JP2005063951A - Dispersion solution, conductive film, and conductive composite material containing thin film-shaped particles having skeleton composed of carbon, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion solution capable of obtaining high conductivity at a temperature as low as possible without deteriorating a dispersion state of a thin-film shaped particles having a skeleton composed of carbon, by which, a conductive coating film and a conductive composite material including thin film-shaped particles can be manufactured without problem in film forming properties, and to provide a manufactured material and a manufacturing method of the above. <P>SOLUTION: The conductive coating film and the conductive composite material are respectively manufactured by using the dispersion solution containing the thin-film shaped particles containing indispensable components (a) to (c) stated below, or using the dispersion solution formed by adding a component (d) in addition, and by drying/removing a dispersion medium from the these dispersion solution. (a) thin film-shaped particles obtained by oxidizing graphite, dispersible in the liquid having a specific dielectric coefficient of 15 or more, having a skeleton composed of carbon, (b) dispersion medium for dispersing the thin film-shaped particles, (c) compounds having reducing action for the thin film-shaped particles, (d) matrix material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dispersion containing thin-film particles having a skeleton made of carbon, a conductive coating film, a conductive composite material, and methods for producing them.

(Thin-film particles with carbon skeleton)
Regarding the thin film particles having a skeleton made of carbon (hereinafter sometimes referred to as “thin film particles”) obtained by oxidizing graphite and dispersible in a liquid having a relative dielectric constant of 15 or more, the following publicly known And the matters disclosed by the present inventors.

  As a two-dimensional anisotropic material having a carbon atom as a skeleton, there is graphite oxide obtained by oxidizing graphite. This graphite oxide is a multilayer structure in which two-dimensional basic layers are stacked, and generally has a very large number of layers. On the other hand, a very thin material having a small number of layers is also produced (for example, see Non-Patent Document 1). The inventors of the present invention previously obtained thin film particles of such graphite oxide (in the case where the number of layers is one, for example, graphene oxide is desirable (graphene is the name of one layer of graphite)) in high yield. In addition to finding a method for producing a thin film-like particle similar to graphite having a very small number of layers (preferably called graphene when the number of layers is one) (see, for example, Patent Document 1) And 2).

Here, the basic layer of graphite oxide is composed of a carbon skeleton having a thickness of one or two carbon atoms (consisting of sp ³ carbon and sp ² carbon, with many sp ³ carbons), and surfaces on both sides of the skeleton. It is considered to have a structure in which an acidic hydroxyl group or the like is bonded to (see, for example, Non-Patent Documents 2 and 3). When the thickness of the carbon skeleton is one carbon atom, there are hydroxyl groups on both sides of the carbon skeleton, and there is very little water between layers, the thickness of the basic layer is 0.61 nm. Further, when the degree of oxidation is high and well dried, the oxygen contained in the graphite oxide is about 40 wt%.

It is known that the graphite oxide thin-film particles are partially or completely reduced to be in an electronic state with many sp ² bonds similar to graphite and have high electrical conductivity. Graphite oxide having enhanced electrical conductivity by reduction can be used as a semiconductor or conductor in a wide range of fields such as semiconductor elements, wiring materials, charging / antistatic fillers, and is extremely useful.

(Conductive coating containing thin film particles)
As a method for producing a conductive coating film obtained by oxidizing graphite and dispersible in a liquid having a relative dielectric constant of 15 or more and blended with thin film particles having a skeleton made of carbon, the following method is used. is there. First, a thin film-like particle dispersion alone or a dispersion containing a binder, pigment, adhesive component, thickener, etc., is applied to the substrate surface, and the dispersion medium is removed to remove the dispersion medium. A film is formed. Thereafter, in order to obtain conductivity, the thin film particles are reduced by heating at a temperature of about 200 ° C. or higher.

  As another method, a method of forming a film by the same method as described above using thin-film particles reduced in advance and having increased conductivity is also possible. In this case, heating for reduction performed after film formation is not necessary. As a method for reducing thin film particles in advance, a method using a reducing agent is known (see, for example, Patent Document 1).

  In addition, although the method of reducing thin film-like particle | grains using a reducing agent after film forming is also considered, since a reducing agent cannot osmose | permeate inside after film forming, only a coating-film surface can be reduced. For this reason, it is difficult to obtain sufficient electrical conductivity, which is inappropriate as a method for producing a conductive coating film.

(Conductive composite material containing thin film particles)
As a method for producing a conductive composite material, which is obtained by oxidizing graphite and is dispersible in a liquid having a relative dielectric constant of 15 or more and blended with thin film particles having a skeleton made of carbon, the following method is used. is there. First, a matrix material (for example, a water-soluble polymer such as polyvinyl alcohol, polycarbonate, etc.) is dissolved or dispersed in a dispersion of thin film particles, and both are mixed well. Then, by removing the dispersion medium, a composite material in which thin film-like particles are blended can be obtained. Thereafter, the composite material can be made conductive by heating at a temperature of about 200 ° C. or more to reduce the thin film particles. By the above method, a conductive composite material in which thin film particles are blended is manufactured.

  As another method, a method of forming a film by the same method as described above using thin-film particles reduced in advance and having increased conductivity is also possible. In this case, heating for reduction performed after the composite material is manufactured becomes unnecessary. As a method for reducing thin film particles in advance, a method using a reducing agent is known (see, for example, Patent Document 1).

Although the conductive composite material containing thin film-like particles is manufactured by the method as described above, the conductivity of the manufactured conductive composite material is affected by the conductivity of the blended thin-film particles. For example, if the conductivity of the composite material is the same, the higher the conductivity of the thin film particles, the lower the addition rate. Since the lower the addition ratio of the conductive material, the less the influence on the characteristics of the matrix material is. Therefore, it is desirable to keep the addition ratio low by increasing the conductivity of the thin film particles as much as possible.
JP 2002-53313 A JP 2003-176116 A NA Kotov et al. Ultrathin Graphite Oxide-Polyelectrolyte Composites Prepared by Self-Assembly: Transition Between Conductive and Non-Conductive States, Adv. Mater., 8, 637 (1996) T. Nakajima et al. A NEW STRUCTURE MODEL OF GRAPHITE OXIDE, Carbon, 26, 357 (1988) M. Mermoux et al. FTIR AND 13C NMR STUDY OF GRAPHITE OXIDE, Carbon, 29, 469 (1991)

  As described above, in the method for producing a conductive coating film containing thin film particles having a skeleton made of carbon, it is necessary to heat at a temperature of about 200 ° C. or higher, or to use thin film particles previously reduced. It was. However, in the case of a method of heating at a temperature of about 200 ° C. or higher, the heat resistance of a substrate such as a substrate to which the coating film is applied or a material such as a component blended in the dispersion liquid to give the coating film a necessary function. If it is low, there is a problem that heating cannot be performed at a temperature necessary for obtaining conductivity and sufficient conductivity cannot be obtained. In addition, when thin film particles previously reduced are used, the thin film particles aggregate in the dispersion due to the reduction, and it is difficult to uniformly apply the film when the film is formed by the dispersion alone. In other words, when holes are formed in some places, or when a binder or the like is used in combination, the thin film-like particles are unevenly present in the coating film.

  On the other hand, as described above, in the conductive composite material including thin film particles, it is desirable that the conductivity of the thin film particles be as high as possible in order to keep the addition rate of the thin film particles as low as possible. Methods for obtaining the conductivity of the thin film particles include heat reduction and reduction with a reducing agent, but each has the following problems. In the case of heat reduction, the higher the heating temperature, the higher the electrical conductivity. However, since heating is performed after the composite material is manufactured, the temperature is limited by the heat resistance of the matrix material. Therefore, when a material having low heat resistance is used as the matrix material, it is difficult to obtain sufficient conductivity. When a reducing agent is used, it is possible to obtain high conductivity. However, since the thin film particles are reduced in the dispersion, the thin film particles start to aggregate in the dispersion, and the manufactured composite material The dispersion state of the thin film-like particles inside deteriorates. If the dispersion state is poor, the electrical conductivity of the composite material becomes low, and as a result, the addition rate becomes high, which is not desirable.

  From the above, high conductivity can be obtained at as low a temperature as possible without deteriorating the dispersion state of the thin film particles having a skeleton made of carbon, and there is no problem in film forming property. Dispersions that can produce membranes and conductive composites, manufactured materials, and methods of manufacturing these have been desired.

As a result of diligent investigations to achieve the above object, the present inventors have completed the present invention. That is, the present invention is as follows.
(1) Dispersion liquid containing thin film particles essentially comprising the following components (a) to (c):
(A) Thin film-like particles having a skeleton made of carbon, obtained by oxidizing graphite and dispersible in a liquid having a relative dielectric constant of 15 or higher;
(B) a dispersion medium for dispersing the thin film particles;
(C) A compound having a reducing action on the thin film-like particles.
(2) The dispersion according to (1) above, wherein the component (c) is a compound having a function of drying and removing the dispersion medium or reducing thin film particles after the dispersion medium is dried and removed.
(3) The dispersion according to (1) above, wherein the thin film-like particles have a thickness of 0.4 nm to 100 nm and a size in the planar direction of 20 nm or more.
(4) The dispersion according to (1), further comprising a matrix material as the component (d).
(5) A method for producing a conductive coating film containing thin film particles, wherein the dispersion liquid described in (1) above is applied onto a substrate, and then the dispersion medium is dried and removed.
(6) The production method according to (5), wherein the heating temperature in the step of drying and removing the dispersion medium is in the range of 30 ° C to 250 ° C.
(7) A conductive coating film produced by the method described in (5) above.
(8) An antistatic coating, an electromagnetic shielding coating, or a conductive wiring using the conductive coating described in (7) above.
(9) A method for producing a conductive composite material including thin film particles, wherein the dispersion medium is dried and removed from the dispersion liquid described in (4).
(10) The manufacturing method according to (9) above, wherein the heating temperature in the step of drying and removing the dispersion medium is in the range of 30 ° C to 250 ° C.
(11) A conductive composite material produced by the method described in (9) above.
(12) A conductive sheet, a conductive film, an antistatic sheet, or an antistatic film using the conductive composite material according to (11) above.

  The use of the dispersion according to the present invention makes it possible to expand the range of choices regarding the heat resistance of a material such as a substrate in producing a conductive coating film containing thin film particles having a skeleton made of carbon. Moreover, in producing a conductive composite material including thin film-like particles having a skeleton made of carbon, not only the choice of the heat resistance of the matrix material is widened but also high conductivity can be obtained at a lower addition rate.

(Dispersion containing thin film particles)
The dispersion containing the thin film-like particles of the present invention includes (a) a thin film-like particle having a skeleton made of carbon, obtained by oxidizing graphite and dispersible in a liquid having a relative dielectric constant of 15 or more, and (b) A dispersion medium for dispersing the thin film particles and (c) a compound having a reducing action on the thin film particles are contained as essential components. Hereinafter, each component will be described.

(A) Thin Film Particles As thin film particles (a) obtained by oxidizing the graphite used in the present invention, the known Brodie method (using nitric acid and potassium chlorate), Staudenmaier method (nitric acid, sulfuric acid, potassium chlorate) ), Hummers-Offeman method (using sulfuric acid, sodium nitrate, potassium permanganate), graphite oxidation by the methods disclosed by the present inventors in JP-A-2002-53313 and JP-A-2003-176116 You can use things.

  For example, Japanese Patent Application Laid-Open Nos. 2002-53313 and 2003-176116 disclose the following methods. First, as the raw material, it is desirable to use highly crystalline graphite with a developed layer structure. More specifically, the diameter of the widest basic layer inside the particle is approximately equal to the diameter of the particle, and the entire particle is single. Graphite having a multilayer structure is desirable. As such graphite, for example, natural graphite (particularly good quality), quiche graphite (particularly one made at high temperature), and highly oriented pyrolytic graphite are known. Further, expanded graphite in which the layers of these graphites are expanded in advance can also be used as a raw material. It should be noted that impurities such as metal elements in the graphite are desirably removed in advance to about 0.5% or less.

  Since the particle size of graphite is reflected in the size of the thin film-like particles to be generated in the plane direction, the size of the thin film-like particles to be synthesized may be selected. In addition, when it is desired to define the shape of the thin film-like particles to be generated in the planar direction, for example, as a square, it may be cut into a square in advance at the stage of the graphite raw material.

  For the oxidation of graphite, the above-mentioned known methods can be used. However, since oxidation is particularly easy to proceed, the Hummers-Offeman method (WS Hummerset al., J. Am. Chem. Soc. 80, 1339 (1958); U.S. Pat. No. 2,798,878 (1957)) is recommended. In these methods, oxidant ions penetrate between graphite layers to form an intercalation compound. Thereafter, by adding water, the intercalation compound is hydrolyzed to become graphite oxide. In this case, it is desirable to oxidize graphite with an oxidation time of at least 30 minutes or more, preferably 3 hours or more per 10 μm of graphite particle diameter.

After the graphite is oxidized, the oxidant remaining in the reaction solution or ions generated by the decomposition of the oxidant and components derived from the ions are removed and purified. This purification can be performed by washing with water or alcohol, but it is desirable to use high-purity water.
Further, it is desirable to thoroughly wash with a sulfuric acid aqueous solution or a mixed aqueous solution of sulfuric acid and hydrogen peroxide before washing with water. For the purification operation by specific washing, known means such as decantation, filtration, centrifugation, dialysis, ion exchange and the like can be used. When the purification operation becomes difficult as purification proceeds, it is desirable to use centrifugal separation, dialysis, and ion exchange, which are relatively high in purification efficiency, and it is particularly desirable to use centrifugal separation.

  By the above operation, separation of the layers proceeds inside many particles of graphite oxide. Furthermore, when it is desired to promote the separation of the layers, the dispersion can be irradiated with ultrasonic waves or heated (desirably 50 to 150 ° C.).

  As the thin film particles used in the present invention, graphite oxide obtained by the above method can be suitably used. In particular, the thickness is 0.4 nm to 100 nm, more preferably 0.4 nm to 10 nm, more preferably 0.4 nm to 5 nm, and the planar size is 20 nm or more, more preferably 1000 nm or more, and even more preferably 10,000 nm or more. Graphite oxide having a very small number of layers is extremely useful because it is easy to reduce due to its thin thickness and there are no other materials having similar properties and characteristics. These can be produced by the methods disclosed in JP 2002-53313 A and JP 2003-176116 A. The size in the plane direction of the thin film-like particles is appropriately selected according to the application and is not particularly limited, but is usually 500 μm or less.

  The thickness and size of the thin film particles can be measured by observation with an atomic force microscope, a transmission electron microscope, or the like.

  The content of the thin film particles is preferably 0.0001% by weight to 20% by weight, more preferably 0.001% by weight to 10% by weight, more preferably the total weight of the dispersion containing the thin film particles of the present invention. Desirably, it is 0.01 to 5 weight%. If the thin film-like particles are contained in this range, the conductivity of the conductive coating film or conductive composite material obtained using the dispersion of the present invention can be sufficiently increased. On the other hand, if the content of the thin film particles is too small, the electrical conductivity may be insufficient. On the other hand, if the content of the thin film particles is too large, the characteristics of other components such as a matrix material may be affected.

(B) Dispersion medium The dispersion medium (b) for dispersing the thin film particles used in the present invention is not particularly limited as long as the thin film particles (a) can be dispersed. Usually, the dispersion medium of the dispersion liquid after the completion of the synthesis of graphite oxide is water, but this dispersion medium is made of water and has a high relative dielectric constant of 15 or more such as methanol, ethanol, acetone, 2-butanone other than water. It is possible to exchange for a polar liquid. As a means for using such a highly polar liquid other than water as the main dispersion medium, a method of diluting by adding a sufficiently large amount of highly polar liquid other than water contained in the original dispersion, water There is a method in which a high-polarity liquid other than water is added and then the supernatant is removed by centrifugation, decantation, etc., and then gradually replaced with a high-polarity dispersion medium other than water.

  It is also possible to use a liquid obtained by mixing several kinds of liquids at an appropriate ratio as a dispersion medium. In this case, a liquid having a relative dielectric constant of less than 15 may be used in part. Even if the relative dielectric constant is less than 15, a compound (for example, tetrahydrofuran, dioxane, etc.) that mutually dissolves in an arbitrary ratio disperses thin film particles even if the ratio in the dispersion medium is 50% by weight or more. Therefore, a liquid having a relative dielectric constant of less than 15 can be exceptionally used as a main dispersion medium.

(C) Compound having a reducing action on thin film-like particles Various reducing agents can be used as the compound (c) having a reducing action on the thin film-like particles used in the present invention. Among them, it is desirable that the compound has a function of drying and removing the dispersion medium or a function of reducing the thin film particles after drying and removing the dispersion medium. Examples of such compound (c) include hydroiodic acid, hydrazine, phosphinic acid, citric acid, sodium thiosulfate, ammonium thiosulfate, sodium hypophosphite, polyacrylic acid, L (+) ascorbic acid, and the like. Can be mentioned.
Hydroiodic acid has a reducing action when the dispersion medium is dried and removed even at about 60 ° C., and hydrazine has a low boiling point (114 ° C.) and is easily decomposed, so that no reducing agent remains in the coating film. Phosphinic acid has characteristics such as low toxicity, and the most suitable compound can be used according to the application.

  The amount of reducing agent to be added cannot be determined in general depending on the type of reducing agent used and the purpose of use of the coating film, but as a rough guideline, the number of moles of carbon atoms in the thin film particles is the standard. The reducing agent is added so that the number of moles of the reducing agent is 1/100 or more and 10 or less, preferably 1/10 or more and 2 or less. As a reason, if it is 1/100 or less, a sufficient reduction effect cannot be obtained, and the conductivity becomes low, which is not desirable. Moreover, since the reducing agent itself deteriorates conductivity when added 10 times or more, it is not desirable to add the reducing agent more than necessary.

(D) Matrix material The dispersion containing the thin film-like particles of the present invention may further contain a matrix material (d). As the matrix material (d), materials according to purposes such as water-soluble polymers such as polyvinyl alcohol and polyethylene oxide, various thermoplastic resins, thermosetting resins, engineering plastics such as polycarbonate, and inorganic polymers can be freely used. You can choose. In order to highly disperse the thin film particles in the matrix material, it is desirable to select a combination of the dispersion medium and the matrix material so that the matrix material can be dissolved in the dispersion.

  The content of the matrix material (d) varies greatly depending on the purpose of use and the like, but is preferably 0.01% by weight to 99% by weight with respect to the total weight of the dispersion containing the thin film-like particles of the present invention. Desirably, it is 0.1 to 90% by weight. The dispersion containing the thin film-like particles of the present invention is, for example, a pigment, a dye, an adhesive component, a binder, a thickener, an anti-aging agent, a filler, a wax, and a softening, as long as the object of the present invention is not impaired. A component imparting specific functions such as an agent, a curing agent, an ultraviolet absorber, an ultraviolet stabilizer, a flame retardant, a surface conditioner, and an antistatic agent can also be included.

(Method for producing conductive coating film)
As a method for producing a conductive coating film, a dispersion of thin film particles containing (a), (b) and (c) as essential components is applied on a substrate, and then the dispersion medium is dried and removed. To do. In this method, since the thin film-like particles are not reduced in advance, the film is formed in a state in which the thin film-like particles before reduction and the reducing agent are added simultaneously (a state in which the thin-film particles are hardly reduced). Unlike the reduction before film formation, there is no problem that the film-formability deteriorates due to aggregation of thin film particles in the dispersion. Moreover, surprisingly, high conductivity can be obtained at a lower temperature without heating at about 200 ° C. after film formation.

  For example, with reducing agents such as citric acid, sodium thiosulfate, sodium hypophosphite, and phosphinic acid, the thin film particles are hardly reduced in the state of the dispersion. Therefore, the reducing agent is left in the dispersion for several days. Even so, the dispersion state of the thin film-like particles is not changed, and the film forming property is not problematic. However, the reduction starts at the stage of removing and drying the solvent after film formation, or at the stage of heating at about 140 ° C. after drying, and a sufficiently high conductivity can be obtained only by heating for about 10 minutes. Further, when hydroiodic acid is used, sufficiently high conductivity can be obtained only by drying at 60 ° C. The reason why the reducing agent functions at the stage where the dispersion medium is removed and dried, or after that, not in the state of the dispersion, is unknown for now, but because of this special effect, the film-forming property may be deteriorated. In addition, high conductivity can be obtained at a low temperature.

  The method for applying the dispersion onto the substrate is not particularly limited, and generally known methods such as a spin coater method, a bar coater method, and a roll coater method can be used. Further, the method for drying and removing the dispersion medium is not particularly limited, and can be generally performed by a known method.

  The heating temperature after drying / removing the dispersion medium or after drying / removing is desirably 30 ° C. to 250 ° C., more desirably 35 ° C. to 225 ° C., and further desirably 40 ° C. to 200 ° C.

If the dispersion containing the thin film-like particles of the present invention is used, the thin film-like particles can be sufficiently reduced even in the above temperature range. If this temperature is too high, the characteristics of the substrate having low heat resistance may be affected. Conversely, if it is too low, the desired conductivity may not be obtained. According to the manufacturing method described above, it is possible to easily manufacture a conductive coating film having a conductivity in the range of 10 ⁻¹³ S / cm to 10 ⁶ S / cm.

  Even when the conductive coating film of the present invention produced in this way is applied to a substrate having low heat resistance, high conductivity can be obtained while keeping the addition rate of thin film particles low. The conductive coating film of the present invention is suitably used for various applications such as an antistatic coating film, an electromagnetic shielding coating film, and conductive wiring.

  For the conductive coating film, antistatic coating film, electromagnetic shielding coating film, conductive wiring, etc. produced by the production method according to the present invention, a material having low heat resistance is used for the material to be used or the substrate to be formed. Can be extremely useful.

(Method for producing conductive composite material)
As a method for producing a conductive composite material, (a), (b) and (c), and (d), drying and removing the dispersion medium from a dispersion of thin film particles containing a matrix material as an essential component. To do. In this method for producing a conductive composite material, the thin-film particles are not reduced in advance, but are combined in a state in which the thin-film particles before reduction and the reducing agent are added at the same time (the thin-film particles are hardly reduced). Since the material is manufactured, unlike the case of reducing the thin film particles before manufacturing the composite material, there is a problem that the dispersibility in the composite material deteriorates due to the aggregation of the thin film particles in the dispersion. I don't get up. In addition, high conductivity is obtained without heating at about 200 ° C. after the composite material is manufactured, and the conductivity is higher than that obtained by normal heat reduction.

  For example, with reducing agents such as citric acid, sodium thiosulfate, sodium hypophosphite, and phosphinic acid, the thin film particles are hardly reduced in the state of the dispersion. Therefore, the reducing agent is left in the dispersion for several days. However, the dispersion state of the thin film-like particles does not change, and even if the composite material is manufactured, the dispersion state in the composite material is not deteriorated. However, the reduction starts at the stage of removing and drying the dispersion medium, or the stage of heating at about 140 ° C. after drying, and a sufficiently high conductivity can be obtained only by heating for about 15 minutes. The electrical conductivity is higher than when heat reduction treatment at 200 ° C. is performed in a system in which no reducing agent is added. Further, when hydroiodic acid is used, sufficiently high conductivity can be obtained only by drying at 60 ° C. The reason why the reducing agent functions at the stage where the dispersion medium is removed and dried, or after that, is not in the state of the dispersion, but the reason why the reducing agent functions now is unknown, but because of this special effect, the dispersibility is not deteriorated. High conductivity can be obtained at a low temperature.

  The heating temperature after drying / removing the dispersion medium or after drying / removing is desirably 30 ° C. to 250 ° C., more desirably 35 ° C. to 225 ° C., and further desirably 40 ° C. to 200 ° C. According to the present invention, since the thin film-like particles can be sufficiently reduced even in the above temperature range, the conductivity of the conductive composite material can be sufficiently increased. If this temperature is too high, the characteristics of the matrix material may be affected when the heat resistance of the matrix material is low, and conversely, if it is too low, the desired conductivity may not be obtained.

According to the manufacturing method described above, a conductive composite material having a conductivity in the range of 10 ⁻¹³ S / cm to 10 ⁶ S / cm can be easily manufactured. The conductive composite material of the present invention thus obtained is suitably used for various applications such as a conductive sheet, a conductive film, an antistatic sheet, and an antistatic film.

  The conductive sheet, conductive film, antistatic sheet, antistatic film, etc. made by the production method according to the present invention can only obtain high conductivity even when a material having low heat resistance is used. In addition, since the conductivity of the thin film-like particles is high, the addition rate can be kept low, which is extremely useful.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail using an Example, this invention is not limited by this.

Example 1
10 g of natural graphite (purity 99.97 wt% or more) is put in a mixed liquid consisting of 7.5 g of sodium nitrate (purity 99%), 621 g of sulfuric acid (purity 96%), 45 g of potassium permanganate (purity 99%), The mixture was left for 5 days at about 20 ° C. with gentle stirring. The obtained high-viscosity liquid was added to 1000 cm ^{3 of} 5 wt% aqueous sulfuric acid solution with stirring for about 1 hour, and further stirred for 2 hours. Hydrogen peroxide (30 wt% aqueous solution) 30g was added to the obtained liquid, and it stirred for 2 hours.
This liquid was purified by centrifugal separation using a mixed aqueous solution of 3 wt% sulfuric acid / 0.5 wt% hydrogen peroxide and centrifugal separation using water to obtain an aqueous dispersion of thin film particles. From the weight change before and after drying a part of the liquid, the concentration of the thin-film particles in the liquid was 0.5 wt%. Further, elemental analysis of the thin film-like particles vacuum-dried at 40 ° C. revealed that oxygen was about 42 wt% and hydrogen was about 2 wt%. Hereinafter, this dispersion is referred to as Dispersion A.
A dispersion was prepared by adding 70 mg of hydroiodic acid (57 wt% aqueous solution) to 1 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. The dispersion medium was dried and removed at 60 ° C. for 30 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 84 (S / cm).

Example 2
A dispersion was prepared by adding 50 mg of L (+) ascorbic acid to 1 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. The dispersion medium was dried and removed at 70 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 0.1 (S / cm).

Example 3
A dispersion was prepared by adding 50 mg of L (+) ascorbic acid to 1 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. After the dispersion medium was dried and removed at 70 ° C. for 10 minutes, a heat treatment was performed at 140 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 1 (S / cm).

Example 4
A dispersion in which 40 mg of hydrazine was added to 3 g of dispersion A was prepared. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. The dispersion medium was dried and removed at 70 ° C. for 10 minutes, and then heat treatment was performed at 130 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 56 (S / cm).

Example 5
A dispersion in which 180 mg of citric acid was added to 3 g of dispersion A was prepared. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. After the dispersion medium was dried and removed at 70 ° C. for 10 minutes, a heat treatment was performed at 140 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 0.5 (S / cm).

Example 6
A dispersion was prepared by adding 150 mg of sodium thiosulfate to 2 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. After the dispersion medium was dried and removed at 70 ° C. for 10 minutes, a heat treatment was performed at 140 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 0.4 (S / cm).

Example 7
A dispersion was prepared by adding 150 mg of ammonium thiosulfate to 3 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. After the dispersion medium was dried and removed at 70 ° C. for 10 minutes, a heat treatment was performed at 140 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 5 (S / cm). When the ammonium thiosulfate on the surface was washed by washing with water, the conductivity was 15 (S / cm).

Example 8
A dispersion was prepared by adding 120 mg of sodium hypophosphite to 3 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. After the dispersion medium was dried and removed at 70 ° C. for 10 minutes, a heat treatment was performed at 140 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 0.5 (S / cm). When the surface sodium hypophosphite was washed by washing with water, the conductivity was 47 (S / cm).

Example 9
A dispersion was prepared by adding 30 mg of phosphinic acid (30 wt% aqueous solution) to 3 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. After the dispersion medium was dried and removed at 70 ° C. for 10 minutes, a heat treatment was performed at 140 ° C. for 10 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 86 (S / cm).

Example 10
A dispersion was prepared by adding 30 mg of phosphinic acid (30 wt% aqueous solution) and 30 mg of polyacrylic acid (average molecular weight of about 5000) to 3 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. The dispersion medium was dried and removed at 70 ° C. for 10 minutes, and then heat treatment was performed at 140 ° C. for 15 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 2 (S / cm). When the phosphinic acid on the surface was washed by washing with water, the conductivity was 6 (S / cm).

Example 11
A dispersion was prepared by adding 30 mg of phosphinic acid (30 wt% aqueous solution) and 100 mg of acrylic paint (Tamiya Co., Ltd., Tamiya Color) to 3 g of dispersion A. The prepared dispersion was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.). The dispersion medium was dried and removed at 70 ° C. for 10 minutes, and then heat treatment was performed at 140 ° C. for 15 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 1 (S / cm).

Example 12
Dispersion A was diluted 10-fold with tetrahydrofuran (THF), centrifuged, and the supernatant was removed. Again, it was diluted 10 times with THF and centrifuged, and then the supernatant was removed. The resulting dispersion of thin film particles in THF was designated as dispersion B. From the change in weight of the liquid before and after drying, the concentration of the thin film-like particles in the liquid was 1 wt%.
A dispersion was prepared by adding 0.1 g of phosphinic acid (30 wt% aqueous solution) to 20 g of dispersion B. 0.8 g of polycarbonate resin was added to the prepared dispersion, mixed well until uniform, and this liquid was dropped onto a polycarbonate resin substrate. The dispersion medium was dried and removed at 70 ° C. for 10 minutes, and then heat treatment was performed at 140 ° C. for 15 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 1 (S / cm).

Example 13
A dispersion was prepared by adding 30 mg of phosphinic acid (30 wt% aqueous solution) and 600 mg of polyacrylic acid (average molecular weight of about 5000) to 3 g of dispersion A. The prepared dispersion was applied onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. Application was performed using a bar coater. The dispersion medium was dried and removed at 70 ° C. for 10 minutes, and then heat treatment was performed at 140 ° C. for 15 minutes. When the electrical conductivity of the obtained film was examined, the electrical conductivity of the film was 2 × 10 ⁻⁴ (S / cm). In addition, electrical conductivity was computed based on the surface resistivity measured by the method according to JIS-K6911, and the thickness of a coating film. The cross section of the film was cut out with an ultramicrotome and observed with a transmission electron microscope (TEM). As a result, the thickness of the thin film-like particles was 10 nm or less.

Example 14
An aqueous dispersion of thin film particles was prepared in the same manner as in Example 1 except that artificial graphite was used instead of natural graphite, and this dispersion was designated as Dispersion C. From the weight change before and after drying a part of the liquid, the concentration of the thin film-like particles in the liquid was 3 wt%.
A dispersion was prepared by adding 2.5 g of water, 30 mg of phosphinic acid (30 wt% aqueous solution) and 600 mg of polyacrylic acid (average molecular weight of about 5000) to 0.5 g of dispersion C. The prepared dispersion was coated on the surface of a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. Application was performed using a bar coater. The dispersion medium was dried and removed at 70 ° C. for 10 minutes, and then heat treatment was performed at 140 ° C. for 15 minutes. When the conductivity of the obtained film was examined, the conductivity of the film was 2 × 10 ⁻⁸ (S / cm). In addition, electrical conductivity was computed based on the surface resistivity measured by the method according to JIS-K6911, and the thickness of a coating film. The cross section of the film was cut out with an ultramicrotome and observed with a transmission electron microscope (TEM). As a result, the thickness of the thin film-like particles was about 200 nm. Although the addition amount of the thin film-like particles in the polyacrylic acid was the same as that in Example 13, the conductivity of the coating film was worse than that in Example 13 because the thin film-like particles were thick.

Comparative Example 1
Dispersion A was dropped onto a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. After drying and removing the dispersion medium at 70 ° C. for 10 minutes, a heat treatment was performed at 140 ° C. for 30 minutes. When the resistance was measured by the two-terminal method and the conductivity of the coating film was calculated, the conductivity of the coating film was 10 ⁻⁵ (S / cm) or less.

Comparative Example 2
A dispersion was prepared by adding 600 mg of polyacrylic acid (average molecular weight of about 5000) to 3 g of dispersion A. The prepared dispersion was applied on a polycarbonate resin substrate (glass transition point 150 ° C.) whose surface was hydrophilized by corona discharge treatment. Application was performed using a bar coater. The dispersion medium was dried and removed at 70 ° C. for 10 minutes, and then heat treatment was performed at 140 ° C. for 15 minutes. When the electrical conductivity of the obtained film was examined, the electrical conductivity of the film was 1 × 10 ⁻¹⁰ (S / cm) or less. In addition, electrical conductivity was computed based on the surface resistivity measured by the method according to JIS-K6911, and the thickness of a coating film.

Example 15
A dispersion was prepared by adding 2.8 g of hydroiodic acid (57 wt% aqueous solution) to 40 g of dispersion A. 0.8 g of polyvinyl alcohol was added to the prepared dispersion and mixed well until uniform. The dispersion medium was dried and removed under conditions of 60 ° C. for 60 minutes to produce a film. When the resistance was measured by the two-terminal method and the conductivity of the film was calculated, the conductivity of the film was 2 (S / cm).

Example 16
A dispersion was prepared by adding 0.4 g of phosphinic acid (30 wt% aqueous solution) to 40 g of dispersion A. 0.8 g of polyvinyl alcohol was added to the prepared dispersion and mixed well until uniform. The dispersion medium was dried and removed at 70 ° C. for 10 minutes to produce a film. Thereafter, heat treatment was performed at 140 ° C. for 15 minutes. When the resistance was measured by the two-terminal method and the conductivity of the film was calculated, the conductivity of the film was 3 (S / cm).

Example 17
A dispersion was prepared by adding 0.4 g of phosphinic acid (30 wt% aqueous solution) to 20 g of dispersion B. 0.8 g of polycarbonate resin was added to the prepared dispersion and mixed well until uniform. The dispersion medium was dried and removed at 70 ° C. for 10 minutes to produce a film. Thereafter, heat treatment was performed at 140 ° C. for 15 minutes. When the resistance was measured by the two-terminal method and the conductivity of the film was calculated, the conductivity of the film was 1 (S / cm).
Since the heating temperature was below the glass transition point of the resin, the shape of the film was maintained after heating.

Example 18
A dispersion was prepared by adding 0.4 g of phosphinic acid (30 wt% aqueous solution) to 20 g of dispersion B. 5 g of polycarbonate resin was added to the prepared dispersion and mixed well until uniform. The dispersion medium was dried and removed at 70 ° C. for 10 minutes to produce a film. Thereafter, heat treatment was performed at 140 ° C. for 15 minutes. The conductivity of the heat-treated film was 1 × 10 ⁻⁵ (S / cm). The conductivity was calculated based on the volume resistivity measured by a method according to JIS-K6911. The cross section of the film was cut out with an ultramicrotome and observed with a transmission electron microscope (TEM). As a result, the thickness of the thin film-like particles was 50 nm.

Example 19
Dispersion C was diluted 10-fold with a tetrahydroxyfuran (THF) solution, and the supernatant was removed by centrifugation. Again, it was diluted 10 times with a THF solution, and the supernatant was removed by centrifugation. The resulting dispersion of thin film particles was designated as dispersion D. From the change in weight of the liquid before and after drying, the concentration of the thin film-like particles in the liquid was 1 wt%.
A dispersion was prepared by adding 0.4 g of phosphinic acid (30 wt% aqueous solution) to 20 g of dispersion D. 5 g of polycarbonate resin was added to the prepared dispersion and mixed well until uniform. The dispersion medium was dried and removed at 70 ° C. for 10 minutes to produce a film. Thereafter, heat treatment was performed at 140 ° C. for 15 minutes. The conductivity of the heat-treated film was 1 × 10 ⁻⁹ (S / cm). The conductivity was calculated based on the volume resistivity measured by a method according to JIS-K6911. The cross section of the film was cut out with an ultramicrotome and observed with a transmission electron microscope (TEM). As a result, the thickness of the thin film-like particles was about 200 nm. Although the addition amount of the thin film-like particles in the film was the same as that in Example 18, the film conductivity was worse than that in Example 18 because the thickness of the thin film particles was thick.

Comparative Example 3
A polyvinyl alcohol film in which thin film-like particles were blended was produced in the same manner as in Example 15 except that hydroiodic acid was not added. When the resistance was measured by the two-terminal method and the conductivity of the film was calculated, the conductivity of the film was 10 ⁻⁸ (S / cm) or less.

Comparative Example 4
A polycarbonate resin film containing thin film particles was prepared in the same manner as in Example 17 except that phosphinic acid was not added. Thereafter, heat treatment was performed at 200 ° C. for 60 minutes. The conductivity of the heat-treated film was 0.04 (S / cm). The conductivity was calculated based on the volume resistivity measured by a method according to JIS-K6911. Compared with Example 17, the heating temperature was increased and the treatment time was lengthened, but the conductivity of the obtained film was lower than that of Example 17.
Moreover, since it heated to the temperature exceeding the glass transition point of resin, a deformation | transformation was confirmed to the film.

Claims (12)

Dispersion containing thin film-like particles essentially comprising the following components (a) to (c):
(A) Thin film-like particles having a skeleton made of carbon, obtained by oxidizing graphite and dispersible in a liquid having a relative dielectric constant of 15 or higher;
(B) a dispersion medium for dispersing the thin film particles;
(C) A compound having a reducing action on the thin film-like particles.   The dispersion liquid according to claim 1, wherein the component (c) is a compound having a function of drying and removing the dispersion medium or reducing the thin film-like particles after the dispersion medium is dried and removed.   The dispersion liquid according to claim 1, wherein the thin film-like particles have a thickness of 0.4 nm to 100 nm and a size in a plane direction of 20 nm or more.   The dispersion of claim 1, further comprising a matrix material as component (d).   A method for producing a conductive coating film containing thin film particles, wherein the dispersion liquid according to claim 1 is applied onto a substrate, and then the dispersion medium is dried and removed.   The manufacturing method of Claim 5 whose heating temperature in the process of drying and removing a dispersion medium exists in the range of 30 to 250 degreeC.   The electroconductive coating film manufactured by the method of Claim 5.   An antistatic coating film, an electromagnetic shielding coating film, or a conductive wiring using the conductive coating film according to claim 7.   The manufacturing method of the electroconductive composite material containing thin film-like particle | grains which dries and removes a dispersion medium from the dispersion liquid of Claim 4.   The manufacturing method of Claim 9 whose heating temperature in the process of drying and removing a dispersion medium exists in the range of 30 to 250 degreeC.   A conductive composite material produced by the method according to claim 9.   A conductive sheet, a conductive film, an antistatic sheet, or an antistatic film using the conductive composite material according to claim 11.