JP2024022237A - Acoustic member film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic member film that has shapeability during molding and followability to a mold, does not cause delamination, and can be peeled off from the mold release film without tearing when the mold release film is peeled off before molding.

SOLUTION: A single-layer acoustic member film has hardenability.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a film for an acoustic member, an acoustic member, a diaphragm, an acoustic transducer, a method of manufacturing an acoustic member, and a method of using a film for an acoustic member for an acoustic member.

With the spread of small electronic devices such as smartphones, PDAs, notebook computers, DVDs, LCD televisions, digital cameras, and portable music devices, the small speakers (usually called micro speakers) and small receivers used in these electronic devices have become increasingly popular. Furthermore, the demand for small electroacoustic transducers such as microphones and earphones is increasing. Polyetherimide (PEI) resin, polyetheretherketone (PEEK) resin, and the like are widely used for the diaphragms used in these electroacoustic transducers.

Furthermore, in recent years, the use of silicone resin in the above-mentioned diaphragm 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; A method of manufacturing a diaphragm using a plate sheet is disclosed. In Patent Document 1, a diaphragm is manufactured by setting a diaphragm sheet in a mold and shaping it, and then peeling a release sheet from the molded product. Since the diaphragm sheet described in Patent Document 1 uses an uncured liquid silicone composition, it can have high formability during molding and can also have high conformability to a mold. .

Japanese Patent Application Publication No. 2018-152817

The diaphragm sheet proposed in Patent Document 1 is made of an uncured liquid silicone composition, and is set in a mold and shaped. Therefore, it is necessary to peel off the mold release film after molding, but the heat and pressure applied during molding often makes it difficult for the mold release film to peel off from the first layer, reducing work efficiency and causing problems when mass-producing. Become.
Therefore, it is desirable that the diaphragm sheet be set in a mold such as a metal mold after peeling off the release film. However, without a release film, the first layer made of the uncured liquid silicone composition will stick to the mold, causing problems such as the molded article not being easily removed from the mold. Furthermore, the diaphragm sheet of Patent Document 1 has poor shape retention before shaping if there is no release film.
Therefore, the present invention provides a film for acoustic components that has shapeability during molding and followability to the mold, does not cause delamination, and can be peeled off from the mold release film without tearing when the mold release film is peeled off before molding. The challenge is to provide the following.

As a result of extensive studies, the present inventors found that the above problems could be solved by creating a film that has curability and controlled the coefficient of static friction on at least one surface, and completed the present invention as described below.

That is, the present invention provides the following [1] to [19].
[1] A single-layer film for acoustic members that has curability.
[2] The film for acoustic members according to the above [1], which has a gel fraction of 60% or more and 90% or less.
[3] The film for acoustic members according to [1] or [2] above, which has the viscoelastic properties shown in (a) below.
(a) Storage elastic modulus E' at a measurement temperature of 20° C. is 0.1 MPa or more and 500 MPa or less.
[4] The film for acoustic members according to any one of [1] to [3] above, which has thermosetting properties.
[5] The film for acoustic members according to any one of [1] to [4] above, which has a crosslinked structure.
[6] The film for acoustic members according to any one of [1] to [5] above, which has the following viscoelastic properties (b) to (d) in a cured state.
(b) Storage elastic modulus E' ₂₀ at a measurement temperature of 20° C. is 0.1 MPa or more and 500 MPa or less.
(c) Storage modulus E' ₁₀₀ at a measurement temperature of 100°C is 0.1 MPa or more and 500 MPa or less.
(d) The ratio (E' ₁₀₀ /E' ₂₀ ) of the storage elastic modulus E' ₁₀₀ to the storage elastic modulus E' ₂₀ is 0.2 or more and 1.0 or less.
[7] The film for acoustic members according to any one of [1] to [6] above, which is a film for diaphragms.
[8] The film for acoustic members according to any one of [1] to [7] above, which is a silicone film.
[9] The film for an acoustic member according to any one of [1] to [8] above, wherein at least one surface has a coefficient of static friction of 3 or less.
[10] An acoustic member obtained by curing the film for an acoustic member according to any one of [1] to [9] above.
[11] A diaphragm obtained by curing the film for acoustic members according to any one of [1] to [9] above.
[12] An acoustic transducer comprising the acoustic member according to [10] above.
[13] An acoustic transducer comprising the diaphragm according to [11] above.
[14] A method for producing an acoustic member, comprising shaping the film for an acoustic member according to any one of [1] to [9] above using a mold.
[15] The method for manufacturing an acoustic member according to [14] above, comprising a step of heating the film for an acoustic member before placing the film for an acoustic member in the mold.
[16] The method for producing an acoustic member according to [14] or [15] above, wherein the heating temperature during shaping is 180°C or more and 260°C or less.
[17] The method for producing an acoustic member according to any one of [14] to [16] above, wherein the shaping time is 1 second or more and 5 minutes or less.
[18] The method for producing an acoustic member according to any one of [14] to [17] above, wherein the acoustic member is shaped by any one of press molding, vacuum forming, and pressure forming.
[19] A method of using the film for acoustic members according to any one of [1] to [9] above for an acoustic member.

According to the present invention, an acoustic member that has shapeability during molding and followability to the mold, does not cause delamination, and can be peeled off from the mold release film without tearing when the mold release film is peeled off before molding. film can be provided.

1 is a cross-sectional view showing the structure of a micro speaker diaphragm 1 according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing the structure of a micro speaker diaphragm 11 according to another embodiment of the present invention. FIG. 3 is a plan view showing the structure of a micro speaker diaphragm 21 according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below unless it exceeds the gist thereof.
Note that, since the boundary between a film and a sheet is not clear, the term "film" in the present invention includes a sheet.

[Film for acoustic components]
The film for acoustic members of the present invention (hereinafter sometimes referred to as "this film") has curability, is a single layer, and is a suitable film for use in acoustic members.
This film has curability and has at least a partially uncured portion, so it has formability, and since it is a single layer, there is no problem of delamination.

<Gel fraction>
The film preferably has a gel fraction of 60% or more and 90% or less. When the gel fraction is within this range, it has appropriate curability, the surface layer portion is appropriately hardened, and the inside can be left uncured or semi-cured, thus exhibiting the effects of the present invention. From the above viewpoint, the gel fraction of the present film is more preferably 60% or more and 85% or less, and even more preferably 65% or more and 80% or less.
Note that the gel fraction was measured by the method described in Examples.

<Viscoelastic properties (storage modulus)>
The present film preferably has the following viscoelastic properties (a).
(a) 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, when the film is laminated to a release film, the film has appropriate hardness and can be easily peeled off from the release film. This also eliminates the fear of breakage occurring during peeling. Moreover, the shape can be maintained 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 appropriate flexibility and has good conformability to a mold during molding and shapeability.
From the above viewpoint, 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, further preferably 1.0 MPa or more and 100 MPa or less, even more preferably 1.2 or more and 10 MPa or less, and 1 Particularly preferred is .5 MPa or more and 5 MPa or less.

Further, the present film preferably has the following viscoelastic properties (b) to (d) in a cured state.
(b) Storage modulus E' ₂₀ at a measurement temperature of 20° C. and a frequency of 10 Hz is 0.1 MPa or more and 500 MPa or less.
(c) Storage modulus E' ₁₀₀ at a measurement temperature of 100° C. and a frequency of 10 Hz is 0.1 MPa or more and 500 MPa or less.
(d) The above E' ₁₀₀ /E' ₂₀ is 0.2 or more and 1.0 or less.

(b) When the storage elastic modulus E' ₂₀ at a measurement temperature of 20° C. and a frequency of 10 Hz is 0.1 MPa or more, it has a certain hardness after curing, so that the handling property after curing becomes good. On the other hand, when _E'20 is 500 MPa or less, when this film is used as a diaphragm, the diaphragm tends to have excellent acoustic properties such as sound quality and reproducibility. From the viewpoint of acoustic properties and handleability after curing, the storage modulus _E'20 at 20°C after curing is more preferably 1 MPa or more and 400 MPa or less, even more preferably 2 MPa or more and 200 MPa or less, and even more preferably 3 MPa or more and 50 MPa or less. The pressure is preferably 4 MPa or more and 10 MPa or less, particularly preferably.

In addition, (c) when the storage modulus E' ₁₀₀ at a measurement temperature of 100°C and a frequency of 10 Hz is 0.1 MPa or more and 500 MPa or less, heat resistance is good and excellent acoustic properties can be obtained even in a high temperature environment. It is expected. From the viewpoint of acoustic properties and handleability after curing, the storage modulus E' ₁₀₀ is more preferably 1 MPa or more and 400 MPa or less, even more preferably 2 MPa or more and 200 MPa or less, even more preferably 3 MPa or more and 50 MPa or less. , 3.5 MPa or more and 10 MPa or less is particularly preferable.

In addition, (d) by setting the storage modulus ratio (E' ₁₀₀ /E' ₂₀ ) within the range of 0.2 or more and 1.0 or less, changes in the elastic modulus due to temperature changes are reduced, and heat resistance is improved. It tends to be good. Furthermore, since the change in elastic modulus when heated is small, the sound quality is less likely to deteriorate in a high temperature environment, making it easier to maintain excellent sound reproduction from low to high temperatures.
From the above viewpoint, the ratio (E' ₁₀₀ /E' ₂₀ ) is more preferably 0.25 or more and 0.99 or less, even more preferably 0.3 or more and 0.97 or less, and 0. More preferably, it is 35 or more and 0.95 or less.
The storage modulus is a value measured by the method described in Examples after curing by a simple method of press molding from two flat plates at a pressure of 0.2 MPa while heating at 200° C. for 2 minutes.

<Static friction coefficient>
The present film preferably has a static friction coefficient of 3 or less on at least one surface. By having a static friction coefficient of 3 or less, the film is easy to handle, and for example, if it has a release film, it is easy to peel off from the release film, and there is no fear of tearing during peeling. . Moreover, the film can be easily peeled off from the mold, and the film can be prevented from sticking to the mold during molding. From the above viewpoint, the static friction coefficient is preferably 2.8 or less, more preferably 2.5 or less, even more preferably 2.3 or less, and particularly preferably 2.1 or less. . The lower limit of the static friction coefficient is not particularly limited, but may be, for example, 0.3 or more, 0.5 or more, or 0.7 or more. The static friction coefficient is required to be 3 or less on at least one surface of the present film, but the static friction coefficient on the other surface may be greater than 3 or may be 3 or less.
Note that the static friction coefficient is a value measured on a stainless steel plate (SUS430), and is a value obtained by the method described in Examples.

The static friction coefficient can be adjusted as appropriate by the film forming method, the film material, the gel fraction of the surface portion, and the like.
Specifically, the static friction coefficient can be adjusted by appropriately adjusting the surface shape, and for example, the static friction coefficient can be reduced by imparting roughness to the surface portion. Methods for adjusting the coefficient of static friction include methods of imparting unevenness by various methods such as sandblasting, shotblasting, etching, engraving, embossing roll transfer, embossing belt transfer, embossing film transfer, and surface crystallization. Can be mentioned. By adding particles to the film, the surface shape can also be changed and the coefficient of static friction can be adjusted.
One specific embodiment is to laminate or extrude the resin composition for forming the present film onto a release film having irregularities on its surface to form a film, and then irradiate the film with radiation from the side of the release film. By crosslinking the surface layer portion as described above and transferring the unevenness of the release film, a film having a static friction coefficient of 3 or less can be manufactured.

<Tensile elongation at break>
The tensile elongation at break of the present film after curing is preferably 100% or more, more preferably 200% or more, and even more preferably 300% or more. If the tensile elongation at break is within this range, the toughness of the film will be high, making it difficult for the film to break due to long-term vibration, and tending to have excellent durability when used in acoustic members such as diaphragms. Note that the tensile elongation at break is preferably as high as possible, and although there is no particular upper limit, it is usually 1500% or less.
The tensile elongation at break was determined by a method according to JIS K7161:2014 at a tensile speed of 200 mm/min at 23°C in the TD (direction perpendicular to the flow direction of the resin) of the film after curing. It can be obtained by measuring the elongation at break.

This film is a curable film, and the type of curing may be any of photocuring, moisture curing, thermosetting, etc., but thermosetting is preferable. Since this film has thermosetting properties, it can be cured during shaping and shaping while being heated, so that shaping properties are even better. In addition, since this film has curability, its gel fraction increases by performing a curing treatment such as heating.

The present film preferably has a crosslinked structure. By having an appropriate crosslinked structure, it becomes easier to obtain a film having suitable viscoelastic properties when crosslinked and cured. In addition, shape retention before curing (that is, before molding) is likely to be improved.
This film may be crosslinked on the surface and uncured on the inside, but considering the film's flexibility, conformability to the mold during molding, and formability, , it is preferable that the film has an appropriate degree of crosslinking. That is, the hardness of the entire film is preferably harder than an uncrosslinked film and softer than a completely cured film.
In the present invention, the presence or absence of a crosslinked structure is determined by the presence of a trace amount of unreacted crosslinking agent in the film and the presence of a crosslinking agent (decomposed) after reaction in the case of a condensation type, and the presence of a crosslinking agent that has been reacted with (decomposed) in the film, and in the case of an addition type, the existence of a It can be identified by the presence of the group.

The thickness of the present film is not particularly limited, but preferably 5 μm or more and 500 μm or less, more preferably 15 μm or more and 400 μm or less, and even more preferably 30 μm or more and 300 μm or less. If the thickness of the film is within this range, it is possible to produce a film with little thickness variation during the film production process, and it is also possible to produce a molded product with a thickness suitable for, for example, a diaphragm.

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. Among them, preferred specific examples include epoxy resin, urethane resin, silicone resin, acrylic resin, phenol resin, unsaturated polyester resin, polyimide resin, and melamine resin. These resins may be used alone or in combination of two or more.
Preferably, the film is a silicone film. When the present film is a silicone film, heat resistance, mechanical strength, etc. will be good, and the above-mentioned viscoelastic properties (a) and (b) to (d) will also be easily satisfied. Furthermore, the tensile elongation at break can be easily adjusted within the desired range described above.
Furthermore, by using a silicone film, it is possible to prevent the film from sticking to the mold during molding, while improving shape retention before molding and formability during molding.

<Silicone film>
The silicone polymer (polyorganosiloxane) used in the silicone film has, for example, a structure represented by the following formula (i).
R _n SiO _(4-n)/2 ...(i)
Here, R is a substituted or unsubstituted monovalent hydrocarbon group which may be the same or different, preferably a monovalent hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, n is a positive number between 1.95 and 2.05.

R is, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and a dodecyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group, an allyl group, a butenyl group, and a hexenyl group. phenyl group, aryl group such as tolyl group, aralkyl group such as β-phenylpropyl group, and some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms or cyano groups, etc. Examples include chloromethyl group, trifluoropropyl group, and cyanoethyl group.

Further, it is preferable that the molecular chain terminals of the polyorganosiloxane according to the present invention are blocked with a trimethylsilyl group, a dimethylvinyl group, a dimethylhydroxysilyl group, a trivinylsilyl group, or the like. Furthermore, it is preferable that the polyorganosiloxane has at least two alkenyl groups in the molecule. Specifically, R is 0.001 mol% or more and 5 mol% or less, preferably 0.005 mol% or more and 3 mol% or less, more preferably 0.01 mol% or more and 1 mol% or less, especially It is preferable to have an alkenyl group of 0.02 mol% or more and 0.5 mol% or less, and it is especially optimal to have a vinyl group. Polyorganosiloxane is basically linear, but may be partially branched. Further, it may be a mixture of two or more types having different molecular structures.

The resin composition for forming the silicone film is preferably a millable type containing polyorganosiloxane. The millable resin composition is non-liquid (e.g., solid or paste) with no self-flowing property at room temperature (25°C) in an uncured state (e.g., uncured state before radiation irradiation); They can be uniformly mixed using a kneader, which will be described later.
Note that the resin composition for forming the silicone film may contain a resin other than silicone resin (polyorganosiloxane).
Commercially available polyorganosiloxanes can also be used, and commercially available mixtures containing additives such as ceria fillers and silica fillers in addition to polyorganosiloxanes may also be used. Specifically, products such as "KE-5550-U", "KE-597-U", and "KE-594-U" manufactured by Shin-Etsu Chemical Co., Ltd. can also be used.

<Radiation>
The silicone film preferably has a semi-crosslinked structure, and is preferably produced by irradiation with radiation.
The radiation is not particularly limited as long as it achieves the effects of the present invention, and includes X-rays, γ-rays, electron beams, β-rays, α-rays, protons, deuterons, heavy ions, neutron beams, meson beams, etc. It will be done.
It is desirable to adjust the radiation dose and radiation irradiation time so that they fall within the above-mentioned ranges of gel fraction and/or storage modulus, depending on the type of radiation.

In addition to the polyorganosiloxane, a crosslinking agent may be added to the resin composition for forming the silicone film, and preferably an organic peroxide is added. By blending an organic peroxide, the silicone film can be easily cured during subsequent shaping.
Considering the flexibility of the film, its conformability to a mold during molding, and its shapeability, it is preferable that the film has an appropriate degree of crosslinking. That is, in terms of hardness, it is preferable that the film be harder than an uncrosslinked film and softer than a completely cured film. For example, it may be in a semi-cured state so that the gel fraction is within a desired range.

Examples of organic peroxides include di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(t- Organic peroxides include alkyl peroxides such as butylperoxy)hexane, aralkyl peroxides such as 2,4-dicumyl peroxide, but from the viewpoint of crosslinking speed and safety, alkyl peroxides 2,5-dimethyl-2,5-di(t-butylperoxy)hexane is particularly preferred.

The amount of organic peroxide in the resin composition for forming a silicone film is preferably 0.01% by mass or more and 10% by mass or less, and 0.03% by mass or more and 5% by mass, based on the total amount of the resin composition. The following is more preferable, 0.05% by weight or more and 4% by weight or less is even more preferable, 0.1% by weight or more and 3% by weight or less is particularly preferable, and particularly preferably 0.3% by weight or more and 2% by weight or less. When the amount of the organic peroxide is within this range, a composition having a sufficient curing rate tends to be safely obtained.

(filling material)
The film may contain fillers. Suitable examples of the filler include silica such as ceria (cerium oxide), fumed silica, and precipitated silica. By containing a filler in this film, it becomes easier to adjust the mechanical properties of the film, such as storage modulus and tensile elongation at break, to appropriate ranges. Moreover, by using a filler, it becomes easier to adjust the viscosity and hardness of the resin composition, and it becomes easier to optimize the balance between the fluidity and secondary processability of the resin composition. Furthermore, there is an advantage that the hardness can be easily adjusted according to the design and acoustic characteristics of the acoustic member.
Note that the filler constitutes a part of the gel fraction in the measurement of the gel fraction, and the gel fraction of the present film increases by containing the filler. By containing a filler, even if the gel fraction becomes high, the hardness of the present film can be increased in the same way as when the gel fraction is increased by crosslinking.

The content of the filler in the resin composition for forming the present film is, for example, 10% by mass or more and 50% by mass or less, preferably 15% by mass or more and 40% by mass or less, more preferably It is 20% by mass or more and 35% by mass or less. Further, the average particle diameter of the filler is, for example, 0.01 μm or more and 20 μm or less, preferably 0.1 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 5 μm or less. The average particle diameter of the filler can be measured as a median diameter (D50) using a particle size distribution measuring device using a laser beam diffraction method or the like.

The resin composition for forming this film may include heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, antibacterial/fungal agents, antistatic agents, lubricants, pigments, and dyes, as long as the effects are not impaired. , flame retardants, impact modifiers, and other various additives.

<Film with release film>
This film may be attached with a release film and used as a film with a release film. The film with a release film includes the above-described main film and a release film provided on at least one side of the main film.
Moreover, in a film with a release film, it is preferable that a release film is provided on both sides of the film.

The release film may be a resin film, or a film having a release layer on which at least one side of the resin film is subjected to release treatment. When the release film has a release layer, it is preferably laminated on the main film so that the release layer contacts the main film.
Resins used for the release film include polyolefin resins such as polypropylene, acrylic resins, polystyrene resins, polyacetal resins, polyamide resins, polyester resins, polycarbonate resins, ABS resins, and polyether ether ketone resins. Examples include resin. 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 150 μm or less, more preferably 7 μm or more and 120 μm or less, even more preferably 10 μm or more and 100 μm or less, particularly preferably 10 μm or more and 80 μm or less.

This film is protected by the release film by attaching the release film. Therefore, the film is prevented from being damaged during transportation. Note that the release film that is laminated when manufacturing the present film may be used as it is, or may be separately laminated on the manufactured present film.
Further, the present film is molded by, for example, extrusion molding as described later, and the release film is preferably peeled off from the present film during molding and then set in a mold such as a metal mold. At that time, the present film can be peeled off from the release film without tearing.

<Production method of this film>
This film can be molded by a general molding method, for example, by extrusion molding or the like. A resin composition for obtaining a film may be obtained by kneading or the like as described below, and then molded by extrusion or the like. In this film, in order to adjust the static friction coefficient to 3 or less, which is a preferable embodiment, the film may be subjected to post-processing such as embossing as described above.
In addition, a mold release film with a static friction coefficient adjusted to 3 or less is produced by laminating a resin composition between or on the mold release film using a mold release film having unevenness. This film may be obtained.

Each resin composition is not particularly limited, but can be obtained, for example, by kneading materials constituting the resin composition. Kneading machines used for kneading include extruders such as single-screw or twin-screw extruders, calendar rolls such as two-roller or three-roller, roll mills, plastomills, Banbury mixers, kneaders, planetary mixers, and other known kneading machines. machine can be used.
The kneading temperature is adjusted as appropriate depending on the type and mixing ratio of the resin, and the presence or absence and type of additives, but in order to moderately lower the viscosity of the resin and make it easier to knead while suppressing crosslinking (curing), the kneading temperature is set at 20°C. The temperature is preferably 150°C or more, more preferably 30°C or more and 140°C or less, even more preferably 40°C or more and 130°C or less, particularly preferably 50°C or more and 120°C or less, and 60°C or more and 130°C or less. It is particularly preferable that the temperature is 110°C or higher.
The kneading time is sufficient as long as the materials constituting the resin composition are mixed uniformly, and is, for example, several minutes to several hours, preferably 5 minutes to 1 hour.

This film can be partially cured by heating, irradiating light, applying moisture, or a combination of these to the film obtained as described above. In the present invention, it is preferable to use radiation because film properties can be easily adjusted and mass production can be carried out quickly.

[Molding]
The present film can be molded into a molded article by being molded with a mold such as a metal mold and cured, and typically, it is preferably shaped into various molded products by being shaped with a mold. Curing may be carried out depending on the characteristics of the film, and may be carried out by heating, light irradiation, moisture application, or a combination thereof, and is preferably carried out by heating. This film is useful as a film for diaphragms, and molded products made of this film are particularly useful as acoustic members such as diaphragms.

In the present invention, the gel fraction of the molded article obtained from the film may be 80% or more. When the gel fraction is 80% or more, it becomes easier to obtain a molded product having storage modulus and mechanical strength suitable for acoustic members. The gel fraction of the molded article is more preferably 85% or more, and even more preferably 90% or more. Further, the upper limit of the gel fraction of the molded article is not particularly limited, and it may be 100% or less, but it is generally lower than 100%, and may be, for example, 99% or less. Note that the gel fraction of the molded product is the gel fraction of the entire molded product, and is preferably measured by sampling evenly in the thickness direction of the molded product. Details of the method for measuring gel fraction are as described in Examples.

<Method for manufacturing molded products>
Molded articles can be obtained using this film. Hereinafter, a method for manufacturing a molded article using this film will be explained. Note that the molded product is preferably an acoustic member described later.
When obtaining a molded article from this film, it is preferable to perform at least the following steps 1 and 2.
Step 1: Step of heating and molding the film using a mold and curing the film Step 2: Peeling the molded and cured film (i.e., molded product) from the mold

Each step will be explained in more detail below.
(Step 1)
In step 1, the film is heated and molded using a mold, and the film is cured to form a molded product. The molded article may be shaped using a mold, whereby it is molded into a desired shape. The molding in step 1 is not particularly limited, and may be performed by any molding method such as vacuum molding, pressure molding, press molding, etc. Among these, press molding is preferable because molding is easier.

As for the mold, a mold depending on the molding method may be prepared, but it is preferable that the mold is provided with unevenness or the like according to the shape of the molded product to be manufactured. As the mold, a metal mold (mold) is typically used, but a resin mold may also be used. For example, if the molded product (diaphragm) has at least either a dome shape or a cone shape as described later, the mold may be provided with irregularities corresponding to the dome shape or the cone shape. Further, when the molded product (diaphragm) has a tangential edge on its surface, the mold may be provided with irregularities corresponding to the tangential edge.

As described above, a release film may be attached to this film, but it is preferable that the film is set in a mold after the release film is peeled off as described above.

In step 1, the heated main film may be shaped with a mold. For example, the main film placed on a mold may be heated and shaped with a mold, or a preheated main film may be placed on a mold. However, it may be shaped using a mold afterwards, or these may be combined. In addition, the film may be heated by any method. For example, when heating a film placed on a mold, the film may be heated by heating the mold and heated by the heat transfer, or it may be heated by other methods. You may.

The heating temperature during shaping or curing is preferably 180°C or more and 260°C or less, more preferably 190°C or more and 250°C or less, and even more preferably 200°C or more and 240°C or less. If the temperature during shaping or curing is within this range, curing tends to be possible at a sufficient speed without the film being melted and deformed by heat.

The shaping time is preferably 1 second or more and 5 minutes or less, more preferably 5 seconds or more and 4 minutes or less, even more preferably 10 seconds or more and 3 minutes or less, and 20 seconds or more and 2 minutes or less. It is particularly preferable that there be. If the heat treatment time required during shaping is within a range, it tends to be sufficiently hardened while maintaining productivity.
The present film is preferably cured while being shaped, but may be cured after being shaped without particular limitation. The shaping time refers to the time during which the film is shaped or cured in the mold, and the mold movement time before the start of shaping and after the end of shaping, and the time required to release the laminate from the mold. shall not be included.

(Step 2)
In step 2, the film molded and cured in step 1 is peeled off from the mold to obtain a molded product. In the present invention, since the gel fraction of the present film is less than a certain value, the film has high formability and high conformability to the mold. Therefore, the molded product can be manufactured with high molding accuracy.
Furthermore, since this film has specific viscoelastic properties, it has high shape retention and good handling properties. Furthermore, the film can be peeled off without tearing when it is peeled off from the mold release film, and the film can be easily set in a mold while maintaining its shape. Since the release film is not laminated, the step of peeling off the release film from the molded product can be omitted, making mass production easier.

[Application]
The film of the present invention can be suitably used for acoustic members. Specifically, it can be suitably used as a film for acoustic members, and particularly as a film for diaphragms. The acoustic member of the present invention, such as a diaphragm, is preferably formed by curing this film, and specifically, it is preferably formed from the above-described molded product. The acoustic member is more preferably a diaphragm, specifically a speaker diaphragm, and can be particularly suitably used as a micro speaker diaphragm for mobile phones and the like.

<Acoustic members>
By appropriately molding this film, it can be made into various acoustic members such as diaphragms.
For example, at least a portion of the acoustic member preferably has a dome shape, a cone shape, or the like. Further, the acoustic member may have a tangential edge on the surface. When the acoustic member has a dome shape or a cone shape, or has a tangential edge, the acoustic member is preferably used as a diaphragm, more preferably a speaker diaphragm.

As described above, an acoustic member having the characteristics of the present film is a preferred embodiment. That is, the coefficient of static friction of one surface of the acoustic member molded using this film, particularly the surface in contact with the mold, can be set to 3 or less, and peeling from the mold becomes easy. The preferred range of the static friction coefficient is as described above.
Furthermore, the acoustic member formed from the present film, which is a single-layer film, has the advantage that there is no problem of delamination.
Furthermore, the acoustic member formed from this film, which is a silicone film, has good heat resistance, mechanical strength, etc., and satisfies the viscoelastic properties (a) and (b) to (d) suitable for the above-mentioned acoustic member. At the same time, it becomes easier to adjust the tensile elongation at break within the desired range described above. Specifically, (b) the storage modulus E' ₂₀ at a measurement temperature of 20°C is 0.1 MPa or more and 500 MPa or less, and (c) the storage elastic modulus E' ₁₀₀ at a measurement temperature of 100°C is 0.1 MPa or more. 500 MPa or less, and (d) the ratio of the storage elastic modulus E' ₁₀₀ to the storage elastic modulus E' ₂₀ (E' ₁₀₀ /E' ₂₀ ) is 0.2 or more and 1.0 or less.
Further, the thickness of the acoustic member can be set to 5 μm or more and 500 μm or less, and good acoustic characteristics can be obtained as an acoustic member such as a diaphragm. Furthermore, since the acoustic member has a crosslinked structure, it becomes easier to satisfy the above viscoelastic properties (b) to (d).

In view of the above points, the inventions according to [20] to [25] below are also embodiments of the present invention.
[20] An acoustic member having a coefficient of static friction of at least one surface of 3 or less.
[21] The acoustic member according to [20] above, which is made of a single-layer film. [22] The acoustic member according to [20] or [21] above, which is made of a silicone film.
[23] The acoustic member according to any one of [20] to [22] above, which has a thickness of 5 μm or more and 500 μm or less.
[24] The acoustic member according to any one of [20] to [23] above, which has a crosslinked structure.
[25] The film for acoustic members according to any one of [20] to [24] above, which has the viscoelastic properties shown in (b) to (d) below.
(b) Storage elastic modulus E' ₂₀ at a measurement temperature of 20° C. is 0.1 MPa or more and 500 MPa or less.
(c) Storage modulus E' ₁₀₀ at a measurement temperature of 100°C is 0.1 MPa or more and 500 MPa or less.
(d) The ratio (E' ₁₀₀ /E' ₂₀ ) of the storage elastic modulus E' ₁₀₀ to the storage elastic modulus E' ₂₀ is 0.2 or more and 1.0 or less.

(diaphragm)
To explain the diaphragm in more detail, the shape of the diaphragm is not particularly limited and is arbitrary, and circular, elliptical, oval, etc. can be selected. Further, a diaphragm generally has a body that vibrates in response to an electric signal or the like, and an edge surrounding the body. The body of the diaphragm is typically supported by edges. The shape of the diaphragm may be a dome shape, a cone shape, a combination thereof, or any other shape used for a diaphragm, as described above.

The present film may form at least a part of the acoustic member; for example, the body or edge of the diaphragm may be formed from the present film, and the edge or body of the diaphragm may be formed from another member. Of course, both the body and the edge may be integrally formed of the present film, or the entire diaphragm may be formed of the present film.

FIG. 1 is a diagram showing the structure of a diaphragm 1 according to an embodiment of the present invention, and is a cross-sectional view of the diaphragm 1, which is circular in plan view, taken 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 part (body) 1a as the center, a recessed part 1b that is attached to the voice coil 2, a peripheral part (edge) 1c, and an external part that is attached to the frame or the like on the outer periphery. It has a pasting part 1d.

FIG. 2 is a diagram showing the structure of a diaphragm 11 according to another embodiment of the present invention, and is a cross-sectional view of the diaphragm 11, which is circular in plan view, taken along a plane passing through the center line of the circle. The diaphragm 11 is a diaphragm for a micro speaker. As shown in FIG. 2, the diaphragm 11 includes a dome portion (body) 11a processed into a dome shape, a recessed fitting portion 11b attached to the voice coil 2, a cone portion 11j processed into a cone shape, and It has a peripheral portion (edge) 11c. As exemplified by the diaphragm 11, a part of the diaphragm may be processed into a dome shape, and another part other than the part may be processed into a cone shape. Note that the diaphragm 11 may be attached at its peripheral edge portion 11c directly to a frame or the like, or may be attached to the frame or the like via another member.

A tangential edge may be provided on the surface of the diaphragm as described above. The tangential edge may be formed of, for example, a groove having a V-shaped cross section. FIG. 3 shows a plan view of a diaphragm 21 according to another embodiment of the invention. The diaphragm 21 includes a tangential edge portion 21g provided with a plurality of tangential edges 21e on the outer peripheral edge of a circular dome portion (body) 21a, and a plurality of tangential edges arranged on the outer periphery of the tangential edge portion 21g. It has a tangential edge portion 21h provided with a tangential edge 21f. Although FIG. 3 shows an example in which two tangential edge portions are provided along the radial direction, there may be only one tangential edge portion or three or more tangential edge portions may be provided along the radial direction. You can.

As described above, the diaphragm is preferably a speaker diaphragm, especially a micro speaker diaphragm. From the viewpoint of suitable use as a microspeaker diaphragm, the diaphragm has a maximum diameter of 25 mm or less, preferably 20 mm or less, and a diaphragm with a maximum diameter of 5 mm or more is preferably used. Note that the maximum diameter is the diameter when the shape of the diaphragm is circular, and the long axis when the shape of the diaphragm is elliptical or oval.

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

Furthermore, in order to make the diaphragm suitable for secondary processing, dustproof, adjust acoustic characteristics, improve design, etc., the surface of the diaphragm may be further coated with an antistatic agent, metal deposited, or sputtered. Processing such as coloring (black, white, etc.) may be performed as appropriate. Furthermore, lamination with a metal such as aluminum or a composite with a nonwoven fabric may be performed as appropriate.

(acoustic transducer)
The acoustic transducer of the present invention is an acoustic transducer comprising the above-described acoustic member, preferably a diaphragm. The acoustic transducer is typically an electroacoustic transducer, and includes speakers, receivers, microphones, earphones, and the like. Among these, the acoustic transducer is preferably a speaker, and preferably a micro speaker such as a mobile phone.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

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

(1) Surface friction coefficient (static friction coefficient)
The coefficient of static friction between each of the front and back surfaces of the film obtained in each Example and Comparative Example and a stainless steel plate (SUS430) was measured. The static friction coefficient was measured twice on the surface of the film before thermoforming obtained in each Example and Comparative Example, and was determined from the average value of these measurements. A specific method for measuring the static friction coefficient is as follows.
Referring to JIS K7125:1999, the surface of this film and the stainless steel plate were kept in contact for 15 seconds before starting the test, and then measurements were carried out in the longitudinal direction (MD) under the following conditions to determine the static friction with the stainless steel plate. The coefficients were evaluated.
・Equipment: Plastic film slip tester (manufactured by Intesco)
・Sliding piece: Total mass 200g (contact area is a square with a side of 63mm)
・Contact area: ^400cm2
・Test speed: 100mm/min
・Temperature: 23℃±2℃
・Relative humidity: 50% ± 10%
(2) Measurement of gel fraction The gel fraction of the film before press molding and after press molding was measured by the following method. Note that, as is clear from the measurement method described below, 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.
(1-1) Approximately 100 mg of a sample was taken by cutting it out evenly in parallel with the thickness direction of the film, and the sample mass (a) was measured.
(1-2) The collected sample was immersed in chloroform for 24 hours at 23°C.
(1-3) The solid content in chloroform was taken out and vacuum dried at 50°C for 7 hours.
(1-4) The mass (b) of the solid content after drying was measured.
(1-5) Using the masses (a) and (b), the gel fraction was calculated based on the following formula (ii).

(3) Storage modulus E'
A 4 mm x 8 cm test piece was cut out from the film obtained in each Example and Comparative Example and obtained as a measurement sample. Using the measurement sample, in accordance with JIS K7244-4:1999, a viscoelastic spectrometer "DVA-200 (manufactured by IT Instrumentation Control Co., Ltd.)" was used, the measurement mode was tensile, the frequency was 10 Hz, and the strain was 0. The storage modulus was measured at 20° C. and 100° C. at a heating rate of 3° C./min.
Note that the storage modulus at 20° C. was measured for the film before and after press molding. Furthermore, after press molding, the storage modulus at 100°C was also measured.

(4) Handling property (4-1) Presence or absence of tearing In the step of manually peeling off the release film from the film with the release film, the presence or absence of tearing was evaluated. Those in which the release film could be peeled off without tearing the film were rated as "○", and those in which part of the film was torn due to the release film were rated as "x".
Note that for various evaluations and measurements other than the presence or absence of tearing, the film was used with the release film removed.
(4-2) Shape retention The shape retention of the films obtained in each Example and Comparative Example before curing was evaluated. When this film was peeled off from the release film and used for various evaluations and measurements, it was rated "〇" if it could be easily manipulated because it retained its shape. Items that were tangled or cut were rated "x".

(5) Shaping property A test piece of about 7 cm x 10 cm was cut out from the film obtained in each Example and Comparative Example and used as an evaluation sample. The evaluation sample was inserted into a mold for a dome-shaped diaphragm with a tangential edge that had been preheated to 230°C, pressed at a pressure of 0.1 MPa, and held in the pressurized state for 20 seconds before pressing the sample. It was taken out from the mold.
Visually check the sample after taking it out, and rate it as ``〇'' if the unevenness is formed according to the mold, or if the unevenness is smaller than the mold or if the unevenness is not formed. The item was rated "x".

(6) Mold adhesion Similar to the above evaluation of moldability and shapeability, a test piece of about 7 cm x 10 cm was cut out from the film obtained in each Example and Comparative Example and used as an evaluation sample. The evaluation sample was inserted into a mold for a diaphragm that had been heated to 230° C. in advance and pressed at a pressure of 0.1 MPa, and the pressurized state was held for 20 seconds, and then the sample was taken out from the mold.
When taking out the evaluation sample from the mold, if the evaluation sample did not stick to the mold and could be taken out easily, it was evaluated as "〇", and if the evaluation sample stuck to the mold and got caught, it was evaluated as "x". .

<Raw materials>
- Silicone rubber (A-1): A mixture of polyorganosiloxane and silica. (Product name "KE-597-U", manufactured by Shin-Etsu Chemical Co., Ltd.)
・Organic peroxide compound silicone rubber (B-1) (hereinafter simply referred to as "organic peroxide"): 2,5-dimethyl-2,5-di(t-butylperoxy)hexane to approx. Silicone rubber containing 40% (trade name "C-8B", manufactured by Shin-Etsu Chemical Co., Ltd.)

Example 1
A millable resin composition ( 1) was obtained. A PET film (1) with a matte surface roughness (Ra) of 0.98 μm was prepared as a release film, and was fed along two calender rolls with a diameter of 100 mm so that the matte surface was on the inside. The resin composition (1) is placed between the release films, and banks are formed on the rolls at a roll temperature of 90°C, and the thickness of the resin composition (1) is adjusted to 100 μm to form a release film. A silicone film was obtained. The obtained silicone film was irradiated with radiation. After irradiating with radiation, the release films on both sides were peeled off to obtain a silicone film sample. The obtained sample was cured by a simple method of press molding from two flat plates at a pressure of 0.2 MPa while heating at 200 ° C. for 2 minutes, assuming that a molded product would be manufactured by shaping. . The surface friction coefficient, gel fraction, and storage modulus of this sample before press molding were measured, and handling properties, formability, and adhesion to the mold were evaluated. In addition, the gel fraction and storage modulus of this sample after press molding were measured. The results are shown in Table 1. Furthermore, the surface friction coefficient of this sample did not change before and after pressing.

Comparative example 1
A sample was obtained in the same manner as in Example 1, except that instead of irradiating with radiation, heat treatment was performed at 200° C. for 2 minutes. The surface friction coefficient, gel fraction, and storage modulus of this sample before press molding were measured, and handling properties, formability, and adhesion to the mold were evaluated. In addition, the gel fraction and storage modulus of this sample after press molding were measured. In addition, from the value of gel fraction, it can be seen that the film of Comparative Example 1 is a film that does not have curability.

As shown in Table 1, the silicone film with a release film of Example 1 was semi-crosslinked by radiation irradiation, so it could be peeled off from the release film without tearing, and after the release film was peeled off. However, the film retains its shape properly and has excellent handling properties.
Furthermore, since the film after press molding (after curing) satisfies the above-mentioned viscoelastic properties (b) to (d), when a diaphragm is molded using the film of Example 1, acoustic properties such as sound quality and playability are improved. You can expect it to be excellent.

When the shapeability of the film obtained in Example 1 was evaluated using the above method, it was found to have a shapeability sufficient for practical use.
Furthermore, in the evaluation of adhesion to the mold, the film obtained in Example 1 was easily taken out without sticking to the mold when the evaluation sample was taken out from the mold.
On the other hand, since the film of Comparative Example 1 was completely cured, it was found that it did not have curability, was hard, had insufficient shapeability, and was inferior in moldability.

The molded product obtained from the film of the present invention can be easily taken out from the mold when producing the molded product, and therefore can be applied to various molded products. It is particularly useful as a film for acoustic members such as diaphragms, and has great industrial significance.

1, 11, 21 Vibration plate 1a, 11a, 21a Dome part (body)
1b, 11b Recessed fitting part 1c, 11c Peripheral part (edge)
1d External pasting part 11j Cone part 21e, 21f Tangential edge 21g, 21h Tangential edge part 2 Voice coil

Claims (19)

A curable, single-layer film for acoustic components. The film for acoustic members according to claim 1, having a gel fraction of 60% or more and 90% or less. The film for acoustic members according to claim 1, having the following viscoelastic properties (a).
(a) Storage elastic modulus E' at a measurement temperature of 20° C. is 0.1 MPa or more and 500 MPa or less. The film for acoustic members according to claim 1, which has thermosetting properties. The film for acoustic members according to claim 1, having a crosslinked structure. The film for acoustic members according to claim 1, which has the following viscoelastic properties (b) to (d) in a state after curing.
(b) Storage elastic modulus E' ₂₀ at a measurement temperature of 20° C. is 0.1 MPa or more and 500 MPa or less.
(c) Storage modulus E' ₁₀₀ at a measurement temperature of 100°C is 0.1 MPa or more and 500 MPa or less.
(d) The ratio (E' ₁₀₀ /E' ₂₀ ) of the storage elastic modulus E' ₁₀₀ to the storage elastic modulus E' ₂₀ is 0.2 or more and 1.0 or less. The film for acoustic members according to claim 1, which is a film for diaphragms. The film for acoustic members according to claim 1, which is a silicone film. The film for acoustic members according to claim 1, wherein at least one surface has a coefficient of static friction of 3 or less. An acoustic member obtained by curing the film for an acoustic member according to any one of claims 1 to 9. A diaphragm obtained by curing the film for acoustic members according to any one of claims 1 to 9. An acoustic transducer comprising the acoustic member according to claim 10. An acoustic transducer comprising the diaphragm according to claim 11. A method for manufacturing an acoustic member, comprising shaping the film for an acoustic member according to any one of claims 1 to 9 using a mold. The method for manufacturing an acoustic member according to claim 14, further comprising the step of heating the film for an acoustic member before placing the film for an acoustic member in the mold. The method for manufacturing an acoustic member according to claim 14, wherein the heating temperature during shaping is 180°C or more and 260°C or less. The method for manufacturing an acoustic member according to claim 14, wherein the shaping time is 1 second or more and 5 minutes or less. The method for manufacturing an acoustic member according to claim 14, wherein the acoustic member is shaped by any one of press molding, vacuum forming, and pressure forming. A method of using the film for acoustic members according to any one of claims 1 to 9 for an acoustic member.