JPH1031883A - Damping material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a damping material preventing the reduction of reading precision and the failure of a magnetic disk due to the vibration of a voice coil motor, restraining the generation of a noise, moreover having an excellent productivity and also capable of dissolving the problem of thickness precision by restraining the vibration of a voice coil motor in a magnetic disk device. SOLUTION: The damping material 12 is arranged between a magnet plate 9 and a housing 14 of a voice coil motor unit 3 in the magnetic disk device. The damping material 12 is formed with an elastomer provided with all the characteristics of (A)-(C). (A) The reduction of the noise level is >=2dB, (B) The stress at the time of 20% compression is 0.5-5Kg/cm<2> , and (C) The amount of generating gas is <=250ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping material used for a magnetic disk drive such as a hard disk drive and a magneto-optical disk drive.

[0002]

2. Description of the Related Art A magnetic disk drive for rotating a magnetic disk such as a hard disk drive or a magneto-optical disk drive generally has a configuration as shown in a plan view of FIG. 1 and a schematic view of FIG. That is, a transducer (not shown) is provided on the slider 6, and the slider 6 is connected to the actuator arm 4 via the suspension device 5.
Attached to. The actuator arm 4 can change the reading position on the magnetic disk 1 by reciprocating left and right by a voice coil motor (not shown) of the voice coil motor unit 3. In this case, vibration caused by the voice coil motor is generated, and the vibration is transmitted to the suspension device 5 via the actuator arm 4. Therefore, the suspension device 5 causes torsional vibration, and the reading accuracy is reduced. In the worst case,
There is a concern that the slider 6 collides with the magnetic disk 1 and the magnetic disk 1 is broken. Further, noise is generated by the vibration of the voice coil motor. In recent years, quietness of the magnetic disk drive has been strongly demanded. 1 and 2, 2 is a spindle motor, 7 is a flexible circuit, 8 is an IC, 9
Is a magnet plate, 10 is a voice coil, 11 is a device base, 13 is a magnet, 14 is a housing, 15 is a disk clamp, 16 is a spacer, and 17 is a screw hole.

In order to solve these problems, a method has been proposed in which a vibration damping material 12 made of a viscoelastic material such as an adhesive or a foam is provided between the voice coil motor and the housing 14. I have. That is, in the case of an adhesive, 10 to 20%
In the case of a foam, the thickness and hardness are adjusted in advance so as to be compressed by about 20 to 60%, and the vibration energy generated from the voice coil motor is converted into heat energy by the viscoelastic properties of these viscoelastic bodies. A method of suppressing the problem such as noise caused by the vibration of the voice coil motor by performing the conversion is adopted.

[0004]

The magnetic disk is easily corroded by corrosive gas, and since the inside of the magnetic disk device is in a sealed state, a small amount of generated gas may contaminate the magnetic disk. Therefore, it is necessary to minimize the amount of gas generated, particularly in a sealed magnetic disk device. However, when silicone is contained in the above-mentioned pressure-sensitive adhesive or foam material, volatile components in the silicone are deposited on the magnetic disk 1,
Since the contact resistance between the magnetic disk 1 and the slider 6 changes, there is a disadvantage that the magnetic disk 1 is broken. In addition, the internal temperature of the magnetic disk drive becomes a high temperature of about 60 to 80 ° C. due to heat generated by the rotation of the spindle motor 2, so that when the above-mentioned polymer material such as volatile silicone is used, gas is generated. It is an easy environment. Further, since the foam is usually used a foaming agent for the purpose of foaming during production, even when using a foam as the viscoelastic body, similarly to the case of using the pressure-sensitive adhesive, it is caused by the foaming agent The amount of generated gas becomes a problem.

[0005] In addition, when an adhesive is used as the viscoelastic body, there are restrictions on the coating speed, the amount of generated gas, and the like.
Usually, only those having a thickness of 0.2 mm or less can be manufactured. Therefore, in order to obtain a thickness of 2 to 5 mm required to be compressed by about 10 to 20% when being disposed between the voice coil motor and the housing 14, the pressure-sensitive adhesive (0.2 mm in thickness) is required. It is necessary to bond about 10 to 25 sheets of the following. Therefore, there is a disadvantage that productivity is inferior, and thickness accuracy is poor because many pieces are bonded.

The present invention has been made in view of such circumstances, and suppresses the vibration of the voice coil motor of the magnetic disk drive, thereby reducing the reading accuracy and destroying the magnetic disk due to the vibration of the voice coil motor. It is an object of the present invention to provide a vibration damping material which prevents noise, suppresses noise generation, is excellent in productivity, and can solve the problem of thickness accuracy.

[0007]

In order to achieve the above object, a vibration damping material according to the present invention comprises a vibration damper disposed between a voice coil motor of a magnetic disk drive and a housing for housing the same. Wherein the vibration damping material comprises the following (A) to (C)
Is formed of an elastomer having all the characteristics described above. (A) Noise level reduction is 2 dB or more. (B) Stress at the time of 20% compression is 0.5 to 5 kg / cm ² . (C) The amount of generated gas is 250 ppm or less.

That is, the present inventors have conducted intensive studies for the purpose of searching for a vibration damping material capable of solving the above-mentioned problems. As a result, if the elastomer having all of the above characteristics (A) to (C) is disposed between the voice coil motor of the magnetic disk device and the housing for housing the same, the voice coil of the magnetic disk device can be obtained. The vibration of the motor can be suppressed, and the deterioration of the reading accuracy and the destruction of the magnetic disk due to the vibration of the voice coil motor can be prevented.
The present inventors have found that generation of noise can be suppressed, and have reached the present invention. Furthermore, since the specific elastomer can be easily obtained to a predetermined thickness by, for example, being put into a mold and being subjected to press working or the like, complicated work such as laminating a plurality of sheets as in a conventional adhesive is required. The process becomes unnecessary. Therefore, it has been found that the productivity is excellent and the problem of thickness accuracy can be solved.

[0009]

Next, an embodiment of the present invention will be described in detail.

As shown in the schematic view of FIG. 2, the vibration damping material of the present invention is disposed between the magnet plate 9 of the voice coil motor unit 3 and the housing 14 by, for example, sticking. Examples of the disposing method include a method of sticking due to the viscosity of the elastomer, a method of providing an adhesive layer on at least one surface of the elastomer, and sticking to at least one of the magnet plate 9 and the housing 14. Can be

The special elastomer forming the vibration damping material of the present invention must have all of the above-mentioned characteristics (A) to (C). Specifically, the special elastomer needs to have a noise level reduction of 2 dB or more. That is, if the reduction of the noise level is less than 2 dB, sufficient vibration suppression characteristics for suppressing the vibration of the voice coil motor cannot be obtained, and sufficient quietness cannot be obtained. The measurement of the noise level reduction follows the method described in ISO 7779. Then, a difference in noise level between a case where the damping material of the present invention is not used and a case where the damping material is used is measured.

Further, the above-mentioned special elastomer contains 20%
The stress at the time of compression needs to be 0.5 to 5 kg / cm ² , and preferably 1 to 3 kg / cm ² . That is, if the stress at the time of 20% compression is less than 0.5 kg / cm ² , the adhesion between the voice coil motor or the housing and the elastomer is reduced, and sufficient vibration damping characteristics cannot be obtained. If the weight exceeds 5 kg / cm ² , the casing, which is usually a processed aluminum product, may not be closed or may be deformed. For the measurement of the stress at the time of 20% compression, first, a sample was cut into a size of 15 mm × 15 mm, a compression test jig was attached to a universal tensile tester, and the sample was set in the compression test jig. ,
The sample is compressed at a speed of 5 mm / min until the thickness of the sample becomes 20%, and the stress at that time is measured. The measurement was performed at 25 ° C.
Perform at × 60% RH.

Further, the above-mentioned special elastomer needs to have an amount of generated gas of 250 ppm or less. That is, if the amount of generated gas exceeds 250 ppm, it causes corrosion and destruction of the magnetic disk. In addition,
The amount of generated gas was measured by placing about 1.5 g of a sample in a 10 ml bottle, heating at 85 ° C for 24 hours, and analyzing the generated gas by gas chroma-mass spectroscopy using the static headspace method using a headspace sampler. I do.
The amount of generated gas is calculated as the weight of generated gas with respect to the weight of the sample.

Such elastomers include isoprene rubber, butadiene rubber, styrene butadiene rubber,
Styrene butadiene styrene rubber, acrylonitrile-
Butadiene rubber, butyl rubber, acrylic rubber, fluorine rubber and the like are preferred.

Further, various additives can be added to the above elastomer as needed within a range satisfying all the characteristics (A) to (C) of the present invention. Examples of the additive include materials commonly used for rubber materials. Specific examples include a vulcanizing agent, a crosslinking agent, a vulcanization accelerator, an antioxidant, an ultraviolet absorber, a tackifier, and a plasticizer. And fillers. In addition, instead of the vulcanizing agent and the crosslinking agent, radiation crosslinking using an electron beam or γ-ray or ultraviolet crosslinking may be used. These may be used alone or in combination of two or more.

Examples of the vulcanizing agent include sulfur compounds such as sulfur and sulfur chloride, and inorganic vulcanizing agents such as selenium and tellurium.

Examples of the crosslinking agent include oximes such as p-quinone dioxime and p, p'-dibenzoylquinone dioxime, nitroso compounds such as poly-p-dinitrosobenzene, hexamethylenediamine carbamate, N, N ′
Polyamines such as -disinnamylidene-1,6-hexanediamine; organic peroxides such as cumene hydroperoxide and benzoyl peroxide; resin vulcanizing agents such as alkylphenol formaldehyde resins; and others such as ammonium benzoate and ammonium adipate.

Examples of the vulcanization accelerator include guanidine compounds such as diphenylguanidine, aldehyde-amine compounds such as n-butyraldehyde-aniline condensate, aldehyde-ammonia compounds such as acetaldehyde ammonia, 2-mercaptobenzothiazole, and dibenzothia. Examples thereof include thiazoles such as zirdisulfide, sulfenamides, tyriums such as tetramethyltyrium monosulfide, and dithiocarbamates such as sodium dimethyldithiocarbamate.

The antioxidants include naphthylamine, diphenylamine, p-phenylenediamine,
Quinoline, hydroquinone derivatives, mono, bis, tri,
Examples thereof include polyphenols, thiobisphenols, hindered phenols, and phosphites.

Examples of the ultraviolet absorber include salicylic acid derivatives, benzophenones and benzotriazoles.

As the tackifier, coumarone resin,
Phenol, terpene resin, petroleum hydrocarbon resin, rosin derivative, turpentine tackifier and the like.

Examples of the plasticizer include phthalic acid derivatives and adipic acid derivatives.

Examples of the filler include calcium carbonate, clay, talc and the like.

The above elastomer may be used as it is, as long as it has sufficient adhesiveness to itself, but if the adhesiveness is insufficient, an adhesive may be applied to one or both sides of the elastomer. You may attach and use. As the adhesive, a material which imparts a sufficient adhesive force to both the elastomer and the adherend and satisfies the condition that the total amount of generated gas combined with the elastomer satisfies the condition of 250 ppm or less.
A commonly used adhesive such as rubber or acrylic can be used.

The thickness of the vibration damping material formed from the specific elastomer is determined by the number of rotations and the size of the voice coil motor,
The distance is appropriately set depending on the size of the magnetic disk device and the like, but is usually 0.5 to 5 mm.

The vibration damping material of the present invention can be manufactured, for example, as follows. That is, a crosslinking agent such as ammonium benzoate and other additives are added to the specific elastomer such as acrylic rubber, and the mixture is kneaded. Next, this is put into a predetermined mold, and the temperature is set to 100 to 190.
By performing press working at a temperature of 5 ° C. and a pressure of 5 to 35 kg / cm ² for 5 to 60 minutes, a desired vibration damping material having a predetermined thickness can be produced.

The damping material can also be produced by kneading and pressing the elastomer in the same manner as described above, and then irradiating with radiation to crosslink. The radiation dose can be set according to the type of radiation and the like. For example, in the case of an electron beam, it can be set to 30 to 150 KGy.

As described above, according to the present invention, complicated work steps such as laminating a plurality of sheets as in the case of a conventional pressure-sensitive adhesive are not required, so that productivity is excellent and the problem of thickness accuracy is solved. Can be.

Next, examples will be described together with comparative examples.

[0030]

EXAMPLES To 100 parts by weight (hereinafter abbreviated as "parts") of an acrylic rubber, 1.5 parts of ammonium benzoate as a crosslinking agent was added and kneaded. Next, this was put into a mold, and the temperature was 170 ° C. and the pressure was 15 kg / cm ² ,
Pressing was performed for 0 minutes to produce a vibration damping material having a thickness of 4 mm.

[0031]

Comparative Example 1 90 parts of 2-ethylhexyl acrylate monomer and 10 parts of acrylic acid monomer were mixed, 1 part of azobisisobutyronitrile was added as a polymerization initiator, and polymerization was carried out in an ethyl acetate solvent. A product obtained by adding 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane as a crosslinking agent to the obtained polymer is coated on a polyester separator and heated at 130 ° C. for 3 minutes to give a thickness of 0. A 1 mm-thick baseless adhesive sheet was obtained. Next, this adhesive sheet was laminated with a laminator for 40 layers,
A vibration damping material having a thickness of 4 mm was produced.

[0032]

Comparative Example 2 A 170 μm-thick double-sided acrylic nonwoven fabric tape was attached to both sides of a 4 mm-thick polyethylene foam to prepare a foam-based pressure-sensitive adhesive sheet.

Using the thus obtained examples and comparative examples, the noise level was reduced, the stress during compression, and the amount of generated gas were measured and evaluated in accordance with the method described above. The results are shown in Table 1 below together with the evaluation of productivity. In the productivity items, ○ indicates that the productivity is excellent, and X indicates that the productivity is poor.

[0034]

[Table 1]

As is clear from the results shown in Table 1, it was confirmed that the products of Examples were excellent in all aspects of reduction in noise level, stress during compression, and amount of generated gas.
In addition, since a predetermined thickness can be easily obtained by performing a press process or the like in a mold, the productivity is excellent and the problem of thickness accuracy can be solved.

On the other hand, the product of Comparative Example 1 exhibited substantially the same characteristics as those of the product of the example with respect to the reduction of the noise level and the stress at the time of compression. It was confirmed that. In addition, since it is necessary to bond a 0.1 mm-thick baseless pressure-sensitive adhesive sheet with a laminator to form a 4 mm-thick vibration damping material, productivity is poor and there is a problem of thickness accuracy. Further, it was confirmed that the product of Comparative Example 2 had a small reduction in noise level and an extremely large amount of generated gas.

[0037]

As described above, the vibration damping material of the present invention is a vibration damping material provided between a voice coil motor of a magnetic disk drive and a housing for housing the same. The vibration material is formed of an elastomer having all of the above-mentioned characteristics (A) to (C). Therefore, the vibration of the voice coil motor of the magnetic disk device can be suppressed, and it is possible to prevent the reading accuracy from being lowered and the magnetic disk from being damaged due to the vibration of the voice coil motor, and to suppress the generation of noise. Furthermore, since the specific elastomer can be easily obtained to a predetermined thickness by, for example, being put into a mold and being subjected to press working or the like, complicated work such as laminating a plurality of sheets as in a conventional adhesive is required. The process becomes unnecessary. Therefore, it is possible to excel in productivity and to solve the problem of thickness accuracy.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a magnetic disk drive.

FIG. 2 is a schematic diagram illustrating an example of a magnetic disk drive.

[Explanation of symbols]

 3 Voice coil motor unit 9 Magnet plate 12 Damping material 14 Housing

Continued on the front page (72) Inventor Hitoshi Matsuoka 1-2-1, Shimozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Keisaku Okada 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko stock In company

Claims (1)

[Claims] 1. A vibration damping material provided between a voice coil motor of a magnetic disk drive and a housing for housing the voice coil motor, wherein the vibration damping material comprises the following (A) to (C): A vibration damping material characterized by being formed of an elastomer having all of the above characteristics. (A) Noise level reduction is 2 dB or more. (B) Stress at the time of 20% compression is 0.5 to 5 kg / cm ² . (C) The amount of generated gas is 250 ppm or less.