JP2010235377A - Carbon nanotube dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon nanotube dispersion which has dispersion stability even in high concentration of carbon nanotube and is easily produced (prepared) and to provide a conductive member on which a coating film of the carbon nanotube dispersion is formed. <P>SOLUTION: In the carbon nanotube dispersion, in which the carbon nanotube, and a nonionic fluorine-based dispersant having perfluoroalkenyl group or the nonionic fluorine-based dispersant and an ampholytic fluorine-based dispersant having a perfluoroalkenyl group are contained in a single solvent of only water or a mixed solvent of a water-soluble organic solvent with water, and the carbon nanotubes are uniformly dispersed. The long term dispersion stability is improved by the nonionic fluorine-based dispersant or the same and the ampholytic fluorine-based dispersant. The carbon nanotube dispersant is adjusted in a simple manner by adding the carbon nanotubes and the fluorine-based dispersant to the solvent and irradiating with ultrasonic wave. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a carbon nanotube dispersion used for forming a conductive coating film and the like, and more particularly, to a carbon nanotube dispersion with improved long-term dispersion stability.

  In recent years, research has been conducted on carbon nanotube dispersions used in the formation of conductive coatings and the production of conductive films. Carbon nanotubes (hereinafter abbreviated as “CNT”) are likely to aggregate due to van der Waals forces between adjacent CNTs, and a strong bundle structure composed of a plurality of CNTs is formed to further increase the aggregation between bundles. It is said to progress.

  As a measure for improving long-term dispersibility, a method of producing a paste by mixing CNT aggregates in a solvent containing amphoteric dispersant molecules, performing ultrasonic treatment, and dispersing CNTs (Patent Document 1), There is also known a method (Patent Document 2) in which a fluoropolymer having a fluorinated group at both molecular ends and coexisting main chain is coexistent with CNTs and stirred for 72 hours in water or an organic solvent.

International Publication No. 05/110594 JP 2004-261713 A

Several CNT dispersion methods have been proposed, but CNT dispersions obtained by simply suspending CNTs in organic solvents or aqueous solvents and low molecular surfactants (dispersants) are added. When the concentration is high, long-term dispersion stability cannot be obtained, and there is a problem that CNT aggregates are generated within several hours. Even when the concentration of CNTs is low, agglomerates are generated in the CNT dispersion during use for a long period of time, so dispersion treatment (for example, ultrasonic irradiation) is always performed during the coating process. Will have to be done. Moreover, it is very difficult to obtain a conductive coating film having a surface resistivity of 10 ³ Ω / □ or less by applying a low-concentration carbon nanotube dispersion on a substrate, and a bar coater or roll coater. In addition, there is a problem that the process cost increases because it is necessary to apply the coating many times.

  The method of adhering an amphoteric dispersant to a part of the carbon nanotubes and dispersing CNT as in Patent Document 1 adds several kinds of auxiliary agents such as a viscosity modifier and an ionic substance in addition to the amphoteric dispersant, and is unnecessary. There is a problem that processing is complicated, such as a process of removing a substance. In addition, since the amphoteric dispersant molecules have a low molecular weight, it is necessary to increase the amount added to stabilize the dispersion, so it is not possible to obtain a conductor having a low surface resistivity, and the light transmittance is reduced. That is expected.

  In addition, the method of coexisting a fluoropolymer with CNTs as in Patent Document 2 and stirring and dispersing in water or an organic solvent for 72 hours is difficult to say because it requires long-time stirring. Is. Further, the synthesis method of the dispersant is complicated and long-term stability is not disclosed.

  The present invention has been made under the circumstances described above, and the problem to be solved is that a conductive coating film can be formed with a small number of coating times, and long-term dispersion can be achieved even if the CNT concentration is increased. Providing a CNT dispersion that has good stability and can be easily manufactured (prepared), and a conductive member (EMI shield, transparent electrode, etc.) on which a coating film of the CNT dispersion is formed Is to provide.

  In order to solve the above problems, the CNT dispersion liquid according to the first invention is a nonionic solvent having a perfluoroalkenyl group and CNT in a single solvent of water alone or a mixed solvent of water and a water-soluble organic solvent. Fluorine-based dispersant is contained, and CNT is dispersed.

  The CNT dispersion according to the second aspect of the present invention includes a single solvent of water alone or a mixed solvent of water and a water-soluble organic solvent, CNT, and a nonionic fluorine-based dispersant having a perfluoroalkenyl group. And an amphoteric fluorine-based dispersant having a perfluoroalkenyl group, and CNTs are dispersed. Here, “amphoteric” means having both cationic and anionic properties.

  In addition, the conductive member according to the present invention is characterized in that a coating film of the CNT dispersion liquid is formed on the surface of a base material.

As in the CNT dispersion according to the first invention, a nonionic fluorine-based dispersant having a perfluoroalkenyl group and a CNT in a single solvent of water alone or a mixed solvent of water and a water-soluble organic solvent If contained, the hydrophobic unit of the above-mentioned dispersant having affinity for CNT is adsorbed on the CNT surface, and then agglomeration of large CNT bundles is loosened by ultrasonic irradiation to form stable C—F bonds. It is possible to efficiently disperse the CNT bundles by using the steric hindrance effect of the fluorine-based dispersant having a bulky perfluoroalkenyl group. In addition, it has a perfluoroalkenyl group having an unsaturated bond (double bond) as a chemical structure of the fluorine-based dispersant and a hydrophilic unit, so that it interacts with the above-mentioned single or mixed solvent having high polarity. In the (solvation), the fluorinated dispersant penetrates between the CNTs one after another, so that the CNTs are dispersed. The CNT peeled off due to the steric hindrance and electrostatic repulsion of the dispersant cannot be approached, and the reaggregation of CNT is suppressed, so that long-term dispersion stability can be improved even if the CNT concentration is high. Therefore, this CNT dispersion has good long-term dispersion stability even when the CNT concentration is increased to less than 450 ppm (360 ppm), as evidenced by experimental data described later. Wet 24 μm) can form a conductive coating film having a surface resistivity of about 10 ³ to 10 ⁵ Ω / □. The concentration of CNT can be further increased, and long-term dispersion stability is good if the dispersant is prepared so that the concentration ratio of the nonionic fluorine-based dispersant to CNT is in the range of 0.5 to 45 CNT dispersion can be obtained.

Further, as in the CNT dispersion according to the second invention, a nonionic fluorine-based dispersant having a perfluoroalkenyl group and an amphoteric fluorine-based dispersant having a perfluoroalkenyl group are used in combination. In addition to the above-mentioned action of the nonionic fluorine-based dispersant, the amphoteric fluorine-based dispersant is adsorbed on the surface of the CNT, and the CNT together with the nonionic dispersant By covering the surface of CNTs, the hydrophilicity and surface potential of CNTs increase, and the action of electrostatic repulsion is strengthened accordingly, compared with the CNT dispersion liquid according to the first invention. Good dispersion stability can be exhibited. Accordingly, as confirmed by the experimental data described later, this CNT dispersion has a ratio of the total concentration of nonionic and amphoteric fluorine-based dispersants to CNT of 1.7 (total) even if the CNT concentration is increased to 1170 ppm. If the concentration is 2000 ppm) to 2.6 (total concentration 3000 ppm), the long-term dispersion stability is good, and the surface resistivity is 10 ³ to 10 ⁴ Ω / □ with a single coating (bar coater Wet 24 μm). A conductive coating film having a degree of conductivity can be formed. The concentration of CNTs can be further increased. If the concentration ratio of the nonionic fluorine-based dispersant to CNTs is in the range of 0.5 to 45 and prepared in combination with an appropriate amphoteric fluorine-based dispersion, long-term It is possible to obtain a high-concentration dispersion of CNTs having good dispersion stability.

  In addition, as described later, these CNT dispersions are obtained by adding CNT and a nonionic fluorine-based dispersant, or a nonionic fluorine-based dispersant and an amphoteric fluorine-based dispersant to a single solvent or a mixed solvent. Since it can be produced in a short time by irradiating several tens of ultrasonic waves, the production is very simple and suitable for mass production. Also, it is possible to use a general mixing apparatus suitable for mass production, such as a bead mill or a homomixer.

In addition, the conductive member of the present invention is manufactured by applying the above CNT dispersion having a high CNT concentration once or several times to the substrate surface using a bar coater or a roll coater, as will be described later. The surface resistivity of the coating film on the surface of the substrate is as low as 10 ² to 10 ⁵ Ω / □, and there is no fear of appearance failure due to CNT aggregation after coating. Therefore, this conductive member is useful for touch panel electrodes, EMI shields, and other uses.

It is the schematic diagram which showed the structure image of the nonionic fluorine-type dispersing agent contained in the CNT dispersion liquid of this invention.

  As described above, the CNT dispersion liquid according to the first invention (hereinafter referred to as the CNT dispersion liquid A) is obtained by adding CNT and a permeate to a single solvent of water alone or a mixed solvent of water and a water-soluble organic solvent. CNT is dispersed by adding a nonionic fluorine-based dispersant having a fluoroalkenyl group, and water in a single solvent and water in a mixed solvent are ion-exchanged water, distilled water, tap water, etc. Is done.

  In addition, the water-soluble organic solvent in the mixed solvent is a highly polar organic solvent having a dielectric constant of 6 or more, such as methanol, ethanol, 1-propanol, isopropanol (IPA), dissolved in water by 5% by weight or more. An organic solvent having a dielectric constant of about 6 to 40, such as 1-butanol, 1-methoxy-2-propanol (PGM), N-methylpyrrolidone and acetonitrile, is preferably used. These water-soluble organic solvents are used singly or in combination with water.

  The mixed solvent is preferably prepared so that the weight ratio of water [weight of water / (weight of water + weight of water-soluble organic solvent)] is 0.1 to 0.99, and the weight ratio of water is 0. When smaller than 0.1, it becomes close to a single organic solvent, and the polarity (dielectric constant) of the solvent is lowered and the action of solvation is weakened. As a result, the electrostatic repulsion between CNTs is weakened. There is a risk that the dispersion stability may be lowered. On the other hand, if the weight ratio of water is greater than 0.99, it is substantially the same as that of a single solvent containing only water, and therefore conforms to the result of a single water system.

  The CNT dispersed in the above single or mixed solvent is a single-walled CNT having a single cylindrical carbon wall around the central axis, or a plurality of cylindrical carbon walls having different diameters around the central axis. Any of the multi-walled CNTs provided concentrically may be used, but the former single-walled CNT is preferably used from the viewpoint of dispersion stability. Among them, single-walled CNTs having a diameter of 0.5 to 3 nm (particularly 1 to 2 nm) are preferably used.

  Further, the dispersant added to the above-mentioned alone or mixed solvent is a fluorine-based dispersant having a perfluoroalkenyl group and a large molecular weight, and specifically, perfluoroalkenyl represented by the following structural formula (1). A dispersant comprising a copolymer of an acrylic monomer having a group and an acrylic monomer having a hydrophilic group such as polyoxyethylene is used. As schematically shown in FIG. 1, the fluorine-based dispersant has a main chain 1 of an acrylic copolymer, a side chain 3 having a perfluoroalkenyl group 2 and a side chain 4 of a hydrophilic group. And having a weight average molecular weight (Mw) of 5,000 to 30,000 and a high molecular weight is preferably used.

  Representative examples of such nonionic fluorine-based dispersants having a perfluoroalkenyl group include PF 730FM (Mw: 10,000, about 25% of the side chain is a PF alkenyl group), FT 710FL (Mw : 30,000, about 50% of the side chain is a perfluoroalkenyl group), and 730 FS of gentent (Mw: 5,000, about 25% of the side chain is a perfluoroalkenyl group) [Nonion manufactured by Neos Co., Ltd. Product number of the functional fluorine-based dispersant].

  When a nonionic fluorine-based dispersant having a perfluoroalkenyl group and CNT are added to the above-mentioned alone or a mixed solvent and irradiated with ultrasonic waves for several tens of minutes to give ultrasonic vibrations, the weight average molecular weight (Mw) Is a 5,000-30,000 high molecular weight, bulky perfluoroalkenyl group and hydrophilic group of a fluorine-based dispersant having a hydrophilic group adsorbed on the surface of the hydrophobic CNT. The hydrophilicity of the outer surface of the CNT is increased, and the adsorption of the dispersant between the CNT bundles is further promoted. Then, due to the steric hindrance effect of the bulky perfluoroalkenyl group, the CNTs are loosened and the dispersion of the CNTs proceeds efficiently. In addition, the perfluoroalkenyl group having a double bond in a polar solvent has a large electron-attracting effect and is negatively charged. Therefore, a repulsive force acts between neighboring CNT bundles, and reaggregation between CNT bundles is suppressed. The Furthermore, bulky fluorine-based dispersants and solvent molecules enter the new CNT between the CNTs, leading to uniform dispersion. Due to the steric hindrance effect and electrostatic repulsion of the further dispersant, the good dispersion state is maintained for a long time. It is maintained. By adjusting the concentration of the dispersant necessary to overcome the CNT cohesive force, a CNT dispersion A having good dispersion stability can be obtained even when the CNT concentration is high.

If the concentration of the nonionic fluorine-based dispersant is in the range of 90 to 360 ppm in the CNT concentration range, adjusting to 45 ppm or more and 4000 ppm or less provides good long-term dispersion stability as supported by experimental data described later. A CNT dispersion A can be obtained. In particular, when the CNT concentration is 45 ppm or more and 360 ppm or less, the concentration of the nonionic fluorine-based dispersant is 45 ppm or more and 1000 ppm or less, and the ratio of the fluorine-based dispersant to the CNT is reduced to achieve good dispersion stability. In addition, the coating film formed by applying Wet 24 μm of this CNT dispersion liquid A with a bar coater can reduce the total amount of light by the amount of the fluorine-based dispersant. The transmittance is as high as 88% or more, and the conductive film has a surface resistivity of about 10 ³ to 10 ⁶ Ω / □.

  Here, “long-term dispersion stability” means that even when the prepared CNT dispersion A is allowed to stand at room temperature for 1 day or longer, CNT aggregates of 0.3 mm or longer are not generated.

  The concentration ratio of the nonionic fluorine-based dispersant to the CNT [concentration of nonionic fluorine-based dispersant / CNT concentration] can be varied in a wide range of 0.5 to 45. When the concentration ratio is smaller than 0.5, the dispersion stability of the CNT dispersion A is lowered. When the concentration ratio exceeds 45, the surface resistivity of the coating film formed by the CNT dispersion A is relatively increased. And since the total light transmittance also becomes low, it is preferable to set it as the ratio range of 0.5-45 as mentioned above.

  In addition, it is difficult to obtain a CNT dispersion having a long-term dispersion stability even when a nonionic non-fluorine dispersant such as polyoxyethylene-polyoxypropylene block copolymer, polyethylene glycol, gelatin or the like is used. is there.

  The CNT dispersion liquid (hereinafter referred to as CNT dispersion liquid B) according to the second invention comprises CNT, a nonionic fluorine-based dispersant having a perfluoroalkenyl group, and a perfluoroalkenyl group in a single or mixed solvent. An amphoteric fluorine-based dispersant having CNTs dispersed therein by ultrasonic irradiation, either alone or in a mixed solvent, CNT, or nonionic fluorine-based dispersant is added to the CNT dispersion A. The same one used is used.

  In the CNT dispersion B, the amphoteric fluorine-based dispersant having a perfluoroalkenyl group used in combination with the nonionic fluorine-based dispersant is a perfluoroalkenyl betaine represented by the following structural formula (2). Etc. are preferably used. As a typical example of the amphoteric fluorine-based dispersant, there can be mentioned Footage 400PR (Mw: 639) manufactured by Neos Co., Ltd. [Product number of amphoteric fluorine-based dispersant manufactured by Neos Co., Ltd.].

  When the amphoteric fluorine dispersant as described above is used in combination with the nonionic fluorine dispersant, the amphoteric fluorine dispersant is added to the CNT together with the nonionic dispersant in addition to the above-mentioned action of the nonionic fluorine dispersant. By covering the surface, the hydrophilicity and surface potential of the outer surface of the CNT are further increased, and the adsorption of the dispersant to the CNT bundle is further promoted. Then, due to the steric hindrance effect of the bulky perfluoroalkenyl group, the CNT is loosened, and the dispersion of the CNT proceeds efficiently. In addition, perfluoroalkenyl groups in polar solvents have a large electron-attracting-inducing effect and are negatively charged accordingly, so that the repulsive action between neighboring CNT bundles is stronger than that of the CNT dispersion A, so that CNT Aggregation is less likely to occur between bundles and between CNTs, and this CNT dispersion B can exhibit uniform dispersibility and long-term dispersion stability. Further, by adjusting the total concentration of both the nonionic and amphoteric fluorine-based dispersants, a CNT dispersion B having good long-term dispersion stability can be obtained even if the CNT concentration is further increased.

For example, when the concentration of CNTs is in the range of 190 ppm or more and less than 1350 ppm, the total concentration of both nonionic and amphoteric fluorine-based dispersants is adjusted in the range of 90 ppm to 5000 ppm, and long-term dispersion stability is good. A CNT dispersion B can be obtained. Such a CNT dispersion B having a high CNT concentration can form a good conductive coating film having a surface resistivity of about 10 ³ to 10 ⁴ Ω / □ by a single coating (Wet 24 μ) using a roll coater or the like. So it is extremely useful.

  The concentration (ppm) of the amphoteric fluorine-based dispersant is preferably ½ or less of the concentration (ppm) of the nonionic fluorine-based dispersant. The perfluoroalkenyl betaine of the structural formula (2) used as an amphoteric fluorine-based dispersant has a molecular weight much smaller than that of a nonionic fluorine-based dispersant, which is a polymer, and has a small steric hindrance effect. Alone, a large amount is necessary. Further, when the amphoteric fluorine-based dispersant is used in combination at a concentration exceeding 1/2 of the concentration of the nonionic fluorine-based dispersant, there arises a disadvantage that the dispersion stability of the CNT dispersion is decreased. These reasons are that although the amphoteric fluorine-based dispersant has a low molecular weight and can impart hydrophilicity to the CNT surface, it has only one bulky perfluoroalkenyl group and prevents CNT aggregation. In order to achieve the effect of steric hindrance due to the group, a large amount of addition is required. However, since the amphoteric fluorine-based dispersant is non-conductive, the conductive performance of the CNT is reduced. In addition, since it is a low molecular weight substance, the adsorption area with the CNT becomes partial, and desorption from the adsorption surface can be considered, so there is a concern that the long-term dispersion stability of the CNT cannot be maintained. The preferred concentration ratio of the amphoteric fluorine-based dispersant to the nonionic fluorine-based dispersant [the concentration of the amphoteric fluorine-based dispersant / the concentration of the nonionic fluorine-based dispersant] is in the range of 0.1 to 0.5. In this range, a CNT dispersion B having good long-term dispersion stability can be obtained as supported by experimental data described later.

  Also, the concentration ratio of both nonionic and amphoteric fluorine-based dispersants to CNT [(concentration of nonionic fluorine-based dispersant + concentration of amphoteric fluorine-based dispersant) / CNT concentration] varies within a wide range. The concentration ratio is preferably 0.5 to 45.

  In addition, when a non-fluorine type dispersant such as 3- (N, N-dimethylstearylammonio) propanesulfonate is used as the amphoteric dispersant, the concentration ratio of the dispersant to CNT is 2 when the CNT concentration is 450 ppm. .6, it is difficult to obtain a CNT dispersion with good long-term dispersion stability. Furthermore, even when only the amphoteric fluorine-based dispersant is used, it is difficult to obtain a CNT dispersion having good dispersion stability or the like unless the CNT concentration is significantly reduced.

  The above CNT dispersion A or B is added to a single solvent or a mixed solvent so that CNT and a nonionic fluorine-based dispersant are in the above-mentioned concentration ratio, or CNT and nonionic fluorine-based dispersant. And the amphoteric fluorine-based dispersant is added so as to have the above-mentioned concentration ratio, and can be produced simply by irradiating with ultrasonic waves for several tens of minutes while cooling using an ultrasonic irradiator. . Also, it is possible to use a general mixing apparatus suitable for mass production, such as a bead mill or a homomixer.

  The conductive member of the present invention is obtained by forming a coating film of the CNT dispersion A or B on the surface of a base material, and a typical embodiment uses a transparent synthetic resin film as the base material. And it is the electroconductive film obtained by forming the electroconductive coating film by coating the said CNT dispersion liquid A or B on the surface using a bar coater or a roll coater, and drying. It can also be manufactured by die coating, which is a precision coating method, spray coating used for three-dimensional shapes, and other spin coating and flow coating.

As the base synthetic resin film, PET or acrylic resin film having excellent transparency and good coatability is particularly preferably used. Further, the thickness of the coating film is not particularly limited. When the CNT dispersion A or B has a high CNT concentration, the coating of the CNT dispersion A or B is sufficient for performance expression such as surface resistivity only by one coating (bar coater Wet 24 μm). In particular, when a highly conductive film having a low surface resistivity (10 ² Ω / □ or less) is obtained, it can be easily achieved by coating a plurality of times.

The coating film of the conductive film obtained in this way was not even entangled and agglomerated with each other while the CNTs were slightly bent, and was uniformly dispersed in a crossed state and contacted at each intersection point. A nonionic fluorine-based dispersant having an alkenyl group, or a nonionic fluorine-based dispersant and an amphoteric fluorine-based dispersant are mixed between CNTs. Therefore, this coating film has good transparency and no fear of appearance failure due to aggregation of CNTs, expresses conductivity by mutual contact of CNTs, and as shown in the experimental data described later, the CNT concentration is 150 ppm or more, When a coating film is formed with a CNT dispersion of 1170 ppm or less, a good film having a surface resistivity of 10 ⁵ Ω / □ or less can be obtained by a single coating of a bar coater Wet 24 μm. Furthermore, a binder, a light stabilizer, a UV absorber, a heat stabilizer, a colorant, a reinforcing agent, a plasticizer, and the like may be optionally added to the CNT dispersion for imparting functions.

  The conductive member of the present invention is not limited to the above-mentioned conductive film, and a smooth base material (film, plate, etc.) such as PET, polycarbonate, nylon as a glass body or inorganic material or synthetic resin molding as a base material It may be an uneven surface, a three-dimensional curved surface, a shape having a step, a fibrous material, a woven fabric, or a spherical material. It goes without saying that by using these base materials and coating the CNT dispersion A or B on the surface to form a coating film, it is possible to form a conductive member suitable for various applications. Yes.

  Next, the performance evaluation test of the CNT dispersion according to the present invention will be described.

[Performance evaluation test of CNT dispersion A]
The mixed solvent shown in Table 1 below has a single-wall CNT having a diameter of 1.3 to 1.8 nm synthesized based on the document Chemical Physics Letters 323 (2000) P580-585, and a perfluoroalkenyl group shown in Table 1. Nonionic fluorine-based dispersants (aftergent 730FM, aftergent 710FL, and aftergent 730FS) were added so as to have the concentrations shown in Table 1, and an ultrasonic irradiator US200 [manufactured by IKA Corporation] was used. The CNT dispersion liquids of sample numbers 1 to 8 were prepared by irradiating with ultrasonic waves at 46 W (24 kHz) for 30 minutes while cooling.

(Evaluation of long-term dispersion stability)
Samples 1 to 8 of each CNT dispersion liquid are allowed to stand at room temperature for 1 day, and 1 to 2 ml of each sample is taken in a 5 ml screw tube. The long-term dispersion stability was examined by visually observing the presence or absence of agglomerates and evaluated as ◯ when no agglomerates of CNTs having a diameter of 0.3 mm or more were observed, and CNTs having a diameter of 0.3 mm or more were evaluated. The thing in which the aggregate was seen was evaluated as x. The results are shown in Table 1 below. Sample 2 was allowed to stand for 1 year, and sample 5 was allowed to stand for 8 months to evaluate long-term dispersion stability.

(Performance evaluation of coating film of CNT dispersion)
Samples 1 to 8 of each CNT dispersion were applied to the surface of an acrylic film having a thickness of 100 μm with a bar coater KC3 (manufactured by RK Print-Coat Instruments Ltd) to a thickness of 24 μm, and dried at 70 ° C. for 10 minutes. Thus, a conductive coating film was formed. Then, the total light transmittance and haze of this coating film-forming film were measured with a direct reading haze computer HGM2-DP [manufactured by Suga Test Instruments Co., Ltd.], and the surface resistivity was further measured by Loresta GP [manufactured by Mitsubishi Chemical Corporation]. ] And measured. In addition, the appearance of this coating film-forming film was observed with the naked eye, and when the aggregate of CNT was not seen, the appearance was good (◯), and when the aggregate was seen, the appearance was poor (×). Judged the quality. These results are shown in Table 1 below.

  For comparison, as shown in Table 1 below, as shown in Table 1, a comparative sample 1 of a CNT dispersion containing no dispersant and a nonionic dispersant (polyoxyethylene-) other than a fluorine-based dispersant having a perfluoroalkenyl group Comparative samples 2 to 5 of CNT dispersions added with polyoxypropylene block copolymer, polyethylene glycol, gelatin) were prepared, and performance evaluation was performed in the same manner as described above. The results are shown in Table 1 below.

  Furthermore, as shown in Table 2 below, a sample of a CNT dispersion containing a nonionic fluorine-based dispersant having a perfluoroalkenyl group (Furgent 730FM), wherein the CNT concentration and the composition of the mixed solvent are Samples 9 to 12 in which the concentration of the fluorinated dispersant was changed to be constant (sample 10 is the same as sample 2 in Table 1), and the concentration of the fluorinated dispersant and the CNT concentration were made constant and water in the mixed solvent. Samples 19 to 19 with different weight ratios of the above were prepared, and samples 20 to 27 were prepared by changing the organic solvent in the mixed solvent by setting the concentration of the fluorinated dispersant constant and the CNT concentration to 90 ppm. Thus, long-term dispersion stability was evaluated. The results are shown in Table 2 below.

From Samples 1 to 8 in Table 1 and Samples 9 to 12 in Table 2, the concentration of nonionic fluorine-based dispersant having a perfluoroalkenyl group is 45 ppm or more and 4000 ppm or less (the concentration ratio of the dispersant to CNT is 0). It can be seen that the CNT dispersion A contained in .5-45) has good long-term dispersion stability. In addition, the total light transmittance of the film on which the coating film was formed by coating once with Bar Coater Wet 24μ with CNT dispersion A was as high as 88.5%, haze was 2.5% or less, and transparency was good. is there. A surface resistivity of 10 ³ to 10 ⁶ Ω / □ is obtained. Also, the film appearance is good with no aggregation.
However, when the CNT concentration is 450 ppm or more as in Sample 6, the long-term dispersion stability is poor in the CNT dispersion A containing only 1000 ppm of the nonionic fluorine-based dispersant.

On the other hand, Comparative Samples 2 to 5 containing only the non-fluorine dispersant have poor long-term dispersion stability. The surface resistivity of the film on which the coating film was formed, excluding Sample 2, was about 10 ¹¹ Ω / □, which was in the range of antistatic properties, and only Comparative Sample 2 was only about 10 ⁶ Ω / □. It only shows electricity. On the other hand, Comparative Sample 1 containing no dispersant has poor long-term dispersion stability.

  Judging comprehensively from the above, the CNT dispersant A of the present invention containing a nonionic fluorine-based dispersant having a perfluoroalkenyl group has a dispersion stability for forming a transparent conductive coating film. It can be seen how useful as a good ink (dispersion liquid, coating liquid, etc.).

  In addition, from Samples 13 to 18 in Table 2, the CNT dispersion A in which the weight ratio of water in the mixed solvent is 0 is poor in long-term dispersion stability, but the weight ratio of water is 0.1 or more, It can be seen that all of the CNT dispersions A adjusted to less than 1 (0.88 or less) have good long-term dispersion stability. From this, it can be estimated that the CNT dispersion A of the present invention in which the weight ratio of water is adjusted to 0.1 to 0.99 has good long-term dispersion stability. Moreover, it can be seen from Sample 19 that the long-term dispersion stability of the CNT dispersion A of the present invention using a single solvent of only water is also good.

  Furthermore, as shown in Samples 20 to 27 in Table 2, the type of organic solvent in the mixed solvent is polar other than ethanol, such as methanol, isopropanol (IPA), N-methylpyrrolidone, acetonitrile, etc. The CNT dispersion A changed to a high organic solvent also has good long-term dispersion stability. Therefore, a mixed solvent of an organic solvent having a dielectric constant ε of 6 or more and water is suitable as the solvent for the CNT dispersion A. You can see that

[Performance evaluation test of CNT dispersion B]
In the mixed solvent shown in Table 3 below, single-walled CNTs having a diameter of 1.3 to 1.8 nm, and a nonionic fluorine-based dispersant having a perfluoroalkenyl group shown in Table 3 (Furgent 710FL), An amphoteric fluorine-based dispersant having a perfluoroalkenyl group shown in Table 3 (Furgent 400PR) was added so as to have a concentration shown in Table 3, and an ultrasonic irradiator US200 [manufactured by IKA Corporation] was used. Then, CNT dispersion B of sample numbers 28 to 35 was prepared by irradiating with ultrasonic waves at 46 W (24 kHz) for 30 minutes while cooling.

  For each CNT dispersion B sample, the long-term dispersion stability, the total light transmittance, haze, and surface resistivity of the coating film-forming film were measured in the same manner as the CNT dispersion A sample. The film appearance was judged as good or bad, and the results are shown in Table 3 below.

  For comparison, as a dispersant, comparative sample 6 containing both nonionic footage 710FL shown in Table 3 and amphoteric 3- (N, N-dimethylstearylammonio) propanesulfonate, and amphoteric Comparative Samples 7 to 10 containing only the above-mentioned Basegent 400PR were prepared, and the dispersion stability of these comparative samples was examined in the same manner as described above. Total light transmittance, haze, and surface resistivity were measured. And the quality of the external appearance of the coating film formation film of these comparative samples 6-10 was investigated similarly. The results are shown in Table 3 below.

CNT dispersion in which the total concentration of the nonionic fluorine-based dispersant and the amphoteric fluorine-based dispersant was 1150 ppm or more and 3000 ppm or less from the samples 28 to 35 (bar coater Wet 24 μ1 coating) of the CNT dispersion B shown in Table 3 It can be seen that the liquid B has good long-term dispersion stability even when the CNT concentration is 191 ppm or more and less than 1350 ppm (1170 ppm or less), which is much higher than the CNT dispersion A. The transparency of the coating film is good, and a surface resistivity of 10 ² to 10 ⁴ Ω / □ can be obtained. That is, the surface resistivity of the film-forming film formed by coating these CNT dispersions B once with a bar coater Wet 24μ is 9.1 × 10 ⁴ Ω / □ or less, and the total light transmittance is 78.6. %, Haze is 3.2% or less, and the film appearance is also good. Furthermore, for example, when the CNT dispersion B of Sample 34 in which a CNT concentration of 1170 ppm, a nonionic fluorine-based dispersant 1500 ppm and an amphoteric dispersant concentration 500 ppm is mixed is applied to an acrylic film three times with a bar coater Wet 24 μ, surface resistivity 2 A conductive film-forming film having a size of 2 × 10 ² Ω / □, a total light transmittance of 72%, and a haze of 3.6% is obtained, and this film has a good appearance. The above CNT dispersion B can be produced by a roll coater, a die coater for precision coating, other spin coating or flow coating.

On the other hand, the comparative sample 6 using both the nonionic fluorine-based dispersant and the amphoteric non-fluorine-based dispersant has poor dispersion stability. In addition, Comparative Samples 7 to 10 containing only the amphoteric fluorine-based dispersant have good long-term dispersion stability when the CNT concentration is as low as 45 ppm. However, long-term dispersion stability is poor at a concentration ratio lower than that. It is. The comparative sample 10 having a relatively high CNT concentration of 191 ppm and a relatively high concentration ratio of the amphoteric fluorine-based dispersant to CNT of 3.9 has a high total light transmittance of the film on which the coating film is formed, and haze is high. The surface resistivity was about 10 ⁴ Ω / □ and the conductivity was relatively good, but the appearance was poor.

  Judging from the above, the CNT concentration without impairing dispersion stability by using a nonionic fluorine-based dispersant having a perfluoroalkenyl group and an amphoteric fluorine-based dispersant having a perfluoroalkenyl group in combination. The CNT dispersion B of the present invention with a high adjusted value is extremely useful as a high-quality dispersion (ink) with good long-term dispersion stability for forming a transparent and highly conductive coating film. I understand.

1 Main chain of acrylic copolymer 2 Perfluoroalkenyl group 3 Side chain having perfluoroalkenyl group 4 Side chain of hydrophilic group

Claims (10)

  Carbon nanotubes and nonionic fluorine-based dispersant having a perfluoroalkenyl group are contained in a single solvent of water alone or a mixed solvent of water and a water-soluble organic solvent, and the carbon nanotubes are dispersed. A carbon nanotube dispersion characterized by.   A single solvent of water alone or a mixed solvent of water and a water-soluble organic solvent, a carbon nanotube, a nonionic fluorine-based dispersant having a perfluoroalkenyl group, and an amphoteric fluorine-based dispersion having a perfluoroalkenyl group A carbon nanotube dispersion liquid containing an agent and having carbon nanotubes dispersed therein.   The nonionic fluorine-based dispersant is made of a copolymer of an acrylic monomer having a perfluoroalkenyl group and an acrylic monomer having a hydrophilic group. The carbon nanotube dispersion liquid according to 2. The carbon nanotube dispersion liquid according to any one of claims 1 to 3, wherein the perfluoroalkenyl group is represented by the following structural formula (1).

The carbon nanotube dispersion liquid according to claim 2, wherein the amphoteric fluorine-based dispersant is a perfluoroalkenyl betaine represented by the following structural formula (2).

  The concentration ratio of the nonionic fluorine-based dispersant to the carbon nanotube [concentration of nonionic fluorine-based dispersant / carbon nanotube concentration] is 0.5 to 45, according to claim 1. Carbon nanotube dispersion.   The concentration ratio of the amphoteric fluorine-based dispersant to the nonionic fluorine-based dispersant [the concentration of the amphoteric fluorine-based dispersant / the concentration of the nonionic fluorine-based dispersant] is in the range of 0.1 to 0.5. The carbon nanotube dispersion liquid according to claim 2, wherein   The weight ratio of water in the mixed solvent [weight of water / (weight of water + weight of water-soluble organic solvent)] is from 0.1 to 0.99. The carbon nanotube dispersion liquid described in 1.   The water-soluble organic solvent in the mixed solvent is selected from the group consisting of methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 1-methoxy-2-propanol, N-methylpyrrolidone, acetonitrile having a dielectric constant of 6 or more. The carbon nanotube dispersion liquid according to claim 1, which is any one kind or two or more kinds of organic solvents.   A conductive member, wherein a coating film of the carbon nanotube dispersion liquid according to any one of claims 1 to 9 is formed on a surface of a base material.

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