JPH06253389A - Diaphragm for speaker - Google Patents

Abstract

PURPOSE:To improve hydrolytic resistant characteristic without damaging the characteristics of superior thermal resistance, high strength and high elastic modulus provided in a polybenzazole fiber and to provide a diaphragm for maintaining acoustic characteristics for a long period of time by arranging cloth for which the specific polybenzazole fiber is used at least in one layer and reinforcing it with a resin. CONSTITUTION:The cloth for which the polybenzazole fiber with the void diameter <=25Angstrom is used is arranged almost in one layer and is reinforced by the resin. The polybenzazole fiber is fiber composed of polybenzoxazole, polybenzothiazole or the random or block copolymer. Pulling strength is >=4.0GPa and pulling elastic modulus is >=140GPa. From the result of experiments, hydrolysis is remarkably improved when the void diameter is <=25Angstrom . The cloth to be used may be nonwoven fabric, knit or woven fabric, however, the woven fabric is preferable from the view point of the balance of internal loss and the specific elastic modulus of the obtained diaphragm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker diaphragm, and more particularly to a speaker diaphragm having a structure in which resin is reinforced with a cloth composed of high-strength and high-modulus fibers.

[0002]

2. Description of the Related Art Conventional speaker diaphragms are mainly made of paper pulp and have a moderate internal loss, but they are divided because they lack specific elasticity and specific strength and lack rigidity. The vibration range originates from the low frequency band, and there is a drawback that peaks and dips occur and squeal occurs due to frequency characteristics. Therefore, it has been reported that the above-mentioned conventional drawbacks can be solved by a speaker diaphragm having a high strength / high elastic modulus fiber reinforced layer or a laminated structure of a high strength / high elastic modulus fiber reinforced layer and a different type back layer. (Japanese Patent Laid-Open No. 1-144
893, 1-144894, 1-144895). Therefore, polybenzazoles such as polyparaphenylenebenzbisthiazole (PBT) and polyparaphenylenebenzbisoxazole) (PBO), which have become known as new high heat resistance, high elastic modulus and high strength organic fibers ( It is considered that PBZ) is also useful as a material for the diaphragm for the speaker. However, conventional polybenzazole fibers may have voids during fiber production or post-processing, and as a result, their water resistance tends to decrease, so that excellent properties as a speaker diaphragm immediately after production are maintained for a long time. It was difficult to maintain.

[0003]

[Problems to be Solved by the Invention]
The present invention improves hydrolysis resistance by reducing the void diameter generated during production without compromising the excellent properties of polybenzazole (PBZ) fibers, namely high tenacity, high modulus, and high heat resistance. An object of the present invention is to provide a diaphragm for a speaker using PBZ fiber that maintains excellent characteristics for a long period of time.

[0004]

It has been known that PBZ fibers have particularly excellent properties as a high elastic modulus and high strength material, and a diaphragm for a speaker including a high strength and high elastic modulus reinforcing layer. Although it was also expected to be applied as a reinforcing fiber for use in steel, it has been found that it has the drawback that its tensile strength decreases in the presence of water. We have
As a result of investigating the cause of the decrease in the tensile strength of PBZ due to water, it was found that the decrease in the strength was due to the hydrolysis of the PBZ molecular chain due to water, and that the infiltration of water from a relatively large void accelerated the hydrolysis action. I found it. This means that reducing the void diameter improves hydrolyzability. As a result of the experiment, it was found that the hydrolyzability was remarkably improved when the void diameter was 25 Å or less. As a result of examining the cause of the manufacturing process on the void diameter, it was found that the phosphoric acid concentration in the coagulation bath had a great influence. As a result of diligent studies, as one of the methods for reducing the void diameter to 25 Å or less, when a fiber is manufactured by spinning a dope composed of a polymer containing PBZ as a main component and polyphosphoric acid, the phosphoric acid concentration in the coagulation bath is 5% or more At that time, I found that the void diameter was 25 Å or less. The PBZ fiber manufactured in this manner has a void diameter of 25 Å or less, and it was found that even a diaphragm for a speaker manufactured using the PBZ fiber exhibited excellent property maintenance with little strength reduction over a long period of time, and thus reached the present invention. did.

Polybenzazole fiber (PBZ) of the present invention
Means a fiber made of polybenzoxazole (PBO) or polybenzthiazole (PBT) or a random or block copolymer thereof. The tensile strength is 4.0 GPa, preferably 4.1 GPa or more, and the tensile elastic modulus is 140 GPa or more, preferably 150 GPa or more. Moreover, the average diameter of the fibers is 50 μm or less, further 25
μm or less is preferable.

The PBZ fiber used for producing the PBZ fiber of the present invention is characterized by having a void diameter of 25 Å or less. As one of the methods for reducing the void diameter to 25 Å or less, in producing a fiber by spinning from a dope composed of a polymer containing PBZ as a main component and polyphosphoric acid,
It was found that the concentration of phosphoric acid in the coagulation bath was 5% or more. Further, it is effective to add an oil agent for the purpose of improving the post-processability. The type of oil agent used in the present invention may include a component acting as a lubricant. It goes without saying that an emulsifier, a stabilizer and the like are used in combination if necessary. As components contained in the oil agent, animal oils, vegetable oils, fatty acid esters, hydrocarbons, higher alcohols, neutral oils such as higher fatty acids, soaps, sulfuric acid esters, sulfonic acids, phosphoric acid esters, surfactants such as ether derivatives, And mixtures thereof, silicone oil, etc. can be used. The oil agent can be applied at one place or at two or more places at the same time during the process from the spinneret to the final winding, and can be performed at any place. It is preferably applied after solidification. If a heat treatment step for increasing the elastic modulus is further required, it is preferable to add a finishing agent after the heat treatment step.

[0007] The method of applying the oil agent to the yarn includes spray application in which the oil agent is atomized, dip application through the oil agent bath,
Any method such as kiss roll application or guide application may be used.
An oil agent may be added to the coagulation bath. The adhesion amount of the oil agent is 0.05 to 7.0 with respect to the dry weight of the fiber to which the oil agent is applied.
Weight% is good. If it is less than 0.05% by weight, the oil agent does not sufficiently cover the fiber surface, and if it is more than 7.0% by weight, an excessive amount of the oil agent scatters, which is not preferable. More preferably 0.
It is 1 to 3.0% by weight. Most preferred is 0.3-
It is 2.0% by weight.

If it is necessary to remove the oil agent after applying the oil agent, an oil agent removing step may be provided in a separate step. The fine powder insoluble in the oil agent means that which acts as a solid lubricant. For example, diameter 10m
Colloidal silica or colloidal alumina of μ or less, or titanium oxide or calcium carbonate of several hundred mμ or less in diameter
Silica gel, calcium phosphate, talc, clay, mica, graphite, molybdenum sulfide and the like having a diameter of several μ can be used. It is necessary that these are smaller than the single yarn diameter in the yarn. The fine powder acts as a solid lubricant on the fiber surface,
It has an effect of preventing adhesion between fibers and an effect of improving water resistance by preventing contact of water. The amount of these fine powders deposited is preferably 5.0% by weight or less based on the dry weight of the fibers. If it is 5.0% by weight or more, the effects of water resistance and adhesion prevention reach the ceiling, which is not preferable. 1.0% by weight
The following is more preferable. Most preferably 0.5
It can be said that the content is less than or equal to weight%.

When the PBZ fiber described above is used in a diaphragm for a speaker, it exhibits excellent characteristics such as high elastic modulus, high rigidity, large internal loss and little squeal, and compared with the conventional spinning method. It was found that this property is maintained for a long period of time because the PBZ fiber is particularly excellent in water resistance, and the present invention has been accomplished. The cloth used in the present invention may be a non-woven fabric, a knit, or a woven fabric, but a woven fabric is preferable from the viewpoint of the balance between the specific elastic modulus and the internal loss of the obtained diaphragm. The woven structure is not particularly limited, but a plain weave structure is preferable from the viewpoint of appearance and decorativeness. Further, the structure of the diaphragm formed of the resin reinforced with such a cloth may be either a single layer structure or a laminated structure, but in consideration of bending rigidity, a cloth using fine denier is laminated with at least 2 plies. It is desirable to use a different structure, such as a fabric having a thick denier and a single layer structure.

Further, as described above, the PBZ of the present invention
A speaker diaphragm consisting of a resin layer reinforced with a fiber cloth exhibits excellent characteristics, but this resin layer is used as a surface layer,
It is also possible to form a speaker diaphragm in the form of a laminated material having different materials as a back layer. This makes it possible to change the acoustic characteristics delicately. As the different material used as the backing layer, for example, FR reinforced with inorganic fibers such as paper pulp and carbon fibers, or organic fibers such as aramid fibers.
The material that has been used as the diaphragm for the speaker such as P can be used, but the material is not particularly limited thereto.

[0011]

EXAMPLES The present invention will be specifically described below with reference to Examples, but the methods for measuring the physical properties used in the evaluation of the present invention are as follows. <Void diameter measurement method> Small angle X-ray scattering intensity measurement
This is done using a Kratki camera. Wrap the sample fiber around the 6 m measuring holder. X-ray output is 45 kv 150 mA
Then, the Cukα ray is used after being monochromaticized with a nickel filter. The vertical limit slit of the Krafty camera was 42 mm, the width limit slit was 0.07 mm, and the length of the light receiving unit slit was 10 mm, and the width limit was 0.14 mm. The measuring range is 0.1 to 3 degrees. The step width is 0.025 degree increments and is accumulated for 30 seconds or more. The background scattering is corrected using the following equation from the measurement results of the sample and air scattering. I = μIsample−Iair μ = Iair (0) / Isample (0) where I is the true scattering intensity, Isample is the measured scattering intensity with the sample, and Iair is the intensity measured without the sample. . After measuring the sample, the intensity is measured at a scattering angle of 0 degree to determine the absorption coefficient of the sample. The void size is measured using a Guinier plot. The logarithm of the scattering angle (I) and the square of the scattering vector (k) are plotted, and a linear approximation is performed for data in which the value of the square of k is 0 to 0.01Å ² , and the following equation is used from the slope (s) of the straight line. Calculate. D = 2 (2S) ^1/2 Water resistance test: Tensile strength in a wet state was used as an evaluation measure of water resistance. After the test piece was immersed in water (20 ° C.) for 200 hours, the sample was taken out from the water and the strength was measured within 1 minute.

Example 1 Spin dope (polyparaphenylene benzobisoxazole having an intrinsic viscosity of 25 at a concentration of 14.7% by weight was dissolved in polyphosphoric acid having a composition expressed as phosphorus pentoxide of 83.7% by weight) Was passed through a metal mesh filter medium and spun at a discharge rate of 0.22 g / min per single hole from a spinneret having a diameter of 0.20 mm and a number of holes of 334 kept at 150 ° C. Flow velocity of the spun yarn is rectified 0.5 m / sec, temperature 70
It cooled with the air cooling airflow of (degreeC). Then, the yarn was introduced into a coagulation bath at 15 ° C. consisting of a 10% phosphoric acid aqueous solution placed 40 cm below the surface of the spinneret and cooled to remove the solvent. After that, the yarn was passed through a first roller having a diameter of 200 mm, then a washing roller having the same diameter, a drying roller, and a heat treatment kneader online, and was wound at a yarn speed of 200 m / min without being substantially stretched. . Drying roller temperature is 170 ℃, 190 ℃, 210 ℃ 2 respectively
Heated for 0 seconds. After that, the yarn was cooled to a temperature of 80 ° C. or lower and wound by a winder. At that time, an air blower was installed at the outlet of the washing roller to remove water adhering to the yarn, and 1% by weight of a polyethylene oxide / polypropylene oxide copolymer having a molecular weight of 9000 was dispersed by using an oil agent supply device using an installed oiling roll. It was The obtained PBO
A water resistance test was conducted on the fibers. The results are shown in Table 1.
A plain woven fabric (density: 1500 denier / 1001 filaments of this PBO fiber, alternating with the warp and weft directions) was added at a ratio of 1: 1.
Warp, weft 13 lines / inch) were produced. A prepreg-processed vinyl ester resin is applied to this woven fabric by a molding die under predetermined conditions (120 ° C., 5 minutes, surface pressure 5 kg / cm ² ).
By heating and pressurizing with, a cone type diaphragm for 8 inches was obtained. As for the physical properties of the obtained cone-type diaphragm 1, the sound velocity and the internal loss were well balanced, and the squeal was small. FIG. 1 (a) shows a frequency characteristic diagram one year after the production of this speaker. This characteristic was almost the same as that immediately after the speaker was manufactured.

Comparative Example 1 A speaker diaphragm was manufactured in the same manner as in Example 1 except that the coagulating bath was water. Table 1 shows the results of a water resistance test conducted on the PBO fibers. In addition, FIG. 1B shows the frequency characteristics of this speaker one year after production. The frequency characteristic immediately after fabrication did not change much from that of FIG. 1A, but it can be seen that the characteristic deteriorates particularly in a high frequency region due to aging.

[0014]

[Table 1]

As is clear from Table 1, the number of kink bands in the PBO fiber can be reduced by treating with an oil agent, and accordingly, the excellent heat resistance of the PBO fiber,
It can be seen that the greatest drawback, that is, hydrolysis resistance, can be improved without impairing the characteristics of high strength and high elastic modulus, and that excellent characteristics as a diaphragm for a speaker can be maintained for a long period of time.

[0016]

As described above, according to the present invention, PBZ
A speaker that exhibits excellent characteristics of fibers, that is, high strength and high elastic modulus, and has improved hydrolysis resistance, which is the biggest drawback, and can maintain excellent characteristics for a long time. I was able to obtain a diaphragm for use.

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[Procedure amendment]

[Submission date] January 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

FIG. 1 is a frequency characteristic diagram of a diaphragm according to the invention.

[Explanation of Codes] a: Frequency characteristics immediately after speaker production, b: Frequency characteristics one year after speaker production.

Claims (2)

[Claims] 1. A fabric reinforced with a resin, which has a tensile strength of 4.0 GPa or more, an initial tensile elastic modulus of 140 GPa or more, and a polybenzazole fiber having a void diameter of 25 Å or less, which is arranged in at least one layer. A diaphragm for speakers, which is characterized by 2. A diaphragm for a speaker, which is a laminated material in which a resin reinforced with a cloth using the polybenzazole fiber according to claim 1 is used as a surface layer and a different material is used as a back layer.