Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-08-04
2001-08-21
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C522S100000, C522S103000, C525S524000
Reexamination Certificate
active
06277930
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to an epoxy resin and, more particularly, to an epoxy resin used for cap seal of a hard disc spindle motor.
(ii) Description of the Prior Art
With the increase of storage capacity in recent years, track density and linear density of hard disc drives have increased as well. Clean spindle motors that do not influence writing or reading of media discs have been sought for use with hard disc drive. For example, when a gas is evolved from constituent members of the spindle motor, the gas accumulates on a contact between a recording head and a recording media to cause a read error. Therefore, members with low outgassing potential have been sought as the respective members constituting the spindle motor.
The rotational speed of the hard disc drive has gradually become higher so as to improve the writing and reading rates of data. More specifically hard disc drives with rotational speeds of 5400 rpm has been replaced by those with rotational speeds of 7200 rpm, and further 10000 rpm. Accordingly, clean members constituting the spindle motor causing no change in chemical and physical properties at high rotational speed have been particularly sought.
FIG. 1
shows a typical construction (plan view) of a hard disc drive, which is composed of a spindle motor
10
, a media disc
11
mounted to the spindle motor, a head
12
for writing and reading information on the media disc, an actuator arm
13
for supporting the head, a pivot
14
serving as a rotating shaft of the actuator arm, and a voice coil motor
15
for moving the actuator arm.
FIG. 2
is a schematic view of the spindle motor in which a portion is cut away to show a sectional view. The spindle motor
10
comprises a stator
30
as a fixed portion and a rotor
20
as a rotating portion. The stator
30
comprises a base
31
, a shaft
32
and a stator coil
33
, while the rotor
20
comprises a hub
21
mounted rotatably to the shaft
32
through a bearing
22
, and a magnet
23
mounted to the hub, the magnet facing to the stator coil. In order to prevent powders, possibly produced by contact between the bearing and shaft, and bearing oil from directly scattering thereby to contaminate the media disc, a cap
26
is fixed on a top surface of the hub
21
to cover the bearing, using a cap sealant
27
. The media disc
11
, which is fixed to a fixture for mounting disc (not shown), is mounted to a flange surface
24
using a tap hole
25
for screwing.
As the cap sealant
27
, for example, two-pack epoxy resin adhesive, UV cationic epoxy resin adhesive and thermosetting epoxy resin adhesive are commonly used. However, the two-pack epoxy resin adhesive is inferior in workability because it takes a long time for mixing before use. The UV cationic epoxy resin adhesive is difficult to cure at the non-irradiated portion, leaving insufficiently cured adhesive. The fluidity of the thermosetting epoxy resin adhesive increases with the increase of the temperature at the beginning of the curing, resulting in poor workability.
Therefore, a one-pack type UV theremosetting epoxy resin composition comprising an epoxy resin, an epoxy resin curing agent, an acrylic monomer and a photopolymerization initiator has recently been used. Consequently, it is possible to satisfy both of the workability and seal strength by coating an uncured resin around a cap, fixing by irradiating the resin with light to obtain a certain strength, and properly curing by heating.
However, it has been found that an epoxy resin adhesive of a conventional composition is not satisfactory as a cap sealant of a spindle motor for high-speed rotation, where a cleaner environment is required due to the increase of the rotational speed, e.g. 5400 rpm, 7200 rpm and 10000 rpm, because outgassing of low molecular materials occurs frequently at these higher rotational speed. According to the present inventor's study, the epoxy resin is not sufficiently cured and the uncured component may leach from within by an influence of vibration due to high-speed rotation.
In light of these problems, it would be desirable to provide a epoxy resin composition that was completed and, portions of which do not leach from within the cured adhesive.
SUMMARY OF THE INVENTION
The present invention provides an epoxy resin composition for spindle motor cap seal, which minimize outgassing even when using in a hard disc drive operating at such high-speed of rotation, and has high reliability.
More specifically, the present invention is directed to an epoxy resin composition used for cap seal of a hard disc drive spindle motor, comprising an epoxy resin having at least one glycidyl group in a molecule as a component (A), a monomer having at least one unsaturated bond group in a molecule (polyfunctional vinyl monomer or monofunctional vinyl monomer) as a component (B), an epoxy resin curing agent as a component (C), a photopolymerization initiator as a component (D), and a partially-esterified unsaturated epoxy resin wherein 10-90% of an epoxy equivalent of a bisphenol type epoxy resin is (meth)acrylated as a component (E).
The invention also provides methods of sealing a cap seal for a hard disc drive motor.
The invention further provides reaction products of the inventive epoxy resin composition.
REFERENCES:
patent: 4568719 (1986-02-01), Tada et al.
patent: 5055378 (1991-10-01), Miyamura et al.
patent: 5439956 (1995-08-01), Nooguchi
patent: 5453973 (1995-09-01), Nishio
patent: 5596023 (1997-01-01), Tsubota et al.
patent: 5696652 (1997-12-01), Satoh
JP 1190779 (Derwent Abstract only), 7/89.
JP 5295087 (Derwent Abstract only), 11/93.
JP 8165459 (Derwent Abstract only), 6/96.
JP 61057909 (Derwent Abstract only), 3/86.
Bauman Steven C.
Loctite Corporation
Sellers Robert E. L.
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