TW201900904A - Sputter target for transparent conductive film - Google Patents

Abstract

The spattering target for transparent conductive film of the present invention comprising an oxide sintered body, the constituent elements of the oxide sintered body are In, Sn, Si and O, or In, Si and O, the content ratio of In is 70.0 mass% or more and 85.0 mass% or less in terms of In2O3, the content ratio of Sn is 0 mass% or more and 10.0 mass% or less in terms of SnO2, the content ratio of Si is 15.0 mass% or more and 20.0 mass% or less in terms of SiO2; wherein, in the X-ray diffraction measurement of the spattering target, all of Si appears as a peak of an indium silicate compound having a tilt-by-tight type structure. The spattering target for forming conductive film of the present invention has low resistivity, can perform DC spattering, and generates less nodules and arcing. Further, by spattering, a transparent conductive film having high film resistivity and high etching processability can be formed.

Description

   Sputter target for transparent conductive film   

The present invention relates to a sputtering target for a transparent conductive film, and more specifically, to a sputtering target for a transparent conductive film that can perform DC sputtering and can form a transparent conductive film with high etching processability.

In the transparent conductive film used in the embedded capacitive touch panel, in order to prevent the display operation from being hindered by low-frequency noise, high resistance and high transmittance are required. Because the conductive film has low resistance, the high-frequency signals used for touch sensing will be completely blocked.

This conductive film is usually formed by sputtering a sputtering target.

High-transmittance materials mainly use ITO, but because of its low resistance, ITO cannot use the conductive film of the built-in capacitive touch panel.

The technology for obtaining a high-resistance material is a technology for adding an insulating oxide to ITO. However, when an insulating oxide is added to ITO, there is a disadvantage that the etching processability is lowered. In applications such as applying etching to a conductive film, It becomes difficult to use.

For example, Patent Document 1 discloses a of ITO as a main raw material, containing from 7.2 to 11.2 atom% of silicon, and the specific resistance of the transparent conductive film 10 ^° to the 10 ³ Ωcm. Patent Document 2 discloses a transparent conductive film having a resistivity of 0.8 to 10 × 10 ^-3 Ωcm obtained by sputtering a transparent conductive film composed of indium oxide, tin oxide, and silicon oxide with a sputtering target. However, the etching processability of any of the conductive films was low.

In addition, many high-resistance films have been proposed, but the resistance of the target used in the film formation of the film also becomes high. When the resistance of the target is high, sputtering cannot be performed with a DC power supply, and a high-resistance film must be produced with an RF power supply, which results in poor productivity.

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent No. 5855948

[Patent Document 2] Japanese Patent No. 4424889

An object of the present invention is to provide a sputtering target that can perform DC sputtering, has fewer bumps or arcs, and can form a transparent conductive film with high specific resistance and high etching processability.

The sputtering target for the transparent conductive film of the present invention includes an oxide sintered body, and the constituent elements of the oxide sintered body are In, Sn, Si, and O, or In, Si, and O, and the content ratio of In is In ₂ O ₃ converted to 70.0% by mass or more and less than 85.0% by mass, the content ratio of Sn is 0% to 10.0% by mass in terms of SnO ₂ , and the content ratio of Si is more than 15.0% by mass to 2.0% by mass in terms of SiO _2. Among them, in the X-ray diffraction measurement of the aforementioned sputtering target, all of the Si systems are shown as spectral peaks of an indium silicate compound having a thortveitite type structure.

The sputtering target for a transparent conductive film preferably has a specific resistance of 2.0 × 10 ² Ωcm or less.

The sputtering target for a transparent conductive film preferably has a relative density of 98.0% or more.

The constituent elements of the transparent conductive film of the present invention are In, Sn, Si, and O, or In, Si, and O, and the content ratio of In is 73.0% by mass or more and 87.0% by mass or less in terms of In ₂ O ₃ , and the content ratio of Sn is SnO _{2 is} converted to 0% by mass or more and 9.0% by mass or less, and the content ratio of Si is 13.0% by mass or more and 18.0% by mass or less in terms of SiO ₂ .

The aforementioned transparent conductive film preferably has a film specific resistance of 1.0 × 10 ⁰ Ωcm or more, and preferably has an etching rate exceeding 11.0 Å / sec.

The manufacturing method of the transparent conductive film of this invention is formed by sputtering the said sputtering target for transparent conductive films.

In the method for manufacturing the transparent conductive film, the specific resistance of the transparent conductive film is preferably 1.0 × 10 ⁰ Ωcm or more, and the etching rate of the transparent conductive film is preferably more than 11.0 Å / sec.

The sputtering target for forming a conductive film according to the present invention has a lower specific resistance, can perform DC sputtering, and has less generation of bumps or arcs. In addition, a transparent conductive film having a high specific resistance and a high etching processability can be formed by sputtering. The manufacturing method of the transparent conductive film of the present invention is capable of manufacturing a transparent conductive film having a high specific resistance and a high etching processability.

FIG. 1 is an X-ray diffraction pattern of the sputtering target obtained in Example 3. FIG.

The sputtering target for the transparent conductive film of the present invention includes an oxide sintered body, and the constituent elements of the oxide sintered body are In, Sn, Si, and O, or In, Si, and O, and the content ratio of In is In ₂ O ₃ converted to 70.0% by mass or more and less than 85.0% by mass, the content ratio of Sn is 0% to 10.0% by mass in terms of SnO ₂ , and the content ratio of Si is more than 15.0% by mass to 20.0% by mass in terms of SiO _2. . The target containing an oxide sintered body like the sputtering target for a transparent conductive film of the present invention naturally contains unavoidable impurities derived from raw materials and the like, and is also included in the sputtering target for a transparent conductive film of the present invention. It also contains unavoidable impurities. The content of the unavoidable impurities in the sputtering target for transparent conductive films of the present invention is usually 100 ppm or less.

In the present invention, the constituent elements refer to constituent elements other than unavoidable impurities in the sputtering target or the transparent conductive film, and the content ratio of each constituent element means the entire sputtering target or the transparent conductive film The content ratio of each constituent element in.

The sputtering target for the transparent conductive film of the present invention is characterized in that the content ratio of Sn is low or does not contain Sn, and it has a relatively high concentration of Si compared to the case of a conventional ITO sputtering target.

The constituent elements of the oxide sintered body are In, Sn, Si, and O, or In, Sn, and O. In the oxide sintered body, the content ratio of In is 70.0% by mass or more and less than 85.0% by mass in terms of In ₂ O ₃ , preferably 73.0% by mass or more and 84.0% by mass or less, and more preferably 76.0% by mass or more and 84.0% by mass. The content of Sn is 0% by mass or more and 10.0% by mass or less in terms of SnO ₂ , preferably 0% by mass or more and 7.0% by mass or less, more preferably 0% by mass or more and 5.0% by mass or less. The content of Si The ratio is more than 15.0% by mass and 20.0% by mass in terms of SiO ₂ , preferably 16.0% by mass or more and 20.0% by mass or less, and more preferably 16.0% by mass or more and 19.0% by mass or less. The composition of the sputtering target for a transparent conductive film is the same as that of the oxide sintered body.

A sputtering target for a transparent conductive film including an oxide sintered body having the aforementioned composition has a lower specific resistance, and therefore, DC sputtering can be performed. The specific resistance of the sputtering target for a transparent conductive film is preferably 2.0 × 10 ² Ωcm or less, more preferably 1.5 × 10 ² Ωcm or less, and even more preferably 1.0 × 10 ² Ωcm or less. Generally, when the target has a specific resistance of about 10 ² Ωcm or less, DC sputtering can be performed.

A sputtering target for a transparent conductive film including an oxide sintered body having the aforementioned composition can form a transparent conductive film having a high specific resistance by sputtering. Therefore, when the transparent conductive film obtained from the aforementioned sputtering target for a transparent conductive film is used in an in-cell type capacitive touch panel, it is possible to prevent the display operation from being hindered by low-frequency noise. When the sputtering target for a transparent conductive film is used, a transparent conductive film having a film specific resistance of 1.0 × 10 ⁰ Ωcm or more can be obtained. The film specific resistance of the transparent conductive film is preferably 1.1 × 10 ⁰ Ωcm or more, and more preferably 1.2 × 10 ⁰ Ωcm or more. The upper limit of the specific resistance of the transparent conductive film is not particularly limited, but is usually 5.0 × 10 ⁵ Ωcm.

A sputtering target for a transparent conductive film including an oxide sintered body having the aforementioned composition is capable of forming a transparent conductive film with high etching processability by sputtering. High etching processability can be evaluated whether the etching rate is fast. The transparent conductive film obtained from the aforementioned sputtering target for a transparent conductive film preferably has an etching rate of more than 11.0 Å / sec, more preferably 11.3 Å / sec or more, even more preferably 15.0 Å / sec or more, and even more preferably Above 20.0Å / sec. The etching rate of the transparent conductive film is etched by immersing a part of the transparent conductive film for 6 minutes in a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) heated to 40 ° C. The difference in film thickness (step difference) and etching time between the place and the place where it was not implemented are calculated.

The specific resistance of a transparent conductive film obtained by sputtering a transparent conductive film containing an oxide sintered body containing In, Sn, and Si with a sputtering target will increase as the Sn and Si content of the target increases. Becomes higher. However, the etching processability of the transparent conductive film cannot be increased when the Si content is large. Therefore, in order to obtain sufficient etching processability of the transparent conductive film, the Sn content of the target must be set to 0% by mass or more and 10.0% by mass or less in terms of SnO ₂ conversion. When the Sn content of the target is set to 0% by mass or more and 10.0% by mass or less in terms of SnO ₂ , the specific resistance of the film becomes low. Therefore, in order to obtain a high specific resistance of the film, it is necessary to increase the Si content of the corresponding component. Therefore, the Si content must be more than 15.0% by mass in terms of SiO ₂ . On the other hand, in order to obtain a high specific resistance, it is sufficient that the Si content is 20% by mass in terms of SiO ₂ , and it is not necessary to be more than this. That is, the sputtering target for a transparent conductive film of the present invention can be combined with a "Sn content of 0% by mass or more and 10.0% by mass or less in terms of SnO ₂ " and "15.0% by mass or more and 20.0% in terms of SiO ₂ conversion". % Si content "and DC sputtering, and the combination thereof can have both high specific resistance and high etching processability of the transparent conductive film after film formation.

The relative density of the aforementioned sputtering target for a transparent conductive film is preferably 98.0% or more, more preferably 98.5% or more, and still more preferably 99.0% or more. When the relative density is 98.0% or more, there is less generation of bumps or arcs, and efficient sputtering can be performed. The upper limit of the relative density is not particularly limited and may exceed 100%. The aforementioned relative density is a value measured according to the Archimedes method.

The aforementioned sputtering target for a transparent conductive film is preferably in an X-ray diffraction measurement, and all of the Si systems are shown by spectral peaks of an indium silicate compound having a yttrium-type structure. That is, the target contains an indium silicate compound having a yttrium-type structure, and when X-ray diffraction measurement is performed on the target, it is preferable that all Si is a silicate having a yttrium-type structure The peak of the indium compound is shown, and it is not shown as a peak of a Si compound other than an indium silicate compound having a yttrium-type structure. The indium silicate compound having a yttrium type structure is, for example, a compound represented by In ₂ Si ₂ O ₇ . Examples of the Si compound other than the indium silicate compound having a yttrium-type structure include SiO ₂ . When the aforementioned sputtering target for a transparent conductive film satisfies this condition, there is no segregation of the insulator, so that the generation of arcs or bumps is reduced.

The sputtering target for a transparent conductive film includes, in addition to an indium silicate compound phase having a yttrium-type structure, for example, an In ₂ O ₃ phase and an In ₄ Sn ₃ O ₁₂ phase.

The aforementioned sputtering target for a transparent conductive film can be produced by, for example, the method shown below.

First, the raw material powder is mixed. The raw material powder is usually In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder. The In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder are mixed so that the contents of In, Sn, and Si in the obtained sintered body fall within the above ranges, respectively. In addition, it was confirmed that the content ratios of In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder in the mixed powder obtained by mixing the raw material powders are respectively the In content converted to In ₂ O ₃ in the oxide sintered body. Ratios, Sn content ratios in terms of SnO ₂ and Si content ratios in terms of SiO ₂ are consistent.

Since the particles of each raw material powder generally exhibit agglomeration, it is preferable to pulverize and mix beforehand, or to pulverize while mixing.

The method for pulverizing and mixing the raw material powder is not particularly limited. For example, the raw material powder can be placed in a mortar and pulverized or mixed by a ball mill.

The obtained mixed powder can also be directly shaped into a shaped body and sintered, but a binder can be added to the mixed powder to form a shaped body as required. The binder may be a binder used in a known powder metallurgy method to obtain a shaped body, such as polyvinyl alcohol, an acrylic emulsion binder, or the like. In addition, a dispersant may be added to the mixed powder to prepare a slurry, the slurry may be spray-dried and dried to prepare granules, and the granules may be formed.

The forming method may be a method used in the conventional powder metallurgy, such as cold pressing, CIP (cold equalizing forming), and the like.

Further, the mixed powder may be temporarily pre-pressed to prepare a preform, and the pulverized powder obtained by the pulverization may be pressurized to form a formed body.

In addition, a molded body may be produced by a wet molding method such as a slit casting method.

The relative density of the formed body is usually 50 to 75%.

A sintered body can be obtained by firing the obtained molded body. The firing furnace used for firing is not particularly limited as long as it can control the cooling rate during cooling, and it can also be a firing furnace generally used in powder metallurgy. The firing environment is preferably an oxygen-containing environment.

From the viewpoint of high density and crack prevention, the temperature rising rate is usually 100 to 500 ° C / h. The firing temperature is 1300 to 1600 ° C, preferably 1400 to 1600 ° C. When the firing temperature is within the aforementioned range, a high-density sintered body can be obtained. The holding time at the aforementioned firing temperature is usually 3 to 30 hours, preferably 5 to 20 hours. When the holding time is within the aforementioned range, a high-density sintered body is easily obtained.

After the temperature is maintained, the temperature in the firing furnace is lowered to be generally 300 ° C./hr or less, and preferably 100 ° C./hr or less, and cooled.

The sintered body obtained in this manner is cut into a desired shape as needed, and is polished, etc., thereby obtaining the aforementioned sputtering target for a transparent conductive film.

The shape of the sputtering target for the transparent conductive film is a flat plate shape, a cylindrical shape, or the like, and is not particularly limited.

The sputtering target for a transparent conductive film is usually used for bonding to a substrate. The substrate is usually made of Cu, Al, Ti, or stainless steel. The bonding material may be a bonding material used for bonding conventional ITO targets, for example, In metal. The bonding method is also the same as that of the conventional ITO target.

By sputtering the transparent conductive film with a sputtering target, a transparent conductive film can be formed. As described above, since the sputtering target for the transparent conductive film has a lower specific resistance, not only RF sputtering but also DC sputtering can be performed.

By sputtering the transparent conductive film with a sputtering target, a transparent conductive film having In, Sn, Si, and O, or In, Si, and O as constituent elements can be obtained. The Sn content ratio and the Si content ratio of the obtained transparent conductive film tend to be lower than the Sn content ratio and the Si content ratio of the aforementioned sputtering target for a transparent conductive film. Thus, the transparent conductive film, In the content ratio of In ₂ O ₃ 73.0 mass% in terms of 87.0% by mass or less, more preferably 74.0 mass% based 87.0 mass%, Sn content ratio of the terms of SnO ₂ 0 The content is more than 0% by mass and not more than 9.0% by mass, preferably 0% by mass or more and 8.0% by mass or less, and the content ratio of Si in terms of SiO ₂ is 13.0% by mass or more and 18.0% by mass or less, preferably 13.0% by mass or more and 16.0% by mass or less. As described above, the obtained transparent conductive film has a high specific resistance and high etching processability. Also, as in the case of the sputtering target for a transparent conductive film, the transparent conductive film may contain unavoidable impurities. The content of the unavoidable impurities in the transparent conductive film is usually 100 ppm or less.

    [Example]    

The measurement methods used in the following examples and comparative examples are shown below.

Target relative density

The relative density of the sputtering target for a transparent conductive film was measured according to the Archimedes method. Specifically, the air mass of the target is divided by the volume (the mass of the target in water / the specific gravity of water at the measurement temperature) to give a percentage relative to the theoretical density ρ (g / cm ³ ) according to the following formula (X) The value is taken as the relative density (unit:%).

ρ = ((C1 / 100) / ρ1 + (C2 / 100) / ρ2 + ‧‧‧ + (Ci / 100) / ρi) ^-1 (X) (where C1 to Ci are the contents of the constituent materials of the target, respectively (Mass%), ρ1 to ρi represent the density (g / cm ³ ) of each constituent substance corresponding to C1 to Ci.)

Since the substances (raw materials) used for target production in the following examples and comparative examples are In ₂ O ₃ , SnO ₂ , and SiO ₂ , the theoretical density can be calculated by applying the following to formula (X), for example. ρ .

C1: mass% of In ₂ O ₃ raw material used for target

ρ1: Density of In ₂ O ₃ (7.18g / cm ³ )

C2: mass% of SnO ₂ raw material used in the target

ρ2: Density of SnO ₂ (6.95g / cm ³ )

C3: mass% of SiO ₂ raw material used in the target

ρ3: density of SiO ₂ (2.20g / cm ³ )

2. Target specific resistance

The specific resistance of the sputtering target was measured by using the Loresta (registered trademark) HP MCP-T410 (series 4 probe TYPE ESP) manufactured by Mitsubishi Chemical Corporation against the surface of the sintered body after processing, and the measurement was performed in the AUTO RANGE mode.

3. Existing state of Si in sputtering target

The existence state of Si in the sputtering target was measured using an X-ray diffraction device SmartLab (registered trademark) manufactured by Rigaku Corporation under the following conditions.

‧Line source: CuKα line

‧ Tube voltage: 40kV

‧ Tube current: 30mA

‧Scanning speed: 5deg / min

‧Step: 0.02deg

‧Scanning range: 2θ = 20 degrees to 80 degrees

4. Film specific resistance of transparent conductive film

The specific resistance of the transparent conductive film was measured using a four-probe measuring instrument K-705RS manufactured by Kyowa Riken.

5. Etching rate of transparent conductive film

The etching rate of the transparent conductive film was etched by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) which had been heated to 40 ° C for 6 minutes, and KLA- The stylus-type surface shape measuring instrument P-15 manufactured by Tencor Corporation measures the difference in height between the place where the etching has been performed and the place where the etching has not been performed, and calculates the difference by dividing the difference between the etching time.

6.In, Sn, Si content ratio of transparent conductive film

For the measurement, a transparent conductive film formed on a copper foil was used. The content ratios of In and Sn are measured by the acid decomposition ICP-OES method using 720 ICP-OES, an ICP emission spectrophotometer made by Agilent Technologies, and the Si content ratio is measured using a spectrophotometer U-2900 manufactured by Hitachi, Ltd. Molybdenum blue absorptiometry was used for the measurement.

[Examples and Comparative Examples]

(Manufacture of sputtering target)

In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder were mixed at a ratio shown in Table 1 using a pellet mill to prepare a mixed powder.

To the aforementioned mixed powder, 6% by mass of polyvinyl alcohol diluted to 4% by mass relative to the mixed powder was added, and the powder was fully impregnated with the polyvinyl alcohol using a mortar, and passed through a 5.5-mesh sieve. The obtained powder was pre-pressed under the conditions of 200 kg / cm ² , and the obtained pre-formed body was pulverized in a mortar. The obtained pulverized material was filled in a mold for pressurization, and formed at a pressurization pressure of 1 t / cm ² for 60 seconds to obtain a molded body.

The obtained formed body was placed in a firing furnace, and oxygen was flowed in the furnace at 1 L / h. The firing environment was set as an oxygen flowing environment, and the heating rate was 350 ° C / h, the sintering temperature was 1550 ° C, The holding temperature was held for 9 hours. Thereafter, it was cooled at a temperature reduction rate of 100 ° C / h. In Comparative Example 7, the firing temperature was 1250 ° C.

An oxide sintered body was obtained in the above manner.

This oxide sintered body was cut to produce a sputtering target. The relative density, specific resistance of the sputtering target, and the existence state of Si in the sputtering target were measured by the methods described above. The results are shown in Table 1.

In the "existing state of Si" in Table 1, the notation of "In ₂ Si ₂ O ₇ " indicates that in the X-ray diffraction measurement, all of the Si in the sputtering target has a spectral peak of In ₂ Si ₂ O ₇ It is shown that the designation of "SiO ₂ + In ₂ Si ₂ O ₇ " indicates that all Si systems in the sputtering target are shown by the spectral peak of SiO _{2 and} the spectral peak of In ₂ Si ₂ O ₇ .

The X-ray diffraction pattern of the sputtering target obtained in Example 3 is shown in FIG. 1. In FIG. 1, the black circles represent the peaks of In ₂ O ₃ , and the black triangles represent the peaks of In ₂ Si ₂ O ₇ . It can be confirmed from FIG. 1 that all the Si in the sputtering target obtained in Example 3 exists as Si in In ₂ Si ₂ O ₇ of an indium silicate compound having a yttrium-type structure.

(Manufacture of transparent conductive film)

The sputtering target was bonded to a copper support plate with In solder, and sputtering was performed under the following conditions. A transparent conductive film having a thickness of 1000 Å was formed on a glass substrate for measurement of specific resistance and etching rate. A 15,000 Å transparent conductive film was formed on a copper foil having a thickness of 1.1 mm. The transparent conductive film was used to measure the Sn content ratio and Si content ratio. Moreover, in Comparative Example 6, since the target has a high specific resistance and no discharge occurs, DC sputtering cannot be performed. Moreover, the target system of Comparative Example 7 often generates arcs and bumps, and cannot form a film stably. Therefore, film formation evaluation cannot be performed.

Device: DC magnetron spattering device, exhaust refrigeration pump, rotary pump

Reaching vacuum degree: 1 × 10 ^-4 Pa

Sputtering pressure: 0.4Pa

Oxygen flow: 0 to 3.0 sccm

The specific resistance, the etching rate, the In content ratio, the Sn content ratio, and the Si content ratio of the obtained transparent conductive film were measured by the methods described above. The condition of the oxygen flow rate is appropriately adjusted to a condition where an amorphous transparent conductive film can be obtained and the specific resistance of the film is the lowest. The results are shown in Table 1.

Claims (9)

A sputtering target for a transparent conductive film includes an oxide sintered body, and the constituent elements of the oxide sintered body are In, Sn, Si, and O, or In, Si, and O, and the content ratio of In is In ₂ O ₃ Converted to 70.0% by mass or more and less than 85.0% by mass, the content ratio of Sn is 0% to 10.0% by mass in terms of SnO ₂ , and the content ratio of Si is more than 15.0% by mass to 20.0% by mass in terms of SiO ₂ ; Among them, in the X-ray diffraction measurement of the aforementioned sputtering target, all of the Si systems are shown as the peaks of the indium silicate compound having a yttrium-type structure. The sputter target for a transparent conductive film as described in item 1 of the scope of the patent application has a specific resistance of 2.0 × 10 ² Ωcm or less.     The relative density of the sputtering target for a transparent conductive film as described in item 1 or 2 of the patent application range is 98.0% or more.     A transparent conductive film whose constituent elements are In, Sn, Si, and O, or In, Si, and O, and the content ratio of In is 73.0% by mass or more and 87.0% by mass or less in terms of In ₂ O _3. The content ratio of Sn is SnO _{2 is} converted to 0% by mass or more and 9.0% by mass or less, and the content ratio of Si is 13.0% by mass or more and 18.0% by mass or less in terms of SiO ₂ . The transparent conductive film described in item 4 of the scope of application for a patent has a film specific resistance of 1.0 × 10 ⁰ Ωcm or more.     The transparent conductive film according to item 4 or 5 of the scope of the patent application has an etching rate of more than 11.0 Å / sec.         A method for manufacturing a transparent conductive film is formed by sputtering a target for a transparent conductive film according to any one of claims 1 to 3 of the scope of patent application.     The method for manufacturing a transparent conductive film according to item 7 in the scope of the patent application, wherein the specific resistance of the transparent conductive film is 1.0 × 10 ⁰ Ωcm or more.     The manufacturing method of the transparent conductive film according to item 7 or 8 of the scope of the patent application, wherein the etching rate of the transparent conductive film is more than 11.0 Å / sec.