Transparent conductive film

Abstract

To provide a transparent conductive film suitable for achieving both low resistance and transparency in a transparent conductive layer.SOLUTION: A transparent conductive film X includes a transparent substrate 10 and a transparent conductive layer 20 in a thickness direction H in that order. The transparent conductive layer 20 is 100 nm or more in thickness. The transparent conductive layer 20 includes an amorphous layer 21 and a crystalline layer 22 in that order from the transparent substrate 10 side. The amorphous layer 21 is 30 nm or more in thickness. The ratio of the thickness of the crystalline layer 22 to the thickness of the transparent conductive layer 20 is 15% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a transparent conductive film.

Background Art

[0002] Conventionally, a transparent conductive film having a resin-made transparent substrate and a transparent conductive layer (transparent conductive layer) provided in order in the thickness direction is known. The transparent conductive layer is used, for example, as a conductor film for forming a transparent electrode in various devices such as a display panel, a touch panel, and a solar cell. The transparent conductive layer is formed, for example, as a crystalline or amorphous conductive oxide layer by forming a conductive oxide on a transparent substrate by a sputtering method. Technologies related to such a transparent conductive film are described, for example, in Patent Document 1 below.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The transparent conductive layer of the transparent conductive film is required to have low resistance. In particular, the requirement is strong for a transparent conductive film for transparent electrode applications. From the viewpoint of low resistance, the transparent conductive layer is preferably crystalline rather than amorphous. On the other hand, the transparent conductive layer of the transparent conductive film is also required to have high transparency. From the viewpoint of transparency, the transparent conductive layer is preferably amorphous rather than crystalline. The low resistance and transparency of the transparent conductive layer are in such a trade-off relationship. However, the present inventors have obtained the following findings.

[0005] In the case where a composite transparent conductive layer in which an amorphous layer and a crystalline layer are laminated is relatively thick, the transparency may be higher than that of an amorphous transparent conductive layer (amorphous single layer). The present invention is based on such findings.

[0006] The present invention provides a transparent conductive film suitable for achieving both low resistance and transparency of a transparent conductive layer.

Means for Solving the Problems

[0007] The present invention [1] is a transparent conductive film including a transparent substrate and a transparent conductive layer provided in this order in the thickness direction, where the transparent conductive layer has a thickness of 100 nm or more, the transparent conductive layer has an amorphous layer and a crystalline layer in this order from the transparent substrate side, the amorphous layer has a thickness of 30 nm or more, and the ratio of the thickness of the crystalline layer to the thickness of the transparent conductive layer is 15% or more.

[0008] The present invention [2] includes the transparent conductive film according to the above [1], where the ratio is 70% or less.

[0009] The present invention [3] includes the transparent conductive film according to the above [1] or [2], where the transparent conductive layer is an indium tin composite oxide layer.

[0010] The present invention [4] includes the transparent conductive film according to the above [3], where the tin oxide ratio of the amorphous layer is higher than the tin oxide ratio of the crystalline layer.

Advantages of the Invention

[0011] In the transparent conductive film of the present invention, as described above, the transparent conductive layer has a thickness of 100 nm or more, the transparent conductive layer has an amorphous layer with a thickness of 30 nm or more and a crystalline layer in this order from the transparent substrate side, and the ratio of the thickness of the crystalline layer to the thickness of the transparent conductive layer is 15% or more. The transparent conductive layer having a thickness of 100 nm or more and the crystalline layer thickness ratio in the transparent conductive layer being 15% or more are suitable for ensuring the low resistance of the transparent conductive layer. A transparent conductive layer having a thickness of 100 nm or more having an amorphous layer and a crystalline layer with a thickness of 30 nm or more in this order from the transparent substrate side is suitable for ensuring the transparency of the transparent conductive layer. Such a transparent conductive film is suitable for achieving both low resistance and transparency of the transparent conductive layer.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0013] A transparent conductive film X as an embodiment of the present invention includes a transparent substrate 10 and a transparent conductive layer 20 in this order in the thickness direction H. The transparent conductive film X has a sheet shape that spreads in a direction (plane direction) orthogonal to the thickness direction H. The transparent conductive film X is, for example, an element provided in a touch sensor device, a light control element, a photoelectric conversion element, a heat ray control member, an antenna member, an electromagnetic wave shielding member, a heater member, a lighting device, and an image display device.

[0014] The transparent substrate 10 is an element that ensures the strength of the transparent conductive film X. The transparent substrate 10 has a first surface 11 and a second surface 12 opposite to the first surface 11.

[0015] The transparent substrate 10 is, for example, a flexible transparent resin film. Examples of the material of the resin film include polyester resin, polyolefin resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, polyimide resin, cellulose resin, and polystyrene resin. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of the polyolefin resin include polyethylene, polypropylene, and cycloolefin polymer. An example of the acrylic resin is polymethacrylate. From the viewpoints of transparency and strength, the material of the resin film is preferably a polyester resin, more preferably PET.

[0016] The transparent substrate 10 may have a multilayer structure in which a cured resin layer (not shown) is formed on one or both sides of the resin film. Examples of the cured resin layer include a hard coat layer and an anti-blocking layer. The cured resin layer is a cured product of a curable resin composition. The curable resin composition contains a curable resin. Examples of the curable resin include polyester resin, acrylic urethane resin, acrylic resin (excluding acrylic urethane resin), urethane resin (excluding acrylic urethane resin), amide resin, silicone resin, epoxy resin, and melamine resin. These curable resins may be used alone or in combination of two or more. Also, examples of the curable resin include ultraviolet curable resin and thermosetting resin.

[0017] The curable resin composition may contain particles. Examples of the particles include inorganic oxide particles and organic particles. Examples of the material of the inorganic oxide particles include silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Examples of the material of the organic particles include polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate.

[0018] From the viewpoint of exhibiting the function of the cured resin layer in the transparent conductive film X, the thickness of the cured resin layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1 μm or more. From the viewpoint of ensuring the transparency of the transparent conductive film X, the thickness of the cured resin layer is preferably 10 μm or less, more preferably 5 μm or less, still more preferably 3 μm or less.

[0019] The first surface 11 (the surface on the side of the transparent conductive layer 20) of the transparent substrate 10 may be surface-modified. Examples of the surface modification treatment include corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

[0020] From the viewpoint of ensuring the strength of the transparent conductive film X, the thickness of the transparent substrate 10 is preferably 1 μm or more, more preferably 10 μm or more, still more preferably 50 μm or more, even more preferably 80 μm or more, and still even more preferably 90 μm or more. From the viewpoint of ensuring the handleability of the transparent substrate 10 in the roll-to-roll method, the thickness of the transparent substrate 10 is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, even more preferably 150 μm or less.

[0021] From the viewpoint of ensuring the transparency of the transparent substrate 10, the total light transmittance (JIS K 7375-2008) of the transparent substrate 10 is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more. The total light transmittance of the transparent substrate 10 is, for example, 100% or less.

[0022] The transparent conductive layer 20 is a film having both light transmissivity and conductivity. In the present embodiment, the transparent conductive layer 20 is disposed on the transparent substrate 10. Specifically, the transparent conductive layer 20 is in contact with the first surface 11 of the transparent substrate 10. Further, the transparent conductive layer 20 has an amorphous layer 21 as the first layer and a crystalline layer 22 as the second layer in this order from the transparent substrate 10 side. In the present embodiment, the amorphous layer 21 is in contact with the transparent substrate 10. The crystalline layer 22 is disposed on the side opposite to the transparent substrate 10 with respect to the amorphous layer 21. In the present embodiment, the crystalline layer 22 is in contact with the amorphous layer 21. The fact that the crystalline layer 22 is disposed on the side opposite to the transparent substrate 10 with respect to the amorphous layer 21 and is in contact with the amorphous layer 21 is preferable from the viewpoint of the flexibility of the transparent conductive layer 20 (suppression of cracking during bending).

[0023] In the present embodiment, the amorphous layer 21 is formed of an amorphous conductive oxide. Examples of the conductive oxide include indium-containing conductive oxides and antimony-containing conductive oxides. Examples of the indium-containing conductive oxide include indium tin composite oxide (ITO), indium zinc composite oxide (IZO), indium gallium composite oxide (IGO), and indium gallium zinc composite oxide (IGZO). Examples of the antimony-containing conductive oxide include antimony tin composite oxide (ATO). From the viewpoint of realizing high transparency and good electrical conductivity of the transparent conductive layer 20, the conductive oxide is preferably an indium-containing conductive oxide, more preferably ITO. ITO may contain a metal or a semimetal other than In and Sn in an amount less than the respective contents of In and Sn.

[0024] The ratio of the amount of tin oxide to the total amount of indium oxide (In2O3) and tin oxide (SnO2) in ITO in the amorphous layer 21 (tin oxide ratio R1) is preferably 11% by mass or more, more preferably 12% by mass or more, still more preferably 12.5% by mass or more, and preferably 15% by mass or less, more preferably 14% by mass or less, still more preferably 13% by mass or less, from the viewpoint of ensuring the amorphousness of the amorphous layer 21. From the viewpoint of ensuring the amorphousness of the amorphous layer 21, the tin oxide ratio R1 is preferably higher than the tin oxide ratio R2 of the crystalline layer 22 described later.

[0025] The tin oxide ratio in ITO can be identified, for example, as follows. First, the abundance ratio of indium atoms (In) and tin atoms (Sn) in ITO as the measurement object is determined by X-ray Photoelectron Spectroscopy. From the respective abundance ratios of In and Sn in ITO, the ratio of the number of Sn atoms to the number of In atoms in ITO is determined. Thereby, the tin oxide ratio in ITO is obtained. Also, the tin oxide ratio in ITO can be specified from the tin oxide (SnO2) content ratio of the ITO target used during sputter film formation.

[0026] Whether a film such as the amorphous layer 21 is an amorphous film can be determined by observing the cross-section of the film (target film) with a field emission transmission electron microscope (FE-TEM). When no crystal grains are confirmed and an amorphous region is confirmed in the cross-sectional observation of the target film by FE-TEM, it can be determined that the target film is an amorphous film.

[0027] In this embodiment, the crystalline layer 22 is formed of a crystalline conductive oxide. Examples of the conductive oxide include the conductive oxide layer described above for the amorphous layer 21. From the viewpoint of realizing the high transparency and good electrical conductivity of the transparent conductive layer 20, the conductive oxide is preferably an indium-containing conductive oxide, more preferably ITO. The material of the crystalline layer 22 and the material of the amorphous layer 21 may be of different types, but are preferably of the same type. The transparent conductive layer 20 having the amorphous layer 21 and the crystalline layer 22 is preferably an indium-containing conductive oxide layer, more preferably an indium tin composite oxide layer.

[0028] The ratio of the amount of tin oxide to the total amount of indium oxide and tin oxide in ITO in the crystalline layer 22 (tin oxide ratio R2) is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, from the viewpoint of ensuring the crystallinity of the crystalline layer 22, and is preferably less than 11% by mass, more preferably 10.5% by mass or less, still more preferably 10% by mass or less.

[0029] Whether a film such as the crystalline layer 22 is a crystalline film can be determined by observing the cross section of the film (target film) with a field emission transmission electron microscope (FE-TEM). When crystal grains are confirmed without confirming an amorphous region in the cross-sectional observation of the target film by FE-TEM, it can be determined that the target film is a crystalline film.

[0030] The thickness (total thickness) of the transparent conductive layer 20 is 100 nm or more. The transparent conductive layer 20 with a thickness of 100 nm or more is suitable for reducing the resistance of the transparent conductive layer 20. From the viewpoint of reducing the resistance of the transparent conductive layer 20, the thickness of the transparent conductive layer 20 is preferably 110 nm or more, more preferably 120 nm or more, still more preferably 125 nm or more. From the viewpoint of the transparency of the transparent conductive layer 20, the thickness of the transparent conductive layer 20 is preferably 300 nm or less, more preferably 200 nm or less, still more preferably 150 nm or less.

[0031] The thickness T1 of the amorphous layer 21 is 30 nm or more. In the transparent conductive layer 20 with a thickness of 100 nm or more, the fact that the thickness T1 of the amorphous layer 21 disposed on the transparent substrate 10 side is 30 nm or more is suitable for ensuring the transparency of the transparent conductive layer 20. From the viewpoint of the transparency of the transparent conductive layer 20, the thickness T1 of the amorphous layer 21 is preferably 45 nm or more, more preferably 50 nm or more. From the viewpoint of reducing the resistance of the transparent conductive layer 20, the thickness T1 is preferably 120 nm or less, more preferably 100 nm or less, and still more preferably 80 nm or less. Further, the ratio of the thickness T1 of the amorphous layer 21 to the thickness (total thickness) of the transparent conductive layer 20 is preferably 30% or more, more preferably 35% or more, and still more preferably 40% or more from the viewpoint of the transparency of the transparent conductive layer 20. The ratio is preferably 85% or less, more preferably 65% or less, and still more preferably 45% or less from the viewpoint of reducing the resistance of the transparent conductive layer 20.

[0032] The ratio of the thickness T2 of the crystalline layer 22 to the thickness (total thickness) of the transparent conductive layer 20 is 15% or more. In the transparent conductive layer 20 with a thickness of 100 nm or more, the fact that the crystalline layer 22 is disposed on the side opposite to the transparent substrate 10 with respect to the amorphous layer 21 and the thickness T2 of the crystalline layer 22 is 15% or more is suitable for ensuring the low resistance of the transparent conductive layer 20. From the viewpoint of the low resistance of the transparent conductive layer 20, the ratio of the thickness T2 of the crystalline layer 22 to the thickness of the transparent conductive layer 20 is preferably 35% or more, more preferably 40% or more, and even more preferably 50% or more. The ratio is preferably 70% or less, more preferably 65% or less, and still more preferably 60% or less from the viewpoint of the transparency of the transparent conductive layer 20. Further, from the viewpoint of the low resistance of the transparent conductive layer 20, the thickness T2 of the crystalline layer 22 is preferably 15 nm or more, more preferably 35 nm or more, still more preferably 40 nm or more, and even more preferably 50 nm or more. From the viewpoint of the transparency of the transparent conductive layer 20, the thickness T2 is preferably 70 nm or less, more preferably 65 nm or less, and still more preferably 60 nm or less.

[0033] The total light transmittance (JIS K 7375-2008) of the transparent conductive layer 20 is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more, from the viewpoint of ensuring the transparency of the transparent conductive layer 20. Further, the total light transmittance of the transparent conductive layer 20 is, for example, 100% or less.

[0034] The specific resistance of the transparent conductive layer 20 is preferably 3.5×10 -4 Ω·cm or less, more preferably 3.2×10 -4 Ω·cm or less, still more preferably 3.0×10 -4 Ω·cm or less, even more preferably 2.8×10 -4 Ω·cm or less, from the viewpoint of reducing the resistance of the transparent conductive layer 20. The specific resistance of the transparent conductive layer 20 is, for example, 0.5×10 -4 Ω·cm or more, 1.0×10 -4 Ω·cm or more, 2.0×10 -4 Ω·cm or more. The method for measuring the specific resistance is as described later in the examples.

[0035] The total light transmittance (JIS K 7375-2008) of the transparent conductive film X is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more. Such a configuration is suitable for ensuring the transparency required for the transparent conductive film X when the transparent conductive film X is provided in a touch sensor device, a dimming element, a photoelectric conversion element, a heat ray control member, an antenna member, an electromagnetic wave shielding member, a heater member, a lighting device, an image display device, and the like. The total light transmittance of the transparent conductive film X is, for example, 100% or less. The method for measuring the total light transmittance is as described later in the examples.

[0036] The transparent conductive film X is manufactured, for example, as follows.

[0037] First, as shown in FIG. 2A, a transparent substrate 10 is prepared (preparation step).

[0038] Next, as shown in FIG. 2B, a first layer 21' is formed on the transparent substrate 10 (first layer forming step). The first layer 21' is an amorphous first conductive oxide layer. This first conductive oxide layer is a layer that maintains its amorphous nature after a heating step (FIG. 2D) described later. In this step, specifically, a conductive oxide is deposited on the first surface 11 of the transparent substrate 10 by sputtering to form an amorphous first conductive oxide layer (first layer 21').

[0039] In the sputtering method, it is preferable to use a sputtering film-forming apparatus capable of implementing the film-forming process in a roll-to-roll manner. In the first layer forming step, when using a roll-to-roll sputtering film-forming apparatus, a long transparent substrate 10 as a work film is run from the pay-out roll to the take-up roll provided in the apparatus, and a material is deposited on the work film to form the first layer 21'. The running speed of the work film is, for example, 0.5 to 5 m / min. Also, in this sputtering method, a sputtering film-forming apparatus having a single film-forming chamber may be used, or a sputtering film-forming apparatus having a plurality of film-forming chambers arranged in order along the running path of the transparent substrate 10 may be used (the same applies to the second layer forming step described later).

[0040] Specifically, in the sputtering method, while introducing a sputtering gas (inert gas) under vacuum conditions into the film-forming chamber provided in the sputtering film-forming apparatus, a negative voltage is applied to the target disposed on the cathode in the film-forming chamber. Thereby, a glow discharge is generated to ionize gas atoms, and the gas ions are made to collide with the target surface at high speed, ejecting the target material from the target surface and depositing the ejected target material on the work film (transparent substrate 10). As the target material, for example, the sintered body of the conductive oxide described above with respect to the amorphous layer 21 is used. Examples of the sputtering gas include argon, krypton, xenon, and mixed gases thereof. The sputtering method is preferably a reactive sputtering method. In the reactive sputtering method, for example, oxygen as a reactive gas is introduced into the film-forming chamber in addition to the sputtering gas.

[0041] The conditions (first sputtering film formation conditions) for film formation by sputtering (sputtering film formation) in the first layer formation process are as follows from the viewpoint of appropriately forming a first conductive oxide layer that maintains amorphousness after the heating process (Fig. 2D) described later.

[0042] The ultimate vacuum degree in the film formation chamber before sputtering film formation is preferably 0.9×10 -4 Pa or less. In the reactive sputtering method, the ratio of the introduction amount of oxygen to the total introduction amount of the sputtering gas and oxygen introduced into the film formation chamber is preferably 1 flow rate % or more, more preferably 2 flow rate % or more, and is preferably 8 flow rate % or less, more preferably 5 flow rate % or less. The film formation temperature (the temperature of the transparent substrate 10 on which the first layer 21' is formed) is preferably -50°C or higher, more preferably -25°C or higher, and is preferably 20°C or lower, more preferably 0.0°C or lower. By adjusting the ultimate vacuum degree, oxygen introduction ratio, film formation temperature, and the atmospheric pressure during film formation in the first layer formation process, a first conductive oxide layer that maintains amorphousness can be formed after the heating process (Fig. 2D).

[0043] In the first layer formation process, examples of the power source for applying voltage to the target include a DC power source, an AC power source, an MF power source, and an RF power source. As the power source, a DC power source and an RF power source may be used in combination. The absolute value of the discharge voltage during sputtering film formation is, for example, 50 V or higher and, for example, 500 V or lower. The horizontal magnetic field intensity on the target is, for example, 10 mT or higher and, for example, 100 mT or lower.

[0044] Next, as shown in Fig. 2C, a second layer 22' is formed on the first layer 21' (second layer formation process). The second layer 22' is an amorphous second conductive oxide layer. This second conductive oxide layer is a layer that is crystallized by the heating process (Fig. 2D) described later. In this process, specifically, a conductive oxide is formed on the first layer 21' by sputtering to form an amorphous second conductive oxide layer (second layer 22'). The first layer 21' and the second layer 22' form an amorphous transparent conductive layer 20'.

[0045] In the sputtering method, it is preferable to use a sputtering film forming apparatus capable of carrying out a film forming process in a roll-to-roll manner. In the second layer forming step, when using a roll-to-roll type sputtering film forming apparatus, a long transparent substrate 10 with a first layer 21' as a work film is run from the pay-out roll to the take-up roll provided in the apparatus, and a material is formed into a film on the work film to form a second layer 22'. The method of carrying out the sputtering method and that the reactive sputtering method is preferable as the sputtering method are the same as those described above for the first layer forming step.

[0046] The conditions for sputtering film formation in the second layer forming step (second sputtering film formation conditions) are as follows from the viewpoint of appropriately forming a second conductive oxide layer crystallized by a heating step (Fig. 2D) described later.

[0047] The ultimate vacuum degree in the film forming chamber before sputtering film formation is preferably 5.0×10 -4 Pa or less. In the reactive sputtering method, the ratio of the introduction amount of oxygen to the total introduction amount of the sputtering gas and oxygen introduced into the film forming chamber is preferably 1% by flow rate or more, more preferably 1.5% by flow rate or more, and is preferably 6% by flow rate or less, more preferably 3% by flow rate or less. The film forming temperature (the temperature of the work film on which the second layer 22' is formed) is preferably -50°C or higher, more preferably -25°C or higher, and is preferably 20°C or lower, more preferably 0.0°C or lower. By adjusting the ultimate vacuum degree, oxygen introduction ratio, film forming temperature, and the atmospheric pressure during film formation in the second layer forming step, a second conductive oxide layer crystallized by a heating step (Fig. 2D) can be formed.

[0048] In the second layer forming step, the power source for applying a voltage to the target, the absolute value of the discharge voltage during sputtering film formation, and the horizontal magnetic field intensity on the target are the same as those described above for the first layer forming step.

[0049] In this manufacturing method, next, as shown in FIG. 2D, the second layer 22' is crystallized by heating to form a crystalline layer 22 (heating step). Examples of the heating means include an infrared heater and an oven. Examples of the heating oven include a heat medium heating type oven and a hot air heating type oven. The environment during heating may be either a vacuum environment or an atmospheric environment. Preferably, heating is carried out in the presence of oxygen. From the viewpoint of ensuring a high crystallization rate, the heating temperature is preferably 100°C or higher, more preferably 120°C or higher. From the viewpoint of suppressing the influence of heating on the transparent substrate 10, the heating temperature is preferably 180°C or lower, more preferably 160°C or lower. From the viewpoint of sufficient crystallization of the crystalline layer 22, the heating time is preferably 5 minutes or longer, preferably 10 minutes or longer, and more preferably 20 minutes or longer. From the viewpoint of shortening the tact time in this step, the heating time is preferably 200 minutes or shorter, more preferably 100 minutes or shorter, and even more preferably 80 minutes or shorter.

[0050] By heating in this step, the second layer 22' is crystallized while maintaining the amorphous nature of the first layer 21', thereby forming a transparent conductive layer 20 (amorphous layer 21, crystalline layer 22). In this step, as a method for crystallizing the second layer 22' while maintaining the amorphous nature of the first layer 21', increasing the tin oxide ratio or Sn concentration of the first layer 21' compared to the second layer 22', and increasing the oxygen introduction amount during the first sputtering film formation compared to the second sputtering film formation can be mentioned (the higher the tin oxide ratio or Sn concentration of the first layer 21', the less likely it is to crystallize during heating).

[0051] In the above manner, the transparent conductive film X is manufactured.

[0052] The transparent conductive layer 20 in the transparent conductive film X may be patterned as schematically shown in FIG. 3. The transparent conductive layer 20 can be patterned by etching the transparent conductive layer 20 through a predetermined etching mask. The patterned transparent conductive layer 20 is, for example, a wiring pattern.

[0053] In the transparent conductive film X, as described above, the transparent conductive layer 20 has a thickness of 100 nm or more, the transparent conductive layer 20 has an amorphous layer 21 with a thickness of 30 nm or more and a crystalline layer 22 in this order from the transparent substrate side, and the ratio of the thickness of the crystalline layer 22 to the thickness of the transparent conductive layer 20 is 15% or more. The fact that the transparent conductive layer 20 has a thickness of 100 nm or more and the thickness ratio of the crystalline layer 22 in the transparent conductive layer 20 is 15% or more is suitable for ensuring the low resistance of the transparent conductive layer 20. The fact that the transparent conductive layer 20 with a thickness of 100 nm or more has an amorphous layer 21 with a thickness of 30 nm or more and a crystalline layer 22 in this order from the transparent substrate side is suitable for ensuring the transparency of the transparent conductive layer 20.

[0054] Therefore, the transparent conductive film X is suitable for achieving both low resistance and transparency of the transparent conductive layer 20. Specifically, as shown by the following examples and comparative examples.

Examples

[0055] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples. Also, the specific numerical values such as the blending amounts (contents), physical property values, parameters, etc. described below can be replaced with the upper limits (numerical values defined as "below" or "less than") or lower limits (numerical values defined as "above" or "exceeding") of the corresponding blending amounts (contents), physical property values, parameters, etc. described in the above "Mode for Carrying Out the Invention".

[0056] 〔Example 1〕 First, a long polyethylene terephthalate (PET) film (product name "GC100-JBN", thickness 100 μm, manufactured by Mitsubishi Chemical Corporation) was prepared as a transparent substrate.

[0057] Next, a conductive oxide was formed on one side (the first side) of the transparent substrate by reactive sputtering to form an amorphous first conductive oxide layer with a thickness of 100 nm as the first layer (the first layer 21' in FIG. 2B) (the first layer forming step). In this step, a roll-to-roll type first sputtering film forming apparatus (DC magnetron sputtering film forming apparatus) was used. The apparatus includes a film forming chamber capable of performing a film forming process while running a work film in a roll-to-roll manner. The sputtering film forming conditions in this step are as follows.

[0058] After evacuating the film forming chamber of the first sputtering film forming apparatus to a final vacuum degree of 0.9×10 -4 Pa, argon as a sputtering gas and oxygen as a reactive gas were introduced into the film forming chamber, and the atmospheric pressure in the film forming chamber was set to 0.2 Pa. The ratio of the oxygen introduction amount to the total introduction amount of argon and oxygen introduced into the film forming chamber was set to about 3.2 flow %. As the target, a sintered body of indium oxide and tin oxide with a tin oxide ratio of 12.5 mass % was used. As the power source for applying voltage to the target, a DC power source was used. The horizontal magnetic field intensity on the target was set to 30 mT. The film forming temperature (the temperature of the transparent substrate on which the first layer is formed) was set to -8°C. The running speed of the PET film as the work film was set to 2.7 m / min.

[0059] Next, a conductive oxide was formed on the first layer on the transparent substrate by reactive sputtering to form an amorphous second conductive oxide layer with a thickness of 25 nm as the second layer (the second layer 22' in FIG. 2C) (the second layer forming step). Thereby, an amorphous transparent conductive layer (the transparent conductive layer 20' in FIG. 2C) was formed on the transparent substrate. In this step, a roll-to-roll type second sputtering film forming apparatus (DC magnetron sputtering film forming apparatus) was used. The apparatus includes a film forming chamber capable of performing a film forming process while running a work film in a roll-to-roll manner. The sputtering film forming conditions in this step are as follows.

[0060] After evacuating the film forming chamber of the second sputtering film forming apparatus to a final vacuum degree of 5.0×10 -4After evacuating the chamber to a vacuum up to Pa, argon as a sputtering gas and oxygen as a reactive gas were introduced into the film deposition chamber, and the pressure in the film deposition chamber was set to 0.2 Pa. The ratio of the introduced amount of oxygen to the total introduced amount of argon and oxygen introduced into the film deposition chamber was set to about 1.5 flow %. As the target, a sintered body of indium oxide and tin oxide with a tin oxide ratio of 10.0 mass % was used. As the power source for applying a voltage to the target, a DC power source was used. The horizontal magnetic field strength on the target was set to 90 mT. The film deposition temperature (the temperature of the work film on which the second layer is formed) was set to -5 °C. The running speed of the PET film as the work film was set to 2.7 m / min.

[0061] Next, the transparent conductive layer (first layer / second layer) on the transparent substrate was heated by a hot air heating oven (heating step). In this step, the heating temperature was set to 140 °C and the heating time was set to 1 hour. By this step, while maintaining the amorphousness of the first layer, the second layer was crystallized to form a transparent conductive layer (transparent conductive layer 20 in FIG. 2D). This transparent conductive layer has an amorphous layer as the first layer after heating (amorphous layer 21 in FIG. 2D) and a crystalline layer derived from the second layer crystallized by heating (crystalline layer 22 in FIG. 2D).

[0062] In the above manner, the transparent conductive film of Example 1 was produced. The transparent conductive layer of the transparent conductive film of Example 1 has an amorphous indium tin composite oxide layer (thickness 100 nm, tin oxide ratio 12.5 mass %) and a crystalline indium tin composite oxide layer (thickness 25 nm, tin oxide ratio 10.0 mass %) in this order from the transparent substrate side.

[0063] [Example 2] A transparent conductive film of Example 2 was produced in the same manner as the transparent conductive film of Example 1, except for the following. In the first layer formation step, the first layer was formed to a thickness of 75 nm, and in the second layer formation step, the second layer was formed to a thickness of 50 nm.

[0064] [Example 3] A transparent conductive film of Example 3 was produced in the same manner as the transparent conductive film of Example 1, except for the following. In the first layer formation step, the first layer was formed to a thickness of 50 nm, and in the second layer formation step, the second layer was formed to a thickness of 75 nm.

[0065] [Comparative Example 1] A transparent conductive film of Comparative Example 1 was produced in the same manner as the transparent conductive film of Example 1, except for the following. In the first layer formation step, the first layer was formed to a thickness of 125 nm, and the second layer formation step was not carried out.

[0066] [Comparative Example 2] A transparent conductive film of Comparative Example 2 was produced in the same manner as the transparent conductive film of Example 1, except for the following. The first layer formation step was not carried out, and in the second layer formation step, the second layer was formed to a thickness of 125 nm.

[0067] [Comparative Examples 3 to 8] Each transparent conductive film of Comparative Examples 3 to 8 was produced in the same manner as the transparent conductive film of Example 1, except for the following. The thickness of the first layer in the first layer formation step and the thickness of the second layer in the second layer formation step were set to the thicknesses shown in Table 1 (in Comparative Example 3, the second layer was not formed, and in Comparative Example 8, the first layer was not formed).

[0068] 〈Thickness of layer〉 The thickness (total thickness) of the transparent conductive layer of each transparent conductive film in Examples 1 to 3 and Comparative Examples 1 to 8 was measured by observation with a field emission transmission electron microscope (FE-TEM). Specifically, first, samples for cross-sectional observation of each transparent conductive layer in Examples 1 to 3 and Comparative Examples 1 to 8 were produced by the FIB micro-sampling method. In the FIB micro-sampling method, an FIB apparatus (product name "FB2200", manufactured by Hitachi) was used, and the acceleration voltage was set to 10 kV. Next, the cross-section of the transparent conductive layer in the sample for cross-sectional observation was observed by FE-TEM, and the thickness of the transparent conductive layer was measured in the observation image. In the same observation, an FE-TEM apparatus (product name "JEM-2800", manufactured by JEOL) was used, and the acceleration voltage was set to 200 kV.

[0069] In Examples 1 to 3 and Comparative Examples 4 to 7, the thickness of the amorphous layer (first layer) was measured by preparing a cross-sectional observation sample from an intermediate workpiece before forming the second layer on the first layer and performing FE-TEM observation of the sample. The thickness of the crystalline layer (second layer) of each transparent conductive layer in Examples 1 to 3 and Comparative Examples 4 to 7 was determined by subtracting the thickness of the first layer from the total thickness of the transparent conductive layer.

[0070] 〈Crystallinity〉 Regarding the first layer and the second layer of each transparent conductive layer in Examples 1 to 3 and Comparative Examples 1 to 8, the crystallinity (amorphous, crystalline) was examined as follows.

[0071] First, for the above-mentioned cross-sectional observation sample, an FE-TEM image was taken at an observation magnification of 2 million times (the sample preparation method and the observation method are the same as those described above for layer thickness measurement). Next, regarding the first layer and the second layer in the photographed image, when lattice fringes (corresponding to the presence of crystal grains) were not confirmed throughout, it was evaluated as amorphous, and when lattice fringes were confirmed throughout, it was evaluated as crystalline. As a result, the following was confirmed. The first layer in Examples 1 to 3 and Comparative Examples 4 to 7 was amorphous, and the second layer in Examples 1 to 3 and Comparative Examples 4 to 7 was crystalline. The transparent conductive layer (first layer) in Comparative Examples 1 and 3 was amorphous. The transparent conductive layer (second layer) in Comparative Examples 2 and 8 was crystalline. These confirmation results are shown in Table 1.

[0072] 〈Specific Resistance〉 The specific resistance of the transparent conductive layer of each transparent conductive film in Examples 1 to 3 and Comparative Examples 1 to 8 was measured. Specifically, it was as follows.

[0073] First, a 100 mm × 50 mm measurement film was cut out from the transparent conductive film. Next, the surface resistance of the transparent conductive layer of the measurement film was measured by the four-terminal method in accordance with JIS K 7194 (1994). Next, the specific resistance (Ω) was calculated by multiplying the surface resistance of the transparent conductive layer by the thickness of the transparent conductive layer. The value is shown in Table 1.

[0074] 〈Total light transmittance〉 The total light transmittance of each transparent conductive film of Examples 1 to 3 and Comparative Examples 1 to 8 was measured in accordance with JIS K 7375-2008 using a “Haze Meter HZ-V3” manufactured by Suga Test Instruments Co., Ltd. The measurement results are shown in Table 1.

[0075] [Evaluation] Among the transparent conductive films (transparent conductive layer thickness: 90 nm) of Comparative Examples 3 to 8, the transparent conductive layer of the transparent conductive film of Comparative Example 3 is an amorphous single layer. The transparent conductive layer of the transparent conductive film of Comparative Example 8 is a crystalline single layer. The transparent conductive layers of the transparent conductive films of Comparative Examples 4 to 7 are composite layers having an amorphous layer and a crystalline layer in this order from the transparent substrate side. The transparent conductive films of Comparative Examples 4 to 7 have a higher total light transmittance than the transparent conductive film of Comparative Example 8, but have a lower total light transmittance than the transparent conductive film of Comparative Example 3. As the thickness ratio of the crystalline layer in the transparent conductive layer increased, the total light transmittance (transparency) decreased.

[0076] Among the transparent conductive films (transparent conductive layer thickness: 125 nm) of Examples 1 to 3 and Comparative Examples 1 and 2, the transparent conductive layer of the transparent conductive film of Comparative Example 1 is an amorphous single layer. The transparent conductive layer of the transparent conductive film of Comparative Example 2 is a crystalline single layer. In contrast, the transparent conductive layers of the transparent conductive films of Examples 1 to 3 are composite layers having an amorphous layer and a crystalline layer in this order from the transparent substrate side. The transparent conductive films of Examples 1 to 3 have a higher total light transmittance (transparency) than either of the transparent conductive films of Comparative Examples 1 and 2. In the transparent conductive films of Examples 1 to 3, as the thickness ratio of the crystalline layer in the transparent conductive layer increases, the total light transmittance (transparency) increases. In addition, the transparent conductive films of Examples 1 to 3 having a transparent conductive layer with a thickness of 125 nm have a lower specific resistance and exhibit lower resistivity than the transparent conductive films of Comparative Examples 4 to 7 having a transparent conductive layer with a thickness of 90 nm.

[0077]

Table 1

Explanation of Symbols

[0078] X Transparent Conductive Film H Thickness Direction 10 Transparent Substrate 11 First Surface 12 Second Surface 20 Transparent Conductive Layer 21 Amorphous Layer 22 Crystalline Layer

Claims

Claim 1 A transparent conductive film comprising a transparent substrate and a transparent conductive layer in this order in the thickness direction, wherein the transparent conductive layer has a thickness of 100 nm or more, the transparent conductive layer has an amorphous layer and a crystalline layer in this order from the transparent substrate side, the amorphous layer has a thickness of 30 nm or more, and a ratio of the thickness of the crystalline layer to the thickness of the transparent conductive layer is 15% or more. A transparent conductive film. Claim 2 The transparent conductive film according to claim 1, wherein the ratio is 70% or less. Claim 3 The transparent conductive film according to claim 1 or 2, wherein the transparent conductive layer is an indium tin composite oxide layer. Claim 4 The transparent conductive film according to claim 3, wherein a tin oxide ratio of the amorphous layer is higher than a tin oxide ratio of the crystalline layer.

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