The flexible wet-style superhydrophobic complex laminate and method of preparing same

Abstract

The present invention relates to a flexible water-based hydrophobic composite laminate comprising: a polymer elastomer layer (100) including a polymer elastomer; a hydrophobic elastomer protrusion pattern layer (200) formed on the polymer elastomer layer and having a first pattern including protrusions (210), wherein the protrusions include a hydrophobic polymer elastomer; and a hydrogel spot pattern layer (300) formed on the polymer elastomer layer (100) and having a second pattern including spots (310) located between the protrusions, wherein the spots include a hydrogel. By forming a hydrophobic elastomer protrusion pattern layer and a hydrogel spot pattern layer on the polymer elastomer layer, the water-based hydrophobic composite laminate of the present invention can simultaneously achieve water molecule absorption and water droplet repulsion, is applicable to various curvatures, and has the effect of being able to be attached and detached multiple times without adhesive at a desired location.

Description

Technology Field

[0001] The present invention relates to a flexible water-based hydrophobic composite laminate and a method for manufacturing the same. Background Technology

[0002] Factors that impede optical transmittance on transparent substrates primarily include fogging and surface contamination. From everyday eyeglasses, goggles, and automotive glass to sensors in various fields, reduced transmittance in these optical substrates leads to visual obstruction. In particular, since recognition errors can occur in critical sensors, potentially resulting in fatal consequences, the need for functional coatings is increasing. Methods to prevent fogging are generally classified into three categories based on surface wettability. First, anti-fogging coatings utilizing hydrophilic polymers and inorganic materials that attract water induce absorption at the molecular level to inhibit surface condensation, or maintain a thin layer of water to minimize transmittance impairment even if condensation occurs. However, this method has the disadvantage that surface contamination can easily occur due to high surface energy. Second, anti-fogging coatings based on superhydrophobic surface wettability allow condensed water droplets to be removed by external force, but they have the limitation of requiring external forces such as gravity. Finally, an anti-fogging coating utilizing binary wettability can reduce surface contamination by forming a structure consisting of a hydrophobic region capable of absorbing water molecules and a hydrophobic capping layer with low surface energy, utilizing both hydrophobic and hydrophilic properties simultaneously. However, due to the high contact angle hysteresis for water droplets, contamination already adsorbed on the surface is difficult to remove, and water droplets may adhere to the surface and impede transmittance.

[0003] Therefore, there is a need for a functional coating that can easily remove surface contamination from optical substrates and simultaneously form a structure capable of effectively absorbing water molecules to prevent fogging and reduce reflection. To this end, water-based hydrophobic composite laminates have been proposed, but this method has drawbacks such as complex processes and difficulty in scaling up to large areas. The problem to be solved

[0004] The objective of the present invention is to provide a water-based hydrophobic composite laminate that prevents fogging by forming a structure that allows surface contamination of an optical substrate to be easily removed and simultaneously effectively absorb water molecules.

[0005] In addition, another objective of the present invention is to provide a water-based hydrophobic composite laminate that prevents fogging of the substrate and simultaneously enables self-cleaning.

[0006] In addition, another objective of the present invention is to provide a flexible water-based hydrophobic composite laminate that simultaneously achieves water molecule absorption and water droplet repulsion, allows for multiple attachments and detachments without adhesive at desired locations, and is applicable to various curvatures.

[0007] In addition, another objective of the present invention is to provide a water-based hydrophobic composite laminate that can be applied not only to optical products but also to high-value-added sensors and products such as sensors for autonomous vehicles or medical endoscopes.

[0008] In addition, another objective of the present invention is to provide a method for manufacturing a water-based hydrophobic composite laminate that enables large-area expansion using a printing method, thereby having no size limitations and realizing the advantages of hydrophilicity and hydrophobicity on a single substrate. means of solving the problem

[0009] According to one aspect of the present invention, a flexible water-based hydrophobic composite laminate is provided, comprising: a polymer elastomer layer (100) comprising a polymer elastomer; a hydrophobic elastomer protrusion pattern layer (200) formed on the polymer elastomer layer and having a first pattern comprising protrusions (210), wherein the protrusions comprise a hydrophobic polymer elastomer; and a hydrogel spot pattern layer (300) formed on the polymer elastomer layer (100) and having a second pattern comprising spots (310) located between the protrusions, wherein the spots comprise a hydrogel.

[0010] In addition, the above polymer elastomer is polydimethylsiloxane (PDMS), Ecoflex, silicone rubber, fluoro silicone rubber, vinyl methyl silicone rubber, styrene-butadiene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer, styrene-butadiene rubber (SBR), butadiene rubber (BR), isobutylene-isoprene rubber (IIR), ethylene propylene rubber (EPR), ethylene propylene diene monomer rubber (EPDM), and isoprene It may include one or more selected from the group consisting of rubber (isoprene rubber, IR), isobutylene rubber (IR), acrylic rubber, acrylonitrile-butadiene rubber (ABR), polyurethane, polyether urethane, polyester urethane, epichlorohydrin rubber, and polychloroprene rubber.

[0011] In addition, the above-mentioned hydrophobic polymer elastomers are each polydimethylsiloxane (PDMS), ecoflex, silicone rubber, fluoro silicone rubber, vinyl methyl silicone rubber, styrene-butadiene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer, styrene-butadiene rubber (SBR), butadiene rubber (BR), isobutylene-isoprene rubber (IIR), ethylene propylene rubber (EPR), ethylene propylene diene monomer rubber (EPDM), and isoprene It may include one or more selected from the group consisting of rubber (isoprene rubber, IR) and isobutylene rubber (isobutylene rubber, IR).

[0012] In addition, the above-mentioned protrusion (210) may include one or more types selected from the group consisting of a cylinder, an elliptical prism, a rhombus, a polygonal prism, a cone, an elliptical cone, a rhombus, and a polygonal pyramid.

[0013] In addition, the first pattern and the second pattern each have a grid shape, and the spot (310) can be adjacent to each of the four protrusions.

[0014] In addition, the upper cross-section of the above protrusion (210) may be positioned higher than the upper cross-section of the above spot (310).

[0015] In addition, the polymer elastomer layer (100) may have a concave hole (110) formed between adjacent protrusions (210), and the spot (310) may be formed inside the concave hole (110), with the upper cross-section of the spot (310) exposed to the outside.

[0016] In addition, the above hydrogel is Poly(ethylene glycol) diacrylate (PEGDA), Poly-hydroxyethyl methacrylate (PHEMA), Tetraethylene glycol dimethacrylate, Poly(ethylene glycol) dimethacrylate, Poly(Guluronate), PCL-PEG-PCL diacrylate, chitosan (CHI), poly(allylamine)-co-poly(ethylene oxide) copolymer (PAH-g-PEG), poly(L-lysine)-co-(polyethylene oxide) copolymer (PLL-g-PEG), polyquaternized-4-vinylpyridine-polyethylene oxide copolymer (poly(quaternized-4-vinylpyridine)-co-poly(ethylene oxide) copolymer (QPVP-co-PEG), polydiallyldimethylammonium chloride-polyethylene oxide copolymer (poly(diallyldimethylammonium chloride)-co-poly(ethylene oxide), PDADMA-co-PEG), polyallylamine-polyacrylamide copolymer (poly(allylamine)-co-polyacrylamide copolymer, PAH-co-PAAM), polyL-lysine-polyacrylamide copolymer (poly(L-lysine)-co-polyacrylamide, PLL-co-PAAM), polyquaternized-4-vinylpyridine-polyacrylamide copolymer (poly(quaternized-4-vinylpyridine)-co-polyacrylamide, QPVP-co-PAAM), polydiallyldimethylammonium chloride-polyacrylamide copolymer (poly(diallyldimethylammonium chloride)-co-polyacrylamide, PDADMA-co-PAAM), carboxymethyl cellulose,CMC), alginic acid (AA), hyaluronic acid (HA), heparin, pectin, poly(acrylic acid)-co-poly(ethylene oxide) copolymer (PAA-co-PEG), polymethacrylic acid-polyethylene oxide copolymer (PMAA-co-PEG), poly(acrylic acid)-co-polyacrylamide copolymer (PAA-co-PAAM), polymethacrylic acid-polyacrylamide copolymer (PMAA-co-PAAM), Iota-carrageenan, Kappa-carrageenan, Lambda-carrageenan, fucoidan, It may include one or more selected from the group consisting of fucogalactan, chondroitin, gellan gum, gum karaya, gum tragacanth, welan gum, xanthan gum, and psyllium seed gum.

[0017] In addition, the carbon atoms of the hydrogel on the surface of the hydrogel spot pattern layer and the carbon atoms of the polymer elastomer on the surface of the polymer elastomer layer may be covalently bonded to each other.

[0018] In addition, the above-mentioned hydrophobic composite laminate (10) may further include an adhesive layer (400) on the polymer elastomer layer (100) in a direction opposite to the direction facing the hydrophobic elastomer protrusion pattern layer (200).

[0019] In addition, the adhesive layer (400) may include a polysiloxane compound prepared by reacting a dimethylsiloxane oligomer having a plurality of vinyl groups at the chain ends with a siloxane oligomer curing agent having hydrogen atoms bonded to silicon atoms within the chain.

[0020] In addition, as in reaction scheme 1, the dimethylsiloxane oligomer may be a compound represented by structural formula 1 below, the siloxane oligomer curing agent may be a compound represented by structural formula 2 below, and the polysiloxane compound may be a polysiloxane compound of structural formula 3 produced by reacting the compound represented by structural formula 1 and the compound represented by structural formula 2.

[0021] [Reaction Equation 1]

[0022]

[0023] In the above reaction equation, m is any one of an integer from 10 to 500, n1 is any one of an integer from 1 to 100, and n2 is any one of an integer from 2 to 50.

[0024] In addition, the adhesive strength of the adhesive layer can be controlled by adjusting the weight ratio of the polymethylsiloxane oligomer and the siloxane oligomer curing agent of the polysiloxane compound of the above structural formula 3.

[0025] In addition, it may be an electronic device comprising any one selected from the group consisting of an optical sensor, an image sensor, a sensor for an autonomous vehicle, and a medical endoscope, which includes the above-mentioned water-based hydrophobic composite laminate.

[0026] According to another aspect of the present invention, a method for manufacturing a water-based hydrophobic composite laminate is provided, comprising: (a) injecting a mixture containing a precursor of a hydrophobic polymer elastomer into a patterned mold and curing it to produce a polymer elastomer layer (100) containing a polymer elastomer and a hydrophobic elastomer protrusion pattern layer (200) formed on the polymer elastomer layer and having a first pattern including protrusions (210), wherein the pillars include a hydrophobic polymer elastomer; and (b) forming a hydrogel spot pattern layer (300) on the polymer elastomer layer (100), wherein the second pattern includes spots (310) located between the protrusions, wherein the spots include a hydrogel.

[0027] In addition, the above mixture may further include benzophenone.

[0028] In addition, the above mixture may contain 1 to 3 weight % of the benzophenone.

[0029] In addition, step (b) can be performed by inkjet printing.

[0030] In addition, the method for manufacturing the above-described water-based hydrophobic composite laminate may further include, after step (b), step (c) of irradiating the hydrogel spot pattern layer with light to covalently bond the carbon atoms of the hydrogel on the surface of the hydrogel spot pattern layer with the carbon atoms of the polymer elastomer on the surface of the polymer elastomer layer.

[0031] In addition, the method for manufacturing the above-described water-based hydrophobic composite laminate may further form an adhesive layer (400) on the polymer elastomer layer (100) of the result of step (a) or step (b) in a direction opposite to the direction facing the hydrophobic elastomer protrusion pattern layer (200) after step (a) or step (b). Effects of the invention

[0032] The flexible water-based hydrophobic composite laminate of the present invention can simultaneously achieve water molecule absorption and water droplet repulsion by forming a hydrophobic elastomer protrusion pattern layer and a hydrogel spot pattern layer on a polymer elastomer layer.

[0033] In addition, the present invention has the effect of preventing fogging on the substrate and simultaneously enabling self-cleaning.

[0034] In addition, the water-based hydrophobic composite laminate of the present invention has the effect of being flexible and applicable to various curvatures by forming a hydrophobic elastomer protrusion pattern layer and a hydrogel spot pattern layer on a polymer elastomer layer.

[0035] In addition, the water-based hydrophobic composite laminate of the present invention has an adhesive layer, which has the effect of allowing it to be attached and detached multiple times at a desired location without adhesive.

[0036] In addition, the present invention can be applied not only to optical products but also to high-value-added sensors and products such as sensors for autonomous vehicles or medical endoscopes.

[0037] In addition, the method for manufacturing a water-based hydrophobic composite laminate of the present invention can manufacture a water-based hydrophobic composite laminate having the above-mentioned effects over a large area, simply and inexpensively. Brief explanation of the drawing

[0038] These drawings are for reference to explain exemplary embodiments of the present invention, and therefore, the technical concept of the present invention should not be interpreted as being limited to the attached drawings. FIG. 1 is a flowchart showing the manufacturing process of a water-based hydrophobic composite laminate according to the present invention. FIG. 2 is a diagram schematically showing the manufacturing steps of a water-based hydrophobic composite laminate according to one embodiment of the present invention. FIG. 3 is a schematic diagram of a water-based hydrophobic composite laminate according to the present invention. FIG. 4 is a schematic diagram showing the hydrophobic characteristics of the water-based hydrophobic composite laminate of the present invention with respect to water droplets. Figure 5 is an optical photograph showing the anti-fogging performance of a laminate according to device Comparative Example 1 and device Example 1. Figure 6 is a graph showing the transmission spectra of a laminate according to device Comparative Example 1, device Example 1, and Comparative Example 1. Figure 7 is an image comparing the contact between a water droplet and a hydrogel in Preparation Example 3, Comparative Example 3, and Example 1 according to the present invention. FIG. 8 is a schematic diagram of the adhesion tester of device embodiment 1. FIG. 9a is a graph showing the adhesion strength of the laminate of Example 1 applied to various substrates, and FIG. 9b is a graph showing the adhesion strength of device Example 1. Figure 10 is a schematic diagram showing the adhesion mechanism by benzophenone between PDMS and a hydrogel pattern. FIG. 11 is a schematic diagram of a hydrogel stability test in which the water-based hydrophobic laminate of the present invention is immersed in water to evaluate adhesive properties. Figure 12 is an optical photograph of the PDMS and hydrogel of Example 1 and Example 2. Figure 13 is an optical photograph showing the uniaxial tensile load test of Example 1 before and after. FIG. 14 shows the advance of water (θ) after the uniaxial tensile load test of Example 1. adv ) and retraction (θ rec This is a graph showing the contact angle. FIG. 15 is an optical photograph of a contaminant (sand, 30-50 mesh) attached to the surface of a laminate according to Example 1 before and after removal with a water droplet. FIG. 16a is an optical photograph of an image sensor according to device embodiment 1, FIG. 16b is an optical photograph showing the self-cleaning characteristics of the image sensor according to device embodiment 1, and FIG. 16c is an optical photograph showing the anti-fogging characteristics of the image sensor according to device embodiment 1 and device comparative example 1. Specific details for implementing the invention

[0039] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention.

[0040] However, the following description is not intended to limit the present invention to specific embodiments, and detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions could obscure the essence of the present invention.

[0041] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to indicate the presence of the features, numbers, steps, actions, components, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, or combinations thereof.

[0042] Additionally, terms including ordinal numbers, such as "first," "second," etc., used below may be used to describe various components, but said components are not limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0043] Furthermore, when it is stated that a component is "formed" or "laminated" on another component, it should be understood that while it may be formed or laminated by being directly attached to the entire surface or one surface of the other component, there may also be other components present in between.

[0045] Hereinafter, a flexible water-based hydrophobic composite laminate and a method for manufacturing the same will be described in detail. However, this is presented as an example and is not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0047] The present invention provides a flexible water-based hydrophobic composite laminate comprising: a polymer elastomer layer (100) comprising a polymer elastomer; a hydrophobic elastomer protrusion pattern layer (200) formed on the polymer elastomer layer and having a first pattern comprising protrusions (210), wherein the protrusions comprise a hydrophobic polymer elastomer; and a hydrogel spot pattern layer (300) formed on the polymer elastomer layer (100) and having a second pattern comprising spots (310) located between the protrusions, wherein the spots comprise a hydrogel.

[0048] In addition, the above polymer elastomer is polydimethylsiloxane (PDMS), Ecoflex, silicone rubber, fluoro silicone rubber, vinyl methyl silicone rubber, styrene-butadiene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer, styrene-butadiene rubber (SBR), butadiene rubber (BR), isobutylene-isoprene rubber (IIR), ethylene propylene rubber (EPR), ethylene propylene diene monomer rubber (EPDM), and isoprene It may include one or more selected from the group consisting of rubber (isoprene rubber, IR), isobutylene rubber (IR), acrylic rubber, acrylonitrile-butadiene rubber (ABR), polyurethane, polyether urethane, polyester urethane, epichlorohydrin rubber, and polychloroprene rubber.

[0049] In addition, the above-mentioned hydrophobic polymer elastomers are each polydimethylsiloxane (PDMS), ecoflex, silicone rubber, fluoro silicone rubber, vinyl methyl silicone rubber, styrene-butadiene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer, styrene-butadiene rubber (SBR), butadiene rubber (BR), isobutylene-isoprene rubber (IIR), ethylene propylene rubber (EPR), ethylene propylene diene monomer rubber (EPDM), and isoprene It may include one or more selected from the group consisting of rubber (isoprene rubber, IR) and isobutylene rubber (isobutylene rubber, IR).

[0050] In addition, the above-mentioned protrusion (210) may include one or more types selected from the group consisting of a cylinder, an elliptical prism, a rhombus, a polygonal prism, a cone, an elliptical cone, a rhombus, and a polygonal pyramid.

[0051] In addition, the first pattern and the second pattern each have a grid shape, and the spot (310) can be adjacent to each of the four protrusions.

[0052] In addition, the upper cross-section of the above protrusion (210) may be positioned higher than the upper cross-section of the above spot (310).

[0053] In addition, the diameter of the lower cross-section of the above-mentioned protrusion (210) may be 5 to 50 μm.

[0054] In addition, the interval between adjacent protrusions (210) may be 5 to 200 μm, which is 1 to 4 times the diameter value.

[0055] In addition, the ratio (a / b) of the spacing (a) between the protrusions (210) and the diameter (b) of the lower cross-section may be 1 to 4.

[0056] In addition, the height of the above-mentioned protrusion (210) may be 15 to 100 μm.

[0057] In addition, the polymer elastomer layer (100) may have a concave hole (110) formed between adjacent protrusions (210), and the spot (310) may be formed inside the concave hole (110), with the upper cross-section of the spot (310) exposed to the outside.

[0058] In addition, the above hydrogel is Poly(ethylene glycol) diacrylate (PEGDA), Poly-hydroxyethyl methacrylate (PHEMA), Tetraethylene glycol dimethacrylate, Poly(ethylene glycol) dimethacrylate, Poly(Guluronate), PCL-PEG-PCL diacrylate, chitosan (CHI), poly(allylamine)-co-poly(ethylene oxide) copolymer (PAH-g-PEG), poly(L-lysine)-co-(polyethylene oxide) copolymer (PLL-g-PEG), polyquaternized-4-vinylpyridine-polyethylene oxide copolymer (poly(quaternized-4-vinylpyridine)-co-poly(ethylene oxide) copolymer (QPVP-co-PEG), polydiallyldimethylammonium chloride-polyethylene oxide copolymer (poly(diallyldimethylammonium chloride)-co-poly(ethylene oxide), PDADMA-co-PEG), polyallylamine-polyacrylamide copolymer (poly(allylamine)-co-polyacrylamide copolymer, PAH-co-PAAM), polyL-lysine-polyacrylamide copolymer (poly(L-lysine)-co-polyacrylamide, PLL-co-PAAM), polyquaternized-4-vinylpyridine-polyacrylamide copolymer (poly(quaternized-4-vinylpyridine)-co-polyacrylamide, QPVP-co-PAAM), polydiallyldimethylammonium chloride-polyacrylamide copolymer (poly(diallyldimethylammonium chloride)-co-polyacrylamide, PDADMA-co-PAAM), carboxymethyl cellulose,CMC), alginic acid (AA), hyaluronic acid (HA), heparin, pectin, poly(acrylic acid)-co-poly(ethylene oxide) copolymer (PAA-co-PEG), polymethacrylic acid-polyethylene oxide copolymer (PMAA-co-PEG), poly(acrylic acid)-co-polyacrylamide copolymer (PAA-co-PAAM), polymethacrylic acid-polyacrylamide copolymer (PMAA-co-PAAM), Iota-carrageenan, Kappa-carrageenan, Lambda-carrageenan, fucoidan, It may include one or more selected from the group consisting of fucogalactan, chondroitin, gellan gum, gum karaya, gum tragacanth, welan gum, xanthan gum, and psyllium seed gum.

[0059] In addition, the carbon atoms of the hydrogel on the surface of the hydrogel spot pattern layer and the carbon atoms of the polymer elastomer on the surface of the polymer elastomer layer may be covalently bonded to each other.

[0060] In addition, the above-mentioned hydrophobic composite laminate (10) may further include an adhesive layer (400) on the polymer elastomer layer (100) in a direction opposite to the direction facing the hydrophobic elastomer protrusion pattern layer (200).

[0061] In addition, the adhesive layer (400) may include a polysiloxane compound prepared by reacting a dimethylsiloxane oligomer having a plurality of vinyl groups at the chain ends with a siloxane oligomer curing agent having hydrogen atoms bonded to silicon atoms within the chain.

[0062] In addition, as in reaction scheme 1, the dimethylsiloxane oligomer may be a compound represented by structural formula 1 below, the siloxane oligomer curing agent may be a compound represented by structural formula 2 below, and the polysiloxane compound may be a polysiloxane compound of structural formula 3 produced by reacting the compound represented by structural formula 1 and the compound represented by structural formula 2.

[0063] [Reaction Equation 1]

[0064]

[0065] In the above reaction equation, m is any one of an integer from 10 to 500, n1 is any one of an integer from 1 to 100, and n2 is any one of an integer from 2 to 50.

[0066] In addition, the adhesive strength of the adhesive layer can be controlled by adjusting the weight ratio of the polymethylsiloxane oligomer and the siloxane oligomer curing agent of the polysiloxane compound of the above structural formula 3.

[0067] In addition, it may be an electronic device comprising any one selected from the group consisting of an optical sensor, an image sensor, a sensor for an autonomous vehicle, and a medical endoscope, which includes the above-mentioned aqueous hydrophobic composite laminate.

[0069] According to another aspect of the present invention, a method for manufacturing a water-based hydrophobic composite laminate is provided, comprising: (a) injecting a mixture containing a precursor of a hydrophobic polymer elastomer into a patterned mold and curing it to produce a polymer elastomer layer (100) containing a polymer elastomer and a hydrophobic elastomer protrusion pattern layer (200) formed on the polymer elastomer layer and having a first pattern including protrusions (210), wherein the pillars include a hydrophobic polymer elastomer; and (b) forming a hydrogel spot pattern layer (300) on the polymer elastomer layer (100), wherein the second pattern includes spots (310) located between the protrusions, wherein the spots include a hydrogel.

[0070] In addition, the above mixture may further include benzophenone.

[0071] In addition, the mixture may contain 1 to 3 weight %, preferably 1 to 2 weight %, of benzophenone.

[0072] In addition, step (b) can be performed by inkjet printing.

[0073] In addition, the method for manufacturing the above-described water-based hydrophobic composite laminate may further include, after step (b), step (c) of irradiating the hydrogel spot pattern layer with light to covalently bond the carbon atoms of the hydrogel on the surface of the hydrogel spot pattern layer with the carbon atoms of the polymer elastomer on the surface of the polymer elastomer layer.

[0074] In addition, the method for manufacturing the above-described water-based hydrophobic composite laminate may further form an adhesive layer (400) on the polymer elastomer layer (100) of the result of step (a) or step (b) in a direction opposite to the direction facing the hydrophobic elastomer protrusion pattern layer (200) after step (a) or step (b).

[0075] Therefore, the water-based hydrophobic composite laminate of the present invention has an anti-fogging effect and simultaneously enables self-cleaning due to superhydrophobicity, making it applicable not only to everyday optical products but also to high-value-added sensors and products such as sensors for autonomous vehicles and medical endoscopes. In particular, in the case of image sensors for autonomous vehicles, accidents caused by recognition errors actually occur, and since most of such recognition errors are attributed to fogging, surface contamination, or ghosting caused by sunlight reflection, the efficiency of the sensor can be maximized through the water-based hydrophobic composite laminate according to the present invention.

[0077] [Example]

[0078] Hereinafter, preferred embodiments of the present invention will be described. However, this is for illustrative purposes only and does not limit the scope of the present invention.

[0080] FIG. 1 is a flowchart showing the manufacturing steps of a water-based hydrophobic composite laminate according to the present invention, and FIG. 2 is a diagram schematically showing the manufacturing steps of a water-based hydrophobic composite laminate according to one embodiment of the present invention.

[0081] Hereinafter, a method for manufacturing a water-based hydrophobic composite laminate of the present invention will be described with reference to FIGS. 1 and 2.

[0083] Preparation of ingredients

[0084] PDMS (Polydimethylsiloxane, Sylgard 184, Dow Corning), hydrogel (Poly(ethylene glycol) diacrylate monomer, Mw = 700 g mol -1), 2-hydroxy-2-methylpropiophenone (photo initiator, Darocur 1173), Benzophenone, Fluorescein sodium salt, Chitosan (CHI, low molecular weight), Carboxymethyl cellulose (CMC, Mw = 250,000 g mol -1 , Sigma-Aldrich). Negative photoresist (SU-8 50, Microchem), Sand (30-50 mesh, Acros Organics), Glass slides (76×26×1 mm, Marienfeld), Deionized (DI) water (18.2 MΩ cm at 25 ℃)

[0086] Preparation Example 1: Preparation of a mixture (PDMS mixture) containing a precursor of a hydrophobic polymer elastomer

[0087] A PDMS mixture was prepared by mixing 50 g of polydimethylsiloxane and 5 g of curing agent so that the weight ratio of polydimethylsiloxane (PDMS) to curing agent was 10:1.

[0089] Preparation Example 2: Preparation of a mixture (PDMS elastomer mixture) containing a precursor of a hydrophobic polymer elastomer having benzophenone

[0090] It was prepared in the same manner as Preparation Example 1, except for adding 1.01g of benzophenone.

[0092] Preparation Example 3: Preparation of a PDMS mold having a cylindrical pattern

[0093] Micro-patterns were transferred onto a wafer. Patterning was performed based on photolithography.

[0094] Specifically, based on a photolithography process, a SU-8 mold was obtained in which a cylindrical micro-pattern was formed in intaglio on a silicon wafer using SU-8 negative photoresist (Microchem) (diameter 25 μm, spacing 100 μm). Polydimethylsiloxane (PDMS, Sylgard® 184, Dow Corning) was poured onto the silicon wafer on which the micro-pattern was transferred and cured at 70°C for 2 hours, after which the cured PDMS was peeled off to produce a PDMS mold with a cylindrical micro-pattern.

[0096] Preparation Example 4: Preparation of a PDMS mold having cylindrical and spot-shaped patterns

[0097] A PDMS mold having cylindrical and spot-shaped patterns was manufactured in the same manner as in Example 3, except that a micro pattern with a cylindrical shape formed as an intaglio was transferred onto a silicon wafer using SU-8 negative photoresist (Microchem) based on a photolithography process, and then a cylindrical pattern was transferred between the micro patterns with a cylindrical shape formed as an intaglio (diameter 110 μm, spacing 15 μm).

[0099] Example 1: Preparation of a water-based hydrophobic composite laminate containing a hydrogel

[0100] The PDMS elastomer mixture prepared in Preparation Example 2 was poured into the PDMS mold having cylindrical and spot-shaped patterns prepared in Preparation Example 4. The mold containing the uncured PDMS mixture was placed in a desiccator and the pressure was lowered to 0.003 MPa at room temperature. As a vacuum was created, air within the structure was expelled, allowing the PDMS mixture to enter the mold effectively. Then, the mixture was cured in an oven set to 70°C for 3 hours to produce a water-based hydrophobic laminate having cylindrical and spot patterns.

[0101] A 50 wt.% hydrogel precursor solution was prepared by dissolving a hydrogel containing 1 wt.% 2-hydroxy-2-methylpropiophenone (photo initiator) in purified water.

[0102] A laminate (aqueous hydrophobic composite laminate) having a hydrogel within a hydrophobic pattern layer having a cylindrical pattern was prepared by inkjet printing the hydrogel precursor solution onto the above aqueous hydrophobic laminate at intervals of 125 μm using a Piezoelectric inkjet printer (JetlabII; MicroFab Technologies, Inc, USA).

[0104] Example 2: Preparation of a water-based hydrophobic laminate containing hydrogels in pillar patterns and spot patterns

[0105] A water-based hydrophobic laminate having a cylindrical pattern and a spot pattern was prepared in the same manner as in Example 1, except that instead of pouring the PDMS elastomer mixture prepared in Example 2 into the PDMS mold having a cylindrical and spot-shaped pattern prepared in Example 4, the PDMS elastomer mixture prepared in Example 1 was poured into the PDMS mold having a cylindrical and spot-shaped pattern prepared in Example 4.

[0107] Comparative Example 1: Untreated substrate (Bare glass)

[0108] Bare glass was used.

[0110] Comparative Example 2: Preparation of a water-based hydrophobic laminate having a columnar pattern and a spot pattern

[0111] A water-based hydrophobic laminate not containing benzophenone and hydrogel was prepared in the same manner as in Example 1, except that the PDMS mixture prepared in Preparation Example 1 was poured into a PDMS mold having a cylindrical and spot-shaped pattern prepared in Preparation Example 4, and then hydrogel inkjet printing was performed.

[0113] Comparative Example 3: Preparation of a water-based hydrophobic laminate containing a hydrogel in a pillar-shaped pattern

[0114] A water-based hydrophobic laminate containing benzophenone and hydrogel in a cylindrical pattern was prepared in the same manner as in Example 1, except that the PDMS elastomer mixture prepared in Example 2 was poured into the PDMS mold having a cylindrical pattern prepared in Example 3.

[0116] Device Example 1: Manufacturing of a device having a water-based hydrophobic composite laminate

[0117] A device having a hydrophobic pattern layer containing a cylindrical pattern and a spot containing a hydrogel was manufactured by attaching the laminate prepared in Example 1 to a glass substrate.

[0119] Device Comparative Example 1: Manufacturing of a device having a water-based hydrophobic composite laminate

[0120] A device having a hydrophobic pattern layer not containing hydrogel was manufactured by attaching a laminate having a pillar pattern and a spot pattern prepared in Comparative Example 2 to a glass substrate.

[0122] [Test Example]

[0124] Test Example 1: Analysis of Anti-fogging Performance

[0125] For the anti-fogging experiment, a glass substrate was placed in a -20 ℃ freezer for 1 hour, then transferred to ambient laboratory conditions (25 ℃, 22% RH), and a fogging analysis was performed by filming for 10 seconds.

[0126] FIG. 4 is a schematic diagram showing the hydrophobic characteristics of the water-based hydrophobic composite laminate of the present invention with respect to water droplets. Referring to FIG. 4, when fogging occurs due to the condensation of water particles caused by the atmosphere and external conditions, it operates as follows. A hydrophobic elastomer protrusion pattern layer (200) imparts hydrophobic characteristics to water droplets, and a spot pattern (310) containing a hydrogel located between the protrusions provides a path for water molecules to condense preferentially, thereby preventing fogging.

[0127] FIG. 5 is an optical photograph showing the anti-fogging performance of a laminate according to Device Comparative Example 1 and Device Example 1, where the scale bar represents 100 μm. Referring to FIG. 5, it was confirmed that water droplets formed over the entire substrate in Device Comparative Example 1, whereas in the substrate according to Device Example 1, the water droplets were absorbed into the hydrogel and remained transparent.

[0128] In addition, the substrate according to device Comparative Example 1 formed extensive fog due to the formation of discontinuous hemispherical droplets on the surface, whereas, conversely, the laminate according to device Example 1 prevented the formation of fog and remained optically transparent throughout the experiment.

[0129] It was found that the hydrophilic polymer layer acts as a hydrophilic reservoir, absorbing water and minimizing fog formation.

[0131] Test Example 2: Transmittance Analysis

[0132] FIG. 6 is a graph showing the transmission spectra of the laminates according to Device Comparative Example 1, Device Example 1, and Comparative Example 1. The transmission spectra were measured using a spectrophotometer (UV-1800, Shimadzu) at 50 nm sec⁻¹. -1 It was measured at the scanning speed of.

[0133] Referring to Fig. 6, it was confirmed that while the transmittance of Comparative Example 1 and Comparative Example 1 decreased to 41% and 64%, respectively, the transmittance of Example 1 maintained a high transmittance of up to 76% in the visible light region (400 nm ≤ λ ≤ 700 nm).

[0135] Test Example 3: Contact Angle Analysis

[0136] Figure 7 is an image comparing the contact between a water droplet and a hydrogel of Preparation Example 3, Comparative Example 3, and Example 1 according to the present invention, with a scale bar of 1 mm. The contact angle was measured using goniometry (SmartDrop, FemtoBiomed Inc.).

[0137] Referring to FIG. 7, the laminate having only a cylindrical pattern of Preparation Example 3 has low surface energy (19-21 mJ m⁻¹). -2 It was confirmed that in Comparative Example 3, water droplets remained on the micropillars, exhibiting only hydrophobic characteristics and showing a contact angle of 167±2°, whereas when a hydrogel was injected between the micropillars, the water droplets came into contact with the hydrogel, resulting in a contact angle of 124±1°. However, in Example 1, the contact angle was 167±1°, confirming that the hydrogel between the spots played an effective role in absorbing water vapor without affecting the contact angle.

[0139] Test Example 4: Adhesion Strength Analysis

[0140] Adhesive strength is 1 cm using a Universal Test Machine (COMETECH). 2 The same pressure of 2N was applied to a sample of the area and measured.

[0141] FIG. 8 is a schematic diagram of an adhesion tester of device Example 1, FIG. 9a is a graph showing the adhesion strength by applying the laminate of Example 1 to various substrates, and FIG. 9b is a graph showing the adhesion strength of device Example 1.

[0142] Referring to Fig. 9a, it was confirmed that the laminate of Example 1 is effectively attached to various transparent substrates such as glass, polystyrene (PS), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), and polycarbonate (PC) without using additional adhesive.

[0143] In addition, referring to FIG. 9b, it was confirmed that an adhesion strength test was conducted by attaching the water-based hydrophobic composite laminate of the present invention to a glass substrate and attaching and detaching it 100 times, and that it exhibited an adhesion strength of 10 ± 1 kPa.

[0145] Test Example 4: Analysis of Hydrogel Adhesion Stability

[0146] Figure 10 is a schematic diagram showing the adhesion mechanism by benzophenone between PDMS and a hydrogel pattern. Referring to Figure 10, it can be seen that benzophenone generates reactive radicals essential for covalently bonding hydrogen atoms in the C-H bonds within the PDMS chains with the hydrogel upon UV irradiation, thereby achieving strong adhesion.

[0147] FIG. 11 is a schematic diagram of a hydrogel stability test to evaluate adhesive properties by immersing the aqueous hydrophobic laminate of the present invention in water. The experiment confirmed the adhesive stability of the hydrogel by immersing the laminate in water for 24 hours.

[0148] Figure 12 is an optical photograph of the PDMS and hydrogel of Example 1 and Example 2, and the scale bar represents 100 μm.

[0149] Referring to Figures 11 and 12, in Example 2 without benzophenone treatment, the PDMS and hydrogel were separated and air pockets within the micropores were observed, whereas in Example 1 with benzophenone treatment, the PDMS and hydrogel remained attached.

[0150] Figure 13 is an optical photograph showing the uniaxial tensile load test of Example 1 before and after, and the scale bar represents 1 μm. The experiment was conducted by performing a uniaxial tensile test with 25 repeated cycles at 50% length deformation.

[0151] Referring to Fig. 13, it was confirmed that there was no change before and after the application of a uniaxial tensile load, thus possessing mechanical durability.

[0152] Figure 14 is a graph showing the advancing (θadv) and receding (θrec) contact angles of water after the uniaxial tensile load test of Example 1, with a standard deviation of 3.

[0153] Referring to Fig. 14, after 25 repeated uniaxial tensile load tests with 50% length deformation, the water's adv (θadv) and retract (θrec) contact angles were 176 ± 3° and 157 ± 2°, respectively, and it was confirmed that there was no change before and after the application of uniaxial tensile load, thus having mechanical durability.

[0155] Test Example 5: Analysis of Self-Cleaning Characteristics

[0156] FIG. 15 is an optical photograph of a contaminant (sand, 30-50 mesh) attached to the surface of a laminate according to Example 1 before and after removal with a water droplet, the scale bar is 1 cm, and the red dashed line indicates the path through which the water droplet passes.

[0157] To verify the self-cleaning properties, sand (30-50 mesh) was dispersed on the surface of the laminate according to Example 1 at a 15° angle, and water droplets were sprayed on the top of the laminate.

[0158] Referring to Fig. 15, experimental results confirmed that when a water droplet rolls off from the laminate, it carries sand along with it.

[0159] Therefore, it was found that the water-based hydrophobic composite laminate according to the present invention can easily remove surface contamination and is capable of self-cleaning.

[0161] Test Example 6: Characterization of Image Sensors

[0162] For the sensor, we used a product called Pixy2, an image recognition sensor. This product is a sensor that recognizes the color of an image, and it recognizes the corresponding color when color information is input.

[0163] FIG. 16a is an optical photograph of an image sensor according to Device Example 1, FIG. 16b is an optical photograph showing the self-cleaning characteristics of an image sensor according to Device Example 1, and FIG. 16c is an optical photograph showing the anti-fogging characteristics of image sensors according to Device Example 1 and Device Comparative Example 1. The scale bar is 1 cm. The anti-fogging characteristics were tested by contacting the image sensors according to Device Example 1 and Device Comparative Example 1 with a Peltier plate (-20°C) for 1 minute, respectively, and then exposing them to ambient conditions of a temperature of 25°C and a relative humidity of 22% RH for 10 seconds. Additionally, the image sensors were set to return a value of s = 1 or s = 2 when recognizing red and yellow, respectively.

[0164] According to FIGS. 16a to 16c, the image sensor with device Example 1 attached, which has surface contamination, initially could not distinguish colors. However, after the contaminated surface was rinsed with water droplets to self-clean the surface contamination, it clearly distinguished colors. In addition, when comparing the image sensors according to device Example 1 and device Comparative Example 1 under fogging conditions exposed by switching to ambient conditions (23.1 ℃, 23.2% RH) in a -10 ℃ freezer, the image sensor according to device Example 1 clearly recognized colors, whereas the image sensor according to device Comparative Example 1 showed errors due to blurring caused by fogging.

[0166] Accordingly, the aqueous hydrophobic composite laminate according to the present invention demonstrates excellent optical properties under various environmental conditions.

[0168] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Explanation of the symbols delete

Claims

Claim 1 A flexible water-based hydrophobic composite comprising: a polymer elastomer layer (100) including a polymer elastomer; a hydrophobic elastomer protrusion pattern layer (200) formed on the polymer elastomer layer and having a first pattern including protrusions (210), wherein the protrusions include a hydrophobic polymer elastomer; a hydrogel spot pattern layer (300) formed on the polymer elastomer layer (100) and having a second pattern including spots (310) located between the protrusions, wherein the spots include a hydrogel; wherein the polymer elastomer layer (100) has a concave hole (110) formed between adjacent protrusions (210), wherein the spots (310) are formed inside the concave hole (110), the upper cross-section of the spots (310) is exposed to the outside, and the upper cross-section of the protrusions (210) is positioned higher than the upper cross-section of the spots (310). A laminate (10). Claim 2 In claim 1, the polymer elastomer is polydimethylsiloxane (PDMS), Ecoflex, silicone rubber, fluoro silicone rubber, vinyl methyl silicone rubber, styrene-butadiene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer, styrene-butadiene rubber (SBR), butadiene rubber (BR), isobutylene-isoprene rubber (IIR), ethylene propylene rubber (EPR), ethylene propylene diene monomer rubber (EPDM), A water-based hydrophobic composite laminate comprising one or more selected from the group consisting of isoprene rubber (IR), isobutylene rubber (IR), acryl rubber, acrylonitrile-butadiene rubber (ABR), polyurethane, polyether urethane, polyester urethane, epichlorohydrin rubber, and polychloroprene rubber. Claim 3 In claim 1, the hydrophobic polymer elastomer is each polydimethylsiloxane (PDMS), ecoflex, silicone rubber, fluoro silicone rubber, vinyl methyl silicone rubber, styrene-butadiene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-isoprene-styrene (SIS) block copolymer, styrene-butadiene rubber (SBR), butadiene rubber (BR), isobutylene-isoprene rubber (IIR), ethylene propylene rubber (EPR), ethylene propylene diene monomer rubber (EPDM), A water-based hydrophobic composite laminate comprising one or more selected from the group consisting of isoprene rubber (IR) and isobutylene rubber (IR). Claim 4 A water-based hydrophobic composite laminate according to claim 1, characterized in that the protrusion (210) comprises one or more types selected from the group consisting of a cylinder, an elliptical prism, a rhombic prism, a polygonal prism, a cone, an elliptical cone, a rhombic pyramid, and a polygonal pyramid. Claim 5 A water-based hydrophobic composite laminate according to claim 1, characterized in that the first pattern and the second pattern each have a grid shape, and the spot (310) each is adjacent to four of the protrusions. Claim 6 delete Claim 7 delete Claim 8 In claim 1, the hydrogel is Poly(ethylene glycol) diacrylate (PEGDA), Poly-hydroxyethyl methacrylate (PHEMA), Tetraethylene glycol dimethacrylate, Poly(ethylene glycol) dimethacrylate, Poly(Guluronate), PCL-PEG-PCL diacrylate, chitosan (CHI), polyallylamine-polyethylene oxide copolymer (poly(allylamine)-co-poly(ethylene oxide) copolymer, PAH-g-PEG), polyL-lysine-polyethylene oxide copolymer (poly(L-lysine)-co-(polyethylene oxide), PLL-g-PEG), polyquaternized-4-vinylpyridine-polyethylene oxide copolymer (poly(quaternized-4-vinylpyridine)-co-poly(ethylene oxide), QPVP-co-PEG), polydiallyldimethylammonium chloride-polyethylene oxide copolymer (poly(diallyldimethylammonium poly(allylamine)-co-poly(ethylene oxide), PDADMA-co-PEG), poly(allylamine)-co-polyacrylamide copolymer (PAH-co-PAAM), poly(L-lysine)-co-polyacrylamide copolymer (PLL-co-PAAM), polyquaternized-4-vinylpyridine-polyacrylamide copolymer (QPVP-co-PAAM), poly(diallyldimethylammonium chloride)-co-polyacrylamide copolymer (PDADMA-co-PAAM),Carboxymethyl cellulose (CMC), alginic acid (AA), hyaluronic acid (HA), heparin, pectin, poly(acrylic acid)-co-poly(ethylene oxide) copolymer (PAA-co-PEG), polymethacrylic acid-polyethylene oxide copolymer (PMAA-co-PEG), poly(acrylic acid)-co-polyacrylamide copolymer (PAA-co-PAAM), polymethacrylic acid-co-polyacrylamide copolymer (PMAA-co-PAAM), Iota-carrageenan, Kappa-carrageenan, Lambda-carrageenan, A water-based hydrophobic composite laminate characterized by comprising one or more selected from the group consisting of fucoidan, fucogalactan, chondroitin, gellan gum, gum karaya, gum tragacanth, welan gum, xanthan gum, and psyllium seed gum. Claim 9 A water-based hydrophobic composite laminate according to claim 1, characterized in that the carbon atoms of the hydrogel on the surface of the hydrogel spot pattern layer and the carbon atoms of the polymer elastomer on the surface of the polymer elastomer layer are covalently bonded to each other. Claim 10 A water-based hydrophobic composite laminate according to claim 1, characterized in that the water-based hydrophobic composite laminate (10) further includes an adhesive layer (400) on the polymer elastomer layer (100) in a direction opposite to the direction facing the hydrophobic elastomer protrusion pattern layer (200). Claim 11 A water-based hydrophobic composite laminate according to claim 10, wherein the adhesive layer (400) comprises a polysiloxane compound prepared by reacting a dimethylsiloxane oligomer having a plurality of vinyl groups at the chain ends with a siloxane oligomer curing agent having hydrogen atoms bonded to silicon atoms within the chain. Claim 12 A water-based hydrophobic composite laminate according to claim 11, characterized in that, as in Reaction Formula 1, the dimethylsiloxane oligomer is a compound represented by Structural Formula 1 below, the siloxane oligomer curing agent is a compound represented by Structural Formula 2 below, and the polysiloxane compound is a polysiloxane compound of Structural Formula 3 produced by the reaction of the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2. [Reaction Formula 1] In the above reaction equation, m is any one of integers from 10 to 500, n1 is any one of integers from 1 to 100, and n2 is any one of integers from 2 to 50. Claim 13 A water-based hydrophobic composite laminate according to claim 12, characterized in that the adhesive strength of the adhesive layer is controlled by adjusting the weight ratio of the dimethylsiloxane oligomer and the siloxane oligomer curing agent of the polysiloxane compound of structural formula 3. Claim 14 An electronic device comprising any one selected from the group consisting of an optical sensor, an image sensor, a sensor for an autonomous vehicle, and a medical endoscope, comprising a water-based hydrophobic composite laminate according to claim 1. Claim 15 (a) a step of injecting a mixture containing a precursor of a hydrophobic polymer elastomer into a mold having a pattern formed therein and curing it to produce a polymer elastomer layer (100) containing a polymer elastomer and a hydrophobic elastomer protrusion pattern layer (200) formed on the polymer elastomer layer and having a first pattern including a protrusion (210), wherein the protrusion includes a hydrophobic polymer elastomer; and (b) forming a hydrogel spot pattern layer (300) on the polymer elastomer layer (100), the second pattern comprising a spot (310) located between the protrusions, wherein the spot comprises a hydrogel; wherein the polymer elastomer layer (100) has a concave hole (110) formed between adjacent protrusions (210), the spot (310) is formed inside the concave hole (110), the upper cross-section of the spot (310) is exposed to the outside, and the upper cross-section of the protrusion (210) is located higher than the upper cross-section of the spot (310). A method for manufacturing a water-based hydrophobic composite laminate. Claim 16 A method for manufacturing a water-based hydrophobic composite laminate, characterized in that, in claim 15, the above mixture further comprises benzophenone. Claim 17 A method for manufacturing a water-based hydrophobic composite laminate according to claim 16, characterized in that the mixture contains 1 to 3 weight % of the benzophenone. Claim 18 A method for manufacturing a water-based hydrophobic composite laminate, characterized in that, in claim 15, step (b) is performed by inkjet printing. Claim 19 A method for manufacturing a water-based hydrophobic composite laminate according to claim 15, wherein the method for manufacturing the water-based hydrophobic composite laminate further comprises, after step (b), (c) a step of irradiating the hydrogel spot pattern layer with light to covalently bond the carbon atoms of the hydrogel on the surface of the hydrogel spot pattern layer with the carbon atoms of the polymer elastomer on the surface of the polymer elastomer layer. Claim 20 In claim 15, the method for manufacturing a water-based hydrophobic composite laminate is characterized by additionally forming an adhesive layer (400) on the polymer elastomer layer (100) of the result of step (a) or step (b) in a direction opposite to the direction facing the hydrophobic elastomer protrusion pattern layer (200) after step (a) or step (b) (c).

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