JP6994064B2 - Functional film - Google Patents

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 materials that require acoustic characteristics such as a vibration system support member of a speaker (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2004-269756 Japanese Unexamined Patent Publication No. 2001-59057

In order to improve the sound quality of the speaker in the above-mentioned damping material application, it is required to minimize the thickness unevenness of the functional film used and 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 it is possible to provide stable sound quality. It was difficult.

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

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

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

< 1 > A solution having a polyurethane elastomer (TPU) concentration of 10 to 25 % by weight, a temperature of 10 to 40 ° C., and a viscosity of 100 to 50,000 mPa · s is coated with an uneven thickness of 8 μm or less to obtain a thickness. Is 10 to 100 μm, and the tolerance is within 2 μm.
Moreover, the difference between the maximum value and the minimum value of both the stress at 5% elongation and the stress at 10% elongation (however, the unit is "N / 20 mm") measured based on JIS K7127 is different. It is a functional film characterized by being within 20% of the minimum value.

< 2 > The functional film according to <1 > used for a vibration system support 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 extremely little thickness unevenness.

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

FIG. 1 is a graph showing the change in temperature of the storage elastic modulus at 0 to 80 ° C. when the hardness of the ester-type polyurethane film of the present invention is different. FIG. 2 is a graph showing the change in temperature of the storage elastic modulus at 0 to 80 ° C. when the hardness of the ether type polyurethane film of the present invention is different. FIG. 3 is a graph showing the change in temperature of the storage elastic modulus at 0 to 80 ° C. when the hardness of the polyester film of the present invention is different.

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

In this way, by keeping the tolerance within 2 μm, the stress when the film is stretched can be suppressed so that the fluctuation is extremely small, and the sound quality of the speaker is extremely good when used as a damping material. It becomes possible to do. In other words, if the tolerance exceeds 2 μm, it becomes difficult to suppress the fluctuation of stress within this range, and it becomes impossible to provide a sufficiently good sound quality to the speaker.

If the thickness is less than 10 μm, it becomes difficult to apply it in a desired application, while if it exceeds 100 μm, it becomes difficult to manufacture it, and in terms of cost, there is no point in making it thicker, 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 is calculated by randomly measuring 30 points in the obtained 1 m × 1 m film. Adopt the average value. 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 points at random 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 the index is generally expressed by elastic modulus, but the rigidity changes as the film becomes thicker, so the above-mentioned Stability of stress during elongation is required. If this stress during elongation is stable, the storage elastic modulus at a temperature that can be expected in a living environment of 0 to 80 ° C. is also stable, and good sound quality is provided, that is, excellent acoustic characteristics are obtained.

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

The thermoplastic elastomer of the functional film of the present invention is produced by a coating method. Thermoplastic elastomers can also be produced by the extrusion method, but in the extrusion method, solid powders or pellets are softened and melted in a heating cylinder and extruded into a mold with a slit with a screw to form the elastomer. These have a large molecular weight and a large variation in viscosity at the time of melting. This variation in viscosity causes uneven thickness during molding, and it is difficult to obtain a film having a uniform thickness. In other words, since the extrusion method uses only solids such as powder and pellets, the only way to control the film thickness is to improve the film thickness accuracy, and to produce a film of uniform thickness, It is extremely difficult because it is necessary to improve the accuracy considerably.

On the other hand, the coating method is a manufacturing method in which a solution is applied with a constant weight (thickness) and the solvent in the solution is volatilized to use a film containing only a solute. However, by adjusting the solid content concentration and the solution viscosity, it is possible to reduce the thickness unevenness.

However, if it is produced by the coating method, the thickness unevenness cannot always be kept within the desired range of the present invention, and after repeated trial and error by the present inventor regarding the conditions, the following conditions are appropriate. I found out. That is, the solid content and coating thickness of the thermoplastic elastomer in the solution containing the thermoplastic elastomer are kept constant, the temperature of the solution is kept constant in the range of 10 to 40 ° C., and the viscosity is kept constant in 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 becomes difficult to impart appearance quality such as unevenness in 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. Will be.

Similarly, when the viscosity is less than 100 mPa · s, it becomes difficult to maintain the appearance quality of the film, and when 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 will change and the thickness unevenness may not be controlled within the desired range. Therefore, the temperature should be within the above temperature range that can be assumed as normal 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 equipment used, and the specific range cannot be determined. In a solution containing 25% by weight of a thermoplastic elastomer, if the thickness unevenness of the coating thickness is 8 μm, the thickness unevenness (tolerance) of the film can be 2 μm, which is within the range of the present invention, and therefore 10 to 30% by weight. Those having a small mass in the range are preferable.

The hydraulic pressure of the solution must be kept constant in order to apply a constant amount of the solution in order to make the thickness of the obtained film uniform. Then, it is possible by keeping the supply amount of the liquid constant.

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

Since the coating amount (thickness) is also determined by the width of the gap, for example, the gap between the backup roll and the knife roll in the roll knife coater, the thickness of the film-formed film is measured to measure the thickness of the film of the present invention. After confirming that it is within the desired range, the coating thickness in the form of a solution during coating is measured, and the coating thickness is adjusted to a set constant coating thickness.

The coater used for coating is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a gravure coater, a reverse roll coater, a kiss coater, a roll knife coater, and a die coater. Among them, 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 is made constant, and in the case of a die coater, the gap between the die mouth and the internal pressure of the die are made constant, so that the coating thickness can be made uniform.

As the solution containing the thermoplastic elastomer, either a solution produced by a solution polymerization method or a solution in which a solid resin produced by bulk polymerization is dissolved in a solvent may be used.

The resin produced by this bulk polymerization is prepared by using a solvent in which a thermoplastic elastomer such as toluene, N, N-dimethylformamide (DMF), methylethylketone (MEK), dimethylacetamide (DMAc), or ethyl acetate is dissolved. Can be obtained.

The thermoplastic elastomer is not particularly limited, and generally known ones can be appropriately selected and used according to the purpose. For example, 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 a property that the change in storage elastic modulus at 0 to 80 ° C. is small are preferable.

As the urethane-based material, for example, a urethane-based polyurethane elastomer (TPU) is preferably used. Among the types of polyols used in the polymerization of TPU, the ester types include, for example, polyethylene adipate (PEA), polybutylene adipate (PBA), polyhexamethylene adipate (PHA), poly3-methylpentane adipate (PMPA). , Polycaprolactone (PCL) and the like. Examples of the ether type include polyols such as polyethylene glycol (PEG), polyproprene glycol (PPG), and polytetramethylene ether glycol (PTMG).

As a 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 of commonly known resins, such as a polyester ester type using polybutylene terephthalate (PBT) for the hard segment and polybutylene adipate (PBA) for the soft segment, can be used.

Examples of the olefin type include a hard segment mixed with an olefin resin such as polyethylene (PE) and polypropylene (PP), and a soft segment mixed with rubber such as ethylene propylene rubber (EPM) and ethylene propylene diene rubber (EPDM). Any of the commonly known resins can 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), and styrene block copolymer (Styrene block copolymer). Any commonly known resin such as SBC) can be used alone or in combination of two or more.

As a polyamide system, for example
Polyether ester type using nylon 6, nylon 11, nylon 12 for the hard segment, polyethylene glycol (PEG), polyproprene glycol (PPG), polytetramethylene ether glycol (PTMG), etc. for the soft segment,
One or a combination of two or more of commonly known resins such as a polyether amide type using polypropylene diamine, polybutylenediamine, etc. in the soft segment can be used.

Further, in the functional film of the present invention, in addition to the above-mentioned thermoplastic elastomer, commonly used additives such as a colorant, a lubricant, an antioxidant, an antistatic agent, etc. are appropriately used depending on the purpose. You may. Further, as this additive, a masterbatch 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. There is no particular limitation on the method of forming a multi-layer structure, and the multi-layer structure may be formed by using a generally known laminating method or the like.

Since the functional film of the present invention has excellent acoustic characteristics and can provide good sound quality, it is not only suitably used for vibration damping materials such as vibration system support members of speakers, but also, for example, acoustic vibration. 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 applications such as the field of precision equipment in general, where thickness accuracy is required and fluctuation of stress during elongation is required to be small.

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

1. 1. Relationship between film thickness and tensile stress Using a solution containing 20.0% by weight of ester-type polyurethane thermoplastic elastomer (TPU), 40% by weight of N-dimethylformamide (DMF), and 40% by weight of methyl ethyl ketone (MEK). The TPU film to be produced is set to have a thickness of 15.0 μm, 17.0 μm, 19.0 μm, and 21.0 μm, respectively, with a viscosity of 5,000.0 mPa · s and a solution temperature of 23.0 ° C. While keeping it constant, it was made into a film using a die coater. At this time, films were produced while keeping the coating film thickness constant at 72.0 μm, 80.0 μm, 94.0 μm, and 100.0 μm in order from the one with the thinnest set thickness (see Table 1 above). Further, the film was produced while keeping the liquid pressure constant by keeping the liquid amount of the solution supplied from the die coater constant.

On the other hand, for the same TPU sample, the thickness is set to 17.0 μm and 19.0 μm, respectively, and a die coater is used, but control for keeping the solid content, solution temperature, coating film thickness, etc. constant is controlled. Instead, a film was made.

For each of the obtained films, the hardness, elastic modulus, average value of film thickness, maximum value, minimum value and tolerance, 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 in thickness for each component, but as described above, the stress fluctuation (rigidity) also increases remarkably as the thickness increases, so that the stress fluctuation during elongation is It was measured in order to grasp the variation in thickness more accurately. In addition, since the values peculiar to the substance can be obtained for the hardness and elastic modulus, they were measured for identification of the sample.

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

Each index of hardness, elastic modulus, viscosity and film thickness, and stress during elongation were measured as follows.

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

Elastic modulus: Measured according to JIS K7424-4 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 a "Viscometer BII type viscometer" manufactured by Toki Sangyo Co., Ltd.

Film thickness: Using a film thickness measuring instrument "Dial Gauge 0.001 mm" manufactured by Ozaki Seisakusho Co., Ltd., 30 points were randomly measured in the obtained 1 m × 1 m film according to JIS Z1072. Of these, the maximum thickness was defined as the maximum value, the minimum thickness was defined as the minimum value, the value obtained by dividing each measured value by 30 was defined as the average value, and the difference between the maximum value and the minimum value was defined as the tolerance.

Stress fluctuation during elongation: Measured at 5 random points on the above 1m x 1m film based on JIS K7127 using the precision universal testing machine "Autograph AG-500NX" manufactured by Shimadzu Corporation. , The difference between the maximum value and the minimum value of those values was taken as the variable value. It can be said that the smaller this fluctuation value is, the more stable sound quality can be provided and the better the acoustic characteristics are.

As can be seen from Tables 1 and 2, the film of the present invention produced by controlling various conditions such as solid content and viscosity by a coating method has a tolerance of 1 μm or less and a uniform thickness with extremely little thickness unevenness. Was obtained. In addition, the stress fluctuation during elongation is also suppressed to a minimum of approximately 0 at 5% elongation, a minimum of approximately 0 at 10% elongation, and within a maximum of 20% at maximum, and vibration control of speakers and the like. It was found that when used as a material, stable sound quality can be provided and the acoustic characteristics are stable.

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

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

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

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

As can be seen from Tables 3 and 4, even if the film is made using ether type TPU, the tolerance is suppressed to within 1 μm when it is made by controlling various conditions such as solid content and viscosity by the coating method. Was done. In addition, the stress fluctuation during elongation is also suppressed to a minimum of 0.01 N / 20 mm at 5% elongation and a minimum of 0.04 N / 20 mm at 10% elongation. It was found that the characteristics were stable.

As a result, if various conditions such as solid content and viscosity are appropriately controlled by the coating method, the film can have a thickness unevenness of 2 μm or less even if it is a different type of thermoplastic elastomer, and stress fluctuation during elongation can be suppressed. It was found that a product with excellent acoustic characteristics can be obtained.

2. 2. Verification of storage elastic modulus In order to say that the acoustic characteristics are good, it is required that there is little fluctuation in the storage elastic modulus in the living environment. Therefore, a film was prepared from the ester type and ether type of TPU, and a plurality of samples of polyester by controlling the solid content, viscosity, etc. as described above by a coating method, and the hardness and storage at 0 to 80 ° C. The change in elastic modulus over temperature was measured. The results are shown in Table 5 for the fluctuation value, which is the difference between the numerical value and the maximum value and the minimum value at 0 ° C, 25 ° C, and 80 ° C, in FIG. 1 for the change in temperature of the ester type of TPU, and the temperature of the ether type. The changes are shown in FIG. 2, and the changes in the temperature of the polyester are shown in FIG. It was confirmed that the tolerances of the obtained films of these samples were all within 2 μm, and the fluctuation of stress during elongation was extremely small.

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

From the results of Table 5 and FIGS. 1 to 3, it was found that the film made of any of the samples had little fluctuation in the storage elastic modulus due to the temperature, and excellent acoustic characteristics could be obtained. In each type, it was found that the lower the hardness, 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-described embodiments, and may include any technical ideas assumed within the scope of the embodiments. ..

INDUSTRIAL APPLICABILITY The present invention is used not only for vibration damping materials such as vibration system support members of speakers, but also for various applications such as the field of precision equipment in general, where thickness accuracy is required and fluctuation of stress during elongation is required to be small. Can be used.

Claims (2)

A solution having a polyurethane elastomer (TPU) concentration of 10 to 25 % by weight, a temperature of 10 to 40 ° C., and a viscosity of 100 to 50,000 mPa · s is applied with a thickness unevenness of 8 μm or less, and the thickness is 10 to 10 to. It is 100 μm and its tolerance is within 2 μm.
Moreover, the difference between the maximum value and the minimum value of both the stress at 5% elongation and the stress at 10% elongation (however, the unit is "N / 20 mm") measured based on JIS K7127 is different. A functional film characterized by being within 20% of the minimum value. The functional film according to claim 1, which is used for a vibration system support member of a speaker.

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