JP7580343B2 - Conductive polymer dispersion and method for producing same, coating composition, and conductive laminate and method for producing same - Google Patents

Description

The present invention relates to a conductive polymer dispersion containing a π-conjugated conductive polymer and a method for producing the same, a coating composition, and a conductive laminate and a method for producing the same.

A conductive polymer dispersion containing a conductive complex in which a π-conjugated conductive polymer is doped with a polyanion may be used as a paint or a component thereof for forming a conductive layer. For example, poly(3,4-ethylenedioxythiophene), a π-conjugated conductive polymer, is difficult to disperse in water, but doping it with polystyrene sulfonic acid to form PEDOT-PSS increases its dispersibility in water. Patent Document 1 discloses a technique for improving the hydrophilicity of a conductive complex and improving its reactivity with epoxy compounds by dispersing the conductive complex in water and leaving it for 180 days or more.

JP 2020-31013 A

In the method of Patent Document 1, the conductive complex is reacted with an epoxy compound, and then dissolved in an organic solvent to form a paint, thereby improving the wettability of the conductive complex to a hydrophobic film substrate. On the other hand, when the conductive complex is not hydrophobized by reaction with an epoxy compound, a water-soluble organic solvent such as alcohol is usually added to the conductive polymer dispersion to improve the wettability of the conductive complex to a substrate such as a film. However, the dispersion stability of the conductive complex in the paint to which the water-soluble organic solvent has been added is not necessarily high, and the dispersibility may decrease several tens of hours after the addition of the water-soluble organic solvent. The conductivity of the conductive layer formed by applying a paint with reduced dispersibility also decreases. For this reason, it is required to maintain the dispersibility of the conductive complex in the paint after obtaining a paint by adding a water-soluble organic solvent to the conductive polymer dispersion that has been subjected to a dispersion treatment.

The inventors have studied thoroughly a method for obtaining a conductive polymer dispersion with improved dispersibility of a conductive complex by devising a method for synthesizing a conductive complex so as to obtain a conductive polymer dispersion with low viscosity at the stage of preparing the conductive polymer dispersion before preparing a coating composition (paint), and a method for producing a conductive polymer dispersion in which the decrease in dispersibility of the conductive complex over time is suppressed even after a water-soluble organic solvent is added to form a coating composition, and have completed the present invention.

The present invention provides a conductive polymer dispersion that has excellent dispersion stability even when coexisting with a water-soluble organic solvent, and a method for producing the same. The present invention also provides a coating composition containing the conductive polymer dispersion, and a conductive laminate using the conductive polymer dispersion or the coating composition, and a method for producing the same.

[1] A method for producing a conductive polymer dispersion containing water and a conductive complex containing a polythiophene-based conductive polymer and a polyanion, the method including a polymerization step of polymerizing a thiophene-based compound in an aqueous solvent in the presence of a polyanion, the method using a hydrogen persulfate compound as an oxidizing agent in the polymerization step.
[2] The method for producing a conductive polymer dispersion liquid according to [1], wherein the hydrogen persulfate compound is potassium hydrogen persulfate or a double salt of potassium hydrogen persulfate, potassium hydrogen sulfate, and potassium sulfate.
[3] The method for producing a conductive polymer dispersion according to [1] or [2], wherein in the polymerization step, polymerization is carried out under conditions such that a sum of the solid content weights of the thiophene compound and the polyanion is 2 parts by mass or more when a weight of the aqueous solvent is 100 parts by mass.
[4] The method for producing a conductive polymer dispersion according to any one of [1] to [3], wherein in the polymerization step, an added amount of the hydrogen persulfate compound is 10 parts by mass or more and 100 parts by mass or less when a weight of the thiophene-based compound is 10 parts by mass.
[5] The method for producing a conductive polymer dispersion according to any one of [1] to [4], wherein the polythiophene-based conductive polymer is poly(3,4-ethylenedioxythiophene) or the polyanion is polystyrenesulfonic acid.
[6] The method for producing the conductive polymer dispersion according to any one of [1] to [5], further comprising an ion exchange step of contacting the conductive polymer dispersion obtained in the polymerization step with at least one of a cation exchange resin and an anion exchange resin.
[7] A conductive polymer dispersion containing a conductive complex containing a polythiophene-based conductive polymer and a polyanion, and water, wherein when a content of the conductive complex is 1 mass % relative to a total mass of the conductive polymer dispersion, the conductive polymer dispersion has a viscosity of 20 mPa s or less at 23° C.
[8] A coating composition comprising the conductive polymer dispersion according to [7] and a water-soluble organic solvent.
[9] A method for producing a conductive laminate, comprising applying the conductive polymer dispersion according to [7] or the coating composition according to [8] to at least a part of a surface of a substrate.
[10] A conductive laminate comprising a substrate and a conductive layer formed on at least a part of the surface of the substrate, the conductive layer being a cured layer of the conductive polymer dispersion according to [7] or the coating composition according to [8].

According to the method for producing a conductive polymer dispersion of the present invention, a conductive polymer dispersion having a low viscosity can be produced without carrying out a high-pressure dispersion treatment using a high-pressure homogenizer or the like.
The conductive polymer dispersion of the present invention exhibits a significantly lower viscosity than conventional products, and also exhibits excellent storage stability when mixed with a water-soluble organic solvent to form a coating composition.
In the conductive laminate of the present invention, the conductive layer has excellent appearance.
According to the method for producing a conductive laminate of the present invention, the above-mentioned conductive laminate can be easily produced.

This invention is believed to contribute to SDG Goal 12, "Responsible Consumption and Production."

In this specification and claims, the lower and upper limits of the numerical ranges indicated with "~" are considered to be included in the numerical range.

<<Conductive polymer dispersion>>
A first aspect of the present invention is a conductive polymer dispersion comprising a conductive complex containing a π-conjugated conductive polymer and a polyanion, and water, and a content of the conductive complex relative to the total mass of the conductive polymer dispersion. The conductive polymer dispersion has a viscosity of 20 mPa·s or less at 23° C. when the content of the conductive polymer in the conductive polymer dispersion is 1% by mass.

[Conductive composite]
The conductive complex contained in the conductive polymer dispersion of this embodiment contains a polythiophene-based conductive polymer and a polyanion. The polyanion in the conductive complex is doped into the polythiophene-based conductive polymer to form a conductive complex having electrical conductivity.

(Polythiophene-based conductive polymer)
The main chain of the polythiophene-based conductive polymer constitutes a π-conjugated system by polymerization of a thiophene-based compound.
Examples of polythiophene-based conductive polymers include polythiophene, poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly(3-chlorothiophene), and poly(3-iodothiophene). thiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), oxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxythiophene), poly(3,4-dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-dihexyloxythiophene), poly(3,4-diheptyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-didecyloxythiophene), poly(3,4-di dodecyloxythiophene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butylenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl-4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), and poly(3-methyl-4-carboxybutylthiophene).
Among these polythiophene-based conductive polymers, poly(3,4-ethylenedioxythiophene) is particularly preferred because of its excellent conductivity, transparency and heat resistance.
The conductive composite may contain one type of polythiophene-based conductive polymer, or two or more types of polythiophene-based conductive polymers.

(Polyanion)
A polyanion is a polymer having two or more monomer units each having an anionic group in the molecule. The anionic group of the polyanion functions as a dopant for a polythiophene-based conductive polymer, improving the conductivity of the polythiophene-based conductive polymer.
The anion group of the polyanion is preferably a sulfo group or a carboxy group.
Specific examples of such polyanions include polymers having a sulfo group, such as polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyacrylic acid esters having a sulfo group, polymethacrylic acid esters having a sulfo group (e.g., poly(4-sulfobutyl methacrylate, polysulfoethyl methacrylate, polymethacryloyloxybenzenesulfonic acid), poly(2-acrylamido-2-methylpropanesulfonic acid), and polyisoprene sulfonic acid; and polymers having a carboxy group, such as polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanecarboxylic acid), and polyisoprene carboxylic acid. The polyanion may be a homopolymer in which a single monomer is polymerized, or a copolymer in which two or more monomers are polymerized.
Among these polyanions, polymers having a sulfo group are preferred, and polystyrene sulfonic acid is more preferred, since they can provide higher electrical conductivity.
The polyanions may be used alone or in combination of two or more kinds.

The weight average molecular weight Mw of the polyanion is preferably from 20,000 to 1,000,000, and more preferably from 50,000 to 800,000.
When the weight average molecular weight Mw is within the above preferred range, the dispersion stability of the conductive composite in the conductive polymer dispersion of this embodiment and in the coating material of the second embodiment described below is further improved.
The weight average molecular weight Mw is an average molecular weight based on mass measured by gel filtration chromatography and calculated as pullulan.

In the polyanion doped into the polythiophene conductive polymer, some of the anion groups are not doped into the polythiophene conductive polymer and have excess anion groups that are not involved in the doping. Since these excess anion groups are hydrophilic groups, the conductive composite has high water dispersibility and low organic solvent dispersibility.
When the number of all anionic groups in the polyanion is taken as 100 mol %, the excess anionic groups are preferably from 30 mol % to 90 mol %, more preferably from 45 mol % to 75 mol %.

The content of polyanion in the conductive complex is preferably in the range of 1 part by mass to 1000 parts by mass to 100 parts by mass of polythiophene-based conductive polymer, more preferably 10 parts by mass to 700 parts by mass, and even more preferably 100 parts by mass to 500 parts by mass. If the content of polyanion is equal to or greater than the lower limit, the doping effect on the polythiophene-based conductive polymer tends to be stronger, and the conductivity becomes higher. On the other hand, if the content of polyanion is equal to or less than the upper limit, the polythiophene-based conductive polymer can be sufficiently contained, so that sufficient conductivity can be ensured.

The content of the conductive complex relative to the total mass of the conductive polymer dispersion of this embodiment is preferably 0.01 mass % or more and 5.0 mass % or less, more preferably 1.0 mass % or more and 4.0 mass % or less, and even more preferably 2.0 mass % or more and 3.0 mass % or less.
When the content is at least as high as the lower limit of the above range, the conductivity of the conductive layer formed by applying the conductive polymer dispersion can be further improved.
When it is equal to or less than the upper limit of the above range, the dispersibility of the conductive complex in the conductive polymer dispersion can be improved, and a uniform conductive layer can be formed.

The viscosity of the conductive polymer dispersion of this embodiment at 23° C. is 20 mPa·s or less, preferably 15 mPa·s or less, more preferably 10 mPa·s or less, and even more preferably 5 mPa·s or less, when the concentration of the conductive complex relative to the total mass of the conductive polymer dispersion is adjusted to 1.0 mass %. The lower limit of the viscosity is not particularly limited, and a guideline is 0.1 mPa·s or more.
Within the above preferred range, it is easy to bring the conductive polymer dispersion into contact with an ion exchange resin, and it is also easy to separate the ion exchange resin after contact. Furthermore, the above low viscosity correlates with high dispersibility of the conductive complex in the conductive polymer dispersion. The conductive polymer dispersion having the above low viscosity does not require high-pressure dispersion treatment using a high-pressure homogenizer or the like, and the conductive layer formed by coating the substrate has excellent conductivity and transparency.
In measuring the viscosity, the conductive polymer dispersion preferably contains only ion-exchanged water as a dispersion medium, and preferably does not contain any additives other than the conductive complex.
The viscosity is measured at 23° C. using a tuning fork vibration viscometer in accordance with JIS Z8803:2011 (viscosity measurement method using a vibration viscometer).

<Coating composition (paint)>
A second aspect of the present invention is a coating composition comprising the conductive polymer dispersion of the first aspect and a water-soluble organic solvent. In the coating composition of this aspect, the conductive complex is in a dispersed state.

The coating composition of this embodiment contains water and a water-soluble organic solvent. The mixture of water and a water-soluble organic solvent is sometimes called an aqueous dispersion medium.

The water-soluble organic solvent is an organic solvent that dissolves in 100 g of water at 20° C. in an amount of 1 g or more.
Examples of the water-soluble organic solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, nitrogen atom-containing solvents, and ester-based solvents.
Examples of alcohol-based solvents include methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 2-methyl-2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, allyl alcohol, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and ethylene glycol monomethyl ether.
Examples of the ether solvent include diethyl ether, dimethyl ether, propylene glycol dialkyl ether, and diethylene glycol diethyl ether.
Examples of the ketone solvent include diethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl amyl ketone, diisopropyl ketone, methyl ethyl ketone, acetone, and diacetone alcohol.
Examples of the nitrogen atom-containing solvent include N-methylpyrrolidone, dimethylacetamide, and dimethylformamide.
The water-soluble organic solvent may be contained alone or in combination of two or more kinds.
In order to improve the applicability of the coating composition of this embodiment to a substrate, the water-soluble organic solvent is preferably an alcohol-based solvent or a ketone-based solvent, and more preferably an alcohol-based solvent.

The content of the water-soluble organic solvent relative to the total mass of the aqueous dispersion medium is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. The content of the water-soluble organic solvent is preferably 90% by mass or less.
When the content is within the above preferred range, the wettability to the substrate can be improved while suppressing deterioration over time of the dispersion stability of the conductive composite in the coating composition of this embodiment.

The water content relative to the total mass of the aqueous dispersion medium is preferably 70 mass% or less, more preferably 60 mass% or less, and even more preferably 50 mass% or less. From the viewpoint of improving the dispersibility of the conductive composite, the water content is preferably 10 mass% or more.
When the content is within the above preferred range, the wettability to the substrate can be improved while suppressing deterioration over time of the dispersion stability of the conductive composite in the coating composition of this embodiment.

The content of the conductive complex relative to the total mass of the coating composition of this embodiment is, for example, preferably 0.01 mass % or more and 4 mass % or less, more preferably 0.1 mass % or more and 3 mass % or less, even more preferably 0.2 mass % or more and 2 mass % or less, and particularly preferably 0.3 mass % or more and 1 mass % or less.
When the content is within the above preferred range, a decrease in the dispersion stability of the conductive composite in the coating composition of this embodiment can be suppressed, and a conductive layer with good conductivity can be formed by applying the composition to a substrate.

<Binder Components>
The coating composition of this embodiment may contain a binder component. The binder component is a resin other than the polythiophene-based conductive polymer and the polyanion or a precursor thereof, and is a thermoplastic resin, or a curable monomer or oligomer that is cured when the conductive layer is formed. The thermoplastic resin becomes the binder resin as it is, and the curable monomer or oligomer becomes the resin formed by curing becomes the binder resin.
The binder component may be one type only, or two or more types may be included.

Specific examples of binder resins derived from binder components include acrylic resins (acrylic compounds), polyester resins, polyurethane resins, polyimide resins, polyether resins, melamine resins, and silicones.
The binder resin contained in the coating composition of this embodiment is preferably a water-dispersible resin, more preferably a water-dispersible emulsion resin. The water-dispersible resin is an emulsion resin or a water-soluble resin.

Specific examples of water-dispersible emulsion resins include acrylic resins (acrylic compounds), polyester resins, polyurethane resins, polyimide resins, melamine resins, etc., which are emulsionized with an emulsifier. Among these, polyester emulsions are preferred because they increase the strength of the coating film formed by applying the coating composition of this embodiment to a substrate. In particular, when applying the composition to a polyester film substrate, polyester emulsions are preferred because they increase the adhesion of the coating film to the substrate.

Specific examples of water-soluble resins include acrylic resins (acrylic compounds), polyester resins, polyurethane resins, polyimide resins, and melamine resins, which have acid groups such as carboxy groups and sulfo groups or their salts. Here, the water-soluble resin is preferably one that dissolves in an amount of 1 g or more, preferably 5 g or more, and more preferably 10 g or more in 100 g of distilled water at 25°C.

The acid groups, such as carboxyl groups and sulfo groups, contained in the water-dispersible resin may form salts with cations, such as sodium ions and potassium ions.

The curable monomer or oligomer may be a thermosetting monomer or oligomer, or a photocurable monomer or oligomer. Here, the oligomer refers to a polymer having a mass average molecular weight of less than 10,000. Note that a polymer having a mass average molecular weight of more than 10,000 does not have curability.
Examples of the curable monomer include an acrylic monomer (acrylic compound), an epoxy monomer, an organosiloxane, etc. Examples of the curable oligomer include an acrylic oligomer (acrylic compound), an epoxy oligomer, a silicone oligomer (curable silicone), etc.
When an acrylic monomer or an acrylic oligomer is used as the binder component, it can be easily cured by heating or light irradiation. When an organosiloxane or a silicone oligomer is used as the binder component, it is possible to impart releasability (non-adhesiveness) to the conductive layer.

When a curable monomer or oligomer is included, it is preferable to further include a curing catalyst. For example, when a thermosetting monomer or oligomer is included, it is preferable to include a thermal polymerization initiator that generates radicals by heating, and when a photocurable monomer or oligomer is included, it is preferable to include a photopolymerization initiator that generates radicals by light irradiation. In addition, when an organosiloxane or silicone oligomer is included, it is preferable to include a platinum catalyst for curing.

The content of the binder component in the coating composition of this embodiment is preferably 100 parts by mass or more and 20,000 parts by mass or less, and more preferably 100 parts by mass or more and 5,000 parts by mass or less, relative to 100 parts by mass of the conductive composite.
When the content is equal to or greater than the lower limit of the above range, the film-forming properties and film strength can be improved when the coating composition of this embodiment is applied to a substrate.
When the content is equal to or less than the upper limit of the above range, a decrease in electrical conductivity due to a decrease in the content ratio of the conductive complex can be suppressed.

(Other additives)
The coating composition and the conductive polymer dispersion may contain other known additives.
Examples of the additives that can be used include surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbing agents.
The surfactant may be a nonionic, anionic or cationic surfactant, with the nonionic surfactant being preferred from the standpoint of storage stability. A polymer surfactant such as polyvinylpyrrolidone may also be added.
Examples of the inorganic conductive agent include metal ions, conductive carbon, etc. Metal ions can be generated by dissolving a metal salt in water.
The antifoaming agent includes silicone resin, polydimethylsiloxane, silicone oil, and the like.
The coupling agent may be a silane coupling agent having a vinyl group or an amino group.
Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, oxanilide-based ultraviolet absorbers, hindered amine-based ultraviolet absorbers, and benzoate-based ultraviolet absorbers.
When the above-mentioned additive is contained, the content ratio is appropriately determined depending on the type of additive, but can be, for example, in the range of 0.001 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the conductive composite.

The coating composition of this embodiment can be produced by adding water, a water-soluble organic solvent, a binder component, other additives, etc. to the conductive polymer dispersion of the first embodiment as appropriate, and mixing them in a conventional manner.

<Method for producing conductive polymer dispersion>
A third aspect of the present invention is a method for producing a conductive polymer dispersion containing water and a conductive complex containing a polythiophene-based conductive polymer and a polyanion, the method including a polymerization step of polymerizing a thiophene-based compound in an aqueous solvent in the presence of a polyanion, and a hydrogen persulfate compound is used as an oxidizing agent in the polymerization step.

An aqueous solution (reaction solution) containing a thiophene-based compound as a monomer and a polyanion in an arbitrary content ratio is prepared, and the thiophene-based compound is polymerized by the action of a hydrogen persulfate compound to form a polythiophene-based conductive polymer. In the reaction solution, the polythiophene-based conductive polymer is naturally doped with the polyanion, and a conductive complex consisting of the polythiophene-based conductive polymer and the polyanion is formed. The content ratio (by mass) of the polythiophene-based conductive polymer:polyanion contained in the formed conductive complex is the same as the content ratio of the thiophene-based compound contained in the reaction solution immediately before the start of polymerization to the content of the polyanion. In other words, the content ratio of the monomer and polyanion blended in the reaction solution is reflected in the content ratio of the polythiophene-based conductive polymer and the polyanion in the formed conductive complex.

The content ratio of the thiophene compound to the polyanion in the reaction solution immediately before the start of polymerization is preferably from (1:2) to (1:5) on a mass basis, more preferably from (1:2) to (1:4.5), and even more preferably from (1:3) to (1:4).
When the content is within the above range, the conductive polymer dispersion liquid of the first embodiment described above can be easily formed.

In the polymerization step, it is desirable to carry out the polymerization under conditions in which the sum of the solid content weights of the thiophene compound and the polyanion is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 3.5 parts by mass or more, when the weight of the aqueous solvent is 100 parts by mass. An upper limit value of the sum is, for example, 7 parts by mass.
When polymerization is carried out within the above preferred range, there is an advantage that the resulting conductive polymer has good electrical conductivity.

The hydrogen persulfate compound which is the oxidizing agent is, for example, a compound having the general formula: MHSO ₅ (M represents any alkali metal such as Na or K), and may be a double salt.
The hydrogen persulfate compound is preferably potassium hydrogen persulfate (also known as potassium monopersulfate or potassium peroxymonosulfate) or a double salt of potassium hydrogen persulfate, potassium hydrogen _sulfate , and _{potassium sulfate} (chemical formula: _{2KHSO5.KHSO4.K2SO4} ). The above suitable compounds make it easier to form a low-viscosity, highly dispersed conductive polymer dispersion.

In the reaction liquid, when the weight of the thiophene compound is 10 parts by mass, the total amount of the hydrogen persulfate compound added is preferably 10 parts by mass or more and 100 parts by mass or less, more preferably 20 parts by mass or more and 80 parts by mass or less, and even more preferably 30 parts by mass or more and 70 parts by mass or less. When it is in the above preferred range, it is easier to form a conductive polymer dispersion liquid with low viscosity and high dispersion.

A catalyst may be added to the reaction solution. The catalyst is not particularly limited as long as it promotes the polymerization of the thiophene-based compound, and examples of the catalyst include transition metal compounds such as ferric chloride, ferric sulfate, ferric nitrate, and cupric chloride. Among them, it is preferable to use a catalyst containing iron, since the polymerization proceeds stably at room temperature.

The content of the catalyst added to the reaction liquid is, for example, preferably 0.001% by mass or more and 2% by mass or less, more preferably 0.005% by mass or more and 1% by mass or less, and even more preferably 0.01% by mass or more and 0.5% by mass or less, relative to the total mass of the reaction liquid.
When the amount is within the above range, the polymerization reaction can proceed stably, so that the formation of a complex with the polyanion present in the reaction system proceeds stably, and a conductive complex with good conductivity can be easily obtained.

The explanation of the polyanion contained in the reaction solution is the same as that of the polyanion in the first embodiment, so duplicate explanations will be omitted.

Specific examples of the thiophene-based compound contained in the reaction solution include compounds that form the monomer units of the polythiophene-based conductive polymer of the first embodiment.

The conductive polymer dispersion of the first embodiment is obtained by the above method. Since the conductive composite formed after the polymerization reaction has excellent dispersibility, there is no need for high-pressure dispersion processing using a high-pressure homogenizer or a high-output dispersion device to reduce the diameter of fine particles.

Before using the conductive polymer dispersion, the catalyst and oxidizing agent added to the reaction liquid may be removed. Examples of the removal method include a method in which the conductive polymer dispersion is brought into contact with an ion exchange resin to adsorb the catalyst and oxidizing agent to the ion exchange resin, and a method in which the conductive polymer dispersion is ultrafiltered to remove the catalyst and oxidizing agent while replacing the dispersion medium. Of these, the method using an ion exchange resin is preferred because it is simple. It is preferred to use a cation exchange resin and an anion exchange resin in combination as the ion exchange resin.

<Conductive laminate>
A third aspect of the present invention is a conductive laminate comprising a substrate and a conductive layer formed on at least a partial surface of the substrate, the conductive layer being a cured layer of the conductive polymer dispersion of the first aspect or the coating composition of the second aspect.

[Conductive layer]
The conductive layer may be formed over the entire surface of any surface of the substrate, or over a portion of the entire surface. In the conductive film, it is preferable that a conductive layer of substantially uniform thickness is formed over substantially the entire surface of one surface or the other surface of the film substrate. When a conductive layer is formed only over a portion of the surface of the substrate, the conductive layer may be, for example, a fine conductive pattern such as a circuit or an electrode, or the conductive layer may be provided on the same surface and the conductive layer may be not provided on the same surface and may be roughly divided.

The average thickness of the conductive layer is, for example, preferably from 10 nm to 100 μm, more preferably from 20 nm to 50 μm, and even more preferably from 30 nm to 30 μm.
When the average thickness of the conductive layer is equal to or greater than the lower limit, high conductivity can be exhibited, and when the average thickness is equal to or less than the upper limit, the adhesion of the conductive layer to the substrate is further improved.

[Substrate]
The substrate may be a substrate made of an insulating material or a substrate made of a conductive material. The shape of the substrate is not particularly limited, and examples thereof include a shape mainly having a flat surface, such as a film or a substrate.
Examples of insulating materials include glass, synthetic resin, and ceramics.
The conductive material may be a metal, a conductive metal oxide, carbon, or the like.

(Film substrate)
When a film substrate is used as the substrate, the conductive laminate becomes a conductive film.
The film substrate may be, for example, a plastic film made of a synthetic resin, such as ethylene-methyl methacrylate copolymer resin, ethylene-vinyl acetate copolymer resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacrylate, polycarbonate, polyvinylidene fluoride, polyarylate, styrene-based elastomer, polyester-based elastomer, polyethersulfone, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyimide, cellulose triacetate, and cellulose acetate propionate.
From the viewpoint of improving the adhesion between the film substrate and the conductive layer, the synthetic resin for the film substrate is preferably a polyester resin, and among these, polyethylene terephthalate is preferable.

The synthetic resin for the film substrate may be either amorphous or crystalline.
The film substrate may be either unstretched or stretched.
The film substrate may be subjected to a surface treatment such as a corona discharge treatment, a plasma treatment, or a flame treatment in order to further improve the adhesion of the conductive layer.

The average thickness of the film substrate is preferably 5 μm to 500 μm, more preferably 20 μm to 200 μm. If the average thickness of the film substrate is equal to or more than the lower limit, the film is less likely to break, and if the average thickness is equal to or less than the upper limit, the film can have sufficient flexibility.
The average thickness of the film substrate is determined by measuring the thickness at 10 randomly selected points and averaging the measured values.

(Glass substrate)
Examples of the glass substrate include an alkali-free glass substrate, a soda-lime glass substrate, a borosilicate glass substrate, and a quartz glass substrate. If the substrate contains an alkali component, the conductivity of the conductive layer tends to decrease, so among the glass substrates, an alkali-free glass is preferred. Here, the alkali-free glass refers to a glass composition having an alkali component content of 0.1 mass% or less relative to the total mass of the glass composition.

The average thickness of the glass substrate is preferably from 100 μm to 3000 μm, more preferably from 100 μm to 1000 μm. If the average thickness of the glass substrate is equal to or more than the lower limit, the glass substrate is less likely to break, and if the average thickness is equal to or less than the upper limit, the conductive laminate can be made thinner.
The average thickness of the glass substrate is determined by measuring the thickness at 10 randomly selected points and averaging the measured values.

<Method for manufacturing conductive laminate>
A fourth aspect of the present invention is a method for producing a conductive laminate, the method comprising applying the conductive polymer dispersion of the first aspect or the coating composition of the second aspect to at least a part of the surface of a substrate to form a conductive layer. The conductive laminate of the third aspect can be produced by the production method of this aspect.

Methods for applying the conductive polymer dispersion or coating composition to any surface of a substrate include, for example, methods using a coater such as a gravure coater, roll coater, curtain flow coater, spin coater, bar coater, reverse coater, kiss coater, fountain coater, rod coater, air doctor coater, knife coater, blade coater, cast coater, or screen coater; methods using a sprayer such as an air spray, airless spray, or rotor dampening; and immersion methods such as dipping.

The amount of the conductive polymer dispersion or coating composition applied to the substrate is not particularly limited, but in consideration of uniform and even application, conductivity, and film strength, the amount is preferably in the range of 0.01 g/ ^m2 or more and 10.0 g/m2 or ^less in terms of solid content.

A coating film made of a conductive polymer dispersion or a coating composition applied onto a substrate is dried to remove at least a portion of the dispersion medium, and then cured to form a conductive layer.
Methods for drying the coating film include heat drying, vacuum drying, etc. Examples of heat drying that can be used include hot air heating and infrared heating.
When heat drying is applied, the heating temperature is appropriately set depending on the dispersion medium used, but is usually within the range of 50° C. to 200° C. Here, the heating temperature is the set temperature of the drying device. A suitable drying time within the above heating temperature range is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 15 minutes.

[Preparation of polyanions]
As a raw material, an aqueous solution (concentration: 25-30%) of poly(sodium 4-styrenesulfonate) having a weight average molecular weight of 70,000 to 200,000 manufactured by Sigma-Aldrich Co., or a powder having a weight average molecular weight of 800,000 was used.
First, ion-exchanged water was added to a powder or aqueous solution of poly(sodium 4-styrenesulfonate) to adjust the solid concentration to 15 wt % to a uniform aqueous solution, and a cation-exchange resin was added until the pH became less than 1. Thereafter, the cation-exchange resin was filtered off using a stainless steel mesh filter, and the solid concentration was adjusted to 10 wt % with ion-exchanged water to obtain an aqueous polystyrenesulfonic acid solution (PSS aqueous solution).
The weight-average molecular weight of PSS was measured using a high performance liquid gel filtration chromatography system with pullulan as a standard substance.

[Preparation of thiophene-based compounds]
Commercially available 3,4-ethylenedioxythiophene (Tokyo Chemical Industry Co., Ltd.) was purchased and purified by vacuum distillation before use in the reaction.

[Example 1]
360g of ion-exchanged water for dilution and 1.0g of ferric sulfate (Tokyo Chemical Industry Co., Ltd.) were added to 137g of an aqueous solution of poly(4-styrenesulfonic acid) with a solid content concentration of 10wt% and a weight average molecular weight of 200,000, and the solution was bubbled with nitrogen at a flow rate of 1L per minute for 10 minutes and stirred under a nitrogen atmosphere and maintained at 25°C. 3.5g of 3,4-ethylenedioxythiophene purified by distillation was added to this aqueous solution. 15.3g of oxone (triple salt of potassium hydrogen persulfate, potassium sulfate, and potassium hydrogen sulfate, chemical formula 2KHSO ₅ ·KHSO ₄ ·K ₂ SO ₄ , Fujifilm Wako Pure Chemical Industries, Ltd.), which is a persulfate compound, was then added as an oxidizing agent, and the mixture was stirred and reacted at 25°C for 30 minutes under a nitrogen atmosphere to synthesize PEDOT-PSS. In this reaction, the sum of the solid weights of the thiophene compound and the polyanion was 3.6 parts by mass when the weight of the water solvent was 100 parts by mass.
To this reaction solution, 60 g of a cation exchange resin and 60 g of an anion exchange resin were added, stirred for 5 minutes, and then allowed to stand for 2 hours. The ion exchange resin was filtered off using a stainless steel mesh filter to obtain a conductive polymer dispersion containing an aqueous dispersion medium and PEDOT-PSS with a solid content concentration of 2.7 wt %.

[Example 2]
A conductive polymer dispersion was obtained in the same manner as in Example 1, except that 137 g of an aqueous poly(4-styrenesulfonic acid) solution having a solid content concentration of 10 wt% and a weight average molecular weight of 800,000 was used and the amount of ion-exchanged water for dilution was changed to 565 g. When the weight of the water solvent during the reaction was taken as 100 parts by mass, the sum of the solid content weights of the thiophene compound and polyanion was 2.5 parts by mass, and the solid content concentration of the conductive polymer dispersion was 2.1 wt%.

[Example 3]
A conductive polymer dispersion was obtained in the same manner as in Example 1, except that 81 g of an aqueous poly(4-styrenesulfonic acid) solution having a solid content concentration of 10 wt% and a weight average molecular weight of 200,000 was used, the amount of ion-exchanged water for dilution was changed to 159 g, and the reaction temperature was changed to 10° C. When the weight of the aqueous solvent during the reaction was taken as 100 parts by mass, the sum of the solid content weights of the thiophene compound and polyanion was 5.0 parts by mass, and the solid content concentration of the conductive polymer dispersion was 3.6 wt%.

[Example 4]
A conductive polymer dispersion was obtained in the same manner as in Example 1, except that 81 g of an aqueous poly(4-styrenesulfonic acid) solution having a solid content concentration of 10 wt% and a weight average molecular weight of 70,000 was used, the amount of ion-exchanged water for dilution was changed to 307 g, and 7.7 g of oxone and 3.0 g of sodium persulfate were used as the oxidizing agents. When the weight of the aqueous solvent during the reaction was taken as 100 parts by mass, the sum of the solid content weights of the thiophene compound and polyanion was 3.1 parts by mass, and the solid content concentration of the conductive polymer dispersion was 2.2 wt%.

[Example 5]
A conductive polymer dispersion was obtained in the same manner as in Example 1, except that the amount of ion-exchanged water for dilution was changed to 1,440 g, the reaction time was changed to 90 minutes, and a step of vacuum concentration was added after filtering out the ion-exchange resin. When the weight of the water solvent during the reaction was taken as 100 parts by mass, the sum of the solid content weights of the thiophene compound and the polyanion was 1.1 parts by mass, and the solid content concentration of the conductive polymer dispersion was 2.0 wt%.

[Comparative Example 1]
Except for using 3.0 g of sodium persulfate as the oxidizing agent, a conductive polymer dispersion was obtained in the same manner as in Example 1. When the weight of the aqueous solvent during the reaction was taken as 100 parts by mass, the sum of the solid content weights of the thiophene compound and the polyanion was 3.6 parts by mass, and the solid content concentration of the conductive polymer dispersion was 2.6 wt %.

[Comparative Example 2]
The conductive polymer dispersion obtained in Comparative Example 1 was subjected to a dispersion treatment using a high-pressure wet-type atomizer to obtain a conductive polymer dispersion having a reduced viscosity.

[Comparative Example 3]
The reaction was carried out in the same manner as in Example 2, except that 3.0 g of sodium persulfate was used as the oxidizing agent, but the reaction solution became highly viscous and gelled. The ion exchange step could not be carried out, and a conductive polymer dispersion could not be obtained.

<Evaluation of Viscosity>
The viscosities at 23°C of the conductive polymer dispersions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were measured using a vibration type viscometer. Furthermore, the viscosities were also measured in the same manner when ion-exchanged water was added to adjust the solid content concentration to 1 wt%. The results are shown in Table 1.
The above viscosity is a value measured at 23° C. using a tuning fork vibration viscometer in accordance with JIS Z8803:2011 (viscosity measurement method using a vibration viscometer).

<Evaluation of Conductivity>
The conductive polymer dispersions obtained in Examples 1 to 5 and Comparative Examples 1 to 2 were adjusted with ion-exchanged water so that the solid content concentration was 1 wt%. 0.01 g of an acetylene-based surfactant (Surfynol 420, manufactured by Nissin Chemical Industry Co., Ltd.) and 50 g of methanol were added to 50 g of this conductive polymer dispersion and thoroughly mixed to obtain a coating composition (paint). This paint was applied to a polyethylene terephthalate film (Lumirror T60, manufactured by Toray Industries, Inc.) using a bar coater with a wet film thickness of 16 μm, and heated and dried at a drying temperature of 100° C. for 1 minute to obtain a conductive film. The surface resistance value of the obtained conductive film was measured using a resistivity meter (Hiresta, manufactured by Nitto Seiko Analytech Co., Ltd.) under the condition of an applied voltage of 10 V. In addition, the appearance of the conductive film was visually evaluated. The results are shown in Table 2.

<Evaluation of Dispersion Stability>
The conductive polymer dispersions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were each adjusted with ion-exchanged water so that the solid content concentration was 1 wt %. 50 g of this conductive polymer dispersion was added to and mixed with 50 g of 2-propanol to obtain a coating composition (paint). When the state of the paint was observed after storage at 40°C for 10 days, the paints of Examples 1 to 5 showed no change even after storage and had high dispersion stability. On the other hand, the paints of Comparative Examples 1 and 2 solidified into a gel and had low dispersion stability.

Claims (10)

A method for producing a conductive polymer dispersion containing a conductive complex including a polythiophene-based conductive polymer and a polyanion, and water, the method comprising the steps of: polymerizing a thiophene-based compound in an aqueous solvent in the presence of a polyanion;
The method for producing a conductive polymer dispersion, wherein a hydrogen persulfate compound is used as an oxidizing agent in the polymerization step. The method for producing a conductive polymer dispersion according to claim 1, wherein the hydrogen persulfate compound is potassium hydrogen persulfate or a double salt consisting of potassium hydrogen persulfate, potassium hydrogen sulfate, and potassium sulfate. The method for producing a conductive polymer dispersion according to claim 1 or 2, wherein in the polymerization step, polymerization is carried out under conditions such that the sum of the solid weights of the thiophene compound and the polyanion is 2 parts by mass or more when the weight of the aqueous solvent is 100 parts by mass. The method for producing a conductive polymer dispersion according to any one of claims 1 to 3, wherein in the polymerization step, the amount of the hydrogen persulfate compound added is 10 parts by mass or more and 100 parts by mass or less when the weight of the thiophene compound is 10 parts by mass. The method for producing a conductive polymer dispersion according to any one of claims 1 to 4, wherein the polythiophene-based conductive polymer is poly(3,4-ethylenedioxythiophene) or the polyanion is polystyrenesulfonic acid. The method for producing the conductive polymer dispersion according to any one of claims 1 to 5, further comprising an ion exchange step in which the conductive polymer dispersion obtained in the polymerization step is brought into contact with at least one of a cation exchange resin and an anion exchange resin. A conductive polymer dispersion liquid containing a conductive complex containing a polythiophene-based conductive polymer and a polyanion, and water,
A conductive polymer dispersion having a viscosity of 20 mPa·s or less at 23° C. when the content of the conductive complex with respect to the total mass of the conductive polymer dispersion is 1 mass %, when a dispersion medium of the conductive polymer dispersion is only ion-exchanged water, and when the conductive polymer dispersion does not contain any additives other than the conductive complex .
(However, this does not include the case where the conductive complex contains a dopant polymer consisting of a copolymer containing a repeating unit a represented by the following general formula (1) and one or more repeating units b selected from the repeating units represented by the following general formulas (2-1) to (2-7).)

[In the formula, R ¹ is a hydrogen atom or a methyl group, Z is a phenylene group, a naphthylene group, or an ester group, if Z is a phenylene group or a naphthylene group, R ² is a linear, branched or cyclic hydrocarbon group having 1 to 12 carbon atoms which may have either a single bond, an ester group, or an ether group, or both, and if Z is an ester group, R ² is a single bond, or a linear, branched or cyclic hydrocarbon group having 1 to 12 carbon atoms which may have either an ether group, or both, and m is 1 to 3. R ³ , R ⁵ , R ⁷ , R ¹⁰ , R ¹² , R ¹³ and R ¹⁵ are each independently a hydrogen atom or a methyl group, and R ⁴ , R ⁶ , R ⁸ , R ¹¹ and R ¹⁴ are each independently a straight-chain, branched or cyclic hydrocarbon group having 1 to 12 carbon atoms which may have either a single bond, an ether group or an ester group or both. R ⁹ is a straight-chain or branched alkylene group having 1 to 4 carbon atoms, and one or two of the hydrogen atoms in R ⁹ may be substituted with a fluorine atom. _{X 1} , X ₂ , X ₃ , X ₄ , X ₆ and X ₇ are each independently a single bond, a phenylene group, a naphthylene group, an ether group, an ester group or an amide group, and X ₅ is a single bond, an ether group or an ester group. Y represents an ether group, an ester group, an amino group, or an amide group, and the amino group and the amide group may contain a hydrogen atom, or a linear, branched, or cyclic hydrocarbon group having 1 to 12 carbon atoms which may contain a heteroatom. Rf ₁ is a fluorine atom or a trifluoromethyl group, Rf ₂ and Rf ₃ are a linear or branched alkyl group having 1 to 4 carbon atoms and having at least one fluorine atom, or a phenyl group substituted with a fluorine atom or a trifluoromethyl group, and n is an integer from 1 to 4. a, b1, b2, b3, b4, b5, b6, and b7 are 0<a<1.0, 0≦b1<1.0, 0≦b2<1.0, 0≦b3<1.0, 0≦b4<1.0, 0≦b5<1.0, 0≦b6<1.0, 0≦b7<1.0, and 0<b1+b2+b3+b4+b5+b6+b7<1.0. A coating composition comprising the conductive polymer dispersion according to claim 7 and a water-soluble organic solvent. A method for producing a conductive laminate, comprising applying the conductive polymer dispersion according to claim 7 or the coating composition according to claim 8 to at least a portion of the surface of a substrate. A conductive laminate comprising a substrate and a conductive layer formed on at least a portion of the surface of the substrate, the conductive polymer dispersion according to claim 7 or a cured layer of the coating composition according to claim 8.