JP6076041B2 - Optical element and optical element manufacturing method - Google Patents

Description

The present invention relates to an optical element and a method for manufacturing the optical element.

Conventionally, when manufacturing an optical element such as a lens used in an optical device such as a camera, in order to suppress flare and ghost due to internal reflection in the optical element, the internal reflection of black or the like on the surface outside the effective diameter of the optical element Preventive paint may be applied.
For example, Patent Document 1 describes an antireflection coating for an inner surface of an optical member characterized by containing black inorganic fine particles having a particle diameter of 0.1 μm or less and a refractive index of 1.5 or more. ing.
Patent Document 2 describes a coating material for an optical element characterized by containing an epoxy resin precursor having a refractive index of 1.65 or more, a curing catalyst, and black particles.

JP-A-7-82510 JP 2009-282488 A

However, the above-described conventional methods for producing an inner surface antireflection coating and an optical element have the following problems.
The inner surface antireflection coating and the optical element coating (inner surface antireflection coating) described in Patent Documents 1 and 2 both have a refractive index of the glass material of the optical element as the optical element becomes smaller and more functional. Focusing on the tendency to increase, an internal reflection preventing paint having a relatively large refractive index is used. Thereby, even if the refractive index of the optical element is high, total reflection at the interface between the optical element and the inner surface antireflection coating is less likely to occur, so that internal reflection due to total reflection is reduced.
However, since the reflectivity of the interface increases as the difference in the refractive index of the medium sandwiching the interface increases, depending on the size of the refractive index of the glass material of the optical element, the high-refractive-index internal antireflection coating does not necessarily have a high reflectivity. It cannot be said that it has a preventive effect.
In most cases, the optical element has an antireflection coating layer on the surface in order to improve the transmittance on the optical surface. Such an antireflection coating layer reduces the reflectance with respect to a specific wavelength or wavelength band using interference of reflected light in the thin film.
Such an antireflection coating layer reduces the reflectivity of the optical surface, and is therefore designed on the assumption that the outermost surface is in contact with air. Therefore, when an internal antireflection coating having a high refractive index is laminated on the outermost surface of the antireflection coating layer, the antireflection action on the design of the antireflection coating layer is impaired, and the reflectance in the antireflection coating layer increases. End up. For this reason, there is a problem that flare and ghost are likely to occur.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical element that can easily reduce the reflectivity of internal reflection even when laminated on an antireflection coating layer, and a method for manufacturing the optical element. And

In order to solve the above problems, the optical element according to the first aspect of the present invention is a base material having an optical surface and a multilayer film in which a single layer film or a plurality of layers having different refractive indexes are laminated, An antireflection coating layer laminated on regions on the inside and outside of the effective diameter of the optical surface on the substrate, and having a refractive index of an outermost layer on the opposite side of the substrate lower than the refractive index of the substrate; and the reflection A low refractive index nano-layer comprising a fluororesin, or magnesium fluoride or hollow silica, which is laminated and disposed in a region on the surface of the base material, including a film formation site outside the effective diameter range of the optical surface in the prevention coating layer It is set as the structure provided with particle | grains and a coloring material, and an internal surface antireflection layer whose refractive index is lower than the refractive index of the outermost layer of the said antireflection coating layer .

In the optical element, it is preferable that the base material has a maximum surface roughness of less than 1 μm in a range covered by the inner surface antireflection layer .

In the method of manufacturing an optical element according to the second aspect of the present invention, a single layer film or a plurality of layers having different refractive indexes are laminated on the inner and outer regions of the effective diameter of the optical surface in the base material having the optical surface . A film forming step for forming an antireflection coating layer , which is a multilayer film, and has an outermost layer on the side opposite to the base material having a refractive index lower than the refractive index of the base material, and the film formed by the film forming step Low refractive index nanoparticles made of fluororesin, magnesium fluoride or hollow silica in a region on the surface of the base material, including a film formation site outside the effective diameter range of the optical surface in the antireflection coating layer And an inner surface antireflection layer forming step of forming an inner surface antireflection layer having a refractive index lower than that of the outermost layer of the antireflection coating layer by applying an inner surface antireflection coating containing a coloring material. The method.

According to the optical element of the present invention, there is an effect that the reflectance of the internal reflection is reduced even when the internal reflection preventing layer is laminated on the reflection preventing coating layer .
According to the method for producing an optical element of the present invention, an inner surface antireflection layer is formed using an inner surface antireflection coating containing a low refractive index nanoparticle made of fluororesin, magnesium fluoride or hollow silica, and a coloring material. Therefore, even if the inner surface antireflection layer is laminated on the antireflection coating layer, it is possible to produce an optical element in which the reflectance of inner surface reflection is reduced.

It is the typical top view of the optical element manufactured by the manufacturing method of the optical element of the 1st Embodiment of this invention, and its AA sectional drawing. It is the typical enlarged view which shows the detailed figure of the B section in FIG. 1, and the structural example of an internal surface antireflection layer. FIG. 2 is a detailed view of a part C in FIG. 1. It is a flowchart which shows the process flow of the manufacturing method of the optical element of the 1st Embodiment of this invention. It is a schematic diagram for demonstrating internal reflection of the optical element manufactured with the manufacturing method of the optical element of the 1st Embodiment of this invention. It is typical process explanatory drawing of the manufacturing method of the optical element of the 1st Embodiment of this invention. It is typical process explanatory drawing of the film-forming process of the modification (1st modification) of the manufacturing method of the optical element of the 1st Embodiment of this invention. It is a typical detailed view of the B section and C section in Drawing 1 of an optical element manufactured by a manufacturing method of an optical element of a 2nd embodiment of the present invention. It is a flowchart which shows the process flow of the manufacturing method of the optical element of the 2nd Embodiment of this invention. It is typical process explanatory drawing of the film-forming process of the manufacturing method of the optical element of the 2nd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.

[First Embodiment]
A method for producing an inner surface antireflection coating and an optical element according to the first embodiment of the present invention will be described.
FIG. 1A is a schematic plan view of an optical element manufactured by the method for manufacturing an optical element according to the first embodiment of the present invention. FIG.1 (b) is AA sectional drawing in Fig.1 (a). FIG. 2A is a schematic detailed view of a portion B in FIG. 2B and 2C are schematic enlarged views showing a configuration example of the inner surface antireflection layer. FIG. 3 is a schematic detailed view of a portion C in FIG.

First, an example of an optical element manufactured by the optical element manufacturing method of the present embodiment will be described.
A lens 1 (optical element) shown in FIGS. 1A and 1B is an example of an optical element manufactured by the optical element manufacturing method of the present embodiment.
The lens 1 is a plano-concave lens in which an inner surface antireflection layer 3 and a black coating layer 4 for preventing inner surface reflection are formed on the surface of a lens substrate 2 (base material) formed by polishing a glass material. It is.

The outer shape of the lens substrate 2 is a circle centered on the optical axis O.
One surface in the thickness direction (hereinafter referred to as the lens thickness direction) along the optical axis O extends from the outer periphery of the first lens surface 2a, which is a concave optical surface, in a direction perpendicular to the optical axis O. And a plane portion 2b composed of a flat surface.
The other surface in the lens thickness direction is composed of a second lens surface 2c which is an optical surface made of a plane orthogonal to the optical axis O.
A lens side surface _2d , which is a cylindrical surface having a diameter _d2d with the optical axis O as the center, is formed on the outer periphery of the flat portion 2b and the outer periphery of the second lens surface 2c.
A chamfered shape may be formed at a corner portion formed by the flat surface portion 2b and the lens side surface 2d and a corner portion formed by the second lens surface 2c and the lens side surface 2d.

The first lens surface 2a and the second lens surface 2c are high-precision smooth surfaces that are mirror-finished by polishing, and have surface accuracy corresponding to the required optical performance within the range of their effective diameters.
As shown in FIG. 1 (a), the effective diameter _{d 1} of the first lens surface 2a is slightly smaller than the outer diameter _{d 2a} of the first lens surface 2a. Further, as shown in FIG. 1 (b), the effective diameter _{d 2} of the second lens surface 2c is, for _example, is set to a size such as _{d 1 <d 2 <d 2d} .
An antireflection coating layer 5 is formed on the surfaces of the first lens surface 2 a and the second lens surface 2 c in order to improve the transmittance of the lens 1.

As the configuration of the antireflection coating layer 5, a single layer film or a multilayer film composed of an appropriate material and layer thickness according to the refractive index, spectral transmittance specification, etc. of the lens substrate 2 can be adopted.
For example, as an example of a single layer film, a thin film layer of magnesium fluoride (refractive index n _d = 1.37 to 1.39) which is a low refractive index material as compared with the glass used for the lens substrate 2 is an appropriate layer. A structure in which a film is formed with a thickness can be employed.
The multilayer film has a structure in which a low refractive index material, a medium refractive index material, and a high refractive material are alternately stacked with an appropriate layer thickness and number of layers from the lens substrate 2 side, and the outermost layer is formed of a low refractive index material. Is possible.
Here, as a low refractive index material used for the multilayer film, a material having a refractive index n _d = 1.37 to 1.5 is used, and as a medium low refractive index material, a refractive index n _d = 1.60. A material having a refractive index n _{d of} about 2.00 to 2.50 is used as a high refractive index material.
Examples of the low refractive index material used for the outermost layer include magnesium fluoride (refractive index n _d = 1.37 to 1.39), silica (refractive index n _d = 1.44 to 1.47), and the like. Can be mentioned.
Hereinafter, the surface of the antireflection coating layer 5 opposite to the lens substrate 2 is referred to as the outermost surface 5a of the antireflection coating layer 5 (see FIG. 2A). In addition, the layer constituting the outermost surface 5a may be referred to as the outermost layer of the antireflection coating layer 5 regardless of whether the antireflection coating layer 5 is a single layer film or a multilayer film.

Planar portion 2b are the outside of the effective diameter d _1, but the surface accuracy is not required as the optical surface, in this embodiment, it consists of the smooth surface formed by polishing, the optical axis O of the lens 1 A plane suitable for positioning along the direction is formed.
The surface roughness of the flat portion 2b is, for example, less than 1 μm at the maximum height. In this embodiment, it is 0 μm as an example.
An antireflection coating layer 5 is formed on the flat portion 2b. The antireflection coating layer 5 may be intentionally formed in order to suppress internal reflection at the flat surface portion 2b, or reliably prevent reflection within the effective diameter of the first lens surface 2a. In order to form the coat layer 5, a secondary layer may be formed.
For this reason, the antireflection coating layer 5 on the flat surface portion 2b may be formed on the entire surface of the flat surface portion 2b, or may be formed only in a partial region adjacent to the first lens surface 2a. Further, the layer thickness of the antireflection coating layer 5 may be the same as that of the first lens surface 2a, or may deviate from the layer thickness of the first lens surface 2a due to film formation variation.
Further, when chamfering is formed at the corners of the flat surface portion 2b and the lens side surface 2d, the antireflection coating layer 5 may not be formed on the chamfering portion, or the antireflection coating layer 5 is formed. It may be.
In the present embodiment, as an example, a case where the antireflection coating layer 5 is formed on the entire surface of the flat portion 2b will be described.

In this embodiment, the lens side surface 2d is processed in order to obtain a dimensional accuracy suitable for holding and positioning in the radial direction of the lens 1, and then, for example, in order to reduce internal reflection by scattering incident light, Roughening is performed by polishing or molding.
The surface roughness of the lens side surface 2d is preferably, for example, 1 μm to 50 μm at the maximum height. In the present embodiment, the surface roughness is prepared by grinding as an example, and the maximum height is 30 μm.

As shown in FIGS. 1B and 2A, the inner surface antireflection layer 3 is provided by being laminated on the antireflection coating layer 5 on the flat surface 2b.
Incidentally, the inner surface antireflection layer 3 may be further provided on the antireflection coating layer 5 outside the effective diameter d ₂ of the effective diameter d ₁ of the outer and the second lens surface 2c of the first lens surface 2a, in some cases, it may be provided only outside the effective diameter d ₂ of the second lens surface 2c. Further, when there is a chamfered portion at the corner portion between the flat portion 2b and the lens side surface 2d and at the corner portion between the second lens surface 2c and the lens side surface 2d, the chamfered portion may be provided.
Since these differences are merely differences in formation locations, an example in the case where they are provided only on the plane portion 2b will be described below as an example.

The structure of the inner surface antireflection layer 3 is light-transmitting, and a coloring material 3A that absorbs light incident from the antireflection coating layer 5 side to the base portion 3B for obtaining adhesion strength with the antireflection coating layer 5. Is a layered portion in which is dispersed. The base portion 3B may contain fine particles and additives other than the color material as necessary.
The thickness of the inner-surface antireflection layer 3 is such that the adhesion strength with the lens base material 2 becomes good and the inner-surface reflection at the flat surface portion 2b is suppressed, so that flare and ghost due to the inner-surface reflected light can be suppressed. There is no particular limitation.
An example of a suitable layer thickness of the inner surface antireflection layer 3 is preferably 1 μm to 50 μm, and more preferably 1 μm to 10 μm.

In the present embodiment, the inner surface antireflection layer 3 is roughly divided into the following two types of configurations.
As shown in FIG. 2B, the first configuration (hereinafter referred to as configuration [a]) is a configuration in which the base portion 3B is mainly composed of a fluororesin layer that is a low refractive index resin layer.
In the second configuration (hereinafter referred to as configuration [b]), as shown in FIG. 2C, the base 3B disperses the low-refractive nanoparticles 3Bb in the resin layer 3Ba, so that the resin layer 3Ba In this configuration, a layer having a refractive index lower than the refractive index is formed.

As the color material 3A used in common for the configurations [a] and [b], an appropriate pigment or dye that can absorb light causing flare or ghost by internal reflection can be used. The color of the color material 3A is preferably black or black.
Examples of pigments suitable as the color material 3A include carbon black and titanium black. Examples of dyes suitable as the colorant 3A include azo dyes, azine dyes, anthraquinone dyes, carbonium dyes, stilbenzene dyes, thiazole dyes, pyrazolone dyes, and phthalocyanine dyes.

The fluororesin used for the base part 3B of the configuration [a] is particularly a fluororesin having a refractive index such that the inner antireflection layer 3 is a layer part having a lower refractive index than the outermost layer of the antireflection coating layer 5. It is not limited. Such a refractive index depends on the refractive index of the outermost layer of the antireflection coating layer 5 and the content of the color material 3A, but is preferably n _d = 1.34 to 1.42, for example, n _d = 1.34 to 1.38 is more preferable.
Examples of the fluororesin that can be suitably used for the configuration [a] include, for example, a fluoroolefin-vinyl ether copolymer (refractive index n _d = 1.38), Cytop (registered trademark) (refractive index n _d = 1.34).

In the configuration [a], the higher the fluorine resin content, the lower the refractive index of the inner surface antireflection layer 3. However, when the content of the color material 3A decreases relatively, the inner surface antireflection layer does not hit the color material 3A. The light passing through 3 increases and the light absorption effect decreases. Therefore, in order to ensure the light absorption effect even if the content of the color material 3A is low, the inner surface antireflection layer 3 must be thickened in order to increase the probability of light irradiation to the color material 3A.
For this reason, in order to suppress the layer thickness of the inner surface antireflection layer 3 to, for example, a thickness of about 10 μm, the content of the color material 3A is preferably 10 wt% (mass%) or more and 90 wt% or less, More preferably, the content is 15 wt% or more and 70 wt% or less.

The resin layer 3Ba in the configuration [b] has a function of forming a layered body that disperses and holds the low refractive index nanoparticles 3Bb and the color material 3A, and is in close contact with and bonded to the antireflection coating layer 5. Yes.
As a material suitable for such a resin layer 3Ba, the low refractive index nanoparticles 3Bb and the colorant 3A can be mixed to obtain a refractive index lower than that of the outermost layer of the antireflection coating layer 5, and mixed. There is no particular limitation as long as the low refractive index nanoparticles 3Bb and the colorant 3A are held in layers and the necessary adhesion strength with the antireflection coating layer 5 is obtained.
Examples of a resin material that can suitably form the resin layer 3Ba include acrylic resin (refractive index n _d = 1.49 to 1.53), epoxy resin (refractive index n _d = 1.55 to 1.61), and the like. Can be mentioned.

As the low-refractive-index nanoparticles 3Bb used in the configuration [b], an appropriate low-refractive material that can be formed into fine particles can be suitably used.
The particle size of the low refractive index nanoparticles 3Bb is made sufficiently smaller than the wavelength of the incident light so that the refractive index can be adjusted by mixing with the resin layer 3Ba. The preferred particle diameter of the low refractive index nanoparticles 3Bb is 10 nm to 100 nm in terms of average particle diameter.
In this embodiment, magnesium fluoride (refractive index n _d = 1.38) or hollow silica (refractive index n _d = 1.3) is adopted as an example of the low refractive index nanoparticles 3Bb.
As the low refractive index nanoparticles 3Bb made of magnesium fluoride, magnesium fluoride particles having an average particle size of about 10 nm to 100 nm can be employed.
As the low refractive index nanoparticles 3Bb made of hollow silica, hollow silica particles having an average particle diameter of about 40 nm to 100 nm can be employed.

What is necessary is just to set suitably the content rate of the low-refractive-index nanoparticle 3Bb in structure [b] by the relationship between the refractive index required as the internal surface antireflection layer 3, and the refractive index of a resin layer.
For example, when the resin layer 3Ba is formed of an acrylic resin and the low refractive index nanoparticles 3Bb are made of hollow silica, the content of the hollow silica is preferably 20 wt% or more.
On the other hand, if the content of the low refractive index nanoparticle 3Bb is too large, the adhesion strength of the inner surface antireflection layer 3 to the antireflection coating layer 5 is lowered, so the content of the low refractive index nanoparticle 3Bb is 70 wt%. % Or less is preferable.

As shown in FIGS. 1B and 3, the black coating layer 4 is provided so as to be laminated on the lens side surface 2 d, and a paint containing a black color material applied to the lens side surface 2 d is solidified. It is a layered part. For this reason, the black coating layer 4 can suppress internal reflection from the lens side surface 2d by absorbing light transmitted through the lens side surface 2d.
As will be described later, in this embodiment, when the antireflection coating layer 5 is formed on the lens 1, the antireflection coating layer 5 does not adhere to the lens side surface 2d. For this reason, the black coating layer 4 is not laminated on the antireflection coating layer 5.
As the coating material for forming the black coating layer 4, any appropriate conventionally used black coating material for preventing internal reflection can be employed. For example, a lens inner surface preventing paint GT-7 (trade name; Canon Kasei Co., Ltd.) can be used.

Next, a method for manufacturing the lens 1 will be described.
FIG. 4 is a flowchart showing a process flow of the method of manufacturing an optical element according to the first embodiment of the present invention. FIGS. 5A, 5B, 5C, and 5D are schematic process explanatory views of a method for manufacturing an optical element according to the first embodiment of the present invention.

  In the optical element manufacturing method of the present embodiment, as shown in FIG. 4, the base material forming step S1, the film forming step S2, the inner surface antireflection layer forming step S3, and the black coating layer forming step S4 are performed in this order. The lens 1 is manufactured.

The base material forming step S <b> 1 is a step of forming the lens base material 2.
In this step, first, the first lens surface 2 a and the second lens surface are formed by cutting or glass mold, and the glass glass material is roughly processed into a shape larger than the outer shape of the lens substrate 2.
Next, the lens side surface 2d is formed by cutting, and the flat surface portion 2b is formed by polishing. In this way, the lens substrate 2 shown in FIG. 5A is formed.
Since the first lens surface 2a, the flat surface portion 2b, and the second lens surface 2c are polished or glass molded, they are smooth surfaces that are mirror-finished.
Above, base material formation process S1 is complete | finished.

Next, a film forming step S2 is performed. This step is a step of forming the antireflection coating layer 5 on the lens substrate 2.
Conventionally, a thin film formation method such as the antireflection coating layer 5 is conventionally performed by a dry process such as a vacuum deposition method or a sputtering method, and a wet process such as a spin coating method, a dip method, a spray method, or a roll coating method. Is known.
In the present embodiment, an example in the case of forming a film by a vacuum deposition method will be described as an example.
As shown in FIG. 5B, the lens substrate 2 is held by a holding jig 50 at the upper part in a vacuum chamber (not shown) with the first lens surface 2a facing downward.
Examples of the holding jig 50 include a pinching yatoy and a dropping yatoy. In this embodiment, a pinching yatoy that holds the lens side surface 2d from the side surface is adopted. The holding jig 50 covers the entire lens side surface 2d adjacent to the flat surface portion 2b, and can hold the lens base 2 so that the end portion is aligned with the flat surface portion 2b.
Further, the holding jig 50 is held by a rotation mechanism (not shown), and thus can be rotated around the vertical axis.
A deposition source 51 made of a solid film forming material for the antireflection coating layer 5 is disposed below the lens substrate 2, and the film forming material is vaporized by a heating source (not shown) to form molecules or atoms of the film forming material. The film forming material particles made of can be scattered.
The deposited film forming material particles reach the first lens surface 2a and the flat surface portion 2b that rotate and move upward, and are deposited to form a thin film layer. Thereby, the antireflection coating layer 5 is formed.

As described above, in the film formation by the vacuum vapor deposition method, the arrival destination of the film forming material particles cannot be strictly controlled. Therefore, the antireflection coating layer 5 having a certain thickness is formed within the effective diameter of the first lens surface 2a. In this case, the film-forming material particles are deposited also on the first lens surface 2 a outside the effective diameter and the flat portion 2 b not covered with the holding jig 50.
Next, after removing the lens base material 2 from the holding jig 50, the lens base material 2 is held so that the second lens surface 2c faces downward, and the antireflection is applied to the second lens surface 2c in the same manner as described above. The coat layer 5 is formed. Also in this case, as described above, if an antireflection coating layer 5 having a constant thickness is formed within the effective diameter of the second lens surface 2c, the second lens surface 2c outside the effective diameter is also formed on the second lens surface 2c. Film material particles accumulate.
When the antireflection coating layer 5 is a single layer film, the film forming step S2 is completed.
In the case where the antireflection coating layer 5 is a multilayer film, the film forming step S2 similar to the above is repeated so that a necessary multilayer film of necessary materials can be obtained by changing the type of the vapor deposition source 51. When all the layered parts are formed, the film forming step S2 is completed.

Next, an inner surface antireflection layer forming step S3 is performed. This step, as shown in FIG. 5 (c), including the deposition site outside the range of the effective diameter d ₁ of the first lens surface 2a of the formed anti-reflective coating layer 5 by a film forming step S2, in the region of the plane portion 2b, a step of forming an inner anti-reflection layer 3 by coating the inner surface antireflection coatings P _3.

Internal reflection preventive paint P ₃ is for forming a base portion 3B of the inner surface antireflection layer 3, heating, or fine particles other than the colorant 3A as necessary to the resin material having curability by irradiation of energy light irradiation or the like Or a solution in which an additive is mixed and a color material 3A.
When forming the internal reflection prevention layer 3 having the structure [a], the paint P ₃ for preventing internal reflection, for example, it can be employed liquid material obtained by mixing a colorant 3A thermosetting fluororesin solution.
When forming the internal reflection prevention layer 3 having the structure [b], the inner surface antireflection coatings P _3, for example, to a solution of the base resin of the thermosetting acrylic resin solution or the like, coloring material and magnesium fluoride or hollow A liquid obtained by mixing low refractive index nanoparticles made of silica can be used.

Coating method to antireflection coating layer 5 on the inner surface antireflection coatings P _3, for example, can be adopted roller coating, coating or the like using an airbrush or brush.
Since the inner surface antireflection layer 3 does not reduce the reflectance by utilizing the interference of light, the inner surface antireflection layer 3 can be formed with a sufficiently thick layer thickness compared to the wavelength of the light that prevents the inner surface reflection. However, a large variation is acceptable as compared with the wavelength of light.
As the coating thickness of the inner-surface antireflection coating P ₃ , an appropriate coating thickness that can obtain the required thickness of the inner-surface antireflection layer 3 can be adopted.

After completing the coating of the inner surface antireflection coatings P _3, to solidify the internal reflection prevention coating P _3. For example, if the internal reflection prevention coating P ₃ is a thermoset, solidified by heating.
Thereby, the inner surface antireflection layer 3 is formed.
Thus, the inner surface antireflection layer forming step S3 is completed.

Next, a black paint layer forming step S4 is performed. This step is a step of forming the black coating layer 4 on the lens side surface 2d.
As shown in FIG. 5 (d), in order to form the black coating layer 4 on the lens side surface 2d of the lens base material 2 on which the inner surface antireflection layer 3 is formed, a black coating composition made of a resin material solution containing a coloring material is used. the P _4, for example, be applied by not shown of the application roller or the like.
For example, if the black paint P ₄ is the lens inner surface prevents paint GT-7 is black paint P ₄ is the main agent, curing agent, a mixed liquid material at an appropriate mixing ratio thinner.
Next, by heating the lens substrate 2 black paint P ₄ is applied, to solidify the black paint P _4. Thereby, the black coating layer 4 is formed and black coating layer formation process S4 is complete | finished.

In this way, the lens 1 as shown in FIGS. 1A and 1B is manufactured.
Incidentally, for example, the internal reflection prevention layer 3 in the case of providing on the outside of the effective diameter d ₂ of the second lens surface 2c is the above internal reflection preventing layer forming step S3, the inner surface antireflection coatings P ₃ to the flat surface portion 2b It is coated with, also coated with the inner surface antireflection coatings P ₃ on the outside of the effective diameter d ₂ of the second lens surface 2c, then solidifying the internal reflection prevention coating P ₃ and heating the lens substrate 2 You can do it.

Next, the operation of the inner surface antireflection layer 3 in the lens 1 will be described.
FIGS. 6A, 6 </ b> B, and 6 </ b> C are schematic views for explaining internal reflection of the optical element manufactured by the method for manufacturing an optical element according to the first embodiment of the present invention.

FIG. 6A is a schematic diagram for explaining the principle of flare generation when the antireflection coating layer 5 is formed on the lens substrate 2.
The antireflection coating layer 5 suppresses reflected light by light interference, and here, with respect to the wavelength of the light beam L ₁ from the inner side of the lens substrate 2 toward the antireflection coating layer 5, the reflectance is theoretically 0. It is designed to be%. This reflectivity is based on the design condition that the outermost surface 5a of the antireflection coat layer 5 is in contact with air having a refractive index n _A = 1, and the refractive index of the lens substrate 2 is a constant value n _L. Is based.
In this case, the light beam L ₁ does not cause internal reflection on the surface of the lens substrate 2 on which the antireflection coating layer 5 is formed, and the light beam L ₁ is transmitted 100% to the outside.

However, the lens 1 is, for example, in contact with or in close proximity to a member such as a lens barrel 6 that can be a reflective surface. Therefore, the light beam L ₁ is part of the light beam L ₂ is absorbed in the lens barrel 6, another is reflected luminous flux L ₃ as a beam L ₃ on the surface of the lens barrel 6, the anti-reflective coating layer 5 incident again, partially in reflectance according to the incident angle is reflected, and other is incident on the lens base material 2 as a light flux L _4.
In this case, the light beam L ₄ becomes the cause of flare and ghost.
In the case where the antireflection coating layer 5 is not provided, transmitted light to the outside is generated and inner surface reflected light is generated according to the reflectance according to the refractive index of the lens substrate 2. For this reason, the re-incident light from the outside and the internally reflected light cause flare and ghost, respectively.

To reduce the amount of transmitted light to the outside of the light beam L _1, as shown in FIG. 6 (b), consider the case of forming a black layer 4 by applying a black paint P ₄ on the surface of the lens substrate 2 .
Black layer 4, the coloring material 4A having a refractive index n _B4 to absorb incident light, are dispersed in the light transmitting resin layer 4B having a refractive index n _PH. As the material of the resin layer 4B, for example, an acrylic resin, the refractive index _{n PH} is used is of about 1.5 to 1.6.
In such a configuration, since the resin layer 4B is in contact with the outermost surface 5a of the antireflection coating layer 5, the design condition that the antireflection coating layer 5 is in contact with air is not satisfied. Therefore, not the reflectance of 0%, the light beam L _1, the light beam L ₅ becomes partially incident on the black layer 4 is transmitted through the anti-coat layer 5 reflecting, others reflected by the antireflection coating layer 5 Thus, the inner surface reflected light L ₆ returns to the inside of the lens substrate 2.
The light beam L ₅ represents either be absorbed to reach the color material 4A of black layer 4, decays after repeated reflections between the colorant 4A.

Outermost surface 5a of the general, the antireflection coating layer 5, since it is composed of a low refractive index material, the refractive index n _PH of the resin layer 4B is not only greater than the refractive index n _A of the air, antireflection The refractive index of the outermost surface 5a of the coat layer 5 is relatively larger.
Thus, when the relationship between the height of the medium in contact with the outermost surface 5a of the antireflection coating layer 5 is reversed from the design condition, two interfaces having a large refractive index difference are generated in the outermost layer of the antireflection coating layer 5. Since the interference does not occur according to the design conditions, the reflectance of the antireflection coating layer 5 is further increased.

On the other hand, although not particularly illustrated, considering the case where the antireflection coating layer 5 of FIG. 6B is deleted and the black coating layer 4 is directly applied to the lens substrate 2, the refraction of the lens substrate 2 is considered. The rate n _L is larger than the refractive index n _PH of the resin layer 4B that does not require such a refractive power in order to ensure the refractive power.
In this case, at the interface between the lens substrate 2 and the black coating layer 4, the light beam L ₁ is incident on the low refractive index layer from the high refractive index layer, so that it corresponds to the difference between the refractive index n _L and the refractive index n _PH . Only internally reflected light is generated. For this reason, although it depends on the size of each refractive index, the internal reflection light is easily reduced as compared with the case where the antireflection coating layer 5 is sandwiched.
Further, the light beam L ₅ that has passed through the black layer 4 is attenuated in the same manner as described above.
Therefore, in order to suppress internal reflection, it is effective to form the black coating layer 4 on the surface of the lens substrate 2 that does not have the antireflection coating layer 5, but the black coating layer 4 on the antireflection coating layer 5. Formation of becomes a factor that deteriorates internal reflection.
However, when the antireflection coating layer 5 is formed by vacuum vapor deposition like the lens 1, it is difficult to form the antireflection coating layer 5 only within the effective diameter, and it is very troublesome even if possible. It will take.

Therefore, in the present embodiment, the inner surface antireflection layer 3 is formed at a site where the antireflection coating layer 5 outside the effective diameter is formed, as shown in FIG.
Internal reflection preventing layer 3, the coloring material 3A having a refractive index n _B3 to absorb incident light, are dispersed in the base portion 3B having a refractive index n _PL.
The refractive index n _PL of the base portion 3B, the configuration [a], in any case of [b], but higher than the refractive index n _A of the air, the medium constituting the outermost surface 5a of the anti-reflection coating layer 5 Lower than refractive index.
Therefore, the base portion 3B with which the outermost surface 5a of the antireflection coating layer 5 is in contact does not satisfy the design conditions, but is closer to the refractive index n _{A of} air than the resin layer 4B of the black coating layer 4, and the refractive index also changes. From the lens substrate 2 toward the inner surface antireflection layer 3, the refractive index is changed from a high refractive index to a low refractive index. For this reason, the reflectance of the antireflection coating layer 5 is smaller than that when the black coating layer 4 is laminated.
As a result, the internal reflection prevention layer 3, the light beam L ₅ having a large amount of light from the light beam L _{5 'is} transmitted through, it is attenuated by the color material 3A.
Further, the inner surface reflected light L ₆ ′ has a lower light intensity than the inner surface reflected light L ₆ .

As described above, in the lens 1, the internal reflection is suppressed by laminating the internal reflection preventing layer 3 on the flat portion 2 b on which the antireflection coating layer 5 is formed.
Moreover, in the lens side surface 2d in which the antireflection coating layer 5 is not formed, the internal reflection is suppressed because the black coating layer 4 is laminated. Furthermore, in this embodiment, since the lens side surface 2d is roughened, incident / exit light is scattered on the lens side surface 2d. For this reason, the light incident on the black coating layer 4 is diffused in a wide range within the black coating layer 4 and efficiently absorbed by the color material 4A. In addition, since the light returning from the lens side surface 2d into the lens substrate 2 is also scattered in a wide range, the light emitted in the direction of flare or ghost is relatively reduced. As described above, in the present embodiment, combined with the action of the lens side surface 2d being a rough surface, inner surface reflected light that becomes flare and ghost is suppressed.

As described above, in the optical element manufacturing method of the present embodiment, the inner surface antireflection layer 3 is formed by the inner surface antireflection coating P ₃ , and thus the inner surface antireflection layer 3 is laminated on the antireflection coating layer 5. Even if it makes it, the lens 1 with which the reflectance of internal reflection was reduced can be manufactured.

[First modification]
Next, a method for manufacturing an optical element according to a modified example (first modified example) of the present embodiment will be described.
FIGS. 7A and 7B are schematic process explanatory views of a film forming process of a modified example (first modified example) of the method of manufacturing an optical element according to the first embodiment of the present invention.

This modification is a modification of the film forming step S2 of the first embodiment, and only the point that the antireflection coating layer 5 is manufactured by the spin coating method in the film forming step S2 is the first embodiment. And different.
Hereinafter, a description will be given centering on differences from the first embodiment.

In the film forming step S2 of this modification, the lens base 2 formed in the same manner as the base forming step S1 of the first embodiment, as shown in FIG. Then, the plane 2b is held on the rotation holding base 52 with the plane 2b facing upward.
The rotation holding base 52 includes a rotation shaft 52a that receives rotation drive from a rotation drive source (not shown), and is provided to be rotatable about a vertical axis.
The lens substrate 2 is held from the side of the lens side surface 2d by the rotation holding base 52 at a position where the optical axis of the first lens surface 2a coincides with the rotation center of the rotation shaft 52a.
Next, the coating liquid C is dropped onto the center of the first lens surface 2a. The coating liquid C is curable by energy irradiation such as heating or light irradiation, and forms the antireflection coating layer 5 at the time of curing.

Next, as shown in FIG. 7B, the rotating shaft 52a is rotated, and the coating liquid C is spread toward the outer peripheral side by the centrifugal force generated at that time. Thereby, the coating liquid C is spread over a range covering the first lens surface 2a and the flat portion 2b.
At this time, the layer thickness of the coating liquid C is controlled by appropriately setting the rotation speed and the rotation time of the rotating shaft 52a according to the viscosity of the coating liquid C. The layer thickness of the coating liquid C is set to a layer thickness that provides the layer thickness of the antireflection coating layer 5 at the time of curing.

When the coating liquid C reaches a predetermined layer thickness, the rotation of the rotating shaft 52a is stopped, and energy such as heating or light irradiation is performed to cure the coating liquid C. Thereby, a layered portion by the coating liquid C is formed.
When the antireflection coating layer 5 is a single layer film, the film forming step S2 is completed.
When the antireflection coating layer 5 is a multilayer film, the film forming step S2 similar to the above is repeated so that the necessary multilayer film of the necessary materials can be obtained by changing the type of the coating liquid C. When all the layered parts are formed, the film forming step S2 is completed.

In this way, the lens base material 2 on which the antireflection coating layer 5 has been formed is subjected to the same internal antireflection layer forming step S3 and black coating layer forming step S4 as in the first embodiment, The lens 1 is manufactured.
Lens 1 of the present modification, the anti-reflection coating layer 5 is only in that has been formed by a spin coating method which is a wet process are different, the internal reflection prevention coating P _3, to form the inner surface antireflection layer 3 Therefore, even when the inner surface antireflection layer 3 is laminated on the antireflection coating layer 5, the lens 1 having a reduced reflectance of inner surface reflection can be manufactured.

[Second Embodiment]
The manufacturing method of the optical element of the 2nd Embodiment of this invention is demonstrated.
FIGS. 8A and 8B are schematic detailed views of the B part and the C part in FIG. 1 of the optical element manufactured by the optical element manufacturing method of the second embodiment of the present invention.

First, an example of an optical element manufactured by the optical element manufacturing method of the present embodiment will be described.
A lens 10 (optical element) shown in FIGS. 1A and 1B is an example of an optical element manufactured by the optical element manufacturing method of the present embodiment.
The lens 10 includes a lens substrate 12 (base material) and an inner surface antireflection layer 13 instead of the lens substrate 2, the inner surface antireflection layer 3, and the black coating layer 4 of the lens 1 of the first embodiment. The formation range of the antireflection coating layer 5 is changed.
Hereinafter, a description will be given centering on differences from the first embodiment.

The lens base 12 has a plano-concave lens with the same outer shape as the lens base 2, and includes a lens side 12 d instead of the lens side 2 d of the lens base 2.
However, the material of the lens substrate 12 is not limited to glass, and synthetic resin is also possible.

The lens side surface 12d is different from the lens side surface 2d in that the lens side surface 2d is a roughened cylindrical surface, whereas the lens side surface 12d is a smooth cylindrical surface.
The lens side surface 12d may be, for example, a smooth surface formed by machining or a smooth surface formed by molding using a smooth mold. As the molding, for example, glass molding or resin molding can be performed according to the material of the lens substrate 12.
The surface roughness of the lens side surface 12d is preferably, for example, less than 1 μm at the maximum height.
Below, the lens base material 12 is demonstrated by the example in the case of manufacturing by glass molding as an example. The lens base 12 having the shape shown in FIGS. 1A and 1B can be formed by using a mold and a ring member that regulates the outer periphery. The surface roughness of the first lens surface 2a, the second lens surface, the flat surface 2b that is not an optical surface, and the lens side surface 12d is determined by the surface shape of the mold and the ring. When the surface roughness increases, mold release becomes difficult. Therefore, when forming by molding, the surface roughness is preferably 10 μm or less at the maximum height. Further, when the plane portion 2b and the lens side surface 12d are formed simultaneously, the portion between the plane portion 2b and the lens side surface 12d becomes an R-shaped free surface because the glass does not contact the mold or the ring. In the present embodiment, as an example, the planar portion 2b and the lens side surface 12d are smooth surfaces.
However, after molding, centering may be performed to form a machined lens side surface 2d. In this case, the surface roughness of the flat portion 2b may be different.

In the lens substrate 12, the formation range of the antireflection coating layer 5 is a flat portion 2b and a lens side surface 12d as shown in FIGS. 8 (a) and 8 (b).
However, as in the first embodiment, it is not necessary to form the antireflection coating layer 5 over the entire portion, and there may be a portion where the flat portion 2b and the lens side surface 2d are exposed. The layer thickness of the antireflection coating layer 5 may be different from the layer thickness on the first lens surface 2a and the second lens surface 2c.
For example, when the antireflection coating layer 5 having a required layer thickness is formed within the effective diameter range of the first lens surface 2a and the second lens surface 2c, the first lens surface 2a and the second lens surface are manufactured. The antireflection coating layer 5 may be formed only on a part outside the effective diameter of 2c.

Internal reflection prevention layer 13, the first embodiment of the internal reflection prevention coating P ₃ having the same configuration as the inner surface antireflection layer 3, the planar portion 2b after the antireflection coating layer 5 is formed, the lens It is a layered portion formed by applying and solidifying the side surface 12d.
As the layer thickness of the inner surface antireflection layer 13, the same layer thickness as that of the inner surface antireflection layer 3 can be adopted.

Next, a method for manufacturing the lens 10 will be described.
FIG. 9 is a flowchart showing a process flow of the optical element manufacturing method according to the second embodiment of the present invention. FIGS. 10A and 10B are schematic process explanatory views of a film forming process of the optical element manufacturing method according to the second embodiment of the present invention.

  In the optical element manufacturing method of the present embodiment, as shown in FIG. 9, the lens 1 is manufactured by performing the base material forming step S11, the film forming step S12, and the inner surface antireflection layer forming step S13 in this order.

The base material forming step S11 is a step of forming the lens base material 12.
In this step, the lens base 12 is formed by press-molding a glass material used for the lens base 12 with a mold having a shape corresponding to the lens base 12. When the lens substrate 12 is centered, a shape having a larger outer diameter than the lens substrate 12 is formed, and then the side surface is centered to form the lens side surface 12d.
Thereby, as for the lens base material 12, the plane part 2b and the lens side surface 12d are smooth surfaces.
Above, base material formation process S11 is complete | finished.

Next, a film forming step S12 is performed. This step is a step of forming the antireflection coating layer 5 on the lens substrate 12, and substantially the same as the film formation step S2 of the first embodiment, the formation of the antireflection coating layer 5 by vacuum deposition. Do the membrane.
However, in the present embodiment, as shown in FIG. 10A, the lens substrate 12 is held using a holding jig 53 different from that in the first embodiment.
The holding jig 53 is configured to hold the outer peripheral portion on the side opposite to the film forming surface in the thickness direction of the lens substrate 12.
For example, when the antireflection coating layer 5 is formed on the first lens surface 2a, the effective diameter outside the second lens surface 2c and the lens side surface 12d on the second lens surface 2c side are held.
In the present embodiment, with the lens substrate 12 held in this manner, the film forming material is vaporized from the vapor deposition source 51 by a heating source (not shown) to form film forming material particles composed of molecules or atoms of the film forming material. It is deposited on the surface of the lens substrate 12.
Thereby, the antireflection coating layer 5 is formed on each of the first lens surface 2a, the flat surface portion 2b, the lens side surface 12d, and the R-shaped free surface between the flat surface portion 2b and the lens side surface 12d.
When the antireflection coating layer 5 is formed on the first lens surface 2a, the lens base 12 is reversed, and the second lens surface 2c is directed toward the vapor deposition source 51 to perform film formation. Thereby, the antireflection coating layer 5 is formed on the second lens surface 2c and the lens side surface 12d covered with the holding jig 53 when forming the second lens surface 2c.
When the antireflection coating layer 5 is a single layer film, the film forming step S12 is completed.
When the antireflection coating layer 5 is a multilayer film, the film forming step S12 similar to the above is repeated so that a necessary multilayer film of necessary materials can be obtained by changing the type of the vapor deposition source 51. When all the layered parts have been formed, the film forming step S12 ends.

The method of holding the lens substrate 12 in this step is particularly suitable when the lens 10 has a small diameter or the lens thickness is thin.
When the lens 10 has a small diameter or a thin lens thickness, the holding jig 50 is held by the holding jig 50 so as to cover the lens side surface 12d of the lens base 12 as in the first embodiment. May have to protrude beyond the film formation surface. However, since the holding jig 50 protruding from the film forming surface becomes a wall surrounding the film forming surface, movement of film forming material particles adhering to the film forming surface from an oblique direction is blocked, and film forming unevenness occurs. It becomes easy to do.
Such film formation unevenness is eliminated by the holding method of the holding jig 53. Instead, the antireflection coating layer 5 is formed on the lens side surface 12d.

Next, an inner surface antireflection layer forming step S13 is performed. This step, as shown in FIG. 10 (b), including the deposition site outside the range of the effective diameter d ₁ of the first lens surface 2a of the formed anti-reflective coating layer 5 by a film forming step S12, flat portion 2b, an area on the lens side 12d, a step of forming an inner anti-reflection layer 13 by applying the first embodiment and the same internal reflection preventive paint P _3.

That is, in this step, on the planar portion 2b and the lens side surface 12d of the lens substrate 12 on which the antireflection coating layer 5 is formed, in the same manner as the inner surface antireflection layer forming step S13 of the first embodiment, the internal reflection prevention coating P ₃ is applied, is further subjected to heat such solidify the internal reflection prevention coating P _3. Thereby, the inner surface antireflection layer 13 is formed.
Thus, the inner surface antireflection layer forming step S13 is completed.
Thereby, the lens 10 is manufactured.

In such a lens 10, the internal reflection is suppressed by laminating the internal reflection preventing layer 13 on the flat portion 2 b on which the reflection preventing coating layer 5 is formed and the lens side surface 12 d.
For this reason, even when the antireflection coating layer 5 is also formed on the lens side surface 12d, the internal reflection can be suppressed satisfactorily.
In the method of manufacturing the optical element of the present embodiment, as in the first embodiment, the internal reflection prevention coating P _3, to form the internal reflection prevention layer 13, the internal reflection prevention layer 13 antireflection coating layer The lens 10 having a reduced reflectivity of the internal reflection can be manufactured even if it is laminated on the substrate 5.

  In the above description of each embodiment and modification, the optical element has been described as an example of a plano-concave lens, but the optical element is not limited to this. For example, a lens such as a meniscus lens, a biconvex lens, a biconcave lens, and a planoconvex lens may be used, and an optical element other than the lens, for example, an optical element such as a prism, a mirror, a filter, and a parallel plate may be used.

  Moreover, all the components described in the above embodiments and modifications can be implemented by being appropriately combined or deleted within the scope of the technical idea of the present invention.

[Internal reflection prevention paint]
Next, Examples 1 to 6 and Comparative Examples 1 and 2 of the inner surface antireflection coating P ₃ common to the first and second embodiments will be described.
Table 1 below collectively shows the coating composition and the curing temperature of Examples 1 to 6 and Comparative Examples 1 and 2.

[Example 1]
In Example 1, a 20 wt% xylene solution of Lumiflon (registered trademark) (manufactured by Asahi Glass Co., Ltd.), which is a fluoroolefin-vinyl ether copolymer, and VALIFAST (registered trademark) BLACK 3830 (trade name; Orient Chemical Industry Co., Ltd.) As shown in Table 1, it is a paint prepared by mixing and mixing well so that the content is 15 wt% and 85 wt%.
Example 1 is an example of an inner surface antireflection coating P ₃ for forming the inner surface antireflection layer 3 having the configuration [a] described in the first embodiment, and Lumiflon (registered trademark) is a base portion. 3B is a fluororesin, and VALIFAST (registered trademark) BLACK 3830 is a black azo dye that becomes the color material 3A.

[Example 2]
In Example 2, sulria (registered trademark) containing hollow silica in a 10% isopropyl alcohol solution of light acrylate DCP-A (trade name; Kyoeisha Chemical Co., Ltd.), which is an acrylic resin, dimethylol-tricyclodecanediacrylate, is used. ) 1110 (trade name; manufactured by JGC Catalysts & Chemicals Co., Ltd.), carbon black, and 1 wt% of α, α'-azobisisobutyronitrile with respect to the acrylic resin, and using a bead mill, Table 1 As shown in FIG. 2, the coating materials were prepared by mixing so that the contents of acrylic resin, hollow silica, and carbon black were 65 wt%, 20 wt%, and 15 wt%, respectively.
Thruria (registered trademark) 1110 is a isopropyl alcohol solution having a solid particle concentration of 20 wt% mixed with hollow silica having an average particle diameter of 50 nm.
Example 2 is an example of the inner surface antireflection coating P ₃ for forming the inner surface antireflection layer 3 having the configuration [b] described in the first embodiment, and the base portion 3B is formed. The hollow silica which is the low refractive index nanoparticles 3Bb and the acrylic resin which is the resin layer 3Ba, and the carbon black is the color material 3A.

[Examples 3 and 4]
In Examples 3 and 4, the hollow silica content of Example 2 was changed to 45 wt% and 70 wt%, respectively, as shown in Table 1.

[Examples 5 and 6]
In Examples 5 and 6, as shown in Table 1, the fluororesin content in Example 1 was changed to 50 wt% and 10 wt%, respectively, and the azo dye content in Example 1 was changed to 50 wt% and 90 wt%, respectively. It is a thing.

[Comparative Examples 1 and 2]
As shown in Table 1, Comparative Example 1 is a coating material prepared by mixing carbon black and the acrylic resin of Example 2 so that the contents are 15 wt% and 85 wt%, respectively.
For this reason, it replaces with the hollow silica of Example 2, and the comparative example 1 becomes a structure which mixed the acrylic resin of the same mass.
Comparative Example 2 is a paint prepared by thoroughly stirring the main agent, curing agent, and thinner of lens inner surface prevention paint GT-7 (trade name; Canon Chemical Co., Ltd.) at a ratio of 8: 1: 7. GT-7 contains no fluororesin or hollow silica for obtaining a low refractive index.

[Evaluation of reflectance of internal antireflection layer]
The reflectance when the coating materials of Examples 1 to 6 and Comparative Examples 1 and 2 were applied on the antireflection coating layer was evaluated as follows.
A glass plate having a diameter of 30 mm and a thickness of 5 mm was prepared using S-LAH58 (trade name; manufactured by OHARA INC., Refractive index: 1.883), which is a glass glass material. The plate surfaces in the thickness direction of the glass flat plate are all finished with a smooth surface.
A single layer film made of magnesium fluoride and having a thickness of 100 nm was formed as an antireflection coating layer 5 on one surface of the flat glass plate by an evaporation method.
Each coating material of Examples 1 to 6 and Comparative Examples 1 and 2 was applied on this antireflection coating layer 5 so as to have a layer thickness of 10 μm at the time of curing. Samples 1-1 and 2-8 were produced by heating for a period of time and curing.
Instead of the magnesium fluoride monolayer film of Sample 1-1, the layer structure of MgF ₂ (90 nm) / ZrO ₂ (122 nm) / Al ₂ O ₃ (155 nm) by vapor deposition (the values in parentheses indicate the layer thickness) A multilayer antireflection coating layer 5 having the above structure is formed, and the coating material of Example 1 is applied onto the antireflection coating layer 5 and heated at 150 ° C. for 1 hour to be cured. Was made.

Evaluation of these samples was performed using an optical measuring device USPM-RU (trade name; manufactured by Olympus Corporation) with a wavelength light in the range of 380 nm to 780 nm, and a glass plate (antireflection coating surface) and internal reflection by vertical incidence. The reflectance at the interface with the prevention paint was measured, and the average value of the reflectance in the range of 380 nm to 780 nm was evaluated.
The production conditions of these samples and the evaluation results are summarized in Table 2 below.

  The evaluation of the reflectance is evaluated as good because the effect of suppressing internal reflection is large when the average value of the reflectance in the range of 380 nm to 780 nm is 3.5% or less, and in Table 2, “○ (good) In the case where the average value of the reflectance exceeds 3.5%, the effect of suppressing the internal reflection is small, so it was evaluated as defective and indicated by “× (no good)”.

According to the evaluation results in Table 2, samples 1-1, 1-2, and 2-6 using the paints of Examples 1 to 6 have an average reflectance of 2.5% and 3.0%, respectively. %, 3.1%, 2.6%, 2.2%, 2.6%, and 2.8%, all of which were judged good.
On the other hand, in Comparative Examples 1 and 2, the average values of the reflectance were 3.6% and 5.0%, respectively, and both were determined to be defective.
Therefore, the paint P ₃ for preventing internal reflection, the configuration [a], even those which form either internal reflection preventing layer 3 of the [b], it can be seen that can be favorably suppressed internal reflection.

Moreover, when the results of Samples 1-1, 5, and 6 are compared, the reflectance increases in this order. This is because in Samples 1-1, 5 and 6, the content of the fluororesin decreases in this order and the content of the azo dye increases, so that the refractive index as the inner antireflection layer 3 increases in this order. It is thought that this is because.
Further, when the results of samples 2, 3, and 4 are compared, the reflectance of these samples decreases in this order. This is because, in Samples 2, 3, and 4, the content of hollow silica increases in this order and the content of acrylic resin decreases, so that the refractive index as the inner surface antireflection layer 3 increases in this order. It is thought that this is because.

On the other hand, since the acrylic resin containing no hollow silica forms the base portion, the internal reflection is larger in the case of Comparative Example 1 having a higher refractive index than that of magnesium fluoride.
Further, in Comparative Example 2 using the GT-7 there is actually used as a black paint coating such as a lens side surface, since no a configuration as the inner surface antireflection coatings P _3, most reflected in the evaluation sample The rate is high.

[Ghost evaluation of optical elements]
The ghost evaluation of the optical element is based on the manufacturing method of the optical element of the first and second embodiments, and the inner surface antireflection layers corresponding to the inner surface antireflection layers 3 and 13 are compared with Examples 1 to 6 and Comparative Example. Evaluation lenses of plano-concave lenses formed by the paints 1 and 2 were manufactured, and the presence or absence of ghosts in these evaluation lenses was evaluated by image evaluation.
Each evaluation lens has a common outer shape, the outer diameter is 3 mm, the lens thickness on the lens side surface is 1 mm, the outer diameter of the first lens surface 2a (the inner diameter of the flat surface portion 2b) is 2 mm, and the first lens surface 2a. The curvature radius is 1.5 mm.
However, in the evaluation lens corresponding to the lens 1, the lens side surface 2d was manufactured as a smooth surface.
The material of each evaluation lens is made of the same glass material as the reflectance evaluation sample.
The conditions of these evaluation lenses and the ghost evaluation results are shown in Table 3 below.

In the evaluation lenses 1-1, 2-8, the antireflection coating layer 5 is formed of a single layer film of magnesium fluoride similar to the sample 1-1, and like the lens 1 of the first embodiment, Examples 1 to 6 and Comparative Examples 1 and 2 were applied only to the flat surface 2b to form an inner surface antireflection layer.
The evaluation lens 1-2 is different from the evaluation lens 1-1 in that the antireflection coating layer 5 is formed of the same multilayer film as the sample 1-2.
The evaluation lens 1-3 was evaluated by applying the paint of Example 1 to the flat surface portion 2b and the lens side surface 2d as in the lens 2 of the second embodiment to form an inner surface antireflection layer. Different from the lens 1-1.
The coating thickness and heating conditions of the paint for each evaluation lens are the same as the preparation conditions of the reflectance evaluation sample.

When the presence or absence of ghost of these evaluation lenses was evaluated, as shown in Table 3 above, ghosts were generated only in the evaluation lenses 7 and 8 using Comparative Examples 1 and 2, and each of Examples 1 to 6 was used. In the evaluation lens, no ghost occurred.
This is thought to be because the internal reflection was suppressed by forming the internal antireflection layer using the paints of Examples 1 to 6.

1, 10 Lens (optical element)
2,12 Lens substrate (base material)
2a First lens surface (optical surface)
2b Plane portion 2c Second lens surface (optical surface)
2d, 12d Lens side surface 3, 13 Inner surface antireflection layer 3A Color material 3B Base part 3Ba Resin layer 3Bb Low refractive index nanoparticle 4 Black coating layer 5 Antireflection coating layer P ₃ Inner surface antireflection coating S1, S11 Base material forming step S2, S12 Film formation step S3, S13 Inner surface antireflection layer formation step S4 Black coating layer formation step

Claims (3)

A substrate having an optical surface;
A single layer film or a multilayer film in which a plurality of layers having different refractive indexes are laminated, and is laminated on the inner side and the outer side of the effective diameter of the optical surface on the base material, and is the outermost layer opposite to the base material An antireflective coating layer having a refractive index lower than the refractive index of the substrate;
Low refraction made of fluororesin, magnesium fluoride, or hollow silica, which is laminated and disposed in a region on the surface of the base material, including a film forming portion outside the effective diameter range of the optical surface in the antireflection coating layer An inner surface antireflection layer containing a refractive index nanoparticle and a coloring material, and having a refractive index lower than the refractive index of the outermost layer of the antireflection coating layer;
An optical element. The substrate has a maximum surface roughness of less than 1 μm in the range covered by the inner surface antireflection layer.
The optical element according to claim 1. In a substrate having an optical surface, a single-layer film or a multilayer film in which a plurality of layers having different refractive indexes are laminated in regions inside and outside the effective diameter of the optical surface, the outermost layer on the side opposite to the substrate A film forming step of forming an antireflection coating layer having a refractive index lower than the refractive index of the substrate ;
In the region on the surface of the base material, including a film formation site outside the effective diameter range of the optical surface in the antireflection coating layer formed by the film formation step, fluororesin, magnesium fluoride or An inner surface antireflection coating comprising a low refractive index nanoparticle made of hollow silica and a colorant is applied to form an inner surface antireflection layer having a refractive index lower than that of the outermost layer of the antireflection coating layer. A method of manufacturing an optical element comprising: an inner surface antireflection layer forming step.

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