JPWO2019013276A1 - Conductive material - Google Patents

Abstract

An object of the present invention is to provide a conductive material that can be formed into a film by a simple method and has excellent conductivity. SOLUTION: The sulfated cellulose crystal shown in Chemical formula 1 obtained from fibrous cellulose having a fiber width in the range of 3 nm to 1500 nm is used as a dopant to complex a polythiophene having a repeating unit represented by Chemical formula 3. The electroconductive material thus obtained has excellent film-forming properties and electroconductivity, and can be suitably used as the electroconductive material. [Selection diagram] Figure 1

Description

  The present invention relates to a conductive material having excellent conductivity, and a method for manufacturing the same, and particularly to a conductive material having excellent coating properties and a method for manufacturing the conductive material.

  At present, materials such as polythiophene, polyaniline, and polypyrrole are known as conductive polymers. Conductive polymers are used as conductive materials for antistatic films, capacitors, transistors and the like because of their transparency and high conductivity. In addition, since conductive polymers have excellent processability, their application fields are diverse.

  It is known that a polythiophene-based conductive polymer has the highest conductivity among the conductive polymers and has excellent light transmittance when used as a thin film, and is therefore an excellent material. A polythiophene-based conductive polymer dispersed in a solvent is poly (3,4-ethylenedioxy) thiophene (hereinafter sometimes referred to as PEDOT) and polystyrene sulfonic acid as a dopant (hereinafter referred to as PSS). Aqueous dispersions of mixtures of A.) are known. Since 3,4-ethylenedioxythiophene (EDOT) has a very low solubility in water, it is dispersed in water by combining PSS with high solubility in water.

  PEDOT / PSS has been actively studied for application to transparent electrodes as an alternative to ITO because of its high conductivity, but it is inferior in conductivity to ITO, and it has been desired to improve conductivity.

  So far, some improved techniques for improving the conductivity of PEDOT / PSS have been reported. For example, Patent Document 1 discloses an example in which a mixed alcohol and a silane coupling agent are mixed to improve the conductive performance. However, in the technique of Patent Document 1, since it is essential that the mixed alcohol is composed of a low-viscosity solvent and a high-viscosity alcohol, a step of mixing these is necessary and 100 parts by weight of the PEDOT / PSS aqueous solution is required. Therefore, it is necessary to add up to 300 parts by weight of the mixed alcohol.

  As described above, the conventional electroconductive materials have drawbacks such as low electroconductivity and the necessity of mixing a large amount of components such as a binder, which has been a barrier to commercialization.

JP, 2005-180708, A

  An object of the present invention is to provide a conductive material which can be formed into a film by a simple method and has excellent conductivity.

  The present inventors have conducted extensive studies in view of such circumstances, and as a result, obtained by complexing polythiophene having a repeating unit (hereinafter, also simply referred to as “polythiophene”) and a sulfated cellulose crystal. It has been found that the composite has excellent film-forming properties and conductivity and can be suitably used as a conductive material. The present invention has been completed by further studies based on such findings.

That is, the present invention provides the inventions of the following modes.
It is a conductive material made of polythiophene, which is obtained from fibrous cellulose having a fiber width of 3 nm to 1500 nm and has the sulfated cellulose crystal shown in Chemical formula 1 as a dopant.

(R ^{1 to} R ⁶ each independently represent a hydrogen atom, a sulfonic acid group or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one is a sulfonic acid group or an alkylsulfonic acid having 1 to 6 carbon chains. Represents a group.)

  The conductive material of the present invention has excellent conductivity and is useful as an electrode material or a wiring material in a photoelectric conversion device such as a solar cell or an organic EL. Further, the conductive material of the present invention has excellent film-forming properties, and can be formed into a film by a simple method without mixing a large amount of components such as a binder, so that the conductive material used for electrodes, wiring, etc. The member can be manufactured by an easy method.

  Further, according to the production method of the present invention, since a complex of polythiophene and anionic polysaccharide is obtained in a dispersion state, a simple method of coating the dispersion to form a film has high conductivity. It becomes possible to manufacture the conductive member of.

FIG. 1 is a conceptual diagram of an example of a defibration processing apparatus. FIG. 2 is a diagram showing an electron micrograph of Example 1. FIG. 3 is a diagram showing an electron micrograph of Example 2. FIG. 4 is a diagram showing an electron micrograph of Example 3. FIG. 5 is a diagram showing an electron micrograph of Comparative Example 1. FIG. 6 is a diagram showing an electron micrograph of Comparative Example 4.

  The conductive material of the present invention is a complex of a sulfated cellulose crystal represented by Chemical formula (1) and a polythiophene having a repeating unit represented by Chemical formula (3) described below (hereinafter, referred to as “polythiophene / sulfated cellulose crystal”). It may be referred to as "complex"). Hereinafter, the conductive material of the present invention will be described in detail.

<Sulfated cellulose crystals>
The sulfated cellulose crystal used in the present invention means a sulfonic acid group or an alkylsulfonic acid group having 1 to 6 carbon chains in fibrous cellulose having a fiber width of 3 to 1500 nm (hereinafter, also referred to as cellulose nanofiber). Is introduced.

  A method for producing fibrous cellulose having a fiber width of 3 to 1500 nm into which the sulfonic acid group is introduced in the sulfated cellulose crystal will be described in detail below.

  Examples of the fibrous cellulose include wood fibers such as conifers and hardwoods, bamboo fibers, sugar cane fibers, seed hair fibers, fibrous cellulose derived from polysaccharides containing natural plants such as leaf fibers, and squirts that are marine organisms. Examples include cellulose contained in seaweed and the like, and cellulose produced by acetic acid bacteria using sugar as a raw material. These fibrous celluloses may be used alone or in combination of two or more. As the polysaccharide, it is preferable to use pulp having an α-cellulose content of 60% to 99% by mass. When the α-cellulose content is less than 60% by mass, the properties such as high strength, heat resistance, high rigidity, high heat resistance and high oxygen barrier properties of cellulose cannot be fully brought out, and the quality deteriorates due to coloring. And the generation of gas due to heat causes problems. Therefore, the α-cellulose content is preferably 60% or more. On the other hand, when 99% by mass or more is used, the fibers are strongly bound to each other by hydrogen bonds, so that it becomes difficult to defibrate the fibers to the nano level.

  As a method of defibrating a polysaccharide with a high-pressure water stream to form fibrous cellulose, there is an underwater counter collision method (hereinafter, also referred to as ACC method) described in JP-A-2005-270891. It introduces natural cellulose fibers suspended in water into two nozzles (Fig. 1: 108a, 108b) facing each other in a chamber (Fig. 4: 107), and jets and collides them toward one point from these nozzles. It is a technique. According to this method, the suspended water of natural microcrystalline cellulose fibers (for example, funacell) is made to collide with each other, and its surface is nanofibrillated and peeled off to improve the affinity with water as a carrier. It is possible to reach a state close to dissolution. The device shown in FIG. 1 is a liquid circulation type, and includes a tank (FIG. 1: 109), a plunger (FIG. 1: 110), two opposing nozzles (FIG. 1: 108a, 108b), and heat as necessary. It is equipped with an exchanger (FIG. 1: 111), and the fine particles dispersed in water are introduced into two nozzles and jetted from the opposing nozzles (FIG. 1: 108a, 108b) under high pressure to cause collision in water. Then, it is cooled by the heat exchanger 111 and returned to the tank 109. The number of repetitions of the circulation cycle of the tank 109 → plunger 110 → chamber 107 → heat exchanger 111 is defined as the number of processing times (pass). In this method, only water is used in addition to natural cellulose fibers, and because the micronization is performed by cleaving only the interaction between the fibers, there is no structural change in the cellulose molecule, and the decrease in the degree of polymerization associated with the cleaving occurs. It is possible to obtain fibrous cellulose in a minimized state. The fiber width and / or fiber length of the fibrous cellulose defined in the present invention can be appropriately increased or decreased by changing the number of times of treatment. For example, the fiber width of the fibrous cellulose can be reduced by increasing the number of times of the treatment. On the other hand, for example, the fiber width of the fibrous cellulose can be increased by reducing the number of times of the treatment.

  The fibrous cellulose obtained as described above has a structural formula represented by the following chemical formula 1 without the structural change of the cellulose molecule because nanofibrization is performed by cleaving only the interaction between natural cellulose fibers. . In other words, the fibrous cellulose used in the present invention has 6 hydroxyl groups in the cellobiose unit in the chemical formula 1.

  In the oncoming collision treatment, the temperature of the object to be treated rises as the number of times is increased, so the object to be treated once subjected to the collision treatment is cooled to, for example, 4 to 20 ° C. or 5 to 15 ° C., if necessary. Good. Further, it is possible to incorporate equipment for cooling into the oncoming collision processing device.

  In the face-to-face collision treatment, by adjusting such treatment conditions (treatment pressure, number of treatments, other nozzle diameter, treatment temperature, etc.), the average fiber width, average fiber length, transmittance, viscosity of the obtained fibrous cellulose can be obtained. Also, the intrinsic viscosity number and the like can be adjusted.

  The fibrous cellulose in the present invention preferably has a fiber width in the range of 3 nm to 1500 nm. Many of the fibers having a fiber width of less than 3 nm do not exist as crystalline fibers and are in a state of being completely dissolved on the molecule. Furthermore, when a sulfate group described below is introduced, the crystallinity is lowered. , EDOT orientation is disturbed and conductivity is not improved. Further, when the fiber width exceeds 1500 nm, it is difficult to uniformly introduce the sulfate group, and it is difficult to prepare a uniform sheet-shaped film, and the conductivity is not improved.

  The fiber length of the fibrous cellulose is 200 to 10,000 nm, preferably 500 to 2000 nm. When the fiber length is 200 nm or less, the crystallinity immediately deteriorates when the sulfate group is introduced, the orientation of EDOT during polymerization is disturbed, and the conductivity of PEDOT is not improved. If the fiber length is 10000 nm or more, it tends to be cocoon-shaped and does not easily exist as a long fiber, so that the sulfuric acid group cannot be uniformly introduced and the conductivity is not improved.

  Here, the measurement of the fiber width and the fiber length of the fibrous cellulose by electron microscope observation is performed as follows. An aqueous suspension of fibrous cellulose having a concentration of 0.001 to 0.01 mass% is prepared, and the suspension is cast on a hydrophilized carbon film-coated grid to obtain a TEM observation sample. When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed by adjusting the magnification according to the width of the constituent fibers.

  To introduce a sulfuric acid group into fibrous cellulose, for example, chlorosulfonic acid, sulfamic acid, halogenosulfonic acid, etc. may be reacted with fibrous cellulose, and fibrous cellulose may have an alkylsulfonic acid group having 1 to 6 carbon atoms. In order to introduce the above, for example, a halogenated alkylsulfonic acid having 1 to 6 carbon atoms or the like may be reacted with fibrous cellulose. In such a reaction, the cellulose type I crystallinity of the sulfated cellulose crystals represented by Formula 1 decreases with the passage of reaction time. More specifically, its crystalline state changes from a cellulose nanofiber state to a cellulose nanocrystal state, and finally becomes an amorphous state. This is explained as follows. When the number of sulfate groups introduced into the hydroxyl groups of fibrous cellulose increases, the electrostatic repulsion force due to the sulfate groups increases. This is because the fibrous cellulose is gradually defibrated with the increase of the electrostatic repulsion force, and the fiber width and the fiber length thereof are gradually shortened. Therefore, as described above, it is necessary to select the fiber width and fiber length of the fibrous cellulose in consideration of the decrease in crystallinity due to the introduction of the sulfate group.

In the present invention, the term "cellulose nanofiber" means a fiber having a fiber width of about 3 to 1500 nm, a fiber length of about 200 to 10000 nm, and a crystallinity of about 60 to 70. The term "cellulose nanocrystal" means that the fiber width is about 1 to 10 nm, the fiber length is about 100 to 300 nm, and the crystallinity is in the range of about 40 to 59. Further, the amorphous form means that the fiber width is about 1 to 10 nm, the fiber length is about 100 to 300 nm, and the crystallinity is a value less than 40.

  Hereinafter, the reaction conditions such as the raw material pretreatment for introducing the sulfate group into the fibrous cellulose, the reaction time, and the reaction temperature will be described in detail.

  Freeze-drying may be performed as a raw material pretreatment. This is because the fibrous cellulose used as a raw material is an aqueous dispersion, so that the dehydration amount becomes insufficient and the reaction efficiency cannot be improved by the method of solvent replacement.

  Further, before introducing the sulfonic acid group, by irradiating the dispersion liquid in which the fibrous cellulose as the raw material is dispersed with ultrasonic waves for 0.3 to 100 Wh, preferably 0.6 to 50 Wh, It is better to improve dispersibility. When the ultrasonic wave is 0.3 Wh or less, the fibrous cellulose remains aggregated and the reaction efficiency is not improved. Further, when the irradiation is performed with an electric energy of more than 100 Wh, the structure of the fibrous cellulose is destroyed, the crystallinity cannot be maintained, and the conductivity of the finally obtained conductive material is lowered.

  Regarding the reaction time and reaction temperature in the production of sulfated cellulose microcrystals, in order to prevent aggregation of the fibrous cellulose and uniformly react with the hydroxyl groups on the fibrous cellulose, 30 seconds to 6 seconds at 0 ° C or higher and lower than 10 ° C. It is advisable to carry out the reaction within the range of time.

<Polythiophene>
The polythiophene used in the present invention has a repeating unit represented by the formula (3).

In the chemical formula (3), R ¹ and R ² each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, or R ¹ and R ² are linked to each other, It represents a dioxyalkylene group having 1 to 8 carbon atoms, an aromatic ring or a 3- to 7-membered alicyclic ring.

  The alkyl group having 1 to 8 carbon atoms may be linear or branched. The alkyl group having 1 to 8 carbon atoms is preferably an alkyl group having 1 to 6 carbon atoms.

  Further, the alkoxy group having 1 to 8 carbon atoms may be linear or branched. The alkoxy group having 1 to 8 carbon atoms is preferably an alkoxy group having 1 to 6 carbon atoms.

When R ¹ and R ² are linked to form a dioxyalkylene group having 1 to 8 carbon atoms, the number of carbon atoms of the dioxyalkylene group is preferably 1 to 6 and more preferably 2 4 are mentioned.

When R ¹ and R ² are linked to form a 3 to 7 membered alicyclic ring, the alicyclic ring is preferably a 4 to 7 membered ring, more preferably a 5 to 6 membered ring. A ring is included.

  The number of repeating units represented by the formula (3) for forming polythiophene is not particularly limited, but examples thereof include about 2 to 50.

  As the monomer compound constituting the repeating unit represented by the formula (3), preferably, at the 3-position and 4-position of the thiophene skeleton, each independently, an alkyl group having 1 to 8 carbon atoms and / or a carbon number. A compound in which an alkoxy group having 1 to 8 is substituted; a 3,4-di-substituted thiophene in which a dioxyalkylene group having 1 to 8 carbon atoms is formed at the 3- and 4-positions of the thiophene skeleton can be mentioned. More specifically, 3,4-dialkylthiophene, 3,4-dialkoxythiophene, 3,4-alkylenedioxythiophene and the like can be mentioned. Among these, 3,4-alkylenedioxythiophene is preferable.

  Preferred specific examples of the monomer compound constituting the repeating unit represented by the formula (3) include, for example, 3,4-dihexylthiophene, 3,4-diethylthiophene, 3,4-dipropylthiophene and 3 , 4-dimethoxythiophene, 3,4-diethoxythiophene, 3,4-dipropoxythiophene, 3,4-dibutoxythiophene, 3,4-methylenedioxythiophene, 3,4-ethylenedioxythiophene, 3, 4-propylenedioxythiophene etc. are mentioned. Among these, 3,4-ethylenedioxythiophene is preferable.

<Polythiophene / sulfated cellulose crystal composite>
The polythiophene / sulfated cellulose crystal composite is produced by oxidative polymerization of thiophene represented by the following formula (4) in the presence of sulfated cellulose crystals, a solvent and an oxidizing agent.

In the chemical formula (4), R ¹ and R ² are the same as above.

  Specifically, a polythiophene / sulfated cellulose crystal complex is obtained by polymerizing thiophene by adding the thiophene represented by Chemical formula (4) and an oxidizing agent to a solution prepared by dissolving sulfated cellulose crystals in a solvent in advance. Obtained in the form of a dispersed solution. In the polythiophene / sulfated cellulose crystal composite thus obtained, the binding mode of the polythiophene and the sulfated cellulose crystal composite is not intended to be limited, but the polythiophene produced by the polymerization reaction and the sulfated cellulose are not limited. It is considered that the crystalline anions are compounded in a doped state.

  As the thiophene represented by the formula (4), preferably, the 3-position and 4-position of the thiophene skeleton are independently substituted with an alkyl group having 1 to 8 carbon atoms and / or an alkoxy group having 1 to 8 carbon atoms. Thiophene; 3,4-di-substituted thiophene having a dioxyalkylene group having 1 to 8 carbon atoms formed at the 3- and 4-positions of the thiophene skeleton. More specifically, 3,4-dialkylthiophene, 3,4-dialkoxythiophene, 3,4-alkylenedioxythiophene and the like can be mentioned. Among these, 3,4-alkylenedioxythiophene is preferable.

  Specific preferred examples of the thiophene represented by the formula (4) include, for example, 3,4-dihexylthiophene, 3,4-diethylthiophene, 3,4-dipropylthiophene, 3,4-dimethoxythiophene, 3, 4-diethoxythiophene, 3,4-dipropoxythiophene, 3,4-dibutoxythiophene, 3,4-methylenedioxythiophene, 3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, etc. Can be mentioned. Among these, 3,4-ethylenedioxythiophene is preferable.

  In the polythiophene / sulfated cellulose crystal composite, the cellulose I type crystallinity represented by the formula I of the sulfated cellulose crystal is preferably in the range of 40 to 53%. When the cellulose type I crystallinity is higher than 53%, the conductivity is not improved because the absolute amount of sulfate group as a dopant is small. When the cellulose I-type crystallinity is less than 40%, the molecular chain of cellulose is disturbed, and accordingly, the orientation of thiophene during polymerization is disturbed, which disturbs the crystal lattice of polythiophene and becomes an obstacle for the conduction path, resulting in the conduction. This is because it causes a decrease in sex. Therefore, in view of the amount as a dopant and the crystallinity of cellulose, it is considered that the cellulose I-type crystallinity is 40 to 53% in a suitable range.

In the polythiophene / sulfated cellulose crystal composite, the ratio of the polythiophene to the sulfated cellulose crystal is not particularly limited, but the higher the ratio of polythiophene, the higher the conductivity, but the dispersibility tends to decrease. In consideration of the above, it is appropriately set according to the type of polythiophene or sulfated cellulose. Specifically, the mass ratio of polythiophene to sulfated cellulose crystals is 1: 0.5 to 1: 8, preferably 1: 1 to 1: 4, and more preferably 1: 1. By satisfying such a mass ratio, it is possible to improve dispersibility in a solvent while providing more excellent conductivity.

  In the production of the polythiophene / sulfated cellulose composite, the amount of the thiophene and the sulfated cellulose crystal represented by the chemical formula (4) used as the raw material compound can satisfy the above-mentioned ratio of the polythiophene and the sulfated cellulose crystal. The range may be set appropriately. Specifically, 12.5 to 400 parts by mass, and preferably 25 to 200 parts by mass of the thiophene represented by Chemical formula (4) is listed per 100 parts by mass of the anionic polysaccharide.

  The oxidizing agent used in the production of the polythiophene / sulfated cellulose crystal composite is not particularly limited as long as it can oxidatively polymerize the thiophene represented by the formula (4), and examples thereof include peroxodisulfate and peroxodisulfate. Sodium disulfate, potassium peroxodisulfate, ammonium peroxodisulfate, inorganic ferric oxide salt, organic ferric oxide salt, hydrogen peroxide, potassium permanganate, potassium dichromate, alkaline perborate salt, iron sulfate ( III), iron (III) chloride and the like. Among these, preferable are peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate, ammonium peroxodisulfate, iron (III) sulfate and iron (III) chloride. These oxidizing agents may be used alone or in combination of two or more.

  In the production of the polythiophene / sulfated cellulose crystal composite, the amount of the oxidizing agent used is not particularly limited, but for example, 0.1 to 5 equivalents, preferably 0, per 1 mole of thiophene represented by Chemical formula (4). .3 to 2 equivalents.

  The solvent used for producing the polythiophene / sulfated cellulose crystal composite may be any solvent that can dissolve the sulfated cellulose crystal composite and can carry out the polymerization reaction of thiophene, and specific examples include an aqueous solvent. And preferably water. Further, as the solvent, an aqueous solvent in which a lower alcohol such as methanol or ethanol or a polar organic solvent such as acetone or acetonitrile is mixed with water may be used. These solvents may be used alone or in combination of two or more.

  In the production of the polythiophene / sulfated cellulose crystal composite, the amount of the solvent used is not particularly limited, but, for example, 1000 to 50000 ml, preferably 3000 to 30000 ml per 1 mole of thiophene represented by Chemical formula (4). Can be mentioned.

  The reaction time and reaction temperature in the production of the polythiophene / sulfated cellulose crystal composite are appropriately set according to the type of thiophene or sulfated cellulose crystals used as a raw material compound, the type of oxidizing agent, etc. To 90 ° C, preferably 10 to 80 ° C, for 1 to 96 hours, preferably 5 to 48 hours.

  By polymerizing the thiophene represented by Formula (4) in the presence of sulfated cellulose crystals as described above, a dispersion solution of a polythiophene / sulfated cellulose crystal complex is obtained. The polythiophene / sulfated cellulose crystal composite thus obtained is in the state of a dispersion obtained after the reaction, or after the polythiophene / sulphated cellulose crystal composite is separated and purified, if necessary, to produce a conductive film. Can be used for

<Conductive film using polythiophene / sulfated cellulose crystal composite>
Since the polythiophene / sulfated cellulose crystal composite has excellent conductivity and film-forming property, it can be used as a conductive film by forming it on a substrate.

Specifically, a conductive film using a polythiophene / sulfated cellulose crystal composite is dried by applying a dispersion liquid containing the polythiophene / sulfated cellulose crystal composite onto the entire surface of a substrate or in a predetermined shape. It is manufactured by removing the solvent.
Before drying, as an additive, ethanol, methanol, hydroxyl group such as ethylene glycol, halogen group, sulfone group, carbonyl group, amino group, imino group, carboxyl group, sulfide group, disulfide group, sulfonyl group, amide group and When the compound having at least one polar group selected from the group consisting of nitrile groups is added to the solvent, the conductivity of the conductive film can be improved. The amount of the compound having a polar group added as an additive is not particularly limited as long as it does not affect the dispersion of the polythiophene / sulfated cellulose crystal composite.

  The method of applying the dispersion liquid containing the polythiophene / sulfated cellulose crystal complex to the substrate is not particularly limited, and examples thereof include spray coating method, spin coating method, blade coating method, dip coating method, casting method, roll coating method. A coating method such as a bar coating method or a die coating method; a wet process such as a patterning method such as printing or inkjet. Of these, spin coating and casting are preferable.

  The drying method is not particularly limited, and examples thereof include heat drying, freeze drying, reduced pressure drying, hot air drying, and supercritical drying. The drying temperature is appropriately set according to the drying method, and is, for example, 50 ° C to 250 ° C, preferably 60 ° C to 150 ° C. By setting the drying temperature to 250 ° C. or lower, it is possible to effectively suppress the decrease in conductivity of the polythiophene / sulfated cellulose crystal composite during drying.

  Examples of the substrate used for forming the film of the polythiophene / sulfated cellulose crystal composite include a glass plate, a plastic sheet, a plastic film and the like. Examples of plastics include polyester, polyethylene, polypropylene, polystyrene, polyimide, polyamide, polyethylene terephthalate, polyethylene naphthalate, epoxy resin, chlorine resin, silicone resin, and blends thereof.

  A conductive film obtained by forming a polythiophene / sulfated cellulose crystal composite film, and a substrate provided with the conductive film are an antistatic film, a wiring of an electronic device represented by an organic EL or a solar cell, an electrode material, or the like. Used as a conductive member. Further, it can be used as various sensors capable of sensing humidity.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

  In Examples and Comparative Examples, the crystallinity of sulfated cellulose crystals, the degree of substitution of sulfate groups, the conductivity of polythiophene / sulfated cellulose crystal composites, the conductivity of polythiophene / sulfated cellulose crystal composites were measured. The measurement of the surface roughness of the membrane, the measurement of the fiber width and the fiber length, and the measurement of the intrinsic viscosity number were carried out by the following measurement methods.

(Measurement method of crystallinity and sulfate group)
Using XRD (Rigaku Corporation: SmartLab-9KW), the crystallinity was calculated using the following formula from the measurement results of the diffraction intensity of I200: lattice plane (200 plane) and Iam: the diffraction intensity of the amorphous part. .
(Formula) Cellulose type I crystallinity (%) = [(I ₂₀₀ -Iam) / I ₂₀₀ ] × 100
Here, I ₂₀₀ shows an X-ray diffraction intensity of 2θ = 22.6 °, and Iam shows an X-ray diffraction intensity of 2θ = 18.5 °.
Further, the degree of substitution of sulfate group was calculated from the result of elemental analysis of the cellulose sulfate crystal.

(Method for measuring conductivity of polythiophene / sulfated cellulose crystal composite)
After subjecting the slide glass to a pretreatment, a conductive film was prepared by a spin coating method using a polythiophene / sulfated cellulose crystal complex solution.
Next, the surface resistance value of the produced conductive film was measured. Specifically, the surface resistance is measured by connecting a 4-probe probe to a resistivity meter (loresta-GP MCP-T610) and pressing the film against the 4-probe probe to determine the conductivity (S / cm) was calculated.

(Method for measuring surface roughness of polythiophene / sulfated cellulose crystal composite)
The surface roughness and the film thickness were measured using a surface shape measuring device (Veeco model: Dektak150).

(Method of measuring fiber width and fiber length)
It was calculated from an electron microscope photograph taken using a field emission scanning electron microscope (Hitachi High-Technologies Corporation model number SU8000).

(Measurement method for intrinsic viscosity)
The solid content of 0.15 g was dissolved in 30 mL of 0.5 M copper ethylenediamine solution, and the viscosity was measured by measuring the flow-down time after keeping the temperature at 25 ° C. using a Canon Fenceke kinematic viscosity tube. went. From the measurement results, the intrinsic viscosity number was calculated according to JIS P 8215: Intrinsic viscosity number measurement method.

(Preparation of cellulose nanofiber by ACC method and measurement of intrinsic viscosity number)
Using softwood pulp and bamboo pulp as raw materials, the number of treatments was changed to obtain 1 wt% of an aqueous dispersion of cellulose nanofibers having different defibration degrees.
Then, the intrinsic viscosity number (ml / g) of the cellulose nanofiber aqueous dispersion was measured. As a result, the one having an intrinsic viscosity value in the range of more than 450 and 570 or less was designated as "NB-B", and the one in the range of 360 or more and 450 or less was designated as "NB-C". Here, the magnitude of the value of the intrinsic viscosity number means that the degree of polymerization of cellulose becomes higher as the value becomes smaller to larger.

(Example 1)
Softwood pulp was used as a raw material and treated by the ACC method to obtain 1 wt% of a cellulose nanofiber dispersion liquid. Next, when the intrinsic viscosity number was measured 3 times, the average value was 480 ml / g (therefore, the cellulose nanofiber dispersion liquid used in this example is NB-B). Next, 2.00 g of cellulose nanofiber was added to 200 ml of N, N-dimethylformamide (DMF), and the mixture was stirred at room temperature for 14 hours or longer. Then, the temperature of the water bath was adjusted to 10 ° C., and after irradiating with an internal ultrasonic wave for 2 minutes, 3.6 ml of chlorosulfonic acid was gradually added dropwise under a nitrogen atmosphere and mixed. The reaction was started by adding chlorosulfonic acid dropwise and the mixture was mixed for 50 minutes. Then, 15 ml of the reaction solution was poured into 150 ml of a saturated ethanol solution of sodium acetate to cause reprecipitation, and the precipitate was washed once with a saturated ethanol solution of sodium acetate and washed with ethanol until the supernatant liquid became neutral. The precipitate was dissolved in water, dialyzed, and then recovered as an aqueous solution to measure the degree of substitution of sulfate groups and the crystallinity of cellulose sulfate crystals. In addition, an electron micrograph of cellulose sulfate crystals was taken, and the results are shown in FIG. Furthermore, the fiber width of the cellulose nanofibers measured using an electron microscope was 3 to 1180 nm.

An aqueous dispersion of sulfated cellulose crystals was prepared at 0.2 wt% of 50 ml, and concentrated hydrochloric acid was added to make it acidic. Next, after adding 0.10 g of EDOT, internal ultrasonic waves were irradiated for 5 minutes to disperse EDOT. Then, 0.19 g of a polymerization initiator, potassium peroxodisulfate, and 0.5 ml of a 1.4 mg / ml aqueous solution of iron (III) sulfate / n-hydrate were added. The mixture was stirred at room temperature for 24 hours and dialyzed with a dialysis membrane for 72 hours or more. Water was used as a solvent, and the solid content was adjusted to 0.60 wt% by re-dispersing in water after drying to dryness by an evaporator to obtain a PEDOT / sulfated cellulose crystal complex aqueous dispersion.
Next, the conductivity of the PEDOT / sulfated cellulose crystal composite and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured.

(Example 2)
The measurement of the degree of substitution of the sulfate group and the crystallinity, the conductivity of the PEDOT / sulfated cellulose crystal composite was conducted in the same manner as in Example 1 except that the reaction was started at the start of dropping chlorosulfonic acid for 60 minutes. The measurement and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured. An electron micrograph of cellulose sulfate crystals was taken, and the results are shown in FIG.

(Example 3)
Measurement of the degree of substitution of sulfate group and crystallinity, PEDOT / sulfated cellulose crystal composite were carried out in the same manner as in Example 1 except that the start of dropping of chlorosulfonic acid was set to 120 minutes (2 hours). Was measured and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite was measured. An electron micrograph of the sulfated cellulose crystals was taken, and the results are shown in FIG.

(Example 4)
Measurement of substitution degree of sulfate group and crystallinity, PEDOT / sulfated cellulose crystal composite were carried out in the same manner as in Example 1 except that the start of dropping of chlorosulfonic acid was set to 180 minutes (3 hours). Was measured and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite was measured.

(Example 5)
Measurement of the degree of substitution of sulfate group and crystallinity, PEDOT / sulfated cellulose crystal composite were carried out in the same manner as in Example 1 except that 270 minutes (4 hours and a half) were set as the reaction start of chlorosulfonic acid. The conductivity of the body and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured.

(Comparative Example 1)
Measurement of the substitution degree of the sulfate group and the crystallinity and the conductivity of the PEDOT / sulfated cellulose crystal composite were conducted in the same manner as in Example 1 except that the start of the dropwise addition of chlorosulfonic acid was changed to 10 minutes. The measurement and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured. In addition, an electron micrograph of cellulose sulfate crystals was taken, and the results are shown in FIG.

(Comparative example 2)
Measurement of the substitution degree of the sulfate group and the crystallinity and the conductivity of the PEDOT / sulfated cellulose crystal composite were carried out in the same manner as in Example 1 except that the reaction start was the start of the dropwise addition of chlorosulfonic acid. The measurement and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured.

(Comparative example 3)
Measurement of the degree of substitution of sulphate groups and the degree of crystallization, PEDOT / sulphated cellulose crystal composite was carried out in the same manner as in Example 1 except that the start of the dropwise addition of chlorosulfonic acid was the start of the reaction and was 300 minutes (5 hours). Was measured and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite was measured.

(Comparative example 4)
Measurement of the degree of substitution of sulfate group and crystallinity, PEDOT / sulfated cellulose crystal composite was carried out in the same manner as in Example 1 except that the start of dropping chlorosulfonic acid was 360 minutes (6 hours). Was measured and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite was measured. In addition, an electron micrograph of cellulose sulfate crystals was taken, and the results are shown in FIG.

(Comparative example 5)
15.0 g of cellulose was stirred in 750 ml of N, N-dimethylformamide (DMF) at room temperature for 14 hours or more. Then, the temperature of the water bath was raised to 50 ° C., 13.90 ml of chlorosulfonic acid was gradually added over 30 minutes, and the mixture was stirred for 5 hours. After completion of the reaction, the reaction solution was poured into 3000 ml of a saturated ethanol solution of sodium acetate for reprecipitation, and the precipitate was washed three times with a saturated ethanol solution of sodium acetate, and washed with ethanol until the supernatant was neutral. Then, the precipitate was dissolved in water and dialyzed with a dialysis membrane (Spectra / Por 3). After dialysis for 72 hours or more, it was lyophilized and collected. Then, the substitution degree of the sulfate group and the crystallinity were measured, and the conductivity of the PEDOT / sulfated cellulose crystal composite was measured.

(Comparative example 6)
Measurement of the degree of substitution of sulfate group and crystallinity, PEDOT / sulfuric acid was carried out in the same manner as in Example 1 except that the use of softwood-derived pulp and the start of dropping chlorosulfonic acid were started for 20 minutes. The conductivity of the sulfonated cellulose crystal composite and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured. Furthermore, the fiber width of the pulp measured using an electron microscope was about 60 μm.

(Comparative Example 7)
Measurement of the degree of substitution of sulfate group and crystallinity, PEDOT / sulfuric acid was performed in the same manner as in Example 1 except that pulp derived from coniferous wood was used and that the start of dropping chlorosulfonic acid was started as the reaction for 30 minutes. The conductivity of the sulfonated cellulose crystal composite and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured.

(Comparative Example 8)
Measurement of the degree of substitution of sulfate groups and crystallinity, PEDOT / sulfuric acid was carried out in the same manner as in Example 1 except that pulp derived from coniferous wood was used and the start of dropwise addition of chlorosulfonic acid was started as the reaction start for 60 minutes. The conductivity of the sulfonated cellulose crystal composite and the surface roughness of the conductive film of the PEDOT / sulfated cellulose crystal composite were measured.

  Each measurement result in Examples 1 to 5 is shown in Table 1, each measurement result in Comparative Examples 1 to 4 is shown in Table 2, and each measurement result in Comparative Examples 5 to 8 is shown in Table 3.

(Discussion of results)
From the results of Tables 1 and 2, the sulfated cellulose crystals having a crystallinity of 40 to 53% are in nanocrystal form (FIGS. 2 to 4), and the sulfated cellulose crystals having a crystallinity of 53% or more are nanofibers. When the sulfated cellulose crystals with a crystallinity of 40% or less are amorphous (FIG. 6) and the pulp-derived sulfated cellulose is microfibrillar, nanocrystalline sulfated cellulose crystals are used. In Examples 1 to 5, the surface roughness was small (about 7 to 14 nm) and the conductivity was excellent. On the other hand, Comparative Examples 1 and 2 using the nanofiber-shaped sulfated cellulose had a large surface roughness value. In Comparative Examples 3 and 4 using amorphous sulfated cellulose, the surface roughness was small, but the conductivity was low.

In Comparative Example 5, although the same amount of sulfate group as in Examples 4 and 5 was introduced, the sulfate group was introduced into the amorphous portion in the pulp, and the average crystallinity of the entire cellulose was increased. Was low and the conductivity was not improved. Further, the sulfated celluloses of Comparative Examples 6 to 8 were inferior in surface roughness and conductivity.

From the above, it was possible to produce a more stable film with a conductive material using nanocrystal-like sulfated cellulose crystals as a dopant, which had excellent conductivity, improved coating properties.

(PEDOT / sulfated cellulose composite made from NB-C)
(Example 7)
Softwood pulp was used as a raw material and treated by the ACC method to obtain 1 wt% of a cellulose nanofiber dispersion liquid. Next, when the intrinsic viscosity number was measured three times, the average value was 370 ml / g (therefore, the cellulose nanofiber dispersion liquid used in this example is NB-C). Then, using this as a raw material, measurement of the degree of substitution of sulphate groups and crystallinity, PEDOT / sulphated cellulose were carried out in the same manner as in Example 1 except that the reaction start was the start of dropwise addition of chlorosulfonic acid. The conductivity of the crystal composite was measured.

(Example 8)
Except for using the cellulose nanofiber dispersion obtained in Example 7 as a raw material, measurement of the degree of substitution of sulfate groups and crystallinity, conductivity of PEDOT / sulfated cellulose crystal composite were conducted in the same manner as in Example 2. Was measured.

(Example 9)
Except for using the cellulose nanofiber dispersion obtained in Example 7 as a raw material, measurement of the degree of substitution of sulfate groups and crystallinity, conductivity of PEDOT / sulfated cellulose crystal composite were conducted in the same manner as in Example 4. Was measured.

(PEDOT / sulfated cellulose composite made from bamboo pulp)
(Example 10)
Measurement of the degree of substitution of sulfate group and crystallinity, conductivity of PEDOT / sulfated cellulose crystal composite were conducted in the same manner as in Example 3 except that bamboo pulp was used as the raw material (hereinafter, sometimes referred to as BB). Was measured.

(Example 11)
The substitution degree of the sulfate group and the crystallinity, and the conductivity of the PEDOT / sulfated cellulose crystal composite were measured in the same manner as in Comparative Example 4 except that bamboo pulp was used as the raw material.

(Comparative Example 9)
PEDOT / PSS was prepared in the same manner as in Example 1 and its conductivity was measured.

  Table 4 shows each measurement result in Examples 7 to 11 and Comparative Example 9.

From the results of Table 4, it can be said that NB-B (Examples 1 to 5) and NB-C (Examples 7 to 9) both have higher conductivity than PEDOT / PSS.
In addition, it can be said that NB-B (Examples 1 to 5) and NB-C (Examples 7 to 9) both have higher conductivity than BB.

(Stability evaluation of PEDOT / sulfated cellulose)
300 μL of the PEDOT / sulfated cellulose dispersion (0.6 wt%) prepared in Examples 2 to 5 and Comparative Example 3 was drop cast on a glass substrate (50 mm × 50 mm) and heated at 120 ° C. for 30 minutes. The surface resistance value was measured (initial).
Then, using PEDOT / sulfated cellulose in Examples 2 to 5 and Comparative Example 3 stored in a dark place at room temperature for 2 years, a sample was prepared under the same conditions as the above-mentioned preparation conditions, and the surface resistance value was measured ( 2Y).
The surface resistance value was measured by connecting a 4-probe probe to a resistivity meter (loresta-GP MCP-T610) and pressing the film against the 4-probe probe.

Table 5 shows the measurement results of the surface resistance values in Examples 2 to 5 and Comparative Example 3.

From the results in Table 5, there was no sample in which the resistance value was remarkably reduced. From this, it can be said that the PEDOT / sulfated cellulose according to the present invention is excellent in stability without decreasing the conductivity performance with the passage of time.

(Surface resistance and conductivity when a compound having a polar group is used)
(Example 12)
Example 1 was repeated except that water was used as a solvent and the solid content (PEDOT / sulfated cellulose crystal complex) was adjusted to 0.30 wt% when the PEDOT / sulfated cellulose crystal complex aqueous dispersion was prepared. Similarly, the surface resistance value was measured.

(Example 13)
When preparing the PEDOT / sulfated cellulose crystal complex dispersion, the one adjusted to have a weight ratio of water to ethanol of 1: 1 was used as a solvent, and the solid content (PEDOT / sulfated cellulose crystal complex) was changed to The surface resistance value, the conductivity and the film thickness were measured in the same manner as in Example 1 except that the content was adjusted to 0.30 wt%.

(Example 14)
When preparing the PEDOT / sulfated cellulose crystal complex dispersion, water was used as a solvent, the solid content (PEDOT / sulfated cellulose crystal complex) was adjusted to 0.30 wt%, and ethylene glycol was further added as an additive. The surface resistance value, conductivity and film thickness were measured in the same manner as in Example 1 except that 3 wt% was added to the solid content.

Table 6 shows the measurement results in Examples 12 to 14.

From the results of Example 12, when the solvent was water alone and the solid content concentration was 0.3%, the surface resistance value could not be measured because the solid content concentration was low.
On the other hand, from the results of Example 13 and Example 14, even when the solid content concentration was 0.3%, when ethanol was used as the dispersion solvent or ethylene glycol was used as the additive, Since it was possible to measure the respective surface resistance values, it can be said that the use of these could improve the conductivity of the PEDOT / sulfated cellulose crystal composite.

Using the PEDOT / sulfated cellulose crystal composite dispersions obtained in Example 5 and Example 11, cast films of PEDOT / sulfated cellulose were prepared on a glass substrate, and the humidity was measured using a humidity chamber. Was changed from 27% to 80% over 2 hours, and the surface resistance value at each humidity was measured.
The measurement results are shown in Table 7.

From the results of Table 7, it can be seen that the surface resistance values are reduced to about 1/2 by changing the humidity from 27% to 80%.
From this, by energizing the PEDOT / sulfated cellulose crystal composite, the humidity can be detected, and further, it can be used as a humidity sensor.

Claims (2)

A conductive material made of polythiophene, which is obtained from fibrous cellulose having a fiber width of 3 nm to 1500 nm and has the sulfated cellulose crystal shown in Chemical formula 1 as a dopant.
Chemical 1
R ^{1 to} R ⁶ each independently represent a hydrogen atom, a sulfonic acid group or an alkylsulfonic acid group having 1 to 6 carbon chains, and at least one is a sulfonic acid group or an alkylsulfonic acid group having 1 to 6 carbon chains. Represents The conductive material comprising polythiophene according to claim 1, wherein the cellulose I-type crystallinity represented by formula 1 of the sulfated cellulose crystal according to claim 1 is 40% to 53%.
[Formula 1]
Cellulose type I crystallinity (%) = [(I ₂₀₀ -Iam) / I ₂₀₀ ] × 100 (1)
I ₂₀₀ shows an X-ray diffraction intensity of 2θ = 22.6 °, and Iam shows an X-ray diffraction intensity of 2θ = 18.5 °.