JPH02152400A - Film for speaker diaphragm - Google Patents

Abstract

PURPOSE:To form a small sized speaker in an excellent way with high reproducing characteristic and stability by using a specific biaxial oriented polyethylene naphthalate film whose intrinsic viscosity, elastic modulus, density and size change rate or the like are within a specific range. CONSTITUTION:The biaxial oriented polyethylene-2,6-naphthalate film whose elastic modulus is 10X10<7> - 17X10<10>dyn/cm<2> in both axes, whose density is 1.356-1,359g/cm<3>, whose size rate of change is 0.6 - 1.0% in both directions while being left for 10min with a free length at 200 deg.C and whose intrinsic viscosity coefficient with a thickness of 50 - 100mum is within 0.45 - 0.70, is used to form a speaker diaphragm. Then the reproducing characteristic, especially less sound quality change under high temperature and high humidity and high stability are attained and the speaker with small size is obtained with excellent forming performance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a film for a speaker (driving plate), and more particularly to a biaxially oriented polyethylene-2 film having specific properties.
The present invention relates to a film for a speaker diaphragm, which is made of a 6-naphthalate film, can produce a speaker movement plate that has excellent high-pitched sound retention properties, has little change in sound quality under high temperature and high humidity conditions, and has excellent moldability.

BACKGROUND ART Conventionally, biaxially oriented polyethylene terephthalate film has been used as a speaker diaphragm made of plastic. However, this polyethylene terephthalate film has a small modulus of elasticity, and in the case of a full-range speaker, the wave number fH is low (both in the high range), and high frequency reproduction is not necessarily good.

Furthermore, in recent years, their use in in-vehicle applications and outdoor applications has increased, and temperature characteristics have become particularly important. For this reason, there is a demand for diaphragm materials that exhibit small dimensional changes under high temperature and high humidity conditions and that do not cause deterioration in sound quality characteristics.

As a solution to this problem, Japanese Patent Application Laid-Open No. 62-26379
Publication No. 7 proposes a speaker diaphragm using a film carrier containing polyethylene naphthalate as a main component or a film in which reinforcing materials such as potassium titanate fibers and alumina powder are mixed into polyethylene naphthalate resin.
It is explained that by using this film, a diaphragm having a thickness of 50 μm or more will not undergo thermal deformation even in an atmosphere at a temperature of 100°C.

However, when this technology is applied to a speaker diaphragm with a thickness of 50 μm or more, when forming the speaker diaphragm, a part of the deep drawn part of the molded product may be cut off, or the molded product may become flat. Wrinkles appeared where they should have been, and the desired shape was lost, resulting in a significantly low yield for commercialization. Also, even if the diaphragm is successfully molded, if it is assembled into a speaker and placed under high temperature and humidity conditions, then various acoustic tests are performed.
There may be a problem that the sound is not faithfully reproduced. This phenomenon occurs because the diaphragm is slightly deformed under high temperature and humidity.

As described above, there are still many problems to be solved regarding the film for the speaker 1 sliding plate using the biaxially oriented polyethylene-2,6-naphthalate film. The key points are (1) to improve moldability as a film for a diaphragm to improve yield during molding, and (2) to fully develop heat resistance.

Purpose of the Invention As a result of intensive research to develop a material for a diaphragm that improves these points, the present inventor has developed a biaxially oriented polyethylene material whose elastic modulus, dimensional change rate, intrinsic viscosity, and density are within specific ranges. We have discovered that 2,6-naphthalate film exhibits extremely excellent properties as the above-mentioned material, and have arrived at the present invention.

Therefore, an object of the present invention is to provide a film with good moldability for use as a speaker diaphragm, and another object of the present invention is to provide a film with excellent playback characteristics, especially high-frequency sound playback characteristics, and to be able to withstand high-temperature, high-humidity atmospheres. An object of the present invention is to provide a film for a speaker diaphragm that has excellent dimensional stability and little change in sound quality.

Structure and Effects of the Invention According to the present invention, an object of the present invention is, firstly, to improve the intrinsic viscosity [
A biaxially oriented polyethylene-2,6-naphthalate film in which η] is in the range of 0.45 to 0.70 must have an elastic modulus of 10xlO10 to 17x1010 in both the biaxial directions.
dyn/Cm2, with a density of 1.356 to 1
, 359 (+/ cm3), and a dimensional change rate when held at a free length of 9,200°C for 10 minutes is in the range of 066 to 1.0% in both directions. This is achieved by using a film for

The polyethylene-2,6-naphthalate in the present invention is modified not only with a polyethylene-2,6-naphthalate homopolymer but also with a small proportion (for example, 10 mol% or less, further 5 mol% or less) of a third component. polyethylene-2,
6-naphthalate copolymer or a small proportion (for example, 20%
Hereinafter, blend polymers in which a third component (10% by weight or less) is mixed are also included.

Such polyethylene-2,6-naphthalate is basically known and can be produced by known methods. For example, polyethylene-2,6-naphthalate is generally produced by a polycondensation reaction of naphthalene-2,6-dicarboxylic acid or its ester-forming derivative and ethylene glycol or its ester-forming derivative in the presence of a catalyst. Manufactured. When producing a copolymer, it is best to add the third component and allow the reaction to occur until the condensation polymerization reaction is completed; and when producing a blend polymer, add the third component to the polymer before film formation. )).

Suitable third components include compounds having a divalent ester-forming functional group, such as oxalic acid, adipic acid, phthalic acid, inphthalic acid, and terephthalic acid.

Dicarboxylic acids or lower alkyl esters thereof such as naphthalene-2,7-dicarboxylic acid, diphenyletherdicarboxylic acid, etc.; p-oxybenzoic acid.

Oxycarboxylic acids or lower alkyl esters thereof such as p-oxyethoxybenzoic acid; or propylene glycol, trimethylene glycol.

Dihydric alcohols such as tetramethlene gelylcol, hexamethylene glycol, neopentyl glycol, etc. can be mentioned.

In addition, polyethylene-2,6-naphthalate may be one in which part or all of the terminal hydroxyl groups and/or carboxyl groups are blocked with an Ichinomiya functional compound such as benzoic acid or methoxypolyalkylene glycol,
Alternatively, it may be modified with a very small amount of a trifunctional or higher functional ester-forming compound such as glycerin, pentaerythritol, etc. to the extent that a substantially linear polymer can be obtained.

Such polyethylene-2,6-naphthalate may be added with a lubricant such as finely divided silica to impart slipperiness to the film.
Talc, clay, etc. can be contained, and other additives such as stabilizers, UV absorbers, colorants, flame retardants, etc. can also be added.

Examples of colorants include carbon black. In this case, the density 2 modulus of the polyethylene=2,6-naphthalate film of the invention.

It is preferable to knead within a range that satisfies the characteristic value of thermal dimensional change rate.

Further, the speaker diaphragm film of the present invention may be colored by dyeing or coating.

In the present invention, the biaxially oriented film made of polyethylene-2,6 naphthalate has an intrinsic viscosity of 0.
．． It needs to be in the range of 45 to 0.70.

More preferably, it is in the range of 0.50 to 0.65. If the limiting viscosity is greater than 0.70, the heat resistance of the deep-drawn diaphragm will decrease, which is not preferable.

On the other hand, if the intrinsic viscosity is less than 0.45, the film may be cut or wrinkled at the deep drawing portion during deep drawing, which is not preferable.

In the present invention, the biaxially oriented film further has an elastic modulus of IOX 1010 to 17X 10" dy in both the biaxial directions.
It must be within the range of n/Cm2. Preferably 10
It is in the range of X1010 to 15X1010dyn/cm2. If the elastic modulus is smaller than 10x1010 dyn/cm2, it is not possible to increase the high frequency common imaging frequency fH,
On the other hand, if it is larger than 17x 1010 dyn/cm2, it becomes difficult to mold it as a speaker diaphragm, and in particular, it becomes difficult to give the diaphragm a delicate cross-sectional shape, which is not preferable.

In the present invention, the biaxially oriented film further has a temperature of 20
The dimensional change rate when treated for 10 minutes at 0°C free length is 0.
．． It needs to be in the range of 8 to 1.0. If this dimensional change rate is greater than 1.0%, the amount of shrinkage during molding of the diaphragm increases, the thickness increases, and deep drawing becomes difficult, which is not preferable. On the other hand, if the dimensionalization rate is less than 0.6%, it is not preferable because it becomes difficult to accurately reproduce the shape of the mold. A more preferable range of dimensional change rate is 0.7 to 0.9%.
It is.

In the present invention, the biaxially oriented film further has a density of 1.
It needs to be in the range of 358 to 1.359 MCm3.

More preferably, it is in the range of 1.357 to 1.358 MCm3.

The biaxially oriented polyethylene-2,6-naphthalate film of the present invention has the above-mentioned limiting viscosity number 5 elastic modulus.

It is necessary to satisfy the dimensional change rate and density, but among these properties, properties other than the intrinsic viscosity number can be obtained by appropriately selecting conditions such as the stretching ratio and heat setting temperature in the biaxial orientation treatment.

For example, after sufficiently drying polyethylene-2,6-naphthalate, it is made into an unstretched film by melt extrusion, and this unstretched film is stretched 3.5 times to 3.8 times in the machine direction at a stretching temperature of 130 to 150°C. Then, in the range of 3.6 times to 3.9 times in the transverse direction, the stretching ratio is larger than [longitudinal stretch ratio + 0.1 times], [longitudinal stretch ratio 〇], and smaller than 21 times. It is preferable to stretch at a temperature of 120 to 150°C and further heat set at 240 to 250°C for 5 seconds to 1 minute. Note that this heat setting may be performed under limited shrinkage. Further, it is preferable to employ an electrostatic adhesion method during melt extrusion.

As mentioned above, the elastic modulus of the film can be adjusted by controlling the stretching ratio and heat setting temperature.

Dimensional change rate and density can be controlled.

The thickness of the biaxially oriented film is 50 to 100 μm, and even 6
0 to 90 μm is preferable.

The biaxially oriented polyethylene-2,6-naphthalate film of the present invention has the following advantages.

Since it has a lower density and a higher elastic modulus than conventional polyethylene terephthalate film, it has a higher inelastic modulus, making it possible to expand the reproduction frequency band, reducing high frequency distortion and improving transient characteristics.

Because the density is low, the weight of the diaphragm is light, and the output level can be increased for the same amount of human power, so there is an advantage that the drive unit can be made lighter and smaller when trying to obtain the same output.

In addition, it has excellent environmental resistance to temperature and humidity, so it can withstand use in automotive and outdoor applications.

Polyethylene terephthalate film has a larger deformation amount than polyethylene-2,6-naphthalate film due to long-term (processing) at 70°C, and lacks heat resistance for use in automotive applications or outdoor applications. On the other hand, polyethylene-2,6-naphthalate polymer has a glass transition temperature of 113°C and polyethylene terephthalate (Tg=
70° C.), it is possible to make a speaker diaphragm with improved heat resistance, so it can be used even in high temperature and humid environments for in-vehicle applications and outdoor applications.

Internal loss (ta) of polyethylene-2,6-naphthalate
nδ) is larger than that of polyethylene terephthalate, it has the advantage that divisional imaging of the diaphragm is restricted, frequency characteristics are flattened, and distortion is reduced.

In particular, according to the film for a speaker diaphragm of the present invention, it is possible to obtain a diaphragm that can be deep-drawn without failure, exhibits sufficient heat resistance when used as a speaker, and has little change in sound quality.

Example The present invention will be further explained below with reference to Examples.

Note that the film properties were measured as follows.

(1) Elastic modulus Measured with a dynamic modulus tester PPM-5R manufactured by Toyo GXY Seisakusho.

(2) Dimensional Change Rate The film sample is cut into strips with a length of 350 mm or more and a width of 10 mm in the measurement direction. Appear to this sample 30
After attaching a gauge of 0 mm and keeping the free length in a constant temperature room controlled to 23° C. x 60% RH for 24 hours or more, the dimension between the gauges is read using a reading microscope. Next, this strip-shaped sample was held in an air oven set at a predetermined temperature (200°C) for a predetermined time (10 minutes), and then heated again at 23° C.
After keeping the free length in a constant temperature and humidity room at ℃ x 60% RH for 24 hours or more, read the dimension between the gauge marks. The difference in dimension between the gauge marks before and after treatment is calculated as a percentage of the original dimension between the gauge marks, and is expressed as a dimensional change rate.

(3) Density Measurement is performed at a temperature of 25±0.1°C using a density gradient tube made of a mixed solution of n-hebutane and carbon tetrachloride. As a density standard, a glass float for density gradient tubes manufactured by Shibayama Kagaku Kikai Seisakusho Co., Ltd. is used.

(4) High-frequency co-occurrence frequency fH The output sound pressure frequency characteristic is determined according to JIS C5531, and determined based on the definition on page 274 of the Audio Handbook (Ohmsha). However, the output is 0, the voltage equivalent to 1W, and the sound pressure at a point of 0.5m are measured.

(5) Heat-resistant The molded speaker diaphragm is left in a constant temperature bath controlled at 85° C. for 100 hours.

Thereafter, the diaphragm was taken out to room temperature and the degree of deformation was observed. Heat resistance is considered good if the initial shape (immediately after molding) is maintained almost as it is, and bad if the deep drawn part or bent part stretches and deforms, or the entire diaphragm is distorted. evaluate.

(6) Formability Cone mold (molded with a sliding plate mold. The diameter of the cone is 40 mm, and the height is 6 mm. A part of the cone has a deep drawing part (height) where the film is bent 180 degrees. 2mm
). The film is passed through a gap (approximately 2 mm) in a mold heated to 233 to 237°C, heated for approximately 10 seconds, and then molded. The moldability is evaluated as poor moldability if the film breaks or wrinkles during molding, and as good moldability if the shape of the cone of the mold can be faithfully traced.

(7) Intrinsic viscosity number phenol/tetrachloroethane (60/40 weight ratio)
It is determined from the solution viscosity measured at 35°C using a mixed solvent.

Examples 1 to 6 and Comparative Examples 1 to 3 Polyethylene-2,6 naphthalate having the intrinsic viscosity shown in Table 1 was melt-extruded and cooled and solidified on a casting drum to prepare unstretched films. Next, this was biaxially stretched and heat set under the conditions shown in Table 1. Thus j
The properties of the biaxially oriented polyethylene-2,6-naphthalate film were as shown in Table 1.

These films were used to form a diaphragm with a diameter of 4
A cone-shaped diaphragm of 01Tl111 was obtained. During molding, the gap between the molds heated to 233-237°C (approximately 3 mm>
The film is fed into a mold, heated, and then pressed with this mold to form a molded product.

The acoustic characteristics of a speaker using this diaphragm were investigated. The results are shown in Table 1.

Table 1 shows that the speaker diaphragm film of the present invention has good moldability and good playback at high temperatures.

Claims (1)

[Claims] 1. A biaxially oriented polyethylene-2,6-naphthalate film having an intrinsic viscosity in the range of 0.45 to 0.70, and having an elastic modulus of 10×10 in both the biaxial directions. ＾1＾0～
It is in the range of 17 x 10^1^0 dyn/cm^2, the density is in the range of 1.356 to 1.359 g/cm^3, and the dimensional change rate when held at 200 ° C free length for 10 minutes is A film for a speaker diaphragm, characterized in that the content is in the range of 0.6 to 1.0% in both biaxial directions. 2. The film for a speaker diaphragm according to claim 1, wherein the film thickness is 50 μm or more and 100 μm or less.