Browse Prior Art Database

Laser Trimmed Dimensions on Optical Disk Photopolymer

IP.com Disclosure Number: IPCOM000037161D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 6 page(s) / 252K

Publishing Venue

IBM

Related People

Eckhoff, H: AUTHOR [+3]

Abstract

Precisely controlled radial dimensions and edge geometry on optical disks with photopolymer (2P) on glass have been obtained with the use of excimer lasers. Inner and outer radii, as well as edge shape (taper), are critical for the 2P layer on an optical disk. The dimensional control is required to maximize available disk space for storage capacity, while a tapered edge is required to obtain a hermetic environmental seal for the corrosion-sensitive magneto-optic layer.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 6

Laser Trimmed Dimensions on Optical Disk Photopolymer

Precisely controlled radial dimensions and edge geometry on optical disks with photopolymer (2P) on glass have been obtained with the use of excimer lasers. Inner and outer radii, as well as edge shape (taper), are critical for the 2P layer on an optical disk. The dimensional control is required to maximize available disk space for storage capacity, while a tapered edge is required to obtain a hermetic environmental seal for the corrosion-sensitive magneto-optic layer.

None of the present methods of edge control during the 2P optical disk fabrication processes are adequate. Photomasking during 2P UV- cure leaves an undesirable uncured excess of polymer on the outer and inner peripheries. The excess is difficult to remove, it contaminates the cured grooves by redepositing some of the sticky uncured polymer, and it leaves a partially uncured border region.

The free flow process is a method by which the 2P in exactly metered volume is dispensed on the disk and allowed to flow out to the edges. Uncontrolled wavy peripheries (Fig. 1) due to the differences in wettability of the glass substrate and stamper, therefore, cause a loss of valuable real estate. Following UV-cure, and stamper-disk separation, the edges are left with an overhang that makes it impossible to get hermeticity when applying the sealing layer in a vacuum system (Fig. 2). The overhang causes discontinuities in the vacuum deposited sealing layer.

(Image Omitted)

Edge beading is created by letting the viscous 2P flow just beyond the stamper edge before UV cure. Sometimes a second bead is added to eliminate the overhang. This process reduces the final disk package reliability due to thermal expansion differences between the height of the bead and the 2P plateau.

Laser trimming eliminates the above problems. Sample optical disks have been prepared with ideal edge dimensions and profiles by using a very short wavelength excimer type laser (Xenon-Chloride, 308nm). Krypton-Fluoride at 248nm or other short wavelength lasers may also be used. Energy at these short wavelengths is absorbed efficiently by only the polymer layer, which removes it ablatively. The glass substrate is almost non-absorbing and, therefore, is not damaged.

Referring to Fig. 3 sample disks were prepared by dispensing the grooving layer polymer between the glass substrate and the grooved stamper, and allowing it to flow out towards the very edges of the substrate. Following UV- cure and removal of the stamper, the disks were placed on a laser rotating table for edge trimming. The laser used for these experiments...