KR20140086748A - Patterned transparent conductive film, method for manufacturing the same and optical display apparatus comprising the same - Google Patents

Abstract

The present invention relates to a patterned transparent conductive film, a method for manufacturing the same and an optical display apparatus comprising the same. More particularly, the present invention includes multiple coating layers which include a metal nanowire on a substrate film; and a pattern part which is formed between the coating layers. The pattern part has a ratio (b/a) of the entire area (b) of the metal nanowire remaining on the pattern part to the area (a) of the pattern part, 50-80%.

Description

[0001] The present invention relates to a patterned transparent conductive film, a method of manufacturing the same, and an optical display device including the patterned transparent conductive film. [0002]

The present invention relates to a patterned transparent conductive film, a manufacturing method thereof, and an optical display device including the same. More specifically, the present invention relates to a patterned transparent conductive film having high pattern visibility and good pattern shape, a method for manufacturing the same, and an optical display device including the same.

BACKGROUND ART [0002] Conductive films are used in many fields such as a touch screen panel and a flexible display included in a display device. The conductive film should have good basic physical properties such as transparency and sheet resistance, and has recently been required to have bending properties as the use area extends to flexible displays.

A film in which an indium tin oxide (ITO) film is laminated on both sides of a base film including a polyethylene terephthalate (PET) film has been used as a conductive film. The ITO film is deposited on a substrate film by a dry deposition method, and is economical and excellent in transparency. However, due to the characteristics of the ITO itself, there is a problem that the resistance may increase and the bending property is poor.

In order to solve this problem, there has been developed a technique for producing a conductive film by coating a conductive polymer, carbon nanotube, metal nanoparticles, etc. on a substrate film by a wet thin film coating method instead of an ITO film. However, this method also has a low transmittance, which is not suitable for a transparent conductive film and may be unreliable. In the case of metal nanoparticles, the dispersibility in the film is low and the resistance can be increased.

Recently, a conductive film prepared by coating a solution containing silver nanowires on a base film by a wet thin film coating method has been developed. This method involves wet-coating a base film with a solution in which silver nanowires are dissolved in water, thereby laminating silver nanowires on the base film. However, this method is also required to prepare a conductive film with a structure in which an overcoat layer prepared by curing a mixture of urethane acrylate and an initiator is added on a silver nanowire coating in order to compensate for adhesion force and solvent resistance to a base film.

The conductive film thus produced is patterned through processes such as exposure, development, and etching. In the patterning process, etching is an essential process for forming a pattern. Depending on the degree of etching, the etching region is distinguished from the non-etched region, so that the pattern visibility can be determined.

Conventionally, the etching solution has been using a solution containing nitric acid or the like. However, since the patterned film obtained therefrom has low pattern visibility, the difference in resistance between the etching region and the non-etched region is small, Lt; / RTI >

In this regard, Korean Patent Laid-Open No. 2009-0112626 discloses a method of patterning a transparent conductive film with an etching solution containing 0.01-40% of nitric acid, a small amount (about 1-100 ppm) of KMnO ₄ and 1% of NaNO ₃ .

An object of the present invention is to provide a patterned transparent conductive film having high pattern visibility and good pattern shape.

Another object of the present invention is to provide a patterned transparent conductive film having a region where the sheet resistance is 0-1.3 k? /? Between the pattern portions made of the coating layer.

It is still another object of the present invention to provide a method for producing the patterned transparent conductive film.

It is still another object of the present invention to provide an optical display device including the patterned transparent conductive film.

One aspect of the present invention is a patterned transparent conductive film comprising: a plurality of coating layers including metal nanowires on a substrate film; And a pattern portion formed between the coating layers. The pattern portion may have a ratio of a total area of the metal nanowires in the pattern portion with respect to an area of the pattern portion in contact with the pattern portion is 50 to 80%.

According to another aspect of the present invention, there is provided a method of manufacturing a patterned transparent conductive film, comprising: patterning a substrate film formed with a coating layer containing metal nanowires, the patterning step comprising: an acid having a pKa of -2.0 to -1.0; And an acid having a pKa of -9.0 to -7.0, an acid having a pKa of 1.0 to 3.0, and an acid having a pKa of 4.0 to 5.0.

The optical display device according to another aspect of the present invention may include the patterned transparent conductive film.

The present invention provides a patterned transparent conductive film having a high pattern visibility, a good pattern shape, and a region having a sheet resistance of 0-1.3 k? Between the pattern portions and having a large resistance difference between pattern portions.

1 is a cross-sectional view of a patterned transparent conductive film according to an embodiment of the present invention.
2 is a conceptual diagram for calculating the area ratio of metal nanowires in the pattern portion according to one embodiment of the present invention.
3 is a method for producing a patterned transparent conductive film according to an embodiment of the present invention.
4 is a cross-sectional photograph of the pattern portion in the patterned transparent conductive film according to Example 1. Fig.
5 is a cross-sectional photograph of the pattern portion in the patterned transparent conductive film of Example 2. Fig.
6 is a cross-sectional photograph of the pattern portion in the patterned transparent conductive film of Comparative Example 1. Fig.

One aspect of the present invention is a patterned transparent conductive film comprising a base film; A coating layer formed on the base film and including metal nanowires and patterned; And a pattern portion formed between the patterned coating layers, wherein a ratio of an area of the metal nanowires existing in the pattern portion to an area of the pattern portion is 50 to 80%, and preferably 50 to 70% .

In the transparent conductive film, a plurality of the patterned coating layers may be formed.

As used herein, the term "pattern portion" may mean a region existing between the patterned coating layers, and a portion of the coating layer before patterning is removed by patterning and etching.

In this specification, the 'area ratio of metal nanowires' refers to the area ratio of the metal nanowires 30 existing in the pattern part to the pattern part of the entire area of the pattern part 40 as shown in FIG. 2 Quot; "

The patterned transparent conductive film of the present invention is characterized in that the ratio of the area of the metal nanowires in the pattern portion is low and the difference between the region removed by etching and the region not removed is clear and the pattern visibility is high, The difference in resistance between the coating layers is evident, so that it can have a good pattern pattern.

1 is a cross-sectional view of a portion of a patterned transparent conductive film according to an embodiment of the present invention.

Referring to Figure 1, a patterned transparent conductive film 100 comprises a substrate film 10 and a plurality of patterned coating layers 20 formed on the substrate film 10, wherein the patterned coating layer 20 And a pattern portion 40 formed between the pattern portion 40 and the pattern portion 40.

The patterned transparent conductive film of the present invention may include a pattern in which the coating layer and the pattern portion are repeatedly arranged.

The coating layer may be a single layer.

The coating layer may be a layer in which metal nanowires are dispersed in the coating layer matrix. As a result, the coating layer can provide conductivity.

The coating layer may be composed of a metal nanowire and a matrix.

The metal nanowires form a conductive network within the matrix. Such a conductive network can impart conductivity to the film and provide flexibility. In addition, the metal nanowire has a better dispersibility than the metal nanoparticles due to the nanowire shape, and the sheet resistance of the conductive film can be remarkably lowered due to the difference between the particle shape and the nanowire shape.

The metal nanowires have the form of microscopic lines having a specific cross-section.

The ratio (L / d, aspect ratio) of the nanowire length (L) to the diameter (d) of the metal nanowire cross section may be 10 to 1,000. In this range, a high conductivity network can be realized even at a low nanowire density, and the sheet resistance after curing can be lowered. Preferably, the aspect ratio may be in the range of more than 500 to 1000 or 501 to 700.

The diameter of the cross section of the metal nanowire may be 100 nm or less. Within this range, a high L / d can be ensured to realize a conductive film having a low conductivity and a low sheet resistance. Preferably, it may be 30 nm to 100 nm.

The metal nanowire may have a length (L) of 20 mu m or more. Within this range, a high L / d can be ensured to realize a conductive film having a low conductivity and a low sheet resistance. Preferably 20 [mu] m to 50 [mu] m.

The metal nanowires may comprise nanowires made of any metal. For example, silver, copper, gold nanowires or mixtures thereof. Silver nanowires or mixtures containing them may be preferably used.

The metal nanowires may be manufactured by a conventional method or commercially available products may be used. For example, it can be synthesized through a reduction reaction of a metal salt (for example, silver nitrate, AgNO ₃ ) in the presence of a polyol and poly (vinylpyrrolidone). Alternatively, a commercially available product of Cambrios (e.g., Clearohm Ink.) May be used.

The metal nanowires may comprise at least 50 wt%, preferably 60-70 wt%, of the coating layer. Within this range, it is possible to provide sufficient conductivity and to form a conductive network.

In the patterned transparent conductive film, the width and length of the coating layer may vary depending on the use of the transparent conductive film. For example, the width may be 10 占 퐉 to 50 占 퐉 and the length may be 10 占 퐉 to 50 占 퐉.

The matrix can form a contour of the conductive film or coating layer, maintain the conductive network form to ensure conductivity, and prevent the conductive network from being corroded by external impact or moisture when mounted on an optical display. To this end, the matrix must be able to maintain a physically rigid appearance to maintain the conductive network of metal nanowires.

The coating layer may have optical transparency in consideration of the intended use of the conductive film. For example, the coating layer may have transparency in the visible light region, e.g., a wavelength of 400 nm to 700 nm. The coating layer has a haze of 3% or less as measured by a haze meter, and a transparency having a total light transmittance of 90% or more. Preferably, the coating layer has a haze of 0.1-3% and a total light transmittance of 90-95%.

The coating layer should have good adhesion to the substrate when considering the use of the conductive film. For this, the water contact angle of the coating layer can be 60-75, preferably 70-75.

The matrix may be made of a material capable of providing such physical properties, for example, a cured product of a composition comprising urethane (meth) acrylate and an initiator.

The matrix in the coating layer is less than 50% by weight, Preferably 30 to 40% by weight.

The thickness of the coating layer may be from 50 nm to 500 nm, preferably from 90 nm to 150 nm. Within this range, the shape of the conductive network can be well maintained and used as a conductive film.

The sheet resistance of the coating layer may be the same as or different from that of the adjacent coating layer, and may be, for example, 80 to 100? / ?.

The pattern portion is a portion formed between the patterned coating layers. In the pattern portion, the ratio (b / a) of the total area (b) of the metal nanowires existing in the pattern portion to the area (a) of the pattern portion may be 50 to 70%. Generally, a portion removed by etching in a conventionally patterned transparent conductive film may have a large number of metal nanowires even after etching. This is because the conventional etching solution does not completely etch.

The total area of the metal nanowires can mean the sum of the areas in which the metal nanowires contact the pattern portion.

On the other hand, the patterned transparent conductive film of the present invention has the above-mentioned ratio of 50 to 80%, thereby ensuring the visibility of the pattern and enhancing the utility in application of the product.

The sheet resistance of the pattern portion may be 0-1.3 k? / ?, preferably 0-1? K? / ?. Within the above range, the transparent conductive film can be used for a touch panel film or the like because the pattern is well formed.

The width of the pattern portion may be 10 占 퐉 to 50 占 퐉. Within the above range, the transparent conductive film can be used as a touch panel film or the like.

The pattern part should have good adhesion to the substrate when considering the use of the conductive film. For this, the water contact angle of the pattern portion may be 60-75, preferably 70-75.

The pattern portion may preferably be a portion of the substrate film. This is because the etching is completed and the coating layer formed on the pattern portion is completely removed. This makes it possible to use the transparent conductive film as a touch panel film or the like.

The difference between the sheet resistance of the coating layer and the pattern portion may be 80? /? -1.3 k? /?, Preferably 80-100? / ?. Within the above range, the transparent conductive film can be used for a touch panel film or the like because the pattern is well formed.

The base film can be used without limitation as long as it can provide flexibility. For example, the substrate film may be formed of a material selected from the group consisting of polyesters including polyethylene terephthalate (PET), polyester naphthalate, polycarbonate, etc., polyolefins, cyclic olefin polymers, polysulfone, polyimide, silicone, polystyrene, , Polyvinyl chloride film, but is not limited thereto.

A functional film may be further laminated on one or both sides of the base film. Examples of the functional film include, but are not limited to, a hard coating layer, an anti-corrosion layer, an anti-glare coating layer, an adhesion promoter, and an oligomer elution preventing layer.

The base film may have a thickness of 10 mu m to 100 mu m. Within the above-mentioned range, it can be used as a film for a touch panel after the conductive film is formed.

According to another aspect of the present invention, there is provided a method of manufacturing a patterned transparent conductive film, comprising: patterning a substrate film formed with a coating layer containing metal nanowires, the patterning being performed using an acid having a pKa of from -2.0 to -1.0; And an acid having a pKa of -9.0 to -7.0, an acid having a pKa of 1.0 to 3.0, and an acid having a pKa of 4.0 to 5.0.

In one embodiment, the method comprises: forming a coating layer containing metal nanowires on a substrate film; applying a photoresist on the coating layer; exposing the pattern forming mask to light; and developing and etching the pattern by etching with the etching solution Step < / RTI >

3 shows a process for producing a patterned transparent conductive film according to an embodiment of the present invention. A method of manufacturing a semiconductor device, comprising: forming a humidity film containing a metal nanowire on a base film; applying a composition for a coating layer on the humidity film to form a coating layer; applying a photoresist on the coating layer; And etching with an etchant.

The metal nanowires may be nanowires of one or more of silver, copper, and gold.

The coating layer containing the metal nanowires can be formed by a wet thin film coating method. Specifically, a coating layer containing metal nanowires can be formed by applying a dispersion solution containing a metal nanowire on a base film to form a humidity film containing metal nanowires, and applying a composition for a coating layer again to form a humidity film.

The thickness of the metal nanowire-containing moisture film is not limited, but may be 20-40 占 퐉.

The dispersion solution containing the metal nanowires may include at least one of an aqueous solvent such as water and alcohol in consideration of the solubility of the metal nanowires.

Prior to application of the composition for the coating layer, the metal nanowire-containing moisture film may be dried and baked. This can facilitate the formation of the humidity film of the composition for the coating layer. For example, a metal nanowire-containing moisture film can be dried and baked at 80-140 ° C for 1 minute to 60 minutes.

Then, the composition for the coating layer is applied on the humidity film. The coating layer can improve the adhesion of the transparent conductive film to a later substrate.

The composition for the coating layer comprises urethane (meth) acrylate and an initiator. Urethane (meth) acrylate is a substance forming a coating layer matrix, and has high affinity with metal nanowires, and can improve adhesion with substrates later. The initiator causes curing of the urethane (meth) acrylate to form a coating layer matrix. The initiator can be used without limitation as long as it absorbs the absorption wavelength of 150 nm to 500 nm and can exhibit a photoreaction. For example, the initiator may be a phosphine oxide series. Specifically, bis-acylphosphine oxide (BAPO), 2,4,6-trimethylbenzoylphosphine oxide (TPO), or a mixture thereof may be used.

A composition for a coating layer is applied to form a humidity film, and then the coating film is formed by curing. The curing can be performed at a UV light quantity of 300-500 mJ / cm ² , but is not limited thereto. Before the curing, the drying step may be performed in consideration of the shape of the coating layer and the curing efficiency.

A photoresist for pattern formation is applied on the formed coating layer and dried. The photoresist can be used without limitation as long as it is conventionally used in the patterning of the transparent conductive film. Then, the mask for pattern formation is placed and exposed to UV to form a pattern on the coating layer.

Then, development and patterning are performed using an etchant. The development is not limited, but can be carried out with a solution of tetramethylammonium hydroxide (TMAH).

In the production method of the present invention, an acid having a pKa of -2.0 to -1.0 as an etchant; And an acid having a pKa of -9.0 to -7.0, an acid having a pKa of 1.0 to 3.0, and an acid having a pKa of 4.0 to 5.0. As a result, the pattern can be formed well in the patterned transparent conductive film to ensure pattern visibility, and the sheet resistance of the pattern portion can be 0-1.3 k? / ?.

The etchant may be an etchant containing 3 wt% or more, preferably 3-10 wt%, of nitric acid.

In one embodiment, an etchant comprising 3-5 wt.% Nitric acid, 75-85 wt.% Phosphoric acid, 1-10 wt.% Acetic acid, and water in the balance may be used.

In another embodiment, an etchant comprising 3-5 wt% nitric acid, 9-19 wt% hydrochloric acid, and a balance of water may be used.

In this specification, the content of 'acid' in the etching solution is based on an acid having an acid concentration of 100% by weight.

The pH of the etchant may be 2-5, preferably 2-4. Within this range, there may be a sufficient conductivity effect.

The etching process with the etching solution can be performed at 30-50 DEG C for 10-20 minutes. Within this range, there may be a conductive effect.

The optical display device according to another aspect of the present invention may include the patterned transparent conductive film or the conductive laminate. The optical display device may include, but is not limited to, a general optical display device including a touch screen panel, an organic light emitting diode (OLED) display device, a liquid crystal display device, and the like.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Specific specifications of the components used in the following examples and comparative examples are as follows.

(A) Metal nanowires: Silver nanowires (Clearohm Ink., Cambrios)

(B) Coating layer Matrix: urethane acrylate

(C) Initiator: bis-acyl-phosphine oxide (BAPO, Darocur 819W, CIBA)

(D) Base film: polyethylene terephthalate (TOYOBO, A1598)

(E) Photoresist: SS-03A9 (Dongwoo Fine-Chem)

(F) Developer: 1% by weight aqueous solution of tetramethylammonium hydroxide (TMAH)

(G) Etching solution

(G1) 5 wt% of nitric acid, 85 wt% of phosphoric acid, and 10 wt% of acetic acid.

(G2) 3% by weight of nitric acid, 19% by weight of hydrochloric acid, and residual water.

(G3) an etching solution containing 2% by weight of nitric acid, 8% by weight of hydrochloric acid and water in a remaining amount.

* Use nitric acid, hydrochloric acid, phosphoric acid, and acetic acid having an acid concentration of 100% by weight of the acid solution.

Example  One

A metal nanowire dispersion solution containing water and methanol as a solvent was prepared, applied onto a substrate film, and a moisture film was formed to a predetermined thickness using a wire bar. Dried in an oven at 80 캜 for 2 minutes, and further baked in an oven at 140 캜. A composition comprising urethane acrylate and an initiator was further applied to form a humidity film, dried in an oven at 50 캜 for 2 minutes, and further baked in an oven at 120 캜. Then, the film was UV-cured in a nitrogen atmosphere at 500 mJ / cm ² in a UV curing machine to prepare a conductive laminate in which a conductive film having a thickness of 150 nm was laminated as a single layer on one surface of the base film.

The obtained transparent conductive film was spin-coated with a photoresist, dried in an oven at 110 캜 for 3 minutes, and subjected to UV exposure using a patterned Cr mask. The pattern width was 10 탆, 20 탆 and 30 탆. The exposed film was put in a developing solution, developed for 10 seconds, and the developed film was dried in an oven at 110 DEG C for 1 minute. Using the etching liquid (G1) as an etchant, the coating was allowed to proceed at 40 占 폚 for 10 minutes to prepare a patterned transparent conductive film.

Example  2

In Example 1, a patterned transparent conductive film was produced by the same method except that the etching solution (G2) was used as an etchant and the process was conducted at 35 DEG C for 5 minutes.

Comparative Example  One

In Example 1, a patterned transparent conductive film was produced in the same manner as in Example 1, except that the etching solution (G3) was used as the etching solution and the coating was conducted at 35 DEG C for 2 minutes.

Comparative Example  2

A patterned transparent conductive film was produced in the same manner as in Example 1, except that the etching solution was not etched.

The following properties of the conductive laminate thus prepared were evaluated, and the results are shown in Table 1 and Figs. 4 to 6.

(1) Haze and total light transmittance: The base film is removed from the conductive laminate. The haze and total light transmittance of the conductive film are measured using a NDH 2000 instrument (Nippon Denshoku) with a haze meter at 400 nm to 700 nm.

The total light transmittance is calculated as the sum of the diffused transmitted light DF and the parallel transmitted light PT. The higher the total light transmittance, the better the transparency. The haze value is calculated as diffusion transmitted light (DF) / parallel transmitted light (PT).

(2) Surface resistance: The surface resistance of the conductive film is measured after 10 seconds from the 4-probe of the sheet resistance meter MCP-T610 (Mitsubishi Chemical Analytech). The coating layer and the pattern portion are respectively measured.

(3) Water contact angle: Fix the conductive film on the glass substrate and measure the contact angle with the pattern part on the coating layer using the SEO Contact Angle Analyzer phoenix 300 equipment.

(4) Frequency of Resistance Measurement of Pattern Portion After Etching: The number of resistances measured for 10 sheets on the etched transparent conductive film was evaluated.

(5) Area ratio of metal nanowires in the pattern portion: The area ratio of the pattern portion (30um width) after etching and the area of the non-patterned portion in the patterned size (400um * 400um) was calculated.

(6) Pattern visibility: The patterned sample was visually observed under three wavelengths and external light (sunlight).

The evaluation criteria for pattern visibility are based on the haze on the experimental data

Phase: Haze 0.15% or less

: Haze 0.15% to less than 0.18%

Bottom: Haze 0.18% or more

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Haze (%) 0.15 0.17 0.18 0.2 Total light transmittance (%) 90.34 90.24 90.19 90.10 Sheet resistance Coating layer
(Ω / □) 82 81 82 80 Pattern portion
(Ω / □) 0 0 1.3k 1.3k Water contact angle (°) 70.45 70.30 70.73 70.62 Frequency of resistance measurement of pattern part after etching 0/10 0/10 5/10 10/10 Area ratio of metal nanowires in the pattern portion (%) 68% 56% 90% 100% Pattern visibility Prize medium Ha Ha

As shown in Table 1, the patterned transparent conductive film of the present invention has good transparency with good haze and total light transmittance, has good transparency, has a high water contact angle and is excellent in adhesion to a substrate, and also has an area ratio of metal nanowires And the sheet resistance of the pattern portion was low, and it was confirmed that the pattern visibility was good and had a good pattern pattern. These results can also be seen from the cross-sectional photographs of the pattern portions in FIG. 4 and FIG.

On the other hand, the patterned transparent conductive film of Comparative Example 1 produced by the conventional etching solution has a haze, a total light transmittance and a water contact angle similar to those of the present invention. However, the area ratio of metal nanowires in the pattern portion is high, It was confirmed that the pattern appearance was poor due to poor pattern visibility. These results can also be seen from the cross-sectional photograph of the pattern part in Fig.

Claims (16)

A plurality of patterned coating layers formed on the substrate film and comprising metal nanowires; And
And a pattern portion formed between the patterned coating layers,
Wherein the pattern portion has a patterned transparent conductive layer having a ratio (b / a) of 50 to 80% of a total area (b) of the metal nanowires existing in the pattern portion with respect to the area (a) film.
The patterned transparent conductive film according to claim 1, wherein the width of the pattern portion is 10 占 퐉 to 50 占 퐉.
The patterned transparent conductive film according to claim 1, wherein the pattern portion comprises at least a part of the base film.
The patterned transparent conductive film according to claim 1, wherein a difference in sheet resistance between the coating layer and the pattern portion is 0-1.3 k? / Square.
The patterned transparent conductive film according to claim 1, wherein a sheet resistance of the pattern portion is 0-1.3 k? / Square.
The patterned transparent conductive film according to claim 1, wherein the coating layer has a sheet resistance of 80-100? / ?.
The patterned transparent conductive film of claim 1, wherein the metal nanowire is at least one of silver, copper, and gold nanowires.
The patterned transparent conductive film according to claim 1, wherein the coating layer comprises urethane (meth) acrylate.
A method of manufacturing a patterned transparent conductive film, the method comprising: patterning a substrate film formed with a coating layer containing metal nanowires, wherein the patterning step comprises etching using an etchant containing at least 3 wt% Way.
10. The method of manufacturing a patterned transparent conductive film according to claim 9, wherein the etching solution contains 3-5 wt% of nitric acid, 75-85 wt% of phosphoric acid, 1-10 wt% of acetic acid, and water in a remaining amount.
10. The method of manufacturing a patterned transparent conductive film according to claim 9, wherein the etching solution comprises 3-5 wt% of nitric acid, 9-19 wt% of hydrochloric acid, and the balance water.
10. The method of claim 9, wherein the coating layer comprises a matrix formed of urethane (meth) acrylate.
The method of manufacturing a patterned transparent conductive film according to claim 9, wherein the coating layer is formed by forming a humidity film containing metal nanowires on the base film, applying the composition for a coating layer on the moisture film, and curing the film.
The method of manufacturing a patterned transparent conductive film according to claim 9, wherein the etchant has a pH of 2-4.
10. The method of claim 9, wherein the etching is performed at 30-50 DEG C for 10-20 minutes.
An optical display device comprising the patterned transparent conductive film of claim 1.

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