KR101465215B1 - Transparent stretchable film for optical-touch-sensor, and preparing method thereof - Google Patents

Abstract

The present invention relates to a film for an optical-touch-sensor and a method for manufacturing the same. The film includes a complex including carbon nanotubes dispersed in a polymer matrix, and is transparent and stretchable. The carbon nanotubes include a single wall carbon nanotubes or multi-wall carbon nanotubes. The polymer includes an insulation polymer or a conductive polymer. The carbon nanotube includes a nitrile functional group, and thus induces reduction of fluorescence.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent stretchable optical touch sensor film,

The present invention relates to a film for an optical touch sensor including a composite including carbon nanotubes dispersed in a polymer matrix and having transparency and stretchability, and a method for producing the film for optical touch sensor.

Flexible or stretchable electronic devices have received considerable attention, and the most common approach is the combination of electrical components with an elastomer. However, it has potential problems in wiring such devices with external rigid components due to strain mismatches in the electrical interconnect. An alternative method is optical signal conversion, especially for sensor applications, without any physical contact with flexible or stretchable devices. Single-walled carbon nanotubes (SWNTs) have superior Raman scattering and near-infrared (nIR) band-gap fluorescence properties. Optical Stability of Single Walled Carbon Nanotubes Optical signals have been actively studied to monitor biological, chemical, and physical environments. The nIR signal has also been used for short range wireless communications.

Korean Patent Laid-Open No. 10-2008-0107688 discloses a method for producing a conductive film for a transparent display comprising carbon nanotubes, but does not include a functional polymer.

Accordingly, the present invention provides a film for an optical touch sensor including a composite including carbon nanotubes dispersed in a polymer matrix and having transparency and stretchability, and a method for producing the film for an optical touch sensor.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

One aspect of the present invention provides a film for an optical touch sensor including a composite including carbon nanotubes dispersed in a polymer matrix, and having transparency and stretchability.

Another aspect of the present invention provides a method of manufacturing a film for an optical touch sensor, which comprises curing a mixed solution containing a carbon nanotube dispersion solution, a polymer, and an ionic liquid to obtain a composite containing carbon nanotubes do.

According to one embodiment of the present invention, the present invention provides a film for an optical touch sensor, which comprises a composite including carbon nanotubes dispersed in a polymer matrix, has transparency and stretchability, The transparent stretchable single-walled carbon nanotube-polymer complex that emits near-infrared fluorescence can enable the paradigm change of the touch-sensing device.

1A is a schematic diagram showing a film synthesis process according to one embodiment of the present invention.
1B is a cross-sectional view of a single-walled carbon nanotubes-polydimethylsiloxane (SWNT-PDMS) and a single-walled carbon nanotubes-poly (SWNT-PVDF-HFP) film according to an embodiment of the present invention FIG.
1C is a graph showing Raman and nIR fluorescence spectra of SWNT dispersions, SWNT-PDMS, and SWNT-PVDF-HFP films, according to one embodiment of the present application.
1D is a photograph showing the results of a stretch test of SWNT-PDMS and SWNT-PVDF-HFP films according to one embodiment of the present invention.
2A is a schematic view of carbon nanotubes wrapped with ethyl cellulose (EC) according to one embodiment of the present invention.
Figures 2b and 2c are fluorescence intensity absorption spectra and contour plots of SWNTs dispersed by ethylcellulose in 4-methyl-2-pentanone, according to one embodiment of the invention.
FIGS. 3a-3d are graphs showing the results of a comparison of the fluorescence spectra of 532 nm (2.33 eV), 640 nm (1.94 eV), 683 nm 1.82 eV) and a Lorentzian fitting of the fluorescence spectrum at an excitation of 786 nm (1.58 eV).
Figure 3e is an image showing the relative amount of the corresponding (n, m) chiral index according to line thickness, according to one embodiment of the invention.
4A and 4B are graphs showing the nIR fluorescence peak and the Raman peak of a SWNT-PDMS film and a SWNT-PVDF-HFP film as a function of carbon nanotube concentration, according to one embodiment of the present invention.
5A-5D illustrate the fluorescence spectra of SWNT dispersions, SWNT-PDMS, and SWNT-PVDF-HFP films at excitation energies of 2.33 eV, 1.94 eV, 1.82 eV, and 1.58 eV, Graph.
5E and 5F are graphs showing optical frequencies according to chiral angles of mode 1 and mode 2, according to one embodiment of the present invention.
6A and 6B are contour plots according to the fluorescence intensities of the SWNT-PDMS film and the SWNT-PVDF-HFP film, according to one embodiment of the present invention.
7A and 7B are graphs showing raw optical signals of SWNT-PDMS films and SWNT-PVDF-HFP films according to a strain function at an excitation wavelength of 785 nm, according to one embodiment of the present invention.
7C is a graph showing fluorescence intensities according to each tube in an SWNT-PDMS film, according to one embodiment of the present invention.
7D is a graph showing the G-mode normalized spectrum of the SWNT-PVDF-HFP film at each temperature, according to one embodiment of the present invention.
8 is a graph showing excellent stretch (stretch) cyclability of a SWNT-PDMS film according to one embodiment of the present invention.
Figure 9 is a graph showing the G-mode normalized spectrum of a SWNT-PDMS film as a function of temperature, according to one embodiment of the invention.
10A is a photograph showing an experimental measurement apparatus used in one embodiment of the present invention.
Figures 10b and 10c show the fluorescence peaks at 0% and 100% strain (elongation) of the SWNT-PVDF-HFP film when repeatedly touched with stainless steel, according to one embodiment of the present invention. Graph.
Figures 10D and 10E are graphs showing fluorescence peaks of 0% strain of SWNT-PVDF-HFP film when repeated untouched, touched with polystyrene and nitrile gloves, according to one embodiment of the present invention.
FIG. 10F is a photograph showing an area diagram of the integrated fluorescence intensity of the carbon nanotube according to one embodiment of the present invention. FIG.
11 is a graph showing the fluorescence peak of a 0% strain of SWNT-PVDF-HFP film when touched with stainless steel, according to one embodiment of the present invention.
12 is an XPS wide scan graph of a polystyrene rod comprising C, O, N, and Si elements, according to one embodiment of the invention.
13 is an FTIR graph of a polystyrene rod, according to one embodiment of the present application.
14A and 14B are graphs showing modulation in nIR fluorescence of a touch responsive SWNT-PDMS film, according to one embodiment of the present invention.
15A and 15B are XPS wide scan graphs and FTIR graphs of nitrile gloves comprising C and N elements, according to one embodiment of the invention.
16 is a function graph of a touch cycle showing the standardized integrated area of fluorescent peaks of carbon nanotubes, according to one embodiment of the present application.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is "on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms "about "," substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

The word " step (or step) "or" step "used to the extent that it is used throughout the specification does not mean" step for.

Throughout this specification, the term "combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Hereinafter, embodiments of the present invention are described in detail, but the present invention is not limited thereto.

The first aspect of the present invention provides a film for an optical touch sensor including a composite including carbon nanotubes dispersed in a polymer matrix, and having transparency and stretchability.

In one embodiment of the present invention, the carbon nanotubes may include single wall carbon nanotubes or multi wall carbon nanotubes, but the present invention is not limited thereto.

In one embodiment of the present invention, the polymer may include, but is not limited to, an insulating polymer or a conductive polymer.

For example, the insulating polymer may include polydimethylsiloxane (PDMS), poly-4-vinylphenol (PVP), polyimide (PI), polystyrene (PS) Polyvinylidene difluoride (PVDF), poly (styrene-butadiene-styrene), SBS, and combinations thereof. However, But may not be limited thereto.

For example, the conductive polymer may be selected from the group consisting of polypyrrole, polyaniline, polythiophene, poly (3,4-ethylenedioxythiophene), poly (3,4-alkylenedioxythiophene) But are not limited to, those selected from the group consisting of poly (3,4-dialkoxythiophene), poly (3,4-dialkoxythiophene), poly (3,4-cycloalkylthiophene) .

In one embodiment of the invention, the carbon nanotubes may include, but are not limited to, a decrease in fluorescence by including a nitrile functional group.

In one embodiment of the invention, the film may be, but not limited to, emitting fluorescence. The film may generate near-infrared fluorescence signals at an elongation of about 600% or less, but may not be limited thereto. For example, the film may be one that generates a near-infrared fluorescence signal at an elongation of about 100%, about 200%, about 300%, about 400%, about 500%, or about 600% But may not be limited.

In one embodiment of the invention, the fluorescence emission may be reduced if the film is touched by an insulator, but the present invention is not limited thereto. For example, the insulator may include, but is not limited to, a polystyrene rod.

Another aspect of the present invention provides a method of manufacturing an optical touch sensor film, which comprises curing a mixed solution containing a carbon nanotube dispersion solution, a polymer, and an ionic liquid to obtain a composite containing carbon nanotubes do.

In one embodiment of the present invention, the carbon nanotube dispersion solution may include, but not limited to, an organic solvent containing a ketone group (> C = O). The ketone group-containing organic solvent may be an aliphatic or aromatic organic solvent containing a ketone group, for example, 4-methyl-2-pentanone, 1,3-dimethyl-2-imidazolidinone Dimethyl-2-imidazolidinone (DMI), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), dimethylformamide (DMF), tetramethylsulfone, (N-methyl-2-pyrrolidone, NMP), acetone, Methyl ethyl ketone, Methyl butyl ketone, MBK, Methyl isobutyl ketone And combinations thereof. The term " a "

In one embodiment of the present invention, the polymer may include, but is not limited to, an insulating polymer or a conductive polymer.

For example, the insulating polymer may include polydimethylsiloxane (PDMS), poly-4-vinylphenol (PVP), polyimide (PI), polystyrene (PS) Polyvinylidene difluoride (PVDF), poly (styrene-butadiene-styrene), SBS, and combinations thereof. However, But may not be limited thereto.

For example, the conductive polymer may be selected from the group consisting of polypyrrole, polyaniline, polythiophene, poly (3,4-ethylenedioxythiophene), poly (3,4-alkylenedioxythiophene) But are not limited to, those selected from the group consisting of poly (3,4-dialkoxythiophene), poly (3,4-dialkoxythiophene), poly (3,4-cycloalkylthiophene) .

In one embodiment of the invention, the ionic liquid is selected from the group consisting of 1-butyl-4-methylpyridinium tetrafluoroborate, 1-ethyl-3-methylimidazolium methyl sulfate, Butyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium ethylsulfate, 3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazoliumbis (trifluoromethylsulfonyl) imide, 3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, and combinations thereof, but is not limited thereto.

In one embodiment of the present invention, the ionic liquid may be contained in the mixed solution in an amount of about 50% by weight to about 100% by weight based on about 100% by weight of the polymer, but may not be limited thereto. For example, for about 100 weight percent of the polymer, the ionic liquid may comprise from about 50 weight percent to about 100 weight percent, from about 50 weight percent to about 90 weight percent, from about 50 weight percent to about 80 weight percent, From about 50 weight percent to about 60 weight percent, from about 60 weight percent to about 100 weight percent, from about 70 weight percent to about 100 weight percent, from about 80 weight percent to about 100 weight percent, or from about 70 weight percent to about 100 weight percent, From about 90% by weight to about 100% by weight, but may not be limited thereto.

In one embodiment of the invention, the curing may be performed at a temperature of about 100 < 0 > C or less, but is not limited thereto. For example, the cure may be performed at a temperature of from about 0 캜 to about 100 캜, from about 0 캜 to about 80 캜, from about 0 캜 to about 60 캜, from about 0 캜 to about 40 캜, From about 10 C to about 100 C, from about 20 C to about 100 C, from about 40 C to about 100 C, from about 60 C to about 100 C, or from about 80 C to about 100 C But may not be limited thereto.

In one embodiment of the present invention, the carbon nanotubes may be contained in an amount of about 0.02% by weight or less based on the total weight% of the film for an optical touch sensor, but the present invention is not limited thereto. For example, the single-walled carbon nanotube may be contained in an amount of about 0.01% by weight or less, or about 0.02% by weight or less based on the total weight% of the film for an optical touch sensor, but the present invention is not limited thereto.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are given for the purpose of helping understanding of the present invention, but the present invention is not limited to the following Examples.

[ Example ]

< SWNT - Synthesis of polymer composite film &gt;

Raw materials HiPco single wall carbon nanotubes (Rice University, 2 mg) were dissolved in 4-methyl-2-pentanone (Sigma Aldrich, 293261, 20 mL) in which EC (Sigma Aldrich, 200697, 0.625-2.5 wt% Using a tip ultrasonic mill (SONIC 7003, 480 W, 10 minutes). The nanotube dispersion was centrifuged at 10,000 rpm (Eppendorf microcentrifuge 5415 D) for 1 hour and the supernatant was used for further experiments. Two different polymers were used: PDMS (Sewang Hitech Silicone, Sylgard Elastomer 184A: 184B = 10: 1 by volume, 1 ml) and PVDF-HFP (Sigma Aldrich, 427160, 0.25 g). Ionic liquid (1-butyl-4-methylpyridinium tetrafluoroborate, Sigma Aldrich, 73261), which improves the dispersibility of single-wall carbon nanotubes and the conductivity of the composites, is additionally mixed with PVDF-HFP at a weight ratio of 0.96: 1 Mixed. In the next step, the nanotube dispersion was mixed with the polymer solution using a homogenizer (TAITEC VP55). Finally, a SWNT-PVDF-HFP composite film was prepared by casting and drying at room temperature overnight. SWNT-PDMS films were synthesized by casting and curing at 60 ° C for 2-3 hours. The nanotube concentration in the composites ranged between 0.0013 wt% and 0.014 wt%.

<Characteristic Analysis>

The transmittance was measured accurately using a UV-vis-nIR spectrophotometer (Shimadzu, UV3600, 300-1,600 nm). Fluorescence was characterized using a fluorescence analyzer (Applied NanoFluorescence, NS-2 nanospectrum laser), first fitted to 2.33 eV, 1.94 eV, 1.81 eV, and 1.58 eV. Two-dimensional contour plots of fluorescence intensity were made with ANF software. The area map of Raman, nIR fluorescence and integrated fluorescence intensity was further analyzed using a Kaiser optical Raman spectrometer (RXN1) at an excitation wavelength of 785 nm. Composite films were stretched using self-contained devices. Temperature dependent fluorescence modulation of SWNTs was investigated using a hot plate. Contact experiments of SWNT-polymer films with stainless steel (or polystyrene) rods were conducted using mechanical strain steps. The conductivity of the film was measured using the four-probe method.

This report describes a transparent stretchable single-walled carbon nanotube-polymer complex that emits excellent Raman and near-infrared fluorescence with fine spatial resolution. The nanotubes wrapped by ethyl cellulose (EC) could be stably dispersed in the stretch polymer matrix up to 600% elongation. Independent adjustments in Raman and fluorescence spectra have been demonstrated to respond to touch and temperature. The optical signal conversion of the transparent stretchable optoelectronic film can enable the change of the paradigm of the touch-sensing device by eliminating the electrical interconnect.

1A is a schematic view of a process of synthesizing a transparent stretchable single-walled carbon nanotube-polymer composite film. First, single wall carbon nanotubes (SWNTs) synthesized by high pressure CO disproportionation (HiPco) process were dispersed by nonionic EC in 4-methyl-2-pentanone using ultrasonic treatment. Successful dispersion of single wall carbon nanotubes in a rigid polymer matrix has been previously reported [RA Graff, JP Swanson, PW Barone, S. Baik, DA Heller, MS Strano, Adv . Mater . 2005, 17,980; TK Leeuw, DA Tsyboulski, PN Nikolaev, SM Bachilo, S. Arepalli, RB Weisman, Nano Lett . 2008 , 8 , 826.]. Here, the present inventors have achieved stable dispersion of single-walled carbon nanotubes in an elastic polymer matrix using EC. The side chain (side chain) of the EC contains an ethoxy group (OC ₂ H ₅ , 48 wt%) and a hydroxyl group (OH, 52 wt%) (Fig. Bulky ethoxy groups give steric hindrance to the dispersion of nanotubes. When the ketone group (> C = O) of the aprotic solvent (4-methyl-2-pentanone) is introduced, intermolecular hydrogen bonding between the hydroxyl groups is broken due to stronger polar interaction. This reduces the polymeric rigidity of the hydrophobic backbone of the EC, which is advantageous for wrapping around the single-walled carbon nanotubes in a helical manner. The mass fraction of EC was optimized (1.875 wt%) to provide the maximum absorbance. (UV-vis-nIR absorption spectrum of dispersed single-walled carbon nanotubes is shown in Figure 2b). The dispersion of single walled carbon nanotubes in 4-methyl-2-pentanone was stable for 6 months. A two-dimensional contour plot of the fluorescence intensity from the semiconducting tube is shown in Figure 2c. Numerous peaks are characteristic and indicate effective dispersion of single walled carbon nanotubes by EC in aprotic solvents. Aggregates of carbon nanotubes reduce band-gap fluorescence due to orthogonal dispersion in the electronic structure and transmission of non-emissive exciton energy to smaller or 0 band-gap tubes. The Lorentzian-fitting of the fluorescence spectrum is provided in Figures 3a-3e, which show abundant adjacent armchair species. In the next step, the supernatant of the dispersed single-walled carbon nanotubes after centrifugation was mixed with a solution of poly (vinylidene fluoride-CO-hexafluoropropylene) (PVDF-HFP) or polydimethylsiloxane (PDMS). Ionic liquid (1-butyl-4-methylpyridinium tetrafluoroborate) was added to PVDF-HFP to improve the ionic conductivity and dispersibility of the nanotubes. Finally, the transparent stretchable film was prepared by solution casting and curing (room temperature or 60 ° C). The PDMS film was electrically insulative and the PVDF-HFP film was lightly conductive (4.96 mS / cm).

Figure 1B shows the transmission spectra of SWNT-PDMS and SWNT-PVDF-HFP films. The transmittance was high (82% for SWNT-PDMS, 90% for 550 nm SWNT-PVDF-HFP film) and the value increased with increasing wavelength. The high transparency in the nIR region allows deep penetration of nanotube nIR fluorescence through the composite film. 1C shows the Raman and nIR fluorescence spectra of single-walled carbon nanotube dispersions, SWNT-PDMS and SWNT-PVDF-HFP films at an excitation wavelength of 785 nm. The spectrum was normalized by G-mode at 1,592 cm ^{& lt; &} quot ^{; 1 &} gt ;, and the radial breathing mode was extended to the degree of insertion. The concentration of nanotubes was optimized to maximize fluorescence above G-mode intensity (0.0027 wt.% For SWNT-PDMS and 0.011 wt.% For SWNT-PVDF-HFP) (Figs. 4A-B). The composite film showed pronounced fluorescence emission, but its intensity was reduced compared to the intensity of the nanotubes dispersed in the solution. The intensity of the peak at 267 cm &lt;&quot; ¹ &gt; As the nanotubes agglomerate, the interband transition of the (10, 2) nanotube was resonated at a 785 nm excitation because of expansion and lower energy shifts. It is possible that the nanotubes are weakly aggregated in the polymer matrix but still emit fluorescence. Figures 5A-5F compare the fluorescence spectra at excitation of 2.33 eV, 1.94 eV, 1.82 eV, and 1.58 eV. In general, the mode specs of the film were slightly displaced to slightly lower energies, but the mod specs were displaced to higher energies. The change was observed before the compressive force acted on the nanotubes after polymer matrix curing. However, some peaks of the two mods were displaced to low energy (Figure 5f). The complexity can come from the combined effects of residual stress, cohesion and different dielectric constants of the polymer matrix. Significant fluorescence was confirmed by two-dimensional contour plots of SWNT-PDMS and SWNT-PVDF-HFP films (Figs. 6A-6B).

As shown in Fig. 1d, the composite film was stretched using a self-fabricating device (K.-Y. Chun, Y. Oh, J. Rho, J.-H. Ahn, Y.-J. Kim, H. R. Choi, S. Baik, Nat. Nanotechnol. 2010, 5, 853.]. The letter "SKKU" clearly appeared, indicating the transparency of the film. The transparency was maintained until the film was stretched to the burst point. The transmittance of nonconductive SWNT-PDMS films was 82% at 0% strain and 91% at 200% strain. The SWNT-PDMS film was elastic when there was a strain greater than 200% and had ruptured. SWNT-PVDF-HFP films were plastically deformed but could be stretched to 600%. The transmittance was 90% and 88.9% at 0% and 600% strain (elongation). Conductivity was maintained during the stretching test (4.96 mS / cm and 4.91 mS / cm at 0% and 600% strain), which represents a significant contribution of the ionic liquid. On the other hand, the nanotube penetration network was stopped at high strain, which reduced the conductivity.

As shown in Fig. 7A, with a 150% increase in strain, the G-mode and fluorescence intensity of the SWNT-PDMS films decreased. This is due to the reduced non-systematic variation in the G-mode normalized fluorescence spectrum, resulting in a decrease in nanotube concentration at the laser focusing point during stretching (Fig. 7a), a SWNT-PVDF-HFP film A similar tendency was observed (Fig. 7B). The elastic modulus of SWNTs is typically ~ 1.25 Tpa several times larger than PDMS (1-5 MPa) or PVDF-HFP (1 GPa) film. This indicates that most of the strain was generated in the composite matrix rather than SWNTs. The maximum strain (~ 5.8 ± 0.9%) of SWNTs at the reported burst point supports this analysis. The stretch cyclicity of SWNT-PDMS films is excellent, indicating excellent stability of EC-wrapped SWNTs in the polymer matrix (Fig. 7C). The fluorescence was first reduced and then restored when the film stretched and relaxed repeatedly between 0% and 100% strain. As shown in FIG. 8, when the strain was continuously increased and relaxed (0? 25? 0? 50? 0? 75? 0? 100? 0? 125? 0%), the fluorescence recovery was also good .

As shown in Figure 7d, the G-mode normalized fluorescence intensity of SWNT-PVDF-HFP films increased with increasing temperature due to thermally generated electron-hole pairs. Equation (1) below illustrates the increase in excitons (N _exc ) of intrinsic semiconductors with increasing temperature:

N _exc ^{= CT 3/2 exp (-E} g / 2kT) (1);

C is the material constant, T is the temperature, E _g Is the band-gap energy, and k is the Boltzmann constant. The increase in temperature results in thermal expansion of the nanotube leading to mode-dependent frequency displacement of the fluorescence. The energy (8,3) of the tube (mod 2) was down-shifted with increasing temperature while the fluorescence energy 6,5 of the nanotube (mod 1) was up-shifted . The same mode-dependent fluorescence displacement in terms of temperature was observed in the polymeric dispersive nanotubes previously described by equation (2) [D. Karaiskaj, C. Engtrakul, T. McDonald, MJ Heben, A. Mascarenhas, Phys . Rev. Lett . 2006 , 96 , 106805 .; L. Yang, J. Han, Phys . Rev. Lett . 2000 , 85 , 154.]:

? E _g = sign (2p + 1) 3t ₀ [(1 +?)? Cos (3?) +? Sin (3?)] (2);

ΔE _g is the displacement of the band-gap energy, p = -1 in mode (mod) 2, p = 1, t _{0 in} mode (mod) Is the carbon-carbon transfer integral,? Is the Poisson's ratio, and? Is the chiral angle of the nanotube. ? and? are the strain along the longitudinal axis and the circumference. The G-mode frequencies of the nanotubes were blue-shifted with increasing temperature (Fig. 7d). The phonon oscillation frequency decreases with increasing energy of the thermally extended CC coupling. Similar modulation in Raman and nIR fluorescence spectra was also observed in SWNT-PDMS films for temperature changes (Figure 9).

10A to 10F show the touch response of the SWNT-PVDF-HFP film. The experimental apparatus is shown in Fig. The film was attached to the bottom of the glass slide by gently pressing the SWNT-PVDF-HFP film against the glass slide. The size of the SWNT-PVDF-HFP film was 5 × 5 × 0.12 mm ³ . The film is touched by an electrically conductive stainless steel or nonconductive polystyrene rod using a mechanical moving stage. As shown in FIG. 10B, the fluorescence of the SWNT-PVDF-HFP film increased as the film was touched by a stainless steel rod at 0% strain. When the rod was separated from the film, the fluorescence again decreased. The standardized integrated area of the fluorescence peak (6, 5) of the nanotubes is shown as a function of the touch cycle in the degree of insertion, and its circulation is good. At room temperature (~ 25 ° C), both the film and the rod were already in thermal equilibrium. Thus, there was no frequency displacement in the G-mode of the nanotube during the touch cycle. Similar optical modulation was observed when the SWNT-PVDF-HFP film was touched by a stainless steel rod with the concentration of other tubes (0.014 wt%) (Fig. 11). The touch sensing performance of the composite film was not significantly altered by the different nanotube concentrations. A similar tendency was also observed when the SWNT-PVDF-HFP film was touched by a stainless steel rod at 100% strain (FIG. 10c). Electrons move from lower work function metals (stainless steel ~ 4.5 eV) to higher work function SWNTs (4.7-5 eV). Electrons injected into the conduction band improve fluorescence upon recombination.

Surprisingly, the fluorescence decreased when the SWNT-PVDF-HFP film was touched by an insulated polystyrene rod (Fig. 10d). The presence of electron-accepting nitrate and silicon oxide functional groups in polystyrene rods was identified in X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) (FIGS. 12 and 13). The chemical composition of the polystyrene rod was confirmed by using an XPS measuring device. Carbon peaks (C1s at 284.6 eV and 286.2 eV) were shown from polystyrene. The Zn and Ca peaks are from the catalyst used for the polymerization. Peaks of the electron acceptor functionalities introduced during the polymerization process could also be ascertained. O1s peaks related to Si-O-Si bonds (529.8 eV), Si-O bonds (531.85 eV) and nitric acid groups (533.59 eV) were observed. An Si2p peak was also identified from the N1s peak and the Si-O bond (102.1 eV) from the nitrate group (399.74 eV). FTIR data also confirmed electron acceptor nitric acid groups and silicon oxide functional groups. Peaks were observed from organic nitrate (1940 cm ^-1 , 1875 cm ^-1 , and 1,280 cm ^-1 ) and nitrate adsorbed on calcium carbonate (758 cm ^-1 ). Silicon oxide peak (884 cm ^- Si-OH bond, and 964 cm ^-1, 1084 cm ^-1, and 815 cm in ^{1 -} Si-O-Si bond in the ¹⁾ was also observed. The charge transfer from the SWNTs to the functional group that draws electrons reduces the nIR fluorescence of the SWNTs.

The presence of electron acceptor sites in polystyrene has also been found in previous contact-fill exchange experiments [CB Duke, TJ Fabish, Phys . Rev. Lett . 1976 , 37 , 1075; TJ Fabish, HM Saltsburg, ML Hair, J. Appl . Phys. 1976 , 47 , 930.]. Similar behavior was observed when the SWNT-PDMS films were touched by stainless steel or polystyrene rods (Fig. 14). This shows the modulation in the nIR fluorescence of a SWNT-PDMS film in response to a touch. Both film and rod were at room temperature (~ 25 ° C). When the SWNT-PDMS film was touched by a stainless steel or polystyrene rod, the fluorescence peak was systematically changed. However, there was no frequency shift in the G-mode of the nanotube. However, the modulation of the fluorescence was probably smaller than that of the SWNT-PVDF-HFP film due to the greater electrical resistance.

Figure 10E shows the reaction of a SWNT-PVDF-HFP film touched by a finger with a nitrile glove. The fluorescence of the film was reduced when touched by a nonconductive nitrile glove similar to a polystyrene rod touched reaction. XPS and FTIR assays confirmed the presence of electron acceptor nitrile functional groups that caused the reduction of nIR fluorescence of SWNTs (Figs. 15A-B). The chemical composition of the nitrile gloves was confirmed using an XPS measuring device. Peaks of the electron accepting nitrile group could be identified (N1s (398.8 eV) from CN of graphite structure and C1s (286.7 eV) from CN or C = N). The FTIR data showed a sharp nitrile peak at 2,235 cm &lt;& quot ^{; 1 &} gt ;. The fluorescence again increased when the finger with the nitrile glove was removed from the film. The frequency of the G-mode was blue-shifted because of the higher temperature of the finger (~ 37 ° C), as shown in the inset. There was a greater variation in the standardized fluorescence intensity due to the polymer and competing mechanism by elevated temperature (Figure 16). The nitrile functional group pulls electrons, but the elevated temperature creates thermally excited electron-hole pairs. Nonetheless, the fluorescence decreased upon touch, indicating that the effect of electron transfer to the glove is better than the thermally generated electron-hole pair. This indicates that the G-mode of the nanotube can be used to sense the temperature change and can be used to monitor the contact response so that fluorescence can be independently multimodal detection. The SWNT-PVDF-HFP film was touched by a Ni 80 / Cr 20 wire of ~ 300 μm diameter, and the domain diagram of the integrated fluorescence intensity of the nanotubes is shown in FIG. Each pixel size was 20 μm × 20 μm. Fluorescence increased selectively in the touched area, indicating a fine spatial resolution. On the whole, fine spatial resolution can be recognized in stretch SWNT-polymer films when there is a distance between the nanotubes. Assuming an individual dispersion of the nanotubes, it was estimated to be as small as ~ 254 nm of the SWNT-PVDF-HFP film at 0% strain.

In summary, small amounts of SWNTs were successfully dispersed by EC in the polymer matrix that emits excellent Raman and nIR fluorescence signals. The SWNT-polymer composite film was transparent and highly stretchable. The maximum strains of SWNT-PDMS and SWNT-PVDF-HFP films were 200% and 600%, respectively. Most of the strains originated in the polymer matrix and the stability of EC-wrapped SWNTs was excellent. Both films showed modulation of fluorescence in response to a touch by a charge transfer mechanism. The G-mode frequency of nanotubes changed with temperature change. The multimodal optical response with good spatial resolution produces a transparent stretchable SWNT-polymer film promising for the touch-sensing material, eliminating the battery and the electrical interconnect for signal transmission.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims (17)

A composite comprising carbon nanotubes dispersed in a polymer matrix,
Wherein the carbon nanotubes include a nitrile functional group, thereby causing a decrease in fluorescence.
Film for optical touch sensor.
The method according to claim 1,
Wherein the carbon nanotube comprises a single-walled carbon nanotube or a multi-walled carbon nanotube.
The method according to claim 1,
Wherein the polymer comprises an insulating polymer or a conductive polymer.
The method of claim 3,
The insulating polymer may be at least one selected from the group consisting of polydimethylsiloxane (PDMS), poly-4-vinyl-phenol (PVP), polyimide (PI), polystyrene (PS), polyvinylidene fluoride (PVDF), polystyrene-butadiene- SBS), and combinations thereof. &Lt; Desc / Clms Page number 13 &gt;
The method of claim 3,
The conductive polymer may be selected from the group consisting of polypyrrole, polyaniline, polythiophene, poly (3,4-ethylenedioxythiophene), poly (3,4-alkylenedioxythiophene) (3,4-dialkoxythiophene), poly (3,4-cycloalkylthiophene), and combinations thereof.
delete The method according to claim 1,
Wherein the film emits fluorescence.
8. The method of claim 7,
Wherein the near-infrared fluorescent signal is generated at an elongation of 600% or less.
The method according to claim 1,
Wherein the fluorescent emission is reduced if the film is touched by an insulator.
Curing a mixed solution containing a carbon nanotube dispersion solution, a polymer, and an ionic liquid to obtain a composite containing carbon nanotubes
/ RTI &gt;
Wherein the carbon nanotubes include a nitrile functional group, thereby causing a decrease in fluorescence.
Method for manufacturing film for optical touch sensor.
11. The method of claim 10,
Wherein the polymer comprises an insulating polymer or a conductive polymer.
12. The method of claim 11,
The insulating polymer may be at least one selected from the group consisting of polydimethylsiloxane (PDMS), poly-4-vinyl-phenol (PVP), polyimide (PI), polystyrene (PS), polyvinylidene fluoride (PVDF), polystyrene-butadiene- SBS), and combinations thereof. &Lt; Desc / Clms Page number 20 &gt;
12. The method of claim 11,
The conductive polymer may be selected from the group consisting of polypyrrole, polyaniline, polythiophene, poly (3,4-ethylenedioxythiophene), poly (3,4-alkylenedioxythiophene) (3,4-dialkoxythiophene), poly (3,4-cycloalkylthiophene), and combinations thereof.
11. The method of claim 10,
The ionic liquid may be selected from the group consisting of 1-butyl-4-methylpyridinium tetrafluoroborate, 1-ethyl-3-methylimidazolium methylsulfate, 3-methylimidazolium ethylsulfate, 1-butyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl- Methyl-imidazolium thiocyanate, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-butyl- Imidazolium bis (trifluoromethylsulfonyl) imide, and combinations thereof. &Lt; Desc / Clms Page number 13 &gt;
The method of claim 10, wherein
Wherein the ionic liquid is contained in the mixed solution in an amount of 50% by weight to 100% by weight based on 100% by weight of the polymer.
11. The method of claim 10,
Wherein the curing is performed at a temperature of 100 DEG C or less.
11. The method of claim 10,
Wherein the carbon nanotube is contained in an amount of 0.02% by weight or less based on the total weight% of the film for an optical touch sensor.

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