JP2004098457A - Composite optical element and manufacturing apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the stabilization and selectability of highly accurate index of refraction of a photo-setting resin which constitutes a composite optical element. <P>SOLUTION: An apparatus for manufacturing the composite optical element by forming a resin layer, which is composed of a photo-setting resin material 11, on the surface of a base material 10 of the optical element is equipped with: a mold member 6 which has a molding surface 8 for transferring a shape with a desired optical function onto the surface of the resin layer; a light irradiation part 12 which applies light to the resin layer 11 supplied between the base material 10 and the molding surface 8, so as to cure the resin material 11; and temperature controllers 5, 7 and 15 which control the temperature of a placement part for placing the mold member 6 or the composite optical element in the process of the curing of the resin material 11, so that the index of the post-curing refraction of the resin material 11 can be a desired value. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for manufacturing an optical element by molding a resin layer on a base material of the optical element.
[0002]
[Prior art]
Conventionally, as one of the molding technologies for composite optical elements represented by diffractive optical elements and aspherical lenses, it is characterized by excellent large-area moldability and high transferability, and is suitable for mass production due to its ease of molding technology. There are known replica molding techniques. In this replica molding technique, a photocurable resin is dropped on a mold forming surface having a shape inverted from a desired optical shape, and a lens blank is pressed and spread from above, and when a desired shape is obtained, a light source is used. To cure the photocurable resin, and release the cured resin together with the lens blank to perform molding.
[0003]
In the optical design stage of a composite optical element manufactured by the replica molding technique, optical design is performed in consideration of an optical shape calculated in advance and material properties of the material so as to satisfy desired optical performance. Taking the design of a diffractive optical element as an example, there are a wide variety of design elements, such as the optical shape of the diffractive optical element itself, as well as the transmittance, refractive index, and elastic modulus of the photocurable resin or glass substrate used.
[0004]
Among these optical design elements, the refractive index of the photocurable resin is one of the extremely important factors in determining the optical performance of the composite optical element, and the design of the optical shape is also required in the initial optical design process. Prior to this, the determination of the desired refractive index and its optical material is prioritized.
[0005]
At present, there are various types of off-the-shelf photocurable resins used in the replica molding technology of the composite optical element in the range of refractive index nd = 1.4 to 1.7. Widely used in the production of elements and aspheric lenses.
[0006]
As a conventional technique for manufacturing a composite optical element, for example, a technique disclosed in Japanese Patent Application Laid-Open No. H10-152510 is cited. In Japanese Patent Application Laid-Open No. H10-152510, a molding die is used for the purpose of enhancing the adhesion between the photocurable resin and the lens blank substrate, or for increasing the curing reactivity of the photocurable resin by light irradiation and shortening the molding tact time. There have been proposals to utilize a heating mechanism.
[0007]
Further, Japanese Patent Application Laid-Open No. 6-344350 proposes a manufacturing process for controlling a mold temperature for the purpose of improving the releasability between a cured resin and a mold.
[0008]
However, these two prior arts do not mention the process of controlling the refractive index of the photocurable resin constituting the composite optical element to be manufactured, and further cause the following problems.
[0009]
[Problems to be solved by the invention]
In a replica molding technology of a composite optical element that forms a desired aspherical shape or a fine shape using an optical resin material on an optical plane or an optical curved surface on a glass substrate, in recent years, a high refractive index-low Photocurable resins having excellent optical properties, such as dispersion materials and low refractive index-high dispersion materials, have been developed one after another. At the same time, however, these new resin materials have properties such as difficulty in photocuring reaction of the resin, unstable refractive index of the cured resin, brittle and fragile cured resin, and low melting point and low glass transition temperature of the resin material. And there are still many that are not suitable as molding materials for replica technology for molding composite optical elements.
[0010]
Among the material properties of these photocurable resins, stabilization of the refractive index of the cured resin after photocuring is one of the most important factors in obtaining desired optical performance of the composite optical element. In order to stabilize the refractive index of the cured resin, it is necessary to mix and refine the resin material itself such as resin monomer and other additives with high precision. The rate depends.
[0011]
The post-curing refractive index in the curing molding process of the photocurable resin is determined by the resin curing rate and the resin curing shrinkage rate, firstly, the resin shrinkage and expansion rate due to the ambient temperature, and even if the same resin is cured. The curing process causes variations in the refractive index.
[0012]
For example, regarding the effect of the former resin curing rate and the resin curing shrinkage rate on the refractive index, a resin with a high resin curing rate, which is light-cured by irradiating a large amount of light, is light-cured by irradiating a small amount of light. The resin has a higher refractive index than the resin having a lower resin curing rate. Generally, a photocurable resin undergoes curing by polymerization or cross-linking reaction caused by generation of radicals due to light irradiation, and as a result, the polymer density increases, so that resin curing shrinkage occurs. This explains that the resin irradiated with a large amount of light and having a high resin curing rate has a higher polymer density due to more advanced resin curing shrinkage, and has an increased refractive index. The curing shrinkage of a photocurable resin as a general optical material is about several percent to 7% for an acrylate resin or a methacrylate resin and about several percent for an epoxy resin when completely cured at room temperature. And methacrylate-based resins have a larger difference in refractive index before and after resin curing.
[0013]
On the other hand, regarding the influence of the latter on the refractive index of the shrinkage and expansion coefficient of the resin due to the ambient temperature, when the same resin is irradiated with the same amount of light in a low-temperature atmosphere and in a high-temperature atmosphere, respectively, the resin cured in the low-temperature atmosphere Has a higher refractive index than a resin cured in a high-temperature atmosphere. In general, a photocurable resin causes a thermal expansion due to a change in ambient temperature and a volume change due to cooling and shrinkage before and after the resin is cured. This is because the intermolecular distance changes due to the increase / decrease in the mobility of the polymer constituting the resin, and at the same time, it also affects the increase / decrease in the polymer density of the resin. From this, it can be explained that the reason why the refractive index of the resin light-cured in a low-temperature atmosphere is increased is that the resin is cured while being cooled and contracted and the polymer density is kept high. The linear expansion coefficient of a photocurable resin as a general optical material is in the range of 2 to 20 × 10 ⁻⁵ [° C. ⁻¹ ].
[0014]
However, in the technique disclosed in Japanese Patent Application Laid-Open No. H10-152510, molding for the purpose of enhancing the adhesion between the photocurable resin and the lens blank substrate or for promoting the curing reaction of the molding resin. This is mold heating, and does not take into account the effects of thermal expansion and cooling shrinkage on the molding resin.
[0015]
Also, in the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 6-344350, a mold temperature control process for improving the releasability between a cured resin and a mold using a mold temperature control mechanism is also used. There is also no consideration of the effects of thermal expansion and cooling shrinkage on the molding resin.
[0016]
Therefore, these conventional photocurable resin curing molding processes do not consider the effects of light irradiation on curing and contraction of the resin and shrinkage and expansion at ambient temperature on the resin refractive index. It cannot cope with high-precision resin refractive index control required for the composite optical element to be developed.
[0017]
Also, at the current production site for replica molded optical products using photocurable resin, the refractive index of the resin is not controlled using the temperature control mechanism, which may cause unstable factors such as temperature changes at the production site. It is not possible to produce products with excellent refractive index stability and uniformity.
[0018]
Furthermore, since the refractive index of the same resin cannot be arbitrarily selected within a variable range of the polymer density due to the contraction or expansion of the resin, the refractive index and the shape of the composite optical element can be freely determined in the optical design stage. The degree is too small.
[0019]
Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize highly accurate refractive index stabilization and selectivity of a photocurable resin constituting a composite optical element.
[0020]
It is another object of the present invention to improve the degree of freedom in the optical design stage of a composite optical element.
[0021]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, a composite optical element manufacturing apparatus according to the present invention forms a resin layer made of a photocurable resin material on a surface of a base material of an optical element. A composite optical element manufacturing apparatus for manufacturing a composite optical element, a mold member having a molding surface for transferring a shape having a desired optical function to a surface of the resin layer, and the base material A light irradiation unit for irradiating the photocurable resin material supplied between the molding surfaces with light to cure the photocurable resin material, and a refractive index of the photocurable resin material after curing becomes a desired value. As described above, the present invention is characterized by including a temperature control means for controlling the temperature of the mounting means for mounting the mold member or the composite optical element in the process of curing the photocurable resin material.
[0022]
In the apparatus for manufacturing a composite optical element according to the present invention, the temperature control unit may include a temperature sensor configured to detect a temperature of the mold member or the placing unit, and a heating unit configured to heat the mold member or the placing unit. Means.
[0023]
In the apparatus for manufacturing a composite optical element according to the present invention, the temperature control means may include a temperature sensor for detecting a temperature of the mold member or the placing means, and a cooling device for cooling the mold member or the placing means. Means.
[0024]
Further, a composite optical element according to the present invention is manufactured using the above-described manufacturing apparatus.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described.
[0026]
(1st Embodiment)
FIG. 1 is a schematic configuration diagram showing a replica molding apparatus for a composite optical element according to a first embodiment of the present invention.
[0027]
In FIG. 1, reference numeral 6 denotes a molding die provided with an inverted shape 8 of a desired optical function shape on its molding surface. A thermocouple temperature sensor 15 and a heater 7 are directly installed on a side surface of the molding die 6, and the temperature of the die is controlled by a heater power supply and a temperature controller 5.
[0028]
The molding die 6 is fixed, and a lens blank 10 is placed on a ring-shaped lens blank holding member 9 in which the molding die 6 is fitted. The alignment with the center axis of the surface is realized by fitting the lens blank 10 into the fitting portion of the lens blank holding material 9.
[0029]
The lens blank 10 is made of glass or plastic material, and has a flat or curved optical surface. The ring-shaped lens blank holding member 9 is held movably up and down. A photocurable resin 11 is supplied onto a molding surface of the molding die 6 by a dispenser (not shown), and an ultraviolet irradiation lamp 12 is provided above the lens blank 10 with ultraviolet rays perpendicular to the optical function surface of the molding die 6. It is installed so as to be incident on.
[0030]
As the ultraviolet curable resin 11, an optical resin such as an acrylate-based, methacrylate-based, or epoxy resin whose polymerization starts at a wavelength near 365 nm is used. A light source such as a lamp having an oscillation peak near a wavelength of 365 nm is used.
[0031]
FIG. 2 is a top view and a side view of the molding die 6 in the present embodiment.
[0032]
The fine shape forming the optical function surface 8 has a blazed diffraction grating having a grating height of 5 to 15 μm and a grating width of 0.1 to 10 mm on a plane at an optical effective diameter of φ20 mm, as shown in the top view. They are arranged concentrically in a convex shape toward the center. In the present embodiment, the temperature control by heating or cooling the molding die 6 may cause a change in the shape of the mold optical surface or the lattice due to its thermal expansion or cooling contraction. Shape correction must be taken into account.
[0033]
FIG. 3 is a top view and a side view of the diffractive optical element 1 manufactured by the molding die 6.
[0034]
The optical function surface 8 ′ of the resin layer formed on the lens blank 10 is formed concentrically as a concave shape toward the center of the blazed diffraction grating, that is, an inverted shape of the molding die 6. In the present embodiment, the diffractive optical element 1 having a fine shape is targeted, but in general, a composite optical element manufactured by a replica molding method includes an aspherical lens, a micro lens, and the like.
[0035]
Hereinafter, a specific curing molding process of the composite optical element according to the present embodiment will be described with reference to FIG.
[0036]
An acrylate-based ultraviolet-curable resin 11 is provided near the center of the molding surface of a molding die 6 having an optical effective diameter of 20 mm whose temperature has been previously adjusted to 80 ± 0.1 ° C. by a temperature controller 5 so as to obtain a desired resin refractive index. Is dropped from a dispenser (not shown), and a flat lens blank substrate 10 on which a silane coupling process has been performed on one side in order to increase the adhesive force with the resin in advance is placed in a ring shape with the coupling processing surface facing down. Into the lens blank holding member 9. At this time, a mechanism for holding the lens blank 10 such as a centering chuck or the like may be provided.
[0037]
Thereafter, the ring-shaped lens blank holding member 9 is lowered, the molding die 6 and the lens blank substrate 10 are relatively approached, and the ultraviolet curable resin 11 is pressed so as to fill the desired thickness and the outer circumference of the optical effective diameter. spread. At this time, the liquid contact speed is adjusted in consideration of the viscosity of the resin and the wettability of the molding surface of the mold in order to prevent air bubbles from being mixed into the ultraviolet curable resin 11 and to prevent the resin from filling the molded shape of the mold. There must be.
[0038]
Thereafter, the resin layer is irradiated with ultraviolet rays for 24 J (40 [mW / cm ² ] × 10 minutes) by the ultraviolet irradiation lamp 12. After the completion of the polymerization and curing, the ring-shaped lens blank holding member 9 is raised, whereby the diffractive optical element 1 composed of the cured resin 11 and the lens blank 10 is peeled from the molding die 6.
[0039]
In the above process, the temperature of the molding die 6 is constantly adjusted to 80 ± 0.1 ° C. However, if more precise temperature control of the molding die is required, the replica molding device itself is set to 80 ± 0.1 ° C. It may be stored in an oven whose temperature is adjusted to an atmosphere of 0.5 ° C.
[0040]
The refractive index of the ultraviolet-curable resin 11 used in the liquid state before photocuring is nd = 1.500 at a normal temperature of 25 ° C. Further, the resin 11 is cured by irradiating it with 24 J (40 [mW / cm ² ] × 10 minutes) of light from an ultraviolet irradiation lamp 12 in an atmosphere of 80 ° C. The polymer is cured at a desired polymer density due to stress relaxation opposite to curing shrinkage caused by irradiation. At this time, the refractive index of the resin when cured at a normal room temperature of 25 ° C. is nd = 1.520, whereas the refractive index of the resin cured in an atmosphere at 80 ° C. is nd = 1.515.
[0041]
However, in the configuration of the present embodiment, high-precision refractive index stabilization and selectivity of the photocurable resin constituting the diffractive optical element are realized, and at the same time, flexibility in the optical design stage of the composite optical element is improved, In addition, a diffractive optical element having a desired shape satisfying a sufficient optical function can be obtained.
[0042]
Further, in the present embodiment, in order to obtain a desired refractive index nd = 1.515 of the photocurable resin constituting the composite optical element, control of the mold temperature at 80 ° C. and 24J (40 [mW / cm ² ] × 10 minutes), but there are various curing process conditions for the mold temperature and the light irradiation amount for any desired resin refractive index.
[0043]
(Second embodiment)
This embodiment differs from the first embodiment only in the mold temperature control mechanism and the amount of light irradiation from the ultraviolet irradiation lamp 12, and the other configuration and process are the same.
[0044]
In the present embodiment, the heater 7 shown in FIG. 1 of the first embodiment is replaced with a cooling device so that the temperature of the molding die 6 can be controlled at a room temperature or lower, so that the molding die 6 can be controlled. Was set to 0 ± 0.1 ° C., and the amount of light irradiation from the ultraviolet irradiation lamp 12 was set to 30 J (40 [mW / cm ² ] × 12.5 minutes).
[0045]
Here, the reason why the light irradiation amount is increased as compared with the first embodiment is to compensate for insufficient curing of the resin due to cooling of the resin. The temperature of the molding die 6 is always controlled to 0 ± 0.1 ° C. However, if more precise temperature control of the molding die is required, the replica molding device itself is set to 0 ± 0.5 ° C. May be stored in a refrigerator whose temperature is adjusted to the atmosphere of the above.
[0046]
The photocurable resin used for molding is the acrylate-based ultraviolet curable resin 11 as in the first embodiment, and the refractive index in a liquid state before photocuring is nd = 1.500 at a normal temperature of 25 ° C. Further, the resin 11 is cured by irradiating it with 30 J (40 [mW / cm ² ] × 12.5 minutes) of light from the ultraviolet irradiation lamp 12 in an atmosphere of 0 ° C., but the resin 11 is cooled and shrunk by temperature control at 0 ° C. The polymer is cured at a desired polymer density by the stress relaxation that is synergistic with the curing shrinkage due to light irradiation. At this time, the refractive index of the resin cured at 25 ° C. in a normal room temperature is nd = 1.520, whereas the refractive index of the resin cured in an atmosphere of 0 ° C. is nd = 1.525.
[0047]
However, in the configuration of the present embodiment, high-precision refractive index stabilization and selectivity of the photocurable resin constituting the diffractive optical element are realized, and at the same time, flexibility in the optical design stage of the composite optical element is improved, In addition, a diffractive optical element having a desired shape satisfying a sufficient optical function can be obtained.
[0048]
Further, in the present embodiment, in order to obtain a desired refractive index nd = 1.525 of the photocurable resin forming the composite optical element, control of the mold temperature at 0 ° C. and 30J (40 [mW / cm ² ] × 12.5 minutes), but there are various curing process conditions for the mold temperature and the light irradiation amount for any desired resin refractive index.
[0049]
(Third embodiment)
This embodiment may be installed in a mold or a molding apparatus as a functional alternative mechanism of the mold temperature control mechanism such as the thermocouple temperature sensor 15 and the heater 7 shown in FIG. 1 which is the first embodiment. Alternatively, it is a configuration having a heating curing mechanism that is installed independently. This heating curing mechanism is composed of a temperature reading sensor section and a heating mechanism section. By heating the photocurable resin after the photocuring by the ultraviolet irradiation lamp 12 is completed, the resin curing rate is further increased, and Reduces polymer density due to thermal expansion.
[0050]
Hereinafter, the curing molding process of the composite optical element in the present embodiment will be described with reference to FIG.
[0051]
A suitable amount of an acrylate-based UV-curable resin 11 is dropped from a dispenser (not shown) near the center of the molding surface of the molding die 6 left at room temperature at 25 ° C., and a silane for increasing the adhesion to the resin in advance from above. The flat plate lens blank substrate 10 that has been subjected to the coupling processing on one side is fitted into the ring-shaped lens blank holding member 9 with the coupling processing surface down. At this time, a mechanism for holding the lens blank 10 such as a centering chuck or the like may be provided.
[0052]
Thereafter, the ring-shaped lens blank holding member 9 is lowered, the molding die 6 and the lens blank substrate 10 are relatively approached, and the ultraviolet curable resin 11 is pressed so as to fill the desired thickness and the outer circumference of the optical effective diameter. spread. At this time, the liquid contact speed must be adjusted in consideration of the viscosity of the resin and the wettability of the mold forming surface in order to prevent air bubbles from entering the resin 11 and to prevent the resin from being filled into the mold shape.
[0053]
Further, after irradiating the resin layer with ultraviolet rays at 5 J (40 [mW / cm ² ] × 2 minutes) by the ultraviolet irradiation lamp 12, the ring-shaped lens blank holding member 9 is lifted, so that the molding die 6 The diffractive optical element 1 composed of the cured resin 11 and the lens blank 10 is peeled off.
[0054]
The diffractive optical element 1 released from the mold at a low irradiation dose of 5 J in an atmosphere at normal temperature and 25 ° C. has a resin strength and viscoelasticity enough to withstand the release, but the resin curing rate is low and insufficient. In general, photocurable resin promotes resin curing by polymerization or cross-linking reaction caused by radical generation by light irradiation, but at the same time, heating of the photocurable resin increases the mobility of the polymer constituting the resin. To further accelerate its curing. Also, in the photocurable resin that has been irradiated with light, residual radicals are present in its composition, and curing continues even without light irradiation. Curing can be accelerated. Therefore, in order to compensate for the insufficient curing of the resin, the diffractive optical element 1 is left for 4 hours in an oven in a 60 ° C. atmosphere, which is a heating and curing mechanism installed independently of the molding apparatus. Thereby, the photocurable resin constituting the diffractive optical element 1 is completely cured, and at the same time, the polymer density is reduced due to the thermal expansion of the resin.
[0055]
In the process shown here, one diffractive optical element is put into the oven, but in consideration of productivity, a large number of diffractive optical elements may be put in at the same time. Since the irradiation time is about 2 minutes, a significant reduction in molding time is expected, and a reduction in production costs can be expected. Further, in the present embodiment, the heating curing mechanism is an oven that is installed independently of the molding apparatus, but may be directly installed in the molding die or the molding apparatus, and immediately after light irradiation by the ultraviolet irradiation lamp 12, Heat curing may be performed on the molding die.
[0056]
The refractive index of the acrylate-based ultraviolet-curable resin 11 used in molding in a liquid state before photocuring is nd = 1.500 at a normal temperature of 25 ° C. Furthermore, after irradiating 5 J (40 [mW / cm ² ] × 2 minutes) of light from an ultraviolet irradiation lamp 12 in a normal temperature 25 ° C. atmosphere, the resin 11 is cured by heating at 60 ° C. for 4 hours. Is cured at a desired polymer density by light irradiation in a normal temperature 25 ° C. atmosphere and curing shrinkage due to heat curing, and furthermore, stress relaxation opposite to thermal expansion due to heat curing. At this time, the refractive index of the resin when cured at a normal room temperature of 25 ° C. is nd = 1.520, whereas the refractive index of the resin cured through the process is nd = 1.515.
[0057]
However, in the configuration of the present embodiment, high-precision refractive index stabilization and selectivity of the photocurable resin constituting the diffractive optical element are realized, and at the same time, flexibility in the optical design stage of the composite optical element is improved, In addition, a diffractive optical element having a desired shape satisfying a sufficient optical function can be obtained.
[0058]
Further, in the present embodiment, in order to obtain a desired refractive index nd = 1.515 of the photocurable resin forming the composite optical element, 5J (40 [mW / cm ² ] × 2 minutes) at room temperature and 25 ° C. And curing at 60 ° C. for 4 hours, there are various curing process conditions for the heating curing condition and the light irradiation amount for any desired resin refractive index.
[0059]
As described above, according to the above embodiment, in replica molding of a composite optical element, the desired refractive index of the photocurable resin forming the composite optical element is determined by using a mold temperature control mechanism or a heat curing mechanism. By manufacturing a composite optical element at a temperature set so as to obtain a refractive index, highly accurate refractive index stabilization and selectivity of a photocurable resin can be realized. This makes it possible to improve the degree of freedom in the optical design stage of the composite optical element and to obtain a composite optical element having a desired shape that satisfies a sufficient optical function.
[0060]
【The invention's effect】
As described above, according to the present invention, it is possible to realize highly accurate refractive index stabilization and selectivity of the photocurable resin forming the composite optical element.
[0061]
Further, the degree of freedom in the optical design stage of the composite optical element can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a replica molding apparatus for a composite optical element according to a first embodiment of the present invention.
FIG. 2 is a top view and a side view of a molding die according to the first embodiment.
FIG. 3 is a top view and a side view of a diffractive optical element manufactured by a molding die.
FIG. 4 is a diagram illustrating a curing molding process of a composite optical element according to a third embodiment.
[Explanation of symbols]
Reference Signs List 5 Temperature controller 6 Mold 7 Heater or cooling device 8 Optical functional surface 8 'of optical mold 9 Optical functional surface of optical element 9 Lens blank holding member 10 Lens blank 11 Photocurable resin 12 UV irradiation lamp

Claims (4)

A composite optical element manufacturing apparatus for manufacturing a composite optical element by forming a resin layer made of a photocurable resin material on the surface of a base material of the optical element,
A mold member having a molding surface for transferring a shape having a desired optical function to the surface of the resin layer,
Light irradiation means for irradiating the photocurable resin material supplied between the base material and the molding surface with light for curing,
Mounting means for mounting the mold member or the composite optical element in the process of curing the photocurable resin material so that the refractive index of the photocurable resin material after curing becomes a desired value. And a temperature control means for controlling the temperature of the composite optical element. The said temperature control means is provided with the temperature sensor which detects the temperature of the said type | mold member or the said placement means, and the heating means which heats the said type | mold member or a placement means, The claim of Claim 1 characterized by the above-mentioned. Equipment for manufacturing composite optical elements. The said temperature control means is provided with the temperature sensor which detects the temperature of the said type | mold member or said installation means, and the cooling means which cools the said type | mold member or said installation means, The said Claim 1 characterized by the above-mentioned. Equipment for manufacturing composite optical elements. A composite optical element manufactured using the manufacturing apparatus according to claim 1.

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