JPH0242280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a support such as an edge or damper that supports a diaphragm of a speaker.

BACKGROUND ART In general, an edge or damper for a speaker is important as a center support for correctly attaching the voice coil to the center of the gap and vibrating the diaphragm correctly. In particular, in the case of a damper, it is required to have an appropriate internal loss that does not resonate with the vibration of the diaphragm, and the frequency characteristics are improved by applying resin or rubber processing to cotton cloth. FIG. 1 is a cross-sectional view of a cone-shaped speaker. The magnet 1 is held between an upper plate 2 and a lower plate 3, and a center pole 4 is placed on the lower plate 3, thereby forming a magnetic circuit. The diaphragm 5 has a voice coil 6 at the opening end of the recess.
A voice coil bobbin 11 wound with a voice coil is connected thereto, and a center cap 15 is placed thereon. The opening edge of the diaphragm 5 is connected to the tip of the frame 8 fixed to the upper plate 2 via an edge 9 with a gasket 1.
Further, the opening end of the concave portion of the diaphragm 5 is supported by a damper 7 fixed to the frame 8 via a bobbin 11 of the voice coil 6.

Various attempts have been made to make the diaphragm of a speaker flame retardant because the voice coil of the speaker generates heat due to excessive input and is used in areas exposed to high temperatures, such as television cabinets. However, traditionally, materials such as cotton cloth coated and impregnated with resin or treated with rubber have been widely used as materials for edges and dampers, and in both cases, flammable materials must be used. This made it difficult to make speakers flame retardant. Therefore, it can be said that flame retardant measures were insufficient for the speaker as a whole.

Conventional flame retardants for speaker diaphragm supports include boric acid, boron compounds, halogen compounds,
There are phosphoric acid compounds, etc. Boric acid and boron-based compounds are highly hygroscopic and significantly deteriorate the moisture resistance of products. Halogen-based compounds themselves do not impart flame retardancy to cotton fabrics and will not be effective unless attached in large quantities. Therefore, these flame retardants have a large influence on the deterioration of the physical properties of the support. Although phosphoric acid compounds have a flame retardant effect on cotton fabric, their decomposition temperature is low, and for example, when molding dampers and edges, it is usually difficult to maintain their shape unless they are formed at temperatures above 200°C. However, since this molding temperature and the decomposition temperature of the phosphoric acid flame retardant are almost in the same range,
making its use difficult. Another problem with halogen flame retardants is that they generate toxic gas when ignited.

SUMMARY OF THE INVENTION The present invention provides a support for a speaker diaphragm that has good and sufficient flame retardancy without affecting its original characteristics.

The support of the speaker diaphragm of the present invention is produced by impregnating a woven or nonwoven fabric with a solution of a salt of a water-soluble cyanamide derivative and a surfactant, drying it, impregnating it with a thermosetting resin, and heating and pressing it after drying to give it a predetermined shape. It is characterized by being molded into.

Examples Examples of the present invention will be described below based on tables.

In the present invention, by using cyanamide, which is a compound with a high decomposition temperature, and further using a derivative with an atomic group containing other flame retardant elements, a synergistic effect of flame retardation is achieved, and a good result is obtained with a small amount of adhesion. This imparts flame retardancy to the support of a speaker diaphragm.

Cyanamide is represented by NC- _NH2 , and examples of derivatives thereof include guanidine of the following formula.

HNC (NH ₂ ) ₂ When used in the form of a salt of HNC (NH 2 ) with phosphoric acid, such as monoguanidine phosphate, diguanidine phosphate, or sulfamic acid, the decomposition temperature is high and the synergistic effect between phosphorus and nitrogen or sulfur occurs. Due to this effect, good flame retardancy can be obtained with a small amount of adhesion. Also,
Cyanamide has low hygroscopicity and exhibits a flame retardant effect even with a small amount of adhesion, so the support for the speaker diaphragm of the present invention also has excellent moisture resistance.

In addition, the salt of guanidine sulfamate is JISK
According to the acute toxicity of medaka mosquitoes based on the -0102 factory wastewater test method, the survival rate after 24 hours at 7000ppm is
100%, and in a similar test with guanidine phosphate salt, the survival rate after 24 hours was 100% at 2500ppm.
It was %. These flame retardants have no problem with their acute toxicity, and since their flame retardant effect is due to the dehydration effect of phosphoric acid or sulfamic acid, no harmful gas is generated when ignited.

Application example 1 Manufacture a support for a speaker diaphragm.

First, a woven fabric of a predetermined shape of #108 cotton fabric was heated with 1 phosphoric acid.
Soak in a guanidine aqueous solution and dry at 100°C for 5 minutes. At this time, 15 to 20% of 1-guanidine phosphate is attached to the cotton cloth.

In addition, cotton cloth is usually coated with glue, and this glue makes it difficult for monoguanidine phosphate to adhere to the cotton cloth. Therefore, in the present invention, a surfactant is also used. Examples of the surfactant include sodium alkyl ether sulfate, sodium alphaolefin sulfonate, fatty acid alkanolamide, and alkyl anoxide, and the amount added is approximately 0.1 to 1.0%.

This is impregnated with an alcoholic solution of phenol,
Dry at 100°C for 5 minutes (phenol adhesion amount is 30-40%).

This is press-molded for 3 seconds using a mold of a predetermined shape at 250°C±5°C. The press pressure at this time is 1.0Kg/
^cm2 .

Application example 2 Similarly, 6 to 9% of diguanidine sulfamic acid was attached to cotton cloth #108, and 30% of phenol was also attached to it.
~40% adhesion. Molding temperature is 250℃±5℃3
Seconds.

Application example 3 Similarly, 15 to 20% of guanidine sulfamate was attached to cotton cloth #108, and 30 to 30% of phenol was attached to it.
Attach 40%. The molding temperature was 250°C±5°C for 3 seconds.

The flame retardancy of the cyanamide derivative in the present invention is determined by the amount of the cyanamide derivative adhered to the cotton cloth, and is not greatly affected by the concentration of the aqueous impregnating solution. That is, the amount of adhesion is adjusted by impregnating cotton cloth and squeezing it with a roll or the like. Further, the effect of the surfactant is sufficient when added in an amount of 0.1 to 1.0%, regardless of the concentration of the cyanamide derivative.

Next, we will discuss the case where ammonium phosphate is used as a conventional flame retardant and application examples 1, 2, and 3 of the present invention.
Compare with JISP-8115 MIT type folding test. The results are shown in Table 1. In both cases, 35% phenol was attached and molding was performed at 250°C ± 5°C for 3 seconds.

Table 1 Application example 1 687.8 times/1.5Kg Application example 2 1485.5 times/1.5Kg Application example 3 1121.0 times/1.5Kg Ammonium phosphate treatment 687.8 times/1.5Kg Phenol only treatment 1132.0 times/1.5Kg In the present invention, In either case, the folding strength remains the same as in the case of treatment with phenol alone. That is, flame retardance can be achieved while maintaining physical properties. In contrast, ammonium phosphate, a phosphoric acid flame retardant, has a decomposition temperature of 190°C to 200°C.
Therefore, a deterioration phenomenon clearly occurs due to the dehydration carbonization effect of phosphoric acid.

The flame retardance of the speaker diaphragm supports of Application Examples 1, 2, and 3 and ammonium phosphate treatment corresponded to UL94V-0.

The formulas of the compounds used in the above application examples and comparisons are as follows.

1-guanidine phosphate HNC (NH ₂ ) ₂ H ₃ PO ₄ 2-guanidine phosphate (HNC (NH ₂ )) ₂ H ₃ PO ₄ guanidine sulfamate HNC (NH ₂ ) HSO ₃ NH ₂ ammonium phosphate NH ₄ H ₂ PO ₄ or (NH ₄ ) ₂ HPO ₄ The flame retardant treatment in the present invention is not limited to cotton fabrics, but can also be applied to woven fabrics and non-woven fabrics made of other natural fibers or chemical fibers. For example, it can be applied to diaphragms such as wood pulp. However, in the case of a diaphragm made of paper, pulp, etc., use of a water-soluble impregnating agent may cause deformation or the like. Therefore, in this case, it is necessary to apply a sizing agent in advance. Further, it is also possible to impregnate and apply a flame retardant and then heat and pressurize it using a mold or the like.

The cotton cloth molding according to the present invention can be used not only as a support for a diaphragm of a speaker, but also for, for example, a center cap, a speaker box net, etc. using cotton cloth.

Effects The damper and edge, which are the supports of the speaker diaphragm of the present invention obtained in this way, are made of cotton cloth or the like, so they are rigid and have a moderate internal loss, and the diaphragm It is suitable as a support for. It also has excellent flame retardancy equivalent to UL94V-0.

Furthermore, since cyanamide derivatives absorb little moisture, the obtained flame-retardant support does not deform due to moisture absorption, and can hold the diaphragm and voice coil in a stable state at the center of the gap, so when assembled into a speaker. A stable support that does not affect its frequency characteristics can be obtained.

As mentioned above, since it has excellent flame retardancy, the risk of ignition is significantly reduced compared to conventional speakers even if the speaker is placed in a high-temperature area near the power source of a television/radio or the like.

Note that guanidine phosphate and guanidine sulfamate are non-toxic and harmless to the human body when used, so no special ventilation equipment is required for their production.

[Brief explanation of drawings]

The drawing is a partial cross-sectional view of a cone-shaped speaker. Explanation of symbols of main parts, 1... Magnet, 2... Upper plate, 3... Lower plate, 4... Center pole, 5... Diaphragm, 6... Voice coil,
7...Damper, 8...Frame, 9...Edge,
10...Gasket, 11...Voice coil bobbin, 15...Center cap.

Claims (1)

[Claims] 1. A support for a speaker diaphragm, which is obtained by impregnating a woven or nonwoven fabric with a solution of a salt of a water-soluble cyanamide derivative and a surfactant, drying it, impregnating it with a thermosetting resin, heating and pressurizing it, and molding it into a predetermined shape.