JP2011114409A - Diaphragm for speaker and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diaphragm for a speaker which is superior in moldability, is light in weight, is highly rigid and has superior frequency characteristics regarding acoustic characteristics. <P>SOLUTION: The diaphragm for the speaker is configured by including a foam layer and a pair of glass cloths integrated with the foam layer so as to expose the intersections of warp and weft on the surface at surface layer parts on both main surfaces of the foam layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a speaker diaphragm that is particularly useful for a planar speaker and a method for manufacturing the same, and in particular, a speaker diaphragm having excellent frequency characteristics with excellent moldability, light weight, high rigidity, and acoustic characteristics, And a manufacturing method thereof.

  Conventionally, various materials are used for speaker diaphragms depending on applications. For example, for the purpose of improving insufficient strength of speaker diaphragms used in cone-type speakers for audio equipment, molded with woven fabrics of high-strength fibers such as aramid fibers, carbon fibers, glass fibers, and natural fibers and chemical fibers Has been proposed (Patent Document 1). However, such a diaphragm is low in strength and cannot satisfy the vibration characteristics in the high sound range.

  For this reason, a base fabric formed by volatilizing or decomposing the oil agent attached to the inorganic fiber woven fabric before the heat treatment by pre-heating the woven fabric impregnated with resin with high rigidity inorganic fibers, Unlike this base fabric, a diaphragm made of a material with a lower density and larger internal loss is bonded with an adhesive and fixed to each other by a heating press, resulting in high sensitivity, a wide reproduction frequency band, and higher harmonics. It has been proposed to provide a cone-type speaker diaphragm having acoustic characteristics such as low distortion (Patent Document 2). However, since such a diaphragm has a woven fabric of inorganic fibers impregnated with resin on the surface, a resin layer having a low elastic modulus covers the surface of the diaphragm, so that the sound pressure characteristic is low. was there.

  From such a viewpoint, in order to improve the vibration characteristics in the high sound range, the impregnated thermosetting resin is provided with a woven cloth in a thermosetting state, and a paper board integrated with thermocompression bonding on the back side of the woven cloth, A cone-type loudspeaker diaphragm excellent in high-frequency vibration characteristics has been proposed by exposing the texture of the woven fabric (Patent Document 3). However, after impregnating the thermosetting resin into the woven fabric to form a prepreg, it has been very difficult to form the fabric so that only the texture of the woven fabric is exposed on the surface side.

  Further, when the above-described diaphragm is used for a flat speaker, the strength is weak and the sound range characteristics cannot be sufficiently satisfied. In order to increase the strength, it is conceivable to use glass fibers as the inorganic fiber woven fabric. However, it has been necessary to increase the thickness of the glass fiber, resulting in a problem that the specific gravity of the entire diaphragm is increased and the sound pressure characteristics are deteriorated.

Japanese Utility Model Publication No. 63-70786 JP 2000-92590 A JP 2009-21832 A

  The present invention has been made in order to solve the above-described problems, and has excellent moldability, light weight, high rigidity, and good frequency characteristics with respect to acoustic characteristics, and particularly vibration for a speaker that can be used as a flat speaker. It aims at providing a board and its manufacturing method.

  In order to achieve the above object, the present invention is integrated with the foam layer such that the intersection of the warp and the weft is exposed on the surface of the foam layer and the surface layer portions of both main surfaces of the foam layer. And a pair of glass cloths. The present invention relates to a speaker diaphragm.

  The present inventors have intensively studied to achieve the above object. As a result, the speaker diaphragm has a structure composed of glass cloth layers arranged on both main surface sides of a specific foam layer, and for the speaker so that only the intersection of the warp and weft of the glass cloth is exposed on the surface. The present inventors have completed the present invention by finding out that the diaphragm is excellent in moldability, light weight, high rigidity, and good frequency characteristics with respect to acoustic characteristics.

  The formability, lightness, and high rigidity are thought to be due to the material composition of the above-described speaker diaphragm, but the frequency characteristic is that only the intersection of the warp and weft of the glass cloth is exposed on the surface. It is thought to be caused by. However, the detailed operational effects are not clarified at present.

  In one example of the present invention, the foam layer has a base material containing a thermosetting resin and a hollow spherical inorganic substance, and a volatile liquid foaming agent in an outer shell made of a thermoplastic resin encapsulated in the base material. In the foamable resin composition, the content of the hollow spherical inorganic substance in the foamable resin composition is 1% by mass to 60% by mass, The content of the heat-expandable microcapsule is preferably 1% by mass to 10% by mass. By using a foamable resin composition that satisfies the above-described requirements, the speaker diaphragm having the above-described configuration can be easily formed.

  In another example of the present invention, the hollow spherical inorganic substance preferably contains at least one selected from the group consisting of a glass balloon, a shirasu balloon, and a silica-alumina balloon. By using these substances, the hollow spherical inorganic substance can be easily formed.

  In still another example of the present invention, the thermally expandable microcapsule preferably has an average particle diameter of 2 μm to 50 μm in an unexpanded state. As a result, when the speaker diaphragm described above is manufactured by the manufacturing method described in detail below, the speaker diaphragm having the above-described configuration can be easily formed, and deterioration of characteristics such as surface smoothness can be suppressed. can do.

  In another example of the present invention, the thermally expandable microcapsule preferably has an expansion start temperature of 70 ° C. to 150 ° C. and a maximum expansion temperature of 150 ° C. to 200 ° C.

  By setting the expansion start temperature in the former range, the thermally expandable microcapsule does not expand when adjusting the expandable resin composition, and expands at the temperature at which the speaker diaphragm is formed by molding or the like. Therefore, there is no problem in manufacturing the speaker diaphragm.

  Further, by setting the maximum thermal expansion temperature in the latter range, the foam layer is formed at the maximum temperature during formation, that is, the temperature at which the foam layer and the glass cloth are integrated as described in detail below. The degree of expansion of the above-mentioned thermally expandable microcapsule can be made as designed. In other words, since the degree of expansion of the thermally expandable microcapsule can be made as designed using the temperature at the time of formation, it is necessary to perform a separate heat treatment or the like in order to make the degree of expansion of the thermally expandable microcapsule as designed. There is no. Therefore, the manufacturing process when manufacturing the speaker diaphragm can be simplified.

Furthermore, in another example of the present invention, it is preferable that the density of the diaphragm is 0.2 g / cm ³ to 1.0 g / cm ³ and the elastic modulus is 3 GPa to 15 GPa. By setting it within such a characteristic range, good frequency characteristics are exhibited and the acoustic characteristics are excellent. The relationship between these physical property values and acoustic characteristics is not clear at present.

  The speaker diaphragm of the present invention can be manufactured by an arbitrary method, and for example, can be manufactured by the following manufacturing method.

  That is, between a pair of glass cloths, a base material containing a thermosetting resin and a hollow spherical inorganic substance, and a volatile liquid foaming agent is contained in an outer shell made of a thermoplastic resin encapsulated in the base material. Foamable expandable microcapsules, wherein the content of the hollow spherical inorganic substance is 1% by mass to 60% by mass, and the content of the thermally expandable microcapsules is 1% by mass to 10% by mass. The first step of disposing the resin composition, the pair of glass cloths and the foamable resin composition are heated to a temperature not lower than the thermal expansion start temperature of the thermally expandable microcapsules, and the foamable resin composition is foamed. And a second step of fusing the pair of glass cloths and the foamable resin composition so that the intersection between the warp and weft of the pair of glass cloths is exposed on the surface. The The butterfly, is a manufacturing method of the speaker diaphragm.

  ADVANTAGE OF THE INVENTION According to this invention, the diaphragm for speakers which has a light frequency, high rigidity, and a favorable frequency characteristic regarding an acoustic characteristic can be provided. Further, according to the present invention, it is possible to provide a manufacturing method for easily manufacturing a speaker diaphragm having such excellent characteristics.

It is a top view of the diaphragm for speakers in an embodiment. It is sectional drawing at the time of cutting the diaphragm for speakers shown in FIG. 1 along the AA line. It is sectional drawing at the time of cutting the diaphragm for speakers shown in FIG. 1 along the BB line. It is explanatory drawing regarding the manufacturing method of the diaphragm for speakers in embodiment. It is explanatory drawing regarding the manufacturing method of the diaphragm for speakers in embodiment. It is a graph which shows the measurement result of the output sound pressure frequency characteristic of the diaphragm for speakers of an example and a comparative example. It is a graph which shows the measurement result of the output sound pressure frequency characteristic of the diaphragm for speakers of an example.

  Hereinafter, the details of the present invention and other features and advantages will be described with reference to the drawings.

(Speaker diaphragm)
FIG. 1 is a plan view of a speaker diaphragm in the present embodiment, FIG. 2 is a cross-sectional view of the speaker diaphragm shown in FIG. 1 taken along the line AA, and FIG. FIG. 3 is a cross-sectional view of the speaker diaphragm shown in FIG. 1 cut along the line BB.

  As shown in FIGS. 1 to 3, the speaker diaphragm 1 of the present embodiment has a foam layer 2 and a pair of glass cloths 3 arranged on both main surface sides of the foam layer 2. The intersections 3A and 3B of the warp and weft of each glass cloth 3 are exposed on the front and back surfaces. In addition, in FIG. 1, the state of one main surface side is shown.

  In this embodiment, the speaker diaphragm has a structure composed of glass cloth layers arranged on both principal surfaces of a specific foam layer, and only the intersection of the warp and weft of the glass cloth is exposed on the surface. By constituting the speaker diaphragm, it has excellent moldability, light weight, high rigidity, and good frequency characteristics with respect to acoustic characteristics.

  The formability, lightness, and high rigidity are thought to be due to the material composition of the above-described speaker diaphragm, but the frequency characteristic is that only the intersection of the warp and weft of the glass cloth is exposed on the surface. It is thought to be caused by. However, the detailed operational effects are not clarified at present.

  Although it does not specifically limit about the glass fiber to be used, High strength glass cloth, such as E glass, T glass, S glass, and R glass, can be used preferably. Although there are no particular limitations on the number of glass fibers converged, 100 to 200 fibers that are usually used can be preferably used.

  The weave density of the glass cloth is preferably 10 to 100 per inch, more preferably 20 to 60. If the weaving density is less than 10 per inch, the elastic modulus of the diaphragm is low, and if it is more than 100, the specific gravity of the diaphragm increases, and the sound pressure characteristics are deteriorated.

  The ratio of the warp and weft of the glass cloth is appropriately determined according to the intersection density to be exposed on the surface. For example, the range of 0.4-1.5, preferably 0.8-1.3 is desirable. If it is out of the range of 0.4 to 1.5, the density of the woven fabric becomes too coarse or too dense, and the sound pressure characteristics may be deteriorated.

  The weave of the glass cloth is not particularly limited, but the plain weave is particularly preferable because of the high effective intersection density. That is, a desired number of intersection density can be easily formed by using plain weave.

  The thickness of the glass cloth is not particularly limited, but is preferably 2.5% to 25% with respect to the total thickness of the diaphragm. If the thickness of the glass cloth is less than 2.5%, the elastic modulus is low, and if it is thicker than 25%, the elastic modulus is high, but any increase in weight results in poor sound pressure characteristics. By setting the glass cloth to the above range, a diaphragm having an appropriate elastic modulus can be obtained.

  The foam layer 2 is, for example, a base material containing a thermosetting resin and a hollow spherical inorganic substance, and a heat in which a volatile liquid foaming agent is accommodated in an outer shell made of a thermoplastic resin enclosed in the base material. An expandable microcapsule, and the content of the hollow spherical inorganic substance in the expandable resin composition is 1% by mass to 60% by mass. It is preferable that content is 1 mass%-10 mass%. By using a foamable resin composition that satisfies the above-described requirements, the speaker diaphragm having the above-described configuration can be easily formed. The details of the foamable resin composition are as described below.

  The thermosetting resin in the foamable resin composition only needs to contain at least an epoxy resin. For example, the thermosetting resin may be composed only of an epoxy resin, or an epoxy resin and other thermosetting resins, for example. It may consist of:

  The epoxy resin preferably contains two or more epoxy groups in one molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD (acetaldehyde) type epoxy resin, glycidyl ester type epoxy resin, fat A cyclic epoxy resin etc. are mentioned, These can be used individually or in mixture of 2 or more types.

  Moreover, the mixture which mixed the epoxy resin of another group or the type | mold with these epoxy resins, or these interaction materials can also be used. Other group or type epoxy resins include, for example, phenol novolac type epoxy resins, cresol novolak type epoxy resins, heterocyclic epoxy resins, hydrogenated (hydrogenated) bisphenol A type epoxy resins, aliphatic epoxy resins, aromatic An epoxy resin, a spirocyclic epoxy resin, or the like obtained by a reaction of an aliphatic, aliphatic, or alicyclic carboxylic acid with epichlorohydrin can be used.

  On the other hand, examples of thermosetting resins other than epoxy resins include phenol resins, polyacetal resins, unsaturated polyester resins, polyimide resins, and the like, and these can be used alone or in admixture of two or more.

Corresponding to such a thermosetting resin, the foamable resin composition preferably contains a curing agent that can react with the thermosetting resin to form a cured product. The curing agent is not particularly limited as long as it can react with a thermosetting resin to form a cured product. For example, as a curing agent for an epoxy resin, an acid anhydride such as methylhexahydrophthalic anhydride. Products, phenolic resins such as novolac-type phenolic resins and cresol novolac-type epoxy resins, phthalic anhydride derivatives, dicyandiamide, imidazole compounds, aluminum chelates, amine complexes of Lewis acids such as BF ₃ , etc. Two or more kinds can be mixed and used.

  Although the content of the curing agent varies depending on the type of the thermosetting resin, the type of the curing agent, and the like, for example, the epoxy resin varies depending on the epoxy equivalent, but is usually 2 mass per 100 mass parts of the epoxy resin. Part to 150 parts by mass is preferable.

  The hollow spherical inorganic substance is added for the purpose of reducing the weight of the foam layer 2, and includes various inorganic balloons such as ceramic balloons such as glass balloons, shirasu balloons, fly ash, silica-alumina balloons, These can be used alone or in admixture of two or more. Among these, it is particularly preferable to use a glass balloon. These substances are easily available, and the above-described hollow spherical inorganic substance can be easily configured.

  The average particle size of the hollow spherical inorganic substance is preferably 30 μm to 150 μm. When the average particle diameter of the hollow spherical inorganic substance exceeds 150 μm, it is not preferable because it is easily broken during formation for obtaining the speaker diaphragm 1 and the surface of the foam layer 2 becomes rough. Further, when the hollow spherical inorganic substance has an average particle size of less than 30 μm, the moldability of the foamable resin composition is lowered, so that the speaker diaphragm 1 is difficult to manufacture, and the foam layer 2 has a unit volume per unit volume. There is a possibility that weight reduction may be difficult due to an increase in the content.

  The content of the hollow spherical inorganic substance is 1% by mass or more and 60% by mass or less, and preferably 5% by mass or more and 50% by mass or less in the whole foamable resin composition. If the content of the hollow spherical inorganic substance is less than 1% by mass, it may be difficult to reduce the weight and increase the rigidity of the foam layer 2, and if it exceeds 60% by mass, the moldability of the foamable resin composition may be reduced. The content of the thermally expandable microcapsule is relatively decreased, and the thermal expansion may be hindered.

It is preferred apparent density of the hollow sphere inorganic material is ^{0.2g / cm 3 ~0.7g / cm 3} . If the apparent density of the hollow sphere inorganic material is less than 0.2 g / cm ^3, fragile during molding to obtain a loudspeaker diaphragm 1, and when it exceeds 0.7 g / cm ^3, weight of the foam layer 2 May become difficult. By making the apparent density of the hollow spherical inorganic substance within the above range, the foam layer 2 can be made lightweight and highly rigid while improving the moldability of the foamable resin composition.

  In addition, it is preferable that the said hollow spherical inorganic substance is surface-treated from a viewpoint of improving adhesiveness with a thermosetting resin. Examples of the surface treatment agent include organic silane compounds, organic titanate compounds, and organic aluminate compounds, and these can be used alone or in combination of two or more.

  Examples of the organic silane compound include vinyltriethoxysilane, vinyl-tris- (2-methoxyethoxy) silane, γ-methacryloxypropylmethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl)- γ-aminopropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, γ-glycidoxypropylmethoxysilane, γ-mercaptopropyltrimethoxysilane and the like may be mentioned. A mixture of more than one species can be used.

  Examples of the organic titanate compound include tetra-i-propyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetrastearyl titanate, triethanolamine titanate, titanium acetylacetonate, titanium lactate, octylene glycol titanate, isopropyl ( N-aminoethylaminoethyl) titanate etc. are mentioned, These can be used individually or in mixture of 2 or more types. Moreover, as an organic aluminate compound, acetoalkoxy aluminum diisopropinate etc. are mentioned, for example.

  The surface treatment of the hollow sphere inorganic substance can be performed by a usual method, for example, the surface treatment agent is dissolved in water or various organic solvents, and the hollow sphere inorganic substance may be immersed in this and dried. Further, for example, a solution obtained by dissolving a surface treatment agent in water or various organic solvents may be added little by little while stirring and stirring the hollow spherical inorganic substance in a mixer such as a Henschel mixer.

  The thermally expandable microcapsules constituting the expandable resin composition (in FIGS. 2 and 3, the thermally expandable microcapsules after expansion are indicated by a symbol “6”) are expanded by the heat at the time of formation. Yes, while reducing the weight of the diaphragm 1 for speakers, and having high rigidity, as described above, the intersections 3A and 3B of the warp and weft of the glass cloth 3 are exposed on the front and back surfaces, so that the frequency characteristics are good with respect to acoustic characteristics. It is added to make it have.

  The thermally expandable microcapsule is composed of a volatile liquid foaming agent and an outer shell made of a thermoplastic resin containing the volatile liquid foaming agent therein. Specifically, a volatile liquid foaming agent that volatilizes at the heating temperature when the diaphragm is formed is wrapped with an outer shell made of a thermoplastic resin that softens at that temperature. By setting it as such, it can expand | swell appropriately with the heat | fever at the time of formation, and, thereby, a foamable resin composition can be made into a foamed state.

  Thus, from the viewpoint of appropriately expanding at the temperature at the time of formation, the content of the volatile liquid foaming agent in the thermally expandable microcapsules, that is, the total amount of the volatile liquid foaming agent and the outer shell is 5% by mass or more and 30%. It is preferable that it is below mass%.

  The expansion start temperature of the thermally expandable microcapsule is preferably 70 ° C. or higher. If the expansion start temperature of the heat-expandable microcapsule is less than 70 ° C., for example, the heat-expandable microcapsule may expand during preparation of the expandable resin composition, specifically during mixing and kneading. In addition, from the viewpoint of appropriately expanding at the temperature at the time of formation, the expansion start temperature of the thermally expandable microcapsule is preferably 150 ° C. or lower.

  Therefore, the thermoplastic resin needs to be appropriately softened at the temperature at the time of formation and expand by volatile expansion of the volatile liquid foaming agent accommodated therein, for example, 70 ° C. to 150 ° C. Those that soften at a temperature of ° C. are preferred. Further, the thermoplastic resin constituting the outer shell is preferably one having a sufficiently large viscosity at the temperature at the time of formation so that the thermoplastic resin does not rupture due to thermal expansion at the time of formation and the capsule state can be maintained.

  Examples of satisfying such conditions include a polymer of vinylidene chloride, acrylonitrile, methacrylonitrile, or methyl methacrylate, or a copolymer of two or more of these, such as vinylidene chloride-acrylonitrile copolymer, vinylidene chloride. -Acrylonitrile-methyl methacrylate copolymer, acrylonitrile-methyl methacrylate copolymer, one or more of these and various monomers including vinyl halide, styrene monomer, vinyl acetate, butadiene, vinylpyridine, chloroprene A copolymer is mentioned.

  This thermoplastic resin may be crosslinkable or crosslinkable with a crosslinking agent such as divinylbenzene, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, triacryl formal, triallyl isocyanate and the like. Among these thermoplastic resins, a homopolymer of (meth) acrylonitrile having a high thermal expansion start temperature and a maximum expansion temperature or a copolymer having a high (meth) acrylonitrile content is preferably used.

  Examples of volatile liquid blowing agents include isobutane, isopentane, normal butane, normal pentane, neopentane, and hexane that are liquid at room temperature and vaporize at the temperature at the time of formation. Among these, low-boiling carbonization such as isobutane and isopentane. Hydrogen is preferred.

  As the volatile liquid blowing agent, those other than the above can be used, for example, specific freons such as dichlorofluoromethane, trichlorofluoromethane, dichlorofluoroethane, dichlorotrifluoroethane, trichlorotrifluoroethane, dichloropentafluoropropane and the like. And alternative freons, hydrocarbons such as petroleum ether, chlorinated hydrocarbons such as methyl chloride, methylene chloride, dichloroethylene, trichloroethane, trichloroethylene, etc., but are not necessarily limited to these.

  The average particle diameter of the thermally expandable microcapsule (outer shell) is preferably 2 μm to 50 μm in an unexpanded state, more preferably 5 μm to 40 μm, and still more preferably 10 μm to 30 μm. If the average particle size of the thermally expandable microcapsule is smaller than the above range, the expansion rate and expansion force at the time of formation may be insufficient, and if larger than the above range, the expansion rate and expansion force at the time of formation may be insufficient. Since it becomes too large, the surface smoothness of the foam layer 2 obtained may be lowered, and the mechanical strength of the speaker diaphragm 1 may be insufficient.

  Furthermore, the maximum expansion temperature of the thermally expandable microcapsules, that is, the temperature at which the expansion coefficient of the thermally expandable microcapsules becomes maximum is preferably 150 ° C. to 200 ° C. Since this embodiment consists of the foam layer 2 and the glass cloth 3 as described above, the maximum temperature at the time of formation, that is, the temperature when the foam layer 2 and the glass cloth 3 are integrated is 150 ° C. to At 200 ° C., the degree of expansion of the thermally expandable microcapsules can be made as designed, so that it is not necessary to perform a separate heat treatment or the like in order to make the degree of expansion of the thermally expandable microcapsules as designed. Therefore, the manufacturing process when manufacturing the speaker diaphragm can be simplified.

  The measurement of the expansion start temperature and the maximum expansion temperature is performed, for example, by placing a thermally expandable microcapsule in a cylindrical aluminum container or the like and applying force from above with a pressure terminal using TMA (TA Instruments). The temperature can be measured by measuring the amount of displacement of the pressure terminal in the vertical direction. The temperature at which the displacement begins to be observed is the expansion start temperature, and the temperature at which the maximum displacement is reached is the maximum expansion temperature. be able to.

  As such an unexpanded thermally expandable microcapsule, a commercially available product can be suitably used, and for example, EXPANCEL [manufactured by Nippon Philite Co., Ltd.] can be mentioned. The outer shell is made of the above-mentioned vinylidene chloride-acrylonitrile copolymer or acrylonitrile-methacrylonitrile copolymer, and the volatile liquid blowing agent is made of isobutane or isopentane.

  Specifically, product number 642,551,461 (outer shell; vinylidene chloride-acrylonitrile copolymer, volatile liquid blowing agent; isobutane, thermal expansion start temperature; about 90 ° C (product number 642), about 100 ° C ( Product number 551), about 110 ° C. (product number 461)), product number 091, 092 (outer shell: acrylonitrile-methacrylonitrile copolymer, volatile liquid blowing agent; isopentane, thermal expansion start temperature: about 130 ° C.), etc. Is mentioned. Since these expand to a size of about 4 times at maximum, they expand to about 60 times in volume.

  Content of a thermally expansible microcapsule is 1 to 10 mass% in the whole foamable resin composition, More preferably, it is 1 to 5 mass%. If the content of the heat-expandable microcapsule is less than the above range, the expansion rate and expansion force at the time of formation may be insufficient, and if the content of the heat-expandable microcapsule is more than the above range, formation Since the expansion coefficient and expansion force at that time become too large, the mechanical strength of the speaker diaphragm 1 may not be sufficient.

  In the foamable resin composition, in addition to the above-described thermosetting resin and the like, and within the limits not deviating from the gist of the present invention, other components such as inorganic filler, coupling agent, antifoaming agent, colorant, A hardening accelerator, a shape maintenance agent, etc. can be contained.

  Examples of the inorganic filler include powders of silica, alumina, talc, calcium carbonate, titanium white, bengara, silicon carbide, boron nitride, and the like, and these can be used alone or in combination of two or more. The average particle size of the inorganic filler is preferably 0.1 μm to 100 μm, more preferably 1 μm to 30 μm, from the viewpoint of fluidity of the foamable resin composition.

  The foamable resin composition can be prepared by applying a known resin composition preparation method. For example, in addition to a thermosetting resin, a hollow spherical inorganic substance, and a thermally expandable microcapsule, as necessary It can be carried out by blending, mixing and kneading the other components to be added. The mixing and kneading for preparing the foamable resin composition is preferably performed at a temperature lower than the thermal expansion start temperature of the thermally expandable microcapsules.

  The foam layer 2 obtained by foaming such a foamable resin composition preferably has a thickness of 100 μm to 5000 μm, for example. Moreover, it is preferable that the foaming ratio of the foam layer 2 is 2-10. If the expansion ratio is smaller than the above range, the specific gravity of the foam layer 2 may be excessively increased, and if it exceeds the above range, the rigidity of the foam layer 2 may not be sufficient.

  Here, the expansion ratio refers to the density of the so-called unfoamed foam layer 2 in which the thermally expandable microcapsules are not thermally expanded, and the density of the foamed foam layer 2 in which the thermally expandable microcapsules are thermally expanded. From “the density of the unfoamed foam layer 2 / the density of the foamed foam layer 2”. The foaming ratio can be adjusted by adjusting the average particle diameter, content, etc. of the thermally expandable microcapsules, for example, and the forming conditions, specifically, the molding temperature, molding time, molding pressure, molding die This can be done by adjusting the clearance or the like.

Further, the speaker diaphragm 1 composed of the foam layer 2 and the covering layer 3 is lightweight, highly rigid, and has a frequency characteristic of 0.2 g / It is preferably cm ^{3 to} 1.0 g / cm ³ , and the elastic modulus (flexural modulus) is preferably 2 GPa to 15 GPa, more preferably 4 GPa to 10 GPa.

(Manufacturing method of speaker diaphragm)
Next, a method for manufacturing the speaker diaphragm 1 shown in FIGS. 1 to 3 will be described.

  FIG. 4 shows an example of the manufacturing method. In this manufacturing method, a pair of upper and lower molding dies 11 and 12 are used, and a pair of glass cloths 3 is first disposed on the opposing inner surfaces 11a and 12a. At this time, when the glass cloth 3 is a sheet-like material such as a metal foil, it can be arranged by being attached to the inner surfaces 11a and 12a. For example, the glass cloth 3 is made of a thermosetting coating material. Thus, in the case of a paint-like thing, it can arrange | position by making it apply | coat to the inner surfaces 11a and 12a.

  Thereafter, in the molding dies 11 and 12, a foamable resin composition 2 a that becomes the foam layer 2 is disposed between the pair of glass cloths 3 that are disposed to face each other on the inner surfaces 11 a and 12 a. The foamable resin composition 2a may be applied to at least one of the pair of glass cloths 3 after arranging the pair of glass cloths 3 in the molds 11 and 12 as described above, You may arrange | position by injection | pouring etc. in the metal mold | die 11 and 12 for molding. Further, before placing in the molding dies 11, 12, a laminate in which the foamable resin composition 2 a is sandwiched between a pair of glass cloths 3 is prepared, and this laminate is placed in the molding dies 11, 12. It can also arrange | position to and can use for hot press molding as shown below.

  And it heat-press-molds by heating and pressurizing the metal mold | die 11 and 12 by which the foamable resin composition 2a and a pair of glass cloth 3 are arrange | positioned inside. By this heating, the thermally expandable microcapsules are thermally expanded to obtain a foamed foam layer 2, and the pair of glass cloths 3 are bonded together by the foam layer 2 to be integrated into a vibration for a speaker. The board 1 can be obtained.

  As the molds 11 and 12, for example, a flat mold, a dome mold, an edge mold or the like can be used, and an appropriate one is selected according to the shape of the speaker diaphragm 1 and the like. Can be used. As the molding method, a known molding method such as compression molding, transfer molding, injection molding or the like can be applied, and among these, for a speaker having a sandwich structure from a foamable resin composition 2a and a pair of glass cloths 3. From the viewpoint of easily obtaining the diaphragm 1, compression molding is preferably used.

  Molding conditions, that is, molding temperature, molding pressure, molding time, mold clearance and the like are not necessarily limited and can be appropriately set. From the viewpoint of appropriately foaming the foamable resin composition 2a, preferably The molding temperature is 150 ° C. to 200 ° C., the molding pressure is 1 MPa to 350 MPa, the molding time is 1 minute to 20 minutes, and the mold clearance is 0.6 mm to 1 mm.

  Moreover, as a manufacturing method of the diaphragm 1 for speakers, a continuous molding method in which the foamable resin composition 2a and the pair of glass cloths 3 are continuously integrated may be applied, for example, a roll laminating method or a double belt. A continuous laminating method such as a pressing method may be applied.

  FIG. 5 shows an example of the manufacturing method by the double belt press method. A laminating apparatus 21 used in this manufacturing method has a pair of upper and lower rotating steel belts 22, and a relatively narrow portion where they face each other is a foamable resin composition 2 a and a pair of glass cloths 3. It becomes the laminating part 23 for heating and pressurizing and integrating.

  The pair of steel belts 22 are configured to move from the right side to the left side in the laminating portion 23 as indicated by arrows in the drawing. Moreover, while being hold | maintained by the roller 25 and changing direction in the roller 25, it is comprised so that it can move continuously to a predetermined direction.

  The clearance of the laminate portion 23, that is, the distance between the opposing surfaces of the pair of steel belts 22 in the laminate portion 23 is the thickness of the speaker diaphragm 1 to be finally obtained, specifically, the foam layer 2 Although it varies depending on the thickness of the glass cloth 3, for example, it is 0.1 mm or more and 2 mm or less.

  The heating in the laminating unit 23 may be performed at a uniform temperature as a whole, but it is preferable to gradually increase the temperature in order from the introduction side (the right side in the figure) of the foamable resin composition 2a and the like. It is preferable that the low temperature region and the high temperature region are sequentially formed from the introduction side. The low temperature region is, for example, 70 ° C. to 150 ° C. from the viewpoint of foaming the foamable resin composition 2a and bonding a pair of glass cloths 3 and smoothing the surface of the foamable resin composition 2a. Is preferred. Moreover, it is preferable that a high temperature area shall be 150 to 200 degreeC from a viewpoint which hardens the foamable resin composition 2a and integrates the whole completely.

  For such a laminating apparatus 21, a pair of glass cloths 3 are continuously introduced from the right side in the figure so as to be drawn into a set of steel belts 22 in the laminating section 23. Further, between the pair of glass cloths 3 introduced into the laminating apparatus 21, the foamable resin composition 2a is continuously introduced by a coating apparatus (not shown).

  And what has arrange | positioned the foamable resin composition 2a between a pair of glass cloth 3 in this way is made to foam the foamable resin composition 2a, for example by letting the low temperature area | region in the laminate part 23 pass first, A pair of glass cloths 3 are bonded together, and the surface of the foamable resin composition 2a is smoothed. Thereafter, the foamed resin composition 2a is cured by, for example, curing the foamable resin composition 2a and completely integrating the foamed resin composition 2a by maximizing the foamability of the foamable resin composition 2a. . Thus, what united the foamable resin composition 2a and a pair of glass cloth 3 can be used as the final speaker diaphragm 1 by cut | disconnecting in a desired shape.

  Hereinafter, the present invention will be described in detail with reference to examples.

Example 1
First, each component was mix | blended in the ratio as shown below, and it knead | mixed for 10 minutes at the rotation speed of 60 rpm using the kneader, and prepared foamable resin composition [1]. The order of adding each component was as described below. It should be noted that the charging order of the components is not necessarily limited to such charging order.

Resin composition [1]
(1) Epoxy resin: 100 parts by mass (2) Curing agent: 35 parts by mass (3) Hollow spherical inorganic substance: 54 parts by mass (4) Thermally expandable microcapsules: 4 parts by mass

Details of each component are as follows.
Epoxy resin: JER807 (trade name), manufactured by Japan Epoxy Resin Co., Ltd. Curing agent: TCG3049B (trade name), manufactured by Kyocera Chemical Co., Ltd. Hollow spherical inorganic substance:
K-37 (trade name), manufactured by Sumitomo 3M, glass balloon, average particle size 50 μm, apparent density 0.37 g / cm 3
-Thermally expandable microcapsules:
(053) DU40 (trade name), manufactured by Nippon Philite Co., Ltd., average particle diameter of 15 μm, expansion start temperature of 100 ° C., maximum expansion temperature of 160 ° C.

  Next, after applying a release agent to the inner surfaces of both molds of the flat mold, AS1067 (trade name, nominal thickness 30 μm, manufactured by Asahi Kasei Electronics Co., Ltd.) is disposed as a pair of glass cloths. In the meantime, the foamable resin composition [1] described above was introduced, and hot press molding was performed for 30 minutes under the conditions of a temperature of 160 to 180 ° C. and a pressure of 5 MPa, to produce a speaker diaphragm having a thickness of 0.4 mm. .

(Example 2)
A speaker diaphragm having a thickness of 0.4 mm was produced in the same manner as in Example 1 except that the resin composition [2] was used.
Resin composition [2]
(1) Epoxy resin: 100 parts by mass (2) Curing agent: 33 parts by mass (3) Hollow spherical inorganic substance: 150 parts by mass

(Example 3)
A speaker diaphragm having a thickness of 0.4 mm was manufactured in the same manner as in Example 1 except that AS2116 (trade name, nominal thickness: 100 μm, manufactured by Asahi Kasei Electronics Co., Ltd.) was used as the glass cloth.

(Comparative Example 1)
A speaker diaphragm was manufactured in the same manner as in Example 1 except that glass epoxy prepreg TLP-551 (trade name, manufactured by Kyocera Chemical Co., Ltd.) having a thickness of 45 μm was used instead of the glass cloth described above.

(Comparative Example 2)
A speaker diaphragm was manufactured in the same manner as in Example 1 except that a polymer film having a thickness of 30 μm (Kapton EN (trade name), manufactured by Toray DuPont) was used instead of the glass cloth described above.

  Next, the following characteristic evaluation was performed about each speaker diaphragm of an above-mentioned Example and a comparative example. The results are shown in Table 1 and FIGS.

(density)
The density of each speaker diaphragm was measured according to JIS K6758.
(Elastic modulus)
The flexural modulus of each speaker diaphragm was measured by a thermal analysis (DMA) method.
(Specific modulus)
From the above elastic modulus and density, it was calculated by “elastic modulus / density”.
(Output sound pressure frequency characteristics)
The speaker diaphragms of Examples 1 to 3 and Comparative Examples 1 and 2 were incorporated in the same speaker, and the frequency characteristics of sound pressure were obtained using a response checker manufactured by Nippon Audio Co., Ltd.

  As is clear from Table 1, the speaker diaphragm of the example manufactured by arranging glass cloth on both main surfaces of the foam layer and exposing the intersection of the warp and the weft, the warp and the weft Compared with the speaker diaphragm of the comparative example in which the intersection is not exposed, the specific elastic modulus is high, and the output in the high sound range is high as shown in FIGS. I understand.

  The present invention has been described in detail based on the above specific examples. However, the present invention is not limited to the above specific examples, and various modifications and changes can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Diaphragm for speakers 2 Foam layer 2a Expandable resin composition 3 Glass cloth 6 Thermal expansion microcapsule (after thermal expansion) 11, 12 Mold for molding,
11a, 12a Inner surface of molding die

Claims (12)

A foam layer;
A pair of glass cloths integrated with the foam layer such that the intersection of the warp and the weft is exposed on the surface in the surface layer portions of both main surfaces of the foam layer;
A speaker diaphragm characterized by comprising: The foam layer includes a base material containing a thermosetting resin and a hollow spherical inorganic substance, and a thermal expansion in which a volatile liquid foaming agent is contained in an outer shell made of a thermoplastic resin, which is contained in the base material. A foamable resin composition containing a conductive microcapsule,
The content of the hollow spherical inorganic substance in the foamable resin composition is 1% by mass to 60% by mass, and the content of the thermally expandable microcapsule is 1% by mass to 10% by mass. The speaker diaphragm according to claim 1.   The speaker diaphragm according to claim 1 or 2, wherein the hollow spherical inorganic substance includes at least one selected from the group consisting of a glass balloon, a shirasu balloon, and a silica-alumina balloon.   4. The speaker diaphragm according to claim 1, wherein the thermally expandable microcapsule has an average particle diameter of 2 μm to 50 μm in an unexpanded state. 5.   5. The speaker according to claim 1, wherein the thermally expandable microcapsule has an expansion start temperature of 70 ° C. to 150 ° C. and a maximum expansion temperature of 150 ° C. to 200 ° C. 6. Diaphragm. 6. The speaker according to claim 1, wherein the diaphragm has a density of 0.2 g / cm ³ to 1.0 g / cm ³ and an elastic modulus of ³ GPa to 15 GPa. Diaphragm. Between a pair of glass cloths, a base material containing a thermosetting resin and a hollow spherical inorganic substance, and a heat in which a volatile liquid foaming agent is contained in an outer shell made of a thermoplastic resin enclosed in the base material. Expandable microcapsules, wherein the content of the hollow spherical inorganic substance is 1% by mass to 60% by mass, and the content of the thermally expandable microcapsules is 1% by mass to 10% by mass. A first step of arranging objects;
The pair of glass cloths and the foamable resin composition are heated to a temperature equal to or higher than the thermal expansion start temperature of the thermally expandable microcapsules to foam the foamable resin composition, and the pair of glass cloths and the foamable composition A second step of fusing the resin composition so that the intersection of the warp and weft of the pair of glass cloths is exposed on the surface;
A method for manufacturing a speaker diaphragm, comprising: The first step is formed by the step of disposing the glass cloths on the opposing inner surfaces of the molding die, and the glass cloths disposed opposite to each other in the molding die. Arranging the foamable resin composition in the space,
The second step includes a step of heating the molding die to be equal to or higher than the thermal expansion start temperature and pressurizing the glass cloth and the foamable resin composition with the molding die. The method for manufacturing a speaker diaphragm according to claim 7. The first step is a step of supplying the pair of glass cloths such that the foamable resin composition and the foamable resin composition are sandwiched in a gap formed between the pair of molding belts. Including
In the second step, the foamable resin composition is heated to the thermal expansion start temperature or higher in the gap, and the glass cloth and the foamable resin composition are pressurized with the pair of molding belts. The manufacturing method of the diaphragm for speakers of Claim 7 characterized by the above-mentioned.   The method for manufacturing a speaker diaphragm according to any one of claims 7 to 9, wherein the thermal expansion start temperature is in a temperature range of 70C to 150C.   The method for manufacturing a speaker diaphragm according to any one of claims 7 to 10, further comprising a third step of expanding the foamable resin composition to the maximum extent.   The method for manufacturing a speaker diaphragm according to claim 11, wherein the third step is performed by heating the foamable resin composition to 150C to 200C.

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