JP3490732B2 - Manufacturing method of plastic aspherical microlens - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, an optical communication device, an optical information processing device and the like .
The present invention relates to a method for manufacturing an aspherical micro lens . 2. Description of the Related Art An aspherical microlens having a minute convex lens portion on one side of a glass plate has been disclosed in Japanese Patent Application Laid-Open No. 60-53 / 1985.
No. 927. [0003] The glass microlens is exposed to ultraviolet light and then heat-treated after irradiating ultraviolet rays to a portion other than a lens portion forming portion of a glass plate containing a noble metal such as Ag. The portion of the glass crystallized. This portion becomes opaque due to light absorption by the colloidal fine particles of Ag in the crystallized portion. At the same time, the density changes, and the transparent glass in the unirradiated portion is made on the principle that the surface portion rises aspherically due to the stress around the crystallized portion to form a lens. [0004] In this method, the heat treatment of the glass sheet needs to be performed at a very high temperature, and a complicated process must be used. In addition, since a glass plate containing a noble metal such as Ag is required, it becomes an expensive microlens, and it is difficult to develop its use. As a method for producing such a lens using plastic, an injection molding method or a casting method using a mold can be used, but it is necessary to obtain optical axis symmetry between convex surfaces of a lens portion formed in a flat plate surface. Very difficult,
There was a problem that a light absorbing layer other than the lens portion could not be formed. [0005] The present inventors have proposed a polymer
When a flat resin composition comprising (A) and the polymer (A) dissolved and containing a photopolymerizable monomer (B) is irradiated with parallel light, a flat plate is formed along the light irradiation direction. Utilizing the fact that a layer structure is formed therein to form a translucent body that scatters light, a photomask as shown in FIG. The irradiation part was polymerized and cured in a translucent state. At this time, the light irradiation portion of the flat resin composition undergoes polymerization shrinkage, and the uncured portion can be made concave. Thereafter, the photomask is removed from the flat surface, and the uncured circular portion of the resin composition is irradiated with diffused light and cured transparently, so that the light scattering portion and the flat surface as shown in the sectional view of FIG. Has a microlens portion having at least one concave surface and optical axis symmetry, and succeeded in developing a plastic aspherical microlens. In the present invention, since parallel light is used for forming the light diffusing portion of the flat resin composition, a lens having very good optical axis symmetry can be obtained. [0007] Monomers used in carrying out the present invention
(B) needs to be photopolymerizable, and among them, radical polymerizable one is most suitable. Specific examples of the radical photopolymerizable monomer include methyl methacrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, 2,2,3,3,4,4,5,5- Fluorinated alkyl (meth) acrylates such as octafluoropropyl (meth) acrylate, 2,2,3,4,4,4-hexafluoropropyl (meth) acrylate, and 2,2,2-trifluoroethyl (meth) acrylate (N = 1.37 to 1.44), (meth) acrylates having a refractive index of 1.43 to 1.62, for example, ethyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth)
Acrylate, hydroxyalkyl (meth) acrylate, alkylene glycol di (meth) acrylate, trimethylolpropane di or tri (meth) acrylate, pentaerythritol di, tri or tetra (meth) acrylate, diglycerin tetra (meth) acrylate, dipenta In addition to erythritol hexa (meth) acrylate and the like, diethylene glycol bisallyl carbonate, fluorinated alkylene glycol poly (meth) acrylate, urethane (meth) acrylate and the like can be mentioned, and these monomers can be used alone or in combination of two or more kinds. It can be used, and styrene, chlorostyrene, vinyl acetate and the like can be used together. The photoinitiated catalysts used for photopolymerizing these monomers (B) include benzophenone, benzoin alkyl ether, 4'-isopropyl-2-hydroxy-2-methyl-propiophenone, 1-hydroxycyclohexylphenyl ketone, benzyl methyl ketal, 2,2-diethoxyacetophenone, chlorothioxanthone, thioxanthone compounds, benzophenone compounds, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, N-methyldiethanolamine ,
Triethylamine and the like. In order to complete the polymerization of the monomer (B) more efficiently, it is possible to mix a heat-initiated catalyst. As the heat-initiated catalyst, a peroxide catalyst is usually used. As the polymer (A) used in the present invention, any polymer can be used as long as it is soluble in the above-mentioned monomer (B). Specific examples thereof include polymethyl methacrylate (n = 1.49), polymethyl methacrylate-based copolymer (n = 1.47 to 1.50), poly-4-methylpentene-1 (n = 1.46), and ethylene / vinyl acetate copolymer (n = 1.
46-1.50), polycarbonate (n = 1.50-1.57), polyvinylidene fluoride (n = 1.42), vinylidene fluoride / tetrafluoroethylene copolymer (n = 1.42-1.46), vinylidene fluoride / tetrafluoroethylene / hexafluoropropene Copolymers (n = 1.40 to 1.46), polyfluorinated alkyl (meth) acrylate polymers, and the like. The resin composition used in the present invention must be formed into a flat plate, and has a viscosity at room temperature of 10,000 poise or more, preferably 25,000 poise or more. Examples of the light source used for curing the flat resin composition of the present invention include a carbon arc lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a low-pressure mercury lamp, a chemical lamp, a xenon lamp, a metal halide lamp, and a laser beam. However, in order to obtain the parallel light used in the first step, it is necessary to irradiate the resin composition used in the present invention after making the light from these light sources into parallel light without fail through a collimating lens. . The present invention has not yet been developed.
And an aspherical microlens made of plastic comprising a light scattering portion as shown in (1) and a transparent microlens portion having at least one flat surface concave and having optical axis symmetry, and a method of manufacturing the same. The plastic microlens according to the present invention can be manufactured by a very simple method as compared with a glass microlens, and is more compact and lighter than a glass microlens. Furthermore, the manufacturing cost is very low. Hereinafter, the present invention will be described in more detail with reference to examples. EXAMPLE 1 50 parts by weight of polymethyl methacrylate, 10 parts by weight of benzyl methacrylate, 33 parts of methyl methacrylate
A mixture consisting of 7 parts by weight of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate and 0.25 part by weight of 1-hydroxycyclohexylphenyl ketone was heated and kneaded at 70 ° C. to dissolve the mixture. I let it. A resin composition (having a viscosity of 100,000 poise at 25 ° C.) is sandwiched between polyester films and has a thickness of 0.1
It was shaped into a 5 mm flat plate. Chromium was vapor-deposited on the flat shaped article, and a photomask having a mask section with a diameter of 1 mm in which a circular portion was made light-opaque was applied, and ultraviolet rays were irradiated using a parallel light source device (UT-501C manufactured by Ushio Inc.). . At this time, the irradiation intensity was 30 mW / cm ² , and the irradiation time was 20 minutes. At this time, the part irradiated with the parallel light becomes translucent,
Polymerization shrinkage occurred, and the portion of the photomask became concave. Thereafter, the photomask is further removed, and a 40 W chemical lamp is irradiated to polymerize and cure the uncured portion.
Transparent curing was possible while maintaining the concave portion. The produced double-sided concave object had a lens function. The concave depth of the concave portion was about 25 μm on both sides from the flat portion. Example 2 The same resin composition as used in Example 1 was used, and this resin composition was sandwiched between polyester films.
It was shaped into a flat plate having a diameter of 5 cm and a thickness of 0.5 mm. A photomask having a mask portion in which a large number of circular portions having a diameter of 650 μm and a pitch interval of 800 μm were made opaque was applied to the flat shaped article, and then the same operation as in Example 1 was performed. The lens part of the obtained micro lens has a diameter of 650 μm,
A flat lens array having an inter-lens pitch of 800 μm and a concave depth of the concave portion of the lens portion of 27 μm was produced. Each lens had uniform performance. Example 3 The same resin composition as used in Example 1 was sandwiched between polyester films to obtain a flat plate having a thickness of 1.0 mm. The same photomask as that used in Example 1 was applied to the flat resin composition surface, and the resin composition was subjected to a photocuring treatment in the same manner as in Example 1. At this time, the same type of aspherical microlens as in Example 1 could be manufactured, but the concave depth of the concave surface was 32 μm. Comparative Example 1 The same photomask as that used in Example 1 was applied to the surface of a 0.5 mm-thick plate-like resin composition sandwiched between the same polyester films produced in Example 1,
As a result of irradiating scattered light with a W chemical lamp for 20 minutes, no concave surface was formed in the mask portion, and no opaque portion was formed in the light irradiated portion. EXAMPLE 4 A resin mixture comprising 50 parts by weight of polymethyl methacrylate, 30 parts by weight of methyl methacrylate, 20 parts by weight of 2,2,3,3-tetrafluoropropyl methacrylate, and 0.25 parts by weight of 1-hydroxycyclohexyl phenyl ketone Was heated and kneaded at 65 ° C. and dissolved to prepare a resin composition. This resin composition had a viscosity of 125,000 poise at 25 ° C. This resin composition was sandwiched between polyester films and shaped into a flat plate having a diameter of 6 cm and a thickness of 0.5 mm. Pitch a small circular mask part with a diameter of 350 μm on this flat shaped object.
A large number of photomasks having a thickness of 390 μm were applied, and then irradiation of parallel light and irradiation of scattered light were performed in the same manner as in Example 1. The lens has a diameter of 350 μm and a pitch of 3
A flat lens array having a thickness of 90 μm and a concave depth of the lens concave surface of 20 μm was produced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an example of a microlens of the present invention. FIG. 2 is a perspective view showing an example of the microlens of the present invention. FIG. 3 is a plan view illustrating an example of a photomask used in the present invention. [Description of Signs] 1... Concave lens portion 2... Light diffusion portion 3... Photomask mask portion 4... Photomask light transmission portion

Continuation of front page (56) References JP-A-6-160608 (JP, A) JP-A-63-153501 (JP, A) JP-A-60-53927 (JP, A) JP-A-64-40903 (JP) , A) JP-A-64-40946 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 1/00-1/08 G02B 3/00-3/14

Claims (1)

(57) [Claim 1] A resin composition of a polymer (A) and a photopolymerizable monomer (B) capable of dissolving the polymer (A) After applying a photomask having a small circular mask portion to the flat plate surface on which is shaped, irradiating parallel light to form a light scattering portion on the flat plate, the scattered light is applied to the flat plate without the photomask. A method for producing a plastic aspherical microlens, comprising irradiating to form a transparent concave lens portion in which at least one of the flat surfaces is concave, has optical axis symmetry, and the total depth of both surfaces is 20 μm or more. .