JP2006119424A - Optical element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of an optical element capable of manufacturing a transparent molding in which the curing of the surface of an optical element adequately proceeds and, further, a molding having an excellent releasing property and an excellent transfer property by solving such the problem in the conventional technique that there is a possibility of of causing curing hindrance when using a radical type photopolymerization initiator and the optical element is colored when using a cationic photopolymerization initiator, in manufacturing the optical element using photosetting resin. <P>SOLUTION: A polymer in which the curing sufficiently proceeds is applied to the surface of a die beforehand and, thereafter, the photosetting resin is molded by using the die. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element such as a lens, a prism, and a diffractive optical element, and a method for manufacturing the same.

Conventionally, in a method for producing an optical element by molding using a photocurable composition, a radical photopolymerization initiator or a cationic photopolymerization initiator is used to initiate polymerization of the photocurable composition. (For example, refer to Patent Document 1).
JP 2000-336127 A

  Of the photopolymerization initiators, radical photopolymerization initiators have the property that curing inhibition occurs in the presence of oxygen. For this reason, if oxygen gas is adsorbed on the surface of the mold, there is a problem that the resin on the mold side is not sufficiently cured and accurate molding is difficult. In particular, when manufacturing a diffraction grating having fine grooves on the surface as an optical element, precise shape transfer is required, but air tends to remain in these grooves, and the problem of inhibition of curing is serious. It was.

  As a method for avoiding the above-described inhibition of curing, it is conceivable that the optical element is molded in a nitrogen gas atmosphere, but a new problem such as an increase in the size of the equipment arises.

  In contrast, cationic photopolymerization initiators do not cause the above-mentioned problems, but many have absorption in the visible light wavelength region, and are not suitable for the production of optical elements. In particular, when an optical element having a thickness of 50 μm or more was produced using a cationic photopolymerization initiator, the optical element was colored, which was not preferable.

  On the other hand, Patent Document 1 discloses a composition comprising a photocurable resin mixed with a cationic photopolymerization initiator and a radical photopolymerization initiator in order to obtain a sufficient curing rate without causing polymerization inhibition. An example of coating an optical fiber with an object is described. However, in this example, since the composition is used for the coating material, not the optical fiber itself, light absorption is not considered. For this reason, when an optical element was manufactured using the composition described in Patent Document 1, it was considered that sufficient transparency could not be obtained.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an optical element capable of manufacturing a precise shape without causing curing inhibition and having a small light absorption, and a method for manufacturing the same. . According to the present invention, since the resin on the mold surface is sufficiently cured on the mold surface, it is possible to produce an optical element having good releasability and good transferability.

  In order to achieve the above object, an optical element manufacturing method according to the present invention includes a coating step of applying a solution in which the polymer 1 is dissolved to the surface of a mold for molding an optical element, and drying and removing the solvent. It comprises a drying step, a supplying step for supplying a composition containing a photopolymerization initiator to the surface of the mold, and a curing step for obtaining the polymer 2 by irradiating the composition with light.

  The optical element manufacturing method may further include a mounting step of mounting an optical element blank serving as a base of the optical element on the composition between the supplying step and the curing step.

  Furthermore, the viscosity of the solution in which the polymer 1 is dissolved is preferably 5000 mPa · s or less, and the film thickness of the polymer 1 after the solvent is removed by drying is preferably 500 μm or less.

  In the present invention, a polymer having a sufficiently advanced reaction is previously applied to the surface of the mold, and the photocurable resin is molded using this mold. An optical element having good moldability and good transferability can be produced.

  Hereinafter, preferred embodiments of the present invention will be described.

  1 to 3 are side cross-sectional views for explaining a manufacturing process of an optical element in the first embodiment of the present invention. In FIG. 1 to FIG. 3, reference numeral 1 denotes a mold having a diffraction grating shape, 2 denotes a lens blank, and 3 denotes a mold fixing frame. 4 represents a photocurable resin, 5 represents a lattice plane, and 6 represents a polymer 1.

  In the manufacturing process, first, a mold 1 having a lattice shape as shown in FIG. 1 is prepared. Such a mold 1 can be formed by cutting a metal such as phosphor bronze using a diamond tool or the like. As the lattice shape, a step shape (multi-level) or a saw blade shape (blaze) is used. Further, the mold 1 is not limited to the one having such a lattice shape, and a mold having a spherical or aspherical optical surface may be used.

  Next, a solution in which the polymer 1 is dissolved is applied to the surface of the mold 1 using a brush or the like. The polymer 1 is obtained by polymerizing a monomer having one ethylenically unsaturated group such as a (meth) acryloyl group in one molecule by an ordinary method, and is transparent and in an organic solvent such as toluene, tetrahydrofuran, chloroform or acetone. A soluble material can be used.

  For example, polystyrene, polymethyl (meth) acrylate, polycarbonate, cyclic olefin resin, polyether polyol urethane resin, copolymers thereof, polymers or copolymers derived from these derivatives, mixtures thereof, and the like can be used. it can.

  The polymer 1 is transparent and preferably has a refractive index difference of 0.01 or less from the polymer 2 obtained by curing the photocuring monomer. If the difference in refractive index is 0.01 or more, an interface is formed between the polymer 1 and the polymer 2 obtained by photocuring, and when used as an optical element, the direction of light changes there, which is not preferable. Preferably, the monomer and chemical structure have the same or similar skeleton.

  The viscosity of the solution in which the polymer 1 is dissolved is preferably 5000 mPa · s or less, and when it is 5000 mPa · s or more, air is easily trapped when cast on the mold surface. The viscosity of the solution is determined by the polymer concentration with respect to the solvent, and can be freely set within a concentration range in which the polymer 1 is dissolved in the solvent.

  Subsequently, the solvent is evaporated by air drying or heating to adhere the polymer 1 to the mold wall surface. The film thickness of the polymer 1 after removing the solvent by drying is 500 μm or less. The thickness of the polymer 1 film is preferably 500 μm or less, and if it is 500 μm or more, the film after drying tends to crack, or peels off from the mold 1 during drying.

  A spin coater may be used for applying the polymer 1. The mold 1 is fixed to the mold fixing frame 3, an appropriate amount of the composition 4 is dropped on the mold 1, and the lens blank 2 is stacked from above to spread the composition 4 as shown in FIG. 2. The composition 4 is a photocurable monomer containing a photopolymerization initiator, and becomes a polymer 2 by being polymerized by light irradiation.

  The polymer 2 is obtained by photopolymerizing a photocurable monomer. As the photocurable monomer, 1 to 5 ethylenically unsaturated groups such as a (meth) acryloyl group, preferably, The monomer which has 2-3 pieces can be mentioned.

  For example, as a photopolymerizable monomer, styrene, methyl (meth) acrylate, N-vinylcarbazole, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylacetamide, N-vinylformamide, methoxyethylene glycol (meth) acrylate, methoxy Polyethylene glycol (meth) acrylate, nonylphenoxyethyl (meth) acrylate, nonylphenoxy polyethylene glycol (meth) acrylate, nonylphenoxypolypropylene glycol (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, phenoxyethyl (meth) ) Acrylate, phenoxy polypropylene glycol (meth) acrylate, butoxy polyethylene glycol (meth) acrylate, alkyl Meth) acrylate, cyclohexyl (meth) acrylate. These radically polymerizable monomers can be used alone or in admixture of two or more.

  The photopolymerization initiator is a compound capable of generating radicals upon irradiation with energy rays such as light. Examples of such a photoradical polymerization initiator include 1-hydroxycyclohexyl phenyl ketone and 2,2-dimethoxy. 2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, Michler's ketone, Examples include benzoin propyl ether and benzoin ethyl ether. A photoinitiator is 0.05 to 10 weight% with respect to a monomer, Preferably it is 0.1 to 5 weight%.

  Examples of monomers include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, and the like. A photosensitizer may be added.

  Furthermore, you may add a compounding agent other than the said component to a monomer as needed. Examples of such compounding agents include antioxidants, ultraviolet absorbers, light stabilizers, thermal polymerization inhibitors, leveling agents, surfactants, storage stabilizers, plasticizers, lubricants, solvents, wettability improvers, fillers. Etc.

  Hereinafter, embodiments of the present invention will be specifically described.

Example 1
1 to 3 are side sectional views showing a manufacturing process of the optical element in Embodiment 1 of the present invention.

  1 to 3, reference numeral 1 denotes a metal mold having a diffraction grating shape, and the surface is processed with a diamond bit to form a saw-toothed (phrase) grating. Reference numeral 2 denotes a lens blank having a diameter of 26 mm made of material BK-7. The mold 1 and the lens blank 2 are arranged to face each other. A high-pressure mercury lamp (not shown) that generates ultraviolet rays is installed above the lens blank 2.

  First, 0.5 cc of a toluene solution (viscosity 300 mPa · s) containing 10 parts by weight of a urethane acrylate polymer (polystyrene equivalent weight average molecular weight: 30000) was dropped on the mold 1 and centrifuged with a spin coater. Cast, apply and dry. Further, after drying at 50 ° C. for 1 hour, the thickness of the urethane acrylate polymer after drying was 10 μm. The mold 1 is fixed to the mold fixing frame 3, and the mold 1 contains 3 parts by weight of Irgacure 184 (radical photopolymerization initiator: manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator. Appropriate amount of functional urethane acrylate monomer 4 is applied, and a lens blank 2 having a diameter of 26 mm made of material BK-7 is placed thereon, and the center axis of lens blank 2 and the center axis of mold 1 are aligned with each other. The functional urethane acrylate monomer 4 was spread.

  After that, after the resin is cured by irradiating ultraviolet rays with a high pressure mercury lamp under conditions of 40 mW and 12 J, the lens blank 2 and the mold 1 are released, and the central thickness 200 μm on one side of the lens blank 2 is the maximum resin. An optical element was obtained in which a diffraction grating-shaped resin layer having a thickness difference of 50 μm and a resin diameter of 20 mm was formed.

  The pitch of the lattice plane 5 was not chipped and could be removed smoothly. The resin layer was transparent.

(Comparative Example 1)
Molding was performed in the same manner as in the first embodiment without applying a toluene solution containing 10 parts by weight of a urethane acrylate polymer on the mold 1. Demolding required about twice as much force as in the first embodiment, and the resin was transparent, but some pitches on the lattice plane 5 were found to be chipped. Further, tackiness (stickiness) was recognized on the surface of the lattice plane 5.

(Comparative Example 2)
A toluene solution (concentration: 0.5%, viscosity: 1 mPa) of a polyfunctional urethane acrylate oligomer containing 1 part by weight of Irgacure 261 was appropriately applied on the mold 1 by 0.5 CC and applied with a spin coater. The film thickness of the urethane acrylate polymer after drying was 0.1 μm. An optical element was obtained by molding in the same manner as in the first embodiment. Demolding required about twice as much force as in the first embodiment, and the resin was transparent, but some pitches on the lattice plane 5 were found to be chipped. Further, the surface of the lattice surface 5 was slightly tacky (sticky).

(Example 2)
The polymer 1 was produced in the same manner as in Example 1 except that polyvinyl carbazole (manufactured by ACROS ORANICS) was used, N-vinyl carbazole (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the monomer, and the reaction temperature was set to 80 ° C. An optical element was obtained in which a diffraction grating-shaped resin layer having a center thickness of 200 μm, a maximum resin thickness difference of 50 μm, and a resin diameter of φ20 mm was formed on one surface of the lens blank 2.

  The pitch of the lattice plane 5 was not chipped and could be removed smoothly. The resin layer was transparent.

  The present invention can be variously modified in addition to the embodiments described above. For example, you may add various compounding agents to the solution which melt | dissolved the polymer 1 as needed. Examples of such compounding agents include mold release agents, surfactants, lubricants, antioxidants, storage stabilizers, ultraviolet absorbers, metal oxide fine particles, inorganic fillers, and the like. The present invention includes all such modifications.

  Although the high-pressure mercury lamp is used in the above embodiment, the present invention is not limited to this, and a metal halide lamp, an ultra-high pressure mercury lamp, a xenon lamp, or the like can also be used.

  Further, the materials themselves and combinations thereof are not particularly limited as long as the conditions are satisfied, and can be selected according to the purpose of use.

FIG. 6 is a side cross-sectional view illustrating a manufacturing process of the optical element in Example 1. FIG. 6 is a side cross-sectional view illustrating a manufacturing process of the optical element in Example 1. FIG. 6 is a side cross-sectional view illustrating a manufacturing process of the optical element in Example 1.

Explanation of symbols

1 Mold 2 Lens blank 3 Mold fixing frame 4 Photo-curing resin

Claims (5)

  A coating process for applying a solution in which the polymer 1 is dissolved to the surface of a mold for molding an optical element, a drying process for drying and removing the solvent, and a supplying process for supplying a photocurable composition to the surface of the mold And a curing step for obtaining the polymer 2 by irradiating the composition with light to cure the optical element.   Furthermore, it is equipped with the mounting process which mounts the optical element blank used as the base material of an optical element on the said composition on the said composition between the said supply process and a hardening process. The manufacturing method of the optical element of description.   The method for producing an optical element according to claim 1, wherein the solution in which the polymer 1 is dissolved has a viscosity of 5000 mPa · s or less.   The method of manufacturing an optical element according to claim 1, wherein the film thickness of the polymer 1 after removing the solvent by drying is 500 μm or less.   An optical element manufactured by the method for manufacturing an optical element according to claim 1.

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