JP7779041B2 - Films, films with release films, diaphragms, laminates, molded products and acoustic transducers - Google Patents

Description

The present invention relates to films used to obtain molded products such as acoustic components, films with release films, and diaphragms, laminates, molded products, and acoustic transducers obtained from these.

For example, with the widespread use of small electronic devices such as smartphones, PDAs, notebook computers, DVD players, LCD TVs, digital cameras, and portable music players, there is growing demand for small speakers (commonly called microspeakers) and receivers used in these electronic devices, as well as small electro-acoustic transducers such as microphones and earphones. Diaphragms used in these electro-acoustic transducers are widely made from resins such as polyetherimide (PEI) and polyether ether ketone (PEEK).

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, as well as 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 produce a diaphragm. Because the diaphragm sheet described in Patent Document 1 uses an uncured liquid silicone composition, it can achieve high shaping properties during molding and also high mold conformability.

Japanese Patent Application Laid-Open No. 2018-152817

As mentioned above, in Patent Document 1, the diaphragm sheet is formed by setting a release film laminated on a first layer made of an uncured liquid silicone composition in a mold. Therefore, the release film needs to be peeled off after molding, but the heat and pressure applied during molding often make it difficult to peel the release film from the first layer, reducing work efficiency and creating problems when it comes to mass production.

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, without a release film, the first layer made of the uncured liquid silicone composition will stick to the mold, causing problems such as making it difficult to remove the molded product from the mold. Furthermore, without a release film, the diaphragm sheet of Patent Document 1 will have poor shape retention before shaping.

The objective of the present invention is to provide a film that can prevent the film from sticking to a mold or other form during molding, while improving shape retention before molding and shapeability and mold conformability during molding.

After extensive research, the inventors discovered that the above-mentioned problems could be solved by using a multi-layer film, setting the static friction coefficient of the outermost and innermost layers to 3 or less, and using a curable intermediate layer, and thus completed the present invention, as described below.

That is, the present invention provides the following [1] to [16].
[1] A film comprising an outermost and innermost layer having a static friction coefficient of 3 or less, and at least one curable intermediate layer disposed between the outermost and innermost layers.
[2] The film according to the above [1], having a gel fraction of 0% or more and 90% or less.
[3] The film according to the above [1] or [2], wherein the gel fraction of each of the outermost and innermost layers is 80% or more.
[4] The film according to any one of the above [1] to [3], which has the following viscoelastic property (a):
(a) The storage modulus E' at a measurement temperature of 20°C is 0.1 MPa or more and 500 MPa or less.
[5] The film according to any one of the above [1] to [4], which has thermosetting properties.
[6] The film according to any one of the above [1] to [5], which has a crosslinked structure.
[7] The film according to any one of the above [1] to [6], which is a silicone film.
[8] The film according to any one of the above [1] to [7], which has the following viscoelastic property (b) after curing:
(b) The storage modulus _E'20 at a measurement temperature of 20°C is 0.1 MPa or more.
[9] The film according to any one of the above [1] to [8], which has the following viscoelastic properties (c) to (e) after curing:
(c) The storage modulus _E'20 at a measurement temperature of 20°C is 0.1 MPa or more and 500 MPa or less.
(d) The storage modulus E' ₁₀₀ at a measurement temperature of 100°C is 0.1 MPa or more and 500 MPa or less.
(e) The ratio (E' ₁₀₀ /E' ₂₀ ) of the storage modulus E' ₁₀₀ to the storage modulus _E ' 20 is 0.4 or more and 1.0 or less.
[10] The film according to any one of the above [1] to [9], which is a film for a diaphragm.
[11] A film with a release film, comprising the film according to any one of [1] to [10] above and a release film provided on at least one surface of the film.
[12] A diaphragm obtained by curing the film according to any one of the above [1] to [10].
[13] A laminate obtained by placing the film according to any one of the above [1] to [10] in a mold and thermoforming it.
[14] A molded article obtained by peeling the laminate according to [13] above from a mold.
[15] The molded article according to [14] above, which is a diaphragm.
[16] An acoustic transducer comprising the diaphragm described in [12] or [15] above.

The present invention provides a film that can prevent the film from sticking to the mold during molding while improving shape retention before molding and formability during molding.

1 is a cross-sectional view showing the structure of a micro speaker diaphragm 1 according to an embodiment of the present invention. FIG. 10 is a cross-sectional view showing the structure of a micro-speaker diaphragm 11 according to another embodiment of the present invention. FIG. 10 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 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."

[film]
The film of the present invention (hereinafter also referred to as the present film) comprises outermost and innermost layers (outermost and innermost layers) having a static friction coefficient of 3 or less, and at least one curable intermediate layer disposed between the outermost and innermost layers.
The film has a relatively hard outermost and innermost layer, which reduces the static friction coefficient of the outermost and innermost layers, preventing the film from sticking to the mold during molding. Furthermore, by using a curable intermediate layer, the film maintains a certain degree of flexibility before molding and is sufficiently cured during molding, resulting in good formability and mold-following ability.
Furthermore, while the intermediate layer is curable and the entire film is relatively flexible, the provision of relatively hard outermost and innermost layers on both surfaces allows the flexible film to be properly maintained by the outermost and innermost layers, resulting in good shape retention before molding and good handleability even without laminating a release film on the film. Therefore, the film can be easily set in a mold and shaped without laminating a release film, and the process of peeling off the release film after shaping can be omitted.

(static friction coefficient)
As described above, the static friction coefficient of both the outermost and innermost layers of the present film is 3 or less. If the static friction coefficient is higher than 3, the present film tends to stick to the mold, making it difficult to achieve good formability. The static friction coefficient of both the outermost and innermost layers is preferably 2.5 or less, more preferably 2 or less, and even more preferably 1.5 or less. By lowering the static friction coefficient of the outermost and innermost layers as described above, sticking to the mold can be further suppressed.
The static friction coefficient of the outermost and innermost layers of the present film is not particularly limited in terms of its lower limit, and may be, for example, 0.3 or more, 0.5 or more, or 0.7 or more. The static friction coefficients of the outermost and innermost layers (i.e., the outermost layer and the innermost layer) may be the same or different from each other.

The static friction coefficient can be appropriately adjusted by the molding method of the outermost/innermost layer, the material of the outermost/innermost layer, and the gel fraction of the outermost/innermost layer. For example, increasing the gel fraction of the outermost/innermost layer tends to make the outermost/innermost layer harder and lower the static friction coefficient. More specifically, by increasing the gel fraction of the outermost/innermost layer to 80% or more, the static friction coefficient can be easily reduced to 3 or less. The static friction coefficient can also be reduced by using a specific resin such as a silicone resin or inorganic particles as the resin constituting the outermost/innermost layer. Furthermore, the static friction coefficient of the outermost/innermost layer can be adjusted by appropriately adjusting the surface shape; for example, the static friction coefficient can be reduced by imparting roughness to the outermost/innermost layer.
The static friction coefficient is the static friction coefficient against a stainless steel plate, and can be measured by a sliding test based on JIS K7125 (1999).

(Gel fraction)
The present film preferably has a gel fraction of 0% or more and 90% or less. When the gel fraction is 90% or less, the film can be easily made flexible before molding and can be sufficiently cured during molding, resulting in sufficient shapeability and moldability, and improved moldability.
From the viewpoint of shaping and molding properties, the gel fraction of the present film is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. The gel fraction of the present film is not particularly limited and may be 0% or more, for example, 10% or more, or 20% or more. The gel fraction of the present film is a value obtained by measuring the gel fraction of the entire film.

As described above, at least one curable intermediate layer is provided between the outermost and innermost layers. The curable intermediate layer preferably has a gel fraction of 0% or more and less than 80%. An intermediate layer with a gel fraction of less than 80% makes it easier to make the film flexible before molding, and can be sufficiently cured during molding, resulting in sufficient shapeability and moldability, and improved moldability.
From the viewpoint of formability and molding, the gel fraction of the intermediate 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.

The curable intermediate layer may consist of one layer or two or more layers, but preferably consists of one layer. Therefore, the present film preferably has a three-layer structure of outermost layer/intermediate layer/innermost layer, but may also have a four-layer or more structure having two or more intermediate layers between the outermost and innermost layers, such as outermost layer/intermediate layer/intermediate layer/innermost layer.
The present film may further include a layer other than the curable intermediate layer between the outermost layer and the innermost layer, for example, an adhesive layer or other layer may be provided between the intermediate layer and the outermost layer or between the intermediate layer and the innermost layer to improve adhesion between these layers. Also, an adhesive layer or other layer may be provided between the intermediate layers.

In the present film, the gel fractions of both the outermost and innermost layers (i.e., the outermost and innermost layers) are preferably 80% or more. When the gel fractions of the outermost and innermost layers are 80% or more, the static friction coefficient described above is easily reduced, and the film is less likely to stick to the mold during molding. Furthermore, by increasing the gel fraction as described above, the outermost and innermost layers of the present film can be made relatively hard even before the film hardens, further improving the shape retention before molding.
From the above viewpoints, the gel fraction of the outermost and innermost layers is more preferably 85% or more, and even more preferably 90% or more. The upper limit of the gel fraction of the outermost and innermost layers 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.
The gel fractions of the outermost and innermost layers (i.e., the outermost layer and the innermost layer) may be the same or different from each other.

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

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.

(Viscoelastic properties)
The present film preferably has the following viscoelastic property (a).
(a) The storage modulus E' at a measurement temperature of 20°C is 0.1 MPa or more and 500 MPa or less.
When the storage modulus E' is 0.1 MPa or more, the present film has a consistent hardness throughout, making it easy to peel from the release film and reducing the risk of tearing during peeling. Furthermore, shape retention can be improved even without a release film. On the other hand, by setting the storage modulus E' to 500 MPa or less, the present film can ensure a consistent flexibility and improve mold-following and shaping properties during molding. From these perspectives, the storage modulus E' of the present film is more preferably 0.5 MPa or more, even more preferably 0.8 MPa or more, and even more preferably 1.0 MPa or more. Furthermore, it is more preferably 300 MPa or less, even more preferably 200 MPa or less, even more preferably 100 MPa or less, and particularly preferably 50 MPa or less.

After curing, the present film preferably has the viscoelastic property (b) below, and also preferably has the viscoelastic property (c) below.
(b) The storage modulus _E'20 at a measurement temperature of 20°C is 0.1 MPa or more.
(c) The storage modulus _E'20 at a measurement temperature of 20°C is 0.1 MPa or more and 500 MPa or less.
The film has a storage modulus _E'20 of 0.1 MPa or more, and therefore has a certain degree of hardness after curing, resulting in good handling properties after curing.
Furthermore, by virtue of the viscoelastic property (c) above, the present film tends to exhibit excellent acoustic properties, such as sound quality and reproducibility, when used in acoustic components such as vibration films. From the viewpoints of acoustic properties and ease of handling after curing, the storage modulus _E'20 at 20°C after curing is preferably 1 MPa or more, more preferably 2 MPa or more, even more preferably 4 MPa or more, more preferably 400 MPa or less, even more preferably 300 MPa or less, even more preferably 200 MPa or less, particularly preferably 100 MPa or less, and most preferably 50 MPa or less.

The present film preferably has the following viscoelastic property (d) after curing.
(d) The storage modulus E' ₁₀₀ at a measurement temperature of 100°C is 0.1 MPa or more and 500 MPa or less.
When the storage modulus _E'100 of the present film after curing is within the above range, it is expected that the film will have good heat resistance and will exhibit excellent acoustic properties even in high temperature environments.
The storage modulus _E'100 is more preferably 1 MPa or more, even more preferably 1.5 MPa or more, even more preferably 2.5 MPa or more, and more preferably 400 MPa or less, even more preferably 300 MPa or less, even more preferably 200 MPa or less, particularly preferably 100 MPa or less, and most preferably 50 MPa or less.

Furthermore, the present film preferably has the following viscoelastic property (e) after curing.
(e) The ratio (E' ₁₀₀ /E' ₂₀ ) of the storage modulus E' ₁₀₀ to the storage modulus _E ' 20 is 0.4 or more and 1.0 or less.
By setting the storage modulus ratio ( _E'100 / _E'20 ) within the above range, the change in elastic modulus due to temperature change becomes small, and heat resistance tends to be good. In addition, since the change in elastic modulus upon heating is small, sound quality is less likely to deteriorate in high-temperature environments, and sound reproduction from low to high temperatures becomes excellent.
The ratio ( _E'100 / _E'20 ) is more preferably 0.5 or more, even more preferably 0.6 or more, and even more preferably 0.65 or more. It is also more preferably 0.99 or less, even more preferably 0.97 or less, even more preferably 0.95 or less, and particularly preferably 0.93 or less.

(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 long-term vibration, and it tends 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.

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.
In the case of curing 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 curing by radiation, 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 present 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, it is advisable to measure in the TD (the direction perpendicular to the flow direction (MD) of the resin).

As described above, the present film is curable by having at least the intermediate layer be curable. The present film may be photocurable, moisture-curable, or thermocurable, but is preferably thermocurable. By having thermocurable properties, the present film can be cured when shaped while being heated, thereby improving formability. Furthermore, if the present film has thermocurable properties, its gel fraction increases when heated. Furthermore, it is sufficient for at least the intermediate layer of the present film to be thermocurable, but the outermost and inner layers may also be thermocurable as appropriate.

The present film preferably has a crosslinked structure. The presence of a crosslinked structure in the present film facilitates improved shape retention before curing (i.e., before molding). Furthermore, the present film preferably has a crosslinked structure in at least the outermost and innermost layers. The presence of a crosslinked structure in the outermost and innermost layers facilitates improved shape retention without significantly impairing the flexibility of the film before curing. Furthermore, the presence of a crosslinked structure in the outermost and innermost layers facilitates adjustment of the gel fraction of the outermost and innermost layers to within the desired range described above.

The thickness of this film is not particularly limited, but is 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 film thickness is within this range, it is possible to produce molded products with a thickness suitable for acoustic components, particularly diaphragms.

The thickness of the intermediate layer is not particularly limited, but is preferably 3 μm or more and 300 μm or less, more preferably 5 μm or more and 200 μm or less, and even more preferably 20 μm or more and 150 μm or less. By making the thickness of the intermediate layer equal to or greater than the above lower limit, an uncured portion with high flexibility and a certain thickness or more will be provided in the film, thereby improving formability and making it easier to improve conformability to the mold during molding. Furthermore, by making the thickness equal to or less than the above upper limit, it is possible to prevent the highly flexible portion from becoming unnecessarily thick, making it easier to improve shape retention before molding. Note that the thickness of the intermediate layer refers to the total thickness when there are two or more intermediate layers.

The ratio of the thickness of the intermediate layer to the thickness of the entire film (intermediate layer/entire film) is preferably 4/10 or greater, more preferably 5/10 or greater, and even more preferably 6/10 or greater. By setting the thickness ratio (intermediate layer/entire film) at or above the above lower limit, a certain proportion of highly flexible portions will be provided in the film, which will make it easier to improve formability and mold-following ability during molding. The thickness ratio (intermediate layer/entire film) is preferably 9.9/10 or less, more preferably 9.8/10 or less, and even more preferably 9.7/10 or less. By setting the thickness ratio (intermediate layer/entire film) at or below the above upper limit, it will be easier to make the outermost and innermost layers at or above a certain thickness.

The thickness of each of the outermost and innermost layers is not particularly limited, but is preferably 1 μm or more and 100 μm or less, more preferably 1 μm or more and 60 μm or less, and even more preferably 1 μm or more and 30 μm or less. By making the thickness of each of the outermost and innermost layers equal to or greater than the above lower limit, shape retention before molding can be improved and sticking to the mold can be prevented. Furthermore, by making the thickness equal to or less than the above upper limit, parts above a certain hardness can be prevented from becoming thicker than necessary, making it easier to improve shapeability and mold conformability during molding.

The thickness of each of the outermost and innermost layers should be smaller than the thickness of the intermediate layer, and the ratio of the thickness of each of the outermost and innermost layers to the thickness of the intermediate layer (each outermost and innermost layer/intermediate layer) is preferably 1/50 or more and less than 1. If the thickness of each of the outermost and innermost layers is smaller than the thickness of the intermediate layer, a highly flexible portion of the film will be contained at a certain thickness ratio, which will make it easier to improve shapeability and mold-following ability during molding. Furthermore, if the ratio (each outermost and innermost layer/intermediate layer) is equal to or greater than the above lower limit, shape retention before molding will be improved and sticking to the mold will be more easily prevented.
From these viewpoints, the ratio (each of the outermost and innermost layers/intermediate layer) is more preferably 1/50 or more and 3/5 or less, and even more preferably 1/50 or more and 2/5 or less.

The intermediate layer and the outermost and innermost layers of the present film are each a resin layer, and the resin constituting each 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. In each layer of the present film, these resins may be used alone or in combination of two or more.
In addition, in the present film, each layer (middle layer, outermost layer, and innermost layer) may use the same type of resin or different types of resins, but it is preferable that the middle layer and the outermost and innermost layers use the same type of resin. That is, for example, if a silicone resin is used for the middle layer, it is preferable that a silicone resin is also used for the outermost and innermost layers. By using the same type of resin, it becomes easier to bond each layer (for example, between the middle layer and the outermost layer, or between the middle layer and the innermost layer) without using an adhesive layer or the like.

The film is preferably a silicone film. A silicone film is one in which any one of the intermediate layer, outermost layer, and innermost layer uses a silicone resin as the resin, and it is particularly preferable that the intermediate layer, outermost layer, and innermost layer all use a silicone resin. When the film is a silicone film, the heat resistance and mechanical strength are improved, and the viscoelastic properties (a) to (e) described above are more likely to be satisfied. Furthermore, the tensile elongation at break and static friction coefficient can be more easily adjusted to fall within the desired ranges described above.

(organopolysiloxane)
The silicone resin used in the intermediate layer and the outermost and innermost layers 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.

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

It is also preferable that the molecular chain terminals of the organopolysiloxane be blocked with trimethylsilyl groups, dimethylvinyl groups, dimethylhydroxysilyl groups, trivinylsilyl groups, or the like. The organopolysiloxane preferably contains at least two alkenyl groups in the molecule. Specifically, it is preferable that the R contains 0.001 mol % to 5 mol %, preferably 0.005 mol % to 3 mol %, more preferably 0.01 mol % to 1 mol %, and particularly 0.02 mol % to 0.5 mol % of alkenyl groups, and it is particularly preferable that it 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 types with different molecular structures.

The organopolysiloxane in the top and bottom layers is preferably crosslinked with a crosslinking agent, preferably an organic peroxide. Therefore, each of the top and bottom layers 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 top and bottom layers should be cured so that the gel fraction falls within the desired range described above. Therefore, the organic peroxide blended into the top and bottom layers is mostly decomposed, and either no organic peroxide is contained in each of the top and bottom layers, or if it is contained, it is only in small amounts.

On the other hand, in the intermediate layer, the organopolysiloxane is preferably in an uncrosslinked state or, if crosslinked, in a partially crosslinked state. Therefore, the intermediate layer is preferably made of a resin composition containing an organopolysiloxane and a crosslinking agent such as an organic peroxide. In this case, the intermediate layer is preferably in an uncured state or, if cured, in a semi-cured state so that the gel fraction falls within the desired range described above. Therefore, it is preferable that the organic peroxide blended into the intermediate layer remains in the organic peroxide state without decomposing much.

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. However, from the standpoint of crosslinking speed and safety, alkyl peroxides, especially 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, are preferred.

The amount of organic peroxide in the resin compositions forming the intermediate layer and the outermost and innermost layers 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 especially preferably 0.3% by mass to 2% by mass. A content of organic peroxide within this range tends to safely produce a composition with a sufficient curing rate. As mentioned above, the organic peroxide contained in the resin composition is mostly decomposed and hardly present in the outermost and innermost layers, but it is preferable for the organic peroxide to be present in the intermediate layer within the above-mentioned range.

The resin composition is preferably a millable type containing organopolysiloxane. Millable type resin compositions are non-liquid (e.g., solid or paste-like) and lack self-flowing properties at room temperature (25°C) when uncured, 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 outermost layers, as described below.

As mentioned above, the resin compositions used in the intermediate layer and the top and bottom layers may be resins other than silicone resins (organopolysiloxanes). In such cases, the top and bottom layers may be layers formed by curing a resin composition containing a resin and a crosslinking agent so that the gel fraction falls within the desired range. Similarly, the intermediate layer may be formed from a resin composition containing a resin and a crosslinking agent. In this case, the resin composition may be uncured or semi-cured so that the gel fraction falls within the specified range.

The intermediate layer, outermost layer, and innermost layer of the present invention may each contain a filler such as a silica-based filler. By incorporating a filler into each layer of the present film, the film's mechanical properties, such as its storage modulus and tensile elongation at break, can be more easily adjusted to an appropriate range. 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 more 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.

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 or more and 50% by mass or less, preferably 15% by mass or more and 40% by mass or less, and more preferably 20% by mass or more and 35% by mass or less, based on the total amount of the resin composition constituting each layer. 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 the median diameter (D50) using a particle size distribution measuring device using a laser light diffraction method or the like.

In the present invention, the resin composition used to form each layer may contain various additives, such as heat stabilizers, antioxidants, UV absorbers, light stabilizers, antibacterial and antifungal agents, antistatic agents, lubricants, pigments, dyes, flame retardants, and impact modifiers, to the extent that the effects are not impaired.

In this film, the resin compositions for forming the outermost layer and the innermost layer may have the same composition, or may have different compositions. Similarly, the resin composition for forming the intermediate layer may have the same composition as the resin compositions for forming the outermost layer and the innermost layer, or may have different compositions. Note that the composition of the resin composition here refers to the composition of the resin composition before it is cured.

In the present invention, commercially available organopolysiloxanes can be used. Alternatively, commercially available mixtures containing additives such as silica-based fillers in addition to organopolysiloxanes 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.

[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 the case of a film with a release film, it is preferable that a release film is provided on both sides of the film. The release film is laminated on the outermost layer, the innermost layer, or both of the outermost and innermost layers of the film.

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 outermost surface and the inner surface of 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 from 5 μm to 100 μm, more preferably from 7 μm to 80 μm, and even more preferably from 10 μm to 50 μm.

The present film is protected by the release film attached thereto. This prevents the film from being scratched during transportation, etc. As described below, the release film may be the release film laminated on the outermost and innermost layers when the present film is manufactured, or may be laminated separately on the manufactured present film.
The present film is molded, for example, by a molding process 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. Even without a release film, the present film has good shape retention even before curing and can be prevented from sticking to the mold during molding by having the specified outermost and inner layers as described above.

[Manufacturing method of the present film]
The present film can be formed by a general forming method, for example, lamination forming, extrusion forming such as co-extrusion, coating, or a combination of these. Among these, lamination forming is preferred in consideration of the ease of forming a multilayer structure with an outermost layer, a back layer, and an intermediate layer.

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.

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 calendar 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 resins, 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, preferably 5 minutes to 1 hour.

The resin composition for the outermost or innermost layer prepared as described above may be laminated on a release film by a conventional method to obtain a laminate, and then the laminate may be heated or the like to cure the resin composition. This results in a laminate (hereinafter also referred to as a "laminate film") in which the outermost or innermost layer is laminated on the release film. In the laminate film, the outermost or innermost layer preferably forms a crosslinked structure by curing, and has a gel fraction of 80% or more as described above.
When the release film has a release-treated surface, the resin composition for the outermost layer may be laminated on the release-treated surface of the release film.
Alternatively, the resin composition for the outermost or innermost layer may be laminated between two release films, and then the resin composition may be appropriately cured by heating or the like, and then one of the release films may be peeled off to obtain the above-mentioned laminated film.

In addition, as described above, in this manufacturing method, by laminating the resin composition for the top and bottom layers onto a release film and curing it, the surfaces of the resulting top and bottom layers have a shape that corresponds to the surface shape of the release film. Therefore, by adjusting the surface shape of the release film, the surface shape of the top and bottom layers can also be adjusted.

Next, an intermediate layer formed from the intermediate layer resin composition is laminated between the laminate films by lamination molding 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/release film, and becomes the above-mentioned film with release film.

[Molded product]
The film can be molded into various articles by being shaped in a mold such as a die and cured. Typically, the film is molded into various articles by being shaped in a mold. Curing can be performed according to the film's properties, and can be performed by heating, light irradiation, moisture application, or a combination of these, but is preferably performed by heating. The molded article is preferably an acoustic component, more preferably 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 to form it in a mold and curing it. Step 2: Peeling the formed and cured film (i.e., the molded product) from the mold.

Each step will be described in more detail below.
(Step 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 in the 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.
That is, in step 1, the film is placed in a mold and thermoformed to obtain a laminate consisting of the mold and the film, and the film is preferably heat-pressed.

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 produced. Typically, a metal mold (metal die) is used, but a resin mold may also be used. For example, as described below, if the molded product (acoustic component) has at least one of a dome shape or a cone shape, the mold may have projections and recesses corresponding to the dome or cone shape. Furthermore, if the molded product (acoustic component) has a tangential edge on its surface, the mold may have projections and recesses corresponding to the tangential edge.

As mentioned above, this film may be attached with a release film, but it is recommended that the release film be removed before setting the film in the mold.

In step 1, the heated film may be shaped using a mold. For example, the film may be placed on a mold and shaped using the mold while being heated, or the film may be preheated and placed on the mold and then shaped using the mold, or a combination of these may be used. The film may also 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.

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 or lower. 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 the heat.

The shaping 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. 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.

(Step 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 static friction coefficient of the outermost and inner layers of the film is low, so the film is prevented from sticking to the mold without the need for a release film or the like, and the molded article obtained from the film can be easily peeled from the mold. In addition, the middle layer of the film has a gel fraction below a certain value, so it has high formability and high conformability to the mold. Therefore, molded articles can be produced with high molding precision.
Furthermore, the provision of the outermost and innermost layers of this film provides high shape retention, good handling even without a release film, and allows the film to be easily set in a mold while maintaining its shape even without a release film. Furthermore, the absence of a release film layer eliminates the step of peeling the release film from the molded product, making mass production easier.

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 with a storage modulus and mechanical strength suitable for acoustic components. The gel fraction of the molded article is more preferably 85% or more, and even more preferably 90% or more. There is no particular upper limit to the gel fraction of the molded article; it may be 100% or less, but it is generally 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 is preferably measured by sampling parallel to the thickness direction of the molded article. Details of the method for measuring the gel fraction are as described above.

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

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.

(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.

The film may form at least a portion of the diaphragm; for example, the body or edge of the diaphragm may be formed from the film, with the edge or body of the diaphragm formed from a separate material. Of course, both the body and edge may be integrally formed from the film, or the entire diaphragm may be formed from the film.

Figure 1 shows 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 Figure 1, the diaphragm 1 has a dome portion (body) 1a at its center, a recessed portion 1b for attaching to the voice coil 2, a peripheral portion (edge) 1c, and an external attachment portion 1d on its outer periphery for attaching to a frame or the like.

Figure 2 shows the structure of a diaphragm 11 in another embodiment of the present invention, and is a cross-sectional view of the circular diaphragm 11 cut along a plane passing through the centerline of the circle when viewed from above. The diaphragm 11 is a diaphragm for a micro-speaker. As shown in Figure 2, the diaphragm 11 has a dome-shaped dome portion (body) 11a at its center, a recessed portion 11b attached to the voice coil 2, a cone portion 11j machined into a cone shape, and a peripheral portion (edge) 11c. As shown in the example of diaphragm 11, the diaphragm may have a portion machined into a dome shape and the remaining portion machined into a cone shape. Note that the peripheral portions 11c of the diaphragm 11 may be attached directly to a frame or the like, or may be attached to a frame or the like via another member.

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

As mentioned above, the diaphragm is preferably a speaker diaphragm, particularly a microspeaker diaphragm. From the perspective of suitable use as a microspeaker diaphragm, the size of the diaphragm should be such that the maximum diameter is 25 mm or less, preferably 20 mm or less, and preferably 5 mm or more. Note that the maximum diameter refers to the diameter if the diaphragm is circular, and the major axis if the diaphragm is elliptical or oval.

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

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

(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.

The present invention will be described in detail below using examples, but the present invention is not limited thereto.

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

(1) Measurement of Gel Fraction 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 according to the method described in the specification. When measuring the gel fraction of the entire film, samples were taken evenly parallel to the thickness direction of the film. For the middle layer of the film before curing, the gel fraction 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.

(2) Storage modulus E'
Test pieces measuring 4 mm x 8 cm were cut from the pre-cured and post-cured films obtained in each Example and Comparative Example to obtain measurement samples. Using these measurement samples, a viscoelasticity spectrometer "DVA-200 (manufactured by IT Measurement & Control Co., Ltd.)" was used in accordance with JIS K7244-4:1999. The measurement mode was tension, the frequency was 10 Hz, the strain was 0.1%, the temperature range was 0 to 300°C, and the temperature was raised at a heating rate of 3°C/min. The storage modulus of the pre-cured film was measured at 20°C. Furthermore, the storage modulus of the cured film was measured at 20°C and 100°C. Measurements were performed in the TD.

(3) Static Friction Coefficient The static friction coefficient between the top and bottom surfaces of the present film obtained in each Example and Comparative Example and a stainless steel plate (SUS430) was measured. The static friction coefficient was measured three times for each of the top and bottom surfaces of the present film obtained in each Example and Comparative Example before thermoforming, and the average value was calculated. The specific method for measuring the static friction coefficient is as follows.
With reference to JIS K7125 (1999), the back or front surface of this film was brought into contact with a stainless steel plate and held there for 15 seconds before the start of the test, and then measurements were carried out in the machine direction (MD) under the following conditions to evaluate the static friction coefficient with the stainless steel plate.
・Device: Plastic film sliding tester (manufactured by Intesco)
- Slider: Total mass 200 g (contact area is a square with a side length of 63 mm)
・Contact area: ^40cm2
Test speed: 100 mm/min
・Temperature: 23℃±2℃
Relative humidity: 50% ± 10%

(4) Handling properties (4-1) Presence or absence of tearing The presence or absence of tearing was evaluated in the process of manually peeling the release film from the film with release film. Films in which the release film could be peeled off without tearing were evaluated as "Good", and films in which a part of the film was torn by 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.
(4-2) Shape Retention The shape retention of the present films obtained in each Example and Comparative Example before curing was evaluated. When the present films were peeled from the release film and used for various evaluations and measurements, those that could be easily handled because their shape was maintained were evaluated as "Good." Those that could not maintain their shape and bent during the handling process, causing the film itself to become tangled or break were evaluated as "Poor."

(5) Moldability and Shapeability 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 dome-shaped diaphragm mold with a tangential edge preheated to 240°C and pressed at a pressure of 0.6 MPa. The pressed state was maintained for 30 seconds, and then the samples were removed from the mold.
After removal, the samples were visually inspected, and samples with the same irregularities as those in the mold were rated "Good", while samples with smaller irregularities than those in the mold or no irregularities at all were rated "Poor".

(6) Adhesion to Mold As in the evaluation of moldability and shaping ability described above, test pieces of approximately 7 cm × 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 pressed state was maintained for 30 seconds, and then the samples were removed from the mold.
When the evaluation sample was removed from the mold, if the evaluation sample did not stick to the mold and could be easily removed, it was evaluated as "Good", and if the evaluation sample stuck to the mold and got caught, it was evaluated as "Poor".

(7) Tensile Breaking Elongation The elongation at break of the cured film in the TD was measured in accordance with JIS K7161:2014 at a tensile speed of 200 mm/min at 23°C.

Example 1
For the outermost and innermost layers, a PET film (1) with a surface roughness (Ra) of 0.88 μm and a PET film (2) with a surface roughness (Ra) of 1.9 μm were prepared as release films. A 20 μm thick silicone rubber (trade name "TSE2571-5U", manufactured by Momentive Performance Materials, Inc.) was laminated between the PET film (1) and the PET film (2) to prepare a cured laminated film, and the PET film (1) was 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 resin composition (1).
The above laminated film was fed along two 100 mm diameter calendar rolls with the cured silicone exposed side facing inward. Resin composition (1) was added between the laminated film between the calendar rolls, and a bank was formed on the roll at room temperature of 25 ° C. and a roll temperature of 90 ° C. The resulting film with release film consisted of release film/outermost layer/intermediate layer/innermost layer/release film so that the thickness of the intermediate layer was 100 μm. The two release films were manually peeled off from the resulting film with release film to obtain this film. The gel fractions of the outermost and innermost layers and intermediate layers of this film, the static friction coefficients of the outermost and innermost layers, and the storage modulus of this film at 20 ° C. were measured. The measurement results and evaluation results of handleability are shown in Table 1.

Assuming the film would be manufactured into a molded article 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, and tensile elongation at break of the cured film were measured.

Comparative Example 1
Instead of the laminated film, a release film (PET film (2)) alone was supplied 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 a release film consisting of release film/intermediate layer/release film so that the thickness of the intermediate layer was 100 μm.
The two release films were peeled off from the resulting film with release films to obtain this film. This film consisted of a single intermediate layer. The gel fraction and static friction coefficient of this film (intermediate layer) were measured, as well as the storage modulus at 20°C. The measurement results and the evaluation results of handleability are shown in Table 1.

Assuming the film was to be molded into a shape suitable for extrusion, the film obtained above was cured using a simple press molding method in which it was heated at 220°C for 2 minutes and pressed between two flat plates at a pressure of 0.2 MPa. The gel fraction, storage modulus, and tensile elongation at break of the cured film were measured.

Comparative Example 2
Instead of a laminated film, a release film (PET film (2)) alone was fed along two calendar rolls with a diameter of 100 mm, and resin composition (1) was poured between the release films between the calendar rolls. A bank was formed on the rolls at room temperature of 25°C and a roll temperature of 90°C, and a film with a release film consisting of release film/intermediate layer/release film was obtained so that the thickness of the intermediate layer was 100 μm. The film with the release film was heated by a simple method of press-molding from two flat plates at a pressure of 0.2 MPa while heating at 220°C for 2 minutes, thereby curing the intermediate layer.
After the intermediate layer was cured, the two release films were peeled off from the resulting film with release films to obtain this film. This film consisted of a single intermediate layer. The static friction coefficient and storage modulus at 20°C of this film (intermediate layer) were measured. The measurement results and the evaluation results of handleability are shown in Table 1.

In addition, since this film had already completed curing, the gel fraction, storage modulus, and tensile elongation at break were measured for this film.

Table 1 below summarizes the evaluation and measurement results for Example 1 and Comparative Examples 1 and 2.

The films of the above examples had a curable intermediate layer and outermost and innermost layers, and the static friction coefficient of the outermost and innermost layers was 3 or less, so they could be sufficiently shaped by molding, had good mold-following ability, and were able to prevent the film from sticking to the mold during molding. Furthermore, because the outermost and innermost layers were relatively hard, the film shape was properly maintained even after the release film was peeled off, exhibiting excellent hanging properties and allowing it to be easily set in the mold.
Furthermore, since the present film after curing satisfies the viscoelastic properties (c) to (e) described above, it is expected that when an acoustic component such as a diaphragm is molded using the film of Example 1, the acoustic component will have excellent acoustic properties such as sound quality and reproducibility. Furthermore, the present film after curing has a high tensile elongation at break, making it less likely to break due to prolonged vibration, and it is also expected that an acoustic component with excellent durability can be provided.

In contrast, the film of Comparative Example 1 had a high coefficient of static friction on the surface, and therefore, although it had good formability and mold conformability, the film stuck to the mold during molding. Furthermore, since it did not have a multilayer structure having an outermost and inner layer and a curable intermediate layer, the entire film was relatively flexible, and therefore it was difficult to properly maintain its shape after the release film was peeled off, and the hanging properties were poor.
In addition, in Comparative Example 2, the static friction coefficient of the surface was low, so the film did not stick to the mold during molding; however, since the film did not have a multilayer structure with outermost and inner layers and a curable middle layer, and the entire film was relatively hard, it could not be sufficiently shaped by molding, and its conformability to the mold was also insufficient.

Claims (21)

A film comprising an outermost layer and an innermost layer having a static friction coefficient of 3 or less as measured by a sliding test based on JIS K7125 (1999), and at least one curable intermediate layer disposed between the outermost layer and the innermost layer,
The ratio of the thickness of the intermediate layer to the thickness of the entire film (intermediate layer/entire film) is 4/10 or more, and the resin composition forming the intermediate layer is a millable type containing an organopolysiloxane,
The film , wherein the outermost and innermost layers contain a silicone resin . The film described in claim 1, wherein the ratio of the thickness of the intermediate layer to the thickness of the entire film (intermediate layer/entire film) is 6/10 or greater. The film according to claim 1 or 2, having a gel fraction of 0% or more and 90% or less. The film according to any one of claims 1 to 3, wherein the outermost and innermost layers contain a cured silicone resin. The film according to any one of claims 1 to 4 , wherein the outermost and innermost layers each have a gel fraction of 80% or more. The film according to any one of claims 1 to 5, wherein the intermediate layer has a gel fraction of 70% or less. The film according to any one of claims 1 to 6 , which has the following viscoelastic property (a):
(a) The storage modulus E' at a measurement temperature of 20°C is 0.1 MPa or more and 500 MPa or less. The film according to any one of claims 1 to 7 , which has thermosetting properties. The film according to any one of claims 1 to 8 , which has a crosslinked structure. The film according to any one of claims 1 to 9 , which is a silicone film. The film according to any one of claims 1 to 10 , which has the following viscoelastic property (b) after curing:
(b) The storage modulus _E'20 at a measurement temperature of 20°C is 0.1 MPa or more. The film according to any one of claims 1 to 11 , which has the following viscoelastic properties (c) to (e) after curing:
(c) The storage modulus _E'20 at a measurement temperature of 20°C is 0.1 MPa or more and 500 MPa or less.
(d) The storage modulus E' ₁₀₀ at a measurement temperature of 100°C is 0.1 MPa or more and 500 MPa or less.
(e) The ratio (E' ₁₀₀ /E' ₂₀ ) of the storage modulus E' ₁₀₀ to the storage modulus _E ' 20 is 0.4 or more and 1.0 or less. The film according to any one of claims 1 to 12, which has a tensile elongation at break of 300% or more after curing. The film according to any one of claims 1 to 13 , which is a film for a diaphragm. A film with a release film, comprising: the film according to any one of claims 1 to 14 ; and a release film provided on at least one surface of the film. A diaphragm obtained by curing the film according to any one of claims 1 to 14 . A laminate obtained by placing the film according to any one of claims 1 to 14 in a mold and thermoforming it. 20. A molded article obtained by peeling the laminate according to claim 17 from a mold. 19. The molded article of claim 18 , which is a diaphragm. An acoustic transducer comprising the diaphragm according to claim 16 or 19 . A method for producing a film, comprising heating a laminate obtained by laminating a resin composition on a release film, laminating an intermediate layer formed from a millable resin composition for an intermediate layer containing an organopolysiloxane between the obtained laminated films so that the ratio of the thickness of the intermediate layer to the thickness of the entire film (intermediate layer/entire film) is 4/10 or more, and peeling off the release film,
A method for producing a film comprising a top and back layer having a static friction coefficient of 3 or less as measured by a sliding test based on JIS K7125 (1999), and at least one curable intermediate layer disposed between the top and back layers , wherein the top and back layers contain a silicone resin .