JPH0550200B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a diaphragm for an electroacoustic transducer using an inorganic scale material. Conventionally, various diaphragms made of inorganic scale materials and thermosetting resins have been devised and actually realized. The reason for this is that the diaphragm has a higher Young's modulus and a larger specific modulus of elasticity than conventional diaphragms made of paper pulp or synthetic resin, for example.
Furthermore, it has excellent moisture resistance and flame retardancy. Conventionally, such diaphragms mainly made of inorganic scale material have been produced by crushing the inorganic scale material to an appropriate particle size, then dispersing it in papermaking water, and forming it into a predetermined shape of the diaphragm, such as a cone shape, using a normal papermaking method. There is a diaphragm that is deposited on a net, impregnated with a thermosetting resin and a curing agent, and press-molded in a diaphragm shape using a heating mold. However, such conventional diaphragms have the following drawbacks. In other words, the above-mentioned work is required for each diaphragm, resulting in extremely poor mass productivity.Unlike paper pulp fibers, inorganic scale material has almost no intertwining with each other, so it is necessary to cut the diaphragm into the shape of the diaphragm. This is extremely difficult, and there are large variations in the shape and physical properties of the molded diaphragm. This invention combines a layer mainly containing inorganic scale material having high density and low elastic modulus and a layer mainly containing inorganic scale material having low density and high elastic modulus, and also has high density and low elastic modulus. This is a method for manufacturing a diaphragm having a three-layer structure including a layer mainly containing an inorganic scale material having an intermediate layer. Graphite powder (density 2.30g/cm ³ , Young's modulus 3.43×
10 ¹² dyn/cm ² , average particle size 60 μm), mica powder (density 2.85 g/cm 2 ) is used as an inorganic scale material with low elasticity and high density.
cm ³ , Young's modulus 1.72×10 ¹² dyn/cm ² , average particle size 200μ
m) is uniformly dispersed in water, allowed to naturally accumulate on a paper screen for about 15 minutes, and then the water is discharged under reduced pressure. Due to the difference in sedimentation speed in each of the above steps, the mica powder with higher density of the two types of inorganic scale materials is deposited on the paper mesh first, forming a layer mainly composed of mica powder, and on top of that, the mica powder with higher density is deposited on the paper screen. A layer consisting mainly of graphite powder is formed. Next, the laminate obtained in the above step is placed upside down on another paper screen, that is, with the graphite layer facing the paper mesh surface. This was done in the same manner as in the previous step, and the paper net was placed in the papermaking water in which mica powder and graphite powder were dispersed, and allowed to accumulate naturally for about 15 minutes. A layer of graphite is deposited. The laminate obtained in the above step was impregnated with a mixture of an epoxy resin and a curing agent and cured to the B stage to obtain a sheet-like prepreg. The prepreg was molded using a cone-shaped press mold (temperature: 170°C, press pressure: 10 kg/cm ² , time: 20 minutes) to obtain a cone-shaped diaphragm. As shown in FIG. 1, the diaphragm 1 has a surface layer mainly composed of graphite powder with high elasticity and low density, an inorganic scale material layer 1a containing some mica powder with low elasticity and high density, and an intermediate layer part An inorganic scale material layer 1b mainly composed of low elasticity and high density mica powder and containing some high elasticity and low density graphite powder is laminated on each layer, and these layers are integrated with an epoxy resin. The composition of the diaphragm 1 was 38.5 wt% mica, 38.5 wt% graphite, and 23 wt% epoxy resin. As mentioned above, this structure was achieved by utilizing the difference in sedimentation speed in water during papermaking due to the difference in density and particle size of the two types of inorganic scale materials. Next, a test piece was cut from the diaphragm and its physical properties were measured, and the following table was obtained.

【table】

[Table] As shown in the above table, it was found that the diaphragm of the embodiment of this invention had superior characteristics compared to the diaphragm of the comparative example. This is because high elastic modulus layers are arranged on the upper and lower surfaces of the diaphragm, and a layer with a lower elastic modulus is interposed between them, thereby adding structural strength due to the Sanderch structure. Furthermore, according to the manufacturing method of the present invention, since there is no clear boundary between the mica layer and the graphite layer, it is possible to prevent deterioration of bending rigidity due to slipping at the interface in this type of sandwich structure, and Peeling can be prevented. In addition, in the method for manufacturing a diaphragm of the present invention, in order to fully utilize the difference in the settling speed of two types of inorganic scale materials in water, the particle size of the low-density inorganic scale material is made small, and the particle size of the high-density inorganic scale material is made small. It is desirable to select a large particle size of the inorganic scale material. Furthermore, in the manufacturing method of the present invention, the same effect can be obtained even if, in the second papermaking step, only the graphite powder is deposited on the mica layer formed in the first papermaking step. As explained above, the present invention includes a process of dispersing in water an inorganic scale material having a low density and a high elastic modulus, and an inorganic scale material having a high density and a low elastic modulus, A process of naturally depositing an inorganic scale material having an elastic modulus and an inorganic scale material having a high density and a low elastic modulus on a papermaking net, and a laminate obtained by the above process is turned upside down and subjected to another papermaking process. A step of placing the inorganic scale material on a net, and dispersing the inorganic scale material having low density and high elastic modulus alone, or the inorganic scale material having low density and high elastic modulus and the inorganic scale material having high density and low elastic modulus. A step of placing the above-described laminate in water for extraction, and adding the inorganic scale material alone having low density and high elastic modulus to the placed laminate, or the inorganic scale material having low density and high elastic modulus. A step of naturally depositing a scale material and an inorganic scale material having high density and a low elastic modulus, and 3 obtained by each of the above steps.
A method for producing a diaphragm for an electroacoustic transducer, comprising the steps of: impregnating a layer laminate with a thermosetting resin to obtain a prepreg; and press-molding the prepreg into a diaphragm shape. A diaphragm with good physical properties can be obtained by an extremely simple manufacturing method, and has excellent practical effects. Note that this invention is not limited to the above embodiments, and other inorganic scale materials other than mica and graphite can be appropriately selected as long as they comply with the gist of the invention. Alternatively, the paper net may be formed in advance into the shape of a diaphragm, and the inorganic scale material may be deposited thereon in accordance with the order of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a diaphragm obtained by the manufacturing method of the present invention. 1a is a layer mainly containing inorganic scale material having low density and high elastic modulus, and 1b is a layer mainly containing inorganic scale material having high density and low elastic modulus.

Claims (1)

[Claims] 1. A process of cutting and dispersing inorganic scale material having low density and high elastic modulus and inorganic scale material having high density and low elastic modulus in water, and dispersing the inorganic scale material having low density and high elastic modulus and high density. a step of naturally depositing an inorganic scale material having a low elastic modulus on a paper screen; a step of turning the laminate obtained in the above step upside down and placing it on another paper screen; The above-mentioned laminated layer in which an inorganic scale material having a high density and a high elastic modulus alone, or an inorganic scale material having a low density and a high elastic modulus and an inorganic scale material having a high density and a low elastic modulus are dispersed in water. a step of arranging the body, and the inorganic scale material having low density and high elastic modulus alone, or the inorganic scale material having low density and high elastic modulus, and the inorganic scale material having high density and low elastic modulus on the mounted laminate. A step of naturally depositing an inorganic scale material, a step of impregnating the three-layer laminate obtained in each of the above steps with a thermosetting resin to obtain a prepreg, and a step of press-molding the prepreg into a diaphragm shape. A method for manufacturing a diaphragm for an electroacoustic transducer, characterized in that: