Low b-value high-transmittance conductive film
Technical Field
The invention relates to the technical field of conductive films, in particular to a low b-value high-transmittance conductive film.
Background
The transparent conductive film is a film which can conduct electricity and has high transmittance in a visible light range, and is widely applied to the fields of display screens, solar cells, light emitting diodes, low-emissivity glass, anti-electromagnetic interference transparent windows and the like. The silver nanowire has good conductivity, excellent light transmittance and bending resistance, and simultaneously has the characteristics of uniform and controllable appearance and high length-diameter ratio, so that the silver nanowire becomes the best choice for the transparent electrode material of the ultra-large flexible touch screen.
The optical and electrical properties of the silver nanowire transparent electrode are competing parameters. In order to realize low surface resistance, silver nanowires with high length-diameter ratio and criss-cross arrangement are fully distributed on a transparent carrier; meanwhile, for the silver wires are lapped more tightly to reduce the resistance, the thickness of most coatings is thicker, so that the yellowing characteristic is more obvious; not only the transmittance and haze of the conductive film are affected, but also the material is wasted and the cost is increased. In order to reduce the yellowing characteristic of the conductive film, a dye may be added to the nano-silver conductive ink, for example, chinese patent publication No. CN104575700A discloses a transparent conductor, and the conductive layer includes a dye to solve the yellowing phenomenon of the conductive layer. However, since the dye is not conductive, direct addition to the conductive ink may impair conductivity and transparency of the conductive film.
Disclosure of Invention
In view of the above technical problems, the present invention provides a conductive film having low resistance, low b value, and high transmittance.
The invention adopts the following technical scheme:
the conductive film with low b-value and high transmittance comprises a substrate layer and a conductive layer positioned on the substrate layer, wherein the conductive layer is formed by coating and curing silver nanowire conductive ink, and blue hollow SiO with the mass fraction of 0.2-1 wt% is added into the silver nanowire conductive ink2And (3) microspheres.
Furthermore, blue hollow SiO with the mass fraction of 0.3-0.65 wt% is added into the silver nanowire conductive ink2And (3) microspheres.
Further, blue hollow SiO2The content of the blue dye in the microspheres is 0.05-5 wt%.
Further, blue hollow SiO2The content of the blue dye in the microspheres is 0.5-2 wt%.
Further, the blue dye is one or more of alizarin blue, basic blue 6B, alcohol blue, water-soluble aniline blue, azo blue, brilliant cresol blue, bromophenol blue, carbazole blue, quinoline blue, indigo, resin phenol blue, methyl blue, methine blue, patent blue A, patent blue V, phthalocyanine, resazurin, benzylazurin, Prussian blue, methylene benzene blue, thymol blue and Trimery benzene blue.
Furthermore, the low b value high transmittance conducting film is prepared by the following method:
(1) taking blue hollow SiO with the mass fraction of 0.2-1 wt%2Adding the microspheres into the silver nanowire conductive ink, oscillating and fully mixing;
(2) unreeling the base material, carrying out corona treatment, coating the conductive ink prepared in the step (1) on the surface of the base material, and curing to obtain the conductive ink.
Further, blue hollow SiO2The microspheres are hollow SiO2The microsphere is obtained by dyeing with blue dye for 60-360 min.
The low b value high transmittance conductive film of the invention is prepared by mixing blue hollow SiO2The microspheres are added into the silver nanowire conductive ink due to the silver nanowires and SiO2HNS carries opposite charges, and the HNS can generate strong electrostatic interaction so as to promote silver nanowires to be on SiO2The uniform distribution of the HNS surface reduces the contact resistance between the silver nanowires, reducing the contact resistance; while blue hollow SiO2Microspheres can reduce the b value of the membrane material according to the CIE Lab color model; the addition of the hollow silicon dioxide microspheres can also improve the hardness and improve the scratch resistance of the nano silver conductive film. The invention is to dye the compound and hollow SiO2The colored chelate formed by the microspheres is adsorbed on the metal nano-wire, and the hollow SiO is fully utilized2The microspheres have the characteristics of reducing the resistance of the conductive film and the effect of reducing b value of the blue dye, and can inhibit the reduction of transparency caused by independently adding the colored compound (dye), thereby obtaining the conductive film with low resistance, low b value and high transparencyA conductive film having a transmittance.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a low b-value high-transmittance conductive film which comprises a substrate layer and a conductive layer positioned on the substrate layer, wherein the conductive layer is formed by coating and curing silver nanowire conductive ink, and blue hollow SiO (silicon dioxide) with the mass fraction of 0.2-1 wt% is added into the silver nanowire conductive ink2Microspheres; preferably, blue hollow SiO2The mass fraction of the microspheres is 0.3-0.65 wt%. More specifically, blue hollow SiO2The content of the blue dye in the microspheres is 0.05-5 wt%; preferably, blue hollow SiO2The content of the blue dye in the microspheres is 0.5-2 wt%.
According to the invention, the dyed hollow silica microspheres are added into the silver nanowire conductive ink, and the colored chelate formed by the dyed compound and the hollow silica microspheres is adsorbed to the metal nanowires, so that the reduction of transparency caused by independently adding the colored compound (dye) can be inhibited.
The invention effectively utilizes the colored polymer microspheres formed by the dyeing compound and the hollow silica microspheres, and combines the advantages of the polymer microspheres and the dyeing agent: the polymer microsphere has the advantages of large specific surface area, uniform particle size, various microsphere surface structures and forms, excellent color saturation of the dye and super-strong durability of the organic pigment. Specifically, the hollow silica microspheres of the invention have the functions of adsorbing pigment particles and reducing pigment attenuation; has optical properties against ultraviolet rays; the ageing resistance and the chemical resistance of the material can be improved by doping the material; dispersed in the material, the strength of the material can be improved. When the dye is added alone, transmittance is reduced, and due to the particle characteristics of the dye, diffuse reflection is likely to occur, thereby causing a serious haze problem of the conductive film.
According to the invention, the hollow silica microspheres are added, so that the synergistic effect with the silver nanowires is realized, the reflection is reduced, and the transmittance is improved. Specifically, in some embodiments of the present invention, the transmittance of AgNW/hollow silica microsphere coated PET (transmittance: 96.5%) and AgNW/silica nanoparticle coated PET (transmittance: 91.0%) was increased by 6.22% and 1.0%, respectively, compared to AgNW coated PET (transmittance: 90.5%), indicating that the anti-reflective effect is mainly due to the synergy of the silica microspheres and AgNW, while the hollow silica microspheres have better anti-reflective properties. According to the invention, the blue dye and the hollow silica microspheres are combined, and the dyed hollow silica microspheres are added into the silver nanowire conductive ink, so that the problem that the transmittance of the conductive film is reduced due to the independent addition of the dye is solved.
Specifically, in some embodiments of the present invention, the substrate layer is a PET substrate. In general, PET has a refractive index of 1.55-1.65, while hollow SiO is added2The refractive index of the conductive layer after the microspheres is 1.25-1.32, which is beneficial to matching the refractive index between air and the base material, thereby improving the light transmittance.
Specifically, in some embodiments of the present invention, silver nanowire conductive ink comprises 0.1-0.5 wt% silver nanowires having a diameter of 10-100nm and an aspect ratio of ≧ 1000. due to excessive silver nanowires causing the conductive film to yellow, the sample is more yellow (or less blue) than the standard according to the CIE Lab color model, i.e., △ b is positive2The microspheres are used for realizing the effect of reducing or eliminating the yellowing, and the b value is reduced, so that △ b tends to be zero, and the visual effect of the conductive film is improved.
More specifically, in some embodiments of the present invention, the blue dye is any one or more of alizarin blue, basic blue 6B, alcohol blue, water soluble aniline blue, azo blue, brilliant cresol blue, bromophenol blue, kalazole blue, quinoline blue, indigo, resin phenol blue, methyl blue, methine blue, patent blue a, patent blue No. five, phthalocyanine, resazurin, azurin, prussian blue, methylene benzene blue, thymol blue, and tricresyl blue.
Specifically, in some embodiments of the present invention, the hollow SiO is prepared by an emulsion process2Microsphere preparation: firstly, 2.5g of Cetyl Trimethyl Ammonium Bromide (CTAB) is added into deionized water at 60 ℃, and ultrasonic dispersion and dissolution are carried out; then 6mL of n-hexadecane is added, and the mixture is stirred for 10min at the rotating speed of 800rpm to form an O/W emulsion system; 20mL of concentrated ammonia water was added, stirring was maintained at 60 ℃ for 30min, followed by dropwise addition of 20mL of Tetraethylorthosilicate (TEOS) and 1.0g of polyvinyl alcohol (PVA), and stirring was continued for 6h to mix well. Cooling to room temperature, washing with anhydrous ethanol and deionized water for three times, and vacuum drying for 24 hr to obtain hollow SiO2And (3) microspheres.
For hollow SiO2The dyeing method of the microspheres comprises the following steps: firstly, weighing blue dye accounting for 0.05-5 wt% of the total weight, dissolving the blue dye in 20ml of absolute ethyl alcohol, weighing hollow SiO2The method comprises the following steps of slowly adding microspheres into a blue dye solution under the condition of magnetic stirring, carrying out magnetic stirring for 10min to balance a system, adjusting the pH of the system to 4 by using 1.0mol/L acetic acid solution, continuously stirring for 10min, transferring the whole dye solution into a stainless steel tank of a dyeing sample tester, sealing, placing the stainless steel tank into the dyeing sample tester, carrying out constant-temperature oscillation for 10min at the temperature of 30 ℃, then heating to 90 ℃ at the heating rate of 5 ℃/min, carrying out constant-temperature dyeing for 60-360min, and taking out the dyeing solution to cool to the room temperature after dyeing is finished. Finally, a certain amount of dyed hollow SiO is weighed2Separating the microsphere solution in a centrifuge tube at 5000rpm, removing supernatant, washing with anhydrous ethanol solution for three times, centrifuging, and oven drying to obtain hollow SiO dyed with dye2And (3) microsphere powder.
Specifically, the low b value high transmittance conductive film is prepared by the following method:
(1) taking blue hollow SiO with the mass fraction of 0.2-1 wt%2Adding the microspheres into the silver nanowire conductive ink, oscillating and fully mixing;
(2) unreeling the PET substrate with the thickness of 125um by coating on a machine, wherein the unreeling speed is 100m/min, and carrying out corona treatment on the PET substrate film, wherein the corona power is 1.0 kw; and (2) uniformly coating the conductive ink prepared in the step (1) on the surface of a PET (polyethylene terephthalate) base film in a slit coating mode, wherein the pumping speed is 30ml/min, the wet film thickness is 30 mu m, the coating speed is 10m/min, the curing temperature is gradient heating of 70-125 ℃, and the curing time is 2min, so that a uniform conductive layer is formed, and the conductive film is obtained.
The low b value high transmittance conductive film of the present invention will be further described with reference to the following embodiments.
Example 1
The low b value high transmittance conductive film of the present embodiment is prepared by the following method:
(1) hollow SiO2Preparing microspheres: first, 2.5g of cetyltrimethylammonium bromide (CTAB) was added to deionized water at 60 ℃ and dissolved by ultrasonic dispersion. Then 6mL of n-hexadecane is added, and the mixture is stirred for 10min at the rotating speed of 800rpm to form an O/W emulsion system. 20mL of concentrated ammonia water was added, stirring was maintained at 60 ℃ for 30min, followed by dropwise addition of 20mL of Tetraethylorthosilicate (TEOS) and 1.0g of polyvinyl alcohol (PVA), and stirring was continued for 6h to mix well. Cooling to room temperature, washing with anhydrous ethanol and deionized water for three times, and vacuum drying for 24 hr to obtain hollow SiO2And (3) microspheres.
(2) Hollow SiO2And (3) dyeing of the microspheres: first, 0.5g of blue dye was weighed out and dissolved in 20ml of absolute ethanol, and 50g of hollow SiO was weighed out2The method comprises the following steps of slowly adding microspheres into a blue dye solution under the condition of magnetic stirring, carrying out magnetic stirring for 10min to balance a system, adjusting the pH of the system to 4 by using 1.0mol/L acetic acid solution, continuously stirring for 10min, transferring the whole dye solution into a stainless steel tank of a dyeing sample tester, sealing, placing the stainless steel tank into the dyeing sample tester, carrying out constant-temperature oscillation for 10min at the temperature of 30 ℃, then heating to 90 ℃ at the heating rate of 5 ℃/min, carrying out constant-temperature dyeing for 120min, and taking out the dyeing solution to cool to the room temperature after dyeing is finished. Finally, a certain amount of dyed hollow SiO is weighed2Separating the microsphere solution in a test tube of a centrifuge at the rotating speed of 5000rpm, removing supernatant, washing with absolute ethanol solution for three times, centrifugally separating, and drying to obtain blue hollow SiO dyed by dye2And (3) microsphere powder.
(3) Taking blue hollow SiO with the mass fraction of 0.2 wt%2And adding the microspheres into the silver nanowire conductive ink, and oscillating and fully mixing.
(4) Unreeling the PET substrate with the thickness of 125um by coating on a machine, wherein the unreeling speed is 100m/min, and carrying out corona treatment on the PET substrate film, wherein the corona power is 1.0 kw; and (3) uniformly coating the conductive ink prepared in the step (3) on the surface of the PET base film in a slit coating mode, wherein the pumping speed is 30ml/min, the wet film thickness is 30 mu m, the coating speed is 10m/min, the curing temperature is gradient temperature rise of 70-125 ℃, and the curing time is 2min, so that a uniform conductive layer is formed, and the conductive film is obtained.
Example 2
The conductive film of this example was prepared in substantially the same manner as in example 1 except that the blue hollow SiO was used in an amount of 0.3 wt% based on the mass fraction2The microspheres are added to the silver nanowire conductive ink.
Example 3
The conductive film of this example was prepared in substantially the same manner as in example 1 except that the blue hollow SiO was used in an amount of 0.5 wt% based on the mass fraction2The microspheres are added to the silver nanowire conductive ink.
Example 4
The conductive film of this example was prepared in substantially the same manner as in example 1 except that the blue hollow SiO was used in an amount of 0.65 wt% based on the mass fraction2The microspheres are added to the silver nanowire conductive ink.
Example 5
The conductive film of this example was prepared in substantially the same manner as in example 1 except that the blue hollow SiO was used in an amount of 0.8 wt% based on the mass fraction2The microspheres are added to the silver nanowire conductive ink.
Example 6
The conductive film of this example was prepared in substantially the same manner as in example 1, except that 1 wt% of blue hollow SiO was used as the material2The microspheres are added to the silver nanowire conductive ink.
Comparative example 1
Method for producing conductive film of this comparative example and example 1Consistently, the difference is only that no blue hollow SiO is added in the silver nanowire conductive ink2And (3) microspheres.
Comparative example 2
The conductive film of this comparative example was prepared in substantially the same manner as in example 1, except that 0.5 wt% of a blue dye was added to the silver nanowire conductive ink.
Comparative example 3
The conductive film of this comparative example was prepared in substantially the same manner as in example 1 except that 0.5 wt% by mass of hollow SiO was used2The microspheres are added to the silver nanowire conductive ink.
Comparative example 4
The conductive film of this comparative example was prepared in substantially the same manner as in example 1 except that hollow SiO was used in an amount of 0.5 wt% in each case2The microspheres and the blue dye with the mass fraction of 0.5 wt% are added into the silver nanowire conductive ink.
The conductive films obtained in examples 1 to 6 and comparative examples 1 to 4 were subjected to performance tests, and the results are shown in table 1.
Table 1 conductive film performance test results
As can be seen from Table 1, in the examples of the present invention, the blue hollow SiO film was formed2The microspheres are added into the silver nanowire conductive ink, on one hand, blue dye is used for reducing the b value of a film material, on the other hand, strong electrostatic action generated between the silver nanowires and SiO2-HNS is used for promoting the uniform distribution of the silver nanowires, so that the contact resistance between the silver nanowires is reduced, and the contact resistance is reduced; meanwhile, the hardness can be improved by adding the hollow silica microspheres. Meanwhile, as can be seen from the results of examples 1-6, the contact resistance can be reduced by utilizing the strong electrostatic interaction between the hollow silica microspheres and the silver nanowires in the early stage with the increase of the hollow silica microspheres, but when the hollow silica microspheres are increased to a certain extentAfter the temperature is over, the contact resistance is increased, and finally, the invention determines the better blue hollow SiO2The content of the microspheres is 0.2-1 wt%. Compared with the method of adding blue dye alone, the method of the invention utilizes the dyed hollow silica microspheres and the synergistic effect between the silver nanowires and the silica microspheres to reduce the resistance of the conductive film, has better antireflection performance, and simultaneously avoids the occurrence of diffuse reflection phenomenon caused by directly adding dye particles, so that the transmittance of the conductive film is improved while the conductive film b is reduced, and the conductive film with low resistance, low b value and high transmittance is obtained.
The present invention has been further described with reference to specific embodiments, but it should be understood that the detailed description should not be construed as limiting the spirit and scope of the present invention, and various modifications made to the above-described embodiments by those of ordinary skill in the art after reading this specification are within the scope of the present invention.