JP2010270205A - Carbon nanotube-containing composition and coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating film excellent in any of light transmissivity, durability and electroconductivity by using a composition in which a VOC is not a main solvent. <P>SOLUTION: An electroconductive polymer, a dopant, a carbon nanotube, water and a dispersant are mixed to prepare a carbon nanotube-containing composition. The obtained carbon nanotube-containing composition is coated and dried to fabricate a coating film. The dispersant preferably contains a water-soluble xylan, and further preferably contains an alcohol. The water-soluble xylan has a number-average polymerization degree of the main chain of ≥6 and ≤5,000. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a carbon nanotube-containing composition and a coating film.

  The transparent conductive film is used for coating a base material such as a liquid crystal display, an electroluminescence display, a plasma display, an electrochromic display, a transparent electrode such as a solar battery or a touch panel, and an electromagnetic shielding material. The most widely used transparent conductive film is a deposited film of indium-tin composite oxide (ITO) (see Non-Patent Document 1).

  In addition, a transparent conductive film made of an organic material using a conductive polymer that can be formed at low temperature and low cost has been proposed. For example, a method for producing a complex of poly (3,4-dialkoxythiophene) with good water dispersibility and a polyanion is disclosed (see Patent Document 1).

Furthermore, an electromagnetic wave shield in which a transparent conductive layer containing ultrafine conductive fibers is formed on at least one side of a substrate, the ultrafine conductive fibers are dispersed without agglomeration and contact each other, and the conductive layer is An electromagnetic wave shield having a sheet resistance of 10 ⁵ Ω / □ or less is disclosed (see Patent Document 2).

  As the carbon nanotube-containing composition that does not aggregate in an aqueous medium, an aqueous composition for conductive coating containing a water-soluble xylan, a resin, and carbon nanotubes is disclosed (see Patent Document 3).

  Patent Document 4 discloses a composition in which a water-soluble organic compound is added to a conductive polymer.

  Patent Document 5 discloses a dispersion containing carbon nanotubes and a conjugated polymer.

  Patent Document 6 discloses a composite material including carbon nanotubes and a conductive polymer.

JP H07-090060 A (published April 4, 1995) Japanese Patent Laid-Open No. 2004-253796 (published on September 9, 2004) JP 2008-217684 A (published September 18, 2008) WO 2004/106404 (released July 20, 2006) JP 2005-809738 A (published April 7, 2005) JP 2008-523234 A (published July 3, 2008)

New transparent conductive film Toray Research Center, Inc. p. 1 (2005)

  In the ITO vapor deposition film, since the metal target contains rare metal indium, the cost of the target is higher than that of a normal film forming process, and the production amount per unit time is high because the production is performed by vacuum batch processing. There were few problems that the price of the film coated with the conductive film was very high. Also, inorganic oxide films such as ITO are poor in flexibility of the coating film, for example, are easily cracked due to the bending of the base material, are likely to cause problems of decrease in conductivity, and for applications that require flexibility. There was a problem that it was difficult to use.

  The thin film formed by applying the coating composition containing the aqueous dispersion of the invention of Patent Document 1 on the substrate solves the problems that occur when ITO is used, but is more conductive than the inorganic oxide film. There is a problem that the polymer is insufficient in transparency, conductivity, and durability.

  Furthermore, in Patent Document 4, the conductivity that has been a problem in Patent Document 1 is improved by using a composition in which a water-soluble organic compound is added to a conductive polymer, but the durability is insufficient. Met.

  On the other hand, the coating liquid for forming the conductive layer of the invention of Patent Document 2 is sufficient in terms of transparency and conductivity of the film after coating, which has been a problem in Patent Document 1, but it is an ultrafine conductive fiber. Since it is difficult to disperse in water, it is prepared by dispersing ultrafine conductive fibers in a solution in which a binder is dissolved in a volatile organic solvent. Therefore, from the viewpoint of environmental safety, a volatile organic compound (hereinafter, referred to in this specification). , “VOC”) is a problem.

  On the other hand, the aqueous composition for conductive coating of the invention of Patent Document 3 improves the water dispersibility by using water-soluble xylan, and the problem of VOC associated with the use of the organic solvent that was a problem in Patent Document 2 However, the coating film produced using this composition has a problem of low electrical conductivity and light transmittance.

  Moreover, the dispersion liquid of patent document 5 had the problem that the dispersion stability of a carbon nanotube was bad.

  The composite material of Patent Document 6 has a problem that the stability of the composite material and the light transmittance are poor because the dispersibility of the carbon nanotubes in the solution used for preparing the material is poor.

  That is, in an organic material that solves the problem of ITO, a transparent conductive film excellent in both conductivity and durability using a composition in which VOC is not a main solvent is not known.

  As a result of intensive studies to solve the above problems, the present inventors have used the carbon nanotube-containing composition containing a conductive polymer, a dopant, carbon nanotubes, water, and a dispersant, and thus the above problems. It was found that the problem was solved, and the invention was completed based on this.

  That is, the present invention is a carbon nanotube-containing composition containing a conductive polymer, a dopant, carbon nanotubes, water and a dispersant.

  Further, the carbon nanotube-containing composition is characterized in that the dispersant contains at least water-soluble xylan.

  Further, the carbon nanotube-containing composition is characterized in that the dispersant further contains an alcohol in addition to the water-soluble xylan.

  Furthermore, it is a carbon nanotube containing composition whose number average polymerization degree of the principal chain of water-soluble xylan is 6 or more and 5000 or less.

  Furthermore, it is a carbon nanotube-containing composition in which the water-soluble xylan is composed of a xylose residue or an acetylated xylose residue, an arabinose residue and a 4-O-methylglucuronic acid residue.

  Furthermore, in the water-soluble xylan, it is a carbon nanotube-containing composition in which the total of the xylose residue and the acetylated xylose residue is 7 to 100 with respect to the arabinose residue 1.

  Furthermore, it is a carbon nanotube-containing composition in which the water-soluble xylan is composed of a xylose residue or an acetylated xylose residue and a 4-O-methylglucuronic acid residue.

  Further, in the water-soluble xylan, the carbon nanotube-containing composition has a ratio of 1 to 100 in total of xylose residue and acetylated xylose residue with respect to 4-O-methylglucuronic acid residue 1.

  Furthermore, it is a carbon nanotube containing composition whose number average molecular weights of the said water-soluble xylan are 1500-1 million.

  Furthermore, it is a carbon nanotube containing composition whose water-soluble xylan is a xylan derived from a woody plant.

  Furthermore, it is a carbon nanotube containing composition whose water-soluble xylan is xylan derived from hardwood.

  Further, the carbon nanotube-containing composition is characterized in that the conductive polymer contains at least polythiophene.

  Furthermore, the carbon nanotube-containing composition is characterized in that the polythiophene contains at least poly (3,4-ethylenedioxythiophene).

  Furthermore, the carbon nanotube-containing composition is characterized in that the carbon nanotube is a single-walled carbon nanotube.

  Furthermore, the carbon nanotube composition is characterized in that the dopant is a Lewis acid.

  Furthermore, the carbon nanotube composition is characterized in that the Lewis acid is a sulfonic acid compound.

  Furthermore, with respect to 100 parts by weight of the carbon nanotube-containing composition, 0.01 to 5 parts by weight of a conductive polymer, 0.1 to 10 parts by weight of a dopant, 0.001 to 5 parts by weight of a carbon nanotube, and 0.15 of a dispersant. It is a carbon nanotube containing composition characterized by containing -40 weight part.

  Moreover, it is a coating film formed by apply | coating and drying the said carbon nanotube containing composition.

  Furthermore, it is a transparent conductive film formed by applying and drying a coating film on a polymer film or glass surface.

  The carbon nanotube-containing composition of the present invention is excellent in environmental safety since VOC is not the main solvent. Moreover, the coating film produced using the carbon nanotube containing composition of this invention turns into a coating film which has favorable transparency, electroconductivity, and durability.

Sample for sheet resistance measurement

  The carbon nanotube-containing composition of the present invention is a carbon nanotube-containing composition containing a conductive polymer, a dopant, a carbon nanotube, water and a dispersant.

  In the present invention, “excellent in durability” means that the sheet resistance is measured by preparing a coating film, and then the sheet resistance is measured after being left in an environmental atmosphere at an air temperature of 20 ° C. and a humidity of 50% for 4 days. It means that there is little change in sheet resistance before and after being left. Specifically, the sample solution is applied to the surface of a PET film (Toray Polyester Film Lumirror # 100-U34), stretched to a certain thickness using a bar coater, and heated and dried at 120 ° C. for 60 minutes to be 550 nm. The film resistance was adjusted to 85 ± 5%, the sheet resistance immediately after preparation of the coating film was a (Ω / □), and the sheet resistance after standing for 4 days was b (Ω / □), the value calculated by the b / a calculation formula (hereinafter referred to as resistance value retention) is small. The resistance value retention is preferably 1.5 or less in order to stably use the coating film for a long period of time.

  The conductive polymer in the present invention includes at least a structure in which a conjugated structure is extended.

  Examples of the conductive polymer include a polythiophene polymer, a polypyrrole polymer, a polyaniline polymer, a polyacetylene polymer, a poly-p-phenylene polymer, and a poly-p-phenylene vinylene polymer. . The polymer may be a homopolymer composed of a single monomer unit, a different monomer unit may be a block copolymer, a random copolymer, or a polymer having a graft polymer structure. Among the above polymers, in the present invention, it is preferable to use a polythiophene polymer because the durability of a coating film formed using the carbon nanotube-containing composition is excellent.

  The polythiophene polymer in the present invention is a structure having a poly-thiophene structure skeleton. For example, poly-3-alkylthiophenes such as polythiophene, poly-3-methylthiophene, poly-3-butylthiophene, poly-3-hexylthiophene, poly-3-octylthiophene, poly-3-dodecylthiophene, poly- Poly-3-alkoxythiophenes such as 3-methoxythiophene, poly-3-ethoxythiophene, poly-3-dodecyloxythiophene, poly (3,4-ethylenedioxythiophene), poly (3,4-dimethoxythiophene) , Poly (3,4-diethoxythiophene), poly (3,4-dipropoxythiophene), poly (3,4-dibutoxythiophene), poly (3,4-dihexyloxythiophene), poly (3,4 -Diheptyloxythiophene), poly (3,4-dioctyloxythiophene) , Poly (3,4-didecyloxythiophene), poly (3,4-didodecyloxythiophene), poly (3,4-propylenedioxythiophene), poly (3,4-butenedioxythiophene), poly Poly-3,4-dialkoxythiophenes such as (3,4-ethylenedioxythiophene), poly-3 such as poly-3-methoxy-4-methylthiophene, poly-3-dodecyloxy-4-methylthiophene -Alkoxy-4-alkylthiophenes, poly-3-thioalkylthiophenes such as poly-3-thiohexylthiophene and poly-3-thiododecylthiophene. Among these, poly-3-alkylthiophenes, poly-3-alkoxythiophenes, and poly-3,4-dialkoxythiophenes are preferably used in terms of excellent dispersibility in a solvent. In particular, it is preferable to use poly (3,4-ethylenedioxythiophene).

  In addition, as a polythiophene-type polymer, it is preferable that the weight average molecular weight is 500-100000 from the point which is excellent in the electroconductivity of the coating film formed using a carbon nanotube containing composition, and the dispersibility to a solvent.

  In the present invention, the content of the conductive polymer is 0.01 to 5 parts by weight when the carbon nanotube-containing composition is 100 parts by weight. This is preferable because it becomes difficult to develop and a stable dispersion state can be expressed. In particular, 0.1 to 3 parts by weight is preferable because not only the stability of the conductive polymer in water but also the state in which the carbon nanotube-containing composition is stably dispersed for a long period of time can be maintained.

  The dopant in the present invention means that when the carbon nanotube-containing composition is dried and formed into a coating film or the like, the electrical resistance value of the coating film is higher than that of the coating film containing only the conductive polymer. The substance is not particularly limited as long as it is a substance capable of lowering. As such a substance, since the conductivity of the conductive polymer is improved, a Lewis acid compound can be preferably used. As the Lewis acid compound in the present invention, for example, sulfonic acid compounds, boric acid compounds, phosphoric acid compounds, chloric acid compounds and the like are preferably used. Since the conductivity of the conductive polymer is excellent, it is preferable to use a sulfonic acid compound.

  Examples of the sulfonic acid compound include polystyrene sulfonic acid, alkyl naphthalene sulfonic acid, methane sulfonic acid, paratoluene sulfonic acid, naphthalene sulfonic acid, trifluoromethane sulfonic acid, show brain sulfonic acid, and polyvinyl naphthalene sulfonic acid.

  These may be used individually by 1 type and may use 2 or more types together. Among these, the use of polystyrene sulfonic acid or alkylnaphthalene sulfonic acid in that the conductivity of the coating film formed using the carbon nanotube-containing composition is improved and the conductive polymer is easily dispersed in water. preferable.

  By controlling the content of the dopant in the organic conductive polymer composition, the sheet resistance of the coating film formed using the organic conductive polymer composition can be controlled to a desired level.

  The content ratio of the dopant in the present invention is 0.1 to 10 parts by weight when the carbon nanotube-containing composition is 100 parts by weight, and the coating film sheet is formed using the carbon nanotube-containing composition. It is preferable because the resistance can be controlled to 10,000 Ω / □ or less. In particular, 0.5 to 7 parts by weight is preferable in controlling the sheet resistance of the coating film formed using the carbon nanotube-containing composition to 2,000 Ω / □ or less.

  A carbon nanotube is an allotrope of carbon and refers to a structure in which a plurality of carbon atoms are combined and arranged in a cylindrical shape. Arbitrary carbon nanotubes can be used as the carbon nanotubes. Examples of carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes, and those in which they are coiled. Single-walled carbon nanotubes are those in which graphite-like carbon atoms are arranged in a single line, and multi-walled carbon nanotubes are those in which two or more layers of graphite-like carbon atoms are concentrically overlapped. The carbon nanotube used in the present invention may be a multi-walled carbon nanotube or a single-walled carbon nanotube, but more preferably it is a single-walled carbon nanotube because it has better conductivity. A carbon nanohorn having a closed shape on one side of the carbon nanotube, a cup-shaped nanocarbon material having a hole on the head, a carbon nanotube having a hole on both sides, and the like can also be used.

  The carbon nanotubes may be purified by washing, centrifugation, filtration, oxidation, chromatography, or the like, or may be unpurified. By using the purified carbon nanotube, the conductivity and durability of the coating film formed using the carbon nanotube-containing composition are improved. Therefore, in the present invention, it is preferable to use purified carbon nanotubes. Note that the diameter, length, and structure (whether single-walled or multi-walled) of the carbon nanotube used are not particularly limited, and any carbon nanotube can be used.

  In the carbon nanotube-containing composition, the carbon nanotubes may be dispersed in a state where they are separated one by one, or may be dispersed in a state where a plurality of carbon nanotubes are bundled. In particular, in order to increase the conductivity, it is preferable that the particles are dispersed one by one.

  Since the carbon nanotube content in the present invention is 0.001 to 5 parts by weight when the carbon nanotube-containing composition is 100 parts by weight, the dispersibility of the carbon nanotubes in the solution can be maintained well. Preferably, the amount of 0.005 to 3 parts by weight can most favorably maintain the dispersibility in the solution, and further the conductivity and light transmission of the coating film obtained by applying and drying the composition. This is preferable because the rate is excellent.

  The addition of carbon nanotubes has revealed an unexpected effect that not only the conductivity of the coating film is improved, but also the durability is improved. Specifically, the coating film prepared using the composition part to which the carbon nanotubes are added has a temperature of 20 ° C. and humidity as compared with the coating film manufactured using the same composition that does not include the carbon nanotubes and other than that. It was revealed that the sheet resistance change before and after being left for 4 days in a 50% environmental atmosphere was ¼ or less.

  The dispersing agent in the present invention is a dispersing aid that can maintain a dispersed state stably for a long period of time when the carbon nanotubes are dispersed in an aqueous solution with a small amount of sedimentation. In particular, in the present invention, water-soluble xylan, alcohol, surfactant, amphoteric ion and the like can be used as the dispersant. Although the said dispersing agent can also be used individually by 1 type, it is also possible to use 2 or more types together.

  The water-soluble xylan in the present invention refers to a molecule containing 6 or more xylose residues linked by β-1,4 bonds, and soluble in 20 ° C. water at 6 mg / mL or more. Water-soluble xylan is not a pure xylose polymer, but a molecule in which at least a part of hydroxyl groups in the xylose polymer are replaced with other substituents (for example, acetyl group, glucuronic acid residue, arabinose residue, etc.). When the hydroxyl group of xylan consisting only of xylose residues is replaced with other substituents, water solubility may be higher than that of xylan consisting of only xylose residues. A molecule in which the hydroxyl group of xylan consisting of only a xylose residue is replaced with another substituent can also be referred to as a molecule having a substituent bonded to a xylose polymer, or a modified xylose polymer. In this specification, the term “modified” refers to a molecule that is modified in comparison with a reference molecule that constitutes a polymer, and not only a molecule produced by artificial manipulation but also a naturally occurring molecule. It also includes molecules that A substance in which a 4-O-methylglucuronic acid residue and an acetyl group are bonded to a xylose polymer is generally called glucuronoxylan. A substance in which an arabinose residue and a 4-O-methylglucuronic acid residue are bonded to a xylose polymer is generally called arabinoglucuronoxylan.

  The water-soluble xylan preferably contains only a xylose residue or a modified product thereof in its main chain, and more preferably contains only a xylose residue or an acetylated xylose residue in its main chain. In this specification, the term “main chain” refers to the longest chain linked by β-1,4 bonds. When water-soluble xylose is linear, the molecule itself is the main chain, and when water-soluble xylose is branched, the longest chain connected by β-1,4 bonds is the main chain. The number average polymerization degree of the main chain of the water-soluble xylan used in the present invention is preferably 6 or more and 5000 or less, more preferably 7 or more and 1000 or less, still more preferably 8 or more and 500 or less, and particularly preferably 9 It is 100 or less and most preferably 10 or more and 50 or less. Controlling the number average polymerization degree of the main chain of the water-soluble xylan within the above range is preferable because the solubility of the water-soluble xylan in water is improved.

  The hydrophilic group can be bonded at any of the 1-position, 2-position, 3-position or 4-position of the xylose residue. The number of hydrophilic group binding sites for one xylose residue may be all four, but preferably three or less, more preferably two or less, and most preferably one. The hydrophilic group may be bonded to all xylose residues of the xylose polymer, but is preferably bonded only to a part of the xylose residues. The ratio of hydrophilic group bonds is preferably 1 or more per 10 xylose residues, more preferably 2 or more per 10 xylose residues, and even more preferably 3 or more per 10 xylose residues. Yes, particularly preferably 4 or more per 10 xylose residues, and most preferably 5 or more per 10 xylose residues. Examples of the hydrophilic group include an acetyl group, 4-O-methyl-α-D-glucuronic acid residue, L-arabinofuranose residue and α-D-glucuronic acid residue.

  In a specific embodiment of the present invention, water-soluble xylan in which another sugar residue is bonded to the 2-position of the xylose residue is preferable. In this water-soluble xylan, the ratio of the total of xylose residues and acetylated xylose residues to other sugar residues is such that the total of xylose residues and acetylated xylose residues is 1 mol per other sugar residue. The amount is preferably 20 mol or less, more preferably 10 mol or less, and further preferably 6 mol or less. The ratio of the total of xylose residues and acetylated xylose residues to other sugar residues is such that the total of xylose residues and acetylated xylose residues is 1 mol or more with respect to 1 mol of other sugar residues. Is preferably 2 mol or more, more preferably 5 mol or more.

  In a specific embodiment of the present invention, water-soluble xylan in which a 4-O-methyl-α-D-glucuronic acid residue is α-1,2-linked at the 2-position of a xylose residue is preferred. In this water-soluble xylan, the ratio of the total of xylose residues and acetylated xylose residues to 4-O-methyl-α-D-glucuronic acid residue is the 4-O-methyl-α-D-glucuronic acid residue. The total of the xylose residue and the acetylated xylose residue is preferably 100 mol or less, more preferably 50 mol or less, and even more preferably 20 mol or less with respect to 1 mol of the group. The ratio of the total of xylose residues and acetylated xylose residues to 4-O-methyl-α-D-glucuronic acid residues is 1 mol of 4-O-methyl-α-D-glucuronic acid residues. The total of the xylose residue and the acetylated xylose residue is preferably 1 mol or more, more preferably 5 mol or more, more preferably 9 mol or more, and more preferably 10 mol or more. More preferably, it is 14 mol or more.

  The number average molecular weight of the water-soluble xylan is preferably 1500 to 1,000,000, more preferably 2000 to 500,000, still more preferably 4000 to 100,000, particularly preferably 5000 to 50,000, Preferably it is 6000-20,000.

  The preferred water-soluble xylan used in the present invention is preferably derived from woody plants. A large amount of water-soluble xylan is contained in plant cell wall portions. Wood is particularly rich in water-soluble xylan. The structure of water-soluble xylan varies depending on the type of plant from which it is derived. It is known that the main component of hemicellulose contained in hardwood wood is glucuronoxylan. Glucuronoxylan contained in hardwood is often composed of xylose residue 10: 4-O-methylglucuronic acid 1: acetyl group 6. It is known that the main component of hemicellulose contained in coniferous wood is glucomannan, and that coniferous wood also contains glucuronoxylan and arabinoglucuronoxylan. The main chain of glucomannan is composed of a mannose residue and a glucose residue, and the ratio is generally mannose residues 3 to 4: glucose residue 1. The water-soluble xylan used in the present invention is more preferably derived from hardwood, more preferably beech, hippopotamus, aspen, elm, beach or oak, more preferably glucuronoxylan. The hemicellulose component of hardwood contains a lot of water-soluble xylan used in the present invention. A water-soluble xylan derived from hardwood is particularly suitable because it contains almost no arabinose residue. Of course, naturally derived water-soluble xylan is a mixture of various molecules having different molecular weights. Naturally-derived water-soluble xylan may be used in a state containing impurities, as long as it can exert its effect, may be used as a population having a broad molecular weight distribution, or a population having a narrower molecular weight distribution. As such, it may be used after being purified to a higher purity.

  Although it is a small amount, water-soluble xylan is also contained in grasses such as conifers, corn, rice and wheat. In the water-soluble xylan derived from these, in addition to the 4-O-methyl-α-D-glucuronic acid residue, an α-L-arabinose residue is covalently bonded to a xylose residue. If the content of the α-L-arabinose residue is too high, the effect as a dispersant may not be obtained. Therefore, xylan having a high content of the α-L-arabinose residue is not suitable for the purpose of the present invention. Hemicellulose extracted from cereals (wheat, rice), kumagi, etc. is arabinoglucuronoxylan mainly composed of xylose, 4-O-methylglucuronic acid and arabinose. Unlike the water-soluble xylan of the present invention, arabinose High content. Even water-soluble xylan derived from herbaceous plants can be used in the present invention by removing at least part of the L-arabinose residue. L-arabinose residues can be removed by known methods such as chemical or enzymatic methods.

  In certain embodiments of the present invention, it is preferred that the water-soluble xylan consists of xylose or acetylated xylose residues, arabinose residues and 4-O-methylglucuronic acid residues. In this embodiment, the total of xylose residues and acetylated xylose residues with respect to L-arabinose residue 1 in water-soluble xylan is preferably 7 or more, more preferably 10 or more, and still more preferably 20 or more. In this embodiment, the total of xylose residues and acetylated xylose residues with respect to L-arabinose residue 1 in water-soluble xylan is preferably 100 or less, more preferably 60 or less, and even more preferably 40 or less.

  Water-soluble xylan is purified from, for example, wood according to a known method. Examples of the method for purifying water-soluble xylan include a method of extracting with delignified wood as a raw material with a potassium hydroxide solution of about 10%. Water-soluble xylan can also be obtained by dispersing powdered cellulose produced from wood in water and drying the filtrate obtained by sequentially filtering this solution through a filter paper, 0.45 μm filter, and 0.2 μm filter.

  In the water-soluble xylan used in the present invention, the ratio of the xylose residue to the L-arabinose residue is preferably 7 mol or more for the xylose residue relative to 1 mol of the L-arabinose residue. It is more preferable that it is 20 mol or more. There is no upper limit to the ratio of xylose residue to 1 mol of L-arabinose residue, and xylose residue is, for example, 100 residues or less, 60 residues or less, 40 residues or less, etc. with respect to 1 mol of L-arabinose residue. It is.

  In a particularly preferred embodiment of the invention, the water-soluble xylan preferably does not contain an L-arabinose residue. Water-soluble xylan consists of xylose residues or acetylated xylose residues and 4-O-methylglucuronic acid residues. In this embodiment, the total of xylose residues and acetylated xylose residues is preferably 1 or more, more preferably 5 or more, with respect to 4-O-methylglucuronic acid residue 1 in water-soluble xylan. More preferably, it is 9 or more, More preferably, it is 10 or more, More preferably, it is 14 or more. In this embodiment, the total of xylose residues and acetylated xylose residues with respect to 4-O-methylglucuronic acid residue 1 in water-soluble xylan is preferably 100 or less, more preferably 50 or less. More preferably, it is 20 or less.

  The alcohol in the present invention refers to a hydroxyl group-containing compound, and examples thereof include aliphatic alcohols, alicyclic alcohols, and aromatic alcohols having 1 to 20 carbon atoms.

  The number of hydroxyl groups in the hydroxyl group-containing compound may be one or two or more. A compound having two or more hydroxyl groups in the compound is preferable because the dispersibility of the carbon nanotube is excellent in the carbon nanotube-containing composition. Examples of compounds having two or more hydroxyl groups include ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, and glycerin. Among these, ethylene glycol and diethylene glycol are In particular, it is preferable because the dispersibility of the carbon nanotube is improved. These may be used individually by 1 type and may use 2 or more types together.

  Since carbon nanotubes are stably dispersed for a long period of time, it is preferable to use water-soluble xylan as a dispersant. Furthermore, it is more preferable that more carbon nanotubes in the carbon nanotube composition can be stably dispersed by containing an alcohol in addition to the water-soluble xylan as a dispersant. By disperse | distributing more carbon nanotubes in a carbon nanotube containing composition, the electroconductivity and durability of the coating film produced using the composition improve more.

  Since the content of the dispersant in the present invention is 0.15 to 40 parts by weight when the carbon nanotube-containing composition is 100 parts by weight, the dispersibility of the carbon nanotubes in the carbon nanotube-containing composition is improved. Particularly preferred is 0.2 to 3 parts by weight because the dispersibility of the carbon nanotubes in the carbon nanotube-containing composition is particularly good.

  The carbon nanotube composition in the present invention is composed of 0.01 to 5 parts by weight of a conductive polymer, 0.1 to 10 parts by weight of a dopant, and 0.001 to 5 parts by weight of a carbon nanotube with respect to 100 parts by weight of the carbon nanotube-containing composition. A carbon nanotube composition characterized by containing 0.15 to 40 parts by weight of a dispersant and a dispersant is preferred. With this content, the carbon nanotube-containing composition is dispersed in the composition, and the coating obtained by applying and drying the carbon nanotube-containing composition is transparent, conductive and durable. Excellent. Conductive polymer 0.1-3 parts by weight, dopant 0.5-7 parts by weight, carbon nanotubes 0.005-3 parts by weight, dispersant 0.2-3 by weight with respect to 100 parts by weight of the carbon nanotube-containing composition. A carbon nanotube composition characterized by containing parts by weight is particularly preferred. By using this content, the carbon nanotubes in the carbon nanotube-containing composition can be stably dispersed for a long period of time.

  Further, a / b is larger than 1 when the sum of the weight part of the conductive polymer and the dopant is a and the weight part of the carbon nanotube is b with respect to 100 parts by weight of the carbon nanotube-containing composition. However, it is preferable because the dispersibility of the carbon nanotube is improved, and it is more preferable that a / b is 2 or more because the light transmittance of the coating film prepared using the composition is excellent.

  Furthermore, in addition to the above components, the carbon nanotube-containing composition in the present invention includes other components such as solvents other than water, ultraviolet absorbers, antioxidants, polymerization inhibitors, surface modifiers, defoamers, Plasticizers and antibacterial agents can be added. These may not be added and may be used individually by 1 type and may use 2 or more types together.

  The main solvent in the present invention refers to a liquid component contained in an amount of 50 parts by weight or more with respect to 100 parts by weight of the carbon nanotube-containing composition. It is preferable for environmental safety that the main solvent is water.

  The coating film in this invention is a coating film formed by apply | coating and drying the said carbon nanotube containing composition. More specifically, it can be obtained by applying and drying a carbon nanotube-containing composition on the surface of a substrate.

  The base material in the present invention refers to a support member for forming a coating film. For example, glass and a polymer film are mentioned. Polymer films include polyester, polyimide, polyamide, polysulfone, polycarbonate, polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyamideimide, polyolefin, polyvinyl alcohol, polyvinylidene chloride, polystyrene, polymethyl methacrylate, Polyvinyl butyral, cellulose, polyphenylene ether, polybutylene terephthalate, polyacrylonitrile, polyphenylene sulfide, polyether ether ketone, polysulfone, polyether sulfone, polyether imide, polylactic acid, blends thereof, and monomers constituting these polymers Containing copolymer, phenol resin, epoxy resin, ABS resin, urethane resin, etc. Substrate (plastic film, plastic sheet, etc.) made of a resin.

  In the present invention, the method for applying the carbon nanotube-containing composition is not particularly limited and can be appropriately selected from known methods, and examples thereof include a coating method and a printing method. These may be used alone or in combination.

  The coating method is not particularly limited and may be appropriately selected from known methods. For example, a roll coating method, a bar coating method, a dip coating method, a gravure coating method, a curtain coating method, a die coating method, a spraying method. Examples thereof include a coating method and a doctor coating method.

  The printing method is not particularly limited and may be appropriately selected from known methods. For example, screen printing method, spray printing method, ink jet printing method, letterpress printing method, intaglio printing method, planographic printing method, etc. Is mentioned.

  In this invention, it is preferable to dry the solution apply | coated by the said application | coating method and to form a coating film. As a drying method in the present invention, a method of drying in an air atmosphere, a method of drying in an inert gas atmosphere, a method of drying under reduced pressure, and the like are preferably used.

  As a method of drying in the air, various methods such as a general hot air drying furnace, a far infrared drying furnace, and a microwave drying furnace can be used. As a method of drying in an inert gas atmosphere, it is preferable to dry in a drying apparatus filled with an inert gas such as a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, a carbon dioxide gas atmosphere, etc. Various methods such as far infrared rays and microwaves can be used.

  Furthermore, as a drying method under reduced pressure, a general reduced pressure drying apparatus can be used.

  The said drying method may be used individually by 1 type, and may be used in combination of 2 or more type.

  The film thickness of the coating film thus formed is not particularly limited, but is preferably 0.001 to 50 μm, more preferably 0.01 to 10 μm in terms of excellent conductivity and light transmittance. Range.

The transparent conductive film in the present invention is a coating film formed by applying a carbon nanotube-containing composition on a polymer film or glass surface and drying, and has a sheet resistance of 10 ⁷ Ω / □ or less and is visible. A coating film in which light is not completely blocked is shown. In the present invention, a transparent conductive film is defined as having a transmittance of 50% or more at 550 nm when the transmitted light intensity is measured with a spectrophotometer. It is preferable that the transmittance is 50% or more because visibility is excellent when used for a surface touch panel of a liquid crystal display. It is more preferable that the transmittance is 80% or more because it is excellent in visibility when used for a surface touch panel of a liquid crystal display and the power consumption of the backlight can be reduced.
The sheet resistance in the transparent conductive film of the present invention is preferably 10,000Ω / □ or less, more preferably 5000Ω / □ or less, and more preferably 2500Ω / □ as the sheet resistance because the applied voltage during use can be reduced. The following is particularly preferable.

  This coating consists of liquid crystal display, electroluminescence display, plasma display, electrochromic display, solar cell, touch panel multi-layer laminated optical disk, light control material and other transparent electrodes, static eliminating material, electromagnetic wave shielding material, heating element, heat ray absorbing film It can be used for a photoelectric device, an imaging device, and the like.

  Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to the following examples.

A solution containing 1.4 parts by weight of a mixture obtained by adding polystyrene sulfonic acid as the dopant to poly (3,4-ethylenedioxythiophene) as the conductive polymer with respect to 100 parts by weight of the solution (manufactured by SIGMA-Aldrich, Poly the (3,4-ethylenedioxythiophene) -poly (styrenesulfonate ) 1.3-1.7% in H 2 O (high-conductivity grade)) represented as PEDOT-PSS stock solution.

(Dispersion stability evaluation method)
After completion of the stirring, the composition is put into a cylindrical glass sample bottle with a bottom having a diameter of 2 cm and a height of 5 cm, and left to stand for 1 hour. Then, gently lift the sample bottle and visually check if solid matter is deposited on the bottom. Further, the sample bottle is tilted by 45 °, and it is similarly confirmed by visual observation whether solid matter is deposited on the bottom surface. In each of the two confirmations, the state in which no deposit was confirmed was marked with ◯, and the other state was marked with x.

(Method for forming coating film and measuring transmittance)
A sample solution was applied to the surface of a PET film (Toray polyester film Lumirror # 100-U34), and bar coater NO. The film was stretched to a certain thickness using No. 9, heated and dried at 120 ° C. for 60 minutes to form a coating film, and then measured using a spectrophotometer (manufactured by JASCO Corporation, V-560). The transmittance of light having a wavelength of 550 nm is hereinafter referred to as “transmittance”. In the present invention, the film thickness of the coating film was adjusted so that the transmittance was 85 ± 5%.

(Measuring method of sheet resistance)
A coating film having a short side of 2 cm and a long side of 4 cm was cut out from the transparent conductive film produced by using the coating film forming method. Subsequently, after masking the surface of the transparent conductive film in the range of 2 cm × 2 cm in the central portion of FIG. 1, ion sputtering (IB-manufactured by Eiko Engineering, IB- Using a 3 type ion coater, gold having a thickness of 50 nm was deposited. The resistance value between A and B in FIG. 1 is measured by a tester (KT-2010 manufactured by Kaise Corporation). The obtained resistance value (Ω) was defined as sheet resistance (Ω / □). It is preferable that the sheet resistance of the coating film immediately after the coating film preparation is 2,500 Ω / □ or less because the applied voltage can be reduced.

(Measurement method of resistance value retention)
The resistance value retention in the present invention refers to measuring the sheet resistance after preparing a coating film and measuring the sheet resistance for 4 days in an environmental atmosphere at an air temperature of 20 ° C. and a humidity of 50%. When the sheet resistance immediately after preparation of the coating film is a (Ω / □) and the sheet resistance after standing for 4 days is b (Ω / □), the value calculated by the formula of b / a is the resistance value retention rate. And

Example 1
To 100 parts by weight of water, 0.4 part by weight of a water-soluble xylan powder (manufactured by Ezaki Glico Co., Ltd.) was added as a dispersant and stirred to obtain a solution. To this solution, 0.1 part by weight of carbon nanotubes (single-walled carbon nanotubes; manufactured by KH Chemical Co.) was added to obtain a mixed solution. Ultrasonic waves were continuously projected onto this mixed solution by an ultrasonic disperser (manufactured by As-One Co., Ltd.) at a cooling water temperature of 25 ° C. for 60 minutes. This mixture was centrifuged at 2000 rps using a centrifuge. The supernatant of the mixture after centrifugation was separated and collected to obtain a carbon nanotube-containing solution. Hereinafter, this liquid is referred to as a solution A.

  The PEDOT-PSS stock solution and the solution A were mixed in the same mass, and ultrasonic waves were continuously projected on the mixed solution by an ultrasonic disperser (manufactured by As-One Co., Ltd.) at a cooling water temperature of 25 ° C. for 30 minutes. When the mixture after ultrasonic irradiation was observed, the dispersion stability was good. Hereinafter, this liquid is referred to as composition B.

  The composition was stored at 20 ° C. for 1 month, but no precipitate was confirmed.

  The composition B immediately after preparation was applied to a PET film (manufactured by Toray Industries, Inc .; thickness: 125 μm) using a bar coater No. 9, and then heated and dried at 120 ° C. for 60 minutes to obtain a transparent conductive film. The sheet resistance was 800Ω / □ and the transmittance was 85%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 960Ω / □. The resistance retention rate was 1.2. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Example 2)
A composition was prepared in the same manner as in Example 1 except that 0.4 parts by weight of the water-soluble xylan powder was changed to 0.6 parts by weight of the water-soluble xylan powder, and a transparent conductive film was produced.

  The dispersion stability of the composition was good. The composition was stored at 20 ° C. for 1 month, but no precipitate was confirmed.

  The sheet resistance of the transparent conductive film was 900Ω / □, and the transmittance was 85%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 1080Ω / □. The resistance retention rate was 1.2. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Example 3)
A composition was prepared in the same manner as in Example 1 except that 0.1 parts by weight of carbon nanotubes were changed to 0.02 parts by weight of carbon nanotubes in Example 1, and a transparent conductive film was produced.

  The dispersion stability of the composition was good. The composition was stored at 20 ° C. for 1 month, but no precipitate was confirmed.

  The sheet resistance of the transparent conductive film was 950Ω / □, and the transmittance was 86%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 1330Ω / □. The resistance retention was 1.4. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

Example 4
In Example 1, 0.4 parts by weight of water-soluble xylan powder was added to 0.2 parts by weight of water-soluble xylan powder, PEDOT-PSS stock solution was added to 95 parts by weight of PEDOT-PSS stock solution, and ethylene glycol (boiling point = 197. A composition was prepared in the same manner as in Example 1 except that 5 parts by weight of 2 ° C. (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and a transparent conductive film was produced.

  The dispersion stability of the composition was good. The composition was stored at 20 ° C. for 1 month, but no precipitate was confirmed.

  The sheet resistance of the transparent conductive film was 400Ω / □, and the transmittance was 85%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 440Ω / □. The resistance retention rate was 1.1. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Example 5)
A composition was prepared in the same manner as in Example 4 except that 5 parts by weight of ethylene glycol was changed to 10 parts by weight of ethylene glycol in Example 4, and a transparent conductive film was produced.

  The dispersion stability of the composition was good. The composition was stored at 20 ° C. for 1 month, but no precipitate was confirmed.

  The sheet resistance of the transparent conductive film was 350Ω / □, and the transmittance was 85%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 380Ω / □. The resistance retention rate was 1.1. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Comparative Example 1)
To 100 parts by weight of water, 0.1 part by weight of carbon nanotubes (single-walled carbon nanotubes; manufactured by KH Chemical Co.) was added to obtain a mixed solution. An ultrasonic wave was continuously projected onto this mixed solution for 60 minutes at a cooling water temperature of 25 ° C. using an ultrasonic disperser (manufactured by As-One Co., Ltd.) to obtain a carbon nanotube-containing solution. Hereinafter, this liquid is referred to as a mixture C.

  A composition was prepared in the same manner as in Example 1 except that the solution A was changed to the mixture C in Example 1.

  This mixture was precipitated and did not disappear even when the ultrasonic irradiation time was extended. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Comparative Example 2)
In Example 1, a composition was prepared in the same manner as in Example 1 except that the carbon nanotubes were excluded, and a transparent conductive film was produced.

  The sheet resistance of the transparent conductive film was 1000Ω / □, and the transmittance was 86%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 2000Ω / □. The resistance retention rate was 2. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Comparative Example 3)
In Example 4, a composition was prepared and a transparent conductive film was prepared in the same manner as in Example 4 except that the carbon nanotubes were excluded.

  The sheet resistance of the transparent conductive film was 500Ω / □, and the transmittance was 86%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 900Ω / □. The resistance retention rate was 1.8. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Comparative Example 4)
In Example 1, a composition was prepared and a transparent conductive film was prepared in the same manner as in Example 1 except that the carbon nanotube and the water-soluble xylan were excluded.

  The sheet resistance of the transparent conductive film was 900Ω / □, and the transmittance was 86%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 1800Ω / □. The resistance retention rate was 2. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

(Comparative Example 5)
In Example 4, a composition was prepared and a transparent conductive film was prepared in the same manner as in Example 4 except that the carbon nanotube and the water-soluble xylan were excluded.

  The sheet resistance of the transparent conductive film was 900Ω / □, and the transmittance was 86%.

  The obtained transparent conductive film was allowed to stand for 4 days in an environmental atmosphere at a temperature of 20 ° C. and a humidity of 50%. The sheet resistance was 1800Ω / □. The resistance retention rate was 2. Table 1 shows the amount of each component added, the composition evaluation results, and the transparent conductive film evaluation results.

Claims (19)

A carbon nanotube-containing composition comprising a conductive polymer, a dopant, carbon nanotubes, water and a dispersant. The carbon nanotube-containing composition according to claim 1, wherein the dispersant contains at least water-soluble xylan. The carbon nanotube-containing composition according to claim 2, wherein the dispersant further contains an alcohol in addition to the water-soluble xylan. The carbon nanotube-containing composition according to claim 2 or 3, wherein the number average polymerization degree of the main chain of the water-soluble xylan is 6 or more and 5000 or less. The carbon nanotube-containing composition according to any one of claims 2 to 4, wherein the water-soluble xylan comprises a xylose residue or an acetylated xylose residue, an arabinose residue, and a 4-O-methylglucuronic acid residue. The carbon nanotube-containing composition according to claim 5, wherein in the water-soluble xylan, the total of the xylose residue and the acetylated xylose residue is 7 to 100 with respect to the arabinose residue 1. The carbon nanotube-containing composition according to any one of claims 2 to 4, wherein the water-soluble xylan comprises a xylose residue or an acetylated xylose residue and a 4-O-methylglucuronic acid residue. The carbon nanotube-containing composition according to claim 7, wherein in the water-soluble xylan, the total of the xylose residue and the acetylated xylose residue is 1 to 100 with respect to 4-O-methylglucuronic acid residue 1. The carbon nanotube-containing composition according to any one of claims 2 to 3, wherein the water-soluble xylan has a number average molecular weight of 1,500 to 1,000,000. The carbon nanotube-containing composition according to any one of claims 2 to 3 and 9, wherein the water-soluble xylan is a xylan derived from a woody plant. The carbon nanotube-containing composition according to claim 10, wherein the water-soluble xylan is derived from hardwood. The carbon nanotube-containing composition according to claim 1, wherein the conductive polymer contains at least polythiophene. The carbon nanotube-containing composition according to claim 12, wherein the polythiophene contains at least poly (3,4-ethylenedioxythiophene). The carbon nanotube-containing composition according to claim 1, wherein the carbon nanotube is a single-walled carbon nanotube. The carbon nanotube-containing composition according to claim 1, wherein the dopant is a Lewis acid. The carbon nanotube-containing composition according to claim 15, wherein the Lewis acid is a sulfonic acid compound. Conductive polymer 0.01-5 parts by weight, dopant 0.1-10 parts by weight, carbon nanotubes 0.001-5 parts by weight, dispersant 0.15-40 with respect to 100 parts by weight of the carbon nanotube-containing composition. The carbon nanotube-containing composition according to any one of claims 1 to 16, comprising a part by weight. The coating film formed by apply | coating and drying the carbon nanotube containing composition in any one of Claims 1-18. The transparent conductive film formed by apply | coating the coating film of Claim 18 to a polymer film or glass surface, and drying.

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