KR20120058019A - Method for forming self-organized anisotropic wrinkle structures - Google Patents

Abstract

PURPOSE: A method for forming self-organized anisotropic wrinkle patterns is provided to form a pattern on a general glass substrate instead of an existing pre-strain control method and make a desired wrinkle pattern large without complicated processes. CONSTITUTION: A surface of an anisotropic material layer on which molecules are arranged is treated by plasma or UV ozone to form an anisotropic thin film. Wrinkles are formed in the alignment direction of the molecules of the anisotropic material layer. Anisotropic materials of the anisotropic material layer are liquid crystal polymers. The liquid crystal polymers are RM(Reactive Mesogen) solutions. The anisotropic material layer on which the molecules are arranged is obtained by coating the anisotropic materials on a surface treated alignment film.

Description

How to form self-assembled anisotropic wrinkle pattern {METHOD FOR FORMING SELF-ORGANIZED ANISOTROPIC WRINKLE STRUCTURES}

The present invention relates to a method of easily forming a self-assembled anisotropic pleat pattern on a large area substrate.

As the modern technology society develops, the demand for high functionalization of devices such as information storage, display (optical), microelectromechanical systems (MEMS), sensors, and the development of new devices is increasing. There is also a lot of research into new ways to make micro patterns of size.

As a technique for making micro / nano sized structures or patterns, a top-down method of forming a desired size shape by mechanically or chemically cutting a macro-scale material and etching it is common. However, there is a disadvantage in that waste of material for making a pattern is excessive and additional devices such as a high precision photomask or an imprint mold of an uneven structure are required.

Thus, as an alternative to this method, a bottom-up that can easily form a microstructure at low cost by using phenomena such as self-assembly between molecules or periodic wrinkles in nature. New patterning methods of the approach have been proposed.

The wrinkled pattern generated on the thin film surface is caused by the difference in physical properties occurring at the interface between the thin upper layer film and the lower substrate. The swelling induced wrinkling caused by the solvent Bi-layer induced wrinkling for applying a heterogeneous thin film to the film, and plasma induced wrinkling using surface modification by plasma without the application of a heterogeneous thin film.

At this time, the size and shape of the generated wrinkle pattern has a constant value according to a given physical property, the direction of the pattern is determined according to the stress distribution of the thin film. As a method of controlling the direction of the wrinkle pattern, a pre-strain control method of controlling the stress distribution by pre-stretching a soft lower substrate is generally used. The direction of the fine pattern is controlled by the pre-strain control method. The schematic diagram to which is shown in FIG. However, this pre-strain control method has a disadvantage that the lower substrate must be a soft material such as polydimethylsiloxane (PDMS), it is difficult to create a uniform stress state on a large area substrate. In addition, the substrate of a soft material such as PDMS is difficult to apply directly to various fields because its optical and mechanical properties are not satisfactory.

Accordingly, it is an object of the present invention to provide a method for forming a pattern on a general glass substrate instead of the existing pre-straining control method and easily forming a desired wrinkle pattern in a large area without complicated additional processes.

In order to achieve the above object, the present invention

Forming an anisotropic thin film by plasma or UV ozone treatment of the surface of the molecularly aligned anisotropic material layer to form a wrinkle in a direction coincident with the molecular orientation direction of the anisotropic material layer, the method of forming a self-assembled anisotropic wrinkle pattern To provide.

According to the method of the present invention, the desired wrinkle pattern can be easily formed on a large area on a substrate of various materials such as a glass substrate and a plastic substrate. In addition, since the method of the present invention is a self-assembled pattern forming method, there is no need for an additional device such as a high-precision photomask or an imprint mold of a concave-convex structure, and thus, the process is very simple. Accordingly, the method of the present invention can be used to produce optical components such as displays or photovoltaic cells, for example, diffusers, prisms, lenticular films, optical gratings, microfluidics, and the like. The formation of channels for micro-fluidics, and other line-and-space patterns can be usefully applied in the fabrication of all devices that can be used.

Figure 1 shows as a schematic diagram to control the direction of the micropattern in accordance with the conventional pre-strain adjustment method,
Figure 2 is a photograph showing the correlation between the degree of molecular orientation of the anisotropic material layer and the direction of the wrinkle pattern ((a): in the case of non-orientation, (b): in the case of orientation),
3 is a schematic diagram illustrating a series of processes for forming a desired self-assembled anisotropic pleat pattern according to one embodiment of the method of the present invention,
Figure 4 is a cross-sectional view according to the film thickness and 2D / 3D atomic force microscope (AFM) image of the self-assembled anisotropic wrinkle pattern formed in Example 1.

The method for forming the self-assembled anisotropic wrinkle pattern according to the present invention is based on controlling the degree of molecular alignment of the anisotropic material and then creating anisotropic wrinkles thereon. The surface of the molecularly aligned anisotropic material layer is formed by plasma or UV ozone. By processing to form an anisotropic thin film, it is characterized in that wrinkles in a direction coinciding with the molecular orientation direction of the anisotropic material layer.

As the anisotropic material of the anisotropic material layer used in the present invention, a liquid crystal polymer having an anisotropic molecular structure is suitable. Examples of the liquid crystal polymer usable in the present invention include a reactive mesogen (RM) solution (RMS) containing a polymerizable end group, specifically LC242 (BASF) and RMS03-001 (Merck) Various products are commercially available.

According to the present invention, molecular alignment of the anisotropic material can be achieved by coating the anisotropic material on an alignment layer surface-treated to have a molecular orientation direction. That is, when the anisotropic material is coated on the prepared alignment layer, the molecules of the anisotropic material are aligned according to the alignment direction of the alignment layer, thereby obtaining a molecularly aligned anisotropic material layer.

The alignment film surface-treated to have the molecular orientation direction is obtained by coating an alignment film forming material on a suitable substrate, drying and performing an alignment process, wherein the substrate is made of various materials including glass substrates and plastic substrates. It can select and use, A specific example of the material for forming an oriented film includes polyimide (PI), polyamic acid and mixtures thereof.

As the alignment process, a photo-alignment method, a rubbing method, a fine pattern alignment method using an imprint technique, and the like, which are commonly used in the liquid crystal device (LCD) field, may be used. Among these, the rubbing method forms a fine groove for liquid crystal alignment later by changing the surface characteristics of the alignment film forming material by brushing the surface of the alignment film forming material while rotating the roller coated with the microfiber at high speed.

When the surface of the molecularly aligned anisotropic material layer thus formed is treated with plasma or UV ozone, a thin anisotropic film is formed on the surface of the anisotropic material layer to generate wrinkles, and the direction of the wrinkles coincides with the molecular orientation of the anisotropic material layer. . If necessary, the formed fine wrinkle pattern can be cured using UV light. At this time, the longer the surface treatment time to the plasma or UV ozone, the higher the bending height of the formed anisotropic wrinkle pattern, it is possible to adjust the surface treatment time according to the desired wrinkle pattern.

The correlation between the degree of molecular orientation (molecular alignment) of the anisotropic material layer and the direction of the wrinkle pattern is shown in FIG. 2. As can be seen in FIG. 2, (a) is a case where a random wrinkled pattern is formed on an unoriented (orientated) liquid crystal polymer, and (b) is an alignment direction on the aligned liquid crystal polymer. It is a case where the one-dimensional line pattern of the matching direction is formed.

A series of steps for forming a desired self-assembled anisotropic pleat pattern according to one embodiment of the method of the present invention is shown in FIG. 3 as a schematic diagram.

Thus, according to the method of the present invention, it is possible to easily form the desired wrinkle pattern on a large area of the substrate of various materials such as glass substrate, plastic substrate. In addition, since the method of the present invention is a self-assembled pattern forming method, there is no need for an additional device such as a high-precision photomask or an imprint mold of a concave-convex structure, and thus, the process is very simple. Accordingly, the method of the present invention can be used to produce optical components such as displays or photovoltaic cells, for example, diffusers, prisms, lenticular films, optical gratings, microfluidics, and the like. The formation of channels for micro-fluidics, and other line-and-space patterns can be usefully applied in the fabrication of all devices that can be used.

The present invention will be described in more detail with reference to the following examples. However, the following examples are only examples of the present invention and the present invention is not limited thereto.

Example 1

1) First, a polyimide (PI) was coated on a glass substrate having a size of 20 m (width) x 25 m (length), followed by drying to form a polyimide thin film.

2) The surface of the polyimide thin film was brushed while the roller coated with the microfiber was rotated at a high speed (rubbing process) to obtain a polyimide alignment layer having a fine groove formed thereon for liquid crystal alignment and having changed surface properties.

3) The liquid crystal polymer RMS03-001C (Merck) was spin-coated on the prepared alignment film under the conditions of 2500 rpm / 20 sec, and the liquid crystal polymer layer molecularly aligned according to the alignment direction of the alignment film was obtained.

4) The surface of the molecular aligned liquid crystal polymer layer thus formed was treated with plasma for 100 seconds to form a self-assembled anisotropic wrinkle pattern in a direction coinciding with the molecular orientation of the liquid crystal polymer layer.

5) The formed wrinkled pattern was cured using UV light.

A cross-sectional view of the self-assembled anisotropic wrinkle pattern formed in Example 1 and a film thickness of a 2D / 3D atomic force microscope image is shown in FIG. 4.

As can be seen from Fig. 4, the shape of the anisotropic pleat pattern made shows a one-dimensional line-and-space pattern coinciding with the rubbing direction, and the shape of the cross section is a sine wave according to the thickness of the coated film. Or a lenticular shape in the form of a half-sine wave. Thus, utilizing such controllable cross-sectional shapes to produce optical components such as diffusers, prisms, lenticular films, optical gratings, etc., forming channels for microfluidics, and other line-and-space patterns can be used. You can expect to be able to build any device that exists.

Claims (7)

Forming an anisotropic thin film by plasma or UV ozone treatment of the surface of the molecularly aligned anisotropic material layer to form wrinkles in a direction coincident with the molecular orientation of the anisotropic material layer, the method of forming a self-assembled anisotropic wrinkle pattern . The method of claim 1,
The anisotropic material of the anisotropic material layer is a liquid crystal polymer, characterized in that the self-assembled anisotropic wrinkle pattern forming method. The method of claim 2,
The liquid crystal polymer is a reactive liquid crystal monomer (RM) solution, characterized in that the self-assembled anisotropic wrinkle pattern forming method. The method of claim 1,
Wherein the molecularly aligned anisotropic material layer is obtained by coating an anisotropic material on a surface treated alignment film to have a molecular orientation direction. The method of claim 4, wherein
The method of forming an self-assembled anisotropic pleat pattern, characterized in that the alignment film surface-treated to have a molecular orientation direction is obtained by coating an alignment film forming material on a substrate, drying and performing an alignment process. The method of claim 5, wherein
The material for forming an alignment film is selected from the group consisting of polyimide (PI), polyamic acid (PA), and mixtures thereof. The method of claim 5, wherein
The orientation process is performed by a photo-alignment method, a rubbing method or an imprint method, characterized in that the self-assembled anisotropic wrinkle pattern forming method.

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