Manufacturing method for narrow-type diaphragm and thin-type diaphragm, speaker-use diaphragm manufactured using same manufacturing method, speaker, electronic apparatus, and movable device
View Patent ↗After beaten, pulp is mixed with a filler to obtain a mixture of the pulp and the filler. Additives are added to the mixture, which is made into pater and then hot-pressed. The filler content of the mixture is in the range of 20 wt % to 80 wt %. After the additives are added, a polymeric viscosity improver with high viscosity is added to produce a narrow diaphragm or a thin compact diaphragm with high aspect ratio. These diaphragms have high rigidity and a wide reproduction frequency range.
1. A method of manufacturing a narrow diaphragm or a thin diaphragm, the method comprising, in the sequence set forth:
beating pulp;
mixing the beaten pulp with a filler so as to form a mixture of the beaten pulp and the filler;
adding a paper-strengthening agent and a sizing agent as additives to the mixture;
making paper from the mixture containing the additives; and
drying the paper by hot-pressing;
wherein a content of the filler in the mixture is in a range of 20 wt % to 80 wt %, inclusive, when the mixture is formed; and
a polymeric viscosity improver made of a polymeric material having a molecular weight of 5,000,000 or greater, and having a viscosity of 12,000 mPa·s/25° C. or greater is added after the additives are added and before making the paper.
2. The method according to claim 1 , wherein adding the additives, an added amount of the viscosity improver is in a range of 0.1% to 5%, inclusive, of a total weight of the mixture.
3. The method according to claim 1 , wherein the viscosity improver is either cationic or zwitterionic.
4. The method according to claim 1 , wherein the beaten pulp has a beating degree in a range from 200 ml to 700 ml, inclusive, according to Canadian standard freeness.
5. The method according to claim 1 , wherein the beaten pulp has a fiber length of not less than 0.8 mm and not more than 3 mm.
6. The method according to claim 1 , wherein the diaphragm has a density in a range from 0.40 g/cm 3 to 1.00 g/cm 3 , inclusive.
7. The method according to claim 1 , wherein
when mixing the beaten pulp and the filler, fine fibrillated fibers are mixed with the beaten pulp and the filler to form the mixture; and
a content of the fine fibrillated fibers in the mixture is in a range from 1 wt % to 30 wt %, inclusive.
8. The method according to claim 7 , wherein the fine fibrillated fibers have a beating degree of 200 ml or less.
9. The method according to claim 1 , wherein the pulp contains bamboo fibers obtained from bamboos of one year old or more.
10. The method according to claim 9 , wherein a lignin content of the bamboo fibers is 20 wt % or less.
11. The method according to claim 1 , wherein the filler is at least one of mica, plant opal, and metal fiber.
12. A loudspeaker diaphragm manufactured by the method of manufacturing the narrow diaphragm or the thin diaphragm according to claim 1 , wherein the filler is contained in a range from 20 wt % to 80 wt %, inclusive.
13. A loudspeaker comprising:
the loudspeaker diaphragm as defined in claim 12 ;
a frame;
a magnetic circuit connected to the frame;
a voice coil disposed in a magnetic gap of the magnetic circuit and fixed in a center of the loudspeaker diaphragm; and
an edge joining the loudspeaker diaphragm and the frame.
14. An electronic apparatus comprising:
a video display unit;
an outer frame enclosing the video display unit; and
the loudspeaker as defined in claim 13 and accommodated inside the outer frame.
15. A movable device comprising:
a driving device;
a body member including the driving device; and
the loudspeaker as defined in claim 13 and mounted in the body member.