Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1998-06-11
2001-04-17
Neyzari, Ali (Department: 2752)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S275400, C428S441000, C428S064400, C430S321000
Reexamination Certificate
active
06219330
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a master disk used for manufacturing an optical disk on which information is recorded, and a method for manufacturing the same.
2. Description of the Related Art
An optical disk such as a compact disk (CD) or a digital versatile disk (DVD) used as a medium for recording and/or reproducing video information, as shown in
FIGS. 1A and 1B
, includes lands
2
each having information pits
2
a,
and grooves
3
positioned between neighboring lands
2
for defining the lands
2
. Recently, much attention has been paid to increasing the capacity of recordable information by forming information pits
3
a
in the grooves
3
of an optical disk
1
.
To manufacture the optical disk
1
, a master disk having a recording plane of the same pattern as the optical disk
1
is generally necessary. In other words, as shown in
FIG. 2
, a master disk
10
having lands
31
, grooves
33
and information pits
32
and
34
, which is of the same pattern as the optical disk
1
, is necessary. To manufacture the master disk
10
, first, a photoresist capable of being photochemically reacted with a laser beam having a predetermined wavelength is coated on a carefully polished glass substrate
20
to a predetermined thickness, to form a photoresist layer
30
. While the substrate
20
is rotated, two laser beams are simultaneously incident onto the substrate
20
, so that the portions of the photoresist layer
30
, where the grooves
33
and the information pits
32
and
34
are to be formed, are exposed to the laser beams. Then, a photochemical reaction occurs in the portions exposed to the laser beams. During the exposing process, one laser beam is deflected to the left and right to expose the portion in which the grooves
33
are to be formed, and the other laser beam exposes the portion where the information pits
32
and
34
are to be formed. Then, the exposed portions are etched and cleaned, thereby finally manufacturing the master disk
10
as shown in FIG.
2
.
Thereafter, a metal film (not shown) is deposited thinly on the recording plane of the master disk
10
and a metal such as nickel is electrically coated on the metal film to then separate the coated film from the master disk
10
. The coated film is used as a stamper in the plastic molding of the optical disk
1
. Such a stamper has surface irregularities exactly opposite to those of the recording plane of the master disk
10
. Accordingly, the optical disk manufactured by using the stamper has the lands, grooves and information pits having the same pattern as the master disk.
However, if the master disk is manufactured in the above-described manner, grooves and information pits are both formed in the same photoresist layer. Thus, the boundary between the grooves and information pits becomes ambiguous, and the angles of the side walls of the groove and information pits with respect to the substrate become lower. Therefore, in the optical disk manufactured using the master disk, the boundary between the groove and information pit becomes ambiguous and the side walls of the grooves and information pits have a low angle. As a result, it is difficult to reproduce the information recorded on the optical disk by a recording/reproducing apparatus, using light diffraction from the boundary between the groove and information pit. Accordingly, the reproduction characteristics of the optical disk are deteriorated. Such a problem becomes serious in a high-definition (HD)-DVD having information tracks at a smaller pitch than the conventional DVD.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an optical-disk master disk with an improved photoresist layer, by which the boundaries between grooves and information pits recessed from the grooves are distinctly defined.
It is another object of the present invention to provide a method of manufacturing an optical-disk master disk, by which the boundaries between grooves and information pits recessed from the grooves are distinctly defined.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the first object, there is provided an optical-disk master disk including a substrate; a first photoresist layer formed on the substrate and capable of photochemically reacting with a laser beam having a predetermined wavelength; a second photoresist layer formed on the first photoresist layer and capable of photochemically reacting with the same laser beam more sensitively than the first photoresist layer; a plurality of first information pits formed in the second photoresist layer; and a plurality of second information pits formed in the first photoresist layer.
To achieve the second object, there is provided a method of manufacturing an optical-disk master disk including the steps of forming, on a substrate, a first photoresist layer capable of photochemically reacting with a laser beam having a predetermined wavelength; forming, on the first photoresist layer, a second photoresist layer capable of photochemically reacting with the same laser beam more sensitively than the first photoresist layer; providing first and second laser beams having the predetermined wavelength; exposing a predetermined portion of the second photoresist layer to the second laser beam; and exposing a predetermined portion of the first photoresist layer, which is under the exposed portion of the second photoresist layer, to the first laser beam.
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Ahn Young-man
Park Chang-min
Ro Myung-do
Neyzari Ali
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
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