between a mask and a substrate. Further, various errors may occur in the alignment of the mask, and thus productivity may be reduced.

BRIEF SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a method of forming an alignment layer using a simplified process.

Further, exemplary embodiments of the present invention provide a method of manufacturing a liquid crystal display (“LCD”) apparatus using the exemplary embodiment of a method of forming the alignment layer.

Still further, exemplary embodiments of the present invention provide an apparatus for forming the alignment layer using the exemplary embodiment of a method of forming the alignment layer.

In accordance with one exemplary embodiment of the present invention, a method of forming an alignment layer includes; providing a substrate having a base substrate and a photosensitive polymer layer disposed on the base substrate, the base substrate including a plurality of unit pixel areas, each of which is divided into a plurality of sub-pixel areas, photoaligning the photosensitive polymer layer by irradiating first light to a first exposure area of a first unit pixel area, the first light being inclined at a first angle with respect to the substrate in a first direction, and substantially simultaneously photoaligning the photosensitive polymer layer by irradiating second light to a second exposure area of a second unit pixel area at substantially the same time as the first light is irradiated to the first exposure area, the second light being inclined at a second angle with respect to the substrate in a second direction.

In one exemplary embodiment of the present invention, a mask is disposed over the substrate, wherein the mask includes; a first mask part which exposes the first exposure area of the first unit pixel area to the first light, and which blocks the second exposure area of the first unit pixel area, and a second mask part which blocks the first exposure area of the second unit pixel area, and which exposes the second exposure area of the second unit pixel area to the second light.

In some exemplary embodiments of the present invention, the first light and the second light may be irradiated to each of the unit pixel areas, so that the photosensitive polymer layer in the first exposure area of each unit pixel area is pretilted in the first direction and the photosensitive polymer layer in the second exposure area of each unit pixel area is pretilted in the second direction.

In one exemplary embodiment, a direction of travel of photons comprising the first light may be substantially opposite to a direction of travel of photons comprising the second light. In one exemplary embodiment, at least one of the exposure energy of the first light, an exposure energy of the second light, the first angle and the second angle may be adjusted to control a magnitude of a photoalignment of the photosensitive polymer layer.

In one exemplary embodiment, the mask may further include a blocking layer which is disposed between the first mask part and the second mask part and which prevents interference between the first light and the second light.

In one exemplary embodiment, the first mask part and the second mask part may be separated from each other, and separately controlled.

In one exemplary embodiment of the present invention, the method may further comprise polarizing an unpolarized ultraviolet light to form the first light and polarizing the unpolarized ultraviolet light to form the second light. In one exemplary embodiment, a first polarization plate may be disposed in a first pathway of the unpolarized ultraviolet light to form the first light, and a second polarization plate may be disposed in a second pathway of the unpolarized ultraviolet light to form the second light. In one exemplary embodiment, the polarization axis of the first light may be substantially parallel with the polarization axis of the second light.

In one exemplary embodiment of the present invention, unpolarized ultraviolet light may pass through a beam splitter to be divided into s-polarized light and p-polarized light, wherein the first light includes the s-polarized light, and the second light includes the p-polarized light which has passed through a ½ wavelength phase-difference plate.

In accordance with another exemplary embodiment of the present invention, an apparatus for forming an alignment layer includes a light source which emits light, a first optical transport system which guides the light and which irradiates first light to a first exposure area of a first unit pixel area defined on a substrate to firstly photoalign a photosensitive polymer layer disposed on the substrate, the first light being inclined at a first angle with respect to the substrate in a first direction, and a second optical transport system which guides the light and which irradiates second light to a second exposure area of a second unit pixel area at substantially the same time as the first light is irradiated to the first exposure area of the first unit pixel to photoalign the photosensitive polymer layer, the second light being inclined at a second angle with respect to the substrate in a second direction.

In some exemplary embodiments of the present invention, the apparatus may further include a mask which includes; a first mask part which exposes the first exposure area of the first unit pixel area to the first light, and which blocks the second exposure area of the first unit pixel area, and the second mask part may block the first exposure area of the second unit pixel area, and expose the second exposure area of the second unit pixel area to the second light. In one exemplary embodiment, the first optical transport system may include a first reflective plate guiding the light and a first polarization plate polarizing the light, and the second optical transport system may include a second reflective plate guiding the light and a second polarization plate polarizing the light. In one exemplary embodiment, the mask may further include a blocking layer disposed between the first mask part and the second mask part, wherein the blocking layer prevents interference between the first light and the second light. In one exemplary embodiment, the first mask part and the second mask part may be separated from each other, and separately controlled. In one exemplary embodiment, a polarization axis of the first polarization plate is substantially parallel with a polarization axis of the second light.

In some exemplary embodiments of the present invention, the apparatus may further include a beam-splitting system which divides the light emitted from the light source into s-polarized light transmitted to the first optical transport system and p-polarized light transmitted to the second optical transport system, the polarization axis of the p-polarized light may be substantially perpendicular to the polarization axis of the s-polarized light. In one exemplary embodiment, the first optical transport system may include a first reflective plate which reflects the s-polarized light to provide the first light, and the second optical transport system may include; a second reflective plate which reflects the p-polarized light toward a direction inclined at the second angle with respect to the second direction, and a ½ wavelength phase-difference plate which converts the p-polarized light reflected by the second reflective plate to an s-polarized light and which transmits the s-polarized light as the second light.

According to some exemplary embodiments of the present invention, the number of steps for forming a photoalignment layer for forming a multi-domain structure may be considerably reduced, so that productivity may be improved.

DETAILED DESCRIPTION OF THE INVENTION

It will be understood that when an element is referred to as being “on,” “connected to” or “coupled to” another element, it can be directly on, connected or coupled to the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

FIG. 1is a flowchart of an exemplary embodiment of a method of forming an alignment layer in accordance with Example Embodiment 1 of the present invention.FIG. 2is a top plan layout view illustrating a unit pixel area of a substrate formed by the method described with reference toFIG. 1.

Referring toFIG. 1, according to an exemplary embodiment of the method of forming an alignment layer in accordance with Example Embodiment 1, a substrate102is prepared (step S10). The substrate102may be a substrate which is substantially completed except for a photoalignment process for forming an alignment layer. Hereinafter, the substrate102is referred to as “lower substrate.”

In one exemplary embodiment, the lower substrate102may be a thin film transistor (“TFT”) substrate wherein pixels are driven by an active matrix driving method using a switching element. In one exemplary embodiment, the lower substrate102may have a substantially rectangular shape. In the exemplary embodiment wherein the lower substrate102has a substantially rectangular shape, a first direction (x) represents a longitudinal direction of the lower substrate, and a second direction (y) represents a horizontal direction of the lower substrate as shown inFIG. 2.

Referring toFIG. 2, the lower substrate102includes a lower base substrate (not shown), a pixel electrode170and a lower photosensitive polymer layer181.

A plurality of unit pixel areas PA is defined on the lower substrate in a matrix formation. The unit pixel area PA includes an individual area where liquid crystal molecules of a liquid crystal display (“LCD”) apparatus are independently controlled.

The unit pixel area PA may be divided into a plurality of unit sub-pixel areas that are also arranged in a matrix formation. InFIG. 2, the unit pixel area PA is divided into four unit sub-pixel areas including a unit sub-pixel area SPA11arranged in row 1, column 1 (hereinafter referred to as “row 1-column 1 unit sub-pixel area”), a unit sub-pixel area SPA12arranged in row 1, column 2 (hereinafter referred to as “row 1-column 2 unit sub-pixel area”), a unit sub-pixel area SPA21arranged in row 2, column 1 (hereinafter referred to as “row 2-column 1 unit sub-pixel area”) and a unit sub-pixel area SPA22arranged in row 2, column 2 (hereinafter referred to as “row 2-column 2 unit sub-pixel area”). In the exemplary embodiment of Example Embodiment 1, the unit pixel area PA has a substantially rectangular shape, but the unit pixel area PA may have various shapes such as a V-shape, a Z-shape, etc.

A plurality of gate lines111, a plurality of data lines121and a TFT are formed on the lower base substrate. The TFT includes a gate electrode112connected to the gate line111and a source electrode122connected to the data line121. The pixel electrode170includes a transparent conductive material, exemplary embodiments of which include indium tin oxide (“ITO”), indium zinc oxide (“IZO”), and other materials having similar characteristics. The transparent conductive material is deposited on the lower substrate and patterned to form the pixel electrode170. The pixel electrode170is connected to a drain electrode124of the TFT.

In one exemplary embodiment, the lower photosensitive polymer layer181may include a photosensitive polymer based on cinnamate. In one such exemplary embodiment, a blend of a photosensitive polymer based on cinnamate and a polymer based on polyimide is coated over the pixel electrode170and cured to form the lower photosensitive polymer layer181.

In one exemplary embodiment, the photosensitive polymer based on cinnamate and the polymer based on polyimide are blended in the weight ratio of 1:9 to 9:1 and dissolved in an organic solvent. In one exemplary embodiment, the polymer dissolved in the organic solvent may be coated on the lower substrate102in a spin-coating method. The polymer layer coated on the lower substrate102is heated and cured to form the lower photosensitive polymer layer181.

FIG. 3is a schematic diagram illustrating an exemplary embodiment of an apparatus for forming an alignment layer using the method described with reference toFIG. 1.

Referring toFIGS. 1 and 3, when the above-mentioned lower substrate102is provided, polarized first light L2is irradiated to a first exposure area on the unit pixel area PA to firstly photoalign the lower photosensitive polymer layer181(step S20). The first light L2is inclined at a first angle with respect to a virtual line parallel with the first direction (x) on the lower substrate102.

At substantially the same time as the first photoalignment process, polarized second light L4is irradiated to a second exposure area of another unit pixel area PA to secondly photoalign the lower photosensitive polymer layer181(step S30). The second light L4is inclined at a second angle with respect to a virtual line parallel with an opposite direction of the first direction (x) on the lower substrate102.

The first exposure area and the second exposure area are defined as areas where each alignment direction is determined by a single scan process that uses the exemplary embodiment of an apparatus1for forming an alignment layer shown inFIG. 3to align the unit pixel area PA. That is, the first exposure area or the second exposure area may each include at least one of the unit sub-pixel areas SPA11, SPA12, SPA21and SPA22.

In one exemplary embodiment, the first exposure area includes the row 1-column 1 unit sub-pixel area SPA11and the row 2-column 1 unit sub-pixel area SPA21. The second exposure area includes the row 1-column 2 unit sub-pixel area SPA12and the row 2-column 2 unit sub-pixel area SPA22. Therefore, the row 1-column 1 unit sub-pixel area SPA11and the row 2-column 1 unit sub-pixel area SPA21are exposed to only one of the polarized first light L2and the polarized second light L4and the row 1-column 2 unit sub-pixel area SPA12and the row 2-column 2 unit sub-pixel area SPA22are exposed to the other of the polarized first light L2and the polarized second light L4.

The first photoalignment process and the secondary photoalignment process may be simultaneously performed by a single scan process wherein the substrate102is moved through a photoalignment apparatus only a single time. The exemplary embodiment of an apparatus1for forming an alignment layer includes a light source10, a first optical transport system50and a second optical transport system30as shown inFIG. 3.

Exemplary embodiments of the light source10may include an ultraviolet lamp irradiating ultraviolet light. In one exemplary embodiment, the light source10may include a first ultraviolet lamp11and a second ultraviolet lamp13. The ultraviolet light emitted from the first and second ultraviolet lamps11and13is unpolarized light. The light from the light source10may be reflected in a desired direction by a reflector15.

The first and the second optical transport system50and30guide the ultraviolet light emitted from the light source10, so that the ultraviolet light is irradiated to the lower photosensitive polymer layer181of the lower substrate102to optically align the lower photosensitive polymer layer181.

A plurality of photosensitive polymer chains is formed on a surface of the lower photosensitive polymer layer181. The polymer chains include a double bond that makes the polymer chains have optical directionality. Since the polymer chains have optical directionality due to the double bond, the polymer chains may be photopolymerized with each other only when the ultraviolet light irradiated to the lower photosensitive polymer layer181has a particular directional polarization axis. As a result of the photopolymerization reaction, the polymer chains tilt toward the incident direction of the polarized ultraviolet light so that the alignment layer has a pretilt angle. Thereby, the pretilt direction of the polymers, and therefore also the alignment layer, may be influenced by the incident direction of the polarized ultraviolet light.

The first optical transport system50irradiates the polarized first light L2to the first exposure area of the unit pixel area PA. The first optical transport system50may include a first reflective plate51, a second reflective plate53and a first polarization plate55. The first reflective plate51reflects a first ultraviolet light L1emitted from the first ultraviolet lamp11toward the second reflective plate53. The second reflective plate53reflects the first ultraviolet light L1toward the first polarization plate55. The first ultraviolet light L1reflected by the second reflective plate53is irradiated to the substrate102through a mask70at the first angle with respect to the lower substrate102in the opposite direction of the first direction (x) in which the lower substrate102is transferred through the exemplary embodiment of the apparatus1by a series of rollers5as shown inFIG. 5. In one exemplary embodiment, the rollers move the substrate102along the x-direction and through the apparatus1.

The first polarization plate55is disposed substantially perpendicular to an irradiating direction of the first ultraviolet light L1. The first polarization plate55converts the first ultraviolet light L1to the polarized first light L2, and guides the polarized first light L2to the first exposure area.

The second optical transport system30irradiates the polarized second light L4to the second exposure area of another unit pixel area PA, at substantially the same time as the irradiation of the polarized first light L2.

The second optical transport system30may include a third reflective plate31, a fourth reflective plate33and a second polarization plate35. The third reflective plate31reflects a second ultraviolet light L3emitted from the second ultraviolet lamp13toward the fourth reflective plate33as shown inFIG. 3. The fourth reflective plate33reflects the second ultraviolet light L3toward the fourth reflective plate33. The second ultraviolet light L3reflected by the fourth reflective plate33is irradiated to the substrate102through the mask70at the second angle with respect to the lower substrate102in the first direction (x) in which direction the lower substrate102is transferred through the exemplary embodiment of the apparatus1.

The second polarization plate35is disposed to be substantially perpendicular to an irradiating direction of the second ultraviolet light L3. The second polarization plate35converts the second ultraviolet light L3to the polarized second light L4, and guides the polarized second light L4to the second exposure area.

The polarization axis of the polarized first light L2and the polarization axis of the polarized second light L4that are projected to the lower substrate102may be substantially parallel with each other.

FIG. 4is a top plan view illustrating the mask shown inFIG. 3.FIG. 5is a side view illustrating a blocking layer77and an incident angle of light proceeding to the mask70.FIG. 6is a front perspective view illustrating an exemplary embodiment of a photoalignment process applied to an exposure area.

Referring toFIGS. 4,5and6, the exemplary embodiment of a method of forming an alignment layer in accordance with the present invention may further include a step of disposing a mask70over the lower substrate102. A first unit pixel area and a second unit pixel area are defined as unit pixel areas adjacent to each other in the first direction (x). The mask70exposes the first exposure area of the first unit pixel area PA to the polarized first light L2, and blocks the second exposure area of the first unit pixel area PA. Further, the mask70may block the first exposure area of the second unit pixel area PA, and expose the second exposure area of the second unit pixel area PA to the polarized second light L4.

Meanwhile, the mask70may include a first mask part72and a second mask part74. In one exemplary embodiment, the first mask part72and the second mask part74may be integrally formed. That is, the mask70may be a single, solitary and indivisible unitary unit. A blocking layer77may be installed between the first mask part72and the second mask part74to prevent the first light L2and the second light L4from interfering with each other. A transmission portion71and a blocking portion73are formed at the first mask part72. In one exemplary embodiment, the size of the transmission portion71may be substantially the same as that of the first exposure area. The second mask part74may include a transmission portion75and a blocking portion76that alternate with those of the first mask part72. Alternative exemplary embodiments include configurations wherein the mask70may be omitted.

FIG. 7is a top plan view illustrating a process of forming an alignment layer on a large-sized lower substrate102by the apparatus shown inFIG. 3.

Referring toFIG. 7, a plurality of exposure areas105is defined on a large-sized lower substrate102. A plurality of masks70is disposed at the plurality of exposure areas105. In one exemplary embodiment, two masks are disposed at each of the plurality of exposure areas105.

When the polarized first light L2and the polarized second light L4are scanned at each of the exposure areas105in a scan direction (e.g., the x-direction), the first exposure area and the second exposure area of one unit pixel area PA are successively photoaligned. The alignment direction of the first exposure area and the second exposure area are substantially opposite to each other.

According to the exemplary embodiment of a method of forming an alignment layer and the exemplary embodiment of an apparatus1for performing the method in accordance with the present invention, the lower photosensitive polymer layer181at the first exposure area and the second exposure area that are spatially divided in the unit pixel area PA is photoaligned to form two domains by a single scan process.

Exposure energies of the polarized first light L2and the polarized second light L4or the first angle and the second angle may be adjusted to control the magnitude of the photoalignment of the lower photosensitive polymer layer181.

The blocking layer77illustrated inFIG. 6may be installed between the first mask part72and the second mask part74to prevent the first light L2and the second light L4from interfering with each other.

FIG. 8is a flowchart describing an exemplary embodiment of a method of manufacturing an exemplary embodiment of an LCD apparatus using the exemplary embodiment of a method of forming an alignment layer shown inFIGS. 1 to 7.FIG. 9is a top plan view illustrating photoalignment directions of an array substrate on which an alignment layer is formed by the process shown inFIGS. 6,7and8.

Referring toFIGS. 6,7,8and9, an array substrate101is manufactured using the previously described exemplary embodiment of a method of forming an alignment layer (step S310). According to the present invention, the lower substrate102illustrated inFIG. 2may be treated by the method of forming an alignment layer shown inFIGS. 1 to 7, to manufacture the array substrate101.

That is, the lower photosensitive polymer layer181in the first exposure area and the second exposure area of the unit pixel area PA is photoaligned in the first direction (x) and the opposite direction of the first direction (x), respectively, by a single scan process using the polarized first light L2and the polarized second light L4as described above, so that a lower alignment is formed on the array substrate101. For example, the row1-column1 unit sub-pixel area SPA11and the row2-column1 unit sub-pixel area SPA21may be both aligned in a first photoalignment direction182substantially parallel the x-axis as shown inFIG. 9. Similarly, the row1-column2 unit sub-pixel area SPA12and the row2-column2 unit sub-pixel area SPA22may be both aligned in a second photoalignment direction184substantially parallel the x-axis and substantially opposite the first photoalignment direction182as shown inFIG. 9.

FIG. 10is a cross-sectional view of the exemplary embodiment of an LCD apparatus taken along lines I-I′ inFIG. 2.FIG. 11is a top plan view illustrating an alignment direction of an opposite substrate on which an upper alignment layer is formed by the exemplary embodiment of a photoalignment process shown inFIGS. 1 to 7.

Referring toFIGS. 10 and 11, an upper photosensitive polymer layer in a third exposure area and a fourth exposure area of the unit pixel area PA is photoaligned in a third direction and a fourth direction by a single scan process using polarized third light and polarized fourth light according to the exemplary embodiment of a method of forming an alignment layer shown inFIGS. 1 to 7, to form an upper alignment layer280, so that an opposite substrate201having the upper alignment layer280is manufactured (step S320).

Here, a third photoalignment direction186and a fourth photoalignment direction188are substantially opposite to each other, and each of the third photoalignment direction186and the fourth photoalignment direction188are substantially perpendicular to the first photoalignment direction182and the second photoalignment direction184. The polarized third light is inclined at a third angle with respect to the third photoalignment direction186, and the polarized fourth light is inclined at a fourth angle with respect to the fourth photoalignment direction188.

In this example embodiment, the opposite substrate201may include an upper base substrate210, a blocking pattern220, a color filter pattern230, an overcoat layer240, a common electrode layer270and an upper alignment layer280.

In one exemplary embodiment, the blocking pattern220is formed on the upper base substrate210, correspondingly to the gate line111, the data line121and the TFT.

The color filter pattern230is formed on the upper base substrate210and in an area corresponding to the unit pixel area PA. In one exemplary embodiment, the color filter pattern230may include color filters such as a red color filter, a green color filter, a blue color filter, etc. In one exemplary embodiment, the red color filter, the green color filter and the blue color filter may be subsequently disposed at each of the unit pixel area PA in the second direction (y).

The overcoat layer240covers the color filter pattern230and the blocking pattern220. The common electrode layer270is formed on the overcoat layer240.

The upper alignment layer280is formed on the common electrode layer270.

FIG. 12is a top plan view illustrating an exemplary embodiment of an LCD apparatus including a combination of the array substrate shown inFIG. 9and the opposite substrate shown inFIG. 11.

Referring toFIGS. 10 and 12, the array substrate101and the opposite substrate201are combined, and liquid crystal molecules are interposed between the two substrates101and201to form the liquid crystal layer301, so that the exemplary embodiment of an LCD apparatus100is manufactured (step S330).

In one exemplary embodiment, lower photoalignment directions182and184of a lower alignment layer180may be substantially perpendicular to upper photoalignment directions186and188of the upper alignment layer280in the unit sub-pixel areas SPA11, SPA12, SPA21and SPA22, as shown inFIG. 12.

Alignment directions C1, C2, C3and C4of each unit sub-pixel area are defined as directions corresponding to vector sums of the lower photoalignment directions182and184and the upper photoalignment directions186and188. The alignment directions C1, C2, C3and C4are different from each other in each of the unit sub-pixel areas SPA11, SPA12, SPA21and SPA22, and thus four domains are formed.

The alignment directions C1and C3diverge from the center of the unit pixel area PA in the unit sub-pixel areas SPA11and SPA22that are diagonally disposed in the unit pixel area PA. The alignment directions C1and C3are opposite to each other. The alignment directions C2and C4converge on the center of the unit pixel area PA in the unit sub-pixel areas SPA12and SPA21that are diagonally disposed in the unit pixel area PA. The alignment directions C2and C4are opposite to each other.

The method of determining the photoalignment directions of the lower alignment layer180and the upper alignment layer280may be variously modified according to alternative exemplary embodiments of a method of forming a multi-domain structure.

Referring back toFIG. 10, in one exemplary embodiment, when an electric field is not applied to the liquid crystal layer301, the liquid crystal molecules310interposed between the array substrate101and the opposite substrate201may be vertically aligned. That is, the LCD apparatus100may be operated in a vertical alignment mode.

The liquid crystal molecules310are inclined at a pretilt angle in the lower photoalignment directions182and184on a surface of the lower alignment layer180, and are inclined at a pretilt angle in the upper photoalignment directions186and188on a surface of the upper alignment layer280.

In one exemplary embodiment, a lower polarization plate190may be disposed at a rear surface of the array substrate101, and an upper polarization plate290may be disposed at an upper surface of the opposite substrate201. In one such exemplary embodiment, the polarization axes of the lower polarization plate190and the upper polarization plate290may be substantially perpendicular to each other. In such an exemplary embodiment, the alignment directions C1, C2, C3and C4are determined so that the liquid crystal molecules310are aligned at approximately 45 degrees with respect to the polarization axes.

FIG. 13is a schematic diagram illustrating an exemplary embodiment of an apparatus for forming an alignment layer in accordance with Example Embodiment 2.

An exemplary embodiment of a method of forming an alignment layer and an exemplary embodiment of a method of manufacturing an exemplary embodiment of an LCD apparatus using the method are substantially the same as those shown inFIGS. 1 to 12. Therefore, repeated and detailed descriptions will be omitted.

An exemplary embodiment of an apparatus800for forming an alignment layer described with reference toFIG. 13may be substantially similar to the exemplary embodiment of an apparatus1described with reference toFIGS. 1 to 7except that a mask870is divided into two mask parts which may be separately controlled. Therefore, the same reference numbers are used for the same or similar elements, and any further descriptions concerning the same or similar elements as those shown inFIGS. 1 to 7will be omitted.

Referring toFIG. 13, the mask870is divided into a first mask part872and a second mask part874. The first mask part872and the second mask part874are sufficiently separated from each other so that first light L2irradiated to a first exposure area and second light L4irradiated to a second exposure area do not interfere with each other.

Further, an interval between a period for photoaligning the first exposure area by the first light L2and a period for photoaligning the second exposure area by the second light L4may be variously adjusted.

FIG. 14is a schematic diagram illustrating another exemplary embodiment of an apparatus for forming an alignment layer in accordance with Example Embodiment 3.

An exemplary embodiment of a method of forming an alignment layer and an exemplary embodiment of a method of manufacturing an exemplary embodiment of an LCD apparatus using the exemplary embodiment of a method are substantially the same as those shown inFIGS. 1 to 12. Therefore, repeated and detailed descriptions will be omitted.

Referring toFIG. 14, an exemplary embodiment of an apparatus1000for forming an alignment layer in accordance with this exemplary embodiment includes a light source, a first optical transport system1034, a second optical transport system1036and a beam-splitting system1032.

The light source is substantially the same as the light source10described with reference to the exemplary embodiment shown inFIG. 3except that the light source includes a single ultraviolet lamp1011.

The beam-splitting system1032includes a first reflective plate1031and a beam splitter1033.

The first reflective plate1031reflects unpolarized ultraviolet light emitted from the ultraviolet lamp1011toward the beam splitter1033. The beam splitter1033divides the unpolarized ultraviolet light into a first s-polarized light and p-polarized light whose polarization axis is substantially perpendicular to the polarization axis of the first s-polarized light.

The first optical transport system1034includes a second reflective plate1035. The second reflective plate1035reflects the first s-polarized light. First light L1is defined as the first s-polarized light reflected by the second reflective plate1035. The first light L1proceeds to a substrate1102at a first angle with respect to the first direction (x). The first light L1is irradiated to a lower photosensitive polymer layer1181in a first exposure area of a first unit pixel area PA through a first mask part1072. Accordingly, the lower photosensitive polymer layer1181in the first exposure area is photoaligned in the first direction (x).

The second optical transport system1036may include a third reflective plate1037and a ½ wavelength phase-difference plate1051. The third reflective plate1037reflects the p-polarized light. Second light L2is defined as the p-polarized light reflected by the third reflective plate1037. The second light L2proceeds to the substrate1102at a second angle with respect to an opposite direction of the first direction (x), and passes through the ½ wavelength phase-difference plate1051. The ½ wavelength phase-difference plate1051converts the second light L2to a second s-polarized light L3. The second s-polarized light L3is irradiated to the lower photosensitive polymer layer1181in the second exposure area through a second mask part1074. Accordingly, the lower photosensitive polymer layer1181in the second exposure area is photoaligned in the opposite direction of the first direction (x).

The exemplary embodiment of an apparatus1000for forming an alignment layer may further include a transfer table for transferring the substrate1102in the first direction (x).

According to the exemplary embodiment of an apparatus1000in accordance with the present invention, an optical loss caused when a polarization plate is used may be prevented. In an apparatus for forming an alignment layer using a polarization plate, such as the exemplary embodiment of an apparatus1illustrated inFIG. 3, light except for p-polarized light or s-polarized light is lost when unpolarized ultraviolet light passes through the first polarization plate55and the second polarization plate35. However, according to this exemplary embodiment, the apparatus1000may use substantially all of the light including the p-polarized light and s-polarized light emitted from the beam splitter1033. Therefore, the optical efficiency of the apparatus1000for forming an alignment layer may be improved.

According to the present invention, a plurality of domains may be formed in an alignment layer in a unit pixel area by a single scan process. Therefore, the number of steps of a photoalignment process for forming a multi-domain structure may be reduced, so that productivity may be considerably improved. The present invention may be applied to an apparatus including an alignment layer.