Pressure-sensitive adhesive sheet and magnetic disc device
Provided is a PSA sheet that has a high level of moisture resistance while maintaining good holding power with reduced gas emission. The PSA sheet provided by this invention comprises a moisture-impermeable layer and a PSA layer provided to one face of the moisture-impermeable layer. The PSA layer comprises a polymer A having a weight average molecular weight of 5×10 4 or higher as a base polymer and a polymer B having a number average molecular weight of 1000 or higher and a weight average molecular weight lower than 5×10 4 .
1. A magnetic disc device comprising
at least one data-recording magnetic disc,
a motor that rotates the magnetic disc,
a magnetic head that at least either reads or writes data on the magnetic disc,
an actuator that moves the magnetic head, and
a housing that houses the magnetic disc, the motor, the magnetic head and the actuator; wherein
the housing is provided with a cover seal,
the cover seal is a pressure-sensitive adhesive sheet comprising:
a moisture-impermeable layer; and
a pressure-sensitive adhesive layer provided to one face of the moisture-impermeable layer, wherein the pressure-sensitive adhesive layer comprises:
a polymer A having a weight average molecular weight of 5×10 4 or higher and 300×10 4 or lower as a base polymer; and
a polymer B having a number average molecular weight of 1000 or higher and a weight average molecular weight lower than 5×10 4 , and
the cover seal has an amount of thermally release gas of 10 μg/cm 2 or less, determined at 130° C. for 30 minutes by gas chromatography/mass spectrometry.
2. The magnetic disc device according to claim 1 , wherein the housing comprises a box-shaped housing base member having a top opening and a cover member to cover the opening.
3. The magnetic disc device according to claim 2 , wherein the housing base member has a recessed portion inner-circumferentially around the top opening and the cover member has an outer rim placed on the bottom of the recessed portion.
4. The magnetic disc device according to claim 1 , wherein the cover member has a hole.
5. The magnetic disc device according to claim 1 , wherein the pressure-sensitive adhesive sheet seals the internal space of the magnetic disc device.
6. The magnetic disc device according to claim 1 , wherein the pressure-sensitive adhesive sheet covers and seals the top face of the housing base member of the magnetic disc device.
7. The magnetic disc device according to claim 1 , capable of heat-assisted magnetic recording.
8. A pressure-sensitive adhesive sheet comprising:
a moisture-impermeable layer; and
a pressure-sensitive adhesive layer provided to one face of the moisture-impermeable layer, wherein the pressure-sensitive adhesive layer comprises:
a polymer A having a weight average molecular weight of 5×10 4 or higher as a base polymer and 300×10 4 or lower; and
a polymer B having a number average molecular weight of 1000 or higher and a weight average molecular weight lower than 5×10 4 ,
wherein the pressure-sensitive adhesive sheet has an amount of thermally release gas of 10 μg/cm 2 or less, determined at 130° C. for 30 minutes by gas chromatography/mass spectrometry.
9. The pressure-sensitive adhesive sheet according to claim 8 , wherein the number average molecular weight of the polymer B is 2000 or higher.
10. The pressure-sensitive adhesive sheet according to claim 8 , wherein the polymer B is at least one species selected among olefinic polymers and diene-based polymers.
11. The pressure-sensitive adhesive sheet according to claim 8 , wherein the polymer B is a polybutene.
12. The pressure-sensitive adhesive sheet according to claim 8 , wherein the polymer A is at least one species selected among rubber-based polymers and acrylic polymers.
13. The pressure-sensitive adhesive sheet according to claim 8 , having a moisture permeability lower than 30 μg/cm 2 ·24 h in the in-plane direction of bonding area of pressure-sensitive adhesive sheet, determined at a permeation distance of 2.5 mm based on the MOCON method.
14. The pressure-sensitive adhesive sheet according to claim 8 , used for sealing the internal space of a magnetic disc device.
15. A release liner-supported pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive sheet according to claim 8 and a release liner protecting the adhesive face of the pressure-sensitive adhesive sheet, wherein the release liner is a non-silicone-based release liner free of a silicone-based release agent.
16. A magnetic disc device comprising the pressure-sensitive adhesive sheet according to claim 8 .
17. The magnetic disc device according to claim 16 , wherein the pressure-sensitive adhesive sheet seals the internal space of the magnetic disc device.
18. The magnetic disc device according to claim 16 , wherein the magnetic disc device has a housing base member and the pressure-sensitive adhesive sheet is a cover seal that covers and seals the top face of the housing base member.
19. The magnetic disc device according to claim 16 , capable of heat-assisted magnetic recording.