Film for acoustic components, film for acoustic components with release film, acoustic components, laminate and acoustic transducer

Abstract

To provide a film for acoustic component that can be peeled off without tearing from the release film when the release film is peeled off before molding, while maintaining high shape retention before molding and high formability and mold-following property during molding.SOLUTION: A film for acoustic component is curable and has the following (a) viscoelastic properties. (a) Storage modulus E' at a measurement temperature of 20°C and a frequency of 10 Hz is between 0.1 MPa and 500 MPa.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film for acoustic members, a film for acoustic members with a release film, and an acoustic member, a laminate, and an acoustic transducer obtained from these. [Background technology]

[0002] For example, the widespread use of small electronic devices such as smartphones, PDAs, notebook computers, DVD players, LCD TVs, digital cameras, and portable music players has led to an increasing demand for small speakers (usually called microspeakers) and receivers used in these electronic devices, as well as small electroacoustic transducers such as microphones and earphones. Polyetherimide (PEI) resin, polyether ether ketone (PEEK) resin, and the like are widely used for the diaphragms used in these electroacoustic transducers.

[0003] In recent years, the use of silicone resins in the above-mentioned diaphragms has also been considered. For example, Patent Document 1 discloses a diaphragm sheet formed by sequentially laminating a release sheet, a first layer made of an uncured liquid silicone composition, and a second layer mainly containing thermoplastic polyurethane, and a method for manufacturing a diaphragm using this diaphragm sheet. In Patent Document 1, the diaphragm sheet is set in a mold and shaped, and then the release sheet is peeled off from the molded product to manufacture a diaphragm. The diaphragm sheet described in Patent Document 1 uses an uncured liquid silicone composition, which allows for high shaping during molding and also allows for high mold conformability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-152817 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, in Patent Document 1, the diaphragm sheet is formed by setting the first layer made of an uncured liquid silicone composition with the release film laminated on it in a mold. Therefore, it is necessary to peel off the release film after molding, but the heat and pressure applied during molding often make it difficult to peel the release film from the first layer, reducing workability and making mass production difficult. Therefore, it is desirable to peel off the release film from the diaphragm sheet before setting it in a mold such as a metal die. However, there is a problem in that the first layer made of the uncured liquid silicone composition is torn when the release film is peeled off. Furthermore, without the release film, the diaphragm sheet of Patent Document 1 has poor shape retention before shaping.

[0006] Therefore, an object of the present invention is to provide a film for acoustic components that has shape retention before molding, shapeability and mold-following ability during molding, and can be peeled off from the release film without tearing when the release film is peeled off before molding. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by providing a film having a specific storage modulus, and have completed the present invention as described below.

[0008] That is, the present invention provides the following [1] to

[11] . [1] A film for acoustic components that is curable and has the following viscoelastic properties (a): (a) The storage modulus E' at a measurement temperature of 20°C and a frequency of 10 Hz is 0.1 MPa or more and 500 MPa or less. [2] The film for acoustic components according to [1] above, which has thermosetting properties. [3] A film for acoustic components according to [1] or [2] above, which has a crosslinked structure. [4] The film for acoustic components according to any one of the above [1] to [3], which has a gel fraction of 90% or less. [5] The film for acoustic components according to any one of the above [1] to [4], which is a silicone film. [6] The film for acoustic components according to any one of the above [1] to [5], which has the following viscoelastic properties (b) to (d) after curing: (b) Storage modulus E' at a measurement temperature of 20°C and a frequency of 10 Hz 20 is 0.1MPa or more and 500MPa or less. (c) Storage modulus E' at a measurement temperature of 100°C and a frequency of 10 Hz 100 is 0.1MPa or more and 500MPa or less. (d) E' above 100 / E' 20 is 0.4 to 1.0. [7] A film for acoustic components with a release film, comprising the film for acoustic components according to any one of [1] to [6] above and a release film provided on at least one side of the film for acoustic components. [8] An acoustic component obtained by curing the film for acoustic components according to any one of [1] to [6] above. [9] A laminate obtained by laminating the film according to any one of the above [1] to [6] on a mold and thermoforming it.

[10] An acoustic component obtained by peeling the laminate described in [9] above from the mold.

[11] An acoustic transducer comprising the acoustic member described in [8] or

[10] above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a film for acoustic components that has shape retention before molding, shapeability during molding, and can be peeled off from a release film without tearing when the release film is peeled off before molding. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing the structure of a micro speaker diaphragm 1 according to one embodiment of the present invention. [Figure 2] FIG. 10 is a cross-sectional view showing the structure of a micro-speaker diaphragm 11 according to another embodiment of the present invention. [Figure 3]FIG. 10 is a plan view showing the structure of a micro-speaker diaphragm 21 according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below as long as they do not depart from the gist of the present invention. The boundary between a film and a sheet is not clear, and therefore, in the present invention, the term "film" encompasses "sheet."

[0012] [Film for acoustic components] The film for acoustic members of the present invention (hereinafter also referred to as the present film) has the following viscoelastic property (a). (viscoelastic properties) (a) The storage modulus E' at a measurement temperature of 20°C and a frequency of 10 Hz is 0.1 MPa or more and 500 MPa or less. When the storage modulus E' is 0.1 MPa or more, the film has a moderate hardness, which makes it easy to peel from the release film and eliminates the risk of tearing during peeling. Furthermore, the film can retain its shape even after the release film is peeled off. On the other hand, when the storage modulus E' is 500 MPa or less, the film has a moderate flexibility, which allows it to conform to the mold and be shaped during molding. From the above viewpoints, E' is preferably 0.5 MPa or more and 300 MPa or less, more preferably 0.8 MPa or more and 200 MPa or less, and even more preferably 1.0 MPa or more and 100 MPa or less.

[0013] Furthermore, the present film preferably has the following viscoelastic properties (b) to (d) after curing. (b) Storage modulus E' at a measurement temperature of 20°C and a frequency of 10 Hz 20 is 0.1MPa or more and 500MPa or less. (c) Storage modulus E' at a measurement temperature of 100°C and a frequency of 10 Hz 100 is 0.1MPa or more and 500MPa or less. (d) E' above 100 / E' 20is 0.4 to 1.0.

[0014] (b) Storage modulus E' at a measurement temperature of 20°C and a frequency of 10 Hz 20 When E' is 0.1 MPa or more, the hardness after curing is constant, and the handling property after curing is good. 20 When the storage modulus E' at 20°C after curing is 500 MPa or less, the acoustic characteristics such as the sound quality and reproducibility of the diaphragm tend to be excellent. 20 is more preferably 1 MPa or more and 400 MPa or less, further preferably 2 MPa or more and 200 MPa or less, and particularly preferably 4 MPa or more and 50 MPa or less.

[0015] Also, (c) Storage modulus E' at a measurement temperature of 100°C and a frequency of 10 Hz 100 When the storage modulus E' is 0.1 MPa or more and 500 MPa or less, the heat resistance is good and it is expected that excellent acoustic properties can be obtained even in a high temperature environment. 100 The pressure is more preferably 1 MPa or more and 400 MPa or less, further preferably 2 MPa or more and 200 MPa or less, and particularly preferably 4 MPa or more and 50 MPa or less.

[0016] Also, (d) the ratio of storage moduli (E' 100 / E' 20 By setting the value of σ in the range of 0.4 to 1.0, the change in elastic modulus with temperature change is small, and heat resistance tends to be good. In addition, since the change in elastic modulus when heated is small, sound quality is less likely to deteriorate in high-temperature environments, and it becomes easier to maintain excellent sound reproduction from low to high temperature ranges. From the above viewpoint, the above ratio (E' 100 / E' 20 ) is more preferably 0.5 to 0.99, even more preferably 0.55 to 0.97, and even more preferably 0.6 to 0.95.

[0017] The present film may be a single-layer film or a laminated film as long as it has the viscoelastic property (a) above and preferably has the viscoelastic properties (b) to (d) above after curing. However, to satisfy the requirement (a) above, it is essential that the film has a certain degree of hardness. In the case of a laminated film, it is desirable that at least one layer of the multilayer film has a certain degree of hardness. In the case of a monolayer film, it is preferable that the film has a crosslinked structure to a degree that satisfies the above condition (a), and in consideration of the flexibility of the film, its ability to conform to a mold during molding, and its shaping ability, it is preferable that the film has an appropriate degree of crosslinking. That is, in terms of hardness, it is preferable that the film is harder than an uncrosslinked film and softer than a fully cured film (a low hardness film).

[0018] Furthermore, in the case of a multilayer film, it is sufficient that some of the layers have a crosslinked structure and high hardness (hereinafter, this may be referred to as a "highly cured layer"). That is, the present film preferably has at least one highly cured layer and at least one uncured layer. Specific examples include a two-layer structure of highly cured layer / uncured layer, a two-type three-layer structure of highly cured layer / uncured layer / highly cured layer, or an uncured layer / highly cured layer / uncured layer. Furthermore, for example, a four-layer structure with two intermediate layers may be used, and an adhesive layer may be present between each layer. In this way, in the case of a laminate film, it is easy to obtain a laminate film that satisfies the above condition (a) by designing one of the layers to have a high hardness, and a laminate structure of highly cured layer / uncured layer / highly cured layer is particularly preferred. The uncured layer herein includes not only a completely uncrosslinked layer but also a partially crosslinked layer, and for example, the above-mentioned low-hardness film can be used as the uncured layer. The gel fraction of the uncured layer is preferably lower than that of the highly cured layer.

[0019] (gel fraction) The present film preferably has a gel fraction of 90% or less. When the gel fraction is 90% or less, the film can be made flexible before molding, sufficient hardening is achieved during molding, and moldability and conformability to a mold are obtained, resulting in moldability sufficient for practical use. From the viewpoint of shaping property and moldability, the gel fraction is preferably 85% or less, more preferably 80% or less. The lower limit of the gel fraction is not particularly limited as long as it is 0% or more, but is preferably 10% or more, more preferably 20% or more. If the gel fraction is 10% or more, it becomes easy to adjust the above condition (a) within the above-mentioned predetermined range, and the present film becomes less likely to tear when the release film is peeled off before molding.

[0020] As described above, the film preferably has at least one highly cured layer and at least one uncured layer. The uncured layer preferably has a gel fraction of 0% or more and less than 80%. When the gel fraction of the uncured layer is less than 80%, the film before molding is easily made flexible, and since the film can be sufficiently cured during molding, the film has sufficient shapeability and conformability to the mold, improving moldability. From the viewpoint of formability and molding, the gel fraction of the uncured layer is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 60% or less. The gel fraction of the intermediate layer is not particularly limited as long as it is 0% or more, but may be, for example, 10% or more, or 20% or more.

[0021] On the other hand, the gel fraction of the highly hardened layer is preferably 80% or more. When the gel fraction of the outermost and innermost layers is 80% or more, the film can be easily peeled from the release film and there is less risk of tearing during peeling. Furthermore, by increasing the gel fraction as described above, the shape retention of the film can be further improved even before the film is hardened. From the above viewpoints, the gel fraction of the highly hardened layer is more preferably 85% or more, and even more preferably 90% or more. The upper limit of the gel fraction of the highly hardened layer is not particularly limited as long as it is 100% or less, but it may generally be lower than 100%, for example, 99% or less.

[0022] Regardless of whether the film is single layer or laminated, if the gel fraction in the film surface is 75% or more, it is possible to prevent the film from becoming difficult to remove from the mold after being pressed between the pressing molds.

[0023] The gel fraction can be measured as follows. 1) Take a sample of approximately 100 mg from the entire film, or from the middle layer, outermost layer, or innermost layer of the film, and measure the mass (a) of the sample. 2) The collected sample is immersed in chloroform at 23°C for 24 hours. 3) Remove the solid content from the chloroform and dry it in vacuum at 50°C for 7 hours. 4) Measure the mass (b) of the solid content after drying. 5) Using the masses (a) and (b), calculate the gel fraction based on the following formula (i).

[0024]

number

[0025] As is clear from the above measurement method, the gel fraction is calculated by including not only the crosslinked components contained in the film but also insoluble components other than the crosslinked components, such as fillers, as gel components. However, for the intermediate layer of the present film before curing, the gel fraction is calculated from the ratio of the gel fraction to the layer thickness of the entire present film and the outermost and innermost layers before curing.

[0026] The present film is a curable film, and the type of curing may be photocurable, moisture curable, or thermosetting, but thermosetting is preferred. The thermosetting nature of the present film allows it to be cured when heated and shaped, resulting in improved formability. Furthermore, when the present film is thermosetting, its gel fraction increases when heated.

[0027] The present film preferably has a crosslinked structure. Having a moderate crosslinked structure makes it easier to obtain a monolayer film that satisfies the requirement for the viscoelastic property (a), as described above. Furthermore, shape retention before curing (i.e., before molding) is more likely to be improved. Furthermore, when the present film is a laminated film, as described above, by having at least one layer of the multilayer structure having a crosslinked structure, it becomes easier to obtain a film that satisfies the requirement of the viscoelastic property (a) above. Such a film can easily improve its shape retention without significantly impairing the flexibility of the film before curing.

[0028] The thickness of the present film is not particularly limited, but is preferably 5 μm to 500 μm, more preferably 15 μm to 400 μm, and even more preferably 30 μm to 300 μm. If the film thickness is within this range, a molded product with a thickness suitable for a diaphragm can be produced.

[0029] (Tensile elongation at break) The present film preferably has a tensile breaking elongation of 100% or more, more preferably 200% or more, and even more preferably 300% or more, after curing. If the tensile breaking elongation is within this range, the toughness of the film increases, making it less likely to break due to prolonged vibration and tending to have excellent durability when used in acoustic components such as diaphragms. The higher the tensile breaking elongation, the better, and although there is no particular upper limit, it is usually 1500% or less.

[0030] The storage modulus and tensile elongation at break may be measured by the methods described in the Examples, but the storage modulus and tensile elongation at break in the cured state may be measured for a film cured so that the gel fraction of the entire film is 80% or more. Specific methods for curing the film to a gel fraction of 80% or more include, for example, curing by heating and curing by radiation. When curing is performed by heating, the heating temperature during curing is preferably 180°C or higher and 260°C or lower, more preferably 190°C or higher and 250°C or lower, and even more preferably 200°C or higher and 240°C or lower. The heating time is preferably from 1 second to 5 minutes, more preferably from 5 seconds to 4 minutes, even more preferably from 10 seconds to 3 minutes, and particularly preferably from 20 seconds to 2 minutes. The pressure during heating is preferably 0.01 MPa or more and 100 MPa or less, and more preferably 0.1 MPa or more and 50 MPa or less. On the other hand, in the case of radiation curing, electron beams, X-rays, gamma rays, etc. can be used as radiation for radiation crosslinking, and by adjusting the type of radiation used and the cumulative exposure dose, the film can be cured to a gel fraction of 80% or more. The details of the methods for measuring the storage modulus and tensile elongation at break are as described in the Examples, and when the film has directionality, measurements should be made in TD (the direction perpendicular to the resin flow direction).

[0031] The present film is composed of a resin layer, and the resin constituting the resin layer is preferably a curable resin, more preferably a thermosetting resin. Specific examples of preferred resins include epoxy resins, urethane resins, silicone resins, acrylic resins, phenolic resins, unsaturated polyester resins, polyimide resins, and melamine resins. When the present film is a multilayer film, it is preferable that all layers are resin layers. Furthermore, in each layer of the present film, these resins may be used alone or in combination of two or more. In addition, when the present film is a multilayer film, each layer may use the same type of resin or different types of resin, but it is preferable to use the same type of resin, which makes it easier to bond each layer together without using an adhesive layer, etc.

[0032] Furthermore, the present film is preferably a silicone film. In the case of a multilayer film, the term "silicone film" means that some of the layers may use silicone resin as the resin, but it is particularly preferable that all layers use silicone resin. When the present film is a silicone film, the heat resistance, mechanical strength, etc. are improved, and the above-mentioned viscoelastic properties (a) and (b) to (d) are also easily satisfied. Furthermore, the tensile elongation at break can be easily adjusted to fall within the above-mentioned desired range.

[0033] (organopolysiloxane) The silicone resin used in the present film includes organopolysiloxane. The organopolysiloxane has, for example, a structure represented by the following formula (ii). R n SiO (4-n) / 2 (ii) Here, R may be the same or different, and are substituted or unsubstituted monovalent hydrocarbon groups, preferably monovalent hydrocarbon groups having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and n is a positive number of 1.95 to 2.05.

[0034] Examples of R include alkyl groups such as a methyl group, ethyl group, propyl group, butyl group, hexyl group, and dodecyl group; cycloalkyl groups such as a cyclohexyl group; alkenyl groups such as a vinyl group, allyl group, butenyl group, and hexenyl group; aryl groups such as a phenyl group and tolyl group; aralkyl groups such as a β-phenylpropyl group; and groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with halogen atoms, cyano groups, or the like, such as a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group.

[0035] The organopolysiloxane preferably has its molecular chain terminals blocked with trimethylsilyl groups, dimethylvinyl groups, dimethylhydroxysilyl groups, trivinylsilyl groups, or the like. The organopolysiloxane preferably has at least two alkenyl groups in the molecule. Specifically, it is preferred that the alkenyl groups account for 0.001 mol % to 5 mol %, preferably 0.005 mol % to 3 mol %, more preferably 0.01 mol % to 1 mol %, and particularly preferably 0.02 mol % to 0.5 mol % of the R groups, and it is particularly preferred that the organopolysiloxane contains vinyl groups. The organopolysiloxane is basically a linear diorganopolysiloxane, but may be partially branched. It may also be a mixture of two or more different molecular structures.

[0036] The organopolysiloxane constituting the resin layer of the present film is preferably crosslinked with a crosslinking agent, preferably an organic peroxide. Therefore, the resin layer is preferably a cured product obtained by curing a resin composition containing an organopolysiloxane and a crosslinking agent such as an organic peroxide. In this case, the resin layer is preferably cured so that the gel fraction falls within the desired range. In the case of the above-mentioned monolayer film, it is preferable that it has an appropriate crosslinked structure and appropriate hardness. It is preferable that it is in a semi-cured state so that the gel fraction is within the above-mentioned desired range. Therefore, it is preferable that the organic peroxide blended into the resin layer constituting the monolayer film is partially decomposed and partially undecomposed and remains in the form of organic peroxide in the resin layer.

[0037] On the other hand, when the present film is a multilayer film, it preferably has at least a highly cured layer and an uncured layer. In the highly cured layer, the organopolysiloxane is preferably crosslinked with an organic peroxide, and the organic peroxide is decomposed and hardly contained. On the other hand, the uncured layer is preferably made of a resin composition containing an organopolysiloxane and a crosslinking agent such as an organic peroxide, and is in an uncured state or a semi-cured state even if cured so that the gel fraction falls within the desired range described above. The organic peroxide blended in the uncured layer is preferably hardly decomposed and is contained in the uncured layer in the form of organic peroxide.

[0038] Furthermore, when the present film is, for example, a two-kind, three-layer laminate film, there are embodiments in which the front and back layers are highly cured layers and the middle layer is an uncured layer, and there are also embodiments in which the front and back layers are uncured layers and the middle layer is a highly cured layer. In either layer configuration, the organopolysiloxane in the uncured layer is in an uncrosslinked state or, if crosslinked, is in a partially crosslinked state (semi-cured state), and the organic peroxide is hardly decomposed and is contained in the uncured layer in the organic peroxide state. On the other hand, in the highly cured layer, the organopolysiloxane is preferably crosslinked by the organic peroxide, and the organic peroxide is decomposed and hardly contained.

[0039] Examples of organic peroxides include alkyl peroxides such as di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, and aralkyl peroxides such as 2,4-dicumyl peroxide. From the viewpoints of crosslinking rate and safety, alkyl peroxides, particularly 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, are preferred.

[0040] The amount of organic peroxide in the resin composition forming the resin layer is preferably 0.01% by mass to 10% by mass, more preferably 0.03% by mass to 5% by mass, even more preferably 0.05% by mass to 4% by mass, particularly preferably 0.1% by mass to 3% by mass, and particularly preferably 0.3% by mass to 2% by mass, based on the total amount of the resin composition. If the amount of organic peroxide is within this range, a composition with a sufficient curing rate tends to be obtained safely. The organic peroxide contained in the resin composition is mostly decomposed and hardly contained in the highly cured layer, but it is preferable that the organic peroxide be contained within the above-mentioned range in the uncured layer.

[0041] The resin composition is preferably a millable type containing an organopolysiloxane. Millable type resin compositions are non-liquid (e.g., solid or paste-like) and lack self-flowing properties at room temperature (25°C) in an uncured state, but can be uniformly mixed using a kneader, as described below. The use of a millable type resin composition in this film improves productivity when processing the resin composition into an intermediate layer or the outermost or innermost layer in the case of a laminated film.

[0042] As described above, the resin composition forming the resin layer may use a resin other than a silicone resin (organopolysiloxane), and in that case, the outermost and innermost layers may be layers formed by curing a resin composition containing a resin and a crosslinking agent so that the gel fraction falls within a desired range. Similarly, the intermediate layer may be formed from a resin composition containing a resin and a crosslinking agent, but in this case, the resin composition may be uncured or semi-cured so that the gel fraction falls within the above-mentioned predetermined range.

[0043] The resin layer constituting the present film may contain a filler such as a silica-based filler. By incorporating a filler, the present film can more easily maintain appropriate ranges for the film's mechanical properties, such as its storage modulus and tensile elongation at break. Furthermore, the use of a filler makes it easier to adjust the viscosity and hardness of the resin composition, and also makes it easier to optimize the balance between the fluidity and secondary processability of the resin composition. Another advantage is that the hardness can be easily adjusted to suit the design and acoustic characteristics of the acoustic component. In addition, the filler constitutes a part of the gel fraction in the measurement of the gel fraction, and the gel fraction of each layer increases by including the filler. Even if the gel fraction increases by including the filler, the hardness of each layer can be increased, just as in the case where the gel fraction increases due to crosslinking.

[0044] Examples of silica-based fillers include fumed silica and precipitated silica, and may be silica-based fillers whose surfaces have been treated with a silane coupling agent. The content of the filler in each layer is, for example, 10% by mass to 50% by mass, preferably 15% by mass to 40% by mass, and more preferably 20% by mass to 35% by mass, based on the total amount of the resin composition constituting each layer. The average particle size of the filler is, for example, 0.01 μm to 20 μm, preferably 0.1 μm to 10 μm, and more preferably 0.5 μm to 5 μm. The average particle size of the filler can be measured as the median diameter (D50) using a particle size distribution analyzer using a laser diffraction method or the like.

[0045] In the present invention, the resin composition for forming the resin layer may contain various additives such as a heat stabilizer, an antioxidant, an ultraviolet absorber, a light stabilizer, an antibacterial / antifungal agent, an antistatic agent, a lubricant, a pigment, a dye, a flame retardant, and an impact resistance modifier, within a range that does not impair the effect.

[0046] When the present film is a laminated film, the resin compositions for forming the layers may have the same composition or different compositions. Note that the composition of the resin composition here means the composition of the resin composition before it is cured.

[0047] In the present invention, commercially available organopolysiloxanes can be used. Alternatively, commercially available mixtures containing an additive such as a silica-based filler in addition to the organopolysiloxane can be used. Specifically, products under the trade names "KE-597-U" and "KE-594-U" manufactured by Shin-Etsu Chemical Co., Ltd. can also be used.

[0048] [Film with release film] The present film described above may be provided with a release film and used as a film with a release film. The film with a release film includes the present film described above and a release film provided on at least one side of the present film. In addition, in the film with release film, it is preferable that release films are provided on both sides of the film.

[0049] The release film may be a resin film or a resin film having a release layer on at least one side of which release treatment has been performed. When the release film has a release layer, it is preferable that the release layer be laminated on the present film so that the release layer is in contact with the present film. Examples of resins used for the resin film include polyolefin resins such as polypropylene, acrylic resins, polystyrene resins, polyacetal resins, polyamide resins, polyester resins, polycarbonate resins, ABS resins, polyether ether ketone resins, etc. Among these, polyester resins are preferred, and polyethylene terephthalate resins are particularly preferred. The thickness of the release film is not particularly limited, but is preferably 5 μm or more and 100 μm or less, more preferably 7 μm or more and 80 μm or less, and even more preferably 10 μm or more and 50 μm or less.

[0050] The present film is protected by the release film attached thereto. This prevents the film from being scratched during transportation, etc. The release film may be the same as the release film laminated during the production of the present film, or may be laminated separately onto the produced present film. The present film is molded, for example, by a molding method as described below, and the release film is preferably peeled off from the present film during molding and then set in a mold such as a die. At this time, the present film can be peeled off from the release film without tearing.

[0051] [Manufacturing method of this film] The present film can be molded by a general molding method, for example, extrusion molding. In the case of a monolayer film, a resin composition for obtaining the monolayer film may be obtained by kneading or the like as described below, and then molded by extrusion molding or the like. Alternatively, the present film with a release film may be obtained by laminating the resin composition between release films by lamination molding. In the case of a single-layer film, it is preferable to semi-cure the film so as to satisfy the viscoelastic property condition (a). The semi-cure conditions are not particularly limited as long as they satisfy the above condition (a). When the present film is a laminated film, it can be formed by, for example, lamination molding, extrusion molding such as co-extrusion, coating, or a combination of these. Among these, lamination molding is preferred in consideration of the ease of forming a multilayer structure with an outermost layer and an intermediate layer.

[0052] When lamination molding is used, it is preferable to first prepare the outermost layer and the innermost layer, and then laminate an intermediate layer between these outermost layer and the innermost layer. More specifically, first, a resin composition for obtaining the outermost layer and the innermost layer (resin composition for the outermost layer or the innermost layer), and a resin composition for obtaining the intermediate layer (resin composition for the intermediate layer) are prepared.

[0053] Each resin composition is not particularly limited, but can be obtained, for example, by kneading the materials that constitute the resin composition. As a kneader used for kneading, a known kneader such as an extruder such as a single-screw or twin-screw extruder, a calendar roll such as a two-roller or three-roller calender roll, a roll mill, a plastomill, a Banbury mixer, a kneader, or a planetary mixer can be used. The kneading temperature is adjusted as appropriate depending on the type and mixing ratio of the resin, and the presence and type of additives. In order to facilitate kneading by appropriately lowering the viscosity of the resin while suppressing crosslinking (curing), the kneading temperature is preferably 20°C or higher and 150°C or lower, more preferably 30°C or higher and 140°C or lower, even more preferably 40°C or higher and 130°C or lower, particularly preferably 50°C or higher and 120°C or lower, and especially preferably 60°C or higher and 110°C or lower. The kneading time may be long enough to uniformly mix the materials constituting the resin composition, and may be, for example, several minutes to several hours, and preferably 5 minutes to 1 hour.

[0054] The method for producing a two-kind, three-layer film of highly cured layer / uncured layer / highly cured layer will be described below. The resin composition for the outermost layer or the innermost layer prepared as described above may be laminated on a release film by a general method to obtain a laminate, and then the laminate may be heated or the like to cure the resin composition, thereby obtaining a laminate in which the outermost layer or the innermost layer is laminated on the release film. When the laminate has a release-treated surface, the resin compositions for the outermost and inner layers are preferably laminated on the release-treated surface of the release film.

[0055] Next, an intermediate layer formed from the intermediate layer resin composition is laminated between the laminate films to obtain the present film. Specifically, the intermediate layer resin composition is introduced in an uncured or semi-cured state between laminate films unwound from two directions, for example, between a pair of rolls. Here, the intermediate layer resin composition is introduced between the laminate films by extruding it from a T-die using an extruder or the like. Furthermore, each laminate film is preferably unwound so that the outermost layer and the innermost layer face each other. Then, the thickness is adjusted by the gap between the rolls as necessary to obtain a laminate in which an uncured or semi-cured intermediate layer is formed between the laminate films. The laminate preferably has a laminate structure of release film / outermost layer / intermediate layer / innermost layer / laminate film, and becomes the above-mentioned film with release film.

[0056] On the other hand, in the case of an uncured layer / highly cured layer / uncured layer configuration, a monolayer film is first obtained by extrusion molding or the like, and then crosslinked and cured to prepare a monolayer film for the highly cured layer. Next, the resin composition for the uncured layer is applied to both sides of the highly cured layer, thereby producing a film of this configuration.

[0057] [Molded products] The present film can be formed into a molded article by molding it in a mold such as a die and curing it, and typically it is formed into various molded articles by molding it in a mold. Curing can be performed depending on the properties of the present film, and can be performed by heating, light irradiation, moisture application, or a combination of these, but is preferably performed by heating. The present film is a film for diaphragms, and the molded article constitutes a diaphragm. When a molded article is to be obtained from the present film, it is preferable to carry out at least the following steps 1 and 2. Step 1: Heating the film, forming it into a mold, and curing the film Step 2: Peeling the molded and cured film (i.e., molded product) from the mold

[0058] Each step will be described in more detail below. (Process 1) In step 1, the film is heated and molded in a mold, and the film is cured to form a molded article. The molded article is preferably formed into a desired shape using a mold. The molding in step 1 is not particularly limited and may be performed by any molding method such as vacuum molding, pressure molding, or press molding. Among these, press molding is preferred because it is easier to form.

[0059] A mold may be prepared according to the molding method, and the mold may have projections and recesses corresponding to the shape of the molded product to be manufactured. A metal mold (metal die) is typically used as the mold, but a resin mold may also be used. For example, as described below, if the molded product (diaphragm) has at least one of a dome shape and a cone shape, the mold may have projections and recesses corresponding to the dome shape or the cone shape. Furthermore, if the molded product (diaphragm) has a tangential edge on its surface, the mold may have projections and recesses corresponding to the tangential edge.

[0060] As described above, a release film may be attached to the film, and the film may be set in the mold after the release film has been peeled off as described above.

[0061] In step 1, the heated film may be shaped in a mold. For example, the film may be placed on a mold and shaped in the mold while being heated, or the film may be preheated and placed on a mold and then shaped in the mold, or a combination of these may be used. The film may be heated by any method. For example, when heating a film placed on a mold, the mold may be heated and the film may be heated by heat transfer, or other methods may be used.

[0062] The heating temperature during shaping or curing is preferably 180° C. or higher and 260° C. or lower, more preferably 190° C. or higher and 250° C. or lower, and even more preferably 200° C. or higher and 240° C. If the temperature during shaping or curing is within this range, the film tends to be able to cure at a sufficient rate without melting or deforming due to heat.

[0063] The shaping time is preferably 1 second to 5 minutes, more preferably 5 seconds to 4 minutes, even more preferably 10 seconds to 3 minutes, and particularly preferably 20 seconds to 2 minutes. If the heat treatment time during shaping is within this range, sufficient curing tends to be achieved while maintaining productivity. The film is preferably cured while being shaped, but may be cured after shaping without any particular limitation. The shaping time refers to the time during which the film is shaped or cured in the mold, and does not include the time required for mold movement before and after shaping, or the time required for releasing the laminate from the mold.

[0064] (Process 2) In step 2, the film formed and cured in step 1 is peeled from the mold to obtain a molded article. In the present invention, the gel fraction of the film is less than a certain value, so the film has high formability and conforms well to the mold. Therefore, the molded article can be produced with high molding precision. In addition, this film has specific viscoelastic properties, resulting in high shape retention and good handling. Furthermore, it can be peeled off from the release film without tearing, and can be easily set in a mold while maintaining its shape. Furthermore, since no release film is laminated, the process of peeling the release film from the molded product can be omitted, making mass production easier.

[0065] In the present invention, the gel fraction of the molded article obtained from the film may be 80% or more. A gel fraction of 80% or more makes it easier to obtain a molded article having a storage modulus and mechanical strength suitable for an acoustic component. The gel fraction of the molded article is more preferably 85% or more, and even more preferably 90% or more. The gel fraction of the molded article is not particularly limited in its upper limit, and may be 100% or less, but generally may be lower than 100%, for example, 99% or less. The gel fraction of the molded article refers to the gel fraction of the entire molded article, and may be measured by sampling uniformly in the thickness direction of the molded article. Details of the method for measuring the gel fraction are as described above.

[0066] [Film uses] As described above, the film of the present invention can be suitably used for acoustic components. The acoustic component of the present invention is obtained by curing the film, and specifically, may be the molded product described above. The acoustic component is preferably a diaphragm, specifically, a speaker diaphragm, and can be suitably used particularly as a micro-speaker diaphragm for mobile phones and the like.

[0067] This film can be formed into various acoustic components such as diaphragms by being appropriately shaped. The acoustic member may have, for example, at least a portion thereof in a dome or cone shape. The acoustic member may also have a tangential edge on its surface. When the acoustic member has a dome or cone shape or a tangential edge, it is preferably used as a diaphragm, more preferably as a speaker diaphragm.

[0068] (diaphragm) To explain the diaphragm in more detail, the shape of the diaphragm is not particularly limited and can be any shape, such as a circle, an ellipse, or an oval. A diaphragm generally has a body that vibrates in response to an electrical signal and an edge surrounding the body. The body of the diaphragm is usually supported by the edge. The shape of the diaphragm may be a dome or a cone, as described above, or a combination of these shapes, or any other shape commonly used for diaphragms.

[0069] The film may form at least a portion of the acoustic member, for example, the body or edge of the diaphragm may be formed by the film, and the edge or body of the diaphragm may be formed by another member. Of course, both the body and edge may be integrally formed by the film, or the entire diaphragm may be formed by the film.

[0070] 1 is a diagram showing the structure of a diaphragm 1 according to one embodiment of the present invention, and is a cross-sectional view of the diaphragm 1, which is circular in plan view, cut along a plane passing through the center line of the circle. The diaphragm 1 is a diaphragm for a micro speaker. As shown in FIG. 1, the diaphragm 1 has a dome portion (body) 1a at the center, a recessed portion 1b to be attached to a voice coil 2, a peripheral portion (edge) 1c, and an external attachment portion 1d on the outer periphery to be attached to a frame or the like.

[0071] FIG. 2 is a diagram showing the structure of diaphragm 11 according to another embodiment of the present invention, and is a cross-sectional view of diaphragm 11, which is circular in plan view, cut along a plane passing through the center line of the circle. Diaphragm 11 is a diaphragm for a micro-speaker. As shown in FIG. 2, diaphragm 11 has a dome-shaped dome portion (body) 11a at its center, a recessed portion 11b attached to voice coil 2, a cone portion 11j machined into a cone shape, and a peripheral portion (edge) 11c. As shown in diaphragm 11, the diaphragm may have a portion machined into a dome shape and the remaining portion machined into a cone shape. Note that diaphragm 11 may have peripheral portions 11c attached directly to a frame or the like, or may be attached to a frame or the like via another member.

[0072] As described above, a tangential edge may be provided on the surface of the diaphragm. The tangential edge may be, for example, a groove having a V-shaped cross section. FIG. 3 shows a plan view of diaphragm 21 according to another embodiment of the present invention. Diaphragm 21 has tangential edge portion 21g, in which multiple tangential edges 21e are provided on the outer periphery of circular dome portion (body) 21a, and tangential edge portion 21h, in which multiple tangential edges 21f are provided around tangential edge portion 21g. Note that while FIG. 3 shows an example in which two tangential edge portions are provided along the radial direction, only one tangential edge portion or three or more tangential edge portions may be provided along the radial direction.

[0073] As mentioned above, the diaphragm is preferably a speaker diaphragm, particularly a micro speaker diaphragm. From the viewpoint of suitable use as a micro speaker diaphragm, the size of the diaphragm is such that the maximum diameter is 25 mm or less, preferably 20 mm or less, and the maximum diameter is preferably 5 mm or more. Note that the maximum diameter refers to the diameter when the diaphragm is circular, and refers to the major axis when the diaphragm is elliptical or oval.

[0074] The diaphragm may be formed from the present film alone, or may be formed from a composite material of the present film and another material. For example, as described above, either the edge or the body may be formed from another material.

[0075] Furthermore, in order to improve the suitability for secondary processing of the diaphragm, its dust resistance, or to adjust its acoustic characteristics and improve its design, the surface of the diaphragm may be further treated as appropriate by coating it with an antistatic agent, vapor-depositing a metal, sputtering it, coloring it (black, white, etc.), etc. Furthermore, it may be appropriately laminated with a metal such as aluminum, or combined with a nonwoven fabric, etc.

[0076] (acoustic transducer) The acoustic transducer of the present invention is an acoustic transducer comprising the above-mentioned acoustic member, preferably a diaphragm. The acoustic transducer is typically an electro-acoustic transducer, and examples thereof include a speaker, a receiver, a microphone, and an earphone. Of these, the acoustic transducer is preferably a speaker, and a micro-speaker for a mobile phone or the like is suitable. [Example]

[0077] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0078] [Evaluation and measurement methods] In this example, various physical properties were measured and the film was evaluated as follows.

[0079] (1) Storage modulus E' Test pieces measuring 4 mm x 8 cm were cut from the pre-cured and cured films obtained in each Example and Comparative Example to obtain measurement samples. Measurements were performed using the measurement samples in accordance with JIS K7244-4:1999 using a viscoelasticity spectrometer "DVA-200 (manufactured by IT Measurement & Control Co., Ltd.)." The films before press molding were measured in tensile mode at a frequency of 10 Hz, a strain of 0.1%, a temperature range of -100 to 300°C, and a heating rate of 3°C / min, and the storage modulus at 20°C was measured. The films after press molding were also measured at a frequency of 10 Hz, a strain of 0.1%, a temperature range of -100 to 300°C, and a heating rate of 3°C / min, and the storage modulus at 20°C and 100°C was measured. Measurements were performed on the TD.

[0080] (2) Measurement of gel fraction According to the method described in the specification, the gel fraction of the entire film before curing, the gel fraction of the outermost and innermost layers of the film before curing, and the gel fraction of the entire film after curing were measured. When measuring the gel fraction of the entire film, a sample was cut in a direction parallel to the thickness direction of the film. In addition, the gel fraction of the middle layer of the film before curing was calculated from the ratio of the gel fraction of the entire film and the outermost and innermost layers to the layer thickness before curing.

[0081] (3) Handling (3-1) Presence or absence of tears In each example and comparative example, the present film was produced with a release film laminated on the top and back surfaces. The release films on the top and back surfaces were manually peeled off from the obtained pre-cured present film, and the presence or absence of tearing was evaluated. Films in which the release films could be peeled off without tearing were evaluated as "good," and films in which a portion of the film was torn due to the release film were evaluated as "poor." In addition, when various evaluations and measurements were performed other than for the presence or absence of tear, the film was used with the release film removed. (3-2) Shape retention The shape retention of the pre-cured films obtained in each Example and Comparative Example was evaluated. When the film was peeled from the release film and used for various evaluations and measurements, the film was evaluated as "good" if it could be easily handled because it maintained its shape, and evaluated as "poor" if it could not maintain its shape and bent during handling, causing the film to become tangled or break.

[0082] (4) Tensile elongation at break The elongation at which the cured film broke was measured in TD at a tensile speed of 200 mm / min in an environment of 23°C according to a method in accordance with JIS K7161:2014.

[0083] (5) Moldability / formability A test piece measuring approximately 7 cm x 10 cm was cut out from the film obtained in each example and comparative example to serve as an evaluation sample. The evaluation sample was sandwiched between a dome-shaped diaphragm mold with a tangential edge preheated to 240°C and pressed at a pressure of 0.6 MPa. The pressurized state was maintained for 30 seconds, and the sample was then removed from the mold.

[0084] (6) Adhesion to the mold As in the evaluation of moldability and shapability described above, test pieces of approximately 7 cm x 10 cm were cut out from the films obtained in each Example and Comparative Example to serve as evaluation samples. The evaluation samples were sandwiched between a diaphragm mold preheated to 240°C and pressed at a pressure of 0.6 MPa. The pressurized state was maintained for 30 seconds, and the samples were then removed from the mold.

[0085] Example 1 Two release films were prepared: PET film (1) with a surface roughness (Ra) of 0.88 μm and PET film (2) with a surface roughness (Ra) of 1.9 μm. A 20 μm thick silicone rubber (product name "TSE2571-5U", manufactured by Momentive Performance Materials) was laminated between PET film (1) and PET film (2), and the cured laminated film was prepared. PET film (1) was then peeled off to expose the cured silicone. 100 parts by mass of a mixture containing organopolysiloxane and silica (trade name "KE-597-U", manufactured by Shin-Etsu Chemical Co., Ltd.) and 1 part by mass of an organic peroxide (trade name "C-8B", manufactured by Shin-Etsu Chemical Co., Ltd., 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, containing approximately 40% by mass of organic peroxide) were kneaded using a planetary mixer at a temperature of 90°C for 10 minutes to obtain a millable type resin composition (1). The two laminated films obtained above were fed along two 100 mm diameter calendar rolls with the silicone-exposed surface facing inward, and resin composition (1) was added between the laminated films between the calendar rolls to form a bank on the rolls at room temperature of 25°C and a roll temperature of 90°C, resulting in a film with a release film consisting of release film / outermost layer / intermediate layer / innermost layer / release film, with the intermediate layer having a thickness of 100 μm. The outermost layer and the innermost layer had thicknesses of 20 μm. When the two release films were peeled off under the above conditions, they peeled off without tearing, and the shape retention was also good. After the release film was peeled off, the gel fraction and storage modulus at 20° C. of this film were measured. The measurement results are shown in Table 1.

[0086] Assuming the production of molded articles using extrusion molding, the film obtained above was cured using a simple press molding method in which it was heated at 220°C for 2 minutes and press-molded using two flat plates at a pressure of 0.2 MPa. The gel fraction (whole film), storage modulus at 20°C and 100°C, and tensile elongation at break of the cured film were measured. The measurement results are shown in Table 1.

[0087] Example 2 Instead of the laminated film, the release film (PET film (2)) used in Example 1 was fed alone along two calendar rolls with a diameter of 100 mm, and resin composition (1) was poured between the release films between the calendar rolls to form a bank on the rolls at room temperature of 25°C and a roll temperature of 90°C, thereby obtaining a film with release film consisting of release film / single film / release film so that the thickness of the resin layer was 100 μm. The film with the release film was semi-cured by a simple method in which the film was press-molded from two flat plates at a pressure of 0.2 MPa while being heated at 150°C for 2 minutes, to obtain a film having the storage modulus and gel fraction shown in Table 1. When the two release films were peeled off under the above conditions, they were peeled off without tearing. Furthermore, the shape retention was also good. After the release film was peeled off, the gel fraction and storage modulus at 20° C. of this film were measured. The measurement results are shown in Table 1. The film was press-cured under the same conditions as in Example 1, and the gel fraction (whole film), storage modulus at 20°C and 100°C, and tensile elongation at break of the resulting cured film were measured.

[0088] Comparative Example 1 A film having a gel fraction as shown in Table 1 was obtained in the same manner as in Example 2, except that the film was not semi-cured. When an attempt was made to peel off the two release films from the obtained film with release films under the above conditions, the film was partially torn, and therefore a clear value for the storage modulus E' could not be obtained.

[0089] The film was cured and its post-curing properties were evaluated using the methods described above. The curing method was a simple press molding method using two flat plates at 0.2 MPa while heating at 220°C for 2 minutes, assuming a molded product. The gel fraction, storage modulus at 20°C and 100°C, and tensile elongation at break were measured for the resulting cured film.

[0090] The evaluation measurement results for Examples 1 and 2 and Comparative Example 1 are shown in Table 1 below.

[0091] [Table 1]

[0092] The film with release film of Example 1, which had an intermediate layer and outermost and innermost layers and in which the outermost and innermost layers were highly hardened layers, could be peeled off from the release film without tearing. Furthermore, because the outermost and innermost layers were relatively hard layers, the shape of the film was properly maintained even after the release film was peeled off, and it was easy to handle. Furthermore, since the cured film satisfies the viscoelastic properties (b) to (d) described above, it is expected that excellent acoustic properties such as sound quality and reproducibility will be achieved when a diaphragm is formed using the film of Example 1. Furthermore, the cured film has a high tensile breaking elongation, making it less likely to break due to prolonged vibration, and it is expected that an acoustic component with excellent durability can be provided.

[0093] Furthermore, the release film-attached film of Example 2, which is a semi-cured single-layer film, could be peeled off from the release film without tearing. Furthermore, the single-layer film is a relatively hard layer, and the film shape is properly maintained even after the release film is peeled off, resulting in excellent handling properties.

[0094] When the moldability and shaping properties of the present films obtained in Examples 1 and 2 were evaluated by the above-mentioned method, they were found to be moldable and shaping properties sufficient for practical use. Furthermore, in the evaluation of the adhesion of the films obtained in Examples 1 and 2 to a mold, the evaluation samples were easily removed from the mold without sticking to the mold.

[0095] In contrast, the relatively flexible film with release film of Comparative Example 1 broke when the release film was peeled off. It also had difficulty in properly maintaining its shape and was poor in handleability.

[0096] Furthermore, when the moldability and shaping properties of the film of Comparative Example 1 were evaluated, it was found to be moldable and shaping properties that were sufficient for practical use. However, when the adhesion to a mold was evaluated, the evaluation sample stuck to the mold and became stuck, causing problems.

Claims

1. A film comprising a resin layer and having thermosetting properties, A film for speaker diaphragms having the following viscoelastic properties (a) and a gel fraction of 10% or more and 90% or less: (a) The storage modulus E' at a measurement temperature of 20°C and a frequency of 10 Hz is 0.1 MPa or more and 500 MPa or less.

2. The resin layer has at least one highly cured layer and at least one uncured layer, 2. The film for a speaker diaphragm according to claim 1, wherein the highly hardened layer has a gel fraction of 80% or more, and the unhardened layer has a gel fraction of 0% or more and less than 80%.

3. The film for a speaker diaphragm according to claim 1 or 2, which has a crosslinked structure.

4. A film for speaker diaphragms described in any one of claims 1 to 3, wherein the resin composition forming the resin layer is a millable type containing organopolysiloxane.

5. The film for a speaker diaphragm according to any one of claims 1 to 4, which is a silicone film.

6. A film for speaker diaphragms described in any one of claims 1 to 5, which, after heat curing, has the viscoelastic properties (b) to (d) below. (b) Storage modulus E′ at a measurement temperature of 20° C. and a frequency of 10 Hz ２０ is 0.1 MPa or more and 500 MPa or less. (c) Storage modulus E′ at a measurement temperature of 100° C. and a frequency of 10 Hz １００ is 0.1 MPa or more and 500 MPa or less. (d) E' above １００ / E' ２０ is 0.4 to 1.0

7. A film for a speaker diaphragm with a release film, comprising: the film for a speaker diaphragm according to any one of claims 1 to 6; and a release film provided on at least one surface of the film for a speaker diaphragm.

8. A speaker diaphragm obtained by curing the film for speaker diaphragms according to any one of claims 1 to 6.

9. A laminate obtained by placing the film for speaker diaphragms according to any one of claims 1 to 6 in a mold and thermoforming it.

10. A speaker diaphragm obtained by peeling the laminate according to claim 9 from the mold.

11. An acoustic transducer comprising the speaker diaphragm according to claim 8 or 10.

Images