HK1079805B - Membranes made of cast polyarylate film - Google Patents

Description

Diaphragm made of polyarylate resin cast film

The invention relates to diaphragms made of cast polyarylate resin films (cast PAR films), in particular to their use as thermoformed microphone diaphragms or thermoformed loudspeaker diaphragms, to the cast RAR films, to a casting solution for producing cast PAR films, to a method for producing thermoformed microphone diaphragms or thermoformed loudspeaker diaphragms, and to a method for producing cast PAR films.

Polymer films composed of Polycarbonate (PC), polyester (PET, PEN), Polyethersulfone (PES), Polyetherimide (PEI), and the like are commonly used to make small diaphragms with diameters below about 10cm for sound effect applications (signal sensors), such as for mobile devices like microphones, mobile phones, laptop computers, Personal Digital Assistants (PDA) or headphones, and also as signal generators, such as for their application in automotive manufacturing. In order to reduce the vibration of the diaphragm (vibrating mass), ensure accurate reproduction of embossed structures (embossed structures) during thermoforming, and further miniaturization, the film is as thin as possible. The aforementioned resin-made film has high mechanical strength, but has a disadvantage in that it generates a "metallic" sound when used as a microphone diaphragm, i.e., it cannot be deformed sufficiently to reproduce a relatively complicated embossed structure. As a result, music and/or human voice signals are distorted during interconversion with electrical signals.

The small microphone diaphragm and the small loudspeaker diaphragm are generally manufactured by thermoforming. This process heats and softens the film prior to thermoforming, for example by Infrared Radiation (IR). The more anisotropic the film, the more it is necessary to control the uniform heating of the film before thermoforming to achieve uniform softening. Cast films are significantly more isotropic than stretched and/or extruded films. PC, polyethylene-2, 6-naphthalate (PEN) or polyethylene terephthalate (PET) extruded films are susceptible to more or less deformation and/or shrinkage due to the internal stresses built up during extrusion/stretching being partially released during heating. Cast films have lower internal stress than extruded/stretched films and are therefore more uniform in their thermoplastic formation and are particularly suitable for the aforementioned applications. However, these polymers, especially PET and PEN, have low solubility, making them unsuitable for use in the manufacture of cast films.

The present invention aims to provide a membrane for manufacturing an acoustic diaphragm. These films can ensure high clarity of human voice and high reproduction of music at a high volume and have high mechanical strength at a high temperature.

Such high requirements, especially for small diaphragms for acoustic applications, mean that even thin films must be uniformly IR heated and perfectly thermoformed.

In recent years, diaphragm-based diaphragms have been mostly made of extruded films. Only in the manufacture of high quality loudspeaker diaphragms is polycarbonate cast films used.

Surprisingly, it has now been found that diaphragms made of cast PAR films have significantly better sound quality than diaphragms made of extruded PC films, extruded PEN films or extruded PEI films and the like, and also have a significant advantage over cast PC films.

Cast PAR films are known to have very good isotropy and high thermal resistance, and have been limited to optical applications (EP-A-0488221, JA-A-08/122526, JA-A-08/134336 and JP-A-08/269214).

The strength of a plurality of materials is measured and the dispersion of the measured values is found to be high because of various defects in the material, the distribution of which is related to the manufacturing process. To make a reliable conclusion about the strength of a material and the distribution of defects within the material requires not only knowledge of the average of the measured tensile stresses (maximum tensile stress, tensile stress at break point), but also knowledge of the statistical distribution of the strength values. One of the plausible statistical methods is based on the extreme value distribution described by w.weibull (ingg.vetenslooks akad. handl., 151(1939), 1-45), which calculates the probability of failure of a given shaped sample under tensile stress σ. The two related tensile stresses, maximum tensile stress and fracture tensile stress, are directly related to the ultimate failure of the material. The maximum tensile stress is the starting point of the abrupt decrease in tensile stress, and the fracture stress is the final tensile stress measured before the material is completely disintegrated.

A study of 40 specimens each shows that the maximum tensile stress and ultimate tensile strength of the inventive cast PAR film materials are superior to those of cast PC films (PC-A and PC-B) composed of two different polycarbonate grades.

It has also been found that cast PAR films have a high damping coefficient and a substantially linear sound quality over a wide range of audio and sound frequencies, and are therefore suitable for sound applications. Diaphragms made from cast PAR films are excellent in the initiation and damping of vibrations and in the uniformity of vibrations over a wide range of audio frequencies and volumes, and have good human clarity.

The invention has found that colored cast PAR films can be heated uniformly and thermoformed and are suitable in particular for producing small diaphragms.

The addition of certain dyes or nonionic surfactants has also been found to improve the poor thixotropy of PAR casting solutions. As a result, the technical measures before or during the casting process are significantly simplified and the overall casting process is significantly improved.

The heat resistance of the finished cast PAR diaphragms is increased (Tg 188 ℃) compared with PC diaphragms (Tg 135 ℃). Diaphragms made of cast PAR films are less prone to shrinkage at high temperatures and are dimensionally stable, and are therefore superior to diaphragms made of extruded PC films, extruded PEI films, extruded PEN films, extruded PES films or extruded PET films. PAR films can be produced as diaphragms with more complex geometries in comparison with extruded and stretched films, for example PC films, PEI films or PEN films.

Owing to the high isotropy, cast PAR films are suitable for use in the production of diaphragms in the form of unstretched films. However, the cast PAR films of the invention can be stretched uniaxially or biaxially as desired before the production of the diaphragms.

PAR diaphragms are very low in flammability even without additives that may affect the vibration of the diaphragm.

It has also been found that diaphragms made from PAR films have improved moisture resistance.

Thermoplastic shaped diaphragms for sound applications are produced from cast PAR films comprising at least polyarylates having the structural elements:

wherein R is¹，R²，R³And R⁴Each is H, C_1-4Alkyl radical, C_1-4Alkoxy or halogen, R₅And R₆Each is H, C_1-4Alkyl radical, C_1-4Alkoxy, phenyl or halogen.

In one of the preferred embodiments, R¹＝R²And R is³＝R⁴And are each H or C_1-4An alkyl group.

In a particularly preferred embodiment, R¹＝R²＝R³＝R⁴And are each H or C_1-4An alkyl group.

In another preferred embodiment, R₅And R₆Each is C_1-4An alkyl group. In a particularly preferred embodiment, R₅＝R₆Is methyl.

By way of example, a polyarylate designated "U-Polymer 100" is available from UNITIKA CHEMICAL K.K., 3-11, Chikkoshinmachi, Skai-shi, Osaka 592, Japan, wherein R is R¹＝R²＝R³＝R⁴Is H and R₅＝R₆A molecular weight of 10,000-.

The thickness of the diaphragm of the present invention may be 5 to 200. mu.m, preferably 5 to 100. mu.m, more preferably 10 to 50 μm.

The excellent damping properties (internal losses) of the PAR films according to the invention make them particularly suitable for producing thermoformed diaphragms for acoustic sensors, in particular for microphone diaphragms and/or loudspeaker diaphragms. They have less "metallic" sound than known diaphragms constructed of other polymers.

The mechanical strength of the PAR diaphragm of the invention is significantly better than that of a PC diaphragm, and the PAR diaphragm has a longer service life when driven electrically at the same rated power and at the same high temperature.

The inventive thermoformed PAR diaphragms are particularly suitable for applications requiring high definition of human speech, for example as diaphragms for microphones or loudspeakers in microphone capsules, mobile telephones, hands-free systems, radios, headsets, computers and PDAs. Another use of the diaphragm is as a signal generator.

The percentages of the dyes and surfactants mentioned below are the percentages by weight of their solids content in the PAR casting solution and/or in cast PAR films produced from said casting solution.

The polyarylate percentage amounts described hereinafter are all weight percentages based on the total weight.

In order to produce the diaphragms according to the invention made of cast PAR films according to claim 1 by thermoforming, for example, the films are heated by Infrared (IR) radiation to improve their variability. The invention proves to be advantageous in this case for the addition of dyes, since a uniform heat absorption and softening can be achieved thereby. Thus, the inventive cast PAR films are easier to process and the quality of the diaphragms produced therefrom is better.

As little as 0.01% of commercially available dyes, for example "C.I. solvent yellow 93" or "Macrolex ® orange R", are sufficient to achieve uniform heating of the inventive PAR cast films. If pure pigments without auxiliaries and/or fillers are used, the addition can also be smaller.

For example, the dye "c.i. solvent yellow 93" is available from BAYER under the trade name "transparent yellow 3G"; or from Kunshan, Shanghai chemical Co., Ltd, Changxi Zhenbei, Kunshan, Jiangsu, China 215334; or from CHINA CHEMICALS, LUXUN mansion 12 th floor G seat, 568, OuYang street, Shanghai, China, 200081; or from HONGMENT CHEMICALS LIMITED, Xinzhuuayaan 32-203, Ningxi Lou, Chinese Pearl sea.

One dye that is equivalent to "c.i. solvent yellow 93" is "BASF thermoplastic yellow 104" from BASF, germany, or "solvent yellow 202" from zhui SKYHIGH CHEMICAL co., ltd., 20/F, Everbright International trade centre, zhui, guangdong, china.

"Macrolex ® orange R" is available, for example, from BAYER, Germany.

The dyes described above in commercial form now contain nonionic polyhydroxy surfactants, the benefits of which for the inventive PAR casting solutions are discussed below.

The inventive PAR casting solutions and/or cast PAR films produced therefrom contain at least one dye and/or one nonionic polyhydroxy surfactant.

The nonionic polyhydroxy surfactants are generally nonionic water-soluble polyalkylene oxides, for example polyethylene oxide or polyethylene glycol (PEO), polypropylene oxide or polypropylene glycol (PPO) or polybutylene oxide (PTMO), which are characterized in common by having the structural element- [ (CH)₂)_x-CHR-O]-, wherein (i) R is H and x is 1 (polyethylene glycol (PEO)); (ii) r is CH₃X is 1 (polyethylene glycol (PPO)); or (iii) R is H and x is 3 (polytetramethylene oxide (PTMO)). The polyhydroxy surfactants are not limited to PEO homopolymers, PPO homopolymers and PTMO homopolymers, but also copolymers thereof, in particular block copolymers and/or mixtures of said polymers, having an average molecular weight of less than 20,000.

One example of a commercially available polyethylene-polypropylene glycol block copolymer is "Pluronic ® PE 6800" from BASF or "Synperonic ® F86 pract" from SERVA.

Structural formula (I) (wherein, R¹，R²，R³And R⁴Each is H, C_1-4Alkyl radical, C_1-4Alkoxy or halogen, R₅And R₆Each is H, C_1-4Alkyl radical, C_1-4Alkoxy, phenyl or halogen) in the presence of a PAR of twoThe casting solution formed in methyl chloride is highly thixotropic and thus cannot be stored as a ready-to-use solution on standing. In order to avoid the casting solution from solidifying in gel form in the storage container, in the transport system, in the filter or in the casting apparatus, great care must be taken to keep it in a continuously oscillating state and to avoid "dead spots".

Surprisingly, it has been found in accordance with the invention that dyes such as "c.i. solvent yellow 93", "solvent yellow 202" or "Macrolex ® orange R" can act as anti-thixotropic agents when added to a PAR casting solution.

Further tests demonstrated that: nonionic polyhydroxy surfactants, such as polyethylene-polypropylene glycol block copolymers, also have the above-described effects when used alone. The thixotropic properties of the PAR casting solutions disappear after addition of the nonionic polyhydroxy surfactants and/or one of the dyes. This greatly simplifies the casting process, and the inventive ready-to-use PAR casting solutions can be stored for several weeks. In contrast, PAR casting solutions without added surfactant and/or dye are completely discarded after standing for several hours.

The polyhydroxy surfactants and dyes may also contain other additives, for example TiO₂。

The inventive PAR casting solutions and/or cast PAR films produced therefrom contain dyes and/or nonionic polyhydroxy surfactants.

In one embodiment, the inventive PAR casting solutions and/or cast PAR films produced therefrom comprise at least one nonionic surfactant from the group of polyethylene glycol, polypropylene glycol and polybutylene oxide, which can be used in the form of their homopolymers, copolymers or block copolymers or mixtures thereof.

In a particularly preferred embodiment, the inventive PAR casting solutions and/or cast PAR films produced therefrom comprise at least one polyethylene glycol-polypropylene glycol block copolymer having an average molecular weight of 6,000-10,000.

In a particularly preferred embodiment, the inventive cast PAR solutions and/or cast PAR films produced therefrom comprise a dye, for example "C.I. solvent yellow 93", "solvent yellow 202" or "Macrolex ® orange R", and/or a nonionic polyhydroxy surfactant, for example "Pluronic ® 6800" or "Synperonic ® F86 pract".

The inventive PAR casting solutions and/or cast PAR films produced therefrom comprise PAR of the formula I according to claim 1 and also comprise from 0.001 to 2%, preferably from 0.001 to 0.15%, of a dye and/or nonionic polyhydroxy surfactant.

The dye and/or surfactant may be dissolved in, for example, acetone, butyl acetate or dichloromethane, preferably dichloromethane.

In a preferred embodiment, dyes such as "c.i. solvent yellow 93", "solvent yellow 202" or "Macrolex ® orange R" themselves contain a nonionic polyhydroxy surfactant such as "Pluronic ® 6800" or "Synperonic ® F86 pract" and form mixtures with them in dissolved form.

The dyes and/or nonionic surfactants are preferably added in controlled fashion to the PAR casting solutions in the form of their solutions in methylene chloride until the desired amount is reached.

In a further preferred embodiment, the dyes and/or nonionic surfactants are dissolved beforehand in the solvent dichloromethane used for the preparation of the PAR casting solutions.

The concentration of the inventive PAR casting solutions in methylene chloride as solvent is preferably from 10% up to the upper solubility limit. Preferably 15-25%, more preferably 20-24%.

In one method for producing a diaphragm, a PAR film softened by heating is deformed in a thermoforming mold and then thermoformed. This can be done, for example, by applying air pressure or vacuum, but also by using a mechanical ram (ram). Different thermoforming methods can be combined.

A preferred method of heating is infrared irradiation.

The final molded diaphragm is then cut from the film by mechanical means, such as with a knife or die, or in a non-contact manner, such as with the aid of a water gun or laser. Stamping or laser cutting is preferred.

The outer edge of the diaphragm may then be bonded to a plastic or metal support ring and connected to a coil with connecting contacts, and then incorporated as a microphone diaphragm or loudspeaker diaphragm together with a permanent magnet into a suitable device as an acoustic signal sensor or generator therein.

To produce cast polyarylate films, the polyarylate casting solutions of the present invention can be applied to a substrate by a suitable casting apparatus, removed from the substrate after initial drying, and then fully dried.

In one preferred embodiment, the cast film is applied to a glass substrate using a suitable casting device or scalpel, initially dried, removed, and finally dried to the desired residual solvent concentration.

In another embodiment, the cast film is applied to a continuous substrate by a suitable casting apparatus, initially dried, removed, and then dried thoroughly to the desired solvent concentration.

In another preferred embodiment, a stainless steel belt having a length of 20 to 100m and one side matte or polished, or alternatively a polished or matte stainless steel roll having a circumference of 5 to 25m, is used as the continuous substrate.

In the case of very thin films with a thickness of less than 20 μm, it is advantageous not to cover the cast film directly onto the substrate but rather onto an intermediate film on the actual substrate, which is advantageous for increasing the stability of the cast film according to the invention and for avoiding strains caused by tensile stresses in the subsequent processing. After the initial drying, the intermediate film is removed together with the cast film from the actual substrate, and the cast film is finally dried. Whether and when the cast film of the present invention separates from the intermediate film is not critical to the present invention. Preferably, the intermediate film is wound onto a roll along with the cast film of the present invention for subsequent processing.

In a preferred embodiment, the intermediate film used comprises a polymer film, preferably a PET film.

In a preferred embodiment, the preliminary drying process before removing the preformed film is carried out directly by infrared irradiation, microwave irradiation or electrical heating, or indirectly by contact with hot air.

In a preferred embodiment, the solvent content of the PAR cast films after peeling is from 5 to 15%. In a further preferred embodiment, the final drying to achieve the desired solvent concentration is carried out in a heatable drying chamber by direct and/or indirect heating. The material is preferably unsupported during the final drying process.

The heating method can be direct heating, such as infrared and/or microwave heating, indirect heating, such as contact with hot air at a certain temperature, or a combination of the two.

In a preferred embodiment, the transport speed of the PAR film is from 1 to 20m/min, preferably from 2 to 50 m/min. At this time, the temperature of the final drying may be 50 to 200 ℃. After final drying, the inventive RAR films had an average thickness of 5-200 μm and a solvent content of less than 1.5%.

The properties of the inventive cast PAR films can be further optimized by the application of coatings. For example, the coating layer may be formed by solution coating or may be formed by lamination. In another embodiment, the coating can also be extruded, in view of the high heat resistance of the PAR film. The coating may further improve the damping properties.

Solution coating methods include, for example, roll coating, knife coating, or spray coating. Suitable solutions include, for example, Polyurethane (PU) solutions or solutions of polyarylates in suitable solvents. PE, PP or PU films are suitable as laminate coatings. For lamination, use may be made of cast films which are not stretched or are stretched unidirectionally or biaxially, or of extruded films, the lamination process having to give long-lasting and sufficiently high adhesion between the layers, for example by additionally using adhesives (adhesive lamination) or true lamination by pressure and heat.

After the drying process, or after the application of the coating, or after the production of the preform (e.g. roll cutting), the cast PAR films according to the invention can be further processed to give diaphragms in a thermoforming apparatus.

Examples

While the following examples 1-13 fully disclose the practice of the present invention, the variability of the process parameters makes numerous other embodiments of the present invention possible. Embodiments employing such variations as defined in the present specification and claims are to be considered as embodiments of the invention and within the scope of the present application.

Example 1

600kg of a "U-Polymer 100" polyarylate (having the formula I, wherein R is R) available from UNITIKA was weighed¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl), 2062kg of dichloromethane was added thereto, and the mixture was stirred at room temperature for 3 hours and dissolved at 39 ℃. 300g of the powdery "C.I. solvent yellow 93" dye from BAYER were added with stirring. The solids content in the lacquer (lacquer) was 22.5%.

A film having a thickness of 100 μm and a width of 110cm was produced from the varnish.

Example 2

600kg of a "U-Polymer 100" polyarylate (having the formula I, wherein R is R) available from UNITIKA was weighed¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl), 2062kg of dichloromethane was added thereto, and the mixture was stirred at room temperature for 3 hours and dissolved at 39 ℃. 300g of powdered "Microlex ® orange R" dye from BAYER was added with stirring. The solids content in the lacquer was 22.5%. A film having a thickness of 100 μm and a width of 110cm was produced from the varnish.

Example 3

300kg of a "U-Polymer 100" polyarylate (having the formula I, wherein R is R) available from UNITIKA was weighed¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl group), 1100kg of dichloromethane was added thereto, stirred at room temperature for 3 hours and dissolved at 39 ℃. 300g of the powdery "C.I. solvent yellow 93" dye from BAYER were added with stirring. The solids content in the lacquer was 21.5%. Films of 20, 25, 30, 40, 60, 80 and 100 μm thickness, 110 and 120cm width were made with this lacquer.

Example 4

For the manual production of cast products (products cast), 0.3 to 2.0kg of paint containing 15 to 24% of polymer are prepared: the "U-Polymer 100" PAR (having the formula I, wherein R is¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl) was added to the solution, stirred at room temperature for 3 hours and dissolved at 39 ℃ with continuous stirring. The paint used for hand-made casting products contained 0.01% "c.i. solvent yellow 93" dye. The cast products were made manually with this lacquer in the DINA4 mode, the film thickness being 15-100 μm.

Example 5

For the manual manufacture of cast products, 0.3-2.0kg of paint containing 15-24% of polymer is prepared: the "U-Polymer 100" PAR (having the formula I, wherein R is¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl) was added to the solution, stirred at room temperature for 3 hours and dissolved at 39 ℃ with continuous stirring. The paint used for hand-made casting products contained 0.01% "Microlex ® orange R" dye. Cast products were produced manually with this lacquer in DIN A4 mode, the film thickness being 15-100. mu.m.

Example 6

For the manual manufacture of cast products, 0.3-2.0kg of paint containing 15-24% of polymer is prepared: "U-Polymer 1" from UNITIKA00' PAR (having the structure I, wherein R¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl) was added to the solution, stirred at room temperature for 3 hours and dissolved at 39 ℃ with continuous stirring. The paint used for the manual manufacture of the cast product contained 0.01% "Pluronic ® PE 6800" surfactant. Cast products were produced manually with this lacquer in DIN A4 mode, the film thickness being 15-100. mu.m.

Example 7

For the manual manufacture of cast products, 0.3-2.0kg of paint containing 15-24% of polymer is prepared: the "U-Polymer 100" PAR (having the formula I, wherein R is¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl) was added to the solution, stirred at room temperature for 3 hours and dissolved at 39 ℃ with continuous stirring. The paint used for hand-made casting products contained 0.001% "c.i. solvent yellow 93" dye. Cast products were produced manually with this lacquer in DIN A4 mode, the film thickness being 15-100. mu.m.

Example 8

For the manual manufacture of cast products, 0.3-2.0kg of paint containing 15-24% of polymer is prepared: the "U-Polymer 100" PAR (having the formula I, wherein R is¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl) was added to the solution, stirred at room temperature for 3 hours and dissolved at 39 ℃ with continuous stirring. The paint used for hand-made casting products contained 0.001% "Microlex ® orange R" dye. Cast products were produced manually with this lacquer in DIN A4 mode, the film thickness being 15-100. mu.m.

Example 9

For the manual manufacture of cast products, 0.3-2.0kg of paint containing 15-24% of polymer is prepared: the "U-Polymer 100" PAR (having the formula I, wherein R is¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl) was added thereto, and stirred at room temperature for 3 hoursAnd dissolved by continuous stirring at 39 ℃. The paint used for the manual manufacture of the cast product contained 0.001% "Pluronic ® PE 6800" surfactant. Cast products were produced manually with this lacquer in DIN A4 mode, the film thickness being 15-100. mu.m.

Comparative example 10

For the manual manufacture of cast products, 0.3-2.0kg of paint containing 15-24% of polymer is prepared: the "U-Polymer 100" PAR (having the formula I, wherein R is¹＝R²＝R³＝R⁴Is H and R₅＝R₆Methyl) was added to the solution, stirred at room temperature for 3 hours and dissolved at 39 ℃ with continuous stirring. The paint used for the hand-made casting product does not contain any dyes and/or surfactants. Cast products were produced manually with this lacquer in DIN A4 mode, the film thickness being 15-100. mu.m.

Example 11

The thixotropic properties of the paint samples prepared in examples 1 to 9 and comparative example 10 were observed at different times after the preparation of the ready-to-use solutions. For this purpose, samples of each paint were loaded into 5 different containers. After 30min, 4h, 8h, 20h and 1-4 weeks, films were prepared if possible by hand casting. The observation results are shown in table 1.

Table 1:

paint	After 30min	After 4 hours	After 8 hours	After 20h	After 4 weeks
						Example 1	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening

Example 2	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening
						Example 3	Can be used for the treatment of the diseases,the stable solution does not become thick	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening
Examples 4 to 6	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening
						Examples 7 to 9	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening	Can be used for stabilizing solution without thickening
Comparative example 10	Quickly thicken	Sharp rise in viscosity	The solution is in gel form and is not usable	Solid gel, no flow after inversion	Solid gel, no flow after inversion

Example 12

In each case, the tensile stress at break and the maximum tensile stress at maximum were determined by the Weibull method for 40-strain film specimens 30 μm thick of each of the 3 materials (PC-B, PAR, PC-A).

Table 2 summarizes the Weibull characteristic phase statistical parameters. The PAR specimens are cast PAR films according to the invention. The PC-A and PC-B samples represent cast polycarbonate films. PC-a is a standard polycarbonate used to make loudspeaker diaphragms from PC cast films. PC-B is composed of a reference PC material and is tested as another similar material other than PC-A.

Table 2:

		tensile stress at break				Maximum tensile stress
										Polymer and method of making same	N	Mean sigma +/-delta sigma MPa]	σc，0[MPa]	σm[MPa]	m	Mean sigma +/-delta sigma MPa]	σc，0[MPa]	σm[MPa]	m
PC-B	40	24.9±5.8	27.3	25.2	4.6	73.5±3.5	75.1	74.0	24.9
										PAR	40	30.9±5.7	33.3	31.3	6.0	77.3±3.4	78.8	77.8	28.3
PC-A	40	42.9±8.7	46.6	43.5	5.3	85.1±6.1	87.8	85.9	16.8

N: number of samples

Mean σ ± Δ σ: arithmetic mean ± standard deviation

σ c, 0: characteristic Strength (crack probability 63.2%)

σ m: median intensity (50% probability of rupture)

m: weibull modulus

The Weibull modulus m characterizes the homogeneity of the material, the ordering of this modulus at maximum tensile stress and tensile stress at rupture being shown below, with higher values of m indicating higher homogeneity and lower dispersion of the measured values.

Maximum tensile stress: m (PC-A) < m (PC-B) < m (PAR)

Tensile stress at break: m (PC-B) < m (PC-A) < m (PAR)

Compared with two cast PC films, the cast PAR films according to the invention have the highest homogeneity and, at the same time, the narrowest distribution of measured values.

Example 13

Comparative life tests between standard and high-performance loudspeakers made with cast PAR films and with cast PC films (PC-A and PC-B in example 12) according to DIN ETS 300019 "Gerate-Entwicklung; umwell bendingngen und Umwell prufungen fur Telekekekoummunikationsanlangen "[ device development; environmental conditions and environmental tests of the communication device ]. PAR stands for the cast PAR films according to the invention. A total of 5 types of loudspeakers were tested, in each of which 50 loudspeakers were sampled for each type and for each diaphragm diameter. Various tests were performed on the microphone, such as repeated temperature cycling (-40 ℃ to 85 ℃) in a high humidity environment, or at 85 ℃ for extended periods of time. Each loudspeaker was tested for a total of 500 hours at a certain electrical load with a "punch through noise" (for a given power on the respective data sheet for each loudspeaker). The test results are limited to qualitative evaluations, since the moment in the test at which the failure occurred always changes. Table 5 lists the results of the evaluations and shows whether there is a large difference between the number of microphones tested and the number of microphones still available after the test. The service life of loudspeaker diaphragms made of inventive cast PAR films is at least comparable to that of current standard materials.

Table 3:

examples	Diameter of diaphragm	Thickness of film	Number of types	PC-B	PC-A	PAR
							13-1	13mm	30μm	4	-	+	+
13-2	16mm	40-60μm	3	-	+	+
							13-3	13mm	30-60μm	8	-	+	+
13-4	23-38mm	40-150μm	24	+	(+)	(+)
							13-5	28mm	100μm	1	-	(+)	+

The service life test is qualified, the damage rate is lowest, the service life test is qualified, and the damage rate is acceptable; failure in life test and high failure rate.

Claims (33)

1. A thermoformed diaphragm made from a cast polyarylate film comprising at least one polyarylate having the following structural units

Wherein R is¹，R²，R³And R⁴Each is H, C_1-4Alkyl radical, C_1-4Alkoxy or halogen, R⁵And R⁶Each is H, C_1-4Alkyl radical, C_1-4Alkoxy, phenyl or halogen.

2. The thermoformed diaphragm of claim 1, wherein R¹＝R²And R is³＝R⁴And are each H or C_1-4An alkyl group.

3. The thermoformed diaphragm of claim 2, wherein R¹＝R²＝R³＝R⁴And are each H or C_1-4An alkyl group.

4. The thermoformed diaphragm of any of claims 1-3, wherein R⁵And R⁶Each is C_1-4An alkyl group.

5. The thermoformed diaphragm of claim 4, wherein R⁵And R⁶Each is methyl.

6. A thermoformed diaphragm according to claim 1, having a thickness of from 5 to 200 μm.

7. A thermoformed diaphragm according to claim 6, having a thickness of from 5 to 100 μm.

8. Use of the thermoformed vibrating membrane according to any one of claims 1 to 7 as a vibrating membrane for sound transducers for acoustic applications.

9. Use according to claim 8, the diaphragm of the sound sensor being the diaphragm of a microphone and/or a loudspeaker.

10. Use according to claim 8, the diaphragm being used in a microphone capsule, a mobile phone, a hands-free system, a listening device, an earphone, a computer, a PDA and/or a signal generator.

11. Use according to claim 10, in a radio or a micro-radio.

12. A casting solution comprising a polyarylate represented by structural formula I of claim 1, a dye and/or a nonionic polyhydroxy surfactant.

13. The casting solution of claim 12, the nonionic polyhydroxy surfactant being selected from the group consisting of: polyethylene glycol, polypropylene glycol and polybutylene oxide, and used in the form of their homopolymers, copolymers, block copolymers or mixtures thereof.

14. The casting solution of claim 12 or 13, the dye being selected from "c.i. solvent yellow 93", "solvent yellow 202", or "Macrolex ® orange R".

15. The casting solution of claim 12, the non-ionic polyhydroxy surfactant being selected from "Pluronic ® PE 6800" or "Synperonic ® F86 pract".

16. The casting solution of claim 12, wherein the dye and/or the nonionic surfactant is present in an amount of 0.001 to 2 wt%.

17. The casting solution of claim 16, wherein the dye and/or the nonionic surfactant is present in an amount of 0.001 to 0.15% by weight.

18. The polyarylate casting solution of claim 12, wherein the polyarylate content is at least 10% by weight.

19. The polyarylate casting solution of claim 18, wherein the polyarylate content is 15 to 25% by weight.

20. A cast film comprising a polyarylate having the structure of formula I as defined in claim 1, a dye and/or a nonionic polyhydroxy surfactant.

21. The cast film of claim 20, wherein the nonionic polyhydroxy surfactant is selected from the group consisting of: polyethylene glycol, polypropylene glycol and polybutylene oxide, and used in the form of their homopolymers, copolymers, block copolymers or mixtures thereof.

22. The cast film of claim 20 or 21, wherein the dye is selected from "c.i. solvent yellow 93", "solvent yellow 202", or "Macrolex ® orange R".

23. A cast film according to claim 20 wherein the said nonionic polyhydroxy surfactant is selected from "Pluronic ® PE 6800" or "Synperonic ® F86 pract".

24. The cast film of claim 20, wherein the dye and/or nonionic surfactant is present in an amount of 0.001 to 2 wt%.

25. The cast film of claim 24, wherein the dye and/or nonionic surfactant is present in an amount of 0.001 to 0.15 wt%.

26. A method of manufacturing a thermoformed diaphragm as claimed in any one of claims 1 to 5 from a cast polyarylate film as claimed in any one of claims 20 to 25, comprising infrared heating of said cast film followed by thermoforming into a diaphragm.

27. A method of preparing a cast polyarylate film as defined in any one of claims 20 to 25, comprising applying a cast polyarylate solution as defined in any one of claims 12 to 19 to a substrate, removing said film from said substrate after initial drying, and then substantially drying.

28. The method of claim 27, comprising coating the polyarylate casting solution on a continuous substrate.

29. The method according to claim 28, wherein the continuous substrate is a steel belt or a polished or matte stainless steel roll having a diameter of 5 to 20 m.

30. The method of any of claims 27 to 29, comprising coating the polyarylate casting solution on an intermediate film disposed on a substrate, peeling off the intermediate film from the substrate after initial drying, and then substantially drying.

31. The method of claim 30, the intermediate film comprising a polyethylene terephthalate film.

32. The method of claim 27, wherein said cast polyarylate film has a thickness of 5-200 μm after final drying.

33. The method of claim 27, further comprising applying a coating to the cast polyarylate film of any of claims 20-25 by solution coating or lamination.