JPS6021699A - Acoustic diaphragm - Google Patents

Abstract

PURPOSE:To obtain an acoustic diaphragm having both large propagation speed and internal loss and a high frequency limit frequency by constituting the diaphragm with a base material containing an alumina ceramic fiber and a colored binder without fibrous structure. CONSTITUTION:100pts.wt. of the ceramic fiber containing nearly 55-95% alumina content is dispersed in water. Further, in order to manufacture to sheets in water, nearly 50-100pts.wt. aqueous soluble organic binder dyed without fibrous structure is added and they are mixed sufficiently. Sulfric alumina is added to said mixture, a pH is adjusted to 4-6, nearly 1-10pts.wt. a sizing agent is added thereto and mixed, and the mixture is manufactured to sheets immediately by using the sheet-making net of a desired diaphragm shape. The wetting ceramic fiber mat removed from the net is dried by using a heat press on the conditions of nearly 140-200 deg.C of metal die temperature and nearly 3-15min of press time so as to constitute the acoustic diaphragm. The acoustic diaphragm formed in this way has both large propagating speed and internal loss and the high frequency limit frequency is high in comparison with a diaphragm using a natural pulp (shown in an alternate long and short dash line).

Description

[Detailed Description of the Invention] The present invention relates to an acoustic diaphragm, and the acoustic diaphragm is constructed of alumina ceramic fibers and a colored binder that has a fiber structure, thereby achieving a high propagation velocity and The internal loss is also large, making it extremely desirable as an acoustic diaphragm.Moreover, the binder used as the constituent material of the acoustic diaphragm can be colored, for example by dyeing, to create a desired color. To provide an acoustic diaphragm that can be easily changed and made into a desired color.

For example, an acoustic diaphragm made of paper made from a mixture of alumina fibers and fibers such as natural pulp has been proposed.

However, the acoustic diaphragm proposed by this proposal contains more than 30% organic fibers such as natural fibers as a binder.
Although it has excellent formability, there is almost no bonding in the areas where there is no binder fiber, especially in the areas where ceramic fibers intersect with each other, so not only is it not possible to obtain sufficiently homogeneous strength, but there is also friction noise in the unbonded areas. This also causes an increase in the distortion characteristics of the speaker.

Also, although alumina ceramic fibers are relatively easy to color with dyes, etc. compared to carbon fibers, for example,
Currently, only white colors have been achieved, and it has not been possible to achieve the desired color for acoustic diaphragms using alumina ceramic fibers.

The present invention eliminates the above-mentioned drawbacks, and examples thereof will be described below.

For example, ceramic fiber containing 55 to 95 parts of alumina (fiber diameter 0.5 to 4 μm, (, Jl fiber length 0
．． 1-1'0 cIrL) 100 parts by weight are dispersed in water.

In order to make the paper in water, a water-soluble acrylamide resin (the resin is About 50 to 100 parts by weight of an anionic resin (with a molecular weight of about 800,000 to 1,000,000), particularly preferably about 80 parts by weight, is added and thoroughly stirred.

Next, sulfuric acid is added to the above mixed solution to adjust the pH to 4 to 6, and about 1 to 10 parts by weight of a sizing agent is added thereto and stirred. Immediately thereafter, paper is made using a paper mesh having a desired diaphragm shape. .

Then, the wet ceramic fiber mat removed from the paper screen is placed in a mold at a temperature of about 140 to 200°C and a pressing time of about 3 to 200°C.
It was dried by heat press for 15 minutes to form the acoustic diaphragm of the present invention.

In this way, an acoustic diaphragm made of a material containing alumina ceramic fibers and a binder that is colored with a dye and does not have a fiber structure has the desirable characteristics of alumina ceramic fibers as a diaphragm. The propagation velocity is high, and since the binder used as a binder does not have a fiber structure, it is unlikely to cause defects such as almost no bonding at the intersections of the alumina ceramic fibers. Therefore, a sufficiently uniform strength can be obtained as a whole, and the distortion characteristics of the speaker will not be increased.

For example, the acoustic diaphragm of the above embodiment has a propagation velocity of 2.2 to 2.6 Km/s, whereas the acoustic diaphragm using natural pulp has a propagation velocity of 1.0 to 2.0 Km/s. The propagation velocity is large, and the internal loss of the alumina bulk is 0.002 to 0.005, whereas the internal loss is sufficiently large at 0.02. As shown by the solid line in the drawing, the frequency characteristics of the speed Jy using the 3.
5KHz, as shown by the dashed line, the frequency characteristics of a speaker using an acoustic diaphragm made of natural pulp.
The upper limit frequency is 2.6 KI4z, and the acoustic diaphragm of this example is excellent.

Further, second harmonic distortion etc. are reduced compared to when natural pulp such as wood pulp is used as the binder.

Furthermore, rather than directly coloring alumina ceramic fibers, dyes are used to color a binder that does not have a fiber structure, such as a water-soluble acrylic resin, which is better than dyeing alumina ceramic fibers. It also has excellent color durability and color.

Furthermore, this acoustic diaphragm is flame retardant, can be made in the same manufacturing process as when using a naturally passive material, and is highly moldable and mass-producible.

Similarly, in the above embodiment, as an essential component of the acoustic diaphragm,
This uses alumina ceramic fibers and a colored binder that does not have a fiber structure, but it may also contain metal oxides or the like. For example, the acoustic diaphragm obtained in Example 2 is immersed in alumina sol (30% alumina aqueous solution), and the acoustic diaphragm element 42 is impregnated with 30 wt. For example, by drying at
An acoustic diaphragm with characteristics such as m/s and internal loss of 0.01 can be obtained.

As mentioned above, since the acoustic diaphragm according to the present invention is made of a material containing alumina ceramic fibers and a colored binder that does not have a fiber structure, the propagation velocity and internal loss are both large. Since the binder that joins the fibers does not have a fiber structure, there is often almost no bonding at the intersections of the alumina ceramic fibers, resulting in uniform strength, sufficient rigidity, and a small structure. The upper limit frequency is high, and since it is colored with a binder without a fiber structure, such as a dye, it has high fire resistance and can be easily colored into any desired color. He has special skills such as being able to make the acoustic diaphragm the color of his choice.

[Brief explanation of the drawing]

The drawing is a graph of the frequency characteristics of the speaker. Patent applicant: Victor Japan Co., Ltd. Agent Katsumi Utaka

Claims (1)

[Claims] An acoustic diaphragm characterized by being constructed of a material containing alumina ceramic fiber and a colored binder that does not have a fiber structure.