Method of manufacturing optical disc master plate

Details Method of manufacturing optical disc master plate Method of manufacturing optical disc master plate

1999-01-14

2001-08-21

Angebranndt, Martin (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making named article

C430S321000, C430S945000, C430S271100, C430S273100, C369S112040, C351S177000, C351S177000

Reexamination Certificate

active

06277545

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing an optical disc master plate, particularly to a method of manufacturing an optical disc master plate employing a SIL (Solid Immersion Lens).
FIG. 7
is an explanatory view illustrating some important steps involved in a conventional method for manufacturing an optical disc master plate with the use of an SIL.
Referring to
FIG. 7
a,
a glass substrate
1
having a predetermined configuration is first coated with an organic Primer such as HMDS (Hexamethyl Di-silazane), and is then spin-coated with a photoresist material dissolved in a solvent, so as to form a predetermined photoresist layer
2
tightly adhered to the surface of the glass substrate
1
.
Subsequently, the solvent is removed by virtue of evaporation. Then, a clean oven is used to pre-bake the glass substrate
1
together with the photoresist layer
2
, thereby forming a stabilized photoresist layer
2
on the glass substrate
1
.
FIG. 8
illustrates a function of an optical system within a recording head. As shown in
FIG. 8
, a recording beam L modulated in accordance with the information to be recorded is directed so as to pass through an objective lens
5
. Thus, the recording beam L is converged, and is then collected on substantially the center of the emitting surface of the SIL
4
. If the SIL
4
is a super spherical lens, an equivalent NA (Numerical Aperture) of an optical system using the SIL
4
may be indicated by the following equation.
NA=n
2
×NA
Here, n is index of refraction of SIL
4
. Therefore, a diameter L of the beam spot of the recording beam may be represented in the following equation, where &lgr; is wavelength of the recording beam.
L
=&lgr;/(
n
2
×NA
)
Subsequently, in an exposure treatment shown in
FIG. 7
b,
a small interval (having a width which is {fraction (1/10)}-¼ of the wavelength &lgr; of the recording beam) is formed between the SIL
4
and the photoresist layer
2
, by virtue of a flying head
3
and an air flow induced by the rotation of the master disc plate. When a light beam exiting from the SIL
4
has a diameter D
1
(
FIG. 9
) and the above small interval is less than ¼ of the wavelength &lgr; of the recording beam, a beam spot on the photoresist layer
2
will also has a diameter of D
1
.
In this way, recording beam L converged by an objective lens
5
is further converged by SIL
4
, and is caused to irradiate the photoresist layer
2
on the glass substrate
1
, so that information may be recorded by cutting pits spirally thereon.
After that, referring to
FIG. 7
c,
a developing process is conducted, thereby obtaining an optical disc master plate on which a plurality of pits are formed in a spiral array.
However, when employing a pit cutting device using the SIL
4
, since the SIL
4
serves to perform a near field recording (near the photoresist layer
2
), it is necessary that the interval between the light exiting surface of the SIL
4
and the photoresist layer
2
of the glass substrate
1
be constantly kept at a width which is ¼ of the wavelength &lgr; of the recording beam.
In this manner, once the photoresist layer
2
of the glass substrate
1
bears a static electricity, a force caused due to such static electricity will act between the SIL
4
and the photoresist layer
2
. As a result, it is difficult to stably keep the above interval between the light exiting surface of the SIL
4
and the photoresist layer
2
of the glass substrate
1
. Moreover, dust or small rubbish will adhere to the photoresist layer
2
, causing a collision between the SIL
4
and the dust or small rubbish attached on the photoresist layer
2
, making it difficult or even impossible to perform a predetermined information recording.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved method for manufacturing an optical disc master plate having antistatic property and a high recording density, so as to solve the above-mentioned problems peculiar to the above-mentioned prior arts.
According to the present invention, there is provided a method of manufacturing an optical disc master plate, comprising the steps of: forming a photoresist layer having an electrically conductivity on a substrate; and irradiating the photoresist layer with a laser beam, using an optical system capable of holding a solid immersion lens on a flying head.
In one aspect of the present invention, the photoresist layer is formed by a photoresist material containing an electrically conductive material or an antistatic agent.
In another aspect of the present invention, a method of manufacturing an optical disc master plate, comprises the steps of: forming a photoresist layer having an electrically conductivity on a substrate; coating the photoresist layer with an electrically conductive material or an antistatic agent; and irradiating the photoresist layer with a laser beam, using an optical system capable of holding a solid immersion lens on a flying head.
In a further aspect of the present invention, a method of manufacturing an optical disc master plate, comprises the steps of: forming a photoresist layer on a substrate; forming on the photoresist layer a photobleachable dye layer having a predetermined electrical conductivity; irradiating the photoresist layer with a laser beam, using an optical system capable of holding a solid immersion lens on a flying head.
In a still further aspect of the present invention, the photobleachable dye layer is formed by a photobleachable material containing an electrically conductive material or an antistatic agent.
In one more aspect of the present invention, the photobleachable material layer has a volume inherent resistance which is less than 10 &OHgr;cm.
In still one more aspect of the present invention, a method of manufacturing an optical disc master plate, comprises the steps of: forming a photoresist layer on a substrate; forming a photobleachable dye layer on the photoresist layer; coating the photobleachable dye layer with an electrically conductive material or an antistatic agent; and irradiating the photoresist layer with a laser beam, using an optical system capable of holding a solid immersion lens on a flying head.
The above objects and features of the present invention will become better understood from the following description with reference to the accompanying drawings.


REFERENCES:
patent: 4150398 (1979-04-01), Kojima et al.
patent: 5121256 (1992-06-01), Corle et al.
patent: 0555583 (1993-08-01), None
patent: 6-243512 (1994-09-01), None
patent: 7-248604 (1995-09-01), None

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