KR101188434B1 - Method for Fabricating Micro- or Nano-Sized Patterns Using Liquid Crystal Phase and Defect Structure Thereof - Google Patents

Abstract

The present invention relates to a method for forming micro or nano size patterns using various phase or defect structures of liquid crystals, and to microlens arrays manufactured by the method. In detail, a pattern formation method and a microlens array may be used as a mask for optical or soft lithography by forming an image or defect of a self-assembleable liquid crystal into a regular structure and using a refractive index change or surface structure according to liquid crystal alignment. It is about.
According to the present invention, a pattern formation method using a phase or defect structure of liquid crystal molecules, a method of manufacturing a microlens array, and a soft lithography pattern formation method form a pattern much faster than conventional methods due to the high mobility of liquid crystals. It is possible to do, and the manufacturing process is simple and the cost is reduced. Once created, the liquid crystal pattern can be used semi-permanently. In addition, since the phase or defect of the liquid crystal can be easily adjusted by an external electric field or a magnetic field or the height of the liquid crystal molecular layer, there is an advantage that it can be easily changed and controlled in a new pattern. In addition, by transferring information on the internal structure and orientation of the liquid crystal which is difficult to directly observe, it is possible to propose a new technique for the analysis of the internal structure.

Description

Method for Fabricating Micro- or Nano-Sized Patterns Using Liquid Crystal Phase and Defect Structure Thereof}

The present invention relates to a method for forming micro or nano size patterns using various phase or defect structures of liquid crystals, and to microlens arrays manufactured by the method. In detail, a pattern formation method and a microlens array may be used as a mask for optical or soft lithography by forming an image or defect of a self-assembleable liquid crystal into a regular structure and using a refractive index change or surface structure according to liquid crystal alignment. It is about.

The development of microlens arrays for use in miniature devices has been a major issue in micro-optics over the past decade. The main concern is for the development of parallel with other optical system components such as light diffusers, biomimetic artificial compound eyes and out-coupling display devices. It has been tailored to the technology for the fabrication of highly regular microlens arrays with good surface characteristics. Some technologies include photolithography, holographic, lithography, photothermal patterning, inkjet printing, and polymeric particle self-assembly. It has been used for the manufacture of lens arrays. Such systems have been studied in detail, but often have problems such as requiring pre-patterned molds, expensive equipment and complex process steps.

Microlens photolithographic fabrication using self-assembled materials has been an attractive challenge in recent years because the technology is very simple, inexpensive and provides a way to produce large area patterns. Several materials, including colloids, hydrogels and liquid crystals, have been used in self-assembled microlens arrays for photolithographic applications. Colloidal microspheres with a diameter of 3 μm were embedded in a transparent polymer membrane and used as a lens to reduce the centimeter scale image to the micrometer scale image in the image plane. These microspheres provide a simple way to create spontaneous assembly with appropriate feature sizes over a wide area and have been used as microlens arrays optimized for visible light. Biomimetic hydrogels have also been used to make microlens arrays for photolithography.

All of these systems have been applied to conventional microlens system morphologies, including spherical or hemispherical geometry with homogeneous refractive indices, but reveal the limitations of forming nanoscale precise patterns, which takes a long time for precise patterns. Or, to overcome the problems of complicated processes and expensive costs is not currently proposed.

Accordingly, the present inventors have made diligent efforts to solve the above problems, and when a pattern is formed using a liquid crystal phase or a defect structure, a precise pattern of micro or nano size can be formed in a short time and the pattern It was confirmed that the fine adjustment of the simple and low cost can be implemented, the present invention was completed.

An object of the present invention is to provide a method for forming a micro or nano pattern using a phase or defect structure of the liquid crystal molecules.

Another object of the present invention is to provide a method of manufacturing a microlens array in which a micro or nano pattern is formed using a phase or defect structure of liquid crystal molecules.

Another object of the present invention is to provide a method of forming a soft lithography pattern using the surface structure of a defect structure of liquid crystal molecules.

In order to achieve the above object, the present invention (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to the phase structure of the liquid crystal molecules in the liquid crystal molecule layer; And (c) forming a micro or nano size pattern in a photoresist using the regular structure of the liquid crystal molecules as a photomask. .

The present invention also comprises the steps of (a) surface treatment; (b) forming a liquid crystal molecule layer on the surface treated substrate; And (c) forming a regular structure according to the structure of the liquid crystal phase in a state in which an external electric field or a magnetic field is applied to the liquid crystal molecule layer.

The present invention also comprises the steps of (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to a defect structure of the liquid crystal molecules in the liquid crystal molecule layer; And (c) forming a micro or nano size pattern on the photoresist using the regular structure of the liquid crystal molecules as a photomask. .

The present invention also comprises the steps of (a) surface treatment; (b) forming a liquid crystal molecule layer on the surface treated substrate; And (c) forming a regular structure according to the defect structure of the liquid crystal in the liquid crystal molecule layer.

The present invention also comprises the steps of (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to a defect structure of the liquid crystal molecules in the liquid crystal molecule layer; (c) applying an ultraviolet curable polymer onto the liquid crystal molecule layer having the defect structure and performing ultraviolet curing; And (d) separating the cured polymer layer from the surface of the liquid crystal.

The present invention also comprises the steps of (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to a defect structure of the liquid crystal molecules in the liquid crystal molecule layer; (c) applying an ultraviolet curable polymer on the liquid crystal molecular layer having the defect structure and performing ultraviolet curing; (d) separating the cured polymer layer from the liquid crystal surface; (e) applying and thermosetting a thermosetting polymer on the ultraviolet cured polymer layer; And (f) it provides a method for forming a micro or nano-sized soft lithography pattern comprising the step of separating the thermoset polymer layer.

The present invention also provides a microlens array fabricated by the soft lithography pattern forming method and having a regular structure including a portion which aggregates light according to a step change in refractive index and a portion where the light passes without refraction. .

According to the present invention, a pattern formation method using a phase or defect structure of liquid crystal molecules, a method of manufacturing a microlens array, and a soft lithography pattern formation method form a pattern much faster than conventional methods due to the high mobility of liquid crystals. It is possible to do, and the manufacturing process is simple and the cost is reduced. Once created, the liquid crystal pattern can be used semi-permanently. In addition, since the phase or defect of the liquid crystal can be easily adjusted by an external electric field or a magnetic field or the height of the liquid crystal molecular layer, there is an advantage that it can be easily changed and controlled in a new pattern. In addition, by transferring information on the internal structure and orientation of the liquid crystal which is difficult to directly observe, it is possible to propose a new technique for the analysis of the internal structure.

1 illustrates a pattern formation process using an image of liquid crystal molecules according to an embodiment of the present invention.
Figure 2 (a) is a liquid crystal molecular layer arranged in a regular structure according to an embodiment of the present invention, (b) is a polarizing microscope result of the liquid crystal pattern, (c) is an optical microscope of the linear pattern transferred to the photoresist (SEM) image and (d) show the atomic force microscope (AFM) image of the linear pattern transferred to the photoresist.
3 is an SEM image showing a difference in pattern formation of a photoresist according to a polarization direction.
4 shows a pattern formation process using a liquid crystal defect structure according to the present invention.
Figure 5 (a) shows the rod-shaped smectic liquid crystal structure and the phase shift according to the temperature according to an embodiment of the present invention, (b) shows a representative polarization optical microscope (POM) image of the TFCD domain, (c) shows a schematic model of the TFCD array.
6 shows a schematic of a photolithography process using a TFCD array mask and the structure of the formed TFCD.
7 illustrates a flexible lithography pattern formation process using a defect structure of liquid crystal molecules according to an embodiment of the present invention.
8 shows SEM and AFM images of TFCD arrays, NOA63 arrays and PDMS arrays.
9 shows an experimental schematic and a photoresist SEM image according to Example 2 of the present invention.
10 shows a schematic of an experimental setup according to Example 3 of the present invention.
11 shows optical microscopic images of images projected by TFCD arrays, NOA63 arrays and PDMS arrays.

The present invention forms a regular structure by using a phase or defect structure of liquid crystal molecules, thereby forming a micro or nano size pattern, applying the same to microlens arrays, and applying soft lithography ( soft lithography).

The present invention in one aspect, (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to the phase structure of the liquid crystal molecules in the liquid crystal molecule layer; And (c) forming a micro or nano size pattern on the photoresist using the regular structure of the liquid crystal molecules as a photomask. .

In the present invention, before the step (a), it may further comprise the step of performing a surface treatment for adjusting the orientation of the liquid crystal molecules on the substrate. The surface treatment may be characterized in that the imide-based polymer, hydrophilic polymer or hydrophobic polymer is coated on the substrate and rubbed in one direction in order to give the orientation of the liquid crystal molecules, preferably polyimide, polyamide (polyamide), nylon (nylon), polyvinyl alcohol, polyethyleneimine, hydrophilic or hydrophobic self-assembled monolayer (SAM) or Teflon (Co) on the substrate, or air or The substrate may be exposed to water and rubbed in one direction.

In the present invention, the step (b) may be characterized by slow cooling after raising above the liquid crystal phase transition temperature. The liquid crystal phase transition temperature may be an isotropic temperature, and when raised above the liquid crystal phase transition temperature, the liquid crystal molecular layer may be uniformly spread on the substrate with fluidity. Subsequently, when an external electric field or magnetic field is applied or is not applied, the liquid crystal molecular sieves are aligned and form a regular structure when they are slowly cooled below the liquid crystal phase transition temperature. When an electric field is applied, the size of the electric field is preferably 0.1 to 50 V / µm.

In the present invention, step (b) may be characterized by determining the phase of the liquid crystal molecules by adjusting the concentration of the liquid crystal molecular sieves forming the liquid crystal molecules. Liquid crystalline molecular sieves refer to molecular sieves that serve as materials for forming liquid crystal molecules. In the case of a breast liquid crystal, a liquid crystal molecule phase may be determined by adjusting the concentration of the liquid crystal molecular sieve, and the liquid crystal molecule phase determined by adjusting the concentration may form various patterns according to the structure of each phase.

In the present invention, the phase of the liquid crystal molecules may be nematic, smectic, cholesteric, columnar, ferroelectric, helical, It may be characterized in that the micelle (micelle), cubic (cubic) or lamellar (lamellar) liquid crystal phase, preferably the liquid crystal molecule phase may be characterized in that the cholesteric liquid crystal phase.

In the present invention, the regular structure of step (b) may be characterized in that it has a linear pattern by the pitch (pitch) of the liquid crystal phase, the linear pattern is a light by the change of the refractive index according to the alignment of the liquid crystal molecules It may be characterized in that it is composed of a portion for condensing the portion and the light is transmitted without refraction.

1 illustrates a pattern forming process, according to one embodiment of the invention. The spiral structure standing uniformly on the cholesteric liquid crystal can be observed with a polarization microscope. Under the influence of polyimide, which induces horizontal alignment, the cholesteric liquid crystal cools the cholesteric phase at an isotropic temperature, and molecular sieves lie parallel to the substrate direction. At this time, a unique color appears according to the spiral period and the thickness of the cell, and when one color comes out from the entire cell, it means a uniformly standing spiral structure. Applying an electric field causes the liquid crystals to align in the direction of the electric field due to the positive dielectric constant of the cholesteric liquid crystals. The aligned liquid crystals are no longer horizontally aligned with the substrate but are vertically aligned. When an appropriate electric field is applied, the axial direction of the spiral is aligned in a direction parallel to the substrate as shown in FIG. The uniformly oriented lying spiral structures have uniformly spaced stripes, such as human hand prints, as shown in FIG.

The spiral structure thus formed may be used as a photomask in a photolithography process. As shown in the optical microscope (SEM) image of FIG. 2C, a photomask using a cholesteric liquid crystal phase may form a line pattern on the photoresist, like a general chrome mask. A typical chrome mask is complicated and requires at least several days to complete, but a mask using a liquid crystal phase is very economical because the manufacturing process is very simple and it takes only a few seconds to several minutes to form a pattern of the mask. As shown in the atomic force microscope (AFM) image of FIG. 2D, the pattern of the photoresist formed by the above method has the same distance between the line pattern of the photoresist and the line pattern of the cholesteric liquid crystal, which is a mask. It can be seen that the cholesteric liquid crystal pattern of the mask is transferred.

3 shows the results of exposure experiments while changing the direction of polarized light to reveal the principle of pattern formation. The direction of the polarized light was irradiated so that it could be compared in the direction parallel to the direction parallel to the spiral axis of the cholesteric liquid crystal. Referring to FIG. 3, light polarized perpendicularly to the helical axis of the cholesteric liquid crystal well formed a pattern in the photoresist, whereas horizontally polarized light did not form a pattern well in the photoresist. This indicates that the cholesteric liquid crystal mask is selective for the polarization of light. The reason why the pattern is well formed in light polarized perpendicular to the helical axis of the cholesteric liquid crystal is because the refractive index of the liquid crystal layer changes periodically in the helical axis direction. That is, light irradiated by the difference in refractive index between the liquid crystal molecules periodically changing along the pattern is collected in a larger refractive index as in the case of passing through the lens. Light that is periodically collected in one place causes a difference in exposure to the photoresist periodically, resulting in a line pattern. On the other hand, light polarized in a direction parallel to the spiral axis maintains the same value in the spiral axis direction as the refractive index of the light passes through the liquid crystal. That is, since there is no periodicity, there is no difference in refractive index between the liquid crystal molecular sieves, so that light does not aggregate and does not cause a difference in exposure amount in the photoresist.

The regular structure of the liquid crystal phase according to the present invention is a microlens arrays itself because it is composed of a portion which aggregates the light by the change of the refractive index according to the orientation of the liquid crystal molecules and a portion where the light is transmitted without being refracted. Can be utilized as

The liquid crystal mask according to the present invention can be formed in various patterns according to the shape and orientation of the mask. Wiring width control can be easily adjusted according to the amount of chiral additive to form the phase of liquid crystal molecules or the intensity of applied electric or magnetic field, and the wiring width can be reduced to several tens of nm by controlling the cycle of cholesteric liquid crystal. It was confirmed. Similar results can be obtained by using other liquid crystal phases other than the cholesteric liquid crystal phase.

In another aspect, the present invention, (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to a defect structure of the liquid crystal molecules in the liquid crystal molecule layer; And (c) forming a micro or nano size pattern on the photoresist using the regular structure of the liquid crystal molecules as a photomask. .

In the present invention, before the step (a), it may further comprise the step of performing a surface treatment for controlling the orientation of the liquid crystal molecules on the substrate, the surface treatment is an imide-based polymer, hydrophilic polymer or hydrophobic It is characterized by coating the polymer on the substrate and rubbing in one direction, preferably, polyimide, polyamide, nylon, nylon, polyvinyl alcohol, polyethyleneimine ), Hydrophilic or hydrophobic self-assembled monolayer (SAM) or Teflon (Teflon) may be coated on the substrate, the substrate is exposed to air or water, and rubbed in one direction. In addition, in the present invention, the step (b) may be characterized by slow cooling after raising above the liquid crystal phase transition temperature.

In the present invention, it is possible to form a regular structure according to the defect of the liquid crystal molecules by adjusting the concentration of the liquid crystal molecular sieves forming the liquid crystal molecules. In the case of breast liquid crystal, the liquid crystal molecules are determined by adjusting the concentration of the liquid crystal molecular sieves, and different liquid crystal molecules are formed for each of the different phases determined by the concentration adjustment. It is possible to form different regular structures.

In the present invention, the defect structure of the liquid crystal molecules may be adjusted in size by adjusting the thickness of the liquid crystal molecule layer. In one embodiment of the present invention, the size of the adjustable liquid crystal defect structure is about 1 to 100 μm.

In the present invention, the defect structure is a toric focal conic domain (TFCD), a parabolic focal conic domain (PFCD), disclination, oily streak or undulation (undulation), and preferably a toric focal conic domain (TFCD) of smectic LCs. The defect structure according to the present invention may be pattern aligned in hexagonal shape through self-assembly.

In one embodiment of the present invention, the periodic toroidal holes of the toric focal conic domain (TFCD) of the smectic liquid crystal are inherent to aggregate the light to be irradiated. Due to molecular orientation it can act as microlens. The flat portions between the toroid holes act like transparent glass and do not refract light. In addition, the present invention takes advantage of the periodic micro or nano sized array as well as the stepwise refractive index distribution of the liquid crystal.

Regular TFCD structures are generated through the control of molecular orientation in the liquid crystal on the surface of the attached substrate. Light passing through the TFCD is refracted and agglomerated to the center of the TFCD by a stepwise refractive index depending on the orientation of the liquid crystal molecules inherent in the TFCD. Therefore, liquid crystal-based TFCD microlenses are optically selective depending on the polarization direction of transmitted light when used as a photomask. Accordingly, the domain size, geometry and symmetry can be adjusted by simply adjusting the amount (or intensity) of light, the size of the TFCD photomask, the tone of the photoresist and the polarization direction of the illumination light source. Micro scale patterns can be obtained.

In one embodiment of the invention, ethyl 4'-hydroxy-4biphenyl carboxylate and 1H, 1H, 2H, 2H, 3H, 3H, 4H, 4H are used to generate the TFCD structure. Rigid and partially fluorinated tail groups prepared by alkylation of perfluorododecyl bromine (1H, 1H, 2H, 2H, 3H, 3H, 4H, 4H-perfluorododecyl bromide) A simple rodlike smectic liquid crystal material can be used that includes a biphenyl core. In Figure 5 (a) shows the phase change according to the molecular structure and temperature of the material. This material continuously produces hexagonal highly ordered TFCD on the surface of the treated glass substrate.

In the present invention, through cooling from isotropic to Smectic A phase, an array of aligned TFCD domains can be produced over a wide area. Cooling is preferably slow cooling and slow cooling at a rate of about −1 ° C./min. The production of TFCD microlens arrays is very quick and simple compared to other soft self-assembly building blocks because the low molecular weight liquid crystal components react quickly on smectic with high mobility. In the present invention, it has been found that creating a uniform TFCD wide scale array on a glass substrate requires only a few seconds.

FIG. 5 (b) shows a representative polarized optical microscopy (POM) image of the TFCD domain of the smectic liquid crystal on a flat PEI coated polyethylene substrate. In FIG. 5B, the formation of highly aligned periodic TFCDs can be seen over a wide area. Each small circular domain corresponds to one TFCD. A closer look at the polarized light microscopy image of the film formed by the liquid crystal reveals that each TFCD exists in a constant, hexagonal array in size and has typical Smematic A phase characteristics. Since the internal structure of the TFCD having a circular shape has a form in which the alignment of liquid crystal molecules radiates radially from the center of the TFCD, a characteristic Maltese cross is observed when the TFCD is transmitted through a polarizing optical microscope. Create a Maltese cross pattern. Outside the circular base (window part), the molecules are aligned perpendicular to the substrate and these parts appear dark in polarized light microscopy images. 5 (c) shows a schematic model of the TFCD array. Small red bars that are regular in hexagon from the glass to the air-liquid crystal interface each point to the mesogenic unit of the liquid crystal. The refractive index of the smectic liquid crystal TFCD may be changed depending on the liquid crystal molecular orientation of the TFCD microlens.

In one embodiment of the invention, a TFCD array was used as the photomask. 6 diagrammatically depicts the generation of a lithographic pattern. The photoresist film is exposed through the fabricated self-assembled organic TFCD photomask. A 2 μm thick photoresist film is spin-coated onto the silicon substrate. In this system, each TFCD can aggregate light. The effective index of refraction can be altered spatially with the inherent liquid crystal molecular orientation increasing to the center portion of the TFCD. Incident light passing through the TFCD is refracted and aggregated to the center of the TFCD. Each TFCD structure may consist of two components. The 'window' part consists of parallel Smectic layers and Smectic liquid crystal molecules are aligned in a direction perpendicular to the substrate. Thus, the direction field of the liquid crystal molecules exactly coincides with the direction in which ultraviolet light is incident. The other structure is the "lens" part, which is the center part of each TFCD. The orientation of the smectic liquid crystal molecules depends on the curved surface of the smectic layer in the TFCD. Light passes straight through the window and agglomerates at a certain focal length in the lens. The combination of functional elements called window and lens elements in a single TFCD photomask structure may allow deformation due to the difference in dose of light in the pattern projected onto the photoresist film. Both optical elements in the TFCD array can be seen in atomic force microscopy (AFM) images as shown in Figure 6 (c).

In addition, since the liquid crystal defect structure is made of a liquid crystal having a birefringence therein, if the polarization is imparted to the light of the ultraviolet light source to be irradiated, a completely different structure can be obtained even if the same liquid crystal defect structure mask is used. However, by changing the polarization direction of the light source, various types of patterns can be produced. In addition to the TFCD liquid crystal defect structure shown in the embodiment of the present invention, various types of liquid crystal defect structures existing in nature show the refractive index distribution according to the liquid crystal alignment, it can be used as a new concept photolithography mask. It is also possible to configure such that opposite patterns are formed by using photoresists of different tones.

In another aspect, the present invention, (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to a defect structure of the liquid crystal molecules in the liquid crystal molecule layer; (c) applying an ultraviolet curable polymer onto the liquid crystal molecule layer having the defect structure and performing ultraviolet curing; And (d) separating the cured polymer layer from the surface of the liquid crystal.

The present invention also comprises the steps of (a) forming a liquid crystal molecule layer on the substrate; (b) forming a regular structure according to a defect structure of the liquid crystal molecules in the liquid crystal molecule layer; (c) applying an ultraviolet curable polymer on the liquid crystal molecular layer having the defect structure and performing ultraviolet curing; (d) separating the cured polymer layer from the liquid crystal surface; (e) applying and thermosetting a thermosetting polymer on the ultraviolet cured polymer layer; And (f) separating the thermoset polymer layer.

In the present invention, the ultraviolet curable polymer may be characterized in that the polyurethane-based polymer, the thermosetting polymer may be characterized in that the siloxane-based polymer. Polydimethylsiloxane (PDMS) is one of the most used materials as the siloxane-based polymer.

The present invention also relates to a microlens array manufactured by the above-described soft lithography pattern forming method, and comprising a portion which aggregates light according to a step change in refractive index and a portion where light passes through it without refracting.

7 illustrates a flexible lithographic pattern formation process, in accordance with an embodiment of the present invention. A liquid crystal molecule layer was formed on the substrate using a simple rod-like Smetic A material containing a hard aromatic group and a fluorinated end. The liquid crystal molecule layer is applied on the surface-treated glass substrate having an isotropic temperature or higher. While cooling from isotropic to smectic, an aligned TFCD array is created over a large area. A negative replica of the TFCD array can be formed by applying an ultraviolet curable pre-polymer onto the surface of the TFCD array. Capillary forces allow the pre-polymer to fill the TFCD's defect structure, so that the pre-polymer layer follows the surface topology of the TFCD. The pre-polymer is then cured by ultraviolet exposure to form negative replication of the TFCD array. The ultraviolet curable polymer is preferably a polyurethane-based polymer, and may include a NOA63 polymer. The formed polymer NOA63 negative replica mold can be used as a secondary mold. The PDMS prepolymer is applied onto an embossed NOA63 substrate and cured for 8 hours at 60 ° C. in a conventional dry oven. The cured PDMS mold shows the same structure as the original TFCD array template. NOA63 and PDMS are both suitable materials for polymer microlens arrays because of their transparency, thermal stability, homogeneous refractive index, and ease of filling these mold shapes in which these polymers are designed.

FIG. 8 shows SEM and AFM images of TFCD array (MLA-1), NOA63 array (MLA-2) and PDMS array (MLA-3), respectively. In FIG. 8 a large area pattern composed of circular TFCDs on the surface of the glass substrate can be seen. TFCDs are arranged in a periodic array with an average center-center distance of 10.5 μm over the glass substrate. Because small liquid crystal molecules react quickly with high mobility and smectic phase, the smectic liquid crystal building block TFCD system is simpler and faster than other soft molding systems or photolithographic methods. Creating a uniform TFCD wide scale array on a substrate is very fast and requires only a few seconds. The domain size, defined as the center-center distance, strongly depends on the liquid crystal film thickness. 8 (b) shows that the height profile of the TFCD array represented by the AFM is a symmetrical structure, and shows a cross section of the TFCD containing circular defects. The depth of the TFCD structure was 2.2 μm at the center of each domain. FIG. 8C shows a representative SEM image of the NOA63 mold prepared in the TFCD array template. NOA63 prepolymers penetrate the voids of the TFCD structure with the help of capillary forces and gravity. As a result, the transferred conical structure is flipped over the structure of the TFCD array. Many replica molds can be made from a master TFCD array mold because the TFCD mold is physically stable under a molding process with the NOA63 pre-polymer. The fluid Smectic A phase TFCD can be preserved for a long time and stable in the molding process because the TFCD formed on Smectic A at room temperature is solidified by changing to a soft crystal phase. Comparison of the TFCD array pattern of the template with the NOA63 microlens array indicates that highly complex densities of micro or nanostructures have been successfully transferred from the TFCD array template to the NOA63 replica. White spots in the SEM image correspond to nano-tips with conical structures. The tip of the nano-tip has a diameter of 250 nm and was measured by SEM and AFM measuring device. The average height of the nano-tips on the conical structure is 1.8 μm, slightly smaller than the depth of the TFCD dimple structure. PDMS microlens arrays were prepared by replica molding of the first NOA63 replica mold and their SEM images are shown in Figure 8 (e). High magnification images show that the recessed structure was created inversely from the MLA-2 mold. These arrays coincide from the TFCD array in overall shape, although the depth of the recessed structure is slightly smaller than that of the original TFCD array mold since it is after two replicate molding processes. The length between all domains in the TFCD, NOA63 and PDMS arrays is the same as can be seen in the AFM and SEM images.

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

Cholesteric  Linear pattern formation using liquid crystal phase structure

(a) On a substrate Liquid crystal molecules  formation

Indium tin oxide (ITO) glass substrates were washed with water, acetone, propane and then coated with horizontally oriented polyimide having a pretilt angle of less than 5 degrees. The coating was spin coated at 2500 rpm for 25 seconds, after which the substrate was placed on a hot plate at 180 ° C. for 90 minutes to evaporate the solvent. The coated substrate was rubbed in one direction using a rubbing machine.

Two substrates were assembled using a micro-bead spacer mixed with UVA-curable polymer material NOA63 to make a cell, and wires for applying an electric field to each substrate of the cell were connected using indium. Thereafter, the cholesteric liquid crystal was injected into the cell using a capillary phenomenon at an isotropic temperature of 40 ° C. or higher. As a cholesteric liquid crystal material, a complex obtained by adding chiral additive CB15 to 5CB, which is a main liquid crystal material, was used.

(b) On the liquid crystal molecules  Regular structure formation

The cell was cooled to 33 ° C. in which a cholesteric liquid crystal phase appeared while applying an electric field of 0.4 V / µm to the cell at 40 ° C. or higher. After fixing the temperature at 31 ° C. below 2 ° C. of the cholesteric liquid crystal phase, the electric field was slowly lowered to 0.22 V / µm to induce the production of a uniformly lying spiral structure.

(c) With photoresist  Warrior

Positive photoresist AZ1505 was spin coated onto a silicon substrate for 30 seconds at a speed of 1500 rpm to obtain 600 nm thickness and the photoresist coated silicon wafer was cured on a 110 ° C. hot plate for 2 minutes. The cured silicon wafer was brought into close contact with the cholesteric liquid crystal cell in which an electric field of 0.22 to 0.25 V / µm was applied, and the wafer was brought into close contact with the cell in ultraviolet light polarized in a direction perpendicular to the spiral axis. At this time, the exposure conditions exposed the amount of polarized light of 100mJ / cm ² in the i-line using a wavelength of 365nm to the photoresist in close contact with the cell.

As a developing solvent, AZ300DIF, a AZ-based photoresist developer, was mixed with primary distilled water in a 3: 1 ratio. The exposed photoresist film was developed, and the developed film was washed with primary distilled water and compressed. It was dried using air or nitrogen gas.

The pattern formed by the above process is shown in FIG. 2B illustrates a POM image of the liquid crystal pattern, and it was confirmed that a linear pattern is formed regularly. Figure 2 (c) shows the SEM image of the linear pattern transferred to the photoresist. 2 (d) shows an AFM image of a preceding pattern transferred to a photoresist, and it was confirmed that the pattern possessed by the liquid crystal was transferred as it is.

Swirl  Pattern Formation Using Liquid Crystal Defect Structure

(a) On a substrate Liquid crystal molecules  formation

The flat glass substrates were washed with water, acetone, propane, and treated with atmospheric plasma for 30-60 seconds, followed by spincoating polyethyleneimine (PEI), which induces horizontal orientation, to ˜40 nm. A liquid crystal material was coated on the surface-treated substrate, and the temperature was raised to 200 ° C. or higher which is higher than the isotropic temperature to form a liquid crystal molecular layer with a uniform thickness on the substrate.

(b) On the liquid crystal molecules  Regular liquid crystal defect formation

Slowly lowering the temperature of the substrate coated with the liquid crystal material above 200 ° C. (195 ° C.) from the temperature at which the smectic liquid crystal phase appears to room temperature exhibiting a soft solid state to form a swirl liquid crystal defect structure, and the defect structure stably at room temperature. It was confirmed to be maintained.

(c) With photoresist  Warrior

The photoresist material was spin coated to a level of 2 μm on a flat silicon wafer plate. The coated silicon wafer was cured for 2 minutes on a 110 ° C. hot plate prior to the exposure process. The liquid crystal defect structure layer formed on the transparent substrate through which light can pass is placed on the photoresist-coated substrate as a photomask. An ultraviolet light source having a wavelength of 345 nm reacting the photoresist was irradiated through the liquid crystal defect structure layer, and the photoresist was developed. As shown in FIG. 9, it was confirmed that the unique patterns of the liquid crystal defect structure were transferred to the focal length of the liquid crystal defect structure lens and the shapes of the transmission region around the lens.

In order to confirm the change in pattern formation according to the polarization direction of the ultraviolet rays, the light polarized in one direction was irradiated and developed by releasing the polarizing plate. As a result, as shown in FIG. 9, there is no difference in the region that transmits light, whereas an anisotropic pattern was obtained because light converges only in the same direction as the polarization direction. Therefore, it was confirmed that a new pattern was formed in an experiment in which only the polarization direction was changed while using the same liquid crystal defect structure.

Swirl  Ductility using surface structure of liquid crystal defect structure Lithography  Pattern formation

(a) On a substrate Liquid crystal molecules  formation

The flat glass substrates were washed with water, acetone, propane, and treated with atmospheric plasma for 30-60 seconds, followed by spincoating polyethyleneimine (PEI), which induces horizontal orientation, to ˜40 nm. A liquid crystal material was coated on the surface-treated substrate, and the temperature was raised to 200 ° C. or higher which is higher than the isotropic temperature to form a liquid crystal molecular layer with a uniform thickness on the substrate.

(b) On the liquid crystal molecules  Regular liquid crystal defect formation

The substrate coated with the liquid crystal material of 200 ° C. or higher was slowly lowered from the temperature at which the smectic liquid crystal phase appeared (195 ° C.) to room temperature exhibiting a soft solid state to form a swirl liquid crystal defect structure and stably maintained. The surface structure of the formed liquid crystal defect structure has a recessed structure such as dimples as shown in FIG.

(c) Fabrication of Transparent Polymer Duplicate Substrate from Liquid Crystal Defect Structure

 The NOA63 monomer, which is an ultraviolet curable polymer, is coated on the prepared liquid crystal defect structure layer. After a few minutes, when the fluidity of the monomer disappears, the monomer is completely cured with a polymer by irradiating ultraviolet rays of 345 nm wavelength for 30 minutes or more. Using a significant drop in adhesion of NOA63 above 70 ° C., the two layers bonded at 80 ° C. are separated from each other. The surface of the separated UV-curable polymer layer has a conical nano / micro structure that is negative (negative) with the surface layer of the recessed liquid crystal defect structure as shown in (c) of FIG.

On the UV curable polymer layer, the PDMS monomer-curing agent mixture, which is a thermosetting polymer, is applied, and bubbles generated during the mixing process are removed. After sufficient heat curing in a 60 ° C. oven for at least 8 hours, the PDMS layer is separated from the UV curable polymer NOA63 layer. In (e) of FIG. 8, since the surface structure formed on the PDMS layer has been subjected to two successive molding processes, it can be seen that it has the same recessed surface structure as the initial liquid crystal defect structure layer.

(d) Evaluation of microlens array characteristics using liquid crystal defect structure and transparent polymer replica

The prepared liquid crystal defect structure layer, the ultraviolet curable polymer layer (NOA63), and the thermosetting polymer layer (PDMS) each have a surface structure capable of aggregation of light. In order to confirm the coherent lens effect of light, as shown in FIG. 10, each layer was disposed between the objective lens and the light source. In order to confirm the coherence of light, the “F” letter selected as an asymmetric letter was placed in front of the light source to aid observation. As a result of observation through an optical microscope through general white light, as shown in FIG. It is confirmed that the "F" phase of is formed correctly. (A), (b), (c) of FIG. 11 are conceptual views showing a principle in which an optical image and a focus are focused on an image formed by a liquid crystal defect structure layer, an ultraviolet curable polymer layer, and a thermosetting polymer layer, respectively.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. something to do. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (52)

A method of forming a micro or nano size pattern comprising the following steps:
(a) forming a liquid crystal molecule layer on the substrate;
(b) forming a regular structure according to the phase structure of the liquid crystal molecules in the liquid crystal molecule layer; And
(c) forming a micro or nano size pattern on the photoresist using the regular structure of the liquid crystal molecules as a photomask.
The method of claim 1, further comprising, prior to step (a), performing a surface treatment for adjusting the orientation of liquid crystal molecules on the substrate.
The method of claim 2, wherein the surface treatment is characterized in that the imide-based polymer, hydrophilic polymer or hydrophobic polymer is coated on the substrate and rubbed in one direction.
The method of claim 2, wherein the surface treatment is polyimide, polyamide, nylon, polyvinyl alcohol, polyethyleneimine, hydrophilic or hydrophobic self-assembled monolayer assembled monolayer (SAM) or Teflon (Co) on the substrate, or the substrate exposed to air or water and rubbed in one direction.
The method of claim 1, wherein the step (b) is characterized by slow cooling after raising above the liquid crystal phase transition temperature.
The method of claim 1, wherein the step (b) determines the phase of the liquid crystal by adjusting the concentration of the liquid crystal molecular sieves forming the liquid crystal molecules.
2. The method of claim 1, wherein step (b) adjusts the regular structure by applying an external electric or magnetic field.
The method of claim 1, wherein the step (b) is slow cooling in a state where an external electric field is applied after raising the liquid crystal phase transition temperature or more.
9. A method according to claim 7 or 8, wherein the magnitude of the electric field is between 0.1 and 50 V / μm.
The phase of claim 1, wherein the phases of the liquid crystal molecules are nematic, smectic, cholesteric, columnar, ferroelectric, and helical. , Micelle, cubic or lamellar liquid crystal phase.
The method of claim 1, wherein the phase of the liquid crystal molecule is a cholesteric liquid crystal phase.
The method of claim 1, wherein the regular structure of step (b) has a linear pattern due to the pitch of the liquid crystal phase.
The method of claim 12, wherein the linear pattern comprises a portion which aggregates light by a change in refractive index according to the alignment of liquid crystal molecules and a portion where the light is transmitted without being refracted.
Method of manufacturing microlens arrays comprising the following steps:
(a) surface treating the substrate;
(b) forming a liquid crystal molecule layer on the surface treated substrate; And
(c) forming a regular structure according to the liquid crystal phase structure in a state in which an external electric or magnetic field is applied to the liquid crystal molecule layer.
15. The method of claim 14, wherein the step (c) is performed after heating to above the liquid crystal phase transition temperature of the liquid crystal molecule layer.
The method of claim 14, wherein the step (c) determines the phase of the liquid crystal by adjusting the concentration of the liquid crystal molecular sieves forming the liquid crystal molecules.
15. The method of claim 14, wherein the liquid crystal phase is a cholesteric liquid crystal phase.
15. The method of claim 14, wherein the regular structure comprises a portion in which light aggregates due to a change in refractive index according to the alignment of liquid crystal molecules and a portion in which light is transmitted without being refracted.
19. A micro-manufactured by the method of any one of claims 14 to 18, and having a regular structure comprising a portion that aggregates light with a change in refractive index according to the orientation of the liquid crystal molecules and a portion where the light is transmitted without being refracted. Lens array.
20. The microlens array of claim 19, wherein the microlens array has a micro or nano size pattern.
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