Conductive piezoelectric laminated film and method for manufacturing the same

Abstract

The present application provides a conductive piezoelectric laminated film with high transparency. The conductive piezoelectric laminated film (10) is composed of a piezoelectric film (1) with a refractive index of 1.30 or more and 1.50 or less, a first coating layer (2) with a refractive index of 1.45 or more and less than 1.60, a second coating layer (3) with a refractive index of 1.60 or more and less than 1.80, and a conductive layer (4) with a refractive index of 1.80 or more and 2.20 or less, which are sequentially overlapped on at least one side of the piezoelectric film (1).

Description

Technical Field

[0001] This invention relates to a conductive piezoelectric laminate and its manufacturing method. Background Technology

[0002] Touch panels are widely used as devices that allow information to be input through direct contact with an image display. A representative form is the capacitive touch panel, which utilizes changes in current capacitance generated between electrodes and a finger. The conductive film used in the touch panel must have high transparency and suppress the generation of tint.

[0003] As such conductive films, conductive films are disclosed, for example, in Patent Documents 1 and 2. Regarding the conductive films disclosed in Patent Documents 1 and 2, polyethylene terephthalate (PET) film is used as the substrate film, and indium tin oxide (ITO) film is formed as the conductive film. The crystallinity of ITO is improved by heat treatment at around 150°C, thereby achieving a conductive film with high transparency and suppression of tint generation.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-074792

[0007] Patent Document 2: Japanese Patent Application Publication No. 2013-25737 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In recent years, there has been increasing interest in technologies that simultaneously sense the position of a finger or other object touching the touch surface, as well as the pressure exerted by the finger or other object on the touch surface. Proposals have been made to achieve this by combining pressure detection sensors composed of piezoelectric sensors. However, when the piezoelectric film used in the piezoelectric sensor is subjected to high-temperature heat treatment, similar to that of a PET film, its color tone is compromised. Therefore, it is difficult to use conductive piezoelectric laminates with piezoelectric films in touch panels. On the other hand, when an amorphous conductive film is used without heat treatment, a yellowish tint originating from the conductive film is generated in the conductive piezoelectric laminate.

[0010] One objective of this invention is to achieve a film with high transparency and appropriate hue in a conductive piezoelectric laminate containing a piezoelectric film.

[0011] Technical solution

[0012] To solve the above problems, the conductive piezoelectric laminate of the present invention is formed by sequentially overlapping a first coating layer, a second coating layer, and a conductive layer on at least one side of a piezoelectric film. The piezoelectric film has a refractive index of 1.30 or higher and 1.50 or lower, the first coating layer has a refractive index of 1.45 or higher and less than 1.60, the second coating layer has a refractive index of 1.60 or higher and less than 1.80, and the conductive layer has a refractive index of 1.80 or higher and 2.20 or lower.

[0013] Furthermore, to address the aforementioned problems, the conductive piezoelectric laminated film manufactured by a method according to one aspect of the present invention is a laminated film formed by sequentially overlapping a first coating layer, a second coating layer, and a conductive layer on at least one side of a piezoelectric film. The manufacturing method includes: a first step of forming a film with a refractive index of 1.30 or higher and 1.50 or lower to manufacture a piezoelectric film; a second step of forming a first coating layer with a refractive index of 1.45 or higher and less than 1.60 on at least one side of the piezoelectric film; a third step of forming a second coating layer with a refractive index of 1.60 or higher and less than 1.80 on the surface of the first coating layer; and a fourth step of forming a conductive layer with a refractive index of 1.80 or higher and 2.20 or lower on the surface of the second coating layer.

[0014] Beneficial effects

[0015] This invention enables the creation of films with high transparency and appropriate hue in conductive piezoelectric laminates containing piezoelectric films. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of a conductive piezoelectric laminate 10 according to one embodiment of the present invention.

[0017] Figure 2 This is a cross-sectional view of a modified example 10' of a conductive piezoelectric laminate 10 according to an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will now be described in detail.

[0019] [Composition of conductive piezoelectric laminate]

[0020] In one embodiment of the present invention, the conductive piezoelectric layer laminate is formed by sequentially overlapping a first coating layer, a second coating layer, and a conductive layer on at least one side of a piezoelectric film. Furthermore, the piezoelectric film has a refractive index of 1.30 or higher and 1.50 or lower, the first coating layer has a refractive index of 1.45 or higher and less than 1.60, the second coating layer has a refractive index of 1.60 or higher and less than 1.80, and the conductive layer has a refractive index of 1.80 or higher and 2.20 or lower.

[0021] In this embodiment, "sequentially overlapping" refers to the state in which the films and layers described above are arranged in the listed order in a laminate containing the films and layers described above. Within the scope of achieving the effects of this embodiment, the films and layers described above can overlap one another directly or overlap with other films or layers in between.

[0022] Furthermore, in the conductive piezoelectric laminate of this embodiment, in addition to the above-described configuration, it also has the following configuration: the refractive index of the first coating is higher than the refractive index of the piezoelectric film.

[0023] In a further preferred embodiment, in addition to the above-described configuration, the second coating has a refractive index that is 0.05 or higher than that of the first coating. This configuration further improves transmittance and hue.

[0024] In this embodiment, "refractive index" refers to the refractive index at a wavelength of 589 nm.

[0025] The refractive indices of the first and second coatings were determined according to JIS K7142. Specifically, for each experimentally produced coating, an Abbe refractometer was used to incident 589 nm wavelength measurement light onto each layer, and measurements were taken three times at 25.0 ± 1.0 °C. The average of the measured values ​​was taken as the refractive index.

[0026] Regarding the refractive index of the conductive layer, Psi(Ψ) and Delta(Δ) were measured using a high-speed spectroscopic ellipsometer with multiple incident angles (JAWoollam, M-2000), and the refractive index at a wavelength of 589 nm was calculated from this.

[0027] The refractive index of the piezoelectric film is determined according to ASTM D542.

[0028] In this embodiment, the conductive piezoelectric layer stack only requires that the first coating layer, the second coating layer, and the conductive layer be sequentially stacked on one side of the piezoelectric film; the composition of the other side is not particularly limited. For example, as... Figure 1 As shown, a conductive piezoelectric laminate 10 can be formed by overlapping the first coating 2, the second coating 3, and the conductive layer 4 only on one side of the piezoelectric film 1. Furthermore, as... Figure 2 As shown, a first coating 2 and 2' can also be formed on both sides of the piezoelectric film 1, and a second coating 3 and a conductive layer 4 can be sequentially overlapped on the surface of the first coating 2 on one side to form a conductive piezoelectric laminate 10'. Alternatively, it can be configured such that the first coating 2, the second coating 3, and the conductive layer 4 are sequentially overlapped on one side of the piezoelectric film 1, and the same applies to the other side.

[0029] The following mainly focuses on Figure 1 The conductive piezoelectric laminate 10 shown is described as one embodiment of the present invention.

[0030] [Piezoelectric film 1]

[0031] In one embodiment of the present invention, the piezoelectric film 10 comprising the conductive piezoelectric laminate refers to a film having piezoelectric properties. For example, the piezoelectric film 1 can be a resin film.

[0032] The refractive index of the piezoelectric film 1 is 1.30 or higher and 1.50 or lower. Preferably, the refractive index of the piezoelectric film 1 is 1.35 or higher and 1.47 or lower, and more preferably, the refractive index of the piezoelectric film 1 is 1.38 or higher and 1.45 or lower. The piezoelectric film 1 that meets these conditions can be manufactured by known methods, and there are no particular limitations on the raw materials or manufacturing methods.

[0033] For example, fluoropolymer-based films can be cited as a type of resin film that satisfies the above conditions. It should be noted that in this embodiment, "fluoropolymer-based" means that fluoropolymer is the main component in the composition constituting the piezoelectric film 1. Furthermore, "fluoropolymer is the main component" means that fluoropolymer is the most abundant resin component in the composition. The content of fluoropolymer in this composition can be 51% by mass or more, 80% by mass or more, or 100% by mass.

[0034] The resin used in this embodiment can be any resin that can be used in the piezoelectric film 1 of the present invention, and can be one or more. For example, fluoropolymers that can be used in the piezoelectric film 1 include vinylidene fluoride resin, tetrafluoroethylene resin, and mixtures thereof.

[0035] Examples of vinylidene fluoride resins include homopolymers of vinylidene fluoride and copolymers of vinylidene fluoride. The content of monomers other than vinylidene fluoride in the copolymers derived from vinylidene fluoride can be appropriately determined within a range that corresponds to the properties of the piezoelectric film 1 for its intended use.

[0036] Examples of monomers other than vinylidene fluoride in copolymers of vinylidene fluoride include hydrocarbon monomers and fluorinated compounds. Examples of hydrocarbon monomers include ethylene and propylene. The fluorinated compound is a fluorinated compound other than vinylidene fluoride, and is a fluorinated compound having a polymerizable structure. Examples of fluorinated compounds include: vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluorohexafluoropropylene, and fluoroalkyl vinyl ethers.

[0037] For example, vinylidene fluoride copolymers can be: vinylidene fluoride copolymers (VDF / TFE) formed by copolymerizing vinylidene fluoride and trifluoroethylene in a mixing ratio of 80:20, and vinylidene fluoride copolymers (VDF / TFE / HFP) formed by copolymerizing vinylidene fluoride, trifluoroethylene, and hexafluoropropylene in a mixing ratio of 40:40:20.

[0038] Examples of tetrafluoroethylene resins include homopolymers of tetrafluoroethylene and copolymers of tetrafluoroethylene. Examples of monomers other than tetrafluoroethylene that constitute the structural units of the copolymer include: ethylene, fluoropropylene, fluoroalkyl vinyl ethers, perfluoroalkyl vinyl ethers, and perfluorom-dioxane.

[0039] Copolymers of vinylidene fluoride and tetrafluoroethylene are also preferred for use as fluoropolymers.

[0040] The piezoelectric film 1 in this embodiment may also contain various additives within the range that achieves the effects of this embodiment. These additives may be one or more, and examples include: plasticizers, lubricants, crosslinking agents, ultraviolet absorbers, pH adjusters, stabilizers, antioxidants, surfactants, and pigments.

[0041] The thickness of the piezoelectric film 1 in this embodiment can be appropriately determined within a range that achieves the effects of this embodiment, depending on the intended use of the conductive piezoelectric laminate 10. If the thickness of the piezoelectric film 1 is too thin, the mechanical strength may be insufficient; on the other hand, if the thickness of the piezoelectric film 1 is too thick, the effect may reach its limit, or the transparency may become insufficient, making it difficult to use in optical applications. The thickness of the piezoelectric film 1 can be appropriately determined, for example, within a range of 10 μm to 200 μm.

[0042] More specifically, from the viewpoint of mechanical strength, the thickness of the piezoelectric film 1 is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Furthermore, from the viewpoint of balancing mechanical strength and economy, the thickness of the piezoelectric film 1 is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. A conductive piezoelectric laminate 10 having a piezoelectric film 1 with a thickness within the above-mentioned range is preferably used in a touch panel.

[0043] [First Coating 2]

[0044] In this embodiment, the first coating 2 is a layer located between the piezoelectric film 1 and the second coating 3.

[0045] The first coating 2 can be as follows Figure 1 As shown, it is disposed only on one surface side of the piezoelectric film 1. From the viewpoint of imparting preferred optical properties to the piezoelectric film 1, it can also be as follows: Figure 2 As shown, it is disposed on both sides. From the viewpoint of improving the transparency of the conductive piezoelectric laminate 10 and preventing the piezoelectric film 1 from discoloring due to the environment, the first coating 2 is preferably disposed adjacent to the piezoelectric film 1 in the thickness direction of the conductive piezoelectric laminate 10.

[0046] The refractive index of the first coating 2 is 1.45 or higher and less than 1.60. Preferably, the refractive index of the first coating 2 is 1.47 or higher and less than 1.57, and more preferably, the refractive index of the first coating 2 is 1.49 or higher and less than 1.55.

[0047] Regarding the material of the first coating 2, any material that satisfies such a refractive index can be appropriately selected from all usable materials. This material can be inorganic or organic, and can be one or more. Furthermore, the material of this coating can also be a hard coating material. Examples of such materials include: melamine resin, urethane resin, (meth)acrylate resin, silane compounds, and metal oxides. It should be noted that "(meth)acrylate" is a general term for acrylic acid and methacrylic acid, referring to one or both of them. In particular, (meth)acrylate resin is preferred from the viewpoints of sufficient transparency, a wide variety of materials, and low raw material costs.

[0048] The material of the first coating 2 may include other materials required to form the coating. If the coating material is a (meth)acrylate resin, a composition consisting of an initiator, oligomers, monomers, and other components is typically used. In this case, the physical properties of the first coating 2 are mainly determined by the oligomers and monomers. Examples of oligomers include monofunctional or polyfunctional (meth)acrylates. Examples of monomers include: urethane (meth)acrylates, epoxy (meth)acrylates, and polyester (meth)acrylates. Furthermore, from the viewpoint of preventing adhesion and maintaining the bonding properties between films, inorganic particles and polymer beads may be added to the material of the first coating 2. Examples of inorganic particles include synthetic silica, talc, diatomaceous earth, calcium carbonate, feldspar, quartz, etc., and synthetic silica is preferred, especially from the viewpoint of improving the quality of the plastic film. Examples of synthetic silica include SiO2.

[0049] The first coating 2 may also contain materials for exhibiting any function. For example, the first coating 2 may also contain an anti-static agent. Examples of anti-static agents include surfactants, antimony pentoxide, indium-tin oxide (ITO), and conductive polymers.

[0050] The thickness of the first coating 2 is not particularly limited. The thickness of the first coating 2 can be 0.3 μm or more and 3.0 μm or less, more preferably 0.5 μm or more and 2.0 μm or less.

[0051] like Figure 2As shown in the conductive piezoelectric laminate 10', by applying the first coatings 2 and 2' to each side of the piezoelectric film 1 respectively, damage and unevenness can be prevented on both sides of the piezoelectric film 1. Therefore, the haze value of the conductive piezoelectric laminate 10' can be further improved.

[0052] The first coating 2 can be a transparent surface protective layer, also known as a hard coating, used to prevent damage.

[0053] Furthermore, by ensuring that the refractive index and thickness of the first coating 2 are within the range specified above, the haze value of the conductive piezoelectric laminate 10 can be improved.

[0054] [Second Coating 3]

[0055] In this embodiment, the second coating 3 is a layer located between the first coating 2 and the conductive layer 4.

[0056] The refractive index of the second coating 3 is 1.60 or higher and less than 1.80. Preferably, the refractive index of the second coating 3 is 1.63 or higher and less than 1.78, more preferably, the refractive index of the second coating 3 is 1.65 or higher and less than 1.75. The refractive index of the second coating 3 is further preferably 0.05 or higher than that of the first coating 2.

[0057] Regarding the material of the second coating 3, any material that satisfies such a refractive index can be appropriately selected from all usable materials. For example, a resin whose refractive index has been adjusted by adding metal oxide particles to a material exemplified as the material of the first coating 2 can be used. The metal oxide particles are preferably materials with a refractive index of 1.50 or higher. Examples of such metal oxide particles include: aluminum oxide, titanium oxide, zirconium oxide, zinc oxide, and tin oxide, among which titanium oxide and zirconium oxide are preferred.

[0058] The material of the second coating 3 is the same as that of the first coating 2, and may include other materials required to form the coating.

[0059] The thickness of the second coating 3 can be, for example, 50 nm or more and 500 nm or less. As an example, the thickness of the second coating 3 can be 90 nm or more and 180 nm or less. Furthermore, as another example, the thickness of the second coating 3 can be 240 nm or more and 310 nm or less. As yet another example, the thickness of the second coating 3 can be set to 380 nm or more and 420 nm or less. By ensuring the thickness of the second coating 3 is within the above ranges, the transmittance and color tone of the conductive piezoelectric laminate 10 can be improved.

[0060] The second coating 3 serves to appropriately adjust the transmittance and hue of the conductive piezoelectric laminate 10. In particular, by adjusting the refractive index and thickness of the second coating 3, a conductive piezoelectric laminate 10 with appropriate optical properties can be produced.

[0061] As will be described later, when the conductive layer 4 in this embodiment is amorphous, the conductive piezoelectric laminate 10 is prone to developing a tint. In order to suppress the generation of such a tint, the refractive index of the first coating 2 and the second coating 3 is particularly important.

[0062] [Conductive layer 4]

[0063] In this embodiment, the conductive layer 4 is formed by overlapping the second coating layer 3.

[0064] In this embodiment, the conductive layer 4 is a planar, conductive structure, also referred to as an electrode. Regarding the conductive layer 4, it is sufficient that the planar distribution exhibits sufficient transparency when assumed to be a single layer; however, the conductive layer 4 itself may not be transparent if such a structure is present. For example, the conductive layer 4 may be composed of conductive components or parts with high transparency, or it may be an extremely thin or extremely fine microstructure composed of opaque materials but exhibiting sufficient transparency.

[0065] The conductive layer 4 can be formed on a transparent substrate or bonded to a transparent coating together with the substrate. The conductive layer 4 can be disposed on at least one side of the piezoelectric film 1. If the first coating 2 is formed on both sides of the piezoelectric film 1, the conductive layer 4 can be disposed on at least one side of the second coating 3. The shape of the conductive layer 4 is not limited; it can be a nanowire, a mesh, or a thin film. The thin film can be a single layer or a multilayered stacked structure.

[0066] The material constituting the conductive layer 4 is not limited, but preferably a metal oxide of at least one metal selected from the group consisting of In, Sn, Zn, Ga, Sb, Ti, Si, Zr, Mg, Al, Au, Ag, Cu, Pd, and W. This metal oxide may also contain metal atoms from the group listed above, as needed. ITO, antimony-tin oxide (ATO), etc., are preferred among these metal oxides, with ITO being particularly preferred. Other representative materials for the conductive layer 4 include silver nanowires, silver mesh, copper mesh, graphene, and carbon nanotubes.

[0067] There is no limit to the thickness of conductive layer 4, from the point that it is made to have a surface resistivity of 1×10⁻⁶. 3From the viewpoint of a continuous coating with good conductivity of less than Ω / sq, a thickness of 10 nm or more is preferred. If this thickness becomes too thick, it may sometimes cause a decrease in transparency, etc.; if the thickness is too thin, the resistance may sometimes increase, and discontinuities may sometimes form in the film structure. From the viewpoint of further improving conductivity, this thickness is preferably 15 nm or more, more preferably 20 nm or more. From the viewpoint of further improving the transparency of the conductive layer 4, the thickness of the conductive layer 4 is preferably less than 55 nm, more preferably less than 45 nm. The thickness of the conductive layer 4 can be determined by a known method of observation of the cross-section of such a laminate.

[0068] The amorphousness of the conductive layer 4 can be determined using X-ray diffraction. Furthermore, this amorphousness can be adjusted by whether and to what extent processes promoting crystallization are performed during the fabrication of the conductive layer 4, such as annealing after its formation.

[0069] Regarding the conductive piezoelectric laminate 10 in this embodiment, to avoid discoloration of the piezoelectric film 1, it is necessary to avoid heating at high temperatures during its processing. Therefore, the material of the conductive layer 4 is sometimes amorphous. Here, amorphous refers to a state of matter that does not have a crystalline structure and whose atoms are arranged irregularly. The fact that the conductive layer 4 is made of an amorphous material can be confirmed, for example, by using X-ray diffraction to detect no crystalline peaks in the material of the conductive layer 4, as described above.

[0070] In this embodiment, the refractive index of the conductive layer 4 is 1.80 or higher and 2.20 or lower. Preferably, the refractive index of the conductive layer 4 is 1.83 or higher and 2.00 or lower, and more preferably, the refractive index of the conductive layer 4 is 1.85 or higher and 1.95 or lower. By ensuring that the refractive index of the conductive layer 4 is within the above range, problems such as interference fringes and reduced visual clarity can be suppressed.

[0071] In one embodiment of the conductive piezoelectric laminate 10, the conductive layer 4 is composed of indium-tin composite oxide. In another embodiment, the conductive layer 4 is composed of indium-tin composite oxide and is an indium-tin composite oxide that is not detected in X-ray diffraction. Based on this configuration, an amorphous conductive layer 4 with a refractive index within a preferred range can be fabricated.

[0072] [Other layers]

[0073] Although not illustrated, the conductive piezoelectric laminate 10 of the present invention only requires the piezoelectric film 1, the first coating layer 2, the second coating layer 3, and the conductive layer 4 to be stacked sequentially. Other layers may also be added appropriately to form the conductive piezoelectric laminate of the present invention. The other layers may be one or more.

[0074] For example, it may also include one or more new coatings that are different from the first coating 2 and the second coating 3.

[0075] When the conductive piezoelectric laminate 10 has a coating different from the first coating 2 and the second coating 3, the total thickness of the coating is 0.3 μm to 4.5 μm. In this embodiment, the "total thickness" of the coating refers to the sum of the thicknesses of each coating of the conductive piezoelectric laminate 10. When the coating is only on one main surface of the piezoelectric film 1, the total thickness is the thickness of the coating on that one main surface. When the coating is on both one main surface and the other main surface of the piezoelectric film 1, the total thickness is the sum of the thickness of the coating on one main surface and the thickness of the coating on the other main surface.

[0076] The conductive piezoelectric laminate 10 can also be used in combination with existing electrode layers. Existing electrode layers, for example, function as sensors for detecting position. Existing electrode layers can be, for example, electrode layers formed by laminating conductive layers onto a film, said film comprising any or more of the following materials: polyethylene terephthalate (PET), cyclic olefin polymer (COP), and polycarbonate (PC). It should be noted that the conductive layer in existing electrode layers can also contain the same material as the conductive layer 4 of the present invention described above.

[0077] In addition, it also includes an adhesive layer and a release layer that abuts against the adhesive layer and can be peeled off as other layers.

[0078] The adhesive layer is a transparent layer with adhesive properties that can bond the conductive piezoelectric layer laminate 10 or any layer constituting the touch panel described later to other layers. The adhesive layer only needs to be a transparent adhesive. Such an adhesive may contain a basic polymer exhibiting transparency and adhesion. Examples of basic polymers include: acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethylene ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy polymers, fluoropolymers, and rubber-based polymers. Examples of rubber-based polymers include natural rubber and synthetic rubber. The basic polymer can be appropriately selected from the examples mentioned above. In particular, acrylic adhesives are preferred from the viewpoints of excellent optical transparency; exhibiting suitable wetting, cohesiveness, and adhesion properties; and also excellent weather resistance and heat resistance.

[0079] Furthermore, additional layers, including those that enhance the optical properties of the conductive piezoelectric layer stack 10, can be added as other layers. For example, an anti-glare layer or an anti-reflection layer may be included.

[0080] An anti-glare layer is a layer containing microparticles that prevents reflection. For example, it can be formed by adding microparticles to a resin that serves as the coating material. An anti-reflective layer is a layer that improves optical properties by adjusting the refractive index. Anti-reflective layers can also be formed using a resin that serves as the coating material.

[0081] In addition, protective layers may be added. For example, known anti-fouling (fingerprint resistant) layers and protective film layers may also be included.

[0082] It should be noted that the thickness of each layer constituting the conductive piezoelectric laminate 10 can be measured by the following method: the conductive piezoelectric laminate 10 is embedded in epoxy resin, and the epoxy resin block is cut open to expose the cross-section of the conductive piezoelectric laminate 10. The cross-section is then observed using a scanning electron microscope. The thickness of the layer only needs to be a representative value of that layer's thickness; it can be the average of any number of measured values, the maximum value, or the minimum value. [Effects of the Conductive Piezoelectric Laminate 10]

[0083] The conductive piezoelectric laminate 10 in the embodiments of the present invention, as described above, is constructed by sequentially overlapping a first coating layer 2, a second coating layer 3, and a conductive layer 4 on at least one side of a piezoelectric film 1. The refractive index of the piezoelectric film 1 is 1.30 or higher and 1.50 or lower, the refractive index of the first coating layer 2 is 1.45 or higher and less than 1.60, the refractive index of the second coating layer 3 is 1.60 or higher and less than 1.80, and the refractive index of the conductive layer 4 is 1.80 or higher and 2.20 or lower. With this configuration, the conductive piezoelectric laminate 10 possesses sufficient piezoelectricity derived from the piezoelectric film 1, and also exhibits high transparency and a suitable hue. Furthermore, in one embodiment, the conductive piezoelectric laminate 10 is configured such that... Figure 1 In this configuration, the uppermost layer has a lower refractive index, while the lowermost layer has a higher refractive index. This configuration enhances the aforementioned effect.

[0084] The conductive piezoelectric laminate 10 exhibits high transparency as described above, making it a preferred choice for use as a pressure detection sensor in devices such as touch panels. By using the conductive piezoelectric laminate 10, the layer structure of devices such as touch panels can be simplified compared to the past, or the overall layer thickness can be reduced. Furthermore, the number and placement freedom of the conductive piezoelectric laminate 10 in devices such as touch panels can be increased.

[0085] [Physical properties of conductive piezoelectric laminate 10]

[0086] From the viewpoint of achieving sufficient light transmittance, the conductive piezoelectric laminate 10 of this embodiment is preferably sufficiently transparent. It should be noted that, in this embodiment, "transparent" means, which can also be appropriately determined depending on the application of the conductive piezoelectric laminate 10, optical properties such as transmitting a desired proportion or more of visible light, suppressing hues, and having sufficiently low turbidity.

[0087] The visible light transmittance of the conductive piezoelectric laminate 10 can be appropriately determined according to its intended use. It should be noted that, as an example of visible light transmittance, the transmittance of light with a wavelength of 550 nm can be measured. 550 nm is the wavelength known as the maximum visible light intensity and is therefore commonly used as a reference value when measuring visible light transmittance. The 550 nm transmittance can be measured, for example, using a haze meter (“NDH7700SPII”, manufactured by Nippon Denshoku Kogyo Co., Ltd.) based on the method described in JIS K7361-1.

[0088] In this embodiment, the transmittance of the conductive piezoelectric laminate 10 at a wavelength of 550 nm (hereinafter referred to as "550 nm transmittance") is preferably 83% or more, and more preferably 85% or more. If the 550 nm transmittance of the conductive piezoelectric laminate 10 is within this range, it is a sufficiently high transmittance for use as a film in devices such as touch panels.

[0089] The degree of hue suppression can be appropriately determined according to the application of the conductive piezoelectric laminate 10. Hue can be evaluated by the L*, a*, and b* values ​​in the L*a*b* color system. The values ​​in the L*a*b* color system can be determined, for example, using a spectrophotometer and the known methods described in JIS Z8722.

[0090] From the viewpoint of achieving stable light transmittance, the conductive piezoelectric laminate 10 of this embodiment preferably does not produce hue. In particular, it is preferable to appropriately suppress the yellow hue originating from the conductive layer 4, so it can also be evaluated using the chromaticity b* value of yellow. It should be noted that the lightness L* value and the chromaticity a* values ​​of red and green are not particularly limited as long as they do not pose a problem when the conductive piezoelectric laminate 10 is used as a touch panel.

[0091] The conductive piezoelectric laminate 10 in this embodiment can have b* ≤ 4, more preferably b* ≤ 3. The conductive piezoelectric laminate 10 within this range suppresses yellow tint and has high transparency, thus it is preferably used in touch panels. It should be noted that the b* value is preferably -4 or higher. Furthermore, the conductive piezoelectric laminate 10 may also have an L* value of 85 or higher and an a* value of 3 or lower. If the conductive piezoelectric laminate 10 has L*, a*, and b* values ​​each within this range, it can effectively suppress tint and has high transparency as a film for devices such as touch panels.

[0092] The degree of turbidity can be appropriately determined based on the intended use of the conductive piezoelectric laminate 10. Turbidity can be evaluated by haze values. Haze values ​​can be measured, for example, using a haze meter based on the method described in JIS K7136.

[0093] The haze value of the conductive piezoelectric laminate 10 in this embodiment is preferably 2% or less, more preferably 1.5% or less, and even more preferably 1.0% or less. The conductive piezoelectric laminate 10 with a haze value within this range sufficiently suppresses turbidity and is therefore preferred for use in devices such as touch panels.

[0094] Regarding the conductive piezoelectric laminate 10 of this embodiment, in applications such as touch panels, the surface resistivity and piezoelectric constant d are... 33 There are no particular limitations as long as it is practically feasible for use in devices such as touch panels.

[0095] The surface resistivity of the conductive piezoelectric laminate 10 can be measured, for example, using a resistivity meter based on a known method described in JIS K 7194. This surface resistivity is preferably, for example, 1 × 10⁻⁶. 3 The surface resistivity is Ω / sq or less, more preferably 400Ω / sq or less, even more preferably 300Ω / sq or less, and even more preferably 200Ω / sq or less. In order to obtain better conductivity in applications such as touch panels, the surface resistivity is preferably lower, and as a lower limit, examples include 10Ω / sq or more and 20Ω / sq or more.

[0096] The piezoelectric constant d of the conductive piezoelectric laminate 10 33 For example, a piezoelectric constant measuring device can be used to measure it. For instance, by clamping the sample with 0.2N, reading the charge generated when a force of 0.15N at 110Hz is applied, and measuring its absolute value, the piezoelectric constant d can be determined. 33 The value is preferably 6 pC / N or more, more preferably 10 pC / N or more, and even more preferably 12 pC / N or more. There is no upper limit to this piezoelectric characteristic, but if it is as described above, from the viewpoint of fully obtaining the desired effect regarding the piezoelectric performance of the piezoelectric film 1, the piezoelectric constant d is considered...33 It is acceptable to have a value of 45 pC / N or less, more preferably 35 pC / N or less, and even more preferably 30 pC / N or less.

[0097] 〔equipment〕

[0098] One embodiment of the present invention provides a device having the conductive piezoelectric laminate 10 described above. This device can be any device as long as it includes the conductive piezoelectric laminate 10 of this embodiment. For example, the position and number of the conductive piezoelectric laminate 10 can be appropriately determined according to the intended use or desired function of the device. The conductive piezoelectric laminate 10 can be used, for example, as a pressure detection sensor for a touch panel or the like in the device.

[0099] When used as a pressure detection sensor for a touch panel, it can also be configured such that the conductive piezoelectric laminate 10 of this embodiment is appropriately added to the laminated structure of a conventional touch panel such as a GFF type or GF2 type. In this case, in the conductive piezoelectric laminate 10 of this embodiment, the electrode layer for detecting pressure and the position sensor for detecting position can be directly laminated or bonded together with an adhesive layer in between. A touch panel with such a configuration can exhibit not only the functions of a conventional touch panel but also the functions arising from the conductive piezoelectric laminate 10; for example, it can be configured as a touch panel that includes both a position sensor and a pressure sensor in a transparent laminated structure.

[0100] It should be noted that, when used as a touch panel, the adhesive layer can be formed not only on the coating but also on other layers bonded to the coating through the adhesive layer. In this case, the adhesive layer may or may not be located on the coating side.

[0101] When the conductive piezoelectric laminate 10 is included in the device, the conductive piezoelectric laminate 10 functions as an electrode, thus reducing the need for electrode layers, such as those made of PET / ITO, in the layer structure of conventional pressure sensors. Therefore, the layer structure of the pressure detection sensor can be simplified compared to the past.

[0102] [Method for manufacturing conductive piezoelectric laminate 10]

[0103] The manufacturing method of the conductive piezoelectric laminate 10 according to this embodiment will be described below. The manufacturing method of this embodiment is a method for manufacturing a laminate formed by sequentially overlapping a first coating layer 2, a second coating layer 3, and a conductive layer 4 on at least one side of a piezoelectric film 1, including: a first step of forming a film with a refractive index of 1.30 or higher and 1.50 or lower to manufacture a piezoelectric film 1; a second step of forming a first coating layer 2 with a refractive index of 1.45 or higher and less than 1.60 on at least one side of the piezoelectric film 1; a third step of forming a second coating layer 3 with a refractive index of 0.60 or higher and less than 1.80 on the surface of the first coating layer 2; and a fourth step of forming a conductive layer 4 with a refractive index of 1.80 or higher and 2.20 or lower on the surface of the second coating layer 3.

[0104] The first step only needs to be the step of making the piezoelectric film 1. The steps can be appropriately changed or added depending on the type of piezoelectric film 1 being made. For example, the piezoelectric film 1 can be made by continuously performing the following steps: a step of making a resin film by conventionally known methods such as casting, hot pressing, and melt extrusion; a step of stretching the resin film; and a step of polarizing the non-polarized resin film.

[0105] In the second step, at least one side of the piezoelectric film 1 produced in the first step only needs to be coated with the material of the first coating layer 2. The coating method can be any conventionally known method and is not particularly limited; however, from the perspective of productivity and manufacturing cost, a wet coating method is particularly preferred. The wet coating method can be any known method; representative methods include: roller coating, spin coating, dip coating, gravure coating, etc. Among these, from the perspective of productivity, methods that can continuously form layers, such as roller coating and gravure coating, are more preferred.

[0106] In applying the material for the first coating layer 2, a doctor blade coater or a gravure coater can be used, for example. After coating, the material can be dried at 50°C to 180°C for 0.5 to 60 minutes. Furthermore, the dried first coating layer 2 can be cured by UV irradiation. UV curing can be achieved, for example, using a UV irradiation device at a concentration of 50 J / cm². 2 ~1200mJ / cm 2 The cumulative light intensity can be obtained by irradiating with UV light. The equipment, material concentration, temperature, and other conditions used in the second process can be appropriately modified with reference to the material and film thickness of the first coating 2.

[0107] In the third step, the material for the second coating layer 3 can be applied to the first coating layer 2 prepared in the second step using known methods. For example, it can be applied using a wet coating method, just like the first coating layer 2. Alternatively, it can be applied together with the conductive layer 4 using a dry coating method. The apparatus, material concentration, and temperature conditions for the third step can be the same as those for the second step. It should be noted that the film thickness of the second coating layer 3 can be adjusted by adjusting the material concentration.

[0108] In the fourth step, a conductive layer 4 can be formed on the second coating 3 produced in the third step using known methods. The conductive layer 4 can be formed by methods such as sputtering, vacuum evaporation, or ion plating, where the material for the conductive layer 4 is adhered. Appropriate methods can be chosen depending on the desired film thickness.

[0109] When using a sputtering method, the inorganic materials constituting the conductive layer 4 described above can be used as the target material, and ITO is a preferred example. The tin oxide concentration of the ITO is, for example, 0.5% by mass or more, preferably 2% by mass or more, and furthermore, for example, 15% by mass or less, preferably 13% by mass or less.

[0110] Examples of sputtering gases include inert gases such as Ar. Furthermore, reactive gases such as oxygen may be used in conjunction, if necessary. When using reactive gases, the flow rate ratio of the reactive gases is not particularly limited, but is, for example, 0.1% to 5% of the total flow rate of the sputtering gas and the reactive gas.

[0111] From the perspective of suppressing the decrease in sputtering rate and discharge stability, the gas pressure during sputtering is, for example, below 1 Pa, preferably below 0.7 Pa.

[0112] The power supply used in sputtering can be any of the following: DC power supply, AC power supply, MF power supply, and RF power supply, or a combination thereof.

[0113] The manufacturing method of this embodiment only includes the first to fourth steps, but may also include other steps. For example, a step of adding other layers to the conductive piezoelectric laminate 10 can be added. In addition, a step of performing corona treatment on the piezoelectric film 1 to improve the adhesion with the first coating layer 2 can be added.

[0114] According to the manufacturing method of this embodiment, a conductive piezoelectric laminate 10 with high transparency and appropriate hue can be manufactured.

[0115] In the manufacturing method of this embodiment, the annealing treatment of the conductive layer 4 may not be performed after the fourth step. By not performing the annealing treatment, the color of the piezoelectric film 1 is not damaged, and thus a conductive piezoelectric layer laminate 10 that is preferably used in devices such as touch panels can be produced.

[0116] This invention is not limited to the embodiments described above. Various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical solutions disclosed in different embodiments are also included within the technical scope of this invention.

[0117] (Summarize)

[0118] The present invention can be represented as follows.

[0119] The conductive piezoelectric laminate of this embodiment 1 is formed by sequentially overlapping a first coating layer, a second coating layer, and a conductive layer on at least one side of a piezoelectric film. The piezoelectric film has a refractive index of 1.30 or higher and 1.50 or lower, the first coating layer has a refractive index of 1.45 or higher and less than 1.60, the second coating layer has a refractive index of 1.60 or higher and less than 1.80, and the conductive layer has a refractive index of 1.80 or higher and 2.20 or lower. This configuration imparts high transparency and a suitable hue to the conductive piezoelectric laminate.

[0120] In this embodiment 2, the conductive piezoelectric laminate has a b* ≤ 4 as described in embodiment 1. This conductive piezoelectric laminate has a suitable hue and is therefore preferably used in devices such as touch panels.

[0121] The conductive piezoelectric laminate of this embodiment 3 exhibits a transmittance of over 83% at a wavelength of 550 nm, as described in embodiments 1 or 2. This conductive piezoelectric laminate possesses high transparency and is therefore preferably used in devices such as touch panels.

[0122] The conductive piezoelectric laminate of embodiment 4 has a haze value of 2.0% or less in any of embodiments 1 to 3. The conductive piezoelectric laminate constructed in this way has sufficiently low turbidity, and is therefore preferably used in devices such as touch panels.

[0123] In this embodiment 5, the conductive piezoelectric laminate is one of the conductive layers in any of embodiments 1 to 4, wherein the conductive layer is composed of an indium-tin composite oxide, and no peaks of the indium-tin composite oxide were detected in X-ray diffraction. Based on this configuration, an amorphous conductive layer with a refractive index within an appropriate range can be fabricated.

[0124] The device of this embodiment 6 possesses a conductive piezoelectric laminate film of any one of embodiments 1 to 5. Based on this configuration, the film structure of the device, such as the touch panel, can be simplified compared to previous designs.

[0125] The manufacturing method of this embodiment 7 is a method for manufacturing a conductive piezoelectric laminated film. The conductive piezoelectric laminated film is a laminated film formed by sequentially overlapping a first coating layer, a second coating layer, and a conductive layer on at least one side of a piezoelectric film. The manufacturing method of the conductive piezoelectric laminated film includes: a first step of forming a film with a refractive index of 1.30 or higher and 1.50 or lower to manufacture a piezoelectric film; a second step of forming a first coating layer with a refractive index of 1.45 or higher and less than 1.60 on at least one side of the piezoelectric film; a third step of forming a second coating layer with a refractive index of 1.60 or higher and less than 1.80 on the surface of the first coating layer; and a fourth step of forming a conductive layer with a refractive index of 1.80 or higher and 2.20 or lower on the surface of the second coating layer. According to this configuration, a conductive piezoelectric laminated film with high transparency and a suitable hue can be manufactured.

[0126] In the manufacturing method of this embodiment 8, the annealing treatment of the conductive layer is not performed after the fourth step, as in embodiment 7. According to this configuration, the color of the piezoelectric film is not damaged, thus enabling the fabrication of a conductive piezoelectric layer laminate that is preferably used in devices such as touch panels.

[0127] Example

[0128] [Example 1]

[0129] A resin film (120 μm thick) made from polyvinylidene fluoride (manufactured by KUREHA Co., Ltd.) with a specific logarithmic viscosity of 1.3 dl / g was stretched at a stretch ratio of 4.2. After stretching, the film was polarized by passing it through a polarization roller to obtain a piezoelectric film. At this time, a DC voltage was applied while increasing it from 0 kV to 12.0 kV, thereby performing polarization. By further heat-treating the polarized film at 130°C for 1 minute, a piezoelectric film with a refractive index of 1.42 and a thickness of 40 μm was obtained.

[0130] A UV-curable resin composition containing amorphous silica and acrylic resin was coated onto the upper surface (surface A) of the piezoelectric film. After drying at 80°C, it was irradiated with ultraviolet light to form a first coating (thickness 0.4 μm, refractive index 1.52). Next, a first coating (thickness 0.4 μm, refractive index 1.52) was also formed on the lower surface (surface B) of the piezoelectric film using the same method. Then, a UV-curable resin composition containing zirconia particles was coated onto the upper surface of the first coating (surface A). After drying at 80°C, it was irradiated with ultraviolet light to form a second coating (thickness 114 nm, refractive index 1.65). Thus, a laminate containing a piezoelectric film, a first coating, and a second coating was obtained.

[0131] Next, on the second coating, an ITO film with a refractive index of 1.88 and a thickness of 30 nm was formed as a conductive layer by reactive sputtering under the following conditions, using a sintered material containing 97% by mass of indium oxide and 3% by mass of tin oxide as the target. Thus, a conductive piezoelectric laminate was obtained.

[0132] [Example 2]

[0133] The thickness of the second coating was changed to 102 nm, and otherwise, a conductive piezoelectric laminate was obtained in the same manner as in Example 1.

[0134] [Example 3]

[0135] The thicknesses of the first coating A, the first coating B, the second coating, and the conductive layer were changed to 1.0 μm, 0.9 μm, 110 nm, and 35 nm, respectively. Otherwise, a conductive piezoelectric layer stack was obtained in the same manner as in Example 1.

[0136] [Example 4]

[0137] The thickness of the second coating was changed to 84 nm, and otherwise, a conductive piezoelectric laminate was obtained in the same manner as in Example 1.

[0138] [Example 5]

[0139] The refractive index of the second coating was changed to 1.75, and the thicknesses of the first coating A, the first coating B, the second coating, and the conductive layer were changed to 1.0 μm, 0.9 μm, 164 nm, and 35 nm, respectively. Otherwise, a conductive piezoelectric layer stack was obtained in the same manner as in Example 1.

[0140] [Example 6]

[0141] The refractive index of the second coating was changed to 1.70, and the thicknesses of the first coating A, the first coating B, the second coating, and the conductive layer were changed to 1.0 μm, 1.0 μm, 105 nm, and 28 nm, respectively. Otherwise, a conductive piezoelectric layer stack was obtained in the same manner as in Example 1.

[0142] [Example 7]

[0143] The refractive index of the first coating was changed to 1.49, and the thicknesses of the first coating B, the second coating, and the conductive layer were changed to 1.0 μm, 100 nm, and 28 nm, respectively. Otherwise, a conductive piezoelectric layer stack was obtained in the same manner as in Example 1.

[0144] [Comparative Example 1]

[0145] No first or second coating is formed; otherwise, a conductive piezoelectric laminate is obtained in the same manner as in Example 1.

[0146] [Comparative Example 2]

[0147] No second coating is formed; otherwise, a conductive piezoelectric laminate is obtained in the same manner as in Example 3.

[0148] [Comparative Example 3]

[0149] The refractive index of the second coating was changed to 1.52, and the thickness of the second coating was set to 133 nm. Otherwise, a conductive piezoelectric laminate was obtained in the same manner as in Example 3.

[0150] [Comparative Example 4]

[0151] The refractive index of the second coating was changed to 1.52, and the thickness of the second coating was set to 212 nm. Otherwise, a conductive piezoelectric laminate was obtained in the same manner as in Example 3.

[0152] [Comparative Example 5]

[0153] A UV-curable resin composition containing hollow silica with a refractive index of 1.35 was coated on the second coating. After drying at 80°C, it was irradiated with ultraviolet light to form a third coating with a thickness of 80 nm. Otherwise, a conductive piezoelectric laminate was obtained by using the same method as in Example 3.

[0154] [Comparative Example 6]

[0155] By changing the refractive index of the first coating to 1.65 and omitting the first coating B, a conductive piezoelectric laminate was obtained in the same manner as in Example 6.

[0156] [Comparative Example 7]

[0157] The refractive index of the first coating was changed to 1.39, the first coating B was not set, and the thickness of the second coating was set to 96 nm. Otherwise, a conductive piezoelectric laminate was obtained in the same way as in Example 6.

[0158] The structures of the conductive piezoelectric laminates of Examples 1-7 and Comparative Examples 1-7 are shown in Table 1.

[0159] [Table 1]

[0160]

[0161] 〔evaluate〕

[0162] The surface resistivity and piezoelectric constant d of the films from Examples 1-7 and Comparative Examples 1-7 were measured respectively. 33 The physical and optical properties of the films were evaluated by measuring the transmittance at 550 nm, haze value, L*, a*, and b*.

[0163] [Physical Property Evaluation]

[0164] (Coating thickness)

[0165] The conductive piezoelectric laminates of Examples 1-7 and Comparative Examples 1-7 were embedded in epoxy resin, and the epoxy resin blocks were cut in such a way that the cross-section of the conductive piezoelectric laminate was exposed. The cross-section of the exposed conductive piezoelectric laminate was observed using a scanning electron microscope (“SU3800”, manufactured by Hitachi HighTech Co., Ltd.) at an accelerating voltage of 3.0 kV and a magnification of 50,000x, and the thickness of the coating in the conductive piezoelectric laminate was measured.

[0166] It should be noted that in measuring the thickness of each coating, the thickness at two points within each coating was measured, and the average value was taken as the thickness of each coating. It should also be noted that under the above observation conditions, the interfaces of each coating were observed to be essentially smooth lines, and the distance between these lines was measured in the thickness measurement of each coating.

[0167] (Thickness of the conductive layer)

[0168] Using the scanning electron microscope described above, the cross-sections of the conductive piezoelectric layer laminates of Examples 1-7 and Comparative Examples 1-7 were observed under conditions of accelerating voltage 3.0 kV and magnification 50,000. The thickness of each ITO film was measured at two locations. The average value of the measured values ​​was calculated as the thickness of the conductive layer.

[0169] (Surface resistivity)

[0170] The surface resistance (Ω / sq, hereinafter referred to as "resistance value") of the conductive piezoelectric laminates of Examples 1-7 and Comparative Examples 1-7 was measured using a resistivity meter ("LorestaGP MCP-T610", manufactured by Mitsubishi Chemical Analytech) according to JIS K 7194. The resistance value was measured three times, and the average of the three measurements was used as a representative value. If the resistance value is below 400 Ω / sq, it can be determined that it is suitable for practical use in devices such as touch panels.

[0171] (piezoelectric constant d) 33 value)

[0172] Using a piezoelectric constant measuring device (“PiezoMeter System PM300”, manufactured by PIEZOTEST), the piezoelectric constant d of the conductive piezoelectric laminates of Examples 1-7 and Comparative Examples 1-7 was determined. 33 The sample was held with 0.2N clamping force, and the charge generated when a force of 0.15N and 110Hz was applied was read. The piezoelectric constant d... 33The measured value may be positive or negative depending on whether the membrane is measured on the front or back side, but the absolute value is stated in this specification. Piezoelectric constant d 33 If the value is 6pC / N or higher, it can be determined that there are no practical problems in its use in devices such as touch panels.

[0173] [Diffraction peaks originating from ITO]

[0174] For each of the conductive piezoelectric layer laminates of Examples 1-7 and Comparative Examples 1-7, diffraction peaks originating from ITO in X-ray diffraction with and without a conductive layer were measured. The presence or absence of this diffraction peak was determined using the in-plane method of the conductive layer surface using an X-ray diffraction apparatus (XRD). In this measurement, the diffraction angle (2θ) ranged from 15.0° to 70.0° at a scanning speed of 1° / min. Details of the measurement conditions are shown below.

[0175] <Measurement Conditions>

[0176] Device: SmartLab manufactured by Rigaku Co., Ltd.

[0177] X-ray source: Cu-Kα ( ), 40kV, 30mA.

[0178] Detector: SC-70.

[0179] Step size: 0.04°.

[0180] Scanning range: 15.0°~70.0°.

[0181] Slit: Entrance slit = 0.2 mm.

[0182] The length of the slit is controlled to be 10mm.

[0183] Light-receiving slit = 20mm.

[0184] No diffraction peaks originating from ITO were detected in the conductive piezoelectric laminates of Examples 1-7 and Comparative Examples 1-7.

[0185] [Optical property evaluation]

[0186] (550nm transmittance)

[0187] Using a haze meter ("NDH7700SPII", manufactured by Nippon Denshoku Kogyo Co., Ltd.), the 550nm transmittance of the conductive piezoelectric laminates of the Examples and Comparative Examples was measured based on the method described in JIS K7361-1. A 550nm transmittance of 83% or higher indicates that the material is suitable for use in devices such as touch panels; 84% or higher is more preferable; and 85% or higher is even more preferable.

[0188] (Haze value)

[0189] Using a haze meter ("NDH7700SPII", manufactured by Nippon Denshoku Kogyo Co., Ltd.), the haze values ​​of the coating used in the examples and the piezoelectric film used in the comparative examples were measured based on the method described in JIS K7136. A haze value of 2.0 or less indicates that it is practically suitable for use in devices such as touch panels. It should be noted that a haze value of 2.0 or less is preferred, more preferably 1.5% or less, and even more preferably 1.0% or less.

[0190] (L* value, a* value, b* value)

[0191] Using a spectrophotometer ("SE7700", manufactured by Nippon Denshoku Kogyo Co., Ltd.), the L*, a*, and b* values ​​in the L*a*b* color system of the conductive piezoelectric laminates of the Examples and Comparative Examples were measured according to the method of JIS Z8722. An L* value of 85 or higher indicates that the material is suitable for use in touch panels and similar devices. An a* value of 3 or lower indicates that the material is suitable for use in touch panels and similar devices. A b* value of 4 or lower indicates that the material is suitable for use in touch panels and similar devices. It should be noted that a b* value of 3 or lower is more preferably acceptable.

[0192] The results of the above evaluation are shown in Table 2.

[0193] [Table 2]

[0194]

[0195] As shown in Table 2, the conductive piezoelectric laminates of Examples 1-7 possess physical properties that are practically applicable to devices such as touch panels, and also have high transparency and a suitable hue. In contrast, the conductive piezoelectric laminates of Comparative Examples 1-7 have a b*>4 and a yellowish hue.

[0196] Industrial availability

[0197] This invention can be used in devices such as touch panels.

[0198] Explanation of reference numerals in the attached figures

[0199] 1: Piezoelectric film;

[0200] 2, 2': First coating;

[0201] 3: Second coating;

[0202] 4: Conductive layer;

[0203] 10, 10': Conductive piezoelectric laminate.

Claims

1. A conductive piezoelectric laminate, which is formed by sequentially overlapping a first coating layer, a second coating layer, and a conductive layer on at least one side of a piezoelectric film. The refractive index of the piezoelectric film is greater than 1.30 and less than 1.

50. The refractive index of the first coating is greater than 1.45 and less than 1.

60. The refractive index of the second coating is greater than 1.60 and less than 1.

80. The refractive index of the conductive layer is above 1.80 and below 2.

20. The refractive index of the first coating is higher than that of the piezoelectric film.

2. The conductive piezoelectric laminate according to claim 1, wherein, b*≤4。 3. The conductive piezoelectric laminate according to claim 1 or 2, wherein, The transmittance at a wavelength of 550nm is over 83%.

4. The conductive piezoelectric laminate according to claim 1 or 2, wherein, The haze value is below 2.0%.

5. The conductive piezoelectric laminate according to claim 1 or 2, wherein, The conductive layer is composed of indium-tin composite oxide. No peaks of the indium-tin composite oxide were detected in the X-ray diffraction.

6. An apparatus having a conductive piezoelectric laminate, wherein the conductive piezoelectric laminate is the conductive piezoelectric laminate as described in any one of claims 1 to 5.

7. A method for manufacturing a conductive piezoelectric laminate, wherein, The conductive piezoelectric laminate is a laminate formed by sequentially overlapping a first coating layer, a second coating layer, and a conductive layer on at least one side of a piezoelectric film. The method for manufacturing the conductive piezoelectric laminate includes: The first step involves forming a film with a refractive index of 1.30 or higher and 1.50 or lower to manufacture a piezoelectric film. In the second step, a first coating with a refractive index of 1.45 or higher and less than 1.60 is formed on at least one side of the piezoelectric film; The third step involves forming a second coating on the surface of the first coating with a refractive index greater than 1.60 and less than 1.80; and In the fourth step, a conductive layer with a refractive index of 1.80 or higher and 2.20 or lower is formed on the surface of the second coating.

8. The method for manufacturing a conductive piezoelectric laminate according to claim 7, wherein, Annealing of the conductive layer is not performed after the fourth process.

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