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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
polycarbonate resin film for a speaker diaphragm and a speaker diaphragm comprising the same.
More specifically, the present invention relates to a polycarbonate resin film for a speaker
diaphragm, in which the surface of the film is roughened, and relates mainly to a film for a small
speaker diaphragm for a headphone or a cellular phone.
2. Description of the Related Art A speaker has a structure in which an electric signal is
converted to vibrational motion by a voice coil and a magnet disposed at the back of the speaker,
and the diaphragm is operated to generate sound. Therefore, large magnets or strong magnets
must be used, which is an obstacle to reducing the weight and cost of the speaker.
Therefore, conventionally, a film made of a resin, such as polyetherimide resin, polyimide resin,
polyethylene terephthalate resin, polyethylene naphthalate resin, polycarbonate resin, etc., has
been used as a material of a diaphragm for a speaker (Japanese Patent Application Laid-Open No.
6-261392) Japanese Examined Patent Publication Nos. 7-101956, 8-47082, and the like).
Among them, the film made of polycarbonate resin can withstand the specification even in the
atmosphere under high temperature and high humidity environment compared with other resin
films, so it is adopted for the diaphragm of speakers such as mobile phone, personal computer
and small radio Further improvement in sound quality is desired in both high and low tone areas.
SUMMARY OF THE INVENTION An object of the present invention is to provide a polycarbonate
resin film for a speaker diaphragm, which is excellent in heat resistance and excellent in sound
quality in a high sound region and a low sound region.
As a result of intensive research aimed at achieving this object, the inventor has found that by
setting the surface of the polycarbonate resin film to a specific range of roughness, a speaker
diaphragm made of polycarbonate resin film with good sound quality can be obtained. The
present invention has been reached.
According to the present invention, a polycarbonate resin film for a speaker diaphragm having a
surface roughness (Ra) of 0.05 to 5.0 μm and a thickness of 10 to 100 μm is obtained.
The thickness of the polycarbonate resin film used in the present invention is in the range of 10
to 100 μm.
When the thickness is more than 100 μm, the function as a diaphragm is inferior, and a film
having a thickness of less than 10 μm is insufficient in strength, and roughening the surface of
the film is industrially difficult, which is not preferable.
Moreover, the surface roughness of the polycarbonate resin film of this invention is 0.05-5.0
micrometers, Preferably it is the range of 0.1-3.0 micrometers.
In the case of a film having a surface roughness of less than 0.05 μm, it is not preferable
because it is equivalent to the sound quality when using a regular mirror film.
On the other hand, when the surface roughness exceeds 5.0 μm, the sound quality is
unfavorably deteriorated.
As a means to make the surface roughness of the polycarbonate resin film in the range of 0.05 to
5.0 μm, inorganic or organic particles are contained in the polycarbonate resin, and this
polycarbonate resin composition is melted and extruded from an extruder, and cooled. The
method of forming a film by roll is preferably adopted.
As a method of containing inorganic or organic particles in a polycarbonate resin, any method
may be adopted as long as it is a method of uniformly dispersing.
For example, a method of masterbatching the particles and the polycarbonate resin in advance
and mixing them with the polycarbonate resin powder, or a method of mixing the particles
directly with the polycarbonate resin powder can be applied.
The method for producing a polycarbonate resin film can be easily obtained from an extruder
using a T-die and a cooling roll. For example, a polycarbonate resin containing particles is fed
from the hopper of a 50 to 150 mm extruder, melted at 260 to 290 ° C., extruded from a T die
of 1000 to 1600 mm in length, and cooled by a cooling roll having a diameter of 300 to 500
mm. Preferably, the film is wound up.
As the above-mentioned inorganic particles, for example, clay, kaolin, silica-alumina-based
viscosity mineral represented by calcined kaolin (hydrous aluminum silicates), silica-magnesiumbased clay mineral represented by talc (hydrous magnesium silicates), Calcium silicate, silica,
alumina, calcium carbonate, aluminum hydroxide and the like can be mentioned. In particular,
talc, kaolin and calcium carbonate are preferable since they have excellent dispersibility in the
polycarbonate resin. Moreover, as said organic particle, the particle | grains which consist of
crosslinked acrylic resin and crosslinked styrene resin are preferable.
The average particle diameter of the inorganic or organic particles is preferably in the range of
0.1 to 10 μm. The use of particles in this size range is preferred because the surface of the film
is likely to be roughened in the desired range.
The range of 0.05-20 weight part is preferable with respect to 100 weight part of polycarbonate
resin, and, as for the content of the said inorganic or organic, the range of 0.1-5 weight part is
more preferable. In this range, the amount of particles dispersed in the film is appropriate, and a
film having a desired surface roughness is easily obtained, which is preferable.
The polycarbonate resin used in the present invention is obtained by reacting dihydric phenol
with a carbonate precursor by an interfacial polymerization method or a melting method.
Representative examples of dihydric phenol include 2,2-bis (4-hydroxyphenyl) propane [common
name bisphenol A], 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxy) Phenyl) cyclohexane,
2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane,
bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone etc. are mentioned, Especially
bisphenol A is preferable. These dihydric phenols can be used alone or in combination of two or
Carbonyl halides, carbonate esters or haloformates are used as the carbonate precursor, and
specific examples include phosgene, diphenyl carbonate or dihaloformates of dihydric phenol.
When producing the polycarbonate resin by reacting the above-mentioned dihydric phenol and
carbonate precursor by interfacial polymerization method or melting method, a catalyst, an end
terminator, an antioxidant of dihydric phenol, etc. are used if necessary. May be
The polycarbonate resin may be a branched polycarbonate resin obtained by copolymerizing a
trifunctional or higher polyfunctional aromatic compound or a polyester carbonate resin
obtained by copolymerizing an aromatic or aliphatic difunctional carboxylic acid, Moreover, the
mixture which mixed 2 or more types of obtained polycarbonate resin may be sufficient.
10,000-100,000 are preferable at a viscosity average molecular weight (M), and, as for the
molecular weight of polycarbonate resin, 15,000-35,000 are more preferable. A polycarbonate
resin having such a viscosity average molecular weight is preferable because sufficient strength
can be obtained and the melt flowability at the time of molding is also good. The viscosity
average molecular weight referred to in the present invention is obtained by inserting the
specific viscosity (η sp) obtained from a solution of 0.7 g of a polycarbonate resin dissolved in
100 ml of methylene chloride at 20 ° C. into the following equation. ηsp / c = [η] + 0.45 ×
[η] 2c (where [[] is the limiting viscosity) [η] = 1.23 × 10 −4 M 0. 83
The polycarbonate resin film of the present invention may contain, if necessary, other
components, for example, thermal stabilizers such as phosphorous acid, phosphoric acid,
phosphite esters, phosphate esters, phosphonate esters, triazoles, etc. Additives such as UV
absorbers such as acetophenone and salicylic acid esters, low molecular weight polycarbonates
of tetrabromobisphenol A and tetrabromobisphenol A, flame retardants such as
decabromodiphenylene ether, and flame retardants such as antimony trioxide You may mix |
The polycarbonate resin film of the present invention is a film for a speaker diaphragm.
As a speaker diaphragm formed from this film, there are a cone diaphragm, a dome diaphragm, a
honeycomb diaphragm and the like, and the speaker diaphragm of the present invention is
particularly suitable for a mobile phone, a personal computer, a small radio, headphones etc. It is
suitable as a small speaker diaphragm used in
The present invention will be further described with reference to the following examples. In the
examples, parts are parts by weight, and the characteristics of the film were measured as follows.
Surface roughness Ra (μm): A polycarbonate resin film was measured with a stylus type surface
roughness meter [manufactured by Tokyo Seimitsu Co., Ltd.] according to JIS B-0610. The cutoff
is 2.5 μm, and the measurement length is 4 mm.
Sound quality: When the diaphragm obtained in the example is attached to a speaker, noise is
reduced more than the diaphragm formed from the smooth polycarbonate resin film with the
same thickness on the surface without lubricant obtained in the comparative example, sound
quality Those with an improvement were shown by ○, and those with no change were shown by
[Examples 1 to 4] 100 parts of polycarbonate resin powder having a viscosity average molecular
weight of 28,500 prepared from bisphenol A and phosgene are added and mixed with a lubricant
according to the amount shown in Table 1, and then this resin is supplied from the hopper of a
90 mm extruder The mixture was melted at 260 to 290 ° C., extruded from a T-die having a
length of 1520 mm, and cooled by a cooling roll having a diameter of 450 mm to obtain
polycarbonate resin films of 20 μm and 50 μm.
The obtained polycarbonate resin film was heated at about 400 ° C. for 1.0 to 1.5 seconds and
then pressure-pressed to obtain a diaphragm having a diameter of 30 mm as shown in FIG.
The diaphragm was incorporated into a mobile phone to evaluate the sound quality.
The evaluation results are shown in Table 1.
The lubricant used here is kaolin having a mean particle size of 0.5 μm (HA kaolin clay
manufactured by Sanyo Klein Co., Ltd.).
Comparative Example A polycarbonate resin film of 20 .mu.m and 50 .mu.m was obtained by the
same method as in the above example except that no lubricant was added.
The surface roughness of both was 0.02 μm. Next, this polycarbonate resin film was used to
obtain a diaphragm in the same manner as in the above example, and the diaphragm was
incorporated into a mobile phone and used for evaluation of sound quality.
According to the present invention, the speaker diaphragm made of the polycarbonate resin film
having a roughened surface according to the present invention can be improved in sound quality
by being incorporated into a portable telephone or the like, and the industrial effects to be
exhibited are outstanding. It is.
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