JPH0363721B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to plastic optical elements made by injection molding, compression molding, etc. Plastic optical elements are made by molding general-purpose resins such as polystyrene resin and polymethyl methacrylate resin as optical resins, and are lightweight.
Demand for it has increased in recent years because it is easy to mass produce. However, with conventional plastic optical elements made of general-purpose resins, the resin properties still have a small refractive index, making the optical elements thick and large.In addition, they have high water absorption, which makes it difficult for the optical elements to change due to changes in environmental conditions. A change in surface precision or a change in the refractive index appears,
It is unstable as an optical system, and has drawbacks such as large optical birefringence, chromatic aberration, and scattered light due to the crystallinity and molecular orientation of the resin material used, as well as a decrease in transparency due to changes over time. This has been a factor hindering the use of plastic optical elements. Furthermore, if the viscosity of the resin composition is high during molding, distortion will remain after cooling and birefringence will likely occur. When melt molding is performed at a relatively high temperature to obtain good fluidity, the stability of the resin material itself is important because thermal decomposition of the resin is observed. Therefore, a resin composition with improved flowability and good moldability has been desired. In particular, reading information using laser light,
In high-precision optical systems used for writing, etc., it is important that the resin materials used as optical elements have low birefringence, water absorption resistance, and impact resistance, and improvements have been desired. .
In this regard, polymethyl methacrylate is a resin with good optical properties as an optical resin, but
It has the drawbacks of high water absorption and large fluctuations in surface precision and refractive index changes due to changes in environmental conditions. An object of the present invention is to provide an optical element whose characteristics such as surface accuracy do not change even when the environment changes. Still another object is to provide an optical element that has improved water absorption while maintaining impact resistance. The object of the present invention is to provide an optical element containing 95% by weight or more of a copolymer of (iso)bornyl methacrylate monomer, wherein the copolymer contains (iso)bornyl methacrylate monomer. for total monomers
This is achieved by an optical element characterized in that it contains methyl methacrylate in a range of 10% by weight or more and 90% by weight or less, and the remainder of all monomers is methyl methacrylate. The (iso)bornyl methacrylate monomer used in the present invention is represented by the following general formula []. General formula [] [In the formula, R ₁ , R ₂ and R ₃ each represent a hydrogen atom or a methyl group. ] In the optical resin composition of the present invention, if the content of (iso)bornyl methacrylate exceeds 90% by weight based on the total monomers, the impact resistance deteriorates, which is not very preferable. When the (iso)bornyl methacrylate monomer of the present invention is used as a copolymer with methyl methacrylate, a significant improvement in impact resistance is observed, and the (iso)bornyl methacrylate monomer/
The ratio of methyl methacrylate is preferably 90/10
~10/90, more preferably 70/30 ~ 30/70. In this case, if the amount of (iso)bornyl methacrylate is less than 10% by weight, there will be no effect on water absorption. The improvement in the water absorption of molded products by the optical resin composition of the present invention is remarkable, especially when compared to polymethyl methacrylate resin molded products in lens systems. Furthermore, constituent materials of the optical resin composition of the present invention will be explained. The polymerization method of the resin composition of the present invention is not particularly limited, but for example, suspension polymerization, solution polymerization,
Bulk polymerization, radiation polymerization, etc. are used. Further, the resin composition in the present invention may contain an ultraviolet absorber to improve light resistance. The ultraviolet absorber may be one that does not reduce the transmittance in the visible range and does not deteriorate other resin properties, such as phenyl o-hydroxysalicylate compounds, o-hydroxybenzoylphenone compounds, etc. -(o-hydroxyphenyl)-
Benzotriazole compounds, cyanoacrylate compounds, etc. can be used. Furthermore, 2,6-di-tert-butyl-p-cresol, 2,4-di-methyl-
6-tert-butylphenol, 2,2-methylenebis(4-methyl-6-tert-butylphenol)
4,4-butylidenebis(3-methyl-6-tert-butylphenol), 4,4-thiobis(3-methyl-6-tert-butylphenol), 1,1,3
- tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, (R: _C12 to _C14 alkyl group) dilaurylthiodiprobionate, distearylthiodipropionate, distearyl β, β-
thiodiptylate,

【formula】

[Formula] P(-O- C ₁₀ H ₂₁ ) ₃ or the like may be contained. The resin composition of the present invention may contain a plasticizer in order to further improve fluidity during molding. As a plasticizer, 2-ethylhexyl phthalate,
Alkyl phthalates such as n-butyl phthalate, isodecanyl phthalate, tridecanyl phthalate, heptyl phthalate, nonyl phthalate, alkyl esters of dibasic acids such as 2-ethylhexyl adipate, cepacic acid, 2-ethylhexyl, tributyl phosphate , phosphoric acid alkyl esters such as trioctyl phosphate, torqueresyl phosphate, triphenyl phosphate, tricylenyl phosphate, epoxidized fatty acid esters such as epoxidized octyl oleate, epoxidized butyl oleate, etc., polyester plasticizers, chlorine Any substance can be used as long as it functions as a plasticizer, such as chemically modified fatty acid esters. Furthermore, two or more of these may be used in combination. In addition, as a mold release agent, silicone oil, dimethylpolysiloxane, polysiloxane, aliphatic fluorocarbon, liquid or solid paraffin, butyl acid phosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, β-chloro Ethyl acid phosphate, di(2-ethylhexyl) phosphate, ethylene glycol acid phosphate, (2-
It may also contain hydroxyethyl methacrylate/acid phosphate, acrylate oligomer, etc. Molding methods for producing optical elements by forming the resin composition of the present invention include injection molding, compression molding, or a combination of injection molding and compression molding, such as the low-links method and micromolding method. Any method that involves melting or semi-melting a mono-carrying resin and molding the resin can be applied. The improvement in stabilizing the properties of the optical resin composition of the present invention from the raw material yields extremely favorable results. The optical resin composition of the present invention has little birefringence,
It is a novel optical resin composition with improved water absorption and impact resistance, and the optical element molded using the optical resin composition of the present invention shows very little change in surface precision and is suitable for optical applications. It becomes an element.
Water absorbency here is expressed in accordance with the ASTMD-570 standard. In addition, surface accuracy is measured by the number of changes in Newton's ring by optical measurement.
Impact resistance refers to the Izot impact strength indicated by the ASTMD-256 standard. Here, birefringence means that light is polarized into two paths, the ordinary wavefront and the extraordinary wavefront, in the medium in which it propagates, and because the speeds are different, a phase relationship occurs between each component, and the characteristics of the medium and the plate The phase difference changes in proportion to the thickness. The phase difference φ is given by φ=2π/λ(n _p −n _c )t. n _p and n _c are the refractive index of the ordinary ray, t is the thickness of the medium, and λ is the wavelength in air. Therefore, birefringence can be determined by optically measuring this phase difference. According to the optical element obtained by molding the resin composition of the present invention, changes in the characteristics of the optical element due to changes in environmental conditions are extremely improved. By applying a coating to the product label, moisture absorption resistance may be further improved, and as a result, dimensional stability may be further improved. Optical elements obtained by molding the resin composition of the present invention include so-called lenses for still cameras, video cameras, telescopes, eyeglasses, hard contact lenses, sunlight condensing lenses, etc. by transmitting light, such as prisms such as pentaprisms, mirrors such as concave mirrors and polygons, optical fibers, light guide elements such as optical waveguides, and disks such as optical video disks and audio disks. An element that performs a function. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. In addition, in the following examples, "parts" indicate "parts by weight." Example 1 (iso)bornyl methacrylate (R ₁ , R ₂ , and R ₃ in the general formula [] are methyl groups) 50 parts Methyl methacrylate 50 parts lauroyl peroxide 0.1 part Butyl acrylate oligomer (MARK FC- manufactured by Adeka Argus) 112) 0.5 parts In a reaction pot equipped with a cooling tube, nitrogen introduction tube, stirring rod, and thermometer, add 1.0 part of calcium phosphate, 0.01 part of sodium dodecylbenzenesulfonate, and 200 parts of distilled water.
Prepare a portion, add the above composition to it, and incubate at 70℃ for 6 hours.
Allowed time to react. After the polymerization was completed, a copolymer was obtained by chlorination, washing with water, filtration, and drying. To this polymer were added 0.2 parts of 2,6-dithyabutyl-4-methylphenol as a heat stabilizer and 0.1 part of a benzotriazole compound (JF-77 manufactured by Johoku Kagaku Co., Ltd.) as an ultraviolet absorber, and pelletized. A resin composition was obtained. This resin composition was injection molded at a resin temperature of 230° C. to produce a lens molded product having a thickness of 3 mm at the center. This will be referred to as Lens Sample-1 of the present invention. Example 2 A lens molded product having a thickness of 3 mm at the center was prepared in the same manner as in Example 1 except that 70 parts of (iso)bornyl methacrylate and 30 parts of methyl methacrylate were used. This will be referred to as Lens Sample-2 of the present invention. Comparative Example 1 A lens molded product was obtained in the same manner as in Example 1, except that 5 parts of (iso)bornyl methacrylate and 95 parts of methyl methacrylate were used. This will be referred to as comparative lens sample-1. Comparative Example 2 Commercial product Acrypet VH [manufactured by Mitsubishi Rayon Co., Ltd.]
A lens molded product was obtained in the same manner as in Example 1 using Polymethyl methacrylate]. This will be referred to as comparative lens sample-2. Table 1 shows a comparison of the characteristic values of the lens samples 1 and 2 of the present invention and comparative lens samples 1 and 2 in Example 1 and Comparative Examples 1 and 2.

[Table] As is clear from Table 1, the resin of the present invention is
This is a novel optical resin that has improved water absorption while maintaining impact resistance, and it can be seen that optical lenses molded using the resin of the present invention have extremely good changes in surface precision due to moisture absorption.

Claims (1)

[Claims] 1. An optical element containing 95% by weight or more of a copolymer of (iso)bornyl methacrylate monomers, wherein the copolymer contains (iso)bornyl methacrylate monomers based on the total monomers. An optical element comprising methyl methacrylate in an amount of 10% by weight or more and 90% by weight or less, with the remainder being methyl methacrylate.