Optical element, optical apparatus, image pickup apparatus, and method of manufacturing optical element

Abstract

The invention discloses an optical element, an optical apparatus, an image pickup apparatus, and a method of manufacturing the optical element. There is provided an optical element including: a glass substrate including a first surface and a second surface opposite the first surface; a resin portion disposed on the first surface; and a light shielding film configured to cover at least a portion of the side surface of the glass substrate and a portion of the first surface. The second surface is one of an incident surface or an exit surface of light. A portion of the light shielding film is provided between the glass substrate and the resin portion. A linear expansion coefficient of the light shielding film is between a linear expansion coefficient of the glass substrate and a linear expansion coefficient of the resin portion.

Description

Technical Field

[0001] The present invention relates to an optical element, an optical device, an image pickup device, and a method for manufacturing an optical element. Background Art

[0002] As one of optical elements, a lens having a transparent substrate such as glass provided with a cured product of a resin composition is known. This type of lens is manufactured using a mold by providing a resin composition between the substrate and the mold and forming a cured product having a desired shape on the surface of the substrate by polymerization or copolymerization. A lens manufactured by such a manufacturing method is called a "replication element".

[0003] So far, a method of reducing internal reflection caused by unnecessary light by forming a light-shielding film on the edge portion of a lens has been known for the purpose of improving the appearance quality of a replication element.

[0004] In Japanese Patent Application Laid-Open No. H07-072309, an aspherical lens as an example of a replication element is disclosed, in which the outermost peripheral edge surface of the cured product of the resin composition is covered with a light-shielding film.

[0005] However, although the optical element disclosed in Japanese Patent Application Laid-Open No. H07-072309 has excellent appearance quality, when the optical element is used in a low-temperature environment, resin cracking may occur in some cases, resulting in problems in the environmental durability of the lens. Summary of the Invention

[0006] An object of the present invention is to provide an optical element having both excellent appearance quality and excellent environmental durability, and a method for manufacturing the optical element.

[0007] According to one aspect of the present invention, there is provided an optical element including: a glass substrate including a first surface and a second surface opposite to the first surface; a resin portion provided on the first surface; and a light-shielding film configured to cover at least a part of a side surface of the glass substrate and a part of the first surface. The second surface is one of a light incident surface and a light exit surface. A part of the light-shielding film is provided between the glass substrate and the resin portion. The linear expansion coefficient of the light-shielding film is between the linear expansion coefficient of the glass substrate and the linear expansion coefficient of the resin portion.

[0008] According to another aspect of the present invention, there is provided a method for manufacturing an optical element including a glass substrate and a resin portion, the glass substrate including a first surface and a second surface opposite to the first surface, the resin portion being provided on the first surface, the second surface being one of a light incident surface and a light exit surface, the method including: a preparation step of preparing a glass substrate having a light-shielding film formed thereon; a filling step of filling a space between the glass substrate and a mold with a resin composition; a curing step of curing the resin composition to form the resin portion; and a mold detachment step of detaching the resin portion from the mold. The light-shielding film is formed on the glass substrate so as to cover at least a part of a side surface of the glass substrate and a part of the first surface. The filling step includes filling with the resin composition such that a space between the light-shielding film and the mold is filled with a part of the resin composition.

[0009] More features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A 、 Figure 1B and Figure 1C are schematic views for illustrating an optical element according to a first embodiment of the present invention.

[0011] Figure 2 is a schematic view for illustrating an optical element according to another embodiment of the present invention.

[0012] Figure 3 is a schematic view for illustrating an optical element according to still another embodiment of the present invention.

[0013] Figure 4A and Figure 4B are schematic views for illustrating a method for manufacturing an optical element according to a first embodiment of the present invention.

[0014] Figure 5 is a schematic view for illustrating an image pickup device according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0015] [First Embodiment]

[0016] Reference Figures 1A to 1C is made to describe an optical element and a method for manufacturing the optical element according to a first embodiment of the present invention.

[0017] First, the configuration of the optical element according to this embodiment will be described with reference to Figures 1A to 1C is a schematic view for illustrating the configuration of an optical element 10 according to this embodiment. Figures 1A to 1C

[0018] Figure 1A ​is a plan view for illustrating the optical element 10. Figure 1B is a sectional view in the thickness direction taken along Figure 1A line A-A' in Figure 1C is a sectional view for illustrating a part of the optical element 10 in an enlarged manner.

[0019] The optical element 10 according to this embodiment is an optical element called a "replication lens". As Figures 1A to 1C illustrated, the optical element 10 according to this embodiment includes a glass substrate 1 and a resin portion 2. The glass substrate 1 is transparent, and the resin portion 2 is a cured product of a resin composition formed on the glass substrate 1. The resin portion 2 is provided in close contact with the first surface 1A of the glass substrate 1. The thickness of the resin portion 2 in the optical axis direction O is not uniform in the radial direction of the optical element 10 and has a non-uniform in-plane distribution. This makes the surface of the resin portion 2 an aspherical shape.

[0020] The optical element 10 according to this embodiment is configured as an aspherical lens by including the resin portion 2, and thus can be manufactured in a short cycle compared with an aspherical lens configured solely of glass. Therefore, according to this embodiment, an aspherical lens can be manufactured at low cost.

[0021] The optical element 10 further includes a light-shielding film 3 that covers at least a part of the side surface 1F of the glass substrate 1 and a part of the outermost periphery of the first surface 1A. The light-shielding film 3 is formed in close contact with the glass substrate 1.

[0022] The glass substrate 1 includes a first surface 1A and a second surface 1B. The first surface 1A includes: an optical surface 1C that is a spherical surface; and a flat surface 1D. The second surface 1B faces the first surface 1A. The optical surface 1C has a concave spherical shape, and the second surface 1B has a convex spherical shape. The flat surface 1D is provided to be connected to the optical surface 1C by surrounding the optical surface 1C via a ridge line 1E. That is, the first surface 1A includes the optical surface 1C, the flat surface 1D provided at the outer edge of the optical surface 1C, and the ridge line 1E that is the boundary line between the optical surface 1C and the flat surface 1D. The second surface 1B is one of the light incident surface and the light exit surface in the optical element 10. Among the two optical surfaces included in the resin portion 2, the surface on the opposite side of the surface that contacts the first surface 1A is the other of the light incident surface and the light exit surface in the optical element 10. Both the first surface 1A and the surface of the resin portion 2 that contacts the first surface 1A are the light refracting surfaces in the optical element 10. That is, the surface including the resin portion 2 in the optical element 10 is in a state of being open to the external air, and no other optical elements are provided on the surface including the resin portion 2.

[0023] AsFigures 1A to 1C As shown in the figure, the resin portion 2 is preferably arranged to extend from the optical surface 1C, across the ridge line 1E, and reach a part of the flat surface 1D. In this case, the distal end 2A of the resin portion 2 is placed on the flat surface 1D.

[0024] A part of the light-shielding film 3 is provided between the resin portion 2 and the glass substrate 1 in the outermost periphery of the resin portion 2. With this configuration, when viewed from the second surface 1B side of the glass substrate 1, the light-shielding film 3 can block the bright lines caused by irregular reflection due to internal reflection of unwanted light entering from the side surface of the outermost periphery of the resin portion 2. Therefore, the appearance quality can be improved. In the present invention, the linear expansion coefficient of the light-shielding film 3 is between the linear expansion coefficient of the glass substrate 1 and the linear expansion coefficient of the resin portion 2. This enables the light-shielding film 3 to reduce the thermal stress caused by the difference in the linear expansion coefficients between the resin portion 2 and the glass substrate 1 in the case of thermal shock such as rapid cooling of the optical element 10. As a result, an optical element 10 with high environmental durability maintained over a long period can be obtained.

[0025] In Figures 1A to 1C In the optical element 10 shown in the figure, the thickness of the resin portion 2 having an aspherical shape at the center P0 which is the center of the spherical optical surface 1C is exceeded by the thickness of the resin portion 2 at a point P1 located between the center P0 and the end, and the thickness at the point P1 is the maximum thickness of the resin portion 2. Here, the thickness of the resin portion 2 refers to the thickness in the optical axis direction O of the optical surface 1C which is a spherical surface of the glass substrate 1. In the present invention, the thickness of the resin portion 2 at the point Px is regarded as the average value of the thicknesses obtained by measuring at a total of three points, namely the point Px, the point Px - 1, and the point Px + 1. The point Px is a certain point in the radial direction of the optical surface 1C. The points Px - 1 and Px + 1 are two points adjacent to the point Px, and the points Px - 1 and Px + 1 are each 0.5 mm away from the point Px in the radial direction of the optical surface 1C. The point Px - 1 is a point located closer to the center P0 than the point Px, and the point Px + 1 is a point located closer to the outer periphery of the optical surface 1C than the point Px. By forming the resin portion 2 into such a shape, the optical element 10 as a replication lens is configured as an aspherical lens having an aspherical shape.

[0026] The optical element 10 preferably satisfies at least one of the following two conditions. One of these conditions is that the ratio of the maximum thickness of the resin portion 2 in the optical axis direction O to the thickness of the resin portion 2 at the center position P0 of the optical surface 1C in the optical axis direction O is 5 or more. The aspherical amount of the optical element 10 having a value of 5 or more as the ratio of the thickness of the resin portion 2 at the point P1 to the thickness of the resin portion 2 at the center position of the optical surface 1C is large, and thus has optical characteristics suitable for the front element of a wide zoom lens.

[0027] The other of these conditions is that the ratio of the minimum thickness of the resin portion 2 in the optical axis direction O to the thickness of the resin portion 2 at the center position of the optical surface 1C in the optical axis direction O is 1 / 5 or less. The aspherical amount of the optical element 10 satisfying this other condition is also large, and thus is more effective in correcting distortion and chromatic aberration. Therefore, using the optical element 10 satisfying this other condition produces excellent image quality in a wide-angle lens, a telephoto lens, etc. that require a particularly wide field of view.

[0028] On the other hand, in a replication lens with a large aspherical amount, due to the influence of an increase in residual stress during molding, cracks are likely to occur in the resin portion 2 due to stress from a thermal shock. This is because when the resin portion 2 is too thick, the thermal stress increases in proportion to the thickness of the resin portion 2, and as a result, the probability of the resin portion cracking rises. Particularly in a part of the resin portion 2 formed on the ridge line 1E, stress concentration from a thermal shock tends to occur, and therefore, it is preferable to insert the light-shielding film 3 on the ridge line 1E as a stress-reducing layer. That is, as Figures 1A to 1C illustrated, the light-shielding film 3 is preferably provided to extend from the flat surface 1D, cross the ridge line 1E, and reach a part of the optical surface 1C. This enables the light-shielding film 3 to also effectively block bright lines. In this case, the distal end 3A of the light-shielding film 3 provided on the first surface 1A is placed on the optical surface 1C.

[0029] However, the configuration of the resin portion 2 and the light-shielding film 3 in the present invention is not limited to Figures 1A to 1C the example illustrated. For example, as Figure 2 illustrated, the light-shielding film 3 may be provided only on at least a part of the flat surface 1D without crossing the ridge line 1E. Additionally, in this case, by inserting the light-shielding film 3 having an appropriate linear expansion coefficient between the resin portion 2 and the glass substrate 1 at the end of the resin portion 2, cracking of the resin portion 2 can be reduced.

[0030] To give another example, as Figure 3As shown in the figure, the resin portion 2 can have its outermost periphery on the optical surface 1C without crossing the ridge line 1E, such that the resin portion 2 is not provided on the flat surface 1D. In this case, the light-shielding film 3 is continuously formed from the flat surface 1D to the optical surface 1C by crossing the ridge line 1E, and as in the example shown in Figure 2 the example shown in the figure, it is important to insert a light-shielding film 3 having an appropriate linear expansion coefficient between the resin portion 2 and the glass substrate 1 at the outermost periphery of the resin portion 2.

[0031] In short, in the present invention, the outermost periphery of the resin portion 2 can be located on either the optical surface 1C or the flat surface 1D, and an essential configuration is to insert a light-shielding film 3 having an appropriate linear expansion coefficient between the resin portion 2 and the glass substrate 1 at the outermost periphery of the resin portion 2. This makes it possible to improve the appearance quality of the optical element 10 and also makes it possible to reduce cracking of the resin portion 2 by reducing thermal stress.

[0032] In the optical element 10 according to this embodiment, when the radius "r" of the optical surface 1C is 100%, the width of the laminated region R, which is the region where the resin portion 2 and the light-shielding film 3 are stacked, in the direction perpendicular to the optical axis direction O is preferably 1% or more and 10% or less. The radius "r" of the optical surface 1C is the distance from the center P0 of the optical surface 1C to the ridge line 1E in the direction perpendicular to the optical axis direction O. When the ratio of the width of the laminated region R to the radius "r" of the optical surface 1C is 1% or more, even when the half-opening angle of the optical element 10 is large, bright lines can be reduced, and thus a decrease in appearance quality can be reduced. In addition, the large width of the laminated region R enables the light-shielding film 3 to effectively function as a stress-reducing layer. When the ratio of the width of the laminated region R to the radius "r" of the optical surface 1C is 10% or less, an increase in the outer diameter of the lens that is not required can be avoided.

[0033] In the present invention, there is no particular limitation on the linear expansion coefficient of the resin portion 2. However, when the linear expansion coefficient of the resin portion 2 is 50 ppm / K or more, which is a value as the linear expansion coefficient away from the glass substrate 1, although the thermal stress is large, the resin portion 2 is also crack-resistant due to the high ductility of the resin portion 2. When the linear expansion coefficient of the resin portion 2 is 150 ppm / K or less, the difference from the linear expansion coefficient of the glass substrate 1 is not too large, so the chance of the thermal stress becoming excessive can be reduced. Therefore, the linear expansion coefficient of the resin portion 2 is preferably 50 ppm / K or more and 150 ppm / K or less. Here, the linear expansion coefficient is a value measured in the normal temperature range from -30°C to 70°C using thermomechanical analysis (TMA) or the like.

[0034] Unlike a cemented lens and other similar lenses, in a replicated lens, the surface of the resin portion 2 on the side opposite to the side in contact with the glass substrate 1 is exposed to the atmosphere. Therefore, the resin portion 2 absorbs moisture in the air and expands. Due to the expansion of the resin portion 2, residual stress is generated in the replicated lens, and thus the resin portion 2 may crack in the case of rapid thermal shock. Therefore, the resin portion 2 of the optical element 1 according to this embodiment preferably has a moisture absorption expansion rate of 0.8% or less. This reduces the expansion of the resin portion 2 due to moisture absorption, thereby being able to further reduce the cracking of the resin portion 2. The moisture absorption expansion rate of the resin portion 2 is more preferably 0.5% or less.

[0035] As described above, by inserting a light-shielding film 3 having an appropriate linear expansion coefficient between the resin portion 2 and the glass substrate 1 at the outermost peripheral portion of the resin portion 2, the optical element 10 can simultaneously have excellent appearance quality and excellent environmental durability.

[0036] As the glass substrate 1, a substrate made of transparent glass can be used. As used herein, the term "transparent" means having a transmittance of 10% or more with respect to light in the wavelength range of 400 nm or more and 780 nm or less. To give a specific example, as the glass substrate 1, a substrate made of general optical glass typified by silicate glass, borosilicate glass, phosphate glass, or made of quartz glass, glass ceramic, etc. can be used.

[0037] Although Figures 1A to 1C illustrates the case where the optical surface 1C has a concave spherical shape and the second surface 1B has a convex spherical shape, the glass substrate 1 is not limited to a specific shape. The optical surface 1C included in the first surface 1A of the glass substrate 1 that is in contact with the resin portion 2 can have a suitable shape selected from a concave spherical shape, a convex spherical shape, an axially symmetric aspherical shape, a flat shape, etc. as a shape suitable for the desired characteristics.

[0038] As Figure 1A illustrated, when observed in a plan view in the direction along the optical axis of the optical element 10 passing through the center P0 of the optical surface 1C that is the center of the lens, the glass substrate 1 preferably has a circular planar shape. In the case where the glass substrate 1 has a circular planar shape, the accuracy of assembling the optical element 10 can be improved when using the optical element 10 as a lens in an optical system as described later.

[0039] In this embodiment, the resin portion 2 is provided on the optical surface 1C of the glass substrate 1 and on a part of the flat surface 1D reached by crossing the ridge line 1E, and is in close contact with the glass substrate 1 or the light-shielding film 3. The surface of the resin portion 2 has an aspherical shape. The resin portion 2 has a linear expansion coefficient different from that of the glass substrate 1. The resin composition 2a (see Figure 4A ) for forming the resin portion 2 is preferably a polymer composition, which is an energy-curable composition suitable for molding using a mold. The energy-curable composition is a composition containing components that are polymerized and cured by imparting one or both of light energy and heat energy to change from an uncured state to a resin. Among the energy-curable compositions, a UV-curable resin composition is more preferably used as the resin composition 2a. As the UV-curable material to be contained in the UV-curable resin composition, for example, a monomer containing a (meth)acrylate group and an epoxy resin containing a (meth)acrylate group can be used. As used herein, the term "(meth)acrylate" means acrylate or methacrylate. That is, for example, the "(meth)acrylate group" means an acrylate group or a methacrylate group.

[0040] The resin portion 2, which is a cured product of the resin composition 2a, is made of an organic material, and thus has a linear expansion coefficient different from that of the glass substrate 1 combined with the resin portion 2. Therefore, when there is a temperature change in the optical element 10 configured as described above, thermal stress is mainly generated in a part of the resin portion 2 located along the ridge line 1E. However, according to this embodiment, as described above, the thermal stress is dispersed, and as a result, cracking of the resin portion 2 due to thermal stress is reduced or prevented.

[0041] The resin composition 2a for forming the resin portion 2 contains a curable material, and a polymerizable monomer can be used as the curable material. Examples of the polymerizable monomer can include: (meth)acrylate monomers such as methyl methacrylate, vinyl methacrylate, methyl acrylate, ethyl acrylate, and butyl acrylate; and vinyl unsaturated monomers such as acrylic acid, styrene, butadiene, and divinylbenzene. For the purpose of making the resin composition 2a easy to handle, adjustments such as increasing the viscosity of the resin composition 2a can be performed by using a polymerizable monomer with a pre-increased molecular weight as the curable material. To adjust the optical properties and mechanical properties, the resin composition 2a can contain organic substances and inorganic substances in addition to the curable material.

[0042] The resin composition 2a may further contain a polymerization initiator. The polymerization initiator may be a photoinitiator or a thermal polymerization initiator, and which of these two initiators is used can be determined by selecting the manufacturing process. However, in the case of performing replication molding for forming the aspherical shape of the resin portion 2, in view of the high curing speed, the polymerization initiator is preferably a photoinitiator.

[0043] Examples of commercially available photoinitiators may include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 1-hydroxycyclohexyl phenyl ketone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 4-phenyldibenzoyl, 4-phenoxydibenzoyl, 4,4′-diphenyldibenzoyl, and 4,4'-diphenoxybenzophenone.

[0044] The content of the photoinitiator in the resin composition 2a preferably falls within the range of 0.01% by mass or more and 10% by mass or less. When the content of the photoinitiator is 0.01% by mass or more, high reactivity can be obtained, and when the content is 10% by mass or less, a decrease in the light transmittance of the resin portion 2 as a cured product can be reduced. The unreacted portion of the polymerization initiator remains in the resin portion 2 as a cured product.

[0045] In addition, the resin composition 2a may contain, for example, a polymerization inhibitor, an antioxidant, a light stabilizer (HALS), a UV absorber, a silane coupling agent, a release agent, a pigment, and a dye as needed.

[0046] The resin portion 2 preferably has high transparency. Specifically, the resin portion 2 preferably has an internal transmittance of 70% or more with respect to light of a wavelength of 400 nm when converted to a thickness of 500 μm. The resin portion 2 also preferably has an Abbe number of 50 or more and 60 or less. When the transparency and Abbe number of the resin portion 2 fall within these value ranges, the optical element 10 can be applied as a lens to optical systems with various optical designs.

[0047] Describe the light-shielding film 3 of the optical element 10 according to this embodiment.

[0048] For the light-shielding coating for forming the light-shielding film 3, a compound containing an epoxy group, inorganic fine particles, a colorant, an amine curing agent, etc. can be used. However, the light-shielding coating is not limited to this, and a material that absorbs visible light with a wavelength from 400 nm to 700 nm can be used. As the colorant made of such a material, for example, a carbon black pigment, a titanium black pigment, an iron oxide pigment, or a copper-iron-manganese composite oxide pigment is used. In the case of using a dye as the colorant, one dye can be used alone, or a mixture of a plurality of dyes as a certain combination of, for example, black, red, yellow, and blue can be used.

[0049] For the light-shielding coating, an epoxy resin and a resin crosslinked with an amine curing product can also be used. As the type of epoxy resin, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, polyfunctional epoxy resin, flexible epoxy resin, brominated epoxy resin, glycidyl ester type epoxy resin, polymer type epoxy resin, and biphenyl type epoxy resin can be used. One type of epoxy resin can be used alone, or a mixture of multiple types of epoxy resins can be used. When using an epoxy resin for the light-shielding coating, in order to cure the compound containing an epoxy group, the light-shielding coating can also contain an amine curing agent. The amine curing agent is not particularly limited as long as the desired properties are satisfied, and known amine curing agents can be used. Specifically, as the amine curing agent, for example, linear aliphatic types, polyamides, alicyclic types, and aromatic curing agents, as well as any other dicyandiamide and adipic dihydrazide can be used. These amine curing agents can be used alone or in combination.

[0050] As the inorganic fine particles, silica fine particles and fine particles such as titanium oxide, zirconium oxide, aluminum oxide, yttrium oxide, cadmium oxide, diamond, strontium titanate, and germanium can be used.

[0051] In the present invention, the linear expansion coefficient of the light-shielding film 3 is between the linear expansion coefficient of the glass substrate 1 and the linear expansion coefficient of the resin portion 2. The linear expansion coefficient of the light-shielding film 3 can be adjusted mainly by the mixing ratio of the inorganic fine particles and the resin contained in the light-shielding film 3.

[0052] Next, reference Figure 4A and Figure 4B gives a description of the method for manufacturing the optical element 10 according to this embodiment. Figure 4A and Figure 4B are cross-sectional views of the component arrangement in the step of forming the resin portion 2 of the optical element 10 illustrated in Figures 1A to 1C on the first surface 1A of the glass substrate 1. The component arrangement in Figure 4A and Figure 4B is illustrated in a cross-section taken along the stacking direction of the glass substrate 1 and the resin portion 2.

[0053] First, in the preparation step, a glass substrate 1 formed with a light-shielding film 3 and a resin composition 2a for forming the resin portion 2 are prepared.

[0054] At this time, it is preferable to perform pretreatment on the first surface 1A of the glass substrate 1 and the surface of the light-shielding film 3 in order to improve the adhesiveness of the resin portion 2, which is the cured product of the resin composition 2a, to be in close contact with the glass substrate 1 and the light-shielding film 3.

[0055] When the glass substrate 1 is made of glass, for example, silane coupling treatment, corona discharge treatment, UV ozone treatment, or plasma treatment can be selected as the pretreatment.

[0056] As a pretreatment, coupling treatment with a silane coupling agent is preferred in view of its ability to further enhance adhesion through direct chemical bonding of the resin portion 2 to the first surface 1A and other surfaces on which the resin portion 2 is formed. That is, before the subsequent filling step, an application step for applying a coupling agent to at least a part of the first surface 1A not covered by the light-shielding film 3 and a part of the surface of the light-shielding film 3 is preferably added.

[0057] Specific examples of the silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 8-methacryloxyoctyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0058] Subsequently, in the filling step, the space between the glass substrate 1 and the mold 4 is filled with the resin composition 2a. Specifically, first, as Figure 4A illustrated, the resin composition 2a is dropped onto the surface of the mold 4. As described above, the resin composition 2a is, for example, a composition of a UV-curable resin containing a photoinitiator. The glass substrate 1 is placed on the ejector 5 and positioned opposite to the mold 4. The mold 4 is, for example, a metal mold having an inverted shape of a desired aspherical shape on its surface and can be manufactured by plating NiP or oxygen-free copper on a metal substrate such as a stainless steel material or a steel material and machining the plated substrate with a precision processing machine. In order to control the mold releasability of the resin portion 2, a release agent can be applied to the surface of the mold 4. The release agent is not limited to a specific type, and for example, a fluorine coating agent can be used as the release agent.

[0059] Subsequently, as Figure 4B illustrated, by lowering the ejector 5 and thus bringing the mold 4 closer to the glass substrate 1, the resin composition 2a is set on the glass substrate 1. By further lowering the ejector 5, the space between the mold 4 and the glass substrate 1 is filled with the uncured resin composition 2a, and the resin composition 2a is formed into a desired shape.

[0060] In the method for manufacturing an optical element according to this embodiment, the filling step includes filling of the resin composition 2a to fill a part of the space between the light-shielding film 3 and the mold 4 with a part of the resin composition 2a. When the resin composition 2a is cured, this completes the insertion of the light-shielding film 3 between the resin portion 2 and the glass substrate 1.

[0061] Subsequently, in the curing step, the resin composition 2a is cured to form the resin portion 2. Here, an example of curing the resin composition 2a by irradiating the resin composition 2a with ultraviolet rays is described.

[0062] As shown Figure 4B Figure 4B As shown in the figure, light irradiation is performed using an ultraviolet light source 6 to irradiate ultraviolet rays from the second surface 1B side of the glass substrate 1 toward a part of the resin composition 2a located between the glass substrate 1 and the mold 4. As a result, the resin composition 2a is polymerized and cured. As a result, a resin portion 2 that is a polymerized and cured product of the resin composition 2a is obtained.

[0063]

[0063] In this step, a part of the space between the filling light-shielding film 3 of the resin composition 2a and the mold 4 is shielded from ultraviolet rays by the light-shielding film 3, and thus remains uncured. One way to form the resin portion 2 between the light-shielding film 3 and the mold 4 is to finish the inner surface of the ejector 5 to a mirror surface. This enables the ultraviolet rays radiated from the ultraviolet light source 6 to reach the space between the light-shielding film 3 and the mold 4 by reflection on the inner surface of the ejector 5. Therefore, a part of the resin composition 2a located between the light-shielding film 3 and the mold 4 can be cured instead of remaining uncured.

[0064]

[0064] Another way to cure a part of the resin composition 2a located between the light-shielding film 3 and the mold 4 is to use a glass material through which ultraviolet rays can pass, so that ultraviolet rays are irradiated not only from the second surface 1B side of the glass substrate 1 but also from the side where the mold 4 is placed. Therefore, a part of the resin composition 2a located between the light-shielding film 3 and the mold 4 can be cured.

[0065]

[0065] The curing step preferably includes irradiating ultraviolet rays with a curing reaction rate of 40% or more and 95% or less for a part of the resin portion 2 formed by curing the resin composition 2a between the light-shielding film 3 and the mold 4. This can promote the detachment of the resin portion 2 as a cured product from the mold in the mold detachment step described later.

[0066]

[0066] Then, in the mold detachment step, the polymerized and cured resin portion 2 is detached from the mold 4, thereby obtaining an optical element 10 including the resin portion 2 formed on the glass substrate 1 and having an aspherical shape.

[0067]

[0067] After forming the resin portion 2, additional irradiation of ultraviolet rays and heat treatment can be performed in the atmosphere or in an oxygen-free atmosphere. In particular, when a part of the resin composition 2a located between the light-shielding film 3 and the mold 4 remains partially uncured after being detached from the mold, it is necessary to cure a part of the resin composition 2a located between the light-shielding film 3 and the mold 4 by additional irradiation of ultraviolet rays from the resin portion 2 side.

[0068] By the above manufacturing method, the optical element 10 according to this embodiment can be manufactured. In the filling step, the resin composition 2a can be dropped onto both the mold 4 and the glass substrate 1, or can be dropped only onto the glass substrate 1. In the case where the resin composition 2a contains a thermal polymerization initiator as a curing initiator, the curing step can include a heat treatment step.

[0069] [Second Embodiment]

[0070] The above optical element 10 according to the first embodiment is applicable to various types of devices and apparatuses such as optical devices and image pickup devices. In this embodiment, as a specific application example of the optical element 10 according to the first embodiment, an optical device and an image pickup device are described.

[0071] (Optical Device)

[0072] Specific application examples of the optical element 10 according to the first embodiment include lenses to be included in an optical device (imaging optical system) for a still camera or a video camera and lenses to be included in an optical device (projection optical system) for a liquid crystal projector. The optical element 10 according to the first embodiment can also be used as a pickup lens for a DVD recorder or the like. Each of these optical devices includes a housing and an optical system placed inside the housing and including at least one lens. The optical device according to this embodiment is characterized in that at least one of these lenses is the optical element 10 according to the first embodiment.

[0073] (Image Pickup Device)

[0074] The image pickup device according to this embodiment is an image pickup device including: a housing; an optical system, placed inside the housing and including at least one lens; and an image pickup element that receives light that has traveled through the optical system. The image pickup device according to this embodiment is characterized in that at least one of at least one of the lenses is the optical element 10 according to the first embodiment.

[0075] Figure 5 is a schematic diagram for illustrating the configuration of a single-lens reflex digital camera 500 as an exemplary embodiment of an image pickup device using the optical element 10 according to the first embodiment. In Figure 5 it, the camera body 502 and the lens barrel 501 as an optical device are engaged with each other, but the lens barrel 501 can be said to be a replaceable lens detachable from the camera body 502.

[0076] Light from a subject is captured by an optical system including a plurality of lenses 503, 505 and other lenses on the optical axis of an imaging optical system disposed inside a housing 520 of a lens barrel 501. The optical element 10 according to the first embodiment can be used, for example, for the lenses 503 and 505. The lens 505 is supported by an inner lens barrel 504 in such a manner that the lens 505 can move relative to an outer lens barrel of the lens barrel 501 for focusing and zooming.

[0077] During an observation period before shooting, light from the subject is reflected by a main mirror 507 inside a housing 521 of the camera body, passes through a prism 511, and is then viewed as a captured image by the shooter through a viewfinder lens 512. The main mirror 507 is, for example, a semi-reflective mirror, and the light passing through the main mirror is reflected by a sub-mirror 508 in the direction of an autofocus (AF) unit 513. This reflected light is used, for example, for distance measurement. The main mirror 507 is attached to and supported by a main mirror holder 540 by adhesion or other methods. At the time of shooting, the main mirror 507 and the sub-mirror 508 are moved to the outside of the optical path by a drive mechanism (not shown), and a shutter 509 is opened so that an image pickup element 510 receives the light that has entered from the lens barrel 501 and has passed through the imaging optical system, and forms a captured light image. The diaphragm 506 is configured such that the brightness and depth of field at the time of shooting can be changed by changing the opening area.

[0078] Although the image pickup device has been described here using a single-lens reflex digital camera, the optical element 10 can be similarly used for a smart phone, a small digital camera, a drone, etc.

[0079] [Example]

[0080] The present invention will be described in more detail below by way of examples. First, a method for evaluating the optical element will be described. The evaluation of the optical element is performed on the appearance of the optical element and lens cracking.

[0081] (Appearance)

[0082] The optical elements obtained in the example and the comparative example are visually observed from the second surface side which is the opposite side of the resin part, and how the bright lines look is evaluated. In this evaluation, the appearance of the bright lines is graded from level A to level C. At level A, the bright lines are completely invisible. At level B, the bright lines are slightly visible but not a problem. At level C, the bright lines are clearly visible.

[0083] (Lens Cracking)

[0084] The optical elements obtained in the examples and comparative examples at room temperature were placed in a freezer controlled to maintain a temperature environment of -40°C, taken out after 24 hours, and restored to a room temperature of 25°C, and then the appearance was evaluated. Stress simulation during rapid cooling at -40°C was also performed by the finite element method to calculate the end of the resin part estimated to be the starting point of cracking.

[0085] The optical elements were classified from A to C in view of lens cracking. Among the optical elements classified as A, the resin part did not crack, and the stress value at the end of the resin part was less than 10 MPa. Among the optical elements classified as B, the resin part did not crack, and the stress value at the end of the resin part was equal to or greater than 10 MPa. Among the optical elements classified as C, the resin part cracked.

[0086] Next, the optical elements according to the examples and comparative examples will be described.

[0087] (Example 1)

[0088] By using Figure 4A and Figure 4B the manufacturing method illustrated in Figures 1A to 1C the optical element 10 illustrated in

[0089] As the glass substrate 1, an optical glass (S-TIM8: manufactured by Ohara Corporation) with a diameter of 44 mm, a flat surface 1D having a width of 5 mm, and a ridge line 1E located between the flat surface 1D and the optical surface 1C was prepared. The glass substrate 1 includes a light-shielding film 3 (GT7-II: manufactured by Canon Chemicals, Inc.). The light-shielding film 3 was formed to have an inner diameter of 33 mm and was applied to reach the optical surface 1C across the ridge line 1E. The glass substrate 1 was formed to have a concave spherical shape with a diameter of 34 mm on one surface (optical surface 1C) and a convex spherical shape with a diameter of 44 mm on the other surface (second surface 1B).

[0090] As the mold 4, the NiP layer plated on the metal substrate was machined by a precision machining machine to form an inverted shape of an aspherical shape as the resin part 2 to be molded.

[0091] For the purpose of reflecting ultraviolet rays, the inner surface of the ejector 5 was subjected to mirror finishing.

[0092] Next, for the purpose of improving the adhesion between the glass substrate 1 and the light-shielding film 3, a silane coupling agent containing a methacrylate group as a functional group was applied to the surfaces of the glass substrate 1 and the light-shielding film 3.

[0093] Next, the space between the mold 4 and the glass substrate 1 is filled with the resin composition 2a. As the resin composition 2a, a composition containing an acrylic monomer having a cyclic hydrocarbon in the main chain and a reactive acrylate group at the terminal and a polymerization initiator (Omnirad 184 (1-hydroxycyclohexyl-phenyl ketone), manufactured by IGM Resins) is used.

[0094] Then, ultraviolet light with a wavelength of 365 nm and an intensity of 10 mW / cm 2 is irradiated onto the entire surface for 200 seconds to cure the resin composition 2a, and the cured product of the resin composition 2a is detached from the mold 4 to form a resin portion 2 on the glass substrate 1. The intermediate obtained by detaching from the mold is placed in an oven and heated at 80 °C for 24 hours to manufacture the optical element according to Example 1.

[0095] In the obtained optical element 10, the width of the laminated region R where the light-shielding film 3 and the resin portion 2 are laminated is measured. The outer diameter of the resin portion 2 (the distance from the center P0 to the distal end of the resin portion 2 in the direction perpendicular to the optical axis direction O) is 35 mm, and the light-shielding film 3 is inserted in a region 1 mm from the outermost periphery of the resin portion 2. The ratio of the width of the laminated region R to the radius of the optical surface 1C is 1 mm / 17 mm × 100% = 6%. The linear expansion coefficients of the glass substrate 1, the light-shielding film 3, and the resin portion 2 are measured in the range from -30 °C to -70 °C using a thermomechanical analysis device TMA (manufactured by METTLER TOLEDO), and are found to be 8 ppm / K, 60 ppm / K, and 100 ppm / K, respectively.

[0096] The absorption expansion rate of the resin portion 2 is measured as follows.

[0097] First, in order to measure the absorption expansion rate, the resin portion 2 is cut from the surface of the separately prepared optical element 10. Specifically, a cut is made in the resin portion 2 on the surface of the optical element 10 using a feather razor, and the film is peeled off by inserting the razor between the adhesive bonding surface of the resin portion 2 and the glass substrate 1. The film thickness distribution in one sample is adjusted so that the fluctuation range of the thickness falls within 10%. The film is given a sliding shape of 10 mm × 1 mm.

[0098] The absorption expansion rate of the peeled film is measured by the tensile load method using a device for measuring the linear expansion coefficient of a material (TMA-4000SE+HC9700 (humidity control type), manufactured by NETZSCH Japan K.K.) under the condition that the temperature and humidity are controlled to 60 °C and 90% RH.

[0099] The curing reaction rate of a part of the resin portion 2 that has been formed between the light-shielding film 3 and the mold 4 is measured using a Fourier transform infrared spectroscopy (FTIR) apparatus (product name: Spectrum One, manufactured by PerkinElmer). Specifically, the peak area related to carbon double bonds in the light absorption spectrum of the resin portion 2 obtained by FTIR is obtained, and the curing reaction rate is calculated by the following expression.

[0100]

[0101] S1: Peak area related to double bonds in the cured state

[0102] S2: Peak area not related to double bonds in the cured state

[0103] S3: Peak area related to double bonds in the uncured state

[0104] S4: Peak area not related to double bonds in the uncured state

[0105] (Example 2)

[0106] The optical element 10 according to Example 2 is manufactured in the same manner as in Example 1, except that an acrylic monomer having a straight-chain hydrocarbon in the main chain is used as the material of the resin composition 2a. The linear expansion coefficient of the resin portion included in the optical element 10 according to Example 2 is 170 ppm / K.

[0107] (Example 3)

[0108] The optical element 10 according to Example 3 is manufactured in the same manner as in Example 1, except that the resin portion 2 is formed to have an outer diameter of 33.8 mm. In the optical element 10 according to Example 3, different from that across the ridge line 1E Figure 3 The resin portion 2 is only formed on the optical surface 1C. The width of the laminated region R is 0.4 mm, and the ratio of the width of the laminated region R to the radius of the optical surface 1C is 0.4 mm / 17 mm × 100% = 2%.

[0109] (Example 4)

[0110] The optical element 10 according to Example 4 is manufactured in the same manner as in Example 1, except that the resin portion 2 is formed to have an outer diameter of 33.2 mm. In the optical element 10 according to Example 4, different from that across the ridge line 1E Figure 3 The resin portion 2 is only formed on the optical surface 1C. The width of the laminated region R is 0.1 mm, and the ratio of the width of the laminated region R to the radius of the optical surface 1C is 0.1 mm / 17 mm × 100% = 0.5%.

[0111] (Example 5)

[0112] The optical element 10 according to Example 5 was produced in the same manner as in Example 1, except that a silane coupling agent having an ethylene group was used as the silane coupling agent. In the optical element 10 according to Example 5, it was observed that the resin portion 2 was not flatly placed on the flat surface 1D.

[0113] (Example 6)

[0114] The resin composition 2a used in Example 1 was mixed with a resin composition 2a containing an acrylic monomer having a urethane in the main chain and containing the above polymerization initiator at a weight ratio of 80:20. This mixture was used as the resin composition 2a. Except for the foregoing, the optical element 10 according to Example 6 was produced in the same manner as in Example 1.

[0115] (Example 7)

[0116] The optical element 10 according to Example 7 was produced in the same manner as in Example 1, except that the reflection of the inner surface of the ejector was not used in the ultraviolet radiation step. In the optical element 10 according to Example 7, the outer diameter of the resin portion 2 was 33.4 mm.

[0117] (Example 8)

[0118] The optical element 10 according to Example 8 was produced in the same manner as in Example 1, except that by using a quartz glass mold, ultraviolet radiation from above and ultraviolet radiation from below were simultaneously performed in the ultraviolet radiation step. In the optical element 10 according to Example 8, the outer diameter of the resin portion 2 was 35.7 mm.

[0119] (Example 9)

[0120] The optical element 10 according to Example 9 was produced in the same manner as in Example 1, except that ultraviolet radiation was additionally performed from the resin portion 2 after the mold was removed. In the optical element 10 according to Example 9, the outer diameter of the resin portion 2 was 35.7 mm.

[0121] (Examples 10, 18, and 20 to 22)

[0122] The optical element 10 according to each of Examples 10, 18, and 20 to 22 was produced in the same manner as in Example 1, except that a mold 4 different from the mold 4 used in Example 1 was used in terms of the shape suitable for the aspherical shape of the resin portion 2.

[0123] (Example 11)

[0124] A coating is obtained by adding QSG-100 (manufactured by Shin-Etsu Chemical Co., Ltd.) to GT7-II (manufactured by CANON Chemicals, Inc.) at a ratio of 20 parts by weight to 100 parts by weight and stirring the mixture until it is homogenized. The light-shielding film 3 is formed on the glass substrate 1 using this coating. The resin composition 2a used here is obtained by mixing the resin composition 2a used in Example 1 with a resin composition 2a containing an acrylic monomer having a cyclic hydrocarbon in the main chain and acrylate groups in the side chain and at the terminal and containing the above polymerization initiator in a weight ratio of 50:50. Except for the foregoing, the optical element 10 according to Example 11 is manufactured in the same manner as in Example 1.

[0125] (Example 12)

[0126] The resin composition 2a used in Example 1 is mixed with the resin composition 2a used in Example 2 at a weight ratio of 30:70, and this mixture is used as the resin composition 2a. Except for the foregoing, the optical element 10 according to Example 12 is manufactured in the same manner as in Example 1.

[0127] (Example 13)

[0128] The optical element 10 according to Example 13 is manufactured in the same manner as in Example 1, except that in the ultraviolet radiation step, ultraviolet radiation is performed simultaneously from above and from below by using a quartz glass mold. In the optical element 10 according to Example 13, the outer diameter of the resin portion 2 is 36.4 mm.

[0129] (Example 14)

[0130] The resin composition 2a used in Example 1 is mixed with a resin composition 2a containing an acrylic monomer having a cyclic hydrocarbon in the main chain and acrylate groups in the side chain and at the terminal and containing the above polymerization initiator in a weight ratio of 80:20. This mixture is used as the resin composition 2a. Except for the foregoing, the optical element 10 according to Example 14 is manufactured in the same manner as in Example 1.

[0131] (Example 15)

[0132] The resin composition 2a used in Example 1 is mixed with the resin composition 2a used in Example 2 at a weight ratio of 40:60, and this mixture is used as the resin composition 2a. Except for the foregoing, the optical element 10 according to Example 15 is manufactured in the same manner as in Example 1.

[0133] (Examples 16, 17, and 19)

[0134] The optical element 10 according to each of Examples 16, 17, and 19 was manufactured in the same manner as in Example 4, except that a mold 4 different from the mold 4 used in Example 4 in terms of the aspherical shape adapted to the resin portion 2 was used.

[0135] (Example 23)

[0136] The resin composition 2a used in Example 1 was mixed with a resin composition 2a containing an acrylic monomer having a urethane in the main chain and containing the above polymerization initiator at a weight ratio of 70:30. The mixture was used as the resin composition 2a. Except for the foregoing, the optical element 10 according to Example 23 was manufactured in the same manner as in Example 1.

[0137] (Comparative Example 1)

[0138] The space between a glass substrate without a light-shielding film and a mold was filled with a resin composition, and after the resin composition was cured, a light-shielding film was formed on a part of the side surface and the flat surface of the glass substrate and on the end of the resin portion. Except for the foregoing, the optical element according to Comparative Example 1 was manufactured in the same manner as in Example 1.

[0139] The curing reaction rate was measured for the end of the resin portion where the light-shielding film was laminated.

[0140] (Comparative Example 2)

[0141] The optical element according to Comparative Example 2 was manufactured in the same manner as in Example 1, except that the inner diameter of the light-shielding film was set to 37 mm and the lamination region R was not included.

[0142] The curing reaction rate was measured for the end of the resin portion.

[0143] (Comparative Example 3)

[0144] 50 parts by weight of titanium oxide (MT-05, a product of TAYCA Co., Ltd.) was added to the coating material for forming the light-shielding film, and the resulting coating material was used to form a light-shielding film on the glass substrate. Except for the foregoing, the optical element according to Comparative Example 3 was manufactured in the same manner as in Example 1. The linear expansion coefficient of the light-shielding film included in the optical element according to Comparative Example 3 was 110 ppm / K.

[0145] The physical properties of the optical elements according to the examples and comparative examples are shown in Table 1-1 below, and the evaluation results are shown in Table 1-2 below.

[0146] In Table 1-1 and Table 1-2, P0 and P1 respectively indicate Figures 1A to 1CThe position corresponding to the center P0 of the optical surface 1C shown in the figure and the point P1 where the resin portion 2 has the maximum thickness. The point P1 is a point separated from the center P0 by 13 mm in the radial direction of the optical surface 1C. The lamination region width ratio in Table 1 indicates the ratio of the width of the region where the resin portion and the light shielding film are laminated to the radius of the optical surface.

[0147] It can be understood from Table 1-1 and Table 1-2 that the optical element 10 according to any one of Examples 1 to 23 is superior to the optical elements of Comparative Examples 1 to 3.

[0148] [Table 1-1]

[0149]

[0150]

[0151] [Table 1-2]

[0152]

[0153] According to the present invention, an optical element having both excellent appearance quality and excellent environmental durability, and a method for manufacturing the optical element can be provided.

[0154] Although the present invention has been described with reference to exemplary embodiments, it is to be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims will be given the broadest interpretation to encompass all such modifications and equivalent structures and functions.

Claims

1. An optical element, comprising: a glass substrate including a first surface and a second surface opposite to the first surface; a resin portion disposed on the first surface; and a light-shielding film configured to cover at least a part of a side surface of the glass substrate and a part of the first surface, wherein the second surface is one of a light incident surface and a light exit surface, wherein a part of the light-shielding film is disposed between the glass substrate and the resin portion, and wherein a linear expansion coefficient of the light-shielding film is between a linear expansion coefficient of the glass substrate and a linear expansion coefficient of the resin portion.

2. The optical element according to claim 1, wherein, A surface of the resin portion on a side opposite to a surface of the resin portion in contact with the glass substrate is exposed to the atmosphere.

3. The optical element according to claim 1 or 2, wherein At least one of the following is satisfied: A ratio of a maximum thickness of the resin portion in an optical axis direction to a thickness of the resin portion in the optical axis direction at a center position of an optical surface of the first surface is 5 or more; and A ratio of a minimum thickness of the resin portion in the optical axis direction to a thickness of the resin portion in the optical axis direction at a center position of an optical surface of the first surface is 1 / 5 or less.

4. The optical element according to claim 1 or 2, wherein The resin portion has a linear expansion coefficient of 50 ppm / K or more and 150 ppm / K or less.

5. The optical element according to claim 1 or 2, Among them, The first surface includes an optical surface, a flat surface provided along an outer edge of the optical surface, and a ridge line as a boundary line between the optical surface and the flat surface, wherein the resin portion is disposed to extend from the optical surface, cross the ridge line, and reach a part of the flat surface, and wherein the light-shielding film is disposed to extend from the flat surface, cross the ridge line, and reach a part of the optical surface.

6. The optical element according to claim 5, wherein, When a radius of the optical surface is given as 100%, a width of a region where the resin portion and the light-shielding film are laminated is 1% or more and 10% or less in a direction perpendicular to the optical axis direction.

7. The optical element according to claim 1 or 2, wherein, A moisture absorption expansion rate of the resin portion is 0.8% or less.

8. An optical device, comprising: A housing; and an optical system including at least one lens placed inside the housing, wherein at least one of the at least one lens is the optical element according to any one of claims 1 to 7.

9. An image pickup device, comprising: A housing; an optical system including at least one lens placed inside the housing; and an image pickup element that receives light that has traveled through the optical system, wherein at least one of the at least one lens is the optical element according to any one of claims 1 to 7.

10. A method of manufacturing an optical element, the optical element including a glass substrate and a resin portion, the glass substrate including a first surface and a second surface opposite to the first surface, the resin portion being disposed on the first surface, the second surface being one of a light incident surface and a light exit surface, The method includes: A preparation step of preparing the glass substrate formed with a light-shielding film; A filling step of filling the space between the glass substrate and the mold with a resin composition; A curing step of curing the resin composition to form the resin portion; And A mold release step of releasing the resin portion from the mold, wherein the light-shielding film is formed on the glass substrate so as to cover at least a part of the side surface and a part of the first surface of the glass substrate, and wherein the filling step includes filling with the resin composition so that a part of the space between the light-shielding film and the mold is filled with a part of the resin composition.

11. The method of manufacturing an optical element according to claim 10, wherein, The surface of the resin portion on the side opposite to the surface of the resin portion in contact with the glass substrate is exposed to the atmosphere.

12. The method for manufacturing an optical element according to claim 10 or 11, wherein, The curing step includes ultraviolet irradiation such that the resin portion formed by curing the part of the resin composition between the light-shielding film and the mold has a curing reaction rate of 40% or more and 95% or less.

13. The method for manufacturing an optical element according to claim 10 or 11, further comprising an application step of applying a coupling agent to at least a part of the first surface not covered by the light-shielding film and a part of the surface of the light-shielding film before the filling step.

Images