Method of manufacturing an optically scannable information carrier

• US 20020020821A1
• Filed: 07/26/2001
• Published: 02/21/2002
• Est. Priority Date: 08/08/2000
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Santen, Helmar, Van Rosmalen, Gerard Eduard
• Granted Patent: US 6,649,093 B2
• Time in Patent Office: Days
• US Class Current: 250/492.2
• CPC Class Codes: G11B 7/122 Flying-type heads, e.g. analogous to Winchester type in magnetic recording
• CPC Class Codes: G11B 7/261 Preparing a master, e.g. exposing photoresist, electroforming
• CPC Class Codes: Y10S 425/81 Sound record

Abstract

The invention relates to a method of manufacturing a master mold (1), which is used to manufacture an optical information disc, such as a CD or DVD. According to the method, a substrate (3) is provided with a photosensitive layer (5), which is subsequently irradiated by means of a radiation beam (7), which is focused to a scanning spot (11) on said layer by means of an optical lens system (9). A liquid, such as water, is supplied into a gap (53) present between the photosensitive layer and an auxiliary lens (59) of the lens system facing said layer. As a result, the size of the scanning spot is decreased and the information density of the information disc to be manufactured is increased.

According to the invention, the liquid is supplied via a supply opening (69) which is positioned immediately adjacent the auxiliary lens (59), in a direction which, viewed from the scanning spot (11), is contrary to a direction (Z) wherein the substrate (3) is moved with respect to the lens system (9). Thus, the liquid supplied via the supply opening is transported immediately and exclusively into said gap (53), so that the amount of liquid to be supplied to fill the gap is limited. The supply opening is formed in a wall portion (65), which extends in an imaginary plane in which also a side wall (63) of the auxiliary lens (59) facing the photosensitive layer is present. As a result, a homogeneous Couette flow of liquid without air inclusions is obtained in the gap. This Couette flow does not cause any undesirable mechanical vibrations of the lens system.

The invention further relates to a method of manufacturing an optical information disc, according to which method a master mold (1) is manufactured in a first step, and the information disc is manufactured in a second step by means of a replica process using said master mold. The invention further relates to a device (25) for the manufacture of a master mold by means of a method according to the invention.

Claims

1. 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, 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.

3. A method as claimed in claim 1 or 2, characterized in that the substrate is disc-shaped and rotated about an axis of rotation which extends perpendicularly to the substrate, while the lens system is displaced substantially in a radial direction with respect to the axis of rotation, the liquid being provided via an outflow opening which, viewed in a tangential direction with respect to the axis of rotation, is upstream from the scanning spot.

4. A method as claimed in claim 1 or 2, characterized in that the liquid is provided via the outflow opening at a flow rate φ

=0,5*V*H*W, where W is at least equal to 2*H*NA/{square root}(n²-NA²), and where V is a velocity at which the substrate is displaced at the location of the scanning spot with respect to the lens system, H is a height dimension of the gap, W is a width over which the liquid, viewed in a direction perpendicular to the displacement direction, is spread into the gap, NA is a numerical aperture of the lens system, and n is an optical refractive index of the liquid.

5. A method as claimed in claim 4, characterized in that the width W is at most approximately 10*H.

6. A method as claimed in claim 4, characterized in that the height H is at least approximately 4 μ

m and at most approximately 100 μ

m.

7. A method as claimed in claim 6, characterized in that the height H is at least approximately 7 μ

m and at most approximately 10 μ

m.

8. A method as claimed in claim 4, characterized in that the outflow opening is round and its diameter is at most approximately 0,5*W.

9. A method as claimed in claim 1 or 2, characterized in that the liquid is extracted from the photosensitive layer, viewed in the displacement direction, downstream from the lens system.

2. 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, 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.

10. 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, 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 from the optical axis and directly adjacent said lens, said outflow opening being situated in a wall, which substantially extends in an imaginary plane wherein a side of the lens facing the photosensitive layer extends.

11. A device as claimed in claim 10, characterized in that a liquid flow provided, in operation, in the gap via the outflow opening has a flow rate φ

=0,5*V*H*W, where W is at least equal to 2*H*NA/{square root}(n²-NA²), and where V is a velocity of the substrate at the location of the optical axis with respect to the lens system, H is a height dimension of the gap, W is a width of the liquid flow, viewed in the radial direction, NA is a numerical aperture of the lens system, and n is an optical refractive index of the liquid.

12. A device as claimed in claim 11, characterized in that the width W is at most approximately 10*H.

13. A device as claimed in claim 11, characterized in that the height H is at least approximately 4 μ

m and at most approximately 100 μ

m.

14. A device as claimed in claim 13, characterized in that the height H is at least approximately 7 μ

m and at most approximately 10 μ

m.

15. A device as claimed in claim 11, characterized in that the outflow opening is round and has a diameter which is at most approximately 0,5*W.

16. A device as claimed in claim 11, characterized in that the side of the lens facing the photosensitive layer is provided with a dam which, viewed in the tangential direction, extends upstream from the optical axis and has a width which is equal to a desired width W of the liquid flow, while the outflow opening is provided in a further dam, which has the same width and, viewed in the tangential direction, connects to the dam of the lens.

17. A device as claimed in claim 10, characterized in that the device comprises an extraction device which is arranged downstream, viewed with respect to the outflow opening and the lens system.

18. A device as claimed in claim 17, characterized in that the extraction device has an extraction mouth which can be displaced, by means of a further displacement device, synchronously with the lens system in a further radial direction with respect to the axis of rotation.