JP7699756B2 - Resin composite material containing carbon nanotubes and method for producing same - Google Patents

Description

The present invention relates to a resin composite material containing carbon nanotubes and a method for producing the same.

General-purpose thermoplastic resins generally have low electrical conductivity, and electrical conductivity is imparted by dispersing a conductive material in the resin. Conventionally, carbon black, ketjen black, and graphite have been used as conductive materials, but these conductive materials require a large amount to be blended with the resin. In addition, because the amount blended is large, they are unsuitable for applications requiring transparency.

In response to these issues, Patent Document 1 proposes a composition for the antistatic layer that combines an energy ray curable resin with conductive particles such as ZnO, ITO, ATO, and SbO2. However, such conductive particles are usually blended in large amounts of 1% by mass or more, which affects the strength, optical properties, and other properties of the molded product.

Also, Patent Document 2 proposes a dispersion of carbon nanotubes containing carbon nanotubes, a dispersant, an organic solvent and/or a resin component. However, although the surface resistance is ¹⁰⁶ to ¹⁰⁹ Ω/sq., the carbon nanotube concentration in the total solid content of the coating film is high at 20% to 33%, and the total light transmittance, which is an index of transparency, is 80% or less, so that transparency and conductivity are not compatible.

Japanese Patent Application Publication No. 09-115334 JP 2007-297255 A

The present invention aims to achieve both electrical conductivity and transparency, and provides a resin composite material having an antistatic layer on a thermoplastic resin substrate that uses carbon nanotubes as a conductive material. Despite the low concentration of carbon nanotubes in the antistatic layer, the present invention provides a resin composite material that has sufficient antistatic performance and maintains high transparency.

The present inventors have conducted extensive research to solve the above problems. As a result, they have found that an antistatic layer (B) formed on a thermoplastic resin substrate (A) contains at least (b1) carbon nanotubes and (b2) polycarbonate resin, and that despite the low concentration of (b1) carbon nanotubes contained in the antistatic layer (B), the layer exhibits sufficient antistatic properties, and further that the resulting resin composite does not significantly impair the total light transmittance in the visible light region of the thermoplastic resin substrate (A).

The present invention was completed through further investigation based on the above findings.

The aspects of the present invention are as follows.
Item 1: A resin composite material having an antistatic layer (B) on a thermoplastic resin substrate (A),
A resin composite material having a surface resistance of 1×10 ⁷ Ω/sq. to less than 1×10 ¹³ Ω/sq. and a total light transmittance of 80% or more in the visible light region,
the (B) antistatic layer is composed of at least (b1) carbon nanotubes and (b2) polycarbonate resin;
The resin composite material (B), wherein the concentration of the carbon nanotubes (b1) in the antistatic layer (B) is 0.005% by mass to 0.1% by mass.
Item 2. The resin composite material according to item 1, wherein the antistatic layer (B) has a thickness of 0.1 μm or more and 20 μm or less.
Item 3. The resin composite material according to item 1 or 2, wherein the carbon nanotube (b1) in the antistatic layer (B) has an outer diameter of 0.1 nm or more and 5 nm or less.
Item 4 A manufacturing method for obtaining the resin composite material according to any one of items 1 to 3,
A step of preparing a carbon nanotube dispersion liquid containing at least (b1) carbon nanotubes, (b2) a polycarbonate resin, and (b3) a polar solvent;
(A) applying the carbon nanotube dispersion onto a thermoplastic resin substrate;
(A) drying the carbon nanotube dispersion liquid applied onto the thermoplastic resin substrate; and (B) forming an antistatic layer.
A method for manufacturing a resin composite material comprising the steps of:
Item 5. The method for producing a resin composite material according to Item 4, wherein in the step of preparing the carbon nanotube dispersion, the concentration of the polar solvent (b3) is 80 to 99 mass % based on the total composition of the carbon nanotube dispersion.
Item 6. The method for producing a resin composite material according to any one of Items 4 and 5, wherein the polar solvent (b3) is at least one selected from the group consisting of halogen-based solvents, ether-based solvents, ketone-based solvents, amine-based solvents, amide-based solvents, nitro-based solvents, and aromatic hydrocarbon-based solvents.

The present invention provides a resin composite material that has sufficient antistatic properties and transparency.

The resin composite of the present invention is composed of (A) a thermoplastic resin substrate and (B) an antistatic layer formed on the (A) thermoplastic resin substrate, and the (B) antistatic layer can be formed by applying a carbon nanotube dispersion liquid containing at least (b1) carbon nanotubes, (b2) a polycarbonate resin, and (b3) a polar solvent onto the (A) thermoplastic resin substrate and drying the layer. By setting the concentration of (b1) carbon nanotubes contained in the (B) antistatic layer to 0.005 to 0.1 mass%, sufficient antistatic properties can be obtained, and further, excellent transparency can be obtained without significantly impairing the total light transmittance in the visible light region that the (A) thermoplastic resin substrate originally has. The resin composite of the present invention will be described in detail below.

In this specification, a numerical value connected with "~" means a numerical range that includes the numerical values before and after "~" as the lower and upper limits. When multiple lower limits and multiple upper limits are listed separately, any lower limit and upper limit may be selected and connected with "~" (however, when an upper limit value that is written as "less than" is connected with "~", the numerical value after "~" (i.e. the upper limit value) is not included in the numerical range).

Resin Composite The resin composite of the present invention is composed of (A) a thermoplastic resin substrate and (B) an antistatic layer, and the (B) antistatic layer is obtained by applying a carbon nanotube dispersion liquid containing at least (b1) carbon nanotubes, (b2) a polycarbonate resin, and (b3) a polar solvent onto the (A) thermoplastic resin substrate and drying the same.

(A) Thermoplastic Resin Substrate The (A) thermoplastic resin substrate in the resin composite of the present invention is not particularly limited as long as it is a resin having a thickness of 2 mm and a transparency of 80% or more in the visible light region (380 nm to 780 nm), and may be the same as or different from the (b2) polycarbonate resin contained in the (B) antistatic layer. Specific examples include polyvinyl chloride resin (PVC resin), polystyrene resin (PS resin), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyester resin (PEs resin), polycarbonate resin (PC resin), polymethyl methacrylate resin (PMMA resin), polyethersulfone resin (PES resin), polyarylate resin (PAR resin), polysulfone resin (PSU resin), etc. It is particularly preferable to use PVC resin, PC resin, and PMMA resin with high total light transmittance in the visible light region. The total light transmittance in the visible light region can be measured according to JIS K7361-1, which is a JIS standard. The specific measurement method is as described in the Examples.

(A) The thermoplastic resin substrate may contain various additives such as antioxidants, ultraviolet absorbers, plasticizers, pigments, dyes, etc., as necessary. In addition, one or both sides may be subjected to a surface modification treatment. By performing the surface modification treatment, in the present invention, the adhesion to the antistatic layer can be improved. Examples of the surface modification treatment include energy ray irradiation treatment (corona discharge treatment, plasma treatment, electron beam irradiation treatment, ultraviolet irradiation treatment) and chemical treatment (immersion in an aqueous solution of an oxidizing agent such as potassium dichromate solution or concentrated sulfuric acid), and any of these methods can be used.

The thickness of the (A) thermoplastic resin substrate is selected appropriately according to the application, such as when flexibility is required for films or tapes, or when rigidity is required for molded products such as trays or boards. There are no particular limitations, but a thickness of 0.01 to 10 mm is preferable.

(B) Antistatic Layer The (B) antistatic layer in the resin composite of the present invention is obtained by applying a carbon nanotube dispersion liquid containing at least (b1) carbon nanotubes, (b2) a polycarbonate resin, and (b3) a polar solvent onto (A) a thermoplastic resin substrate, followed by drying.

(b1) Carbon Nanotube The (b1) carbon nanotube used in the present invention is not particularly limited, and may be a carbon nanotube manufactured by any of the methods known as common manufacturing methods, such as the arc discharge method, the laser evaporation method, and the chemical vapor deposition method (CVD method). Considering the purity and productivity of the carbon nanotube, it is preferable to use a carbon nanotube manufactured by the chemical vapor deposition method (CVD method). In addition, the type of carbon nanotube is not particularly limited, and may be a single-walled carbon nanotube, a double-walled carbon nanotube, or a multi-walled carbon nanotube.

From the viewpoint of more suitably exerting the effects of the present invention, the outer diameter of the (b1) carbon nanotube is not particularly limited, but the lower limit is preferably 1.0 nm or more, more preferably 1.2 nm or more, and even more preferably 1.5 nm or more. The upper limit is preferably 5.0 nm or less, more preferably 3.0 nm or less, and even more preferably 2.0 nm or less. The outer diameter of the carbon nanotube can be determined by measuring 100 tubes using a Raman spectrometer and a transmission electron microscope, and averaging the measurements.

In order to more effectively exert the effects of the present invention, the length of the (b1) carbon nanotube is not particularly limited, but the lower limit may be 10 nm or more, 10 μm or more, 1 mm or more, or 10 mm or more, and the upper limit is 100 mm or less. The measurement method is also not particularly limited, and may be the length of a single carbon nanotube, or may be a state in which the carbon nanotubes are aggregated together to form a bundle (bundle state).

In addition, the lower limit of the G/D ratio, which is the intensity ratio of the G band to the D band of (b1) carbon nanotubes, is preferably 10 or more, more preferably 20 or more, and even more preferably 30 or more. The G/D ratio is measured by a Raman spectrometer, and is calculated as the peak intensity ratio of the G band (near 1590 cm ^-1 ) to the D band (near 1300 cm ^-1 ) in a Raman spectrum measured by a resonance Raman scattering method (excitation wavelength 532 nm). A higher G/D ratio indicates a smaller amount of defects in the carbon nanotube structure.

(b1) The carbon purity of the carbon nanotubes is not particularly specified, but is, for example, 95% or more, preferably 98% or more, and more preferably 99% or more. By removing as many impurities as possible, such as metals, the dispersibility of the carbon nanotubes can be improved.

(b2) Polycarbonate resin The (b2) polycarbonate resin used in the present invention may be composed of a single polycarbonate resin or an alloy with other resins, and is not particularly limited. In addition, it may contain known additives such as light blocking agents, ultraviolet absorbing agents, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, crosslinking agents, antiblocking agents, antioxidants, etc. as other components depending on the application and environment.

The polycarbonate resin used in the present invention may be a commercially available product. Specific examples include the Panlite series manufactured by Teijin Limited, the Iupilon series and Novarex series manufactured by Mitsubishi Engineering Plastics Corporation, the Polyca Ace series manufactured by Sumitomo Bakelite Co., Ltd., and the SD Polyca series manufactured by Sumika Polycarbonate Co., Ltd.

(b3) Polar Solvent The polar solvent (b3) used in the present invention is not particularly limited, and examples thereof include halogen-based solvents such as methylene chloride, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, and chlorobenzene; ether-based solvents such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketone-based solvents such as methyl ethyl ketone, acetone, and cyclohexanone; acetate-based solvents such as propylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone; and carbonate-based solvents such as ethylene carbonate and propylene carbonate. amide-based solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, 2-pyrrolidone, N-methyl-2-pyrrolidone; nitro-based solvents such as nitromethane, nitrobenzene, and aromatic hydrocarbon-based solvents such as toluene and xylene; sulfide-based solvents such as dimethyl sulfoxide and sulfolane; phosphoric acid-based solvents such as hexamethylphosphoramide and tri-n-butyl phosphate; alcohol-based solvents such as methanol, ethanol, and 1-propanol; and organic acid-based solvents such as formic acid, acetic acid, and propionic acid.

Among the polar solvents (b3) above, halogen-based solvents, ether-based solvents, ketone-based solvents, amine-based solvents, nitro-based solvents, amide-based solvents, and aromatic hydrocarbon-based solvents are preferred, and at least one selected from the group consisting of methylene chloride, chloroform, diethyl ether, tetrahydrofuran, 1,4-dioxane, methyl ethyl ketone, acetone, cyclohexanone, triethylamine, pyridine, acetonitrile, N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, 2-pyrrolidone, N-methyl-2-pyrrolidone, toluene, and xylene is preferred, and it is more preferred to use methylene chloride, chloroform, 2-pyrrolidone, tetrahydrofuran, toluene, cyclohexanone, or N-methyl-2-pyrrolidone.

The concentration of the polar solvent (b3) used in the present invention is not particularly limited as long as the carbon nanotubes can be uniformly dispersed when producing the carbon nanotube dispersion liquid and the viscosity can be adjusted to suit the coating method of the antistatic layer. As a specific example, the lower limit is preferably 84% by mass or more, and more preferably 86% by mass or more. The upper limit is preferably 94% by mass or less, and more preferably 92% by mass or less.

In addition, other compounding agents may be contained as long as they do not impair the effects of the present invention. Examples of other compounding agents include adhesion promoters, defoamers, and surface conditioners. These can be appropriately selected from known compounds depending on the application of the resin composite material of the present invention.

Method for Producing Carbon Nanotube Dispersion The carbon nanotube dispersion used in the present invention can be produced by mixing or dispersing (b1) carbon nanotubes, (b2) a polycarbonate resin, and (b3) a polar solvent, together with any additives that may be added as necessary.
The mixing or dispersion method is not particularly limited as long as it is a method that can uniformly disperse or mix each component to such an extent that (b1) carbon nanotubes cannot be visually confirmed as aggregates. Examples of dispersion devices include homogenizers, bead mills, ball mills, basket mills, attrition mills, universal mixers, clear mixers, ultrasonic waves, jet mills, and shear dispersion treatment. For the shear dispersion treatment, products such as "Nano Jet Pal JN20" (manufactured by Jokou Co., Ltd.) and "Nano Vaita L-ES" (manufactured by Yoshida Kikai Kogyo Co., Ltd.) can be used.

Manufacturing method of resin composite material The manufacturing method of the resin composite material is to form an antistatic layer (B) on a thermoplastic resin substrate (A). The method of forming the antistatic layer (B) is not particularly limited, but examples thereof include a method of applying a carbon nanotube dispersion onto the thermoplastic resin substrate (A) and then drying the same, or a method of spraying a carbon nanotube dispersion onto the thermoplastic resin substrate (A) and then drying the same.

(A) There are no particular restrictions on the method for applying the carbon nanotube dispersion to the thermoplastic resin substrate, but the carbon nanotube dispersion can be applied to the thermoplastic resin substrate by an appropriate method, such as screen printing, a bar coater, a knife coater, a spin coater, an applicator, etc., depending on the desired coating thickness. It can also be applied by spray coating using a sprayer.

Conventional drying equipment such as heater type, hot air drying type, infrared irradiation type, vacuum type, etc. can be used to dry the polar solvent (b3) contained in the coating film. For example, the temperature for removing the polar solvent (b3) is about 20°C to 100°C, and it is preferable to increase the temperature stepwise so as not to leave any air bubble marks on the (B) antistatic layer. The drying time is preferably about 20 minutes to 240 minutes at each stepwise increase in temperature. As for the environment inside the drying equipment, as described above, either normal pressure or vacuum may be used as long as it is possible to prevent air bubble marks from being formed on the (B) antistatic layer.

The concentration of (b1) carbon nanotubes in the (B) antistatic layer obtained by drying may be, as a lower limit, 0.005% by mass or more, 0.0075% by mass or more, or 0.01% by mass or more. Also, as an upper limit, it may be 0.1% by mass or less, 0.075% by mass or less, or 0.05% by mass or less. By being in this range, good results can be obtained in terms of electrical conductivity and total light transmittance in the visible light region.

The concentration of the (b2) polycarbonate resin in the (B) antistatic layer obtained by drying may be, as a lower limit, 96.99% by mass or more, 96.9925% by mass or more, or 96.995% by mass or more. Also, as an upper limit, it may be 99.95% by mass or less, 99.925% by mass or less, or 99.9% by mass or less.

The concentration of other compounding agents in the (B) antistatic layer obtained by drying is preferably 3% by mass or less. It may contain no other compounding agents and may be substantially composed of only (b1) carbon nanotubes and (b2) polycarbonate resin.

The thickness of the (B) antistatic layer after drying is preferably 0.1 μm or more, more preferably 1.0 μm or more, and even more preferably 2.0 μm or more. The upper limit is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 12 μm or less.

In the present invention, in order to achieve both electrical conductivity and transparency, it is preferable that the carbon nanotube concentration (mass %) in the antistatic layer and the film thickness (μm) satisfy the following relational expression.
Relational formula: 0.001≦carbon nanotube concentration×film thickness ² <5

The resin composite material of the present invention obtained by the above manufacturing method has excellent antistatic properties and does not significantly impair the total light transmittance in the visible light region that the (A) thermoplastic resin substrate originally has, and therefore can be suitably used in applications requiring electrical conductivity and transparency.

The lower limit of the electrical conductivity of the resin composite of the present invention is preferably 1×10 ⁷ Ω/sq. or more, more preferably 2.5×10 ⁷ Ω/sq. or more, and even more preferably 5×10 ⁷ Ω/sq. or more. The upper limit is preferably less than 1×10 ¹³ Ω/sq., more preferably 7.5×10 ¹² Ω/sq. or less, and even more preferably 5×10 ¹² Ω/sq. or less. By being within this numerical range, sufficient electrical conductivity is ensured in applications requiring antistatic properties, and therefore the material can be suitably used.

The total light transmittance in the visible light region of the resin composite of the present invention is preferably 80% or more, more preferably 82% or more, and even more preferably 84% or more. By having a value equal to or greater than this, the material can be suitably used in applications requiring transparency.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

First, the materials used in the examples and comparative examples described below will be described below. Note that carbon nanotubes are sometimes abbreviated as CNT.
(A) Thermoplastic resin substrate
PC resin board made by AS ONE, thickness 2mm, total light transmittance 89%
PMMA resin substrate AS ONE, thickness 2mm, total light transmittance 89%
(B) Antistatic layer (b1) Carbon nanotubes Carbon nanotubes Osaka Soda Co., Ltd., single-walled CNT, outer diameter 2.0 nm, G/D ratio 76
Carbon black: Mitsubishi Chemical, #960 (comparison material)
(b2) Polycarbonate resin Polycarbonate resin Teijin, Panlite L-1225Y
Polymethylmethacrylate resin: Mitsubishi Chemical's ACRYPET VH001 (comparison material)
(b3) Polar solvent: Chloroform (manufactured by Wako Pure Chemical Industries, Ltd.)

Next, the evaluation method will be explained below.

(Thickness of Antistatic Layer)
The thickness of the antistatic layer of the resin composite material can be determined by measuring the thickness of the substrate before the carbon nanotube dispersion is applied and the thickness of the resin composite material after the drying process using a micrometer, and the difference between these is the thickness of the antistatic layer. In order to stabilize the conditions, the substrate was left to stand for 48 hours under conditions of 23°C and 50% RH before the measurement, and the measurement was also performed under the same conditions.

(Surface resistance value)
The surface resistance of the antistatic layer of the resin composite was measured using a Hiresta (Hiresta-UX MCP-HT800, manufactured by Nitto Seiko Analytech). In order to stabilize the conditions, the sample was left to stand for 48 hours under conditions of 23°C and 50% RH before the measurement, and the measurement was also performed under the same conditions. The molded surface was measured at three points with an applied voltage of 10V, and the average value was taken as the surface resistance. The evaluation criteria were set as follows and the evaluation was performed.
◯: Less than 1×10 ¹³ Ω/sq. ×: 1×10 ¹³ Ω/sq. or more

(Total light transmittance)
Based on JIS K-7361-1 (Plastics - Test method for total light transmittance of transparent materials - Part 1: Single beam method), the total light transmittance of the resin composite was measured at a measurement wavelength of 380 to 780 nm using an ultraviolet-visible-near infrared spectrophotometer (UV-3600i SHIMAZU, using an integrating sphere unit ISR-603). The evaluation criteria were set as follows and the evaluation was performed.
○: 80% or more ×: Less than 80%

[Preparation Example 1] Carbon nanotube dispersion 1
As shown in Table 1, 0.0025% by mass of carbon nanotubes, 9.9975% by mass of polycarbonate resin, and 90% by mass of chloroform were weighed out and shaken for 1 hour using a shaker to dissolve the resin components. Next, the carbon nanotubes were coarsely crushed and roughly dispersed for 10 minutes using a homomixer (TK Robomix, manufactured by Primix Corporation). Then, the carbon nanotubes were finely dispersed using a high-pressure emulsifying and dispersing device (Nanovater L-ES, manufactured by Yoshida Kikai Kogyo Co., Ltd.) to prepare carbon nanotube dispersion liquid 1.

[Preparation Example 2] Carbon nanotube dispersion 2
Carbon nanotube dispersion liquid 2 was prepared in the same manner as in Preparation Example 1, except that the carbon nanotubes were changed to 0.0015 mass % and the polycarbonate resin was changed to 9.9985 mass % as shown in the composition in Table 1.

[Preparation Example 3] Carbon nanotube dispersion 3
Carbon nanotube dispersion 3 was prepared in the same manner as in Preparation Example 1, except that the carbon nanotubes were changed to 0.001 mass % and the polycarbonate resin was changed to 9.999 mass % as shown in the composition in Table 1.

[Preparation Example 4] Carbon nanotube dispersion 4
Carbon nanotube dispersion liquid 4 was prepared in the same manner as in Preparation Example 1, except that the carbon nanotubes were changed to 0.005% by mass and the polycarbonate resin was changed to 9.995% by mass, as shown in the composition in Table 1.

[Preparation Example 5] Carbon nanotube dispersion 5
Carbon nanotube dispersion liquid 5 was prepared in the same manner as in Preparation Example 1, except that the carbon nanotubes were changed to 0.0025% by mass and the polymethyl methacrylate resin was changed to 9.9975% by mass, as shown in the composition in Table 1.

Preparation Example 6 Carbon Black Dispersion As shown in the composition in Table 1, a carbon black dispersion was prepared in the same manner as in Preparation Example 1, except that the carbon black was changed to 0.0025 mass % and the polycarbonate resin was changed to 9.9975 mass %.

[Example 1]
(A) A PC resin substrate was used as a thermoplastic resin substrate, and the carbon nanotube dispersion 1 obtained in Preparation Example 1 was applied to the substrate using an applicator (experimental apparatus coater 3
Using a drying agent (manufactured by Imoto Machinery Co., Ltd.), the coating was uniformly applied onto a PC resin substrate so that the thickness of the antistatic layer (B) would be 10 μm after the drying process. The drying process was carried out at 50° C. for 1 hour and then at 70° C. for 1 hour while gradually increasing the temperature conditions to prevent air bubbles from being generated between the coating film and the substrate, to remove the solvent, forming an antistatic layer (B), and thus obtaining a resin composite material of the present invention. The solid content concentrations of the (b1) carbon nanotubes and (b2) polycarbonate resin in the antistatic layer after the drying process are as shown in Table 2. The evaluation results of the obtained resin composite material are also shown in Table 2.

[Examples 2 and 3]
A resin composite was obtained in the same manner as in Example 1, except that the carbon nanotube dispersion 1 was applied onto the PC resin substrate so that the antistatic layer after the drying step had a thickness of 5 μm (Example 2) or 2.5 μm (Example 3). The solid content concentrations of (b1) the carbon nanotubes and (b2) the polycarbonate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 2.

[Example 4]
A resin composite was obtained in the same manner as in Example 1, except that the carbon nanotube dispersion 1 used in Example 1 was replaced with carbon nanotube dispersion 2. The solid content concentrations of (b1) the carbon nanotubes and (b2) the polycarbonate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 2.

[Examples 5 and 6]
A resin composite was obtained in the same manner as in Example 1, except that the carbon nanotube dispersion 2 was applied onto the PC resin substrate so that the antistatic layer after the drying step had a thickness of 5 μm (Example 5) or 2.5 μm (Example 6). The solid content concentrations of (b1) the carbon nanotubes and (b2) the polycarbonate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 2.

[Example 7]
A resin composite was obtained in the same manner as in Example 1, except that the carbon nanotube dispersion 1 used in Example 1 was replaced with carbon nanotube dispersion 3. The solid content concentrations of (b1) the carbon nanotubes and (b2) the polycarbonate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 2.

[Examples 8 and 9]
A resin composite was obtained in the same manner as in Example 1, except that the carbon nanotube dispersion 3 was applied onto the PC resin substrate so that the antistatic layer after the drying step had a thickness of 5 μm (Example 8) or 2.5 μm (Example 9). The solid content concentrations of (b1) the carbon nanotubes and (b2) the polycarbonate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 2.

[Examples 10 and 11]
A resin composite was obtained in the same manner as in Example 1, except that the carbon nanotube dispersion 1 used in Example 1 was changed to carbon nanotube dispersion 4, and carbon nanotube dispersion 4 was applied to the PC resin substrate so that the antistatic layer after the drying process had a thickness of 5 μm (Example 10) or 2.5 μm (Example 11). Table 2 shows the solids concentrations of (b1) carbon nanotubes and (b2) polycarbonate resin in the antistatic layer after drying, and the evaluation results of the resin composite.

[Example 12]
A resin composite was obtained in the same manner as in Example 1, except that a PMMA resin substrate was used instead of the PC resin substrate used in Example 1. The solid content concentrations of (b1) the carbon nanotubes and (b2) the polycarbonate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 2.

[Comparative Example 1]
The same procedure as in Example 1 was repeated, except that Carbon Nanotube Dispersion Liquid 4 was used instead of Carbon Nanotube Dispersion Liquid 1 used in Example 1, and Carbon Nanotube Dispersion Liquid 4 was applied to the PC resin substrate so that the thickness of the antistatic layer after drying would be 10 μm. The solid concentration of each of the (b1) carbon nanotubes and (b2) polycarbonate resin in the antistatic layer after drying, and the evaluation results of the resin composite are shown in Table 3.

[Comparative Example 2]
A resin composite was obtained in the same manner as in Example 1, except that the carbon nanotube dispersion 5 was used instead of the carbon nanotube dispersion 1 used in Example 1. The solid content concentrations of (b1) the carbon nanotubes and (b2) the polymethyl methacrylate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 3.

[Comparative Example 3]
A resin composite was obtained in the same manner as in Example 1, except that a carbon black dispersion was used instead of the carbon nanotube dispersion 1 used in Example 1. The solid content concentrations of (b1) carbon black and (b2) polycarbonate resin in the antistatic layer after drying and the evaluation results of the resin composite are shown in Table 3.

The results in Tables 2 and 3 suggest that with an appropriate carbon nanotube concentration and coating thickness, antistatic properties and transparency can be achieved simultaneously, and that the present invention can be fully applied to applications requiring both transparency and antistatic properties. In addition, it was expected that good conductivity and transparency would be obtained when the (b2) polycarbonate resin of the (B) antistatic layer and the (A) thermoplastic resin substrate were made of the same material, as in Examples 1 to 11, but a comparison of Example 12 and Comparative Example 2 revealed that, contrary to expectations, conductivity could not be achieved unless the resin used in the antistatic layer was polycarbonate resin.

The resin composite material of the present invention has sufficient electrical conductivity and transparency, and can therefore be used widely in applications requiring both antistatic properties and transparency.

Claims (3)

A manufacturing method for obtaining a resin composite material having an antistatic layer (B) on a thermoplastic resin substrate (A) , comprising the steps of:
A step of preparing a carbon nanotube dispersion liquid containing at least (b1) carbon nanotubes, (b2) a polycarbonate resin, and (b3) a polar solvent;
(A) applying the carbon nanotube dispersion onto a thermoplastic resin substrate;
(A) drying the carbon nanotube dispersion liquid applied onto the thermoplastic resin substrate; and (B) forming an antistatic layer .
The resin composite has a surface resistance of 1×10 ⁷ Ω/sq. to less than 1×10 ¹³ Ω/sq. and a total light transmittance in the visible light region of 80% or more,
The method for producing a resin composite material , wherein the concentration of the carbon nanotubes (b1) in the antistatic layer (B) is 0.005% by mass to 0.1% by mass . 2. The method for producing a resin composite material according to claim 1 , wherein in the step of preparing the carbon nanotube dispersion, the concentration of the polar solvent (b3) is 80 to 99 mass % based on the total composition of the carbon nanotube dispersion. 2. The method for producing a resin composite material according to claim 1, wherein the polar solvent (b3) is at least one selected from the group consisting of halogen-based solvents, ether-based solvents, ketone-based solvents, amine-based solvents, amide -based solvents, nitro-based solvents, and aromatic hydrocarbon-based solvents.