KR102037957B1 - Method of Preparing Optical Structure Having Controlled Liquid Crystal Alignment Using Softlithography and Optical Structure Prepared Thereby - Google Patents

Abstract

The present invention provides a method and method for manufacturing a liquid crystal alignment control optical structure using soft lithography which induces the formation of a defect structure having a regular arrangement by controlling the orientation of the organic liquid crystal monomolecules in a partition system made by soft lithography. The present invention relates to a liquid crystal alignment control optical structure manufactured by the present invention, which simultaneously produces surface defects, rubbing effects, and restraint effects that cannot be established at the same time, while generating a defect structure having a regular arrangement, and is uniformly aligned in a large area. It is possible to implement an orientation control platform that generates various defect structures.

Description

Method of preparing liquid crystal alignment control optical structure using soft lithography and a liquid crystal alignment control optical structure manufactured by the above method.

The present invention relates to a method for manufacturing a liquid crystal alignment control optical structure using soft lithography, and to a liquid crystal alignment control optical structure manufactured by the above method. The present invention relates to a method for manufacturing a liquid crystal alignment control optical structure using soft lithography that controls the partition wall system to induce the generation of a defect structure having a regular arrangement, and a liquid crystal alignment control optical structure manufactured by the method.

One of the useful ways to fabricate functional nanostructures that express specific structural and electro-optic properties is to assemble spontaneously stable structures in search of thermodynamic stability of the basic units of the structure. It has attracted attention in the field of science and technology.

Until recently, the development of the technology of obtaining the uniaxially oriented liquid crystal film by suppressing the generation of a defect structure required in major industries using liquid crystal has been intensively studied. However, in order to understand the cause of defect structure and basic understanding of structure, research on control and orientation method of defect structure is essential. Another interesting research topic in this regard is the fabrication of regularly ordered arrays of self-assembled assemblies. However, this still requires expensive process costs and a long time. In order to generate the periodic arrangement of the defect structure, an artificial process is performed, and typical processes include mechanical friction, chemical surface modification, or implementation of restraining effect using microchannels.

M. C. Choi et al. And HT Jung et al. Disclose periodically aligned defects when a liquid crystal having a smectic phase is located in a limited space treated with specific surface conditions (MC Choi et al., PNAS, 2004, 101, 17340-17344). HT Jung et al., J. Mater. Chem. 2011, 21, 18381-18385).

A common way to impose a confined space on the liquid crystal material is to use microchannels made of surface-treated silicon or polymer material. In this method, where the surface area is larger than the volume, the liquid crystal material reacts more finely to boundary conditions. do. In the liquid crystal phase, the arrangement of the liquid crystals is changed by different boundary conditions. In particular, when the smectic liquid crystal is placed under these conditions, the closer to the molecular-philic substrate, the parallel to the direction of the substrate, The closer it is, the more it tries to arrange vertically. Therefore, due to the physicochemical properties of the molecules, the orientation is tangential from the wall to the center, forming a defect structure called a toric focal conic domain (TFCD) with a conical structure and periodically aligned along the channel direction. In addition to this method, a rubbing technique may be used as a process for controlling molecular arrangement of liquid crystals. It is a technique that mechanically processes the surface of a polymer film to form grooves in one direction and orients the liquid crystals along the direction of the processed grooves, and it is reported that the orientation due to rubbing is effectively controlled when using liquid crystals passing through the nematic phase. There is a bar (Korean Patent Publication No. 2006-0048682). International Publication No. WO2016-137488 A1 also discloses the fabrication of channels in glass articles by laser damage and etching.

Recently, the researched trend has been limited because microchannels based on silicon or polymer materials are mainly used for defect structure control, so that the channel walls and the lower ends should be coated with a polymer film that induces the same surface conditions. Both substrates could not be implemented on the same system because phased substrates could not be controlled by a rubbing process.

Accordingly, the present inventors have made diligent efforts to solve the above problems, and as a result, the alignment of the organic liquid crystal monomolecules is controlled and orderly arranged in the partition system by transferring the polymer-based microchannels to other grooved substrates using a soft lithography technique. Simultaneously, it is possible to simultaneously create surface defects, rubbing and restraining effects that have not been established, and to realize an orientation control platform that generates various defect structures that are uniformly aligned in a large area. This invention was completed.

An object of the present invention is to control the alignment of liquid crystals using softlithography, which enables a simple and fast process to control the chemical properties of the surface of the channel using soft lithography and to provide a rubbing condition control and restraint effect. It is to provide a method of manufacturing an optical structure.

Another object of the present invention is to provide a liquid crystal alignment control optical structure that can compensate for the optical crosstalk (low black color) implementation of the disadvantages of the existing LCD, and applicable to all LC modes such as IPS, PVA, TN cells, etc. have.

In order to achieve the above object, the present invention comprises the steps of (a) injecting the liquid crystal molecules at an isotropic temperature of the liquid crystal molecules between the upper substrate and the lower substrate to maintain a constant interval; (b) placing a polymer mold having a predetermined barrier structure on the upper substrate, and then applying heat thereon to transfer the barrier structure to the lower substrate; And (c) provides a method for producing a liquid crystal alignment control optical structure using softlithography comprising the step of cooling the liquid crystal molecules to generate a phase transition.

The present invention also provides a liquid crystal alignment control optical structure manufactured by the above method, characterized in that an array of defect structures of a focal conic domain (FCD) appears in a large area.

According to the present invention, it is possible to variously control the orientation of the liquid crystal molecules by simultaneously implementing the restraint, surface modification control / rubbing condition adjustment effect on one glass substrate. This makes it possible to apply to the liquid crystal having a nematic phase and smectic phase, which is difficult to control the orientation, and to control the structure and physical properties of the more complex liquid crystal molecules, thereby making it widely applicable to electro-optical devices and patterning fields through the orientation of nanoparticles. Can be. In addition, it is possible to improve the LCD technology because it is possible to prevent optical crosstalk and improve the black level by adding a dye or changing a substrate.

The resulting optical structures can be used in potential optical and patterning applications and in a variety of applications in the field of displays as well as electro-optical devices.

In addition, unlike conventional methods of etching a surface or using laser damage to make a barrier system into a glass substrate, it is a simple process requiring a relatively low cost and a short process by transferring using a polymer mold that can be used continuously.

1 is a molecular structure of (a) the 8CB liquid crystal used in the present invention, and (b) a polarization microscope image of the liquid crystal defect structure according to the rubbing conditions.
2 is a schematic diagram illustrating a process of a liquid crystal alignment platform using a soft lithography technique according to the present invention.
3 is a polarization microscope image of the defect structure control according to the conflicting surface boundary conditions and rubbing process conditions according to an embodiment of the present invention.
4 is a schematic view of a liquid crystal alignment corresponding to the defect structure observed in FIG. 3.
5 is an image of the brush texture observed in the partition wall according to an embodiment of the present invention observed with a polarizing microscope and a fluorescence microscope.
FIG. 6 is a polarization microscope image photographing defect structure control according to rubbing conditions when surface boundary conditions of a partition and a lower substrate are equalized according to an embodiment of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein and the experimental methods described below are well known and commonly used in the art.

In the present invention, the method of imparting different boundary conditions to the partition and the lower substrate, the rubbing effect on the lower substrate, and the confining effect through the channel are simultaneously independent of the soft lithography technique. We developed a unique and groundbreaking orientation control platform that can be provided as a technology to create various defect structures that are uniformly aligned in large area.

Therefore, in one aspect, the present invention includes the steps of: (a) injecting liquid crystal molecules at an isotropic temperature of the liquid crystal molecules between the upper substrate and the lower substrate to maintain a constant interval; (b) placing a polymer mold having a predetermined barrier structure on the upper substrate, and then applying heat to transfer the barrier structure to the lower substrate; And (c) cooling the liquid crystal molecules to generate a phase transition. The present invention relates to a method for manufacturing a liquid crystal alignment control optical structure using softlithography.

The present invention is a technology to create a liquid crystal alignment platform that can simultaneously implement the confinement effect, chemical surface modification control, mechanical orientation direction control by transferring the partition system to the glass substrate using a soft lithography technique. Simultaneous independent constraint, surface modification, and rubbing effects, which have been difficult to implement in the conventional liquid crystal alignment method, can be realized in a simplified and relatively short process. Through the above invention, the alignment of liquid crystal monomolecules having a nematic phase and a smectic phase in turn can be achieved. The surface boundary conditions and rubbing conditions can be adjusted and controlled at the micrometer or nanometer level to create various periodic defect structures.

The present invention based on the soft lithography technique can generate various defect structures because the surface boundary conditions of the lower end and the partition wall of the transferred microchannel can be treated differently and the direction of mechanical alignment can be adjusted at the same time.

The liquid crystal alignment control platform according to the present invention results from the addition of simple soft lithography techniques to the process. A microchannel made of silicon is used as a mold to fabricate a polydimethylsiloxane (PDMS) mold, which is a porous polymer material, and the fabricated mold is used to transfer barrier ribs having a micrometer-level spacing onto another glass substrate. The glass substrate is treated with a hydrophilic polymer solution that induces liquid crystal alignment parallel to the substrate and determines the presence or absence of a rubbing process according to the needs of the user. The polymer mold is placed on the grooved substrate in the same direction as the groove or perpendicular to the groove, and a small molecular polymer solution is introduced into the inlet and injected through capillary force, which induces boundary conditions different from those processed on the substrate. As a result, a groove is formed in the lower substrate to induce uniaxial alignment, and a liquid crystal alignment system is completed in the partition wall to give different boundary conditions. In addition, by controlling the presence or absence of rubbing, the direction of the formed groove and the direction of the partition wall can be made additionally adjustable parameters through which the structure can be controlled according to various orientations.

The liquid crystal alignment platform process including the soft lithography technique according to the present invention is shown in FIG. 2.

The 8CB liquid crystal molecules are injected using capillary force at a low clustered and non-arranged isotropic temperature on the thus prepared platform and are cooled to nematic and smecting phases to express various optical structures. First, when no groove is formed in the lower substrate, the liquid crystal molecules are gradually elastically deformed from the wall toward the center of the channel on the nematic phase. In the partition, the directors of the molecules are vertically aligned in the channel direction. It means that parallel arrangements are made toward the central part. When the transition to the smectic phase, the molecules form a layered structure, resulting in a defect structure different from the nematic phase, and the FCD defect array oriented in one direction at the center of the channel and the brush-like texture at the partition wall. Can be. In the Smectic phase, splay deformation of the spreading pattern is preferred. In the partition, the layered structure must be equally spaced while satisfying the boundary conditions between the air and the polymer membrane, and thus the elastic deformation is suppressed and the layer is tilted. Unique layered structures showing ups and downs will be developed. This corresponds to a brush-like texture observed in the partition wall, which was observed with a fluorescence microscope (FIG. 5). In the central part, where the effect from the wall is relatively weak, a curvature is formed to simultaneously match the boundary condition caused by air with the boundary condition caused by the substrate, which results in a skewed FCD defect and at lower smectic temperatures This leads to a TFCD defect array that is thermodynamically more stable. Next, when the groove through the rubbing process is present in the same direction as the channel on the lower substrate, the liquid crystal material is affected by the conflicting alignment force at the partition and the lower center portion. The bulkhead receives a force oriented perpendicular to the channel direction depending on the surface boundary conditions, and a force oriented parallel to the channel direction at the lower center of the center where the uniaxial alignment force of the groove is stronger, which is clearly distinguished from the nematic view. This can be verified through the domain (Figure 3 (b)). As mentioned earlier, when the transition to the smectic phase, the arrangement of the nematic phase is maintained. As shown in FIG. 3 (e), the brush-like texture is observed on the wall and the FCD alignment is aligned in the channel direction at the center. Finally, when the groove direction and the channel direction are perpendicular to each other, the boundary condition of the barrier and the orientation direction of the lower substrate coincide with each other, which can be confirmed through the single domain shown in the nematic image (FIG. As the transition to the smectic phase, the arcs of the FCD formed along the direction of the grooves, and at lower temperatures, the zigzag pattern, which alternates with the FCD defects, was observed periodically.

3 is a polarization microscope image of a defect structure control that appears when conflicting surface boundary conditions and rubbing process conditions are different. In the case of (a, d, g), rubbing is not applied to the lower substrate, and in the case of (b, e, h), the rubbing direction and the channel direction coincide with each other, and (c, f, i) The optical texture obtained when the direction of rubbing and the channel direction are perpendicular to each other is shown.

Therefore, in the present invention, the lower substrate may not have a groove, or a groove in the same direction as the upper substrate and the polymer mold may be formed in the lower substrate, or in a direction perpendicular to the upper substrate and the polymer mold. Grooves may be formed in the lower substrate.

In the present invention, the polymer mold may be a porous polymer material manufactured using a microchannel made of silicon as a mold, and preferably, the polymer mold may be polydimethylsiloxane (PDMS).

In the present invention, before the step (a) may further comprise the step of coating the lower substrate with a polymer molecule.

It may further comprise a step of rubbing after the coating step.

The method may further include coating a polymer mold having a predetermined barrier structure on the upper substrate of step (b) and then coating the upper substrate with a small molecular polymer film.

The liquid crystal molecule may be 4'-n-octyl-4-cyano-biphenyl represented by Chemical Formula 1 (4'-n-octyl-4-cyano-biphenyl).

[Formula 1]

The molecular structure of the 8CB liquid crystal used in the present invention is shown in FIG. 1 (a), and FIG. 1 (b) shows a polarization microscope image of the liquid crystal defect structure according to rubbing conditions.

Figure 1 (a) shows the molecular structure of the 8CB liquid crystal used in the present invention, this material has an isotropic phase, a nematic phase, a smectic phase in sequence with the temperature drop. Changes in optical textures and liquid crystal defects that occur when a sandwich cell made by combining a substrate coated with a polymer molecule and a substrate coated with a polymer molecule is not rubbed (pristine) or cooled when it is cooled from isotropic temperature The polarization microscope images of each observed are shown in FIG. 1 (b).

In the manufacturing method of the present invention, the liquid crystal molecules may be phase shifted into the nematic phase and the smectic phase.

The liquid crystal molecules are 8CB (4′-n-octyl-4-cyano-biphenyl) and have an isotropic phase, a nematic phase, and a smectic phase in sequence during cooling. In general, since nematic liquid crystals have a long-range order, control of orientation by rubbing occurs to a relatively distant molecule, and the controlled arrangement is transferred to the smectic phase. In other words, when the nematic liquid crystals arranged in one axis become a smecting phase having a layer while cooling, various optical textures are displayed according to surface boundary conditions. As a representative example, a defect structure called TFCD or FCD appears in large areas depending on the presence or absence of a rubbing process between a substrate treated with a molecular material and a substrate treated with a molecular-phobic material.

Step (b) in the manufacturing method of the present invention puts a polymer mold having a predetermined barrier structure on the upper substrate, and then heats to evaporate the solvent, and removes the polymer mold, 1.5 ~ 2 at a temperature of 150 ~ 200 ℃ Curing for time may transfer the barrier rib structure to the underlying substrate.

The present invention relates to a liquid crystal alignment control optical structure which is manufactured by the above method in another aspect, wherein a defect structure array of a focal conic domain (FCD) appears in a large area.

The cone structure may be a toric focal conic domain (TFCD).

In the present invention, the width of the defect structure is 10 ~ 15㎛, the depth may have a recessed topographical characteristic of 100 ~ 300nm.

In implementing the method of the present invention, various liquid crystal alignment control optical structures may be manufactured according to the shape of the lower substrate.

First, when there was no groove in the lower substrate, it was confirmed that a liquid crystal alignment control optical structure having an FCD defect array oriented in one direction at the center of the channel and a brush-like texture at the partition portion could be produced.

Therefore, in another aspect, the present invention relates to a liquid crystal alignment control optical structure, which is manufactured by a method in which no groove is formed in a lower substrate, and a brush texture is formed on a side wall of each of the TFCD arrays in the lower substrate. will be.

Next, when grooves in the same direction as the upper substrate and the polymer mold were dug into the lower substrate, it was confirmed that a liquid crystal alignment control optical structure in which brush textures were formed on the sidewalls and FCD arrays were expressed in the lower substrate, respectively.

Accordingly, the present invention is also manufactured by a method in which grooves in the same direction as the upper substrate and the polymer mold are dug into the lower substrate in another aspect, and brush textures are formed on the sidewalls and FCD arrays are respectively expressed in the lower substrate. It relates to a liquid crystal alignment control optical structure characterized in that.

In addition, when grooves in a direction perpendicular to the upper substrate and the polymer mold were dug into the lower substrate, it was confirmed that a liquid crystal alignment control optical structure in which a zigzag pattern in which FCD defects were alternately formed was expressed.

Accordingly, the present invention also provides a zigzag pattern in which a groove in a direction perpendicular to the upper substrate and the polymer mold is dug into the lower substrate, and an zigzag pattern in which FCD defects are alternately formed is expressed from another viewpoint. It relates to a liquid crystal alignment control optical structure.

The 8CB liquid crystal molecules are injected using capillary force at a low clustered and non-arranged isotropic temperature on the thus prepared platform and are cooled to nematic and smecting phases to express various optical structures. In the case where there is no groove in the lower substrate, liquid crystal molecules gradually undergo elastic deformation from the wall to the center of the channel in the nematic phase. In the partition, the directors of the molecules are vertically aligned in the channel direction. It means that the array is parallel to the part. When the transition to the smectic phase, the molecules form a layered structure, resulting in a defect structure different from the nematic phase, and the FCD defect array oriented in one direction at the center of the channel and the brush-like texture at the partition wall. Can be. In the Smectic phase, the Splay deformation of the spreading pattern is preferred. In the partition, the layer structure must be equally spaced while satisfying the boundary conditions between the air and the polymer membrane. Unique layered structures showing ups and downs will be developed. This corresponds to a brush-like texture observed in the partition wall (FIG. 5). In the central part, where the effect from the wall is relatively weak, a curvature is formed to simultaneously match the boundary condition caused by air with the boundary condition caused by the substrate, which results in a skewed FCD defect and at lower smectic temperatures This leads to a TFCD defect array that is thermodynamically more stable. Next, when the groove through the rubbing process is present in the same direction as the channel on the lower substrate, the liquid crystal material is affected by the conflicting alignment force at the partition and the lower center portion. The bulkhead receives a force oriented perpendicular to the channel direction depending on the surface boundary conditions, and a force oriented parallel to the channel direction at the lower center of the center where the uniaxial alignment force of the groove is stronger, which is clearly distinguished from the nematic view. This can be verified through the domain (Figure 3 (b)). As mentioned earlier, when the transition to the smectic phase, the arrangement that was held on the nematic phase is maintained. As shown in FIG. 3 (e), a brush-like texture is observed on the wall and an FCD alignment is aligned in the channel direction at the center. Finally, when the groove direction and the channel direction are perpendicular to each other, the boundary condition of the barrier and the orientation direction of the lower substrate coincide with each other, which can be confirmed through the single domain shown in the nematic image (FIG. 3 (c)). As the transition to the smectic phase occurs, arcs of FCDs are formed along the direction of the grooves, and at lower temperatures, zigzag patterns are created periodically, alternating with FCD defects.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not to be construed as being limited by these examples.

EXAMPLE

Example  One

Fabrication of Sandwich Cells

Prior to testing the liquid crystal alignment platform, two kinds of sandwich cells were fabricated to observe the optical texture according to rubbing and surface boundary conditions. In order to make the surface boundary condition the same as the platform, the upper substrate was coated with a molecular-phobic polyimide and the lower substrate was coated with a molecular-philic polyimide. A 5 μm bead was placed between the two substrates to give a constant spacing. The bottom substrate of one kind of sandwich cell was used to create a groove engraved uniaxially using a rubbing machine (RMS-50-M, Namil).

PDMS ( polydimethylsiloxane ) Mold  making

The microchannel (depth: 7 μm, width: 20 μm) produced through photolithography was converted into acetone (acetone, SAMCHUN chemical), ethanol (ethyl alcohol, SAMCHUN chemical), and tertiary distilled water (18.3MΩ / cm, Human Corp.). After cleaning cleanly using.), The treated substrate was exposed to oxygen plasma (100W, running time 5min) to create an environment in which hydroxyl groups were exposed to the surface. 100 ml of small molecule self-assembled monolayer FOTS (perfluorooctyltrichlorosilane, Gelest) in 2 ml vials were placed in a desiccator with a substrate and exposed for 1 hour in a vacuum environment for physical deposition. Thereafter, the substrate was taken out and left for 1 hour in a heating stage heated to 120 ° C. for chemical bonding of the small molecule molecules and the substrate.

PDMS (polydimethylsiloxane) base (base) and crosslinker (crosslinker agent) was mixed in a ratio of 10: 1, and then mixed well. The uncrosslinked PDMS mixture was poured into microchannels and left in vacuum for one hour to remove bubbles. The cured PDMS membrane was then cured in an oven at 65 ° C. for 4 hours and the cured PDMS membrane was separated from the silicon microchannels.

With surface boundaries Loving  Condition Adjustable  Polymer based micro channel system

The glass substrate was washed with acetone (acetone, SAMCHUN chemical), ethanol (ethyl alcohol, SAMCHUN chemical), and tertiary distilled water (18.3 MΩ / cm, Human Corp.) in that order. In order to induce the orientation of the liquid crystal molecules, a hydrophilic polyimide solution, an imide-based polymer, was spin-coated on a substrate and cured by soft baking and hard baking at 90 ° C. and 200 ° C., respectively. The presence of rubbing depends on the defect structure to be made. In the rubbing process, a rubbing machine (RMS-50-M, Namil) was used to rub the glass substrate in one direction to form a groove. The PDMS mold prepared in the previous step was placed so that a closed channel was formed on the glass substrate. At this time, the liquid crystal alignment system of three conditions can be made, one of which puts the PDMS mold on the non-rubbing substrate, the other of which puts the mold in the same direction as the rubbing direction and the channel direction, and finally the rubbing. This is the case where the channel direction is perpendicular to the direction in which the direction is given. A hydrophobic polyimide solution was dropped at the channel inlet formed by the glass substrate and the mold to inject the polymer material through the capillary effect. Thereafter, the solvent was removed at 90 ° C. for 15 minutes, and then the PDMS mold was removed from the substrate. When heated at 200 ° C. for 2 hours to cure the partition wall formed of the small molecule polymer, the microchannel having the orientation force in one direction is completed on the lower substrate while the boundary conditions between the lower substrate and the sidewall are different.

When the surface boundary condition of the side wall and the boundary condition of the lower substrate were the same, a hydrophilic polyimide solution was injected into the channel formed by combining the glass substrate and the mold, and the following procedure was performed in the same manner.

Liquid Crystal Material Preparation and Injection

The liquid crystal used in the present invention has an isotropic phase, a nematic phase, and a smectic phase in the course of cooling with 8CB (4′-n-octyl-4-cyano-biphenyl, Synthon Chemicals).

To observe by fluorescence microscope, the fluorescent dye N, N'-bis (2,5-di- tert- butylphenyl) -3,4,9,10-perylenedicarboximide (BTBP) was mixed with 8CB at 0.01wt% and 60 The solvent was removed by heating to 캜. The dye absorbs light in the 488nm region and emits light in the 510-550nm region.

The liquid crystal alignment platform fabricated in the above process was placed on a heating end (Linkam LTS420) heated above isotropic temperature (42 ° C.) and the liquid crystal was injected through the capillary effect.

variety Optical texture  observe

The optical texture appearing on each liquid crystal phase was observed through a polarization microscope (LV 100-POL, Nikon) while cooling from an isotropic temperature at 1 ° C./min using a hot stage.

Observation was made at smectic temperature using a fluorescence microscope (LSFCM, Nikon) to obtain detailed information on molecular orientation. At this time, since the maximum brightness when the direction of the dye and the laser match, and the minimum brightness when the vertical direction, it was confirmed the molecular orientation through this.

3 is a polarization microscope image of a defect structure control that appears when conflicting surface boundary conditions and rubbing process conditions are different. In FIGS. 3A, 3D, and 3G, rubbing is not applied to the lower substrate, and in FIGS. 3B, 3E, and 3H, the rubbing is performed. 3 (c), 3 (f) and 3 (i) show optical textures obtained when the rubbing direction and the channel direction are perpendicular to each other.

When the groove through the rubbing process is present in the same direction as the channel in the lower substrate, the liquid crystal material is affected by the conflicting alignment force at the partition wall and the lower center portion. The bulkhead receives a force oriented perpendicular to the channel direction depending on the surface boundary conditions, and a force oriented parallel to the channel direction at the lower center of the center where the uniaxial alignment force of the groove is stronger, which is clearly distinguished from the nematic view. This can be verified through the domain (Figure 3 (b)). As mentioned above, when the transition to the smectic phase, the arrangement that was held on the nematic phase is maintained. As shown in FIG. 3 (e), the brush-like texture is observed on the wall and the FCD alignment is aligned in the channel direction at the center. Finally, when the groove direction and the channel direction are perpendicular to each other, the boundary condition of the barrier and the orientation direction of the lower substrate coincide with each other, which can be confirmed through the single domain shown in the nematic image (FIG. 3 (c)). As the transition to the smectic phase, the arcs of the FCD formed along the direction of the grooves, and at lower temperatures, the zigzag pattern, which alternates with the FCD defects, was observed periodically.

4 is a schematic view of a liquid crystal alignment corresponding to the defect structure observed in FIG. 3. The upper images are the top-down view, and the lower images correspond to the cross-section view. In the case of FIG. 4A, the brush textures are formed on the sidewalls, and the TFCD defects (green marking) arrays are formed in the center of the channel. In the case of FIG. 4 (b), the brush texture appears on the sidewall and the FCD defect array appears in the center of the channel due to the rubbing effect parallel to the channel direction. The red area of the bottom image means that the polar angle of the molecules gradually changes from the front to the back of the screen. In the case of Figure 4 (c) due to the rubbing effect perpendicular to the channel direction, the zigzag pattern alternates FCD defects appear. The nail ("T") represents the change in the directors whose ends are towards the inside of the screen, and the red dots and lines represent the hyperbolic curve of the FCD defect.

=530nm)를 삽입한 후 관찰된 이미지에 해당한다. 도 5(d) 및 도 5(e)는 형광현미경으로 관찰되었으며 분자의 배향과 일치하는 형광염료의 배향이 레이저와 같은 방향일 때 밝기가 최대가 되며 수직일 때 최소가 된다. 표시된 화살표는 레이저의 방향을 의미한다.FIG. 5 is an image of a brush texture observed in a partition wall using a polarization microscope and a fluorescence microscope. FIG. 5 (a), 5 (b) and 5 (c) were observed with a polarizing microscope, and the right image of FIG. 5 (a) and the image of FIG. 5 (c) are retardation plates (retardation plate,

= 530 nm) corresponds to the observed image. 5 (d) and 5 (e) are observed under a fluorescence microscope, and the brightness is maximized when the orientation of the fluorescent dye coinciding with the orientation of the molecule is the maximum and the minimum when the orientation is vertical. The arrows indicated indicate the direction of the laser.

In order to demonstrate the flexibility of the present invention, the experiment was carried out by changing the surface condition of the barrier rib to a polymer molecule, and is shown in FIG. 6.

6 is a polarization microscope image of the defect structure control according to the rubbing conditions when the surface boundary conditions of the barrier rib and the lower substrate are the same. 6 (a), 6 (d) and 6 (g), no rubbing is applied to the lower substrate, and rubbing in FIGS. 6 (b), 6 (e) and 6 (h). 6 (c), 6 (f), and 6 (i) show optical textures obtained when the direction of rubbing and the channel direction are perpendicular to each other.

Through this, it was confirmed that the same optical structure is implemented on Smectic even under different rubbing process conditions. When the experiment was conducted under three different conditions, the semi-molecular TFCD defect structure appeared in the partition and the four lobes along the direction of the groove appeared at the center of the channel because the hydrophilic boundary condition from the partition oriented the tangent from the wall. The TFCD structures were observed to align.

Therefore, by using a simple soft lithography technique, a microchannel with conflicting surface boundary conditions can be fabricated and a process technology for controlling rubbing conditions on the underlying substrate can be used to control various optical structures while controlling the presented parameters even with the same liquid crystal materials. It is thought to be able to express.

In the present invention, although the experiment was conducted with liquid crystal molecules having a smectic phase and a nematic phase, more complicated liquid crystal materials will be controlled based on the liquid crystal alignment platform. The technique can be extended to create barriers at the nanoscale using nanoscale channel molds, which means that liquid crystal molecules can be easily oriented at the micro or nanometer level. In addition, since the main material for making the partition wall is a polymer material in a liquid state, the color of the partition wall can be made black by properly mixing the dye having black color. If this technology is applied to an LCD (Liquid Crystal Display), the bulkhead is erected to prevent optical crosstalk between the pixels, allowing independent data generation of each pixel, and when using black bulkheads, the Plasma Display Panel Since the contrast ratio can be increased by improving the black level, which is lower than that of the PDP, it is expected to lead to the development of a technology that can compensate for the limitations of the optical crosstalk and the black level, which are disadvantages of the LCD.

As described above in detail specific parts of the present invention, it will be apparent to those skilled in the art that these specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. will be. Thus, the substantial scope of the present invention will be defined by the claims and their equivalents.

Claims (17)

Method for manufacturing a liquid crystal alignment control optical structure using softlithography comprising the following steps:
(a) injecting liquid crystal molecules at an isotropic temperature of the liquid crystal molecules between the upper substrate and the lower substrate maintaining a constant interval;
(b) placing a polymer mold having a predetermined barrier structure on the upper substrate, and then applying heat to transfer the barrier structure to the lower substrate; And
(c) manufacturing a liquid crystal alignment control optical structure, characterized in that the liquid crystal molecules are cooled to generate phase transitions so that a defect structure array of a conical structure (FCD) appears in a large area.
The method for manufacturing a liquid crystal alignment control optical structure according to claim 1, wherein the lower substrate is not provided with a groove.
The method of claim 1, wherein grooves in the same direction as the upper substrate and the polymer mold are formed in the lower substrate.
The method of claim 1, wherein a groove in a direction perpendicular to the upper substrate and the polymer mold is formed in the lower substrate.
The method of claim 1, wherein the polymer mold is a porous polymer material manufactured by using a microchannel made of silicon as a mold.
The method of claim 5, wherein the polymer mold is polydimethylsiloxane (PDMS).
The method of claim 1, further comprising: coating the lower substrate with a molecular polymer film before step (a).
The method of claim 7, further comprising a step of rubbing after the coating step.
The liquid crystal alignment control optical structure of claim 1, further comprising: placing a polymer mold having a predetermined barrier structure on the upper substrate of step (b), and then coating the upper substrate with a small molecular polymer film. Manufacturing method.
The liquid crystal alignment of claim 1, wherein the liquid crystal molecule is 4'-n-octyl-4-cyano-biphenyl represented by Chemical Formula 1. Method for producing a control optical structure.
[Formula 1]

The method for producing a liquid crystal alignment control optical structure according to claim 1, wherein the liquid crystal molecules are cooled to generate a phase transition between the nematic phase and the smectic phase.
The method of claim 1, wherein the step (b) comprises placing a polymer mold having a predetermined barrier structure on the upper substrate, and then applying a heat to remove the solvent and the polymer mold, at a temperature of 150 to 200 ° C. for 1.5 to 2 hours. A method of manufacturing a liquid crystal alignment control optical structure, characterized in that to harden during the transfer to transfer the partition structure to the lower substrate.
The liquid crystal alignment control optical structure manufactured by the method according to any one of claims 1 to 12, wherein a defect structure array of a focal conic domain (FCD) appears in a large area.
The liquid crystal alignment control optical structure of claim 13, wherein the defect structure has a recessed topographical characteristic having a width of 10 to 15 μm and a depth of 100 to 300 nm.
The liquid crystal alignment control optical structure manufactured by the method of claim 2, wherein a brush texture is formed on a side wall of the TFCD array in the lower substrate, respectively.
The liquid crystal alignment control optical structure manufactured by the method of claim 3, wherein the sidewalls each have a brush texture and an FCD array is expressed in the lower substrate.
A liquid crystal alignment control optical structure manufactured by the method of claim 4, wherein a zigzag pattern in which FCD defects are alternately formed is expressed.

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