JP2018017930A - Optical element and optical system and imaging apparatus having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a reflectance in an optical element in which a region having a higher refractive index is disposed on the outermost surface side than a region containing voids and having a lowest refractive index.SOLUTION: An optical element 10 includes a substrate 1 and an antireflection film 6 disposed on the substrate 1. The antireflection film 6 has a first region 2 including voids and having a uniform refractive index in the thickness direction, and a second region 3 disposed on the opposite side to the substrate 1 with respect to the first region. The refractive index of the second region 3 increases with the distance from the substrate 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical element used in an optical system such as an imaging apparatus.

  By reducing the reflectance of an optical element such as a lens used in the optical system, it is possible to reduce the occurrence of ghosts and flares and improve the transmittance.

  In order to sufficiently reduce the reflectance of the optical element, it is effective to use a material having a low refractive index for the air-side layer in the antireflection film provided on the optical element. As a material having a low refractive index, a porous material containing voids inside is known. However, when the porous material is used for the most air layer of the antireflection film, the antireflection performance is likely to change due to contamination. . This is because the refractive index of the porous material changes as a result of oil or the like adhering to the porous material and penetrating into the voids.

  In order to reduce the contamination of the layer formed of the porous material from the outside, it is effective to provide a layer for protecting the porous material on the layer formed of the porous material. Patent Document 1 discloses an antireflection film having a structure in which a fluororesin layer (refractive index: 1.40) having water repellency and oil repellency is provided on a layer (refractive index: 1.27) formed of a porous material. Have been described.

JP 2009-168986 A

  However, since the antireflection film of Patent Document 1 has a fluororesin layer having a higher refractive index than that of the porous material on the surface side of the layer made of the porous material, the reflectance cannot be sufficiently reduced. There is a fear.

  An object of the present invention is to reduce the reflectance in an optical element that includes a void and has a region having a higher refractive index than the region having the lowest refractive index on the surface side.

  The optical element of the present invention is an optical element comprising a substrate and an antireflection film provided on the substrate, and the antireflection film includes a gap and has a uniform refractive index in the thickness direction. A first region and a second region provided on a side opposite to the substrate with respect to the first region, and the refractive index of the second region increases as the distance from the substrate increases. It is characterized by that.

  According to the present invention, it is possible to reduce the reflectance in an optical element that includes a void and has a region having a higher refractive index than a region having the lowest refractive index on the surface side.

It is the schematic of an optical element. FIG. 4 is a diagram showing the reflectance characteristics of the optical element of Example 1. FIG. 6 is a diagram showing the reflectance characteristics of the optical element of Example 2. FIG. 6 is a diagram showing the reflectance characteristics of the optical element of Example 3. FIG. 6 is a diagram showing the reflectance characteristics of the optical element of Example 4. FIG. 10 is a diagram showing the reflectance characteristics of the optical element of Example 5. It is a figure which shows the reflectance characteristic of the optical element of Example 6. It is a figure which shows the reflectance characteristic of the optical element of Example 7. It is a figure which shows the reflectance characteristic of the optical element of Example 8. FIG. 10 is a diagram showing the reflectance characteristics of the optical element of Example 9. It is a figure which shows the reflectance characteristic of the optical element of Example 10. FIG. 10 is a diagram showing the reflectance characteristics of the optical element according to Example 11. It is a figure which shows the reflectance characteristic of the optical element of Example 12. It is sectional drawing which shows the structure of an optical system. It is the schematic of an imaging device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, it is assumed that the refractive index is a value for light of 550 nm.

  FIG. 1 is a schematic view showing an optical element 10 of the present embodiment. The optical element 10 includes a substrate 1 and an antireflection film 6. As the substrate 1, glass, plastic or the like can be used. The shape of the substrate 1 is not limited to a flat plate shape, and may be a shape having a curvature such as a lens or a film shape.

  The antireflection film 6 has a first region 2 and a second region 3. The 1st field 2 is constituted including the space inside. By including voids inside, the effective refractive index of the first region 2 can be lowered. The effective refractive index of the first region 2 is uniform in the thickness direction. Here, even if the effective refractive index in the first region 2 changes in the thickness direction, the effective refractive index change amount changes the effective refractive index in the first region 2 in the thickness direction. If the size is within 5% of the average value, the effective refractive index can be considered uniform in the thickness direction.

  Moreover, the 2nd area | region 3 is provided in the opposite side to the board | substrate 1 with respect to the 1st area | region 2, and reduces that the 1st area | region 2 is contaminated from the outside. In addition, the refractive index of the second region 3 is not uniform in the thickness direction, and changes so that the refractive index increases as the distance from the substrate 1 increases. A third region 5 having a uniform refractive index in the thickness direction may be provided on the opposite side of the second region 3 from the first region 2. In the antireflection film 6, a plurality of layers may be provided between the first region 2 and the substrate 1. Hereinafter, a region constituted by a plurality of layers provided between the first region 2 and the substrate 1 is referred to as a fourth region 4.

  In general, in order to reduce the reflectance of an optical element with a multilayer antireflection film, it is preferable to use a material having a low refractive index, such as a porous material, as the most air-side layer of the antireflection film. This is because the reflectance can be further reduced by reducing the refractive index difference at the interface between the antireflection film and the air.

  On the other hand, in order to reduce the contamination of the antireflection film from the outside, it is necessary to provide a protective layer including a highly antifouling material on the most air side. However, in general, the refractive index of a material having high antifouling property is relatively high. For this reason, when a layer having a high refractive index such as a protective layer is provided on the most air side, the reflectance can be increased by reflection at the interface between the protective layer and air and at the interface between the protective layer and the lower layer.

  On the other hand, in the antireflection film 6 of the optical element 10 of the present embodiment, the second region whose refractive index increases as it is away from the substrate 1 on the side opposite to the substrate 1 with respect to the first region 2. A region 3 is provided to protect the first region 2. By providing the second region 3 as described above, the change in the refractive index between the first region 2 and the second region 3 can be moderated. Therefore, it is possible to reduce the amount of increase in reflectivity by providing a region having a higher refractive index than that of the first region 2 on the surface side of the first region 2.

  The refractive index at the position closest to the substrate 1 in the second region 3 is preferably equal to the effective refractive index of the first region 2. Accordingly, the refractive index can be continuously changed at the boundary between the first region 2 and the second region 3, and the reflectance can be further reduced.

Further, when the refractive index of the first region 2 is n ₁ , and the refractive index at the position farthest from the substrate 1 in the second region 3 is n ₂ , n ₂ is set larger than n ₁ and the following conditions are satisfied. It is preferable to satisfy the formulas (1) and (2).
1.1 ≦ n ₁ ≦ 1.3 (1)
1.25 ≦ n ₂ ≦ 1.4 (2)

The n ₁ and n ₂ is in the range satisfying the formula (1) and (2), it is possible to further reduce the reflectance.

In order to further reduce the reflectivity, when the thickness of the first region 2 is d ₁ [nm] and the thickness of the second region 3 is d ₂ [nm], the following conditional expression (3) And (4) should be satisfied.
50 ≦ d ₁ ≦ 130 (3)
5 ≦ d ₂ ≦ 50 (4)

  Note that the second region 3 may include a gap as in the first region 2. As a result, the refractive index of the second region 3 can be reduced, and the change in the refractive index can be reduced at the boundary between the first region 2 and the second region 3. As a result, the reflectance can be further reduced.

  Furthermore, it is preferable that the 2nd area | region 3 contains the material with high antifouling property. As such a material, an organic fluorine compound having high water repellency is preferably used. The bond between carbon and fluorine in the organic fluorine compound has a very high binding energy, and has an excellent water repellency because the surface tension is very small. In particular, among organic fluorine compounds, a fluororesin has high oil repellency in addition to water repellency and excellent antifouling properties. Since the second region 3 includes a material having water repellency and oil repellency, the antifouling property of the optical element 10 can be improved.

  In order to improve the antifouling property of the optical element 10, it is preferable to provide the third region 5. This is because by providing a uniform region in the thickness direction as in the third region 5 to protect the first region 2, it is possible to reduce the deterioration of the antifouling property due to wear. In the case where the third region 5 is provided, it is preferable that the third region 5 includes a material having water repellency and oil repellency. In this case, even if the second region 3 does not necessarily contain a material having water repellency and oil repellency, the antifouling property of the optical element 10 can be improved.

  Further, when the third region 5 is provided, the refractive index of the third region is preferably equal to the refractive index at the position farthest from the substrate 1 in the second region 3. Thereby, the refractive index can be continuously changed at the boundary between the second region 3 and the third region 5, and the reflectance can be further reduced.

Furthermore, when the thickness of the third region 5 is d ₃ [nm], it is preferable that the following conditional expression is satisfied.
0 <d ₃ ≦ 10 (5)

  By satisfying Expression (5), the reflectance of the optical element 10 can be reduced even when the third region 4 is provided.

  Moreover, the 1st area | region 2 should just be formed including the space | gap. For example, the first region 2 including voids can be formed by aggregating a plurality of fine particles. The fine particles include fine particles of inorganic oxides such as silicon oxide and magnesium fluoride. In order to improve the friction resistance and adhesion, it is preferable to form the fine particles by binding them with a binder. The shape of the fine particles is preferably a chain shape. The chain-shaped fine particles are fine particles formed by connecting a plurality of particles in a chain shape. Thereby, the physical strength of the first region 2 can be improved while providing a gap in the first region 2.

  By increasing the number of layers constituting the fourth region 4, the reflectance can be reduced in a wider wavelength range. For this reason, it is preferable that the 4th area | region 4 is comprised by 2 or more layers, and it is more preferable that it is comprised by 6 or more layers. At this time, the fourth region 4 includes a high refractive index layer having a refractive index higher than that of the first region 2 and a low refractive index layer having a refractive index larger than that of the first region 2 and smaller than that of the high refractive index layer. It is preferable to provide. In addition, when more layers than two layers are stacked in the fourth region, it is preferable to configure the fourth region 4 by alternately stacking low refractive index layers and high refractive index layers. Thereby, the reflectance can be reduced in a wider wavelength range.

  Each layer constituting the fourth region 4 is made of inorganic oxide such as silicon oxide, titanium oxide, tantalum oxide, zirconium oxide, chromium oxide, niobium oxide, cerium oxide, hafnium oxide, yttrium oxide, magnesium fluoride, or the like. What is necessary is just to comprise.

  Next, a method for manufacturing the optical element 10 of the present embodiment will be described.

  First, the fourth region 4 is laminated on the substrate 1 by vapor deposition, sputtering, or the like. Next, a layer including voids is formed using a sol-gel method. Specifically, a liquid in which fine particles are dispersed is applied to the fourth region 4 formed on the substrate 1 using a spin coater or the like. Thereafter, a layer including voids can be formed on the fourth region 4 by drying and baking.

  Next, the first region 2 and the second region 3 are formed. When a solution containing an organic fluorine compound or the like is applied to a layer containing voids, the solution penetrates through the voids to a certain depth. At this time, the deeper the penetration depth, the smaller the amount of penetration of the solution. Thus, the 1st area | region 2 and the 2nd area | region 3 can be formed by performing the drying and baking after infiltrating the solution containing an organic fluorine compound etc. in the layer containing a space | gap.

  That is, the portion of the layer containing voids where the solution did not penetrate corresponds to the first region 2 having a uniform refractive index in the thickness direction because the porosity is uniform in the thickness direction. On the other hand, the portion where the solution has permeated corresponds to the second region 3 in which the refractive index increases as the distance from the substrate 1 increases because the refractive index increases according to the amount of the permeated solution.

  At this time, if the amount of the applied solution is larger than the amount of the solution that penetrates, the third region 5 is formed on the second region 3. Thus, the optical element 10 of this embodiment can be obtained easily by forming the 1st area | region 2 and the 2nd area | region 3 using a sol-gel method.

  In the manufacturing method described above, the size of the voids of the layer including the voids formed on the fourth region 4 is adjusted, and the concentration and viscosity of the solution applied to the layer including the voids are adjusted. By doing so, the depth of penetration of the solution into the layer including the voids can be adjusted. As a result, the thicknesses of the first region 2 and the second region 3 can be adjusted.

Next, specific examples relating to the optical element of the present invention will be described. The first region 2 in Examples 1 to 12 described below, the second region 3, the third region 5, like chains obtained by the following procedure SiO ₂ particles coating solution 13, 14, 15 And a perfluoropolyether solvent.

(1) Preparation of chain SiO ₂ particle dispersion 11 2-propanol (IPA) dispersion of chain SiO ₂ particles (IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., average particle size 12 nm, solid content concentration 15 mass) %) Was replaced with 1-propoxy-2-propanol (manufactured by Sigma) from IPA using an evaporator. Thus 1-propoxy-2-propanol dispersion of obtained was chain SiO ₂ particles (solid concentration 17 wt%) and chain SiO ₂ particle dispersion 11 (solid concentration 17 wt%). The solvent ratio of the chain SiO ₂ particle dispersion 11 was IPA: 1-propoxy-2-propanol = 7.5: 92.5.

(2) Preparation of Binder Solution 12 Tetraethoxysilane (TEOS, manufactured by Tokyo Chemical Industry Co., Ltd.) 18.5 g and 10 equivalent of 0.1 wt% phosphinic acid 16.0 g of TEOS as catalyst water at 20 ° C. The mixture was stirred for 60 minutes in a water bath. The solution thus obtained is used as a binder solution 12.

(3) Adjustment of chain-like SiO ₂ particle coating solutions 13, 14, and 15 The chain-like SiO ₂ particle dispersion 11 prepared in (1) was adjusted to 251.3 g (solid content concentration 17 wt%) in (2). 33.4 g of binder solution 12 was added. Thereafter, 174.5 g of 1-propoxy-2-propanol and 546.5 g of ethyl lactate were added and stirred for 60 minutes. This is designated as chain-like SiO ₂ particle coating solution 13.

27.3 g of the binder solution 12 prepared in (2) was added to 251.3 g of the chain SiO ₂ particle dispersion 11 (solid content concentration 17 wt%) prepared in (1). Thereafter, 174.5 g of 1-propoxy-2-propanol and 550.7 g of ethyl lactate were added and stirred for 60 minutes. This is designated as chain-like SiO ₂ particle coating solution 14.

22.2 g of the binder solution 12 prepared in (2) was added to 251.3 g of the chain SiO ₂ particle dispersion 11 (solid content concentration 17 wt%) prepared in (1). Thereafter, 174.5 g of 1-propoxy-2-propanol and 555.4 g of ethyl lactate were added and stirred for 60 minutes. This is designated as chain-like SiO ₂ particle coating solution 15.

The chain SiO ₂ particle coating liquids 13, 14, and 15 have different binder amounts. Therefore, the effective refractive index when a layer including voids is formed using these coating liquids varies depending on the amount of binder.

[Example 1]
Table 1 shows the configuration of the optical element 10 in Example 1. The substrate 1 is S-BSL7 manufactured by OHARA. The fourth region 4 is composed of a total of eight layers.

  In the optical element 10 of the present embodiment, both the third region 5 and the second region 3 contain perfluoropolyether which is a fluororesin. This can reduce the contamination of the first region 2 from the outside.

  FIG. 2 shows the spectral reflectance in the optical element 10 of the present embodiment. As shown in FIG. 2, the reflectance (solid line) when light is incident on the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. Further, the reflectance (dotted line) when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm. The reflectance can be reduced by providing the first region 2 and the second region 3 as in the optical element 10 of the present embodiment.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided by the vacuum evaporation method in the board | substrate 1 (The product made by OHARA, S-BSL7) 30 mm in diameter and 1 mm in thickness. Next, 0.2 ml of the chain SiO ₂ particle coating solution 13 was dropped, and spin coating was performed at 3400 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 2]
Table 2 shows the configuration of the optical element 10 in Example 2. As in the first embodiment, the substrate 1 uses S-BSL7 manufactured by OHARA. In this embodiment, the number of layers stacked on the substrate 1, the optical constant, and the thickness are different. In the present embodiment, the fourth region 4 is composed of a total of seven layers.

  In the optical element 10 of the present embodiment, the third region 5 and the second region 3 both contain perfluoropolyether, which is a fluororesin, as in the first embodiment. This can reduce the contamination of the first region 2 from the outside.

  FIG. 3 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 3, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (made by OHARA, S-BSL7) 30 mm in diameter and 1 mm in thickness by the sputtering method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 14 was dropped, and spin coating was performed at 3730 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 3]
Table 3 shows the configuration of the optical element 10 in Example 3. In this example, unlike Example 1 and Example 2, L-BAL43 manufactured by OHARA was used for the substrate 1.

  In the present embodiment, the fourth region 4 is composed of a total of seven layers. The third region 5 and the second region 3 both contain perfluoropolyether, which is a fluororesin, as in the first and second examples. This can reduce the contamination of the first region 2 from the outside.

  FIG. 4 shows the spectral reflectance in the optical element 10 of the present embodiment. As shown in FIG. 4, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (The product made by OHARA, L-BAL43) 30 mm in diameter and 1 mm in thickness by the sputtering method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 15 was dropped, and spin coating was performed at 3870 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 4]
Table 4 shows the configuration of the optical element 10 in Example 4. In this example, as in Example 3, L-BAL43 manufactured by OHARA was used for the substrate 1. The number of layers laminated on the substrate 1, the optical constants, and the thickness are different from those in Example 3.

  In the present embodiment, the fourth region 4 is composed of a total of eight layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain perfluoropolyether which is a fluororesin similarly to Examples 1-3. This can reduce the contamination of the first region 2 from the outside.

  FIG. 5 shows the spectral reflectance in the optical element 10 of the present embodiment. As shown in FIG. 5, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (OHARA company make, L-BAL43) 30 mm in diameter and thickness 1mm with the vacuum evaporation method. Next, 0.2 ml of chain-like SiO ₂ particle coating solution 13 was dropped, and spin coating was performed at 3580 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 5]
Table 5 shows the configuration of the optical element 10 in Example 5. In this embodiment, unlike the first to fourth embodiments, S-LAL14 manufactured by OHARA is used for the substrate 1. In the present embodiment, the fourth region 4 is composed of a total of eight layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain the perfluoropolyether which is a fluororesin similarly to Examples 1-4. This can reduce the contamination of the first region 2 from the outside.

  FIG. 6 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 6, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided by the vacuum evaporation method to the board | substrate 1 (The product made by OHARA, S-LAL14) of diameter 30mm and thickness 1mm. Next, 0.2 ml of the chain SiO ₂ particle coating solution 15 was dropped, and spin coating was performed at 3620 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 6]
Table 6 shows the configuration of the optical element 10 in Example 6. In the present embodiment, as in the fifth embodiment, S-LAL14 manufactured by OHARA is used for the substrate 1. The number of layers stacked on the substrate 1, the optical constant, and the thickness are different from those in Example 5.

  In the present embodiment, the fourth region 4 is composed of a total of seven layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain the perfluoropolyether which is a fluororesin similarly to Examples 1-5. This can reduce the contamination of the first region 2 from the outside.

  FIG. 7 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 7, the reflectance when light is incident on the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (The product made by OHARA, S-LAL14) 30 mm in diameter and 1 mm in thickness by the sputtering method. Next, 0.2 ml of chain-like SiO ₂ particle coating solution 13 was dropped, and spin coating was performed at 3720 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 7]
Table 7 shows the configuration of the optical element 10 in Example 7. In this embodiment, unlike Embodiments 1 to 6, S-LAH64 manufactured by OHARA is used for the substrate 1. In the present embodiment, the fourth region 4 is composed of a total of eight layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain perfluoropolyether which is a fluororesin similarly to Examples 1-6. This can reduce the contamination of the first region 2 from the outside.

  FIG. 8 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 8, the reflectance when light is incident on the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (The product made by OHARA, S-LAH64) 30 mm in diameter and 1 mm in thickness by the vacuum evaporation method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 13 was dropped, and spin coating was performed at 3570 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 8]
Table 8 shows the configuration of the optical element 10 in Example 8. In this embodiment, unlike Embodiments 1 to 7, S-BAH28 manufactured by OHARA is used for the substrate 1. In the present embodiment, the fourth region 4 is composed of a total of seven layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain perfluoropolyether which is a fluororesin similarly to Examples 1 thru | or 7. This can reduce the contamination of the first region 2 from the outside.

  FIG. 9 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 9, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (made by OHARA, S-BAH28) 30 mm in diameter and 1 mm in thickness by the sputtering method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 15 was dropped, and spin coating was performed at 3630 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 9]
Table 9 shows the configuration of the optical element 10 in Example 9. In this embodiment, unlike the first to eighth embodiments, S-LAH58 manufactured by OHARA is used for the substrate 1. In the present embodiment, the fourth region 4 is composed of a total of eight layers. The third region 5 and the second region 3 both contain perfluoropolyether, which is a fluororesin, as in Examples 1 to 8. This can reduce the contamination of the first region 2 from the outside.

  FIG. 10 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 10, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (made by OHARA, S-LAH58) of diameter 30mm and thickness 1mm by the vacuum evaporation method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 14 was dropped, and spin coating was performed at 3700 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 10]
Table 10 shows the configuration of the optical element 10 in Example 10. In this example, as in Example 9, S-LAH58 manufactured by OHARA was used for the substrate 1. The number of layers stacked on the substrate 1, the optical constant, and the thickness are different from those in Example 9.

  In the present embodiment, the fourth region 4 is composed of a total of seven layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain the perfluoro polyether which is a fluororesin similarly to Examples 1-9. This can reduce the contamination of the first region 2 from the outside.

  FIG. 11 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 11, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (OHARA company make, S-LAH58) 30 mm in diameter and 1 mm in thickness by the sputtering method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 13 was dropped, and spin coating was performed at 3780 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 11]
Table 11 shows the configuration of the optical element 10 in Example 11. In this embodiment, unlike Embodiments 1 to 10, S-LAH79 manufactured by OHARA is used for the substrate 1. In the present embodiment, the fourth region 4 is composed of a total of eight layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain perfluoropolyether which is a fluororesin similarly to Examples 1 thru | or 10. This can reduce the contamination of the first region 2 from the outside.

  FIG. 12 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 12, the reflectance when light is incident on the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (The product made by OHARA, S-LAH79) 30 mm in diameter and 1 mm in thickness by the vacuum evaporation method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 14 was dropped, and spin coating was performed at 3700 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

[Example 12]
Table 12 shows the configuration of the optical element 10 in Example 12. In this example, as in Example 11, S-LAH79 manufactured by OHARA was used for the substrate 1. The number of layers stacked on the substrate 1, the optical constant, and the thickness are different from those in Example 11.

  In the present embodiment, the fourth region 4 is composed of a total of seven layers. Moreover, the 3rd area | region 5 and the 2nd area | region 3 contain the perfluoropolyether which is a fluororesin similarly to Examples 1-11. This can reduce the contamination of the first region 2 from the outside.

  FIG. 13 shows the spectral reflectance in the optical element 10 of this example. As shown in FIG. 13, the reflectance when light enters the optical element 10 perpendicularly is 0.1% or less in the wavelength range of 400 nm to 700 nm. The reflectance when light is incident on the optical element 10 at an angle of 45 degrees is 1% or less in the wavelength range of 400 nm to 700 nm.

  In addition, the optical element 10 of a present Example can be formed in the following procedures.

First, the 4th area | region 4 was provided in the board | substrate 1 (The product made by OHARA, S-LAH79) 30 mm in diameter and 1 mm in thickness by the sputtering method. Next, 0.2 ml of the chain SiO ₂ particle coating solution 15 was dropped, and spin coating was performed at 3700 rpm for 20 seconds.

  Furthermore, 0.2 ml of Durasurf DS-1101S135 (solid content concentration 0.10% by mass) manufactured by Harves Co., Ltd. was dropped as a perfluoropolyether solution, and spin coating was performed at 3000 rpm for 20 seconds. Then, it heated for 30 minutes at 140 degreeC in the hot air circulation oven.

By applying each solution under such conditions, the perfluoropolyether solution can be permeated into a part of the void inside the chain SiO ₂ . Thereby, the optical element 10 which has the 1st area | region 2 where a refractive index is uniform, and the 2nd area | region 3 which becomes large as a refractive index leaves | separates from the board | substrate 1 can be created.

  As described in Examples 1 to 12, even if the refractive index of the substrate 1 is variously changed, the reflectance is reduced by providing the antireflection film 6 having the first region 2 and the second region 3. I understand that I can do it.

[Modification]
In addition, the manufacturing method of the optical element 10 mentioned above is an example to the last. As long as the first region 2 including a void and having a uniform refractive index in the thickness direction and the second region 3 having a refractive index that increases with distance from the substrate 1 can be obtained, other methods may be used. An optical element may be manufactured.

  For example, the second region 3 may be formed using sputtering or vapor deposition. First, a layer including voids is formed on the fourth region 4. Thereafter, a film is formed on the layer including the voids by sputtering or vapor deposition. At this time, by performing film formation while changing the gas flow rate, a layer whose refractive index increases as the distance from the substrate 1 increases can be formed.

  Alternatively, by using a plurality of film formation sources and performing film formation while changing the film formation amount for each film formation source, it is possible to form a layer whose refractive index increases as the distance from the substrate 1 increases. When the optical element 10 is formed in this way, the entire layer including the gap corresponds to the first region 2, and the entire layer whose refractive index increases as the distance from the substrate 1 increases corresponds to the second region 3. .

[Optical system]
Next, an optical system as an embodiment of the present invention will be described. Reflected light on the surface of each optical element constituting the optical system can cause flare and ghost.

  FIG. 14 shows the optical system 100. The optical system 100 includes a plurality of optical elements G101 to G111. In the optical system 100, an antireflection film 6 having the same characteristics as the antireflection film 6 of the optical element 10 described in any of Examples 1 to 13 is provided on the object side surface of the optical element G102. In FIG. 14, reference numeral 102 denotes a stop, and 103 denotes an image plane.

  As described in Examples 1 to 13, by providing the antireflection film 6 on the object side surface of the optical element G102, the reflectance of the object side surface of the optical element G102 can be reduced. By using the optical element G102 having such a low reflectance surface in the optical system 100, it is possible to reduce the occurrence of ghosts and flares. Further, the optical element G101 is provided with a region containing perfluoropolyether having a high antifouling property on the most surface side. Therefore, it is possible to reduce the change in reflectance due to external contamination.

  Although the case where the antireflection film 6 is provided on the object side surface of G102 has been described, the antireflection film 6 may be provided on both surfaces of G102, or the antireflection film 6 may be provided only on the surface on the imaging surface 103 side. It may be provided. Moreover, although the example which provided the antireflection film 6 in the optical element G102 in the optical system 100 was demonstrated, you may provide the antireflection film 6 in another optical element. Further, the antireflection film 6 may be provided on a plurality of optical elements.

  Further, the optical system of the present invention is not limited to the one used in an imaging device described later, and can be applied to various optical systems such as binoculars, projectors, and telescopes.

[Imaging device]
Next, an imaging device as an embodiment of the present invention will be described.

  FIG. 15 shows a digital camera 300 as an imaging apparatus. The digital camera 300 includes the optical system 100 described above in the lens unit 301. An imaging element 303 such as a CCD or a CMOS sensor is disposed on the main body 302 on the imaging surface 103 of the optical system 100.

  Since the digital camera 300 includes the optical system 100, it is possible to obtain a high-quality image with reduced generation of ghosts and flares.

  15 shows an example in which the main body 302 and the lens unit 301 are integrated, the present invention may be applied to a lens apparatus that can be attached to and detached from the imaging apparatus main body. Such a lens device is used as an interchangeable lens for a single-lens camera, for example. In this case, FIG. 14 can also be viewed as a state in which the lens device 301 having the optical system 100 is attached to the imaging device main body 302.

  The preferred embodiments and examples of the present invention have been described above, but the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes can be made within the scope of the gist.

DESCRIPTION OF SYMBOLS 10 Optical element 1 Board | substrate 2 1st area | region 3 3rd area | region 6 Antireflection film

Claims (20)

An optical element comprising a substrate and an antireflection film provided on the substrate,
The antireflection film is
A first region containing voids and having a uniform refractive index in the thickness direction;
A second region provided on the opposite side of the substrate with respect to the first region,
The refractive index of the second region increases as the distance from the substrate increases. When the refractive index of the first region is n ₁ and the refractive index at the position farthest from the substrate in the second region is n ₂ , n ₂ is larger than n ₁ ,
1.1 ≦ n ₁ ≦ 1.3
1.25 ≦ n ₂ ≦ 1.4
The optical element according to claim 1, wherein the following conditional expression is satisfied. When the thickness of the first region is d ₁ [nm] and the thickness of the second region is d ₂ [nm],
50 ≦ d ₁ ≦ 130
5 ≦ d ₂ ≦ 50
The optical element according to claim 1, wherein the following conditional expression is satisfied.   4. The optical element according to claim 1, wherein a refractive index at a position closest to the substrate in the second region is equal to a refractive index of the first region. 5.   The optical element according to any one of claims 1 to 4, wherein the second region contains an organic fluorine compound.   6. The third region according to claim 1, further comprising a third region having a uniform refractive index in a thickness direction on the opposite side to the first region with respect to the second region. An optical element according to 1. When the thickness of the third region is d ₃ [nm],
0 <d ₃ ≦ 10
The optical element according to claim 6, wherein the following conditional expression is satisfied.   The optical element according to claim 6 or 7, wherein the third region contains an organic fluorine compound.   The optical element according to claim 6, wherein a refractive index at a position farthest from the substrate in the second region is equal to a refractive index of the third region.   Between the first region and the substrate, there is a high refractive index layer that is larger than the refractive index of the first region, and a low refractive index that is larger than the first region and smaller than the high refractive index layer. The optical element according to any one of claims 1 to 9, wherein a refractive index layer is provided.   The optical element according to claim 1, wherein the second region includes a gap.   The optical element according to claim 11, wherein the second region includes chain-shaped fine particles.   The optical element according to any one of claims 1 to 12, wherein the second region includes fine particles and a binder that bonds the fine particles to each other.   The optical element according to claim 12, wherein the fine particles are inorganic oxide fine particles.   The optical element according to claim 1, wherein the first region includes chain-shaped fine particles.   The optical element according to claim 1, wherein the first region includes fine particles and a binder that bonds the fine particles to each other.   The optical element according to claim 15, wherein the fine particles are inorganic oxide fine particles. Comprising a plurality of optical elements,
An optical system, wherein at least one of the optical elements is an optical element according to any one of claims 1 to 17.   An image pickup apparatus comprising: an image pickup element; and the optical system according to claim 18.   A lens apparatus comprising the optical system according to claim 18, wherein the lens apparatus is detachable from an imaging apparatus main body.

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