Collection filter and method for manufacturing transparent conductive film using same

Abstract

To provide a collection filter which enables manufacture of a transparent conductive film having low resistance.SOLUTION: A collection filter 1 includes a filter film 11 which has one surface, and has a porous structure for filtering a nanocarbon material from a dispersion medium containing a nanocarbon material, and a dense film 12 formed with an opening 12a for passing a dispersion medium therethrough. The opening 12a is formed in such an inverse tapered shape that a first width Wa on the inlet side of the dispersion medium opposite to the filter film 11 is smaller than a second width Wb on the bottom side as the filter film 11 side.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a collection filter made of a nanocarbon material such as carbon nanotubes (hereinafter referred to as CNTs), and a method for producing a transparent conductive film using the same. [Background technology]

[0002] Patent Document 1 discloses a structure that can achieve high transmittance and low resistance in a transparent conductive film in which a CNT pattern is formed on a transparent substrate. In this structure, CNTs are collected by filtering a dispersion medium using a CNT aerosol or dispersion liquid, and then the collected CNTs are transferred to a transparent substrate to produce a transparent conductive film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-44839 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 does not describe the detailed structure of the filter for filtering CNTs. However, as a result of intensive research by the present inventors, it was confirmed that simply forming openings in the filter for storing CNTs does not reduce the resistance of CNTs. Specifically, when openings are simply formed in the filter by photolithography, the sidewalls of the openings are perpendicular to the filter surface or have a forward tapered shape, with the opening dimensions larger upstream and smaller downstream in the dispersion medium supply channel. When CNTs are collected using a filter with openings of this shape, the internal pressure of the collection chamber fluctuates, changing the CNT synthesis conditions. As a result, the CNTs do not properly penetrate the openings, resulting in inconsistent CNT quality and variability, making it impossible to reduce the resistance of the transparent conductive film.

[0005] In view of the above, an object of the present invention is to provide a collection filter that enables the production of a low-resistance transparent conductive film, and a method for producing a transparent conductive film using the same. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the collection filter described in claim 1 has a filter membrane (11) having one surface and a porous structure that filters nanocarbon material from a dispersion medium containing nanocarbon material, and a dense membrane (12) formed on the one surface, having an opening (12a) that allows the dispersion medium to pass through and having a density that blocks the passage of the dispersion medium in a portion different from the opening, and the opening has a first width (Wa) on the inlet side for the dispersion medium opposite the filter membrane that is smaller than a second width (Wb) on the bottom side that is on the filter membrane side.

[0007] In this way, in a collection filter having a dense film with openings on one side of the filter membrane, the openings have an inverted tapered shape with a first width smaller than a second width. By using such a collection filter, fluctuations in the internal pressure of the chamber where the nanocarbon material is collected can be suppressed, and changes in the synthesis conditions of the nanocarbon material can be suppressed. This makes it possible to reduce the resistance of the pattern made of nanocarbon material.

[0008] The method for manufacturing a transparent conductive film described in claim 6 uses a collection filter to manufacture a transparent conductive film including a pattern (22) composed of a nanocarbon material (20), and includes the steps of: placing the collection filter in a chamber into which a dispersion medium containing the nanocarbon material is supplied, with the dense film side facing upstream in the dispersion medium supply path and the filter film side facing downstream in the dispersion medium supply path; collecting the nanocarbon material in an opening by supplying the dispersion medium into the chamber and passing the dispersion medium through the collection filter; after collecting the nanocarbon material, placing a transparent substrate (21) on the dense film side of the collection filter; and removing the collection filter from the transparent substrate to transfer the nanocarbon material to the transparent substrate and form a pattern (22) with the nanocarbon material.

[0009] In this way, a collection filter with an inverted tapered opening formed in the dense film is used, and by passing a dispersion medium through the collection filter, nanocarbon materials can be collected within the openings. At this time, the collected nanocarbon material and the dense film are not in close contact with each other, reducing the contact area between the dense film and the carbon material. Therefore, even when the carbon material is collected, the dispersion medium can pass through the gaps between the carbon material and the dense film, preventing an increase in pressure loss in the collection filter. This suppresses fluctuations in the internal pressure of the chamber used to collect the carbon material, stabilizing the synthesis conditions for the carbon material and enabling stable quality and low resistance of patterns made of carbon material.

[0010] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0011] [Figure 1A] 1 is a cross-sectional view of a collection filter according to a first embodiment. FIG. [Figure 1B] FIG. 2 is a scanning electron microscope (SEM) image of the collection filter according to the first embodiment. [Figure 2A] 5A to 5C are cross-sectional views showing a manufacturing process of the collection filter. [Figure 2B] 2B is a cross-sectional view showing the manufacturing process of the collection filter following FIG. 2A. [Figure 2C] 2C is a cross-sectional view showing the manufacturing process of the collection filter following FIG. 2B. [Figure 2D] 2D is a cross-sectional view showing the manufacturing process of the collection filter following FIG. 2C. [Figure 2E] 2D. FIG. [Figure 3A] 1A to 1C are cross-sectional views showing a manufacturing process of a transparent conductive film using a collection filter. [Figure 3B] 3B is a cross-sectional view showing the manufacturing process of the transparent conductive film subsequent to FIG. 3A. FIG. [Figure 3C] 3C is a cross-sectional view showing the manufacturing process of the transparent conductive film subsequent to FIG. 3B. [Figure 3D] 3D is a cross-sectional view showing the manufacturing process of the transparent conductive film subsequent to FIG. 3C. [Figure 3E] FIG. 3E is a cross-sectional view showing the manufacturing process of the transparent conductive film subsequent to FIG. 3D. [Figure 4A] FIG. 10 is a cross-sectional view showing how CNTs are captured when the openings of the dense film have a forward tapered shape. [Figure 4B] FIG. 4B is a cross-sectional view showing the state of capturing CNTs following FIG. 4A. [Figure 5A] FIG. 10 is a diagram showing how CNTs are captured when the openings of the dense film have an inverse tapered shape. [Figure 5B] FIG. 5B is a cross-sectional view showing the state of capturing CNTs following FIG. 5A. [Figure 6] FIG. 10 is a diagram showing the relationship between the CNT collection time and the pressure ratio when the openings of the dense film are inversely tapered and when the openings are forwardly tapered. [Figure 7] FIG. 10 is a diagram showing the results of measuring the sheet resistance of a CNT pattern when the openings in the dense film are inversely tapered and when they are forwardly tapered. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, parts that are identical or equivalent to each other will be denoted by the same reference numerals.

[0013] (First embodiment) A first embodiment will be described. In this embodiment, a collection filter suitable for manufacturing a transparent conductive film having a CNT pattern that can be applied to a heater or the like, and a method for manufacturing a transparent conductive film having a CNT pattern using the same will be described.

[0014] As shown in FIGS. 1A and 1B, the collection filter 1 has a configuration in which a patterned dense film 12 is provided on a filter film 11.

[0015] The filter membrane 11 is a membrane filter made of a porous material capable of filtering CNTs from a dispersion medium such as an aerosol, which serves as a gaseous dispersion medium containing CNTs, or a colloidal solution, which serves as a liquid dispersion medium. The filter membrane 11 has an air permeability, i.e., the time required for a specified volume of air to pass through per unit area and unit pressure difference, of 20 seconds or less. High air permeability increases the internal pressure of the chamber during the production of a transparent conductive film with a CNT pattern. Therefore, an air permeability of 20 seconds or less is preferable to keep the internal pressure at a certain level. For example, polyimide can be used as the filter membrane 11. While the filter membrane 11 can also be made of materials other than polyimide, polyimide is preferable considering the processability during patterning of the dense film 12, which will be described later. Specifically, during photolithography for patterning the dense film 12, excessive light reflection from the underlying filter membrane 11 results in exposure in areas other than the desired location, resulting in poor processability. However, using polyimide reduces reflection and enables accurate exposure. This makes it possible to form the dense film 12 in a precise pattern. The thickness of the filter film 11 is set so that it can capture CNTs and obtain the above-mentioned air permeability, and when the filter film 11 is made of polyimide, it is set to, for example, 20 to 200 μm. When a dispersion medium containing CNTs is passed through the filter film 11, the CNTs are filtered by the filter film 11, and the CNTs can be left on the surface of the filter film 11.

[0016] The dense film 12 is a film in which openings 12a of a desired pattern are formed. The dense film 12, apart from the openings 12a, is made of a dense material that blocks the passage of the CNT-containing dispersion medium used to manufacture the CNT pattern, such as a dry film resist or a thin metal film. The openings 12a are formed by photoetching the dense film 12 and have a shape corresponding to the shape of the CNT pattern to be manufactured. For example, the CNT pattern can be a stripe-like pattern in which multiple straight lines are arranged in parallel at equal intervals. The width of the openings 12a, i.e., the dimension in the direction perpendicular to the longitudinal direction of each line of the CNT pattern on the plane of the dense film 12, is such that a first width Wa on the inlet side opposite the filter film 11 is narrower than a second width Wb on the bottom side facing the filter film 11. Therefore, in a cross section along the width direction as shown in Figures 1A and 1B, the openings 12a have an inverted tapered shape that gradually widens from the inlet side toward the bottom side.

[0017] Specifically, the first width Wa and the second width Wb are set so as to satisfy the relationship that the ratio of the second width Wb to the first width Wa is greater than 1 and less than 2.

[0018] The reason for setting an upper limit to the ratio of the second width Wb to the first width Wa is that if the dense film 12 protrudes too much inward from the openings 12a on the side opposite the filter film 11, the openings 12a will be crushed on the inlet side, causing the first width Wa to change. In particular, when the collection filter 1 is used repeatedly, the inlet side of the openings 12a will be crushed, making it impossible to accurately form the desired CNT pattern. For this reason, the ratio of the second width Wb to the first width Wa is set to be less than 2. However, the upper limit of the ratio of the second width Wb to the first width Wa is not necessarily limited to being less than 2, as it depends on the required accuracy of the CNT pattern and the durability of the dense film 12.

[0019] The upper limit of the first width Wa is arbitrary, but if it is too large, the effect of forming the opening 12a in an inverted tapered shape, as described below, will be reduced. Therefore, it is recommended to set it to 50 μm or less, preferably 10 μm or less, which will enable high light transmittance. The lower limit of the first width Wa is also arbitrary, but depends on the manufacturing limitations of the opening 12a. The manufacturing limitations of the opening 12a depend on the material of the dense film 12. For example, if the dense film 12 is made of a dry film, the first width Wa can be set to approximately 5 μm. Depending on the material of the dense film 12, the first width Wa can also be set to approximately 2 μm.

[0020] Although the first width Wa on the inlet side and the second width Wb on the bottom side of the opening 12a have been described, the opening 12a can be said to have an inverted tapered shape as long as the first width Wa is less than the second width Wb. The shape of the sidewall of the opening 12a is not critical. For example, the sidewall of the opening 12a may be flat from the inlet side to the bottom side, and the width of the opening 12a may change at a constant rate along the thickness of the dense film 12. Alternatively, the sidewall of the opening 12a may be curved from the inlet side to the bottom side, and the rate at which the width of the opening 12a increases or decreases from the inlet side to the bottom side may be gradually increased or decreased. Alternatively, the sidewall of the opening 12a may be uneven from the inlet side to the bottom side, and the unevenness may be randomly formed from the inlet side to the bottom side.

[0021] The thickness of the dense film 12 is also arbitrary. However, it is desirable to form a thick film to reduce the resistance of the CNT pattern, and the lower limit of the thickness of the dense film 12 is set to, for example, 5 μm, and the thickness is preferably greater than that, and a thick film of 10 μm or more is more preferable. The upper limit of the thickness of the dense film 12 is preferably set to 50 μm or less, taking into consideration the processing accuracy by photoetching when forming the openings 12 a in the dense film 12.

[0022] Furthermore, the aspect ratio of the opening 12a, i.e., the ratio of the depth D to the first width Wa on the inlet side of the opening 12a, is determined by the film thickness of the dense film 12. When the aspect ratio of the opening 12a is set to 0.1 or more to form a thick CNT film, if the opening 12a has a forward tapered shape, the internal pressure of the chamber where the CNTs are collected is likely to fluctuate, and the CNT synthesis conditions are likely to change. This results in unstable CNT quality and variations, making it impossible to achieve low resistance. For reasons that will be explained later, even with such a high aspect ratio, by making the opening 12a reverse tapered, fluctuations in the internal pressure of the chamber where the CNTs are collected can be suppressed, thereby suppressing changes in the CNT synthesis conditions. Therefore, it is possible to stabilize the quality of CNTs and achieve low resistance, even with a high aspect ratio.

[0023] Next, a method for manufacturing a transparent conductive film having a CNT pattern using the collection filter 1, including a method for manufacturing the collection filter 1 of this embodiment configured as described above, will be described with reference to FIGS. 2A to 2E and 3A to 3E.

[0024] First, as shown in FIG. 2A, a filter film 11 is prepared. As described above, polyimide or the like is used for the filter film 11. Next, as shown in FIG. 2B, a roll coater 100 is prepared, which includes an application roller 100b and a transport roller 100c, on whose surface a film-like resist material 100a is disposed. The filter film 11 is then passed through the roll coater 100. As a result, as shown in FIG. 2C, a dry film resist 13 is applied to one side of the filter film 11. The thickness of the applied dry film resist 13 is arbitrary, but as described above, it is preferable that the thickness be 10 μm or more.

[0025] Next, as shown in Figures 2D and 2E, a photolithography-etching process is performed to pattern the dry film resist 13 to form openings 12a, thereby obtaining a dense film 12. Specifically, as shown in Figure 2D, an exposure mask 101 such as a metal mask is prepared, and the exposure mask 101 is placed on the dry film resist 13. The exposure mask 101 is then irradiated with i-line light to expose the dry film resist 13 at the locations where the openings 12a are to be formed. Then, as shown in Figure 2E, the exposed areas are removed by etching, thereby obtaining a dense film 12 in which the openings 12a have been formed.

[0026] At this time, the opening 12a is made to have an inverse tapered shape based on the exposure conditions and development conditions. For example, the exposure conditions are set to 70 mJ / cm 2 The exposure dose is increased by increasing the exposure time, or the development time is lengthened to 1 minute. Furthermore, since the diffuse reflection conditions of the filter film 11 are factors that determine the shape of the opening 12a, the diffuse reflection conditions of the filter film 11 are also selected so that the opening 12a has an inverse tapered shape. As described above, when the filter film 11 is made of polyimide, the diffuse reflection conditions can also be optimized. In this way, the opening 12a can have an inverse tapered shape.

[0027] 2D and 2E show an example of a positive type in which the exposed portion is removed, but a negative type in which the exposed portion remains may also be used. In this case, the position where the opening 12a is to be formed is masked, and the other portions are exposed to light. Here, the dense film 12 is made of a dry film resist 13, but if it is made of a metal thin film, the opening 12a can be made to have an inverse tapered shape by setting the exposure conditions and development time for the metal thin film. For example, if the metal thin film is to have an inverse tapered shape, the exposure conditions can be set to 70 mJ / cm 2 In other words, the development time is longer than when a forward tapered shape is used.

[0028] In this way, the collection filter 1 having the dense membrane 12 disposed on one side of the filter membrane 11 can be manufactured.

[0029] The collection filter 1 is then placed in a chamber (not shown) that can supply CNTs. This chamber can supply a dispersion medium, such as an aerosol (gas-phase dispersion medium containing CNTs) or a colloidal solution (liquid-phase dispersion medium), and CNTs can be collected by passing the dispersion medium through the collection filter 1. Specifically, the chamber is equipped with an installation stand with a passage corresponding to the collection filter 1. The collection filter 1 is placed on this installation stand with the dense membrane 12 side of the collection filter 1 facing upstream of the dispersion medium supply path and the filter membrane 11 side facing downstream of the dispersion medium supply path. When the collection filter 1 is placed on the installation stand, the collection filter 1 separates the space upstream from the space downstream of the dispersion medium supply path, allowing the dispersion medium containing CNTs to pass through the opening 12a of the collection filter 1. Therefore, when a dispersion medium containing CNTs is supplied into the chamber with the collection filter 1 installed, CNTs 20 are collected within the opening 12a, as shown in Figure 3A.

[0030] The collection may be stopped when the CNTs 20 have been collected until the opening 12a is filled, but if the collection is continued further, the CNTs 20 will be collected so that they protrude outside the opening 12a, forming a T-shaped CNT pattern.

[0031] Next, the collection filter 1 with the CNTs 20 collected is removed from the chamber, and as shown in FIG. 3B, the collection filter 1 is placed on one surface of the transparent substrate 21 with the dense film 12 side, i.e., the side on which the CNTs 20 are arranged, facing toward the transparent substrate 21. The transparent substrate 21 is preferably made of a flexible material, such as a transparent plastic film, that allows light to pass through and allows visibility to the side opposite the transparent substrate 21. By placing the collection filter 1 with the CNTs 20 collected on one surface of the transparent substrate 21 in this manner, one end of the CNTs 20 is in contact with the transparent substrate 21. When the collection filter 1 is lifted in this state, the collection filter 1 is removed, and the CNTs 20 are transferred to the transparent substrate 21, as shown in FIG. 3C. As a result, for example, the portion of the collection filter 1 that protrudes outside becomes wider than the portion located within the opening 12a, resulting in an inverted T-shaped cross section of the CNTs 20.

[0032] Thereafter, as shown in Fig. 3D, the transparent substrate 21 onto which the CNTs 20 have been transferred is immersed in a doping solution 102, whereby the height of the CNTs 20 is reduced to about 1 / 10, for example, 1.0 to 5.0 µm, as shown in Fig. 3E, thereby forming a CNT pattern 22. In this way, a transparent conductive film having a CNT pattern 22 arranged on one surface of the transparent substrate 21 can be manufactured.

[0033] In this embodiment, the opening 12a has a reverse tapered shape. Therefore, when collecting the CNTs 20 in the opening 12a shown in Fig. 3A, fluctuations in the internal pressure of the chamber can be suppressed, and the CNT synthesis conditions can be stabilized, thereby stabilizing the quality of the CNTs 20, that is, the quality of the CNT pattern 22. The reason for this will be explained in comparison with the case where the opening 12a has a forward tapered shape.

[0034] As shown in FIG. 4A, if the opening 12a has a forward tapered shape in which the first width Wa at the inlet side is larger than the second width Wb at the bottom side, the state shown in FIG. 4B results when the CNTs 20 are collected. That is, the CNTs 20 are collected along the sidewall of the opening 12a and are in close contact with the sidewall, increasing the contact area between the dense film 12 and the CNTs 20. Furthermore, since the CNTs 20 and the dense film 12 are in close contact with each other, there is almost no gap between the CNTs 20 and the dense film 12, which limits the amount of dispersion medium passing through and increases the pressure loss of the collection filter 1. This causes fluctuations in the internal pressure of the chamber, which changes the CNT synthesis conditions, resulting in unstable and variable quality of the CNTs 20, making it impossible to achieve a low resistance CNT pattern 22.

[0035] In contrast, if the opening 12a has an inverted tapered shape, with the first width Wa at the inlet side smaller than the second width Wb at the bottom side, as shown in FIG. 5A, the CNTs 20 are collected as shown in FIG. 5B. That is, the CNTs 20 are collected with a gap between the sidewall of the opening 12a and the CNTs 20, and the CNTs 20 are not tightly attached to the sidewall, resulting in a small contact area between the dense film 12 and the CNTs 20. This allows the dispersion medium to pass through the gap between the CNTs 20 and the dense film 12 during collection, preventing pressure loss in the collection filter 1 from increasing. This suppresses fluctuations in the chamber's internal pressure and stabilizes CNT synthesis conditions, thereby stabilizing the quality of the CNT pattern 22 and reducing its resistance.

[0036] 3C , when CNTs 20 are transferred to transparent substrate 21, if opening 12a has an inverse tapered shape, the contact area between the sidewall of opening 12a and CNTs 20 is small, and therefore CNTs 20 easily peel off from dense film 12. This makes it possible to easily transfer CNTs 20, and also makes it possible to suppress defects in CNT pattern 22 caused by the occurrence of portions where CNTs 20 cannot be peeled off from dense film 12.

[0037] To confirm that the above effect could actually be achieved, we investigated the relationship between the CNT 20 collection time and the pressure ratio of the chamber's internal pressure, as well as the sheet resistance [Ω / □] of the resulting transparent conductive film, for both cases where the opening 12a was tapered and where it was tapered. Figures 6 and 7 show these results. The pressure ratio of the chamber's internal pressure refers to the ratio of the pressure in the upstream space across the collection filter 1 to the pressure in the downstream space.

[0038] As shown in Figure 6, in the case of the forward tapered shape, the pressure ratio increases as the collection time increases. Specifically, after 15 minutes of collection, the pressure ratio increases by 2.1 times compared to the initial value. On the other hand, in the case of the reverse tapered shape, although the pressure ratio increases as the collection time increases, it does not change much and is kept at about one-third of that in the case of the forward tapered shape. Specifically, after 15 minutes of collection, the pressure ratio increases by only about 1.35 times compared to the initial value. This also shows that by making the opening 12a in a reverse tapered shape, fluctuations in the internal pressure of the chamber can be suppressed.

[0039] 7, the sheet resistance [Ω / □] was 150 [Ω / □] when the opening 12a was tapered forward, while it was 120 [Ω / □] when the opening 12a was tapered in reverse. This shows that when the opening 12a is tapered in reverse, the quality of the CNT 20 is stabilized, thereby achieving low resistance.

[0040] As described above, in this embodiment, the collection filter 1 includes a dense film 12 having openings 12a corresponding to the CNT pattern 22 to be formed on one surface of the filter membrane 11, and the openings 12a have an inverted tapered shape. By using this collection filter 1, fluctuations in the internal pressure of the chamber in which the CNTs 20 are collected can be suppressed, and changes in the CNT synthesis conditions can be suppressed. This makes it possible to stabilize the quality of the CNTs 20 even with a high aspect ratio, and to achieve a low resistance CNT pattern 22.

[0041] Furthermore, the transparent conductive film having the CNT pattern 22 formed as in this embodiment can be applied, for example, as a heater. Examples of such heaters include a heater used in defrosting operations in vehicle air conditioners. In this case, the transparent conductive film can be attached to an outdoor unit or other device prone to frost buildup, allowing it to function as a heater. Additionally, the heater can also be used as a defrosting and anti-condensation heater for maintaining the functionality of sensors for vehicle perimeter monitoring, such as LiDAR (Light Detection and Ranging), cameras, and millimeter-wave radar, as well as a front windshield. Specifically, the transparent conductive film can function as a heater for heating sensors and the front windshield when ice or fogging occurs, thereby removing the ice or fogging and ensuring sensor functionality.

[0042] Furthermore, the transparent conductive film can be applied to heaters placed in various locations within the vehicle cabin, such as a foot heater placed on the underside of the dashboard. When used in such a heater, it is desirable to make the CNT pattern 22 inconspicuous, so it is preferable that the overall light transmittance of the CNT pattern 22 and transparent substrate 21 be high. The light transmittance is determined by the line width and density of the lines constituting the CNT pattern 22 and the material and thickness of the transparent substrate 21, but it is preferable that the line width of each line of the CNT pattern 22 be 10 μm or less so that it is not visible.

[0043] Furthermore, by using the dry film resist 13 as the dense film 12, the dense film 12 can be formed by a simple process that does not require spin coating or baking, compared to when it is formed by conventional coating. Furthermore, the dry film resist 13 can be in a roll form as shown in Fig. 2B, and since it can be wound up again into a roll after coating using a roll-to-roll method, high mass productivity can be achieved.

[0044] (Other embodiments) The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the claims.

[0045] For example, in the above embodiment, the cross-sectional shape of each line constituting the CNT pattern 22 is an inverted T-shape as shown in FIG. 2E , but other shapes are also possible. That is, as long as the cross-sectional shape includes linear portions whose height direction is normal to one surface of the transparent substrate 21, each linear portion may or may not have a portion extending along one surface of the transparent substrate 21, as in the inverted T-shape. Furthermore, the portion extending along one surface of the transparent substrate 21 from each linear portion may be thinner than the adjacent linear portion over the entire area. In this structure, CNTs are formed on one surface of the underlying transparent substrate 21. Since the thinner the CNT film thickness, the higher the light transmittance, the transparent conductive film can be configured with a desired light transmittance even when covered with thin CNTs.

[0046] In the above embodiment, a line-and-space structure is formed by arranging multiple linear lines in a stripe pattern. However, this is merely one example of a line-and-space structure. That is, any structure may be used as long as portions where CNT lines are arranged and portions where CNT lines are not arranged are alternately arranged on a cross section of the CNT pattern 22 cut in one direction on one surface of the transparent substrate 21. For example, the CNT pattern 22 may be formed in a rectangular lattice pattern in which multiple linear lines intersect with each other, or in a honeycomb pattern in which multiple hexagonal shapes are arranged.

[0047] In addition, in the above embodiment, the transparent substrate 21 is used to manufacture a transparent conductive film, but the collection filter 1 can be applied to manufacture not only transparent conductive films but also conductive films including the CNT pattern 22. In that case, a non-transparent substrate may be used instead of the transparent substrate 21.

[0048] Furthermore, in the above embodiment, an example is given in which CNTs are used as the nanocarbon material, but nanocarbon materials such as carbon nanobelts (CNBs), graphene, fullerene, etc. may also be used. In other words, although the CNT pattern 22 is shown as a pattern made of a nanocarbon material, a pattern may be made of other nanocarbon materials. [Explanation of symbols]

[0049] 1. Collection filter 11 Filter membrane 12 Dense membrane 12a opening 13 Dry film resist 21 Transparent base material 22 CNT patterns Wa First width Wb 2nd width

Claims

1. a filter membrane (11) having a porous structure and one surface for filtering the nanocarbon material from a dispersion medium containing the nanocarbon material; a dense membrane (12) formed on the one surface, having openings (12a) for passing the dispersion medium therethrough, and having density that blocks the passage of the dispersion medium in areas other than the openings; The opening of the collection filter has a first width (Wa) on the inlet side of the dispersion medium opposite the filter membrane that is smaller than a second width (Wb) on the bottom side that is on the filter membrane side.

2. 2. The collection filter according to claim 1, wherein the opening has an aspect ratio, which is the ratio of the depth (D) of the opening to the first width, of 0.1 or more.

3. 3. The collection filter according to claim 1, wherein the first width is 50 μm or less.

4. 4. The collection filter according to claim 1, wherein the dense film has a thickness of 10 [mu]m or more and 50 [mu]m or less.

5. 5. The collection filter of claim 1, wherein the ratio of the second width to the first width is greater than 1 and less than 2.

6. A method for producing a transparent conductive film, comprising the steps of: using the collection filter according to any one of claims 1 to 5 to produce a transparent conductive film including a pattern (22) made of a nanocarbon material (20), disposing the collection filter in a chamber into which a dispersion medium containing the nanocarbon material is supplied, with the dense membrane side facing the upstream side of a supply path of the dispersion medium and the filter membrane side facing the downstream side of the supply path of the dispersion medium; supplying the dispersion medium into the chamber and passing the dispersion medium through the collection filter to collect the nanocarbon material in the opening; After collecting the nanocarbon material, a transparent substrate (21) is disposed on the dense film side of the collection filter; removing the collection filter from the transparent substrate to transfer the nanocarbon material to the transparent substrate and form the pattern with the nanocarbon material.

Images