JP2017007312A - Conductive laminated body and method for producing conductive laminated body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive laminated body having high conductivity even after molding, and in which the increase of haze value is suppressed.SOLUTION: Provided is a conductive laminated body forming a conductive layer 5 by forming an undercoat layer 2 including a polyurethane resin and silica particles on a base material 1, subjecting a coating liquid including carbon nanotubes to coating 3 on the undercoat layer 2 and further applying an overcoat layer 4 thereon. Also provided is a molding using the conductive laminated body. The molding can be utilized, e.g., to a touch sensor using the molding.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive laminate. More specifically, the present invention relates to a conductive laminate having high conductivity even after molding and in which an increase in haze value is suppressed.

  Conventionally, conductive laminates have been used for various products such as touch panel applications such as resistive film type and capacitance type, electronic paper applications, and digital signage applications. Indium tin oxide (hereinafter referred to as ITO), silver nanowires (hereinafter referred to as AgNW), carbon nanotubes (hereinafter referred to as CNT), conductive polymers, and the like are used as a conductive material for developing conductivity. In the above applications, it is mostly used on a flat or flexible substrate, and the necessity of molding the conductive laminate has not been so much required. So far, studies have been made on CNT suitable for a flexible substrate requiring flexibility, and Patent Document 1 proposes a conductive laminate using a CNT having excellent bending resistance as a conductive film.

  However, from the viewpoint of operability and design, a three-dimensional touch panel instead of a flat surface will be required in the future. ITO and AgNW that have been studied so far have no flexibility, and after the molding process, the surface resistance value increases significantly due to the occurrence of cracks in the ITO layer and the AgNW itself breaking, etc. As a result, it becomes impossible to take conduction, and as a conductive laminate It is expected that this function cannot be maintained. Therefore, in order to suppress changes in the surface resistance value after molding, studies have been made with CNT and a conductive polymer, which are inherently more flexible and advantageous for molding.

  Patent Document 2 proposes a moldable molding conductive film with improved dispersibility of CNTs as an antistatic treatment application to prevent static electricity generated in a molded synthetic resin molded product and prevent the adhesion of dust. Has been made. Further, Patent Document 3 proposes a curved surface molded body using CNT as a conductive layer for use as a vehicle lamp equipped with a heating element.

JP 2012-66580 A JP 2006-35772 A JP 2010-45014 A

  However, in Patent Document 1, the bending resistance is excellent. However, when molding is performed, conductivity is not exhibited after molding due to CNT tearing or cracks in the transparent protective film. In Patent Document 2, a conductive film for molding using CNT is proposed, and a surface resistance value below a certain level is maintained even after molding, but its haze value is large, and it can be used as a touch sensor application. Have difficulty. Further, Patent Document 3 does not propose a touch sensor application.

  Therefore, in view of the above problems, an object of the present invention is to provide a conductive laminate having high conductivity even after molding and having a suppressed haze value.

In order to solve the problems, the present invention comprises the following methods.
(1) A conductive laminate having a conductive layer containing carbon nanotubes on a substrate, the haze value after being stretched by 20% being 3.0% or less.
(2) The conductive laminate according to (1), wherein the conductive layer contains a polyurethane resin.
(3) The conductive laminate according to (1) or (2), wherein the conductive layer contains silica particles.
(4) The conductive laminate according to any one of (1) to (3), wherein the base material includes a thermoplastic resin.
(5) The conductive laminate according to (4), wherein the thermoplastic resin is at least one resin selected from the group consisting of a polycarbonate resin, an acrylic resin, and a cyclic olefin resin.
(6) The conductive laminate according to any one of (1) to (5), which satisfies the following [A] or [B].
[A] Total light transmittance is 80% or more and 93% or less, and surface resistance value is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less [B] Conductive layer light absorption is 1% or more and 10 % And a surface resistance value of 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less (7) An undercoat layer containing a polyurethane resin and silica particles is formed on a substrate, and the undercoat The method for producing a conductive laminate according to any one of (1) to (6), wherein the conductive layer is formed by coating a coating liquid containing carbon nanotubes on the layer.
(8) A molded body using the conductive laminate according to any one of (1) to (6).
(9) A touch sensor using the conductive laminate according to any one of (1) to (6) or the molded article according to (8).

  Since the conductive laminate of the present invention has a small increase in haze value after molding, a molded body having a low haze value and maintaining conductivity can be obtained by molding. That is, it is suitable as a conductive laminate for a device in which the haze value of a molded body is important, such as a curved or three-dimensional capacitive touch panel, a touch switch, or a touch sensor.

It is a cross-sectional schematic diagram of the electrically conductive laminated body of this invention.

  Hereinafter, modes for carrying out the invention will be described.

[Conductive laminate]
The conductive laminate used in the present invention includes at least a base material and a conductive layer containing carbon nanotubes.

  The conductive laminate of the present invention preferably has a haze value of 3.0% or less after stretching 20%, more preferably 2.0% or less, and particularly preferably 1.0% or less. preferable. It is preferable that the haze value after stretching the conductive laminate by 20% is 3.0% or less because the appearance is good when used for a touch panel or a touch switch.

  The surface resistance value of the conductive laminate is appropriately determined depending on the stretching ratio of the molded body, and the surface resistance value when the conductive laminate is stretched twice is preferably 10Ω / □ or more and 2,000Ω / □ or less. Moreover, although it determines suitably according to the device to be used, For example, in the case of a touch switch, Preferably it is 100-2,000 ohm / square, More preferably, it is 100-1,000 ohm / square, More preferably, it is 100-500 ohm / square. It is. For example, in the case of a touch panel, it is preferably 10 to 1,000 Ω / □, more preferably 50 to 500 Ω / □, and still more preferably 100 to 300 Ω / □. Within these ranges, the IC controller can be easily designed and good operability can be obtained.

  Moreover, you may provide functional layers, such as an overcoat layer, on an undercoat layer or a conductive layer between a base material and a conductive layer as needed for an interlayer adhesive improvement or a reliability improvement.

[Base material]
The base material used in the present invention preferably contains a thermoplastic resin. Although it does not specifically limit as a thermoplastic resin, In order to obtain a transparent conductive laminated body, a thermoplastic resin with a high transmittance | permeability is used preferably. Specifically, the total light transmittance at a wavelength of 380 to 780 nm is preferably 80% or more, and the total light transmittance is more preferably 90% or more. As such thermoplastic resin having high transmittance, polycarbonate resin, acrylic resin, cyclic olefin resin, polyethylene terephthalate resin, polyvinyl chloride resin, polystyrene resin, triacetyl cellulose resin, polyethylene resin, polypropylene resin, polylactic acid resin, etc. Can be mentioned. Among these, a resin having good moldability is preferable, and the base material preferably includes at least one resin selected from the group consisting of a polycarbonate resin, an acrylic resin, and a cyclic olefin resin. Among these, it is particularly preferable to include a polycarbonate resin.

  In addition, from the viewpoints of handleability and moldability, the thickness of the substrate is preferably 50 to 1,000 μm, and more preferably 100 to 500 μm.

  Furthermore, the base material may be subjected to a surface treatment as necessary. The surface treatment may be provided with a physical treatment such as corona discharge, plasma treatment, glow discharge, flame treatment, or a resin layer. In addition, an easily adhesive layer may be formed. For example, additives such as an antistatic agent, an ultraviolet absorber, a plasticizer, a lubricant, and a filler may be added within a range not impairing the effects of the present invention. There may be. The kind of base material is not limited to the above, and an optimal one can be selected from transparency, durability, flexibility, cost, etc. according to the application.

  Moreover, you may provide a hard-coat layer as a protective layer in the opposite surface on which a conductive layer is laminated | stacked. The hard coat layer in this case is not particularly limited as long as it has a hardness that can suppress the occurrence of scratches.

[Conductive layer]
The “conductive layer” in the present invention refers to a layer in which a layer containing carbon nanotubes described later and an undercoat layer are combined, and when there is an overcoat layer described later, the overcoat layer is also included in the conductive layer. In the present invention, the thickness of the conductive layer is preferably 20 nm or more and 2,000 nm or less. From the viewpoint of conductivity and weather resistance, it is more preferably from 50 nm to 1,500 nm, and further preferably from 100 nm to 1,000 nm.

  Moreover, it is preferable that the conductive layer of this invention contains a polyurethane resin from a viewpoint which suppresses the crack which generate | occur | produces at the time of extending | stretching and can suppress a haze value raise. Moreover, it is preferable that a conductive layer contains a silica particle from a viewpoint of the electroconductive improvement of a conductive layer, and the adhesive improvement of a base material and a conductive layer.

[Method for producing conductive layer]
In the present invention, for example, the conductive layer is produced by forming a layer containing carbon nanotubes after forming an undercoat layer on a substrate. Further, an overcoat layer may be further laminated after forming a layer containing carbon nanotubes. Since the overcoat layer may penetrate into the carbon nanotube-containing layer and the undercoat layer and form a layer in a mixed state, there is a clear interface between the carbon nanotube-containing layer, the undercoat layer, and the overcoat layer. May not exist.

[Undercoat layer]
In this invention, it is preferable to have an undercoat layer on a base material. By having an undercoat layer, the adhesion of the layer containing carbon nanotubes can be improved, and the surface roughness of the conductive laminate can be adjusted. The undercoat layer in the present invention preferably contains a stretchable thermoplastic resin. Specifically, it is preferable to use a thermoplastic resin containing at least one resin selected from the group consisting of polyurethane resin, polycarbonate resin, polyester resin, polyether resin, acrylic resin, polyvinyl chloride resin and cyclic olefin resin. Of these, polyurethane resins are particularly preferred because of their high elongation and excellent water resistance and solvent resistance.

  Normally, a polyurethane resin is a polymer composed of a copolymer of a polyol component and an isocyanate component, but the polyol component imparts high extensibility, flexibility, etc., and a urethane bond formed by copolymerization of the polyol component and the isocyanate component. Provides toughness and solvent resistance. Therefore, in the present invention, a polyurethane resin in which a polyol component and an isocyanate component are blended according to the molding magnification may be used.

  Examples of the polyol component include polyether polyols and polyester polyols. Specific examples of the polyether polyol include polyoxypropylene glycol and polyoxytetramethylene glycol. Examples of the polyester polyol include adipic acid as a carboxylic acid, Examples of the phthalic acid and polyhydric alcohol include polyester polyols obtained by polycondensation of ethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

  Examples of the isocyanate component include aliphatic isocyanates and aromatic isocyanates. Specific examples include tetramethylene diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, and diphenylmethane diisocyanate.

  Furthermore, the undercoat layer in the present invention preferably contains silica particles. By including silica particles, it is preferable from the viewpoint of improving the adhesion of the layer containing carbon nanotubes, improving the adhesiveness due to surface irregularities, and adjusting the hydrophilicity by surface modification of the silica particles. The size of the silica particles is preferably in the range of 5 nm to 500 nm, more preferably 20 nm to 200 nm, since a good dispersion state can be obtained without impairing the transparency of the conductive laminate.

  The silica particles used in the present invention may be surface-modified, improve the coating properties of the carbon nanotube dispersion, and the dispersant, which is an insulator contained in the carbon nanotube-containing layer, is preferential to the undercoat layer. Since the conductivity of the layer containing the carbon nanotubes is improved by being adsorbed on the surface, it is preferably subjected to a hydrophilic treatment. The shape of the silica particles is not particularly limited, but a spherical shape or a flat shape having a large surface area is preferable.

  In the undercoat layer in the present invention, it is preferable that silica particles are dispersed in a thermoplastic resin. Since the silica particles are dispersed in the thermoplastic resin, the elongation of the thermoplastic resin present between the silica particles is large when the undercoat layer is stretched, and cracking is preferably suppressed when stretched.

  In the present invention, the mass ratio of the thermoplastic resin and the silica particles in the undercoat layer is a thermoplastic resin: silica from the viewpoint of an increase in haze value during stretching, adhesion between the substrate and the conductive layer, and conductivity of the layer containing the carbon nanotubes. Particle = 80: 20-40: 60 is preferable, and 70: 30-50: 50 is more preferable.

[Method for producing undercoat layer]
In the present invention, the method for providing the undercoat layer on the substrate is not particularly limited. Known wet coating methods such as spray coating, dip coating, spin coating, knife coating, kiss coating, gravure coating, slot die coating, roll coating, bar coating, screen printing, inkjet printing, pad printing, other types of printing methods Etc. are available. Further, a dry coating method may be used. As the dry coating method, physical vapor deposition such as sputtering or vapor deposition, chemical vapor deposition, or the like can be used. Moreover, application | coating may be performed in multiple times and it may combine two different types of application | coating methods. Preferred coating methods are wet coating gravure coating, bar coating, and die coating.

  After the coating step, the solvent is removed from the undercoat coating solution containing the undercoat component applied in the drying step. Solvent removal methods include convection hot-air drying where hot air is applied to the substrate, radiant heat drying where the substrate absorbs infrared rays by radiation from an infrared drying device, and heats and heats to dry. It is possible to apply conductive heat drying that is heated and dried by heat conduction. Of these, convection hot air drying is preferred because of its high drying rate.

  In the present invention, the thickness of the undercoat layer is not particularly limited. From the viewpoint that the dispersant, which is an insulator contained in the carbon nanotube-containing layer, is preferentially adsorbed to the undercoat layer, and from the viewpoint of suppressing cracks when stretched, it should be in the range of 15 nm to 2,000 nm. Is preferred.

  In the present invention, the water contact angle of the undercoat layer is preferably 40 ° or less from the viewpoint of applicability of the carbon nanotube dispersion on the undercoat layer. When the water contact angle exceeds 40 °, the carbon nanotube dispersion may not be uniformly applied on the undercoat.

  The water contact angle of the undercoat layer can be measured using a commercially available contact angle measuring device. The water contact angle is measured in accordance with JIS R 3257 (1999) by dripping 1 to 4 μL of water onto the surface of the undercoat layer with a syringe in an atmosphere of room temperature of 25 ° C. and relative humidity of 50%. The angle formed between the tangent at the edge of the droplet and the surface of the undercoat layer is determined.

[carbon nanotube]
The carbon nanotube used in the present invention is not particularly limited as long as it has a shape obtained by winding one surface of graphite into a cylindrical shape. Single-wall carbon in which one surface of graphite is wound in one layer. Both nanotubes and multi-walled carbon nanotubes wound in multiple layers can be applied. Among them, in particular, carbon nanotubes in which 50 single-walled carbon nanotubes in which one surface of graphite is wound in two layers are contained in 100 or more, This is preferable because the conductivity and the dispersibility of the carbon nanotubes in the coating dispersion are extremely high. More preferably, 75 or more of 100 are double-walled carbon nanotubes, and most preferably 80 or more of 100 are double-walled carbon nanotubes. In addition, the fact that 50 of the double-walled carbon nanotubes are contained in 100 may be expressed as 50% of the double-walled carbon nanotubes. In addition, the double-walled carbon nanotube is preferable because the original function such as conductivity is not impaired even if the surface is functionalized by acid treatment or the like.

  For example, the carbon nanotube is manufactured as follows. A powdery catalyst in which iron is supported on magnesia is present in the entire horizontal cross-sectional direction of the reactor in a vertical reactor, and methane is supplied in the vertical direction into the reactor. The carbon nanotubes containing single- to five-layer carbon nanotubes can be obtained by contacting the carbon nanotubes at 200 ° C. to produce carbon nanotubes and then oxidizing the carbon nanotubes. Carbon nanotubes can be manufactured and then subjected to an oxidation treatment to increase the ratio of single-layer to five-layer, particularly the ratio of two- to five-layer. The oxidation treatment is performed, for example, by a nitric acid treatment method. Nitric acid is preferred because it acts as a dopant for the carbon nanotubes. The dopant is a function of giving a surplus electron to the carbon nanotube or taking away the electron to form a hole, thereby generating a freely movable carrier, thereby improving the conductivity of the carbon nanotube. Is. The nitric acid treatment method is not particularly limited as long as the carbon nanotube of the present invention can be obtained, but is usually performed in an oil bath at 140 ° C. The nitric acid treatment time is not particularly limited, but is preferably in the range of 5 to 50 hours.

[Dispersant]
As the carbon nanotube dispersant, a surfactant, various polymer materials (water-soluble polymer material, etc.) and the like can be used, and an ionic polymer material having high dispersibility is preferable. Examples of the ionic polymer material include an anionic polymer material, a cationic polymer material, and an amphoteric polymer material. Any type can be used as long as it has a high carbon nanotube dispersibility and can maintain dispersibility, but an anionic polymer material is preferred because of its excellent dispersibility and dispersion retainability. Of these, carboxymethylcellulose and its salts (sodium salt, ammonium salt, etc.) and polystyrenesulfonic acid salt are preferable because they can efficiently disperse carbon nanotubes in the carbon nanotube dispersion.

  In the present invention, when carboxymethyl cellulose salt or polystyrene sulfonate is used, examples of the cationic substance constituting the salt include alkali metal cations such as lithium, sodium and potassium, and alkaline earth such as calcium, magnesium and barium. Metal cation, ammonium ion, or monoamineamine, diethanolamine, triethanolamine, morpholine, ethylamine, butylamine, coconut oil amine, tallow amine, ethylenediamine, hexamethylenediamine, diethylenetriamine, polyethyleneimine and other onium ions, Alternatively, these polyethylene oxide adducts can be used, but are not limited thereto.

[solvent]
In the present invention, the solvent used in the carbon nanotube dispersion liquid is preferably water from the viewpoints that the dispersant can be easily dissolved and that the waste liquid can be easily treated.

[Carbon nanotube dispersion]
Although the preparation method of the carbon nanotube dispersion liquid used in this invention is not specifically limited, For example, it can carry out in the following procedures. Since the treatment time at the time of dispersion can be shortened, once a dispersion liquid containing carbon nanotubes in a concentration range of 0.003 to 0.15 mass% in the dispersion medium is prepared, dilution is performed to obtain a predetermined concentration. It is preferable to do. In the present invention, the mass ratio of the dispersant to the carbon nanotube (dispersant / carbon nanotube) is preferably 10 or less. Such a preferable range is preferable because it is easy to uniformly disperse, but is less affected by a decrease in conductivity. The mass ratio is more preferably 0.5 to 9, further preferably 1 to 6, and the mass ratio of 2 to 3 is particularly preferable because high transparent conductivity can be obtained.

  As a dispersing means at the time of preparation, a carbon nanotube and a dispersing agent are mixed and dispersed in a dispersion medium commonly used for coating production (for example, ball mill, bead mill, sand mill, roll mill, homogenizer, ultrasonic homogenizer, high pressure homogenizer, ultrasonic device, And mixing using an attritor, a resolver, a paint shaker, and the like. Moreover, you may disperse | distribute in steps, combining these some mixing dispersers. Among them, the method of preliminarily dispersing with a vibration ball mill and then dispersing using an ultrasonic device is preferable because the dispersibility of the carbon nanotubes in the obtained coating dispersion liquid is good.

[Method for producing carbon nanotube-containing layer]
In the present invention, the layer containing carbon nanotubes is produced through a coating process in which a carbon nanotube dispersion is applied to a substrate and a drying process in which the dispersion medium is subsequently removed. In the present invention, the method for applying the dispersion on the substrate or the undercoat layer is not particularly limited. Known application methods such as spray coating, dip coating, spin coating, knife coating, kiss coating, gravure coating, slot die coating, bar coating, roll coating, screen printing, inkjet printing, pad printing, other types of printing, etc. Available. Moreover, application | coating may be performed in multiple times and it may combine two different types of application | coating methods. The most preferred application methods are gravure coating, bar coating, and die coating.

  After the coating step, the dispersion medium is removed from the carbon nanotube dispersion containing the dispersant applied in the drying step. Solvent removal methods include convection hot-air drying where hot air is applied to the substrate, radiant heat drying where the substrate absorbs infrared rays by radiation from an infrared drying device, and heats and heats to dry. It is possible to apply conductive heat drying that is heated and dried by heat conduction. Of these, convection hot air drying is preferred because of its high drying rate.

  In the present invention, the layer containing carbon nanotubes refers to a layer containing solids containing carbon nanotubes and a dispersant after removing the dispersion medium from the carbon nanotube dispersion.

[Adjustment of carbon nanotube coating amount]
The amount of the carbon nanotube dispersion liquid applied on the substrate or the undercoat layer depends on the concentration of the carbon nanotube dispersion liquid, and therefore may be appropriately adjusted so as to obtain a desired surface resistance value. The coating amount of the carbon nanotube in the present invention can be easily adjusted in order to achieve various uses that require electrical conductivity. For example, the coating amount is ^{1mg / m 2 ~40mg / m 2} .

[Overcoat layer]
The resin used for the overcoat layer in the present invention can be selected according to the characteristics required for the conductive laminate, and is excellent in surface hardness, acrylic resin and polyester resin that can be adhered to the substrate, and excellent in stretch followability. A polyurethane resin or the like can be suitably used. Further, these plural resins can be used in combination. Among them, a polyurethane resin excellent in stretchability and a resin crosslinked with urethane acrylate having a urethane skeleton are preferably used.

  The thickness of the overcoat layer used in the present invention is preferably 15 to 450 nm, more preferably 40 to 300 nm, still more preferably 45 to 200 nm, and particularly preferably 50 to 100 nm. When the thickness of the overcoat layer is thinner than 15 nm, the conductivity stabilizing effect at the time of bonding the adhesive layer may not be sufficiently exhibited. When the thickness of the overcoat layer is greater than 450 nm, the amount of carbon nanotubes present on the surface of the conductive layer decreases, and the contact resistance value may increase.

[Method for producing overcoat layer]
The overcoat layer is prepared by adjusting the solids concentration so that the thickness after drying the paint containing the resin used for the overcoat layer is the desired thickness, and the reverse coat method, gravure coat method, rod coat method, bar It is preferable to apply by a coating method, a die coating method, a spray coating method, a spin coating method or the like. The paint containing a resin can be used in a state where the resin is dissolved in a solvent or the resin is dispersed in a dispersion medium. As the solvent and dispersion medium used in the paint containing the resin used for the overcoat layer of the present invention, water, an organic solvent, and the like can be used. From the viewpoint of coating suitability, water, alcohol solvents such as isopropyl alcohol and ethanol Ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as cyclohexanone and methyl ethyl ketone, and hydrocarbon solvents such as xylene and toluene are preferably used. These solvents may be used alone or in combination of two or more.

  Various additives can be blended in the coating material containing the resin used for the overcoat layer, if necessary, as long as the effect of the overcoat layer is not impaired. For example, a catalyst, an antioxidant, a light stabilizer, a stabilizer such as an ultraviolet absorber, a surfactant, a leveling agent, an antistatic agent, or the like can be used.

  Next, it is preferable to dry the coated film after application to remove the solvent and the dispersion medium. Here, there is no restriction | limiting in particular as a heat source used for drying, Arbitrary heat sources, such as a steam heater, an electric heater, and an infrared heater, can be used. The heating temperature is preferably 50 to 150 ° C. The heat treatment time is preferably several seconds to 1 hour. Furthermore, the temperature may be constant during the heat treatment, or the temperature may be gradually changed. Moreover, you may heat-process, adjusting humidity in the range of 20 to 90% RH by relative humidity during a drying process. You may perform the said heat processing in the state enclosed with air | atmosphere or inert gas.

  Next, the composition of the coating film can be modified by subjecting the coating film containing the dried resin as necessary to an active energy ray irradiation treatment such as ultraviolet irradiation to obtain the overcoat layer of the present invention. The ultraviolet treatment may be performed only once or repeated twice or more. The oxygen concentration during the ultraviolet treatment is preferably 1.0% or less, more preferably 0.5% or less, from the viewpoint of composition control of the overcoat layer. The relative humidity may be arbitrary. In the ultraviolet treatment, it is more preferable to reduce the oxygen concentration using nitrogen gas.

  As the ultraviolet ray generation source, a known source such as a high pressure mercury lamp metal halide lamp, a microwave type electrodeless lamp, a low pressure mercury lamp, a xenon lamp or the like can be used.

Integrated light quantity of ultraviolet irradiation is preferably from ^{50~3,000mJ / cm 2, 100~1,000mJ / cm} 2 is more preferable. The accumulated light amount is preferably 50 mJ / cm ² or more because a desired overcoat layer can be obtained. Moreover, it is preferable if the integrated light quantity is 3,000 mJ / cm ² or less because damage to the polymer substrate can be reduced.

[Transparent conductivity]
The conductive laminate of the present invention preferably satisfies the following [A] or [B].
[A] The total light transmittance is 80% or more and 93% or less, and the surface resistance is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less.
[B] The light absorption rate of the conductive layer is 1% or more and 10% or less, and the surface resistance value is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less.

  Satisfying [A] or [B] is preferable because it becomes a conductive laminate excellent in transparent conductivity and can be suitably used for a touch sensor, a touch panel, electronic paper, and a touch switch.

  Here, a typical example of the transparency index is the total light transmittance, and the total light transmittance of a conductive laminate including one conductive layer has a practical meaning. The total light transmittance varies depending on the reflectance of the conductive layer surface layer and the anticonductive surface of the substrate. For example, when the reflectivity of the conductive layer surface layer or the anticonductive surface of the substrate is high, the total light transmittance is low. That is, since the total light transmittance is a value that can be adjusted depending on the type of the overcoat layer and the substrate, the light absorption rate of the conductive layer may be used as an index of transparency. The light absorption rate of the conductive layer is a comparable value regardless of the type of the overcoat layer or the base material. Further, a typical index of conductivity is a surface resistance value, and a surface resistance value of a conductive laminate including one conductive layer has a practical meaning.

From the viewpoint of transparent conductivity, since it is suitably used for a resistive film type touch panel that requires high total light transmittance, it is more preferable to satisfy the following [A] or [B].
[A] The total light transmittance is 85% or more and 93% or less, and the surface resistance value is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less.
[B] The light absorption rate of the conductive layer is 1% or more and 8% or less, and the surface resistance value is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less.

Since it is suitably used for a capacitive touch panel that requires a low surface resistance value, it is particularly preferable to satisfy the following [A] or [B].
[A] The total light transmittance is 85% or more and 93% or less, and the surface resistance is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ³ Ω / □ or less.
[B] The light absorption rate of the conductive layer is 1% or more and 8% or less, and the surface resistance value is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ³ Ω / □ or less.

[Haze value]
In the conductive laminate of the present invention, the haze value when the conductive laminate is stretched twice is preferably from 0% to 5%, more preferably from 0% to 3%, and even more preferably from 0% to 1%. is there. The haze value here is a value measured based on JIS-K7361 (1997). When the haze value is in this range, for example, when used for a touch sensor, a touch panel, or a touch switch, it can be used favorably without deteriorating the display quality, which is preferable.

[Method for producing conductive laminate]
In the conductive laminate of the present invention, an undercoat layer containing a polyurethane resin and silica particles is formed on a substrate, and the conductive layer is formed by coating a coating liquid containing carbon nanotubes on the undercoat layer. A method for producing a conductive laminate is preferred. By coating a coating liquid containing carbon nanotubes on the undercoat layer, it is preferable because a good network structure can be obtained in which the contact distance between the carbon nanotubes is short.

[Molding process]
The conductive laminate of the present invention can be molded using various molding methods. It can be formed by a forming method such as vacuum forming, compressed air forming, compressed air vacuum forming combining vacuum forming and compressed air forming, press forming, plug forming, laminate forming, in-mold forming, and insert forming. In the present invention, the properties of the resin used for the base material of the conductive laminate, the properties of the resin used for the layer laminated on the base material, and the thickness and the molding method are selected in accordance with the shape to be molded. be able to.

  The draw ratio is determined by the material properties and thickness used for the base material of the conductive laminate, but if it is in the range of more than 1 time and less than 2 times in a temperature environment above the glass transition point of the base material, the productivity is increased. It is preferable because the retardation after stretching is easy to control. That is, it is preferable that the conductive laminate is stretched more than 1 time and 2 times or less under a temperature environment equal to or higher than the glass transition point of the substrate. In addition, it is preferable that the stretching is performed at Tg or more because the phase difference is kept low even when stretching. The stretching temperature is preferably in the range of Tg + 30 degrees or less, more preferably in the range of Tg + 20 degrees or less, and still more preferably in the range of Tg + 10 degrees or less. A stretching temperature in this range is preferable because wrinkles and sagging are difficult to enter and can be molded well.

[Molded body]
The molded product as used in the present invention refers to a product obtained by molding the conductive laminate of the present invention by, for example, the method described in the above-mentioned section [Molding]. Moreover, the molded object of this invention can also be used by bonding with a decorative film and another resin material.

[Usage]
Since the conductive laminate of the present invention has a small increase in haze value after stretching, it can be particularly preferably used for a display device such as a three-dimensional touch panel or electronic paper. Furthermore, the conductive laminate of the present invention can be suitably used for a touch sensor, a capacitive touch switch, a capacitive touch panel, a planar heating element, an electrode for an electric solar cell, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples. The measurement method used in this example is shown below.

<Measurement method>
(1) Weight average molecular weight of dispersant The weight average molecular weight of the dispersant was calculated by comparing with a calibration curve with polyethylene glycol using a gel permeation chromatography method.
Apparatus: LC-10A series manufactured by Shimadzu Corporation Column: GF-7M HQ manufactured by Showa Denko KK
Mobile phase: 10 mmol / L Lithium bromide aqueous solution Flow rate: 1.0 ml / min
Detection: differential refractometer column temperature: 25 ° C.

(2) Surface resistance value Using a non-contact type resistivity meter (NC-10, NC-10) at the center of the conductive laminate cut to a size of 100 mm x 50 mm, the value measured by the eddy current method is the surface. Resistance value was used.

(3) Total light transmittance, haze value Based on JIS K 7361 (1997), it measured using turbidimeter NDH4000 by Nippon Denshoku Industries Co., Ltd.

(4) Conductive layer light absorptivity (4-1) Conductive surface reflectance, conductive surface reverse surface reflectance The surface opposite to the measurement surface has a 60 ° gloss (JIS Z 8741 (1997)) of 10 or less. After the surface was uniformly roughened with a water resistant sandpaper of No. 320 to 400, a black paint was applied and colored so that the visible light transmittance was 5% or less. Conductive surface reflectivity and conductive surface reverse surface reflectance measurements at 550 nm were performed with a spectrophotometer (Spectrophotometer UV-3150 manufactured by Shimadzu Corporation) at an incident angle of 5 ° from the measurement surface. It was.

(4-2) Light transmittance With a spectrophotometer (Spectrophotometer UV-3150, manufactured by Shimadzu Corporation), light was incident from the conductive surface, and light transmittance was measured at 550 nm.

(4-3) Conductive layer light absorptivity Derived from the conductive surface reflectance, conductive surface reverse surface reflectance, and light transmittance measured in (4-1) and (4-2) using the following equation.
Conductive layer light absorption rate (%) = 100% −light transmittance (%) − conductive surface reflectivity (%) − conductive surface reverse surface reflectivity (%) (1).

(5) Thickness of each layer The thickness of each layer of the conductive laminate was measured by TEM observation of the cross section. The cross section of the conductive laminate to be measured was thinned with a focused ion beam device (FIB, Focused Ion Beam) (“FB2000A” manufactured by Hitachi High-Technology Co., Ltd.), and a transmission electron microscope (TEM) (Transmission Electron Microscope) (Hitachi High Co., Ltd.). Technology “H7100FA”) was used. The interface was judged from the contrast difference of the obtained image, and the total thickness of the undercoat layer, the layer containing carbon nanotubes, and the overcoat layer was measured as the conductive layer thickness. The observation was performed in the range of 20,000 times to 100,000 times, and the measurement was performed by selecting a magnification at which the conductive layer thickness was 50% or more in the vertical direction within one field of view.

(6) Identification of resin contained in conductive layer The conductive layer of the sample was analyzed by the FT-IR-ATR method. 1,550～1,530Cm ^-1 indicating a urethane bond, ^1,770 shows the CO double bond -1, ^{760 cm} -1, if having a peak at all 3,250～3,350Cm ^-1 indicating the NH bond The conductive layer was judged to contain a urethane resin.

(7) Total light transmittance after stretching, haze value The conductive laminate was cut into a length of 150 mm and a width of 20 mm, and the temperature inside the tank of a tensile tester (manufactured by Tensilon Yamato Scientific Co., Ltd.) was adjusted at 160 ° C. The laminate was placed so as to have a test length of 50 mm, and the conductive laminate was heated for 1 minute. Thereafter, while maintaining the temperature in the tank, the film was stretched by 10 mm at a pulling speed of 50 mm / min (20% stretching), fixed as it was for 10 seconds, and then the sample was taken out. Based on JIS K 7361 (1997), the central part of the sample obtained under the above conditions was measured using a turbidimeter NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd.

(8) Surface resistance value after stretching The conductive laminate was cut into a length of 150 mm and a width of 20 mm, the temperature inside the tank of a tensile tester (manufactured by Tensilon Yamato Kagaku Co., Ltd.) was adjusted at 160 ° C., and the conductive laminate was tested. It installed so that it might become 50 mm long, and the electrically conductive laminated body was heated for 1 minute. Thereafter, while maintaining the temperature in the tank, the film was stretched by 10 mm at a pulling speed of 50 mm / min (20% stretching), fixed as it was for 10 seconds, and then the sample was taken out. A central portion of the sample obtained under the above conditions was measured using an eddy current method with a non-contact type resistivity meter (NC-10, manufactured by Napson Co., Ltd.) as a surface resistance value after stretching.

(9) Light absorption rate of conductive layer after stretching The conductive laminate was cut into a length of 150 mm and a width of 20 mm, and the temperature inside the tank of a tensile tester (manufactured by Tensilon Yamato Kagaku Co., Ltd.) was adjusted at 160 ° C. Was installed so that the test length was 50 mm, and the conductive laminate was heated for 1 minute. Thereafter, while maintaining the temperature in the tank, the film was stretched by 10 mm at a pulling speed of 50 mm / min (20% stretching), fixed as it was for 10 seconds, and then the sample was taken out. The sample obtained under the above conditions was measured by the same method as (4) conductive layer light absorptivity, and the value derived from equation (1) was defined as the conductive layer light absorptivity after stretching.

Example 1
[Preparation of undercoat layer]
An undercoat layer was prepared by the following operation.

  An aqueous dispersion of polyurethane resin (“Superflex 150” solid content concentration: 30% by mass manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the resin for the undercoat layer, and an aqueous dispersion of silica particles (“Nissan Chemical Industries, Ltd.“ “Snowtex OUP” (solid content concentration: 15 mass%) was used as the silica particles contained in the undercoat layer. Superflex 150, Snowtex OUP, and pure water were mixed at a mass ratio of 5.25: 4.5: 5.25 to obtain a coating solution for preparing an undercoat layer having a solid content of 15% by mass. A polycarbonate film having a thickness of 100 μm (“Iupilon E2000” manufactured by Mitsubishi Engineering Plastics Co., Ltd.) was used as the substrate. Using a UR100 line gravure roll, the rotation ratio of the gravure roll with respect to the line speed was set to 1.5 times, and the coating liquid for the undercoat layer was applied onto the substrate. After coating, the film was dried in a dryer at 125 ° C. for 1 minute. The thickness of the undercoat layer produced by this method was about 800 nm, and the mass ratio of the resin and silica particles in the undercoat layer was 7: 3.

[Preparation of carbon nanotube synthesis catalyst]
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 1000 g of magnesium oxide (MJ-30 manufactured by Iwatani Corporation) was added to this solution, and after vigorously stirring with a stirrer for 60 minutes, 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 160 ° C. and held for 6 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 3 hours in the atmosphere. The bulk density was 0.32 g / mL. Further, when the filtrate was analyzed by an energy dispersive X-ray analyzer (EDX), iron was not detected. From this, it was confirmed that the added iron (III) ammonium citrate was supported on the entire amount of magnesium oxide. Furthermore, from the EDX analysis result of the catalyst body, the iron content contained in the catalyst body was 0.39% by mass.

[Production of carbon nanotubes]
Carbon nanotubes were synthesized using the catalyst. A catalyst layer was prepared 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. 129 g of this catalyst-attached carbon nanotube composition was stirred in 4.8 mL of a 4.8N hydrochloric acid aqueous solution for 1 hour to dissolve the catalyst metal iron and the carrier MgO. 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.

[Oxidation treatment of carbon nanotubes]
The carbon nanotube composition was added to concentrated nitric acid (primary assay 60-61 mass% manufactured by Wako Pure Chemical Industries, Ltd.) having a mass of about 300 times. Thereafter, the mixture was heated to reflux with stirring in an oil bath at about 140 ° C. for 24 hours. After heating to reflux, the nitric acid solution containing the carbon nanotube-containing composition was diluted twice with ion-exchanged water and suction filtered. The carbon nanotube composition was stored in a wet state containing water after washing with ion-exchanged water until the suspension of the filtered material became neutral. When the average outer diameter of the carbon nanotube composition was observed with a high-resolution transmission electron microscope, it was 1.7 nm. The proportion of double-walled carbon nanotubes was 90% by mass, the Raman G / D ratio measured at a wavelength of 532 nm was 80, and the combustion peak temperature was 725 ° C.

[Production of Carboxymethyl Cellulose with Weight Average Molecular Weight: 35,000]
10 mass% sodium carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd., Cellogen 5A (weight average molecular weight: 80,000, molecular weight distribution (Mw / Mn): 1.6, degree of etherification: 0.7)) aqueous solution 500 g was added to a three-necked flask and adjusted to pH 2 using primary sulfuric acid (Kishida Chemical Co., Ltd.). This container was transferred to 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 reaction was stopped by adjusting the pH to 10 using a 28% by mass aqueous ammonia solution (manufactured by Kishida Chemical Co., Ltd.). 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% by mass. Dialysis tube (Spectral Laboratories, Biotech CE dialysis tube (fractionated molecular weight: 3,500-5,000D) obtained by cutting 20 g of 10% by weight aqueous sodium carboxymethylcellulose (weight average molecular weight: 35,000) into 30 cm. In addition, the dialysis tube was floated in a beaker containing 1,000 g of ion-exchanged water and dialyzed for 2 hours, and then dialyzed again for 2 hours after replacing with 1,000 g of new ion-exchanged water. After repeating this operation three times, dialysis was carried out for 12 hours in a beaker containing 1,000 g of new ion-exchanged water, and an aqueous sodium carboxymethylcellulose solution was taken out from the dialysis tube, which was concentrated under reduced pressure using an evaporator. Dry using a freeze dryer As a result, powdered sodium carboxymethylcellulose was obtained with a yield of 70% by mass, the weight average molecular weight by gel permeation chromatography was the same as that before dialysis, and the peak in gel permeation chromatography spectrum. The area of sodium carboxymethylcellulose before dialysis was 57% by mass, whereas the peak area of ammonium sulfate decreased after dialysis, and the peak area of carboxymethylcellulose sodium was improved to 91% by mass.

[Preparation of carbon nanotube dispersion]
Using this 10% by mass aqueous sodium carboxymethylcellulose (weight average molecular weight: 35,000) aqueous solution, the carbon nanotube-containing composition in a wet state (25 mg in terms of dry mass), 3.5% by mass sodium carboxymethylcellulose (Daiichi Kogyo Seiyaku ( 1.8 g of aqueous solution hydrolyzed by serogen 5A (weight average molecular weight: 35,000), zirconia beads (manufactured by Toray Industries, Inc., “Traceram” (registered trademark)), bead size: 0.8 mm 13.3 g was added to the container, and the pH was adjusted to 10 using a 28% by mass aqueous ammonia solution (manufactured by Kishida Chemical Co., Ltd.). When this container was shaken for 2 hours using a vibration ball mill (manufactured by Irie Trading Co., Ltd., VS-1, frequency: 1,800 cpm (60 Hz)), a carbon nanotube paste was prepared. The amount of the dispersant adsorbed in the paste was 88% by mass, and the particle size was 2.9 μm.

  Next, this carbon nanotube-containing composition paste was diluted with ion-exchanged water so that the concentration of the carbon nanotube-containing composition was 0.15% by mass, and again adjusted to pH 10 with 28% by mass ammonia aqueous solution with respect to 10 g of the diluted solution. It was adjusted. The aqueous solution was subjected to a dispersion treatment under ice-cooling with an ultrasonic homogenizer (manufactured by Ieda Trading Co., Ltd., VCX-130) output 20 W, 1.5 minutes (2 kW · min / g). The liquid temperature during dispersion was adjusted to 10 ° C. or lower. The obtained liquid was centrifuged at 10,000 G for 15 minutes with a high-speed centrifuge (Tomy Seiko Co., Ltd., MX-300) to obtain 9 g of a carbon nanotube dispersion. The average diameter of the dispersion of the carbon nanotube-containing composition as measured by AFM in the dispersion was 1.7 nm and was isolated and dispersed. The length of the carbon nanotube-containing composition dispersion was 3.9 μm. Then, water was added and it prepared so that the density | concentration of a carbon nanotube containing composition might be 0.06 mass% by final concentration, and it was set as the film coating liquid.

[Production of a layer containing carbon nanotubes]
The film coating solution produced by the production method was applied onto the undercoat layer by a bar coating method and dried to produce a layer containing carbon nanotubes. The number of the bar coat is No. 6, the drying temperature is 100 ° C. and the drying time is 60 seconds.

[Preparation of overcoat layer]
A urethane acrylate (“UF-8001G” manufactured by Kyoeisha Chemical Co., Ltd.) is diluted with a solvent in which isopropyl alcohol and ethyl acetate are mixed at a mass ratio of 7: 3 to a solid content concentration of 2.0% by mass, and a photopolymerization initiator. ("IRGACURE184" manufactured by BASF) was added in an amount of 5% by mass based on the resin solids to obtain an overcoat coating solution. This coating solution was applied onto the layer containing carbon nanotubes with a bar coater number 8 and dried at 125 ° C. for 1 minute using a hot air oven. Furthermore, UV irradiation was performed using a UV irradiation apparatus (“ECS-301” manufactured by Eye Graphics Co., Ltd.) at a dose of 400 mJ / cm ^{2 in} a nitrogen atmosphere to form an overcoat layer. The overcoat layer, the layer containing carbon nanotubes, and the undercoat layer did not have a clear interface, and the thickness of the conductive layer including the overcoat layer, the layer containing carbon nanotubes, and the undercoat layer was 820 nm.

  The haze value of the conductive laminate thus produced was 0.3%, and the haze value after stretching the conductive laminate by 20% was 0.3%.

(Example 2)
A conductive laminate was produced in the same manner as in Example 1 except that the gravure roll used for producing the undercoat layer was changed to the UR100 line, and the haze values before and after stretching of the conductive laminate were measured.

(Example 3)
A conductive laminate was prepared in the same manner as in Example 1 except that no overcoat layer was provided, and the haze values before and after stretching of the conductive laminate were measured.

Example 4
A conductive laminate was prepared in the same manner as in Example 1 except that the material used as the overcoat layer was changed to hexafunctional acrylate (“Light Acrylate DPE-6A” manufactured by Kyoeisha Chemical Co., Ltd.), and the conductive laminate was stretched. The haze values before and after were measured.

(Comparative Example 1)
The coating liquid for undercoat layer preparation was adjusted with the following procedures. An aqueous dispersion of hydrophilic acrylic-modified polyester resin (“Pesresin A647-GEX” manufactured by Takamatsu Yushi Co., Ltd., solid content concentration: 20% by mass) is used as the resin for the undercoat layer, and an aqueous dispersion of silica particles (Nissan Chemical Industries, Ltd.) “Snowtex OUP” solid content concentration: 15% by mass) was used as the silica particles contained in the undercoat layer. The pesresin A647-GEX, Snowtex OUP, and pure water were mixed at a mass ratio of 2.6: 10.9: 1.5 to obtain a coating solution for preparing an undercoat layer having a solid content of 5% by mass. A conductive laminate was prepared in the same manner as in Example 1 except that the coating solution for preparing the undercoat layer was used and no overcoat layer was provided, and haze values before and after stretching of the conductive laminate were measured.

(Comparative Example 2)
The coating liquid for undercoat layer preparation was adjusted with the following procedures. Tetrafunctional silica (“Colcoat N-103X” solid content concentration: 2.0% by mass) manufactured by Colcoat Co., Ltd. was diluted with isopropyl alcohol to obtain a coating solution for preparing an undercoat layer having a solid content of 1% by mass. A conductive laminate was prepared in the same manner as in Example 1 except that the coating solution for preparing the undercoat layer was used and no overcoat layer was provided, and haze values before and after stretching of the conductive laminate were measured.

1: Base material 2: Undercoat layer 3: Layer containing carbon nanotubes 4: Overcoat layer 5: Conductive layer

Claims (9)

  A conductive laminate having a conductive layer containing carbon nanotubes on a substrate, the haze value after being stretched by 20% being 3.0% or less.   The conductive laminate according to claim 1, wherein the conductive layer includes a polyurethane resin.   The conductive laminate according to claim 1, wherein the conductive layer contains silica particles.   The conductive substrate according to claim 1, wherein the base material contains a thermoplastic resin.   The conductive laminate according to claim 4, wherein the thermoplastic resin is at least one resin selected from the group consisting of a polycarbonate resin, an acrylic resin, and a cyclic olefin resin. The electrically conductive laminated body in any one of Claims 1-5 which satisfy | fills the following [A] or [B].
[A] Total light transmittance is 80% or more and 93% or less, and surface resistance value is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less [B] Conductive layer light absorption is 1% or more and 10 % And the surface resistance value is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁴ Ω / □ or less.   The conductive layer is formed by forming an undercoat layer containing a polyurethane resin and silica particles on a substrate, and coating the undercoat layer with a coating liquid containing carbon nanotubes. The manufacturing method of the electrically conductive laminated body in any one of -6.   The molded object using the electrically conductive laminated body in any one of Claims 1-6.   The touch sensor using the electrically conductive laminated body in any one of Claims 1-6, or the molded object of Claim 8.

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