Stacked film for supporting a transparent conductive layer

Abstract

A laminated film (20) has a base film (16) for supporting a transparent conductive layer (17) and a protective film (14) supporting the base film (16) via an adhesive layer (15). The base film (16) and the protective film (14) each contain a cyclic olefin resin. The base film (16) has a film thickness of 5 μm to 40 μm. The base film (16) has a heat shrinkage rate A (%) in the width direction of 0.01% to 0.20% when heated at 140°C for 90 minutes. When the heat shrinkage rate of the protective film (14) in the width direction when heated at 140°C for 90 minutes is set as B (%), 0.02 ≤ A / B ≤ 0.50.

Description

Technical Field

[0001] The present invention relates to a laminated film for supporting a transparent conductive layer, for example, used in the manufacture of touch sensor panels. Background Technology

[0002] Many mobile displays incorporate touch panels. These touch panels typically use a transparent conductive film supported by a substrate film. This transparent conductive film is obtained by peeling the protective film and adhesive layer together from a laminate containing a transparent conductive layer, which is formed by laminating a substrate film supporting the transparent conductive layer and a protective film through an adhesive layer.

[0003] Here, Patent Document 1 discloses an example of the above-mentioned laminate with a transparent conductive layer. In Patent Document 1, the substrate film and the protective film are made of PET (polyethylene terephthalate) resin, and curling is suppressed by reducing the absolute value of the difference in thermal shrinkage rates between the substrate film and the protective film.

[0004] However, due to the very high birefringence of PET resin, rainbow patterns occur when assembling a substrate film containing PET resin into a display. Furthermore, the sensitivity of foreign object detection decreases during the inspection process when using a protective film containing PET resin. Therefore, the use of cyclic olefin resins (COP resins) in both the substrate film and the protective film has been investigated. For example, in Patent Document 2, by employing COP resins in both the substrate film and the protective film, dimensional changes caused by thermal shrinkage of the substrate film and the protective film are suppressed, thereby controlling the amount and direction of curling.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 5506011 (refer to claims 1, paragraphs

[0032] and

[0076] ) Figure 1 , Figure 2 wait)

[0008] Patent Document 2: Japanese Patent Application Publication No. 2016-107503 (refer to claims 1, paragraphs

[0095] ,

[0105] , and

[0106] ). Figure 1 wait) Summary of the Invention

[0009] However, in recent years, there has been a demand for flexibility in displays, and the same applies to touch panels. To meet this flexibility requirement, there is a need for further thinning of transparent conductive films. In addition, to improve productivity, there is a need to manufacture transparent conductive films in a roll-to-roll manner.

[0010] Therefore, when using a protective film containing COP resin that suppresses dimensional changes caused by heat shrinkage and a thin substrate film containing COP resin, and laminating the protective film and substrate film together through an adhesive layer to form a transparent conductive layer on the substrate film, and then peeling the protective film and adhesive layer together from the substrate film to produce a thin transparent conductive film, it was found that the transparent conductive film deformed during the peeling process. This is believed to be because when the substrate film is thin, it is pulled towards the protective film side through the adhesive layer during peeling, resulting in wrinkles in the substrate film. If the transparent conductive film deforms, the transparent conductive layer may be damaged (e.g., broken) when the transparent conductive film is rolled into a roll.

[0011] In particular, in Patent Document 2, due to the low thermal shrinkage rate of the protective film, the shrinkage stress generated during heating is small, and because the glass transition temperature (Tg) of the protective film is low, the stress generated during heating is mitigated. Therefore, insufficient residual stress is achieved, requiring a high peeling force to peel off the protective film. Thus, it is believed that when the substrate film is thin, it is easily pulled towards the protective film side during the peeling process, and the transparent conductive film is more prone to deformation.

[0012] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a laminated film for supporting a transparent conductive layer, which can suppress the deformation of the transparent conductive film when the protective film after the transparent conductive layer is formed is peeled off, even if the substrate film is thin, thereby enabling the production of thin transparent conductive films with high productivity.

[0013] One aspect of the laminated film of the present invention is a laminated film for supporting a transparent conductive layer of a transparent conductive film, comprising: a substrate film for supporting the transparent conductive layer, and a protective film for supporting the substrate film via an adhesive layer.

[0014] The aforementioned substrate film and the aforementioned protective film each contain cyclic olefin resin.

[0015] The thickness of the aforementioned substrate film is 5 μm to 40 μm.

[0016] The width-direction thermal shrinkage rate A (%) of the above-mentioned substrate film after heating at 140°C for 90 minutes is 0.01% to 0.20%.

[0017] When the thermal shrinkage rate in the width direction of the above protective film is set as B (%) after heating at 140°C for 90 minutes,

[0018] 0.02≤A / B≤0.50.

[0019] Based on the above-described laminated film structure, even if the substrate film is thin, deformation of both the substrate film and the transparent conductive layer (transparent conductive film) can be suppressed when the protective film after the transparent conductive layer is formed on the substrate film is peeled off. Therefore, thin transparent conductive films can be manufactured with high productivity using a roll-to-roll method. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view showing the general configuration of a touch panel display device according to an embodiment of the present invention.

[0021] Figure 2 This is a cross-sectional view showing other components of the aforementioned touch panel display device.

[0022] Figure 3 It means in Figure 1 or Figure 2 A flowchart illustrating the manufacturing process of the transparent conductive film used in the touch sensor panel of a touch panel display device.

[0023] Figure 4 This is a cross-sectional view showing the manufacturing process of the aforementioned transparent conductive film.

[0024] Figure 5 This is an explanatory diagram showing the general configuration of a manufacturing apparatus for an optical film contained in a laminated film used in the manufacture of the aforementioned transparent conductive film.

[0025] Figure 6 This is a flowchart illustrating the manufacturing method of the aforementioned optical film. Detailed Implementation

[0026] An embodiment of the present invention will be described below with reference to the accompanying drawings. It should be noted that, in this specification, when a numerical range is expressed as A to B, this numerical range includes the lower limit A and the upper limit B.

[0027] [Touch panel display device]

[0028] Figure 1 This is a cross-sectional view showing the general configuration of the touch panel display device 1 according to this embodiment. The touch panel display device 1 is configured to have a touch sensor panel 3 on the display unit 2. The display unit 2 is configured, for example, as a liquid crystal display device, but it may also be configured as other display devices such as an organic EL (Electro-Luminescence) display device, which is called an OLED (Organic Light-Emitting Diode).

[0029] The touch sensor panel 3 is constructed by sequentially stacking an adhesive layer 13, a transparent conductive film 12, another adhesive layer 13, another transparent conductive film 12, and another adhesive layer 13 on a glass substrate 11, which serves as a transparent substrate. Each transparent conductive film 12 is constructed by sequentially stacking a substrate film 16 and a transparent conductive layer 17. Of the two transparent conductive films 12, for the transparent conductive film 12 closer to the glass substrate 11, the substrate film 16 is closer to the glass substrate 11 than the transparent conductive layer 17. For the other transparent conductive film 12 (the transparent conductive film 12 closer to the display section 2), the substrate film 16 is closer to the display section 2 than the transparent electrode layer 17.

[0030] Figure 2 This is a cross-sectional view showing other components of the aforementioned touch panel display device 1. For example... Figure 2 As shown, the touch sensor panel 3 of the touch panel display device 1 can be constructed by sequentially stacking an adhesive layer 13, a transparent conductive film 12, and an adhesive layer 13 on a glass substrate 11. In this configuration, for the transparent conductive film 12, the substrate film 16 is closer to the display portion 2 than the transparent conductive layer 17.

[0031] exist Figure 1 or Figure 2 In its configuration, the transparent conductive layer 17 can be made of, for example, indium oxide (ITO) containing tin oxide or a conductive film containing metal nanowires. From the viewpoint of flexibility and good bending durability, even with repeated bending, the transparent conductive layer 17 is preferably made of a conductive film containing metal nanowires. The adhesive layer 13 is, for example, made of an optical adhesive film. The transparent conductive film 12 can be manufactured, for example, as follows.

[0032] [Method for manufacturing transparent conductive film]

[0033] Figure 3 This is a flowchart illustrating the manufacturing method of the transparent conductive film 12. Additionally, Figure 4 This is a cross-sectional view showing the manufacturing process of the transparent conductive film 12. The transparent conductive film 12 includes a laminated film preparation process (S1), a transparent conductive layer formation process (S2), and a protective film peeling process (S3).

[0034] (S1: Laminated film preparation process)

[0035] In step S1, a laminated film 20 is prepared. This laminated film 20 is formed by laminating a protective film 14 and a substrate film 16 together with an adhesive layer 15. The substrate film 16 is a thin film having a thickness of 5 μm to 40 μm, as described below. Here, the laminated film 20 is pre-wound into a roll. It should be noted that a cured resin layer (hard coating) can be formed on at least one side of the substrate film 16. Details of such a laminated film 20 are described below.

[0036] (S2: Transparent conductive layer formation process)

[0037] In step S2, the rolled-up laminate 20 is extracted, and a transparent conductive layer 17 is formed on the substrate film 16 of the extracted laminate 20 to obtain a laminate 10 with a transparent conductive layer. For example, by handling the laminate 20 in a vacuum apparatus, the transparent conductive layer 17 is formed on the substrate film 16 using a vacuum process such as sputtering or evaporation to obtain a laminate 10 with a transparent conductive layer. It should be noted that the transparent conductive layer 17 can be etched into a desired shape. Alternatively, the transparent conductive layer 17 can be formed by coating the composition constituting the transparent conductive layer 17 onto the surface of the substrate film 16 and drying it to obtain a laminate 10 with a transparent conductive layer. In either case, the obtained laminate 10 with a transparent conductive layer is rolled into a roll.

[0038] (S3: Protective film peeling process)

[0039] In step S3, the laminate 10 with the transparent conductive layer, which has been rolled into a roll, is pulled out, and the protective film 14 and the adhesive layer 15 are peeled off from the laminate 10 with the transparent conductive layer. This yields a thin transparent conductive film 12 having a transparent conductive layer 17 on a thin substrate film 16. The obtained transparent conductive film 12 is then rolled into a roll.

[0040] Thus, according to the above-described method for manufacturing the transparent conductive film 12, a thin transparent conductive film 12 can be manufactured in a roll-to-roll manner by using a laminated film 20 having a thin substrate film 16. Therefore, a thin transparent conductive film 12 can be manufactured with high productivity.

[0041] [Details of the laminated membrane]

[0042] Next, the details of the laminated film 20 described above will be explained. The laminated film 20 is a laminated film used to support the transparent conductive layer 17 contained in the transparent conductive film 12. The laminated film 20 has a substrate film 16 for supporting the transparent conductive layer 17 and a protective film 14 that supports the substrate film 16 through an adhesive layer 15.

[0043] Both the substrate film 16 and the protective film 14 contain cyclic olefin resin (COP resin). This eliminates the defects that occur when using, for example, PET resin as the film material. Specifically, it prevents the generation of rainbow patterns in the display or a decrease in the sensitivity of foreign object detection during the inspection process.

[0044] The thickness of the substrate film 16 is 5 μm to 40 μm. When the thickness of the substrate film 16 is within the above range, the formation of cracks in the substrate film 16 during bending and handling of the transparent conductive film 12 can be reduced, thus reducing damage (e.g., breakage) to the transparent conductive layer 17. Therefore, a thin transparent conductive film 12 can be manufactured with high productivity using a roll-to-roll method. That is, a laminated film 20 suitable for manufacturing thin transparent conductive films 12 with high productivity can be realized.

[0045] Furthermore, if the thickness of the substrate film 16 is less than 5 μm, it is too thin and prone to cracking when the transparent conductive film 12 is bent during transport using a transport roller. As a result, the transparent conductive layer 17 on the substrate film 16 is prone to breakage, leading to poor electrical conductivity. Conversely, if the thickness of the substrate film 16 exceeds 40 μm, the transparent conductive layer 17 on the substrate film 16 is easily stretched and broken in the circumferential direction of the roller when the transparent conductive film 12 is bent during transport, still resulting in poor electrical conductivity.

[0046] Furthermore, the thermal shrinkage rate A (%) in the width direction of the substrate film 16 after heating at 140°C for 90 minutes is 0.01% to 0.20%. As a result, damage to the transparent conductive layer 17 can be suppressed during the heat processing of the transparent conductive layer 17 (including drying) and during the peeling of the protective film 14, and a laminated film 20 suitable for manufacturing the transparent conductive film 12 can be realized.

[0047] Furthermore, if the heat shrinkage rate A exceeds 0.20%, the heat shrinkage of the substrate film 16 during the heating process of the transparent conductive layer 17 will be too large. It is believed that the transparent conductive layer 17 on the substrate film 16 cannot keep up with the shrinkage of the substrate film 16 and is prone to breakage, easily leading to poor electrical conductivity. Conversely, if the heat shrinkage rate A is less than 0.01%, the shrinkage stress generated in the substrate film 16 during the heating process of the transparent conductive layer 17 is small, and sufficient residual stress cannot be obtained. Therefore, it is difficult to uniformly peel the protective film 14 from the substrate film 16, resulting in portions where the substrate film 16 is partially pulled towards the protective film 14. It is believed that in such portions, the transparent conductive layer 17 on the substrate film 16 will partially break, easily leading to poor electrical conductivity.

[0048] In addition, when the thermal shrinkage rate in the width direction of the protective film 14 is set as B (%) after heating at 140°C for 90 minutes,

[0049] 0.02≤A / B≤0.50.

[0050] By satisfying this condition, the protective film 14 can be peeled off from the substrate film 16 by utilizing the difference in thermal shrinkage rates between the substrate film 16 and the protective film 14. Therefore, the protective film 14 can be easily peeled off even without weakening the adhesive strength of the adhesive layer 15.

[0051] The mechanism by which this effect is manifested is speculated as follows: During the formation of the transparent conductive layer 17, when the laminated film 20 is heated, the shrinkage forces during heating differ between the protective film 14 and the substrate film 16. Subsequently, upon cooling (returning to room temperature), residual stress is generated in the adhesive layer 15 and the protective film 14. When the protective film 14 is peeled off from the roll-shaped laminated film 20, not only is tension generated along the long side of the peeling roller, but also shrinkage occurs along the width direction based on the aforementioned residual stress. Therefore, by taking advantage of the peeling process, the protective film 14 can be peeled off with less force.

[0052] This makes peeling off the protective film 14 easier, so that the substrate film 16 is less likely to be pulled toward the protective film 14 side during peeling, and the transparent conductive layer 17 supported by the substrate film 16 is less likely to be pulled toward the protective film 14 side. As a result, deformation of the transparent conductive film 12 (causing wrinkles and creases) can be reduced during peeling off the protective film 14.

[0053] Furthermore, if A / B exceeds 0.50, the difference in thermal shrinkage rates between the substrate film 16 and the protective film 14 is small (A / B is close to 1), making it difficult to peel the protective film 14 from the substrate film 16 using the difference in thermal shrinkage. As a result, a high peeling force is required to peel the protective film 14. If the peeling force of the protective film 14 is high, the transparent conductive film 12 is easily pulled towards the protective film 14 side and deformed during peeling. On the other hand, if A / B is less than 0.02, the thermal shrinkage rate B of the protective film 14 is too large relative to the thermal shrinkage rate A of the substrate film 16. In this case, the protective film 14 undergoes significant thermal shrinkage during the heating process of the transparent conductive layer 17, making the ends of the protective film 14 easy to peel off, thus making it difficult to peel the protective film 14 uniformly from the substrate film 16 in the width direction during peeling. As a result, the substrate film 16 is prone to wrinkling during the peeling of the protective film 14, and the transparent conductive film 12 is prone to deformation.

[0054] Furthermore, since the protective film 14 can be easily peeled off even without weakening the adhesive strength of the adhesive layer 15, it is possible to prevent the protective film 14 from peeling off from the substrate film 16 during transport before peeling due to the adhesive strength of the adhesive layer 15. As a result, the peeled protective film 14 will not be rolled into the transport rollers, thus preventing the laminate 10 with the transparent conductive layer from breaking.

[0055] Preferably, the protective film 14 has a thickness of 40 μm to 100 μm, which is thicker than the substrate film 16. In this configuration, the shrinkage force caused by heat in the protective film 14 can be appropriately generated relative to the thickness of the substrate film 16. Therefore, during the handling of the transparent conductive layer 17 during heat processing, wrinkles in the substrate film 16 due to the thermal shrinkage of the protective film 14 can be reduced. Thus, damage to the transparent conductive layer 17 on the substrate film 17 can be reduced when the laminate 10 with the transparent conductive layer is wound up. In addition, the mechanical strength of the protective film 14 can be sufficiently ensured, and damage (e.g., cracks) to the protective film 14 during handling can also be sufficiently reduced.

[0056] Furthermore, as described above, from the viewpoint of exhibiting good bending durability, it is preferable that the transparent conductive layer 17 is composed of a conductive film containing metal nanowires. Thus, it can be said that the substrate film 16 is preferably used to support the conductive film containing metal nanowires, which serves as the transparent conductive layer 17, to form a laminated film 20.

[0057] [Regarding the materials used on each floor, etc.]

[0058] Next, the materials of each layer constituting the above-described laminate 10 with a transparent conductive layer will be described.

[0059] <Transparent Conductive Film>

[0060] (Substrate film)

[0061] From the viewpoint of easy control of optical properties, the substrate film preferably contains a cyclic olefin resin.

[0062] As a cyclic olefin resin, there is no particular limitation as long as it is a resin having units consisting of monomers composed of cyclic olefins (cyclic olefins). The cyclic olefin resin used as a substrate film can be either a cyclic olefin polymer (COP) or a cyclic olefin copolymer (COC). Cyclic olefin copolymers refer to amorphous cyclic olefin resins that are copolymers of cyclic olefins with olefins such as ethylene.

[0063] As described above, cyclic olefins include both polycyclic and monocyclic cyclic olefins. Examples of polycyclic cyclic olefins include norbornene, methyl norbornene, dimethyl norbornene, ethyl norbornene, ethylidene norbornene, butyl norbornene, dicyclopentadiene, dihydrodicyclopentadiene, methyldicyclopentadiene, dimethyldicyclopentadiene, tetracyclododecene, methyltetracyclododecene, dimethyltetracyclododecene, tricyclopentadiene, and tetracyclopentadiene. Examples of monocyclic cyclic olefins include cyclobutene, cyclopentene, cyclooctene, cyclooctadiene, cycloocttriene, and cyclododecadiene.

[0064] Cycloolefin resins are available as commercially available products, such as "ZEONOR" manufactured by Zeon Corporation of Japan, "ARTON" manufactured by JSR Corporation, "TOPAS" manufactured by Polyplastics Corporation, and "APEL" manufactured by Mitsui Chemicals Corporation.

[0065] For the substrate film, etching treatments or primer treatments such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, formation, and oxidation can be pre-applied to improve the adhesion with the transparent conductive layer formed on the substrate film. Additionally, before forming the transparent conductive layer, the surface of the substrate film can be cleaned and dust-removed by solvent cleaning or ultrasonic cleaning, as needed.

[0066] The glass transition temperature of the cyclic olefin resin forming the substrate film is preferably 130°C or higher, more preferably 140°C or higher. This helps to suppress warping after the heat treatment process, improve dimensional stability, and ensure the yield of subsequent processes.

[0067] (Transparent conductive layer)

[0068] The constituent material of the transparent conductive layer is not particularly limited as long as it contains inorganic substances, but preferably a metal oxide selected from at least one metal selected from indium, tin, zinc, gallium, antimony, titanium, silicon, zirconium, magnesium, aluminum, gold, silver, copper, palladium, and tungsten. This metal oxide may further contain metal atoms shown in the above group as needed. For example, indium oxide (ITO) containing tin oxide and tin oxide (ATO) containing antimony are preferred.

[0069] There is no particular limitation on the thickness of the transparent conductive layer, in order to achieve a surface resistivity of 1×10⁻⁶. 3 A continuous conductive film with good conductivity of Ω / □ or less is preferably 10 nm or more in thickness. If the film thickness is too thick, it can lead to a decrease in transparency, etc. Therefore, a thickness of 15–35 nm is preferred, and more preferably 20–30 nm. If the thickness of the transparent conductive layer is less than 10 nm, the surface resistance of the film becomes high, and it is difficult to achieve a continuous conductive film. Furthermore, if the thickness of the transparent conductive layer exceeds 35 nm, it can sometimes lead to a decrease in transparency, etc.

[0070] There are no particular limitations on the method for forming the transparent conductive layer; well-known methods can be used. Specifically, examples include dry processes such as vacuum evaporation, sputtering, and ion plating. Alternatively, an appropriate method can be used depending on the desired film thickness.

[0071] The transparent conductive layer can be crystallized by heat annealing (e.g., at 80–150°C for approximately 30–90 minutes in an atmospheric atmosphere) as needed. Crystallization of the transparent conductive layer reduces its resistance and improves its transparency and durability. There are no particular limitations on the method used to transform the amorphous transparent conductive layer into a crystalline one; air-circulating ovens, IR heaters, etc., can be used.

[0072] Regarding the definition of "crystalline material," a transparent conductive film with a transparent conductive layer formed on the substrate film is immersed in 5% by weight hydrochloric acid at 20°C for 15 minutes, followed by washing and drying. The inter-terminal resistance between terminals within a 15mm span is measured using a testing instrument. If the inter-terminal resistance exceeds 10kΩ, it indicates that the ITO film has completed its transformation into crystalline material. It should be noted that the surface resistivity value can be measured based on JIS K7194 using the four-terminal method.

[0073] Furthermore, the transparent conductive layer can be patterned by etching or the like. The patterning of the transparent conductive layer can be performed using photolithography, a technique already well-known. An acid is preferably used as the etching solution. Examples of acids include inorganic acids such as hydrogen chloride, hydrogen bromide, sulfuric acid, nitric acid, and phosphoric acid, organic acids such as acetic acid, mixtures thereof, and aqueous solutions thereof. For example, in transparent conductive films used in capacitive touch panels and matrix resistive film touch panels, it is preferable that the transparent conductive layer is patterned into stripes. It should be noted that when patterning the transparent conductive layer by etching, if the transparent conductive layer is crystallized first, it can sometimes be difficult to pattern it by etching. Therefore, annealing of the transparent conductive layer is preferably performed after patterning the transparent conductive layer.

[0074] When forming a transparent conductive layer using dry processes such as sputtering, it is preferable to transport the substrate film in a state where a protective film is laminated with an adhesive layer, forming the transparent conductive layer on the substrate film, and then continuously processing it in a roll-to-roll manner to produce a long strip of laminated body with the transparent conductive layer. By producing a laminated body with the transparent conductive layer, breakage of the laminated body with the transparent conductive layer can be prevented during the roll-to-roll process, ensuring the yield of subsequent processes.

[0075] Metal nanowires

[0076] Metal nanowires can also be used as materials to form transparent conductive layers. Metal nanowires are conductive materials made of metal, with needle-like or wire-like shapes and a diameter of nanometers. Metal nanowires can be straight or curved. When using a transparent conductive layer composed of metal nanowires, by making the metal nanowires into a mesh-like structure, even a small number of metal nanowires can form good conductive paths, resulting in a transparent conductive film with low resistance. Furthermore, by making the metal nanowires into a mesh-like structure, openings can be formed in the gaps between the meshes, resulting in a transparent conductive film with high light transmittance.

[0077] The ratio of the thickness d to the length L of the aforementioned metal nanowires (aspect ratio: L / d) is preferably in the range of 10 to 100,000, more preferably in the range of 50 to 100,000, and particularly preferably in the range of 100 to 10,000. Using metal nanowires with such a large aspect ratio allows for good interlacing, enabling high conductivity with a small amount of metal nanowires. As a result, a transparent conductive film with high light transmittance can be obtained.

[0078] It should be noted that in this specification, "thickness of metal nanowires" refers to the diameter when the cross-section of the metal nanowire is circular, the minor axis when it is elliptical, and the longest diagonal when it is polygonal. The thickness and length of the metal nanowires can be confirmed using a scanning electron microscope or a transmission electron microscope.

[0079] The thickness of the aforementioned metal nanowires is preferably less than 500 nm, more preferably less than 200 nm, particularly preferably in the range of 10–100 nm, and most preferably in the range of 10–50 nm. Within this range, a transparent conductive layer with high light transmittance can be formed.

[0080] The length of the aforementioned metal nanowires is preferably in the range of 2.5 to 1000 μm, more preferably in the range of 10 to 500 μm, and particularly preferably in the range of 20 to 100 μm. Within this range, a transparent conductive film with high conductivity can be obtained.

[0081] As the metal constituting the aforementioned metal nanowires, any suitable metal can be used, as long as it has high conductivity. Examples of metals constituting the aforementioned metal nanowires include silver, gold, copper, and nickel. Additionally, materials in which these metals have been plated (e.g., gold-plated) can be used. From the viewpoint of conductivity, silver or copper is preferred.

[0082] Any suitable method can be used as a method for manufacturing the aforementioned metal nanowires. Examples include methods such as reducing silver nitrate in solution, applying an external voltage or current to the front end of a probe on the precursor surface, and continuously forming the aforementioned metal nanowires by drawing the metal nanowires from the front end of the probe. In the method of reducing silver nitrate in solution, silver nanowires can be synthesized by liquid-phase reduction of silver salts such as silver nitrate in the presence of polyols such as ethylene glycol and polyvinylpyrrolidone.

[0083] Uniformly sized silver nanowires can be mass-produced, for example, based on the methods described in Xia, Y. et al., Chem. Mater. (2002), 14, 4736-4745, and Xia, Y. et al., Nano letters (2003) 3(7), 955-960.

[0084] The aforementioned transparent conductive layer can be formed by coating the aforementioned transparent substrate with a transparent conductive layer forming composition containing the aforementioned metal nanowires. More specifically, a dispersion (transparent conductive layer forming composition) obtained by dispersing the aforementioned metal nanowires in a solvent can be coated onto the aforementioned transparent substrate, and the coating layer can be dried to form a transparent conductive layer.

[0085] Examples of solvents mentioned above include water, alcohols, ketones, ethers, hydrocarbons, and aromatics. From the perspective of reducing environmental impact, water is preferred.

[0086] The dispersion concentration of the metal nanowires in the composition for forming a transparent conductive layer containing the above-mentioned metal nanowires is preferably in the range of 0.1% to 1% by mass. If it is within such a range, a transparent conductive layer with excellent conductivity and light transmittance can be formed.

[0087] The composition for forming a transparent conductive layer containing the aforementioned metal nanowires may further contain any suitable additives, depending on the intended purpose. Examples of such additives include corrosion-resistant materials that prevent corrosion of the metal nanowires and surfactants that prevent the aggregation of the metal nanowires. The type, number, and amount of additives used may be appropriately determined according to the intended purpose. Furthermore, the composition for forming a transparent conductive layer may contain any suitable binder resin, as needed, provided that the effects of the present invention are achieved.

[0088] As a coating method for the composition for forming a transparent conductive layer containing the above-mentioned metal nanowires, any suitable method can be used. Examples of coating methods include spraying, rod coating, roller coating, die coating, ink jet coating, screen coating, dip coating, letterpress printing, gravure printing, and gravure printing.

[0089] As a drying method for the coating layer, any suitable drying method can be used (e.g., natural drying, air drying, heat drying). For example, in the case of heat drying, a representative drying temperature is in the range of 100 to 200°C, and a representative drying time is in the range of 1 to 10 minutes.

[0090] When the aforementioned transparent conductive layer contains metal nanowires, the thickness of the transparent conductive layer is preferably in the range of 0.01 to 10 μm, more preferably in the range of 0.05 to 3 μm, and particularly preferably in the range of 0.1 to 1 μm. Within such a range, a transparent conductive film with excellent conductivity and light transmittance can be obtained.

[0091] When the above-mentioned transparent conductive layer contains metal nanowires, the total light transmittance of the above-mentioned transparent conductive layer is preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more.

[0092] (Adhesive layer)

[0093] As an adhesive layer, it can be used without particular restrictions as long as it is transparent. Specifically, for example, substances based on polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethylene ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy polymers, fluorinated polymers, natural rubber, and synthetic rubber can be appropriately selected. In particular, from the viewpoint of excellent optical transparency, appropriate wetting, coagulation, and adhesion properties, as well as excellent weather resistance and heat resistance, acrylic adhesives are preferred.

[0094] There are no particular limitations on the method for forming the adhesive layer. Examples include coating the adhesive composition onto the release liner, drying it, and then transferring it onto the protective film (transfer printing); directly coating the adhesive composition onto the protective film and drying it (direct printing); and using co-extrusion methods, etc. It should be noted that adhesive additives, plasticizers, fillers, antioxidants, UV absorbers, silane coupling agents, etc., may also be appropriately used in the adhesive as needed.

[0095] The preferred thickness of the adhesive layer is 5 μm to 100 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 35 μm.

[0096] (Protective film)

[0097] Considering the ease of operation, such as winding with rollers, the protective film is preferably formed of an amorphous resin. As the amorphous resin, cyclic olefin resins with excellent transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy are preferred. From the viewpoint of suppressing warping after heat treatment and improving dimensional stability, cyclic olefin resins are also preferred.

[0098] The glass transition temperature of the amorphous resin that forms the protective film is preferably 130°C or higher, more preferably 140°C or higher. This suppresses warping after heat treatment, improves dimensional stability, and ensures the yield of subsequent processes.

[0099] Similar to the substrate film, the protective film can undergo pre-treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, formation, oxidation, or immersion coating to improve adhesion to the adhesive layer on the protective film. Furthermore, before forming the adhesive layer, the surface of the protective film can be cleaned and dust-removed as needed using solvent cleaning or ultrasonic cleaning.

[0100] The thickness of the protective film is preferably 10–150 μm, more preferably 30–110 μm, and even more preferably 40–100 μm. Within this thickness range, the mechanical strength of the protective film can be ensured, and wrinkles in the substrate film caused by thermal shrinkage of the protective film during the handling of the laminated body during the heating process of the transparent conductive layer can be reduced.

[0101] [Membrane manufacturing method]

[0102] The aforementioned substrate film and protective film (hereinafter also referred to as "optical film") are manufactured, for example, by solution casting. Figure 5 This is an explanatory diagram showing the outline configuration of the optical film manufacturing apparatus 31 according to this embodiment. Figure 6 This is a flowchart illustrating the manufacturing method of the aforementioned optical film. The optical film manufacturing method of this embodiment is a method for manufacturing optical films using a solution casting method, including: a stirring preparation step (S31), a casting step (S32), a peeling step (S33), a first drying step (S34), a stretching step (S35), a second drying step (S36), a shearing step (S37), an embossing step (S38), and a winding step (S39). Each step will be described below.

[0103] <Stirring Preparation Process>

[0104] In the stirring preparation process, at least the resin and solvent are stirred in the stirring tank 51 of the stirring device 50 to prepare a coating that is cast on the support 33 (endless tape). For example, a cyclic olefin resin can be used as the resin. A mixture of good and bad solvents can be used as the solvent. It should be noted that a good solvent refers to an organic solvent that has the property of dissolving resin (solubility), such as 1,3-dioxolane, THF (tetrahydrofuran), methyl ethyl ketone, acetone, methyl acetate, and methylene chloride (dichloromethane). On the other hand, a bad solvent refers to a solvent that does not have the property of dissolving resin on its own, such as methanol and ethanol.

[0105] <Cast casting process>

[0106] In the casting process, the coating prepared in the stirring preparation process is fed to the casting mold 32 via a conduit using a pressurized quantitative gear pump or the like, causing the coating to be cast from the casting mold 32 onto a casting position on a support 33 formed by an endless stainless steel belt driven by an infinitely rotating conveyor. The cast coating is then dried on the support 33 to form a cast film 35 (base film). The slope of the casting mold 32, i.e., the direction in which the coating is ejected from the casting mold 32 to the support 33, can be appropriately set such that the angle between the surface of the support 33 (the surface of the cast coating) and the normal is within the range of 0° to 90°.

[0107] The support 33 is held by a pair of rollers 33a and 33b and a plurality of rollers (not shown) located between them. A drive device (not shown) is provided on one or both of the rollers 33a and 33b to apply tension to the support 33, thereby applying tension to the support 33 and using it in a taut state.

[0108] In the casting process, the cast film 35 formed by the coating material cast on the support 33 is heated on the support 33 to evaporate the solvent until the cast film 35 can be peeled off from the support 33 using the peeling roller 34. Methods for evaporating the solvent include: blowing air from the base film side, using liquid heat conduction from the back of the support 33, and using radiant heat conduction from the surface and back side, etc., which can be used individually or in combination as appropriate.

[0109] <Stripping Process>

[0110] After drying and curing or cooling and solidifying to a film strength sufficient to peel the cast film 35 off the support 33 in the casting process described above, the cast film 35 is peeled off in the peeling process using the peeling roller 34 while maintaining its self-supporting properties.

[0111] It should be noted that the amount of residual solvent on the cast film 35 on the support 33 at the time of peeling is preferably in the range of 50 to 120% by mass, depending on the strength of the drying conditions and the length of the support 33. When peeling is performed at a time with a high amount of residual solvent, if the cast film 35 is too soft, the planarity will be damaged during peeling, and wrinkles and sagging caused by peeling tension will easily occur. Therefore, the amount of residual solvent at the time of peeling is determined in a way that balances economic speed and quality. It should be noted that the amount of residual solvent is defined by the following formula.

[0112] Residual solvent content (mass%) = (Mass of base film before heat treatment - Mass of base film after heat treatment) / (Mass of base film after heat treatment) × 100

[0113] The heat treatment for determining the amount of residual solvent refers to a heat treatment at 115°C for 1 hour.

[0114] <First Drying Process>

[0115] The cast film 35, peeled off from the support 33, is dried using a drying apparatus 36. Inside the drying apparatus 36, the cast film 35 is transported using multiple transport rollers arranged in a serrated pattern when viewed from the side, during which the cast film 35 is dried. The drying method within the drying apparatus 36 is not particularly limited; generally, hot air, infrared radiation, heated rollers, microwaves, etc., are used to dry the cast film 35. From a simplicity perspective, the method of drying the cast film 35 using hot air is preferred. It should be noted that the first drying step can be performed as needed.

[0116] <Stretching Process>

[0117] In the stretching process, the cast film 35, dried by the drying device 36, is stretched using a tenter frame 37. The stretching direction at this time can be either the film transport direction (MD direction: Machine Direction), the width direction perpendicular to the transport direction within the film surface (TD direction: Transverse Direction), or either of these directions. In order to improve the flatness and dimensional stability of the film during the stretching process, a tenter frame method is preferred, where the two side edges of the cast film 35 are fixed and stretched using clamps or the like. It should be noted that drying can be performed within the tenter frame 37 during the stretching process.

[0118] <Second Drying Process>

[0119] The cast film 35, stretched by the tenter frame 37, is dried using a drying apparatus 38. Inside the drying apparatus 38, the cast film 35 is transported using multiple transport rollers arranged in a serrated pattern when viewed from the side, during which the cast film 35 is dried. There are no particular limitations on the drying method used in the drying apparatus 38; generally, hot air, infrared radiation, heated rollers, microwaves, etc., are used to dry the cast film 35. From a simplicity perspective, the method of drying the cast film 35 using hot air is preferred.

[0120] After being dried by the drying device 38, the cast film 35 is transferred to the winding device 41 to form the optical film F.

[0121] <Shearing process, embossing process>

[0122] A shearing section 39 and an embossing section 40 are sequentially arranged between the drying unit 38 and the winding unit 41. In the shearing section 39, a shearing process is performed where the optical film F being manufactured is transported while its two ends in the width direction are cut using a slitting machine. The portion of the optical film F remaining after the ends are cut constitutes the product portion, which is a film product. On the other hand, the portion cut from the optical film F is recovered via a chute and reused as part of the raw material for film production.

[0123] After the shearing process, the embossing section 40 performs embossing (knurling) on ​​both ends of the optical film F in the width direction. Embossing is performed by pressing a heated embossing roller against both ends of the optical film F. Fine irregularities are formed on the surface of the embossing roller, and these irregularities are created at both ends by pressing the roller against them. This embossing process effectively suppresses winding misalignment or adhesion (film sticking to each other) during the subsequent winding process.

[0124] <Winding Process>

[0125] Finally, the embossed optical film F is wound up using the winding device 41 to obtain a raw material roll (film roll) of optical film F. That is, in the winding process, the film roll is manufactured by simultaneously transporting and winding the optical film F into a core. The winding method for the optical film F can utilize a commonly used winder, employing tension control methods such as constant torque, constant tension, taper tension, and programmed tension control with constant internal stress, which can be used appropriately. The roll length of the optical film F is preferably 1000–7200 mm. Furthermore, the width is preferably 1000–3200 mm, and the film thickness can be appropriately adjusted within the range of 10–150 μm.

[0126] [Example]

[0127] The following describes specific embodiments of the present invention, but the present invention is not limited to these embodiments.

[0128] Example 1

[0129] <Making of Protective Film P-1>

[0130] (Preparation of coatings)

[0131] The following composition was added to a stirred tank and stirred until the components dissolved. The solution was then filtered through a filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm to prepare a cyclic olefin polymer solution.

[0132] <Coating Composition>

[0133] Cyclic olefin polymer (manufactured by JSR Corporation, "ARTON" (registered trademark)) 150 parts by weight

[0134] 380 parts by weight of dichloromethane

[0135] Next, the following composition containing the cyclic olefin polymer solution prepared above is fed into a disperser to prepare a particulate dispersion.

[0136] <Particulate Dispersion>

[0137] Particulate matter (AEROSIL R812: manufactured by NIPPON AEROSIL, primary average particle size: 7nm, apparent specific gravity 50g / L) 4 parts by weight

[0138] 76 parts by weight of dichloromethane

[0139] 10 parts by weight of cyclic olefin polymer solution

[0140] Then, 100 parts by mass of the above cyclic olefin polymer solution and 0.75 parts by mass of the above particulate dispersion are mixed to prepare a coating for film formation.

[0141] (Making of the protective film)

[0142] Next, using an endless tape casting apparatus, the film-forming coating prepared above is uniformly cast onto a stainless steel strip support at a temperature of 31°C with a width of 1800 mm. The temperature of the stainless steel strip support is controlled at 28°C.

[0143] The solvent is evaporated on a stainless steel strip support until the residual solvent content in the cast (cast) film reaches 30% by mass. Next, the cast film (base film) is peeled off from the stainless steel strip support with a peel tension of 128 N / m. While drying the peeled base film, it is stretched in the longitudinal direction at a stretch ratio of 20% (1.20 times) using a transport tension, and then transported in the tenter frame stretching device at a stretch ratio of 40% (1.40 times) in the width direction. At this time, the drying conditions from peeling to tenter frame are adjusted so that the residual solvent content during stretching is 5% by mass. In addition, the temperature of the tenter frame stretching device is set at 135°C, and the stretching speed is set at 200% / min.

[0144] Next, the stretched base film (membrane) is introduced into a drying device, where it is dried simultaneously using multiple rollers. Afterward, the ends of the resulting film in the width direction are cut, and then embossed to produce a protective film P-1 with a dried film thickness of 60 μm.

[0145] <Fabrication of Substrate Film F-1>

[0146] The coating used in the production of the protective film P-1 described above is cast onto a stainless steel strip support. Then, the solvent is evaporated on the stainless steel strip support until the residual solvent content in the cast (cast) film reaches 30% by mass. Next, the cast film (base film) is peeled off from the stainless steel strip support at a peel tension of 128 N / m. The peeled base film is introduced into a drying area and dried simultaneously using multiple rollers. Then, while the base film is heated to 160°C, it is stretched by 5% in the width direction using a tenter frame. After shearing the two ends of the resulting film in the width direction, embossing is performed to produce a substrate film F-1 with a dried film thickness of 18 μm.

[0147] <Fabrication of L-1 laminated film>

[0148] (Preparation of adhesive S-1)

[0149] An acrylic polymer with a weight average molecular weight of 600,000 was obtained by conventional solution polymerization with a butyl acrylate / acrylic acid ratio of 100 / 6 (by weight). An acrylic adhesive was prepared by adding 6 parts by weight of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical, trade name "TETRAD C" (registered trademark)) to 100 parts by weight of this acrylic polymer.

[0150] (Fabrication of laminated films)

[0151] Adhesive S-1, as described above, is applied to the demolded surface of the PET film after demolding treatment. The film is then heated at 120°C for 60 seconds to form an adhesive layer with a thickness of 20 μm. Next, the PET film is bonded to the protective film P-1 prepared above via the adhesive layer. Subsequently, the PET film is peeled off, resulting in a protective film P-1 with an adhesive layer formed on one side of the protective film P-1.

[0152] Next, the protective film P-1 with the adhesive layer and the substrate film F-1 prepared above are bonded together through the adhesive layer to form a laminated film L-1.

[0153] <Fabrication of Transparent Conductive Film M-1>

[0154] (Formation of transparent conductive layer A)

[0155] In Y. Sun, B. Gates, B. Mayers, & Y. Xia, “Crystalline silver nanowires by soft solution processing”, Nano Letters, (2002), 2(2): 165-168, silver nanowires are obtained by dissolving silver sulfate in ethylene glycol in the presence of polyvinylpyrrolidone (PVP) and reducing it. That is, in this embodiment, silver nanowires are synthesized using a modified polyol method described in U.S. Provisional Application No. 60 / 815,627 (Cambrios Technologies Corporation).

[0156] (Fabrication of a laminate with a transparent conductive layer)

[0157] Using a trench coating machine, an aqueous dispersion of silver nanowires (ClearOhm™, Ink-AAQ, manufactured by Cambrios Technologies Corporation) synthesized in the above method, containing 0.5% w / v of silver nanowires (short axis diameter approximately 70 nm–80 nm, aspect ratio greater than 100), was coated onto the substrate film F-1 of the laminated film L-1 with a dried film thickness of 1.5 μm. The mixture was then dried. Subsequently, it was subjected to a pressure of 2000 kN / m... 2 A pressure treatment is applied to form a transparent conductive layer A on the substrate film F-1, resulting in a laminate with the transparent conductive layer. The laminate with the transparent conductive layer is then wound into a roll.

[0158] (Peeling off the protective film)

[0159] While extracting and transporting the rolled-up laminate with the transparent conductive layer, the protective film P-1 and adhesive S-1 are peeled off together. This yields a transparent conductive film M-1 with the transparent conductive layer A supported by the substrate film F-1. Finally, the obtained transparent conductive film M-1 is rolled into a roll.

[0160] Examples 2-7, Comparative Examples 1-8

[0161] With the heat shrinkage rate A of the substrate film and the heat shrinkage rate B of the protective film set to the values ​​listed in Table 1, during the fabrication of the substrate film and the protective film, the residual solvent amount when peeling the substrate film from the support, the film thickness, the stretching ratio in the long and width directions of the tenter frame, and the stretching temperature were adjusted. Otherwise, substrate films F-2 to F-10 and protective films P-2 to P-8 were fabricated using the same method as in Example 1. Then, substrate films F-1 to F-10 and protective films P-1 to P-8 were appropriately selected in the combinations listed in Table 1 and laminated using adhesive S-1 or adhesive S-2 to obtain laminated films L-2 to L-15. It should be noted that the preparation method of adhesive S-2 is described below.

[0162] Subsequently, in the same manner as in Example 1, a transparent conductive layer A is formed on the substrate film to produce a roll-shaped laminate with the transparent conductive layer. Then, by pulling out the roll-shaped laminate with the transparent conductive layer and peeling off the protective film and adhesive together, transparent conductive films M-2 to M15 are obtained. Finally, the obtained transparent conductive films M-2 to M-15 are wound into rolls.

[0163] (Preparation of adhesive S-2)

[0164] The epoxy crosslinking agent (Mitsubishi Gas Chemical, trade name "TETRAD C (registered trademark)") was changed to 4 parts by weight. Otherwise, the same procedure as the preparation of adhesive S-1 was carried out to prepare adhesive S-2.

[0165] "evaluate"

[0166] (1) Thickness measurement

[0167] The thickness of the protective film and the substrate film was measured using a micrometer-type thickness gauge (Mitutoyo).

[0168] (2) Thermal shrinkage rate in the width direction

[0169] The thermal shrinkage rate in the width direction of the substrate film and protective film was determined as follows. Specifically, the substrate film and protective film were cut into pieces 100 mm wide and 100 mm long (the cut films are referred to as "test pieces"). Cross marks (× marks) were made at two points at both ends of the width direction. The length (mm) between the two points at the center of the cross marks before heating was measured using a CNC three-dimensional measuring machine (LEGEX774 manufactured by Mitutoyo Co., Ltd.). The test pieces were then placed in an oven for heat treatment (140°C, 90 minutes). After cooling at room temperature for 1 hour, the length (mm) between the two points after heating was measured again using the CNC three-dimensional measuring machine. The measured value was substituted into the following formula to calculate the thermal shrinkage rate in the width direction.

[0170] Heat shrinkage rate (%) = [{length before heating (mm) - length after heating (mm)} / length before heating (mm)] × 100

[0171] (3) Deformation during peeling

[0172] The deformation of the transparent conductive film when the protective film with the adhesive layer is peeled off is evaluated based on the following evaluation criteria.

[0173] Evaluation Criteria

[0174] ○: The transparent conductive film did not deform at all during the peeling of the protective film, nor did it deform after being rolled up.

[0175] △: The transparent conductive film deforms during the peeling of the protective film, but does not deform after being rolled up.

[0176] ×: The transparent conductive film deforms during the peeling of the protective film, and the deformation remains after winding.

[0177] (4) Power-on test

[0178] The prepared transparent conductive film was cut into pieces 100 mm wide and 100 mm long (the cut pieces were referred to as "test pieces"). The test pieces were then heated at 120°C for 40 minutes using a hot air circulating oven. Subsequently, the surface resistivity of the test pieces was measured at nine locations using the four-terminal method according to JIS K 7194, and evaluated based on the following evaluation criteria.

[0179] Evaluation Criteria

[0180] ○: Of the 9 parts, 0 parts have a surface resistance of 110Ω / □ or higher.

[0181] △: Of the 9 locations, there is 1 location with a surface resistance of 110Ω / □ or higher.

[0182] ×: Of the 9 parts, there are more than 2 parts with a surface resistance of 110Ω / □ or higher.

[0183] (5) Bending and electrical durability

[0184] The prepared transparent conductive film was cut into pieces 200 mm wide and 100 mm long (the cut pieces were referred to as "test pieces"). The test pieces were then heated in a hot air circulating oven at 120°C for 40 minutes. Subsequently, the test pieces were bent 180 degrees in the width direction (with the long side as the bending axis) between two glass plates with a bending diameter of 3 mmΦ, and then placed in an environment of 60°C and 90% RH for 500 hours. Afterwards, the surface resistivity of the bent portion of the test piece was measured using the four-terminal method according to JIS K7194, and evaluated based on the following evaluation criteria.

[0185] Evaluation Criteria

[0186] ○: Surface resistivity is below 110Ω / □.

[0187] △: Surface resistance is greater than 110Ω / □ and less than 200Ω / □.

[0188] ×: Surface resistance is greater than 200Ω / □.

[0189] The evaluation results of Examples 1-7 and Comparative Examples 1-8 are shown in Table 1.

[0190]

[0191] According to Table 1, in Comparative Examples 5 and 6, the bending conductivity durability was poor (×). In Comparative Example 6, the substrate film thickness was 3 μm. It was believed that because the substrate film was too thin, cracks easily formed in the substrate film when the transparent conductive film with a transparent conductive layer formed on it was bent and transported by rollers. As a result, the transparent conductive layer broke, resulting in poor conductivity. In Comparative Example 5, the substrate film thickness was 50 μm. It was believed that because the substrate film was too thick, the transparent conductive layer on the substrate film was stretched and broken in the circumferential direction of the rollers when the transparent conductive film was bent and transported by rollers, resulting in poor conductivity.

[0192] In contrast, in Examples 1-7, the thickness of the substrate film is 5μm to 40μm, and the transparent conductive film exhibits good bending conductivity (○ or △). Therefore, it can be said that in Examples 1-7, the breakage of the transparent electrode layer during the bending and handling of the transparent conductive film with rollers can be suppressed, and thin transparent conductive films can be manufactured with high productivity through roll-to-roll operation.

[0193] Furthermore, in Comparative Examples 3 and 4, poor electrical conductivity occurred. In Comparative Example 3, the thermal shrinkage rate A of the substrate film was 0.25%, which was relatively high. It was believed that due to excessive thermal shrinkage of the substrate film during the heating process of the transparent conductive layer, the transparent conductive layer on the substrate film could not keep up with the shrinkage of the substrate film and thus broke, resulting in poor electrical conductivity. In Comparative Example 4, the thermal shrinkage rate A of the substrate film was 0.001%, which was relatively low. The shrinkage stress generated by the substrate film during the heating process of the transparent conductive layer was small, and sufficient residual stress was not obtained. Therefore, it was believed that it was difficult to peel the protective film uniformly from the substrate film. During peeling, part of the substrate film was pulled towards the protective film side, causing the transparent conductive layer 17 to break, resulting in poor electrical conductivity.

[0194] In contrast, in Examples 1-7, the thermal shrinkage rate A in the width direction of the substrate film was 0.01% to 0.20%, and good results (○ or △) were obtained in the electrical conduction test. Therefore, it can be said that in Examples 1-7, the breakage of the transparent conductive layer can be suppressed during the heating process of the transparent conductive layer and the peeling of the protective film, thus manufacturing a transparent conductive film.

[0195] Furthermore, in Comparative Examples 1 and 2, the transparent conductive film deformed during the peeling of the protective film. In Comparative Example 1, the A / B ratio was 0.60, which was relatively large. Since the difference in thermal shrinkage rates between the substrate film and the protective film was small, it was difficult to peel the protective film from the substrate film using the difference in thermal shrinkage. Therefore, it was assumed that a high peeling force was used to peel the protective film, resulting in the transparent conductive film being pulled towards the protective film side and deforming. In Comparative Example 2, the A / B ratio was 0.01, which was relatively small. The thermal shrinkage rate B of the protective film was relatively large compared to the thermal shrinkage rate A of the substrate film. Therefore, during the heating process of the transparent conductive layer, the protective film underwent significant thermal shrinkage, and the ends of the protective film peeled off. During peeling, it was difficult to peel the protective film uniformly from the substrate film in the width direction. As a result, it was assumed that wrinkles formed in the substrate film and the transparent conductive film deformed during the peeling of the protective film.

[0196] It should be noted that in Comparative Example 7, to facilitate the peeling of the protective film, a laminate with a transparent conductive layer was fabricated by laminating the protective film and the substrate film using an adhesive S-2, which has a weaker adhesive force than adhesive S-1. In this configuration, because the adhesive force of adhesive S-2 is weak, the protective film naturally peels off during the handling of the laminate with the transparent conductive layer. The peeled protective film is rolled into the transport rollers, and the remaining film breaks, making it impossible to perform various evaluations.

[0197] In Comparative Example 8, the thermal shrinkage rate A of the substrate film and the thermal shrinkage rate B of the protective film were set identically to those in Example 3 of Patent Document 2. In this configuration, it was assumed that because the value of A / B was too large (the value of A / B was close to 1), it was impossible to peel the protective film off the substrate film using the difference in thermal shrinkage, and the protective film was peeled off with a high peeling force, resulting in deformation of the transparent conductive film.

[0198] Examples 8-11

[0199] With the protective film thickness as shown in Table 2, during the fabrication of the protective film, the residual solvent amount when peeling the base film from the support, the film thickness, the stretching ratio in the long and width directions of the tenter frame, and the stretching temperature were adjusted. Otherwise, protective films P-9 to P-12 were fabricated using the same method as in Example 1. Then, laminated base film F-1 was laminated onto each of the protective films P-9 to P-12 using adhesive S-1 to fabricate laminated films L-16 to L-19. After forming a transparent conductive layer A on the laminated films L-16 to L-19, the protective films P-9 to P-12 were peeled off to fabricate transparent conductive films M-16 to M-19.

[0200] "evaluate"

[0201] (6) Wrinkles in the transport of laminated films

[0202] During the process of forming a transparent conductive film, the transport state of the laminated film is observed and evaluated based on the following evaluation criteria.

[0203] Evaluation Criteria

[0204] ◎: No wrinkles were generated during the handling of the laminated film.

[0205] ○: Fine wrinkles are generated during the handling of the laminated film, but the wrinkles disappear when the laminated film is wound up.

[0206] ×: Fine wrinkles are generated during the handling of laminated films, and wrinkles remain after the laminated films are wound up.

[0207] The evaluation results of Examples 8-11 are shown in Table 2. For reference, wrinkles in the transport of laminated films in Example 1 were also evaluated according to the same evaluation criteria, and the results are also shown in Table 2.

[0208]

[0209] According to Table 2, it can be said that if the thickness of the protective film is 40μm to 100μm and is thicker than that of the substrate film, wrinkles can be effectively reduced during the handling of the laminated films. This is because within the aforementioned thickness range of the protective film, a shrinkage force caused by the heat of the protective film can be appropriately generated, thus further reducing the wrinkles in the substrate film caused by the thermal shrinkage of the protective film during the handling of the transparent conductive layer during heat processing.

[0210] Example 12

[0211] The transparent conductive layer A is replaced with the transparent conductive layer B, and otherwise the same procedure as in Example 1 is followed to fabricate the transparent conductive film M-20. More details are as follows.

[0212] <Fabrication of Transparent Conductive Film M-20>

[0213] (Preparation of the resin composition for forming the cured resin layer)

[0214] A curable resin composition containing spherical particles is prepared, the curable resin composition comprising: 100 parts by weight of a UV-curable resin composition (manufactured by DIC Corporation, trade name "UNIDIC (registered trademark) RS29-120") and 0.2 parts by weight of acrylic spherical particles with a maximum particle size of 1.9 μm (manufactured by Soken Chemical Co., Ltd., trade name "MX-180TA").

[0215] (Formation of the cured resin layer)

[0216] The prepared curable resin composition containing spherical particles is coated onto the surface of the substrate film F-1 of the laminated film L-1 to form a coating layer. Next, the coating layer is irradiated with ultraviolet light from the side where the coating layer is formed to form a cured resin layer with a thickness of 1.0 μm.

[0217] (Formation of transparent conductive layer B)

[0218] A laminated film L-1 with a cured resin layer is fed into a roll-up sputtering apparatus. A 27 nm thick amorphous indium tin oxide (ITO) layer (composition: SnO2 10 wt%) is deposited on the surface of the cured resin layer to create a laminate with a transparent conductive layer. More specifically, after performing a glow discharge pretreatment on the surface of the cured resin layer, the laminated film L-1 with the cured resin layer is positioned opposite an ITO target in the vacuum chamber of a magnetron sputtering apparatus, achieving a vacuum of 2 × 10⁻⁶ argon. -3 Under a Torr environment, sputtering deposition was performed at an applied voltage of DC 9kW and a speed of 1m / min. Next, referring to paragraphs

[0046] to

[0050] of Japanese Patent Application Publication No. 11-243296, an ITO conductive film was formed on the surface of the cured resin layer formed on the substrate film F-1 as a transparent conductive layer B. After obtaining a laminate with the transparent conductive layer, the protective film P-1 with adhesive S-1 was peeled off while being transported to produce a transparent conductive film M-20. Then, the produced transparent conductive film M-20 was wound into a roll.

[0219] "evaluate"

[0220] (7) Durability under repeated bending

[0221] The prepared transparent conductive film M-20 was placed in a hot air circulating oven and heated at 120°C for 40 minutes. Subsequently, using a durability testing machine (manufactured by YUASASYSTEM, product name "Planar Body Unloaded U-Shaped Expansion Tester"), the transparent conductive layer was repeatedly bent with the inner side facing inwards under the following conditions: minimum bending diameter: 3mmφ, speed: 30 times / minute, number of bends: 50,000, and test temperature: 23°C. Then, the surface resistivity of the sample was measured using the four-terminal method according to JIS K7194, and evaluated based on the following evaluation criteria. It should be noted that the rate of change of surface resistivity was calculated using the following formula.

[0222] The rate of change of surface resistivity (%) = {(Surface resistivity after 50,000 bends - Surface resistivity before bending) / (Surface resistivity before bending)} × 100

[0223] Evaluation Criteria

[0224] ◎: The rate of change of surface resistivity is greater than 10% and less than 20%.

[0225] ○: The rate of change of surface resistivity is greater than 20% and less than 30%.

[0226] ×: The rate of change of surface resistivity is more than 30%.

[0227] The evaluation results of Example 12 are shown in Table 3. For comparison, the repeated bending durability of Example 1 was also evaluated according to the same evaluation criteria, and the results are also shown in Table 3.

[0228]

[0229] In Example 1, a conductive film containing silver nanowires was used as the transparent conductive layer A. In contrast, in Example 12, an ITO conductive film was used as the transparent conductive layer B. It is evident that the conductive film containing silver nanowires exhibits superior durability under repeated bending compared to the ITO conductive film, and is less prone to breakage. Therefore, it can be said that using a conductive film containing silver nanowires as the transparent conductive layer is preferable.

[0230] 〔Replenish〕

[0231] Based on the above, the laminated film described in this embodiment can be expressed as follows.

[0232] 1. A laminated film, characterized in that it is a laminated film for supporting a transparent conductive layer of a transparent conductive film, comprising: a substrate film for supporting the transparent conductive layer, and a protective film for supporting the substrate film via an adhesive layer.

[0233] The aforementioned substrate film and the aforementioned protective film each contain cyclic olefin resin.

[0234] The thickness of the aforementioned substrate film is 5 μm to 40 μm.

[0235] The width-direction thermal shrinkage rate A (%) of the above-mentioned substrate film after heating at 140°C for 90 minutes is 0.01% to 0.20%.

[0236] When the thermal shrinkage rate in the width direction of the above protective film is set as B (%) after heating at 140°C for 90 minutes,

[0237] 0.02≤A / B≤0.50.

[0238] 2. The laminated film according to 1 above, characterized in that the thickness of the protective film is 40 μm to 100 μm and is thicker than the thickness of the substrate film.

[0239] 3. The laminated film according to 1 or 2 above, characterized in that it is a conductive film containing metal nanowires used to support the above-mentioned transparent conductive layer.

[0240] Furthermore, the laminate with a transparent conductive layer described in this embodiment can be expressed as follows.

[0241] 4. A laminate with a transparent conductive layer, characterized in that it comprises a transparent conductive layer on the substrate film of the laminated film described in any one of the above 1 to 3.

[0242] Furthermore, the method for manufacturing the transparent conductive film described in this embodiment can be expressed as follows.

[0243] 5. A method for manufacturing a transparent conductive film, characterized by comprising the following steps:

[0244] The process of forming the transparent conductive layer on the substrate film of the laminated film described in any one of the above 1 to 3 to produce a laminated body with a transparent conductive layer, and then winding the laminated body with the transparent conductive layer into a roll.

[0245] The process of extracting the above-mentioned laminate with the transparent conductive layer, peeling the above-mentioned protective film from the above-mentioned laminate with the transparent conductive layer, and rolling the transparent conductive film with the above-mentioned transparent conductive layer on the above-mentioned substrate film into a roll.

[0246] The embodiments of the present invention have been described above, but the scope of the present invention is not limited thereto. It can be expanded or modified within the scope of the present invention without departing from the spirit of the present invention.

[0247] Industrial availability

[0248] The laminated film for supporting the transparent conductive layer of the present invention can be used to manufacture transparent conductive films, for example, those used in touch sensor panels of touch panel display devices.

[0249] Symbol Explanation

[0250] 10. Laminated composite with a transparent conductive layer

[0251] 12 Transparent conductive film

[0252] 14 Protective film

[0253] 15 Adhesive layer

[0254] 16 Substrate film

[0255] 17 Transparent conductive layer

[0256] 20-layer film

Claims

1. A laminated film, which is a laminated film for supporting a transparent conductive layer of a transparent conductive film, comprising: a substrate film for supporting the transparent conductive layer and a protective film for supporting the substrate film by an adhesive layer. The substrate film and the protective film each contain a cyclic olefin resin. The thickness of the substrate film is 5 μm to 40 μm. The width-direction thermal shrinkage rate A of the substrate film after heating at 140°C for 90 minutes is 0.01% to 0.20%. When the thermal shrinkage rate in the width direction of the protective film after heating at 140°C for 90 minutes is defined as B (in percentage),... 0.02≤A / B≤0.50 in, The protective film has a thickness of 40μm to 100μm and is thicker than the substrate film.

2. The laminated film according to claim 1, used to support the conductive film containing metal nanowires as the transparent conductive layer.

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