Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
  • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
  • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
  • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
  • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/12—Esters of monohydric alcohols or phenols
  • C08F220/14—Methyl esters, e.g. methyl (meth)acrylate
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics

Definitions

• the present invention is directed to a novel low hygroscopic methacrylic copolymer. More specifically, the present invention relates to specific tert-butylcyclohexyl methacrylate units and methyl methacrylate units, and, if desired, specific ethylenically unsaturated copolymerizable with these monomer units. It contains a saturated compound unit and in a specific ratio, and has colorlessness, transparency, moldability, low birefringence, and thermal stability, as well as low moisture absorption and excellent heat resistance, and therefore The present invention relates to a low-hygroscopic methacrylic copolymer suitable for a material of molded articles such as an optical element base and a light-transmitting extruded plate. The present invention also relates to a molded article made from the low hygroscopic methacrylic copolymer.
• the optical element substrate referred to in the present invention means a body substrate of the optical element.
• optical element as used herein is a general term for instruments that utilize optical characteristics such as light transmission, refraction, and reflection.
• the optical element include, for example, an optical information recording disk (hereinafter referred to as an optical disk), an optical information recording card, an optical information recording sheet, and an optical information recording film. , Lenses, mirrors, and prisms.
• Light-transmitting extruded plates include, for example, signboards, displays, partitions, daylighting windows, TV front panels, liquids Crystal display device front plate and the like. Background art
• methyl methacrylate resin is an optically superior resin with excellent transparency and low birefringence.
• optical element substrates such as optical disk substrates or light-transmitting plates. It is widely used as a material for products that function by transmitting light.
• this methyl methacrylate resin has high hygroscopicity, which causes dimensional changes, warpage, deformation, etc. due to the absorption of moisture, and also has poor heat resistance. It has the drawback of lowering, deforming, etc., and its use is actually restricted.
• discs of various types such as read-only discs, write-once discs, and rewritable discs are in practical use as optical discs. These discs require various properties such as transparency, moldability, low birefringence, heat stability, low moisture absorption, and heat resistance, but all of these properties are required. No resin that satisfies the above has yet been found, and in fact optical discs based on conventional resins are subject to many restrictions. For example, in the case of a video disc, which is a kind of read-only disc, a methyl methacrylate resin is conventionally used as a base material.
• methacrylic Methyl acid resin has high hygroscopicity, and the base is formed using this resin, metal is deposited on one side, and the protective film is coated. The fact is that warping and deformation are prevented by sticking the pieces together, and they are put to practical use.
• compact discs digital audio discs
• polycarbonate resin is conventionally used as the base material.
• the two disc bases are not bonded together, they are deformed due to moisture absorption and have low heat resistance, so that they can be left in a car in summer.
• Methyl methacrylate resin which is liable to be deformed under such a high temperature environment, is not used as a disc base material.
• Polycarbonate resin on the other hand, has poor moldability and large birefringence, but compact discs are practically used because they are relatively small and do not require high precision as optical discs. .
• the base material is a resin that has excellent transparency, moldability, low birefringence, and thermal stability, which are the characteristics of methyl methacrylate resin, and that also has excellent moisture absorption and heat resistance. If the used optical disc can be obtained, it can be used advantageously as any type of disc such as a read-only disc, a write-once disc, and a rewritable disc.
• the resin obtained by copolymerizing isopropyl methacrylate originally has low thermal stability.
• the residual resin is purified by a purification method in which the obtained resin is dissolved in a solvent and reprecipitated. Even with resin with reduced monomer content, when performing high-temperature melt molding at 280 ° C, which is used to obtain high pit reproducibility in injection molding for molding optical disc substrates, significant coloring and decomposition foaming occur simultaneously. It is difficult to obtain good molded products.
• An object of the present invention is to provide colorlessness, transparency, moldability, thermal stability, excellent heat resistance, and excellent low hygroscopicity while maintaining sufficient mechanical strength. It is an object of the present invention to provide a low-hygroscopic methacrylic copolymer suitable for a base material and a material for molded articles such as an extruded plate.
• the present inventors have conducted intensive studies to achieve the above object, and as a result, obtained a resin obtained by copolymerizing methyl methacrylate and at least tert-butylcyclohexyl methacrylate.
• Methyl methacrylate resin has excellent transparency, moldability and low birefringence inherent in methyl methacrylate resin, and maintains the mechanical strength while maintaining the water absorption (equilibrium water absorption) of methyl methacrylate. It was surprisingly found that the resin can be reduced to about 1% compared to about 2%. In the past, it has been important to keep the moisture-absorbing resilience low in the zero-stroke optical disc base material.
• the moisture-absorbing warpage is to be improved, the moldability, the birefringence, and the mechanical strength are reduced.
• the reality is that they have to sacrifice and suffer from technical dilemmas. Therefore, solving such a technical dilemma, Moreover, the water absorption is 50% lower than that of methyl methacrylate resin.
• the present invention which makes it possible to keep the temperature as low as about%, is durable. It is expected to be useful as a material for various other products.
• the present invention has been made based on these findings. That is, according to the present invention, (A) 2 to 30 mol% of tert-butyl cyclohexyl methacrylate unit, (B) 60 to 98 mol% of methyl methacrylate unit, (C) Equation (1)
• R is a hydrogen atom or a methyl group
• R 2 is a phenyl group, a methyl-substituted phenyl group or
• the content of the tert-butylcyclohexyl methacrylate unit as the component (A) is 2 to 30 mol% based on the total molar amount of components (A), (B) and (C), and the amount of hexyl tert-butyl methacrylate unit is less than the above range
• the low hygroscopicity and high heat resistance which are features of the present invention, are not sufficiently exhibited. If it exceeds the above range, the hygroscopicity and the heat resistance are improved, but the mechanical strength is lowered, which is not preferable.
• the preferred content of tert-butylcyclohexyl unit is 5 to 20 mol%.
• Tert-butylcyclohexyl methacrylate has ortho, meta and para isomers, each of which has a cis form and a trans form.
• any of them can be used, and a mixture in any ratio can be used.
• These contents in the copolymer of the present invention can be quantified by gas chromatography analysis.
• the content of methyl methacrylate unit as the component (B) is as follows:
• the preferred content of the component (B) is 70 to 94 mol%.
• an ethylenically unsaturated compound unit copolymerizable with the component (A) and the component (B). can be contained as the component (C).
• Such an ethylenic compound monomer has the formula (1) Wherein R is a hydrogen atom or a methyl group,
• R 2 is a phenyl group, a methyl-substituted phenyl group or
• alkyl group substituted by 0)] Represents an alkyl group substituted by 0)]].
• monomers include alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, and 2-ethyl hexyl acrylate.
• Fluorinated alkyl esters of acrylic acid such as trifluoromethyl acrylate and 1,1,1,1-acryloyl acrylate; or aromatic vinyls such as styrene, ⁇ -methylstyrene and ⁇ -methylstyrene Compounds can be listed.
• the content of the component (C) is 0 to 30 mol%, preferably 2 to 20 mol%, based on the total molar amount of the components ( ⁇ ), ( ⁇ ) and (C).
• the area to be reinforced by the present invention is shown in a triangular view. Therefore, it is shown. In the figure, the shaded area is the area.
• the copolymer of the present invention can be produced by commonly used polymerization methods such as cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization.
• a monomer mixture comprising tert-butyl butycyclohexyl methacrylate and methyl methacrylate and, if desired, an ethylenically unsaturated compound of the formula (1) is added.
• a solution prepared by dissolving in a solvent of an aromatic hydrocarbon such as toluene or ethylbenzene can be used.
• the polymerization is carried out by suspension polymerization or emulsion polymerization, it can be carried out using water as a medium.
• the polymerization can be initiated by free radicals generated by ordinary heating or irradiation.
• the quantitative ratio of each component of the monomer mixture is substantially the same as the quantitative ratio of the monomer units of the components (A), (B), and (C) of the target copolymer. The quantity ratio can be increased.
• any initiator generally used in radical polymerization can be used.
• azo compounds such as azobisisobutyronitrile, Organic peroxides such as ruperoxide, lauroyl peroxyside, and tert-butylperoxy-12-ethylhexanoate are particularly preferred.
• the amount used is generally in the range of 0.01 to 10% by weight of the total amount of the monomers.
• any molecular weight regulator generally used in radical polymerization can be used, for example, petizolemercaptan, octylmenolecaptan, dodecylmesolecaptan, thioglycolic acid. 2-Ethylhexyl Any mercaptan compound is particularly preferred.
• the temperature for polymerizing the copolymer of the present invention is particularly restricted is not usually 0: L 5 0 e C, preferred properly 5 0: is selected in the range of I 2 0 ° C.
• the optimum polymerization temperature is determined in consideration of the polymerization method, the polymerization apparatus, the polymerization initiator, the molecular weight regulator, the properties of the obtained copolymer resin, and the like. After the polymerization is carried out for about 120 to 150 minutes, it is further cured for about 1 hour to obtain the copolymer of the present invention.
• the weight average molecular weight of the copolymer according to the present invention is in the range of 10 ⁇ 10 ′.
• the case of obtaining a molded article such as a light transmissive plate by direct polymerization as cast method 1 0 ' may take the relatively high weight ⁇ molecular mass of ⁇ 1 0 tau.
• injection molded articles such as optical discs, they are usually 1X1 ( ⁇ ⁇ 2X10. It is a marauder, preferably 5X10- ⁇ 1.5X). 1 0 5, more preferably 5 X 1 ( ⁇ 1 X 1 0 s.
• the weight-average molecular weight is in the range of 1 ⁇ 10 S to 3 ⁇ 10 5.
• the preferred range is 1.5 X 10 5 2.5 X 10 s .
• the weight average molecular weight is less than 1 ⁇ 10 5 , sufficient mechanical strength and dimensional stability cannot be obtained, and if it exceeds 3 ⁇ 10 s , it will not be extruded under normal extrusion molding conditions, and When extruded, thermal decomposition and coloring occur.
• the weight-average molecular weight mentioned here is measured by GPC (gel permeation chromatography) using standard polystyrene as a standard sample.
• the content can be measured by ' a C-NMR method (nuclear magnetic resonance method). That is, the copolymer is converted to a deuterated solvent.
• the copolymerization suspension according to the present invention can be used alone, but its properties such as excellent transparency, moldability, low birefringence, thermal stability, low moisture absorption, and high heat resistance are impaired. It can be blended with other resins such as polymethyl methacrylate, acrylonitrile-styrene copolymer, methyl methacrylate-styrene copolymer within the range not specified. .
• the amount of the residual monomer is small. % By weight, preferably 2% by weight or less, and more preferably 1% by weight or less.
• the copolymer of the present invention can be made into a practically sufficiently low residual monomer by polymerizing under the above-mentioned ordinary polymerization conditions, but the copolymer having a very low residual monomer content can be obtained. In order to obtain the union, it is preferable to apply a usual residual monomer removal method.
• Methods for removing the residual monomer include a method in which the obtained copolymer is heated in an air stream, a method in which the copolymer is heated under reduced pressure, and a method in which the copolymer is extruded under reduced pressure using a vented extruder. .
• Various properties of the resin can also be improved by adding generally known additives to the copolymer resin of the present invention within a range that does not significantly impair the excellent characteristics thereof.
• additives for example, various antioxidants, heat stabilizers, ultraviolet absorbers, sequestering agents, lubricants, release agents, plasticizers, impact resistance improvers, antistatic agents, flame retardants, preservatives, dyes, pigments Etc. can be added.
• methacrylic copolymer resin of the present invention it is possible to obtain various useful molded products utilizing the characteristics of the copolymer of the present invention by a molding method well known in the field of plastics technology. it can.
• a light-transmissive extruded plate can be obtained by subjecting the copolymer resin of the present invention to extrusion molding. That is, the copolymer resin of the present invention melted by the extruder is taken over by a temperature controlled re-rolling machine. It is processed into a flat plate by drawing it on a tool.
• the temperature conditions at the time of extrusion and withdrawal are selected depending on the characteristics of the extruded plate or the application, but it is generally appropriate to carry out extrusion in the range of 200 to 280 ° C.
• Light-transmitting extruded plates obtained by extrusion molding are, for example, signboards, displays, partitions, daylighting windows, television front panels, liquid crystal display front panels, etc., with low moisture absorption, high heat resistance, transparency, and heat stability. It exhibits high performance due to its excellent properties and mechanical strength.
• a light-transmitting plate made of the copolymer resin of the present invention having a high weight-average molecular weight and a high strength can be obtained by a casting method, and can be advantageously used for various applications.
• the copolymer resin of the present invention can mold various optical element bases by injection molding or compression molding, but is preferably molded by injection molding in view of productivity, dimensional accuracy and the like.
• the optical element base means the body base of the optical element.
• Specific examples of the optical element include, for example, optical information recording; ⁇ disk (hereinafter referred to as optical disk), optical information recording; @card, optical information recording sheet, optical type Examples include information recording films, lenses, mirrors, and prisms.
• tail lamps and meter covers for automobiles can be obtained advantageously by injection molding.
• the optical disk is obtained by injection molding the methacrylic copolymer resin of the present invention using a disk-shaped mold having fine irregularities on one side. Then, a memory functional film, a reflective film, and a protective film are provided on the substrate, and if necessary, these two sheets are attached with or without an air or solid intermediate layer. It is obtained by letting it go.
• a flat plate is obtained by cast polymerization or extrusion molding, and then, the flat plate is further compression-molded. It can also be obtained directly by cast polymerization.
• Optical discs are various types of optical information recording discs that record information by light or read information recorded by light, such as read-only discs, write-once discs, and rewritable discs. Includes disks. Also, in addition to a disc consisting of a single base such as a compact disc, a disc in which two bases are pasted together such as a video disc is included. In addition to general disks that have a signal, or have fine irregularities that should become a signal on the surface of the substrate, include disks that have a smooth substrate surface coated with a memory layer such as metal or dye. In addition, a magneto-optical disk in which the memory layer is a magnetic material is also included.
• the optical disc substrate obtained by forming the methacrylate-based copolymer of the present invention has excellent transparency, moldability, and low transparency characteristic of methyl methacrylate resin. It has birefringence and thermal stability, and also has hygroscopicity, a disadvantage of methyl methacrylate resin. And the heat resistance is greatly improved.
• the resin has low hygroscopicity and high heat resistance. It can be used under more severe conditions such as high humidity and high temperature.
• an optical disk substrate made of the copolymer resin of the present invention is used for a compact disk substrate in which a polycarbonate resin is conventionally used, the resin has low birefringence and has poor moldability. Because it is good, more accurate discs can be obtained easily.
• the optical disk base of the present invention is larger than a compact disk, which has been difficult to put into practical use in the past, and has a large amount of recorded information composed of a single base similar to a compact disk. It is preferably used.
• the sample was dissolved in acetone, which contains n-butyl alcohol as an internal standard, and quantified by temperature-assisted gas chromatography.
• the 13 C nucleus at a specific site of each component of the copolymer was analyzed by a nuclear magnetic resonance (NMR) method to determine the composition ratio. Measurement conditions are accumulated number 1 2 by dissolving the sample copolymer DM SO- d s at a temperature of 7 0 ° C, 0 0 0 times, was analyzed in a quantitative mode.
• NMR nuclear magnetic resonance
• the beaded polymer obtained by the polymerization was dissolved in dichloromethane (50 in Z 30 ml) to prepare a sample solution, and the gel permeation chromatography (GPC) was determined to be f ⁇ . From the measurement results, a weight average molecular weight was calculated using a calibration curve obtained by measuring the molecular weight of standard polystyrene, which was converted to methyl methacrylate. (4) Tensile breaking strength
• birefringence was measured for a portion of 50 discs from the center of the disc with an information sign on one side. .
• test piece was used as a test piece, one side of which was covered with a Saran film, and left for 48 hours in an atmosphere at a temperature of 50 ° C and a relative humidity of 90%.
• warpage of the test piece (the difference in height between the center and the midpoint of the side when the flat plate was placed on a horizontal surface) was measured.
• This monomer phase is added to the aqueous phase, suspended by stirring, and the air in the separable flask is replaced with nitrogen.After stirring, the temperature is maintained at 75 ° C for 2 hours to polymerize. Was performed. Further, in order to complete the polymerization reaction, the temperature was raised to 95 ° C., and then kept at this temperature for 1 hour. Then, polymerization The system was cooled to room temperature, and the content was filtered, washed with water and dried to obtain a colorless bead polymer.
• the obtained beaded polymer is stranded using a vent-type twin-screw extruder with a screw diameter of 30 ° at 230 °° and a vacuum of 7300 ° ⁇ g or more.
• the pellets were extruded and cut with a cutter to obtain granules (pellets).
• test piece was obtained by injection molding the obtained pellet at 230 ° C. using a 3 oz screw-type injection molding machine.
• Tables 1 and 2 show the results of analysis of the beaded polymer and test piece obtained above.
• Example 15 (Optical disk base)
• Example 1 Using a precision injection molding machine (Meiki Seisakusho M-200-800 DM), the pellet obtained in Example 1 was used to obtain a 300-w Got the base.
• the injection molding temperature was 290 ° C, the injection pressure and injection speed were high and high.
• This base was fixed to a vapor deposition device, and aluminum vapor deposition was performed under a vacuum of 10 to s Hg. Further, as a protective film, UV coating (coated with acrylic resin and cross-linked by ultraviolet irradiation) ) To create a single-sided deposition substrate. The birefringence and the warpage due to moisture absorption were measured for the single-sided evaporation substrate. Table 3 shows the results. Examples 16 to 28 8. (Optical disk base)
• Example 2 9 Extruded plate
• Polymerization was carried out in the same manner as in Example 1 except that the amount of N-octyl mercaptan was changed to 0.16 parts by weight. Peletz I got Next, this pellet was screwed using a screw-type 3 Omni 0 vent type twin screw extruder equipped with a plate die.
• Example 4 Polymerization was carried out in the same manner as in Example 1 except that the monomer composition and the amount of the molecular weight modifier (n-octyl mercaptan) added were changed as shown in Table 4, and the polymerization was carried out under the same conditions as in Example 29. An extruded plate was prepared, and the moisture absorption warpage was measured. The results are shown in Table 4.
• IBA isobutyl acrylate
• MArmethyl acrylate St styrene
• IBOMA isobornyl methacrylate
• CHMA cyclohexyl methacrylate
• the figure is a triangular view showing the area covered by the present invention.
• the shaded area is the area of the present invention.
• the methacrylic copolymer of the present invention has excellent transparency, moldability, low birefringence, and heat stability characteristic of methyl methacrylate resin, and has the disadvantages of methyl methacrylate resin. This is a new resin whose moisture absorption and heat resistance are greatly improved without sacrificing mechanical strength. Since the methacrylic copolymer has such excellent characteristics, the molded article can be advantageously used for various applications.
• optical information recording disks optical disks
• Optical information recording card optical information recording sheet
• optical information recording film optical information recording film
• lens mirror
• prism optical transmission fiber
• signboard display, partition
• It is suitable for use as a light-transmitting plate used for a lighting window, a front panel of a television, a front panel of a liquid crystal display, and the like.

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Optical Record Carriers And Manufacture Thereof (AREA)

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Citations (8)

• 1988
  • 1988-01-07 DE DE19883890136 patent/DE3890136C2/de not_active Expired - Lifetime
  • 1988-01-07 WO PCT/JP1988/000009 patent/WO1989006248A1/ja active Application Filing
  • 1988-01-07 DE DE19883890136 patent/DE3890136T1/de active Pending
  • 1988-07-22 GB GB8817580A patent/GB2223024B/en not_active Expired

Patent Citations (8)

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