JP7103271B2 - Laminated sheet - Google Patents

Description

The present invention relates to laminated sheets, diaphragms, and speakers.

Porous films with a large number of fine pores are separation membranes used for the production of ultrapure water, purification of chemicals, water treatment, etc., moisture permeable and waterproof films used for clothing and sanitary materials, electronic devices and houses. It is used in various fields such as a heat insulating film used for building materials and a battery separator used for batteries and the like. However, it has been difficult to use in applications where rigidity is required due to the innumerable pores inside.

A speaker diaphragm that vibrates to generate sound is known as an application of a porous film that requires rigidity. With the widespread use of small electronic devices (for example, mobile phones, notebook computers, smartphones, etc.), the demand for small speakers (so-called micro-speakers) and microphones is increasing.

In order to make the diaphragm easier to vibrate and to reduce the size, a diaphragm made of a foam sheet, which is a kind of resin porous film capable of vibrating with a weak force, is being studied.
For example, Patent Document 1 describes the use of a foam sheet containing a polypropylene resin as a main component for a diaphragm.
Further, as an effort to enhance the rigidity of the foamed sheet, Patent Document 2 describes a laminated structure with a non-woven fabric, and Patent Document 3 describes a laminated structure with an aluminum face material.

Japanese Unexamined Patent Publication No. 2011-178956 JP-A-2007-258864 Japanese Unexamined Patent Publication No. 2004-064726

As disclosed in Patent Document 2 and Patent Document 3, by laminating a porous film and another sheet, both rigidity and weight reduction can be achieved to some extent, but as described above, Due to further miniaturization of electronic devices, there has been a demand for a laminated sheet that is lighter in weight, has excellent rigidity, and does not peel off between laminated films even when an external force such as vibration for a long time is applied.
An object of the present invention is to provide a laminated sheet which is lightweight, has excellent rigidity, and has excellent adhesive strength between films.

The present invention is a laminated sheet in which a resin layer and a porous film are sequentially provided on at least one side of a base film, the tensile elastic modulus of the laminated sheet is 1000 to 2500 MPa, and the average pore diameter of the porous film is 0. It relates to a laminated sheet in the range of 01 to 1 μm.

Since the laminated sheet of the present invention is lightweight, has excellent rigidity, and has excellent adhesive strength between sheets, it is suitably used as a diaphragm for a speaker or the like.

Next, the present invention will be described based on examples of embodiments. However, the present invention is not limited to the embodiments described below.

1. 1. Base film The base film is not limited in material and composition as long as it has the required rigidity.

The base film may be a single layer or a multi-layer, but is preferably a single layer. When the base film has multiple layers, it may have two layers or three or more layers.

The base film is preferably made of a resin, and preferably made of a polyester resin. Even in the case of multiple layers, it is preferable that each layer is made of a polyester resin.
The polyester-based resin contains at least 50% by mass or more of polyester, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 100% by mass.

The polyester may be a homopolyester or a copolymerized polyester. When it is made of homopolyester, it is preferably obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol and the like. As a typical homopolyester, polyethylene terephthalate can be exemplified.

Examples of the dicarboxylic acid component of the copolymerized polyester include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, sebacic acid and the like, and ethylene glycol as the glycol component. , Diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like.

Specific examples of the polyester include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN).

Other resins include polyarylates, polyether sulfone, polycarbonate, polyether ketone, polysulfone, polyphenylene sulfide, polyester liquid crystal polymer, triacetyl cellulose, cellulose derivative, polypropylene, polyamides, polyimide (PI), polycycloolefin. Kind and the like can be exemplified. Among the resins, PET, PEN, and PI are preferable in terms of handleability.

The base film may contain particles for the purpose of imparting slipperiness to the film surface and for the main purpose of preventing scratches in each step.
The type of the particles is not particularly limited. For example, inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, benzoguanamine. Examples include organic particles such as resin. These may be used alone or in combination of two or more.
As the particles, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the polyester production process can also be used.
The shape of the particles is not particularly limited. For example, it may be spherical, lumpy, rod-shaped, flat-shaped, or the like.
Further, the hardness, specific gravity, color and the like of the particles are not particularly limited. Two or more kinds of these series of particles may be used in combination, if necessary.

The average particle size of the particles is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2.5 μm or less. Further, 0.01 μm or more is preferable, and 0.5 μm or more is more preferable. If it exceeds 5 μm, the surface roughness of the base film becomes too coarse, and problems may occur when various surface functional layers are formed in a subsequent step.

When particles are used, the particle content is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less of the base film. Further, 0.01% by mass or more is preferable, and 2% by mass or more is more preferable. By setting the particle content in such a range, it is possible to achieve both slipperiness and transparency of the film, which is preferable.

The method of adding the particles to the base film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage in the production of polyester. It is preferable to add the ester after the esterification or transesterification reaction is completed.

If necessary, conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers and the like can be added to the base film.

The thickness of the base film is not particularly limited as long as it can be formed as a film, and is preferably 9 to 125 μm, more preferably 12 to 100 μm, and even more preferably 12 to 75 μm.

The base film can be formed, for example, by forming the resin composition into a film shape by a melt film forming method or a solution film forming method. In the case of a multi-layer structure, co-extrusion may be performed.
Further, it may be uniaxially stretched or biaxially stretched, and a biaxially stretched film is preferable from the viewpoint of rigidity.

From the viewpoint of using a general-purpose film, the tensile elastic modulus of the base film is preferably 2.0 GPa or more and 4.5 GPa or less, more preferably 2.0 GPa or more and 4.0 GPa or less, and further preferably 2.0 GPa or more. It is 5 GPa or less. Among them, a polyester film having the tensile elastic modulus is preferable in terms of versatility.

2. Resin layer The resin layer in the laminated sheet of the present invention is made of a resin as a main component, preferably a thermoplastic resin. The resin layer may contain particles, a cross-linking agent, and the like as components other than the resin.

From the viewpoint of achieving both the adhesiveness between the porous film and the base film and the durability such as solvent resistance and heat resistance, the resin layer is preferably made of an acrylic resin, a polyester resin, or a mixture thereof. More preferably, it is made of an acrylic resin.

2-1. Acrylic resin The acrylic resin is preferably obtained by polymerizing one or more kinds selected from the group consisting of acrylic acid esters, vinyl-based monomers, methacrylic acid esters, and crosslinkable monomers. Those obtained by polymerizing monomers containing two or more types are more preferable, and those having a structural unit derived from these monomers are preferable.
For example, those obtained by polymerizing a monomer containing two or more kinds include a combination of a crosslinkable monomer and an acrylic acid ester, a combination of a crosslinkable monomer and a methacrylic acid ester, and methacryl. A combination of acid esters and vinyl-based monomers is preferably exemplified.

When two types of monomers (A / B) are used, the blending ratio (A / B) is a mass ratio, preferably 90/10 to 10/90, more preferably 80/20 to 40/60. , More preferably 70/30 to 40/60. In this case, the monomer A is preferably allyl acrylate, allyl methacrylate, 1-acryloxy-3-butene, 1-methacryloxy-3-butene, and the monomer B is pentaerythritol triacrylate or polyethylene glycol. Diacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate are preferable.

The crosslinkable monomer refers to a monomer having two or more polymerizable functional groups in one molecule.
Examples of the crosslinkable monomer include allyl acrylate, allyl methacrylate, 1-acryroxy-3-butene, 1-methacryloxy-3-butene, 1,2-diacryloxy-ethane, 1,2-dimethacryloxy-ethane, and the like. 1,2-Diacryloxy-propane, 1,3-diacryloxy-propane, 1,4-diacryloxy-butane, 1,3-dimethacryloxy-propane, 1,2-dimethacryloxy-propane, 1,4-dimethacryloxy-butane, triethylene Glycoldimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, triethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate , Divinylbenzene, 1,4-pentadiene, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate and the like. These may be used alone or in combination of two or more.

Examples of acrylates include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, and amyl acrylate. , Acrylic acid acyclic alkyl ester such as isoamyl acrylate, n-hexyl acrylate, 2-ethyl hexyl acrylate, pentadecyl acrylate, dodecyl acrylate; acrylic acid cyclic alkyl ester such as cyclohexyl acrylate, isobornyl acrylate; acrylate; Acrylic acid aryl esters such as phenyl and naphthyl acrylate; functional group-containing acrylic acid non-cyclic alkyl esters such as 2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, and glycidyl acrylate are exemplified.

Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate and amyl methacrylate. Acyclic alkyl esters of methacrylic acid such as isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate and dodecyl methacrylate; cyclic alkyl esters of methacrylic acid such as cyclohexyl methacrylate and isobornyl methacrylate; methacrylic acid. Methacrylic acid aryl esters such as phenyl; functional group-containing acyclic alkyl esters of methacrylic acid such as 2-hydroxyethyl methacrylate, 2-methoxyethyl methacrylate, and glycidyl methacrylate are exemplified. These may be used alone or in combination of two or more.

The method of polymerizing the resin constituting the resin layer is not limited, but it is preferably photocured using a photopolymerization initiator. The photopolymerization initiator is not particularly limited, and examples thereof include a ketone-based photopolymerization initiator and an amine-based photopolymerization initiator.
In addition, a sensitizer may be used in combination with the photocuring initiator, if necessary.

The content of the photopolymerization initiator in the acrylic resin used in the resin layer is preferably in the range of 1 to 10 parts by mass of the photopolymerization initiator when the total of the monomers is 100 parts by mass. ..
When the amount of the photopolymerization initiator is 1 part by mass or more, the desired polymerization initiation effect can be obtained, and when the amount of the photopolymerization initiator is 10 parts by mass or less, yellowing of the resin layer can be suppressed. The photocurable initiator and sensitizer are preferably used in a proportion of 20% by mass or less based on the solid content of the photocurable composition.

2-2. Polyester-based resin The polyester-based resin is preferably a copolymerized polyester in order to adjust the melting point. Examples of the dicarboxylic acid component of the copolymerized polyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and one or more of sebacic acid, and examples of the glycol component include ethylene glycol, diethylene glycol, and propylene glycol. , Butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like, or two or more thereof.

Further, in order to improve the adhesiveness to the porous sheet, the polyester may contain polyalkylene glycols. Examples of polyalkylene glycols include polyethylene glycol, polytetramethylene glycol, polypropylene glycol and the like. The molecular weight of the polyalkylene glycol is preferably 10,000 or less, more preferably 8,000 or less in order to ensure the transparency of the film.

2-3. Particles The resin layer may contain particles to improve slipperiness and blocking.
For example, inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, benzoguanamine. Examples include organic particles such as resin. These may be used alone or in combination of two or more of them.

2-4. Cross-linking agent When a cross-linking agent is used, it is preferable to use an oxazoline compound, an isocyanate compound, an epoxy compound, a melamine compound, and a carbodiimide compound. Above all, from the viewpoint of improving adhesion, it is more preferable to use at least one of the oxazoline compound and the isocyanate compound.
When such a cross-linking agent is contained, a component for promoting cross-linking, for example, a cross-linking catalyst or the like can be used in combination at the same time.

3. 3. Porous film The porous film in the present invention has an average pore diameter of 0.01 to 1 μm.
The material of the porous film is not limited, but in order to efficiently perforate pores having an average pore diameter in the range specified in the present invention, the main component is preferably a resin, more preferably a thermoplastic resin, and an olefin resin. Is even more preferable, and a propylene-based resin is even more preferable.
The porous film preferably contains an elastomer in addition to the resin, and the elastomer is more preferably a vinyl aromatic elastomer. By adding the elastomer, a fine and highly uniform porous structure can be efficiently obtained, and the shape and diameter of the pores can be easily controlled.
Further, the porous film preferably contains a crystal nucleating agent from the viewpoint of controlling crystals and efficiently obtaining pores, and may contain other additives such as an antioxidant.
The propylene resin, vinyl aromatic elastomer, and crystal nucleating agent will be described in detail below.

3-1. Propylene-based resin Examples of the propylene-based resin include homopolypropylene (propylene homopolymer), or propylene and ethylene, 1-butene, 1-pentene, 1-hexene, 1-hexene, 1-octene, 1-nonen or 1-. Examples thereof include a random copolymer with α-olefin such as decene, a block polymer, and the like. Among these, homopolypropylene is more preferably used from the viewpoint of mechanical strength.

Further, the propylene-based resin preferably has an isotactic pentad fraction showing stereoregularity of 80 to 99%, more preferably 83 to 98%, and further preferably 85 to 97%. When the isotactic pentad fraction is 80% or more, the mechanical strength is good. On the other hand, the upper limit of the isotactic pentad fraction is specified by the upper limit value that can be obtained industrially at present, but this is limited to the case where a resin with higher regularity at the industrial level is developed in the future. is not. The isotactic pentad fraction is a three-dimensional structure in which all five methyl groups, which are side chains, are located in the same direction as the main chain formed by a carbon-carbon bond composed of five consecutive propylene units. Or it means the ratio. ¹³ Obtained from the pentad unit in the polypropylene molecular chain measured by the signal in the methyl group region of the C-NMR spectrum. The attribution of the signal in the methyl group region is described in A.I. Zambelli et al. (Macromol. 8, 687 (1975)).

Further, the propylene resin preferably has Mw / Mn, which is a parameter indicating the molecular weight distribution, of 1.5 to 10.0. It is more preferably 2.0 to 8.0, and even more preferably 2.0 to 6.0. The smaller the Mw / Mn, the narrower the molecular weight distribution. However, by setting the Mw / Mn to 1.5 or more, sufficient extrusion moldability can be obtained, and mass production is possible industrially. On the other hand, by setting Mw / Mn to 10.0 or less, sufficient mechanical strength can be secured. Mw / Mn is measured by the GPC (Gel Permeation Chromatography) method.

The melt flow rate (MFR) of the propylene-based resin is not particularly limited, but the MFR is usually preferably 0.5 to 15 g / 10 minutes, and 1.0 to 10 g / 10 minutes. Is more preferable. By setting the MFR to 0.5 g / 10 minutes or more, it is possible to have a sufficient melt viscosity at the time of molding and secure high productivity. On the other hand, by setting the MFR to 15 g / 10 minutes or less, sufficient strength can be secured. The MFR is measured in accordance with JIS K7210-1 (2014) under the conditions of a temperature of 230 ° C. and a load of 2.16 kg.

The method for producing the propylene-based resin is not particularly limited, and is represented by a known polymerization method using a known polymerization catalyst, for example, a multisite catalyst represented by a Ziegler-Natta type catalyst or a metallocene catalyst. Examples thereof include a polymerization method using a single-site catalyst.

Examples of propylene resins include the trade names "Novatec PP" and "WINTEC" (manufactured by Japan Polypropylene Corporation), "Versify", "Notio", "Toughmer XR" (manufactured by Mitsui Chemicals), "Zeras" and "Thermoran" (Mitsubishi Chemical). "Sumitomo Noblen" "Tough Serene" (Sumitomo Chemicals), "Prime Polypropylene" "Prime TPO" (Prime Polymer), "Adflex" "Adsil" "HMS-PP (PF814)" (Sun Aromar) (Manufactured by), "Inspire" (manufactured by Dow Chemical Co., Ltd.), and other commercially available products can be used.

3-2. Vinyl Aromatic Elastomer The vinyl aromatic elastomer is a type of thermoplastic elastomer containing a styrene component as a part of the component, and is a copolymer consisting of a soft component (for example, a butadiene component) and a hard component (for example, a styrene component). It is a polymer.

In addition, examples of the type of copolymer include random copolymers, block copolymers, and graft copolymers. Generally, various block copolymers such as a linear block structure and a radial branch block structure are known. In the present invention, any structure may be used.

When the vinyl aromatic elastomer is contained in the present invention, it is preferable to include the vinyl aromatic elastomer having a melt flow rate (MFR) of 1 g / 10 minutes or less at a temperature of 230 ° C. and a load of 2.16 kg. The shape of the vinyl aromatic elastomer dispersed in the polypropylene-based resin changes depending on the difference in viscosity with the resin, but if it is an MFR within the above range, the shape tends to be spherical. Unlike a domain having a large aspect ratio, a spherically dispersed domain is preferable because the uniformity of the porous structure obtained by the subsequent stretching step tends to be high and the physical property stability is excellent. Further, when the MFR is within the above range, stress is likely to be concentrated on the domain interface portion between the matrix having a high elastic modulus and the domain having a low elastic modulus during the stretching step, so that a pore starting point is likely to occur and the porosity is likely to occur. ..

The vinyl aromatic elastomer preferably has a styrene content of 10 to 40% by mass, more preferably 10 to 35% by mass. When the styrene content in the vinyl aromatic elastomer is 10% by mass or more, the domain can be effectively formed in the polypropylene-based resin, and when the styrene content is 40% by mass or less, the domain is excessively formed. Large domain formation can be suppressed.

3-3. Crystal nucleating agent It is preferable to further mix the crystal nucleating agent in the porous film. By mixing the crystal nucleating agent, the crystallization of the propylene-based resin is particularly promoted, and the crystal structure becomes densely uniform. Therefore, the propylene-based resin in the film before stretching is composed of a densely homogenized crystal portion and an amorphous portion existing between the crystal portions, and a large amount of vinyl aromatic elastomer is present in the amorphous portion of the propylene-based resin. do. Therefore, the porosity that occurs at the interface between the dense crystal part of the propylene resin and the vinyl aromatic elastomer due to stretching is facilitated by the improvement of the elastic modulus that accompanies the crystallization of the matrix, and by the dense homogenization of the crystals. The resulting porous structure also facilitates the formation of a dense and uniform porous structure.

The content of the crystal nucleating agent is preferably 1.0 × 10 ^-3 to 5.0 parts by mass with respect to 100 parts by mass of the propylene resin.

Examples of the crystal nucleating agent include the α crystal nucleating agent and the β crystal nucleating agent described below, but the α crystal nucleating agent is preferable because a more uniform pore structure is formed.

Examples of α-crystal nucleating agents include inorganic compounds such as talc, myoban, silica, titanium oxide, calcium oxide, magnesium oxide, carbon black, and clay minerals; malonic acid, succinic acid, adipic acid, maleic acid, azelaic acid, and sebacine. Acids, dodecandic acid, citric acid, butanetricarboxylic acid, butanetetracarboxylic acid, naphthenic acid, cyclopentanecarboxylic acid, 1-methylcyclopentanecarboxylic acid, 2-methylcyclopentanecarboxylic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, 1-Methylcyclohexanecarboxylic acid, 4-methylcyclohexanecarboxylic acid, 3,5-dimethylcyclohexanecarboxylic acid, 4-butylcyclohexanecarboxylic acid, 4-octylcyclohexanecarboxylic acid, cyclohexanecarboxylic acid, 4-cyclohexane-1,2-dicarboxylic acid Carboxylic acids excluding aliphatic monocarboxylic acids such as acids, benzoic acids, toluic acids, xylyl acids, ethyl benzoic acids, 4-t-butyl benzoic acids, salicylic acids, phthalic acids, trimellitic acids, pyromellitic acids; Ortho- or basic salts of group monocarboxylic acids such as lithium, sodium, potassium, magnesium, calcium, strontium, barium, zinc and aluminum; Aryl phosphate-based compounds such as lithium-bis (4-t-butylphenyl) phosphate; among the aryl phosphate-based compounds, cyclic polyvalent metal aryl phosphate-based compounds and acetic acid, lactic acid, propionic acid, acrylic acid, Octylic acid, isooctylic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, 12-hydroxystearic acid, ricinolic acid, behenic acid, erucic acid, montanoic acid , Melicic acid, stearoyl lactic acid, β-N-laurylaminopropionic acid, β-N-methyl-N-lauroylaminopropionic acid and other fatty acid group monocarboxylic acids such as lithium, sodium or potassium salt and other fatty acid monocarboxylic acid alkali metals Salt or mixture with basic aluminum, lithium, hydroxy, carbonate, hydride; poly3-methyl-1-butene, poly3-methyl-1-pentene, poly3-ethyl-1-pentene, poly4-methyl -1-Penten, Poly4-methyl-1-hexene, Poly 4,4-dimethyl -1-Pentene, Poly 4,4-Dimethyl-1-Hexene, Poly 4-Ethyl-1-Hexene, Poly 3-Ethyl-1-Hexene, Polyallyl Naphthalene, Polyallyl Norbornane, Atactic Polystyrene, Syndiotactic Polystyrene , Polydimethylstyrene, polyvinylnaphthalene, polyallylbenzene, polyallyltoluene, polyvinylcyclopentene, polyvinylcyclohexane, polyvinylcyclopeptane, polyvinyltrimethylsilane, polyallyltrimethylsilane and other high molecular compounds.

Specific examples of commercially available α-crystal nucleating agents include "Gelall D" series manufactured by Shin Nihon Rika Co., Ltd., "Gelall MD" series, "NA" series manufactured by ADEKA Corporation, "Millad" series manufactured by Milliken Chemical Co., Ltd., and "Hyperform". Series, BASF's "IRGACLEAR" series, etc.

Examples of the β crystal nucleating agent include amide compounds; tetraoxaspirones; quinacridones; iron oxide having a nanoscale size; potassium 1,2-hydroxystearate, magnesium benzoate or magnesium succinate, magnesium phthalate and the like. Alkaline or alkaline earth metal salts of carboxylic acids typified by; aromatic sulfonic acid compounds typified by sodium benzenesulfonate or sodium naphthalene sulfonate; di or triesters of di or tribasic carboxylic acids; phthalocyanine blue Phthalocyanin-based pigments typified by the above; two-component compounds composed of a component A which is an organic dibasic acid and a component B which is an oxide, hydroxide or salt of a Group IIA metal of the periodic table; Examples thereof include a composition composed of a magnesium compound.

As a specific example of a commercially available β crystal nucleating agent, a β crystal nucleating agent “NJester NU-100” manufactured by Shin Nihon Rika Co., Ltd., and as a specific example of a polypropylene polymer to which a β crystal nucleating agent is added, Aristech Co., Ltd. Examples thereof include polypropylene "Bepol B-022SP" manufactured by Borealis, polypropylene "Beta (β) -PP BE60-7032" manufactured by Borealis, and polypropylene "BNX BETAPP-LN" manufactured by mayo.

3-4. Thickness and Porosity The thickness of the porous film is preferably 5 to 300 μm, more preferably 10 to 200 μm, still more preferably 20 to 150 μm.

The porosity of the porous film is a numerical value indicating the ratio of the space portion of the porous film, and is preferably 40 to 70%. As the lower limit, 40% or more is more preferable, and 45% or more is further preferable. On the other hand, as the upper limit, 70% or less is more preferable, and 65% or less is further preferable.
When the porosity is 40% or more, it can contribute to the weight reduction of the laminated sheet. Further, when the porosity is 70% or less, the strength of the film can be maintained. The method for measuring the porosity is as follows.
The actual amount W ₁ of the measurement sample is measured, the mass W ₀ when the porosity is 0% is calculated based on the density of the resin composition, and the porosity is calculated from these values based on the following formula. ..
Porosity (%) = {(W ₀ -W ₁ ) / W ₀ } x 100

3-5. Average Pore Diameter The average pore diameter of the porous film is 0.01 to 1 μm, preferably 0.02 to 0.9 μm, and particularly preferably 0.03 to 0.8 μm. By setting the average pore diameter of the porous film to 0.01 to 1 μm, the resin layer partially penetrates into the porous film when it is bonded to the base film, and acts as an anchor effect to improve the adhesive strength. Can be improved. The average pore size of the porous film can be measured using a palm poromometer (PMI, 500PSI type) by the bubble point method based on JIS K3832: 1990, and specifically, the method described in Examples. Can be measured.

4. Laminated sheet The laminated sheet of the present invention has a tensile elastic modulus in the range of 1000 to 2500 MPa. The tensile modulus in the present invention is measured by the method of JIS K7127.
When the tensile elastic modulus is 1000 MPa or more, when used as a diaphragm, reproducibility in a high temperature range is ensured, and the material has sufficient rigidity (stiffness) to be used as a diaphragm edge material. From the above viewpoint, the tensile elastic modulus is more preferably 1200 MPa or more, and particularly preferably 1400 MPa or more. On the other hand, if the tensile elastic modulus is 2500 MPa or less, for example, in the case of a diaphragm of a microspeaker, the lowest resonance frequency (f0) even if a film having a thickness of 20 to 40 μm, which is excellent in handleability and durability at high output, is used. : F-Zero) is sufficiently low, which is preferable because the reproducibility of the bass range is ensured and the sound quality is good. From the above viewpoint, the tensile elastic modulus is more preferably 2400 MPa or less, and particularly preferably 2300 MPa or less.

The laminated sheet of the present invention preferably has a specific elastic modulus in the range of 1.0 to 2.5 (m ² / s ² ) / ¹⁰⁶ . If the specific elastic modulus is 1.0 (m ² / s ² ) / ¹⁰⁶ or more, when used as a diaphragm, reproducibility in the high temperature range is ensured, and despite its light weight, the diaphragm It has enough rigidity to be used as an edge material. From the above viewpoint, the specific elastic modulus is more preferably 1.2 (m ² / s ² ) / ¹⁰⁶ or more, and particularly preferably 1.4 (m ² / s ² ) / ¹⁰⁶ or more. On the other hand, if the specific elastic modulus is 2.5 (m ² / s ² ) / ¹⁰⁶ or less, for example, in the case of a diaphragm of a microspeaker, the thickness is 20 to excellent in handleability and durability at high output. Even if a 40 μm film is used, the lowest resonance frequency (f0: F-zero) is sufficiently low, the reproducibility of the low frequency range is ensured, and the sound quality is good, which is preferable. From the above viewpoint, the specific elastic modulus is more preferably 2.4 (m ² / s ² ) / ¹⁰⁶ or less, and particularly preferably 2.3 (m ² / s ² ) / ¹⁰⁶ or less.

The laminated sheet of the present invention preferably has an adhesive strength of 0.4 N / 25 mm or more between the porous film and the base film.
The adhesive strength between the porous film and the base film in the present invention is the adhesion between the porous film and the base film, which is measured in a laminated sheet having a resin layer between the porous film and the base film. It is strength. Specifically, the strength is obtained by a 180 ° peeling test conforming to JIS Z0237. The base film is fixed to a hard surface, the porous film is folded back 180 ° from the base film, and the film is peeled off at a speed of 300 mm / min. It is the stress at the time. The measurement may be performed by fixing the porous film on a hard surface and peeling off the base film.
The higher the adhesive strength, the more preferable, but 0.5 N / 25 mm or more is more preferable. When the adhesive strength is 0.4 N / 25 mm or more, the porous film does not peel off from the base film even when an external force is continuously applied due to long-term use.
Although it is not clear why the laminated sheet of the present invention can obtain high adhesive strength, good adhesiveness is maintained by the anchoring effect of the resin layer component biting into the porous film when the porous film and the resin layer are bonded together. It is also inferred that they are doing it.

5. Method for Manufacturing Laminated Sheet The laminated sheet of the present invention can be manufactured by laminating a resin layer and a porous film on at least one side of a base film so as to be sequentially provided.
Specifically, a composition constituting a resin layer dissolved in a solvent (hereinafter, also referred to as a resin layer composition) is applied to at least one surface of a base film and dried to obtain a resin layer. The porous film is laminated and heated from the porous film side or from the base film side with a heat source to obtain a laminated sheet in which the base film and the porous film are in close contact with each other. Here, by slightly melting the resin layer on the surface of the base material in contact with the porous film, a laminated sheet having excellent adhesive strength can be obtained.
Further, similarly, the resin layer and the porous film may be sequentially provided on both sides of the base material. In that case, the layer structure is a porous film / resin layer / base film / resin layer / porous film.
Examples of the solvent in the resin layer composition include ketone solvents such as methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, diacetone alcohol, and acetone; and alcohol solvents such as pentanol, hexanol, heptanol, and octanol. Solvents: Ether-based solvents such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, and propylene glycol monomethyl ether acetate; methyl acetate, ethyl acetate, butyl acetate, methoxybutyl acetate, amyl acetate, propyl acetate, etc. Ester-based solvents such as ethyl lactate, methyl lactate and butyl lactate; organic solvents such as hydrocarbon solvents such as toluene, xylene, solvent naphtha, hexane, cyclohexane, ethylcyclohexane, methylcyclohexane, heptane, octane and decane are exemplified. .. These organic solvents may be used alone or in combination of two or more.
Further, in order to protect the porous film, the base material, or both from friction or the like during processing, the protective film may be laminated on one side or both sides for processing. Examples of the heat source to be used include heat press machines such as irons, laminators, heating rolls, heat sealing devices, calendar devices, and roll press devices.

6. Diaphragm and speaker The diaphragm of the present invention is made of the laminated sheet. That is, from a laminated sheet in which a resin layer and a porous film are sequentially provided on at least one side of the base film, the tensile elastic modulus is 1000 to 2500 MPa, and the average pore diameter of the porous film is in the range of 0.01 to 1 μm. It is a diaphragm.
Since the diaphragm of the present invention is lightweight, has excellent rigidity, and has excellent adhesive strength between the films used, it is preferably used for a speaker, particularly a micro speaker or the like.

Further, the speaker of the present invention includes the diaphragm. That is, it is composed of a laminated sheet in which a resin layer and a porous film are sequentially provided on at least one side of the base film, the tensile elastic modulus is 1000 to 2500 MPa, and the average pore diameter of the porous film is in the range of 0.01 to 1 μm. It is a speaker equipped with a diaphragm.
Since the speaker of the present invention is provided with a diaphragm that is lightweight, has excellent rigidity, and has excellent adhesive strength between the films used, the minimum resonance frequency (f0: Fzero) is sufficiently low, the reproduction of the bass range is ensured, and the sound quality is good. Is.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the following examples.
The measurement method and evaluation method are as follows.

(1) Average Pore Diameter The average pore diameter of the porous film was measured by a bubble point method based on JIS K3832: 1990 using a palm poromometer (manufactured by PMI, 500 PSI type).

(2) Tension elastic modulus The obtained laminated sheet was measured under the condition of a temperature of 23 ° C. in accordance with JIS K7127.

(3) Density A laminated sheet was randomly measured at 10 points using a 1/1000 mm dial gauge, and the average thickness T and the actual amount W were measured, and these values were calculated based on the following formula. The density was calculated.
Density ρ = {W / T}

(4) Specific elastic modulus The specific elastic modulus was calculated from the measured tensile elastic modulus E and the density ρ based on the following formula.
Specific elastic modulus = {E / ρ}

(5) Adhesive strength A strip-shaped test piece with a width of 25 mm parallel to the extrusion direction was cut out from the laminated sheet, and a 180 ° peeling test was performed under the condition of a speed of 300 mm / min in accordance with JIS Z0237, and the measurement obtained as a result. The value (N / 25 mm) was defined as the adhesive strength between the layers.

(6) Comprehensive evaluation Each sheet obtained in Examples and Comparative Examples was judged according to the following judgment criteria.
(criterion)
A (good): The specific elastic modulus of the sheet is 1.0 to 2.5 (m ² / s ² ) / ¹⁰⁶ , and the adhesive strength is 0.4 N / 25 mm or more.
B (poor): The specific elastic modulus of the sheet is not 1.0 to 2.5 (m ² / s ² ) / ¹⁰⁶ , and / or the adhesive strength is less than 0.4 N / 25 mm.

(T1 to T5: Porous film)
The various materials used in the following production examples of the porous film were prepared as follows.
(Propene resin)
A-1; Homopolypropylene (Novatec PP FY6HA, MFR: 2.4 g / 10 minutes [230 ° C, 2.16 kg load], Mw / Mn = 3.2, manufactured by Japan Polypropylene Corporation)
-A-2; Homopolypropylene (Novatec PP FY4, MFR: 5.0 g / 10 minutes, [230 ° C, 2.16 kg load], manufactured by Japan Polypropylene Corporation)
(Elastomer)
B-1; styrene-ethylene / propylene block copolymer (grade name: SEPTON1001, styrene content: 35% by mass, MFR: 0.1 g / 10 minutes, manufactured by Kuraray Co., Ltd.)
B-2; Styrene-ethylene / butylene-styrene block copolymer (grade name: SEPTON8004, styrene content: 31% by mass, MFR: <0.1 g / 10 minutes, manufactured by Kuraray)
B-3; Styrene-ethylene / propylene-styrene block copolymer (grade name: SEPTON2005, styrene content: 20% by mass, MFR: <0.1 g / 10 minutes, manufactured by Kuraray Co., Ltd.)
B-4; α-olefin copolymer (Toughmer PN3560, MFR: 6.0 g / 10 minutes [230 ° C, 2.16 kg load], manufactured by Mitsui Chemicals, Inc.)
(Crystal nucleating agent)
C-1: 1,3: 2,4-O- (4-methylbenzylidene) -D-sorbitol; "Gelol MD-LM30G" (manufactured by Shin Nihon Rika Co., Ltd .; α crystal nucleating agent)
C-2: 2,6-naphthalenedicarboxylic acid dicyclohexylamide; "NJester NU-100" (manufactured by Shin Nihon Rika Co., Ltd .; β crystal nucleating agent)
(Antioxidant)
D-1; tris (2,4-di-t-butylphenyl) phosphite and tetrakis [3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionic acid] pentaerythritol 1: 1 mixture (IRGANOX-B225, manufactured by BASF)

(Manufacture of Porous Film T1)
70 parts by mass of polypropylene resin (A-1), 30 parts by mass of vinyl aromatic elastomer (B-1), and 0.1 parts by mass of crystal nucleating agent (C-1) are mixed and 240 by twin screw extruder. The mixture was melt-extruded at ° C. to obtain a mixture (M-1). A T-die having a lip opening of 1 mm was formed by using a mixture (M-1) in an extruder, and was guided by a cast roll to obtain a non-porous film-like product. After that, the non-porous film-like material is stretched at a low temperature by applying a draw ratio of 100% (longitudinal stretching ratio 2.0 times) between the roll set at 20 ° C. and the roll set at 40 ° C. using a longitudinal stretching machine. gone. Next, high-temperature stretching was performed by multiplying the rolls set at 120 ° C. with a draw ratio of 50% (longitudinal stretching ratio 1.5 times). The film after longitudinal stretching is preheated in a film tenter facility (manufactured by Kyoto Machinery Co., Ltd.) at a preheating temperature of 145 ° C. and a preheating time of 12 seconds, then stretched 3.0 times in the transverse direction at a stretching temperature of 145 ° C., and then 150. Heat treatment was performed at ° C. to obtain a porous film T1.

(Manufacture of Porous Film T2)
70 parts by mass of polypropylene resin (A-1), 30 parts by mass of vinyl aromatic elastomer (B-2), and 0.1 parts by mass of crystal nucleating agent (C-1) are mixed and 240 by twin screw extruder. The mixture was melt-extruded at ° C. to obtain a mixture (M-2). Then, the porous film T2 was obtained by the same method as in Example 1.

(Manufacture of Porous Film T3)
70 parts by mass of polypropylene resin (A-1), 30 parts by mass of vinyl aromatic elastomer (B-3), and 0.1 parts by mass of crystal nucleating agent (C-1) are mixed and 240 by twin screw extruder. The mixture was melt-extruded at ° C. to obtain a mixture (M-3). Then, the porous film T3 was obtained by the same method as in Example 1.

(Manufacture of Porous Film T4)
Mix 100 parts by mass of propylene resin (A-1), 0.2 parts by mass of crystal nucleating agent (C-2), and 0.1 parts by mass of antioxidant (D-1), and use a twin-screw extruder. A mixture (M-4) was obtained by melt extrusion at 280 ° C. A T-die having a lip opening of 1 mm was formed by using a mixture (M-4) in an extruder, and was guided by a cast roll to obtain a non-porous film-like product. Then, the non-porous film-like material was subjected to longitudinal stretching by applying a draw ratio of 65% in three stages (longitudinal stretching ratio 4.5 times) between rolls set at 105 ° C. using a longitudinal stretching machine. The film after longitudinal stretching is preheated in a film tenter facility (manufactured by Kyoto Machinery Co., Ltd.) at a preheating temperature of 150 ° C. and a preheating time of 12 seconds, then stretched 3.5 times in the transverse direction at a stretching temperature of 150 ° C., and then 155. Heat treatment was performed at ° C. to obtain a porous film T4.

(Manufacturing of double glazing T5)
A mixture (M-5) was obtained by mixing 70 parts by mass of a propylene resin (A-2) and 30 parts by mass of an elastomer (B-4) and melt-extruding at 240 ° C. with a twin-screw extruder. A T-die with a lip opening of 1 mm is used to form a mixture (M-5) on the front and back layer side extruder and a mixture (M-1) on the middle layer side extruder, and is guided by a cast roll to form a multi-layer non-porous film. I got a mixture. Then, the multi-layer non-porous film-like material was subjected to longitudinal stretching by applying a draw ratio of 65% in three stages (longitudinal stretching ratio 4.5 times) between rolls set at 105 ° C. using a longitudinal stretching machine. The film after longitudinal stretching is preheated in a film tenter facility (manufactured by Kyoto Machinery Co., Ltd.) at a preheating temperature of 150 ° C. and a preheating time of 12 seconds, then stretched 3.5 times in the transverse direction at a stretching temperature of 150 ° C., and then 155. Heat treatment was performed at ° C. to obtain a multi-layer film T5 having a non-porous layer on the surface.

(Base film F1)
Mitsubishi Chemical's polyethylene terephthalate (PET) film Diafoil "T100 type 75 μm"

(Resin layer composition)
Acrylic resin (UC026: manufactured by Mitsubishi Chemical Co., Ltd.) 100 parts by mass Acrylic resin (BR-87: manufactured by Mitsubishi Chemical Co., Ltd.) 100 parts by mass Silica particles (SIRMIBK15WT% -B14: manufactured by CIK Nanotech Co., Ltd.) 5 Parts by mass Methyl ethyl ketone (MEK) 300 parts by mass 100 parts by mass of toluene A resin layer composition adjusted to a solid content concentration of 20% by mass was prepared by the above formulation.

[Example 1]
The resin layer composition was applied to both sides of the base film F1 so that the coating amount after drying was 0.7 g / m ² , and dried at 120 ° C. for 1 min to provide a resin layer.
Next, the porous film T1 was laminated on the surface of the resin layer, and a pressure of 110 ° C. and 4 kg / cm ² was applied for 1 minute with a hot press to obtain a laminated sheet.

[Example 2]
In Example 1, the porous film was produced in the same manner as in Example 1 except that the porous film was changed to T2, to obtain a laminated sheet.

[Example 3]
In Example 1, the porous film was produced in the same manner as in Example 1 except that the porous film was changed to T3, and a laminated sheet was obtained.

[Example 4]
In Example 1, the porous film was produced in the same manner as in Example 1 except that the porous film was changed to T4, and a laminated sheet was obtained.

[Comparative Example 1]
The evaluation was carried out only with the base film F1.

[Comparative Example 2]
The evaluation was carried out only with the porous film T1.

[Comparative Example 3]
In Example 1, the porous film was produced in the same manner as in Example 1 except that the porous film was changed to the double glazing film T5, and a laminated sheet was obtained.

The composition, characteristics, and evaluation of each laminated sheet obtained in the above Examples and Comparative Examples are shown in Table 1 below.

From Examples 1 to 4, since the laminated sheet of the present invention has a high specific elastic modulus, it is lightweight and has excellent rigidity, and since it has high adhesive strength, each layer is hard to peel off, and its effect when used as a diaphragm of a speaker. Can be expected.

The laminated sheet of the present invention can be suitably used for applications requiring rigidity and weight reduction, and in particular, it can be used as a diaphragm for a microspeaker or the like used in an electronic device.

Claims (8)

It is a laminated sheet in which a resin layer and a porous film are sequentially provided on at least one side of the base film, the tensile elastic modulus of the laminated sheet is 1000 to 2500 MPa, and the average pore diameter of the porous film is 0.01 to 1 μm. Laminated sheet that is a range. The laminated sheet according to claim 1, wherein the base film is made of a polyester resin. The laminated sheet according to claim 1 or 2, wherein the porous film is made of a polypropylene resin. The laminated sheet according to any one of claims 1 to 3, wherein the resin layer is made of an acrylic resin. The laminated sheet according to any one of claims 1 to 4, wherein the specific elastic modulus of the laminated sheet is in the range of 1.0 to 2.5 (m ² / s ² ) / ¹⁰⁶ . The laminated sheet according to any one of claims 1 to 5, wherein the adhesive strength between the porous film and the base film is 0.4 N / 25 mm or more. A diaphragm made of the laminated sheet according to any one of claims 1 to 6. A speaker including the diaphragm according to claim 7.