JP2020027225A - Optical element, optical device, and method of manufacturing optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element in which deterioration of optical performance due to water absorption in a use environment is suppressed. An optical element having a first base material 11, a resin 12 on the first base material 11, and a second base material 13 on the resin 12, wherein the resin 12 is an optical element. The effective portion 15 and the non-optical effective portion 16 located on the outer circumference of the optical effective portion 15 are provided, and the ratio of the elastic modulus of the non-optical effective portion 16 to the elastic modulus of the optical effective portion 15 is 1.01 or more and 1.19. It is below. [Selection diagram] Figure 1

Description

  The present invention relates to an optical element used for an optical device such as a camera, and a method for manufacturing the optical element.

  An optical element for a camera, video, or other optical device has an optical element having a structure in which a substrate (substrate), a photocurable resin or a thermosetting resin, and another substrate are sequentially laminated in the optical axis direction. Is widely used. Various production methods have been proposed for such an optical element. For example, Patent Document 1 discloses a method for curing a photocurable adhesive in order to prevent the photocurable resin agent from dripping on the outer peripheral surface of the base material. Is disclosed. In the adhesive curing device described in Patent Document 1, a light source for irradiating a light-curable resin agent interposed between two substrates with a light beam is provided, and the light-curable adhesive is cured by the light beam to form two substrates. Glue. Further, there is provided a reflecting member that reflects a light beam that radially spreads at least outward from the outer peripheral surface of the base material from the light source, and irradiates the outer peripheral surface joint of the two base materials. This describes that the photocurable resin agent is prevented from dripping on the outer peripheral surface of the base material.

JP-A-5-163037

  However, in an optical element manufactured by a conventional manufacturing method as described in Patent Document 1, there is a problem that optical performance is deteriorated in an environment in which an optical device having the optical element is used.

  Specifically, in the use environment, the resin of the optical element absorbs water vapor in the atmosphere of the use environment. The resin expands by absorbing water. The resin expanded by water absorption pushes up and deforms the base material in contact with the resin. In particular, when the substrate has a concave shape, the vicinity of the center of the concave shape is thin, and the mechanical strength of the substrate is low. Therefore, the deformation of the base material due to the water absorption expansion of the resin is remarkable. Further, the resin changes its refractive index by absorbing water. Whether the refractive index increases or decreases due to water absorption depends on the refractive index of the photocurable resin before water absorption, but the refractive index generally changes so as to approach the refractive index 1.33 of water.

  Water absorption of the resin in the use environment proceeds unevenly from the outer periphery of the base material in contact with the atmosphere toward the center of the base material. The optical performance of the optical element is degraded due to the deformation of the base material and the change in the refractive index of the resin caused by the expansion of the resin.

  The present invention has been made in view of the above problems. That is, an object of the present invention is to provide an optical element in which a decrease in optical performance due to water absorption in a use environment is suppressed.

  An optical element according to one embodiment of the present invention is an optical element including a first base, a resin on the first base, and a second base on the resin. The resin has an optically effective portion and a non-optically effective portion located on the outer periphery of the optically effective portion, and the ratio of the elastic modulus of the non-optically effective portion to the elasticity of the optically effective portion is 1.01 or more. 19 or less.

  Further, an optical device according to another embodiment of the present invention is an optical device including at least one optical element, and the optical element is an optical element according to one embodiment of the present invention.

  Furthermore, a method for manufacturing an optical element according to another aspect of the present invention includes a step of laminating a first base material, an uncured resin, and a second base material in this order, Is cured so that the ratio of the elastic modulus of the non-optically effective portion to the elastic modulus of the optically effective portion becomes 1.01 or more and 1.19 or less, and the non-optically effective portion is formed on the outer periphery of the optically effective portion. And the following.

According to one embodiment of the present invention, there is provided an optical element in which a decrease in optical performance due to water absorption in a use environment is suppressed.
According to another aspect of the present invention, there is provided an optical apparatus having the above-described optical element.
Further, according to another aspect of the present invention, there is provided a method for manufacturing the optical element.

1A and 1B are a top view and a cross-sectional view of an optical element according to one embodiment of the present invention. FIG. 4 is a cross-sectional view for explaining a method for manufacturing an optical element according to one embodiment of the present invention. 1A and 1B are a top view and a cross-sectional view of an optical element according to one embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating an example of a preferred embodiment of an optical device according to another aspect of the present invention.

An optical element according to one embodiment of the present invention will be described with reference to FIG.
1A and 1B are a top view and a cross-sectional view illustrating an optical element according to one embodiment of the present invention.

  The optical element 10 according to one embodiment of the present invention includes a first base 11, a resin 12 on the first base 11, and a second base 13 on the resin 12. The first substrate 11, the resin 12, and the second substrate 13 have a structure in which they are sequentially laminated in the direction of the optical axis O.

  As the first base material 11 and the second base material 13, those having a shape used for ordinary optical equipment, such as a flat, spherical, or aspherical uneven shape, can be used.

  The first base material 11 and the second base material 13 are made of glass or resin, and are preferably glass. Further, on the surfaces of the first base material 11 and the second base material 13, an antireflection film, a thin film for improving the adhesion to the resin 12, or the like may be formed.

  The resin 12 is a photocurable resin or a thermosetting resin, and has appropriate material properties such as a refractive index, a transmittance, a viscosity, and a cure shrinkage so that desired optical properties and good moldability are obtained. You can select and use one. For example, the thermosetting resin includes an epoxy resin and the like, and the photocurable resin includes an acrylic resin, an epoxy resin and a fluororesin.

  The resin 12 is formed such that the surface 14 where the first base material 11 and the second base material 13 are in contact with the resin 12 is formed on the outer periphery of one of the first base material 11 and the second base material 13 having a smaller diameter. Covering up. The resin 12 has an optically effective portion 15 and a non-optically effective portion 16 located on the outer periphery of the optically effective portion 15. The non-optically effective portion 16 is formed in an annular shape so as to surround the outer periphery of the optical element 10. The optically effective portion 15 is a region through which light used through the optical element 10 is transmitted, and the non-optically effective portion 16 is a first base material 11 or a second base material forming the optical element 10 from the outer periphery of the optically effective portion 15. 13 is a region up to the outer periphery of one of the base materials having a small diameter.

In the present invention, the non-optically effective portion 16 of the resin 12 of the optical element 10 has a higher elastic modulus than the optically effective portion 15. That is, the ratio of the elastic modulus of the non-optically effective portion 16 to the elastic modulus of the optically effective portion 15 in the resin 12 is 1.01 or more and 1.19 or less. Further, the ratio of the elastic modulus of the non-optically effective portion 16 to the elastic modulus of the optically effective portion 15 is preferably 1.05 or more and 1.19 or less.
In the present invention, since the non-optically effective portion 16 has a higher elastic modulus than the optically effective portion 15 as described above, the optical element 10 according to one embodiment of the present invention suppresses a decrease in optical performance due to water absorption in a use environment. The possible reasons are as follows.

  By applying light or heat to the resin 12 used for the optical element 10, polymerization and crosslinking of the resin 12 is started, and the curing reaction proceeds. As the curing reaction proceeds, the form of the resin 12 changes from liquid to solid, and the elastic modulus of the resin 12 increases as the curing reaction proceeds. On the other hand, in the resin 12, the cross-linking polymerization becomes dense as the curing reaction proceeds, and the water absorption decreases. That is, in the curing reaction of the resin 12, the higher the elastic modulus, the lower the water absorption.

  In the present invention, the non-optically effective portion 16 has a higher elastic modulus than the optically effective portion 15. That is, the non-optically effective portion 16 has lower water absorption than the optically effective portion 15. Since the non-optically effective portion 16 is formed in a ring shape on the outer periphery of the optical element 10, it is possible to suppress the invasion of water over the outer periphery of the optical element 10 due to its low water absorption. Thereby, the change in the refractive index due to the water absorption of the resin 12 and the deformation of the first base material 11 and the second base material 13 due to the water absorption expansion of the resin 12 are suppressed.

  Furthermore, when water invades the optically effective portion 15, the deformation of the first base material 11 and the second base material 13 due to the water absorption and expansion of the optically effective portion 15 is formed annularly on the outer periphery of the optical element 10. It is suppressed by the non-optically effective portion 16 having a high elastic modulus.

  As described above, in the optical element 10 according to one embodiment of the present invention, it is considered that a decrease in optical performance due to water absorption in a use environment is suppressed.

  When the curing reaction of the resin 12 has progressed sufficiently and the resin 12 has been completely cured, the curing reaction does not proceed even if further light or heat is applied, and the elastic modulus of the resin 12 converges to a constant value. When the resin 12 is, for example, a photocurable resin, the curing reaction of the resin 12 proceeds by the irradiation of ultraviolet rays, and at the same time, the bonds of the molecules constituting the resin 12 are broken. Therefore, when a large amount of ultraviolet light is irradiated until complete curing, the deterioration of the resin 12 due to the irradiation of the ultraviolet light becomes remarkable.

  In a state where the resin 12 is deteriorated by the irradiation of the ultraviolet rays, since the dense polymerized cross-linking structure of the resin 12 is broken by breaking the molecular bond, water molecules can easily enter the resin 12. That is, when the elastic modulus increases along with the curing reaction of the resin 12, the water absorption of the resin 12 decreases at first, but when the resin 12 is almost completely cured, the water absorption increases.

  In the present invention, the ratio of the modulus of elasticity of the non-optically effective portion 16 of the resin 12 to the modulus of elasticity of the resin 12 after completely cured is 0.95 or more and 0.99 or less, and the elasticity of the resin 12 after completely cured is obtained. The ratio of the elastic modulus of the optically effective portion 15 of the resin 12 to the modulus is preferably 0.80 or more and 0.94 or less.

  When the ratio of the modulus of elasticity of the non-optically effective portion 16 of the resin 12 to the modulus of elasticity of the resin 12 after being completely cured is 0.95 or more, it is possible to effectively suppress the entry of moisture in the atmosphere. . Further, since the ratio of the elastic modulus of the non-optically effective portion 16 of the resin 12 to the elastic modulus after the resin 12 is completely cured is 0.99 or less, it is possible to suppress an increase in water absorption due to deterioration of the resin 12. Can be.

  In particular, the elastic modulus of the non-optically effective portion 16 of the resin 12 is preferably 3 GPa or more. The elastic modulus of the resin 12 changes depending on the ambient temperature, but the above value is a value measured at an ambient temperature of 23 ° C. The elastic modulus of the resin 12 can be measured using a rheometer or a nano indenter.

  In the present invention, the curing reaction rate of the optically effective portion 15 of the resin 12 is preferably 75% or more and less than 94%, and the curing reaction rate of the non-optically effective portion 16 of the resin 12 is preferably 94% or more and 99% or less. . When the curing reaction rate of the non-optically effective portion 16 of the resin 12 is 94% or more, the infiltration of moisture in the atmosphere can be effectively suppressed. The rise can be suppressed. In addition, if the curing reaction rate of the optically effective portion 15 of the resin 12 is 75% or more, a certain degree of polymerization cross-linked structure of the resin is formed, and water absorption expansion in the optically effective portion 15 can be suppressed. If it is less than 94%, the difference in water absorption expansion in the lens radial direction can be reduced, and local deformation of the optical element can be suppressed.

  Further, the resin 12 preferably contains inorganic fine particles. By containing the inorganic fine particles, the water absorption of the resin 12 is reduced, and the effect of the present invention can be enhanced. In addition, the elastic modulus of the resin 12 is increased by containing the inorganic fine particles. Thereby, the effect of suppressing the deformation of the first base material 11 and the second base material 13 due to the water absorption and expansion of the optically effective portion 15 by the non-optically effective portion 16 having a high elastic modulus can be obtained.

As the inorganic fine particles, fine particles of an inorganic compound such as ZrO ₂ , SiO ₂ , TiO ₂ and ITO can be used.
The particle size of the inorganic fine particles contained in the resin 12 is preferably 5 nm or more and 100 nm or less. When the particle size of the inorganic fine particles is 5 nm or more, the elasticity can be increased by reducing the water absorption in the resin. When the particle size of the inorganic fine particles is 100 nm or less, an optical element having good transmittance can be manufactured. When the particle size of the inorganic fine particles exceeds 100 nm, the scattered light from the fine particles increases, and the transmittance of the optical element decreases. The weight content of the inorganic fine particles contained in the resin 12 is preferably 1% or more and 30% or less. When the weight content of the inorganic fine particles is 1% or more, the elasticity can be increased by reducing the water absorption in the resin. When the weight content of the inorganic fine particles is 30% or less, an optical element having good transmittance can be manufactured. If the weight content of the inorganic fine particles exceeds 30%, the scattered light from the fine particles increases, and the transmittance of the optical element decreases.

Consider a case where the surface 14 of the first base material 11 that contacts the resin 12 is a convex spherical surface, and the surface 14 of the second base material 13 that contacts the resin 12 is a concave spherical surface. At this time, the absolute value of the radius of curvature of the convex spherical surface of the first base material 11 is | r ₁ |, and the absolute value of the radius of curvature of the concave spherical surface of the second base material 13 is | r ₂ | It is preferable that | r ₁ | ≧ | r ₂ |. Thereby, the volume of the resin 12 of the non-optically effective portion 16 is reduced, water absorption from the non-optically effective portion 16 is suppressed, and deformation of the first base material 11 and the second base material 13 due to water absorption expansion is suppressed. can do.

  In the present invention, the size of the region of the non-optically effective portion 16 of the resin 12 can be appropriately designed according to the mode in which the optical element 10 is used. It is preferable that the length in the outer peripheral direction of 16 be 0.5 mm or more and 3.5 mm or less. Preferably, one of the smaller diameters of the first base material 11 and the second base material 13 has a circular projected shape in a direction perpendicular to the optical axis O, and has a length in the outer circumferential direction of the optically effective portion 15. The ratio of the length in the outer peripheral direction of the non-optically effective portion 16 to the ratio is not less than 1/19 and not more than 7/50. Here, the length in the outer peripheral direction of the optically effective portion 15 is a length from the boundary surface between the optically effective portion 15 and the non-optically effective portion 16 to the center of the optically effective portion 15. The length of the non-optically effective portion 16 in the outer circumferential direction is defined as a point corresponding to the outer periphery of the smaller diameter substrate of the two substrates forming the optical element 10 of the non-optically effective portion 16. This is the length of a line drawn perpendicular to the tangent at the boundary between 15 and the non-optically effective portion 16.

  When the ratio of the length of the non-optically effective portion 16 in the outer circumferential direction to the length of the optically effective portion 15 in the outer circumferential direction is 1/19 or more, the first base material 11 accompanying the water absorption expansion of the optically effective portion 15 is formed. In addition, the effect of suppressing deformation of the second base material 13 can be enhanced. Further, since the ratio of the length of the non-optically effective portion 16 in the outer circumferential direction to the outer circumferential direction of the optically effective portion 15 is 7/50 or less, the size of the optical element 10 does not become too large. A sufficient area can be secured.

  The optical element 10 may have a diffraction grating forming resin 17 on a surface 14 of the first base material 11 or the second base material 13 which is in contact with the resin 12, as shown in FIG. . At this time, the diffraction grating forming resin 17 may have a region larger than the optically effective portion 15, but it is preferable that the region of the diffraction grating forming resin 17 in contact with the non-optically effective portion 16 is as small as possible.

  Although FIGS. 1 and 3 show an example in which the optically effective portion 15 and the non-optically effective portion 16 are made of the same resin 12, the optically effective portion 15 and the non-optically effective portion 16 may be made of different resins. Good.

(Method of manufacturing optical element)
A method of manufacturing an optical element according to another aspect of the present invention includes a step of laminating a first substrate, an uncured resin, and a second substrate in this order, Curing such that the ratio of the elastic modulus of the non-optically effective portion to the elastic modulus of the optically effective portion is 1.01 or more and 1.19 or less, and forming the non-optically effective portion on the outer periphery of the optically effective portion; Having.

  Hereinafter, a method for manufacturing an optical element according to another embodiment of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view for explaining a method for manufacturing an optical element according to another embodiment of the present invention.

  First, as shown in FIG. 2A, an appropriate amount of uncured resin 12 is placed on the first base material 11. The uncured resin 12 can be placed on the first base material 11 by, for example, dripping with a dispenser. Next, as shown in FIG. 2B, a force is applied to the second base material 13 in the direction of the arrow shown in FIG. 2B, and the uncured resin 12 is applied to the first base material 11. It spreads between the first base material 11 and the second base material 13 until it reaches a desired thickness. At this time, the first base material 11 or the second base material 13 may be rotated around the optical axis to spread the uncured resin 12 concentrically.

  Thereby, the first substrate 11, the uncured resin 12, and the second substrate 13 can be laminated in this order. The uncured resin 12 is used in an amount sufficient to spread to the outer peripheries of the first base material 11 and the second base material 13 when expanded to a desired thickness.

  Subsequently, as shown in FIG. 2C, energy 18 such as light or heat is applied to the uncured resin 12 so that the ratio of the elastic modulus of the non-optically effective portion 16 to the elasticity of the optically effective portion 15 is reduced. The uncured resin 12 is cured so as to be 1.01 or more and 1.19 or less, and a non-optically effective portion is formed on the outer periphery of the optically effective portion.

  As a method of curing the resin 12 so that the elastic modulus of the optically effective portion 15 and the elasticity of the non-optically effective portion 16 have the above relationship, for example, the curing reaction proceeds more in the non-optically effective portion 16 than in the optically effective portion 15. As described above.

  Specifically, for example, when the resin 12 is a photo-curable resin, first, the entire uncured resin 12 is irradiated with light to be primarily cured. Subsequently, a portion where the first base material 11 or the second base material 13 is in contact with the optically effective portion 15 is covered with a light-shielding plate, and the non-optically effective portion 16 of the resin 12 is further irradiated with light only to the non-optically effective portion 16. 16 is subjected to secondary curing. When the resin 12 is cured by irradiation with light, the atmosphere may be filled with an inert gas such as nitrogen or vacuum.

  Alternatively, a light source for irradiating the optically effective portion 15 and a light source for irradiating the non-optically effective portion 16 are separately prepared, and the optically effective portion 15 and the non-optically effective portion 16 of the resin 12 are independently cured. Good. By appropriately designing the conditions such as the type of each light source, the light intensity, and the irradiation time individually in the optically effective portion 15 and the non-optically effective portion 16, the non-optically effective portion 16 is compared with the optically effective portion 15. It can be cured so that the curing reaction proceeds.

  At this time, for example, of the light-irradiated surface of the first base material 11 or the second base material 13, the part irradiated with the light incident on the optically effective part 15 and the light irradiated on the optically effective part 15 are irradiated. A light source including the light source is covered with a light shielding member. Thereby, the optically effective portion 15 can be cured independently of the non-optically effective portion 16. In addition, the non-optically effective portion 16 can be cured independently of the optically effective portion 15 by using a light source for irradiating the non-optically effective portion 16 outside the light shielding member.

  When the resin 12 is a thermosetting resin, for example, first, the entire resin 12 is first cured by heating. Subsequently, the heating member is used in such a manner that the resin is heated by being brought into contact with the base material, and the heating member is attached to a portion of the first base material 11 or the second base material 13 which is in contact with the non-optically effective portion 16. Then, only the non-optically effective portion 16 of the resin 12 is cured by heating. Thus, the non-optically effective portion 16 can be cured so that the curing reaction proceeds more than the optically effective portion 15.

  Further, a heating member for heating and curing the optically effective portion 15 and a heating member for heating and curing the non-optically effective portion 16 may be separately prepared. For example, first, a heat insulating material is provided between a heating member for heating and curing the optically effective portion 15 and a heating member for heating and curing the non-optically effective portion 16. Next, each heating member is heated so that the temperature of the heating member for heating and curing the non-optically effective portion 16 is higher than the temperature of the heating member for thermally curing the optically effective portion 15. After that, by bringing each heating member into contact with the first base material 11 or the second base material 13, the non-optically effective portion 16 is cured so that the curing reaction proceeds more than the optically effective portion 15. Can be.

(Optical equipment)
Next, an optical apparatus according to another embodiment of the present invention will be described with reference to FIG. An optical device according to another aspect of the present invention is an optical device including at least one optical element, wherein the optical element is the optical element according to one embodiment of the present invention. An optical apparatus according to another embodiment of the present invention can be used for a telescope, binoculars, microscope, camera, endoscope, and the like having an optical element.

  FIG. 4 is a cross-sectional view illustrating an example of a preferred embodiment of an optical apparatus according to another aspect of the present invention. The optical device shown in FIG. 4 is specifically an interchangeable lens barrel of a single-lens reflex camera.

  In the optical system of the lens barrel 30, lenses 21 to 28 and the optical element 20 are arranged perpendicular to the optical axis O inside the housing 29. The left side of FIG. 4 is the surface of the lens barrel 30, and the right side of FIG.

  By disposing the optical element 20 according to one embodiment of the present invention at an appropriate position in the optical system, a lens barrel capable of capturing a high-definition and high-quality image can be provided.

<Preparation of optical element>
(Example 1)
As the first substrate 11, a glass spherical lens having a diameter of 35 mm (hereinafter, referred to as lens 1) was used. The surface 14 of the lens 1 which is in contact with the resin 12 is convex and has a radius of curvature of 130.0 mm. In addition, as the second base material 13, a glass spherical lens having a diameter of 35 mm (hereinafter, referred to as lens 2) was used. The surface 14 of the lens 2 that contacts the resin 12 is concave and has a radius of curvature of 130.0 mm.

  As the resin 12, a photocurable resin (hereinafter, referred to as photocurable resin 1) made of a colorless and transparent sulfur-containing acrylic resin (UV1000, manufactured by Mitsubishi Chemical Corporation) was used.

First, the surface 14 of the lens 1 and the lens 2 which is in contact with the photocurable resin 1 was subjected to a silane coupling treatment for strengthening the adhesion to the photocurable resin 1. Specifically, a silane coupling agent diluted to a few percent with a solvent is applied to the surface 14 of the lens 1 and the lens 2 by spraying, and this is dried in an oven at 100 ° C. for 1 hour. A ring layer was formed.
Subsequently, 120 mg of the uncured photocurable resin 1 was dropped on the lens 1 using a dispenser. Then, the lens 2 is pressed against the uncured photo-curable resin 1, and the thickness between the lens 1 and the lens 2 is 0.1 mm on the optical axis and 0.08 mm on the outer periphery of the optical element. Expanded to become.

Then, using an ultraviolet irradiation lamp, the ultraviolet light of the light intensity 20 mW / cm ² was irradiated for 600 seconds to the entire photo-curable resin 1 through the lens 2. Subsequently, a shielding plate was disposed between the ultraviolet irradiation lamp and the optically effective portion 15, and the non-optically effective portion 16 was irradiated with ultraviolet light having a light intensity of 20 mW / cm ² through the lens 2 for 1200 seconds. The length in the radial direction of the non-optically effective portion 16 of the photocurable resin 1 was 2 mm.

  Further, in order to reduce the residual stress due to the curing reaction of the photocurable resin 1, the optical element 1 according to Example 1 was manufactured by being left in an atmosphere at 60 ° C. for 10 hours.

(Example 2)
As the first substrate 11, a glass spherical lens having a diameter of 57 mm (hereinafter referred to as lens 3) was used. The surface 14 of the lens 3 which is in contact with the resin 12 is convex and has a radius of curvature of 40.6 mm. Further, a glass spherical lens having a diameter of 63 mm (hereinafter, referred to as lens 4) was used as the second base material 13. The surface 14 of the lens 4 that contacts the resin 12 is concave and has a radius of curvature of 40.65 mm.

As the resin 12, a photo-curable resin 2 obtained by adding ZrO ₂ fine particles having a particle size of 10 nm or less to the photo-curable resin 1 so as to be 20% by volume was used. As the diffraction grating forming resin 17, a colorless and transparent photocurable acrylic resin (RC-C001, DIC Corporation) was used.

  First, the silane coupling treatment was performed on the surface 14 of the lenses 3 and 4 that was in contact with the photocurable resin 2 in the same manner as in Example 1.

Further, the uncured diffraction grating forming resin 17 was put into a mold having an inverted shape of the diffraction grating, and the lens 3 was brought into contact with the diffraction grating forming resin 17 from the side opposite to the mold. Thereafter, the diffraction grating forming resin 17 was irradiated with ultraviolet light from the ultraviolet irradiation lamp through the lens 3 to be cured, and then released. At this time, the diffraction grating forming resin 17 was irradiated with ultraviolet light having a light intensity of 20 mW / cm ² for 300 seconds.

  Subsequently, 310 mg of the uncured photocurable resin 2 was dropped on the diffraction grating forming resin 17 cured on the lens 3 using a dispenser. Further, the lens 4 is pressed against the photocurable resin 2, and the thickness on the optical axis is 0.05 mm between the lens 4 and the diffraction grating forming resin 17 or the lens 3, and the thickness around the optical element. Was 0.05 mm.

Next, the entire photocurable resin 2 was irradiated with ultraviolet light having a light intensity of 32 mW / cm ² for 1000 seconds through the lens 4 using an ultraviolet irradiation lamp. Subsequently, using a light guide in which a plurality of optical fibers are arranged in an annular shape according to the shape of the non-optically effective portion 16, a plurality of spot lights are simultaneously irradiated only on the non-optically effective portion 16. At this time, ultraviolet light having a light intensity of 32 mW / cm ² per spot light was irradiated for 5000 seconds. The length in the radial direction of the non-optically effective portion 16 of the photocurable resin 2 was 3.5 mm.

  Further, in order to reduce the residual stress due to the curing reaction of the photocurable resin 2, the optical element 2 according to Example 2 was manufactured by being left in an atmosphere at 60 ° C. for 10 hours.

(Example 3)
An optical element 3 according to Example 3 was manufactured in the same manner as in Example 1 except that the following conditions were used in manufacturing the optical element 1 according to Example 1.

  As the first base material 11, a glass spherical lens having a diameter of 20 mm (hereinafter, referred to as a lens 5) was used. The surface 14 of the lens 5 in contact with the resin 12 is convex and has a radius of curvature of 100.0 mm. Further, as the second base material 13, a glass spherical lens having a diameter of 20 mm (hereinafter referred to as a lens 6) was used. The surface 14 of the lens 6 in contact with the resin 12 is concave and has a radius of curvature of 34.72 mm.

As the resin 12, a photocurable resin 3 obtained by adding 5% by volume of SiO ₂ fine particles having a particle diameter of 20 nm or less to a colorless and transparent epoxy resin was used.

  The photocurable resin 3 was spread between the lens 5 and the lens 6 so that the thickness on the optical axis was 1 mm and the thickness on the outer periphery of the optical element was 0.03 mm.

In curing the photocurable resin 3, the entire photocurable resin 3 was irradiated with ultraviolet light having a light intensity of 46 mW / cm ² through the lens 5 for 300 seconds using an ultraviolet irradiation lamp. Subsequently, a shielding plate was disposed between the ultraviolet irradiation lamp and the optically effective portion 15, and the non-optically effective portion 16 was irradiated with ultraviolet light having a light intensity of 46 mW / cm ² through the lens 5 for 1200 seconds. The length in the radial direction of the non-optically effective portion 16 of the photocurable resin 3 was 0.5 mm.

(Comparative Examples 1 and 2)
In the production of the optical element 1 according to the example 1, except that the conditions of the photocuring of the photocurable resin 1 were changed, the comparative optical element 1 according to the comparative example 1 and the comparative example 2 were modified in the same manner as in example 1. Comparative optical element 2 was produced.
In Comparative Example 1, the entire photocurable resin 1 was irradiated with ultraviolet light having a light intensity of 20 mW / cm ² through the lens 2 for 1500 seconds using an ultraviolet irradiation lamp. Subsequently, a shielding plate was disposed between the ultraviolet irradiation lamp and the optically effective portion 15, and the non-optically effective portion 16 was irradiated with ultraviolet light having a light intensity of 20 mW / cm ² through the lens 2 for 3500 seconds.
In Comparative Example 2, the entire photocurable resin 1 was irradiated with ultraviolet light having a light intensity of 20 mW / cm ² through the lens 2 for 150 seconds using an ultraviolet irradiation lamp. Subsequently, a shielding plate was disposed between the ultraviolet irradiation lamp and the optically effective portion 15, and the non-optically effective portion 16 was irradiated with ultraviolet light having a light intensity of 20 mW / cm ² through the lens 2 for 950 seconds.

(Comparative Example 3)
A comparative optical element 3 according to Comparative Example 3 was produced in the same manner as in Example 3 except that the conditions for photocuring the photocurable resin 3 were changed in the production of the optical element 3 according to Example 3.
In Comparative Example 3, a shielding plate was disposed between the ultraviolet irradiation lamp and the non-optically effective portion 16, and the optically effective portion 15 was irradiated with ultraviolet light having a light intensity of 46 mW / cm ² through the lens 2 for 280 seconds. Subsequently, the shielding plate was removed, and the entire photocurable resin 3 was irradiated with ultraviolet light having a light intensity of 46 mW / cm ² through the lens 2 for 20 seconds.

<Evaluation>
The following evaluations were performed on the optical elements 1 to 3 according to Examples 1 to 3 and the comparative optical elements 1 to 3 according to Comparative Examples 1 to 3.

(Elastic modulus)
The elastic modulus of the resin 12 was measured using a nano indenter as follows.
First, a cross section of the optical element was cut out and polished. Subsequently, indentation measurement was performed on the surface to be measured of the resin with a fine diamond indenter at a depth of 5 to 20 μm, and the elastic modulus was calculated from the obtained result. The indentation measurement was performed on the optically effective portion 15, the non-optically effective portion 16, and the completely cured resin 12 of the resin 12.
The elastic modulus of the resin 12 at the time of complete curing was measured as follows. The method of measuring the elastic modulus is the same as the method using the nano indenter described above, and therefore the description thereof is omitted. In order to define the elastic modulus of the photocurable resin at the time of complete curing, first, the change in the elastic modulus with respect to the irradiation amount of ultraviolet light is measured. Specifically, the section of the resin 12 of the optical element cut out by polishing was irradiated with ultraviolet light a plurality of times, and the elastic modulus of each was measured. It shows that the elastic modulus increases as the ultraviolet light is irradiated and converges to a constant value. The convergence value of the elastic modulus was calculated by fitting analysis, and the convergence value was used as the elastic modulus at the time of complete curing. In order to define the elastic modulus of the thermosetting resin at the time of complete curing, heat is applied to the resin 12, the respective elastic moduli are similarly measured, and their convergence values may be calculated.
Table 1 shows the results.

(Curing reaction rate)
The curing reaction rates in the optically effective portion 15 and the non-optically effective portion 16 of the resin 12 were calculated by analyzing an IR spectrum of the resin measured by an FT-IR spectrometer.
Specifically, in order to measure the curing reaction rate of the photocurable resin, a change in the IR spectrum with respect to the irradiation amount of ultraviolet light was measured. The cross section of the resin 12 of the optical element cut out by polishing was irradiated with ultraviolet light a plurality of times, and the IR spectra of the surface of the optically effective portion 15 and the surface of the non-optically effective portion 16 were measured using a micro total reflection measurement method. . As the IR spectrum, a reaction spectrum such as a carbon double bond part of acrylic acid which is reduced by a curing reaction and a reference spectrum such as a carbonyl group which does not change even by the curing reaction were measured.
The peak area of the reaction spectrum decreases with the irradiation of ultraviolet light and converges to a constant value. This convergence value is defined as the peak area of the reaction spectrum at the time of complete curing. The curing reaction rate for each irradiation amount of ultraviolet light was calculated using a value obtained by dividing the peak area of the reaction spectrum for each irradiation amount by the peak area of the reference spectrum. By normalizing the calculated values with the values at the time of complete curing and calculating the reciprocal thereof, the curing reaction rate for each irradiation amount can be obtained.
In order to measure the curing reaction rate of the thermosetting resin, heat may be applied to the resin 12, and the IR spectrum measurement and the curing reaction rate may be calculated in the same procedure.
Table 1 shows the results.

(Optical performance)
The optical performance of each optical element according to each example and comparative example was evaluated as follows using a Fizeau interferometer.

First, the transmitted wavefront of each optical element was measured by a Fizeau interferometer. The obtained transmitted wavefront was fitted, and the PV value was read from the phase cross section of the transmitted wavefront passing through the center of the lens.
In the fitting of the transmitted wavefront, the spherical component of the transmitted wavefront is removed using a computer program and converted into a plane component. The transmitted wavefront contains phase information such as the refractive index and optical shape of each material constituting the optical element. By analyzing the cross section of the phase information, it is possible to evaluate changes in the refractive index and the shape of the material due to water absorption. In particular, the PV value of the phase cross section can remarkably show the shape warpage of the outer periphery and the change in the refractive index due to water absorption expansion of the optical element. For example, when water enters the outer periphery of the optical element and the refractive index of the material becomes higher, the phase of the outer periphery of the optical element in which water has entered is measured to be later than the phase of the center of the optical element in which water has not entered. You.

  Subsequently, a test simulating long-term use was performed by putting each optical element into a high-temperature and high-humidity tank at an ambient temperature of 60 ° C. and a humidity of 90% for 1000 hours.

After the test, the transmitted wavefront was measured again to read the PV value, and the change in the PV value before and after the test was calculated.
Table 1 shows the results.

  In the evaluation of the optical performance, the larger the amount of change in the PV value, the greater the decrease in the optical performance due to water absorption of the resin 12.

  Table 1 shows that in the optical elements according to Examples 1 to 3, a decrease in optical performance due to absorption of water into the resin was suppressed.

Reference Signs List 10 optical element 11 first base material 12 resin 13 second base material 15 optically effective portion 16 non-optically effective portion

Claims (9)

A first substrate, a resin on the first substrate, and an optical element having a second substrate on the resin,
The resin has an optically effective portion and a non-optically effective portion located on the outer periphery of the optically effective portion,
A ratio of the elastic modulus of the non-optically effective portion to the elastic modulus of the optically effective portion is 1.01 or more and 1.19 or less;
An optical element, characterized in that: The ratio of the modulus of elasticity of the non-optically effective portion to the modulus of elasticity of the resin after complete curing is 0.95 or more and 0.99 or less,
The ratio of the elastic modulus of the optically effective portion to the elastic modulus of the resin after complete curing is 0.80 or more and 0.94 or less.
The optical element according to claim 1.   The optical element according to claim 1, wherein the non-optically effective portion has an elastic modulus of 3 GPa or more.   The optical element according to claim 1, wherein the resin contains inorganic fine particles. The surface of the first base material that is in contact with the resin is a convex spherical surface, and the surface of the second base material that is in contact with the resin is a concave spherical surface,
The absolute value of the radius of curvature of the convex spherical surface of the first substrate is | r ₁ |, and the absolute value of the radius of curvature of the concave spherical surface of the second substrate is | r ₂ | 5. The optical element according to claim ₁ , wherein | r ₁ | ≧ | r ₂ |.   One of the smaller diameters of the first base material and the second base material has a circular projected shape in a direction perpendicular to an optical axis, and the non-optical element has a non-optical length with respect to a length in an outer peripheral direction of the optically effective portion. The optical element according to any one of claims 1 to 5, wherein the ratio of the length of the effective portion in the outer peripheral direction is from 1/19 to 7/50.   The optical element according to any one of claims 1 to 6, wherein the length of the non-optically effective portion in the outer peripheral direction is 0.5 mm or more and 3.5 mm or less.   An optical device having at least one optical element, wherein the optical element is the optical element according to any one of claims 1 to 7. Laminating a first substrate, an uncured resin, and a second substrate in this order;
The uncured resin is cured so that the ratio of the elastic modulus of the non-optically effective portion to the elastic modulus of the optically effective portion becomes 1.01 or more and 1.19 or less. Forming a part,
A method for producing an optical element, comprising:

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