Liquid crystal display device comprising a reactive mesogen that fixes liquid crystal molecules to form a liquid crystal domain

A display device that prevents occurrence of a phenomenon where a boundary portion of a pixel region becomes dark, and a method of manufacturing the same. The display device includes a first substrate arrangement including a domain forming layer having a depression pattern for forming a liquid crystal domain in a pixel region, and a pixel electrode arranged on the domain forming layer, a second substrate arrangement including a common electrode arranged on an entire surface facing the first substrate arrangement, a liquid crystal layer arranged between the first and second substrate arrangements and including a plurality of liquid crystal molecules and a reactive mesogen (RM) to fix the liquid crystal molecules to form the liquid crystal domain, a sealant arranged between the first and second substrate arrangements to adhere the first and second substrate arrangement together and a light blocker arranged between the sealant and the liquid crystal layer to block light incident from an external side of the sealant.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on the 11, Mar. 2010 and there duly assigned Serial No. 10-2010-0021840.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device for displaying an image by using liquid crystals and a method of manufacturing the same.

2. Description of the Related Art

Generally, a liquid crystal display panel includes an array substrate on which switching devices for driving each pixel region are formed, a counter substrate facing the array substrate, and a liquid crystal layer disposed between the array substrate and the counter substrate. The liquid crystal display panel displays an image by controlling transmittance of light via a voltage applied to the liquid crystal layer.

Meanwhile, in a patterned vertical alignment (PVA) mode, i.e., a VA mode of operation for a liquid crystal display device, a viewing angle of the liquid crystal display device may be improved by forming a liquid crystal domain by arranging liquid crystal molecules in different directions by using a patterned transparent electrode.

SUMMARY OF THE INVENTION

The present invention provides a display device that prevents occurrence of a phenomenon where a boundary portion of a pixel region becomes dark and a method of manufacturing the same.

According to an aspect of the present invention, a display device includes a first substrate arrangement including a domain forming layer having a depression pattern for forming a liquid crystal domain in a pixel region, and a pixel electrode arranged on the domain forming layer, a second substrate arrangement including a common electrode arranged on an entire surface facing the first substrate arrangement, a liquid crystal layer arranged between the first and second substrate arrangements and including a plurality of liquid crystal molecules and a reactive mesogen (RM) to fix the liquid crystal molecules to form the liquid crystal domain, a sealant arranged between the first and second substrate arrangements to adhere the first and second substrate arrangement together and a light blocker arranged between the sealant and the liquid crystal layer to block light incident from an external side of the sealant.

The light blocker may include a material having a higher refractive index than that of the liquid crystal layer. The light blocker may include an organic material having a higher refractive index than that of the liquid crystal layer. The light blocker may be arranged to surround the liquid crystal layer. The first substrate arrangement may include a switching device that includes a contact electrode electrically connected to the pixel electrode, the depression pattern being arranged on the contact electrode to expose the contact electrode. The first substrate arrangement may further include a storage line, the contact electrode overlapping the storage line. The domain forming layer may include a color filter. At least one depression pattern may be arranged within the pixel region of the first substrate arrangement.

According to another aspect of the present invention, there is provided a method of manufacturing a display device that includes preparing a first substrate arrangement including an organic layer and a pixel electrode arranged on the organic layer, the organic layer having a depression pattern to form a liquid crystal domain of a pixel region, preparing a second substrate arrangement including a common electrode arranged on an entire surface facing the first substrate arrangement, coating a sealant on at least one side of the first and second substrate arrangements, forming a light blocker on one side of the sealant, the light blocker to block light incident from an external side of the sealant, applying a liquid crystal composition between the first and second substrate arrangements, the liquid crystal composition including a plurality of liquid crystal molecules and a plurality of reactive mesogen monomers and forming a liquid crystal layer by irradiating light on the liquid crystal composition arranged between the first and second substrate arrangements while applying a voltage between the pixel electrode and the common electrode.

The light blocker may include a material having a higher refractive index than that of the liquid crystal layer. The light blocker may include an organic material having a higher refractive index than that of the liquid crystal layer. The light blocker may be arranged to surround the liquid crystal layer. The forming of the liquid crystal layer may include applying a first voltage to the common electrode, applying a second voltage lower than the first voltage to the pixel electrode and irradiating light on the first and second substrate arrangements. The sealant may be arranged to surround the light blocker.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.FIG. 1is a plan view of a display device according to an embodiment of the present invention,FIG. 2Ais a cross-sectional view taken along a line I-I′ ofFIG. 1, andFIG. 2Bis a cross-sectional view taken along a line II-II′ ofFIG. 1. Liquid crystal layers300inFIGS. 2A and 2Binclude liquid crystal molecules310and a reactive mesogen (RM) cured product320in a non-electric field, i.e., when no voltage is applied between a pixel electrode PE and a common electrode250.

Referring toFIGS. 1,2A, and2B, the display device according to the current embodiment of the present invention includes a first substrate arrangement100, a second substrate arrangement200and the liquid crystal layer300. The first substrate arrangement100includes a first base substrate110, first and second gate lines GL1and GL2, a storage line STL, a gate insulation layer120, first and second data lines DL1and DL2, a thin film transistor SW constituting a switching device, a passivation layer140, a domain forming layer150, the pixel electrode PE, and a first alignment layer AL1.

The first and second gate lines GL1and GL2may extend along a first direction D1on the first base substrate110or may instead be arranged in parallel to each other in a second direction D2different from the first direction D1. The second direction D2may be, for example, perpendicular to the first direction D1. The storage line STL is disposed between the first and second gate lines GL1and GL2and may extend along the first direction D1. The gate insulation layer120is formed on the first base substrate110to cover the first and second gate lines GL1and GL2and the storage line STL. The first and second data lines DL1and DL2may extend along the second direction D2on the gate insulation layer120or may instead be arranged in parallel to each other in the first direction D1. The first and second data lines DL1and DL2may respectively cross the first and second gate lines GL1and GL2and the storage line STL. In the first substrate arrangement100, a pixel region P may be defined by the first and second gate lines GL1and GL2, and the first and second data lines DL1and DL2. The pixel electrode PE may be formed in the pixel region P.

The thin film transistor SW may include a gate electrode GE connected to the first gate line GL1, an active pattern AP formed on the gate insulation layer120so as to correspond to the gate electrode GE, a source electrode SE connected to the first data line DL1and overlapping the active pattern AP, a drain electrode DE spaced apart from the source electrode SE and overlapping the active pattern AP, and a contact electrode CNT extending from the drain electrode DE to the pixel region P. The contact electrode CNT may extend from the drain electrode DE to the storage line STL to overlap the storage line STL. The active pattern AP may include a semiconductor layer130aand an ohmic contact layer130bsequentially stacked on the gate insulation layer120. The passivation layer140may be disposed on the gate insulation layer120to cover the first and second data lines DL1and DL2, the source electrode SE, the drain electrode DE, and the contact electrode CNT.

The domain forming layer150may be formed on the passivation layer140. The domain forming layer150may planarize the first substrate arrangement100. The domain forming layer150includes a depression pattern152formed in the domain forming layer150. The depression pattern152is formed in the pixel region P, and may form a liquid crystal domain of the pixel region P. The depression pattern152may be formed on the domain forming layer150in a dot type, may be formed on the contact electrode CNT so as to correspond to the contact electrode CNT and may be formed as a dot type aperture for exposing a part of the contact electrode CNT. Even when the depression pattern152is formed in the dot type aperture, leakage of light in an area where the depression pattern152is formed may be prevented by the storage line STL and the contact electrode CNT, which are formed below the depression pattern152. The domain forming layer150may be made out of an organic material or an inorganic material. According to another embodiment of the present invention, the domain forming layer150may include an organic layer made out of an organic material or and an inorganic layer made out of an inorganic material, and the depression pattern152may be formed in the organic or inorganic layer.

The pixel electrode PE is disposed on the domain forming layer150and in the pixel region P, may be made out of a transparent conductive material, may be formed to cover the entire depression, pattern152and may be electrically connected to the thin film transistor SW by contacting the contact electrode CNT through the depression pattern152. Because an area of the pixel electrode PE on the depression pattern152includes an area of the pixel electrode PE on the inclined surface of the depression pattern152, with respect to regions having the same area in a plane, an area of the pixel electrode PE on the depression pattern152is relatively larger than an area of the pixel electrode PE formed on a flat region of the domain forming layer150. Accordingly, when an electric field is formed between the first and second substrate arrangements100and200, an intensity of an electric field in an area adjacent to the depression pattern152may be relatively higher than an intensity of an electric field in the flat region where the depression pattern152is not formed. Lastly, the first alignment layer AL1may be formed on the entire surface of the first base substrate110including the pixel electrode PE.

The second substrate arrangement200includes a second base substrate210facing the first substrate arrangement100, a black matrix pattern220, first through third color filters232,234, and236an over coating layer240, the common electrode250, and a second alignment layer AL2. In the present invention, the over coating layer240may be omitted.

The black matrix pattern220may be formed on the second base substrate corresponding to areas where the first and second gate lines GL1and GL2, the first and second data lines DL1and DL2, and the thin film transistor SW are formed. The first through third color filters232,234, and236may be formed in areas of the second base substrate210defined by the black matrix pattern220. For example, the first color filter232may be formed in an area of the second base substrate210corresponding to the pixel region P in which the pixel electrode PE is formed. The second color filter234may be formed in the first direction D1from the first color filter232, and the third color filter236may be formed on an opposite side of the first color filter232than that of the second color filter234, which is in the −D1direction from first color filter232. The over coating layer240is formed on the second base substrate210where the black matrix pattern220and the first through third color filters232,234, and236are formed, and may planarize the second substrate arrangement200.

The common electrode250may be formed on the over coating layer240. The common electrode250may be made out of a transparent conductive material. The common electrode250may be formed on the entire surface of the second substrate arrangement200without a separate pattern. In other words, the liquid crystal domain of the liquid crystal layer300may be formed by the pixel electrode PE that changes an intensity of an electric field via the depression pattern152and the common electrode250that has no pattern. Lastly, the second alignment layer AL2is formed on the second base substrate210on which the common electrode250is formed, and may be formed on the entire surface of the second substrate arrangement200.

The liquid crystal layer300is disposed between the first substrate arrangement100and the second substrate arrangement200, and includes the liquid crystal molecules310and the RM cured product320. The alignment of the liquid crystal molecules310is changed by an electric field formed between the pixel electrode PE and the common electrode250, thereby adjusting transmittance of light. The liquid crystal molecules310may have negative dielectric anisotropy.

A major axis of the liquid crystal molecules310adjacent to the first substrate arrangement100and/or the second substrate arrangement200may be arranged perpendicular to the surface of the first base substrate110and/or the second base substrate210when no voltage is applied between the pixel electrode PE and the common electrode250. A major axis of the liquid crystal molecules adjacent to the depression pattern152may be arranged perpendicular to a surface of a sidewall of the domain forming layer150based on the surface of the sidewall of the domain forming layer150forming the depression pattern152.

The RM cured product320may be disposed between the liquid crystal molecules310. The RM cured product320may be disposed between the liquid crystal molecules310adjacent to the pixel electrode PE and/or the common electrode250. In detail, the RM cured product320may be disposed between the liquid crystal molecules310adjacent to the first alignment layer AL1. Also, the RM cured product320may be disposed between the liquid crystal molecules310adjacent to the second alignment layer AL2.

The RM cured product320maintains the liquid crystal molecules310adjacent to the first substrate arrangement100and/or the second substrate arrangement200in a pre-tilt state based on the surface of the first base substrate110and/or the second base substrate210, even when an electric field is not formed between the pixel electrode PE and the common electrode250. The RM cured product320may be formed when RM monomers330ofFIG. 3Fare polymerized by exposure to an external light when the display device is being manufactured.

FIG. 2Cis a cross-sectional view of the display device ofFIG. 2Bwhen a voltage is applied thereto. Referring toFIG. 2C, when an electric field is formed between the pixel electrode PE and the common electrode250, a direction of the electric field inside the pixel region P is in general perpendicular to the surface of the first substrate arrangement100and/or the surface of the second substrate arrangement200.

However, the direction of the electric field bends between an edge of the pixel electrode PE and the common electrode250. The direction of the electric field also bends between an edge of another pixel electrode adjacent to the pixel electrode PE and the common electrode250as indicated by the dotted lines inFIG. 2C. Accordingly, the liquid crystal domain between the adjacent pixel regions P may be divided as the liquid crystal molecules310are arranged to emit light toward different points of the common electrode250between the adjacent pixel electrodes PE.

An electric field in an area adjacent to the depression pattern152has a shape converging toward a point of the common electrode250, for example, toward an area of the common electrode250corresponding to the depression pattern152, since the electric field pre-tilts the liquid crystal molecules310due to sidewalls of the depression pattern152.

Turning now toFIGS. 3A through 3F,FIGS. 3A through 3Fare cross-sectional views for describing a method of manufacturing the display device ofFIG. 2B.FIGS. 3A through 3Fare cross-sectional views taken along a line II-II′ ofFIG. 1, and the method will be described with reference toFIGS. 1,2B and2C, and3A through3F.

FIGS. 3A through 3Care cross-sectional views for describing a method of preparing the first substrate arrangement100ofFIG. 2B. Referring toFIG. 3A, a gate metal layer (not shown) is disposed on the first base substrate110, and the gate metal layer is patterned through a photolithography process to form a gate pattern including the first and second gate lines GL1and GL2, the gate electrode GE, and the storage line STL.

The gate insulation layer120is disposed on the first base substrate110on which the gate pattern is formed. The gate insulation layer120may be made out of silicon oxide, silicon nitride, or the like.

The active pattern AP is formed on the first base substrate110on which the gate insulation layer120is disposed. The active pattern AP may include semiconductor layer130aand ohmic contact layer130bsequentially disposed on the gate insulation layer120. The semiconductor layer130amay include amorphous silicon, and the ohmic contact layer130bmay include amorphous silicon doped with a high purity n-type impurity.

A data metal layer (not shown) is disposed on the first base substrate110on which the active pattern AP is formed, and the data metal layer may be patterned through a photolithography process to form a source pattern including the first and second data lines DL1and DL2, the source electrode SE, the drain electrode DE, and the contact electrode CNT.

The passivation layer140and the domain forming layer150are sequentially disposed on the first base substrate110on which the source pattern is formed. The passivation layer140may be made out of silicon oxide, silicon nitride, or the like. Examples of a material used to form the domain forming layer150include organic materials, such as a positive type photoresist composition and a negative type photoresist composition, and inorganic materials, such as silicon oxide and silicon nitride. The domain forming layer150may include a color filter.

Referring toFIG. 3B, the depression pattern152is formed by patterning the domain forming layer150. The depression pattern152may be formed on the contact electrode CNT that may overlap the storage line STL. The depression pattern152may be an aperture that exposes the passivation layer140on the contact electrode CNT.

Next, a passivation aperture142is formed by removing the passivation layer140exposed through the depression pattern152. The passivation aperture142is formed on the contact electrode CNT. A part of the contact electrode CNT may be exposed through the passivation aperture142and the depression pattern152.

Referring toFIG. 3C, a transparent electrode layer (not shown) is disposed on the first base substrate110including the domain forming layer150on which the depression pattern152is formed, and the transparent electrode layer is patterned to form the pixel electrode PE. The transparent electrode layer may be made out of indium tin oxide (ITO), indium zinc oxide (IZO), or the like.

Then, the first alignment layer AL1is disposed on the first base substrate110on which the pixel electrode PE is formed. The first alignment layer AL1may include a vertical alignment material that vertically aligns the liquid crystal molecules310.

As above, the first substrate arrangement100according to the current embodiment of the present invention, including the gate pattern, the gate insulation layer120, the active pattern AP, the source pattern, the passivation layer140, the domain forming layer150having the depression pattern152, the pixel electrode PE, and the first alignment layer AL1may be prepared.

Turning now toFIG. 3D,FIG. 3Dis a cross-sectional view for describing a method of preparing the second substrate arrangement200ofFIG. 2B. Referring toFIG. 3D, the black matrix pattern220is formed on the second base substrate210. The black matrix pattern220may be formed by ejecting an organic ink or patterning a metal layer through a photolithography process.

The first through third color filters232,234, and236are formed on the second base substrate210on which the black matrix pattern220is formed. For example, the first color filter232may be formed, the second color filter234may be formed on the second base substrate210including the first color filter232, and the third color filter236may be formed on the second base substrate210including the first and second color filters232and234. The first through third color filters232,234, and236may be formed by patterning a color photoresist layer through a photolithography process or by ejecting a color ink.

The over coating layer240may be disposed on the second base substrate210including the black matrix pattern220and the first through third color filters232,234, and236. The over coating layer240may be made out of acryl resin. A transparent electrode layer (not shown) may be formed on the second base substrate210on which the over coating layer240is formed, thereby forming the common electrode250. The common electrode250may be formed to cover the entire surface of the second base substrate210without having to pattern the transparent electrode layer. The common electrode250may be made out of ITO or IZO. The second alignment layer AL2may be disposed on the second base substrate210on which the common electrode250is formed. The second alignment layer AL2may cover the entire surface of the second base substrate210on which the common electrode250is formed. Accordingly, the second substrate arrangement200according to the current embodiment of the present invention, including the black matrix pattern220, the first through third color filters232,234, and236, the over coating layer240, the common electrode250, and the second alignment layer AL2may be prepared.

Turning now toFIG. 3E,FIG. 3Eis a cross-sectional view for describing a method of assembling the first and second substrate arrangements100and200. Referring toFIG. 3E, a one drop filling (ODF) process is performed to assemble the first and second substrate arrangements100and200. The ODF process is a process of coating a sealant170on any one side of the first or second substrate arrangement100or200, dropping liquid crystals on another of the first or second substrate arrangement100or200, and then adhering the first and second substrate arrangements100and200together and then hardening the sealant170. By using the ODF process, a process time and an amount of liquid crystals used may be remarkably reduced compared to a conventional process of adhering and hardening first and second substrate arrangements by using a main sealant, injecting liquid crystals via a capillary phenomenon, and then completing the adhesion of the first and second substrate arrangements by using an end sealant.

However, when the ODF process is performed, ultraviolet (UV) rays are irradiated only on an area where the sealant170is coated so as to harden the sealant170. That is, the UV rays are prevented from being irradiated on the liquid crystals by disposing a shield mask190on the liquid crystals in the pixel region P. However, even when the shield mask190is used, the UV rays irradiated from the side of the sealant170cannot be entirely blocked, and thus the liquid crystal layer300may be hardened in a vertical state by the UV rays irradiated from the side of the sealant170. Also, due to such a hardened liquid crystal layer300formed at a boundary portion of the pixel region P, the boundary portion may become dark. Accordingly, the UV rays may be replaced by a straight line, but when the straight line is used, a separate optical system needs to be designed, and a manufacturing cost of the display device increases.

Thus, the display device according to an embodiment of the present invention includes a light blocker180on one side of the sealant170so as to block the UV rays irradiated from the side of the sealant170. In other words, the amount of the UV rays irradiated from the side of the sealant170is minimized by forming a lens using an organic layer having a high refractive index on an external side of the liquid crystal layer300.

In detail, when the light blocker180is formed on the external side of the liquid crystal layer300by using an organic layer having a higher refractive index than that of the liquid crystal layer300, the UV rays irradiated from the side of the sealant170are not incident on the pixel region P but are refracted to travel in a thickness direction of the display and are emitted to the outside of the light blocker180as indicated by an arrow L ofFIG. 3E. As described above, a phenomenon where the boundary portion of the pixel region P becomes dark by hardening of the liquid crystal layer300along the boundary portion via UV rays irradiated from the side of the sealant170during the ODF process may be prevented.

Turning now toFIG. 3F,FIG. 3Fis a cross-sectional view for describing a method of forming the liquid crystal layer300ofFIG. 2B. Referring toFIG. 3F, the liquid crystal molecules310and the RM monomer330are disposed between the first and second substrate arrangements100and200. The liquid crystal molecules310and the RM monomer330may be randomly disposed between the first and second substrate arrangements100and200.

Next, a first voltage Vcom is applied to the common electrode250, and a second voltage Vdata different from the first voltage Vcom is applied to the pixel electrode PE. When the first voltage Vcom is applied to the common electrode250and the second voltage Vdata is applied to the pixel electrode PE, an electric field is formed between the pixel electrode PE and the common electrode250. When the electric field is formed, the major axis of the liquid crystal molecules310is tilted in a direction perpendicular to a direction of the electric field.

The first voltage Vcom may have a higher level than the second voltage Vdata. In detail, the first voltage Vcom may be about 0 V, and the second voltage Vdata may have a negative value. The second voltage Vdata may be, for example, about −5 V.

A light is irradiated on the first and second substrate arrangement100and200while the liquid crystal molecules310are pre-tilted due to the electric field between the first and second substrate arrangements100and200. The light may be, for example, UV rays. The RM monomers330may photo-react and be polymerized due to the light, thereby forming the RM cured product320disposed between the liquid crystal molecules310. Accordingly, the liquid crystal layer300disposed between the first and second substrate arrangement100and200according to the current embodiment of the present invention, may be formed.

According to the current embodiment of the present invention, the liquid crystal domain may be formed by the depression pattern152of the domain forming layer150, without having to form a separate pattern in the common electrode250. Accordingly, an aperture ratio of the pixel region P may be improved, and a viewing angle of the display device may be improved. Also, since the common electrode250does not have a separate pattern, misalignment of the first and second substrate arrangements100and200is completely prevented. In addition, a manufacturing process is simplified by omitting a separate process of patterning the common electrode250. Accordingly, productivity and display quality of the display device may be improved.

According to the above display device and the method of manufacturing the same, a phenomenon where a boundary portion of a pixel region becomes dark by hardening a liquid crystal layer in the boundary portion via UV rays irradiated from a side of a sealant during an ODF process may be prevented.