Effect of insulation layer on transcribability and birefringence distribution in optical disk substrate

Abstract

As the need for information storage media with high storage density increases, digital video disks (DVDs) with smaller recording marks and thinner optical disk substrates than those of conventional DVDs are being required. Therefore, improving the replication quality of land-groove or pit structure and reducing the birefringence distribution are emerging as important criteria in the fabrication of high-density optical disk substrates. We control the transcribability and distribution of birefringence by inserting an insulation layer under the stamper during injection-compression molding of DVD RAM substrates. The effects of the insulation layer on the geometrical and optical properties, such as transcribability and birefringence distribution, are examined experimentally. The inserted insulation layer is found to be very effective in improving the quality of replication and leveling out the first peak of the gapwise birefringence distribution near the mold wall and reducing the average birefringence value, because the insulation layer retarded the growth of the solidified layer.

Semi-crystalline poly(4-methyl-1-pentene) polymers for replication of high aspect ratio diffractive features

“…This was due to the higher injection speeds than for thin substrates. The good replication in thick substrates may also be due to the higher effective flow of the polymer melt during injection [21,30]. Despite the high injection speed, P4MP1 (B) showed poor replication of 500 nm line widths in thicker substrates (figure 7).…”

“…Novel technical solutions such as infrared assisted heating systems and multilayer mold structures (consisting of metallic heating layer and oxide insulation layer) for rapid heating and cooling have been developed as a solution to this problem [17][18][19][20]. Multilayer structures have shown not only better replication of features but also improved optical properties [21]. Other relevant parameters are molding pressures, injection speed, mold insert material, filling time, direction of the grooves in the insert and use of vacuum in the mold [22][23][24][25][26][27].…”

“…The injection molding process becomes more complex as the thickness of the plastic part decreases [29]. Lower quality of the replicated features and poorer optical properties have been particularly associated with thin substrates [10,21,30]. In addition, replication may be affected by interfacial factors such as wettability, friction and adhesion between the polymer and the mold containing nano and sub-micron features.…”

Design and fabrication of a metallic nanostamp using UV nanoimprinting and electroforming for replicating discrete track media with feature size of 35 nm

“…To overcome these limitations, discrete track media (DTM), bit-patterned media, and energy-assisted magnetic recording media, which divide the storage space physically or magnetically, have been proposed. 9,10 In this study, we designed and fabricated a metallic nanostamp with an 80-mm-diameter DTM pattern, consisting of a data track, a servo track, and an alignment track. During the last decade, several soft lithographic techniques tried to replace standard photolithography.…”

Construction of Injection Mold with MEMS RTD Sensor and MEMS Heater for Micro/Nano Molding Process

“…Kim and Suh, 4) Liou and Suh, 5) and Kim and Niemeyer 6) suggested an insulated mold insert for retaining the heat in the mold cavity. Inoue et al 7) and Kang et al 8,9) replicated the high density optical disc substrate using insulation layer. Jansen 10) and Kim et al 11) suggested the method using electric heater and Kurosaki et al 12) used IR laser as a heater.…”