WO2023042848A1

WO2023042848A1 - Transparent conductive film

Info

Publication number: WO2023042848A1
Application number: PCT/JP2022/034351
Authority: WO
Inventors: 望藤野; 泰介鴉田
Original assignee: 日東電工株式会社
Priority date: 2021-09-17
Filing date: 2022-09-14
Publication date: 2023-03-23
Also published as: KR20240018403A

Abstract

A transparent conductive film (X) according to the present invention comprises a transparent resin substrate (10) and a crystalline transparent conductive layer (20) in this order in the thickness direction (D). The transparent conductive layer (20) includes an indium-tin composite oxide layer having a tin oxide proportion of less than 10 mass%. The transparent conductive layer (20) has a first resistance value R1 (Ω/□), and has a second resistance value R2 (Ω/□) after a heat treatment under the heating conditions of 160ºC and 30 minutes. The difference R1-R2 between the first resistance value R1 and the second resistance value R2 is at least 1.5 Ω/□.

Description

transparent conductive film

The present invention relates to transparent conductive films.

Conventionally, there has been known a transparent conductive film that includes a transparent base film made of resin and a transparent conductive layer (transparent conductive layer) in order in the thickness direction. Transparent conductive layers are used, for example, as conductive films for forming transparent electrodes in various devices such as liquid crystal displays, touch panels, and solar cells. The transparent conductive layer is formed, for example, by depositing a conductive oxide on the substrate film by sputtering. Techniques related to such transparent conductive films are described, for example, in Patent Document 1 below.

JP 2017-71850 A

A conventional transparent conductive film is manufactured, for example, as follows. First, an amorphous transparent conductive layer is formed on a substrate film in a film forming chamber of a sputtering film forming apparatus. Next, the transparent conductive layer on the substrate film is heated in a hot air heating oven. This heating converts the transparent conductive layer from amorphous to crystalline (crystallization step). The higher the heating temperature, the higher the crystallinity of the formed crystalline transparent conductive layer and the lower the resistance value of the same layer.

If the heating temperature in the crystallization process is too high, problems such as dimensional changes and deformation will occur in the resin base film. Therefore, in the crystallization process, it is necessary to heat the transparent conductive layer at a temperature that does not cause such problems (a temperature that is not too high).

However, when a conventional transparent conductive film having a transparent conductive layer crystallized in the above-described crystallization process undergoes a relatively high-temperature heating process in the manufacturing process of a device comprising the same film, the resistance value of the transparent conductive layer may rise. An increase in the resistance value of the transparent conductive layer in the transparent conductive film after production is not preferable because it affects device performance.

The present invention provides a transparent conductive film suitable for suppressing an increase in the resistance value of the transparent conductive layer due to heating during the device manufacturing process.

The present invention [1] is a transparent conductive film comprising a transparent resin substrate and a crystalline transparent conductive layer in this order in the thickness direction, wherein the transparent conductive layer has a tin oxide content of 10% by mass. The transparent conductive layer has a first resistance value R1 (Ω/□) and a second resistance value R2 (Ω/□) after heat treatment at 160° C. for 30 minutes. Ω/□), and a difference R1−R2 between the first resistance value R1 and the second resistance value R2 is 1.5Ω/□ or more.

The present invention [2] includes the transparent conductive film according to [1] above, wherein the difference R1-R2 between the first resistance value R1 and the second resistance value R2 is 10Ω/□ or less.

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

The present invention [4] includes the transparent conductive film according to any one of [1] to [3] above, wherein the transparent conductive layer has a thickness of 150 nm or less.

The present invention [5] includes the transparent conductive film according to any one of [1] to [4] above, wherein the first resistance value R1 is 220Ω/□ or less.

In the transparent conductive film of the present invention, as described above, the crystalline transparent conductive layer includes an indium tin composite oxide (ITO) layer having a tin oxide ratio of less than 10% by mass, and the transparent conductive layer is heated at 160 ° C. and the difference R1-R2 between the second resistance value R2 after heat treatment under the heating conditions of 30 minutes and the first resistance value R1 (before heat treatment) is 1.5Ω/□ or more. The fact that the transparent conductive layer is a crystalline film is suitable for suppressing large fluctuations in the resistance value of the transparent conductive layer due to subsequent heating. When the transparent conductive layer contains an ITO layer with a tin oxide content of less than 10% by mass, an amorphous transparent conductive layer is formed in which an increase in resistance value due to heating after heat crystallization is suppressed in the transparent conductive film manufacturing process. suitable for In this transparent conductive film, the second resistance value R2 after heat treatment (160° C., 30 minutes) is lower than the first resistance value R1 before heat treatment by 1.5Ω/□ or more. Such a transparent conductive film is suitable for suppressing an increase in the resistance value of the transparent conductive layer due to heating during the device manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of one Embodiment of the transparent conductive film of this invention. The case where the transparent conductive layer includes a plurality of layers is shown. 2 represents a method for manufacturing the transparent conductive film shown in FIG. 3A represents a process of preparing a resin film, FIG. 3B represents a process of forming a functional layer on the resin film, FIG. 3C represents a process of forming a transparent conductive layer on the functional layer, and FIG. 3D. represents the step of crystallizing the transparent conductive layer. In the transparent conductive film shown in FIG. 1, it represents the case where the transparent conductive layer is patterned.

A transparent conductive film X as one embodiment of the transparent conductive film of the present invention comprises a transparent resin substrate 10 and a transparent conductive layer 20 in the thickness direction D in this order. The transparent conductive film X has a sheet shape extending in a direction perpendicular to the thickness direction D (plane direction). The transparent conductive film X is one element provided in a touch sensor device, a light control device, a photoelectric conversion device, a heat ray control member, an antenna member, an electromagnetic wave shield member, a heater member, a lighting device, an image display device, and the like.

The transparent resin base material 10 includes a resin film 11 and a functional layer 12 in this order in the thickness direction D in this embodiment.

The resin film 11 is a base material that secures the strength of the transparent conductive film X. Moreover, the resin film 11 is a transparent resin film having flexibility. Examples of materials for the resin film 11 include polyester resin, polyolefin resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, polyimide resin, cellulose resin, and polystyrene resin. Polyester resins include, for example, polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Polyolefin resins include, for example, polyethylene, polypropylene, and cycloolefin polymers. Examples of acrylic resins include polymethacrylate. As the material of the resin film 11, polyester resin is preferably used, and PET is more preferably used, for example, from the viewpoint of transparency and strength.

The functional layer 12 side surface of the resin film 11 may be subjected to a surface modification treatment. Surface modification treatments include, for example, corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

From the viewpoint of ensuring the strength of the transparent conductive film X, the thickness of the resin film 11 is preferably 1 µm or more, more preferably 10 µm or more, and even more preferably 30 µm or more. The thickness of the resin film 11 is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, still more preferably 100 μm or less, and particularly preferably, from the viewpoint of ensuring handleability of the resin film 11 in a roll-to-roll system. is 75 μm or less.

The total light transmittance (JIS K 7375-2008) of the resin film 11 is preferably 60% or higher, more preferably 80% or higher, and even more preferably 85% or higher. Such a configuration is applicable when the transparent conductive film X is 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 shield member, a heater member, a lighting device, an image display device, or the like. It is suitable for securing the transparency required for the transparent conductive film X. The total light transmittance of the resin film 11 is, for example, 100% or less.

The functional layer 12 is arranged on one surface side of the resin film 11 in the thickness direction D. In this embodiment, the functional layer 12 contacts the resin film 11 . Further, in the present embodiment, the functional layer 12 is a hard coat layer that makes it difficult for scratches to form on the exposed surface (the upper surface in FIG. 1) of the transparent conductive layer 20 .

The hard coat layer is a cured product of a curable resin composition. The curable resin composition contains a curable resin. Examples of curable resins include polyester resins, acrylic urethane resins, acrylic resins (excluding acrylic urethane resins), urethane resins (excluding acrylic urethane resins), amide resins, silicone resins, epoxy resins, and melamine resins. . These curable resins may be used alone, or two or more of them may be used in combination. From the viewpoint of ensuring high hardness of the hard coat layer, the curable resin is preferably at least one selected from the group consisting of acrylic urethane resins and acrylic resins.

In addition, examples of curable resins include ultraviolet curable resins and thermosetting resins. As the curable resin, an ultraviolet curable resin is preferable from the viewpoint of improving the production efficiency of the transparent conductive film X because it can be cured without heating to a high temperature.

The curable resin composition may contain particles. Particles include, for example, inorganic oxide particles and organic particles. Materials for inorganic oxide particles include, for example, silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Materials for the organic particles include, for example, polymethylmethacrylate, polystyrene, polyurethane, acrylic-styrene copolymers, benzoguanamine, melamine, and polycarbonate.

The surface of the functional layer 12 on the side of the transparent conductive layer 20 may be subjected to surface modification treatment. Surface modification treatments include, for example, corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

The thickness of the functional layer 12 as the hard coat layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and still more preferably 1 μm or more, from the viewpoint of expressing sufficient scratch resistance in the transparent conductive layer 20 . be. The thickness of the functional layer 12 as a hard coat layer is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 5 μm or less, and particularly preferably 3 μm or less, from the viewpoint of ensuring the transparency of the functional layer 12 .

The thickness of the transparent resin substrate 10 is preferably 1 µm or more, more preferably 10 µm or more, even more preferably 15 µm or more, and particularly preferably 30 µm or more. The thickness of the transparent resin substrate 10 is preferably 520 μm or less, more preferably 320 μm or less, still more preferably 220 μm or less, even more preferably 120 μm or less, and particularly preferably 80 μm or less. These configurations regarding the thickness of the transparent resin substrate 10 are suitable for ensuring the handleability of the transparent conductive film X.

The total light transmittance (JIS K 7375-2008) of the transparent resin substrate 10 is preferably 60% or higher, more preferably 80% or higher, and even more preferably 85% or higher. Such a configuration is applicable when the transparent conductive film X is 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 shield member, a heater member, a lighting device, an image display device, or the like. It is suitable for securing the transparency required for the transparent conductive film X. The total light transmittance of the transparent resin substrate 10 is, for example, 100% or less.

The transparent conductive layer 20 is arranged on one side in the thickness direction D of the transparent resin substrate 10 . In this embodiment, the transparent conductive layer 20 is in contact with the transparent resin substrate 10 . The transparent conductive layer 20 is a crystalline film having both optical transparency and electrical conductivity. Such a transparent conductive layer 20 is made of, for example, a conductive oxide. The fact that the transparent conductive layer 20 is a crystalline film is suitable for suppressing large fluctuations in the resistance value of the transparent conductive layer 20 due to subsequent heating.

Whether the transparent conductive layer (the transparent conductive layer 20 on the transparent resin substrate 10 in the transparent conductive film X) is a crystalline film can be determined by planar observation of the transparent conductive layer with a transmission electron microscope (TEM). . In the planar observation of the transparent conductive layer with a TEM, when crystal grains are confirmed without an amorphous region, it can be determined that the transparent conductive layer is a crystalline film. In preparing a sample for planar observation of the transparent conductive layer in the transparent conductive film, after fixing the transparent conductive film to a sample holder of an ultramicrotome, a microtome knife was set at an extremely acute angle with respect to the transparent conductive layer, The knife cuts the transparent conductive layer so as to be substantially parallel to the exposed surface of the transparent conductive layer. Thereby, a transparent conductive layer sample as a sample for planar observation can be obtained.

The fact that the transparent conductive layer is a crystalline film can also be determined by cross-sectional observation of the transparent conductive layer with a field emission transmission electron microscope (FE-TEM). When the cross section of the transparent conductive layer is observed by FE-TEM and crystal grains are found without any amorphous regions, it can be determined that the transparent conductive layer is a crystalline film. The method for confirming that the transparent conductive layer is a crystalline film by FE-TEM is specifically described later with regard to Examples.

Whether the transparent conductive layer is a crystalline film can also be determined, for example, by the following method. First, the transparent conductive layer is immersed in hydrochloric acid having a concentration of 5% by mass at 20° C. for 15 minutes. Next, the transparent conductive layer is washed with water and then dried. Next, on the exposed plane of the transparent conductive layer (the surface of the transparent conductive layer 20 opposite to the transparent resin substrate 10 in the transparent conductive film X), the resistance between a pair of terminals separated by a distance of 15 mm (between the terminals resistance). In this measurement, when the resistance between terminals is 10 kΩ or less, it can be determined that the transparent conductive layer is a crystalline film.

The transparent conductive layer 20 (crystalline) includes an indium tin composite oxide layer (first ITO layer) containing less than 10% by mass of tin oxide. Indium tin composite oxide (ITO) is one of conductive oxides. The tin oxide ratio in the ITO layer is specifically the ratio of the tin oxide content to the total content of indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₂ ) in the ITO forming the same layer. . As will be described later, the transparent conductive layer 20 including the first ITO layer is crystallized by heating the transparent conductive layer 20' after the amorphous transparent conductive layer 20' including the first ITO layer is formed. It is formed by Including the first ITO layer in the transparent conductive layer 20 is suitable for forming an amorphous transparent conductive layer (transparent conductive layer 20' described later) that suppresses an increase in resistance value due to heating after thermal crystallization. .

The proportion of tin oxide in the first ITO layer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more, from the viewpoint of ensuring the durability of the transparent conductive layer 20. , more preferably 1.5% by mass or more, particularly preferably 2% by mass or more. The proportion of tin oxide in the first ITO layer is determined from the standpoint of ease of formation of an amorphous transparent conductive layer in the later-described sputtering film formation, and an increase in the resistance value of the transparent conductive layer 20 due to heating after heat crystallization. From the viewpoint of suppressing the is 4% by mass or less.

The tin oxide ratio in ITO can be identified, for example, as follows. First, by X-ray Photoelectron Spectroscopy, the abundance ratio of indium atoms (In) and tin atoms (Sn) in ITO as an object to be measured is determined. The ratio of the number of Sn atoms to the number of In atoms in ITO is obtained from the abundance ratios of In and Sn in ITO. This gives the percentage of tin oxide in ITO. Further, the tin oxide ratio in ITO can also be specified from the tin oxide (SnO ₂ ) content ratio of the ITO target used for sputtering film formation.

The transparent conductive layer 20 may include layers other than the first ITO layer (with a tin oxide content of less than 10% by mass). Other layers include, for example, an ITO layer (second ITO layer) having a tin oxide ratio of 10% by mass or more, and a layer formed of a conductive oxide other than ITO. From the viewpoint of achieving both high transparency and good electrical conductivity of the transparent conductive layer 20, the other layer is preferably the second ITO layer.

The tin oxide ratio of the second ITO layer (tin oxide ratio of 10% by mass or more) is preferably 11% by mass or more, more preferably 12% by mass, from the viewpoint of reducing the resistance value of the transparent conductive layer 20 after thermal crystallization. % or more, more preferably 13 mass % or more. From the viewpoint of ensuring the crystallinity of the transparent conductive layer 20 after heating, the proportion of tin oxide in the second ITO layer is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. be.

Other conductive oxides include, for example, indium-containing conductive oxides other than ITO and antimony-containing conductive oxides. Examples of the indium-containing conductive oxide include indium zinc composite oxide (IZO), indium gallium composite oxide (IGO), and indium gallium zinc composite oxide (IGZO). Antimony-containing conductive oxides include, for example, antimony-tin composite oxide (ATO).

FIG. 2 illustrates a case where the transparent conductive layer 20 is composed of two layers, a first layer 21 and a second layer 22, as an example of a case where the transparent conductive layer 20 is composed of a plurality of layers including a first ITO layer. show. In FIG. 2, the first layer 21 or the second layer 22 is the first ITO layer. The second layer 22 is preferably the first ITO layer from the viewpoint of suppressing an increase in the resistance value due to heating of the transparent conductive layer 20 after thermal crystallization. In FIG. 2, the boundary between the first layer 21 and the second layer 22 is depicted by a virtual line. If the composition of the first layer 21 and the composition of the second layer 22 are not significantly different, the boundary between the first layer 21 and the second layer 22 cannot be clearly distinguished.

From the viewpoint of reducing the resistance of the transparent conductive layer 20, the thickness of the transparent conductive layer 20 is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. In addition, the thickness of the transparent conductive layer 20 is preferably 300 nm or less, more preferably 150 nm or less, even more preferably 120 nm or less, still more preferably 100 nm or less, and particularly preferably, from the viewpoint of suppressing cracking of the transparent conductive layer 20 due to heating. is 80 nm or less.

When the transparent conductive layer 20 includes the first layer 21 and the second layer 22 , the ratio of the thickness of the second layer 22 to the total thickness of the first layer 21 and the second layer 22 is the lowest of the transparent conductive layer 20 . From the viewpoint of resistance, it is preferably 1% or more, more preferably 5% or more, and still more preferably 7% or more. In addition, the ratio of the thickness of the second layer 22 to the total thickness of the first layer 21 and the second layer 22 is preferably 99% or less from the viewpoint of ensuring high crystallinity in the transparent conductive layer 20 after heating. , more preferably 95% or less, still more preferably 90% or less, still more preferably 60% or less, and particularly preferably 50% or less.

The transparent conductive layer 20 has a first resistance value R1 (Ω/□) and a second resistance value R2 (Ω/□) after heat treatment under heating conditions of 160° C. and 30 minutes. The resistance values R1 and R2 are each represented by surface resistivity. Surface resistivity can be measured by the four-probe method according to JIS K7194 (1994). Specifically, the method of measuring the resistance values R1 and R2 is as described later with regard to the examples.

A difference R1-R2 between the first resistance value R1 and the second resistance value R2 is 1.5Ω/□ or more. Such a configuration is suitable for suppressing an increase in the resistance value due to subsequent heating in the transparent conductive layer 20 . From the viewpoint of suppressing an increase in the resistance value due to post-heating of the transparent conductive layer 20, the difference R1-R2 is preferably 3 Ω/□ or more, more preferably 4 Ω/□ or more, still more preferably 5 Ω/□ or more, and particularly preferably 6Ω/□ or more. In addition, from the viewpoint of suppressing the amount of change in the resistance value due to post-heating of the transparent conductive layer 20, the difference R1-R2 is preferably 10 Ω/□ or less, more preferably 9.5 Ω/□ or less, and still more preferably 9 Ω/□. Below, it is particularly preferably 8Ω/□ or less.

The ratio R2/R1 of the second resistance value R2 to the first resistance value R1 is preferably 0.990 or less, more preferably 0.950 or less, from the viewpoint of suppressing an increase in resistance value due to subsequent heating of the transparent conductive layer 20. , more preferably 0.900 or less, particularly preferably 0.880 or less. In addition, from the viewpoint of suppressing the resistance value variation due to post-heating of the transparent conductive layer 20, the ratio R2/R1 is preferably 0.650 or more, more preferably 0.700 or more, and still more preferably 0.800 or more. More preferably 0.850 or more, particularly preferably 0.900 or more.

From the viewpoint of reducing the resistance of the transparent conductive layer 20, the first resistance value R1 is preferably 240 Ω/□ or less, more preferably 220 Ω/□ or less, even more preferably 200 Ω/□ or less, and even more preferably 180 Ω/□ or less. It is more preferably 160Ω/□ or less, and particularly preferably 150Ω/□ or less. The first resistance value R1 is, for example, 1Ω/□ or more. The first resistance value R1 can be controlled, for example, by adjusting various conditions when the transparent conductive layer 20 is formed by sputtering (the same applies to the second resistance value R2). The conditions include, for example, the temperature of the base (transparent resin substrate 10 in this embodiment) on which the transparent conductive layer 20 is formed, the amount of oxygen introduced into the film formation chamber, the pressure in the film formation chamber, and the target of horizontal magnetic field strength.

From the viewpoint of reducing the resistance of the transparent conductive layer 20, the second resistance value R2 is preferably 240 Ω/□ or less, more preferably 220 Ω/□ or less, even more preferably 200 Ω/□ or less, and even more preferably 180 Ω/□ or less. It is more preferably 160Ω/□ or less, and particularly preferably 150Ω/□ or less. The second resistance value R2 is, for example, 1Ω/□ or more.

The total light transmittance (JIS K 7375-2008) of the transparent conductive film X is preferably 60% or higher, more preferably 80% or higher, still more preferably 85% or higher. Such a configuration is applicable when the transparent conductive film X is 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 shield member, a heater member, a lighting device, an image display device, or the like. It is suitable for securing the transparency required for the transparent conductive film X. The total light transmittance of the resin film 11 is, for example, 100% or less.

The transparent conductive film X is produced, for example, as follows.

First, as shown in FIG. 3A, a resin film 11 is prepared.

Next, as shown in FIG. 3B, the functional layer 12 is formed on one surface of the resin film 11 in the thickness direction D. A transparent resin substrate 10 is produced by forming the functional layer 12 on the resin film 11 .

The above-mentioned functional layer 12 as a hard coat layer can be formed by applying a curable resin composition on the resin film 11 to form a coating film, and then curing the coating film. When the curable resin composition contains an ultraviolet curable resin, the coating film is cured by ultraviolet irradiation. When the curable resin composition contains a thermosetting resin, the coating is cured by heating.

The exposed surface of the functional layer 12 formed on the resin film 11 is subjected to surface modification treatment as necessary. When plasma processing is performed as surface modification processing, argon gas, for example, is used as an inert gas. Also, the discharge power in the plasma treatment is, for example, 10 W or more and, for example, 5000 W or less.

Next, as shown in FIG. 3C, an amorphous transparent conductive layer 20' is formed on the transparent resin substrate 10 (transparent conductive layer forming step). Specifically, a sputtering method is used to form a film of material on the functional layer 12 of the transparent resin substrate 10 to form an amorphous transparent conductive layer 20 ′. The transparent conductive layer 20' is an amorphous film having both light transmittance and conductivity (the transparent conductive layer 20' is converted into the crystalline transparent conductive layer 20 by heating in the crystallization step described later. ).

In the sputtering method, it is preferable to use a sputtering film forming apparatus that can carry out the film forming process by a roll-to-roll method. In the production of the transparent conductive film X, when a roll-to-roll type sputtering deposition apparatus is used, the long transparent resin substrate 10 is run from a supply roll provided in the apparatus to a take-up roll, and the transparent A material is deposited on the resin base material 10 to form the transparent conductive layer 20'. In the sputtering method, a sputtering film forming apparatus having one 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 resin substrate 10 may be used. A film apparatus may be used (when forming the transparent conductive layer 20′ including the first layer 21 and the second layer 22 described above, a sputtering film forming apparatus having two or more film forming chambers is used. do).

Specifically, in the sputtering method, while introducing a sputtering gas (inert gas) under vacuum conditions into a film forming chamber provided in a sputtering film forming apparatus, a negative voltage is applied to a target placed on a cathode in the film forming chamber. is applied. As a result, glow discharge is generated to ionize the gas atoms, the gas ions collide with the target surface at high speed, the target material is ejected from the target surface, and the ejected target material is deposited on the transparent resin substrate 10. . As the target material, for example, the sintered body of the conductive oxide described above with regard to the transparent conductive layer 20 is used. Examples of the sputtering gas include rare gases. Noble gases include, for example, argon and krypton. The sputtering gas may be a mixed gas of multiple rare gases.

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 deposition chamber in addition to the sputtering gas. 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 deposition chamber is, for example, 0.01 flow % or more and, for example, 15 flow % or less.

The atmospheric pressure in the film formation chamber during film formation by the sputtering method (sputter film formation) is, for example, 0.02 Pa or more and, for example, 1 Pa or less.

The temperature of the transparent resin substrate 10 during sputtering film formation is, for example, 180° C. or less. The temperature of the transparent resin substrate 10 during sputtering film formation is preferably set to It is 20° C. or lower, more preferably 10° C. or lower, still more preferably 5° C. or lower, still more preferably 0° C. or lower, and particularly preferably -5° C. or lower. The temperature is, for example, -50°C or higher, -20°C or higher, or -10°C or higher.

　The power supply for applying voltage to the target includes, for example, a DC power supply, an AC power supply, an MF power supply, and an RF power supply. As a power supply, a DC power supply and an RF power supply may be used together. 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.

In this manufacturing method, next, as shown in FIG. 3D, the amorphous transparent conductive layer 20' is converted into the crystalline transparent conductive layer 20 by heating under vacuum (crystallization step). In this step, a vacuum heating device with a contact heating unit is used. Contact heating units include, for example, heated rolls and heated blocks. A vacuum heating apparatus equipped with a heating roll is preferable for carrying out the crystallization process by the roll-to-roll method. That is, in this step, it is preferable to heat the transparent conductive layer 20' on the transparent resin substrate 10 by bringing it into contact with a heating roll in a vacuum heating device. Contact heating with a heating roll is suitable for efficiently crystallizing the transparent conductive layer 20' under vacuum.

In this step, the heating temperature is preferably 120°C or higher, more preferably 140°C or higher, and even more preferably 160°C or higher, from the viewpoint of ensuring a high crystallization rate. The heating temperature is preferably less than 200° C., more preferably 180° C. or less, and even more preferably 170° C. or less, from the viewpoint of suppressing the influence of heating on the transparent resin substrate 10 . From the viewpoint of sufficient crystallization of the transparent conductive layer 20, the heating time is preferably 10 seconds or longer, preferably 30 seconds or longer, and more preferably 45 seconds or longer. From the viewpoint of shortening the tact time in this step, the heating time is preferably 60 minutes or less, more preferably 30 minutes or less, even more preferably 10 minutes or less, and particularly preferably 5 minutes or less.

Preferably, the series of processes from the transparent conductive layer forming step to the crystallization step described above are carried out on one continuous line while the work film is run in a roll-to-roll manner. More preferably, the work film is never exposed to the atmosphere during the process in one continuous line.

The transparent conductive film X is manufactured as described above.

The transparent conductive layer 20 in the transparent conductive film X may be patterned as schematically shown in FIG. By etching the transparent conductive layer 20 through a predetermined etching mask, the transparent conductive layer 20 can be patterned. The patterning of the transparent conductive layer 20 may be performed before the crystallization process described above or after the crystallization process. The patterned transparent conductive layer 20 functions, for example, as a wiring pattern.

In the transparent conductive film X, as described above, the crystalline transparent conductive layer 20 includes an indium tin composite oxide layer with a tin oxide ratio of less than 10% by mass, and the transparent conductive layer 20 is heated at 160 ° C. for 30 minutes. The difference R1-R2 between the second resistance value R2 after heat treatment under the heating conditions of and the first resistance value R1 (before heat treatment) is 1.5 Ω/□ or more, preferably 3 Ω/□ or more, It is more preferably 4 Ω/□ or more, still more preferably 5 Ω/□ or more, and particularly preferably 6 Ω/□ or more. The fact that the transparent conductive layer 20 is a crystalline film is suitable for suppressing large fluctuations in the resistance value of the transparent conductive layer 20 due to post-heating, as described above. The fact that the transparent conductive layer 20 includes the first ITO layer (with a tin oxide ratio of less than 10% by mass) is an amorphous transparent conductive layer that suppresses an increase in resistance value due to heating after heat crystallization, as described above. 20'. In the transparent conductive film X, the second resistance value R2 after heat treatment (160° C., 30 minutes) is lower than the first resistance value R1 before heat treatment by 1.5Ω/□ or more. The transparent conductive film X as described above is suitable for suppressing an increase in the resistance value of the transparent conductive layer 20 due to heating during the device manufacturing process.

In the transparent conductive film X, the functional layer 12 may be an adhesion improving layer for achieving high adhesion of the transparent conductive layer 20 to the transparent resin substrate 10 . The configuration in which the functional layer 12 is an adhesion improving layer is suitable for ensuring adhesion between the transparent resin substrate 10 and the transparent conductive layer 20 .

The functional layer 12 may be a refractive index adjusting layer (index-matching layer) for adjusting the reflectance of the surface (one side in the thickness direction D) of the transparent resin substrate 10 . The configuration in which the functional layer 12 is a refractive index adjusting layer is suitable for making the pattern shape of the transparent conductive layer 20 less visible when the transparent conductive layer 20 on the transparent resin substrate 10 is patterned.

The functional layer 12 may be a peeling functional layer for practically peeling the transparent conductive layer 20 from the transparent resin substrate 10 . The configuration in which the functional layer 12 is a peeling functional layer is suitable for peeling the transparent conductive layer 20 from the transparent resin substrate 10 and transferring the transparent conductive layer 20 to another member.

The functional layer 12 may be a composite layer in which a plurality of layers are arranged in the thickness direction D. The composite layer preferably includes two or more layers selected from the group consisting of a hard coat layer, an adhesion improving layer, a refractive index adjusting layer, and a release functional layer. Such a configuration is suitable for compositely expressing the above-described functions of each selected layer in the functional layer 12 . In a preferred embodiment, the functional layer 12 includes an adhesion improving layer, a hard coat layer, and a refractive index adjusting layer on the resin film 11 toward one side in the thickness direction D in this order. In another preferred embodiment, the functional layer 12 includes, on the resin film 11, a release functional layer, a hard coat layer, and a refractive index adjusting layer in this order toward one side in the thickness direction D.

The transparent conductive film X is used in a state where it is fixed to an article and the transparent conductive layer 20 is patterned as necessary. The transparent conductive film X is attached to an article via, for example, an adhesive functional layer.

Articles include, for example, elements, members, and devices. That is, examples of articles with a transparent conductive film include elements with a transparent conductive film, members with a transparent conductive film, and devices with a transparent conductive film.

Devices include, for example, light control devices and photoelectric conversion devices. Examples of the light control device include a current-driven light control device and an electric field drive light control device. Current-driven light control devices include, for example, electrochromic (EC) light control devices. Examples of electric field-driven light control devices include PDLC (polymer dispersed liquid crystal) light control devices, PNLC (polymer network liquid crystal) light control devices, and SPD (suspended particle device) light control devices. Examples of photoelectric conversion elements include solar cells. Solar cells include, for example, organic thin-film solar cells and dye-sensitized solar cells. Examples of the member include an electromagnetic wave shield member, a heat ray control member, a heater member, and an antenna member. Devices include, for example, touch sensor devices, lighting devices, and image display devices.

Examples of the above-mentioned fixation functional layer include an adhesive layer and an adhesive layer. As a material for the fixing function layer, any material can be used without particular limitation as long as it is transparent and exhibits a fixing function. The fixation functional layer is preferably made of resin. Examples of resins include acrylic resins, silicone resins, polyester resins, polyurethane resins, polyamide resins, polyvinyl ether resins, vinyl acetate/vinyl chloride copolymers, modified polyolefin resins, epoxy resins, fluorine resins, natural rubbers, and synthetic rubbers. be done. As the resin, an acrylic resin is preferable because it exhibits adhesive properties such as cohesiveness, adhesiveness, and moderate wettability, is excellent in transparency, and is excellent in weather resistance and heat resistance.

The fixing functional layer (the resin forming the fixing functional layer) may contain a corrosion inhibitor to suppress corrosion of the transparent conductive layer 20 . The fixing functional layer (resin forming the fixing functional layer) may contain a migration inhibitor (for example, the material disclosed in JP-A-2015-022397) in order to suppress migration of the transparent conductive layer 20 . Further, the fixing functional layer (resin forming the fixing functional layer) may contain an ultraviolet absorber in order to suppress deterioration of the article when it is used outdoors. Examples of ultraviolet absorbers include benzophenone compounds, benzotriazole compounds, salicylic acid compounds, oxalic acid anilide compounds, cyanoacrylate compounds, and triazine compounds.

Further, when the transparent resin substrate 10 of the transparent conductive film X is fixed to an article via the fixing functional layer, the transparent conductive layer 20 (including the transparent conductive layer 20 after patterning) in the transparent conductive film X is exposed. In such a case, a cover layer may be arranged on the exposed surface of the transparent conductive layer 20 . The cover layer is a layer that covers the transparent conductive layer 20 , and can improve the reliability of the transparent conductive layer 20 and suppress functional deterioration due to damage to the transparent conductive layer 20 . Such a cover layer is preferably made of a dielectric material, more preferably a composite material of a resin and an inorganic material. Examples of the resin include the resins described above for the fixing functional layer. Inorganic materials include, for example, inorganic oxides and fluorides. Inorganic oxides include, for example, silicon oxide, titanium oxide, niobium oxide, aluminum oxide, zirconium dioxide, and calcium oxide. Examples of fluorides include magnesium fluoride. In addition, the cover layer (mixture of resin and inorganic material) may contain the above-described corrosion inhibitor, migration inhibitor, and ultraviolet absorber.

The present invention will be specifically described below with reference to examples. However, the invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, parameters, etc. described below are the corresponding compounding amounts ( content), physical properties, parameters, etc., upper limits (values defined as “less than” or “less than”) or lower limits (values defined as “greater than” or “greater than”).

[Example 1]
An ultraviolet curable resin containing an acrylic resin was applied to one surface of a long polyethylene terephthalate (PET) film (thickness: 50 μm, manufactured by Toray Industries, Inc.) as a transparent resin film to form a coating film. Next, the coating film was cured by ultraviolet irradiation to form a hard coat layer (thickness: 2 μm). In this manner, a transparent resin base material including a resin film and a hard coat (HC) layer as a functional layer was produced.

Next, an amorphous transparent conductive layer was formed on the HC layer of the transparent resin substrate by a reactive sputtering method (transparent conductive layer forming step). In this step, a roll-to-roll type sputtering deposition apparatus (DC magnetron sputtering deposition apparatus) was used. The apparatus includes a first film-forming chamber and a second film-forming chamber in which the film-forming process can be performed while the work film is run in a roll-to-roll manner. Specifically, in this step, the first sputtering film formation in the first film formation chamber and the second sputtering film formation in the second film formation chamber were sequentially performed. In the first sputtering film formation, a first layer (thickness: 11 nm) was formed on the transparent resin substrate. In the subsequent second sputtering deposition, a second layer (thickness 11 nm) was formed on the first layer. The conditions for each sputtering film formation in this example are as follows.

In the first sputtering deposition, the sputtering deposition apparatus (first deposition chamber, second deposition chamber) is evacuated until the ultimate vacuum in the first deposition chamber reaches 0.9 × 10 ^-4 Pa. After that, argon as a sputtering gas and oxygen as a reactive gas were introduced into the first film forming chamber, and the pressure inside the first film forming chamber was set to 0.4 Pa. The ratio of the amount of oxygen introduced to the total amount of argon and oxygen introduced into the first deposition chamber was about 1.8 flow rate %. A first sintered body of indium oxide and tin oxide (with a tin oxide concentration of 3% by mass) was used as a target. A DC power supply was used as a power supply for applying voltage to the target. The horizontal magnetic field strength on the target was set to 90 mT. The film formation temperature (the temperature of the transparent resin base material on which the transparent conductive layer is laminated) was -5°C.

In the second sputtering film formation, after the sputtering film forming apparatus is evacuated, argon as a sputtering gas and oxygen as a reactive gas are introduced into the second film forming chamber, and the atmospheric pressure in the second film forming chamber is changed. was set to 0.4 Pa. The ratio of the amount of oxygen introduced to the total amount of argon and oxygen introduced into the second film forming chamber was set to about 1.9 flow rate %. A first sintered body of indium oxide and tin oxide (with a tin oxide concentration of 3% by mass) was used as a target. A DC power supply was used as a power supply for applying voltage to the target. The horizontal magnetic field strength on the target was set to 90 mT. The film formation temperature was -5°C.

Next, the transparent conductive layer on the transparent resin substrate was heated by being brought into contact with a heating roll in a vacuum heating device and crystallized (crystallization process). In this step, the heating temperature was set to 160° C., the heating time was set to 1 minute, and the transparent conductive layer was heated and crystallized under vacuum.

A series of processes from the transparent conductive layer formation process to the crystallization process described above were carried out on one continuous line while the work film was run in a roll-to-roll method. The work film was never exposed to the atmosphere during this process.

The transparent conductive film of Example 1 was produced as described above. The transparent conductive layer of the transparent conductive film of Example 1 is made of an ITO film (concentration of tin oxide: 3% by mass) and is crystalline.

[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 sputtering film formation in the transparent conductive layer forming step, a second sintered body of indium oxide and tin oxide (with a tin oxide concentration of 10% by mass) was used as a target to form an amorphous first layer having a thickness of 125 nm. formed.

The transparent conductive layer (thickness: 136 nm) of the transparent conductive film of Example 2 consisted of a first layer of ITO (percentage of tin oxide: 10% by mass, thickness: 125 nm) and a second layer of ITO (percentage of tin oxide: 3% by mass). , thickness 11 nm) in order from the transparent resin substrate side and is crystalline (the ratio of the thickness of the first layer to the thickness of the transparent conductive layer is 92%, and the thickness of the second layer is The thickness percentage is 8%).

[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 crystallization step, the transparent conductive layer on the transparent resin substrate was heated in a hot air heating oven. The heating temperature was 160° C. and the heating time was 1 hour. In this step, the transparent conductive layer was heated and crystallized in the atmosphere.

[Comparative Example 2]
A transparent conductive film of Comparative Example 2 was produced in the same manner as the transparent conductive film of Example 2, except for the following. In the crystallization process, the transparent conductive layer on the transparent resin substrate was heated in a hot air heating oven. The heating temperature was 160° C., and the heating time was 1 hour. In this step, the transparent conductive layer was heated and crystallized in the atmosphere.

[Comparative Example 3]
A transparent conductive film of Comparative Example 3 was produced in the same manner as the transparent conductive film of Example 1 except for the following. In the transparent conductive layer forming step, a transparent conductive layer with a thickness of 22 nm was formed using the second sintered body (tin oxide concentration: 10% by mass) as each target in the first and second sputtering depositions.

[Comparative Example 4]
A transparent conductive film of Comparative Example 4 was produced in the same manner as the transparent conductive film of Example 2, except for the following. In the transparent conductive layer forming step, a transparent conductive layer having a thickness of 136 nm was formed using the second sintered body (tin oxide concentration: 10% by mass) as each target in the first and second sputtering film formation.

<Thickness of transparent conductive layer>
The thickness of the transparent conductive layer of each transparent conductive film in Examples 1 and 2 and Comparative Examples 1 to 4 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 and 2 and Comparative Examples 1 to 4 were prepared by the FIB microsampling method. In the FIB microsampling method, an FIB device (product name "FB2200", manufactured by Hitachi) was used with an acceleration voltage of 10 kV. Next, the cross section of the transparent conductive layer in the sample for cross section observation was observed by FE-TEM, and the thickness of the transparent conductive layer was measured in the observed 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.

The thickness of the first layer of the transparent conductive layer in Example 2 and Comparative Example 2 was obtained by preparing a sample for cross-sectional observation from the intermediate product before forming the second layer on the first layer, and measuring the thickness of the sample. Measured by FE-TEM observation. The thickness of the second layer of each transparent conductive layer in Example 2 and Comparative Example 2 was obtained by subtracting the thickness of the first layer from the total thickness of each transparent conductive layer in Example 2 and Comparative Example 2.

<crystalline>
The crystallinity of each transparent conductive layer in Examples 1 and 2 and Comparative Examples 1 to 4 was examined by cross-sectional observation with FE-TEM. Specifically, first, samples for cross-sectional observation of each transparent conductive layer in Examples 1 and 2 and Comparative Examples 1 to 4 were prepared by the FIB microsampling method. In the FIB microsampling method, an FIB device (product name "FB2200", manufactured by Hitachi) was used, and the acceleration voltage was set to 10 kV. Next, an FE-TEM device (product name “JEM-2800”, manufactured by JEOL) was used to photograph the cross section of the transparent conductive layer in the sample for cross section observation at a magnification at which crystal grains can be clearly confirmed (the accelerating voltage was 200 kV). ). In each of the transparent conductive layers in Examples 1 and 2 and Comparative Examples 1 and 2, it was confirmed that crystal grains grew over the entire region in the plane direction and thickness direction of the same layer (plane direction/thickness direction confirmed to be crystalline in all directions). On the other hand, in each of the transparent conductive layers in Comparative Examples 3 and 4, it was confirmed that there were regions in which crystal grains did not grow in the plane direction and thickness direction of the same layer ( It was not confirmed to be crystalline throughout). From these results, the crystallinity of each transparent conductive layer of Examples 1 and 2 and Comparative Examples 1 and 2 was evaluated as "good", and the crystallinity of each transparent conductive layer of Comparative Examples 3 and 4 was evaluated as "poor". ” was evaluated. Table 1 shows the evaluation results.

<Resistance change due to heating>
The transparent conductive films of Examples 1 and 2 and Comparative Examples 1 to 4 were examined for changes in resistance value due to post-heating. Specifically, it is as follows.

First, the first resistance value R1 (surface resistivity before heat treatment) of the transparent conductive layer of the transparent conductive film was measured by the four-terminal method according to JIS K 7194 (1994). Next, the transparent conductive film was heat-treated in a hot air heating oven. In the heat treatment, the heating temperature was 160° C. and the heating time was 30 minutes. Next, the second resistance value R2 (surface resistivity after heat treatment) of the transparent conductive layer of the transparent conductive film was measured by the four-probe method according to JIS K 7194 (1994). Then, the difference R1-R2 between the first resistance value R1 and the second resistance value R2 was obtained. The values are shown in Table 1. Table 1 also shows the ratio (R2/R1) of the second resistance value R2 to the first resistance value R1.

X transparent conductive film D thickness direction 10 transparent resin substrate 11 resin film 12 functional layer 20 transparent conductive layer 21 first layer 22 second layer

Claims

A transparent conductive film comprising a transparent resin base material and a crystalline transparent conductive layer in this order in the thickness direction,
The transparent conductive layer comprises an indium tin composite oxide layer with a tin oxide content of less than 10% by mass,
The transparent conductive layer has a first resistance value R1 (Ω/□) and a second resistance value R2 (Ω/□) after heat treatment under heating conditions of 160° C. and 30 minutes,
A transparent conductive film, wherein a difference R1-R2 between the first resistance value R1 and the second resistance value R2 is 1.5Ω/□ or more.
The transparent conductive film according to claim 1, wherein the difference R1-R2 between the first resistance value R1 and the second resistance value R2 is 10Ω/□ or less.
The transparent conductive film according to claim 1, wherein the transparent conductive layer comprises the indium-tin composite oxide layer.
The transparent conductive film according to any one of claims 1 to 3, wherein the transparent conductive layer has a thickness of 150 nm or less.
The transparent conductive film according to any one of claims 1 to 3, wherein the first resistance value R1 is 220Ω/□ or less.