JP2020109175A - Functional film - Google Patents

Abstract

To provide a functional film that is used for a vibration system support member of a speaker or the like and has a very small thickness unevenness.SOLUTION: The functional film comprises a thermoplastic elastomer, and has a thickness of 10 to 100 μm, and a tolerance in thickness unevenness of 2 μm or less. When it is measured for stress at 5% elongation and stress at 10% elongation on the basis of JIS-K7127, each shows a fluctuation range between the maximum value and minimum value of 20% or less.SELECTED DRAWING: None

Description

The present invention relates to a functional film made of a thermoplastic elastomer.

It is known to use a functional film made of a thermoplastic elastomer mainly for vibration damping material applications such as a vibration system supporting member of a speaker that requires acoustic characteristics (see, for example, Patent Documents 1 and 2).

JP 2004-269756 A JP, 2001-59057, A

In order to improve the sound quality of the speaker in the above-mentioned vibration damping material application, it is required to reduce the thickness unevenness of the functional film used and to make the thickness uniform.

However, since the thermoplastic elastomer has a large molecular weight of about 100,000 to 500,000 and a large viscosity variation at the time of melting, it is difficult to obtain a film having a uniform thickness, and stable sound quality can be provided. It was difficult.

An object of the present invention is to provide a functional film having extremely small thickness unevenness.

The present inventor has obtained the following findings as a result of earnest studies to solve the above problems. That is, it is a finding that the coating method can suppress the thickness unevenness of the film obtained by controlling the solid content concentration, viscosity, etc. in the solution containing the thermoplastic elastomer within a desired range.

The present invention is based on the knowledge of the present inventor, and means for solving the above problems are as follows.

<1> Made of a thermoplastic elastomer, having a thickness of 10 to 100 μm, a tolerance of 2 μm or less, and both stresses at 5% elongation and 10% elongation measured according to JIS K7127, Each of the functional films is characterized in that the fluctuation range between the maximum value and the minimum value is within 20%.

<2> The solution is the functional film according to <1>, containing 10 to 50% by weight of the thermoplastic elastomer.

<4> The thermoplastic elastomer is the functional film according to <1> or <2>, which is at least one of urethane type, polyester type, polyamide type, olefin type, and styrene type.

<5> The thermoplastic elastomer is the functional film according to any one of <1> to <3>, which is a polyurethane elastomer (TPU).

<6> The functional film according to any one of <1> to <4>, which is used for a vibration system supporting member of a speaker.

According to the present invention, it is possible to provide a highly accurate functional film having a thickness tolerance of 2 μm or less and having an extremely small thickness unevenness.

This makes it possible to obtain good sound quality in applications in which the functional film is used such as in vibration damping materials.

FIG. 1 is a graph showing changes over time in storage elastic modulus at 0 to 80° C. when hardness is varied in the ester type polyurethane film of the present invention. FIG. 2 is a graph showing changes over time in the storage elastic modulus at 0 to 80° C. when the ether type polyurethane film of the present invention has different hardness. FIG. 3 is a graph showing changes with time in storage elastic modulus at 0 to 80° C. when hardness is varied in the polyester film of the present invention.

The functional film of the present invention is made of a thermoplastic elastomer, has a thickness of 10 to 100 μm, and has a tolerance (unevenness in thickness) of 2 μm or less, more preferably 1 μm or less.

In this way, by setting the tolerance within 2 μm, it is possible to suppress the stress when the film is stretched so that the fluctuation is extremely small, and the sound quality of the speaker is very good when used for the vibration damping material. It becomes possible to do. In other words, when the tolerance exceeds 2 μm, it becomes difficult to suppress the stress variation within this range, and it becomes impossible to provide the speaker with sufficiently good sound quality.

When the thickness is less than 10 μm, it is difficult to apply it in a desired application, while when it exceeds 100 μm, it is difficult to manufacture, and it is meaningless to increase the thickness further, which is not preferable.

The thickness of this functional film can be measured according to JIS Z1072 using a commercially available film thickness measuring device, and in the obtained film of 1 m×1 m, it is calculated by randomly measuring 30 points. The average value is used. The tolerance is the difference between the maximum value and the minimum value.

The stress fluctuation can be measured based on JIS K7127, and the difference between the values measured at 5 random positions in the above-mentioned 1 m×1 m film is used as the fluctuation value. In order to stably provide good sound quality, stable film rigidity is required, and its index is generally expressed by elastic modulus, but since the rigidity changes as the film becomes thicker, Stable stress during elongation is required. If the stress during extension is stable, the storage elastic modulus at a temperature that can be assumed in a living environment of 0 to 80° C. is also stable, and good sound quality is provided, that is, acoustic characteristics are excellent.

The hardness of the film is not particularly limited. In other words, if the film has a thickness tolerance of 2 μm or less, good sound quality can be provided without being affected by the hardness.

The thermoplastic elastomer of the functional film of the present invention is produced by a coating method. The thermoplastic elastomer can also be produced by an extrusion method, but in the extrusion method, solid powder or pellets are softened and melted in a heating cylinder and extruded by a screw into a die having a slit to form the thermoplastic elastomer. These have a large molecular weight and have large variations in viscosity when melted. This variation in viscosity causes unevenness in thickness during molding, and it is difficult to obtain a film having a uniform thickness. In other words, in the extrusion method, since only solid contents such as powder and pellets are used, the only way to control the film thickness is to increase the film forming accuracy, and to produce a film of uniform thickness, It is extremely difficult because the precision must be increased considerably.

On the other hand, the coating method is a method of applying a solution with a constant weight (thickness) and volatilizing the solvent in the solution to use a film of only solute. Also, by adjusting the solid content concentration and the solution viscosity, it becomes possible to reduce the thickness unevenness.

However, when the coating method is used, the thickness unevenness cannot always be kept within the desired range of the present invention, and the inventors of the present invention have made trial and error about the conditions, and the following conditions are appropriate. I understood. That is, the solid content and coating thickness of the thermoplastic elastomer in the solution containing the thermoplastic elastomer are kept constant, and the temperature of the solution is kept constant at 10 to 40° C. and the viscosity is kept constant within the range of 100 to 50,000 mPa·s. Make a film while keeping it.

The concentration of the thermoplastic elastomer in the solution is preferably 10 to 50% by weight. If it is less than 10% by weight, it is difficult to impart appearance quality such as unevenness to the film, while if it exceeds 50% by weight, the viscosity becomes high and it is difficult to suppress the thickness unevenness within the desired range of the present invention. Becomes

Similarly, if the viscosity is less than 100 mPa·s, it is difficult to maintain the appearance quality of the film, and if it exceeds 50,000 mPa·s, it becomes difficult to suppress the thickness unevenness within a desired range. The viscosity can be measured according to JIS Z7117-1.

If the temperature of the solution is outside the above range, the viscosity may change, and the thickness unevenness may not be controlled within a desired range. Therefore, the temperature of the solution is set within the above temperature range that can be assumed as room temperature.

The solid content and coating thickness of the thermoplastic elastomer in the solution containing the thermoplastic elastomer differ depending on the performance and scale of the manufacturing apparatus used, and the specific range cannot be defined. In a solution containing 25% by weight of the plastic elastomer, if the thickness unevenness of the coating thickness is 8 μm, the thickness unevenness (tolerance) of the film is 2 μm, which is within the range of the present invention. Those having a small mass in the range are preferable.

In order to make the thickness of the obtained film uniform, the liquid pressure of the solution must be kept constant because the solution is applied in a constant amount.For example, in the comma coater, the height of the liquid surface and the die coater are used. Then, it becomes possible by keeping the supply amount of the liquid constant.

Even if a fixed amount of the solution is applied, the solid content does not become a uniform dissolved mass unless the solid content in the solution is constant during the production. Therefore, the solid content must be kept constant as described above. In particular, the solvent used for the solution is mainly an organic solvent, which easily volatilizes, and the solid content may fluctuate due to the volatilization of the solvent, so that it is not easy to keep it constant. Therefore, the solution is supplied from a closed container during the production of the film.

The coating amount (thickness) is also determined by the width of the gap, such as the gap between the backup roll and the knife roll in a roll knife coater. Therefore, the thickness of the formed film is measured and After confirming that it is within the desired range, the coating thickness in solution during coating is measured and adjusted to the set constant coating thickness.

The coater used for coating is not particularly limited, and those normally used may be appropriately selected according to the purpose, and examples thereof include a gravure coater, a reverse roll coater, a kiss coater, a roll knife coater, and a die coater. Among these, a roll knife coater and a die coater are preferable because the coating thickness can be controlled relatively easily. In the case of a roll knife coater, the gap between the backup roll and the knife roll can be made constant, and in the case of a die coater, the gap at the die port and the internal pressure of the die can be made constant, so that a uniform coating thickness can be obtained.

As the solution containing the thermoplastic elastomer, either a solution produced by a solution polymerization method or a solution obtained by dissolving a solid resin produced by bulk polymerization with a solvent may be used.

The resin produced by the bulk polymerization is dissolved in a solvent in which a thermoplastic elastomer such as toluene, N,N-dimethylformamide (DMF), methyl ethyl ketone (MEK), dimethyl acetamide (DMAc), and ethyl acetate is dissolved. Can be obtained.

There is no particular limitation on the thermoplastic elastomer, and conventionally known ones can be appropriately selected and used according to the purpose. Examples thereof include urethane-based, polyester-based, polyamide-based, olefin-based, and styrene-based ones. These may be used alone or in combination of two or more.

Among these, those having the property of having little change in storage elastic modulus at 0 to 80° C. are preferable.

As the urethane-based material, for example, urethane-based polyurethane elastomer (TPU) is preferably used. Examples of the ester type in the type of polyol used in the polymerization of TPU include polyethylene adipate (PEA), polybutylene adipate (PBA), polyhexamethylene adipate (PHA), and poly-3-methylpentane adipate (PMPA). And polyols such as polycaprolactone (PCL). Examples of the ether type include polyols such as polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetramethylene ether glycol (PTMG).

As the polyester type, for example,
Polyester/ether type using polybutylene terephthalate (PBT) for the hard segment and polytetramethylene ether glycol (PTMG) for the soft segment,
One or a combination of two or more commonly known resins, such as a polyester/ester type resin using polybutylene terephthalate (PBT) for the hard segment and polybutylene adipate (PBA) for the soft segment, can be used.

Examples of the olefins include a mixture of an olefin resin such as polyethylene (PE) and polypropylene (PP) in the hard segment and a rubber such as ethylene propylene rubber (EPM) and ethylene propylene diene rubber (EPDM) in the soft segment. Any one of the commonly known resins may be used alone or in combination of two or more.

Examples of the styrene type include styrene ethylene butylene styrene block copolymer (SEBS), styrene butadiene rubber (SBR), styrene ethylene propylene styrene block copolymer (SEPS), styrene butadiene (SB), styrene block copolymer ( Any commonly known resin such as SBC) can be used alone or in combination of two or more.

As a polyamide-based material, for example,
Polyether ester type using nylon 6, nylon 11, nylon 12 for the hard segment, polyethylene glycol (PEG), polypropylene glycol (PPG) polytetramethylene ether glycol (PTMG), etc. for the soft segment,
One or a combination of two or more resins that are generally known, such as a polyetheramide type resin using polypropylenediamine or polybutylenediamine for the soft segment, can be used.

Further, the functional film of the present invention, in addition to the above-mentioned thermoplastic elastomer, as the additive, a colorant, a lubricant, an antiaging agent, an antistatic agent or the like which can be usually used, is appropriately used according to the purpose. May be. Further, as this additive, a master batch diluted with a polymer or a filler may be used.

The functional film of the present invention may have a single-layer structure or a multi-layer structure. The method for forming a multilayer structure is not particularly limited, and a generally known lamination method or the like may be used to form a multilayer structure.

INDUSTRIAL APPLICABILITY The functional film of the present invention has excellent acoustic characteristics and can provide good sound quality. Therefore, for example, the functional film is not only suitably used for a vibration damping material such as a vibration system support member of a speaker, but also, for example, acoustic vibrations. It can also be used for acoustic applications other than vibration damping materials such as materials and sound absorbing materials. Further, in addition to acoustic applications, it can also be used in various fields in which precision in thickness is required and variation in stress during extension is small, such as in the field of precision equipment.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

1. Relationship between film thickness and tensile stress A solution containing 20.0% by weight of an ester type polyurethane thermoplastic elastomer (TPU), 40% by weight of N-dimethylformamide (DMF) and 40% by weight of methyl ethyl ketone (MEK) was used. The TPU films produced were set to have thicknesses of 15.0 μm, 17.0 μm, 19.0 μm, and 21.0 μm, respectively, and the viscosity was 5.000.0 mPa·s and the solution temperature was 23.0° C. A film was formed using a die coater while keeping it constant. At this time, a film was produced while keeping the coating film thickness constant at 72.0 μm, 80.0 μm, 94.0 μm, and 100.0 μm in order of decreasing set thickness (see Table 1 above). Further, the film was produced while keeping the liquid pressure of the solution supplied from the die coater constant.

On the other hand, although the same TPU sample was set to have thicknesses of 17.0 μm and 19.0 μm, respectively, and a die coater was used, control was performed to keep the solid content, solution temperature, coating film thickness, etc. particularly constant. The film was produced without doing.

With respect to each of the obtained films, hardness, elastic modulus, average value, maximum value, minimum value and tolerance of film thickness, and stress fluctuation (N/20 mm) at 5% elongation and 10% elongation were measured.

Here, the purpose of the measurement is to evaluate the variation of the thickness for each component, but as described above, the stress variation (rigidity) significantly increases as the thickness increases. It was measured in order to grasp the thickness variation more accurately. Further, with respect to hardness and elastic modulus, numerical values peculiar to the substance can be obtained, and thus the hardness and the elastic modulus were measured to identify the sample.

The results are shown in Table 2. In each case, the hardness was 91 A and the elastic modulus was 29.0 MPa.

The hardness, elastic modulus, viscosity, film thickness indexes, and stress during elongation were measured as follows.

Hardness: Measured according to JIS K6253 using a durometer (spring type rubber hardness meter).

Elastic Modulus: Measured according to JIS K7244-4 in a 25° C. environment using a dynamic viscoelasticity measuring device “Q800” manufactured by TA Instruments Japan Co., Ltd.

Viscosity: Measured according to JIS Z7117-1 using "Viscometer BII viscometer" manufactured by Toki Sangyo Co., Ltd.

Film thickness: According to JIS Z1072, a film thickness measuring device “Dial Gauge 0.001 mm” manufactured by Ozaki Seisakusho Co., Ltd. was used to measure 30 points at random in the obtained 1 m×1 m film. Of these, the maximum thickness was the maximum value, the minimum thickness was the minimum value, the value obtained by dividing each measured value by 30 was the average value, and the difference between the maximum value and the minimum value was the tolerance.

Stress variation during elongation: Measured at 5 points randomly on the above-mentioned 1 m×1 m film using a precision universal testing machine “Autograph AG-500NX” manufactured by Shimadzu Corporation based on JIS K7127. , The difference between the maximum and minimum of these values was taken as the variation value. It can be said that the smaller the variation value, the more stable the sound quality can be provided and the better the acoustic characteristics.

As can be seen from Table 1 and Table 2, in the film of the present invention produced by controlling various conditions such as solid content and viscosity by the coating method, the tolerance is within 1 μm, and the thickness is extremely uniform and the thickness is uniform. I got that. In addition, the stress variation during extension is also suppressed to a minimum of approximately 0 at 5% extension, a minimum of approximately 0 even at 10% extension, and within 20% even at the maximum. It was found that when used as a material, it can provide stable sound quality and have stable acoustic characteristics.

On the other hand, in the case of the conventional film produced without controlling various conditions, the tolerance greatly exceeds 2 μm, and the stress variation at the time of extension is 0.05 N/20 mm or more at the time of 5% extension and 0.1 N at the time of 10% extension. /20 mm or more, the maximum fluctuation range was 20% or more in any extension, and it was found that stable sound quality was difficult to obtain.

Further, from these facts, it was found that it is necessary to make the thickness unevenness extremely small within 2 μm in order for the film to provide excellent acoustic characteristics.

Subsequently, as shown in Table 3, for a solution containing 10 to 50% by weight (solid content) of an ether type TPU having different hardness and elastic modulus, the viscosity and the coating film thickness are adjusted according to the set thickness, A film was produced in the same manner as the ester type TPU described above while keeping the various conditions during coating constant. The hardness and elastic modulus shown in Table 3 are estimated values after the production before the production.

With respect to each of the obtained films, hardness, elastic modulus, average value, maximum value, minimum value and tolerance of film thickness, and stress fluctuation (N/20 mm) at 5% elongation and 10% elongation were measured. The results are shown in Table 4. The measuring method of each index is the same as that of the ester type TPU described above.

As can be seen from Tables 3 and 4, even a film produced by using an ether type TPU can have a tolerance within 1 μm when produced by controlling various conditions such as solid content and viscosity by a coating method. Was given. In addition, the stress variation at the time of extension is 0.01 N/20 mm at the time of 5% extension, the minimum is 0.04 N/20 mm at the time of 10% extension, and in both cases, the variation range is suppressed to within 10% at the maximum. It was found that the characteristics were stable.

As a result, if various conditions such as solid content and viscosity are properly controlled by the coating method, even for different types of thermoplastic elastomers, a film with thickness unevenness of 2 μm or less can be formed to suppress stress fluctuation during stretching. It was found that a product having excellent acoustic characteristics was obtained.

2. Verification of storage elastic modulus In order to have good acoustic characteristics, it is required that the storage elastic modulus does not fluctuate in the living environment. Therefore, a film is prepared from a plurality of samples of ester type and ether type of TPU, and polyester by controlling the solid content and the viscosity as described above by the coating method, and the hardness and storage at 0 to 80° C. The change in elastic modulus with temperature was measured. The results are shown in Table 5 for the numerical values at 0° C., 25° C. and 80° C. and the fluctuation value which is the difference between the maximum value and the minimum value, the temperature change of the ester type of TPU is shown in FIG. The change is shown in FIG. 2, and the change in the temperature of polyester is shown in FIG. In addition, it was confirmed that the tolerances of the obtained films of these samples were all within 2 μm, and the variation of the stress during stretching was extremely small.

The hardness of the film produced from each sample was measured by the method described above, and the storage elastic modulus was measured in the same manner except that the measurement temperature was changed.

From the results shown in Table 5 and FIGS. 1 to 3, it was found that the films produced by any of the samples had little variation in storage elastic modulus due to temperature, and excellent acoustic characteristics were obtained. It was found that the lower the hardness of each type, the smaller the fluctuation of the storage elastic modulus.

Although the embodiments and examples of the present invention have been described in detail above, the functional film of the present invention is not limited to the above-mentioned embodiments, and may include any technical ideas assumed within the scope thereof. ..

INDUSTRIAL APPLICABILITY The present invention is applied to various applications in which precision of thickness is required and variation in stress during extension is small, in addition to use as a damping material such as a vibration system supporting member of a speaker Can be used.

Claims (5)

It is made of a thermoplastic elastomer, has a thickness of 10 to 100 μm, and has a tolerance of 2 μm or less.
Further, the functional film is characterized in that the variation width between the maximum value and the minimum value of both the stress at 5% elongation and the stress at 10% elongation measured according to JIS K7127 is within 20%, respectively. .. The functional film according to claim 1, wherein the solution contains 10 to 50% by weight of the thermoplastic elastomer. The functional film according to claim 1, wherein the thermoplastic elastomer is at least one of urethane type, polyester type, polyamide type, olefin type, and styrene type. The functional film according to claim 1, wherein the thermoplastic elastomer is a polyurethane elastomer (TPU). The functional film according to any one of claims 1 to 4, which is used for a vibration system supporting member of a speaker.

Images