TWI578335B - A carbon nanotube transparent electrode ink having high dispersibility and viscosity controllable performance - Google Patents

Description

Highly dispersed, viscosity-controlled carbon nanotube transparent electrode ink

The invention relates to a conductive ink containing a carbon nanotube, in particular to a carbon nanotube composite conductive ink with high dispersion and good controllability.

The carbon nanotube is a carbon material having a typical layered hollow structure. The body of the carbon nanotube is composed of a hexagonal graphite carbon ring structural unit, and has a special structure (the radial dimension is nanometer order) One-dimensional quantum material with an axial dimension of the order of microns. Its tube wall is composed of several layers to tens of layers of coaxial tubes, and the layer is kept at a fixed distance of about 0.34 nm, and the diameter is generally 2-20 nm. The P electrons of the carbon atoms of the carbon nanotubes form a wide range of delocalized π bonds, so the conjugation effect is remarkable. Since the structure of the carbon nanotubes is the same as that of graphite, it has good electrical properties. For this reason, carbon nanotubes have received much attention in the field of electronic science as an electrode material. The advantage is that as a transparent electrode material, excellent photoelectric properties, super-aligned carbon nanotubes can be spun with excellent mechanical properties. The film is pulled, and the carbon nanotubes are more resistant to environmental corrosion and are not affected by the environment.

However, due to the strong van der Waals force (~500eV/μm) and the large aspect ratio (>1000) between the carbon nanotubes, it is easy to form a large tube bundle, which is difficult to disperse and greatly restricts its excellentness. The development of photoelectric performance and the development of practical applications. Although the transparent electrode prepared by the film-forming process of the carbon nanotube super-aligned film has been widely applied on the touch screen (CN1016254665A), its surface resistivity is large (greater than 1000 Ω/□) and the transmittance is 80%. Compared to electronic devices that require higher and higher transparent electrode films, such carbon nanotube films consume a lot of power and can affect the performance of the device due to the thermal effects of the electrodes themselves.

The invention is based on the application of the carbon nanotube tube solution blending process in the transparent electrode material, and provides a high-dispersion, viscosity-regulated carbon nanotube transparent electrode ink, which is processed by ultrasonic dispersion, mechanical stirring, cell pulverization and the like. The method of composite technology realizes the uniform dispersion of the carbon nanotubes and the organic carrier, and the prepared ink has good stability and viscosity control.

Highly dispersed, viscosity-controlled carbon nanotube transparent electrode ink consists of the following components and their weight percentages: 1. Pure carbon nanotube powder 0.03-1%, 2. Carrier 0.2%-0.5%, 3. The carrier is 0.2%-0.5%, 4, the solvent is 98%-99%, the carrier 1 is an alkylating agent ammonium salt, the carrier 2 is a water-soluble anionic acidic substance, and the solvent is water.

The alkylating agent ammonium salt is cetyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, tetradecyltrimethylammonium hydroxide, benzyltrimethylammonium hydroxide One or several combinations.

The water-soluble anionic acidic substance is butyl benzoic acid (PT) dodecylbenzenesulfonic acid, phthalic acid, p-tert-butylbenzoic acid, p-hydroxybenzoic acid, β-phenylacrylic acid, phenylacetic acid, water One or several combinations of salicylic acid.

The carbon nanotube powder is a single-walled carbon nanotube, a multi-walled carbon nanotube, a double-walled carbon nanotube or a modified carbon nanotube.

The preparation method of the high-dispersion and viscosity-controllable carbon nanotube transparent electrode ink comprises the following steps: 1) taking a part of the solvent to prepare the carrier 1 and the carrier 2 into an aqueous solution; 2) dispersing the pure carbon nanotube powder material in the In the aqueous solution of carrier one; 3) adding the remaining solvent; 4) dropping the aqueous solution of the second solution under stirring.

The steps (2) and (3) employ ultrasonic dispersion, and the step (4) employs magnetic stirring.

The method for preparing the pure carbon nanotube powder is: dispersing the carbon nanotube in a supersonic wave into a suspension in methanol, and then placing the carbon nanotube suspension in a UV light cleaning machine, and centrifuging, and obtaining Carbon nanotube powder; the powder is added to a mixed aqueous solution of concentrated HNO ₃ and ammonium persulfate, the magnet is stirred, refluxed at 120 ° C for 5 h (hours), centrifuged, and repeatedly centrifuged with deionized water to the middle. Sex, dry pure carbon nanotube powder.

The pure carbon nanotube powder is prepared by dispersing the carbon nanotube into a suspension in an organic solvent, allowing it to swell, centrifuging, and washing; adding to concentrated nitric acid, reacting at 120 ° C for 4 h, and centrifuging. Clean to neutral, dry and pure carbon nanotube powder.

The invention finds that when the carrier 1 and the carrier 2 are mixed at a certain concentration, a viscoelastic solution system with adjustable viscosity is formed. The invention adopts its viscosity-adjustable property to disperse a high-concentration carbon nanotube, and the viscous dispersion is easy to form a film. The film-forming carrier is easily desorbed in ethanol and remains little on the surface of the film after further water washing.

When the viscosity of the dispersion formed by mixing the carrier 1 and the carrier 2 is 10-20 Pa.s, the carbon nanotubes can be effectively dispersed.

The ink of the invention has good dispersibility, good stability and adjustable viscosity, and the formed carbon nanotube transparent conductive film layer has good electrical conductivity and optical transmittance and flexibility in the visible light range. The conductivity of the flexible carbon nanotube transparent conductive film can be adjusted at (100 Ω / □ - 1 M Ω / □). The carbon nanotube conductive ink has low preparation cost, energy saving and environmental protection, and the product has no toxicity to human body, no side effect, and the process is simple.

Figure 1 is an SEM image of a pure single-walled carbon nanotube (SWCNT) in which A, B are images of different magnifications.

2 is an SEM image of a pure single-walled carbon nanotube film in which A, B, and C are images of different magnifications.

The present invention will be further described in detail below with reference to the embodiments.

Example 1

1) Purification of single-walled carbon nanotubes: 0.05 g of single-walled carbon nanotubes (SWCNTs) were ultrasonically dispersed in 20 ml of methanol for 20 min to form a SWCNT suspension. The SWCNT suspension was placed in a UV light washer for 40 min to obtain SWCNT powder; 20 ml of deionized water was placed in a single-mouth flask, and 10 ml of concentrated HNO ₃ (68 wt%) was added, and 5 wt% of persulfuric acid was added. The ammonium (APS) aqueous solution was uniformly mixed, and then the purified SWCNT powder was added, and the magnetic particles were stirred, and refluxed at 120 ° C for 5 hours. The deionized water was repeatedly centrifuged (7000 rpm, 10 min) three times to obtain a purified single-walled carbon nanotube (see Fig. 1).

2) The purified single-walled carbon nanotubes were dispersed in 0.05 M of 3 ml of cetyltrimethylammonium hydroxide (CTAOH), and 16 ml of water was added thereto, and ultrasonically dispersed for 15 minutes. In this mixed system, 0.15-0.2ml of 0.45M p-tert-butylbenzoic acid was gradually added under the condition of magnetic stirring to form a highly dispersed carbon nano-dispersion system with adjustable viscosity, and the viscosity was adjustable within 10-20 Pa.s. .

Example 2:

1) 0.05 g of SWCNT was added to 40 ml of ethyl benzoate solvent, ultrasonically dispersed for 40 min, allowed to stand for 2 days, centrifuged, and then centrifuged with deionized water in ethanol. The swollen SWCNT was added to 30 ml of concentrated nitric acid, and reacted at 120 ° C for 4 h. After taking out, it was centrifuged several times until the supernatant was substantially clarified, and the centrifugation solution was nearly neutral. The powder of the single-walled carbon nanotube obtained was centrifuged (see Fig. 1).

2) The purified single-walled carbon nanotubes were dispersed in 0.05 M of 3 ml of dodecyltrimethylammonium hydroxide, and then added with 18 ml of water, and ultrasonically dispersed for 15 minutes. In this mixed system, 0.1-0.2 ml of 0.3 M phthalic acid was gradually added under the condition of magnetic stirring. A highly dispersed carbon nano-dispersion system with adjustable viscosity is formed. Its viscosity is adjustable within 10-20Pa.s.

Example 3:

1) 0.05 g of SWCNT was added to 40 ml of dimethylformamide (DMF), ultrasonically dispersed for 40 min, allowed to stand for 48 h, centrifuged, and then centrifuged with deionized water in ethanol. The swollen SWCNT was added to 30 ml of concentrated nitric acid, and reacted at 120 ° C for 4 h. After taking out, it was centrifuged several times until the supernatant was substantially clarified, and the centrifugation solution was nearly neutral. The powder of the single-walled carbon nanotube obtained by centrifugation is shown in Fig. 1.

2) The purified single-walled carbon nanotubes were dispersed in 0.05 M of 3 ml of benzyltrimethylammonium hydroxide, and then added with 13 ml of water, and ultrasonically dispersed for 15 minutes. In this mixed system, 0.15-0.2 ml of 0.3M phthalic acid was gradually added under the condition of magnetic stirring to form a highly dispersed carbon nano-dispersion system with adjustable viscosity, and the viscosity was adjustable within 10-20 Pa.s.

Experimental example:

1. Preparation method of carbon nano conductive film

The highly dispersed viscosity-adjustable carbon nanotube conductive ink of the invention can be used to prepare fine electrode patterns by using spin coating and laser ablation technology at room temperature, and can also adopt inkjet printing and the like. A one-time preparation of the fine structure electrode pattern is realized, and the morphology of the prepared film is shown in FIG.

The composite conductive ink of the invention has strong process operability, and can adopt the inkjet printing technology, the spin coating technology and the matching lithography technology, and can realize carbon preparation on the surface of glass, transparent crystal, transparent ceramic, polymer film and the like. The nano-conductive film layer has a film surface topography as shown in FIG.

In the carbon nanotube dispersion, the carbon nanotubes have good dispersion properties, forming a single bundle of network dispersion. After the carbon nanotube tube is coated on the surface of the PET film, it is immersed in ethanol or HNO _{3 to} form a relatively uniform network of carbon nanotube film.

The film properties of carbon nano-conductive films are shown in Table 1:

The carbon nano-transparent conductive film layer formed by the ink of the present invention has good electrical conductivity and optical transmittance and flexibility in the visible light range. The conductivity of the flexible carbon nanotube transparent conductive film can be adjusted at (100 Ω / □ - 1 M Ω / □). The carbon nano-conductive ink has low preparation cost, energy saving and environmental protection, and the product has no toxicity to the human body, has no side effects, and has simple process. Compared with the performance of carbon nano-conductive polymer electrode materials at home and abroad, the performance of the carbon nano-flexible electrode material prepared by the invention is at a leading level. See Table 2.

The carbon nanotube flexible electrode ink developed by the invention and the transparent flexible conductive film prepared by the invention have good application prospects in the flexible transparent electrodes required for display devices such as touch screens, solar cells and OLEDs.

Claims (6)

A highly dispersed, viscosity-controllable carbon nanotube transparent electrode ink consisting of the following components and their weight percentages: (1) pure carbon nanotube powder 0.03-1%, (2) carrier 0.2%- 0.5%, (3) carrier two 0.2%-0.5%, (4) solvent 98%-99%, the carrier one is cetyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide One or a combination of tetradecyltrimethylammonium hydroxide and benzyltrimethylammonium hydroxide, the carrier of which is p-tert-butylbenzoic acid, butylbenzoic acid, phthalic acid One or several combinations, the solvent being water. The high-dispersion, viscosity-controllable carbon nanotube transparent electrode ink according to claim 1, wherein the carbon nanotube powder is a single-walled carbon nanotube, a multi-wall carbon nanotube, Double-walled carbon nanotubes or modified carbon nanotubes. A method for preparing a carbon nanotube transparent electrode ink with high dispersion and controllable viscosity according to any one of claims 1 to 2, comprising the following steps; (1) taking a part of a solvent to carry a carrier 1 and a carrier 2 Prepare an aqueous solution, (2) disperse the pure carbon nanotube powder material in an aqueous solution of the carrier 1, (3) add the remaining solvent, and (4) drip the aqueous solution of the second solution under stirring. The preparation method according to claim 3, wherein the steps (2) and (3) are ultrasonic dispersion, and the step (4) is magnetic stirring. The preparation method according to claim 3, wherein the pure carbon nanotube powder is prepared by ultrasonically dispersing a carbon nanotube into a suspension in methanol, and then placing the suspension. Irradiation in a UV light washer, centrifugation, to obtain a carbon nanotube powder; the powder is added to a mixed aqueous solution of concentrated HNO ₃ and ammonium persulfate, the magnet is stirred, refluxed at 120 ° C for 5 h, centrifuged, used The deionized water is repeatedly centrifuged to neutrality, and the pure carbon nanotube powder is dried. The preparation method according to claim 3, wherein the pure carbon nanotube powder is prepared by dispersing a carbon nanotube in an organic solvent to form a suspension, allowing to stand for swelling, centrifugation, and cleaning. Then added to concentrated nitric acid, reacted at 120 ° C for 4 h, centrifuged, washed to neutral, and dried to obtain pure carbon nanotube powder.