DE19921943A1 - Substrate for optical data storage, based on homo-, co- and/or block polymers of vinylcyclohexane, and has specified moment of inertia and specific density - Google Patents

Abstract

Substrate based on homo-, co- and/or block polymers of vinylcyclohexane has a moment of inertia of 280-50 g/cm<2> and a specific density of 1-0.8 g/cm<3>. The comonomers are selected from at least two of olefins, acrylic acid derivatives, maleic acid derivatives, vinyl ethers and vinyl esters.

Description

Transparent plastics such as aroma can be used as a substrate for optical data storage table polycarbonate, polymethyl methacrylate or polystyrene can be used. Also addition copolymers of ethylene and a norbornene derivative or one Tetracyclododecene derivative and hydrogenated products from ring-opened metathesis polymers from norbornene or tetracyclododecene are possible.

For very high densities of data storage (<5, especially <10 Gbytes, related on a disc with a diameter of 120 mm), however, is not a common substrate materials can be used without restriction. In addition there are very low birefringence and water absorption, high heat resistance, with sufficient mecha properties and low melt viscosity required at the same time.

Aromatic polycarbonates have very good mechanical properties and Dimensional stability, but too high birefringence and water absorption.

Polystyrene has too high birefringence and low heat resistance on.

Polymethyl methacrylate has too high water absorption and insufficient shape retention efficiency.

Addition copolymers of ethylene and a non-polar norbornene or tetracyclo dodecene have low birefringence and almost no water absorption.

However, these materials are very expensive to manufacture. Leave the materials are difficult to manufacture in optically pure quality. The presence of gel components also reduces their applications as optical materials. The separation of the  Catalysts and cocatalysts require considerable technical effort bound.

Water absorption of the substrate material and the associated swelling leads especially with asymmetrical optical data carriers (e.g. CD, MO, MD, ASMO, DVR) to an additional deformation (e.g. increase in Angular tilt). This leads to a deterioration in the readout signal (higher grid, higher cross talk) and does not leave the maximum permissible Data density too or requires complex electronic / optical correction modules (Tiltservo) (F. Bruder, R. Plaetschke, H. Schmid, Jpn. J. Appl. Phys. Vol. 37 (1998) 2120).

Swelling of the substrate layers can in particular at interfaces to informa tion and protective layers lead to mechanical stresses that a be cause accelerated detachment of the information layers from substrate layers.

The invention relates to substrates based on homo- and / or copolymers of vinylcyclohexane, where comonomers are selected from at least one of the group of olefins, acrylic acid derivatives, maleic acid derivatives, vinyl ethers and vinyl esters or mixtures thereof from at least 2 comonomers, the moment of inertia of Substrate in general from 280 to 50 g / cm ² , particularly preferably from 260 to 100 g / cm ² , very particularly preferably from 250 to 150 g / cm ² , determined by torsional vibration, and the specific density from 1 to 0.8 g / cm ³ , preferably 0.98 to 0.90 g / cm ³ .

The invention further relates to an optical substrate, which in particular with high-focusing optics (high numerical aperture <45) very little interference by birefringence, characterized in that the path difference of the Light that falls on the substrate, depending on the angle of incidence at lower right and deviating angles up to 27 °, a difference in the passage below  differs generally from 0 to 60 nm, preferably from 0 to 50 nm, very particularly preferably from 0 to 40 nm.

The substrates according to the invention are distinguished by high dimensional stability, high transparency, low birefringence and high heat resistance and are therefore extremely suitable as substrate material for optical data storage media net. The substrates are particularly suitable for the production of optical Storage media with high storage density.

Vibrations of the data carrier are reduced compared to those currently used data carriers, for example polycarbonate.

The saturation water absorption of an optical blank according to the invention Storage medium is generally less than 0.5%, preferably less than 0.2%, very particularly preferably less than 0.1%, especially less than 0.06% measured according to DIN 53 495.

The material has a high modulus of elasticity. This is associated with a high bending strength which in turn allows the construction of dimensionally stable substrate plates. Thinner substrate thicknesses allow higher data densities because optics with higher numerical aperture NA and low laser wavelength λ become less critical (Spat diameter ~ λ / NA, G. Bonwkuis, J. Braat, A. Huijser, J. Pasman, G. van Rosmaten, K. Schonhauer, Immiuk, Principles of Optical Disc Systems (Adam Hilger Ltd., 1995).

At high speeds of the optical disk, there is less elongation Information layer in the radial direction. This is especially true for high data density is important for high security of reading and writing of the information.  

The optical transmission is greater than 89% for wavelengths greater than 400 nm. The Material is therefore a preferred optical material for short and boring Light, especially for wavelengths from 300 to 800 nm.

Substrates with low differences in path difference depending on the input angle of incidence of light, are particularly suitable for improving optoelectronics write-in and read-out signals and are ideal substrates for only readable, be writable and rewritable data carriers.

The materials have a high heat resistance Tg and allow high Operating and service temperatures.

Other materials with and without preparation can be used on the optical plates deposit surface action. In order to modify the surface if necessary grains are particularly suitable for plasma or wet chemical processes.

Preferred materials for deposition are metals, metal compounds and Dyes.

Particularly suitable metals are aluminum, gold, silver, copper, tin, zinc, Germanium, antimony, tellurium, terbium, iron, cobalt, gadolinium and their Alloys.

Particularly suitable metal compounds are zinc oxide, silicon oxide, silicon Nitrogen compounds and zinc sulfide.

Cyanine, phthalocyanine and azo dyes are suitable as dyes.

These materials can be applied by spin coating and sputtering techniques become.  

The following are examples of optical data storage media:

• - Magneto-optical disc (MO disc)
• - Mini disc (MD)
• - ASMO (MO-7) ("Advanced storage magnetooptic")
• - DVR (12 Gbyte disc)
• - MAMMOS ("Magnetic Amplifying magneto optical system")
• - SIL and MSR ("Solid immersion lens" and "magnetic superresolution")
• - CD-ROM (Read only memory)
• - CD, CD-R (recordable), CD-RW (rewritable), CD-I (interactive), Photo-CD
• - Super audio CD
• - DVD, DVD-R (recordable), DVD-RAM (random access memory); DVD = digital versatile disc
• - DVD-RW (rewritable)
• - PC + RW (phase change and rewritable)
• - MMVF (multimedia video file system)

Preference is given to substrates made of a vinylcyclohexane-based polymer with the recurring structural unit of the formula (I)

in which
R ¹ and R ^{2 are} independently hydrogen or C ₁ -C ₆ alkyl, preferably C ₁ -C ₄ alkyl and
R ³ and R ⁴ independently of one another for hydrogen or for C ₁ -C ₆ alkyl, preferably C ₁ -C ₄ alkyl, in particular methyl and / or ethyl, or R ³ and R ⁴ together for alkylene, preferably C ₃ - or C ₄ alkylene (fused-on 5- or 6-membered cycloaliphatic ring),
R ^{5 represents} hydrogen or C ₁ -C ₆ alkyl, preferably C ₁ -C ₄ alkyl,
R ¹ , R ² and R ⁵ independently of one another in particular represent hydrogen or methyl.

In addition to the stereoregular head-tail linkage, the linkage can unite have a small proportion of head-to-head connection. The vinylcyclohexane is based rende amorphous predominantly syndiotactic polymer can be branched through centers be and z. B. have a star-shaped structure.

The comonomers used in the polymerization of the starting polymer (optionally substituted polystyrene) are preferably used and also incorporated into the polymer: olefins with generally 2 to 10 carbon atoms, such as, for example, ethylene, propylene, isoprene, isobutylene, butadiene, C ₁ - C ₈ - preferably C ₁ -C ₄ alkyl esters of acrylic or methacrylic acid, unsaturated cycloaliphatic hydrocarbons, e.g. B. cyclopentadiene, cyclohexene, cyclohexadiene, optionally substituted norbornene, dicyclopentadiene, dihydrocyclopentadiene, optionally substituted tetracyclododecenes, nuclear alkylated styrenes, α-methylstyrene, divinylbenzene, vinyl esters, vinyl acids, vinyl ethers, vinyl acrylate, mixtures of methylene nitrile, vinyl nitrate, Monomers.

Amorphous vinylcyclohexane polymers which can also be used are those with a syndiotactic diad fraction, determined by two-dimensional NMR spectroscopy, from 50.1 to 74%, preferably from 52-70%. Methods for microstructure elucidation using ¹³ C- ¹ H correlation spectroscopy of the methylene carbon atoms of a polymer backbone are generally known and are described, for. B. by AMP Ros and O. Sudmeijer (AMP Ros, O. Sudmeijer, Int. J. Polym. Anal. Charakt. (1997), 4, 39.).

The birefringence determined on these substrates, measured on the basis of the rheo-optical constant C _R, is less than or equal to 0.3 GPa ^-1 , the amount is more than a power of ten less than that for polycarbonate (C _R = + 5.4 GPa ^-1 ). The measurement method of the rheo-optic constant is described in EP-A 0621 297. The plane-parallel 150 to 1000 µm specimens required for this can be produced by melt pressing or film casting. The material can be considered to be birefringent compared to polycarbonate.

The vinylcyclohexane (co) polymers generally have absolute molecular weights weight M w weight average of 1000-10000000, preferably of 60000-1000000, most preferably 70000-600000, determined by light scattering.

The vinylcyclohexane (co) polymers are particularly preferred absolute Molecular weights from 100,000 to 450,000 g / mol. The molecular ge weight distribution is preferably by a polydispersity index (PDI = Mw / Mn) characterized from 1 to 3, wherein an optionally present oligomer fraction to to a molecular weight of 2000 not to calculate the polydispersity index is taken into account. Any oligomer content up to an Mw of 3000, based on the weight of the polymer, is less than 5%.

The copolymers can be present both statistically and as block copolymers.

The polymers can have a linear chain structure as well as through Co-Ein have branching points (e.g. graft copolymers). The branching centers include e.g. B. star-shaped or branched polymers. The fiction Moderate polymers can use other geometric forms of the primary, secondary,  Tertiary, optionally quaternary polymer structures have what is called their helix, Double helix, leaflet etc. or mixtures of these structures.

Styrene-isoprene copolymers are particularly preferred, in particular poly (styrene Block co-isoprene) and star-shaped poly (styrene block co-isoprene).

Block copolymers include di-blocks, tri-blocks, multi-blocks and star-shaped Block copolymers.

The VCH (co) polymers are made by using derivatives of styrene with the corresponding monomers radical, anionic, cationic, or by metal Complex initiators or catalysts polymerized and the unsaturated aromati then fully or partially hydrogenated bonds (see, e.g., WO 94/21694, EP-A 322 731).

The VCH (co) polymers can also be produced, for example, by hydration tion of aromatic polystyrenes or their derivatives in the presence of a catalyst, where as the solvent is an ether which has no α-hydrogen atom on one Has adjacent carbon atom ether function, or a mixture of such ethers or a mixture of at least one of the ethers mentioned with for hydrogenation reactions suitable solvents.

The hydrogenation of the starting polymers is carried out according to generally known methods (for example WO 94/21 694, WO 96/34 895, EP-A-322 731). A1s catalysts can be used in a variety of known hydrogenation catalysts. Preferred metal catalysts are mentioned, for example, in WO 94/21 694 or WO 96/34 896. Any catalyst known for the hydrogenation reaction can be used as the catalyst. Catalysts with a large surface area (for example 100-600 m ² / g) and a small average pore diameter (for example 20-500 Å) are suitable. Furthermore, catalysts with a small surface area (e.g. ≧ 10 m ² / g) and large average pore diameters are suitable, which are characterized in that 98% of the pore volume has pores with pore diameters greater than 600 Å (e.g. approx 1000-4000 Å) (see e.g. US-A 5,654,253, US-A 5,612,422, JP-A 03076706). In particular, Raney nickel, nickel on silicon dioxide or Siliciumdi oxide / aluminum oxide, nickel on carbon as a carrier and / or precious metal catalysts, z. B. Pt, Ru, Rh, Pd used.

The reaction is generally carried out at temperatures between 0 and 500 ° C preferably between 20 and 250 ° C, especially between 60 and 200 ° C leads.

The solvents which are customary for hydrogenation reactions are described for example in DE-AS 11 31 885 (see above).

The reaction is generally preferred at pressures from 1 bar to 1000 bar 20 to 300 bar, in particular 40 to 200 bar, carried out.

The substrates are made from the thermoplastic molding compositions containing mono- and / or copolymers based on vinylcyclohexane and optionally others Common additives, such as processing aids, stabilizers, made by the Molding compounds can be processed at temperatures above 280 ° C.  

Examples example 1

The 40 l autoclave is flushed with inert gas (nitrogen). The polymer solution and the catalyst is added (Table 1). After closing, more will be added then exposed to hydrogen with protective gas. After relaxing the respective hydrogen pressure is set and while stirring to the corresponding one Heated reaction temperature. The reaction pressure is increased after the water material absorption kept constant. The reaction time is defined by the heating of the Approach up to the time when the hydrogen intake reaches its saturation level strives.

When the reaction has ended, the polymer solution is filtered. The product is from Solvent freed and processed into granules.

From the granules, z. B. shouldersticks, optical plates and further test specimens were produced to determine the physical properties (Table 2).  

Table 1

Hydrogenation of polystyrene

Example 2 Manufacture of poly (styrene block co-isoprene)

The syntheses are carried out using standard inert gas techniques. 138 kg abs. Cyclohexane are placed in a 250 l reactor. 6.3 kg abs. Styrene are at Added room temperature to the reactor. The temperature is raised to 55 ° C, 102 ml (0.255 mol) of n-butyllithium (23% in n-hexane) are added to the reactor ben. The reaction mixture is heated to 70 ° C. and stirred for 30 minutes.

1.4 kg abs. Isoprene and 6.3 kg abs. Styrene are simultaneously in the reactor give. The mixture is kept at 70 ° C. for 2 hours. The reaction solution is cooled to room temperature and a solution of 10 g of 2-propanol in 500 g of cyclo hexane is added. The polymer solution is at 16.6 wt .-% at 40 to 45 ° C. concentrated in a vacuum.  

Example 3 Manufacture of hydrogenated poly (styrene block co-isoprene)

22 kg of the polymer solution (Example 2) are placed in a 40 l autoclave under a stick transferred fabric. After adding 421.5 g of Ni-5136 P (Engelhard) the autoclave charged several times with nitrogen and hydrogen. The reaction solution is at 100 bar heated to 170 ° C. After the heating phase, the reaction is started by a Automatic pressure at 150 bar up to pressure constant and two hours stirred.

The catalyst is filtered from the polymer solution. The polymer solution is stabilized with 4000 ppm Irganox XP 420 FF (Ciba Geigy, Basel, Switzerland), freed from the solvent at 240 ° C and further processed as granules.

As a comparative example A, a blank CD (CD substrate) is produced from one Bisphenol A polycarbonate (Makrolon CD 2005, Bayer AG, Leverkusen, Germany), and as examples B and C CD blanks made of poly vinylcyclohexane-based polymers according to Examples 1 and 3, used. The Blank CDs are made on an injection molding machine from Netstal, type Diskjet 600 manufactured. The CD blanks according to Example B and C show in comparison to common substrate material according to Comparative Example A (Table 2) for Ver as an optical storage medium of high density, the important combination of low moment of inertia, low water absorption, high dimensional stability (high modulus of elasticity), low specific density, low difference of the gear under different depending on the angle of incidence of light, high optical transparency at short and long wavelengths, as well as low birefringence at the same time existing high heat resistance. Example C shows a further optimized one Rheo-optic constant CR, with a very small difference in the path difference in Dependence of the angle of incidence of the light and has a glass temperature on the Level of polycarbonate.

Claims (6)

1. Substrates based on homo-, co- and / or block polymers of vinyl cyclohexane, comonomers being selected from the group of olefins, acrylic acid derivatives, maleic acid derivatives, vinyl ethers and vinyl esters or mixtures thereof of at least 2 comonomers, characterized in that the The moment of inertia of the substrate is 280 to 50 g / cm ² and the specific density is 1 to 0.8 g / cm ³ . 2. Substrates according to claim 1, characterized in that the moment of inertia is 260 to 100 g / cm ² . 3. Substrates according to claim 1 or 2, characterized in that the specific density is 0.98 to 0.90 g / cm ³ . 4. Substrates according to claims 1 to 3, based on one or a mixture of vinylcyclohexane (co) polymers of the recurring structural unit of the formula (I)
in which
R ¹ and R ^{2 are} independently hydrogen or C ₁ -C ₆ alkyl and
R ³ and R ⁴ independently of one another represent hydrogen or C ₁ -C ₆ alkyl or R ³ and R ⁴ together represent alkylene,
R ^{5 represents} hydrogen or C ₁ -C ₆ alkyl. 5. Substrates based on styrene-isoprene block and / or copolymers. 6. Substrate according to one or more of the preceding claims, since characterized by the fact that the path difference of the light which affects the Substrate falls depending on the angle of incidence at vertical and from it deviating angles up to 27 °, a difference in the path difference in generally from 0 to 60 nm.