KR102500132B1 - Method for Preparing Polymer Colloidal Crystal Patterns Using Organic Solvents - Google Patents

Abstract

In the present disclosure, after forming a dense colloidal crystal monolayer, based on the thermodynamic properties of the polymer (or main component polymer) and the organic solvent in the colloid, (i) swelling-shrinkage by sequential combination of good solvent and nonsolvent, or (ii) A method for producing a non-dense colloidal crystal monolayer by inducing shrinkage using co-insolubility in a water-co-solvent mixed solvent is described.

Description

Method for preparing polymer colloidal crystal monolayer using organic solvent {Method for Preparing Polymer Colloidal Crystal Patterns Using Organic Solvents}

The present disclosure relates to a method for preparing a polymer colloidal crystal monolayer using an organic solvent. More specifically, the present disclosure, after forming a close-packed colloidal crystal monolayer, based on the thermodynamic properties of the polymer (or main component polymer) and the organic solvent in the colloid, (i) good solvent-non-solvent A method for producing a non-close-packed colloidal crystal monolayer by inducing swelling-shrinkage by the sequential combination of it's about

Micro-scale and nano-scale patterns are generally manufactured through lithography and etching methods, and can alternatively be implemented by a method of manufacturing colloidal patterns using colloids. In this regard, a colloidal pattern manufacturing technique is called "colloidal lithography" and has been utilized to manufacture patterns or inorganic structures by applying lithography or etching techniques to close-packed colloidal crystals.

When lithography and etching techniques are used, special equipment must be used to form a pattern, and when a colloidal pattern is prepared on a micro/nano level structure formed on a polymer-based substrate or substrate based thereon, the surface of the polymer substrate Alternatively, since it is necessary to form a pattern while minimizing damage to the structure, very precise manufacturing conditions are required. Therefore, research on forming a pattern through a wet method without special equipment has been continuously conducted.

Research on the production of colloidal crystal patterns through the wet method involves forming colloids in a non-close-packed pattern at the solution-air interface or solution-solution interface, and then using a substrate with an electric charge opposite to that of the colloid. It is known that a pattern can be prepared by using or by forming conditions that can minimize the capillary force between the arrayed colloidal particles. As another method, after coating a close-packed colloidal crystal monolayer on a soft polymer substrate, stretching the used soft polymer substrate or inducing swelling by a solvent [0003] A method is known in which a non-dense pattern of colloidal crystal monolayer is produced and then transferred to a substrate. These strategies depend on the concentration and charge of the colloid, the evaporation rate of the dispersion medium and the physical/mechanical properties of the mold.

Nevertheless, there has been a continuous demand for research into a method that is reproducible in pattern formation, has a simple process compared to lithography/etching techniques, and is easily accessible. In this regard, a method of converting a pattern by performing a simple operation of immersion in an aqueous salt solution or by adjusting the temperature of an aqueous medium has been proposed (Korean Patent Nos. 1864674, 2019-0088423, etc.). However, the above method has limitations in forming patterns under various conditions, such as the type of substrate to which a colloidal crystal pattern can be applied, in that an aqueous salt solution or an aqueous medium is used.

Accordingly, there is a demand for a pattern formation method capable of converting a dense colloidal crystal pattern or monolayer film into a non-dense colloidal crystal pattern or monolayer film through simple manipulation under various conditions while overcoming the technical limitations of the prior art.

In the present disclosure, it is intended to provide a method for preparing a polymer colloidal crystal pattern that can be easily applied to various uses by selecting and combining organic solvents instead of aqueous salt solutions and controlling the composition thereof.

According to the first aspect of the present disclosure,

a) forming a monolayer film having a dense crystal pattern of a polymer colloid on a surface of a substrate; and

b) (i) After swelling the colloid in the monolayer film by bringing the monolayer film having the dense crystal pattern into contact with the first organic solvent, which is a good solvent capable of inducing swelling of the colloid polymer, the cost of being incompatible with the colloid polymer A second organic solvent is added to shrink the colloidal polymer in the mixed solvent including the first organic solvent and the second organic solvent so that the diameter of the colloidal polymer is smaller than the diameter of the colloidal polymer in the monolayer film having the dense crystal pattern formed in step a). A monolayer film having a non-dense crystal pattern of a polymer colloid is formed by induction, or (ii) a monolayer film having a dense crystal pattern is brought into contact with a mixed solvent containing water and a co-solvent to cause contraction of the colloid by co-non-dissolution. converting a polymer colloid into a monolayer film having a non-dense crystalline pattern by inducing;

A method for producing a non-dense colloidal crystal pattern comprising a is provided.

According to an exemplary embodiment, when the colloid is swollen by contact with the first organic solvent in (i) of step b), the corrected Flory-Huggins interaction parameter of the colloid and the solvent system (corrected Flory-Huggins When the value of interaction parameter; χ _α is less than 0.5, and the colloid is contracted by the addition of the second organic solvent in (i) of step b), the corrected Flory-Huggins interaction parameter of the colloid and the solvent system. The value χ _α can exceed 0.5.

According to an exemplary embodiment, the lattice constant of each of the monolayer film having a colloidal dense colloidal crystal pattern formed in step a) and the monolayer film having a non-dense colloidal crystal pattern of colloid formed in step b) is 100 nm. It can range up to 100 μm.

According to an exemplary embodiment, a distance between colloidal particles in the monolayer of the dense colloidal crystal pattern may be less than 1 nm, and a distance between colloidal particles in the monolayer of the non-dense colloidal crystal pattern may be at least 1 nm.

According to an exemplary embodiment, the substrate may be an inorganic substrate or an organic substrate, and may have a flat or curved surface.

According to an exemplary embodiment, in (i)) of step b), the volume fraction of the first organic solvent in the mixed solvent may be adjusted in the range of 0.001 to 0.4.

According to an exemplary embodiment, in (i) of step b), a step of partially removing the first organic solvent may be performed prior to adding the second organic solvent.

According to an exemplary embodiment, the particle diameter and thickness of the colloid in the monolayer film having the dense colloidal crystal pattern formed in step a) range from 100 nm to 100 μm and from 10 nm to 50 μm, respectively, and The particle diameter and thickness of the colloid in the monolayer film having the non-dense colloidal crystal pattern formed in step b) may range from 50 nm to 50 μm and from 20 nm to 30 μm, respectively.

According to an exemplary embodiment, the co-solvent in (ii) of step b) may be at least one selected from the group consisting of alcohol having 3 or less carbon atoms, DMSO, THF, 1,4-dioxane, and acetone.

According to an exemplary embodiment, the alcohol in (ii) of step b) may be methanol.

According to an exemplary embodiment, the mole fraction of alcohol in the mixed solvent in (ii) of step b) may be adjusted in the range of 0.15 to 0.5.

According to an exemplary embodiment, the non-dense colloidal crystal pattern may be fixed using a fixing component during or after step b).

According to a second aspect of the present disclosure,

An optical material having a monolayer film having a non-dense colloidal crystal pattern manufactured according to the above method is provided.

According to an exemplary embodiment, the optical material may be an anti-reflective material.

In order to prepare a non-dense colloidal crystal pattern from a dense colloidal crystal pattern, the existing colloid-based lithography technique mainly applies an aqueous salt solution, so it has been pointed out that the application field is limited, but provided according to the specific examples of the present disclosure. In this method, the polymer colloidal crystal pattern can be converted by selecting a solvent and/or adjusting the composition of the solvent system. In this pattern conversion, the process time is short and reproducibility is high without requiring special equipment or equipment, and it is also advantageous in terms of versatility because it can be effectively applied to organic substrates such as polymers or plastics in addition to inorganic substrates. In addition, it has the advantage of being able to easily implement pattern conversion even on a structured (structured) surface of a curved surface (specifically, a convex surface or a concave surface) including a flat surface. In addition, when forming a pattern on a transparent substrate made of glass or PET, it can be applied as an optical member by increasing the light transmittance of the substrate, and furthermore, it can be used in various industrial fields (eg, solar, display, automobile materials, etc.) Use is also expected.

1 is a diagram schematically showing the principle of solution lithography for producing a monolayer film of a non-dense colloidal crystal pattern from a monolayer film of a dense colloidal crystal pattern;
Figure 2 is a SEM photograph (A, B) of a poly(N-isopropylacrylamide-co-allylamine) colloidal dense crystalline monolayer. The monolayer was first immersed in THF for 10 minutes and then immersed in a THF/DEE mixture (φ _THF = 0.02). SEM pictures of non-dense colloidal crystal patterns produced by immersion (immersion time: 5 minutes (C, D) and 10 minutes (E, F));
3 is a SEM photograph showing the morphology of colloidal crystal patterns at various volume fractions (φ _THF ) of THF in a THF/DEE mixture used as a non-solvent (A: 0.1, B: 0.2, C: 0.3 , Ra, Ma: 0.4, Bar: 0.5);
4 is a graph showing the change in colloidal diameter according to the volume fraction of THF (φ _THF ) in the THF/DEE mixture used as a non-solvent, and _FIG . ₀ ) is a graph showing the ratio of the colloidal diameter (d) in the colloidal crystal pattern;
5 is obtained after the monolayer was first deposited in ethanol for 10 minutes (A, B) and 1 hour (C, D), respectively, and then deposited in an ethanol-DEE mixture (φ _EtOH =0.02) for 10 minutes. SEM pictures showing colloidal crystal patterns;
Fig. 6 is a SEM photograph showing the colloidal crystal pattern obtained after the monolayer was first immersed in methanol over 10 minutes and then in a methanol-DEE mixture (φ _EtOH = 0.02) for 10 minutes;
7 is a photograph showing the color of a silicon wafer in a methanol-water solution of different mole fractions of methanol (χ _M ) (a), and colloidal crystals formed after immersing a monolayer film in a methanol-water solution (χ _M = 0.4). SEM pictures showing the pattern (B, C),
8 is a SEM photograph (a-c) showing a colloidal pattern formed on the surface of concave curved PDMS (pore diameter: about 4.5 μm),
9 is an SEM photograph (a, b) showing a colloidal crystal pattern formed on a PET film;
10 is a graph showing transmittance when a glass slide and a dense colloidal monolayer film and a colloidal crystal pattern are respectively coated on a glass slide, and transmittance when a PET film and a dense colloidal monolayer film and a colloidal crystal pattern are respectively coated on the glass slide ( go, i) and
11 is a SEM photograph (a, b) showing a pattern fixed to a NOA 68 photocurable polymer thin film on a slide glass and a PET film, respectively, and a non-fixed colloidal crystal pattern and NOA 68 photocurable polymer on the slide glass and PET film, respectively. It is a graph (C, D) showing the transmittance of the pattern immobilized as a thin film, and
FIG. 12 is SEM photographs (a, b) showing colloidal crystal patterns fixed with glutaraldehyde in a methanol-water solution (χ _M =0.15) for 6 hours.

The present invention can all be achieved by the following description. The following description should be understood as describing preferred embodiments of the present invention, but the present invention is not necessarily limited thereto. In addition, the accompanying drawings are for understanding, and the present invention is not limited thereto, and details of individual components can be properly understood by the specific purpose of the related description to be described later.

Terms used in this specification may be defined as follows.

"Close-packed" may refer to a photonic crystal in a state where the colloids used to form the photonic crystal form the crystal while closely (closely) arranging or contacting each other, and more specifically, In the case where the colloid is a spherical particle, it can be understood to mean a colloidal crystal state when the lattice constant substantially matches the diameter of the particle. On the other hand, "non-close-packed" is a state in which the colloids used to form the photonic crystal are not contacted and maintain a predetermined distance (not densely or non-densely) to form the crystal. It can mean the photonic crystal of the case, and more specifically, when the colloid is a spherical particle, the lattice constant can be expressed as the sum of the aperture of the particle and the spacing (or distance) between the particles. can be understood as

“Nanoscale” can broadly mean that the largest dimension of a feature is on the nanometer scale, for example in the range of about 0.1 to 1000 nm, specifically about 1 to 700 nm.

“Soft” means capable of reversibly deforming (eg, expanding or contracting) in a manner that does not damage or break at a given strain level (eg, from about 1 to 1000%, specifically from about 10 to 500%). It can be understood to mean the properties of the material.

"External stimulus responsiveness" can be understood to mean a property that exhibits a behavior that changes according to external stimuli.

"Hydrogel" is also called "hydrogel" and can refer to a three-dimensional, hydrophilic or amphiphilic polymer network capable of absorbing large amounts of water, usually as a cross-linked polymer of hydrophilic monomers. These polymer networks may be homopolymers or copolymers and exhibit insolubility due to the presence of covalent chemical or physical (ionic, hydrophobic interactions, entanglement, etc.) cross-links. As a result, the hydrogel can swell and contract in an aqueous medium.

"Solubility parameter" may refer to an index for predicting whether a certain substance dissolves in another substance to form a solution, and may be represented by Equation 1 below.

[Equation 1]

In the above equation, δ _D is dispersion forces, δ _p is permanent dipole-permanent dipole forces, and δ _H is hydrogen bonding forces. Details on solubility parameters are described in "HANSEN SOLUBILITY PARAMETERS, A User's Handbook," Charles M. Hansen, Second Edition, CRC Press, 2007, which is incorporated herein by reference.

"Contacting" narrowly means direct contact between two objects, but in a broad sense it can be understood that any additional component may be intervened.

It can be understood that the expressions "on" and "above" are used to refer to the concept of relative position. Therefore, not only when other components or layers are directly present in the mentioned layers, other layers (intermediate layers) or components may be interposed or present therebetween. Similarly, the expressions “under”, “under” and “below” and “between” may also be understood as relative concepts of position. In addition, the expression “sequentially” may also be understood as a relative positional concept.

In this specification, when it is said that a certain component is "included", it means that it may further include other components and / or steps unless otherwise stated.

According to one embodiment of the present disclosure, after forming a dense colloidal crystal monolayer on a substrate, (i) swelling and shrinkage by sequential combination of good solvent and non-solvent, or (ii) in combination of water and co-solvent A method for producing a non-dense colloidal crystal monolayer by inducing shrinkage using co-insolubility that occurs is provided.

According to one embodiment, a crystalline monolayer (specifically, a two-dimensional crystal pattern) of a colloid of external stimulus-responsive polymer particles (specifically, nanoparticles) formed on a substrate is a medium surrounding the colloid (specifically, Structural change occurs due to thermodynamic interaction between the solvent system) and the polymer constituting the colloid (especially, the main polymer). At this time, the principle that the size (or diameter) of the colloidal particles is changed by the interaction between the solvent system and the polymer around the colloid, and the initial dense colloidal crystal pattern is converted into a non-dense colloidal crystal pattern is used.

In this way, after the dense crystal pattern is converted into a non-dense crystal pattern, distinguishable optical characteristics (specifically, color of the substrate) may be exhibited, and the change may be recognized or identified using the naked eye or a device.

According to an exemplary embodiment, in a dense colloidal crystal pattern or monolayer film (in a dried state), the colloidal particles constituting the same may typically have a nanoscale dimension, but in some cases, a microscale (e.g., characteristic As an example, the particle size (diameter) of a colloid in a monolayer film having a dense colloidal crystal pattern ranges from about 100 nm to about 100 μm, specifically from about 150 nm to about 100 μm. up to 10 μm, more specifically from about 200 nm to about 2 μm. In addition, the thickness (height) of the colloid may range, for example, from about 10 nm to about 50 μm, specifically from about 20 nm to about 5 μm, and more specifically from about 50 nm to about 1 μm. However, typically, the size and thickness of the colloidal particles in the dense pattern may be in the nanoscale range (up to about 1000 nm in the maximum dimension of the feature), and the size and thickness of the colloidal particles described above may be understood as exemplary. .

According to an exemplary embodiment, in the dense colloidal crystal pattern, the distance or spacing (s) between the colloidal particles is, for example, less than about 1 nm (specifically less than about 0.1 nm, more specifically substantially in contact with each other). State), and at this time, the ratio of diameter/thickness may be, for example, in the range of about 2 to 10 (specifically about 3 to 9, more specifically about 4 to 8).

On the other hand, in the non-dense colloidal crystal pattern, the colloidal particle size (diameter) is, for example, from about 50 nm to about 50 μm, specifically from about 100 nm to about 5 μm, more specifically from about 500 nm to 1 μm, and its thickness (or height) is, for example, from about 20 nm to about 30 μm, specifically from about 40 nm to about 2.5 μm, more specifically from about 50 nm to about 0.5 μm. range can be In addition, the distance or interval (s) between the colloidal particles is, for example, at least about 1 nm (specifically, from about 3 nm to about 10 μm, more specifically from about 5 nm to about 1 μm, particularly specifically about 10 nm to about 0.1 μm), and the diameter/thickness ratio may range, for example, from about 1 to 5 (specifically from about 1 to 3, more specifically from about 1 to 2). However, typically, the size and thickness of the colloidal particles in the non-dense pattern may be in the nanoscale range (up to about 1000 nm in the maximum dimension of the feature), and the size and thickness of the colloidal particles described above may be understood as exemplary. there is.

According to an exemplary embodiment, even when a transition is made from a dense colloidal crystal pattern to a non-dense colloidal crystal pattern, the lattice constant of the crystal pattern is, for example, about 100 nm to about 100 μm, specifically about 150 to 700 nm, more specifically, within a range of about 200 to 500 nm, and thus crystal properties (or photonic crystal properties) can be substantially maintained.

According to an exemplary embodiment, the polymer constituting the colloid may be a polymer having a response to external stimuli known in the art, for example, a hydrogel polymer.

According to exemplary embodiments, these hydrogel polymers are poly(N-isopropylacrylamide) [poly(N-isopropylacrylamide), pNIPAM], poly(N-isopropyl acrylamide-co-allylamine) [poly(N -isopropyl acrylamide-co-allylamine), poly(NIPAM-co-AA)], poly(N-isopropyl acrylamide-co-2-(dimethylamino)ethyl methacrylate)[poly(Nisopropylacrylamide-co-2- (dimethylamino)ethyl methacrylate), poly(NIPAM-co-DMAEMA)], poly(N-isopropyl acrylamide-co-2-(dimethylamino)ethylacrylate)[poly(N-isopropyl acrylamide-co-2- (dimethylamino)ethyl acrylate), poly(NIPAM-co-DMAEA)], poly(N-isopropyl acrylamide-co-acrylic acid)[poly(N-isopropyl acrylamide-co-acrylic acid), poly(NIPAM-co- AAc)], poly(N-isopropyl acrylamide-co-methacrylic acid), poly(NIPAM-co-MAAc)], poly(N,N-diethyl Acrylamide)[poly(N,N-diethylacrylamide)], poly(N-vinylcaprolactam)[poly(N-vinlycaprolactam)], poly(ethylene glycol)[poly(ethylene glycol)], poly(ethylene glycol- It may be at least one selected from the group consisting of b-propylene glycol-b-ethylene glycol) [poly(ethylene glycol-b-propylene glycol-b-ethylene glycol)]. According to certain embodiments, the polymer may be poly(N-isopropyl acrylamide).

According to a specific embodiment, the colloid-forming polymer may have a lower critical solution temperature (LCST), wherein the LCST is, for example, about 0 to 100 °C, specifically about 10 to 70 °C, more specifically about It may be set within the range of 25 to 60 °C. As described below, the polymer having LCST is applicable when a dense pattern is converted into a non-dense pattern using co-insolubility occurring in a combination of water and a co-solvent (particularly, alcohol).

According to another embodiment, the colloidal pattern can be formed using particles composed of various polymers other than polymer particles composed of hydrogel polymers as the material of the colloidal particles. In this regard, if the particles made of a specific polymer can be swollen by a specific organic solvent, the solvent can act as a good solvent (first organic solvent), and if the polymer particles are not swollen by a specific solvent (eg For example, when the polymer constituting the colloidal particles has low or no miscibility with the corresponding solvent), this solvent can be applied to the patterning process as a non-solvent (second organic solvent).

As an example, in the case of cross-linked polystyrene or poly(methyl methacrylate) particles, they do not correspond to hydrogel polymers that swell with water. However, it can be swollen by organic solvents such as THF and dichloromethane, which are good solvents, and can be converted from a dense pattern to a non-dense pattern when a non-solvent such as diethyl ether is used. From this point of view, in addition to polystyrene and PMMA, polymer particles based on poly(ethylene glycol), polymer particles based on poly(propylene glycol), and the like may also be applicable depending on the selection of the organic solvent.

Therefore, one of the biggest advantages of the method of forming a non-dense pattern using an organic solvent rather than an aqueous salt solution as in the present embodiment is that the type of colloid used is not limited to hydrogels that can be swollen by water. , It is particularly useful when it is desired to convert a dense pattern crystal monolayer film composed of particles made of various polymers into a non-dense pattern.

Formation of a monolayer film having a colloidal dense colloidal crystal pattern

According to one embodiment, a step of forming a dense crystal pattern of colloidal particles on a substrate is first performed on a substrate, which is not limited to a specific method, but may be implemented in the following exemplary method:

In this regard, the substrate may typically be one capable of providing a flat surface. According to another embodiment, it may have a curved surface, for example, a curved (convex or concave) surface having a micro scale. At this time, the radius of curvature of the surface of the curved surface is, for example, at least about 100 nm, specifically from about 500 nm to about 500 μm, more specifically from about 1 to 100 μm, particularly from about 2 to about 30 μm. can In certain embodiments, the radius of curvature may range from about 3 to 10 μm. Also, illustratively, in the case of a concave surface, its pore diameter ranges, for example, from about 1 to 8 μm, specifically from about 2 to 6 μm, more specifically from about 2.5 to 5 μm, particularly from about 3 to 4 μm. can be A substrate having such a curved surface (ie, a structured substrate) can be manufactured through a known method, and is disclosed in, for example, Korean Patent Application No. 2019-6087 of the present inventors. These documents are incorporated by reference into the present disclosure.

According to an exemplary embodiment, as long as the substrate can form a crystal pattern of colloidal particles, the material thereof is not particularly limited, and various inorganic and/or organic-based materials may be used. For example, as a substrate material, silicon wafer, silicon/silicon oxide glass, quartz cover glass, ITO (indium tin oxide), ZnO, TiO ₂ , poly(dimethylsiloxane); PDMS), polyurethane ), polyimide (polyethylene; PE), polypropylene (PP), poly(methyl methacrylate); PMMA), polystyrene (PS), and polyethylene terephthalate ( At least one selected from the group consisting of poly(ethylene terephtalate); PET) (including copolymers or mixtures thereof) may be used. In addition, the dimensions (for example, thickness, and/or length or width) of the substrate are not particularly limited as long as the thickness of the material used can be freely adjusted. Illustratively, the thickness of the substrate may be, for example, at least about 50 μm, specifically at least about 100 μm, more specifically at least about 200 μm, and commercially a thickness of tens of micrometers or more, and even up to several tens of millimeters. range is also possible.

In this regard, when an aqueous salt solution is used as in the prior art, an oxide may be formed depending on the type on a metal substrate (eg, a copper-based substrate, an aluminum-based substrate, etc.) among inorganic substrates. Although a pattern can be formed using a substrate, it may be preferable to use an organic solvent because there is a possibility of corrosion due to the use of an aqueous salt solution. Furthermore, as described later, when forming a pattern on an arbitrary substrate using an organic solvent, the pattern method most suitable for the substrate can be applied with more freedom, and the colloid-forming polymer is also limited to the hydrogel polymer. In addition to the substrates listed above, various types of substrates may be used, such as various polymers may be used. Therefore, the present embodiment provides the advantage of substantially broadening the selection range of substrates.

According to an exemplary embodiment, in order to form a dense pattern, a dispersion of colloidal particles may be prepared first. At this time, when the polymer constituting the colloidal particles is a hydrogel polymer, the formation of a dense pattern may be induced by adjusting the temperature of the medium (specifically, the aqueous medium) if necessary. As an example, it may have a large diameter at a relatively low temperature (eg, below the LCST), while having a small diameter at a relatively high temperature (eg, above the LCST). That is, at a temperature lower than the LCST, the polymer chain hydrates and swells or expands, while at a temperature equal to or higher than the LCST, it dehydrates and contracts in the form of a coil-to-globular transition. Illustratively, depending on the temperature of the aqueous medium, the diameter (eg, hydrodynamic diameter) of the colloidal particles varies in the range of about 1 to 70%, specifically about 10 to 60%, and more specifically about 20 to 50%. can do. As such, the size of the colloid in the monolayer film forming the dense pattern may be controlled by controlling the temperature of the aqueous medium.

Then, the aqueous product is added (eg, dropwise-addition) to the surface of the still water-based medium (water) to disperse colloidal particles at the interface between the gaseous atmosphere (eg, air) and the aqueous medium. can be induced to exist in the form of a crystalline monolayer. The colloidal monolayer film may be formed by self-assembly of colloidal particles, and may exhibit, for example, a hexagonal lattice, specifically a regular hexagonal lattice.

On the other hand, even if the colloid can be swollen, it is advantageous to have a characteristic of not peeling off from the substrate by a specific binding force. In this case, the specific binding force may be a secondary bond such as electrostatic attraction, a hydrogen bond, a polar-polar bond, or a van der Waals bond, or a primary bond including covalent and coordinate bonds.

Then, upon transferring (contacting) the monolayer film of colloidal particles formed on the surface of the aqueous medium to the surface of the substrate, a crystalline monolayer film may be formed in a dense colloidal crystal pattern on the substrate. Illustratively, the colloid may be attached to the substrate using electrostatic attraction, eg the colloid may exhibit a positive charge while the substrate may exhibit a negative charge. At this time, the zeta potential (30 ℃) of the polymer colloid may be in the range of about 5 to 30 mV, specifically about 10 to 20 mV, while the zeta potential (30 ℃) of the substrate is, for example, about -1 to -50 mV (specifically about -5 to -30 mV) and about -1 to ??50 mV (specifically about -5 to -30 mV), but this can be understood as an example.

According to an exemplary embodiment, the temperature at which the monolayer film of colloidal particles is transferred onto the surface of the substrate is, for example, in the range of about 0 to 100 °C, specifically about 10 to 70 °C, more specifically about 20 to 60 °C. can be adjusted in The transfer temperature may be adjusted to form a dense crystal pattern in consideration of the material of the colloidal polymer used, the boiling point of the solvent (medium), and the material of the substrate.

Then, a step of drying the substrate on which the dense crystal pattern is formed may be optionally performed. The drying temperature is not particularly limited, and is, for example, about 0 to 150 ° C., specifically room temperature. .

Preparation of non-dense crystalline patterns

An example of converting a monolayer of a dense colloidal crystal pattern formed on various substrates into a monolayer of a non-dense colloidal crystal pattern according to one embodiment of the present disclosure is shown in FIG. 1 .

Referring to the drawings, unlike in the prior art, a colloidal dense crystal pattern formed on a substrate is converted into a non-dense crystal pattern through the following two methods by selecting a solvent and adjusting its composition in a solvent system in contact with a colloidal monolayer film. conversion steps can be performed.

(i) Preparation of non-dense crystal patterns through sequential combination of two organic solvents (good solvent and non-solvent)

According to one embodiment, the previously prepared dense crystal pattern (eg, in a dried state) can be converted into a non-dense crystal pattern by sequentially contacting two organic solvents, that is, a good solvent and a non-solvent, respectively. . At this time, the good solvent can induce swelling by thermodynamic interaction with the colloidal polymer (or the main polymer of the colloid), while the non-solvent can induce shrinkage by the thermodynamic interaction with the colloidal polymer (or the main polymer of the colloid). .

According to an exemplary embodiment, each selection of a good solvent (inducing swelling of a colloid) and a non-solvent (inducing shrinkage of a colloid) and a combination (or pair) thereof is a calibrated Flory-Huggins interaction parameter (χ _α ) can be used to select.

In general, the Flory-Huggins interaction parameter (χ _FH ) for a solvent-gel system can be determined according to Equation 2 below.

[Equation 2]

In the above formula, δ _s and δ _p are the solubility parameters of the solvent and the polymer, respectively,

R is the gas constant,

T is the temperature, and

ν is the molar volume of the polymer chain segments in the polymer gel.

Details on the Florey-Huggins interaction parameter (χ _FH ) are described in CS Brazel, SL Rosen, Fundamental Principles of Polymeric Materials, 3rd Ed., John-Wiley & Sons, Inc., 2012, which is It is incorporated by reference into this disclosure. In the above formula, ν can be measured from the density of the gel. For example, the density of a poly(N-isopropylacrylamide)-based gel is 1.35 g/cm 3 .

However, in the case of the equation for χ _FH , since it is known to be valid for a regular solution system, it can be expressed as in Equation 3 below by reflecting polarity and hydrogen bonding components based on the Hansen solubility parameter.

[Equation 3]

In the above formula, each of δ _d,s and δ _d,p is the dispersion component of the solvent and polymer, δ _p,s and δ _p,p are each of the polar component of the solvent and polymer, and δ _{h ,s} and δ _h,p are the hydrogen bond components of the solvent and polymer, respectively, and

R, T and ν are as described above.

However, in the case of the expression for χ _H , it is suitable when δ _d is dominant compared to δ _p and δ _h , but in the case of certain polymers (eg acrylate polymers), the χ _H value is often excessively reflected. can Therefore, the corrected Flory-Huggins interaction parameter (χ _α ) can be derived by introducing the empirical correction constant α as shown in Equation 4 below. Details are given in T. Lindvig, ML Michelsen, GM Kontogeorgis, Fluid Phase Equilibria 2002, 203, 247, which is incorporated by reference into the present disclosure.

[Equation 4]

In the above equation, α may be about 0.6 as a correction constant, and

R, T and ν are as described above.

As an example, when the colloidal polymer is a poly(N-isopropylacrylamide)-based gel, the Flory-Huggins interaction parameters and the corrected Flory-Huggins interaction parameters measured at 298 K for various solvents are shown in Table 1 below. shown in

δ δ _d δ _p δ _h |δ _solvent ?? δ _polymer | χ _F χ _H χ _a tetrahydrofuran
(THF) 9.5 8.2 2.8 3.9 1.98 0.55 0.53 0.32 ethanol 12.9 7.7 4.3 9.5 1.42 0.29 0.15 0.09 methanol 14.3 7.4 6.0 10.9 2.78 1.09 0.63 0.38 diethyl ether 7.6 7.1 1.4 2.5 3.88 2.13 1.26 0.76

According to one embodiment, the corrected Flory-Huggins interaction parameter (χ _α ) value between the colloidal polymer of the dense crystal pattern and the solvent system is, for example, less than about 0.5 (specifically less than about 0.49, more specifically about 0). may exceed 0.4), and when the above requirements are satisfied, the colloidal particles constituting the dense crystal pattern may be swollen by absorbing the solvent by contact with the first organic solvent. As an example, the first organic solvent may be, for example, at least one selected from the group consisting of tetrahydrofuran (THF), methanol, ethanol, acetone, dichloromethane, and chloroform.

According to an exemplary embodiment, the contact time between the first organic solvent and the dense crystal pattern is not particularly limited as long as the pattern can be formed, but is, for example, from about 0.1 minute to about 24 hours, specifically from about 1 minute to about 24 hours. Up to about 12 hours, more specifically in the range of about 10 minutes to about 2 hours. In addition, the contact temperature is also not particularly limited, and may be, for example, about 0 to 100 ° C., specifically room temperature.

As described above, as the colloidal polymer in the dense crystal pattern swells through contact with the solvent system composed of the first organic solvent, the size (diameter) of the colloidal particles is increased by, for example, at least about 5% compared to before contact. Specifically, it may increase by at least about 10%, more specifically by at least about 20% to 100%, and in some cases may increase by more than 100%.

Next, a step of adding a second organic solvent that is a non-solvent to the dense crystal pattern swollen in the first organic solvent may be performed. As a result, the solvent system surrounding the colloidal particles forms a mixed solvent of the first organic solvent and the second organic solvent.

At this time, the second organic solvent may be selected from solvents having a corrected Flory-Huggins interaction parameter (χ _α ) value described above, for example, greater than about 0.5, specifically greater than about 0.7, and more specifically greater than about 0.75. can In an exemplary embodiment, the second organic solvent is at least one selected from the group consisting of diethyl ether (DEE), hexane, cyclohexane, benzene, and toluene. can

As the second organic solvent is added, the colloidal particles previously swollen in the mixed solvent of the first organic solvent and the second organic solvent contract to form a non-dense crystal pattern.

In this regard, the thermodynamic state of the mixed solution and the colloidal particles can also be expressed using the calibrated Flory-Huggins interaction parameters. As described above, when the value of the corrected Flory-Huggins interaction parameter (χ _α ) between the colloidal polymer and the mixed solvent (solvent system) is less than 0.5, the solvent system has the ability to dissolve the polymer constituting the colloidal particles. On the other hand, swelling occurs, but by adjusting to exceed 0.5, miscibility between the solvent system and the polymer constituting the colloidal particles is reduced, and the swollen particles can be shrunk.

The reason why the non-dense pattern is formed by adding the second organic solvent so that the corrected Flory-Huggins interaction parameter value is within a specific range is that when particles made of various polymers are swollen by a good solvent, the number of polymer chains constituting them The ductility of the polymer chain is expressed due to the plasticization phenomenon. At this time, most polymers exhibit ductility in a good solvent and increase in particle size as they swell. In this situation, when a non-solvent is added, In particular, it is believed that this is because the non-dense pattern can be converted when the addition amount of the non-solvent is adjusted so that the corrected Flory-Huggins interaction parameter value exceeds 0.5.

In particular, through the addition of the second organic solvent, shrinkage is induced to a size smaller than the size of the colloidal particles before swelling (specifically, the dense crystal pattern in a dried state) by contact with the first organic solvent to form a non-dense crystal pattern It is worth noting that the conversion to That is, the solvent system by such a mixed solvent is in a state in which a solvent capable of swelling colloidal particles and a solvent capable of shrinking them are mixed, and at this time, the thermodynamic state of the colloidal particles of the mixed solution is similar to that of the first organic solvent. A non-dense crystal pattern can be formed if a relationship capable of shrinking enough to be smaller than the size of the colloidal particles in the dense crystal pattern before contact is established. Although the present disclosure is not bound by any particular theory, the reason for the smaller size compared to the initial colloidal particles (colloidal particles prior to contact with the first organic solvent) can be explained as follows:

Since the polymer chains in the colloid are solvated in the good solvent through secondary bonding by the first organic solvent (good solvent), the colloidal particles are swollen. It exists in a state of admixture with a solvent. In this case, the mixed solvent shrinks the polymer chains in the particles due to the presence of the non-solvent, and this process continues to occur as the ratio of the non-solvent increases. It is known that the extended or coiled polymer chain due to the presence of a good solvent can change the shape of the chain due to the presence of a non-solvent, and generally, as the composition of the non-solvent increases, that is, the polymer chain becomes more As the solubility decreases, it changes to a globular structure. At this time, at the point where the corrected Flory-Huggins interaction parameter is 0.5, all solvents can no longer form secondary bonds with the polymer chains, and thermodynamically, the polymer chains have the Gibbs free energy of mixing value becomes 0. In this case, the polymer chain is rapidly collapsed and the size of the polymer particle is rapidly contracted by pushing out the solvent. In general, since the solvent used in manufacturing a monolayer film can be thermodynamically mixed with the polymer chains in the particle, the size of the particle exists in a relatively large state when forming the monolayer film. The particles are swollen, and during this process, a non-solvent is added to induce shrinkage, and at this time, it is determined that a pattern is formed in which the shrinkage rate is smaller than the size of the particles when dried.

In an exemplary embodiment, a step of partially removing the first organic solvent may be optionally performed prior to the addition of the second organic solvent in order to easily reach the thermodynamic conditions leading to the formation of the non-dense crystal pattern. can However, the amount of the first organic solvent to be removed in advance may vary depending on the types of good solvents and non-solvents constituting the mixed solvent. The volume fraction of the first organic solvent in the mixed solvent (based on the sum of the volumes of the first organic solvent and the second organic solvent) under conditions capable of forming the aforementioned non-dense crystal pattern is, for example, about 0.001 to 0.4; Typically it can be adjusted within the range of about 0.005 to 0.3, more typically about 0.01 to 0.2.

In addition, the contact temperature and time between the solvent system and the colloidal crystal pattern during the contraction process in the mixed solvent may be determined within the range set in the swelling step using the first organic solvent, but the first and second organic solvents used It can be changed according to the type of the solvent system, whether or not additional components (eg, fixing components to be described later) are incorporated in the solvent system, and the type thereof. Also, during swelling, the contact temperature with the first organic solvent may be the same or different, and the contact time may also be the same or different.

The size (diameter) of the colloidal particles shrunk by the mixed solvent system is, for example, less than about 1%, specifically less than about 10%, more specifically about It may be a level of less than 50%, and in this case, the properties of the non-dense crystal pattern are as described above.

(ii) Preparation of non-dense crystal pattern using co-insolubility between water and co-solvent

According to another exemplary embodiment of the present disclosure, a peculiar phenomenon that occurs when two kinds of good solvents are combined in a specific composition to prepare a colloidal non-dense crystal pattern, that is, co-nonsolvency ) shape can be used.

Specifically, water and a co-solvent each correspond to a good solvent that can swell the colloidal particles with respect to the polymeric colloid. However, when a mixed solvent system in which water and a co-solvent are mixed at a specific molar ratio is prepared and brought into contact with a previously prepared monolayer film having a dense colloidal crystal pattern, miscibility with the polymer constituting the colloid is rapidly reduced. , resulting in colloidal particles being contracted to produce the desired non-dense crystalline pattern.

According to an exemplary embodiment, the co-solvent combined with water may be at least one selected from alcohols having 3 or less carbon atoms (specifically, aliphatic alcohols), DMSO, THF, 1,4-dioxane, acetone, and the like. In this case, the alcohol having 3 or less carbon atoms may be, for example, methanol, ethanol, or a combination thereof, and more specifically, methanol.

At this time, the mole fraction of the cosolvent (specifically alcohol, more specifically methanol) in the mixed solvent containing the water-cosolvent may be adjusted to induce a co-dissolution phenomenon, for example, about 0.15 to 0.5, Specifically, it may be set within the range of about 0.17 to 0.45, more specifically about 0.2 to 0.4.

After the non-dense crystal pattern is formed by performing the above-described method (i) or (ii), a post-treatment process in which at least one of a solvent washing step, a drying step, and the like is selected may be selectively performed.

According to this specific embodiment, a predetermined pattern can be formed on a substrate without performing conventional lithography techniques or etching. When such a solution lithography technique is applied, not only a flat inorganic substrate, but also a structured surface (eg, For example, curved surfaces), and is advantageous for patterning colloidal crystals on polymer-based substrates that are not damaged by the etching process. In addition, the process time is short, and a pattern with good reproducibility can be formed without using a special device.

In addition, the non-dense colloidal crystal pattern may exhibit different optical properties, such as light transmittance, than the dense colloidal crystal pattern. In particular, when a pattern is formed on a transparent substrate such as a glass substrate or a PET film, light transmittance of the substrate may be increased. In particular, it is possible to broaden the range of application as an optical material, such as being patterned on a PET film to achieve better light transmittance than a glass substrate in the visible light band. Also, when the dense colloidal crystal pattern is converted to a non-dense colloidal crystal pattern, since the patterned surface is composed of colloid and air, the average refractive index in the layer has a value between air and colloid. As a result, since the reflectance of the substrate can be reduced, an anti-reflective function can be provided.

Fixation of non-dense colloidal crystal patterns

According to another embodiment of the present disclosure, when a non-dense colloidal crystal pattern formed using a solvent system is exposed to external stimuli or environments such as moisture, the converted non-dense pattern may change, so fixing it may be desirable. As described above, the method of patterning a colloidal monolayer on a substrate by controlling the selection and composition of a solvent is suitable for fixation of patterned colloidal particles according to a given situation and purpose. At this time, an immobilized component, for example, an organic component such as a polymer may be used.

According to an exemplary embodiment, a curable polymer (eg, photocurable polymer) may be used as a component for fixing the pattern. In this regard, as polymers usable for immobilization, for example, polyurethane (Polyurethane, PU), polydimethylsiloxane (PDMS), NOA (Noland Optical Adhesive), epoxy, acrylic, etc. At least one may be selected. Among them, NOA-based polymers (for example, commercially available from Norland Products and trade names NOA 61, NOA 63, NOA 65, NOA 68, etc.) are liquid UV curable containing polyfunctional thiol and polyfunctional allyl monomers. It is a monomer mixture (or precursor). As an example, NOA 68 contains about 45 to 65 weight percent mercapto-ester and 5 to 20 weight percent tetrahydrofurfuryl methacrylate.

Alternatively, at least one selected from glutaraldehyde, glycerol diglycidyl ether, and the like may be used as a fixing component. In the case of glutaraldehyde, it has a -NH ₂ group on the side chain of a colloidal polymer (eg, pNIPAM, poly(NIPAM-co-AA) as an amide group-containing polymer), so that the amine group in the colloid via glutaraldehyde It is believed that a cross-linking reaction between livers may occur, and that glutaraldehyde itself may be polymerized in an aqueous solution to provide an immobilization function.

According to an exemplary embodiment, the non-dense patterning may be formed and then fixed, alternatively, the non-dense patterning may be performed together with or simultaneously with the fixing. Specifically, the fixing component is a solvent system for forming a non-dense crystal pattern, that is, a mixed solvent of a good solvent and a non-solvent (ie, a mixed solvent formed by swelling with a good solvent and subsequently combining a non-solvent), Alternatively, it can be introduced by being contained in a mixed solvent containing water and a co-solvent (when using co-insolubility). At this time, the amount of the fixing component is, for example, about 1 to 10% by weight, specifically about 5 to 9% by weight, more specifically about 7 to 8% by weight based on the weight of the solvent system. do.

Illustratively, a precursor (monomer) of a photocurable polymer is incorporated (introduced) into a solvent system (in particular, a mixed solvent of a first organic solvent and a second organic solvent) inducing colloidal shrinkage to form a dense crystal pattern on a substrate. - Patterning and fixation may be performed by converting into a dense crystal pattern and subsequently irradiating with light (eg, ultraviolet rays).

On the other hand, when glutaraldehyde or the like is used, the fixing component is introduced into a solvent system (for example, a combination of water and a co-solvent (specifically, alcohol)), but the contact time with the dense crystal pattern is reduced. This can be done in an appropriately selected manner. As an example, the immobilization time can be set longer than in the case of not containing the immobilization component, so that the immobilization component is sufficiently absorbed on the pattern. In this case, the time required for patterning and fixation may be adjusted within the range of, for example, about 5 to 26 hours, specifically about 6 to 20 hours, and more specifically about 8 to 18 hours. In this case, the patterning and immobilization temperatures are, for example, about 10 to 60 °C, specifically about 20 to 55 °C, and more specifically about 25 to 50 °C can be adjusted. However, the above-described numerical range may be understood as an example.

Through the above-described immobilization process, even if moisture (water) or the like comes into contact with the patterned (ie, non-dense patterned) substrate, it is possible to maintain crystal or optical properties.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but the following examples are provided to more easily understand the present invention, but the present invention is not limited thereto.

Example

The materials used in this example are as follows.

- N -isopropylacrylamide (98%) was purchased from Wako Chemical, Ltd.

- Tetrahydrofuran (THF) and methanol were purchased from J. T. Baker.

- Ethanol was purchased from Fisher Scientific.

- Diethyl ether was purchased from Samchun Chemicals.

- Polyethylene terephthalate (PET) film (thickness: 5 mm), allylamine (98%), potassium persulfate (> 99%), N , N′ -methylene bis-(acrylamide) (99%) and isopropyl Alcohol (IPA, 99.5%) was purchased from Sigma-Aldrich.

- Sylgard 184, α,α′-azobis (isobutyronitrile) (AIBN, 98.0%) was purchased from Acros.

- Single-sided silicon wafer (P type, <100>-oriented, 525 ± 25 μm thickness) and slide glass (22 × 22 mm ² ) were purchased from Namkang Hi-Tech and Paul Marienfeld GmbH & Co., respectively.

In addition, the equipment used for characterization in this embodiment is as follows.

- The hydrodynamic diameter and zeta-potential of the colloid were measured by dynamic light scattering (DLS, Nano-ZS90, Marvern Instrument).

- Scanning electron microscopy (SEM, S-4800, HITACHI) was used to investigate the morphology of colloidal crystal monolayers.

Preparation Example 1

Poly( N -isopropylacrylamide-co-allylamine) Synthesis of colloids

In 100 mL deionized water, 1.5 g N-isopropylacrylamide as a monomer and 0.08 g N,N′-methylene bis(acrylamide) as a crosslinking agent were dissolved, and the aqueous mixture was heated to 80° C. in a round-bottom flask. After reaching thermal equilibrium, 70 μL of comonomer allylamine and 2 mL of potassium persulfate aqueous solution (0.025 g/mL) were successively added.

At this time, the composition of the monomer mixture was 91.8 wt% of N-isopropylacrylamide, 4.9 wt% of allylamine, and 3.3 wt% of N,N′-methylene bis(acrylamide).

The polymerization reaction was carried out at 80° C. for 2 hours with continuous stirring of the solution. The aqueous colloidal suspension was cooled on an ice bath and stored in a refrigerator prior to use. Thus, when the colloid was dispersed in deionized water, its hydrodynamic diameter changed from 467 ± 7 nm at 25 °C (less than LCST (33 °C)) to 240 ± 2 nm at 50 °C.

Example 1

As shown in FIG. 1, a non-dense colloidal crystal pattern was formed on a substrate using the previously prepared colloid.

Formation of a crystalline monolayer film of dense colloid on a flat substrate

The previously prepared aqueous hydrogel colloidal suspension was centrifuged, then the supernatant was discarded and the cake redispersed in ethanol. The purification process was repeated one more time, and the colloid was finally dispersed in isopropyl alcohol (IPA).

Deionized water was filled into a Petri dish, and colloids dispersed in isopropyl alcohol were dropped onto the surface of the deionized water to form a colloidal crystal monolayer at the air-water interface. Then, the dense colloidal crystalline monolayer film was rapidly transferred (transferred) to the substrate using a silicon wafer (1.3×1.3 cm ² ) and a PET film as substrates. The monolayer film was dried at room temperature.

In the case of preparing a dense monolayer film on glass, two bare glasses were overlapped to prevent partial adsorption of colloid on the rear surface of the glass. Then, the overlapped bare glass was used to move the dense monolayer formed at the air-water interface to one side of the glass. After moving, the glass on the rear side was removed.

An SEM analysis was performed on a dense colloidal crystal monolayer formed on a silicon wafer substrate, and the results are shown in FIGS. 2A and 2B.

From the figure, it can be confirmed that a dense crystal pattern is formed on the flat substrate. At this time, the dense colloid monolayer is attached to the substrate through the electrostatic attraction between the positively charged colloid and the negatively charged silicon wafer substrate. According to FIG. 2(a), the lattice constant of the dense colloidal crystal monolayer was 379 ± 14 nm, similar to the diameter of the colloid in the monolayer (ie, 372 ± 16 nm). Also, referring to FIG. 2B, the colloid has a flat shape with a thickness of about 40 nm, which is due to evaporation of water/isopropanol used in the manufacturing process of the monolayer film.

Preparation of non-dense colloidal crystal patterns from dense colloidal crystal patterns

A flat silicon wafer substrate on which a dense colloidal crystalline monolayer was formed was immersed in 5 mL of tetrahydrofuran (THF; χ _α = 0.32) at 25° C. for 10 minutes, and then 4.8 mL of THF was removed. Then, 10 mL of diethyl ether (DEE; χ _α = 0.76) was added to maintain the substrate in a mixed solution having a volume fraction of THF (φ _THF ) of 0.02. At this time, the substrate was treated while changing the immersion time of 5 minutes and 10 minutes, respectively. Then, the sample was taken out and dried at 60°C. SEM analysis was performed on the obtained sample, and the results are shown in FIGS. 2C and 2LA (immersion time: 5 minutes) and FIGS. 2M and 2F (immersion time: 10 minutes).

According to FIG. 2C, the lattice constant was measured to be 379 ± 14 nm, which was similar to that of the dense colloidal monolayer, indicating that the colloidal crystal pattern was successfully formed. In addition, the diameter of the colloid was estimated to be 221 ± 13 nm.

According to FIG. 2D, most of the colloids can be seen that fibril is formed at the end of the particle, which is determined to be formed in the process of separating the colloid from the surrounding 6 colloids. According to FIG. 2E and FIG. 2B, when the immersion time in the THF-DEE mixed solution increased to 10 minutes, the fabric decreased. At this time, the colloidal diameter was 217 ± 19 nm, and the colloidal height was approximately 97 nm.

On the other hand, the single-layer-coated silicon wafer surface showed color (mixture of green and blue) changing according to the direction immediately after the addition of DEE. The color did not change during the drying process of the substrate (see the insets of FIGS. 2C and 2E, respectively). As such, it is believed that the color change is mainly caused by the conversion of a dense pattern to a non-dense pattern.

In addition, since the colloidal diameter was substantially the same regardless of the immersion time in the THF-DEE mixed solvent (226 ㅁ 16 nm at 2 hours), the patterns shown in FIGS. 2C to 2E were uniform throughout the silicon wafer substrate. was formed

Example 2

A flat silicon wafer substrate having a dense colloidal crystalline monolayer was prepared according to Example 1, and immersed in 5 mL THF at 25° C. for 10 minutes, and then 4.0 mL of THF was removed. Then, 9 mL of DEE was added and maintained for 10 minutes in a mixed solution having a volume fraction of THF (φ _THF ) of 0.1. The sample was taken out and dried at 60°C. Samples were obtained by treating in a mixed solution in which φ _THF was adjusted to 0.2, 0.3, 0.4 and 0.5, respectively, in this manner. The results are shown in FIGS. 3A to 3B. At this time, φ _THF was 0.1 (a), 0.2 (b), 0.3 (c), 0.4 (d, e), and 0.5 (f).

Referring to FIGS. 3A to 3C, the colloidal diameters were 224 ± 20 nm, 220 ± 22 nm, and 218 ± 17 nm, respectively, which were similar to the colloidal size of 217 ± 19 nm when φ _THF was 0.02. . On the other hand, when φ _THF was 0.4, different results were observed through repeated experiments. In the first two experiments (Fig. 3a), the colloid diameter increased (286 ± 14 nm) compared to the case where φ _THF was 0.3. In the other three experiments, the colloid was in a dense pattern (Fig. 3E), and its diameter was 362 ± 21 nm. Based on all results, the average colloidal diameter was 309 ± 41 nm. These results suggest that the diameter is sensitive to slight changes in the thermodynamic conditions of the solvent composition. When φ _THF was 0.5 (Fig. 3 bar), all colloidal particles showed a dense pattern, and their diameter was 368 ± 13 nm.

Meanwhile, FIG. 4 is a graph showing the diameter of colloidal particles in the monolayer film according to the volume fraction of THF in the mixed solution, and summarizes the analysis results for the colloidal diameter. The diameter of the colloids in the non-dense pattern remained almost constant until φ _THF reached 0.3, after which it increased rapidly. Since the average solubility parameter of the solvent mixture can be measured using φ _THF and φ _DEE , the χ _α value for the THF-DEE mixture and the polymer gel was calculated.

On the other hand, in FIG. 4B, the result of observing the change (d / d ₀ ) of the colloidal particles according to the χ _α value between the polymer constituting the colloid and the mixed solvent is shown. Referring to FIG. 4B, the d/d ₀ value was kept constant until the χ _α value (φ _THF : 0.3) decreased to 0.58. After that, the d/d ₀ value rapidly increased and the χ _α value (φ _THF : 0.5) reached almost 1 from 0.49.

These results were fitted using a sigmoidal curve to include a trend line, and the start point, inflection point, and end point where the size of the particles rapidly changed were predicted.

According to the above results, the transition starting point was observed at χ _α value of 0.56, and the inflection point was observed at χ _α value of 0.54. The transition is almost complete at χ _α ≤0.50, and d/d ₀ reaches χ _α values of 0.50 and 0.49 to 0.98 and 0.99, respectively. This value approximates the theoretical theta condition (χ=0.5).

As such, it can be seen that a non-dense colloidal crystal pattern can be realized through appropriate selection of a good solvent (χ _α <0.5) and non-solvent (χ _α >0.5) combination (or pair) and appropriate solvent composition for the colloidal polymer. .

Example 3

A flat silicon wafer substrate on which a dense colloidal crystalline monolayer was formed was prepared according to Example 1, and immersed in 5 mL ethanol at 25° C. for 10 minutes (FIG. 5A, B) or 1 hour (FIG. 5C, D). After that, 4.8 mL of ethanol was removed. Then, 10 mL of DEE was added and maintained for 10 minutes in a mixed solution having a volume fraction of ethanol (φ _EtOH ) of 0.02. The sample was taken out and dried at 60°C. The analysis results of the samples are shown in FIGS. 5A to 5B.

Referring to Figs. 5A and 5B, the colloidal diameter of the non-dense crystal pattern (immersion time in ethanol: 10 minutes) was 240 ± 17 nm. Also, according to Figs. 5c and 5d, the colloidal diameter (immersion time in ethanol: 1 hour) of the non-dense crystal pattern was 232 ± 11 nm. Compared to the case of THF-DEE, the colloidal diameter increased by 10 to 20 nm. In addition, the colloid in the pattern was closer to a hexagon than the colloid in the pattern obtained in the case of THF-DEE, and the fabric was mostly formed at the edge of the hexagon. These results suggest that the selection of a good solvent for the colloid can affect the morphological characteristics of the colloid in the pattern, and the formation of the pattern can be precisely controlled.

Example 4

According to Example 1, a flat silicon wafer substrate having a dense colloidal crystalline monolayer was prepared, dipped in 5 mL methanol at 25° C. for 10 minutes, and then 4.8 mL of methanol was removed. Then, 10 mL of DEE was added to the mixed solution having a volume fraction of methanol (φ _MeOH ) of 0.02 and maintained for 10 minutes. The sample was taken out and dried at 60°C. The results of SEM analysis of the non-dense colloidal crystal pattern formed using the methanol-DEE pair are shown in FIG. 6 .

The χ _α value of methanol was 0.38, which was similar to THF (χ _α = 0.32). Referring to Figure 6, the colloidal shape was similar to the shape obtained when using a THF-DEE pair.

Example 5

Preparation of non-dense crystal patterns using methanol-water co-insolubility

According to Example 1, a flat silicon wafer substrate on which a dense colloidal crystalline monolayer was formed was prepared, and mixed solvents were prepared while changing the mole fraction of the methanol-water mixed solvent at 25 ° C. The substrate was immersed in each of these solutions. A pattern was made. Then, the sample was dried at 150° C. to obtain a pattern. At this time, the mole fraction (x _M ) of methanol in the mixed solvent was changed from 0.05 to 0.55.

Optical images (a) and SEM images (b, c) of the colloidal crystal pattern formed after depositing the monolayer in a methanol-water solution (x _M = 0.4) are shown in FIG. 7 .

As shown in Fig. 7(a), the color of the substrate did not change at x _M values of 0.05 and 0.1. However, the x _M value started to change to blue from 0.15. The color is maintained until the x _M value is 0.5, and disappears at x _M value of 0.55. In this regard, the change in color of the substrate means that a structure different from that of the monolayer film is formed.

According to Figs. 7B and 7C, the pattern had a disk-like shape, and its diameter was 294 ± 12 nm. These results support that non-dense colloidal crystal patterns can be formed by introducing co-insolubles that can induce volume transitions of colloids. That is, within a certain methanol-molar composition, the mixed solution can contract the colloid, thereby forming a pattern.

Example 6

- Fabrication of non-dense colloidal crystal patterns on concave surface substrates

In order to form a dense pattern monolayer on the concave surface structure, a colloidal monolayer with a dense pattern was first prepared on a slide glass using polystyrene (PS) microspheres as a building block. PS microspheres with a diameter of about 6 μm were synthesized by modifying the method described in the literature (Can. J. Chem. 1985, 63, 209). The PS microspheres thus prepared were centrifuged and redispersed using ethanol to purify. The purification process was repeated more than twice, and the purified microspheres were finally redispersed in 1-butanol.

A certain amount of the dispersion in which PS was dispersed in a butanol medium was dropped on the surface of deionized water to form a colloidal crystal monolayer. Then, the colloidal crystal monolayer was transferred to slide glass. In order to periodically form a concave structure, Sylgard 184 precursor (a mixture in which a siloxane oligomer and a crosslinking agent are combined in a weight ratio of 10:1) was added onto the PS-based colloidal crystal monolayer. After curing the mixture at 60° C. for 6 hours, the PDMS film was separated from the substrate and further cleaned by immersion in pure acetone at 55° C. for 2 hours (hemispheric diameter of concave structure surface: about 4.5 μm). Finally, a monolayer film of a dense pattern was transferred onto the surface of the concave structure.

A non-dense colloidal crystal monolayer was produced on the concave surface structure using a THF-DEE solvent pair according to the same procedure as in Example 1 (the deposition time of the substrate was set to 10 minutes). Then, the sample was dried at 60° C. to obtain a pattern. An analysis was performed on the obtained pattern, and the results are shown in FIG. 8 .

8A to 8A are SEM images showing colloidal patterns formed on the concave PDMS surface, respectively.

As shown in FIGS. 8A and 8B, the colloidal pattern is structured in the pores of the substrate, but as shown in FIG. 8C, some portions where the pattern is not formed are also found. However, overall, it can be said that the substrate is well structured within the pores, and the above results are sufficient to suggest the possibility of forming a colloidal pattern on the micro-level structured surface without damaging the structure through the method according to the embodiment. It is judged to be

- Fabrication of a non-dense colloidal crystal pattern on a substrate made of PET film

A monolayer film of a non-dense colloidal crystal pattern was formed according to the same procedure as in Example 1 except for using a PET film (1.5 × 1.5 cm 2 ) substrate (immersed in a THF-DEE mixed solvent for 10 minutes). , analyzed using SEM. The results are shown in FIGS. 9A and 9B.

The film obtained in the figure showed an iridescent green color depending on the viewing angle (Fig. 9A inset). According to FIG. 9B, the colloidal crystal pattern was a spherical colloid, and its diameter was 208±10 nm. The lateral SEM image (FIG. 8D) shows that an aligned dome-shaped polymer pattern with a height of about 120 nm was formed.

- The non-dense colloidal pattern not only exhibits a color that changes color depending on the viewing angle due to its photonic crystal properties, but also retains anti-glare properties at visible light frequencies. FIG. 10 shows the transmittance of a pure slide glass without a pattern (hereinafter referred to as bare glass) and a slide glass coated with a dense colloidal crystal pattern and a non-dense colloidal crystal pattern. According to the figure, the transmittance of the bare glass was about 90%, and the glass coated with the dense crystal pattern showed a transmittance of 90-91% at 400 nm or more. On the other hand, the glass coated with the non-dense crystal pattern exhibited a higher transmittance than the bare glass at 455 nm or more, and a maximum transmittance of 94.6% at 519 nm. In addition, the transmittance at 800 nm was 92.7%.

10I shows transmittance of a PET film and a PET film coated with a dense colloidal crystal pattern and a non-dense colloidal crystal pattern. The transmittance of the PET film in the range of 400-800 nm ranged from 85.4 to 88%. When coated with a dense crystal pattern, the transmittance increased to 87.6-89%. The PET film coated with the non-dense crystal pattern exhibited higher transmittance than the bare PET film in the band of 435 nm or more, and the transmittance in the band of 489 nm or more was 90% or more. In addition, it exhibited a maximum transmittance of 93.1 at 633 nm. In addition, transmittance exceeding 92% was maintained until 800 nm (92.4% at 800 nm).

When the dense colloidal crystal monolayer is converted to a non-dense colloidal crystal pattern, the light reflectance from the interface between the medium and the substrate is the Fresnel equation at normal incidence of light, that is, [( n _o - n _s )/( n _o + n _s )] ² can be measured from the refractive indices of the medium (n ₀ ) and the substrate (n _s ). Therefore, the reflectance of the substrate can be reduced by introducing a colloidal pattern having an intermediate refractive index between air and the transparent substrate (refractive index (n) of glass: 1.5, refractive index (n) of PET film: 1.575).

Also, the patterns mostly have geometrical properties similar to domes. In this case, a gradual change in refractive index is expected from the non-dense crystal pattern, which means that an anti-glare function can be imparted to the substrate.

Example 7

Dense crystal patterns were coated on each of the glass substrate and the PET film according to the same procedure as in Example 6. After each substrate was immersed in a 5 mL THF solution, 4.8 mL of THF was removed, and then 10 mL of DEE containing 0.1% by weight of the photocurable polymer precursor was added to form a pattern for 24 hours, and at the same time, the photocurable polymer The precursor (NOA 68) was sufficiently adsorbed on the patterned surface. After the substrate was taken out of the solution and dried, the substrate was cured for 3 minutes using a UV lamp.

11(a) and 11(b) show SEM images of the non-dense crystal pattern immobilized with the photocurable polymer on the slide glass and the PET film, respectively. According to the figure, the non-dense pattern was well maintained even when patterning and immobilization were performed simultaneously.

According to this embodiment, a non-dense crystal pattern was fixed using a light-curable polymer, and such a light-curable polymer is known to maintain light transparency in the visible light band. After performing the immobilization process, even when the water droplet contacts the patterned substrate, the color that changes depending on the viewing angle is preserved. At this time, the water contact angle on the pattern when the pattern was not fixed was 86 ° (glass substrate) and 81 ° (PET film). On the other hand, the water contact angles after immobilization were 103° (glass substrate) and 118° (PET film).

According to FIG. 11C, the transmittance of the glass having a fixed pattern decreased by about 1.5-2.5% in the visible light frequency compared to the non-fixed case, but was still higher than that of the bare glass at 473 nm or more (1.5-2% more). height).

According to FIG. 11D, the transmittance of the PET substrate with the fixed non-dense pattern decreased by 0.5-1% compared to the non-fixed case, but the substrate with the fixed pattern still had transmittance higher than that of the bare PET film by 2% or more. showed

On the other hand, the non-dense colloidal pattern is altered or damaged when exposed to a good solvent (eg, water) regardless of its preparation method, while exhibiting stability against non-solvents such as DEE. For example, the structure of the non-dense crystalline pattern changes when exposed to water. Therefore, it is necessary to fix these patterns. To this end, a non-dense crystal pattern fixed by depositing a dense crystal pattern coated on a silicon wafer substrate for 6 hours using a methanol-water mixed solvent (x _M : 0.15) containing 7.8% by weight of glutaraldehyde. was manufactured. The results are shown in FIGS. 12A and 12B.

According to Fig. 12A, the colloidal diameter was 275 ± 18 nm. Also, referring to FIG. 12B, an ordered array of colloids was maintained.

As described above, colloidal crystal patterns can be formed simply and with high reproducibility through proper combination of a good solvent and non-solvent pair, control of the mole fraction in a mixed solvent of water and co-solvent, etc. without special equipment or strict condition restrictions. . In addition, the shape of the colloid can be adjusted according to the solvent pair introduced for patterning. In particular, when the solution lithography method according to the embodiment is applied, an advantage of simultaneously performing patterning and immobilization on a substrate is provided.

All simple modifications or changes of the present invention belong to the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims.

Claims (20)

a) forming a monolayer film having a dense crystal pattern of a hydrogel polymer colloid on a surface of a substrate; and
b) (i) contact the monolayer film having the dense crystal pattern with a first organic solvent, which is a good solvent capable of inducing swelling of the hydrogel polymer colloid, to swell the colloid in the monolayer film, and mix with the hydrogel polymer colloid The hydrogel polymer colloid in a monolayer film having a dense crystal pattern formed in step a) in a mixed solvent containing the first organic solvent and the second organic solvent by adding a second organic solvent, which is a non-chemical non-solvent, Forming a monolayer film having a non-dense crystal pattern of the hydrogel polymer colloid by inducing shrinkage to be smaller than the diameter of the colloid, or (ii) having the dense crystal pattern in a mixed solvent containing water and a co-solvent, both of which are good solvents. converting the hydrogel polymer colloid into a monolayer film having a non-dense crystal pattern by contacting the monolayer film to induce contraction of the hydrogel polymer colloid by co-non-dissolution;
Including,
Here, when the colloid is swollen by contact with the first organic solvent in (i) of step b), the corrected Flory-Huggins interaction parameter (χ _α ) value of the colloid and the solvent system is less than 0.5, In addition, when the colloid is contracted by the addition of the second organic solvent in (i) of step b), the corrected Flory-Huggins interaction parameter value (χ _α ) of the colloid and the solvent system is adjusted to exceed 0.5. A method for producing non-dense colloidal crystal patterns. delete The method according to claim 1, wherein the lattice constant of each of the monolayer film having a colloidal dense colloidal crystal pattern formed in step a) and the monolayer film having a non-dense colloidal crystal pattern of colloid formed in step b) is 100 nm at 100 nm. A method for producing a non-dense colloidal crystal pattern, characterized in that the range is up to μm. The method according to claim 1, wherein the distance between colloidal particles in the monolayer film having the dense colloidal crystal pattern is less than 1 nm, and the distance between colloidal particles in the monolayer film having the non-dense colloidal crystal pattern is at least 1 nm. A method for producing a non-dense colloidal crystal pattern. The method of claim 1, wherein the substrate is an inorganic substrate or an organic substrate and has a flat or curved surface. The non-dense colloidal crystal according to claim 1, wherein the volume fraction of the first organic solvent in the mixed solvent in (i) of step b) is adjusted to induce co-insolubility in the range of 0.001 to 0.4. How to make a pattern. 7. The method of claim 6, wherein a step of partially removing the first organic solvent is performed prior to the addition of the second organic solvent in (i) of step b). The method according to claim 1, wherein the particle diameter and thickness of the colloid in the monolayer film having the dense colloidal crystal pattern formed in step a) range from 100 nm to 100 μm and from 10 nm to 50 μm, respectively, and
wherein the particle diameter and thickness of the colloid in the monolayer film having the non-dense colloidal crystal pattern formed in step b) range from 50 nm to 50 μm and from 20 nm to 30 μm, respectively. A method for producing a colloidal crystal pattern. The method of claim 1, wherein the molar fraction of the co-solvent in the mixed solvent in step b) (ii) is controlled within a range of 0.15 to 0.5. The method of claim 1, wherein the co-solvent in step b) (ii) is at least one selected from the group consisting of alcohol having 3 or less carbon atoms, DMSO, THF, 1,4-dioxane and acetone. A method for producing dense colloidal crystal patterns. 11. The method of claim 10, wherein the alcohol is methanol. The method of claim 1, wherein the material of the hydrogel polymer colloid is poly (N-isopropyl acrylamide) [poly (N-isopropylacrylamide), pNIPAM], poly (N-isopropyl acrylamide-co-allylamine) [poly (N-isopropyl acrylamide-co-allylamine), poly(NIPAM-co-AA)], poly(N-isopropyl acrylamide-co-2-(dimethylamino)ethyl methacrylate)[poly(Nisopropylacrylamide-co- 2-(dimethylamino)ethyl methacrylate), poly(NIPAM-co-DMAEMA)], poly(N-isopropyl acrylamide-co-2-(dimethylamino)ethyl acrylate)[poly(N-isopropyl acrylamide-co- 2-(dimethylamino)ethyl acrylate), poly(NIPAM-co-DMAEA)], poly(N-isopropyl acrylamide-co-acrylic acid), poly(NIPAM- co-AAc)], poly(N-isopropyl acrylamide-co-methacrylic acid), poly(NIPAM-co-MAAc)], poly(N,N- Diethylacrylamide)[poly(N,N-diethylacrylamide)], poly(N-vinylcaprolactam)[poly(N-vinlycaprolactam)], poly(ethylene glycol)[poly(ethylene glycol)], poly(ethylene Preparation of a non-dense colloidal crystal pattern, characterized in that it is at least one selected from the group consisting of glycol-b-propylene glycol-b-ethylene glycol) [poly(ethylene glycol-b-propylene glycol-b-ethylene glycol)] method. The method of claim 1, wherein the first organic solvent is at least one selected from the group consisting of tetrahydrofuran (THF), methanol, ethanol, acetone, dichloromethane, and chloroform, and
Wherein the second organic solvent is at least one selected from the group consisting of diethyl ether (DEE), hexane (n-hexane), cyclohexane, benzene and toluene (non- A method for producing dense colloidal crystal patterns. The non-dense crystal pattern of claim 1, further comprising fixing the non-dense crystal pattern of the colloidal polymer using a fixing component during or after step b) is performed. A method for producing a colloidal crystal pattern. 15. The non-dense colloidal crystal pattern of claim 14, wherein the fixing component is a photocurable polymer and is at least one selected from the group consisting of polyurethane, polydimethylsiloxane, NOA, epoxy, and acrylic. Manufacturing method of. 16. The method of claim 15, wherein step b) is carried out in a state in which a precursor of a photocurable polymer as a fixing component is contained in the mixed solvent of (i) or the mixed solvent of (ii), and a non-dense colloidal crystal pattern is formed. A method for producing a non-dense colloidal crystal pattern, characterized in that it is formed and then immobilized by light irradiation. 15. The method of claim 14, wherein the fixing component is at least one selected from the group consisting of glutaraldehyde and glycerol diglycidyl ether. 18. The method for producing a non-dense colloidal crystal pattern according to claim 17, wherein step b) is carried out in a state in which the fixing component is contained in the mixed solvent of (i) or the mixed solvent of (ii). An optical material having a monolayer film having a non-dense colloidal crystal pattern prepared according to any one of claims 1 and 3 to 18. An optical material having a monolayer film having a non-dense colloidal crystal pattern prepared according to any one of claims 1 and 3 to 18.

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