JPH01102501A - Optical molding - Google Patents

Abstract

PURPOSE:To provide a molding which has excellent light transmittability and a low water absorptivity and is extremely less cambered (deformed) by water absorption by forming the molding of a resin which contains a specific repeating unit and has <=0.2% water absorptivity in conformity with ASTM D570. CONSTITUTION:The molding consisting of the resin having a specific polyvinyl ether structure has extremely little double refraction, the excellent light transmittability and the low water absorptivity, is extremely less cambered at the time of water absorption and has good heat resistance and mechanical strength. The specific polyvinyl ether structure refers to the repeating unit expressed by the formula I. In the formula, R is a monocyclic or polycyclic satd. hydrocarbon group of >=7C which may be substd. with an alkyl group or alkoxy group of <=4C.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a material with extremely low birefringence, excellent light transmittance, low water absorption, and excellent mechanical properties and heat resistance. 0 Regarding optical molded products [Prior technology] So-called optical discs such as digital audio discs and laser vision are rapidly becoming popular due to their advantages such as long life based on high-density, large-capacity recording and non-contact playback! It's starting to change. In recent years, write-once discs and erasable discs that allow users to record information have appeared, and with the development of recording methods, the level of demand for the recording properties of the base material has also increased. In particular, three important properties are low water absorption (low water absorption resistance), low birefringence, and high heat resistance. The materials K currently used as substrate materials are mainly glass and θ plastic materials, but glass has disadvantages such as low mass production, high cost, heavy weight, and breakability, so plastic materials are more mainstream. . In addition, regarding optical lenses such as concave/convex lenses and 7-lens lenses, and optical elements such as diffraction gratings,
Due to the same reasons as optical disks, as applications expand, emphasis is being placed on plastics for optical disks as well.Polymethyl resins are currently particularly used as resins for transparent optical materials such as those mentioned above. methacrylate) (PMMA)
and polycarbonate (PC), but although PMMA has extremely low birefringence, it has high water absorption (moisture absorption), and water absorption causes anti-9 and deformation. It has the disadvantage that it tends to lead to a decline in sexual performance. In particular, when used in an optical recording medium consisting of a single substrate such as a digital audio disc, faithful reproduction of information may become impossible. In addition, further improvement in heat resistance is desired. On the other hand, PC has a low water absorption property, a low water absorption property, and has no problem with heat resistance, but it has the disadvantage of high birefringence.

For relatively small-diameter products such as digital audio discs and small-diameter lenses, it is possible to suppress birefringence below the required level (by controlling the molding conditions with high precision); This is extremely difficult for lenses with large diameters.

Various attempts have been made to modify PMMA and PC by copolymerization, blending, etc. to overcome the drawbacks of using them as optical moldings. For example, a method for improving the water absorption warpage (deformation) of PMMA is to copolymerize cyclo-silyl methacrylate, etc.
54) and those copolymerized with bornyl methacrylate (
JP-A-58-162651) is known, but all of these improve water absorption (deformation) but do not improve heat resistance, or unreacted monomers remain and adversely affect the properties. It has nine drawbacks and is not practical. In addition, it is a product that copolymerizes benzyl methacrylate (Jikai 1@58-11515).In order to reduce water absorption, increasing the copolymerization ratio of benzyl methacrylate increases birefringence and at the same time decreases heat resistance. I don't like it. Methods to reduce the birefringence of PC include copolymerization and blending to increase the fluidity during melting and reduce the birefringence caused by residual stress in molded products (Japanese Patent Application Laid-Open No. 60-166321.6O- 215051) and those using specific bisphenol derivatives (Japanese Unexamined Patent Publication No. 6
0-166322), but it is extremely difficult to reduce the K to a low level like PMMA.

PMMA-? The application of resins other than PC to optical materials is also being considered; for example, styrene resin (q#
8-83009) has a problem in that it has high birefringence and very low surface hardness and is easily scratched. Furthermore, polyester resins (JP-A-58-150147) have particular drawbacks regarding birefringence.

[Problem to be solved by the invention]

As mentioned above, PMMA-? PC has problems when used as optical moldings, and various known methods for improving these problems either do not completely solve them or, even if they are solved, do so at the expense of other properties. As a result, a material suitable for use as an optical molding material cannot be obtained. Furthermore, even if new materials are used, there are still some problems. The purpose of the present invention is to have all the characteristics Ksi required when used in optical molded products, that is, extremely low birefringence, excellent light transmittance, and low water absorption and resistance to water absorption. An object of the present invention is to provide an optical molding material with very little deformation) and excellent mechanical properties and heat resistance. ,
Molded products made of resins with a specific polyvinyl ether structure have extremely low birefringence, excellent light transparency, low water absorption, extremely little curling when water is absorbed, and good heat resistance and mechanical strength. This discovery led to the present invention. That is, the present invention is an optical molded article characterized by using a resin having a specific polyvinyl ether structure.

A specific polyvinyl ether structure is represented by the formula This is one unit of repetition.

+CH2-CH It is essential that the above R has one or more cyclic saturated hydrocarbon groups. When R is other than the above, for example, resins such as methyl, ethyl, and propyl have low glass transition points and are not practical. Furthermore, cyclic saturated hydrocarbons having 6 or less carbon atoms, such as resins with cyclohexyl groups without substituents, have similarly low glass transition points, and the number of carbon atoms constituting the 0 ring, which is not practical, is generally 5' to 20. It is better to be within the range of. If the number of carbon atoms is too small, the glass transition point will be low, similar to the case of methyl, ethyl, etc. mentioned above.On the other hand, if the number of carbon atoms is too large, it will be difficult to achieve a high degree of polymerization, resulting in a decrease in mechanical strength. Since it becomes weak and brittle, it is unsuitable for use in the present invention. The preferred cyclic saturated hydrocarbon group has 7 to 18 carbon atoms. There is no particularly preferable range for the number of rings, but in a polycyclic saturated hydrocarbon group, the rings may be connected to each other by a bond, such as a cyclohexylshiffyl hexyl group, or a norbornyl group. They may share a carbon atom like a group.

It may be included in the form of a composition with a mer.

If the content is less than 20% by weight, the effect of improving birefringence, water resistance and water absorption resistance to warping (deformation) is undesirable.

The resin used in the present invention preferably contains a repeating unit represented by the following formula (II) as a component other than formula CI).

In the above formula (If), the number of carbon atoms constituting the cyclic saturated hydrocarbon group is generally preferably within the range of 5 to 2 o.

If the number of carbon atoms is too small, the glass transition point will be low, similar to the case of methyl, ethyl, etc. mentioned above, which is a problem.On the other hand, if the number of carbon atoms is too large, it will be difficult to achieve a high degree of polymerization, resulting in mechanical problems. The cyclic saturated hydrocarbon group preferably has 7 to 18 carbon atoms. There is no particularly preferable range for the number of rings, but in a polycyclic saturated hydrocarbon group, the rings may be connected to each other by a bond as in a cyclohexylcyclohexyl group, or as a carbon bond as in a norbornyl group. O which may share an atom Specific examples of the cyclic saturated hydrocarbon group used in the present invention include the following.

(1) Those whose basic skeleton is a norbornyl group, dimethanodecahydronaphthyl group, or trimethachthtradecahydroanthryl group (z) Those whose basic skeleton is an adamantyl group (8)
Others Among the above, those belonging to (1) and (2) K are more preferable from the viewpoint of heat resistance. In the former case, the bond may be located at any carbon position, and may be in the exo or endo form. Even if the latter K>, the bond may be located at any carbon position.

In addition, the repeating unit of formula (n) may be one type or two or more types. Even when it is composed of multiple types of repeating units, it may be a copolymer or a composition.

The resin used in the present invention can be produced according to a known method for producing vinyl ether polymers.

That is, for example, the corresponding vinyl ether monomer can be made to have a high molecular weight by ordinary cationic polymerization using a Brønsted acid such as sulfuric acid or a Lewis acid such as boron trifluoride or titanium tetrachloride as an initiator in an inert atmosphere. When a resin having multiple types of R is obtained by copolymerization, a mixture of corresponding monomers may be used as a starting material. Formula (1
) The same applies to the case of obtaining a copolymer with K, which does not apply. As a reaction solvent for polymerization, a solvent used in ordinary cationic polymerization, such as toluene, methylene chloride, or a methylene chloride/hexane mixed solvent, is used.

The reaction temperature is usually in the range of about -100°C to about 30°C, but in order to obtain a polymer with a high molecular weight, it is preferable to lower the initiator concentration and carry out the polymerization at a low temperature of -30°C or lower. However, recently reported iodine-containing initiator systems such as hydrogen iodide/zinc iodide (C, Okamoto et al., P
olymer Prepr,, Jpn, 36(2)
.

237 (1987)), the molecular weight can be sufficiently increased even at high temperatures near room temperature, which is industrially advantageous.

In the case of cationic copolymerization, a third comonomer may also be added, and examples of the third comonomer include the following.

Methyl vinyl ether, ethyl vinyl ether, 2-9
aa Lower alkyl vinyl ethers having 4 or less carbon atoms, such as ethyl vinyl ether, isopropyl vinyl ether, and isobutyl vinyl ether; olefin monomers having 2 to 8 carbon atoms, such as isobutylene, cyclopentene, cyclohexene, cycloheptene, and 2,3-dimethyl-2-butene; Note that styrene and styrene derivatives such as p-methylstyrene and p-isopropylstyrene can also be copolymerized, but when a styrene derivative is introduced into the polymer, birefringence increases, so the copolymerization ratio is about 30% by weight. It should be kept below.

Copolymerization is also possible by radical polymerization. As the form of the polymerization reaction, bulk, solution or suspension polymerization using azobisisobutyronitrile or benzoyl peroxide as an initiator, emulsion polymerization using potassium beroxonisulfate or the like as an initiator, etc. can be adopted. The third comonomer used in radical polymerization is preferably an acrylic acid alkyl ester such as methyl acrylate or cyclohexyl acrylate, or an alkyl methacrylate such as methyl methacrylate, t-butyl methacrylate, or cyclohexyl methacrylate. These include ester, acrylonitrile, methacrylonitrile, etc. Incidentally, styrene and styrene derivatives such as p-methylstyrene and p-isopropylstyrene can also be copolymerized, but as in the case of cationic copolymerization, the copolymerization ratio should be approximately 30% by weight or less due to birefringence. It should be stopped.

Through the above polymerization reaction, the polymer can be obtained in the form of a lump or dissolved or dispersed in a solvent, but if necessary, it can be poured into a poor solvent such as methanol to remove unreacted materials, oligomers with a low degree of polymerization, emulsifiers, and dispersants. etc. can be removed.

The molecular weight of the obtained resin is not particularly limited as long as it is sufficient to provide a molded article. Number average molecular weight (polystyrene equivalent) determined by gel permeation chromatography (GPC) is s, ooo or more, preferably 10,0
00 or more is sufficient. If o is 5,000 or more, the mechanical properties will be good.

When the resin used in the present invention is a composition.

As a method for preparing it, any known method can be used, such as mixing in the melt, or reprecipitation after dissolving it in a common solvent. The resin to be blended is not particularly limited as long as it has good compatibility, but examples include (i) poly-4-methylpentene, polyvinylcyclohexane, and Polymers of α-olefins such as allylcyclohexane and polyallylnorbornane (11) Polymers containing so-called internal olefins such as cyclohexene, norbornene, norbornadiene, dimetanooctahydronaphthalene, trimetanododecahydroanthracene <it) Polymethyl methacrylate, poly Examples include poly(meth)acrylic acid alkyl esters such as cyclohexyl methacrylate and polybornyl methacrylate.゛The optical molded article of the present invention can be molded by any known method, for example, melt molding methods such as extrusion molding, injection molding, and injection compression molding. At this time, the resin temperature is usually 200 to 30
0°C, and the mold temperature is set in the range of 40 to 180°C.

During molding, known additives such as heat stabilizers, light stabilizers, antistatic agents, lubricants, inorganic or organic fillers, dyes, pigments, etc. may be added as necessary.

The optical molded product of the present invention can be formed into a flat plate or simple shape and then subjected to high-order processing such as laminating it with inorganic or organic materials, forming it into a complex shape by adhesion or fusion, or embossing the surface. It is also possible to do so.

When the resin of the present invention is used, for example, as a substrate for a read-only optical recording medium, an m-substrate is obtained by injection molding or the like using a mold in which groups, signals, etc. are recorded as necessary. Then, a film of metal such as aluminum is formed on the information surface by a method such as vacuum evaporation, and then a protective polymer layer is formed or two layers are pasted together. The information recording layer may be provided on a flat substrate using the resin of the present invention using a photocurable resin by the so-called 2P method. Further, the information recording section can be configured using any other method. For example, tellurium oxide or terbium is added to the surface of the molded substrate.
For example, a thin film of an inorganic material such as an iron-cobalt alloy or an organic material such as a cyanine dye is provided.

Taking advantage of the above-mentioned excellent characteristics, the optical molded article of the present invention can be used in the following applications.

(1) Lenses such as concave/convex lenses or Fresnel lenses for glasses, cameras, loupes, video projectors, etc. (H) Diffraction gratings for optical disc player pickups, etc. Various optical elements such as prisms and beam splitters (1V) Optical disk substrate material (i) Optical card substrate (vl) Liquid crystal display element substrate (vid) Lighting equipment parts (viii) Various signboards [Examples] The present invention will be explained in more detail with reference to Examples below.

Note that the physical property values were measured according to the following method.

(2) Number average molecular weight and molecular weight distribution: Determined by cpc (polystyrene equivalent).

■ Glass transition point: Differential thermal analysis method (in nitrogen, heating rate 1
0° C./min).

■ Light transmittance: The transmittance of light at a wavelength of 766 nm of a sample molded to a thickness of 2 mm by heat press was measured using a spectrophotometer. ■ Birefringence (retardation): Diameter 40 mm, thickness 6
The sample molded in 2 was heated and rolled to a thickness of 1 in. Measurements were made at a point 30 m from the center using a helium-neon laser (wavelength AASN) as a light source and applying the principle of a polarizing microscope (Polymer Science Society (Refer to Kyoritsu Shuppan, vol. 17, p. 26, edited by the Polymer Experimental Science Editorial Committee, ``Kobunshi Experimental Science,'' 1984)).

■ Photoelastic coefficient: 2FMX10cmx2 by heat press
■The method of Soejima et al. using a helium-neon laser light source for a thickly formed plate (edited by the Society of Polymer Science and Technology's Editorial Committee for Polymer Experiments, Vol. 10, 9.296 (198
3) Kyoritsu Shuppan).

■ Young's modulus: Measured using a tensile tester and strain gauge based on the relationship between stress and the resulting elongation of the sample.

■ Surface hardness: lead wire hardness test (JIS K-5400)
According to

■Water absorption rate: Determined in accordance with ASTM D570.

■ Water absorption reaction' Aluminum was evaporated to a thickness of 1000 mm on one side of a 2 cm x 10 cIn x 2-thick plate sample.
This was immersed in distilled water at 23° C., and the maximum value of warpage (lifting in the center) was defined as the water absorption reaction.

Example 1 200d of dry toluene and 23η (0.16 mmol) of boron trifluoride ethyl ether complex were placed in a polymerization tube purged with nitrogen, and after sufficiently cooling with a dry ice-methanol pass, neopentyl vinyl ether was distilled from calcium hydride. Add 18.2F (0.16 mol) to 2
Polymerization was carried out for 4 hours.

After the reaction was stopped by adding a small amount of methanol, it was diluted by adding 100 Wtl of toluene, and the white polymer was reprecipitated and recovered by pouring it into 21 methanol. From the fact that no vinyl group absorption was observed in the 1H NMR spectrum of the obtained polymer and from the results of elemental analysis, it was confirmed that it was an addition polymer of neopentyl vinyl ether. The number average molecular weight (polystyrene equivalent) by GPCK was 110,000, and the molecular weight distribution was 2.86.

It was confirmed that the obtained polymer had a glass transition point of 125° C.) and had sufficient heat resistance. Furthermore, various test pieces were molded from the above-mentioned polymer and their physical properties were measured.

For comparison, the physical properties of polymethyl methacrylate and bisphenol A polycarbonate were also measured, and the results are also shown in Table 1.

It can be seen that in the case of following the examples of the present invention, it has excellent physical properties as an optical component〇Characteristics as an optical recording medium SIM-4 made by Technoplus Co., Ltd. using the molding material of the present invention
749A injection molding machine outer diameter 1351% inner diameter 1,5
cm, using an injection molded substrate with a thickness of 1.2 vm,
An evaluation of the writing/reading/erasing characteristics of an optical disk in which fermented tellurium was deposited as a recording layer on the surface using a vacuum evaporation method showed that the performance was exactly the same as when polymethyl methacrylate was used as the substrate. .

In addition, those using polymethyl methacrylate are heated at 40°C.
When left for 120 hours at a relative humidity of 95 degrees, a reaction occurred due to moisture absorption, making it impossible to use it as a recording medium, whereas the molding material of the present invention did not exhibit any moisture absorption reaction under the same conditions. No deterioration of properties over time due to moisture absorption was observed.0 Properties as a substrate for a diffraction grating A smooth substrate molded using the molding material of the present invention was coated with According to the method, pattern exposure was performed by irradiating ultraviolet rays through a photomask for molecular weight diffraction gratings. A diffraction grating was prepared by vacuum drying to remove unreacted 3-benzoylbenzophenone.There was virtually no change in wavefront aberration before and after being left for 24 hours at 40°C and 95% relative humidity. Ta.

For comparison, when a diffraction grating was similarly prepared using polymethyl methacrylate as a substrate and evaluated, the wavefront aberration increased.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that isobutyl vinyl ether was used instead of neopentyl vinyl ether to obtain poly(isobutyl vinyl ether). The polymer had a number average molecular weight of 100,000 and was completely unmoldable.

Examples 2 to 4 Various vinyl ether monomers were synthesized by an ether exchange reaction between the corresponding alcohol and isobutyl vinyl ether using mercuric acetate as a catalyst. Purification of the monomer was carried out using column chromatography using silica gel and hexane as a developing solvent.

Example 1 except that the monomer was changed to various copolymer compositions.
Polymerization was carried out in the same manner as above to obtain a polymer. The copolymer composition of the obtained polymer was determined by elemental analysis and IHNMR spectrum, and is shown in Table 2 in correspondence with various physical property values.

Table 2 shows that the copolymers according to the examples of the present invention have excellent physical properties as optical parts. Examples 5 to 7 The poly(neopentyl vinyl ether) obtained in Example 1 and various Polymer was melt-kneaded at 240°C to obtain a molding material. Table 3 shows the structure of the polymer used in the blend, its blend ratio, and various physical property values of the resulting composition.

It can be seen that the compositions according to the examples of the present invention have excellent physical properties as optical components.

Margins below [Effects of the Invention] As described above, by using the molding material of the present invention, a molded product suitable for optical use, that is, having the following 1ifF properties, is provided.

■ Light transmittance is 85% or more. Excellent light transmittance.

■ The absolute value of the photoelastic coefficient is 30 x 10-” d/d
)'n or less, with little birefringence.

■ High glass transition point (usually 90°C or higher, preferred).

(temperature range of 100 to 200°C) Good heat resistance.

■ Water absorption rate is low at 0.2% or less, and there is extremely little chance of warping or deformation due to water absorption.

■High surface hardness makes it hard to get scratches○ Patent applicant RiRashi Co., Ltd.

Claims (7)

[Claims] (1) An optical molded article made of a resin containing a repeating unit represented by the following formula (I) and having a water absorption rate of 0.2% or less according to ASTM D570. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (R is a monocyclic or polycyclic saturated hydrocarbon group with 7 or more carbon atoms which may be substituted with an alkyl group with 4 or less carbon atoms or an alkoxy group) (2) In the formula (I), the R group is an alkyl group having 4 or less carbon atoms, or a norbornyl group which may be substituted with one or more alkoxy groups, a dimethanodecahydronaphthyl group, or a trimetanotetradecahydroanthryl group An optical molded article according to claim 1. (3) The optical molded article according to claim 1, wherein the R group in formula (I) is an adamantyl group optionally substituted with one or more alkyl groups or alkoxy groups having 4 or less carbon atoms. (4) The optical molded article according to claim 1, 2, or 3, wherein the resin has a number average molecular weight of 5,000 or more. (5) The optical molded article according to claim 1, which has a glass transition temperature of 90° C. or higher. (6) The optical molded article according to claim 1, which has a glass transition temperature in the range of 100°C or more and 200°C or less. (7) The absolute value of the photoelastic coefficient is 30×10^-^1^3c
Claims 1 to 6 which are less than or equal to m^2/dyn
The optical molded article described in any of the above.