WO2023113508A1 - Structures for physical unclonable function using spontaneous chiral symmetry breaking and method of preparing same - Google Patents

Abstract

The present invention relates to structures for a physical unclonable function using spontaneous chiral symmetry breaking and a method of preparing same. More specifically, by using a chiral photonic crystal, in which chiral symmetry breaking occurs, to form an unclonable chiral random pattern that can be observed with an optical microscope and a mobile phone camera, and using the chiral random pattern in a physical unclonable function (PUF), it is possible to produce, through existing photo-lithography methods, a desired pattern that is highly secure, has high information density, and exhibits high performance in properties such as reproducibility, uniqueness, high information density, high recognition ratio, unpredictability, or reconfigurability.

Description

Structure for preventing physical replication using spontaneous chiral symmetry breaking and manufacturing method thereof

The present invention relates to a structure for preventing physical replication using spontaneous chiral symmetry breaking and a method for manufacturing the same, and more particularly, by using a chiral photonic crystal in which chiral symmetry breaking occurs, it is non-replicable and can be observed with an optical microscope and a mobile phone camera. A physical unclonable structure using spontaneous chiral symmetry breaking, which forms a chiral random pattern and uses it for a physical unclonable function (PUF), and a manufacturing method thereof.

A chiral material has an optical activity, and an optical rotation phenomenon in which a polarization axis of linearly polarized light passing through a chiral medium rotates clockwise or counterclockwise occurs. The degree and direction of rotation is due to the intrinsic properties and chirality of the material. In general, chiral organic materials contain a chiral center in their molecular structure. However, there are cases in which achiral molecules form chiral structures through self-assembly. In this case, there is no preference for right- or left-handed chiral structures, so the two structures are randomly formed. This is called ‘spontaneous chiral symmetry breaking’ and it is known that the probability of formation of structures with different chirality is 50%.

An authentication system based on a physical unclonable function (PUF) has recently been developed for unforgeable anti-counterfeiting. PUF, also known as physical one-way function, is a technology that creates a security key that prevents physical copying by making subtle changes to the structure of semiconductors developed in the same process. Represents a physical entity with a function. PUFs are fabricated using the inherent randomness of the physical microstructure of hardware in most integrated circuits (ICs). Since the chip fabrication process involves many complex lithography steps to integrate billions of devices, differences in the physical microstructure between chips are unavoidable and unpredictable, making it impossible for hackers to create clones of chips within a finite timeframe. In addition, conventional IC-based PUFs have been a strong security method so far because nondeterministic exponential time is required for data decryption using brute force trials by hackers. However, as quantum computers are developed, existing IC-based PUFs will be easily exposed to risks, so a new type of PUF that can store higher entropy information and is impossible to duplicate is needed.

In Non-Patent Documents 2 to 20, when the security code is leaked to the outside, there is a problem that it becomes vulnerable to hacking and requires a new device for new security. Moreover, it has a disadvantage that it can be easily detected by a general method ( Non-Patent Documents 3, 5, 7, 8, 10, 12, 17, 19 and 22).

Therefore, as a result of diligent efforts to solve the above problems, the inventors of the present invention formed a non-replicable chiral random pattern using a chiral photonic crystal in which chiral symmetry breaking occurs, and made it a physically unclonable function (PUF). By using it, it is possible to have high information density and security while showing high performance in characteristics such as reproducibility, uniqueness, unpredictability, and reconfigurability. It was confirmed that the desired patterning can be produced through the photo-lithography method, and the present invention was completed.

[Prior art literature]

[Patent Literature]

Republic of Korea Patent No. 10-2249409

Republic of Korea Patent No. 10-2195795

Republic of Korea Patent No. 10-1328975

[Non-Patent Literature]

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3. Lin, Y. et al. Unclonable Micro-Texture with Clonable Micro-Shape towards Rapid, Convenient, and Low-Cost Fluorescent Anti-Counterfeiting Labels. Small 17, 2100244 (2021).

4. Zhang, T. et al. Random Nanofracture-Enabled Physical Unclonable Function. Adv. Mater. Technol. 6, 2001073 (2021).

5. Hu, Y. et al. Flexible and Biocompatible Physical Unclonable Function Anti-Counterfeiting Label. Adv. Funct. Mater. 31, 2102108 (2021).

6. Jing, L. et al. Multigenerational Crumpling of 2D Materials for Anticounterfeiting Patterns with Deep Learning Authentication. Matter 3, 2160-2180 (2020).

7. Martinez, P. et al. Laser Generation of Sub-Micrometer Wrinkles in a Chalcogenide Glass Film as Physical Unclonable Functions. Adv. Mater. 32, 2003032 (2020).

8. Liu, Y. et al. Unclonable Perovskite Fluorescent Dots with Fingerprint Pattern for Multilevel Anticounterfeiting. ACS Appl. Mater. Interfaces 12, 39649-39656 (2020).

9. Hu, Z. et al. Physically unclonable cryptographic primitives using self-assembled carbon nanotubes. Nature Nanotech 11, 559-565 (2016).

10. Liu, Y. et al. Inkjet-printed unclonable quantum dot fluorescent anti-counterfeiting labels with artificial intelligence authentication. Nat. Commun. 10, 2409 (2019).

11. Arppe-Tabbara, R., Tabbara, M. & Sørensen, T. J. Versatile and Validated Optical Authentication System Based on Physical Unclonable Functions. ACS Appl. Mater. Interfaces 11, 6475-6482 (2019).

12. Carro-Temboury, M. R., Arppe, R., Vosch, T. & Sørensen, T. J. An optical authentication system based on imaging of excitation-selected lanthanide luminescence. Sci. Adv. 4, e1701384 (2018).

13. Zhang, R. et al. Nanoscale diffusive memristor crossbars as physical unclonable functions. Nanoscale 10, 2721-2726 (2018).

14. Hwang, K.-M. et al. Nano-electromechanical Switch Based on a Physical Unclonable Function for Highly Robust and Stable Performance in Harsh Environments. ACS Nano 11, 12547-12552 (2017).

15. Geng, Y. et al. High-fidelity spherical cholesteric liquid crystal Bragg reflectors generating unclonable patterns for secure authentication. Sci. Rep. 6, 26840 (2016).

16. Demirok, U. K., Burdick, J. & Wang, J. Orthogonal Multi-Readout Identification of Alloy Nanowire Barcodes. J. Am. Chem. Soc. 131, 22-23 (2009).

17. Tian, L. et al. Plasmonic Nanogels for Unclonable Optical Tagging. ACS Appl. Mater. Interfaces 11 (2016).

18. Bae, H. J. et al. Self-organization of maze-like structures via guided wrinkling. Sci. Adv. 3, e1700071 (2017).

19. Gu, Y. et al. Gap-enhanced Raman tags for physically unclonable anticounterfeiting labels. Nat. Commun. 11, 516 (2020).

20. Nakayama, K. Optical security device providing fingerprint and designed pattern indicator using fingerprint texture in liquid crystal. Opt. Eng. 51, 040506 (2012).

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Summary of Invention

An object of the present invention is to provide a chiral structure for PUF having excellent reproducibility, originality, unpredictability, reconfigurability, high information density and security, and a manufacturing method thereof.

In order to achieve the above object, the present invention provides an HNF photonic crystal structure obtained by randomly patterning helical nanofilaments (HNF) in which bent liquid crystal molecules are grown in a twisted layered structure by self-assembly.

The present invention also includes (a) irradiating ultraviolet rays to helical nanofilament (HNF) to align the axis of the liquid crystal contained in the HNF perpendicular to the direction of irradiation of the ultraviolet rays; and (b) forming an HNF photonic crystal by cooling the vertically aligned HNF to a B4 phase temperature of the liquid crystal to reorient an axis of the liquid crystal parallel to an ultraviolet irradiation direction to obtain an HNF photonic crystal structure. A method for manufacturing an HNF photonic crystal structure is provided.

1 shows (a) a helical nanofilament (HNF) formed through self-assembly from azobenzene-dimer molecules; (b) a schematic diagram of a method for fabricating an HNF photonic crystal; (c) A polarized light microscope image of a photopatterned HNF photonic crystal and a hidden chiral random pattern.

Figure 2 is (a) a method of binarization using Θ = 80 ° experimental image of the HNF photonic crystal film; (b) six morphological features of each chiral domain; (c) Encoding capacity for one unit cell. The black triangles represent the information density calculated from the ranks for area, roundness, aspect ratio, and orientation. Red triangles are information densities computed from ranks for locations; (d) information density according to the number of unit cells; (e) Misrecognition rates calculated from the ranks for each morphological feature. The yellow, purple, green, blue, and cyan lines are for direction, roundness, aspect ratio, area, and position, respectively.

3 shows experimental images of (a) Θ=90° and (c) Θ=80° of a photonic crystal having 64 unit cells; (b) a binarized image obtained by segmenting the patterned photonic crystal region in (a) image; (d) an image obtained by multiplying (b) and (c) images; (e) setting the boundary of the patterned photonic crystal region; (f) centering of each unit cell; (g) dividing the processed image into unit cell images having a specific size; (h) image black and white processing; (i) image binarization according to the chirality of the domain; (j) separation of each domain according to chirality; (k) It is a diagram showing morphological feature extraction of each domain.

4 is (a) a polarized light microscope image of a patterned HNF photonic crystal; (b) A schematic diagram of the linear polarization rotation phenomenon occurring in an area not irradiated with UV light (left) and an area irradiated with UV light (right); (c) a graph of optical rotation (α) according to wavelength in an area not irradiated with ultraviolet light; (d) a graph of optical rotation according to wavelength in an area irradiated with ultraviolet light; (e) It is the color coordinate system of each chiral domain according to the angle of the polarizer.

5 is a similarity index (Sf) obtained through pairwise comparison with matrices obtained from experimental images. (a) two 6 x 6 x 128 matrix data obtained by scanning the sample twice; (b) It is a diagram for an example of a method for calculating a similarity index by comparing 128 two-dimensional matrices.

6 is (a) a schematic diagram of a process of registering a matrix obtained from the morphological features of a patterned photonic crystal in a database and a process of authenticating a matrix obtained from the morphological features of a newly fabricated photonic crystal through an existing database; (b) Reliability evaluation of the proposed authentication method according to the number of unit cells. Red, light blue, and blue bars denote true-negative rate (TNR), false-negative rate (FNR), and true-positive rate (TPR), respectively; (c) Robustness test against noise. Green, purple, and orange lines mean when the number of unit cells is 64, 128, and 256, respectively; (d) It is a drawing of the reproducibility test using different microscopes according to the number of unit cells.

7 is a distribution diagram of the time required for (a) true authentication and (b) false authentication through hierarchical authentication methods; (c) It is a diagram of the amount of database that decreases step by step according to the number of unit cells.

8 is an image used for a robustness test against noise.

9 is images used in reproducibility tests using different microscopes. (a) Images obtained with an upright microscope; (b) These are images obtained with an inverted microscope

10 shows (a) different patterns can be obtained by reconstructing the same sample as a polarizing microscope image when Θ = 80 °, 90 °, and 100 ° for a reconfigurability test, and different chiral random structure is obtained. (b) Thermal stability test and (c) solvent stability test of the fabricated chiral photonic crystal. (d) It is a view of observing a chiral random pattern using a smart phone.

DETAILED DESCRIPTION OF THE INVENTION AND SPECIFIC EMBODIMENTS

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

In the present invention, an organic molecular structure in which spontaneous chiral symmetry breaking occurs is made of a photonic crystal, and the randomness generated during spontaneous chiral symmetry breaking is recorded in a film form. The film produced is a single film with high information density. It was confirmed that it can be used as a PUF and shows high performance in reproducibility, uniqueness, unpredictability, and reconfigurability.

Accordingly, in one aspect, the present invention relates to an HNF photonic crystal structure obtained by randomly patterning helical nanofilaments (HNF) in which bent liquid crystal molecules are grown in a twisted layered structure by self-assembly.

Hereinafter, the present invention will be described in detail.

The term 'helical nanofilament (HNF)' used in the present invention refers to a structure in which liquid crystal molecules having a curved shape are twisted with a lattice period of about 200 to 300 nm to form a layered structure.

The term 'photonic crystal' used in the present invention refers to a structure having a lattice period of a length similar to the wavelength of light (several hundred nm). Interference occurs, and light at a wavelength that causes constructive interference is reflected. Even in the case of HNF, it has a grating period of several hundred nm, and when they are arranged, a photonic crystal reflecting light of a specific wavelength can be formed (HNF photonic crystal).

The term 'B4 phase temperature of liquid crystal' used in the present invention varies depending on the molecular structure, but most of the molecules used in the present invention are known to have a B4 phase at a temperature of 140 ° C or lower.

As used herein, the term 'random pattern' refers to a pattern in which HNF photonic crystals twisted in different directions are randomly formed at a level of several microns.

The term 'random patternization' used in the present invention can be interpreted as a concept of two-dimensional random arrangement of random patterns. To put it simply, it can be seen as randomly scattering black and white random shapes on a two-dimensional plane. That is, it can be referred to as two-dimensional random pattern production.

The present invention uses spontaneous chiral symmetry breaking, one of the characteristics of randomness in nature, to record randomness on an optically observable film and apply it as a physical unclonable function (PUF). will be.

Existing registered patents focus on the formation and color modulation technology of chiral photonic crystals. In the present invention, not only the optical activity of chiral photonic crystals is used, but also the possibility of application to PUFs can be suggested by using spontaneously generated chiral structures in different directions. An organic molecular structure in which spontaneous chiral symmetry breaking occurs is made of a photonic crystal, and the randomness of the natural world that occurs when spontaneous chiral symmetry breaking occurs is recorded in the form of a film. Recorded randomness can be converted into a digital code through an image processing process. Also, through a statistical approach, it was proved that the recorded randomness is close to the ideal randomness. The film produced through this suggests that it can be used as a PUF with high information density as a single film, and the produced PUF film can be used in terms of reproducibility, uniqueness, unpredictability, and reconfigurability. It was confirmed that high performance was exhibited.

In the present invention, spontaneous chiral symmetry breaking was used to fabricate a new PUF. Spontaneous chiral symmetry breaking occurs when a material has a chiral structure and there is no preference for one chiral property. It is known from many studies that the probability of having different chirality in a material is 50% when this symmetry breaking occurs. Chiral symmetry breaking occurs in various organic molecules or supramolecules, but in a situation where substances having different chirality are mixed, detecting their chirality is not easily detected by conventional methods, so it is difficult to detect it as PUF. application was not possible. In order to solve this problem, the present invention solves the above problems by using a material having a helical nano filament (HNF) structure and suggests that it can be applied to PUF.

In the present invention, the bent liquid crystal molecule may be at least one selected from the group consisting of azobenzene-dimer, MHOBOW of Formula 1 and NOBOW of Formula 2:

[Formula 1]

[Formula 2]

In the present invention, the azobenzene-dimer may be represented by Formula 3:

[Formula 3]

In Formula 3, L is a straight-chain or branched-chain alkylene group, a cycloalkylene group, a haloalkylene group, an arylene group, a heteroarylene group, an arylenealkylene group, an alkylenearylene group, an alkyleneheteroarylene group, a heteroarylenealkylene group, An alkylene ester group or an alkylene amide group, and the heteroarylene group is a divalent radical containing a heteroatom selected from fluorine, oxygen, sulfur and nitrogen,

R ₁ and R ₂ are each independently selected from a straight-chain or branched-chain alkyl group, a cycloalkyl group, a haloalkyl group, an alkoxy group, a cycloalkoxy group, an aryl group, a heteroaryl group, an aryloxy group, an alkoxyheteroaryl group, a heteroaryloxyalkyl group, An alkylheteroaryl group, an alkylaryl group, an arylalkyl group, an alkylheteroaryl group, an alkylester group, an alkylamide group, or an acryl group, and the heteroaryl group is a monovalent radical containing a heteroatom selected from fluorine, oxygen, sulfur, and nitrogen. .

In L of Formula 3, preferably, the straight-chain alkylene group is a C1-C12 straight-chain alkylene group, the branched-chain alkylene group is a C1-C12 branched-chain alkylene group, and the cycloalkylene group is a C3-C13 cycloalkylene group. , The haloalkylene group is a C1-C12 alkylene group substituted with fluorine, chlorine or iodine, the arylene group is a C6-C13 arylene group, the heteroarylene group is a C5-C13 heteroarylene group, the arylene alkylene group is a C7 -C13 arylene alkylene group, alkylene arylene group C7-C13 alkylene arylene group, alkylene heteroarylene group C6-C13 alkylene heteroarylene group, heteroarylene alkylene group C6-C13 heteroaryl group It may be a lenalkylene group.

As used herein, the term "substituted" refers to a case in which any one or a plurality of hydrogen atoms of a designated atom are substituted by a substituent of a designated group, and the condition is that the designated atom must not exceed the normal valence, and as a result, stable after substitution. It is necessary to create a compound.

In R1 and R2 of Formula 1, preferably, the straight-chain alkyl group is a C1-C12 straight-chain alkyl group, the branched-chain alkyl group is a C1-C12 branched-chain alkyl group, the cycloalkyl group is a C3-C13 cycloalkyl group, and the haloalkyl group is A C1-C12 alkyl group substituted with fluorine, chlorine or iodine, an alkoxy group is a C1-C12 alkoxy group, a cycloalkoxy group is a C3-C13 cycloalkoxy group, an aryl group is a C6-C13 aryl group, a heteroaryl group is a C5- C13 heteroaryl group, aryloxy group is C7-C12 aryloxy group, alkoxyheteroaryl group is C7-C13 alkoxyheteroaryl group, heteroaryloxyalkyl group is C7-C13 heteroaryloxyalkyl group, alkylheteroaryl group is C7-C13 C13 alkylheteroaryl group, alkylaryl group is C7-C13 alkylaryl group, arylalkyl group is C7-C13 arylalkyl group, alkylheteroaryl group is C6-C13 alkylheteroaryl group, alkyl ester group is C2-C13 alkyl ester The group, the alkylamide group may be a C1-C12 alkylamide group.

In another aspect, the present invention provides: (a) irradiating ultraviolet rays to helical nanofilament (HNF) to align the axis of the liquid crystal contained in the HNF perpendicular to the direction of irradiation of the ultraviolet rays; and (b) forming an HNF photonic crystal by cooling the vertically aligned HNF to a B4 phase temperature of the liquid crystal to reorient an axis of the liquid crystal parallel to an ultraviolet irradiation direction to obtain an HNF photonic crystal structure. It relates to a method for manufacturing an HNF photonic crystal structure.

In one embodiment of the present invention, a helical nanofilament structure using curved liquid crystal molecules can be expressed by introducing an azo group into a dimer molecule in which two rod-shaped liquid crystal molecules are bound by a flexible alkyl group. When the liquid crystal molecules including the azo group are irradiated with ultraviolet light, they have a property of being aligned perpendicular to the direction of ultraviolet light irradiation. Using this, unpolarized ultraviolet rays are irradiated from the high-temperature nematic/smectic phase to align the liquid crystals, and the supramolecular helical nanofilament structure that develops as the temperature decreases can be controlled.

In the present invention, preferably, the azobenzene-dimer may be represented by Formula 4:

[Formula 4]

In Formula 4, R ₁ and R ₂ are each independently a straight-chain or branched-chain alkyl group, a cycloalkyl group, a haloalkyl group, an alkoxy group, a cycloalkoxy group, an aryl group, a heteroaryl group, an aryloxy group, an alkoxyheteroaryl group, and a heteroaryl group. An oxyalkyl group, an alkylheteroaryl group, an alkylaryl group, an arylalkyl group, an alkylheteroaryl group, an alkylester group, an alkylamide group, or an acryl group, and a heteroaryl group containing a heteroatom selected from fluorine, oxygen, sulfur, and nitrogen. is a radical

As a more specific embodiment of the present invention, the azobenzene dimer may be one or more selected from the group consisting of Chemical Formula 4-1, Chemical Formula 4-2, Chemical Formula 4-3 and Chemical Formula 4-4.

[Formula 4-1]

[Formula 4-2]

[Formula 4-3]

[Formula 4-4]

In the present invention, the structure can be used for a physical unclonable function (PUF).

In the present invention, the structure may be in the form of a film or flake.

In the production method of the present invention, the bent liquid crystal molecules, in particular, the azobenzene-dimer, are as described above.

In one embodiment of the present invention, a photoreactive molecule may be used to control a supramolecular structure formed by liquid crystal molecules, thereby forming a photonic crystal. A sandwich cell composed of a black substrate and a transparent substrate is fabricated, liquid crystal is injected into the cell in the isotropic phase, and after the injection is completed, a photomask is placed on the cell and cooling is performed while irradiating ultraviolet light thereon. The supramolecular structure of the portion irradiated with ultraviolet rays is regularly controlled, and a photonic crystal pattern in the visible light region is formed. The formed photonic crystal can be reversibly reused by raising and lowering the temperature. This is a groundbreaking technology for the commercialization of photonic crystals, such as simplification of the existing photonic crystal manufacturing process, reduction of material cost, and reusable patterning.

In the present invention, the non-photonic crystallized HNF film was not manufactured with a security code, but only the HNF photonic crystal film was manufactured with a security code, and then statistical analysis was performed. The HNF photonic crystal film can be easily manufactured in the desired shape and size in the photolithography step of the manufacturing process, and the chiral random pattern is clearly distinguished by the optical rotation phenomenon occurring in the chiral photonic crystal (FIG. 1). When this chiral photonic crystal is formed, since there is no preference for the chiral direction, both the right twisted structure and the left twisted structure are formed with equal probability. Through image processing and statistical approaches, it can be confirmed that the probability of being twisted in different directions and their arrangement have a random pattern with a randomness similar to the level of randomness in nature (Fig. 1). The random pattern film produced in this way can guarantee uniqueness, high information density, and high recognition rate among the characteristics of PUF (FIGS. 4 and 5), and has excellent characteristics in unpredictability and reconfigurability. show However, it has low reproducibility due to the pixel-based image processing method. In order to solve this problem, additional patterning such as alignment marks through metal deposition can be used, but the material used in the present invention has a liquid crystal phase. As a result, high randomness may be lost or structure formation may be hindered.

When ultraviolet rays are irradiated on azobenzene-dimer molecules containing an azo moiety, they have the property of being oriented perpendicular to the direction of ultraviolet irradiation. Using this, ultraviolet rays are irradiated from the high-temperature nematic/smectic phase to align liquid crystals, and HNF structures that are expressed as their temperature goes down are controlled. The axis of the controlled helical HNF is reorientated parallel to the direction of ultraviolet irradiation to form a chiral photonic crystal in which the helical pitch of the helical structure is formed in the visible light region. In the case of a photonic crystal having chirality, an optical rotation phenomenon in which incident linearly polarized light rotates due to optical activity exists. Optical rotation is amplified in the driving wavelength region (photonic band gap), and the degree and direction of optical rotation are different for each wavelength. This degree of rotation can be detected by rotating one polarizer in a polarizing microscope. A photomask was introduced to produce a patterned chiral photonic crystal to serve as an alignment mark, and a film capable of distinguishing chirality by color was produced using the tendency of optical rotation that occurs (FIG. 4). Since the spontaneous chiral symmetry breaking and photonic crystal formation occur as independent events, it was confirmed that the randomness confirmed in FIG. 2 is maintained even after the photonic crystallization process, even after patterning. Through image processing, these random patterns could be produced as digitized codes (FIG. 5). When several patterns manufactured through different microscopes are analyzed, it can be confirmed that the same pattern and different patterns can be distinguished with a low false acceptance rate (FAR) and false rejection rate (FRR). This means that it is possible to solve the problem of low reproducibility occurring in random patterns without forming photonic crystals (FIGS. 6 and 7).

A photonic crystal patterning process uses a conventional photolithography process. Patterned HNF photonic crystals are formed by selectively irradiating ultraviolet rays using a photomask with a desired pattern, and at the same time, HNF photonic crystals twisted in different directions are randomly formed.

In the present invention, it has a high degree of freedom for the shape of the pattern. It is possible to create a desired deterministic security code, rather than patterning that only serves as a simple alignment display, and hide a chiral random pattern that functions as a PUF inside the code. As shown in FIG. 4, a QR code is produced through a patterning process and a chiral random pattern is hidden therein, enabling double security and producing a code with very high security that cannot be duplicated (FIG. 8 and FIG. 9).

The fabricated patterned photonic crystallization film can be reconstructed through heat treatment and an additional exposure process. A new pattern can be fabricated through an iterative process, and it can be confirmed that a new chiral random pattern is formed even if the fabricated pattern uses the same sample (FIG. 10). This means that neither the producer nor the predictor of which chiral random pattern will be formed cannot be replicated. In addition, this film shows that it has a reconfigurability function that can produce a completely new random pattern by an additional process when exposed to hacking. It was confirmed that this PUF film produced by chiral spontaneous symmetry breaking has a stable structure up to ~110 ° C, and is stable in most polar protic solvents encountered in everyday life. In addition, if it is made large enough, it can be observed through a general smartphone, so accessibility is excellent.

Hereinafter, preferred embodiments are presented to aid understanding of the present invention, but the following examples are merely illustrative of the present invention, and various changes and modifications are possible within the scope and spirit of the present invention. It is obvious to those skilled in the art, It goes without saying that these variations and modifications fall within the scope of the appended claims.

[Example]

Example 1: Preparation of PUF Film of Randomly Patterned HNF Photonic Crystals

First, a sandwich cell using two glass substrates was fabricated. The distance between the two substrates was maintained using silica beads of several μm. The liquid crystal sample was injected into the cell using capillary force at around 170° C., which is the temperature of the isotropic phase. After the injection of the liquid crystal was completed, a photomask having a desired pattern was placed on the upper plate, and then ultraviolet light having a wavelength of 365 nm was irradiated thereon to perform a photolithography process. At this time, liquid crystal molecules were oriented by ultraviolet rays and cooled at a uniform cooling rate (1°C/min) to cause phase transition at the same time. Here, a temperature controller (Linkam TMS94) was used to control the cooling rate. Cooling proceeded to the solid B4 phase, and the total required time was about 30 minutes. The final HNF photonic crystal exhibits a reflective color due to the uniformly formed helical nanostructure. In the case of the used azobenzene-dimer, HNF having a size (>10 μm) that can be observed with a general optical polarization microscope is formed. HNFs in both directions are randomly formed, and these patterns are produced as digitized codes through image processing using Matlab.

The azobenzene-dimer used in this example is a compound represented by Chemical Formula 4-2, and formed a chiral structure having a size (>10 μm) that can be observed with a general optical polarizing microscope (FIG. 1). When this chiral structure was formed, since there was no preference for the chiral direction, both the right twisted structure and the left twisted structure were formed with equal probability. As shown in FIGS. 2 and 3, it was confirmed through image processing and statistical approaches that the probabilities of being twisted in different directions and their arrangement have randomness similar to the level of randomness in nature.

[Formula 4-2]

When ultraviolet rays are irradiated on azobenzene-dimer molecules containing an azo moiety, they have the property of being oriented perpendicular to the direction of ultraviolet irradiation. Using this, ultraviolet rays are irradiated from the high-temperature nematic/smectic phase to align liquid crystals, and HNF structures that are expressed as their temperature decreases are controlled. The axis of the controlled helical HNF is reorientated parallel to the direction of ultraviolet irradiation to form a chiral photonic crystal in which the helical pitch of the helical structure is formed in the visible light region. In the case of a photonic crystal having chirality, an optical rotation phenomenon in which incident linearly polarized light rotates due to optical activity exists. Optical rotation is amplified in the driving wavelength region (photonic band gap), and the degree and direction of optical rotation are different for each wavelength. This degree of rotation can be detected by rotating one polarizer in a polarizing microscope. A photomask was introduced to produce a patterned chiral photonic crystal to serve as an alignment mark, and a film capable of distinguishing chirality by color was produced using the tendency of optical rotation that occurs (FIG. 4).

The non-photonic crystallized HNF film was not produced with a security code, but only the HNF photonic crystal film was produced with a security code, and then statistical analysis was performed. The HNF photonic crystal film can be easily manufactured in the desired shape and size in the photolithography step of the manufacturing process, and the chiral random pattern is clearly distinguished by the optical rotation phenomenon occurring in the chiral photonic crystal (FIG. 1).

Example 2: Binarization and digitization method of experimental image of HNF film

As shown in FIGS. 2 and 3, the security code was produced only for the HNF photonic crystal film, and the binarization and digitization method was newly improved to exponentially increase the information density of the security code. Here's how. First, a Θ=80° experimental image of the patterned HNF photonic crystal film is obtained. Here, each circular photonic crystal is defined as one unit cell. Chiral random patterns are distributed in each unit cell, and are separated into right-handed and left-handed chiral patterns according to color differences. Chiral patterns separated into right-handedness and left-handedness are further classified according to the morphological characteristics of the pattern, which include the number of patterns, area, roundness, aspect ratio, location, and alignment direction. Since each unit cell includes two types of chirality, information on six types of morphological features can be stored in a 6x6x2 matrix. Unlike the existing binarization and digitization methods, in the newly improved method, the information density can be dramatically improved to about 1013,000 when the number of unit cells of the security code is 256 by appropriately adjusting the interval between classes for each feature, and the false recognition rate has the advantage of minimizing It takes an astronomical amount of time, about 10199 years, to predict the password of a security code with an information density of about 1013000 using brute force trials. Therefore, by newly improving the binarization and digitization method, the originality of the further improved security code, high information density, and high recognition rate can be guaranteed.

Example 3: Security code authentication method

The improved authentication method provides a fast authentication method and a reading reliability of 99.9% or higher based on hierarchical authentication of morphological characteristics. First, the authenticated security code is stored in a database in the form of a matrix. Then, the newly created chiral pattern is digitized in the form of a matrix and compared with the data stored in the database through a five-step screening process by calculating a similarity index. For example, if the similarity index for the 'direction' morphological feature exceeds the threshold, the value for the next morphological feature is compared, and it is determined as true if all five steps are passed. However, if the similarity index does not exceed the threshold, the screening process is terminated and the newly created chiral pattern is determined to be false. In addition, the recognition rate increases as the number of unit cells increases, shows a high recognition rate for external noise, and reproducible results are obtained even when observed with different microscopes. The newly proposed hierarchical authentication method does not require additional algorithmic modification when a new sample is added to the database, and on average it takes 5.14 seconds to determine true and 2.34 seconds to determine false, ensuring high accuracy and fast authentication speed. .

Example 4: Reconstitution potential of PUF film

The fabricated patterned photonic crystallization film can be reconstructed through heat treatment and an additional exposure process. It was confirmed that a new pattern can be fabricated through an iterative process, and that a new chiral random pattern is formed even if the fabricated pattern uses the same sample (FIG. 10). This means that the manufacturer cannot predict which chiral random pattern will be formed and that replication is also impossible.

In addition, it was confirmed that this film has reconfigurability to produce a completely new random pattern by an additional process when exposed to hacking.

It was confirmed that this PUF film produced by chiral spontaneous symmetry breaking has a stable structure up to ~110 ° C, and is stable in most polar protic solvents encountered in everyday life. In addition, if it is made large enough, it can be observed through a general smartphone, so accessibility is excellent.

In the present invention, a non-replicable chiral random pattern is formed using a chiral photonic crystal in which chiral symmetry breaking occurs, and it is confirmed that this can be applied to a PUF. A chiral structure in a film can be detected simply by rotating the polarizer, and it can be digitized and applied as a security code.

Chiral domains through spontaneous chiral symmetry breaking of the material proposed in the present invention are formed much larger than the diffraction limit of visible light, can form photonic crystals, and have the characteristics of being easily observable by an optical method. Therefore, unlike other materials in which chiral domains are difficult to observe, it makes it possible to apply it as a film with security.

Compared to existing PUFs, it can be manufactured with a simpler process and shows high performance in characteristics such as reproducibility, uniqueness, unpredictability, and reconfigurability.

In the prior art, when the security code is leaked to the outside, it becomes vulnerable to hacking and requires a new device for new security. However, in the present invention, when the security code is hacked, a new security code can be generated without destroying the device through a post-processing process. In addition, since it can be implemented as a single organic material without additional align markers or materials, the manufacturing process is easy compared to high security.

In addition, the present invention is a security code based on chiral optical characteristics, which is easy to manufacture and difficult to detect by a general method compared to other optical PUFs. The photolithography-based fabrication process enables the fabrication of a double security code that hides a non-deterministic pattern in a deterministic pattern, so it has high versatility compared to previously reported technologies and much better performance than existing known technologies (exponentially increased information density, It has the advantage of having a high and fast recognition rate) and originality.

The present invention is a technology having high information density and security, and has the advantage of being able to produce desired patterning through an existing photolithography process. This can replace all existing systems for personal authentication or security at the point when existing security keys become invalid in the upcoming quantum computing era.

Having described specific parts of the present invention in detail above, it will be clear to those skilled in the art that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, the substantial scope of the present invention will be defined by the claims and their equivalents.

Claims (12)

1. An HNF photonic crystal structure obtained by randomly patterning helical nanofilaments (HNF) in which bent liquid crystal molecules are grown in a twisted layered structure by self-assembly.
2. The HNF photonic crystal structure according to claim 1, wherein the bent liquid crystal molecule is at least one selected from the group consisting of azobenzene-dimer, MHOBOW of Chemical Formula 1 and NOBOW of Chemical Formula 2.

   [Formula 1]

   

   [Formula 2]

   
3. The HNF photonic crystal structure according to claim 2, wherein the azobenzene-dimer is represented by Formula 3:

   [Formula 3]

   

   In Formula 3, L is a straight-chain or branched-chain alkylene group, a cycloalkylene group, a haloalkylene group, an arylene group, a heteroarylene group, an arylenealkylene group, an alkylenearylene group, an alkyleneheteroarylene group, a heteroarylenealkylene group, An alkylene ester group or an alkylene amide group, and the heteroarylene group is a divalent radical containing a heteroatom selected from fluorine, oxygen, sulfur and nitrogen,

   R ₁ and R ₂ are each independently selected from a straight-chain or branched-chain alkyl group, a cycloalkyl group, a haloalkyl group, an alkoxy group, a cycloalkoxy group, an aryl group, a heteroaryl group, an aryloxy group, an alkoxyheteroaryl group, a heteroaryloxyalkyl group, An alkylheteroaryl group, an alkylaryl group, an arylalkyl group, an alkylheteroaryl group, an alkylester group, an alkylamide group, or an acryl group, and the heteroaryl group is a monovalent radical containing a heteroatom selected from fluorine, oxygen, sulfur, and nitrogen. .
4. The HNF photonic crystal structure according to claim 3, wherein the azobenzene-dimer is represented by Chemical Formula 4:

   [Formula 4]

   

   In Formula 4, R ₁ and R ₂ are each independently a straight-chain or branched-chain alkyl group, a cycloalkyl group, a haloalkyl group, an alkoxy group, a cycloalkoxy group, an aryl group, a heteroaryl group, an aryloxy group, an alkoxyheteroaryl group, and a heteroaryl group. An oxyalkyl group, an alkylheteroaryl group, an alkylaryl group, an arylalkyl group, an alkylheteroaryl group, an alkylester group, an alkylamide group, or an acryl group, and a heteroaryl group containing a heteroatom selected from fluorine, oxygen, sulfur, and nitrogen. is a radical, and n is an odd number from 3 to 11.
5. The HNF photonic crystal structure according to claim 4, wherein the azobenzene dimer is at least one selected from the group consisting of Formula 4-1, Formula 4-2, Formula 4-3, and Formula 4-4.

   [Formula 4-1]

   

   [Formula 4-2]

   

   [Formula 4-3]

   

   [Formula 4-4]

   
6. The HNF photonic crystal structure according to claim 1, which is for physical copy protection.
7. The HNF photonic crystal structure according to claim 1, which is in the form of a film or flake.
8. A manufacturing method of the HNF photonic crystal structure of claim 1 comprising the following steps:

   (a) irradiating ultraviolet rays to helical nanofilaments (HNFs) to vertically orient an axis of liquid crystal contained in the HNFs with respect to a direction of irradiation of ultraviolet rays; and

   (b) forming an HNF photonic crystal by cooling the vertically aligned HNF to the B4 phase temperature of the liquid crystal to reorient the axis of the liquid crystal parallel to the direction of ultraviolet irradiation to obtain an HNF photonic crystal structure.
9. The method of claim 8, wherein the bent liquid crystal molecule is at least one selected from the group consisting of azobenzene-dimer, MHOBOW of Formula 1, and NOBOW of Formula 2:

   [Formula 1]

   

   [Formula 2]

   
10. The method of claim 9, wherein the azobenzene-dimer is represented by Chemical Formula 3:

    [Formula 3]

    

    In Formula 3, L is a straight-chain or branched-chain alkylene group, a cycloalkylene group, a haloalkylene group, an arylene group, a heteroarylene group, an arylenealkylene group, an alkylenearylene group, an alkyleneheteroarylene group, a heteroarylenealkylene group, An alkylene ester group or an alkylene amide group, and the heteroarylene group is a divalent radical containing a heteroatom selected from fluorine, oxygen, sulfur and nitrogen,

    R ₁ and R ₂ are each independently selected from a straight-chain or branched-chain alkyl group, a cycloalkyl group, a haloalkyl group, an alkoxy group, a cycloalkoxy group, an aryl group, a heteroaryl group, an aryloxy group, an alkoxyheteroaryl group, a heteroaryloxyalkyl group, An alkylheteroaryl group, an alkylaryl group, an arylalkyl group, an alkylheteroaryl group, an alkylester group, an alkylamide group, or an acryl group, and the heteroaryl group is a monovalent radical containing a heteroatom selected from fluorine, oxygen, sulfur, and nitrogen. .
11. 11. The method of claim 10, wherein the azobenzene-dimer is represented by Chemical Formula 4:

    [Formula 4]

    

    In Formula 4, R ₁ and R ₂ are each independently a straight-chain or branched-chain alkyl group, a cycloalkyl group, a haloalkyl group, an alkoxy group, a cycloalkoxy group, an aryl group, a heteroaryl group, an aryloxy group, an alkoxyheteroaryl group, and a heteroaryl group. An oxyalkyl group, an alkylheteroaryl group, an alkylaryl group, an arylalkyl group, an alkylheteroaryl group, an alkylester group, an alkylamide group, or an acryl group, and a heteroaryl group containing a heteroatom selected from fluorine, oxygen, sulfur, and nitrogen. is a radical, and n is an odd number from 3 to 11.
12. The method of claim 11, wherein the azobenzene-dimer is at least one selected from the group consisting of Chemical Formula 4-1, Chemical Formula 4-2, Chemical Formula 4-3, and Chemical Formula 4-4:

    [Claim 4-1]

    

    [Claim 4-2]

    

    [Claim 4-3]

    

    [Claim 4-4]

    

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