JP2010102829A - Evaluation method of liquid containing graphite oxide particle, manufacturing method of liquid containing graphite oxide particle, and manufacturing method of conductor using the evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation method of liquid containing graphite oxide particles capable of easily and efficiently evaluating homogeneity of liquid containing graphite oxide particles. <P>SOLUTION: The evaluation method of the liquid containing graphite oxide particles includes a measuring process to determine particle-size distribution of the graphite oxide particles in the liquid containing graphite oxide particles by a liquid-phase sedimentation type particle-size distribution determining method, and a comparing process to compare the particle-size distribution measured in the measuring process with a reference particle-size distribution. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for evaluating a graphite oxide particle-containing liquid, a method for producing a graphite oxide particle-containing liquid using the same, and a method for producing a conductor.

  In recent years, the search for a material having a high shape anisotropy and its application are rapidly progressing. In the case where a large number of such substances are combined with other substances, it is expected that various properties such as high strength will be exhibited at a low addition rate. Also, if the shape is very thin linear (1D) or very thin planar (2D) and the material is an electrically semiconductor or good conductor, the physical properties can be used in the case of a single or a small number of aggregates. It is also expected to produce a quantum effect.

Graphite oxide is known as an anisotropic planar material having a carbon atom as a skeleton. Graphite oxide is a kind of graphite intercalation compound obtained by oxidizing graphite by a specific method. Graphite oxide is a multilayer structure in which two-dimensional basic layers are stacked, and the number of layers is generally very large. The basic layer of graphite oxide consists of a carbon skeleton with a thickness of one or two carbon atoms counted in a zigzag carbon array and a sp ³ bond-dominant carbon skeleton with a slight tendency to sp ² bonds, and both sides of the skeleton. It is thought that it has the structure which has the acidic hydroxyl group couple | bonded with the surface (for example, nonpatent literatures 1-3).

  As such a graphite oxide, a very thin one having a small number of layers has also been made (for example, Non-Patent Document 4), and the present inventors have previously made such graphite oxide (when the number of layers is one). For example, graphene oxide (graphene is the name of one layer of graphite)) is found in a method for producing a high-yield thin film-like particle, and it is reduced to reduce the number of graphite ( When the number of layers is one, it is desirable to call it graphene.) Similar thin film-like particles have been obtained (Patent Documents 1 to 3).

  The number of basic layers of the above-described graphite oxide particles varies depending on the degree of purification. The difference in the number of layers in the basic layer becomes the difference in the thickness of the particles, and the difference in the thickness affects the aspect ratio (ratio between the size of the particles in the plane direction and the thickness). The smaller the thickness, the higher the aspect ratio (that is, the higher the shape anisotropy), and the higher the effect as a filler. For example, when graphite oxide particles are added to a resin, the larger the aspect ratio of the graphite oxide particles, the more the resin can be made conductive by adding a smaller amount of graphite oxide particles.

While the thickness of the particles greatly affects performance, there is currently no simple method for evaluating the thickness of particles with high shape anisotropy. A general method is to place some particles in the dispersion on a substrate and evaluate the thickness of the particles by observation with an atomic force microscope (for example, Non-Patent Document 5 below).
JP 2002-53313 A JP 2003-176116 A JP 2005-63951 A “Graphite Intercalation Compound”, Chapter 5, Carbon Society of Japan, Realize (1990) T. Nakajima et al. A NEW STRUCTURE MODEL OFGRAPHITE OXIDE, Carbon, 26, 357 (1988) M. Mermoux et al. FTIRAND 13C NMR STUDY OF GRAPHITE OXIDE, Carbon, 29, 469 (1991) NA Kotov et al. UltrathinGraphite Oxide-Polyelectrolyte Composites Prepared by Self-Assembly: TransitionBetween Conductive and Non-Conductive States, Adv. Mater., 8, 637 (1996) Stankovich etal, J. Mater. Chem., 2006, 16, 155-158, Stankovich et al, Carbon44 (2006) 3342-3347

  By the way, when manufacturing the graphite oxide particle containing liquid containing a graphite oxide particle, the thickness of each particle is an important factor which determines performance, and it is necessary to manage the thickness of a graphite oxide particle appropriately.

  However, when preparing a plurality of graphite oxide particle-containing liquids and evaluating their homogeneity, just evaluating the thickness of a very small part of the particles in the graphite oxide particle-containing liquid with atomic force microscopy, Since the thickness of the whole particle in the liquid is not evaluated, it is difficult to satisfactorily evaluate the homogeneity, and it is also difficult to stabilize the performance of the conductive film manufactured using the same. is there.

  For this reason, establishment of the evaluation method which evaluates the thickness of the whole particle | grains in a graphite oxide particle containing liquid in order to ensure the homogeneity of a graphite oxide particle containing liquid was desired.

  The present invention has been made in view of the above circumstances, and a method for evaluating a graphite oxide particle solution that can easily and effectively evaluate the homogeneity of a graphite oxide particle-containing solution, and a method for producing a graphite oxide particle-containing solution using the same. And it aims at providing the manufacturing method of a conductor.

  The inventors of the present invention have made extensive studies to solve the above problems. In the course of the study, it was examined to measure the particle size distribution by liquid phase sedimentation type particle size distribution measurement method. The liquid phase sedimentation type particle size distribution measurement method is a method for measuring the particle size distribution of particles by utilizing the fact that the sedimentation speed of particles in the liquid phase varies depending on the particle size of the particles. However, the liquid phase sedimentation particle size distribution measurement method assumes that the particles are spherical, and the graphite oxide particles have high shape anisotropy and have a shape far from the spherical shape. For this reason, even if the particle diameter of the particles is the same, the present inventors considered that the settling speed may differ depending on the posture of the particles when settling in the liquid phase. That is, when the thickness direction of the graphite oxide particles is close to the horizontal direction, the particle settling speed is large because the resistance of the particles to the liquid phase is small, and when the thickness direction of the graphite oxide particles is close to the vertical direction, It was thought that the sedimentation rate of the particles would decrease because of the large resistance of the particles to the phase. That is, the present inventors found no correlation between the thickness of the graphite oxide particles and the sedimentation rate in the liquid phase, and the total thickness of the graphite oxide particles was determined using the liquid phase sedimentation type particle size distribution. It was considered extremely difficult to evaluate.

  However, when the present inventors made a conductive film using a graphite oxide particle-containing liquid whose particle size distributions approximated each other using the liquid phase sedimentation type particle size distribution measurement method, surprisingly, the conductive films were almost the same. It became clear that resistance value was shown. From this, the present inventors have found that the graphite oxide particle-containing liquid is homogeneous, and the closeness of the particle size distribution can be an indicator of the homogeneity of the graphite oxide particle-containing liquid. Furthermore, the present inventors also changed the sedimentation rate of the graphite oxide particles having a high aspect ratio (= (maximum size in the plane direction of the particles) / (thickness)) with a slight difference in thickness. Therefore, it has also been found that the liquid phase sedimentation type particle size distribution measurement method is simple and effective as a method for evaluating the total thickness of particles in a graphite oxide particle-containing liquid, that is, as a method for evaluating a graphite oxide-containing particle-containing liquid. The present invention has been completed.

  That is, the present invention measures the particle size distribution of the graphite oxide particles in the graphite oxide particle-containing liquid containing the graphite oxide particles using a liquid phase precipitation type particle size distribution measuring method, and the measurement step. A comparison step of evaluating a graphite oxide particle-containing liquid by comparing a particle size distribution with a reference standard particle size distribution.

  Further, the present invention provides a thinning step for thinning graphite oxide particles, and a graphite oxide particle-containing liquid containing the graphite oxide particles thinned in the thinning step. The particle size distribution of the graphite oxide particles in the graphite oxide particle-containing liquid evaluated in the evaluation step is not approximate to the reference particle size distribution, the reference particle size distribution The graphite oxide particle-containing liquid is obtained by repeating the thinning step and the evaluation step so as to approximate the same, thereby obtaining a graphite oxide particle-containing liquid having a particle size distribution approximate to the reference particle size distribution.

  According to the present invention, since the graphite oxide particle-containing liquid having a particle size distribution approximate to the reference particle size distribution is obtained, a highly homogeneous graphite oxide particle-containing liquid can be obtained.

  Furthermore, the present invention provides a conductor forming liquid preparation step for preparing a conductor forming liquid containing the graphite oxide particle-containing liquid produced by the method for producing a graphite oxide particle-containing liquid, and forming the conductor forming liquid in a film shape And a film forming step of forming a conductor including a conductive film by drying, and a method of manufacturing a conductor.

  According to this conductor manufacturing method, a conductor including a conductive film having desired performance can be obtained. When a plurality of such conductors are manufactured, a conductor having substantially the same performance can be stably manufactured.

  According to the present invention, there is provided a method for evaluating a graphite oxide particle-containing liquid capable of simply and effectively evaluating the homogeneity of the liquid graphite oxide-containing liquid, a method for producing a graphite oxide particle-containing liquid using the same, and a method for producing a conductor. Is done.

  Hereinafter, embodiments of the present invention will be described in detail.

[Method for producing conductor]
First, an embodiment of a method for manufacturing a conductor will be described.

  First, prior to description of an embodiment of a method for manufacturing a conductor, a configuration of a conductor manufactured by the manufacturing method will be described with reference to FIG.

  FIG. 1 is a side view showing an example of a conductor manufactured by the method for manufacturing a conductor according to the present embodiment. As shown in FIG. 1, the conductor 100 of the present embodiment includes a base material 1 and a conductive film 2 provided on one surface 1 a of the base material 1.

  Examples of the substrate 1 include a glass plate, a polyethylene terephthalate film, and a polycarbonate film.

  The conductive film 2 has conductivity, and is obtained by applying a conductor forming liquid containing graphite oxide particles on one surface 1a of the substrate 1 to form a film and then drying it. .

  Next, a method for manufacturing the conductor 100 will be described with reference to FIG.

  FIG. 2 is a flowchart showing a method for manufacturing the conductor 100. As shown in FIG. 2, the manufacturing method of the conductor 100 first manufactures a graphite oxide particle-containing liquid containing graphite oxide particles (S100 to S103), and a conductor forming liquid containing the obtained graphite oxide particle-containing liquid. Is prepared (S104), and then the conductive film 2 is formed on the substrate 1 using this conductor forming liquid to obtain the conductor 100 (S105). Therefore, first, a method for producing a graphite oxide particle-containing liquid will be described.

(Method for producing graphite oxide particle-containing liquid)
The graphite oxide particles in the graphite oxide particle-containing liquid are obtained by oxidizing graphite.

  Various types of graphite can be used for the graphite used as a raw material for the above graphite oxide particles. However, highly crystalline graphite with a developed layer structure has a high yield in the production of graphite oxide and has a small number of basic layers. It is preferable because graphite is easily obtained. As such graphite, natural graphite (particularly good quality), quiche graphite (particularly made at high temperature), highly oriented pyrolytic graphite are preferably used, and expanded graphite in which the layers of these graphites are expanded in advance. Are also preferably used. Further, it is desirable that impurities such as metal elements in the graphite have been removed in advance until it becomes about 0.5% by mass or less.

  The graphite oxide particles are produced by, for example, a method of oxidizing graphite (Hummers-Offeman method) using sulfuric acid, sodium nitrate, or potassium permanganate.

  In this method, first, sodium nitrate, sulfuric acid, potassium permanganate, and graphite are mixed to cause sulfate ions to enter between the graphite layers, thereby generating a sulfuric acid-graphite intercalation compound in the reaction solution (intercalation compound generation step: S100). Here, when the ratio of sodium nitrate, sulfuric acid, and potassium permanganate is, for example, sodium nitrate 10 by mass ratio with sulfuric acid 828 and potassium permanganate 60, sulfuric acid-graphite intercalation compound is effectively generated. can do.

  Next, the sulfuric acid-graphite intercalation compound is hydrolyzed by adding water to the reaction solution to generate graphite oxide particles (hydrolysis step: S101). Thus, a reaction liquid containing graphite oxide particles is obtained.

  Subsequently, impurity ions such as sulfate ions and manganese ions remaining in the reaction solution are removed and the reaction solution is purified to obtain a graphite oxide particle-containing solution (purification step: S102).

  Here, examples of the method for removing impurity ions remaining in the reaction solution include a method of sequentially performing a solvent addition operation and a solvent removal operation. For the solvent removal operation, known means such as decantation, filtration, centrifugation, dialysis, and ion exchange can be used. In decantation and filtration, since sedimentation is slow, the purification time becomes long, and filtration is hardly possible due to clogging with graphite oxide particles. Therefore, centrifugation capable of purification in a relatively short time is more preferable.

  In the purification step, from the viewpoint of preventing aggregation of graphite oxide particles, a liquid having a relative dielectric constant of 15 or more is preferably used as the solvent, and water is particularly preferably used. Here, it is particularly preferable to use ion-exchanged water among water.

  Separation of layers in the graphite oxide particles proceeds by the purification step, and the graphite oxide particles are thinned. That is, the refining step corresponds to the thinning step in the method for producing a graphite oxide particle-containing liquid according to the present invention.

(Method for evaluating graphite oxide particle-containing liquid)
In the present embodiment, the graphite oxide particle-containing liquid is evaluated after the purification step (evaluation step: S103). Here, a method for evaluating the graphite oxide particle-containing liquid will be described.

  First, in this evaluation method, the particle size distribution of the graphite oxide particles in the graphite oxide particle-containing liquid is measured using a liquid phase precipitation type particle size distribution measurement method (measurement step: S103A).

Here, the particle size distribution means the thickness distribution of the entire graphite oxide particles. The apparatus for measuring such particle size distribution is not particularly limited as long as it is an apparatus for performing a liquid phase sedimentation type particle size distribution measuring method. For example, an ultracentrifugal automatic particle size distribution measuring apparatus CAPA-700 manufactured by HORIBA can be used. It is. The CAPA-700 has a theory that spherical particles having a diameter (D) and a density (ρ) existing in a solvent having a density (ρ ₀ ) and a viscosity coefficient (η ₀ ) settle at a constant speed according to the Stokes sedimentation equation. Applied (HORIBA ultracentrifugal automatic particle size distribution analyzer CAPA-700 manual). However, the Stokes sedimentation equation is an equation for spherical particles, and does not reflect the exact particle size of particles with high shape anisotropy. That is, the particle size measured by this apparatus is a particle size on the assumption that the particles are spherical, and therefore the particle size value itself has no meaning for particles having high shape anisotropy. However, when the density of the solvent (ρ ₀ ), the viscosity coefficient (η ₀ ), and the density of the graphite oxide particle-containing liquid (ρ) are the same, the value of the obtained particle size corresponds to the sedimentation rate, The smaller the value, the slower the sedimentation rate. For this reason, even if the value of the particle size itself is meaningless, the above apparatus is useful when relatively comparing graphite oxide particle-containing liquids and evaluating whether the two are relatively homogeneous.

Here, in the above apparatus, it is necessary to input conditions such as solvent density, viscosity coefficient and particle density at the time of measurement, but as described above, since the particle size value itself has no meaning, it is actually Different values may be input, and it is not always necessary to input a correct value (when the solvent is water, the density of water is 1 g / cm ³ ).

  Next, the particle size distribution measured in this way is compared with a reference reference particle size distribution to evaluate the graphite oxide particle-containing liquid (comparative step: S103B). At this time, if the particle size distribution of the graphite oxide particle-containing liquid does not approximate the reference particle size distribution, the graphite oxide particle-containing liquid is evaluated as not good, and if approximate, the graphite oxide particle-containing liquid is evaluated as good. . Thus, by measuring the liquid phase sedimentation particle size distribution, the homogeneity of the graphite oxide particle-containing liquid can be easily and effectively evaluated.

  Here, the “reference particle size distribution” can be arbitrarily selected.

As an index that can compare the closeness of the shape between the reference particle size distribution and the measured particle size distribution, for example, an R ² value can be used. The R ² value is a value regarding the particle size distribution of the graphite oxide particles in the graphite oxide particle-containing liquid as compared with the reference particle size distribution, and the amount serving as a reference for the particle size D _i (i = 1 to n) is X _{When i} (i = 1 to n) and the amount of the sample to be compared is Y _i (i = 1 to n), the calculation is performed as follows.

Here, the R ² value takes a value of 0 to 1, and the closer to 1, the closer the distribution is. For example, if the R ² value is 0.70 or more, it is evaluated that the measured particle size distribution approximates the reference particle size distribution. Here, it is preferable to evaluate that the measured particle size distribution and the reference particle size distribution are approximate when the R ² value is 0.80 or more, and approximate when the R ² value is 0.90 or more. More preferably, it is evaluated that In this case, the approximation between the particle size distribution of the graphite oxide particle-containing liquid related to the measurement and the reference particle size distribution is considerably increased, so that the graphite oxide particle-containing liquid related to the measurement is brought close to the graphite oxide particle-containing liquid having the reference particle size distribution. be able to.

  In the evaluation step, if it is evaluated that the graphite oxide particle-containing liquid is not good, the graphite oxide particle is further obtained by repeatedly performing the purification step and the evaluation step on the graphite oxide particle-containing liquid. This is because the particle size distribution of is close to the reference particle size distribution. Thus, a graphite oxide particle-containing liquid evaluated as good is obtained.

  Since the particle size distribution of the graphite oxide particle-containing liquid evaluated as good in this way is close to the standard distribution, a highly homogeneous graphite oxide particle-containing liquid can be obtained.

  Hereinafter, the evaluation method of the graphite oxide particle-containing liquid will be described in detail by taking, as an example, an ultracentrifugal automatic particle size distribution analyzer CAPA-700 manufactured by HORIBA.

In CAPA-700, as in many other devices, if the solvent density (ρ ₀ ), viscosity coefficient (η ₀ ), and particle density (ρ) are set, particles existing in the liquid due to the difference in sedimentation speed The particle size distribution can be measured. Furthermore, the centrifugal force can be changed according to the speed at which the particles to be measured settle. The solvent density (ρ ₀ ), viscosity coefficient (η ₀ ), and particle density (ρ) do not need to use the actual solvent / particle values, so that a comparable particle size distribution can be obtained. An appropriate value may be selected. For example, an aqueous dispersion of graphite oxide particles obtained by sufficiently purifying graphite oxide particles produced by Hummers-Offeman method using natural graphite SNO-2 (purity 99.97% by mass or more) manufactured by ESC Corporation as a raw material The particle size distribution was measured with CAPA-700. In this case, a good particle size distribution could be measured under the conditions shown in Table 1 below. Here, as to whether the particle size distribution is good or not, the particle size distribution in which the amount (%) (area basis) is less than 2% and the particle size of 2% or more exists to the same extent. It is judged on the basis of whether or not. “Amount (%) (area standard)” will be described later.

  Here, the rotation speed corresponds to the centrifugal force applied during sedimentation, and the higher the rotation speed, the stronger the centrifugal force is applied and measured.

FIG. 3 shows the results of Measurement 1 and Measurement 2 in which the same sample was measured twice under the above measurement conditions. In FIG. 3, the horizontal axis represents the particle size of the particles, and the vertical axis represents the amount (%) (area basis). The amount (%) (area basis) represents the ratio of the sum of the areas of the circles of particles having a certain particle diameter to the total area of the circles obtained by using the particle diameter as the diameter for all particles. Therefore, for example, in the particle size distribution, if the amount (%) of one particle size is the same as the amount (%) of another particle size, the sum of the areas of the circles with the particle size being the diameter is the same. It is not that the number of particles is equal. 4 and 5, the horizontal axis and the vertical axis are the same as those in FIG. According to the results shown in FIG. 3, a good particle size distribution is obtained, and the reproducibility during the second measurement is also good. The R ² value of measurement 2 relative to measurement 1 was 0.95.

  FIG. 4 is a graph showing the results of the particle size distribution measurement performed under the same conditions as described above in the purification steps 1 to 6. The number indicating the purification step indicates that the larger the purification step, the more advanced the purification. From the results shown in FIG. 4, as the refinement progresses and the thickness of the graphite oxide particles decreases, the peak of the particle size distribution shifts to a smaller value of the particle size, and the particle size distribution measured by CAPA-700 is It can be seen that the thickness sufficiently reflects the thickness of the particles.

  Here, in the graphite oxide particle-containing liquid obtained as described above, the shape of the graphite oxide particles is flat. When the shape of the graphite oxide particles is a flat plate shape, the shape anisotropy is increased, and the conductive film 2 in the conductive film 2 necessary for expressing the conductivity as compared with the graphite oxide particles having a small shape anisotropy. The content rate of the graphite oxide particles can be reduced, the resulting detachment of the graphite oxide particles from the conductive film 2 can be suppressed, and the transparency of the conductive film 2 can be increased.

  When the shape of the graphite oxide particles is flat, the average particle size of the graphite oxide particles is preferably 100 nm or more, and the average thickness is preferably 0.4 nm to 100 nm. In particular, the average thickness is more preferably 0.4 nm to 10 nm. In this case, the number of basic layers in the graphite oxide is very small, the average thickness is thin, the reduction is easy, and the shape anisotropy is remarkably high, so that the conductive film 2 is made conductive. It becomes possible to reduce the content rate of the graphite oxide particles in the conductive film 2 necessary for this. For this reason, high transparency is obtained for the conductive film 2 and the detachment of the graphite oxide particles from the conductive film 2 can be remarkably suppressed.

  The “average particle size” of the graphite oxide particles means the average value of the particle sizes in the plane direction of the graphite oxide particles when the five graphite oxide particles are observed using an optical microscope or an electron microscope. To do. Here, “particle diameter” refers to the length of the longest diagonal line of graphite oxide particles when the graphite oxide particles are observed using an optical microscope or an electron microscope.

  The “average thickness” of the graphite oxide particles refers to the average value of the thicknesses measured for the five graphite oxide particles using an atomic force microscope.

  Next, the graphite oxide particle-containing liquid evaluated as good as described above is usually mixed with a dispersion medium. Thus, a conductor forming liquid containing the graphite oxide particle-containing liquid is prepared (conductor forming liquid preparing step: S104).

  At this time, an appropriate dispersion medium to be mixed with the graphite oxide particle-containing liquid can be selected as necessary. However, when water is used as a solvent used in the purification process, the dispersion medium can be used as a dispersion medium. It is preferable to use since the replacement is unnecessary and the cost can be reduced.

  However, even when water is used as the solvent used in the purification process, it is not always necessary to use water as the dispersion medium. For example, methanol, ethanol, acetone, 2-butanone, or the like, a highly polar liquid having a relative dielectric constant of 15 or more. May be used. As a means for using such a highly polar liquid other than water as the main dispersion medium, a method of diluting by adding a sufficiently large amount of highly polar liquid other than water than the water contained in the original dispersion, other than water And a method of gradually exchanging the dispersion with a highly polar dispersion medium other than water by repeating the removal of the supernatant by centrifugation and decantation after adding the highly polar liquid. It is also possible to use a liquid obtained by mixing several kinds of liquids at an appropriate ratio as a dispersion medium. In this case, a liquid having a relative dielectric constant of less than 15 may be used in part.

  In the conductor forming liquid preparation step, a compound having a reducing action and a polymer material may be further added to the graphite oxide particle-containing liquid in addition to the dispersion medium. Various reducing agents can be used as the compound having such a reducing action. In particular, before removing the dispersion medium by drying the conductor formation liquid, the process of removing the dispersion medium by drying the conductor formation liquid without reducing the oxygen content in the graphite oxide particles by 10 mass% or more. A reducing agent having an action of reducing graphite oxide particles after drying the body-forming liquid and removing the dispersion medium is more preferable.

  Here, whether or not this reducing agent does not reduce the amount of oxygen in the graphite oxide particles by 10 mass% or more before drying the conductor forming liquid and removing the dispersion medium can be measured as follows. it can. That is, first, a liquid consisting only of graphite oxide particles, a reducing agent, and a dispersion medium having the same ratio as the conductor forming liquid was prepared, and the reducing agent was removed after standing at 25 ° C. for 1 hour, and contained in the liquid at this time. Measure the amount of oxygen in the oxidized graphite particles. And the difference of this measured amount of oxygen and the amount of oxygen in the graphite oxide particle measured beforehand in the state which is not made to contact with a reducing agent is calculated. Thus, it can be determined whether the reducing agent does not reduce the oxygen content in the graphite oxide particles by 10 mass% or more.

  In this case, the graphite oxide particles are reduced by the reducing agent after drying the conductor forming liquid and removing the dispersion medium, or after drying the conductor forming liquid and removing the dispersion medium. The deterioration of the dispersion state can be suppressed, and as a result, even if the content of the graphite oxide particles is low, the obtained conductor 100 has higher conductivity. Furthermore, when the reducing agent having the above structure is included in the conductor forming liquid, it is possible to reduce the graphite oxide particles only by heating the conductor forming liquid at a low temperature as compared with the case where the reducing agent is not used. .

  Examples of the reducing agent include hydroquinone, resorcinol, catechol, pyrogallol, gallic acid, L-cysteine, hydroiodic acid, hydrazine, phosphinic acid, citric acid, sodium thiosulfate, ammonium thiosulfate, and hypophosphorous acid. Sodium, polyacrylic acid, L (+) ascorbic acid and the like can be mentioned, among which hydroquinone, pyrogallol, and phosphinic acid are preferably used because higher conductivity is obtained.

  As the polymer material, it is desirable to use a material that is dispersed or dissolved in the dispersion medium. Moreover, the said conductor formation liquid may further contain a binder as needed. In this case, it is preferable to use a material that is dispersed or dissolved in the dispersion medium as the binder. If the polymer material and the binder are materials that are dispersed or dissolved in the dispersion medium, it is possible to easily obtain a conductor forming liquid in which substantially all materials are uniformly dispersed or dissolved.

  Note that if the polymer forming liquid contains a large amount of a polymer material or a binder, an error is likely to occur in the particle size distribution measurement result of the graphite oxide particles. For this reason, rather than measuring and evaluating the particle size distribution of the conductor forming liquid containing a large amount of the polymer material or binder, the polymer material or binder is used in a large amount as performed after the purification step. It is preferable to perform evaluation by measuring the particle size distribution of the liquid containing graphite oxide particles not contained in the sample.

  Examples of the polymer material or binder include inorganic materials such as silica sol and organic silane, polycarbonate resin, polystyrene resin, polyvinyl chloride resin, methacrylic resin, fluororesin, polyimide resin, polyamide resin, polyamideimide resin, and polyvinyl alcohol resin. And organic emulsions in which these materials are dispersed in a suitable solvent.

  Next, the conductor forming liquid obtained as described above is applied onto one surface 1a of the substrate 1 to form a film, and then the conductor forming liquid is dried. Thus, the manufacture of the conductor 100 is completed (film formation step: S105).

  The method of applying the conductor forming liquid is not particularly limited as long as it can be applied onto the one surface 1a of the base material 1. For example, a spin coater method, a bar coater method, a roll coater method or the like may be used. it can.

  Also, the drying of the conductor forming liquid is not particularly limited, and can be performed by a general method.

  The step of drying the conductor forming liquid to remove the dispersion medium or the heating temperature thereafter is preferably 30 ° C to 250 ° C, more preferably 40 ° C to 200 ° C.

  In this way, the conductive film 2 in which graphite oxide particles are dispersed can be obtained on the substrate 1. In addition, when the film | membrane obtained on the base material 1 contains unreduced graphite oxide particles and does not have conductivity, the graphite oxide particles may be partially or completely reduced as necessary. It may be. Examples of the method for reducing the graphite oxide particles include a method of performing a heat treatment at about 200 ° C. on the conductor forming liquid.

  Further, as described above, the graphite oxide particles are partially or completely reduced at a lower temperature as long as the conductor forming liquid contains the reducing agent as described above without performing the heat treatment at a high temperature as described above. The conductive film 2 can obtain higher conductivity.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the graphite oxide particle-containing liquid after the purification process is the object of evaluation, but the graphite oxide particle-containing liquid to be evaluated is not limited to that after the purification process, and the graphite oxide particles Any process may be used as long as the process is thinned. An example of such a process is an ultrasonic treatment process.

In addition to the R ² value, a specific value such as the average particle size or the minimum particle size may be used as an index when comparing the particle size distributions.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to a following example at all.

Example 1
10 g of natural graphite SNO-2 (purity 99.97% by mass or more) manufactured by ESC Corporation, from 7.5 g of sodium nitrate (purity 99%), 621 g of sulfuric acid (purity 96%), and 45 g of potassium permanganate (purity 99%) And then left at about 20 ° C. for 5 days with gentle stirring. The obtained high-viscosity liquid was added to 1000 cm ³ of a 5% by mass sulfuric acid aqueous solution with stirring for about 1 hour, and further stirred for 2 hours. Hydrogen peroxide (30 mass% aqueous solution) 30g was added to the obtained liquid, and it stirred for 2 hours.

  This solution is subjected to centrifugation using a mixed aqueous solution of 3% by mass sulfuric acid / 0.5% by mass hydrogen peroxide, and then purified by repeating the centrifugation using water to disperse the graphite oxide particles in water. A liquid was prepared.

In the middle of the purification, the purified liquid was subjected to particle size distribution measurement of the graphite oxide particle-containing liquid using an ultracentrifugal automatic particle size distribution measuring apparatus CAPA-700 manufactured by HORIBA. The conditions shown in Table 2 below were used for the measurement.

By the above method, particle size distribution measurement was performed by CAPA-700 in the middle of purification, and four types of graphite oxide particle-containing liquids were prepared based on the R ² value being 0.9 or more.

FIG. 5 shows the particle size distribution measurement results of the four types of graphite oxide particle-containing liquids thus produced. The R ² values of run ² to 4 calculated based on run 1 were 0.92 (run 2), 0.91 (run 3), and 0.92 (run 4). The concentration of these four types of dispersions was adjusted to 1.3% by mass, and 13 g of water-based glass squirrel (manufactured by JSR, solid content 40% by mass, water 60% by mass) with respect to 10 g of the dispersion. 0.5 g hydroquinone, 8 g water and 8 g methanol were added and mixed well to obtain a mixed dispersion. Subsequently, this mixed dispersion was designated as No.1. 2 was applied onto glass using a bar coater (application thickness: 4.58 μm) to form a film, and then the dispersion medium was dried and removed. Thereafter, heat treatment was performed at 140 ° C. for 180 minutes. Thus, a conductor having a coating film on glass was obtained.

When the area resistivity of the coating film obtained using the dispersions of run 1 to 4 was examined, the area resistivity was as follows.
When run1 dispersion is used: 1 × 10 ⁹ (Ω / □)
When run2 dispersion is used: 2 × 10 ⁹ (Ω / □)
When run3 dispersion is used: 1 × 10 ⁹ (Ω / □)
When a dispersion of run4 is used: 2 × 10 ⁹ (Ω / □)

(Comparative Example 1)
Four types of aqueous dispersions of graphite oxide particles were prepared in the same manner as in Example 1 except that the particle size distribution measurement by CAPA-700 was not performed, and a coating film was prepared using these dispersions. And when the area resistivity of the coating film obtained from four types of dispersions was examined, the area resistivity was
1 × 10 ⁹ (Ω / □)
1 × 10 ¹⁰ (Ω / □)
5 × 10 ⁹ (Ω / □)
2 × 10 ⁹ (Ω / □)
The resistance variation was large.

  From the results of Example 1 and Comparative Example 1, in Example 1 in which a dispersion prepared in the same manner was evaluated by liquid phase sedimentation type particle size distribution measurement, the reproducibility of the resistance of the conductive film prepared using the same was used. Was found to be expensive.

  Therefore, according to the present invention, it was confirmed that a highly homogenous dispersion can be produced.

It is a side view which shows an example of the conductor manufactured by the manufacturing method of the conductor which concerns on this invention. It is a flowchart which shows the manufacturing method of the conductor which concerns on this invention. It is a graph which shows a particle size distribution when the same sample is measured twice by liquid phase sedimentation type particle size distribution measurement. It is a graph which shows a particle size distribution when liquid phase sedimentation type particle size distribution measurement is performed at each stage of purification. 3 is a graph showing the particle size distribution of graphite oxide particles in four types of graphite oxide particle-containing liquids obtained by the method for producing a graphite oxide particle-containing liquid according to Example 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base material, 2 ... Conductive film, 100 ... Conductor.

Claims (3)

A measurement step of measuring the particle size distribution of the graphite oxide particles in the graphite oxide particle-containing liquid containing the graphite oxide particles using a liquid phase sedimentation type particle size distribution measurement method;
A comparison step of evaluating the graphite oxide particle-containing liquid by comparing the particle size distribution measured in the measurement step with a reference reference particle size distribution;
The evaluation method of the graphite oxide particle containing liquid characterized by including. A thinning process for thinning graphite oxide particles;
An evaluation step of evaluating the graphite oxide particle-containing liquid containing the graphite oxide particles thinned in the thinning step by the method for evaluating a graphite oxide particle-containing liquid according to claim 1,
When the particle size distribution of the graphite oxide particles in the graphite oxide particle-containing liquid evaluated in the evaluation step is not close to the reference particle size distribution, the thinning step and the reference particle size distribution are approximated to the reference particle size distribution. By repeating the evaluation step, a graphite oxide particle-containing liquid having a particle size distribution approximate to the reference particle size distribution is obtained.
A method for producing a graphite oxide particle-containing liquid. A conductor forming liquid preparation step of preparing a conductor forming liquid containing the graphite oxide particle-containing liquid produced by the method for producing a graphite oxide particle-containing liquid according to claim 2;
A film forming step of forming the conductor forming liquid into a film and then drying to form a conductor including a conductive film;
The manufacturing method of the conductor characterized by including.

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