JP7509690B2 - Crystallized indium tin composite oxide film, transparent conductive film and method for producing same - Google Patents

Description

The present invention relates to a crystallized indium tin composite oxide film, a transparent conductive film, and a method for manufacturing the same, and more particularly to a crystallized indium tin composite oxide film, a transparent conductive film comprising the same, and a method for manufacturing the same.

Conventionally, transparent conductive films are known to have a transparent conductive film mainly composed of crystalline indium oxide on a transparent plastic film substrate. Crystalline transparent conductive films usually contain multiple crystal grains.

For example, a transparent conductive film has been proposed having a thickness of 20 nm and an average crystal grain size (average grain size) of 130 nm (see, for example, Example 6 of Patent Document 1 below).

JP 2010-28275 A

In recent years, transparent conductive films are required to have lower surface resistance. To this end, proposals have been made to make the transparent conductive films thicker.

However, as the transparent conductive film becomes thicker, the average crystal grain size becomes smaller, which causes the problem of reduced chemical resistance.

The present invention provides a transparent conductive film that has low surface resistance while having excellent chemical resistance, and a method for producing the same.

The present invention (1) includes a crystallized indium tin composite oxide film having a thickness of 35 nm or more and containing crystal grains having an average grain size of 110 nm or more.

This crystalline indium tin composite oxide film is thick, at 35 nm, and has low surface resistance.

In addition, this crystallized indium tin composite oxide film contains crystal grains with a large average grain size of 110 nm or more, and therefore has excellent chemical resistance.

Therefore, this crystallized indium tin composite oxide film has low surface resistance while also having excellent chemical resistance.

The present invention (2) includes a crystallized indium tin composite oxide film described in (1) which includes an area in which the proportion of tin oxide is 8 mass% or more.

This crystallized indium tin composite oxide film can reduce surface resistance.

The present invention (3) includes a transparent conductive film comprising a transparent film substrate and a crystallized indium tin composite oxide film described in (1) or (2) arranged on one surface in the thickness direction of the film substrate.

This transparent conductive film has the above-mentioned crystallized indium tin composite oxide film, and therefore has low surface resistance while also having excellent chemical resistance.

The present invention (4) includes a transparent conductive film described in (3), in which one surface in the thickness direction of the transparent film substrate has an arithmetic mean roughness Ra of 1.0 nm or less.

In this transparent conductive film, one surface in the thickness direction of the transparent film substrate has a small arithmetic mean roughness Ra of 1.0 nm or less, so that the inhibition of crystal growth can be suppressed in the amorphous indium tin composite oxide film disposed on one surface in the thickness direction of the transparent film substrate. Therefore, crystal grains with a large average grain size can be formed in the crystallized indium tin composite oxide film. As a result, the crystallized indium tin composite oxide film of the transparent conductive film has excellent chemical resistance.

The present invention (5) is a method for producing a transparent conductive film according to (2) or (3), comprising a first step of forming an amorphous indium tin composite oxide film by sputtering on one surface in the thickness direction of the transparent film substrate, and a second step of heating the amorphous indium tin composite oxide film to form a crystallized indium tin composite oxide film, in which the first step of sputtering is performed in the presence of an inert gas having a partial pressure of 0.4 Pa or more.

In the first step of the method for producing this transparent conductive film, sputtering is performed in the presence of an inert gas with a high partial pressure of 0.4 Pa or more, which allows the formation of crystal grains with a large average grain size. As a result, a transparent conductive film having a crystallized indium tin composite oxide film with excellent chemical resistance can be produced.

The crystallized indium tin composite oxide film obtained by the manufacturing method of the present invention has low surface resistance and excellent chemical resistance.

FIG. 1 is a cross-sectional view of one embodiment of the crystallized indium tin composite oxide film and transparent conductive film of the present invention. FIG. 2 is a cross-sectional view of a modified example of the transparent conductive film shown in FIG. 3A and 3B are image-processed SEM photographs taken in the evaluation of the examples, with FIG. 3A showing Reference Example 1 and FIG. 3B showing Comparative Example 2.

<One embodiment>
[Crystallized indium tin composite oxide film]
An embodiment of the crystallized indium tin composite oxide film of the present invention will be described.

This crystallized indium tin composite oxide film has one side and the other side that face each other in the thickness direction. The crystallized indium tin composite oxide film has a film shape that extends in a plane direction perpendicular to the thickness direction.

The thickness of the crystallized indium tin composite oxide film is 35 nm or more. If the thickness of the crystallized indium tin composite oxide film is below the above lower limit, the surface resistance of the crystallized indium tin composite oxide film cannot be reduced.

The thickness of the crystallized indium tin composite oxide film is preferably 38 nm or more, more preferably 40 nm or more, even more preferably 45 nm or more, particularly preferably 50 nm or more, most preferably 55 nm or more, and even more preferably 60 nm or more, 70 nm or more, 80 nm or more, 100 nm or more, 125 nm or more, or 150 nm or more. If the thickness of the crystallized indium tin composite oxide film is equal to or greater than the above-mentioned lower limit, the surface resistance of the crystallized indium tin composite oxide film can be sufficiently reduced.

In addition, the upper limit of the thickness of the crystallized indium tin composite oxide film is not particularly limited from the viewpoint of reducing the surface resistance of the crystallized indium tin composite oxide film. The thickness of the crystallized indium tin composite oxide film is usually 1000 nm or less, and 500 nm or less.

This crystallized indium tin composite oxide film contains crystal grains. A plurality of crystal grains (see reference numeral 9 in FIG. 3A) are present in the crystallized indium tin composite oxide film. The plurality of crystal grains are present, for example, throughout the entire surface direction and the entire thickness direction of the crystallized indium tin composite oxide film. Each of the plurality of crystal grains is partitioned by a crystal grain boundary (see reference numeral 10 in FIG. 3A).

The average grain size of the crystal grains is 110 nm or more.

The average grain size is the average grain size measured when one side of the crystallized indium tin composite oxide film in the thickness direction is observed using an SEM, and the details of the measurement method are described in detail in the examples below.

3B, if the average grain size of the crystal grains 9 falls below the lower limit, the occupancy rate per unit area of the crystal grain boundaries 10 in the crystallized indium tin composite oxide film 1 increases excessively. In this case, when one surface in the thickness direction of the crystallized indium tin composite oxide film 1 is exposed to a liquid chemical and the above-mentioned crystal grain boundaries 10 become an entrance for the penetration path of the chemical, the occupancy rate per unit area of this entrance also increases, resulting in a significant decrease in chemical resistance.

The average grain size of the crystal grains is preferably 130 nm or more, more preferably 150 nm or more, even more preferably 170 nm or more, particularly preferably 200 nm or more, most preferably 250 nm or more, and even more preferably 300 nm or more, 400 nm or more, or 450 nm or more. If the average grain size of the crystal grains is equal to or greater than the above-mentioned lower limit, the deterioration of the chemical resistance of the crystallized indium tin composite oxide film can be sufficiently suppressed.

The material of the crystallized indium tin composite oxide film is crystalline indium tin composite oxide (ITO). ITO is a composite oxide containing indium (In) and tin (Sn) as essential components. Specifically, ITO contains tin oxide (SnO ₂ ) and indium oxide (In ₂ O ₃ ) as main components.

The tin oxide content is, for example, 0.5 mass% or more, preferably 3 mass% or more, more preferably 5 mass% or more, even more preferably 8 mass% or more, and particularly preferably 9 mass% or more, relative to the total amount of tin oxide and indium oxide, and is, for example, 20 mass% or less, preferably 15 mass% or less.

If the content of tin oxide is equal to or higher than the lower limit described above, the surface resistance of the crystallized indium tin composite oxide film can be reduced. If the content of tin oxide is equal to or lower than the upper limit described above, the crystallized indium tin composite oxide film has excellent strength.

The content of indium oxide is the remainder of the content of tin oxide in the total amount described above. ITO may also contain additional components other than the main components (essential components), specifically, additional components such as Zn, Ga, Sb, Ti, Si, Zr, Mg, Al, Au, Ag, Cu, Pd, W, Fe, Pb, Ni, Nb, Cr, and Ga.

In addition, the crystallized indium tin composite oxide film may include a region in which the proportion of tin oxide is 8% by mass or more. When the crystallized indium tin composite oxide film includes a region in which the proportion of tin oxide is 8% by mass or more, the surface resistance of the crystallized indium tin composite oxide film can be reduced.

For example, the crystallized indium tin composite oxide film includes a first region (see reference numeral 11) as an example of a region in which the proportion of tin oxide is 8% by mass or more, and a second region (see reference numeral 12) in which the proportion of tin oxide is lower than the proportion of tin oxide in the first region. Specifically, the crystallized indium tin composite oxide film includes a layered first region and a layered second region arranged on one surface in the thickness direction of the first region, in that order. Note that the boundary between the first region and the second region is not confirmed by observation with a measuring device, and it is permitted to be unclear. Note that this crystallized indium tin composite oxide film may have a concentration gradient in which the tin oxide concentration gradually increases from one surface to the other surface in the thickness direction. When the crystallized indium tin composite oxide film includes the second region in addition to the first region described above, the desired crystallization speed can be obtained by adjusting the ratio of the region.

The proportion of tin oxide in the first region is preferably 9% by mass or more, more preferably 10% by mass or more and 20% by mass or less.

The ratio of the thickness of the first region to the thickness of the crystallized indium tin composite oxide film is, for example, more than 50%, preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. If the ratio of the thickness of the first region is equal to or greater than the above-mentioned lower limit, the ratio of tin oxide in the crystallized indium tin composite oxide film can be increased, and therefore the surface resistance of the crystallized indium tin composite oxide film can be sufficiently reduced. The ratio of the thickness of the first region to the thickness of the crystallized indium tin composite oxide film is, for example, 99% or less, preferably 97% or less.

The proportion of tin oxide in the second region is, for example, less than 8 mass%, preferably 7 mass% or less, more preferably 5 mass% or less, and even more preferably 4 mass% or less, and is, for example, 1 mass% or more, preferably 2 mass% or more, and more preferably 3 mass% or more.

The ratio of the proportion of tin oxide in the first region to the proportion of tin oxide in the second region (proportion of tin oxide in the first region/proportion of tin oxide in the second region) is, for example, 1.5 or more, preferably 2 or more, more preferably 2.5 or more, and is, for example, 5 or less, preferably 4 or less.

The tin oxide concentration in each of the crystallized indium tin composite oxide film, the first region, and the second region is measured by X-ray photoelectron spectroscopy. Alternatively, the tin oxide content can be estimated from the known composition of the target used when forming the amorphous indium tin composite oxide film by sputtering.

The surface resistance of the crystallized indium tin composite oxide film is, for example, 60 Ω/□ or less, preferably 50 Ω/□ or less, more preferably 45 Ω/□ or less, even more preferably 40 Ω/□ or less, particularly preferably 30 Ω/□ or less, and most preferably 20 Ω/□ or less.
If the surface resistance of the crystallized indium tin composite oxide film is equal to or less than the above upper limit, excellent electrical properties can be exhibited when the crystallized indium tin composite oxide film is patterned and used as an electrode.

The lower limit of the surface resistance of the crystallized indium tin composite oxide film is not particularly limited. For example, the surface resistance of the crystallized indium tin composite oxide film is usually more than 0 Ω/□ and is 1 Ω/□ or more. The surface resistance of the crystallized indium tin composite oxide layer 7 is measured by a four-terminal method.

In addition, the arithmetic mean roughness Ra of the other surface in the thickness direction of the crystallized indium tin composite oxide film is the same as, for example, the arithmetic mean roughness Ra of the other surface in the thickness direction of the transparent film substrate, since the other surface in the thickness direction of the crystallized indium tin composite oxide film closely adheres to and follows one surface in the thickness direction of the transparent film substrate described below. Specifically, the arithmetic mean roughness Ra of the other surface in the thickness direction of the crystallized indium tin composite oxide film is, for example, 2 nm or less, preferably 1 nm or less, more preferably 0.75 nm or less, even more preferably 0.5 nm or less, and is, for example, 0.001 nm or more.

[Transparent conductive film]
Next, a transparent conductive film including the above-mentioned crystallized indium tin composite oxide film will be described with reference to FIG.

The transparent conductive film 3 has a film shape extending in the surface direction. The transparent conductive film 3 comprises a transparent film substrate 2 and a crystallized indium tin composite oxide film 1, which are arranged in this order toward one side in the thickness direction. The transparent conductive film 3 comprises a transparent film substrate 2 and a crystallized indium tin composite oxide film 1 disposed on one surface in the thickness direction of the transparent film substrate 2. Preferably, the transparent conductive film 3 comprises only the transparent film substrate 2 and the crystallized indium tin composite oxide film 1.

The transparent film substrate 2 forms the outer shape of the transparent conductive film 3. The transparent film substrate 2 is transparent. The transparent film substrate 2 includes, for example, an antiblocking layer 5, a transparent film 6, a hard coat layer 7, and an optical adjustment layer 8, which are arranged in this order toward one side in the thickness direction. The transparent film substrate 2 includes an antiblocking layer 5, a transparent film 6 arranged on one side in the thickness direction of the antiblocking layer 5, a hard coat layer 7 arranged on one side in the thickness direction of the transparent film 6, and an optical adjustment layer 8 arranged on one side in the thickness direction of the hard coat layer 7. Preferably, the transparent film substrate 2 includes only the antiblocking layer 5, the transparent film 6, the hard coat layer 7, and the optical adjustment layer 8.

The anti-blocking layer 5 imparts anti-blocking properties to the surfaces of the transparent conductive films 3 that are in contact with each other, for example, when the transparent conductive films 3 are laminated in the thickness direction. The material of the anti-blocking layer 5 is, for example, an anti-blocking composition. Examples of the anti-blocking composition include the mixtures described in JP 2016-179686 A. The mixture contains, for example, a resin (binder resin) such as an acrylic resin, and inorganic and/or organic particles (preferably organic particles such as polystyrene). The thickness of the anti-blocking layer 5 is, for example, 0.1 μm or more, and, for example, 10 μm or less.

The transparent film 6 is an essential layer in the transparent film substrate 2. The transparent film 6 is a transparent substrate for ensuring the mechanical strength of the transparent conductive film 3. The transparent film 6 has a film shape and extends in the plane direction. The transparent film 6 is in contact with one surface in the thickness direction of the antiblocking layer 5. Examples of materials for the transparent film 6 include resins such as cycloolefin resin (COP) and polyester resin (polyethylene terephthalate (PET) etc.). Preferably, cycloolefin resin is used. The transparent film 6 is isotropic or birefringent. The transparent film substrate 2 is preferably isotropic. The birefringence in the in-plane direction of the transparent film substrate 2 is, for example, 100 or less, preferably 50 or less, and is, for example, 0 or more. The thickness of the transparent film 6 is, for example, 10 μm or more, and, for example, 100 μm or less.

The hard coat layer 7 is an abrasion protection layer for preventing scratches from occurring on the transparent conductive film 3. The hard coat layer 7 is in contact with one surface in the thickness direction of the transparent film 6. The material of the hard coat layer 7 is, for example, a hard coat composition. Examples of the hard coat composition include the mixtures described in JP 2016-179686 A. The mixture contains, for example, a resin (binder resin) such as an acrylic resin or a urethane resin. The thickness of the hard coat layer 3 is, for example, 0.1 μm or more, and, for example, 10 μm or less.

The optical adjustment layer 8 is a layer that suppresses the visibility of the pattern formed from the crystallized indium tin composite oxide film 1 and adjusts the optical properties (specifically, the refractive index) of the transparent conductive film 3. The optical adjustment layer 8 is in contact with one surface in the thickness direction of the hard coat layer 7. The material of the optical adjustment layer 8 is, for example, an optical adjustment composition. Examples of the optical adjustment composition include the mixture described in JP 2016-179686 A. The mixture contains, for example, a resin (binder resin) such as an acrylic resin and inorganic and/or organic particles (preferably inorganic particles such as zirconia). The thickness of the optical adjustment layer 8 is, for example, 0.05 μm or more, and, for example, 1 μm or less.

The arithmetic mean roughness Ra of one surface in the thickness direction of the optical adjustment layer 8 is, for example, 2 nm or less, preferably 1 nm or less, more preferably 0.75 nm or less, even more preferably 0.5 nm or less, and is, for example, 0.001 nm or more. The arithmetic mean roughness Ra of one surface in the thickness direction of the optical adjustment layer 8 is determined in accordance with JIS B0681-6 (2017).

The thickness of the transparent film substrate 2 is, for example, 10 μm or more and, for example, 100 μm or less. The total light transmittance of the transparent film substrate 2 is, for example, 80% or more, preferably 90% or more and, for example, 99% or less.

The arithmetic mean roughness Ra of one surface in the thickness direction of the transparent film substrate 2 is the same as the arithmetic mean roughness Ra of the optical adjustment layer 8 described above.

If the arithmetic mean roughness Ra of one surface in the thickness direction of the transparent film substrate 2 is equal to or less than the above-mentioned upper limit, when the amorphous indium tin composite oxide film is heated to form the crystallized indium tin composite oxide film 1, the growth of crystal grains from the surface in contact with one surface in the thickness direction of the transparent film substrate 2, i.e., the other surface in the thickness direction of the amorphous indium tin composite oxide film, toward one side in the thickness direction can be promoted. Therefore, the average grain size of the crystal grains can be increased.

The crystallized indium tin composite oxide film 1 is in contact with one thickness-wise surface of the transparent film substrate 2. One thickness-wise surface of the crystallized indium tin composite oxide film 1 is exposed toward one side in the thickness direction. The other thickness-wise surface of the crystallized indium tin composite oxide film 1 is in close contact (contact) with one thickness-wise surface of the transparent film substrate 2. As described above, the arithmetic mean roughness Ra of the other thickness-wise surface of the crystallized indium tin composite oxide film 1 is, for example, 2 nm or less, preferably 1 nm or less, more preferably 0.75 nm or less, even more preferably 0.5 nm or less, and is, for example, 0.001 nm or more.

The transparent conductive film 3 has a thickness of, for example, 15 μm or more and, for example, 120 μm or less. The transparent conductive film 3 has a total light transmittance of, for example, 80% or more, preferably 90% or more and, for example, 99% or less.
[Method of manufacturing transparent conductive film]
Next, a method for producing the transparent conductive film will be described.

The method for manufacturing the transparent conductive film 3 includes a first step of forming an amorphous indium tin composite oxide film by sputtering on one surface in the thickness direction of the transparent film substrate 2, and a second step of heating the amorphous indium tin composite oxide film to form a crystallized indium tin composite oxide film 1. In this manufacturing method, each layer is arranged in order, for example, by a roll-to-roll method.

In the first step, a transparent film substrate 2 is first prepared.

For example, a transparent film 6 is prepared. Next, a hard coat layer 7, an anti-blocking layer 5, and an optical adjustment layer 8 are disposed on the transparent film 6.

Specifically, first, a diluted solution of the hard coat composition and a diluted solution of the antiblocking composition are applied to both sides of the transparent film 6 in the thickness direction, and after drying, the hard coat composition and the antiblocking composition are cured by ultraviolet light irradiation. As a result, a hard coat layer 7 and an antiblocking layer 5 are formed on both sides of the transparent film 6 in the thickness direction. Then, a diluted solution of the optical adjustment composition is applied to one side of the hard coat layer 7 in the thickness direction, and after drying, the optical adjustment composition is cured by ultraviolet light irradiation. As a result, an optical adjustment layer 8 is formed. As a result, a transparent film substrate 2 is prepared, which is a laminated film having an antiblocking layer 5, a transparent film 6, a hard coat layer 7, and an optical adjustment layer 8 in order toward one side in the thickness direction.

Next, in the first step, sputtering is performed on one surface in the thickness direction of the transparent film substrate 2. Specifically, in a sputtering device, one surface in the thickness direction of the transparent film substrate 2 is placed facing a target made of indium tin composite oxide, and sputtering is performed in the presence of an inert gas. At this time, in addition to the inert gas described above, a reactive gas such as oxygen can also be present.

Examples of inert gases include rare gases such as argon. The partial pressure of the inert gas in the sputtering device is, for example, 0.1 Pa or more, preferably 0.3 Pa or more, more preferably 0.5 Pa or more, and even more preferably 0.55 Pa or more, and is, for example, 10 Pa or less. If the partial pressure of the inert gas is equal to or higher than the lower limit described above, the energy of the atoms of the inert gas during sputtering is lowered. This makes it possible to suppress the amorphous indium tin composite oxide film from taking in atoms of the inert gas. As a result, the growth of crystal grains can be promoted. This allows the average grain size of the crystal grains to be increased.

The pressure inside the sputtering apparatus is the total pressure of the partial pressure of the inert gas and the partial pressure of the reactive gas.

In addition, the first target and the second target having different tin oxide concentrations can be arranged in order in the sputtering device along the transport direction of the transparent film substrate 2. The material of the first target is, for example, ITO ( _SnO2 concentration: 8 mass% or more) in the first region described above. The material of the second target is, for example, ITO ( _SnO2 concentration: less than 8 mass%) in the second region described above.

By the above sputtering, an amorphous indium tin composite oxide film is formed on one thickness-wise surface of the transparent film substrate 2.

In addition, when the amorphous indium tin composite oxide film is formed by sputtering using the above-mentioned first target and second target, the amorphous indium tin composite oxide film has a first amorphous layer and a second amorphous layer having different tin oxide concentrations, arranged in order toward one side in the thickness direction. The materials of the first amorphous layer and the second amorphous layer are the same as the materials of the first target and the second target. Specifically, the _SnO2 concentration in the ITO of the first amorphous layer is, for example, 8 mass% or more. The _SnO2 concentration in the ITO of the second amorphous layer is, for example, less than 8 mass%.

The ratio of the thickness of the first amorphous layer to the thickness of the amorphous indium tin composite oxide film is, for example, more than 50%, preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. The ratio of the thickness of the first amorphous layer to the thickness of the crystallized indium tin composite oxide film is, for example, 99% or less, preferably 97% or less.

This amorphous indium tin composite oxide film has not yet been crystallized, that is, it is not the crystallized indium tin composite oxide film of the present invention. The amorphous indium tin composite oxide film is a precursor film (intermediate material) for obtaining a crystallized indium tin composite oxide film.

This results in an amorphous laminate film consisting of a transparent film substrate 2 and an amorphous indium tin composite oxide film.

Then, in the second step, the amorphous laminate film is heated. For example, the amorphous indium tin composite oxide film is heated by a heating device such as an infrared heater or an oven.

The heating conditions are not particularly limited. The heating temperature is, for example, 90°C or higher, preferably 110°C or higher, and, for example, 160°C or lower, preferably 140°C or lower. The heating time is, for example, 30 minutes or longer, more preferably 60 minutes or longer, and, for example, 5 hours or shorter, preferably 3 hours or shorter.

As a result, the amorphous indium tin composite oxide layer is crystallized to form a crystallized indium tin composite oxide film 1 containing multiple crystal grains, as shown in Figure 1.

In addition, when the amorphous indium tin composite oxide film includes a first amorphous layer and a second amorphous layer, the crystallized indium tin composite oxide film 1 includes a first layer 11 and a second region 12 corresponding to the first amorphous layer and the second amorphous layer, respectively.

As described above, this crystallized indium tin composite oxide film 1 has a thickness of 35 nm or more and contains crystal grains with an average grain size of 110 nm or more.

This produces a transparent conductive film 3 comprising a transparent film substrate 2 and a crystallized indium tin composite oxide film 1.

Then, the crystallized indium tin composite oxide film 1 is patterned on the transparent conductive film 3, for example, by etching. The patterned crystallized indium tin composite oxide film 1 is used as an electrode for a touch panel (touch sensor) or the like.

This crystallized indium tin composite oxide film 1 has a thickness of 35 nm and therefore has low surface resistance.

In addition, this crystallized indium tin composite oxide film contains crystal grains with a large average grain size of 110 nm or more, and therefore has excellent chemical resistance.

Therefore, the crystallized indium tin composite oxide film 1 of this transparent conductive film 3 has excellent chemical resistance.

In addition, since the crystallized indium tin composite oxide film 1 includes a first region 11 in which the proportion of tin oxide is 8% by mass or more, the surface resistance of the crystallized indium tin composite oxide film 1 can be reduced.

In addition, since this transparent conductive film 3 has the above-mentioned crystallized indium tin composite oxide film 1, it has excellent chemical resistance while having low surface resistance.

In addition, in this transparent conductive film 3, if one surface in the thickness direction of the transparent film substrate 2 has a small arithmetic mean roughness Ra of 1.0 nm or less, inhibition of crystal growth of the amorphous indium tin composite oxide film disposed on one surface in the thickness direction of the transparent film substrate 2 can be suppressed, and crystal grains having a large average grain size can be formed in the crystallized indium tin composite oxide film 1. As a result, the transparent conductive film has excellent chemical resistance.

In the first step of the method for producing this transparent conductive film 3, sputtering is performed in the presence of an inert gas with a high partial pressure of 0.4 Pa or more, thereby forming crystal grains with a large average grain size in the crystallized indium tin composite oxide film 1. As a result, a transparent conductive film 3 including a crystallized indium tin composite oxide film 1 with excellent chemical resistance can be produced.

In the modified example, the same reference numerals are used for the same components and steps as in the first embodiment, and detailed descriptions thereof will be omitted. In addition, the modified example can achieve the same effects as in the first embodiment, unless otherwise specified. Furthermore, the first embodiment and its modified example can be appropriately combined.

The crystalline indium tin composite oxide film may not include a second region in which the proportion of tin oxide is less than 8% by mass, and may include only a first region in which the proportion of tin oxide is 8% by mass or more.

The transparent film substrate 2 is not particularly limited as long as it has a transparent film 6. For example, the present invention includes a first embodiment in which the transparent film substrate 2 has only the transparent film 6, a second embodiment (two-layer structure) in which the transparent film substrate 2 has the transparent film 6 and one layer selected from the group consisting of the antiblocking layer 5, the hard coat layer 7, and the optical adjustment layer 8, and a third embodiment (three-layer structure) in which the transparent film substrate 2 has the transparent film 6 and two layers selected from the group consisting of the antiblocking layer 5, the hard coat layer 7, and the optical adjustment layer 8.

As an example of the third embodiment (three-layer structure), as shown in Figure 2, the transparent film substrate 2 does not have a hard coat layer 7 (see Figure 1), and only has an anti-blocking layer 5, a transparent film 6 and an optical adjustment layer 8.

The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is not limited to the examples and comparative examples. In addition, the specific numerical values of the compounding ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding compounding ratio (content ratio), physical property value, parameter, etc. described in the above "Form for carrying out the invention".

Reference Example 1
First, a transparent film 6 made of a cycloolefin resin (COP film, thickness 40 μm, manufactured by Zeon Corporation, “ZEONOR” (registered trademark), in-plane birefringence 0.0001) was prepared.

Next, a diluted solution of a hard coat composition consisting of a binder resin (urethane polyfunctional polyacrylate, product name "UNIDIC", manufactured by DIC Corporation) was applied to one surface in the thickness direction of the transparent film 6, and a diluted solution of an antiblocking composition containing a binder resin (urethane polyfunctional polyacrylate, product name "UNIDIC", manufactured by DIC Corporation) and particles (crosslinked acrylic-styrene resin particles, product name "SSX105", diameter 3 μm, manufactured by Sekisui Plastics Corporation) was applied to the other surface in the thickness direction of the transparent film 6, and then after drying, ultraviolet rays were irradiated to both surfaces in the thickness direction of the transparent film 6, thereby hardening the hard coat composition and the antiblocking composition. As a result, a hard coat layer 7 having a thickness of 1 μm was formed on one surface of the transparent film 6, and an antiblocking layer 5 having a thickness of 1 μm was formed on the other surface in the thickness direction of the transparent film 6.

Next, a diluted solution of an optical adjustment composition containing zirconia particles and an ultraviolet-curable resin (acrylic resin) ("Opstar Z7412", manufactured by JSR Corporation, refractive index 1.62) was applied to one surface in the thickness direction of the hard coat layer, dried at 80°C for 3 minutes, and then irradiated with ultraviolet light. This formed an optical adjustment layer 8 with a thickness of 0.1 μm on one surface in the thickness direction of the hard coat layer 7. This resulted in a laminated film consisting of the antiblocking layer 5, transparent film 6, hard coat layer 7, and optical adjustment layer 8 being obtained as the transparent film substrate 2.

Then, an amorphous indium tin composite oxide layer 1 having a thickness of 39.7 nm was formed on one thickness-wise surface of the optical adjustment layer 8 by sputtering.

In detail, first, a first target made of ITO with a tin oxide concentration of 10% by weight and a second target made of ITO with a tin oxide concentration of 3.3% by weight were placed in a sputtering device in order from the upstream side to the downstream side in the conveying direction of the transparent film substrate 2. Then, sputtering was performed so that the thickness ratio of the first amorphous layer in the amorphous indium tin composite oxide film and the thickness ratio of the second amorphous layer were 95% and 5%, respectively. The amorphous indium tin composite oxide film includes a first amorphous layer (tin oxide concentration 10% by mass) and a second amorphous layer (tin oxide concentration 3.3% by mass) in order toward one side in the thickness direction.

By adjusting the argon flow rate during sputtering, the argon partial pressure in the sputtering apparatus was adjusted to 0.35 Pa. The pressure in the sputtering apparatus was 0.42 Pa.

This resulted in the production of an amorphous laminate film having, in order, an anti-blocking layer 5, a transparent film 6, a hard coat layer 7, an optical adjustment layer 8 and an amorphous indium tin composite oxide layer.

The amorphous laminate film was then heated at 130°C for 90 minutes to crystallize the amorphous indium tin composite oxide layer, thereby preparing a crystallized indium tin composite oxide film 1.

This resulted in the production of a transparent conductive film 3 having an antiblocking layer 5, a transparent film 6, a hard coat layer 7, an optical adjustment layer 8 and a crystallized indium tin composite oxide film 1, as shown in Figure 1.

In addition, the crystallized indium tin composite oxide film 1 included a first region 11 and a second region 12 resulting from the first amorphous layer and the second amorphous layer, respectively.

Comparative Example 1 to Comparative Example 2
The same treatment as in Reference Example 1 was carried out except that the formulation was changed according to the description in Table 1.

Example 2
The same treatment as in Reference Example 1 was carried out, except that instead of the hard coat layer 7 and the optical adjustment layer 8 in Reference Example 1, an optical adjustment layer 8 having a thickness of 0.7 μm was formed.

In other words, as shown in Figure 2, this transparent film substrate 2 does not have a hard coat layer 7, but instead has an anti-blocking layer 5, a transparent film 6, and an optical adjustment layer 8, in that order.

The optical adjustment layer 8 was prepared by applying a diluted solution of an optical adjustment composition containing zirconia particles, silica particles, and an ultraviolet-curable resin (acrylic resin) ("TYZ72-A12", manufactured by Toyochem Co., Ltd., refractive index 1.72) to one side in the thickness direction of the transparent film 6, drying it at 80°C for 3 minutes, and then irradiating it with ultraviolet light.

Examples 3 to 5, Reference Example 6
The same treatment as in Example 2 was carried out except that the formulation was changed according to the description in Table 1.

Example 7
The same treatment as in Example 2 was carried out except that the sputtering apparatus was not provided with a second target and the recipe was changed according to the description in Table 1.

The amorphous indium tin composite oxide film does not include a second amorphous layer, but includes a first amorphous layer. The crystallized indium tin composite oxide film 1 does not include a second region 12, but includes a first region 11.

<Evaluation>
The following items were evaluated, and the results are shown in Table 1.

[Average grain size]
In each of the examples and comparative examples, one surface in the thickness direction of the crystallized indium tin composite oxide film 1 of the transparent conductive film 3 was observed using an SEM.

The multiple polygonal particles observed in the SEM observation are defined as ITO crystal grains. The area of each of the multiple crystal grains was then calculated. The average value of the square root of the area of each crystal grain divided by pi (π) and multiplied by two was calculated as the average diameter of the crystal grains.

In the SEM observation, a field image of 1500 nm in length and 1500 nm in width was obtained. In this field image, the grain boundaries separating the crystal grains were identified. Based on this, the area of multiple crystal grains was calculated. The grain size of one crystal grain was approximated by doubling the square root of the area of one crystal grain divided by pi (π). Note that crystal grains with a grain size of less than 20 nm were excluded from the calculation of the average value.

In other words, only the areas and numbers of multiple crystal grains that have a grain size of 20 nm or more and that are not protruding from the field of view image (i.e., the entire crystal grain is contained within the field of view image) among the crystal grains observed in the above-mentioned field of view image were used to calculate the average value, and the resulting average value was regarded as the "average grain size of the crystal grains."

The apparatus and measurement conditions are as follows.
SEM device: Hitachi High-Technologies scanning electron microscope SU8020
Acceleration voltage: 0.8 kV
FIG . 3A shows an image-processed SEM photograph of Reference Example 1, and FIG. 3B shows an image-processed SEM photograph of Comparative Example 2.

[Surface resistance of crystallized indium tin composite oxide film]
The surface resistance of the crystallized indium tin composite oxide film 1 of the transparent conductive film 3 in each of the Examples and Comparative Examples was measured by a four-terminal method. The surface resistance was evaluated based on the following criteria.
⊚: The surface resistance was 40 Ω/□ or less.
A: The surface resistance was 60 Ω/□ or less and more than 40 Ω/□.
×: The surface resistance was more than 60 Ω/□.

[Chemical resistance of crystallized indium tin composite oxide film]
In each of the Examples and Comparative Examples, one surface in the thickness direction of the crystallized indium tin composite oxide film 1 of the transparent conductive film 3 was scratched with a cutter knife.

Then, the transparent conductive film 3 was immersed in a 16% by mass aqueous solution of ammonium persulfate at 20°C for 5 minutes. Then, it was immersed in a 3% by mass aqueous solution of potassium hydroxide at 30°C for 20 minutes.

Thereafter, the scratches were observed under an optical microscope, and the chemical resistance was evaluated based on the following criteria.
×: Many cracks extending from the scratches were observed.
◯: The above-mentioned cracks were found only in very small amounts.
⊚: No cracks as described above were observed.

[Arithmetic mean roughness Ra of transparent film substrate]
The arithmetic mean roughness Ra of one surface in the thickness direction of the transparent conductive film 3 before the amorphous indium tin composite oxide film was formed, i.e., the transparent film substrate 2, was measured using an atomic force microscope (Nonoscope IV, manufactured by Digital Instruments Corporation) in accordance with JIS B0681-6 (2017). An area (field of view image) of 1 μm × 1 μm on one surface in the thickness direction of the transparent film substrate 2 was observed with the atomic force microscope.

[Ratio of tin oxide in crystallized indium tin composite oxide film]
First, the tin oxide content in the amorphous indium tin composite oxide film was determined from the tin oxide concentrations in the first target and the second target, and the ratio of the thickness of the first amorphous layer to the thickness of the second amorphous layer in the amorphous indium tin composite oxide film.

Assuming that there is no change in the tin oxide concentration during the conversion from an amorphous indium tin composite oxide film to a crystalline indium tin composite oxide film, the tin oxide content in the amorphous indium tin composite oxide film was estimated as the tin oxide content in the crystalline indium tin composite oxide film.

The above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to a person skilled in the art are included in the scope of the claims below.

A crystalline indium tin composite oxide film is provided on the transparent conductive film.

Reference Signs List 1 Crystallized indium tin composite oxide film 2 Transparent film substrate 3 Transparent conductive film 9 Crystal grains 11 First region

Claims (2)

A transparent film substrate;
a crystallized indium tin composite oxide sputtered film disposed on one surface of the transparent film substrate in a thickness direction;
The one surface in the thickness direction of the transparent film substrate has an arithmetic average roughness Ra of 1.0 nm or less,
The crystalline indium tin composite oxide sputtered film is
A region having a tin oxide content of 9% by mass or more;
A thickness of 35 nm or more,
A transparent conductive film comprising crystal grains having an average grain size of 110 nm or more. A method for producing the transparent conductive film according to claim 1 ,
a first step of forming an amorphous indium tin composite oxide sputtered film by sputtering on one surface in the thickness direction of the transparent film substrate;
A second step of heating the amorphous indium tin composite oxide sputtered film to form a crystallized indium tin composite oxide sputtered film ,
The method for producing a transparent conductive film, wherein the first step is performed in the presence of an inert gas having a partial pressure of 0.4 Pa or more.

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