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JP2008219739

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DESCRIPTION JP2008219739
An object of the present invention is to provide a biaxially oriented polyester film for a flat
speaker substrate, which is excellent in both heat resistance dimensional stability and rigidity, so
that distortion of a substrate film due to heat generation of a coil is small and sound quality
reproducibility is excellent. A thermal contraction rate when processed at 200 ° C. for 10
minutes is 0% or more and 0.5% or less each in the longitudinal direction and width direction,
and a Young's modulus is 6 GPa or more and 8 GPa or less each in the longitudinal direction and
width direction, 2. A biaxially oriented polyester film for a flat speaker substrate, wherein the
variation in film thickness represented by the following formula (1) is 0% or more and 10% or
less. Variation of film thickness (%) = {(maximum value of film thickness−minimum value of film
thickness) / average value of film thickness} × 100 (1) 【Selection view】 None
Biaxially Oriented Polyester Film for Flat Speaker Substrate and Laminated Member for Flat
Speaker Made of the Same
[0001]
The present invention relates to a thin biaxially oriented polyester film for a flat speaker
substrate, and more specifically, as a substrate of a flat speaker having a structure in which a coil
is laminated on a vibrating membrane circuit substrate of a flat speaker, The present invention
relates to a biaxially oriented polyester film for flat speaker substrate, which is small in distortion
and excellent in sound quality reproducibility.
[0002]
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1
Conventionally, biaxially oriented films such as polyethylene terephthalate and polyethylene
naphthalate have been studied as diaphragms for speakers made of plastic (Patent Documents 1,
2, 3 and the like).
In recent years, space saving of a speaker is calculated | required and development of the flat
speaker thinner than before is advanced. Such a flat speaker is suitable for a wall-mounted TV, an
attached speaker of a notebook computer, etc. because it can be thin. In addition, it becomes
possible to incorporate in the pillar and sun visor etc of the car.
[0003]
Various configurations have been proposed as flat speakers, but as an example, flat tensions are
given to the four sides of a rectangular diaphragm, and a flat speaker driven by a vibrator from
the back side of this diaphragm has been proposed. Since the all-around tension flat-panel
speaker is configured to drive point vibration of the back central part of the diaphragm, the
stroke of the diaphragm is restricted by the length of the short side, and the length of the long
side is low band reproduction The ability to play bass is difficult because it can not be exploited.
Therefore, Patent Document 4 proposes providing an indication frame around the vibrating film,
and applying a tensile tension in a part direction, etc., and discloses polyethylene naphthalate as
a material of the vibrating film.
[0004]
In the case of a flat speaker, the main part of the diaphragm has a flat shape, so the strength near
the center of the diaphragm may be structurally weak. In this regard, for example, Patent
Document 5 proposes that the main part be formed thicker than the edge in order to improve the
strength and to improve the sound quality, and polyethylene terephthalate, polycarbonate, or the
like as the material of the diaphragm. Polyethylene naphthalate, polyether imide, polyimide and
the like have been proposed.
[0005]
On the other hand, the flat speaker proposed in Patent Document 6 includes a flat yoke made of
an iron plate (magnetic metal plate), and a plurality of permanent magnets attached to one
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2
surface of the yoke with the magnetic axis perpendicular to the surface. The yokes are attached
at predetermined intervals in the plane direction of the yoke so that the polarities are opposite to
each other. A diaphragm in which spiral coils (hereinafter sometimes referred to as a conductive
circuit) are stacked is disposed in parallel near the poles of the planar magnet disposed on a
plane.
[0006]
However, in a flat speaker of the type shown in Patent Document 6, a spiral coil occupies most of
the area of the diaphragm, and each coil generates heat by Joule heat, so a base film which is a
substrate of the diaphragm. The impact of heat on can not be ignored. In addition, such a flat
speaker may contact with a permanent magnet when the vibrating membrane vibrates to a large
extent, and may generate noise. This problem becomes more pronounced when distortion of the
vibrating membrane occurs due to the above-mentioned heat generation.
[0007]
JP-A-7-284193 JP-A-1-256298 JP-A-2-152400 JP-A-2001-275187 JP-A-2004-328531
International Publication WO99 / 03304
[0008]
The object of the present invention is to solve the problems of the prior art and to use a film
excellent in both heat resistant dimensional stability and rigidity as a substrate film of a
diaphragm of a flat speaker, thereby causing distortion of the substrate film due to heat
generation of a coil. The object of the present invention is to provide a biaxially oriented
polyester film for a flat speaker substrate which is small and excellent in sound quality
reproducibility.
[0009]
As a result of intensive studies to solve the above problems, the present inventors have found
that a biaxially oriented polyester film having a small dimensional change at 200 ° C., a certain
rigidity, and a small variation in film thickness is flat. By using as a film for a substrate of a
speaker, in a flat speaker having a structure in which a coil is laminated on the film for a
substrate, generation of noise is reduced because distortion of the substrate film due to heat
generation of the coil is small. It has been found that the sound quality reproducibility itself is
also improved when the present invention is completed.
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3
[0010]
That is, according to the present invention, the object of the present invention is to set the heat
shrinkage ratio at 0.degree. 6 GPa or more and 8 GPa or less, and the following formula (1):
Variation of film thickness (%) = {(maximum value of film thickness−minimum value of film
thickness) / average value of film thickness} × 100 (1) This is achieved by the biaxially oriented
polyester film for flat speaker substrate, wherein the variation in film thickness represented by is
0% or more and 10% or less.
[0011]
In the flat speaker substrate film of the present invention, as a preferable embodiment, the
polyester is polyethylene naphthalene dicarboxylate, the total light transmittance is 50% or more,
and the film surface roughness WRa is 1 nm to 100 nm. Having at least one of the following, that
the density of the film is 1.3 g / cm <3> or more and 1.4 g / cm <3> or less, and the film
thickness is 5 μm or more and 125 μm or less Is also included as a preferred embodiment.
[0012]
The biaxially oriented polyester film for a flat speaker substrate of the present invention is
suitably used as a vibrating membrane or a vibrating membrane circuit board of a flat speaker.
Furthermore, the present invention relates to a laminate member for a flat speaker, in which a
metal foil or a coil is disposed on at least one side of the biaxially oriented polyester film for a flat
speaker substrate of the present invention.
[0013]
The biaxially oriented polyester film of the present invention is excellent in heat-resistant
dimensional stability at 200 ° C., has a certain rigidity, and has little variation in film thickness,
and thus has a structure in which a coil is laminated on a substrate film When used as a film for a
substrate of a flat speaker, the distortion of the substrate film due to the heat generation of the
coil is small, so that the generation of noise is reduced, and the sound quality reproducibility
itself is also improved when having these film characteristics. .
[0014]
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Hereinafter, the present invention will be described in detail.
<Polyester> The polyester film of the present invention is formed of polyester obtained by
condensation polymerization of dicarboxylic acid and glycol.
Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid and
naphthalene dicarboxylic acid, and examples of the glycol component include ethylene glycol,
1,4-butanediol, 1,4-cyclohexanedimethanol and 1,6-hexanediol.
[0015]
Among the polyesters obtained by these components, polyethylene terephthalate and
polyethylene naphthalene dicarboxylate are particularly preferable as the main component, and
polyethylene naphthalene dicarboxylate is most preferable in terms of balance of dimensional
stability at high temperature and rigidity.
The polyethylene naphthalene dicarboxylate comprises naphthalene dicarboxylic acid as a
dicarboxylic acid component and ethylene glycol as a glycol component.
Here, "main" means that it is 80 mol% or more of all repeating structural units in the polymer
component.
In the polyethylene naphthalene dicarboxylate of the present invention, 80 mol% or more of all
repeating units are ethylene-2,6-naphthalene dicarboxylate, ethylene-2,7-naphthalene
dicarboxylate, ethylene-1,5-naphthalene dicarboxy It is preferable that it is at least 1 sort (s)
selected from the group which consists of rates, and it is preferable that it is ethylene 2, 6naphthalene dicarboxylate especially. More preferably, 90 mol% or more, particularly preferably
95 mol% or more of all repeating units is ethylene-2,6-naphthalene dicarboxylate, and in
particular, substantially single weight of polyethylene-2,6-naphthalene dicarboxylate It is
preferable to be combined.
[0016]
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5
The polyethylene naphthalene dicarboxylate of the present invention may be a polyethylene
naphthalene dicarboxylate copolymer having a copolymer component of 20 mol% or less. When
the polyethylene naphthalene dicarboxylate is a copolymer, a compound having two ester
forming functional groups in the molecule can be used as a copolymer component. Such
compounds include, for example, oxalic acid, adipic acid, phthalic acid, sebacic acid,
dodecanedicarboxylic acid, isophthalic acid, terephthalic acid, 2,7-naphthalenedicarboxylic acid,
1,5-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid. Acids, dicarboxylic acids
such as 4,4'-diphenyldicarboxylic acid, phenylindane dicarboxylic acid, tetralin dicarboxylic acid,
decaline dicarboxylic acid, diphenyl ether dicarboxylic acid, etc .; oxycarboxylic acids such as phydroxybenzoic acid, p-oxyethoxybenzoic acid etc. Or diethylene glycol, propylene glycol,
trimethylene glycol, tetramethylene glycol, hexamethylene glycol, cyclohexane methylene glycol,
neopentyl glycol, bisphenol sulfone Emissions oxide adducts, ethylene oxide adducts of bisphenol
A, can be used diethylene glycol, dihydric alcohols such as such as polyethylene oxide glycol.
These copolymerization components may be used alone or in combination of two or more.
Among the copolymerization components, as an acid component, isophthalic acid, terephthalic
acid, 4,4'-diphenyldicarboxylic acid, 2,7-naphthalenedicarboxylic acid, p-hydroxybenzoic acid,
and as a glycol component, diethylene glycol, trimethylene Ethylene oxide adducts of glycol,
hexamethylene glycol, neopentyl glycol and bisphenol sulfone can be mentioned as preferred
examples.
[0017]
In addition, polyethylene naphthalene dicarboxylate may be, for example, one having a terminal
hydroxyl group and / or carboxyl group partially or wholly blocked with a monofunctional
compound such as benzoic acid or methoxypolyalkylene glycol, or, for example, It may be
copolymerized with a small amount of glycerin, a trifunctional or higher ester forming compound
such as pentaerythritol or the like within the range in which a substantially linear polymer is
obtained.
[0018]
The constituent component of the polymer in the polyester film of the present invention is
mainly composed of a homopolymer or copolymer of polyethylene naphthalene dicarboxylate,
but it may be a mixture with other polyesters or organic polymers other than polyester. Good.
Polyethylene terephthalate, polyethylene isophthalate, polytrimethylene terephthalate,
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polyethylene 4,4'-tetramethylene diphenyl dicarboxylate, polyethylene-2,7- as polyester or
organic polymer other than polyester which can be mixed with polyethylene naphthalene
dicarboxylate Naphthalene dicarboxylate, polytrimethylene-2,6-naphthalenedicarboxylate,
polyneopentylene-2,6-naphthalenedicarboxylate, poly (bis (4-ethyleneoxyphenyl) sulfone) -2,6naphthalene Among them, polyesters such as dicarboxylates can be mentioned, among which
polyethylene isophthalate, polytrimethylene terephthalate, polytrimethylene-2,6naphthalenedicar Kishireto, poly (bis (4-ethyleneoxy) sulfone) -2,6-naphthalene dicarboxylate are
preferred. These polyesters or organic polymers other than polyester may be used alone or in
combination of two or more.
[0019]
In the polyester of the present invention, a low polymerization degree polyester is directly
obtained by the reaction of a dicarboxylic acid and a glycol, or a low polymerization degree
polyester is obtained by an ester exchange reaction of a lower alkyl ester of a dicarboxylic acid
and a glycol. It can be produced by a method of further polymerizing in the presence of a
polymerization catalyst to obtain a polyester. The intrinsic viscosity of the polyester film after
being formed into a biaxially oriented film is preferably 0.4 dl / g or more at 35 ° C. in ochlorophenol.
[0020]
<Additives> In order to improve the handleability of the film, the biaxially oriented polyester film
of the present invention may be added with inactive particles and the like within the range that
does not impair the effects of the invention. As inert particles, for example, inorganic particles
(for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide etc.) containing
an element of periodic table IIA, IIB, IVA, IVB, crosslinked silicone resin, It is possible to contain
fine particles made of a highly heat resistant polymer such as crosslinked polystyrene and
crosslinked acrylic resin particles. When inert particles are contained, the average particle
diameter of the inert particles is preferably in the range of 0.001 to 5 μm, and is preferably 0.01
to 10% by weight, more preferably 0.05 to 5% by weight based on the total weight of the film. It
is preferable to contain in the range of%. The biaxially oriented polyester film of the present
invention may optionally contain a small amount of an ultraviolet absorber, an antioxidant, an
antistatic agent, a light stabilizer, and a heat stabilizer.
[0021]
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<Heat Shrinkage> The biaxially oriented polyester film of the present invention is subjected to
heat treatment at 200 ° C. for 10 minutes for the purpose of enhancing the heat resistant
dimensional stability against heat generation of the coil, longitudinal direction (hereinafter
referred to as longitudinal film formation) It is necessary that the thermal contraction rates in the
direction, MD direction and width direction (hereinafter referred to as lateral direction, TD
direction) be 0% or more and 0.5% or less, respectively. Is 0.1% or more and 0.4% or less. If the
heat shrinkage ratio exceeds the upper limit, when the coil is used as a substrate film of a flat
speaker having a structure in which the coil is laminated on a substrate film, the heat of the coil
deforms the film and distortion occurs to generate noise. The sound quality repeatability of the
speaker is reduced. The heat shrinkage at 200 ° C. is preferably smaller if it is in the range of
0.5% or less. On the other hand, when the thermal contraction rate is less than 0%, conversely,
deformation occurs due to film expansion. As a specific means for bringing the heat shrinkage
ratio into this range, stretching in the film longitudinal direction and width direction is performed
at a magnification range of 2.8 to 3.8 times, and further at a temperature range of 200 to 250 °
C. It can be achieved by heat setting treatment followed by heat relaxation treatment at a
relaxation temperature of 0.5 to 5% in the longitudinal direction and / or width direction at a
temperature range of 150 ° C. to 230 ° C.
[0022]
<Young's Modulus> In the biaxially oriented polyester film of the present invention, Young's
modulus in the longitudinal direction and width direction of the film is preferably 6 GPa or more
and 8 GPa or less, more preferably 6.1 GPa or more and 7.0 GPa or less, particularly preferably Is
6.1 GPa or more and 6.8 GPa or less. If the Young's modulus is less than the lower limit, the film
does not have stiffness, so the performance as a vibrating film is low, which adversely affects the
acoustic characteristics. On the other hand, when the Young's modulus exceeds the upper limit,
the thermal shrinkage at 200 ° C. exceeds 0.5%, and film deformation occurs when the coil
generates heat. The Young's modulus in the longitudinal direction and the width direction of the
film can be adjusted by the magnification during stretching, and is achieved by performing the
stretching in the film longitudinal direction and the width direction in the magnification range of
2.8 to 3.8 times, respectively. Ru.
[0023]
<Variation of Film Thickness> In the biaxially oriented polyester film of the present invention, the
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variation of film thickness represented by the following formula (1) needs to be 0% or more and
10% or less. The variation of the film thickness is more preferably 0% or more and 5% or less.
Variation of film thickness (%) = {(maximum value of film thickness−minimum value of film
thickness) / average value of film thickness} × 100 (1) where each item of the above equation
(1) is a hitting point It can be determined by the following measurement method using a film
thickness meter. That is, the thickness is measured at any 50 locations in the film width direction
and at any 50 locations along the longitudinal direction at a position near the center of the film
width, and the number average value of all 100 locations is the average value of the film
thicknesses. Do. In addition, the average value of 5 points from the larger one of the measured
values among the 100 measured values is taken as the maximum value of the film thickness, and
the average value of the 5 measured points from the smaller 100 values is filmed It is the
minimum value of thickness. When the variation in film thickness exceeds the upper limit, the
variation in vibration occurs, the performance as a vibrating film is reduced, and the acoustic
characteristics are reduced. The variation of the film thickness is preferably smaller within the
above range.
[0024]
The variation in film thickness of the present invention can be achieved by adjusting the draw
ratio and the heat setting temperature, and like the heat shrinkage rate, the stretching in the film
longitudinal direction and the width direction is 2.8 to 3.8 times each And a heat setting process
at a temperature range of 200 to 250.degree. Also, within this range, the variation decreases as
the draw ratio increases. Furthermore, the variation in film thickness can be made smaller when
the temperature during heat setting processing is lower within such a range.
[0025]
<Total Light Transmittance> The total light transmittance of the biaxially oriented polyester film
of the present invention is preferably 50% or more, more preferably 60% or more, and
particularly preferably 70% or more. If the total light transmittance is less than the lower limit,
the transparency is reduced when used as a flat speaker substrate film, and the alignment
accuracy in processing the coil may be reduced. Here, the total light transmittance of the film is
determined in accordance with JIS K7105. In order to achieve the total light transmittance, it is
preferable that the additive content blended in the film is in the range of 0.05 to 5% by weight.
[0026]
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<Film Surface Roughness WRa> The biaxially oriented polyester film of the present invention
preferably has a film surface roughness WRa (central surface average roughness) of 1 nm or
more and 100 nm or less. The film surface roughness WRa is more preferably 5 nm or more and
80 nm or less. When the film surface roughness WRa is less than the lower limit, the slipperiness
at the time of film processing may be reduced to lower the productivity. On the other hand, when
the film surface roughness WRa exceeds the upper limit, the adhesion with the coil disposed on
the substrate film is reduced, or the processing accuracy of the coil is reduced when forming the
coil by processing the metal foil Sometimes.
[0027]
<Density> The biaxially oriented polyester film of the present invention preferably has a density
of 1.3 g / cm <3> or more and 1.4 g / cm <3> or less. The lower limit of the density of the film is
preferably 1.33 g / cm <3> or more, more preferably 1.35 g / cm <3> or more. The upper limit of
the film density is preferably 1.38 g / cm <3> or less, more preferably 1.36 g / cm <3> or less.
When the density is less than the lower limit, the change in sound quality is large, and the
acoustic characteristics may be deteriorated. On the other hand, when the density exceeds the
upper limit, the film may become brittle due to the high crystallinity of the film. In order to make
the density of the film fall within this range, stretching in the film longitudinal direction and
width direction is performed at a magnification range of 2.8 to 3.8 times, respectively, and heat
setting is further performed at a temperature range of 200 to 250 ° C. It can be achieved by
doing.
[0028]
<Thickness> The thickness of the biaxially oriented polyester film of the present invention is not
particularly limited, but is preferably 5 μm or more and 125 μm or less, more preferably 7 μm
or more and 100 μm or less, still more preferably 10 μm or more and 50 μm or less,
particularly preferably 10 μm More than 30 μm. When the film thickness is less than the lower
limit, sound quality reproducibility may be insufficient as a substrate film for flat speakers. On
the other hand, when film thickness exceeds an upper limit, handling property may fall.
[0029]
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10
<Loss Elastic Modulus Peak> The biaxially oriented polyester film of the present invention
preferably has a loss elastic modulus peak (sometimes referred to as E ′ ′) of 80 to 180 ° C.,
more preferably 90 to 170 ° C. The temperature is more preferably 100 to 160 ° C.,
particularly preferably 130 to 156 ° C. When the loss elastic modulus peak is less than the
lower limit, the molecular orientation of the film is not sufficient and the performance as a
vibrating film may be deteriorated, which may adversely affect the acoustic characteristics. On
the other hand, when the loss elastic modulus peak exceeds the upper limit, the thermal
shrinkage at 200 ° C. may exceed 0.5%, and film deformation may occur when the coil
generates heat. In the present invention, the loss elastic modulus peak of the film is measured
from room temperature to 200 ° C. at a load of 10 g and a frequency of 10 Hz using an
apparatus for measuring dynamic viscoelasticity, for example, a Vibron apparatus of DDV-01FP
manufactured by Orientec Co., Ltd. It can be obtained by a measurement method in which the
temperature is raised at a temperature rising rate of ° C / min. In order to bring the loss
modulus peak into such a range, stretching in the film longitudinal direction and width direction
is carried out at a magnification range of 2.8 to 3.8.
[0030]
<Coating Layer> In the present invention, a coating layer can be provided on at least one side of
the polyester film. The coating layer formed by coating is mentioned as an example of a coating
layer. As a binder resin which forms a coating film layer, each resin of a thermoplastic resin and
a thermosetting resin can be used, and polyester, polyimide, polyamide, polyesteramide,
polyvinyl chloride, poly (meth) acrylic acid ester, polyurethane, Polyvinyl chloride, polyolefins
and copolymers and blends thereof are mentioned.
[0031]
<Film Film-Forming Method> The biaxially oriented polyester film of the present invention can be
produced using a conventionally known film-forming method such as a tenter method or an
inflation method. The pre-dried polyester resin is supplied to an extruder heated to 280 ° C. and
molded into a sheet from a T-die. The film extruded from the T-die is solidified by cooling with a
cooling drum having a surface temperature of 10 to 60 ° C., this unstretched film is heated by
roll heating, infrared heating or the like, and stretched in the longitudinal direction to obtain a
longitudinally stretched film. It is preferable to perform this stretching using the circumferential
speed difference of two or more rolls. The stretching temperature is preferably higher than the
glass transition point (Tg) of the polyester, and more preferably 20 to 40 ° C. higher than the
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Tg.
[0032]
The longitudinally stretched film is then sequentially subjected to transverse stretching, heat
setting and heat relaxation treatment to obtain a biaxially oriented film, which is carried out
while the film is being run. The transverse stretching treatment is performed while starting at a
temperature 20 ° C. higher than the glass transition point (Tg) of the polyester and raising the
temperature to a temperature (120-30 ° C.) lower than the melting point (Tm) of the polyester.
The start temperature of the transverse stretching is preferably (Tg + 40) ° C. or less. Moreover,
it is preferable that the maximum temperature of transverse stretch is a temperature lower by
100 to 40 ° C. than Tm.
[0033]
The temperature rise in the transverse drawing process may be continuous or stepwise
(sequential). Usually, the temperature is raised sequentially. For example, the transverse
stretching zone of the stenter is divided into a plurality of sections along the film traveling
direction, and the temperature is raised by flowing a heating medium at a predetermined
temperature for each zone. When the transverse stretching start temperature is too low, film
breakage may occur. When the maximum transverse stretching temperature is lower than (Tm120) ° C., the heat shrinkage of the film may be increased. On the other hand, when the
transverse stretching maximum temperature is higher than (Tm-30) ° C., the film becomes too
soft, and film breakage may occur due to disturbance or the like.
[0034]
The stretching ratio is preferably 2.8 times or more and 3.8 times or less in both the longitudinal
direction and the transverse direction. The lower limit of the stretching ratio is more preferably
3.0 times or more. The upper limit of the draw ratio is more preferably 3.6 times or less, still
more preferably 3.4 times or less, and particularly preferably 3.3 times or less. If the draw ratio
is less than the lower limit, a sufficient Young's modulus may not be obtained. When the draw
ratio exceeds the upper limit, the thermal shrinkage may exceed the upper limit.
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[0035]
The biaxially stretched film is then subjected to a heat setting process. The heat setting improves
the thermal dimensional stability of the film. Further, by performing heat setting treatment,
crystallization of the polymer proceeds and the density of the film becomes high. The heat
fixation is preferably performed at a temperature of (Tm-100) ° C. or higher. The heat setting
temperature is preferably 200 to 250 ° C., and more preferably 220 to 245 ° C. In addition, in
order to further enhance the thermal dimensional stability, heat relaxation treatment is further
performed at a relaxation temperature of 0.5 to 5% in the longitudinal direction and / or the
width direction in the temperature range of 150 to 230 ° C. for 1 to 60 seconds after heat
setting. And annealing at 50 to 80.degree. C. may be performed. The biaxially oriented polyester
film thus obtained can be further laminated with a functional layer such as a coating film layer, a
metal thin film, a hard coat layer or the like on one side or both sides.
[0036]
<Planar Speaker Substrate> The biaxially oriented polyester film of the present invention can be
used for flat speaker substrate applications, and is preferably used as a diaphragm or a
diaphragm circuit board in which spiral coils are disposed on both sides of the substrate film, In
particular, it can be preferably used as a diaphragm circuit board. The biaxially oriented
polyester film of the present invention is excellent in heat-resistant dimensional stability at 200
° C., has a certain rigidity, and has little variation in film thickness, so a flat speaker having a
structure in which a coil is laminated on a substrate film. When the film is used as a substrate
film of the above, distortion of the substrate film due to heat generation of the coil is small,
generation of noise is reduced, and furthermore, sound quality reproducibility is excellent due to
these film characteristics.
[0037]
The spiral coil formed on the polyester film is a method of pattern etching a copper-clad laminate
film called a subtractive method to form a wiring pattern, electroless plating on a substrate film
called an additive method, or electroless plating and electrolysis It can form also by any method
of the method of forming a wiring pattern by combined use of plating. Another example is a
method of forming a circuit using a conductive paste.
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[0038]
In general, in the subtractive method, the dimensional stability of the wiring pattern is low due to
the side etching, and it is difficult to reduce the variation in impedance of the coil. However, in
the additive method, the dimensional stability of the wiring pattern is high. The variation in the
coil impedance can be further reduced.
[0039]
A metal foil can be laminated on a substrate film as a pre-process to be processed into a coil.
The metal foil is exemplified by copper foil and aluminum foil. As these metal foils, it is possible
to use ones obtained by a general method such as ones produced by rolling and ones produced
by electrolysis. As a method of laminating these metal foils, a method of using an adhesive, a
method of melting a film surface layer and direct sealing, etc. may be mentioned. Although an
adhesive agent can use a commercially available thing, curable resin is preferable from a heat
resistant viewpoint. As the curable resin, epoxy resin, phenol resin, acrylic resin, polyimide resin,
polyamide resin, polyisocyanate resin, polyester resin, polyphenyl ether resin, alicyclic olefin
polymer and the like can be mentioned. Further, as a method of not using an adhesive, a method
of forming a metal foil directly on a substrate film by plating, sputtering, cladding or the like may
be used.
[0040]
Although any of the above methods may be used to form a coil on a substrate film, in the case of
the flat speaker of the present invention, no adhesive is used because the acoustic properties may
be adversely affected by the effect of the adhesive. The method of forming on a substrate film is
more preferable. Alternatively, a spiral coil may be formed on a substrate film, and a coverlay
may be further laminated. Examples of the type of cover lay include films and solder resists.
When a film type is used, it is preferable to use the same material as the substrate film because
curling may occur after bonding. Other components can be blended into the coverlay film as
desired. As the compounding agent, UV absorbers, soft polymers, fillers, heat stabilizers, weather
stabilizers, anti-aging agents, leveling agents, antistatic agents, slip agents, anti-blocking agents,
anti-fogging agents, dyes, pigments, natural Oils, synthetic oils, waxes, emulsions, fillers,
hardeners, flame retardants and the like.
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[0041]
Hereinafter, the present invention will be described in detail by way of examples, but the present
invention is not limited to these examples. Each characteristic value was measured by the
following method. Further, parts and% in the examples mean parts by weight and% by weight,
respectively, unless otherwise specified.
[0042]
(1) Intrinsic viscosity It measured at 35 degreeC, using o-chlorophenol as a solvent (unit: dl / g).
The intrinsic viscosity of the film was determined by sampling a biaxially oriented film.
[0043]
(2) Heat shrinkage rate The longitudinal direction and the width direction of the biaxially
oriented film are marked, and a 30 cm square film of which the exact length has been measured
beforehand is put into an oven set at a temperature of 200 ° C. without load. After standing for
10 minutes, take out, return to room temperature and read the dimensional change. From the
length (L0) before the heat treatment and the dimensional change (ΔL) due to the heat
treatment, the heat shrinkage rates in the longitudinal direction and the width direction were
determined according to the following equation (2). The thermal contraction rate in each
direction was evaluated with the number of samples n = 5, and the average value was used.
Thermal contraction rate (%) = ΔL / L0 × 100 (2)
[0044]
(3) Young's modulus A biaxially oriented film is cut into a sample width of 10 mm and a length of
15 cm in a room adjusted to a temperature of 20 ° C. and a humidity of 50% using Tensilon
UCT-100 type manufactured by ORIENTEC Co., 100 mm, tensile speed 10 mm / min, chart speed
500 mm / min, and Young's modulus is calculated from the tangent of the rising portion of the
obtained load-elongation curve. The Young's modulus in the longitudinal direction refers to the
longitudinal direction of the film as the measurement direction, and the Young's modulus in the
width direction refers to the transverse direction of the film as the measurement direction. Each
Young's modulus was measured 10 times, and the average value was used.
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[0045]
(4) Density Measured according to JIS Standard C2151.
[0046]
(5) Total Light Transmittance The total light transmittance Tt (%) was measured according to JIS
K7105.
[0047]
(6) Film surface roughness WRa A measurement area of 246.6 μm × 187.5 μm (0.0462 mm
<2>) with a measurement magnification of 25 times using a non-contact three-dimensional
roughness meter (NT-2000) manufactured by WYKO Under the conditions, central surface
average roughness (WRa) is determined by the following equation (3) by surface analysis
software built in the roughness meter.
The measurement was repeated 10 times, and their average value was used.
[0048]
<img class = "EMIRef" id = "202712113-00002" /> Here, Z jk is the direction when measuring
direction (246.6 μm) and the direction (187.5 μm) orthogonal to it are divided into M and N
respectively Height on the 3D roughness chart at the jth and kth positions of
[0049]
(7) Variation in film thickness and film thickness Using the dot film thickness meter, thickness is
measured at any 50 locations in the film width direction and at any 50 locations along the
longitudinal direction at a position near the center of the film width. It measured and made the
number average value of all 100 places into film thickness.
Moreover, the variation (%) of film thickness was calculated | required according to following
formula (1).
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Variation of film thickness (%) = {(maximum value of film thickness−minimum value of film
thickness) / average value of film thickness} × 100 (1) where each item of the above equation
(1) is a hitting point It can be determined by the following measurement method using a film
thickness meter. That is, the thickness of a total of 100 places is measured according to the
measuring method of said film thickness, and let the number average value of all 100 places be
an average value of film thickness. In addition, the average value of 5 points from the larger one
of the measured values among the 100 measured values is taken as the maximum value of the
film thickness, and the average value of the 5 measured points from the smaller 100 values is
filmed It is the minimum value of thickness.
[0050]
(8) Dynamic loss elastic modulus peak temperature A biaxially oriented film is cut into a width of
4 mm and a length of 50 mm, and using a Vibron device made by Orientec Co., Ltd., DDV-01FP,
load 10 g, frequency 10 Hz from room temperature to 200 ° C. The temperature is raised and
measured at a temperature rising rate of 5 ° C./min. The peak temperature of the dynamic loss
modulus is determined from the obtained chart.
[0051]
(9) Acoustic characteristics A biaxially oriented film is formed as a vibrating membrane circuit
board, spiral coils are formed on both sides, disposed parallel to the plane on which the planar
magnet is disposed, and incorporated into a planar speaker. Measure the frequency
characteristics in accordance with JIS C5532 and compare the frequency characteristics of the
film not subjected to the following accelerated test with the film subjected to the accelerated test,
and whether the frequency characteristic changed before and after the accelerated test ,
According to the following criteria. Moreover, about the film which did the accelerated test, the
generation | occurence | production presence or absence of the noise called chatter was
evaluated in accordance with the following reference | standard. As an accelerated test for
measuring the influence of film deformation due to coil heat generation on acoustic
characteristics, the film after coil formation is unloaded without load in an oven set at a
temperature of 200 ° C., allowed to stand for 10 minutes, and then taken out; It was
incorporated into a flat speaker after returning to room temperature. :: No change in frequency
characteristics before and after accelerated test, and no generation of noise such as chattering in
film evaluation after accelerated test ○: There is a slight change in frequency characteristics
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before and after accelerated test, but film evaluation after accelerated test No generation of noise
such as chattering x: There is a large change in frequency characteristics before and after the
acceleration test, and generation of noise such as chattering in the film evaluation after the
acceleration test
[0052]
Example 1 0.1% spherical silica particles having an average particle diameter of 0.3 μm are
added to polyethylene-2,6-naphthalenedicarboxylate resin, and the mixture is supplied to an
extruder heated to 290 ° C. to obtain 290 °. It was formed into a sheet from a C die. Further,
the unstretched film obtained by cooling and solidifying this sheet with a cooling drum having a
surface temperature of 60 ° C. is led to a group of rolls heated to 140 ° C., and stretched 3.1
times in the longitudinal direction (longitudinal direction) It cooled by the roll group.
Subsequently, both ends of the longitudinally stretched film were introduced into a tenter while
being held by clips, and stretched 3.3 times in a direction (width direction) perpendicular to the
longitudinal direction in an atmosphere heated to 150 ° C. Thereafter, heat setting is performed
in a tenter at a temperature condition of 235 ° C., and after heat relaxation in a 2% width
direction at 200 ° C., it is gradually cooled uniformly to room temperature to obtain a 25 μm
thick biaxially oriented film. The The properties of the obtained film are shown in Table 1. The
film of this example was excellent in heat-resistant dimensional stability at 200 ° C., and did not
generate noise even in the acoustic characteristic evaluation, and was excellent in sound quality
reproducibility.
[0053]
[Example 2] The same operation as in Example 1 is repeated except that the draw ratio in the
longitudinal direction is 3.0 times, the draw ratio in the width direction is 3.2, and the
temperature condition of heat relaxation is 230 ° C. The The properties of the obtained film are
shown in Table 1. The film of this example was excellent in heat-resistant dimensional stability at
200 ° C., and did not generate noise even in the acoustic characteristic evaluation, and was
excellent in sound quality reproducibility.
[0054]
[Example 3] The same operation as in Example 1 was performed except that the heat setting
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treatment temperature was 250 ° C., the temperature condition of heat relaxation was 230 °
C., and 2% heat relaxation was performed in both the longitudinal direction and width direction. I
repeated it. The properties of the obtained film are shown in Table 1. The film of this example
was excellent in heat resistant dimensional stability at 200 ° C., and no noise was generated in
the acoustic characteristic evaluation.
[0055]
[Example 4] The same operation as in Example 1 was repeated except that the heat setting
temperature was changed to 210 ° C. The properties of the obtained film are shown in Table 1.
The film of this example was excellent in heat resistant dimensional stability at 200 ° C., and no
noise was generated in the acoustic characteristic evaluation.
[0056]
Comparative Example 1 0.1% of spherical silica particles having an average particle diameter of
0.3 μm is added to polyethylene terephthalate resin, supplied to an extruder heated to 280 ° C.,
and molded into a sheet from a die of 280 ° C. did. Further, the unstretched film obtained by
cooling and solidifying this sheet with a cooling drum having a surface temperature of 20 ° C. is
led to a group of rolls heated to 110 ° C., and stretched 3.1 times in the longitudinal direction
(longitudinal direction) It cooled by the roll group. Subsequently, the longitudinally stretched film
was guided to a tenter while holding both ends of the film with clips, and stretched 3.3 times in a
direction (width direction) perpendicular to the longitudinal direction in an atmosphere heated to
120 ° C. Thereafter, heat setting is performed in a tenter at a temperature condition of 230 °
C., and after heat relaxation in a 2% width direction at 200 ° C., it is gradually cooled uniformly
to room temperature to obtain a 25 μm thick biaxially oriented film. The The properties of the
obtained film are shown in Table 1. The film of this comparative example was poor in the heat
resistant dimensional stability at 200 ° C., noise was generated even in the acoustic
characteristic evaluation, and the sound quality reproducibility was poor.
[0057]
Comparative Example 2 The draw ratio in the longitudinal direction is 2.5 times, the draw ratio in
the width direction is 2.6 times, the heat setting temperature is 180 ° C., and the conditions of
heat relaxation are changed to 240 ° C., 3%. The same operation as in Example 1 was repeated
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except for the above. The properties of the obtained film are shown in Table 1. The film of this
comparative example is poor in the heat resistant dimensional stability at 200 ° C., noise is
generated in the acoustic property evaluation, and the sound quality reproducibility is poor
because the Young's modulus is low.
[0058]
Comparative Example 3 As in Example 1 except that the draw ratio in the longitudinal direction
was 3.5 times, the draw ratio in the width direction was 3.6 times, the heat setting temperature
was 245 ° C., and heat relaxation was not performed. Repeated operation. The properties of the
obtained film are shown in Table 1. The film of this comparative example was poor in the heat
resistant dimensional stability at 200 ° C., noise was generated even in the acoustic
characteristic evaluation, and the sound quality reproducibility was poor.
[0059]
[0060]
When the biaxially oriented polyester film in the present invention is used as a substrate film of a
flat speaker having a structure in which a coil is laminated on a substrate film, the dimensional
change in heat resistance is small and distortion of the substrate film due to heat generation of
the coil. Has a smaller noise generation, has both heat resistant dimensional stability and rigidity,
and has a small variation in film thickness, so that it has an effect of being excellent in sound
quality reproducibility.
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