An antistatic optical protective film and a method for manufacturing the same

Abstract

The application discloses an antistatic optical protective film and a preparation method thereof. The film comprises at least a substrate layer and an adhesive layer for bonding with an optical film. The substrate layer is made of a polyester film with or without an antistatic agent, and the adhesive layer is made of a thermally cured adhesive or an ultraviolet light cured adhesive with an antistatic agent. An electrically conductive layer is formed between the substrate layer and the adhesive layer. The substrate layer and the adhesive layer can both contain the antistatic agent. In the case that the substrate layer contains the antistatic agent, static electricity during peeling of the protective film can be conducted to the substrate layer through the adhesive layer, so that the problem of static electricity residue does not occur. The electrically conductive layer is a dense electrically conductive structure formed by a metal conductive material, and the resistivity of the electrically conductive layer is much smaller than that of the substrate layer and the adhesive layer. Therefore, even if the electric conductivity of the substrate layer and the adhesive layer is uneven, the locally gathered static electricity can be easily conducted away by the electrically conductive layer, so that the defect of uneven dispersion of the antistatic agent can be solved.

Description

Technical Field

[0001] This application relates to the field of optical thin film technology, and in particular to protective films for protecting optical thin films, especially to an antistatic optical protective film and its preparation method. Background Technology

[0002] Optical thin films, such as brightness enhancement films, polarizers, reflective films, and optical compensation films, are widely used in electronic products such as LCD displays, solar cells, computers, and mobile phones. To protect the surfaces of these optical films from damage, dust, fingerprints, etc., before use, a protective film is applied. When these optical films need to be assembled, the protective film is peeled off to expose the usable surfaces. Since both the protective film and the protected optical film are typically made of plastic, static electricity is generated between the peeling surfaces when the protective film is removed. If this static electricity remains on the optical film, it can affect the components of electronic products, potentially damaging them. Furthermore, residual static electricity can attract dust, affecting the use of the optical film. To reduce the harmful effects of static electricity, protective films are usually made with antistatic properties. This is typically achieved by adding antistatic agents to the protective film or its surface to direct static electricity away from the film and prevent it from accumulating on the optical film, thus avoiding any impact from static electricity on the optical film and the electronic products using it.

[0003] CN 109957347 B discloses an antistatic silicone protective film, comprising a substrate layer and an organosilicone adhesive coated on the surface of the substrate layer. The organosilicone adhesive formulation, based on nano-graphite powder, additionally adds 2-aminobenzimidazole and potassium monododecyl phosphate to address the problem of static electricity buildup affecting automated continuous production during the use of the protective film. In this prior art, the substrate layer of the protective film is insulating. During automated production, the machinery comes into contact with the substrate layer, and the static electricity absorbed by the organosilicone adhesive cannot be discharged by the machine. A portion of the static electricity generated during the peeling of the protective film always remains on the protected product, resulting in a less than ideal antistatic effect.

[0004] CN 116218006 B discloses an antistatic optical protective film, including an optical base film and an antistatic coating applied to the surface of the optical base film. This prior art employs a highly complex antistatic coating preparation process to achieve the antistatic effect. Similar to the aforementioned prior art, the optical base film in this prior art is also insulating, and the antistatic coating cannot conduct static electricity outwards. Moreover, as this prior art emphasizes, the antistatic coating suffers from compatibility issues, requiring complex processes to ensure uniform curing of the antistatic components. This implies that the antistatic coating may exhibit differences in conductivity in different areas; static electricity in areas with poor conductivity cannot be dissipated, and the static electricity problem will still exist.

[0005] CN 105733464 B discloses an optical protective film for a liquid crystal polarizer. The protective film has a multi-layer structure, with a functional layer coated on one side of a biaxially stretched transparent polyester film. This functional layer has scratch resistance, stain resistance, and antistatic properties. A pressure-sensitive adhesive layer is coated on the other side of the polyester film, and a silicone release film is attached to the adhesive layer. In this prior art, the antistatic functional layer is on the outermost side of the protective film, separated by an insulating polyester film and a pressure-sensitive adhesive layer. Therefore, this prior art optical protective film can only prevent external static electricity from affecting the polarizer; the static electricity generated when peeling off the optical protective film cannot be discharged at all. During the assembly of a liquid crystal display, the static electricity generated when peeling off the optical protective film will severely affect the polarizer.

[0006] CN 106010323 B discloses an antistatic surface protective film, which has a transparent resin-based substrate film. The surface of the substrate film is sequentially laminated with a polyurethane adhesive layer (without antistatic agent), an antistatic agent layer, and a release film after peeling treatment. In this prior art protective film, the release film needs to be removed, and then the antistatic agent layer comes into contact with the protected surface. Since adhesion requires an adhesive layer, the antistatic agent layer needs to be very thin, thin enough for the adhesive layer to pass through and exert its adhesive effect. The adhesive layer and substrate film of this prior art are non-conductive; only a very thin antistatic agent layer is used to receive static electricity, but it cannot conduct it away, resulting in static electricity residue on the protected surface. Furthermore, the conductive composition of the antistatic agent layer may be uneven, making it difficult to ensure antistatic effectiveness in all areas. Summary of the Invention

[0007] The technical problem to be solved by this application is to provide an antistatic optical protective film and its preparation method, so as to reduce or avoid the problems mentioned above.

[0008] To address the aforementioned technical problems, this application proposes an antistatic optical protective film for attaching to the working surface of an optical film to protect it. The antistatic optical protective film comprises at least a substrate layer and an adhesive layer for bonding with the optical film. The substrate layer is composed of a polyester film containing or without an antistatic agent, and the adhesive layer is composed of a thermosetting adhesive or a UV-curable adhesive containing an antistatic agent. A conductive layer is formed between the substrate layer and the adhesive layer.

[0009] Preferably, the conductive layer is formed by vapor deposition or vacuum sputtering of a metallic conductive material on the side surface of the substrate layer opposite the adhesive layer.

[0010] Preferably, the conductive layer partially covers the surface of the substrate layer.

[0011] Preferably, the conductive layer is formed on the surface of the substrate layer in a diagonally intersecting structure.

[0012] Preferably, the conductive layer is formed on the surface of the substrate layer in the form of a mesh structure with holes.

[0013] Preferably, the antistatic optical protective film is provided with outwardly protruding tabs.

[0014] This application also proposes a method for preparing the above-mentioned antistatic optical protective film, comprising the following steps: providing a substrate layer, forming a conductive layer on one side surface of the substrate layer by vapor deposition or vacuum sputtering, coating and curing an adhesive layer containing an antistatic agent on the outside of the conductive layer of the substrate layer, and preparing the antistatic optical protective film.

[0015] Preferably, the preparation method further includes the following step: die-cutting the prepared antistatic optical protective film to form outwardly protruding lugs.

[0016] Preferably, the preparation method further includes the following steps: subjecting the surface of the substrate layer to corona treatment or activation treatment, and partially masking the surface to form a conductive layer that partially covers the surface of the substrate layer.

[0017] Preferably, a conductive layer is formed in the gaps of the corresponding masking film by vapor deposition or vacuum sputtering, and an adhesive layer is formed on the outside of the conductive layer after the masking film is removed.

[0018] Both the substrate layer and the adhesive layer of this application can contain antistatic agents. When the substrate layer contains antistatic agents, the static electricity generated during the peeling of the protective film can be conducted to the substrate layer through the adhesive layer, thus eliminating the problem of static electricity residue. Since the conductive layer is a dense conductive structure formed by a metallic conductive material, its resistivity is much lower than that of the substrate layer and the adhesive layer. Therefore, even if there is uneven conductivity in the substrate layer and the adhesive layer, locally accumulated static electricity can be easily conducted away by the conductive layer, thus solving the defect of uneven dispersion of antistatic agents. Attached Figure Description

[0019] The accompanying drawings are intended only to illustrate and explain this application and do not limit the scope of this application.

[0020] Figure 1 The diagram shown is an exploded perspective view of an antistatic optical protective film applied to an optical thin film according to a specific embodiment of this application.

[0021] Figure 2 The diagram shown is an exploded perspective view of an antistatic optical protective film according to a specific embodiment of this application.

[0022] Figure 3The diagram shown is an exploded perspective view of an antistatic optical protective film according to another specific embodiment of this application. Detailed Implementation

[0023] To provide a clearer understanding of the technical features, objectives, and effects of this application, specific embodiments are now described with reference to the accompanying drawings. Identical components are denoted by the same reference numerals.

[0024] like Figure 1 As shown, this application proposes an antistatic optical protective film 10 for attaching to and protecting the working surface of an optical thin film 20. The optical thin film 20 can be any existing thin film that requires protection of its working surface, including but not limited to brightness enhancement films, polarizers, reflective films, optical compensation films, or the screen or outer surface of any electronic device, etc.

[0025] Furthermore, such as Figure 1 As shown, the antistatic optical protective film 10 of this application includes at least a substrate layer 11 and an adhesive layer 12 for bonding with the optical film 20; wherein, the substrate layer 11 is composed of a polyester film containing or not containing an antistatic agent, and the adhesive layer 12 is composed of a thermosetting adhesive or an ultraviolet curing adhesive containing an antistatic agent.

[0026] Unlike existing technologies where only a portion of the structure contains antistatic agents, the substrate layer 11 and adhesive layer 12 of this application can both contain antistatic agents. When the substrate layer 11 contains antistatic agents, the static electricity during the peeling of the protective film can be conducted to the substrate layer 11 through the adhesive layer 12, thus avoiding the problem of static electricity residue.

[0027] On the other hand, considering the potential for defects in the uniformity of antistatic agent dispersion, localized areas of the substrate layer 11 and adhesive layer 12 may have insufficient conductivity. That is, if a corresponding location in the substrate layer 11 and adhesive layer 12 happens to lack antistatic agent and become non-conductive, static electricity at that location will be difficult to dissipate. Therefore, further, as... Figure 2 As shown in Figure 3, the antistatic optical protective film 10 of this application also has a conductive layer 13 formed between the substrate layer 11 and the adhesive layer 12. The conductive layer 13 is formed by vapor deposition or vacuum sputtering of a metallic conductive material on the side surface of the substrate layer 11 opposite to the adhesive layer 12.

[0028] Since the conductive layer 13 disposed between the substrate layer 11 and the adhesive layer 12 is a dense conductive structure formed by a metallic conductive material, such as copper, aluminum, silver, gold, etc., its resistivity is much lower than that of the substrate layer 11 and the adhesive layer 12 with added antistatic agent. Therefore, even if the conductivity of the substrate layer 11 and the adhesive layer 12 is uneven, the static electricity that accumulates locally can be easily conducted away by the conductive layer 13 with almost zero resistivity, thus solving the defect of uneven dispersion of antistatic agent.

[0029] In one specific embodiment of this application, the thickness of the substrate layer 11 is preferably 20-250 μm, the thickness of the adhesive layer 12 is preferably 5-15 μm, and the thickness of the conductive layer 13 is preferably 0.1-1 μm.

[0030] The antistatic agent contained in the substrate layer 11 and the adhesive layer 12 can be any one or more suitable antistatic agents in the prior art, including but not limited to nano-metal particles, metal wires, conductive graphite, carbon nanotubes, monoglycerides, sorbitan esters, ethoxyamines, polythiophene-type antistatic agents, polystyrene sulfonate, compounds containing alkylene oxides, and mixtures of metal salts. The adhesive layer 12 of this application can be prepared by adding a suitable antistatic agent to any existing thermosetting or UV-curing adhesive and coating it onto the surface of the conductive layer 13, then curing it by heating or UV irradiation to form the antistatic agent-containing adhesive layer 12.

[0031] The polyester constituting the substrate layer 11 of this application may be, for example, formed by polycondensation of a dicarboxylic acid and a diol. For example, the dicarboxylic acid components include, but are not limited to, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 3,4'-diphenyl ether dicarboxylic acid, hexahydrophthalic acid, 2,7-naphthalenedicarboxylic acid, phthalic acid, 4,4'-methylenebisbenzoic acid, oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, 3-methyl adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, 1,11-undecanedicarboxylic acid, 1,10-decanedicarboxylic acid, undecanediic acid, 1,12-dodecanedicarboxylic acid, hexadecanediic acid, docosanodiic acid, tetradecanediic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,1-cyclohexanediacetic acid, fumaric acid, maleic acid, and hexahydrophthalic acid. Furthermore, it can be used alone or in combination with two or more other acids. For example, the diol components include, but are not limited to, ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, glycol, diethylene glycol, triethylene glycol, poly(ethylene ether) glycol, and poly(butylene ether) glycol. Alcohols, branched diols, hexanediol or combinations thereof or their derivatives, 1,4-cyclohexanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-2,4-pentanediol, neopentanediol, 2-methyl-1,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,5-ethyl-1,3-hexanediol, 2,2-diethyl-1,3-propanediol, 1,3-hexanediol. Alternatively, they can be used alone or in combination of two or more.

[0032] The polyester constituting the substrate layer 11 of this application may also be formed from hydroxycarboxylic acids and their esterifying derivatives, or it may be formed from cyclic esters. For example, the hydroxycarboxylic acid components include, but are not limited to: lactic acid, citric acid, malic acid, tartaric acid, glycolic acid, 3-hydroxybutyric acid, p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, 4-hydroxycyclohexanecarboxylic acid, etc. The esterifying derivatives of the hydroxycarboxylic acids include, but are not limited to: dimethyl terephthalate, dimethyl isophthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl 3,4'-diphenyl ether dicarboxylate, dimethyl hexahydrophthalate, dimethyl 2,7-naphthalenedicarboxylate, dimethyl phthalate, dimethyl 4,4'-methylenebisbenzoate, dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl azelaate, dimethyl 1,3-cyclohexanedicarboxylate, and dimethyl 5-sulfoisophthalate. Furthermore, they can be used alone or in combination. For example, the cyclic esters include, but are not limited to: ε-caprolactone, β-propiolactone, β-methyl-β-propiolactone, δ-valerolactone, glycolide, lactide, etc. Furthermore, they can be used alone or in combination.

[0033] The polyester constituting the substrate layer 11 of this application is preferably polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, poly(1,4-cyclohexanediol) terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene naphthalate and copolymers thereof, particularly preferably polyethylene terephthalate (PET) and copolymers thereof.

[0034] The polyester constituting the substrate layer 11 of this application, taking PET as an example, is preferably manufactured as diethyl terephthalate through esterification or transesterification of terephthalic acid or dimethyl terephthalate and ethylene glycol, or industrially manufactured through polycondensation using a catalyst under high temperature and vacuum. In one specific embodiment, esterification can be performed using terephthalic acid, ethylene glycol, cyclohexanediol, a catalyst, and a heat stabilizer as raw materials; or esterification can be performed using terephthalic acid, ethylene glycol, isophthalic acid, a catalyst, and a heat stabilizer as raw materials. In another specific embodiment, the catalyst is any one of Ti / Si-based non-heavy metal catalysts and antimony trioxide, and its addition amount is 0.01% to 0.09% of the polyester mass. In another specific embodiment, the heat stabilizer is a phosphoric acid compound, and its addition amount is 0.0003% to 0.030% of the polyester mass; the phosphoric acid compound includes any one of phosphoric acid, phosphorous acid, polyphosphoric acid, trimethyl phosphate, triphenyl phosphate, and triethyl phosphate. Another specific embodiment of the polyester preparation method is as follows: 5.0 kg of terephthalic acid, 2.2 kg of ethylene glycol, and 1.10 g of germanium dioxide are added to a 20 L general-purpose polymerization reactor. An esterification reaction is carried out at 230–265 °C and 0.2–0.3 MPa (gauge pressure). When the water output reaches 1200 ml, the pressure is released to atmospheric pressure, and 1.025 g of triethyl phosphate is added. The mixture is stirred at atmospheric pressure for 10 minutes, then the temperature and pressure are raised and lowered to below 280 °C and 100 Pa. After the reaction is completed in 1–3 hours, the mixture is extruded, pelletized, and dried to obtain the polyester suitable for use as the substrate layer 11. Antistatic agents can be added at different stages of polyester preparation, such as the esterification stage or the polycondensation stage, to obtain a polyester with antistatic properties. The prepared polyester can be used to prepare a polyester film containing antistatic agents through melt extrusion and biaxial stretching processes, which can be used as the substrate layer 11 of this application. Alternatively, a polyester film suitable for use as the substrate layer 11 of this application can also be prepared directly from polyester without added antistatic agents.

[0035] Furthermore, because the conductive layer 13 formed on the surface of the substrate layer 11 is relatively dense, its surface adhesion is reduced. Therefore, the adhesive layer 12 coated on the outside of the conductive layer 13 may detach from the substrate layer 11 and remain on the surface of the optical film 20 during peeling. To avoid this, the conductive layer 13 of this application is designed to partially cover the surface of the substrate layer 11, such as... Figure 2 and 3 As shown. Among them, in Figure 2 In the specific embodiment shown, the conductive layer 13 is formed on the surface of the substrate layer 11 in a diagonally intersecting structure. Figure 3In the specific embodiment shown, the conductive layer 13 is formed on the surface of the substrate layer 11 in a mesh structure with holes 131. By partially covering the substrate layer 11, a portion of the surface is bonded to the adhesive layer 12, thereby avoiding the problem of reduced adhesion caused by the conductive layer 13. This improves antistatic properties while avoiding the defect of reduced adhesive layer adhesion.

[0036] Of course, since the conductive layer 13 partially covers the substrate layer 11, the area of ​​the exposed part of the substrate layer 11 is reduced. In order to improve the adhesion of the substrate layer 11, the surface of the substrate layer 11 can be subjected to corona treatment or activation treatment to improve the surface roughness of the substrate layer 11 and further improve the adhesion between the substrate layer 11 and the adhesive layer 12.

[0037] In addition, to facilitate the smooth peeling of the protective film 10 from the surface of the optical film 20, in the illustrated embodiment, the antistatic optical protective film of this application is provided with outwardly protruding tabs 111. The conductive layer 13 has protrusions corresponding to the shape of the tabs 111. Therefore, during the peeling operation, the tabs 111 and the conductive layer 13 can be held by conductive equipment or by the worker's hand or antistatic gloves, allowing static electricity to be smoothly conducted away during the peeling process. In this case, the substrate layer 11 of the protective film 10 does not actually need to contain an antistatic agent; the problem of static electricity residue can be solved simply by the combination of the conductive adhesive layer 12 and the conductive layer 13. Of course, without the tabs 111 and the corresponding conductive layer protrusions, static electricity needs to be conducted from the inside to the outside of the substrate layer 11 during peeling. Therefore, the substrate layer 11 in this case needs to be composed of a polyester film containing an antistatic agent.

[0038] Furthermore, based on the structure of the antistatic optical protective film proposed in this application, this application also proposes a method for preparing the aforementioned antistatic optical protective film. Specifically, the preparation method of this application includes the following steps: providing a substrate layer 11; forming a conductive layer 13 on one side surface of the substrate layer 11 by vapor deposition or vacuum sputtering; coating and curing an adhesive layer 12 containing an antistatic agent on the outside of the conductive layer 13 of the substrate layer 11; and preparing the antistatic optical protective film 10. The substrate layer 11 provided may or may not contain an antistatic agent. That is, without the tabs 111, the substrate layer 11 of this application needs to contain an antistatic agent, while with the tabs 111, the substrate layer may or may not contain an antistatic agent.

[0039] Correspondingly, the preparation method of this application may further include the following steps: die-cutting the prepared antistatic optical protective film to form outwardly protruding tabs 111. Evaporation or vacuum sputtering typically forms a conductive layer 13 across the entire width of the substrate layer 11. Therefore, die-cutting allows for the simultaneous formation of the tabs 111 and the corresponding protrusions of the conductive layer 13. Furthermore, the coating of the adhesive layer 12 can be set according to the size of the optical film 20. Therefore, no adhesive is needed at the location of the tabs 111. Thus, when the protective film is attached to the optical film 20, there will be no adhesive at the location of the tabs 111, and there is no need to worry about stickiness or dust accumulation. Figure 2 and 3 As shown.

[0040] Furthermore, the preparation method of this application may further include the following steps: subjecting the surface of the substrate layer 11 to corona treatment or activation treatment, and partially masking the surface to form a conductive layer 13 that partially covers the surface of the substrate layer 11. During evaporation or vacuum sputtering, metal vapor adheres to the entire surface of the substrate layer 11. In order to obtain... Figure 2 or Figure 3 The structure of the conductive layer 13 shown requires the use of baffles or other structures to shield the parts where the conductive layer 13 does not need to be formed, so that the conductive layer 13 can be formed to partially cover the surface of the substrate layer 11.

[0041] In another specific embodiment of this application, the preparation method may further include the following steps: attaching a masking film (not shown in the figure) corresponding to the shape of the conductive layer 13 to the surface of the substrate layer 11; forming the conductive layer 13 in the gaps of the masking film by vapor deposition or vacuum sputtering; removing the masking film and then forming an adhesive layer 12 on the outside of the conductive layer 13. Compared with the baffle solution, the masking film solution used in this embodiment can achieve continuous vapor deposition or sputtering of the entire substrate layer 11, which can greatly improve production efficiency, while the baffle solution can only form a portion of the conductive layer 13 before proceeding to the next part of the production.

[0042] Those skilled in the art should understand that although this application is described by way of multiple embodiments, not every embodiment contains only one independent technical solution. This description is merely for clarity, and those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of this application.

[0043] The above description is merely an illustrative embodiment of this application and is not intended to limit the scope of this application. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of this application shall fall within the scope of protection of this application.

Claims

1. An antistatic optical protective film, used to be attached to the working surface of an optical thin film (20) for protection, characterized in that, The antistatic optical protective film (10) includes at least a substrate layer (11) and an adhesive layer (12) for bonding with the optical film (20); wherein the substrate layer (11) is composed of a polyester film containing or not containing an antistatic agent, and the adhesive layer (12) is composed of a thermosetting adhesive or a UV-curing adhesive containing an antistatic agent; a conductive layer (13) is formed between the substrate layer (11) and the adhesive layer (12); the conductive layer (13) is formed on the side surface of the substrate layer (11) opposite to the adhesive layer (12) by vapor deposition or vacuum sputtering of a metal conductive material, and the conductive layer (13) partially covers the surface of the substrate layer (11); the antistatic optical protective film is provided with outwardly protruding tabs (111), and the conductive layer (13) has protrusions corresponding to the shape of the tabs (111).

2. The antistatic optical protective film as described in claim 1, characterized in that, The conductive layer (13) is formed on the surface of the substrate layer (11) in a diagonal cross structure.

3. The antistatic optical protective film as described in claim 1, characterized in that, The conductive layer (13) is formed on the surface of the substrate layer (11) in a mesh structure with holes (131).

4. A method for preparing the antistatic optical protective film as described in claim 1, characterized in that, The process includes the following steps: providing a substrate layer (11), partially masking the surface of the substrate layer (11), forming a conductive layer (13) partially covering the surface of the substrate layer (11) by vapor deposition or vacuum sputtering on one side of the substrate layer (11), coating and curing an adhesive layer (12) containing an antistatic agent on the outside of the conductive layer (13) of the substrate layer (11), die-cutting the obtained antistatic optical protective film to form outwardly protruding tabs (111) and making the conductive layer (13) form protrusions corresponding to the shape of the tabs (111), and obtaining the antistatic optical protective film (10).

5. The preparation method according to claim 4, characterized in that, The preparation method further includes the following steps: subjecting the surface of the substrate layer (11) to corona treatment or activation treatment.

6. The preparation method according to claim 4, characterized in that, The preparation method further includes the following steps: attaching a masking film corresponding to the shape of the conductive layer (13) to the surface of the substrate layer (11), forming the conductive layer (13) in the gaps of the masking film by vapor deposition or vacuum sputtering, removing the masking film, and then forming an adhesive layer (12) on the outside of the conductive layer (13).

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