Based on nano silver wire transparent conductive film of thermoplastic transparent polymer and preparation method thereof
?
Technical field
The invention provides structure of a kind of nano silver wire transparent conductive film based on the thermoplastic transparent polymer and preparation method thereof.
Background technology
Transparent conductive film is the function film that has than high visible light transmissivity and certain conductive capability, be widely used in LCD, touch-screen, electroluminescent device and the thin-film solar cells as transparency electrode, and as anti-static coating and electro-magnetic screen layer.Transparent conductive film can be realized high visible light transmissivity and higher conductivity simultaneously, transmission when therefore can guarantee optical photon and charge carrier.Up to the present, the best transparent conductive material of combination property is tin-doped indium oxide (ITO), can visible light transmissivity be 80% the situation side of being issued to resistance less than 10 Ω, resistivity is lower than 1.5 * 10
-4Ω cm
-1But ito surface is facing following several serious problem.The first, global indium resource is about to be exhausted, and price climbs up and up, and this situation shows the Rapid Expansion of market and thin-film solar cells market and production capacity along with LCD flat panel and further aggravates; The second, need expensive vacuum coating equipment and under higher substrate temperature, just can prepare high-quality ito thin film, equipment investment is huge; The 3rd, in the time of need being deposited on the flexible base, board, substrate temperature is less than 200 usually
oC, it is best that difficult quality reaches, and in use along with the bending of substrate, the easy cracking destruction of ITO.
In order to overcome these difficulties, university and industrial quarters have been developed multiple novel transparent conductive film material, and wherein most typical example is conducting polymer, aluminium-doped zinc oxide (AZO), carbon nano-tube (CNT) and Graphene transparent conductive film.Yet the conductivity of conducting polymer is low, have stronger absorption, poor chemical stability in the visible region; Aluminium-doped zinc oxide and ITO have the problem of easy cracking equally, and because zinc oxide is amphoteric oxide, chemistry and environmental stability are good inadequately; And carbon nano tube transparent conductive thin-film is difficult to realize simultaneously low square resistance and high visible light transmissivity because the contact resistance between the carbon nano-tube is bigger.The conducing composite material that conducting nanowires in the past (nanotube) and visible transparent polymer constitute evenly mixes conducting nanowires (nanotube) and polymer, disperses block, fiber or the film of formation given shape mostly according to certain ratio.Because organic polymer can hinder electric transmission between the nano wire (nanotube), so in order to realize that the mixed proportion that high conductive capability will differentiate susceptance rice noodles (nanotube) has relatively high expectations, but reduced visible light transmissivity inevitably.Document (S. De etc., Silver nanowire networks as flexible, transparent, conducting films:extremely high DC to optical conductivity ratios, Acs Nano 3 (2009) 1767-1774) reported a kind of method that on polyethylene terephthalate (PET) film, prepares the nano silver wire conductive layer, but the poor adhesive force between nano silver wire and the PET, conductive layer has been glued destruction easily, and the surface is smooth inadequately, surface undulation may still have suitable gap apart from practical application up to 100 nanometers ~ 300 nanometers.
So, develop visible light transmissivity height, square resistance little, can on flexible substrate, stablize and use and the good novel transparent conductive film of chemical stability, have using value in antistatic, electromagnetic shielding, solar cell, touch-screen, flexible demonstration and Electronic Paper field, economic and social benefit is fine.
Summary of the invention
The present invention proposes a kind of nano silver wire transparent conductive film based on the thermoplastic transparent polymer, comprise thermoplastic transparent polymer and nano silver wire conductive layer, it is characterized in that: continuous nano silver wire conductive network is embedded in the surface of thermoplastic transparent polymer, part nano silver wire surface is exposed in the air, constitutes flexible transparent conductive film.
The present invention adopts following technical scheme:
1. nano silver wire transparent conductive film based on the thermoplastic transparent polymer, it is characterized in that: continuous nano silver wire conductive network is embedded in the thermoplastic transparent polymer surfaces, part nano silver wire surface is exposed in the air, constitutes flexible transparent conductive film; To 1000 nanometers, length is between 100 nanometers to 100 micron in 10 nanometers for the diameter of nano silver wire; The preparation method of described transparent conductive film is elder generation's depositing silver nano wire conductive network on hard substrate, then with thermoplastic transparent polymer matrix film and surface deposition the hard substrate of nano silver wire conductive network be close together, by under vacuum environment or non-vacuum environment, thermoplastic transparent polymer matrix film and hard substrate being carried out certain pressurization and heat treated, cool off removal pressure at last, the thermoplastic transparent substrate is separated from hard substrate, obtained needed transparent conductive film.
2. 1 described transparent conductive film, it is characterized in that: the visible light transmissivity of transparent conductive film can overregulate the concentration of nano silver wire or by selecting different thermoplastic polymers to come the transmitance of conductive film is regulated between 10%-98%; The square resistance of transparent conductive film can be regulated by the concentration of regulating nano silver wire between 0.5 ohm ~ 10000 ohm.
3. 1 described transparent conductive film, it is characterized in that: the visible light transmissivity of used thermoplastic transparent polymer is more than 10%, is preferably more than 60%; Thermoplastic transparent polymer glass temperature range is 50
oC-500
oC, and in the heating and cooling process tangible decomposition, crystallization and metachromatism can not take place; Used thermoplastics is preferentially selected transparent thermoplastics and derivatives thereof such as polyvinyl chloride, polyphenyl dioctyl phthalate glycol ester, polymethyl methacrylate, polyethylene, polypropylene, polystyrene, Merlon, polyurethane and polytetrafluoroethylene for use.
4. 1 described transparent conductive film, it is characterized in that: the nano silver wire conductive network is to be the contiguous network structure that main body forms with the nano silver wire, can fill other the nano material with conductivity as required, comprise carbon nano-tube, or Graphene, or ruthenium-oxide, or nickel oxide, or zinc oxide, or tin oxide, or ITO, or silver, or copper, or gold, or the composite material of the nanostructure of one or more materials in aluminum formation.
The high length-diameter ratio (〉 100 of nano silver wire) helps on substrate, having certain visible light transmissivity in the high performance continuous conduction network of formation.The method that proposes according to people such as Tang (
Rapid and high-yield synthesis of silver nanowires using air-assisted polyol method with chloride ions.Colloids and Surfaces a-Physicochemical and Engineering Aspects 338 (2009) 33-39), silver nitrate is by reduction of ethylene glycol, form the nano silver wire structure under the effect of polyvinylpyrrolidone, NaCl and oxygen, its structure and microscopic appearance are as depicted in figs. 1 and 2.The flow process that begins to prepare the transparent conductive film above this thermoplastic transparent polymer matrix film from nano silver wire as shown in Figure 3.Nano silver wire is dispersed in the liquid medium, can adopts several different methods (vacuum filtration, spraying, spin coating, dipping and silk screen printing etc.) all can go up then and form uniform nano silver wire conductive network (among Fig. 3 3) at hard substrate (among Fig. 3 1).The hard substrate can be common float glass, smooth metal surface or the organic board of good heat resistance.
Select for use thermoplastic transparent organic polymer (among Fig. 3 2), preferentially to select polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), nylon (Nylon), Merlon (PC), polyurethane (PU), polytetrafluoroethylene (PTFE), PETG transparent thermoplasticss such as (PET) for use as the host material of nano silver wire transparent conductive film.Then at a certain temperature with thermoplastic transparent substrate and surface deposition the hard substrate of nano silver wire conductive network be close together.By under vacuum environment or non-vacuum environment, thermoplastic transparent matrix and hard substrate being carried out certain pressurization and heat treated, get rid of the gas between thermoplastic matrix and the hard substrate.The temperature of heating is higher than the softening temperature of thermoplastic matrix.Heating a period of time, it is softening to make that the thermoplastic conductive polymer takes place, and in the while nano silver wire embedded polymer thing, and the other part surface of nano silver wire still contacts with the hard substrate surface.Cooling back removal pressure is separated thermoplastic transparent matrix from the hard substrate, all nano silver wires all are left on thermoplastic transparent organic polymer matrix surface and keep original electric conductivity.So just formed have stronger anti-mechanical friction performance based on thermoplastic nano silver wire flexible transparent conductive film.Final form based on the nano silver wire structure of transparent conductive film of thermoplastic transparent polymer as shown in Figure 3.
The part nano silver wire embeds in the substrate, be deposited on scheme above the hard substrate with respect to nano silver wire, have at least three tangible advantages: first: improved the firm degree and the reliability of nano silver wire transparent conductive film greatly, solved the difficult problem that nano silver wire comes off easily substantially; The second, the part nano silver wire is embedded in substrate the inside, has reduced and airborne aqueous vapor, and oxygen or have the gas contact of polluting character can strengthen the chemical stability of nano silver wire and prolong useful life of conductive film; The 3rd, all nano silver wires embed in the organic substrate, have reduced the roughness of conductive film, make that the conductive film surface ratio is more smooth.
As typical thermoplastic transparent polymer, PVC has the softening temperature at lower temperature, can not take place significantly to decompose in heating process and transmitance decline, therefore can be used as matrix and constitute flexible transparent conductive film.Fig. 4 is embedded in the atomic force microscope picture of the transparent conductive film on PVC surface for nano silver wire, wherein the pattern of nano silver wire is still high-visible, but is embedded among the PVC.Fig. 5 is embedded in the transmittance curve of transparent conductive film among the PVC for the nano silver wire of variable concentrations.As seen from Figure 6, after the Ag nano wire was transferred among the PVC, square resistance can have decline slightly, because after certain temperature sintering, can partly come off attached to the organic substance on the Ag nanowire surface causes the contact between the Ag nano wire better, and side's resistance descends.Compare between 0.1-10% before the amount that side resistance descends and the original transfer printing.The nano silver wire conductive network is before being transferred to PVC, if with its adhesiveness of 3M adhesive tape test, most nano silver wire all can be glued by the 3M adhesive tape, thereby loses original conductive capability.The square change in resistance of nano silver wire transparent conductive film before and after being adhered to that Fig. 7 inlays for the PVC surface by the 3M adhesive tape.For various settled densities, the increase value of its side's resistance is all in 2 Ω.
That the present invention can be used for is antistatic, electromagnetic shielding, solar cell, touch-screen, the flexible demonstration and field such as Electronic Paper.
Description of drawings
The scanning electron microscope diagram of Fig. 1 nano silver wire, the diameter of most nano silver wires are between the 30-100 nanometer, and length is between the 1-20 micron.
The transmission electron microscope figure of Fig. 2 nano silver wire.
Fig. 3 is based on the preparation flow schematic diagram and the structural representation thereof of the nano silver wire transparent conductive film of thermoplastic transparent polymer.Wherein 1 is ganoid hard substrate (for example glass), 2 is thermoplastic transparent polymer matrix, 3 is nano silver wire continuous conduction network, process 4 is illustrated in the process of the uniform nano silver wire conductive network of deposition on the hard substrate, process 5 expressions are close to the thermoplastic transparent plastic on the nano silver wire network and heating and pressurization, make nano silver wire embed the process of softening polymer surfaces, and process 6 expressions are cooled off and the process of transparent polymer from the hard substrate surface isolation, finally formed needed nano silver wire transparent conductive film based on the thermoplastic transparent polymer.
Fig. 4 nano silver wire is embedded in the atomic force microscope figure on PVC sheets surface.
The nano silver wire of the different settled densities of Fig. 5 is embedded in the transmittance curve of the flexible transparent conducting film that constitutes in the PVC sheets.
The square resistance of the nano silver wire of Fig. 6 deposition on glass before and after heat embeds the PVC sheet.
The square resistance increase value after the nano silver wire transparent conductive film is adhered to by the 3M adhesive tape is inlayed on Fig. 7 PVC sheet surface.
Embodiment
Below embodiments of the invention are further elaborated.
Embodiment 1
Get the aqueous suspension solution of the nano silver wire of designated volume, vacuum filtration forms 32 mg/m on filter membrane
2The homogeneous conductive network.Be transferred to above the clean glass substrate at following nano silver wire conductive network of certain temperature and pressure then.Get polyvinyl chloride substrate (2 millimeters of thickness, visible light transmissivity 88.3%), be pressed on above the nano silver wire conductive network, note getting rid of whole air.Evenly pressurization about 1 * 10 on the polyvinyl chloride substrate
5Pa puts into heating furnace at 150-250
ZeroInsulation is 10-60 minute in the C scope, takes out natural cooling then, and the PVC sheet is stripped down from glass, and the nano silver wire conductive network all is embedded into PVC sheet surface.
The visible light transmissive rate curve of resulting Ag-PVC transparent conductive film as shown in Figure 5, the visible light transmissivity of PVC-Ag transparent conductive film (550 nanometer) is 83.7%, square resistance is 209 Ω.
Embodiment 2
Get the aqueous suspension solution of the nano silver wire of designated volume, vacuum filtration forms 64 mg/m on filter membrane
2The homogeneous conductive network.Be transferred to above the clean glass substrate at following nano silver wire conductive network of certain temperature and pressure then.Get polyvinyl chloride substrate (2 millimeters of thickness, visible light transmissivity 88.3%), be pressed on above the nano silver wire conductive network, note getting rid of whole air.Evenly pressurization about 1 * 10 on the polyvinyl chloride substrate
5Pa puts into heating furnace at 150-250
ZeroInsulation is 10-60 minute in the C scope, takes out natural cooling then, and the PVC sheet is stripped down from glass, and the nano silver wire conductive network all is embedded into PVC sheet surface.
The visible light transmissive rate curve of resulting Ag-PVC transparent conductive film as shown in Figure 5, the visible light transmissivity of PVC-Ag transparent conductive film (550 nanometer) is 74.5%, square resistance is 32 Ω.
Embodiment 3
Get the ethanol aaerosol solution of the nano silver wire of designated volume, spraying forms uniform nano silver wire conductive network on glass, and nano silver wire density is about 80 mg/m
2Get polyvinyl chloride substrate (2 millimeters of thickness, visible light transmissivity 88.3%), be pressed on above the nano silver wire conductive network, note getting rid of whole air.Evenly pressurization about 1 * 10 on the polyvinyl chloride substrate
5Pa puts into heating furnace at 150-250
ZeroInsulation is 10-60 minute in the C scope, takes out natural cooling then, and the PVC sheet is stripped down from glass, and the nano silver wire conductive network all is embedded into PVC sheet surface.The visible light transmissivity of the transparent conductive film that obtains (550 nanometers) is 71.3%, and square resistance is 18.3 Ω.
Embodiment 4
Get the ethanol aaerosol solution of the nano silver wire of designated volume, spin coating forms uniform nano silver wire conductive network on glass.About 115 mg/m of nano silver wire network settled density that form
2Get polyvinyl chloride substrate (2 millimeters of thickness, visible light transmissivity 88.3%), be pressed on above the nano silver wire conductive network, note getting rid of whole air.Evenly pressurization about 1 * 10 on the polyvinyl chloride substrate
5Pa puts into heating furnace at 150-250
ZeroInsulation is 10-60 minute in the C scope, takes out natural cooling then, and the PVC sheet is stripped down from glass, and the nano silver wire conductive network all is embedded into PVC sheet surface.The visible light transmissivity of the transparent conductive film that obtains (550 nanometers) is 68.3%, and square resistance is 14.2 Ω.
Though the present invention discloses as above with preferred embodiment; so it is not of the present invention in order to limit; have in the technical field under any and know the knowledgeable usually; in not breaking away from spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is as the criterion as the claim person of defining that look claims.