The birefringence problem in optical disk substrates: A modeling approach

Greener, J.; Kesel, Raymond; Contestable, Beverly A.

doi:10.1002/aic.690350313

Cited by 25 publications

(10 citation statements)

References 41 publications

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“…A 3. 8 value for the impact resistance ratio of the 10% gradient material over the homopolymer shows the synergis- Since the homogeneous composition of the I P N is supposed to produce intermediate properties of the two components to a certain extent, the higher synergistic properties of the gradient polymers should be explained in terms of layer composition. As a uniform macroscopic strain was observed throughout the sample in tensile experiments, the stress has to be distributed in a nonuniform way.…”

Section: Resultsmentioning

confidence: 99%

Mechanical and rheological properties of styrene/acrylic gradient polymers

Jasso

Martinez

Mendizábal

1995

J of Applied Polymer Sci

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SYNOPSISA butyl acrylate monomer with a small amount of photosensitizer was diffused into a slightly crosslinked polystyrene matrix. After a certain swelling time, the diffusion gradient was either fixed (by rapid photopolymerization in situ) to form a gradient polymer or changed to form an interpenetrating polymer network (IPN), once thermodynamic equilibrium was achieved. Chemical compositions were determined by FTIR. Mechanical and rheological measurements were performed using a universal testing machine and dynamic rheometer, respectively. Impact properties were evaluated with a Falling Dart Impact Tester. Compared to the IPN materials, the gradient polymers exhibit higher moduli, considerable strain, and similar impact resistance. They are also able to retain plastic properties at higher temperatures. Differences in chemical structure of equivalent layers for gradient and IPN polymers yield such differences in properties. 0 1995 John Wiley & Sons, Inc. INTRODUCTIONIn recent years, the production of about 2 billion pounds of polymer blends per year in the United States was reported.' Furthermore, while the annual growth rate of the plastics industry was 2-496, that of the polymer alloys and blends was 9-11%.2 That production and growth rate has been based mainly on research made over the last two decades on multicomponent polymers. Scientific interest and the technical importance of polymer blends is due to several reasons: First, no new polymers need to be synthesized; in addition, based on thermodynamic studies of phase equilibria in multicomponent polymer systems, blending feasibility has become less o b~c u r e .~-~ Besides, because of their heterogeneous nature, polymer blends lead to systems with two or more phases whose properties depend not only on the individual characteristics of the components, but also on the method of p r e p a r a t i~n .~-~ The long-term * To whom correspondence should be addressed.Journal of Applied Polymer Science, Vol. 58, 2207Vol. 58, -2212Vol. 58, (1995 stability of the properties of such systems can noticeably be affected if the components have the tendency to phase-separate. Blend structure stability and low birefringence can be enhanced if phase separation is restricted to the microscopic level: Furthermore, if the phases are interconnected, the morphology leads to a synergistic performan~e.6,~~~-" For that reason, slightly crosslinked interpenetrated polymer networks offer a good way of making stable products of better performance than that of copoly m e r~.~. " Even, further, if a continuous change in the composition structure of interpenetrated macromolecules is achieved throughout a polymer blend, a continuous change in individual properties would be expected.13 The spatial gradient formed in that way opens up the possibility of making polymer systems with tailor-made properties for different apOne method to prepare such structures is by sequential polymerization. A convenient profile throughout the sample can be reached by diffusing a monomer into a polymer mat...

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Section: Resultsmentioning

confidence: 99%

Mechanical and rheological properties of styrene/acrylic gradient polymers

Jasso

Martinez

Mendizábal

1995

J of Applied Polymer Sci

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“…Shyu and Isayev 6 showed that the birefringence in conventional injection-molded parts was very sensitive to the processing parameters such as mold temperature and packing pressure. Greener et al 7 constructed an analytical model to predict the birefringence level in an injection-molded disk with direct application to optical disk substrates and emphasized the role of moldwall temperature in reducing the orientation buildup during the injection-molding process. Wu and White 8 experimentally examined the effects of rapid cooling on birefringence during injection molding and compression molding of polycarbonate optical disk.…”

Section: Introductionmentioning

confidence: 99%

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

2002

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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.

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“…However, PC has some deficient characteristics that deter its use in some areas. Poor moldability is one of the most serious of PC's defects that make it difficult to utilize PC for a substrate of optical‐data disk with higher memory density 13–21. For higher memory density optical data storage systems, pits or grooves, which record or address the memory, should be replicated on the substrate surface with the finer feature and at the narrower track pitches 13–17.…”

Section: Introductionmentioning

confidence: 99%

“…For higher memory density optical data storage systems, pits or grooves, which record or address the memory, should be replicated on the substrate surface with the finer feature and at the narrower track pitches 13–17. In addition, as the size and the spacing of the pits or grooves become smaller, reduction of birefringence becomes increasingly important to maintain the required signal/noise level 13, 17–21. Poor moldability of PC has restricted the process window to extremely high melt temperatures and mold temperatures, even for the standard substrate molding.…”

Section: Introductionmentioning

confidence: 99%

Phase morphology of polystyrene–polyarylate block copolymer/polycarbonate blends and their application to disk substrates

Ohishi¹,

Ikehara²,

Nishi³

2001

J of Applied Polymer Sci

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Polystyrene-polyarylate (PS-PAr) block copolymer was applied as a moldability modifier of polycarbonate (PC). From the 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) extraction results, PS-PAr block copolymer was demonstrated to copolymerize with PC via an in situ reaction between the PAr chain and PC. As a result of the chemical bonding between PS and PC chains, the PS dispersed domain in the PS-PAr block copolymer/PC blend could be reduced, on average, to a size smaller than the visible light wavelength. In particular, by adjusting PAr composition to 30 wt % in the fed PS-PAr block copolymer during the melt-mixing process, the PS domain size was completely reduced to be smaller than the visible light wavelength. As a result the blend substrate could satisfy the transparency required for the optical disk substrate with higher memory density: homogeneity under polarizing light, clarity on the reflective plate, and transparency at 400 nm. The melt viscosity could be lowered to the equal viscosity level of PC at about 30°C higher temperature by blending PC 15 wt % with the PS-PAr block copolymer. The lowered melt viscosity could reduce the retardation in the optical disk substrate, which was equivalent to that of the PC substrate processed at 30°C higher. In addition, the PS-PAr block copolymer/PC blend could attain the exact groove transcription at 20°C lower mold temperature than that of PC as a result of the lowered elastic modulus caused by the PS-rich phase. These features of the PS-PAr block copolymer/PC blend indicated a potential to offer an improved process window for the substrate molding. Because of its excellent transparency and a potential for processing flexibility, the PS-PAr block copolymer/PC blend would be a promising material for optical disk substrates with higher memory density.

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The birefringence problem in optical disk substrates: A modeling approach

Cited by 25 publications

References 41 publications

Mechanical and rheological properties of styrene/acrylic gradient polymers

Mechanical and rheological properties of styrene/acrylic gradient polymers

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

Phase morphology of polystyrene–polyarylate block copolymer/polycarbonate blends and their application to disk substrates

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