JP2012066580A - Transparent conductive laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent conductive laminate the conductive film of which is made of carbon nanotubes (CNTs) which have a high transparent conductivity and a neutral color tone of transmitted light and is excellent in curving resistance.SOLUTION: The transparent conductive laminate 103 keeps a carbon nanotube conductive film 102 and a transparent protective film installed at least on one face of a transparent base material 101 having 20-188 μm thickness in this order from the transparent base material side, wherein the thickness of the transparent protective film is within 10-120 nm, the minimum value point of a reflectivity curve of the transparent protective film side is within a wavelength range of 280-700 nm, and the average reflectivity of the transparent protective film side in a wavelength range of 380-780 nm is 2.5% or less.

Description

  The present invention relates to a transparent conductive laminate having a carbon nanotube (hereinafter sometimes abbreviated as CNT) as a conductive film and a transparent protective film thereon. More specifically, it is a transparent conductive laminate having excellent bending resistance, such as a liquid crystal display (hereinafter sometimes abbreviated as LCD), an organic electroluminescence element (hereinafter also abbreviated as OLED), and display-related, touch panel. The present invention relates to a transparent conductive laminate used for light control glass and electronic paper, and more particularly to a transparent conductive laminate used for electronic paper.

  As a material for forming the conductive film of the transparent conductive laminate, there is indium-tin oxide (hereinafter referred to as ITO). ITO is widely used as a conductive layer material in a transparent conductive laminate for electronic paper because of its high conductivity and excellent environmental resistance (for example, Patent Document 1).

  However, when a transparent conductive laminate in which ITO is a conductive layer material is used for electronic paper, the required bending resistance is still insufficient, and further improvement is desired.

  On the other hand, development of a transparent conductive laminate using CNT as a conductive film is also progressing. CNT can be coated with a conductive film at room temperature and under atmospheric pressure, and can be formed by a simple process. Moreover, since it is rich in flexibility, even when a conductive film is formed on a flexible substrate, it is possible to follow the flexibility of the substrate. Furthermore, when a film is used as the substrate, the conductive film can be continuously formed, so that the process cost can be further reduced. These conductive films can improve the transparent conductivity by increasing the dispersibility of CNTs and reducing the film thickness. Conventionally, a transparent conductive laminate using CNT as a conductive film has been proposed in which a transparent resin is applied and formed on the CNT conductive film in order to improve the durability and the scratch resistance of a thin conductive film. (For example, refer to Patent Document 2 and Patent Document 3). However, the transparent conductive laminate using CNT as the conductive film has insufficient transparent conductivity, and has not yet been replaced with the ITO transparent conductive laminate in various applications.

JP 2003-123559 A (Claims) Japanese Patent No. 3665969 (Claims) International Publication No. 2005-104141 Pamphlet (Example 1)

  An object of the present invention is to provide a transparent conductive laminate suitable for electronic paper, having high transparent conductivity and excellent bending resistance.

  The present invention employs the following means in order to solve such problems. That is, a transparent conductive laminate in which a CNT conductive film and a transparent protective film are provided in this order from the transparent base material side on at least one surface of a transparent base material having a thickness of 20 to 188 μm, and the thickness of the transparent protective film is 10 The minimum value of the reflectance curve on the transparent protective film side is in the wavelength range of 280 to 700 nm, and the average reflectance on the transparent protective film side in the wavelength of 380 to 780 nm is 2.5% or less. It is a transparent conductive laminate.

A preferred embodiment of the transparent conductive laminate of the present invention is (1) the thickness of the transparent protective layer is in the range of 50 to 120 nm,
(2) The minimum value of the reflectance curve on the transparent protective film side is in a wavelength range of 350 to 550 nm,
(3) The difference between the refractive index of the transparent protective film and the refractive index of the CNT conductive film is 0.3 or more, the refractive index of the CNT conductive film is higher than the refractive index of the transparent protective film, and the refractive index of the CNT conductive film Is in the range of 1.6 to 1.9,
(4) L ^* , a ^* , b ^* based on JIS Z8729 of the transparent conductive laminate, transmitted light color tone a ^* in the display color system is −2.0 or more and 2.0 or less, and b ^* is −2.0 or more 2.0 or less,
(5) The surface resistance value on the transparent protective film side is 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁸ Ω / □ or less.
The transparent conductive laminate of the present invention is preferably used for electronic paper.

  According to the present invention, on the CNT conductive film provided on the transparent substrate, the transparent protective film having specific reflection characteristics is formed by adjusting the refractive index and the film thickness. The visible light reflectance on the CNT conductive film side can be reduced without affecting the resistance value, and a transparent conductive laminate having excellent transparent conductivity and bending resistance can be provided with high productivity. Moreover, since the transparent conductive laminated body of this invention is excellent in transparent electroconductivity and bending resistance, it can be used especially suitably for the transparent electrode of electronic paper.

The schematic diagram which shows an example which applied the transparent conductive laminated body of this invention to electronic paper It is the schematic of a bending resistance test. It is the schematic of a fluidized bed vertical reactor.

  The present invention uses a conductive film made of CNTs as a conductive film, and has repeatedly conducted intensive studies on a transparent laminate having high transparency and high conductivity, neutral color tone, and high bending resistance. When the CNT conductive film and the transparent protective film are laminated in this order, the refractive index and thickness of the transparent protective film are adjusted, and the reflective properties of the transparent protective film are set to a specific range, the above problems can be solved at once. It has been investigated.

  The transparent substrate used in the present invention refers to a transparent support substrate. In the present invention, the term “transparent” means that the visible light transmittance is high. Specifically, the total light transmittance at a wavelength of 380 to 780 nm is 80% or more, more preferably 90% or more. A specific example of such a transparent substrate is a transparent resin.

  Moreover, the transparent base material used for this invention is 20-188 micrometers in thickness. With such a thickness, it is possible to reduce a change in resistance value with respect to repeated bending and stretching. If the electronic paper can be bent and stretched and wound up when not used, the advantage that the storage space can be reduced can be obtained. In addition, electronic paper can be bent or stretched as paper as an alternative medium for paper, such as being attached to a curved surface, so that it is desired that the electrical conductivity does not change. From these viewpoints, bending resistance is required for the electronic paper and the transparent conductive substrate which is a member thereof. In addition, a roll-to-roll system can be adopted by using a rollable film, and the production cost can be reduced. From the viewpoint of ease of handling during production, the transparent substrate preferably has a thickness of 20 μm or more. More preferably, it is 100 μm or more. Moreover, in order to implement | achieve the practical bending required for an electronic paper, it is preferable to set it as 188 micrometers or less.

  As the resin constituting the transparent substrate used in the present invention, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyimide, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate , Polymethyl methacrylate, alicyclic acrylic resin, cycloolefin resin, triacetyl cellulose and the like.

  Furthermore, the transparent substrate may be subjected to a surface treatment as necessary. The surface treatment may be provided with a physical treatment such as glow discharge, corona discharge, plasma treatment, flame treatment, or a resin layer. In the case of a film, a film having an easy adhesion layer may be used. The kind of the supporting substrate is not limited to the above, and an optimal one can be selected from transparency, durability, flexibility, cost, etc. according to the application.

  Next, the CNT conductive film will be described. The CNT conductive film in this invention should just contain CNT. In the present invention, the CNT used for the CNT conductive film may be any of single-walled CNTs, double-walled CNTs, and multilayered CNTs having three or more layers. Those having a diameter of about 0.3 to 100 nm and a length of about 0.1 to 20 μm are preferably used. In order to increase the transparency of the CNT conductive film and reduce the surface resistance, single-walled CNTs and double-walled CNTs having a diameter of 10 nm or less and a length of 1 to 10 μm are more preferable.

  Moreover, it is preferable that impurities such as amorphous carbon and catalytic metal are not contained in the aggregate of CNTs as much as possible. When these impurities are contained, they can be appropriately purified by acid treatment or heat treatment. This CNT is synthesized and manufactured by arc discharge method, laser ablation method, catalytic chemical vapor phase method (method using a catalyst in which a transition metal is supported on a carrier in the chemical vapor phase method), etc. A catalytic chemical vapor phase method that can reduce the generation of impurities such as amorphous carbon is preferable. Furthermore, you may add another nanosized electroconductive material as needed.

  In the present invention, the CNT conductive film can be formed by applying a CNT dispersion. In order to obtain a CNT dispersion, it is common to perform a dispersion treatment with a CNT and a solvent using a mixing and dispersing machine or an ultrasonic irradiation device, and it is desirable to add a dispersant.

  The dispersant is not particularly limited as long as CNT can be dispersed. However, in terms of adhesion to the substrate of the CNT conductive film coated and dried on the transparent substrate, hardness of the film, and scratch resistance. It is preferable to select a polymer of a synthetic polymer or a natural polymer. Furthermore, a crosslinking agent may be added within a range that does not impair the 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, polyvinylpyrrolidone. 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. The derivative means a conventionally known compound such as ester or ether. These may be used alone or in combination of two or more. Of these, polysaccharides and derivatives thereof are preferred because of their excellent carbon nanotube dispersibility. Furthermore, cellulose and derivatives thereof are preferable because of high film forming ability. Of these, esters and ether derivatives are preferable, and specifically, carboxymethyl cellulose and salts thereof are preferable.

  The refractive index of the CNT conductive film is preferably in the range of 1.6 to 1.9. When the refractive index of the CNT conductive film is 1.6 or more, the difference in refractive index from the CNT conductive film is 0.3 or more, which is preferable because a transparent protective film material that is inexpensive and has good productivity can be used. . A refractive index of 1.9 or less is preferable because the thickness of the transparent protective film can be reduced and an increase in the surface resistance value can be suppressed. The refractive index of the CNT conductive film can be controlled by adjusting the blending ratio of CNT and dispersant in the CNT conductive film.

  The mixing ratio of the CNT and the dispersing agent is preferably a mixing ratio in which the refractive index of the CNT conductive film is in the range of 1.6 to 1.9 and there is no problem in adhesion to the substrate, hardness, and scratch resistance. Specifically, the CNT is preferably in the range of 10% by mass to 90% by mass with respect to the entire conductive film. More preferably, it is the range of 30 mass%-70 mass%. When the CNT is 10% by mass or more, the transparent conductivity necessary for the touch panel or the light control glass is easily obtained, and the uniformity of the transparent conductivity in the wet coating is improved, which is preferable. When the content is 90% by mass or less, the dispersibility of CNTs in a solvent is improved and is less likely to aggregate, which makes it easy to obtain a good CNT-coated film and good productivity. Further, the coating film is also strong, and it is preferable because scratches hardly occur during the production process and the uniformity of the surface resistance value can be maintained.

  The CNT conductive film reflects and absorbs light depending on the physical properties of the CNT itself. Therefore, in order to increase the transmittance of the transparent conductive laminate including the CNT conductive film provided on the transparent support substrate, a transparent protective film is provided with a transparent material on the CNT conductive film, and the wavelength on the transparent protective film side It is effective to set the average reflectance at 380 to 780 nm to 2.5% or less. When the average reflectance is 2.5% or less, a performance with a total light transmittance of 80% or more when used for electronic paper can be obtained with good productivity.

  In the transparent conductive laminate of the present invention, the transparent protective film provided on the CNT conductive film also serves to improve the scratch resistance of the CNT conductive film and prevent the CNT from falling off in addition to the optical role described above. .

  In order to reduce the average reflectance, the transparent protective film preferably has a refractive index lower than that of the CNT conductive film and a difference from the refractive index of the CNT conductive film of 0.3 or more. Note that the larger the difference between the refractive index of the transparent protective film and the refractive index of the carbon nanotube conductive film, the lower the reflectivity, but this is preferable. It becomes as follows. When the refractive index of the transparent protective film is higher than the refractive index of the CNT conductive film, the average reflectance is higher than when the CNT conductive film is used alone. Further, it is preferable that the difference in refractive index is 0.3 or more because a control range for neutral transmitted light and an average reflectance of 2.5% or less is widened, and a process margin in production is expanded.

  The transparent protective film is not particularly limited as long as it is a substance that falls within the above range. However, the transparent protective film is preferably composed of an inorganic compound, an organic compound, and an inorganic / organic composite and having a cavity inside. Single substances include inorganic compounds such as silicon oxide, magnesium fluoride, cerium fluoride, lanthanum fluoride, calcium fluoride, polymers containing silicon elements and fluorine elements, acrylic resins, melamine resins, epoxy resins, etc. Examples of organic compounds and composites include silica, acryl and other fine particles and monofunctional or polyfunctional (meth) acrylic acid esters, or / and siloxane compounds, and / or organic compounds having perfluoroalkyl groups. Examples thereof include a mixture with a polymer obtained by polymerizing monomer components, a mixture of organic compounds such as an acrylic resin, a melamine resin, and an epoxy resin.

  Specific examples of the silicon oxide include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane, and methyltrimethoxysilane. , Methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, n-butyltrimethoxysilane N-butyltriethoxysilane, n-pentyltrimethoxysilane, n-pentyltriethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, vinyltrimethoxysilane Vinyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 2-hydroxypropyltrimethoxysilane, 2-hydroxy Propyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltri Ethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltri Ethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidop Trialkoxysilanes such as propyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, vinyltriacetoxysilane, and organoalkoxysilane alcohols such as methyltriacetyloxysilane and methyltriphenoxysilane A sol-gel coating film formed by hydrolysis / polymerization reaction from water, acid, or the like, or a sputter deposition film of silicon oxide can be used.

  The film thickness of the transparent protective film is not particularly limited as long as the average reflectance on the transparent protective film side at a wavelength of 380 to 780 nm is 2.5% or less, preferably 10 nm to 120 nm, more preferably 50 to 120 nm. When the thickness of the transparent protective film is 10 nm or more, the film strength increases, and the function of protecting the CNT conductive film such as durability and scratch resistance is improved. On the other hand, when the thickness is 120 nm or less, interference fringes due to light interference are not visually recognized, the transmission color tone is neutral, and the increase in the surface resistance value of the CNT conductive film when the transparent conductive laminate is bent can be suppressed. it can. The film thickness here is an optical film thickness obtained from the light interference phenomenon, and is generally expressed by the following equation.

d = λ / 4n (1)
(D: optical film thickness (nm), λ: wavelength indicating minimum reflectance (nm), n: refractive index of transparent protective film)
The transparent protective film may contain particles, a conductive agent, an antistatic agent, an ultraviolet absorber, a leveling agent, a slip activator, and other components as necessary.

  As a method for forming the transparent protective film on the CNT conductive film, an optimum method may be selected depending on the material to be formed, and dry methods such as vacuum deposition, EB deposition, sputter deposition, cast, spin coating, dip coating, bar General methods such as wet coating methods such as coating, spraying, blade coating, slit die coating, gravure coating, reverse coating, screen printing, mold coating, printing transfer, and ink jetting can be used. In particular, a wet coating method using a micro gravure or the like that can form the transparent protective film uniformly in the range of 10 nm to 120 nm and with good productivity is preferable.

The transmitted light color tone a ^* and b ^* values in the L ^* , a ^* , and b ^* display color system based on JIS Z8729 (2004) of the transparent conductive laminate of the present invention are preferably both a ^* and b ^* values. -2.0 or more and 2.0 or less, More preferably, both are -1.0 or more and 1.0 or less. Since the absorption rate of the CNT conductive film increases in the region of 450 nm or less, a transparent protective film is formed on the CNT conductive film, and the minimum value of the reflectance curve on the transparent conductive protective film side is preferably in the wavelength range of 280 to 700 nm. More preferably, by making it exist in the wavelength range of 350 to 550 nm, more preferably in the wavelength range of 350 to 450 nm, it is possible to balance absorption and reflection in the visible light region, and a ^* value and b ^* value And neutral light transmission light can be obtained. As shown in the equation (1), the minimum value of the reflectance curve can be controlled by the refractive index n and the film thickness of the transparent protective film. Therefore, the minimum value can be adjusted to the above wavelength range by appropriately adjusting. .

The surface resistance value on the transparent protective film side of the transparent conductive laminate of the present invention is preferably 1 × 10 ⁰ Ω / □ or more, 1 × 10 ⁸ Ω / □ or less, more preferably 1 × 10 ¹ Ω / □ or more, It is 1.5 × 10 ³ or less. By being in this range, it can be preferably used as a transparent conductive laminate for electronic paper. That is, if it is 1 × 10 ⁰ Ω / □ or more, the transmittance can be increased, and if it is 1 × 10 ⁸ Ω / □ or less, power consumption can be reduced.

  The transparency of the transparent conductive laminate of the present invention is preferably such that the total light transmittance at a wavelength of 380 to 780 nm is 80% or more. More preferably, the transmittance is 85% or more. If the transmittance is 80% or more, the visibility of the electronic paper can be improved. As a method for increasing the transmittance, in addition to the above-described method of setting the average reflectance at a wavelength of 380 to 780 nm on the transparent protective film side to 2.5% or less, the thickness of the transparent support substrate is generally thin. And a method of selecting a material having a high transmittance. Further, by improving the dispersibility of CNTs, a desired surface resistance value can be obtained with a thinner CNT conductive film, and the transmittance can be increased.

  Next, the electronic paper of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing an example in which the transparent conductive laminate of the present invention is applied to electronic paper. The electronic paper has a structure in which transparent microcapsules 107 are arranged without a gap between the transparent conductive laminate 103 of the present invention disposed at the upper portion and the lower electrode composite body 110 disposed at the lower portion. The transparent conductive laminate 103 disposed on the top is composed of a transparent substrate 101 and a CNT conductive film 102, and the lower electrode composite 110 is composed of a lower electrode 108 and a support substrate 109. A macrocapsule 107 contains positively charged white pigment particles 104 and negatively charged black pigment particles 106 together with a transparent dispersion medium 105.

  In the electronic paper shown in FIG. 1, an electric field is generated between two electrodes by voltage application from an external control circuit, and positively charged white pigment particles 104 and negatively charged black pigment particles 106 are contained in a transparent dispersion medium 105. When the pigment particles of the color selected by any voltage are collected on the display surface side of the capsule, black and white display is performed, and black and white display is selected for each pixel formed by the minute electrodes. Since the pigment particles do not move easily even when the voltage is turned off, they can be read like printed matter.

  By using a transparent substrate having a thickness of 20 to 188 μm, it is possible to provide a transparent conductive laminate that can be bent and stretched, and since the degree of freedom in shape is large, it can be suitably used as electronic paper. In addition, a carbon nanotube conductive film and a transparent protective film are provided in this order from the transparent base material side on at least one surface of the transparent base material, and the thickness of the transparent protective film is in the range of 10 to 120 nm, thereby resisting even when bent. A transparent conductive laminate having no change in value or a small value can be provided, and it can be suitably used as electronic paper because of its high durability. Further, by setting the minimum value of the reflectance curve on the transparent protective film side to a wavelength range of 280 to 700 nm, more preferably a wavelength range of 350 to 550 nm, and even more preferably a wavelength range of 350 to 450 nm, the neutral transparent A conductive laminate is obtained, and high-quality display is possible. Furthermore, by setting the average reflectance on the transparent protective film side at a colorless wavelength of 380 to 780 nm to 2.5% or less, a performance with a total light transmittance of 80% or more when used for electronic paper can be obtained with high productivity. Therefore, it is preferable.

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to the following examples. First, an evaluation method in each example and comparative example will be described.
(1) Refractive index About the coating film formed on the silicon wafer, using a high-speed spectrometer M-2000 (manufactured by JA Woollam), the change in the polarization state of the reflected light of the coating film was measured at an incident angle of 60 degrees, Measurements were made at 65 degrees and 70 degrees, and the refractive index at a wavelength of 550 nm was obtained by calculation using analysis software WVASE.
(2) The average reflectance at wavelengths of 380 nm to 780 nm, the minimum value of the reflectance curve at wavelengths of 200 nm to 1200 nm, the optical film thickness of the transparent protective film The surface opposite to the transparent measurement surface (the surface on which the transparent protective film is provided) The surface is uniformly roughened with a 320-400 water-resistant sandpaper so that the 60 ° C. gloss (JIS Z 8741 (1997)) is 10 or less, and then black so that the visible light transmittance is 5% or less. The paint was applied and colored. Using a spectrophotometer (UV-3150) manufactured by Shimadzu Corporation, the absolute reflection spectrum in the wavelength region of 200 nm to 1200 nm was measured at an interval of 1 nm at an incident angle of 5 degrees from the measurement surface, and the average at a wavelength of 380 nm to 780 nm. The wavelength indicating the reflectance and the minimum value of the reflectance in the region of 200 nm to 1200 nm was determined.

d = λ / 4n
(D: optical film thickness (nm), λ: wavelength indicating minimum reflectance (nm), n: refractive index of transparent protective film)
(3) a ^* , b ^* value Based on JIS Z8729 (2004), the transmittance of the transparent conductive laminate was measured using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3150) with a D65 light source of 2 ° 380 to 380. The transmittance spectrum at 780 nm was measured at intervals of 1 nm, and was measured by the transmission chromaticity calculation result of the XYZ (CIE1976) color system.
(4) Total light transmittance Based on JIS-K7361 (1997), it measured using turbidimeter NDH2000 (made by Nippon Denshoku Industries Co., Ltd.).
(5) Surface resistance value The surface resistance of the transparent protective film side was measured at a central portion of a 100 mm × 50 mm sample by a four-probe method using a low resistance meter (manufactured by Dia Instruments, Loresta EPMCP-T360).
(6) Bending resistance See FIG. The transparent conductive laminate was sampled to 50 mm × 140 mm, and a silver paste electrode (ECM-100 AF4820 manufactured by Taiyo Ink Mfg. Co., Ltd.) was applied in a range of 10 mm width and 50 mm length along both short sides of this sample, 90 ° C. And dried for 30 minutes to obtain the terminal electrode 201. A metal cylinder 202 having a diameter of 5 mm is fixed to the side of the transparent conductive laminate 203 of this sample, and the holding angle of the cylinder from 0 ° (the sample is in a flat state) to the cylinder along the cylinder. Was bent 20 times within a range of 180 ° (in a folded state with a cylinder). When the resistance value between the terminal electrodes before bending is R ₀ and the resistance value after bending is R, the resistance value change rate represented by R / R ₀ is used as an index of bending resistance. The resistance between terminal electrodes was measured with a digital multimeter (KT-2011 manufactured by Kaise Corporation). The number of measurement N was 1.
Next, the CNT coating liquid used in the present invention will be described.

(Catalyst adjustment)
2.459 g of ammonium iron citrate (green) (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 500 mL of methanol (manufactured by Kanto Chemical Co., Inc.). To this solution, 100 g of light magnesia (manufactured by Iwatani Corporation) was added, stirred at room temperature for 60 minutes, dried under reduced pressure while stirring at 40 ° C. to 60 ° C. to remove methanol, and a metal salt was supported on the light magnesia powder. A catalyst was obtained.

(CNT composition production)
CNTs were synthesized in a fluidized bed vertical reactor schematically shown in FIG. The reactor 301 is a cylindrical quartz tube having an inner diameter of 32 mm and a length of 1200 mm. A quartz sintered plate 302 is provided at the center, an inert gas and source gas supply line 305 is provided at the lower part of the quartz tube, and an exhaust gas line 306 and a catalyst charging line 304 are provided at the upper part. Furthermore, a heater 307 surrounding the circumference of the reactor is provided so that the reactor can be maintained at an arbitrary temperature. The heater 307 is provided with an inspection port 308 so that the flow state in the apparatus can be confirmed.

  12 g of the catalyst was taken, and the catalyst 309 shown in the “catalyst adjustment” portion was set on the quartz sintered plate 302 through the catalyst charging line 304 from the sealed catalyst supplier 303. Subsequently, supply of argon gas from the source gas supply line 305 was started at 1000 mL / min. After the inside of the reactor was placed in an argon gas atmosphere, the temperature was heated to 850 ° C.

  After reaching 850 ° C., the temperature was maintained, and the argon flow rate of the raw material gas supply line 305 was increased to 2000 mL / min to start fluidization of the solid catalyst on the quartz sintered plate. After confirming fluidization from the heating furnace inspection port 308, methane was further supplied to the reactor at 95 mL / min. After supplying the mixed gas for 90 minutes, the flow was switched to a flow of only argon gas, and the synthesis was terminated.

  The heating was stopped and the mixture was allowed to stand at room temperature. After the temperature reached room temperature, a CNT composition containing the catalyst and CNT (hereinafter, this composition is referred to as a CNT composition with catalyst) was taken out from the reactor.

  After 23.4 g of the catalyst-attached CNT composition shown above was placed in a magnetic dish and heated at 446 ° C. for 2 hours in the muffle furnace (FP41, manufactured by Yamato Kagaku Co., Ltd.) that had been heated to 446 ° C. in advance. , Removed from the muffle furnace. Next, in order to remove the catalyst, the heat-treated CNT composition with catalyst was added to a 6N hydrochloric acid aqueous solution and stirred at room temperature for 1 hour. The recovered product obtained by filtration was further added to a 6N aqueous hydrochloric acid solution and stirred at room temperature for 1 hour. After filtering this and washing with water several times, 57.1 mg of the CNT composition from which magnesia and metals have been removed can be obtained by drying the filtrate in an oven at 120 ° C. overnight. By repeating the above operation, 500 mg of a CNT composition from which magnesia and metal were removed (hereinafter, this composition is referred to as a catalyst-removed CNT composition) was prepared.

  Next, 80 mg of the catalyst-removed CNT composition was added to 27 mL of concentrated nitric acid (1st grade Assay 60-61%, manufactured by Wako Pure Chemical Industries, Ltd.), and heated with stirring in an oil bath at 130 ° C. for 5 hours. After completion of heating and stirring, the nitric acid solution containing CNTs was filtered, washed with distilled water, and 1266.4 mg of a CNT composition was obtained in a wet state containing water.

(CNT coating solution)
In a 50 mL container, 10 mg of the above CNT composition (converted at the time of drying), 10 mg of sodium carboxymethyl cellulose (Sigma, 90 kDa, 50-200 cps) as a dispersing agent, weighed to 10 g with distilled water, ultrasonic homogenizer output 20 W, Dispersion treatment was performed for 20 minutes under ice cooling to prepare a CNT coating solution. The obtained liquid was centrifuged at 10,000 G for 15 minutes with a high-speed centrifuge to obtain 9 mL of the supernatant. The concentration was adjusted by adding pure water to 145 mL of the supernatant obtained by repeating this operation a plurality of times, and a CNT coating solution A having a CNT concentration of about 0.04% by mass that can be applied by a coater (the mixing ratio of CNT and dispersant was 1: 1). )
(Refractive index of coating film of CNT coating liquid)
The refractive index of the CNT conductive film coated and dried on quartz glass was 1.82.

Next, the material of the transparent protective film will be described.
(Transparent protective film material 1)
In a 100 mL plastic container, 20 g of ethanol was added, and 40 g of n-butyl silicate was added and stirred for 30 minutes. Thereafter, 10 g of 0.1N hydrochloric acid aqueous solution was added, and the mixture was stirred for 2 hours (hydrolysis reaction) and stored at 4 ° C. The next day, this solution was diluted with isopropyl alcohol, toluene and n-butanol mixed solution (mixing mass ratio 2 to 1 to 1) so that the solid content concentration was 1.0% by mass. The refractive index of the film obtained by applying this solution to a silicon wafer and drying was measured by the method (1). The refractive index was 1.44.
(Transparent protective film material 2)
Forse Seed 420C (solid content concentration 50 mass%, acrylic resin) manufactured by China Paint Co., Ltd. was diluted with toluene to a solid content concentration of 1.0 mass%. This liquid was applied to a silicon wafer, dried at 60 ° C. for 1 minute, irradiated with ultraviolet rays at 1.0 J / cm ² , and the refractive index of the cured film was measured by the method (1). The refractive index was 1.50.
(Transparent protective film material 3)
0.83 g of poly [melamine-co-formaldehyde] solution (manufactured by Aldrich, solid content concentration 84 mass%, 1-butanol solution), 0.3 g of solid epoxy resin 157S70 (manufactured by Japan Epoxy Resin), and 98.9 g of 2-butanone was added and stirred at room temperature for 30 minutes to prepare a uniform resin solution. Separately, 0.1 g of thermal polymerization initiator Curezol 2MZ (manufactured by Shikoku Kasei Co., Ltd.) was dissolved in 9.9 g of 1-propanol to prepare a thermal initiator solution. 100 ml of the aforementioned resin solution and 1 ml of the thermal initiator solution are mixed to obtain a thermosetting resin composition solution (solid content concentration of about 1% by mass, melamine resin: solid epoxy resin = 70 parts by mass: 30 parts by mass). It was. The refractive index of the silicon oxide film coated and dried on this silicon wafer was measured by the method (1). The refractive index was 1.60.

Example 1
A polyethylene terephthalate film having a thickness of 100 μm, Lumirror (registered trademark) U46 (manufactured by Toray Industries, Inc.) as a base material, and Folceed 420C (solid content concentration 50 mass%) manufactured by China Paint Co., Ltd. on one side with toluene, A hard coating agent diluted to a solid content concentration of 30% by mass is applied with a micro gravure coater (gravure wire number 200UR, gravure rotation ratio 100%), dried at 60 ° C. for 1 minute, and then irradiated with UV rays at 1.0 J / cm ² and cured. And a hard coat layer having a thickness of 3 μm was provided.

  Next, the operation of applying the CNT coating liquid to the opposite surface provided with the hard coat layer with a micro gravure coater (gravure wire number 100UR, gravure rotation ratio 80%) and drying at 80 ° C. for 1 minute was repeated twice to obtain surface resistance. A CNT conductive film having a value of 260Ω / □ was provided. The total line transmittance of this transparent conductive film with a CNT conductive film was 82.8%.

  Next, a coating liquid of transparent protective film material 1 having a solid content concentration of 1.0 mass% is applied on the CNT conductive film by microgravure coating (gravure wire number 110UR, gravure rotation ratio 170%), and dried at 125 ° C. for 1 minute. Then, a transparent conductive laminate was obtained, and (2) to (6) were evaluated.

(Example 2)
Using a polyethylene terephthalate film with a thickness of 188 μm, Lumirror U46 as a base material,
A hard coat agent similar to that in Example 1 was applied at a gravure wire number of 100 UR and a gravure rotation ratio of 100%, dried and cured with ultraviolet rays to provide a hard coat layer having a thickness of 5 μm.

The CNT coating liquid was applied to the opposite surface provided with the hard coat layer by the same coating method as in Example 1,
A CNT conductive film having a surface resistance value of 225Ω / □ was provided. The total line transmittance of this transparent conductive film with a CNT conductive film was 82.1%. Next, a coating liquid of transparent protective film material 1 having a solid content concentration of 1.0 mass% is applied on the CNT conductive film by microgravure coating (gravure wire number 110UR, gravure rotation ratio 100%), and dried at 125 ° C. for 1 minute. Then, a transparent conductive laminate was obtained, and (2) to (6) were evaluated.

(Example 3)
In the same manner as in Example 2, a CNT conductive film was provided on the opposite surface on which the hard coat layer and the hard coat layer were provided. The surface resistance value of the CNT conductive film was 231 Ω / □, and the total line transmittance of the transparent conductive film with the CNT conductive film was 82.6%.

Next, a coating liquid of the transparent protective film material 1 having a solid content concentration of 1.0 mass% is applied on the CNT conductive film by microgravure coating (gravure wire number 100UR, gravure rotation ratio 100%) and dried at 125 ° C. for 1 minute. Then, a transparent conductive laminate was obtained, and (2) to (6) were evaluated.
Example 4
In the same manner as in Example 2, a CNT conductive film was provided on the opposite surface on which the hard coat layer and the hard coat layer were provided. The surface resistance value of the CNT conductive film was 240Ω / □, and the total line transmittance of the transparent conductive film with the CNT conductive film was 82.5%.

  Next, a coating liquid of transparent protective film material 1 having a solid content concentration of 1.0 mass% is applied on the CNT conductive film by microgravure coating (gravure wire number 80UR, gravure rotation ratio 100%), and dried at 125 ° C. for 1 minute. Then, a transparent conductive laminate was obtained, and (2) to (6) were evaluated.

(Example 5)
In the same manner as in Example 2, a CNT conductive film was provided on the opposite surface on which the hard coat layer and the hard coat layer were provided. The surface resistance value of this CNT conductive film was 260Ω / □, and the total line transmittance of this transparent conductive film with a CNT conductive film was 83.1%.

Next, a coating liquid of the transparent protective film material 1 having a solid content concentration of 1.0 mass% is applied on the CNT conductive film by microgravure coating (gravure wire number 55UR, gravure rotation ratio 80%) and dried at 125 ° C. for 1 minute. Then, a transparent conductive laminate was obtained, and (2) to (6) were evaluated.
(Example 6)
In the same manner as in Example 2, a CNT conductive film was provided on the opposite surface on which the hard coat layer and the hard coat layer were provided. The surface resistance value of this CNT conductive film was 243Ω / □, and the total line transmittance of this transparent conductive film with a CNT conductive film was 82.5%.

Next, a coating liquid of the transparent protective film material 2 having a solid content concentration of 1.0 mass% is applied on the CNT conductive film by microgravure coating (gravure wire number 110UR, gravure rotation ratio 120%) and dried at 60 ° C. for 1 minute. After that, ultraviolet rays were irradiated at 1.0 J / cm ² and cured to obtain a transparent conductive laminate, and (2) to (6) were evaluated.
(Example 7)
In the same manner as in Example 2, a CNT conductive film was provided on the opposite surface on which the hard coat layer and the hard coat layer were provided. The surface resistance value of the CNT conductive film was 260Ω / □, and the total line transmittance of the transparent conductive film with the CNT conductive film was 83.5%.

Next, a coating liquid of transparent protective film material 1 having a solid content concentration of 1.0 mass% is applied on the CNT conductive film by microgravure coating (gravure wire number 150UR, gravure rotation ratio 100%) and dried at 125 ° C. for 1 minute. Then, a transparent conductive laminate was obtained, and (2) to (6) were evaluated.
(Comparative example 1) Evaluation of (2)-(6) was carried out using a commercially available substrate thickness of 175 μm and ITO film High Beam (registered trademark) (manufactured by Toray Film Processing Co., Ltd.).
Comparative Example 2 The hard coat layer was provided in the same manner as in Example 2. On the other side, a CNT coating solution was applied with a bar coater # 10 and dried at 80 ° C. for 1 minute to provide a CNT conductive film having a surface resistance value of 260Ω / □. The total light transmittance of this transparent conductive film with a CNT conductive film was 82.1%. Next, a coating liquid of the transparent protective film material 1 having a solid content concentration of 1.0 mass% was applied on the CNT conductive film with a bar coater # 14 and dried at 125 ° C. for 1 minute to obtain a transparent conductive laminate (2 ) To (6) were evaluated.
(Comparative Example 3) A transparent conductive laminate was obtained in the same manner as in Comparative Example 2 except that the coating liquid of the transparent protective film material 1 was applied with a bar coater # 20, and evaluations (2) to (6) were performed.
(Comparative Example 4) A transparent conductive laminate was obtained in the same manner as in Comparative Example 2 except that the coating liquid of the transparent protective film material 3 was applied with a bar coater # 8, and evaluations (2) to (6) were performed.

In the films of the transparent conductive laminates of Examples 1 to 7, the optical thickness on the transparent conductive protective film side is in the range of 10 to 120 nm, the total line transmittance is 85% or more, and the transmitted light color tone a ^* value and b ^* value are both A transparent conductive film suitable for electronic paper use was obtained, which had a transmittance of -2.0 to 2.0, a high bending resistance of 1.1, a high neutral color, strong bending.

  On the other hand, Comparative Example 1 has extremely poor bending resistance. The transmitted light was recognized as yellow. Moreover, Comparative Examples 2, 3, and 4 are inferior in terms of transmittance. In Comparative Example 2, the transmitted light was further recognized as yellow. Further, in Comparative Examples 2 and 3, the bending resistance is 1.2 or more, which exceeds the change within 10%, which is generally regarded as a threshold value of resistance value fluctuation. In actual use conditions, a severer situation than the anti-bending test described in this example is assumed. In that case, the difference in the resistance value change rate between the example and the comparative example is larger than the result obtained in this test. Will grow.

DESCRIPTION OF SYMBOLS 101 Transparent base material 102 CNT electrically conductive film 103 Transparent electrically conductive laminated body 104 Positively charged white pigment particle 105 Transparent dispersion medium 106 Negatively charged black pigment particle 107 Microcapsule 108 Lower electrode 109 Support base material 110 Lower electrode complex 201 Terminal Electrode 202 Metal cylinder 203 Transparent conductive laminate 301 Reactor 302 Quartz sintered plate 303 Sealed catalyst feeder 304 Catalyst input line 305 Source gas supply line 306 Exhaust gas line 307 Heater 308 Inspection port 309 Catalyst

Claims (7)

  A transparent conductive laminate in which a carbon nanotube conductive film and a transparent protective film are provided in this order from the transparent base material side on at least one surface of a transparent base material having a thickness of 20 to 188 μm, and the transparent protective film has a thickness of 10 to 10 It is in the range of 120 nm, the minimum value of the reflectance curve on the transparent protective film side is in the wavelength range of 280 to 700 nm, and the average reflectance on the transparent protective film side in the wavelength of 380 to 780 nm is 2.5% or less. Transparent conductive laminate.   The transparent conductive laminate according to claim 1, wherein the thickness of the transparent protective layer is in the range of 50 to 120 nm. The transparent conductive laminate according to claim 1 or 2, wherein the minimum value of the reflectance curve on the transparent protective film side is in a wavelength range of 350 to 550 nm.   The difference between the refractive index of the transparent protective film and the refractive index of the carbon nanotube conductive film is 0.3 or more, the refractive index of the carbon nanotube conductive film is higher than the refractive index of the transparent protective film, and the carbon nanotube conductive film The transparent conductive laminate according to any one of claims 1 to 3, wherein the refractive index is in the range of 1.6 to 1.9. L ^* , a ^* , b ^* based on JIS Z8729 of the transparent conductive laminate, transmitted light color tone a ^* in the display color system is −2.0 to 2.0, and b ^* is −2.0 to 2.0 It is the following, The transparent conductive laminated body in any one of Claims 1-4. The transparent conductive laminate according to claim 1, wherein the transparent protective film has a surface resistance value of 1 × 10 ⁰ Ω / □ or more and 1 × 10 ⁸ Ω / □ or less.   Electronic paper using the transparent conductive laminate according to any one of claims 1 to 6.

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