Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
1998-10-15
2001-02-27
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S321000, C430S945000, C430S273100, C430S271100, C369S112040, C359S508000, C359S664000
Reexamination Certificate
active
06194129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a master optical disk, and more particularly to a method of manufacturing a master optical disk wherein high-density cutting is effected by using a solid immersion lens (SIL)
2. Description of the Related Art
Conventionally, a technique is known in which information is recorded on an optical disk by using a solid immersion lens (hereafter, referred to as the SIL).
Here, referring to
FIGS. 6A
to
6
C, a description will be given of the essential steps of the process for manufacturing a master optical disk.
(1) Step of Coating with a Photoresist (see
FIG. 6A
)
After a glass substrate
50
worked into a predetermined shape is coated with an organic primer such as hexamethyldisilazane (HMDS) so as to enhance adhesion to a photosensitive material (photoresist), the glass substrate
50
is spin-coated with a photoresist
51
, as shown in FIG.
6
A.
Then, a solvent in the photoresist
51
is allowed to evaporate, and the glass substrate
50
with the photoresist
51
coated thereon is prebaked by using a clean oven or the like so as to stabilize the film of the photoresist
51
.
(2) Exposure Step (see
FIG. 6B
)
A recording signal is supplied to a recording head of a cutting apparatus (not shown) from a external circuit (not shown), recording light is turned on and off by an optical modulator (not shown), and recording light L is introduced to an objective lens
52
, as shown in FIG.
7
.
At this time, the recording light L which is converged by the objective lens is made incident upon the spherical surface of an SIL
53
, and the recording light L is converged substantially on the center of a flat surface, i.e., an emergent surface, of the SIL
53
.
In this case, if it is assumed that a super spherical lens is used as the SIL
53
, an equivalent numerical aperture NA of the optical system using the SIL becomes
NA=n
2
×NA
where n is the refractive index of the SIL.
Accordingly, if the wavelength of the laser light is assumed to be &lgr;, the beam spot diameter L
BEAM
of the recording light is determined by
L
BEAM
=&lgr;/(n
2
×NA)
More specifically, the recording light L converged by the objective lens
52
is made incident upon the SIL
53
disposed spaced apart by a gap (see
FIG. 7
) from the surface of the photoresist
51
, is converged by the SIL
53
, and is applied to the photoresist
51
on the glass substrate
50
, thereby cutting (recording) information spirally.
At this time, the beam diameter at the emergent surface of the SIL
53
becomes &phgr;D1 as shown in the detailed explanatory diagram of
FIG. 8
, and becomes substantially equal to the beam diameter on the photoresist
51
if the gap is set to effect near-field recording, i.e., if the gap is set to a distance less than the ¼ wavelength of the recording light.
(3) Development Step (see
FIG. 6C
)
Next, as development process is effected, a master glass disk is formed in which recess-shaped pits are arranged spirally on its surface.
In the case where the above-described conventional cutting apparatus is used, since the SIL
53
effects near-field recording with respect to the photoresist
51
on the glass substrate
50
, the recording light L is converged (with a diameter of &phgr; D1) inside the SIL
53
. Hence, there has been a problem in that the power density in the vicinity of the emergent surface of the SIL
53
becomes high, resulting in the deterioration (so-called tarnish) of the SIL such as clouding.
In addition, dust which is present in the air even in a clean room is generally larger than the gap interval (10 [nm] to 100 [nm]) of the SIL. Hence, there has been a problem in that as the dust enters the gap portion due to static electricity and the like, the floating head is sprung up, making accurate writing impossible until the interval between the SIL and a protective film is restored to its original interval.
In addition, there has been another problem in that dust becomes attached to the substrate of the optical disk due to static electricity, and the SIL, the protective film, or the photoresist is defected by the attached dust.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a method of manufacturing a master optical disk which is capable of manufacturing a master optical disk which prevents the deterioration of the SIL and allows high-density recording to be effected.
To attain the above-described objects, according to a first aspect of the invention, there is provided a method of manufacturing a master optical disk by using an optical system having a solid immersion lens body so as to converge recording light on an optical disk substrate for cutting thereof. The method includes the steps of: coating an optical film on a photoresist applied to the optical disk substrate; exposing the photoresist through the optical film by using the optical system; and removing the optical film.
In accordance with the first aspect of the invention, in the optical-film coating step, the photoresist applied to the optical disk substrate is coated with the optical film for converging the recording light on the optical disk substrate in cooperation with the solid immersion lens body.
In the exposure step, the photoresist is exposed through the optical film by using the optical system in a state in which the solid immersion lens body is held by the floating head.
In the optical-film removing step, the optical film is removed.
According to a second aspect of the invention, in the first aspect of the invention, the photoresist is non-soluble to water, and the optical film is water soluble, and the optical-film removing step includes a washing step for washing the optical disk substrate having the photoresist and the optical film coated thereon with water.
In accordance with the second aspect of the invention, in addition to the effect derived from the first aspect of the invention, since the optical film is water soluble, in the washing step in the optical-film removing step, the optical disk substrate having the photoresist and the optical film coated thereon is washed.
According to a third aspect of the invention, in the first aspect of the invention, the optical film is formed of an electrically conductive material.
In accordance with the third aspect of the invention, in addition to the effect derived from the first aspect of the invention, since the optical film is formed of an electrically conductive material, it becomes difficult for dust to attach to the optical film due to static electricity.
According to a forth aspect of the invention, in the first aspect of the invention, the optical film includes an electrically conductive material.
In accordance with the forth aspect of invention, in addition to the effect derived from the first aspect of the invention, since the optical film includes an electrically conductive material, it becomes difficult for dust to attach to the optical film due to static electricity.
According to a fifth aspect of the invention, in the first aspect of the invention, the optical film includes an antistatic agent.
In accordance with the fifth aspect of the invention, in addition to the effect derived from the first aspect of the invention, since the optical film includes an antistatic agent, it becomes difficult for dust to attach to the optical film due to static electricity.
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Higuchi Takanobu
Kasono Osamu
Kuribayashi Hiroki
Angebranndt Martin
Pioneer Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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