Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Including step of mold making
Reexamination Certificate
2001-07-26
2003-11-18
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Including step of mold making
C264S001330, C264S001370, C425S174400, C425S175000, C425S810000
Reexamination Certificate
active
06649093
ABSTRACT:
The invention relates to a method of manufacturing an optically scannable information carrier, which method comprises a first step wherein a master mold is manufactured, and a second step wherein, by means of the master mold or by means of a daughter mold manufactured by means of said master mold, the information carrier is manufactured by means of a replica process, in which first step a photosensitive layer provided on a substrate is irradiated by means of a modulated radiation beam which is focused to a scanning spot on the photosensitive layer by means of an optical lens system, the substrate and the lens system being moved relatively to each other, and a liquid being provided in a gap which is present between the photosensitive layer and a lens of the lens system facing said photosensitive layer.
The invention further relates to a method of manufacturing a master mold, which is used in the manufacture of an optically scannable information carrier, according to which method, a photosensitive layer provided on a substrate is irradiated by means of a modulated radiation beam which is focused to a scanning spot on the photosensitive layer by means of an optical lens system, the substrate and the lens system being moved relatively to each other, and a liquid being provided in a gap which is present between the photosensitive layer and a lens of the lens system facing said photosensitive layer.
The invention also relates to a device for the manufacture of a master mold, which is used in the manufacture of an optically scannable information carrier, which device is provided with a table which can be rotated about an axis of rotation, on which table a substrate with a photosensitive layer can be placed, and with a radiation source, an optical lens system for focusing a radiation beam generated in operation by the radiation source to a scanning spot on the photosensitive layer, a displacement device by means of which the lens system can be displaced with respect to the axis of rotation mainly in a radial direction, and a liquid supply means for providing a liquid in a gap between the photosensitive layer and a lens of the lens system facing said photosensitive layer.
A method and a device, of the types mentioned in the opening paragraphs, for the manufacture of a master mold are disclosed in JP-A-10255319. In accordance with the known method, a photosensitive layer is applied to a disc-shaped substrate made from glass. The substrate is secured onto a table of the known device. The table and the substrate are rotated about an axis of rotation extending perpendicularly to the substrate, and the lens system is displaced, at a comparatively low rate, in a radial direction with respect to the axis of rotation, so that the scanning spot of the radiation beam formed on the photosensitive layer follows a spiral-shaped track on the photosensitive layer. The radiation beam, which is a laser beam in the known device, is modulated such that a series of irradiated and non-irradiated elements is formed on the spiral-shaped track, which series correspond to a desired series of information elements on the information carrier to be manufactured. The photosensitive layer is subsequently developed, so that the irradiated elements are dissolved and a series of depressions are formed in the photosensitive layer. Next, a comparatively thin aluminum layer is sputtered onto the photosensitive layer, which aluminum layer is subsequently provided with a comparatively thick nickel layer by means of an electrodeposition process. The nickel layer thus formed is subsequently removed from the substrate and forms the master mold to be manufactured, which is provided, in the manner described above, with a disc-shaped surface having a series of raised portions corresponding to the desired series of information elements on the information carrier to be manufactured. The master mold thus manufactured can suitably be used in the manufacture of the desired information carriers, however, in general, a number of copies, so-called daughter molds are made by means of the master mold in a replica process. These daughter molds are used to manufacture the desired information carriers by means of a further replica process, generally an injection molding process. In this manner, the required number of master molds, which are comparatively expensive, is limited. Such a method of manufacturing an optically scannable information carrier, such as a CD or DVD, having pit-shaped information elements by means of a master mold or by means of a daughter mold manufactured by means of said master mold is commonly known and customary.
In accordance with the known method, the gap present between the photosensitive layer and the lens of the lens system facing said photosensitive layer is filled with water. For this purpose, the known device is provided with an outflow opening, which is situated near the axis of rotation of the table. The water supplied via the outflow opening is spread, under the influence of centrifugal forces, substantially throughout the surface of the photosensitive layer, so that also said gap is filled with water. Since water has a considerably larger optical refractive index than air, the provision of water in said gap leads to a substantial increase of an angle which the rays originating from the radiation beam and the optical axis of the lens system include at the location of the scanning spot. As a result, the scanning spot of the radiation beam on the photosensitive layer is reduced considerably, so that a much larger number of irradiated and non-irradiated elements can be formed on the photosensitive layer, and the information carrier to be manufactured has a higher information density.
A drawback of the known method and the known device resides in that the liquid film formed in said gap is not always homogenous as a result of air inclusions in said liquid film. As a result, impermissible faults develop in the photosensitive layer. In addition, the inhomogeneous liquid film exerts varying forces on the lens system. Since the lens system can be displaced in directions perpendicular and parallel to the photosensitive layer by means of an actuator to focus and position the radiation beam on the photosensitive layer, and this actuator has a limited rigidity in said directions, the varying forces exerted by the liquid film cause undesirable vibrations of the lens system in said directions, which may also lead to impermissible faults in the photosensitive layer. A further drawback of the known method and the known device resides in that a comparatively large quantity of liquid must be supplied. As a result, the known device must be provided with extensive measures to preclude undesirable contact between the liquid and other parts of the device.
It is an object of the invention to provide a method of manufacturing an optically scannable information carrier, a method of manufacturing a master mold, and a device for the manufacture of a master mold of the types mentioned in the opening paragraphs, wherein the above-mentioned drawbacks of the known method and the known device are precluded as much as possible.
To achieve this, a method in accordance with the invention for the manufacture of an optically scannable information carrier and a method in accordance with the invention for the manufacture of a master mold are characterized in that the liquid is provided via an outflow opening which, viewed in a displacement direction of the substrate at the location of the scanning spot relative to the lens system, is situated upstream from the scanning spot and directly adjacent said lens, said outflow opening being provided in a wall, which substantially extends in an imaginary plane wherein a side of the lens facing the photosensitive layer extends.
To achieve this object, a device in accordance with the invention for the manufacture of a master mold is characterized in that the liquid supply means comprises an outflow opening which, viewed in a tangential direction with respect to the axis of rotation, is situated upstream f
Van Rosmalen Gerard Eduard
Van Santen Helmar
Belk Michael E.
Vargot Mathieu D.
LandOfFree
Method of manufacturing an optically scannable information... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing an optically scannable information..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing an optically scannable information... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3175888