Method for manufacturing electroconductive film, touch panel, and display panel

Abstract

Provided are an organic resin material that makes it possible to uniformly fix an electroconductive carbon material over the entirety of an electroconductive film formation region, a method for manufacturing an electroconductive film using the organic resin material, and a touch panel and a display panel each comprising an electroconductive film manufactured by means of the manufacturing method.　The method comprises: a step (A) for applying an organic resin material containing a polymer obtained by reacting an aliphatic tetracarboxylic acid dianhydride with an aliphatic diamine onto a base material to form an organic resin layer; a step (B) for applying a dispersion liquid containing a dispersant and carbon nanotubes onto the organic resin layer after the step (A) to form a coating film; a step (C) for drying the coating film after the step (B); and a step (D) for depositing a dispersant extraction liquid after the step (C), thereby removing the dispersant from the coating film.

Description

Conductive film manufacturing method, touch panel, display panel

[0001] The present invention relates to a method for manufacturing a conductive film, and also to a touch panel and a display panel.

[0002] In recent years, semiconductor devices have been developed that have electrodes and wiring formed from conductive films of nanocarbon materials. Conventionally, electrodes and wiring in semiconductor devices have often been formed from metals such as copper and aluminum. However, nanocarbon materials, particularly carbon nanotubes (hereinafter sometimes abbreviated as "CNTs"), have attracted considerable attention as semiconductor device materials because they can be constructed much thinner than metal or metal oxide films and exhibit high conductivity. Furthermore, because conductive films formed from nanocarbon materials can be formed into films that exhibit high transparency to visible light, there has been a trend toward their active adoption in semiconductor optical elements.

[0003] In light of the above-mentioned background, various proposals have been made regarding materials and manufacturing methods, particularly for conductive films made of CNTs. For example, Patent Document 1 listed below discloses a composition containing a solvent and CNTs as a composition with improved dispersibility of CNTs.

[0004] JP 2010-214837 A

[0005] However, conductive films made from the above-mentioned compositions have the problem of being prone to aggregation during drying and other processes, resulting in a loss of homogeneity. CNT transparent conductive films exhibit conductivity by forming a circuit through which current flows when fibrous CNTs are folded like nonwoven fabric. Therefore, unlike metal films and metal oxide films, it has been difficult to construct films with stable characteristics, and it has been difficult to achieve stable electrical properties.

[0006] In particular, in semiconductor devices such as LSIs, which are becoming increasingly miniaturized, the wiring width is extremely narrow, so when wiring is formed using a conductive film of CNTs, there are issues such as the formation of wiring that is partially high in resistance or is prone to breakage.

[0007] Furthermore, when used in light-emitting elements, touch panels, and the like, it is necessary to form a conductive film as thin as possible to increase transparency to visible light, and it is also necessary to form a conductive film with high conductivity and uniformity. Even in such cases, similar to semiconductor devices such as LSIs, the problem of conductive film breakage occurs easily. More specifically, for example, when wiring constituting a touch panel is formed with a width of 50 μm or less, or when forming lead wires from contact holes with a width of 50 μm or less when forming pixel electrodes of a display panel, breakage is particularly likely to occur.

[0008] In view of the above problems, the present invention aims to provide an organic resin material that can fix a conductive carbon material evenly over the entire conductive film formation area, as well as a method for manufacturing a conductive film using the organic resin material, and a touch panel and a display panel that include a conductive film manufactured by the manufacturing method.

[0009] The method for producing a conductive film of the present invention includes: a step (A) of applying an organic resin material containing a polymer having structural units derived from an aliphatic tetracarboxylic dianhydride and an aliphatic diamine onto a substrate to form an organic resin layer; a step (B) of applying a dispersion containing a dispersant and carbon nanotubes onto the organic resin layer after performing the step (A) to form a coating film; a step (C) of drying the coating film after performing the step (B); and a step (D) of applying a dispersant extract to remove the dispersant from the coating film after performing the step (C).

[0010] In the above-described production method, the step (D) may be a step of removing the dispersant from the coating film by immersing the substrate in a dispersant extract.

[0011] In the above-mentioned production method, the step (D) may be a step of immersing the dispersant in an extract of the dispersant which is an alkaline aqueous solution.

[0012] In the above-described manufacturing method, the organic resin material may further contain a crosslinking agent.

[0013] In the above production method, the polymer may have a content of structural units derived from the aliphatic tetracarboxylic dianhydride in the range of 70 to 100 parts by mass.

[0014] In the above production method, the polymer may have a content of the structural unit derived from the aliphatic diamine in the range of 70 to 100 parts by mass.

[0015] In the above production method, the aliphatic diamine contained in the polymer may contain an alicyclic diamine.

[0016] In the above-described production method, the step (B) may be a step of applying the dispersant containing an alkali-soluble polymer having one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, and a phenolic hydroxyl group.

[0017] In the above-described manufacturing method, the step (B) may be a step of applying the dispersion liquid containing the dispersant including a polymer having a polyamic acid structure and an organic solvent onto the organic resin layer.

[0018] In the above manufacturing method, the step (B) may be a step of applying the dispersion liquid, in which the content of the dispersant relative to the carbon nanotubes is in the range of 1,000 mass % to 100,000 mass %, onto the organic resin layer.

[0019] The touch panel of the present invention includes a conductive film produced by the above-described manufacturing method.

[0020] The display panel of the present invention comprises a conductive film produced by the above-described manufacturing method.

[0021] According to the present invention, an organic resin material capable of uniformly fixing a conductive carbon material over the entire conductive film formation area is provided, and a method for manufacturing a conductive film using the organic resin material, as well as a touch panel and a display panel equipped with a conductive film manufactured by the manufacturing method, are realized. Furthermore, according to the present invention, the conductive film is less likely to peel from the substrate even when treated with a strong alkaline water such as alkaline development, resulting in less electrical defects. Furthermore, the manufacturing method can form a conductive film that has excellent resistance to organic solvents with high dissolving power, such as N-methylpyrrolidone.

[0022] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments and is not to be construed as limiting the invention.

[0023] The following will first describe the configuration of a display panel 1 as one embodiment, followed by a detailed description of one embodiment of a method for manufacturing a conductive film included in the display panel 1. Then, a verification and evaluation experiment was conducted to confirm the effects of the present invention using one example of the method for manufacturing a conductive film of the present invention, and the details of the verification and evaluation experiment will be described last.

[0024] [Display Panel] The following describes the overall configuration of one embodiment of a display panel 1. Fig. 1 is a schematic diagram showing the overall configuration of one embodiment of the display panel 1. The display panel 1 has a substrate 2, and one surface of the substrate 2 is provided with an element region 2a and a peripheral region 2b.

[0025] The substrate 2 is formed of a light-transmitting material, specifically, for example, a glass substrate, a quartz substrate, or an organic resin substrate. Examples of materials for organic resin substrates include polyimide. The thickness of the organic resin substrate can be set to a few μm to a few tens of μm, making it possible to realize a flexible sheet display.

[0026] The element region 2a is a region where elements for displaying images are formed. In the element region 2a, a lower layer electrode is provided, and an insulating layer is provided on the lower layer electrode. An organic resin layer is provided on the insulating layer, and a conductive film is provided on the organic resin layer.

[0027] Polymers whose main chains or side chains exhibit physical adsorption properties are used as solubilizers that interact with carbon materials such as carbon nanotubes (CNTs) and achieve solvation. Typical examples include conjugated polymers such as poly(paraphenylene vinylene), whose main chains adsorb via π-π interactions, and carboxymethyl cellulose and chitosan, whose main chains rely on CH-π interactions to play an important role.

[0028] The reason why the organic resin layer of the present invention exhibits CNT adhesiveness is believed to be the result of physical adsorption due to CH-π interactions with the aliphatic polyamic acid main chain.

[0029] Furthermore, in the polymer containing structural units derived from an aliphatic tetracarboxylic dianhydride and an aliphatic diamine, the aliphatic tetracarboxylic dianhydride and the aliphatic diamine may be, respectively, a tetracarboxylic dianhydride having an alicyclic structure and a diamine having an alicyclic structure, but the tetracarboxylic dianhydride having an alicyclic structure is preferably an alicyclic tetracarboxylic dianhydride having no linking groups between the alicyclic structures, and the diamine having an alicyclic structure is preferably a diamine having one or more alicyclic structures such as a cyclopentane ring or cyclohexane ring in one molecule, the alicyclic structures being bonded via a linking group such as a methylene group. The reason why the CNT adhesion of these polymers of tetracarboxylic dianhydrides having an alicyclic structure and diamines having an alicyclic structure is improved is not clear, but it is thought to have the effect of increasing the area on which the CNTs and the polymer physically adsorb.

[0030] (In formula (1), A is a tetravalent organic group constituting a tetracarboxylic acid, B is a divalent organic group constituting a diamine, and a is a positive integer.)

[0031] In formula (1), A has a single bond or an alicyclic structure, and B may be a single bond or a structure derived from a diamine having a monoalicyclic structure, or a structure derived from a diamine having one monoalicyclic structure such as a cyclopentane ring or a cyclohexane ring per molecule. A cyclohexane ring is particularly preferred as the monoalicyclic ring. If the cyclohexane ring contains an alkyl group having 1 to 6 carbon atoms, this may affect the adsorption of CNTs. Therefore, from the standpoint of adsorption, it is preferable not to have an alkyl group having 1 to 6 carbon atoms.

[0032] The content of the structural unit derived from the aliphatic tetracarboxylic dianhydride contained in the polymer is preferably 70 to 100 parts by mass, more preferably 80 to 100 parts by mass, in terms of improving the adsorption ability for CNT. Furthermore, the content of the structural unit derived from the aliphatic diamine contained in the polymer is preferably 70 to 100 parts by mass, more preferably 80 to 100 parts by mass, in terms of improving the adsorption ability for CNT. Furthermore, in the polymer, the tetracarboxylic dianhydride preferably has an alicyclic structure, and the diamine preferably has an alicyclic structure.

[0033] The material for the organic resin layer can be synthesized from the above-mentioned tetracarboxylic dianhydride and diamine, each having an alicyclic structure, using a method similar to that used for existing polyamic acids. The material for the conductive film formed from an organic material containing such a polymer is CNT. As for the type of CNT, single-walled carbon nanotubes or multi-walled carbon nanotubes with two or more walls can be used, and single-walled carbon nanotubes are preferred.

[0034] A conductive film made of carbon nanotubes has a transmittance that varies depending on the film thickness, but it is a transparent conductive film that is transparent to visible light.

[0035] The coating film is formed by applying a dispersion containing carbon nanotubes and a dispersant. The dispersant is not particularly limited, but it is preferable to use a polyamic acid having a structural moiety represented by formula (2) in order to improve the dispersibility of the carbon nanotubes.

[0036] (In formula (2), D is a tetravalent organic group constituting a tetracarboxylic acid, E is a divalent organic group constituting a diamine, and b is a positive integer.)

[0037] Specific examples of the tetravalent organic group constituting the tetracarboxylic acid represented by D include pyromellitic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,3,6,7-anthracenetetracarboxylic acid, 1,2,5,6-anthracenetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4-biphenyltetracarboxylic acid, bis(3,4-dicarboxyphenyl)ether, 3,3'4,4'-benzophenonetetracarboxylic acid, bis(3,4-dicarboxyphenyl)sulfone, bis(3,4-dicarboxyphenyl)methane, 2,2-bis(3,4-dicarboxyphenyl)propane, 1,1,1,3,3,3-hexafluoro-2,2- Examples of suitable tetracarboxylic acid dianhydrides include aromatic tetracarboxylic acid dianhydrides such as bis(3,4-dicarboxyphenyl)propane, bis(3,4-dicarboxyphenyl)dimethylsilane, bis(3,4-dicarboxyphenyl)diphenylsilane, 2,3,4,5-pyridinetetracarboxylic acid, and 2,6-bis(3,4-dicarboxyphenyl)pyridine; alicyclic tetracarboxylic acid dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 2,3,5-tricarboxycyclopentylacetic acid, and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic acid; and aliphatic tetracarboxylic acid dianhydrides such as 1,2,3,4-butanetetracarboxylic acid. These tetracarboxylic acid dianhydrides may be used alone or in combination.

[0038] Specific examples of the divalent organic group constituting the diamine represented by E include p-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, diaminodiphenylmethane, diaminodiphenyl ether, 2,2'-diaminodiphenylpropane, bis(3,5-diethyl-4-aminophenyl)methane, diaminodiphenyl sulfone, diaminobenzophenone, diaminonaphthalene, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 1,3-bis(4-aminophenyl)anthracene ... Examples of suitable diamines include aromatic diamines such as bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)diphenyl sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-aminophenyl)hexafluoropropane, and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane; alicyclic diamines such as bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclohexyl)methane, and cholestanyl 3,5-diaminobenzoate; aliphatic diamines such as 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, and 1,6-diaminohexane; and silicon diamines such as 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane. These diamines may be used alone or in combination.

[0039] Furthermore, D in the above formula (5) is preferably a cyclobutane ring, which is preferable because the ring structure is decomposed by light irradiation or heating, causing a structural change in the polyamic acid, making it easier to remove the dispersant. Furthermore, the above dispersion may contain an organic solvent as a dispersion medium.

[0040] [Manufacturing Method] A method for manufacturing a conductive film will be described with reference to Figures 2 to 4. Figures 2 to 4 are drawings that schematically show the steps of forming a conductive film. In the method for manufacturing a conductive film of this embodiment, a conductive film is formed on an insulating layer formed on a substrate.

[0041] As shown in FIG. 2, an organic resin material containing a polymer having a hydrocarbon group is applied onto the substrate 2 on which the insulating layer 10 has been formed, to form an organic resin layer 20 (corresponding to step (A)).

[0042] As shown in Fig. 3, a dispersion liquid containing CNTs is applied onto the organic resin layer 20 to form a pattern of a coating film 30 (corresponding to step (B)). For convenience, Fig. 3 illustrates the coating film 30 as if it were formed over the entire surface of the organic resin layer 20.

[0043] In this step, a pattern is formed by a coating film of a dispersion liquid containing CNTs on the organic resin layer 20 using a printing technique such as casting, screen printing, or inkjet printing. After the pattern is formed, the solvent contained in the coating film is removed by drying, and the CNTs are fixed on the organic resin layer 20 to form a conductive film 40 (corresponding to step (C)), as shown in FIG. 4 .

[0044] For convenience, FIG. 4 shows the conductive film 40 formed over the entire surface of the organic resin layer 20, but the pattern of the conductive film 40 can be adjusted as appropriate.

[0045] After the solvent is removed by drying, a dispersant extract is applied to the conductive film formed on the substrate, and the dispersant is removed from the pattern of the coated film (corresponding to step (D)). In addition to the above-mentioned method of forming a pattern by printing, this step of forming a conductive film pattern can also employ a method in which a dispersion is applied to the entire organic resin layer formed on the substrate, followed by drying and washing, and then a photosensitive resist layer for patterning is separately formed on the conductive film. In this case, after the photosensitive resist layer is formed, the conductive layer is removed by etching, and the remaining photosensitive resist layer is also removed.

[0046] While any combination of dispersant and dispersant extract may be used, it is preferable to use an alkali-soluble polymer having a functional group that improves solubility in an alkaline aqueous solution as the dispersant, and an alkaline aqueous solution as the dispersant extract. By using an alkaline aqueous solution as the dispersant extract, it becomes possible to selectively leave CNTs that are difficult to disperse in an alkaline aqueous solution on the organic resin layer.

[0047] Furthermore, by using such an alkali-soluble polymer in the process, it is possible to share materials with other processes using photosensitive resist layers that similarly use an alkaline aqueous solution for development, thereby significantly improving productivity.

[0048] As the alkaline aqueous solution, for example, an aqueous solution of KOH (potassium hydroxide), NaOH (sodium hydroxide), sodium carbonate, or TMAH (tetramethylammonium hydroxide) can be suitably used.

[0049] Furthermore, these dispersants may contain a molecular structure that reacts with light or heat to decompose or undergo a structural change, thereby improving the solubility in an alkaline aqueous solution. By using such a dispersant and applying light or heat after forming a conductive film, the solubility is improved, and then a dispersant extract is applied, thereby further improving the efficiency with which the dispersant is removed from the pattern formed by the coated film.

[0050] As a molecular structure exhibiting such a function, for example, the polyamic acid structure of the dispersant may contain a moiety such as cyclobutane that can be decomposed by light or heat to change the entire structure of the polyamic acid. The dispersant may also contain an acid-dissociable group. The acid-dissociable group is a group that generates an acidic group such as a carboxyl group or a phenolic hydroxyl group upon the action of an acid.

[0051] Examples of the acid-dissociable group include a group having a t-butoxy structure and a group having an acetal structure. The acid that acts on the acid-dissociable group is an acid generated from an acid generator that generates acid when exposed to light or heat. Therefore, the dispersion contains an acid generator together with a dispersant having an acid-dissociable group.

[0052] The conductive film formed on the organic material layer can be formed through the following steps.

[0053] The method for applying the CNT-containing composition can be any suitable method, such as spray coating, roll coating, rotary coating (spin coating), slit die coating (slit coating), bar coating (bar coating), solution immersion, ink jetting, etc. The conductive film is formed to a constant thickness by a predetermined method.

[0054] The CNT-containing composition to be applied onto the organic material layer preferably has a dispersant content relative to the CNT in the range of 1,000 to 100,000 mass %. By having the dispersant content relative to the CNT within this range, non-uniformity of the solvent during the drying step is prevented, and the aggregation and localization of the CNTs that accompanies drying is suppressed.

[0055] In order to improve the purity of the conductive film, it is preferable to perform a baking process to remove the solvent or a solution immersion process to remove the dispersant. Among the above-mentioned coating methods, the slit die coating method or the inkjet method is preferable from the viewpoint of the uniformity of the coating film thickness and the liquid saving. Furthermore, the inkjet method is more preferable from the viewpoint of being able to pattern the electrode by coating alone.

[0056] By employing the above-described method for forming a conductive film, the conductive film formed on the organic resin layer exhibits unique electrical properties, has excellent adhesion to the organic resin layer, and also has good chemical resistance and flatness.

[0057] Furthermore, because the CNTs contained in the coating film exhibit high adhesion to the organic resin layer, they are prevented from localizing due to solvent aggregation during the drying process. Furthermore, even during the solution immersion process for removing the dispersant, CNT peeling and aggregation do not occur, and localization of the CNTs is prevented. Therefore, even when forming wiring with a very narrow pattern width, localized high-resistance areas and disconnections are unlikely to occur.

[0058] The method for manufacturing a conductive film of this embodiment includes forming an insulating layer on a substrate, forming an organic resin layer after the insulating layer is formed, and forming a conductive film made of CNTs on the organic resin layer.

[0059] Furthermore, the CNTs contained in the dispersion preferably include at least one of single-walled nanotubes and multi-walled nanotubes. According to this method for producing a conductive film, a semiconductor device can be formed in which the adhesion between the organic resin layer and the conductive film is even better. Furthermore, the production yield is also improved.

[0060] Furthermore, the above-described method for manufacturing a conductive film can be applied not only to the manufacture of the display panel 1 but also to the manufacture of a transparent conductive film used in a touch panel.

[0061] The organic resin layer can be formed using a radiation-sensitive composition for forming an organic resin layer through the steps shown below. The organic resin layer formed by this formation method exhibits unique electrical properties, excellent adhesion to CNTs, and good chemical resistance and flatness. Furthermore, this formation method involves heating at 140°C or less, thereby suppressing thermal degradation of the substrate and elements attached to the substrate. Each step is described in detail below.

[0062] [Step (1)] In this step, a coating film is formed on an insulating layer using the radiation-sensitive composition. Specifically, the radiation-sensitive composition is applied to the surface of the insulating layer to form a coating film of the radiation-sensitive composition. In addition, in order to remove the solvent contained in the coating film, a pre-bake treatment is preferably performed in this step.

[0063] The radiation-sensitive composition can be applied by any suitable method, such as spraying, roll coating, rotary coating (spin coating), slit die coating, bar coating, or inkjet coating. Among these, inkjet coating is preferred. Prebaking conditions vary depending on the types and proportions of each component, but can be, for example, 60°C to 130°C for approximately 30 seconds to 10 minutes. The thickness of the coating film formed after prebaking is preferably 0.1 μm to 5 μm, more preferably 0.1 μm to 1 μm, and even more preferably 0.2 μm to 0.4 μm.

[0064] [Step (2)] In this step, a part of the coating film is irradiated (exposed) to radiation. Specifically, the coating film formed in step (1) is irradiated with radiation through a mask having a predetermined pattern. Depending on the pattern of the mask used, it is possible to form patterns such as contact hole formation, line and space formation, etc.

[0065] The radiation used here may be, for example, ultraviolet light, far ultraviolet light, X-rays, charged particle beams, etc. The mask used may be a multi-tone mask such as a halftone mask or a gray-tone mask.

[0066] Examples of ultraviolet rays include g-rays (wavelength 436 nm), i-rays (wavelength 365 nm), and KrF excimer laser light (wavelength 248 nm). Examples of X-rays include synchrotron radiation. Examples of charged particle beams include electron beams. Of these types of radiation, ultraviolet rays are preferred, and ultraviolet rays with a wavelength of 200 nm or more and 380 nm or less are more preferred. The radiation exposure dose is 1,000 J / m ２ ~20,000J / m ２ is preferred.

[0067] In some cases, post-exposure baking (PEB) may be performed after the exposure.

[0068] [Step (3)] In this step, the irradiated coating film is developed. Specifically, the coating film irradiated in step (2) is developed with a developer to remove the irradiated portions. Examples of the developer that can be used include an alkaline aqueous solution in which potassium hydroxide, sodium carbonate, triethanolamine, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, or the like is dissolved in water, and organic solvents such as ethanol, isopropyl alcohol, acetone, ethyl acetate, and butyl acetate.

[0069] The developing method may be, for example, a puddle method, a dipping method, a swing immersion method, a shower method, etc. The developing time varies depending on the formulation of the radiation-sensitive composition, but may be, for example, 30 to 120 seconds.

[0070] [Step (4)] In this step, the coating film obtained after step (3) can be heated. The coating film is cured by heat treatment (post-baking) using a heating device such as a hot plate or an oven.

[0071] The upper limit of the heating temperature in this step is 140° C., and the heating temperature may be 130° C., 125° C., or 115° C. According to this formation method, the coating film can be formed into a good shape even by heating at such a relatively low temperature.

[0072] [Synthesis Example] A verification and evaluation experiment was carried out to confirm whether the organic resin film containing a polymer derived from a tetracarboxylic dianhydride and an aliphatic diamine according to the present invention allows CNTs applied to a substrate to be firmly and uniformly fixed to the conductive film formation region, and the results are described below.

[0073] Synthesis of polymer containing structural units derived from aliphatic tetracarboxylic dianhydride and aliphatic diamine <Synthesis of polymer> 1. Synthesis of polyamic acid [Synthesis Example 1] <Aliphatic tetracarboxylic dianhydride>

[0074] Aromatic tetracarboxylic dianhydride

[0075] Aliphatic diamines

[0076] <Aromatic ring-containing diamine>

[0077] <Imidization Auxiliary Agent>

[0078] Cross-linking agent

[0079] 100 parts by mole of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (TA-1) as a tetracarboxylic dianhydride and 100 parts by mole of 1,3-bis(aminomethyl)cyclohexane (DA-1) as a diamine compound were dissolved in N-methyl-2-pyrrolidone (NMP) and reacted at room temperature for 6 hours to obtain a solution containing 15% by mass of polyamic acid (referred to as polymer (PA-1)). The solution was further diluted with NMP and butyl cellosolve in a ratio of 8:2, and a crosslinking agent (B-1) was added to obtain a 2% by mass solution of polyamic acid (referred to as organic resin film solution (SL-1)).

[0080] Synthesis Examples 2 to 24 The same operation as in Synthesis Example 1 was carried out, except that the types of tetracarboxylic dianhydride and diamine compound used were changed as shown in Table 1, to obtain polyamic acid solutions (polymers (PA-2) to (PA-14)).

[0081]

[0082] 2. Preparation and Evaluation of CNT-Containing Dispersion Composition (1) Preparation of Dispersion Composition

[0083] 100,000 parts by mass of NMP as a solvent was added to a vessel containing 10 parts by mass of single-walled carbon nanotubes (SWNTs) and 1,000 parts by mass of the polymer (paa-1) obtained in Synthesis Example 1 as a dispersant. Next, ultrasonic dispersion was carried out for 60 minutes to prepare a dispersion composition (S-1).

[0084] (2) Formation of Conductive Film Substrate SL-1 was applied to a glass substrate by spin coating (setting conditions: 1500 rpm, rotation time: 20 seconds). Next, the substrate was heated on a hot plate (100°C x 1 min) and then dried in an oven (200°C x 30 min) to form an organic resin film.

[0085] CNT dispersion S-1 was applied to a glass substrate having an organic resin film by spin coating (setting conditions: 500 rpm, rotation time: 30 seconds) and dried for 10 minutes on a hot plate at 80°C to form a multilayer coating film consisting of an organic resin film and a mixed film of CNT and dispersion material. The thickness of this multilayer coating film was 0.1 µm at the center of the glass substrate.

[0086] The glass substrate was immersed in a petri dish filled with a 5 wt% aqueous solution of sodium hydroxide for 1 minute to extract and remove the dispersed material from the laminated coating film. The glass substrate was then removed and air was used to blow off any remaining liquid on the substrate, and it was then dried on a hot plate at 110°C for 1 minute to obtain a conductive film substrate with only CNTs present on the organic resin film.

[0087] (3) Evaluation of NMP Resistance of Organic Resin Layer The dispersion composition (S-1) obtained in (1) above was applied by spin coating onto an organic resin layer formed from the organic resin film solutions (SL-1) to (SL-39), and dried on a hot plate at 80°C for 10 minutes to form a coating film having a thickness of 0.1 μm at the center of the substrate. This coating film was observed under a microscope at 50x magnification to check for the presence or absence of areas where the formed organic resin layer and S-1 were compatible and unevenness had occurred. The evaluation was as follows: "Excellent (◎)" when no unevenness was observed, and "Good (○)" when slight unevenness was observed. The evaluation was as follows: "Poor (×)" when unevenness occurred throughout the coating film. The results are shown in Table 2 below.

[0088] (4) Evaluation of Dispersion Extract Resistance of Organic Resin Layer The dispersion composition (S-1) obtained in (1) above was applied by spin coating onto the organic resin layer formed from the organic resin film solutions (SL-1) to (SL-39), and dried on a hot plate at 80 ° C. for 10 minutes to form a coating film with a film thickness of 0.1 μm at the center of the substrate. The glass substrate was immersed in a petri dish filled with a 5 wt % aqueous sodium hydroxide solution for 1 minute to extract and remove the dispersion material from the laminated coating film. The surface of the obtained CNT film was then observed under a microscope, and if the formed organic resin layer was dissolved by the dispersion extract and unevenness or cloudiness occurred, it was rated as poor (×), if slight unevenness was observed it was rated as good (◯), and if no unevenness was observed it was rated as excellent (◎).

[0089] (5) Evaluation of CNT Adhesion on Organic Resin Film The surface resistivity (Ω / □) of the obtained CNT film was measured using Loresta GP (manufactured by Mitsubishi Chemical Analytical).

[0090] When the amount of CNT adhered to the organic resin film is large, the surface resistivity value becomes small. 5 If the value is less than Ω / □, it is marked as "Good"; if it is less than 10 6 Ω / □ to 10 7 When the value of Ω / □ is shown, it is marked as "△", and when the value of Ω / □ is shown, it is marked as "△". 5 Ω / □ or less and 10 6 Ω / □ to 10 7 If the Ω / □ values ​​are mixed, it is marked as "Good" or "Poor." If the value is outside the measurable range of the Loresta GP and no value is obtained (10 8 A high resistance value of 0.1Ω / □ or more was marked "X." The results are shown in Table 2 below.

[0091] (6) Overall Judgment The overall judgment was "poor (x)" if the NMP resistance of the organic resin layer was "poor (x)", or the dispersion extract resistance was "poor (x)", or the CNT adhesion was "poor (x)", and in other cases, the judgment was made based on the same criteria as for the CNT adhesion.

[0092]

[0093] 1: Display panel 2: Base material 2a: Element region 2b: Peripheral region 10: Insulating layer 20: Organic resin layer 30: Coating film 40: Conductive film

Claims

1. A method for producing a conductive film, comprising: a step (A) of applying an organic resin material containing a polymer having structural units derived from an aliphatic tetracarboxylic dianhydride and an aliphatic diamine onto a substrate to form an organic resin layer; a step (B) of applying a dispersion containing a dispersant and carbon nanotubes onto the organic resin layer after the step (A) to form a coating film; a step (C) of drying the coating film after the step (B); and a step (D) of removing the dispersant from the coating film by applying a dispersant extract after the step (C).

2. The method for producing a conductive film according to claim 1, wherein the step (D) is a step of removing the dispersant from the coating film by immersing the substrate in a dispersant extract.

3. The method for producing a conductive film according to claim 2, wherein the step (D) comprises immersing the substrate in an extract of the dispersant which comprises an alkaline aqueous solution.

4. The method for producing a conductive film according to claim 1, wherein the organic resin material further contains a crosslinking agent.

5. The method for producing a conductive film according to claim 1, wherein the polymer has a content of structural units derived from the aliphatic tetracarboxylic dianhydride in the range of 70 to 100 parts by mass.

6. The method for producing a conductive film according to claim 1, wherein the polymer has a content of structural units derived from an aliphatic diamine in the range of 70 to 100 parts by mass.

7. The method for producing a conductive film according to claim 1, wherein the aliphatic diamine contained in the polymer contains an alicyclic diamine.

8. The method for producing a conductive film according to claim 1, wherein the step (B) comprises applying the dispersant containing an alkali-soluble polymer having one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, and a phenolic hydroxyl group.

9. The method for producing a conductive film according to claim 1, wherein the step (B) comprises applying the dispersion liquid containing the dispersant including a polymer having a polyamic acid structure and an organic solvent onto the organic resin layer.

10. A method for producing a conductive film as described in claim 1, wherein the step (B) involves applying the dispersion liquid onto the organic resin layer, the content of the dispersant relative to the carbon nanotubes being within the range of 1,000% by mass to 100,000% by mass.

11. A touch panel comprising a conductive film produced by the manufacturing method according to any one of claims 1 to 10.

12. A display panel comprising a conductive film produced by the method according to any one of claims 1 to 10.

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