JP2016012159A - Method for manufacturing conductive laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent conductive laminate excellent in stability of a resistance value and conductivity with transparency.SOLUTION: A method for manufacturing a conductive laminate is provided, which comprises bringing an acid into contact with a conductor having a conductive layer containing carbon nanotube on a substrate, and then laminating an adhesive layer on a surface of the conductor where the conductor layer is present. The conductive layer comprising carbon nanotube preferably contains an ionic dispersant. A method for bringing the acid into contact with the conductor is preferably carried out by one of immersion, coating, and spraying. The acid is one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and an organic acid. The concentration of the acid is 1 to 90 wt.%. The adhesive layer is a transparent adhesive layer for optical use.

Description

  The present invention relates to a method for producing a conductive laminate. More specifically, the present invention relates to a method for producing a conductive laminate having excellent stability. The conductive laminate of the present invention is used as an electrode such as a capacitive touch panel that requires sticking of an adhesive layer.

  A carbon nanotube is a nanomaterial having a cylindrical shape formed by winding a single sheet of graphite. A single-walled carbon nanotube is a single-walled carbon nanotube, a multi-walled carbon nanotube is a multi-walled carbon nanotube, What is wound in two layers is called a double-walled carbon nanotube. Carbon nanotubes themselves have excellent intrinsic conductivity and are expected to be used as conductive materials.

  Applications using the conductivity of carbon nanotubes include, for example, clean room members, display members, automobile members, and the like, which are used for antistatic, conductive, radio wave absorption, electromagnetic wave shielding, and imparting near-infrared cut properties. Since the carbon nanotube has a high aspect ratio and can form a conductive path with a small amount, the carbon nanotube can be a conductive material excellent in light transmittance and drop-off resistance as compared with conventional conductive fine particles such as carbon black. For example, it is known to use a carbon nanotube as a transparent conductive thin film for optics.

  The optical transparent conductive thin film is used as a transparent electrode member of a touch panel, for example. Inside the touch panel, a double-sided adhesive sheet is used to fix the transparent electrode and the plastic that serves as the reinforcing plate, and between the transparent electrodes. To use the transparent conductive thin film as a touch panel, it is necessary to attach an adhesive layer. Yes (Patent Document 1).

  On the other hand, high conductivity is required to use carbon nanotubes as a conductive material. Carbon nanotubes are obtained as a mixture of those having metallic properties and those having semiconducting properties during synthesis. In order to obtain high conductivity, it is necessary to separate carbon nanotubes obtained as a mixture of metallic and semiconducting properties, but there are many technical difficulties in the separation technique, and it has not been realized at present. More simply, if a semiconducting carbon nanotube can be changed to a metallic carbon nanotube, it can be easily used as a conductive material. Therefore, a doping technique that raises conductivity by changing carbon nanotubes having semiconductivity into metallic carbon nanotubes by chemically or electrochemically doping carbon nanotubes has attracted attention (Patent Document 2). .

JP 2010-115818 A JP 2012-214300 A

Although there is a description in Patent Document 1 that a transparent conductive film containing carbon nanotubes and an adhesive layer are bonded together, the surface resistance value of the transparent conductive film is as large as 10 ⁹ Ω / □ or less, which is a problem for use as a transparent electrode member. There is. Moreover, there is no description regarding the stability of the resistance value, and it is considered that the stability of the resistance value is lowered by bonding the adhesive layer.

  Although Patent Document 2 has a description of treating a transparent conductive film containing carbon nanotubes with nitric acid, there is no description of attaching an adhesive layer, and the obtained transparent conductive film cannot be applied to touch panel applications. Nitric acid is used to improve the conductivity of the carbon nanotube thin film, and stability is not taken into consideration.

  This invention is made | formed in view of the said problem and the situation, The solution subject includes the conductor which has a conductive layer containing a carbon nanotube on a base material which can be utilized as transparent electrode members, such as a touch panel. An object of the present invention is to provide a method for producing a stable highly conductive laminate.

As a result of intensive studies, the inventors of the present invention have a stable resistance value and a surface resistance value of 10 by contacting an acid with a conductor having a conductive layer containing carbon nanotubes, and then bonding an adhesive layer. It has been found that a highly conductive laminate of ³ Ω / □ or less can be produced, and has led to the present invention.

That is, the present invention is characterized by the following.
<1> A method for producing a conductive laminate, in which an acid is brought into contact with a conductor having a conductive layer containing carbon nanotubes on a substrate, and then an adhesive layer is bonded to the surface of the conductor having the conductive layer.
<2> The method for producing a conductive laminate according to <1>, wherein the conductive layer including the carbon nanotube includes an ionic dispersant.
<3> The method for producing a conductive laminate according to any one of <1> or <2>, wherein the acid contacting method is any one of dipping, coating, and spraying.
<4> The method for producing a conductive laminate according to any one of <1> to <3>, wherein the acid is any one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and an organic acid.
<5> The method for producing a conductive laminate according to any one of <1> to <4>, wherein the acid concentration is 1 to 90% by weight.
<6> The method for producing a conductive laminate according to any one of <1> to <5>, wherein the adhesive layer is an optical transparent adhesive layer.

  According to the present invention, a conductive material having a conductive layer containing carbon nanotubes on a base material is brought into contact with an acid, and then an adhesive layer is bonded, whereby the resistance value is excellent in stability and excellent in transparent conductivity. A conductive laminate can be obtained.

  Hereinafter, the present invention will be described in detail together with preferred embodiments.

  In the method for producing a conductive laminate of the present invention, a conductor having a conductive layer containing carbon nanotubes on a substrate is brought into contact with an acid, and then an adhesive layer is bonded to the surface of the conductor having the conductive layer. By producing a conductive laminate through such steps, a conductive laminate excellent in resistance value stability can be obtained as compared with the case where any treatment is not performed. The effect of improving the stability of the conductive laminate is that by adopting such a manufacturing method, the effect of suppressing the loss of the nitric acid doping effect over time by sticking the adhesive layer and the moisture in the environment are reduced. It is considered that the increase in the resistance value due to absorption can be achieved by a combination of the effects of suppressing the nitric acid dope.

[carbon nanotube]
In the present invention, carbon nanotubes are used as the conductive material. A carbon nanotube has a shape in which one surface of graphite is wound into a cylindrical shape, and a single-walled carbon nanotube is formed by winding one layer, a double-walled carbon nanotube is formed by winding two layers, and three or more layers are formed. The rolled material is called multi-walled carbon nanotube.

  As the carbon nanotube dispersion liquid and the conductor obtained thereby, any of single-walled, double-walled, and multi-walled carbon nanotubes can be used depending on required application characteristics. A single-layer to double-layer carbon nanotube with a small number of layers can be used to obtain a conductor with higher electrical conductivity and higher light transmittance. When two or more layers of carbon nanotubes are used, optical properties depend on the optical wavelength. It is possible to obtain a conductor with less property. In order to obtain a highly light-transmitting conductor, it is preferable that 50 or more of 100 carbon nanotubes having a single-layer to two-layer structure are included, and in particular, the double-walled carbon nanotube includes 100 carbon nanotubes. It is preferable that the number is 50 or more because the conductivity and dispersibility are extremely high. Multi-walled carbon nanotubes of three or more layers generally have low crystallinity and low conductivity, and have a large diameter and a small number of contacts per unit amount of carbon nanotubes in the conductive layer, resulting in low transparent conductivity.

  The number of carbon nanotube layers can be measured, for example, by preparing a sample as follows. When the composition is a composition in which carbon nanotubes are dispersed in a medium such as a liquid, when the solvent is aqueous, the composition is appropriately diluted with water to a concentration that can be easily seen, dropped on the collodion film by several μL, air-dried, and then directly transmitted. The carbon nanotubes on the collodion film are examined with a scanning electron microscope. When the solvent is non-aqueous, the solvent is once removed by drying, then dispersed again in water, diluted as appropriate, dropped several μL onto the collodion film, air-dried, and observed with a transmission electron microscope. The number of carbon nanotube layers in the conductor can be observed in the same manner as the composition before coating. When collecting carbon nanotubes from a conductor, the conductor can be examined with a transmission electron microscope by observing a section that has been embedded in an epoxy resin and then cut into a thickness of 0.1 μm or less using a microtome or the like. it can. Alternatively, the carbon nanotubes can be extracted with a solvent and examined by observation with a high-resolution transmission electron microscope in the same manner as in the case of the composition. The concentration of carbon nanotubes in the liquid dropped on the collodion film may be a concentration at which the carbon nanotubes can be observed one by one, and is, for example, 0.001% by weight.

  The number of carbon nanotube layers is measured, for example, as follows. Observe at 250,000 times using a transmission electron microscope, and measure the number of layers of 100 carbon nanotubes arbitrarily extracted from the field of view where 10% or more of the field area is carbon nanotubes in a 75 nm square field of view. To do. When 100 lines cannot be measured in one field of view, measurement is performed from a plurality of fields until 100 lines are obtained. At this time, one carbon nanotube is counted as one if some carbon nanotubes are visible in the field of view, and both ends are not necessarily visible. In addition, even if it is recognized as two in the field of view, it may be connected outside the field of view and become one, but in that case, it is counted as two.

  The diameter of the carbon nanotubes is not particularly limited, but the average value of the outer diameters of the carbon nanotubes having the number of layers in the above preferred range is 1 nm to 10 nm, and those within the range of 1 to 3 nm are preferably used. The average value of the outer diameter was observed at 250,000 times using the transmission electron microscope, and was arbitrarily extracted from a field of view in which 10% or more of the field area was carbon nanotubes in a 75 nm square field of view 100 It is an arithmetic mean value when the sample is observed by the same method as measuring the number of layers of the carbon nanotubes and the outer diameter of the carbon nanotubes is measured.

  The carbon nanotubes may be modified at the surface or at the ends with functional groups or alkyl groups, or may be doped with nitric acid, alkali metals, or halogens. For example, it may be functionalized with a carboxyl group or a hydroxyl group by heating in an acid. Doping is preferable because the conductivity of the carbon nanotube is improved.

  The length of the carbon nanotube is not particularly limited, but is preferably 0.5 μm or more, more preferably 1 μm or more because a conductive path cannot be efficiently formed if it is too short. If the upper limit is too long, the dispersibility tends to decrease, so it is preferably 10 μm or less.

  The length of the carbon nanotube can be examined using a field emission scanning electron microscope as will be described later. In the case of the composition, several μL is dropped on a mica substrate and air-dried, and then examined with a field emission scanning electron microscope. If necessary, it can be observed after exposing the carbon nanotubes by using a solvent, ion sputtering, or firing at 350 ° C. for 30 minutes in an air atmosphere.

  The length of the carbon nanotubes in the conductor can be observed in the same manner as in the case of the above composition in the composition before coating. The concentration of the carbon nanotubes to be dropped is preferably a concentration at which the carbon nanotubes can be observed one by one, and may be appropriately diluted. For example, it is 0.01% by weight.

  When collecting carbon nanotubes from a conductor, the carbon nanotubes can be extracted from the conductor using a solvent and then observed by the same method as that for the composition.

  Regarding the length of the carbon nanotube, a sample was prepared by the above method and observed with a field emission scanning electron microscope, and a photo was taken where 10 or more carbon nanotubes were included in a 15 μm square field of view. Measure the length. The length of 100 carbon nanotubes arbitrarily extracted from the visual field is measured along the length direction. When 100 lines cannot be measured in one field of view, measurement is performed from a plurality of fields until 100 lines are obtained. By measuring the length of a total of 100 carbon nanotubes, the length and number of carbon nanotubes contained in the 100 can be confirmed. In the present invention, if the number of carbon nanotubes in the range of 0.5 μm or less is 30 or less, the contact resistance can be reduced and the light transmittance can be improved, and the carbon nanotube is preferably 1 μm or less. The number of carbon nanotubes in the range is more preferably 30 or less out of 100. Furthermore, in the present invention, it is preferable that the number of carbon nanotubes in the range of 10 μm or more is 30 or less out of 100 because dispersibility can be improved. When the length of the carbon nanotube is long and the entire length is not visible in the field of view, the length of the carbon nanotube in the field of view is measured. If the length is within 10 μm, it is regarded as the length of the measured value. The number of carbon nanotubes in the range of 0.5 to 10 μm is counted assuming that the length exceeds 10 μm.

  Moreover, in order to obtain a conductor excellent in transparent conductivity, it is preferable to use high-quality carbon nanotubes with high crystallinity. A carbon nanotube with a high degree of crystallinity itself is excellent in electrical conductivity. However, such high-quality carbon nanotubes form bundles and aggregates more firmly than carbon nanotubes with low crystallinity, so it is very difficult to disperse them one by one and stably disperse them. It is difficult to. Therefore, in order to obtain a highly conductive conductor using carbon nanotubes having a high degree of crystallinity, a carbon nanotube dispersion technique is very important.

The carbon nanotube used in the present invention is not particularly limited, but a carbon nanotube having linearity and high crystallinity is preferable because of high conductivity. Carbon nanotubes with good linearity are carbon nanotubes with few defects and high carbon nanotube crystallinity. The crystallinity of the carbon nanotube can be evaluated by Raman spectroscopy. Although there are various laser wavelengths used in the Raman spectroscopic analysis method, 532 nm and 633 nm are used here. The Raman shift observed in the vicinity of 1590 cm ⁻¹ in the Raman spectrum is called a graphite-derived G band, and the Raman shift observed in the vicinity of 1350 cm ⁻¹ is called a D band derived from defects in amorphous carbon or graphite. That is, a carbon nanotube having a higher G / D ratio, which is the ratio of the peak height of the G band and the D band, has higher linearity and higher crystallinity and higher quality.

  In the carbon nanotube used in the present invention, a wavelength of 633 nm is used when evaluating the Raman G / D ratio. The higher the G / D ratio, the better. However, if it is 30 or more, it can be said to be a high-quality carbon nanotube. Preferably it is 40 or more, More preferably, it is 50 or more. There is no particular upper limit, but it is usually 200 or less. In addition, solid Raman spectroscopy such as carbon nanotubes may vary depending on sampling. Therefore, at least three places and another place are subjected to Raman spectroscopic analysis, and an arithmetic average thereof is taken.

The carbon nanotube used in the present invention is produced, for example, as follows.
A powdery catalyst in which iron is supported on magnesia is made to exist in the entire horizontal cross-sectional direction of the reactor in a vertical reactor, and methane is circulated in the vertical direction in the reactor, and methane and the above catalyst are mixed in 500 to 1200. It is obtained by oxidizing the carbon nanotubes after contacting them at 0 ° C. to produce the carbon nanotubes. That is, carbon nanotubes containing single- to double-walled carbon nanotubes can be obtained by the carbon nanotube synthesis method.

  Examples of the oxidation treatment of carbon nanotubes include treatment with nitric acid, mixed acid, and hydrogen peroxide. The treatment of carbon nanotubes with hydrogen peroxide means that the carbon nanotubes are mixed in, for example, commercially available 34.5% hydrogen peroxide water so as to be 0.01 wt% to 10 wt%, and the temperature is set to 0 to 100 ° C. For 0.5 to 48 hours. The treatment of carbon nanotubes with a mixed acid means that the carbon nanotubes are mixed in, for example, a concentrated sulfuric acid / concentrated nitric acid (3/1) mixed solution so as to be 0.01% by weight to 10% by weight. It means to react at temperature for 0.5 to 48 hours. As the mixing ratio of the mixed acid, the ratio of concentrated sulfuric acid / concentrated nitric acid can be set to 1/10 to 10/1 according to the amount of single-walled carbon nanotubes in the generated carbon nanotubes. The treatment of carbon nanotubes with nitric acid means that the carbon nanotubes are mixed in, for example, commercially available nitric acid 40 to 80% by weight so as to be 0.01% by weight to 10% by weight, and the temperature is 60.degree. It means reacting for 5 to 48 hours.

  Further, the oxidation treatment of the carbon nanotube is performed by a method of firing, for example. The temperature of the calcination treatment is not particularly limited as long as the carbon nanotube used in the present invention is obtained, but is usually selected in the range of 300 to 1000 ° C. Since the oxidation temperature is affected by the atmospheric gas, it is preferable to perform the baking treatment at a relatively low temperature when the oxygen concentration is high and at a relatively high temperature when the oxygen concentration is low. Examples of the calcination treatment of the carbon nanotubes include a method of calcination in the range of the combustion peak temperature of carbon nanotubes ± 50 ° C. in the atmosphere. If the oxygen concentration is higher than the atmosphere, the calcination treatment is lower than this. Usually, the temperature range is selected, and if it is low, the higher temperature range is selected. In particular, when the firing treatment is performed in the atmosphere, it is preferably performed within the range of the combustion peak temperature ± 15 ° C.

  By performing such an oxidation treatment, it becomes possible to selectively remove impurities such as amorphous carbon and single-walled CNTs having low heat resistance in the product. Purity can be improved. At the same time, since the surface of the carbon nanotube is functionalized, the affinity with the dispersion medium and additives is improved, so that the dispersibility is improved. Among these oxidation treatments, treatment with nitric acid is particularly preferable.

  These oxidation treatments may be performed immediately after the synthesis of the carbon nanotubes or after another purification treatment. For example, when iron / magnesia is used as the catalyst, the oxidation treatment may be performed after the purification treatment for removing the catalyst with an acid such as hydrochloric acid, or the oxidation treatment may be performed after the oxidation treatment. May be performed.

[Dispersion of carbon nanotubes]
In the present invention, the conductive layer containing carbon nanotubes can be formed by applying a carbon nanotube dispersion. In order to obtain a carbon nanotube dispersion, it is common to perform a dispersion treatment with a carbon nanotube together with a solvent using a mixing and dispersing machine or an ultrasonic irradiation device, and it is desirable to add a dispersant.

  As the dispersant used in the present invention, a so-called polymer-based dispersant is preferably used. At this time, if the molecular weight is too small, the interaction between the dispersant and the carbon nanotube is weakened, so that the bundle of carbon nanotubes cannot be sufficiently solved. On the other hand, if the molecular weight is too large, the entanglement of the polymer chain with the carbon nanotubes becomes too strong, so that the dispersant cannot be completely removed in the process of removing the excessive dispersant, resulting in deterioration of conductivity. The range of the weight average molecular weight of the polymer used as the dispersant is from 10,000 to 400,000, particularly preferably from 10,000 to 250,000, and more preferably from 10,000 to 60,000. The said weight average molecular weight points out the molecular weight computed by making contrast with the calibration curve by polyethyleneglycol using the gel permeation chromatography method.

  In order to sufficiently unravel the carbon nanotube bundles contained in the carbon nanotube dispersion liquid, an excessive amount of dispersant is required with respect to the carbon nanotubes. This excess dispersant is deposited in the form of a film at the interface of the conductive layer when the dispersion is applied to form a conductive layer. Therefore, when a conductor is produced using the carbon nanotube dispersion of the present invention, an excess is required. It is preferable to have a step of removing a dispersant. However, when the dispersant is too large to be removed, the conductivity inhibition by the excessive dispersant is too great, and the surface resistance value of the formed carbon nanotube conductive layer is deteriorated. On the other hand, when the amount of the dispersant contained in the dispersion is small, the bundle of carbon nanotubes cannot be completely solved.

  That is, the amount of the dispersant contained in the carbon nanotube dispersion liquid of the present invention is preferably an amount that is excessive beyond that adsorbed on the carbon nanotubes and does not inhibit the conductivity. The dispersant is preferably 100 parts by weight or more and 2000 parts by weight or less, more preferably 200 parts by weight or more and 1000 parts by weight or less based on parts by weight.

  The type of the dispersant is not limited as long as carbon nanotubes can be dispersed, and can be selected from synthetic polymers and natural polymers. The type of polymer is not particularly limited as long as carbon nanotubes can be dispersed, and is preferably selected from synthetic polymers and natural polymers with good dispersibility. Synthetic polymers include, for example, polyether diol, polyester diol, polycarbonate diol, polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, acetal group-modified polyvinyl alcohol, butyral group-modified polyvinyl alcohol, silanol group-modified polyvinyl alcohol, Ethylene-vinyl alcohol copolymer, ethylene-vinyl alcohol-vinyl acetate copolymer resin, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylic resin, epoxy resin, modified epoxy resin, phenoxy resin, modified phenoxy resin, phenoxy Ether resin, phenoxy ester resin, fluorine resin, melamine resin, alkyd resin, phenol resin, polyacryl Bromide, polyacrylic acid, polystyrene sulfonic acid, polyethylene glycol, may be selected from polyvinyl pyrrolidone and derivatives thereof. Natural polymers include, for example, polysaccharides such as starch, pullulan, dextran, dextrin, guar gum, xanthan gum, amylose, amylopectin, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, cellulose and the like It can be selected from derivatives. A derivative means a conventionally known compound such as an ester, ether, or salt. Among these, it is particularly preferable to use a polysaccharide from the viewpoint of improving dispersibility. These may be used alone or in combination of two or more. In addition, an ionic polymer is preferably used because of its excellent carbon nanotube dispersibility and conductivity. Among these, those having an ionic functional group such as sulfonic acid and carboxylic acid are preferable because of high dispersibility and conductivity. By using a dispersing agent with good dispersibility, it is possible to improve the transparent conductivity by releasing the bundle of carbon nanotubes. Use polystyrene sulfonic acid, chondroitin sulfate, hyaluronic acid, carboxymethyl cellulose and their derivatives. In particular, the use of carboxymethylcellulose, which is a polysaccharide having an ionic functional group, and derivatives thereof is most preferable.

  In the present invention, a carbon nanotube dispersion is prepared using carbon nanotubes, a dispersant and a solvent. The dispersion may further contain other additives, and may be in liquid form or semi-solid form such as paste or gel, but liquid form is preferred. In the present invention, the dispersion refers to a liquid in which the obtained composition is visually free of precipitates and aggregates and is free of sediments and aggregates visually after standing for at least 24 hours. In addition, the content of carbon nanotubes with respect to the entire dispersion is preferably 0.01 wt% or more and 20 wt% or less, and preferably 0.01 to 10 wt%.

  The aqueous solvent used in the present invention is not limited as long as the dispersant is dissolved and the carbon nanotubes are dispersed, and water and solvents miscible with water can be used. Solvents include ethers (dioxane, tetrahydrofuran, methyl cellosolve, etc.), ether alcohols (ethoxyethanol, methoxyethoxyethanol, etc.), esters (methyl acetate, ethyl acetate, etc.), ketones (cyclohexanone, methyl ethyl ketone, etc.), alcohols (Ethanol, isopropanol, phenol, etc.), lower carboxylic acids (acetic acid, etc.), amines (triethylamine, trimethanolamine, etc.), nitrogen-containing polar solvents (N, N-dimethylformamide, nitromethane, N-methylpyrrolidone, acetonitrile, etc.) , Sulfur compounds (such as dimethyl sulfoxide) can be used.

  Among these, it is particularly preferable from the viewpoint of dispersibility of carbon nanotubes to contain water, alcohol, ether, and a combination solvent thereof. The pH range of the carbon nanotube dispersion is preferably weakly acidic to alkaline, more preferably pH 6-12, and particularly preferably pH 6-8. The pH of the carbon nanotube dispersion can be adjusted by adding an acidic substance or a basic substance according to the definition of Arrhenius to the carbon nanotube dispersion. Examples of the acidic substance include protic acids such as nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, borohydrofluoric acid, hydrofluoric acid, perchloric acid and the like, organic carboxylic acids, organic sulfonic acids, and the like. . Furthermore, examples of the organic carboxylic acid include formic acid, acetic acid, succinic acid, benzoic acid, phthalic acid, maleic acid, fumaric acid, malonic acid, tartaric acid, citric acid, lactic acid, succinic acid, monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid. Trifluoroacetic acid, nitroacetic acid, triphenylacetic acid and the like. Examples of the organic sulfonic acid include alkylbenzene sulfonic acid, alkyl naphthalene sulfonic acid, alkyl naphthalene disulfonic acid, naphthalene sulfonic acid formalin polycondensate, melamine sulfonic acid formalin polycondensate, naphthalene disulfonic acid, naphthalene trisulfonic acid, dinaphthylmethane. Examples include disulfonic acid, anthraquinone sulfonic acid, anthraquinone disulfonic acid, anthracene sulfonic acid, and pyrene sulfonic acid. Among these, preferred are volatile acids that volatilize during coating and drying, such as nitric acid and hydrochloric acid.

  Examples of the basic substance include ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide and the like. Among these, preferred is a volatile base that volatilizes during coating and drying, such as ammonia.

  The pH of the carbon nanotube dispersion is adjusted by adding the acidic substance and / or basic substance to a desired pH while measuring the pH. Examples of the pH measurement method include a method using a pH test paper such as litmus test paper, a hydrogen electrode method, a quinhydrone electrode method, an antimony electrode method, a glass electrode method, etc. Among them, the glass electrode method is simple and requires the required accuracy. Is preferable. Specifically, it is measured by a pH meter (manufactured by Toa Denpa Kogyo Co., Ltd., HM-30S). In addition, when an acidic substance or a basic substance is excessively added to exceed a desired pH value, a substance having the opposite characteristics may be added to adjust the pH. Nitric acid is preferable as an acidic substance applied for such adjustment, and ammonia is preferable as a basic substance.

  The carbon nanotube dispersion can be prepared by mixing and dispersing carbon nanotubes, a dispersant and a solvent, which are commonly used for coating production (for example, ultrasonic homogenizer, vibration mill, jet mill, ball mill, bead mill, sand mill, roll mill, homogenizer, high pressure homogenizer). , An ultrasonic device, an attritor, a dissolver, a paint shaker, etc.) to produce a dispersion. Among them, it is preferable to disperse using ultrasonic waves because the dispersibility of the carbon nanotubes is improved. The carbon nanotubes to be dispersed may be in a dry state or a state containing a solvent. However, it is preferable to disperse the carbon nanotubes in a state containing a solvent without being dried after purification because the dispersibility is improved.

  The carbon nanotube dispersion liquid may contain, for example, various polymeric materials such as a surfactant and a conductive or nonconductive polymer as other additives in addition to the dispersant and the carbon nanotube. Moreover, content of an additive can be added in the range which does not inhibit the effect of this invention.

[Base material]
In the present invention, the carbon nanotube dispersion can be applied by a method described later to form a conductor.

  The substrate used for the production of the conductor obtained by applying the carbon nanotube dispersion of the present invention is not particularly limited in shape, size, and material as long as the carbon nanotube dispersion can be applied and the obtained conductive layer can be fixed. It can be selected depending on the intended use, and may be, for example, a film, a sheet, a board, paper, a fiber, or a particulate form. For example, if the material is an organic material, polyester, polycarbonate, polyamide, acrylic, polyurethane, polymethyl methacrylate, cellulose, triacetyl cellulose, amorphous polyolefin and other resins, and inorganic materials are stainless steel, aluminum, iron, gold It can be selected from metals such as silver, glass and carbon materials. When a resin film is used as the substrate, a conductive film excellent in adhesiveness, stretchability and flexibility can be obtained, which is preferable. The thickness of the preferable base material in that case is not specifically limited, It can take various ranges from moderate thickness to very thin thickness. For example, the substrate can be between about 1 and about 1000 μm thick. In a preferred embodiment, the thickness of the substrate can be from about 5 to about 500 μm. In another preferred embodiment, the thickness of the substrate is from about 10 to about 200 μm.

  The substrate may be subjected to surface hydrophilization treatment such as corona discharge, glow discharge treatment or ozone treatment as necessary. Alternatively, an undercoat layer may be provided. The material for the undercoat layer is preferably a highly hydrophilic material.

  In addition, the substrate should be used in combination with a hard coat that has been given the wear resistance, high surface hardness, solvent resistance, contamination resistance, fingerprint resistance, etc. on the opposite side to which the carbon nanotubes are applied. Can do.

  In addition, it is preferable to use a transparent base material as the base material because a conductor excellent in transparency and conductivity can be obtained. A transparent substrate means that the total light transmittance is 50% or more.

[Application of carbon nanotube dispersion]
In the present invention, the method for applying the carbon nanotube dispersion liquid is not particularly limited. Known coating methods such as wire bar coating, die coating, gravure coating, micro gravure coating, dip coating, spray coating, roll coating, spin coating, doctor knife coating, kiss coating, slit coating, slit die coating, blade coating, extrusion Coating, screen printing, gravure printing, inkjet printing, pad printing, and other types of printing can be used. The application may be performed any number of times, and two different application methods may be combined. The most preferable application method is wire bar coating or die coating.

  Since the coating thickness (wet thickness) also depends on the concentration of the coating solution, it does not need to be specified if the desired conductivity can be obtained. However, among these, the thickness is preferably 0.01 μm to 50 μm. More preferably, it is 0.1 micrometer-20 micrometers.

  The coating thickness (dry thickness) can be measured by observing the cross section of the conductor. For example, the coating thickness can be observed with a transmission microscope, and may be stained if necessary. A preferable dry thickness is not specified as long as desired conductivity is obtained, but is preferably 0.001 to 5 μm. More preferably, it is 0.001-1 micrometer.

  When the carbon nanotube dispersion is an aqueous dispersion, a wetting agent may be added to the composition when it is applied on the substrate. By adding a wetting agent such as a surfactant or alcohol to the non-hydrophilic substrate, the composition can be applied to the substrate without being repelled. Among these, alcohol is preferable, and methanol, ethanol, propanol, and isopropanol are preferable among alcohols. Lower alcohols such as methanol, ethanol and isopropanol are highly volatile and can be easily removed when the substrate is dried after coating. In some cases, a mixture of alcohol and water may be used.

  Thus, after apply | coating a carbon nanotube dispersion liquid to a base material, it is preferable to remove an unnecessary solvent by methods, such as air drying, a heating, and pressure reduction, and to dry the formed conductive layer. Thereby, the carbon nanotube forms a three-dimensional stitch structure and is fixed to the base material. Of these, drying by heating is preferred. The drying temperature may be the temperature at which the solvent can be removed and is not higher than the heat resistant temperature of the base material.

  Since the conductive layer contains an excessive dispersant, it is preferable to remove the excess dispersant. This operation facilitates the dispersion of charges and improves the conductivity of the conductive composite. As a method for removing the excessive dispersant, there is a method of washing the dispersant by drying the conductive layer and then immersing it in a solvent or spraying the solvent onto the conductive layer. The solvent for washing is not particularly limited as long as it is capable of dissolving a component that lowers the transparent conductivity to be removed, such as an additive or an excessive amount of a dispersant, and does not remove carbon nanotubes. Specific examples include water, alcohols, and acetonitrile.

  As another removal method, there is a method in which a dispersing agent adsorption layer capable of adsorbing an excessive dispersing agent is provided on a substrate in advance. As the dispersant adsorption layer, it is preferable to use a hydrophilic inorganic oxide. More preferred are silica, titania and alumina. These substances have a hydroxyl group which is a hydrophilic group on the surface and are preferable because high hydrophilicity can be obtained. Further, the dispersant absorbing layer may be a composite of these inorganic oxides and resin, for example, a composite of silica fine particles and polysilicate. The reason why the dispersant can be removed by the dispersant adsorption layer is not clear, but the following may be considered. That is, when a dispersant having a hydrophilic group, such as an ionic dispersant, is used as a dispersant for carbon nanotubes, the dispersant has a higher affinity for the dispersant adsorption layer than the carbon nanotubes themselves. It is thought that it is possible to remove the dispersant locally from the periphery of the carbon nanotubes because the excess dispersant is selectively transferred to the dispersant adsorption layer at the same time as the nanotube dispersion is applied.

  When an ionic dispersant is used as a dispersant for carbon nanotubes, it has a hydrophilic group, so that it is susceptible to environmental changes such as high temperature and high humidity, and there is a problem that resistance value stability is poor. After applying the carbon nanotube dispersion to the base material to form a conductor and then contacting with acid, the hydrophilic group of the ionic dispersant is hydrophobized on the base material, and the carbon nanotube is fixed in a highly dispersed state. Therefore, the resistance value can be stabilized for a long time while maintaining high conductivity.

[Contact with acid]
In the present invention, after the carbon nanotube dispersion is applied to a substrate to form a conductor and then contacted with an acid, the transparent conductivity and wet heat resistance can be improved. Examples of the acid to be contacted include proton acids such as nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, borohydrofluoric acid, hydrofluoric acid, and perchloric acid, and organic carboxylic acids and organic sulfonic acids. It is done. Furthermore, examples of the organic carboxylic acid include formic acid, acetic acid, succinic acid, benzoic acid, phthalic acid, maleic acid, fumaric acid, malonic acid, tartaric acid, citric acid, lactic acid, succinic acid, monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid. Trifluoroacetic acid, nitroacetic acid, triphenylacetic acid and the like. Examples of the organic sulfonic acid include alkylbenzene sulfonic acid, alkyl naphthalene sulfonic acid, alkyl naphthalene disulfonic acid, naphthalene sulfonic acid formalin polycondensate, melamine sulfonic acid formalin polycondensate, naphthalene disulfonic acid, naphthalene trisulfonic acid, dinaphthylmethane. Examples include disulfonic acid, anthraquinone sulfonic acid, anthraquinone disulfonic acid, anthracene sulfonic acid, and pyrene sulfonic acid. Among these, it is preferable to use nitric acid because it is a strong acid and has little influence on the substrate.

  In the present invention, the acid concentration is preferably 1% by weight to 90% by weight, particularly preferably 10% by weight to 70% by weight, and more preferably 50% by weight to 70% by weight. is there.

  In the present invention, the acid contacting method is not particularly limited. For example, a method of immersing a conductor in an acid solution (immersion), a method of applying an acid solution to a surface of a conductor having a conductive layer (application), and wiping the acid solution into a mist to wipe the surface of a conductor having a conductive layer. The method of applying (spraying) and the method of applying the vapor of the acid solution to the surface of the conductor having the conductive layer (steam) can be used, but from the viewpoint of safety, the dipping method and the coating method are preferably used.

  In the present invention, the time for contacting the acid with the conductor is not particularly limited, but is preferably 10 seconds or longer and 10 minutes or shorter from the viewpoint of productivity.

  The conductor after being brought into contact with the acid is preferably sufficiently washed with water in order to remove excess acid. Examples of the cleaning method include a flowing water method and a dipping method.

[Overcoat layer]
It is also preferable that after forming a conductor containing the carbon nanotubes of the present invention in a conductive layer, the conductor contacted with an acid is overcoated with a binder material capable of forming an organic or inorganic transparent film. By overcoating, it is effective for further charge dispersion and movement. Further, the conductor contains a binder material capable of forming an organic or inorganic transparent film in the carbon nanotube dispersion, and is applied to the substrate, and then heated as necessary to dry or bake (harden) the coating film. Can also be obtained. The heating conditions at that time are appropriately set according to the binder type. When the binder is photocurable or radiation curable, the coating film is cured by irradiating the coating film with light or radiation immediately after coating, not by heat curing. As the radiation, ionizing radiation such as electron beam, ultraviolet ray, X-ray and gamma ray can be used, and the irradiation dose is determined according to the binder type.

  The binder material is not particularly limited as long as it is used for conductive paints, and various inorganic and organic binders, that is, transparent inorganic polymers or precursors thereof (hereinafter sometimes referred to as “inorganic polymer binders”). Or an organic polymer or a precursor thereof (hereinafter sometimes referred to as “organic polymer binder”) can be used. Examples of inorganic polymer binders include sols of metal oxides such as silica, tin oxide, aluminum oxide and zirconium oxide, or hydrolyzable or thermally decomposable organometallic compounds (organophosphorus compounds, Organic boron compounds, organic silane compounds, organic titanium compounds, organic zirconium compounds, organic lead compounds, organic alkaline earth metal compounds, and the like. Specific examples of hydrolyzable or thermally decomposable organometallic compounds are alkoxides or partial hydrolysates thereof, lower carboxylates such as acetate, and metal complexes such as acetylacetone.

  When these inorganic polymer binders are baked, a glassy inorganic polymer transparent film or matrix made of an oxide or a composite oxide can be formed. The inorganic polymer matrix is generally glassy, has high hardness, excellent scratch resistance, and high transparency.

  The organic polymer binder may be thermoplastic, thermosetting, or radiation curable such as ultraviolet rays or electron beams. Examples of suitable organic binders include polyolefins (polyethylene, polypropylene, etc.), polyamides (nylon 6, nylon 11, nylon 66, nylon 610, etc.), polyesters (polyethylene terephthalate, polybutylene terephthalate, etc.), silicone resins, vinyl resins ( Polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyacrylate, polystyrene derivatives, polyvinyl acetate, polyvinyl alcohol, etc.), polyketone, polyimide, polycarbonate, polysulfone, polyacetal, fluororesin, phenol resin, urea resin, melamine resin, epoxy resin , Polyurethanes, cellulosic polymers, proteins (gelatin, casein, etc.), chitin, polypeptides, polysaccharides, polynucleotides, and other organic polymers , As well as precursors of these polymers (monomer or oligomer). These can form transparent coatings or matrices simply by evaporation of the solvent, or by thermal curing or curing with light or radiation.

The organic polymer binder is preferably a compound having an unsaturated bond that can be radically polymerized and cured by radiation or light. This is a monomer, oligomer, or polymer having a vinyl group or a vinylidene group. Examples of this type of monomer include styrene derivatives (such as styrene and methylstyrene), acrylic acid or methacrylic acid or derivatives thereof (such as alkyl acrylate or methacrylate, allyl acrylate or methacrylate), vinyl acetate, acrylonitrile, and itaconic acid. The oligomer or polymer is preferably a compound having a double bond in the main chain or a compound having acryloyl or methacryloyl groups at both ends of the straight chain. This type of radical polymerization curable binder has a high hardness, excellent scratch resistance, and can form a highly transparent film or matrix.

  The amount of the binder used may be an amount sufficient for overcoating, or an amount sufficient for obtaining a viscosity suitable for coating when mixed in a liquid. If the amount is too small, the coating will not be successful, and if the amount is too large, the conductivity will be hindered. The thickness of the overcoat layer is preferably 1 nm or more and less than 1000 nm, and more preferably 10 nm or more and 200 nm or less.

[Adhesive layer]
The present invention is characterized in that after forming a conductor containing carbon nanotubes in a conductive layer, an adhesive layer is bonded to the surface having the conductive layer of the conductor brought into contact with an acid. In the present invention, the pressure-sensitive adhesive layer includes a pressure-sensitive adhesive, and is used for bonding the conductive surface of the conductor to another optical member such as a different conductor or a cover glass. For example, in a capacitive touch panel used for a smartphone or the like, a transparent adhesive is bonded to the conductive surface of a conductor as an adhesive layer, and the conductive layer of the adhesive layer is further electrically connected to the surface not bonded to the conductor. It is necessary to paste the bodies together. The thickness of the adhesive layer is preferably 1 μm or more and 1000 μm or less, and more preferably 5 μm or more and 100 μm or less.

  As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer in the present invention, a vinyl polymerization system, rubber system, condensation polymerization system, thermosetting resin system, silicone system, or the like can be used. Among these, examples of the vinyl polymerization pressure-sensitive adhesive include acrylic, styrene, vinyl acetate-ethylene copolymer system, and vinyl chloride-vinyl acetate copolymer system. Examples of the rubber-based pressure-sensitive adhesive include butadiene-styrene copolymer system (SBR), butadiene-acrylonitrile copolymer system (NBR), chloroprene polymer system, and isobutylene-isoprene copolymer system (butyl rubber). Examples of the condensation polymerization pressure-sensitive adhesive include polyester. Furthermore, examples of the thermosetting resin-based pressure-sensitive adhesive include epoxy resin-based, urethane resin-based, and formalin resin-based adhesives. Among these, acrylic adhesives are preferably used in consideration of transparency, weather resistance, heat resistance, moist heat resistance, substrate adhesion, and the like. Furthermore, it is preferable to use a pressure-sensitive adhesive component that does not contain an acid.

[Usage]
The conductive laminate having a conductive layer containing the carbon nanotube of the present invention in contact with an acid and bonded with an adhesive layer is highly conductive and stable without an increase in resistance due to loss of dope or moisture absorption. Therefore, it can be used as a member for clean rooms such as anti-static shoes and anti-static plates, a display for electromagnetic wave shielding, near-infrared cut, transparent electrode, touch panel, radio wave absorption, and automobile member. In particular, it exhibits particularly excellent performance as a display-related transparent electrode such as a touch panel, a liquid crystal display, organic electroluminescence, and electronic paper, which mainly require surface smoothness. In particular, the plastic film for optical filters can be used as a display device by bonding. It is very important that the resistance layer has high stability in the completed form of the conductive layer, and particularly exhibits excellent performance as a capacitive touch panel application.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. In the examples, the light transmittance, the surface resistance value, and the molecular weight of the dispersant were measured by the methods described above.

  Carbon nanotubes were obtained as follows.

(Reference Example 1)
[Examples of catalyst preparation for carbon nanotubes]
About 24.6 g of iron (III) ammonium citrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 6.2 kg of ion-exchanged water. About 1 kg of magnesium oxide (MJ-30 manufactured by Iwatani Chemical Industry Co., Ltd.) was added to this solution, and after vigorously stirring for 60 minutes with a stirrer, the suspension was introduced into a 10 L autoclave container. At this time, 0.5 kg of ion exchange water was used as a washing solution. In a sealed state, it was heated to 200 ° C. and held for 2 hours. Thereafter, the autoclave container was allowed to cool, the slurry-like cloudy substance was taken out from the container, excess water was filtered off by suction filtration, and a small amount of water contained in the filtered material was dried by heating in a 120 ° C. drier. The obtained solid content was collected on a sieve and the particle size in the range of 10 to 20 mesh was recovered while being finely divided in a mortar. The granular catalyst body shown on the left was introduced into an electric furnace and heated at 600 ° C. for 6 hours in the atmosphere. The bulk density was 0.26 g / mL. From the atomic absorption analysis of the catalyst body, the iron content in the catalyst body was 0.38% by weight.

[Process for producing carbon nanotube-containing composition]
Carbon nanotubes were synthesized using the above catalyst. A catalyst layer was formed by taking 132 g of the solid catalyst and introducing it onto a quartz sintered plate at the center of the reactor installed in the vertical direction. While heating the catalyst layer until the temperature in the reaction tube reaches about 860 ° C., nitrogen gas is supplied from the bottom of the reactor toward the top of the reactor at 16.5 L / min so as to pass through the catalyst layer. Circulated. Thereafter, while supplying nitrogen gas, methane gas was further introduced at 0.78 L / min for 60 minutes and aeration was performed so as to pass through the catalyst body layer to cause a reaction. The introduction of methane gas was stopped, and the quartz reaction tube was cooled to room temperature while supplying nitrogen gas at 16.5 L / min to obtain a carbon nanotube composition with a catalyst. By using 128 g of this catalyst-attached carbon nanotube composition and stirring in 400 mL of a 4.8N hydrochloric acid aqueous solution for 1 hour, iron as the catalyst metal and MgO as the carrier were dissolved. The obtained black suspension was filtered, and the filtered product was again put into 400 mL of a 4.8N hydrochloric acid aqueous solution, treated with MgO, and collected by filtration. This operation was repeated three times to obtain a carbon nanotube composition from which the catalyst was removed.

[Purification process of carbon nanotube: liquid phase oxidation treatment + ammonia treatment + re-nitric acid treatment]
About 300 times the weight of concentrated nitric acid (first grade 1.38 (60%) manufactured by Kishida Chemical Co., Ltd.) was added to the dry weight of the obtained carbon nanotube-containing composition in the wet state. Thereafter, the mixture was heated to reflux with stirring in an oil bath heated to about 140 ° C. ± 4 ° C. for about 24 hours. After heating under reflux, the inside diameter was allowed to cool to room temperature, and the nitric acid solution containing the carbon nanotube-containing composition was diluted 2 times with ion-exchanged water, and an Omnipore membrane filter (filter type: 1.0 μm JA) manufactured by Millipore was used. Suction filtration was performed using a 90 mm filter. After washing with ion-exchanged water until the suspension of the filtered material became neutral, a carbon nanotube composition was obtained in a wet state containing water. The wet cake containing the obtained carbon nanotube-containing composition was added to 0.3 L of a 28% aqueous ammonia solution (special grade manufactured by Kishida Chemical Co., Ltd.) and stirred at room temperature for 1 hour. Thereafter, the solution was subjected to suction filtration using a 90 mm inner diameter filter equipped with an omnipore membrane filter (filter type: 1.0 μm JA) manufactured by Millipore. Thereafter, the membrane was washed with ion-exchanged water until the wet cake on the membrane filter became near neutral, and a carbon nanotube composition was obtained in a wet state containing water.

  The wet cake containing the obtained carbon nanotube-containing composition was added to 0.3 L of a 60% aqueous nitric acid solution (first grade 1.38 (60%) manufactured by Kishida Chemical Co., Ltd.). After stirring for 24 hours at room temperature, the mixture was subjected to suction filtration using a 90 mm inner diameter filter equipped with an Omnipore membrane filter (filter type: 1.0 μm JA) manufactured by Millipore. Thereafter, the membrane was washed with ion-exchanged water until the wet cake on the membrane filter became near neutral. The carbon nanotube-containing composition was stored in a wet state containing water. A part of the carbon nanotube-containing filter cake was collected, dried by heating at 120 ° C. overnight, and the concentration of the carbon nanotube-containing composition in the wet was calculated from the weight after drying.

  The dry weight (per 100 g of catalyst body) of the carbon nanotube-containing composition calculated by multiplying the total weight of the obtained carbon nanotube-containing composition in the wet state by the concentration of the carbon nanotube-containing composition was 0.257 g.

  As a result of Raman spectroscopic analysis of the carbon nanotube composition at a wavelength of 532 nm, the G / D ratio of the carbon nanotube-containing composition was 61. The G / D ratio of the carbon nanotube-containing composition at a wavelength of 633 nm was 60.

(Reference Example 2)
[Dispersant adsorption layer preparation example]
A dispersant adsorbing layer in which hydrophilic silica fine particles having a diameter of 30 nm were exposed was prepared by using the polysilicate as a binder by the following operation.

  Megaaqua hydrophilic DM coat (manufactured by Ryowa Co., Ltd., DM-30-26G-N1) containing about 30 nm of hydrophilic silica fine particles and polysilicate in a solid content concentration of 1% by mass was used as a coating solution for producing a silica film.

  The said coating liquid for silica film preparation was apply | coated on the polyethylene terephthalate (PET) film (Toray Co., Ltd. product Lumirror U46) using wire bar # 4. After application, the film was dried in a dryer at 120 ° C. for 1 minute to prepare a PET film substrate provided with an undercoat layer.

(Reference Example 3)
[Hydrolysis of carboxymethyl cellulose]
10 mass% sodium carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd., Cerogen (registered trademark) 5A (weight average molecular weight: 80000, molecular weight distribution (Mw / Mn): 1.6, degree of etherification: 0.7) ) 500 g of an aqueous solution was added to a three-necked flask, and the aqueous solution was adjusted to pH 2 using primary sulfuric acid (Kishida Chemical Co., Ltd.). This container was transferred into an oil bath heated to 120 ° C., and subjected to a hydrolysis reaction for 9 hours with stirring under heating and reflux. After allowing the three-necked flask to cool, the aqueous solution was adjusted to pH 7 using a 28% aqueous ammonia solution (manufactured by Kishida Chemical Co., Ltd.), and the reaction was stopped. The weight average molecular weight of the sodium carboxymethylcellulose after hydrolysis was calculated by comparing with a calibration curve with polyethylene glycol using a gel permeation chromatography method. As a result, the weight average molecular weight was about 35,000 and the molecular weight distribution (Mw / Mn) was 1.5. The yield was 97%.

[Preparation of carbon nanotube dispersion]
15 mg of carbon nanotubes (carbon nanotube composition obtained in Reference Example 1 containing 15 mg of carbon nanotubes in terms of dry mass), 10% by mass sodium carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd., obtained above) Serogen 5A hydrolyzate (weight average molecular weight 35000)) 38 mg aqueous solution (dispersant / carbon nanotube weight ratio 2.5) was weighed, distilled water was added to 10 g, and 28 mass% ammonia aqueous solution (Kishida Chemical Co., Ltd.) To a pH of 7, using an ultrasonic homogenizer output of 20 W, and dispersing for 1.5 minutes under ice cooling to prepare a carbon nanotube dispersion. The obtained liquid was centrifuged at 10,000 G for 15 minutes with a high-speed centrifuge to obtain 9 g of a carbon nanotube dispersion. In the residual liquid after obtaining the supernatant, no precipitate of a size that can be visually observed was found.

[Coating carbon nanotube dispersion]
After adding ion-exchanged water to the dispersion to adjust to 0.055% by mass, it was applied to the substrate provided with the undercoat layer obtained in Reference Example 2 or the PET film substrate using wire bar # 7. The carbon nanotube composition was fixed by drying in a dryer at 140 ° C. for 1 minute (hereinafter, a film on which the carbon nanotube composition was fixed is referred to as a carbon nanotube-coated film). The coating amount of carbon nanotube was calculated to be 5.8 mg / m ² .

(Example 1)
[Immersion in nitric acid]
The carbon nanotube-coated film obtained in Reference Example 3 was immersed in 30 g of concentrated nitric acid (60%) at room temperature for 20 seconds, then rinsed in 30 g of ion-exchanged water for 10 seconds and dried at room temperature.

[Production of terminal electrode]
The carbon nanotube-coated film was sampled to 50 mm × 100 mm. The total light transmittance of this sample was 85.1%. The total light transmittance was measured using a haze meter (NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd.). A silver paste electrode (ECM-100 AF4820 manufactured by Taiyo Ink Mfg. Co., Ltd.) was applied along the short sides of this sample in a range of 5 mm wide and 50 mm long, and dried at 90 ° C. for 30 minutes to form a terminal electrode.

[Adhesion layer bonding and resistance change observation]
When the light-transmitting acrylic pressure-sensitive adhesive (8146-1, manufactured by 3M) was bonded to the carbon nanotube-coated surface of the above film and the resistance value between terminals was measured, it was 227Ω. Thereafter, the resistance change rate was calculated by comparing the resistance value between the terminals after being left for 2 weeks under the condition (A) of 23 ° C. and 50% RH and the resistance value between the terminals before being left as it was. When the resistance value between the terminal electrodes before standing for 2 weeks is R ₀ and the resistance value after standing is R, (R−R ₀ ) / R ₀ is defined as the resistance value change rate. The resistance between terminal electrodes was measured with a card high tester (3244 manufactured by Hioki Electric Co., Ltd.). The resistance value change rate was 18.6%.

(Example 2)
[Nitric acid application]
The carbon nanotube-coated film obtained in Reference Example 3 was coated with concentrated nitric acid (60%) at room temperature using wire bar # 8 and dried at room temperature. This film was sampled to 50 mm × 100 mm in the same manner as in Example 1. The total light transmittance of this sample was 84.6%. A silver paste electrode was applied to this sample in the same manner as in Example 1 to obtain a terminal electrode. A light-transmitting acrylic pressure-sensitive adhesive (manufactured by 3M, 8146-1) was bonded to the carbon nanotube-coated surface of this film, and the resistance value between terminals was measured to be 243Ω. Thereafter, the resistance value change rate was calculated by comparing the inter-terminal resistance value after standing for 2 weeks under the condition (A) of 23 ° C. and 50% RH and the inter-terminal resistance value before the treatment. The resistance value change rate was 6.6%. The amount of nitric acid applied was calculated to be 7.2 g / m ² .

(Example 3)
The carbon nanotube-coated film obtained in Reference Example 3 was coated with concentrated nitric acid (60%) at room temperature using wire bar # 8, washed with 10 g of ion-exchanged water for 10 seconds, and dried at room temperature. This film was sampled to 50 mm × 100 mm in the same manner as in Example 1. The total light transmittance of this sample was 84.4%. A silver paste electrode was applied to this sample in the same manner as in Example 1 to obtain a terminal electrode. A light-transmitting acrylic pressure-sensitive adhesive (8146-1, manufactured by 3M) was bonded to the carbon nanotube-coated surface of this film, and the resistance value between terminals was measured to be 210Ω. Thereafter, the resistance value change rate was calculated by comparing the inter-terminal resistance value after standing for 2 weeks under the condition (A) of 23 ° C. and 50% RH and the inter-terminal resistance value before the treatment. The resistance value change rate was 20.9%. Moreover, the electroconductive laminated body produced similarly was wet-heat-treated for 2 weeks on the conditions (B) of 33 +/- 5 degreeC and 95 +/- 3% RH. The resistance change rate was calculated by comparing the inter-terminal resistance value after the wet heat treatment with the inter-terminal resistance value before the treatment. The resistance value change rate was 20.3%.

Example 4
[Immersion in hydrochloric acid]
The carbon nanotube-coated film obtained in Reference Example 3 was immersed in 30 g of concentrated hydrochloric acid (35%) at room temperature for 20 seconds, then rinsed in 30 g of ion-exchanged water for 10 seconds and dried at room temperature. This film was sampled to 50 mm × 100 mm in the same manner as in Example 1. The total light transmittance of this sample was 85.3%. A silver paste electrode was applied to this sample in the same manner as in Example 1 to obtain a terminal electrode. When the light-transmitting acrylic pressure-sensitive adhesive (8146-1, manufactured by 3M) was bonded to the carbon nanotube-coated surface of this film and the resistance value between terminals was measured, it was 272Ω. Thereafter, the resistance value change rate was calculated by comparing the inter-terminal resistance value after standing for 2 weeks under the condition (A) of 23 ° C. and 50% RH and the inter-terminal resistance value before the treatment. The resistance value change rate was 27.6%.

(Comparative Example 1)
The carbon nanotube-coated film obtained in Reference Example 3 was coated with concentrated nitric acid (60%) at room temperature using wire bar # 8, washed with 10 g of ion-exchanged water for 10 seconds, and dried at room temperature. This film was sampled to 50 mm × 100 mm in the same manner as in Example 1. The total light transmittance of this sample was 84.5%. A silver paste electrode was applied to this sample in the same manner as in Example 1 to obtain a terminal electrode. The resistance value between terminals of this sample was measured and found to be 214Ω. Thereafter, the resistance value change rate was calculated by comparing the inter-terminal resistance value after standing for 2 weeks under the condition (A) of 23 ° C. and 50% RH and the inter-terminal resistance value before the treatment. The resistance value change rate was 39.9%. Moreover, the electroconductive laminated body produced similarly was wet-heat-treated for 2 weeks on the conditions (B) of 33 +/- 5 degreeC and 95 +/- 3% RH. The resistance change rate was calculated by comparing the inter-terminal resistance value after the wet heat treatment with the inter-terminal resistance value before the treatment. The resistance value change rate was 39.6%.

(Comparative Example 2)
The carbon nanotube-coated film obtained in Reference Example 3 was sampled to 50 mm × 100 mm as in Example 1. The total light transmittance of this sample was 84.4%. A silver paste electrode was applied to this sample in the same manner as in Example 1 to obtain a terminal electrode. When the light-transmitting acrylic pressure-sensitive adhesive (8146-1, manufactured by 3M) was bonded to the carbon nanotube-coated surface of this film and the resistance value between terminals was measured, it was 158Ω. Thereafter, the resistance value change rate was calculated by comparing the inter-terminal resistance value after standing for 2 weeks under the condition (A) of 23 ° C. and 50% RH and the inter-terminal resistance value before the treatment. The resistance value change rate was 54.5%. Moreover, the electroconductive laminated body produced similarly was wet-heat-treated for 2 weeks on the conditions (B) of 33 +/- 5 degreeC and 95 +/- 3% RH. The resistance change rate was calculated by comparing the inter-terminal resistance value after the wet heat treatment with the inter-terminal resistance value before the treatment. The resistance value change rate was 138.4%.

  Table 1 summarizes the results of Examples 1 to 4 and Comparative Examples 1 and 2.

Claims (6)

A method for producing a conductive laminate, comprising contacting a conductor having a conductive layer containing carbon nanotubes on a substrate with an acid, and then bonding an adhesive layer to the surface of the conductor having the conductive layer. The method for producing a conductive laminate according to claim 1, wherein the conductive layer containing carbon nanotubes contains an ionic dispersant. The method for producing a conductive laminate according to claim 1, wherein the acid contact method is any one of dipping, coating, and spraying. The method for producing a conductive laminate according to claim 1, wherein the acid is any one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, and an organic acid. The method for producing a conductive laminate according to any one of claims 1 to 4, wherein the acid concentration is 1 to 90% by weight. The method for producing a conductive laminate according to claim 1, wherein the adhesive layer is a transparent adhesive layer for optics.