Optical element, optical instrument, imaging apparatus, and method for manufacturing optical element

Abstract

To provide an optical element that has both excellent appearance quality and excellent environmental durability.SOLUTION: An optical element comprises: a glass substrate that has a first surface and a second surface opposite to the first surface; a resin part that is provided on the first surface; and a light shielding film that covers at least part of a side face of the glass substrate and part of the first surface. The second surface is a light incident surface or a light emission surface. The light shielding film is partially provided between the glass substrate and the resin part. The coefficient of linear expansion of the light shielding film is between the coefficient of linear expansion of the glass substrate and the coefficient of linear expansion of the resin part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical element, an optical device, an imaging apparatus, and a method for manufacturing an optical element.

Background Art

[0002] As one of the optical elements, a lens in which a cured product of a resin composition is provided on a transparent base material such as glass is known. Such a lens is manufactured by using a mold, providing a resin composition between the base material and the mold, and polymerizing or copolymerizing to form a cured product having a desired shape on the surface of the base material. A lens manufactured by such a manufacturing method is called a replica element. Conventionally, for the purpose of improving the appearance quality of a replica element, a method of reducing internal reflection due to unnecessary light by forming a light-shielding film on the flange portion of the lens is known. Patent Document 1 discloses, as an example of a replica element, an aspherical lens formed such that the outermost peripheral end face of a cured product of a resin composition is covered with a light-shielding film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, although the optical element disclosed in Patent Document 1 has excellent appearance quality, cracks may occur in the resin when it is used in a low-temperature environment, and there are problems with the environmental durability of the lens. An object of the present invention is to provide an optical element having excellent appearance quality and excellent environmental durability, and a method for manufacturing the optical element.

Means for Solving the Problems

[0005] An optical element according to one aspect of the present invention includes a glass substrate having a first surface and a second surface facing the first surface, a resin portion provided on the first surface, and a light-shielding film covering at least a part of the side surface of the glass substrate and a part of the first surface, wherein the second surface is a light incident surface or a light exit surface, a part of the light-shielding film is provided between the glass substrate and the resin portion, and 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.

[0006] A method for manufacturing an optical element according to another aspect of the present invention includes a glass substrate having a first surface and a second surface facing the first surface, and a resin portion provided on the first surface, and is a method for manufacturing an optical element in which the second surface is a light incident surface or a light exit surface, and includes a preparation step of preparing the glass substrate on which a light-shielding film is formed, a filling step of filling a resin composition between the glass substrate and a mold, 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 of the glass substrate and a part of the first surface, and the filling step includes filling the resin composition such that a part of the resin composition is filled between the light-shielding film and the mold.

Effects of the Invention

[0007] According to the present invention, it is possible to provide an optical element having excellent appearance quality and excellent environmental durability, and a method for manufacturing the optical element.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0009] [First embodiment] An optical element and a method for manufacturing an optical element according to a first embodiment of the present invention will be described with reference to FIG.

[0010] First, the configuration of the optical element according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the configuration of an optical element 10 according to this embodiment. Fig. 1(a) is a plan view showing the optical element 10. Fig. 1(b) is a cross-sectional view in the thickness direction taken along line AA' in Fig. 1(a). Fig. 1(c) is a cross-sectional view showing an enlarged portion of the optical element 10.

[0011] The optical element 10 according to this embodiment is a type of optical element known as a replica lens. As shown in FIG. 1, the optical element 10 according to this embodiment has a transparent glass substrate 1 and a resin portion 2, which is a cured product of a resin composition formed on the glass substrate 1. The resin portion 2 is provided in close contact with a 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, but has a non-uniform distribution within the surface. This gives the surface of the resin portion 2 an aspherical shape.

[0012] The optical element 10 according to this embodiment is configured as an aspherical lens using the resin portion 2, and therefore can be manufactured in a high cycle compared to aspherical lenses configured only from glass. Therefore, according to this embodiment, aspherical lenses can be manufactured inexpensively.

[0013] The optical element 10 also includes a light-shielding film 3 that covers at least a part of the side surface 1F and a part of the outermost periphery of the first surface 1A of the glass substrate 1. The light-shielding film 3 is formed in close contact with the glass substrate 1. The glass substrate 1 has a first surface 1A composed of a spherical optical surface 1C and a flat surface 1D, and a second surface 1B facing the first surface 1A. The optical surface 1C is concave spherical, and the second surface 1B is convex spherical. The flat surface 1D is provided so as to surround the optical surface 1C via a ridge line 1E and connect to the optical surface 1C. That is, the first surface 1A has 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 or the light exit surface of the optical element 10. Also, among the two optical surfaces of the resin part 2, the surface on the opposite side to the surface in contact with the first surface 1A is the other of the light incident surface or the light exit surface of the optical element 10. Note that the first surface 1A and the surface of the resin part 2 in contact with the first surface 1A are each a light refracting surface in the optical element 10. That is, the surface composed of the resin part 2 in the optical element 10 is in a state of being open to the outside air, and no other optical elements are provided on the surface composed of the resin part 2.

[0014] As shown in FIG. 1, the resin part 2 is preferably provided so as to spread from the optical surface 1C across the ridge line 1E to a part of the flat surface 1D. At this time, the end 2A of the resin part 2 is provided on the flat surface 1D.

[0015] A part of the light shielding film 3 is provided between the resin part 2 and the glass substrate 1 at the outermost periphery of the resin part 2. By doing so, when viewed from the second surface 1B side of the glass substrate 1, the light shielding film 3 can block the bright lines that are irregularly reflected by the internal reflection of the unnecessary light taken in from the side surface of the outermost periphery of the resin part 2, so that the appearance quality can be improved. Also, 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 part 2. By doing so, when a thermal shock occurs such that the optical element 10 is rapidly cooled, the light shielding film 3 can relieve the thermal stress caused by the difference in the linear expansion coefficients between the resin part 2 and the glass substrate 1, and an optical element 10 having excellent environmental durability over a long period can be obtained.

[0016] In the optical element 10 shown in Fig. 1, the thickness of the resin part 2 having an aspherical shape is the maximum thickness that is thicker than the thickness at the center P0 at a point P1 located between the center P0, which is the center of the aspherical optical surface 1C, and the end. Here, the thickness of the resin part 2 refers to the thickness in the optical axis direction O with respect to the optical surface 1C, which is a spherical surface of the glass substrate 1. In the present invention, the thickness of the resin part 2 at a certain point Px in the radial direction of the optical surface 1C is defined as the average value of the thicknesses measured at three points: the point Px, and two adjacent points Px - 1 and Px + 1 that are 0.5 mm apart from the point Px in the radial direction of the optical surface 1C. Here, 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. With the resin part 2 being formed in such a shape, the optical element 10, which is a replica lens, is configured as an aspherical lens having an aspherical shape.

[0017] The optical element 10 preferably satisfies at least one of the following two conditions. One is that the ratio of the maximum thickness in the optical axis direction O of the resin part 2 to the thickness in the optical axis direction O of the resin part 2 at the center position P0 of the optical surface 1C is 5 or more. The optical element 10 in which the ratio of the thickness of the resin part 2 at the point P1 to the thickness of the resin part 2 at the center position of the optical surface 1C is 5 or more has a large aspherical amount, and thus has optical characteristics that can be suitably used as the front lens of a wide-angle zoom lens.

[0018] The other condition is that the ratio of the minimum thickness in the optical axis direction O of the resin part 2 to the thickness in the optical axis direction O of the resin part 2 at the center position of the optical surface 1C is 1 / 5 or less. The optical element 10 that satisfies this condition also becomes a lens with a large aspherical amount, so that the correction of distortion and chromatic aberration becomes more effective. Therefore, by using the optical element 10 that satisfies this condition, excellent image quality can be obtained in wide-angle lenses, telephoto lenses, etc., where a particularly wide field of view is required.

[0019] On the other hand, in a replica lens with a large aspherical amount, due to the influence of large residual stress during molding, cracks are likely to occur in the resin part 2 due to stress caused by thermal shock. This is because if the thickness of the resin part 2 is too thick, the thermal stress increases according to the thickness, and as a result, the probability of the resin part cracking increases. In particular, in the resin part 2 formed on the ridge line 1E, stress concentration due to thermal shock is likely to occur, so it is preferable to interpose the light-shielding film 3 as a stress relaxation layer on the ridge line 1E. That is, as shown in FIG. 1, it is preferable that the light-shielding film 3 is provided so as to extend from the flat surface 1D across the ridge line 1E to a part of the optical surface 1C. Thereby, it is also possible to effectively block the bright line with the light-shielding film 3. At this time, the end 3A of the light-shielding film 3 provided on the first surface 1A is in a state of being provided on the optical surface 1C. However, the configurations of the resin part 2 and the light-shielding film 3 in the present invention are not limited to the example shown in FIG. 1. For example, as shown in FIG. 2, the light-shielding film 3 may be provided only on at least a part of the flat surface 1D without straddling the ridge line 1E. Also in this case, by interposing the light-shielding film 3 having an appropriate coefficient of linear expansion between the glass substrate 1 and the resin part 2 at the end of the resin part 2, cracking of the resin part 2 can be suppressed.

[0020] Further, for example, as shown in FIG. 3, the resin part 2 may have the outermost periphery on the optical surface 1C without straddling the ridge line 1E, and the resin part 2 may not be provided on the flat surface 1D. In this case, the light-shielding film 3 is continuously formed from the flat surface 1D across the ridge line 1E to the optical surface 1C. At the outermost periphery of the resin part 2, it is important to interpose the light-shielding film 3 having an appropriate coefficient of linear expansion between the glass substrate 1 and the resin part 2, similar to the example shown in FIG. 2. In short, in the present invention, the outermost periphery of the resin part 2 may be either on the optical surface 1C or the flat surface 1D. At the outermost periphery of the resin part 2, it is an essential configuration to interpose the light-shielding film 3 having an appropriate coefficient of linear expansion between the glass substrate 1 and the resin part 2. Thereby, the appearance quality of the optical element 10 can be improved, and further cracking of the resin part 2 due to thermal stress relaxation can be suppressed.

[0021] In the optical element 10 according to this embodiment, the width of the laminated region R, where the resin portion 2 and the light-shielding film 3 are laminated, in a direction perpendicular to the optical axis direction O is preferably 1% or more and 10% or less, when the radius r of the optical surface 1C is taken as 100%. Here, 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 a direction perpendicular to the optical axis direction O. If the ratio of the width of the laminated region R to the radius r of the optical surface 1C is 1% or more, bright lines can be suppressed even when the half-open angle of the optical element 10 is large, and deterioration of the appearance quality can be suppressed. Furthermore, the large width of the laminated region R allows the light-shielding film 3 to function effectively as a stress relaxation layer. Furthermore, if the ratio of the width of the laminated region R to the radius r of the optical surface 1C is 10% or less, unnecessary increases in the outer diameter of the lens can be avoided.

[0022] In the present invention, there is no particular limitation on the linear expansion coefficient of the resin portion 2. However, if the linear expansion coefficient of the resin portion 2 is 50 ppm / K or more, the value will be different from that of the glass substrate 1, and while thermal stress will be large, the high toughness of the resin portion 2 will make it less likely to crack. Furthermore, if the linear expansion coefficient of the resin portion 2 is 150 ppm / K or less, the difference with the linear expansion coefficient of the glass substrate 1 will not be too large, and excessive thermal stress can be prevented. 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 using thermomechanical analysis (TMA) or the like in the room temperature range of -30°C to 70°C.

[0023] Unlike cemented lenses and the like, replica lenses have the surface of the resin portion 2 opposite to the side in contact with the glass substrate 1 exposed to the atmosphere. As a result, the resin portion 2 absorbs moisture in the air and expands. The expansion of the resin portion 2 generates residual stress in the replica lens, which may cause the resin portion 2 to crack when subjected to a sudden thermal shock. For this reason, the water absorption expansion coefficient of the resin portion 2 of the optical element 10 according to this embodiment is preferably 0.8% or less. This suppresses the water absorption expansion of the resin portion 2 and further suppresses cracking of the resin portion 2. It is more preferable that the water absorption expansion coefficient of the resin portion 2 is 0.5% or less. As described above, by interposing the light-shielding film 3 having an appropriate linear expansion coefficient between the resin part 2 and the glass substrate 1 at the outermost periphery of the resin part 2, the optical element 10 can have both excellent appearance quality and environmental durability.

[0024] The glass substrate 1 can be made of transparent glass. In this specification, "transparent" means that the transmittance of light in the wavelength range of 400 nm to 780 nm is 10% or more. Specifically, the glass substrate 1 can be made of common optical glass, such as silicate glass, borosilicate glass, and phosphate glass, as well as quartz glass and glass ceramics. 1 shows a case where optical surface 1C is concave spherical and second surface 1B is convex spherical, but there are no particular limitations on the shape of glass substrate 1. The shape of optical surface 1C of first surface 1A, which is the surface of glass substrate 1 that comes into contact with resin part 2, can be appropriately selected from concave spherical, convex spherical, axisymmetric aspherical, flat, etc., depending on the desired characteristics.

[0025] 1(a), the glass substrate 1 preferably has a circular planar shape when viewed in a plane along the optical axis of the optical element 10, which passes through the center P0 of the optical surface 1C, which is the center of the lens. When the glass substrate 1 has a circular planar shape, the precision with which the optical element 10 is assembled can be improved when the optical element 10 is used as a lens in an optical system, as will be described later.

[0026] In this embodiment, the resin part 2 is provided in close contact with the glass substrate 1 or the light-shielding film 3 on the optical surface 1C of the glass substrate 1 and on a part of the flat surface 1D straddling the ridge line 1E. The surface of the resin part 2 has an aspherical shape. The resin part 2 has a coefficient of linear expansion different from that of the glass substrate 1. The resin composition 2a (see Fig. 4(a)) for forming the resin part 2 is a polymerizable composition, and is preferably an energy-curable composition suitable for molding using a mold. The energy-curable composition is a composition containing a component that polymerizes and cures into a resin by applying either one or both of light energy and thermal energy from an uncured state. Among energy-curable compositions, the resin composition 2a is more preferably an ultraviolet-curable resin composition. As the ultraviolet-curable material contained in the ultraviolet-curable resin composition, for example, a monomer having a (meth)acrylate group and an epoxy resin can be used. In this specification, the notation with (meth)acrylate means acrylate or methacrylate. That is, for example, the (meth)acrylate group means an acrylate group or a methacrylate group.

[0027] Since the resin part 2, which is a cured product of the resin composition 2a, is made of an organic material, when combined with the glass substrate 1, the coefficient of linear expansion is different between the glass substrate 1 and the resin part 2. Therefore, when a temperature change occurs in the optical element 10 as described above, thermal stress mainly occurs in the resin part 2 at the ridge line 1E. However, according to this embodiment, as described above, such thermal stress can be dispersed to suppress or prevent cracking of the resin part 2 due to thermal stress.

[0028] The resin composition 2a for forming the resin part 2 contains a curable material, and a polymerizable monomer may be used as the curable material. Examples of the polymerizable monomer include (meth)acrylate monomers such as methyl methacrylate, ethylene methacrylate, methyl acrylate, ethyl acrylate, and butyl acrylate, and ethylenically unsaturated monomers such as acrylic acid, styrene, butadiene, and divinylbenzene. Further, for the purpose of facilitating the handling of the resin composition 2a, an adjustment may be made to thicken the resin composition 2a by using a polymerized polymerizable monomer as a curable material in advance. The resin composition 2a may contain other organic and inorganic substances other than the curable material in order to adjust the optical and mechanical properties. Further, the resin composition 2a can contain a polymerization initiator. The polymerization initiator may be a photopolymerization initiator or a thermal polymerization initiator, and can be determined according to the manufacturing process to be selected. However, when performing replica molding for forming the aspherical shape of the resin part 2, from the viewpoint of a high curing rate, the polymerization initiator is preferably a photopolymerization initiator.

[0029] Examples of commercially available photopolymerization initiators include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 1-hydroxycyclohexyl phenyl ketone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 4-phenylbenzophenone, 4-phenoxybenzophenone, 4,4'-diphenylbenzophenone, and 4,4'-diphenoxybenzophenone.

[0030] The content of the photopolymerization initiator in the resin composition 2a is preferably in the range of 0.01% by mass or more and 10% by mass or less. If the content of the photopolymerization initiator is 0.01% by mass or more, high reactivity can be obtained, and if it is 10% by mass or less, a decrease in the light transmittance of the resin part 2 as a cured product can be suppressed. Note that unreacted polymerization initiator remains in the resin part 2 as a cured product. In addition, the resin composition 2a may contain a polymerization inhibitor, an antioxidant, a light stabilizer (HALS), an ultraviolet absorber, a silane coupling agent, a release agent, a pigment, a dye, etc., if necessary.

[0031] The resin part 2 preferably has high transparency. Specifically, the resin part 2 preferably has an internal transmittance of 70% or more with respect to a wavelength of 400 nm in terms of a thickness of 500 μm. Also, the Abbe number of the resin part 2 is preferably 50 or more and less than 60. If the transparency and the Abbe number of the resin part 2 are within these value ranges, it is possible to cope with various optical designs when using the optical element 10 as a lens in an optical system.

[0032] The light-shielding film 3 of the optical element 10 according to the present embodiment will be described. For the light-shielding paint for forming the light-shielding film 3, a compound having an epoxy group, inorganic fine particles, a colorant, an amine-based curing agent, etc. can be used, but it is not limited thereto, and a material that absorbs visible light with a wavelength of 400 nm to 700 nm may be used. As a colorant as such a material, for example, pigments such as carbon black, titanium black, iron oxide, and copper-iron-manganese composite oxide are used. Also, when using a dye as a colorant, one type may be used, or a plurality of dyes such as black, red, yellow, and blue may be mixed. Furthermore, resins obtained by crosslinking epoxy resins and amine-based cured products can be used for the light-shielding coating. Examples of epoxy resins that can be used include bisphenol A type, bisphenol F type, multifunctional epoxy resins, flexible epoxy resins, brominated epoxy resins, glycidyl ester type epoxy resins, polymeric epoxy resins, and biphenyl type epoxy resins. One type of epoxy resin may be used alone, or multiple types may be mixed. When an epoxy resin is used for the light-shielding coating, the light-shielding coating may further contain an amine-based curing agent to cure the compound having an epoxy group. The amine-based curing agent is not particularly limited as long as it satisfies the desired properties, and known amine-based curing agents can be used. Specific examples of amine-based curing agents that can be used include linear aliphatic, polyamide, alicyclic, aromatic, and other dicyandiamide and adipic acid dihydrazide curing agents. These may be used alone or in combination. As the inorganic fine particles, fine particles of silica, titanium oxide, zirconium oxide, aluminum oxide, yttrium oxide, cadmium oxide, diamond, strontium titanate, germanium, or the like can be used. 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 resin and inorganic fine particles contained in the light-shielding film 3.

[0033] Next, a manufacturing method of the optical element 10 according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view showing the arrangement of each member in the step of forming the resin portion 2 of the optical element 10 shown in Fig. 1 on the first surface 1A of the glass substrate 1. Fig. 4 shows the arrangement of each member in a cross section taken along the lamination direction of the glass substrate 1 and the resin portion 2.

[0034] First, in a preparation step, the glass substrate 1 on which the light-shielding film 3 is formed and the resin composition 2a for forming the resin portion 2 are prepared. Here, in order to improve the adhesion between the glass substrate 1, the light-shielding film 3, and the resin part 2 which is the cured product of the resin composition 2a, it is preferable to perform a pretreatment on the first surface 1A of the glass substrate 1 and the surface of the light-shielding film 3. When the glass substrate 1 is made of glass, as the pretreatment, for example, silane coupling treatment, corona discharge treatment, UV ozone treatment, plasma treatment, etc. can be selected.

[0035] From the viewpoint that the adhesion can be further enhanced by directly chemically bonding the surface for forming the resin part 2 such as the first surface 1A and the resin part 2, it is preferable to perform a coupling treatment using a silane coupling agent as the pretreatment. That is, it is preferable to further have a coating step of 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 before the next filling step.

[0036] Specific examples of the silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 8-methacryloxyoctyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0037] Subsequently, in the filling step, the resin composition 2a is filled between the glass substrate 1 and the mold 4. Specifically, first, as shown in FIG. 4(a), the resin composition 2a is dropped onto the surface of the mold 4. The resin composition 2a is, for example, a composition of an ultraviolet curable resin containing a photoinitiator as described above. Also, the glass substrate 1 is placed on the ejector 5 and arranged at a position facing the mold 4. The mold 4, for example, has an inverted shape of a desired aspherical shape on its surface, and is a mold that can be produced by cutting a metal base material such as stainless steel or steel material with NiP plating or electroless copper plating applied thereon using a precision processing machine. Also, a release agent may be applied to the surface of the mold 4 to control the releasability of the resin part 2. The type of the release agent is not particularly limited, but for example, a fluorine coating agent can be used as the release agent.

[0038] Subsequently, as shown in FIG. 4(b), by lowering the ejector 5 so that the mold 4 approaches the glass substrate 1, the resin composition 2a is provided on the glass substrate 1. The ejector 5 is further lowered to fill the uncured resin composition 2a between the mold 4 and the glass substrate 1, and it is molded into a desired shape.

[0039] In the manufacturing method of the optical element according to the present invention, the filling step includes filling the resin composition 2a such that a part of the resin composition 2a is filled between the light shielding film 3 and the mold 4. By doing so, the light shielding film 3 can be interposed between the resin part 2 and the glass substrate 1 when the resin composition 2a is cured.

[0040] Subsequently, in the curing step, the resin composition 2a is cured to form the resin part 2. Here, an example of curing the resin composition 2a by irradiating it with ultraviolet rays will be described. As shown in FIG. 4(b), by irradiating ultraviolet rays from the side of the second surface 1B of the glass substrate 1 toward the resin composition 2a between the glass substrate 1 and the mold 4 using the ultraviolet light source 6, the resin composition 2a is polymerized and cured. Thereby, the resin part 2 which is a polymerization cured product of the resin composition 2a is obtained.

[0041] In this step, since the ultraviolet rays are shielded by the light shielding film 3 and the resin composition 2a filled between the light shielding film 3 and the mold 4 is not irradiated with ultraviolet rays, it remains uncured. Therefore, a method of making the inner surface of the ejector 5 mirror-like can be mentioned in order to form the resin part 2 between the light shielding film 3 and the mold 4. Thereby, the ultraviolet rays irradiated from the ultraviolet light source 6 are reflected by the inner surface of the ejector 5 and can enter between the light shielding film 3 and the mold 4. Thereby, the resin composition 2a between the light shielding film 3 and the mold 4 can be cured without leaving it uncured.

[0042] As another method of curing the resin composition 2a between the light-shielding film 3 and the mold 4, a method may be employed in which a glass material that is permeable to ultraviolet rays is used as the material of the mold 4, and ultraviolet rays are irradiated not only from the side of the second surface 1B of the glass substrate 1 but also from the side where the mold 4 is disposed. Thereby, it becomes possible to cure the resin composition 2a between the light-shielding film 3 and the mold 4.

[0043] The curing step preferably includes irradiating ultraviolet rays so that the curing reaction rate of the resin portion 2 formed by curing the resin composition 2a between the light-shielding film 3 and the mold 4 is 40% or more and 95% or less. Thereby, the resin portion 2 can be easily released in the release step described later as a cured product. Thereafter, in the release step, by releasing the polymerized and cured resin portion 2 from the mold 4, an optical element 10 having an aspherical resin portion 2 formed on the glass substrate 1 is obtained. Note that after forming the resin portion 2, additional irradiation with ultraviolet rays or heat treatment may be performed in the air or in an oxygen-free atmosphere. In particular, when a part of the resin composition 2a between the light-shielding film 3 and the mold 4 remains uncured even after release, it is necessary to additionally irradiate ultraviolet rays from the side of the resin portion 2 to cure the resin composition 2a between the light-shielding film 3 and the mold 4.

[0044] By the above manufacturing method, the optical element 10 according to the present embodiment can be manufactured. In the filling step, the resin composition 2a may be dropped onto both the mold 4 and the glass substrate 1, or may be dropped only onto the glass substrate 1. Further, when the resin composition 2a contains a thermal polymerization initiator as a curing initiator, the curing step may include a heat treatment step.

[0045] [Second Embodiment] The optical element 10 according to the first embodiment can be applied to various devices and apparatuses such as optical devices and imaging devices. In this embodiment, an optical device and an imaging device will be described as specific application examples of the optical element 10 according to the first embodiment.

[0046] (Optical Device) Specific application examples of the optical element 10 according to the first embodiment include lenses constituting optical devices (photography optical systems) for cameras and video cameras, and lenses constituting optical devices (projection optical systems) for liquid crystal projectors. It can also be used as a pickup lens for DVD recorders and the like. These optical devices have a housing and an optical system having at least one lens disposed within the housing. The optical device according to this embodiment is characterized in that at least one of the lenses is the optical element 10 according to the first embodiment.

[0047] (imaging device) The imaging device according to this embodiment includes a housing, an optical system having at least one lens disposed within the housing, and an imaging element that receives light that has passed through the optical system, and is characterized in that at least one of the lenses is the optical element 10 according to the first embodiment.

[0048] 5 is a schematic diagram showing the configuration of a single-lens reflex digital camera 500, which is an example of a preferred embodiment of an imaging device using the optical element 10 according to the first embodiment. In Fig. 5, a camera body 502 is coupled to a lens barrel 501, which is an optical device, and the lens barrel 501 is a so-called interchangeable lens that can be attached to and detached from the camera body 502. Light from a subject is captured via an optical system consisting of multiple lenses 503, 505, etc., arranged on the optical axis of the imaging optical system inside housing 520 of lens barrel 501. Optical element 10 according to the first embodiment can be used for lenses 503, 505, for example. Here, lens 505 is supported by inner barrel 504 and is movably supported with respect to the outer barrel of lens barrel 501 for focusing and zooming. During the observation period before shooting, the light from the subject is reflected by the main mirror 507 inside the housing 521 of the camera body, passes through the prism 511, and then the photographed image is projected onto the photographer through the viewfinder lens 512. The main mirror 507 is, for example, a half mirror, and the light passing through the main mirror is reflected by the sub-mirror 508 in the direction of the AF (auto focus) unit 513. For example, this reflected light is used for distance measurement. Also, the main mirror 507 is mounted and supported on the main mirror holder 540 by adhesion or the like. During shooting, the main mirror 507 and the sub-mirror 508 are moved out of the optical path via a drive mechanism (not shown), the shutter 509 is opened, and the imaging element 510 receives the light that has entered from the lens barrel 501 and passed through the imaging optical system to form a photographed optical image. Further, the aperture 506 is configured to be able to change the brightness and depth of focus during shooting by changing the aperture area. Here, although the imaging device has been described using a single-lens reflex digital camera, the optical element 10 can be similarly used in a smartphone, a compact digital camera, a drone, or the like.

[0049] [Embodiment] The present invention will be described in more detail below using embodiments. First, a method for evaluating the optical element will be described. The evaluation of the optical element was performed on the appearance of the optical element and lens cracks.

[0050] (Appearance) The optical elements obtained in each example and comparative example were visually observed from the second surface side, which is the surface opposite to the resin part, and the appearance of the bright lines was evaluated. At that time, the level where no bright lines were visible at all was ranked as A, the level where bright lines were slightly visible but not problematic was ranked as B, and the level where bright lines were clearly visible was ranked as C.

[0051] (Lens Crack) The optical elements obtained in each example and comparative example were placed in a freezer maintained at a temperature environment of -40°C from room temperature. After 24 hours, the optical elements were taken out and returned to 25°C at room temperature, and then the appearance of the optical elements was evaluated. Also, a stress simulation during rapid cooling at -40°C was performed by the finite element method, and the thermal stress at the end of the resin part, which was presumed to be the starting point of the crack, was calculated. Optical elements in which cracks do not occur in the resin part and the stress value at the end of the resin part is less than 10 MPa are ranked as A, optical elements in which cracks do not occur in the resin part and the stress value at the end of the resin part is 10 MPa or more are ranked as B, and optical elements in which cracks have occurred in the resin part are ranked as C.

[0052] Next, the optical elements according to each example and comparative example will be described. (Example 1) Using the manufacturing method shown in FIG. 4, the optical element 10 shown in FIG. 1 was manufactured. As the glass substrate 1, an optical glass (S-TIM8, manufactured by Ohara Inc.) with a diameter of 44 mm having a flat surface 1D with a width of 5 mm and a ridge line 1E between the flat surface 1D and the optical surface 1C was prepared. The glass substrate 1 has a light-shielding film 3 (GT7-II: manufactured by Canon Chemicals Co., Ltd.). The light-shielding film 3 is formed with an inner diameter of 33 mm and is painted up to the optical surface 1C across the ridge line 1E. The shape of the glass substrate 1 is such that one surface (optical surface 1C) has a concave spherical shape with a diameter of 34 mm, and the other surface (second surface 1B) has a convex spherical shape with a diameter of 44 mm. As the mold 4, a NiP layer plated on a metal base material was machined by a precision machining machine to form a shape in which the aspherical shape of the resin part 2 to be formed was inverted. The inner surface of the injector 5 was mirror-finished for the purpose of reflecting ultraviolet rays.

[0053] Next, a silane coupling agent having a methacryl group as a functional group was applied to the surfaces of the glass substrate 1 and the light-shielding film 3 for the purpose of improving the adhesion between the glass substrate 1 and the resin part 2.

[0054] Next, the resin composition 2a was filled between the mold 4 and the glass substrate 1. As the resin composition 2a, one containing an acrylic monomer having a cyclic hydrocarbon in the main chain and a reactive acrylate group at the end and a polymerization initiator (Omnirad184 (1-hydroxycyclohexyl-phenyl ketone), manufactured by IGM Resins) was used. Thereafter, the intensity of 365 nm wavelength is 10 mW / cm 2The ultraviolet rays were irradiated onto the entire surface of the resin composition 2a for 200 seconds to cure the resin composition 2a, and the cured product of the resin composition 2a was released from the mold 4 to form the resin portion 2 on the glass substrate 1. The intermediate obtained by release was placed in an oven and heated at 80°C for 24 hours to produce the optical element according to Example 1. The width of the laminated region R between the light-shielding film 3 and the resin portion 2 in the obtained optical element 10 was measured. The outer diameter of the resin portion 2 (the distance in the direction perpendicular to the optical axis direction O from the center P0 to the end of the resin portion 2) was 35 mm, and the light-shielding film 3 was interposed in the outermost peripheral 1-mm region. The ratio of the width of the laminated region R to the radius of the optical surface 1C was 1 mm / 17 mm × 100% = 6%. When the linear expansion coefficients of the glass substrate 1, the light-shielding film 3, and the resin portion 2 were measured in the range of -30°C to 70°C using a thermomechanical analyzer TMA (manufactured by METTLER TOLEDO), they were 8 ppm / K, 60 ppm / K, and 100 ppm / K, respectively.

[0055] The water absorption expansion rate of the resin portion 2 was measured as follows. First, the resin portion 2 was cut out from the surface of the optical element 10 separately prepared for measuring the water absorption expansion rate. Specifically, a cut was made in the resin portion 2 on the surface of the optical element 10 using a feather razor, and the razor was inserted into the adhesive surface between the resin portion 2 and the glass substrate 1 to peel off the film. The thickness distribution of the film within one sample was made such that the fluctuation range of the thickness was within 10%. The shape of the film was a strip shape of 10 mm × 1 mm. The water absorption expansion rate of the peeled-off film was measured by the tensile load method using an apparatus (TMA-4000SE+HC9700 (humidity control type), manufactured by NETZSCH Japan) for measuring the linear expansion coefficient of the material while controlling the temperature and humidity to 60°C and 90% RH. The curing reaction rate of the resin portion 2 formed between the light-shielding film 3 and the mold 4 was measured using a Fourier transform infrared spectroscopic analyzer (FTIR) (product name: Spectrum One, manufactured by PerkinElmer, Inc.). Specifically, the peak area related to the carbon double bond in the absorption spectrum of the resin portion 2 obtained by FTIR was determined and calculated using the following formula.

Equation

[0056] Example 2 Except for using an acrylic monomer having a linear hydrocarbon in the main chain as the material of the resin composition 2a, the optical element 10 according to Example 2 was produced in the same manner as in Example 1. The linear expansion coefficient of the resin portion of the optical element 10 according to Example 2 was 170 ppm / K.

[0057] Example 3 An optical element 10 according to Example 3 was fabricated in the same manner as in Example 1, except that the resin portion 2 was formed so that the outer diameter was 33.8 mm. In the optical element 10 according to Example 3, the resin portion 2 was formed only on the optical surface 1C without spanning the ridge line 1E, as shown in Fig. 3. Furthermore, the width of the laminated region R was 0.4 mm, and the ratio of the width of the laminated region R to the radius of the optical surface 1C was 0.4 mm / 17 mm x 100% = 2%.

[0058] Example 4 An optical element 10 according to Example 4 was fabricated in the same manner as in Example 1, except that the resin portion 2 was formed so that the outer diameter was 33.2 mm. In the optical element 10 according to Example 4, the resin portion 2 was formed only on the optical surface 1C without spanning the ridge line 1E, as shown in Fig. 3. Furthermore, the width of the laminated region R was 0.1 mm, and the ratio of the width of the laminated region R to the radius of the optical surface 1C was 0.1 mm / 17 mm x 100% = 0.5%.

[0059] Example 5 An optical element 10 according to Example 5 was produced in the same manner as in Example 1, except that a silane coupling agent having a vinyl group was used as the silane coupling agent. In the optical element 10 according to Example 5, lifting of the resin portion 2 was observed on the flat surface 1D.

[0060] (Example 6) As the resin composition 2a, a mixture of the resin composition 2a used in Example 1 and a resin composition 2a containing an acrylic monomer having a urethane in the main chain and the above polymerization initiator at a weight ratio of 80:20 was used. Otherwise, the optical element 10 according to Example 6 was produced in the same manner as in Example 1.

[0061] (Example 7) The optical element 10 according to Example 7 was produced in the same manner as in Example 1, except that the internal reflection of the ejector was not used in the ultraviolet irradiation step. In the optical element 10 according to Example 7, the outer diameter of the resin portion 2 was 33.4 mm.

[0062] (Example 8) The optical element 10 according to Example 8 was produced in the same manner as in Example 1, except that ultraviolet irradiation was performed simultaneously from above and below using a mold made of quartz glass in the ultraviolet irradiation step. In the optical element 10 according to Example 8, the outer diameter of the resin portion 2 was 35.7 mm.

[0063] (Example 9) The optical element 10 according to Example 9 was produced in the same manner as in Example 1, except that additional ultraviolet irradiation was performed from the resin portion 2 side after demolding. In the optical element 10 according to Example 9, the outer diameter of the resin portion 2 was 35.7 mm.

[0064] (Examples 10, 18, 20 to 22) The optical elements 10 according to Examples 10, 18, and 20 to 22 were 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 for the shape corresponding to the aspherical shape of the resin portion 2.

[0065] (Example 11) A light-shielding film 3 was formed on a glass substrate 1 using a paint obtained by adding 20 parts by weight of QSG-100 (Shin-Etsu Chemical Co., Ltd.) to 100 parts by weight of GT7-II (Canon Chemical Co., Ltd.) and stirring until uniform. The resin composition 2a used was a 50:50 mixture of the resin composition 2a used in Example 1 and a resin composition 2a containing an acrylic monomer having a cyclic hydrocarbon in its main chain and acrylate groups at its side chain and terminal, and the polymerization initiator. An optical element 10 according to Example 11 was fabricated in the same manner as in Example 1 except for the above.

[0066] Example 12 The resin composition 2a used was a mixture of the resin composition 2a used in Example 1 and the resin composition 2a used in Example 2 in a weight ratio of 30:70. Otherwise, the optical element 10 according to Example 12 was produced in the same manner as in Example 1.

[0067] Example 13 An optical element 10 according to Example 13 was produced in the same manner as in Example 1, except that in the ultraviolet irradiation step, a mold made of quartz glass was used and ultraviolet irradiation was performed simultaneously from above and below. In the optical element 10 according to Example 13, the outer diameter of the resin portion 2 was 36.4 mm.

[0068] Example 14 The resin composition 2a used was a mixture of the resin composition 2a used in Example 1 and a resin composition 2a containing an acrylic monomer having a cyclic hydrocarbon in the main chain and acrylate groups at the side chain and terminal, and the polymerization initiator, in a weight ratio of 80:20. Except for this, the optical element 10 according to Example 14 was produced in the same manner as in Example 1.

[0069] Example 15 The resin composition 2a used was a mixture of the resin composition 2a used in Example 1 and the resin composition 2a used in Example 2 in a weight ratio of 40:60. Otherwise, the optical element 10 according to Example 15 was produced in the same manner as in Example 1.

[0070] (Examples 16, 17, 19) Optical elements 10 according to Examples 16, 17, and 19 were produced in the same manner as in Example 4, except that a mold 4 different from the mold 4 used in Example 4 was used for the aspherical shape of the resin part 2.

[0071] (Example 23) As the resin composition 2a, a mixture of the resin composition 2a used in Example 1 and a resin composition 2a containing an acrylic monomer having urethane in the main chain and the above polymerization initiator at a weight ratio of 70:30 was used. Otherwise, an optical element 10 according to Example 23 was produced in the same manner as in Example 1.

[0072] (Comparative Example 1) An optical element according to Comparative Example 1 was produced in the same manner as in Example 1, except that after filling a resin composition between a glass substrate without a light-shielding film and a mold and curing it, a light-shielding film was formed on the side surface and a part of the flat surface of the glass substrate and the end of the resin part. Note that the curing reaction rate was measured for the end of the resin part on which the light-shielding film was laminated.

[0073] (Comparative Example 2) An optical element according to Comparative Example 2 was produced 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 laminated region R was not provided. Note that the curing reaction rate was measured for the end of the resin part.

[0074] (Comparative Example 3) An optical element according to Comparative Example 3 was produced in the same manner as in Example 1, except that 50 parts by weight of titanium oxide (MT-05: manufactured by Teika Co., Ltd.) was added to the paint for forming the light-shielding film, and the obtained paint was used to form a light-shielding film on the glass substrate. Note that the linear expansion coefficient of the light-shielding film of the optical element according to Comparative Example 3 was 110 ppm / K.

[0075] Table 1 shown below summarizes the physical properties and evaluation results of the optical elements according to each example and comparative example.

[0076] In Table 1, P0 and P1 respectively indicate positions corresponding to the center P0 of the optical surface 1C shown in FIG. 1 and the point P1 where the resin portion 2 has the maximum thickness. The point P1 is a point 13 mm away from the center P0 in the radial direction of the optical surface 1C. Further, the laminated 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. According to Table 1, it can be seen that the optical elements 10 according to Examples 1 to 23 are all superior to the optical elements of Comparative Examples 1 to 3.

[0077]

Table 1

[0078] The disclosure according to the embodiment of the present invention includes the following configurations and methods. (Configuration 1) A glass substrate having a first surface and a second surface facing the first surface, A resin portion provided on the first surface, A light shielding film covering at least a part of the side surface of the glass substrate and a part of the first surface, The second surface is a light incident surface or an 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, An optical element characterized by the above. (Configuration 2) The ratio of the thickness of the resin portion in the optical axis direction at the center position of the optical surface of the first surface to the maximum thickness of the resin portion in the optical axis direction is 5 or more, and The ratio of the thickness of the resin portion in the optical axis direction at the center position of the optical surface of the first surface to the minimum thickness of the resin portion in the optical axis direction is 1 / 5 or less, The optical element according to Configuration 1, satisfying at least one of the above. (Configuration 3) 3. The optical element according to claim 1, wherein the resin portion has a linear expansion coefficient of 50 ppm / K or more and 150 ppm / K or less. (Configuration 4) the first surface has an optical surface, a flat surface provided on an outer edge of the optical surface, and a ridge line that is a boundary line between the optical surface and the flat surface, the resin portion is provided so as to extend from the optical surface across the ridge line to a part of the flat surface, 4. The optical element according to any one of configurations 1 to 3, wherein the light-shielding film is provided so as to extend from the flat surface across the ridge line to a part of the optical surface. (Configuration 5) The optical element according to configuration 4, wherein the width of the region where the resin portion and the light-shielding film are stacked in a direction perpendicular to the optical axis direction is 1% or more and 10% or less when the radius of the optical surface is 100%. (Configuration 6) 6. The optical element according to any one of configurations 1 to 5, wherein the resin portion has a coefficient of swelling due to water absorption of 0.8% or less. (Configuration 7) 1. An optical instrument comprising: a housing; and an optical system having at least one lens disposed within the housing, 7. An optical device, wherein at least one of the lenses is the optical element according to any one of aspects 1 to 6. (Configuration 8) An imaging device having a housing, an optical system having at least one lens disposed in the housing, and an imaging element that receives light that has passed through the optical system, 7. An imaging device, wherein at least one of the lenses is the optical element according to any one of configurations 1 to 6. (Method 1) A method for manufacturing an optical element comprising: a glass substrate having a first surface and a second surface opposite to the first surface; and a resin portion provided on the first surface, wherein the second surface is a light entrance surface or light exit surface, a preparation step of preparing the glass substrate on which a light-shielding film is formed; a filling step of filling a resin composition between the glass substrate and the mold; A curing step of curing the resin composition to form the resin part; A mold release step of releasing the resin part; and has The light-shielding film is formed on the glass substrate so as to cover at least a part of the side surface of the glass substrate and a part of the first surface; The filling step includes filling the resin composition so that a part of the resin composition is filled between the light-shielding film and the mold. A method for manufacturing an optical element. (Method 2) The curing step includes irradiating ultraviolet rays so that the curing reaction rate of the resin part formed by curing the resin composition between the light-shielding film and the mold is 40% or more and 95% or less. The method for manufacturing an optical element according to Method 1. (Method 3) Before the filling step, the manufacturing method of the optical element according to Method 1 or 2 further includes 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.

Explanation of reference numerals

[0079] 1 Glass substrate 1A First surface 1B Second surface 1C Optical surface 1D Flat surface 1E Ridge line 1F Side surface 2 Resin part 2a Resin composition 4 Mold 5 Injector 10 Optical element R Laminated area 500 Imaging device (digital camera) 501 Optical instrument (lens barrel) [[ID=…]]502 Camera body 503 Lens 505 Lens

Claims

1. A glass substrate having a first surface and a second surface facing the first surface, A resin portion provided on the first surface, A light-shielding film covering at least a part of the side surface of the glass substrate and a part of the first surface, The second surface is an incident surface or an exit surface of light, 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, An optical element characterized by the above.

2. The ratio of the thickness of the resin portion in the optical axis direction at the center position of the optical surface of the first surface to the maximum thickness of the resin portion in the optical axis direction is 5 or more, and The ratio of the thickness of the resin portion in the optical axis direction at the center position of the optical surface of the first surface to the minimum thickness of the resin portion in the optical axis direction is 1 / 5 or less, The optical element according to claim 1, satisfying at least one of the above.

3. The optical element according to claim 1, wherein the linear expansion coefficient of the resin portion is 50 ppm / K or more and 150 ppm / K or less.

4. The first surface has an optical surface, a flat surface provided at the outer edge of the optical surface, and a ridge line serving as a boundary line between the optical surface and the flat surface, The resin portion is provided so as to extend from the optical surface across the ridge line to a part of the flat surface, The light-shielding film is provided so as to extend from the flat surface across the ridge line to a part of the optical surface. The optical element according to claim 1.

5. The width in the direction perpendicular to the optical axis direction of the region where the resin portion and the light-shielding film are laminated is 1% or more and 10% or less when the radius of the optical surface is 100%. The optical element according to claim 4.

6. The optical element according to claim 1, wherein the water absorption expansion rate of the resin portion is 0.8% or less.

7. An optical device having a housing and an optical system having at least one lens disposed in the housing, The optical device, wherein at least one of the lenses is the optical element according to any one of claims 1 to 6.

8. An imaging device having a housing, an optical system having at least one lens disposed in the housing, and an imaging element that receives light that has passed through the optical system, The imaging device, wherein at least one of the lenses is the optical element according to any one of claims 1 to 6.

9. A method for manufacturing an optical element having a glass substrate having a first surface and a second surface facing the first surface, and a resin portion provided on the first surface, wherein the second surface is an incident surface or an exit surface of light. A preparation step of preparing the glass substrate on which a light-shielding film is formed. A filling step of filling a resin composition between the glass substrate and a mold. A curing step of curing the resin composition to form the resin portion. A demolding step of demolding the resin portion. It has. The light-shielding film is formed on the glass substrate so as to cover at least a part of the side surface of the glass substrate and a part of the first surface. The filling step includes filling the resin composition such that a part of the resin composition is filled between the light-shielding film and the mold. A method for manufacturing an optical element.

10. The curing step includes irradiating ultraviolet rays so that the curing reaction rate of the resin portion formed by curing the resin composition between the light-shielding film and the mold is 40% or more and 95% or less. The method for manufacturing an optical element according to claim 9.

11. Before the filling step, it further has a coating 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. The method for manufacturing an optical element according to claim 9 or 10.

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