Optical thin film, method for manufacturing the same, optical element, and optical instrument

Abstract

When an anti-reflective coating, conventionally applied to glass lenses, is applied to a plastic lens, the difference in thermal expansion between the plastic substrate and the anti-reflective coating causes significant expansion of the plastic substrate in high-temperature environments. This leads to a problem where the anti-reflective coating cannot keep up with the expansion of the substrate and is prone to fracture (cracking). Therefore, we aim to realize a new optical thin film that achieves both the desired optical properties and the suppression of crack formation. [Solution] The optical thin film of this disclosure includes one or more MO mixed layers (11) in which organometallic compounds are mixed within a layer formed by the physical deposition of magnesium fluoride.

Description

[Technical Field]

[0001] This invention relates to optical thin films, methods for manufacturing the same, optical elements, and optical devices. [Background technology]

[0002] In recent years, there has been a growing trend to replace glass lenses with plastic lenses in general-purpose lenses such as automotive and surveillance lenses, driven by the need for lighter weight and lower costs. However, there is approximately a 10-fold difference in the coefficient of thermal expansion between plastic and inorganic thin films. Therefore, when an anti-reflective coating, which was conventionally applied to glass lenses, is applied to a plastic lens, the difference in thermal expansion between the plastic substrate and the anti-reflective coating causes the plastic substrate to expand significantly in high-temperature environments. This leads to a problem where the anti-reflective coating cannot keep up with the expansion of the substrate and is prone to fracture (cracking).

[0003] As a technique for suppressing the occurrence of cracks in optical thin films that cover such resin lenses, a technique is known that involves a multilayer film including a laminated structure of a layer formed using a high refractive index dielectric material and a layer formed using a low refractive index dielectric material, wherein the range of compressive stress or Young's modulus of each layer is defined (see, for example, Patent Document 1).

[0004] Furthermore, a technique is known that suppresses crack formation by limiting the ratio of the film thickness of the low-refractive-index dielectric material layer closest to the substrate to the total film thickness of the multilayer film (see, for example, Patent Documents 2 and 3).

[0005] Furthermore, as part of this technology, there is also a known technique that uses a substrate with heat resistance of 105°C or higher, and that limits the total thickness and stress range of the multilayer film to improve the heat resistance of the multilayer film (see, for example, Patent Document 4). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-21893 [Patent Document 2] Japanese Patent Publication No. 2019-144552 [Patent Document 3] Special Publication No. 2015-129129 [Patent Document 4] Japanese Patent Publication No. 2019-66600 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, there are limits to adjusting film stress in this way, and if film stress is adjusted to suppress crack formation, the anti-reflective performance may become insufficient due to design constraints.

[0008] Generally, a known method for reducing the reflectivity of anti-reflective coatings is to deposit a low-refractive-index material on the outermost layer of the coating. Among these, magnesium fluoride (MgF2) has a lower refractive index compared to other low-refractive-index materials such as SiO2, and is widely used as an anti-reflective coating material on glass substrates.

[0009] However, MgF2 typically exhibits strong tensile stress, and when used as a film material for resin substrates, it can crack under high-temperature conditions, making it difficult to use MgF2 on resin substrates. Therefore, conventional methods for controlling film stress rarely use MgF2, and instead rely solely on adjusting film thickness using materials other than MgF2.

[0010] Furthermore, in addition to film stress, MgF2 also presents a challenge in that it becomes weaker and has poor scratch resistance when deposited at temperatures below 200°C. Generally, when coating optical resin substrates, it is necessary to deposit the film below the glass transition temperature of the resin, so the film is deposited at temperatures below 200°C (actually below 100°C considering changes in the substrate's shape). In this case, if the outermost layer is made of MgF2, scratch resistance cannot be ensured, resulting in a film that is not suitable for practical use.

[0011] Due to these challenges, using MgF2 on resin substrates is difficult, and plastic lenses with anti-reflective properties and heat resistance equivalent to glass lenses have not yet been commercialized.

[0012] Although the aforementioned patent documents all describe film designs with enhanced heat resistance, they do not use MgF2 (Patent Documents 1, 3, and 4 do not mention MgF2 at all, and Patent Document 2 does not include any examples using MgF2). As a result (since SiO2 or a mixed compound mainly composed of SiO2, which has a higher refractive index than MgF2, is used as the optical outermost layer), there is a problem that the anti-reflective film has a narrow reflection band or high reflectivity.

[0013] One aspect of the present invention aims to realize a novel optical thin film that achieves desired optical properties and suppresses crack formation. [Means for solving the problem]

[0014] To solve the above problems, an optical thin film according to one aspect of the present invention includes one or more MO mixed layers in which organometallic compounds are mixed within a layer formed by the physical deposition of magnesium fluoride.

[0015] Furthermore, in order to solve the above problems, an optical element according to one aspect of the present invention comprises a substrate and the above-mentioned optical thin film supported thereon.

[0016] Furthermore, in order to solve the above-mentioned problems, an optical device according to one aspect of the present invention has the above-mentioned optical element.

[0017] Also, in order to solve the above problems, a method for manufacturing an optical thin film according to one aspect of the present invention includes a step of forming a layer by physical vapor deposition of a dielectric material on a substrate in an atmosphere containing an organometallic compound and a reactive gas, and forming a mixed layer in which the organometallic compound is mixed in the layer made of an oxide, oxynitride or nitride of the dielectric material. The step of forming the mixed layer includes a step of forming a MO mixed layer in which the organometallic compound is mixed in a layer formed by physical vapor deposition of magnesium fluoride using magnesium fluoride for the dielectric material.

Advantages of the Invention

[0018] According to one aspect of the present invention, it is possible to realize a new optical thin film in which the manifestation of desired optical characteristics and the suppression of crack generation are achieved.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram schematically showing the configuration of an example of an optical thin film according to an embodiment of the present invention. [Figure 2] It is a diagram schematically showing the configuration of another example of an optical thin film according to an embodiment of the present invention. [Figure 3] It is a diagram schematically showing the configuration of a first example in an apparatus for manufacturing an optical thin film according to an embodiment of the present invention. [Figure 4] It is a diagram schematically showing the configuration of a second example in an apparatus for manufacturing an optical thin film according to an embodiment of the present invention. [Figure 5] It is a diagram schematically showing the configuration of a third example in an apparatus for manufacturing an optical thin film according to an embodiment of the present invention. [Figure 6] It is a diagram schematically showing the configuration of a fourth example in an apparatus for manufacturing an optical thin film according to an embodiment of the present invention. [Figure 7] It is a diagram schematically showing the configuration of a fifth example in an apparatus for manufacturing an optical thin film according to an embodiment of the present invention. [Figure 8] It is a diagram showing a graph of the element ratios of optical thin film 1 and optical thin film 2 in an example of the present invention. [Figure 9]This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 5 in Example 5 of the present invention at wavelengths of 350 to 750 nm. [Figure 10] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 6 in Example 6 of the present invention at wavelengths of 350 to 750 nm. [Figure 11] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 7 in Example 7 of the present invention at wavelengths of 350 to 750 nm. [Figure 12] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 8 in Example 8 of the present invention at wavelengths of 350 to 750 nm. [Figure 13] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 9 in Example 9 of the present invention at wavelengths of 350 to 750 nm. [Figure 14] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 10 in Example 10 of the present invention at wavelengths of 350 to 750 nm. [Figure 15] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 11 in Example 11 of the present invention at wavelengths of 350 to 750 nm. [Figure 16] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 12 in Example 12 of the present invention at wavelengths of 350 to 750 nm. [Figure 17] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 13 in Example 13 of the present invention at wavelengths of 350 to 750 nm. [Figure 18] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film 14 in Example 14 of the present invention at wavelengths of 350 to 950 nm. [Figure 19] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film C2 in Comparative Example 2 of the present invention at wavelengths of 350 to 750 nm. [Figure 20] This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film C3 in Comparative Example 3 of the present invention at wavelengths of 350 to 750 nm. [Figure 21]This figure shows a graph of the spectral reflectance (calculated value) of the optical thin film C4 in Comparative Example 4 of the present invention at wavelengths of 350 to 750 nm. [Modes for carrying out the invention]

[0020] [Optical thin film] An optical thin film according to an embodiment of the present invention includes one or more MO-containing layers. The optical thin film may be a single layer consisting only of MO-containing layers, or it may be a multilayer film consisting of MO-containing layers and other layers. An optical thin film as a single layer of MO-containing layers is suitable, for example, as a surface protective layer for an optical element.

[0021] An MO mixed layer is a layer in which organometallic compounds are mixed with magnesium fluoride, which is deposited by physical vapor deposition (PVD). The MO mixed layer contains magnesium fluoride (MgF2) and organometallic compounds. For example, if the two compounds form a sea-island structure in the MO mixed layer, one side of the sea-island is magnesium fluoride and the other side is the organometallic compound.

[0022] The MO mixed layer may contain one or more compounds other than organometallic compounds, such as their oxidation reaction products, their oxynitrides, and their nitrides. Organometallic compounds and compounds derived from these organometallic compounds are also called "organometallic material compounds." These organometallic material compounds may be minor components constituting the mixed layer, or trace components in the mixed layer.

[0023] The organometallic compound can be any material that can be deposited by chemical vapor deposition (CVD). Examples of such compounds include organic compounds containing one or more elements selected from the group consisting of Si, Al, Ti, Hf, and Mg. These organometallic compounds are preferred from the viewpoint of achieving desired anti-reflective properties in multilayer optical thin films. More specifically, examples of organometallic material compounds include organic SiO2, organic TiO2, organic Al2O3, organic Hf2O3, and organic MgF2. In a single MO mixed layer, there may be one or more organometallic material compounds.

[0024] The content of organometallic material compounds in the MO mixed layer can be appropriately determined according to the desired film properties such as compressive stress in the optical thin film, and the optical properties such as reflectance, depending on the application of the optical thin film. The magnesium fluoride content in the MO mixed layer is expressed by the amount of magnesium (Mg), a metallic element contained in the magnesium fluoride, and the organometallic material compound content in the MO mixed layer is indicated by the content of metallic elements (such as Si) contained in the organometallic material compound. The content of organometallic material compounds in the MO mixed layer can be, for example, 1 to 90% by mass.

[0025] Figure 1 schematically shows the optical thin film of this embodiment, which is a single layer film. Thus, the optical thin film of this embodiment may be an MO mixed layer 11 formed on a substrate 10. The substrate 10 is a plate-shaped substrate and is a carrier on which the optical thin film 1 is supported on its surface. The substrate 10 is, for example, a resin optical element such as a resin lens.

[0026] The MO-mixed layer 11 is a layer in which an organometallic material compound is mixed by CVD within a layer made of magnesium fluoride by PVD. The layer made of magnesium fluoride by PVD has strong tensile stress, but the layer made of organometallic material compound by CVD has strong compressive stress. As a result, the MO-mixed layer 11 has the optical properties of the layer made of magnesium fluoride by PVD, and the tensile stress of that layer is reduced. Therefore, the MO-mixed layer 11 has sufficiently low tensile stress (or compressive stress), and can adequately follow the thermal expansion of the substrate 10 even at high temperatures, thereby preventing the occurrence of cracks in the MO-mixed layer 11 (optical thin film).

[0027] As mentioned above, the optical thin film may consist only of an MO-containing layer, but it may also be a multilayer film in which the MO-containing layer and other layers overlap. In this embodiment, such an optical thin film is a multilayer film formed by stacking two or more dielectric layers having different refractive indices, and may include the above-mentioned MO-containing layer as at least one of the dielectric layers. Having a multilayer optical thin film in this way is preferable from the viewpoint of improving optical properties such as anti-reflective properties of the optical thin film.

[0028] The number and position of MO-containing layers in the stacking direction of the multilayer film are not limited. For example, the MO-containing layers may be surface layers, bottom layers (the layers closest to the substrate), or intermediate layers located between them.

[0029] For example, the optical thin film, which is a multilayer film in this embodiment, may include a configuration in which a first layer, which includes a layer made of a first dielectric material by PVD, and a second layer, which includes a layer made of a second dielectric material by PVD and has a different refractive index than the first layer, are alternately stacked. At least one of the first and second layers may be an MO mixed layer, or the multilayer film may have an additional MO mixed layer separate from the first and second layers.

[0030] In a multilayer optical thin film, it is preferable to include an MO-containing layer as the optical outermost layer from the viewpoint of suppressing damage to the optically functional layer. The "optically outermost layer" refers to the layer located on the outermost surface (for example, the side opposite the substrate) among the optically functional layers in the multilayer film. The "optically functional layer" is, for example, a layer in the multilayer film that is designed and formed to exhibit a desired refractive index, and may be the MO-containing layer mentioned above, the first layer, or the second layer.

[0031] Furthermore, various functional films, such as adhesion films, protective films, anti-fouling films, and conductive films described later, which are not substantially optically functional but are designed and formed to exhibit other functions, are not included in the "optically functional layer." However, within the scope to which the effects of this embodiment can be obtained, the optical thin film may further include layers other than the "optically functional layer."

[0032] A multilayer optical thin film containing an MO mixed layer is suitable as an anti-reflective film, and is suitable from the viewpoint of improving the anti-reflective properties of the anti-reflective film and improving the durability of the anti-reflective film (suppression of crack occurrence).

[0033] The first dielectric material and the second dielectric material can be appropriately determined within a range in which the optical properties of the first and second layers are substantially different, and may be the same or different. Such dielectric materials are materials that constitute the structure of the above layers and may be the main components of the first or second layer. The dielectric material may be a material that can form layers by PVD, for example, and more specifically, it may be a material that constitutes each layer in a conventional multilayer anti-reflective film. The dielectric layer made of such a material is not particularly limited, but may be a layer of oxide, oxynitride, or nitride of the dielectric material by physical vapor deposition of the dielectric material containing one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce. Having such a structure in the dielectric layer is preferable from the viewpoint of realizing desired optical properties of the optical thin film, such as anti-reflective properties when it is a multilayer film.

[0034] Furthermore, the dielectric layer in the multilayer film may be a mixed layer (DO mixed layer) in which an organometallic compound is mixed within a layer of the dielectric material, similar to the MO mixed layer described above. That is, the dielectric layer in the multilayer film may include a DO mixed layer in which an organometallic compound is mixed within a layer of oxide, oxynitride, or nitride of a dielectric material containing one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce, which is formed by physical vapor deposition of the dielectric material. The inclusion of a DO mixed layer in the multilayer film is preferable not only from the viewpoint of improving the anti-reflective properties of optical thin films, but also from the viewpoint of appropriately adjusting the film stress to suppress crack generation, as it allows the film stress of the alternating stacked structure in the multilayer film to be adjusted towards compressive stress (low tensile or compressive stress).

[0035] Examples of dielectric materials mentioned above include TiO2, ZrO2, ZrO2+TiO2, La2O3, La2O3+TiO2, Nb2O5, Hf2O3, Al2O3, SiO2, Pr2O3, and SiO2. x N yand CeO2 are included. The "+" above indicates a mixture or a compound thereof. Thus, in a single mixed layer, the dielectric material may be one or more of the exemplified materials.

[0036] It is preferable that the dielectric material described above contains Ti, and that the first or second layer is a titanium PVD layer, from the viewpoint of achieving the desired anti-reflective properties in the optical thin film of this embodiment.

[0037] Thus, in the multilayer film, the first and second layers may be either an MO mixed layer or an DO mixed layer, or both may be separate MO mixed layers or DO mixed layers. Furthermore, one or both of the first and second layers in the multilayer film may be layers made of dielectric material by PVD. For example, the optical thin film in the form of a multilayer film according to this embodiment may have a configuration in which two or more mixed layers are alternately stacked, or it may have a configuration in which mixed layers and layers made of dielectric material by PVD are alternately stacked.

[0038] Figure 2 schematically shows the optical thin film of this embodiment, which is a multilayer film. The optical thin film 21 is formed on a substrate 10 and has a laminated structure of multiple layers. The optical thin film 21 has, in order from the substrate 10 side, an alternating laminated structure of an adhesion layer 14, a low refractive index layer 12, and a high refractive index layer 13, as well as an MO mixed layer 11.

[0039] The adhesion layer 14 is a layer composed of, for example, an organometallic material compound. The adhesion layer 14 is formed by CVD of the organometallic compound and has compressive stress depending on the type of organometallic material compound. When the substrate 10 is made of resin, the adhesion layer 14 has good adhesion to both the substrate 10 and the low refractive index layer 12 or the high refractive index layer 13.

[0040] The low refractive index layer 12 is a layer containing a dielectric material that exhibits a lower refractive index than the film made of the dielectric material contained in the high refractive index layer 13, and has film stress depending on the type of dielectric material contained in the film. For example, the low refractive index layer 12 may be a film made of SiO2 by PVD, in which case the low refractive index layer 12 has compressive stress. The low refractive index layer 12 may be a layer made of SiO2 by PVD, or it may be a DO mixed layer containing SiO2.

[0041] The high refractive index layer 13 is a layer containing a dielectric material that exhibits a higher refractive index than the film made of the dielectric material contained in the low refractive index layer 12, and has a film stress corresponding to the type of dielectric material contained in the film. For example, the high refractive index layer 13 may be a film made by PVD of TiO2, or it may be a DO mixed layer containing TiO2.

[0042] The optical thin film 21 exhibits optical properties (anti-reflective properties) due to its alternating stacked structure of a low refractive index layer 12 and a high refractive index layer 13, and the MO mixed layer 11 located on its surface. Furthermore, the optical thin film 21 has specific film stresses resulting from the three layers: the adhesion layer 14, the alternating stacked structure, and the MO mixed layer 11. The film stress of the optical thin film 21 can be substantially represented by the sum of the film stresses of each layer: the adhesion layer 14, the low refractive index layer 12, the high refractive index layer 13, and the MO mixed layer 11. The film stress of each layer can be determined according to the thickness of each layer.

[0043] In this embodiment, the optical thin film preferably has a film stress of +200 to -1000 MPa when the tensile stress is positive and the compressive stress is negative, from the viewpoint of suppressing the occurrence of cracks due to temperature changes, especially at high temperatures. From the above viewpoint, the film stress of the optical thin film can be appropriately determined based on the requirements of the structure of the optical thin film or the application of the optical thin film. For example, from the above viewpoint, the film stress of a single-layer optical thin film is preferably +200 MPa or less. Also, from the above viewpoint, the film stress of a multilayer optical thin film is preferably -100 to 1000 MPa. The film stress of an optical thin film tends to decrease as the amount of organometallic material compound in the mixed layer increases, and in multilayer films, it tends to decrease as the thickness of the film with compressive stress increases, and increase as the thickness of the film with tensile stress increases.

[0044] Furthermore, the optical properties of the optical thin film in this embodiment, such as its anti-reflective properties, can be appropriately determined according to the application of the optical thin film. For example, the reflectivity of the optical thin film in this embodiment is preferably 0.5% or less for light with a wavelength of 450 to 600 nm. A reflectivity of 0.5% or less for light with a wavelength of 450 to 600 nm is preferable from the viewpoint of increasing visible light transmittance, and is therefore suitable for applications such as camera lenses for video.

[0045] Alternatively, the reflectivity of the optical thin film in this embodiment is preferably 1.5% or less for light with a wavelength of 400 to 850 nm. A reflectivity of 1.5% or less for such wavelengths is desirable from the viewpoint of increasing the transmittance of visible to near-infrared light, and is therefore suitable for applications such as FA (industrial) or camera lenses for surveillance and automotive use.

[0046] Thus, the optical thin film of this embodiment exhibits excellent anti-reflective performance and can suppress the occurrence of cracks due to temperature changes. Therefore, this optical thin film is suitable as an anti-reflective coating for plastic lenses in markets where high environmental resistance is required, such as automotive lenses.

[0047] [Method for manufacturing optical thin films] The optical thin film of this embodiment described above can be manufactured by a method that includes a mixed layer formation step for forming the aforementioned mixed layer.

[0048] The mixed layer formation process is a process of generating a layer of dielectric material on a substrate by physical deposition in an atmosphere containing an organometallic compound and a reactive gas. Through such a mixed layer formation process, a mixed layer can be formed in which an organometallic compound is mixed within a layer of oxide, oxynitride, or nitride of the dielectric material. This mixed layer formation process can be carried out by synchronizing a CVD process, in which an organometallic compound gas (precursor gas) or a reactive gas is introduced and reacted, with a PVD film deposition process using magnesium fluoride or the aforementioned dielectric material as a raw material. In the mixed layer formation process, the organometallic compound is mixed into the mixed layer by CVD of the organometallic compound under the PVD film deposition conditions of magnesium fluoride or the dielectric material.

[0049] In this embodiment, the mixed layer formation step includes a step of forming an MO mixed layer in which an organometallic compound is mixed within a layer formed by the physical deposition of magnesium fluoride, using magnesium fluoride as the dielectric material. The MO mixed layer can be fabricated in the same way as other (known) dielectric material layers by using magnesium fluoride as the dielectric material in this manner.

[0050] The PVD film deposition process can be carried out by irradiating the dielectric material with an electron beam from an electron gun, sputtering, or resistance heating. Furthermore, it is preferable to carry out the PVD film deposition process under conditions that further generate plasma, ions, or heat as auxiliary agents, from the viewpoint of appropriately setting the conditions for PVD of the dielectric material and for the formation of organometallic material compounds by CVD and their mixing into the mixed layer. In addition, the PVD film deposition process may be carried out in an atmosphere containing a reactive gas from the viewpoint of replenishing specific elements in the dielectric material into the mixed layer. The reactive gas may be appropriately selected according to the specific elements mentioned above, and examples include oxygen and nitrogen.

[0051] The various conditions for the PVD film deposition process to create the mixed layer are appropriately adjusted to conditions under which CVD of organometallic compounds occurs in parallel. Such conditions may be determined experimentally or estimated by calculation. CVD of organometallic compounds can be suitably carried out by reacting the organometallic compound with a reactive gas in the presence of plasma, ions, or heat generated auxiliaryly during the PVD film deposition process. In this embodiment, it is preferable to carry out the PVD film deposition process under PVD conditions that take into account such organometallic compound CVD conditions, from the viewpoint of appropriately adjusting the magnitude of the compressive stress of the optical thin film and the properties of the optical thin film.

[0052] The supply of the precursor gas in the PVD film deposition process described above may be carried out at any time during the film deposition process, either before or simultaneously with the start of the film deposition process, or at any time between the start and end of the film deposition process. Furthermore, the supply of the precursor gas may be stopped before or at the end of the film deposition process. From the viewpoint of producing a mixed layer with a stable composition and structure, it is preferable to carry out the PVD film deposition process after creating conditions that allow for both PVD film deposition and CVD of organometallic compounds.

[0053] The conditions for the PVD film deposition process of dielectric materials and the CVD conditions for organometallic compounds may be constant or variable. For example, by changing the PVD film deposition conditions, the amount of precursor gas supplied, and the amount of reactive gas supplied, it is possible to gradually or stepwise change the composition of a single mixed layer in the thickness direction.

[0054] The substrate in the manufacturing method of this embodiment may be an optical component that will be coated with the optical thin film in the manufacturing method of the optical thin film. The substrate may be an optical element or another component (such as a transparent film). Optical elements will be described later.

[0055] As described above, the organometallic compound used in CVD is preferably a compound used as a precursor gas in CVD. The organometallic compound is appropriately selected from compounds that can become an organometallic material compound alone or by reaction with a reactive gas. Examples of the metal element of the organometallic compound include Al, Ti, Ta, Si, Hf, and Mg. Examples of the organometallic compound containing such a metal element include trimethylaluminum (TMA, (CH3)3Al), tetrakis(dimethylamino)titanium (TDMAT, Ti[N(CH3)2]4), tetraethyl orthosilicate (TEOS, Si(OC2H5)4), trimethylsilane (SiH(CH3)3), hexamethyldisiloxane (HMDSO, (CH3)3SiOSi(CH3)3), decamethyltetrasiloxane (C 10 H 30 O3Si4), hexamethylcyclotrisiloxane (C6H 18 O3Si3), tetramethylsilane (Si(CH3)4), tetrakis(dimethylamido)hafnium (TDMAHf (Hf[N(CH3)(C2H5)])), bis(2,2,6,6-tetramethyl-3,5-heptanedionato)magnesium (Mg(TMHD)2, (Mg(C 11 H 19 O2)2)), and bis(methylcyclopentadienyl)magnesium (C 14 H 18 Mg 10 ), etc. are included.

[0056] The conditions of the film formation process by PVD can be appropriately determined according to the material of the layer or the substrate, etc. For example, when producing a mixed layer when a plastic resin lens is used as the substrate, the film formation temperature is preferably 100 °C or lower from the viewpoint of suppressing the shape change of the substrate because the glass transition temperature (Tg) of the substrate is approximately 140 to 150 °C. Thus, the above conditions can be appropriately determined.

[0057] [Manufacturing Equipment] The above manufacturing method can be carried out using an apparatus comprising a PVD film deposition apparatus and a CVD gas supply device capable of supplying CVD gas into the chamber of the film deposition apparatus. Such a manufacturing apparatus can be configured, for example, by connecting an external CVD gas supply device to a synchronized vacuum deposition apparatus equipped with a plasma gun. With such a configuration, it becomes possible to perform vacuum deposition (PVD) while circulating CVD gas into the chamber of the vacuum deposition apparatus.

[0058] In a PVD (Physical Vapor Deposition) deposition apparatus, vacuum deposition can be carried out, for example, by irradiating a dielectric material placed in a crucible with an electron beam to evaporate the material. Alternatively, by flowing a reactive gas (such as O2 or N2) through the chamber, it is possible to fabricate dielectric films of any oxide, nitride, oxynitride, etc., derived from the dielectric material.

[0059] On the other hand, the CVD gas supply device can supply any gas at any flow rate by appropriately replacing the raw material tank and flow meter of the device according to the type of gas. The CVD gas introduced into the chamber reacts with the dielectric material evaporated by electron beam irradiation, and an organic-doped dielectric film (i.e., the aforementioned mixed layer) is produced.

[0060] Furthermore, the above-mentioned film formation reaction can be accelerated by applying plasma irradiation (ion irradiation or heat, etc.) during film formation. Applying an RF bias to the substrate side is also effective in accelerating the reaction. The manufacturing method applied to the manufacturing method of this embodiment will be described in more detail below.

[0061] <First example of manufacturing equipment> As shown in Figure 3, the manufacturing apparatus 200 is equipped with an evaporation dome 220 at the top of the chamber 210. An evaporation source 230 and a plasma gun 250 are positioned opposite the evaporation dome 220 within the chamber 210. The chamber 210 also has a first gas inlet 240 for supplying reactive gas to the space between the evaporation dome 220 and the evaporation source 230 and plasma gun 250, and a second gas inlet 260 for supplying precursor gas.

[0062] Chamber 210 is configured to be depressurized. Evaporation dome 220 is configured to accommodate multiple substrates, which will be described later. Evaporation source 230 includes, for example, a crucible and an electron gun that irradiates the crucible with an electron beam. Plasma gun 250 is a plasma source in which the plasma strength can be varied by changing parameters such as discharge voltage. First gas inlet 240 is connected to a source of reactive gases such as oxygen (e.g., a cylinder) and is configured to supply these gases into chamber 210 at a desired flow rate. Second gas inlet 260 is connected to a source of precursor gas (e.g., a cylinder) and is configured to supply this gas into chamber 210 at a desired flow rate.

[0063] Thus, the manufacturing apparatus 200 is equipped with a PVD film deposition mechanism by vacuum deposition, and further equipped with a precursor gas supply mechanism. Such a manufacturing apparatus 200 can be constructed, for example, by adding a precursor gas supply device to an existing PVD film deposition apparatus.

[0064] In the manufacturing of optical thin films, a substrate such as a resin lens is placed in the deposition dome 220. Then, magnesium fluoride or, if necessary, other dielectric materials such as titanium oxide are filled into the crucible of the deposition source 230. In addition, a supply source for reactive gas and inert gas for discharge is connected to the first gas inlet 240, and a cylinder of precursor gas is connected to the second gas inlet 260.

[0065] A precursor gas is supplied into the chamber 210 from the second gas inlet 260, and a reactive gas and an inert gas for discharge, such as argon gas, are supplied from the first gas inlet 240. The chamber 210 is then depressurized to a specific vacuum level. The argon gas may be supplied by another supply device (not shown). In this way, an atmosphere of precursor gas and reactive gas is formed in the chamber 210. Next, an electron beam is irradiated from the electron gun onto the crucible of the deposition source 230. At the same time, for example, argon plasma is released into the chamber 210 from the plasma gun 250.

[0066] The dielectric material in the crucible is deposited on the surface of the substrate inside the deposition dome 220 by plasma-assisted vacuum deposition, forming a layer. Meanwhile, the precursor gas supplied into the chamber 210 from the second gas inlet 260 reacts with the reactive gas from the first gas inlet 240 in the presence of argon plasma from the plasma gun 250, and is deposited on the surface of the substrate inside the deposition dome 220. In this way, a mixed layer (the aforementioned MO mixed layer or DO mixed layer) is created on the substrate in which reactants of organometallic compounds are mixed within the PVD layer of dielectric material.

[0067] When the operation of the deposition source 230 is stopped, only the reactants of the organometallic compound are deposited on the substrate, and the aforementioned adhesion layer is formed. When the supply of precursor gas from the second gas inlet 260 is stopped, only the film derived from the dielectric material of the PVD is deposited on the substrate, and the aforementioned high refractive index layer or low refractive index layer is formed. By appropriately controlling the operation of the manufacturing apparatus 200 in this way, the aforementioned adhesion layer and multilayer film can be formed on the surface of the substrate.

[0068] As described above, in this embodiment, a mixed layer can be fabricated by simultaneously performing two film deposition methods, PVD and CVD. The mixed layer has different physical properties from the layer produced by PVD using a mixture of dielectric material and organometallic material compound as raw materials. This is thought to be because the growth mechanism of the mixed layer, which is fabricated synchronously by PVD and CVD as in this embodiment, is different from that of the layer produced by PVD deposition of the above mixture.

[0069] A typical characteristic of the mixed layer in this embodiment is that it has compressive stress. In this embodiment, a high refractive index material that tends to have tensile stress is deposited on the substrate by PVD, and an organometallic compound (organosilicon compound in this embodiment) that has strong compressive stress is deposited on the substrate by CVD. This reduces the tensile stress of the PVD layer, which originally has tensile stress, or changes it to compressive stress. Therefore, as described above, even if the optical thin film of this embodiment includes the aforementioned mixed layer and a high refractive index layer with tensile stress, the optical thin film as a whole can have compressive stress.

[0070] Furthermore, the stress of the optical thin film can be controlled by adjusting quantitative conditions of the organometallic material compound in the layer being formed, such as the flow rate of the precursor gas. Therefore, by adjusting these conditions, it is possible to fabricate an optical thin film that has a high refractive index and high compressive stress.

[0071] This results in a multilayer optical thin film that has equivalent reflectivity to conventional multilayer films with high-refractive-index and low-refractive-index layers, while not cracking even at high temperatures of 110°C or higher. Furthermore, according to the embodiment of the present invention, the excellent optical properties of MgF2, which exhibits excellent optical properties despite being prone to cracking due to strong tensile stress, are brought out by the MO mixed layer, and the strong tensile stress caused by MgF2 is further reduced by the MO mixed layer. Therefore, even if the optical thin film of this embodiment is used as an optical thin film for plastic lenses, an optical thin film with high durability (no cracking) can be obtained.

[0072] <Second example of manufacturing equipment> Other examples of apparatus that may be used in the manufacturing method of this embodiment are described below. In the following descriptions of manufacturing apparatus examples, for the sake of clarity, components having the same function as those described in the previously mentioned examples will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0073] Figure 4 schematically shows the configuration of a second example of the optical thin film manufacturing apparatus of this embodiment. As shown in Figure 4, the manufacturing apparatus 300 has the same configuration as the manufacturing apparatus 200 described above, except that it has an ion gun 350 instead of a plasma gun 250.

[0074] The ion gun 350 injects, for example, cations derived from argon gas toward the substrate in the deposition dome 220. The dielectric material in the crucible is deposited on the surface of the substrate inside the deposition dome 220 by ion-assisted vacuum deposition, forming a layer. The precursor gas supplied into the chamber 210 from the second gas inlet 260 reacts with the reactive gas from the first gas inlet 240 in the presence of ions from the ion gun 350, and is deposited on the surface of the substrate inside the deposition dome 220.

[0075] The manufacturing apparatus 300 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 200 described above. The manufacturing apparatus 300 is advantageous in terms of increasing the density of the produced layer.

[0076] <Third example of manufacturing equipment> Figure 5 schematically shows the configuration of a third example of the optical thin film manufacturing apparatus according to this embodiment. As shown in Figure 5, the manufacturing apparatus 400 has the same configuration as the manufacturing apparatus 200 described above, except that it has a high-frequency power supply 450 instead of a plasma gun 250.

[0077] The high-frequency power supply 450 applies a negative charge to the substrate. The dielectric material in the crucible, for example, ionizes and becomes positively charged, attracting it to the substrate and depositing. The precursor gas supplied into the chamber 210 from the second gas inlet 260 reacts with the reactive gas from the first gas inlet 240 in the presence of plasma caused by the voltage applied to the substrate by the high-frequency power supply 450, and deposits on the surface of the substrate within the deposition dome 220.

[0078] The manufacturing apparatus 400 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 200 described above. The manufacturing apparatus 400 is advantageous in terms of improving the adhesion of the produced layer to the substrate.

[0079] <Fourth example of manufacturing equipment> Figure 6 schematically shows the configuration of a fourth example of the optical thin film manufacturing apparatus according to this embodiment. As shown in Figure 6, the manufacturing apparatus 500 has the same configuration as the manufacturing apparatus 200 described above, except that it has a sputtering source 530 instead of an evaporation source 230.

[0080] The sputtering source 530 is equipped with a power supply for charging a target metal material of the dielectric material. A positive argon plasma, for example, generated by the plasma gun 250, is collided with the negatively charged target, and metal atoms ejected from the surface of the target react with a reactive gas and deposit on the substrate, forming a layer of dielectric material. Meanwhile, as mentioned above, the precursor gas reacts with the reactive gas in the presence of the plasma and deposits on the surface of the substrate.

[0081] The manufacturing apparatus 500 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 200 described above. The manufacturing apparatus 500 is advantageous in terms of increasing the adhesion of the produced layer to the substrate.

[0082] <Fifth example of manufacturing equipment> Figure 7 schematically shows the configuration of a fifth example of the optical thin film manufacturing apparatus according to this embodiment. The manufacturing apparatus 600 includes a chamber 610, a stage 620, a sputtering source 530, a first gas inlet 240, a plasma radical source 650, and a second gas inlet 260.

[0083] Chamber 610 has a first chamber where a sputtering source 530 is located and a second chamber where a plasma radical source 650 is located. The first and second chambers are in communication with each other. Stage 620 is a component that holds a substrate on its surface. Stage 620 is positioned across the first and second chambers and is located within Chamber 610 so as to be rotatable in a direction that allows the held substrate to alternately pass through the first and second chambers. Plasma radical source 650 generates, for example, argon plasma and also generates radicals of reactive gases.

[0084] When the substrate on stage 620 is in the first chamber, a layer of dielectric metallic material is fabricated on the surface of the substrate by sputtering. When the substrate on stage 620 is in the second chamber, radicals from the reactive gas react with the metallic material in the layer on the substrate. In this way, a layer of dielectric material is fabricated on the substrate by reactive sputtering. Meanwhile, as mentioned above, the precursor gas is deposited on the surface of the substrate while reacting with the reactive gas in the presence of plasma.

[0085] The manufacturing apparatus 600 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 200 described above. The manufacturing apparatus 600 is advantageous in terms of forming a thinner layer.

[0086] <Other examples of manufacturing equipment> The aforementioned manufacturing apparatus may further include a quantitative mechanism for the plasma or ions generated in the chamber, or a mechanism for analyzing the composition of the gas in the chamber, such as a Q-mass (quadrupole mass spectrometer). Thus, the manufacturing apparatus in this embodiment may further include a mechanism for detecting the conditions inside the chamber.

[0087] Furthermore, the film deposition operation in the aforementioned manufacturing apparatus may be performed by an operator or by a control device such as a computer. The control device may, for example, acquire information on film deposition conditions in response to input signals of the layer material, layer stress, and layer thickness, and output a control signal to the manufacturing apparatus according to this information. The information on film deposition conditions may be data from previous operations, data calculated based on predetermined correlations between each condition, or data obtained by machine learning or regression analysis. The control device may be replaced by a logic circuit that implements some or all of the functions of the control block in the control device, an integrated circuit on which the logic circuit is formed, or a quantum computer that implements the functions of the control block. Furthermore, if the manufacturing apparatus has a mechanism for detecting conditions in the chamber, the control device may also include a functional configuration that further references the detected condition signals and outputs a control signal.

[0088] Furthermore, the high-frequency power supply 450 of the manufacturing apparatus 400 may be other power supplies as long as PVD and CVD are compatible. For example, the manufacturing apparatus may have a DC power supply instead of a high-frequency power supply, or it may have both a high-frequency power supply and a DC power supply and apply a superimposed voltage from both power supplies.

[0089] [Optical elements] An optical element according to one embodiment of the present invention comprises a substrate and an optical thin film of this embodiment formed on the surface of the substrate. The substrate is a material that can become an optical element exhibiting specific optical properties on its own. Examples of substrates include lenses, prisms, filters, and beam splitters. In the optical element of this embodiment, the optical thin film may be arranged on one or both of the light incident and light exit portions of the substrate, or it may be formed over the entire surface of the substrate.

[0090] The substrate material is typically a light-transmitting material, such as glass and resin. As mentioned above, the optical thin film of this embodiment has high anti-reflective properties (low reflectivity) and compressive stress. On the other hand, plastic resin has a coefficient of thermal expansion about 10 times greater than that of glass, making it more susceptible to deformation (expansion or contraction) with heat. The optical thin film of this embodiment has compressive stress, which gives it high conformability to deformation in the planar direction. Therefore, from the viewpoint of making the effect of preventing cracks due to thermal deformation more pronounced, it is preferable in this embodiment that the substrate is made of plastic resin, and in such a form, the reliability of the optical element in the temperature environment is further enhanced, which is more beneficial.

[0091] Examples of plastic resins used as substrate materials include plastic resins suitable for optical lenses, and more specifically, cycloolefin resins, polycarbonate resins, acrylic resins, epoxy resins, fluororesins, silicone resins, polyethylene resins, polypropylene resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, polyamide resins, polyacetal resins, fluorene-based polyester resins, modified polyphenylene ether resins, polybutylene terephthalate resins, polyethylene terephthalate resins, and liquid crystal polymers. Furthermore, for automotive plastic lenses, high heat-resistant resins developed for automotive use are more preferable. The above substrate may also be a resin substrate in which a hard coat containing the above resin is applied to the resin lens.

[0092] Furthermore, in this embodiment, the optical thin film may include other layers besides the aforementioned mixed layer, to the extent that the effects of the present invention can be obtained.

[0093] For example, the optical element may further have an adhesion layer interposed between the substrate and the optical thin film. This adhesion layer is a layer that enhances the adhesion between the substrate and the optical thin film (the substrate and the MO mixed layer, or the substrate and the layer closest to the substrate in the multilayer film). This adhesion layer may be a layer composed of the organometallic material compound described above. This layer composed of the organometallic material compound can be manufactured, for example, by CVD of the organometallic compound described above. Having an adhesion layer in the optical thin film is preferable from the viewpoint of enhancing the adhesion of the optical thin film to the surface of the material, such as a resin substrate.

[0094] Furthermore, for example, the optical element may have a protective film on the surface of the optical thin film. This protective film is a layer formed on the surface of the optical thin film to prevent damage to the optical thin film (for example, a layer to prevent surface scratches). This protective film may be a layer formed by PVD of the dielectric material described above. The protective film only needs to have a thickness sufficient to prevent damage to the optical thin film, and it is preferable that it has a thickness insufficient to exhibit optical functions, in order to exhibit the desired functions while suppressing the influence on the optical properties of the optical thin film, thereby suppressing damage to the surface of the optical thin film and further improving the reliability of the optical element. From this viewpoint, it is preferable that the protective film is sufficiently thin, and the thickness of the protective film is preferably 50 nm or less. The thickness of the protective film may be, for example, 5 nm or more, from the viewpoint of being able to prevent damage to the optical thin film.

[0095] Furthermore, for example, the optical element may have an antifouling film on the surface of the optical thin film. This antifouling film is a layer for preventing the adhesion of dirt (e.g., fine powder or oil) to the surface of the optical thin film. This antifouling film may be, for example, a fluorine-based water-repellent / oil-repellent film. This fluorine-based water-repellent / oil-repellent film can be manufactured, for example, by wet coating or vacuum deposition. The thickness of the antifouling film may be, for example, 10 to 50 nm, from the viewpoint of suppressing the influence on the optical properties of the optical thin film and from the viewpoint of fully exhibiting the desired antifouling effect.

[0096] Furthermore, for example, the optical element may have a conductive film on the surface of the optical thin film. This conductive film is a layer for shielding from electromagnetic noise or preventing static charge buildup. The conductive film may be, for example, ITO or IZO. The conductive film can be fabricated, for example, by sputtering or vacuum deposition. The thickness of the conductive film may be, for example, 5 to 50 nm, from the viewpoint of suppressing the influence on the optical properties of the optical thin film and from the viewpoint of fully exhibiting the desired conductive effect.

[0097] It is preferable that the other layers described above do not have optical properties that substantially affect the designed optical properties of the optical thin film. On the other hand, since the other layers are formed overlapping with the optical thin film, they may affect the film stress of the optical thin film. Therefore, if the optical element further has such other layers, the film stress of the optical thin film in the optical element may include the film stress due to the other layers. The material of the other layers described above can be appropriately selected from the viewpoint of such film stress. For example, the adhesion layer is preferably a layer composed of the organometallic material compound described above, from the viewpoint that the entire optical thin film has a sufficiently small tensile stress or a sufficiently high compressive stress compared to a multilayer film (or a specific DO mixed layer described above) that may contain a material having tensile stress.

[0098] As mentioned above, the optical thin film of this embodiment has high conformability to deformation in the planar direction. Furthermore, the optical thin film of this embodiment is useful for coating plastic lenses with high heat resistance specifications, which are in demand these days. In addition, the optical element of this embodiment is useful for lenses intended for use in high-temperature environments, such as in automobiles.

[0099] [Optical equipment] An optical device according to an embodiment of the present invention has the aforementioned optical elements. Examples of such optical devices include zoom lenses, single-lens reflex cameras, in-vehicle cameras, surveillance cameras, eyeglasses, binoculars, and telescopes. Because the optical device of this embodiment has the aforementioned optical elements, it can exhibit the desired optical function even in environments with large temperature fluctuations and can have high reliability in such environments.

[0100] 〔summary〕 Controlling the film stress can be an effective measure to prevent cracking in anti-reflective coatings for plastic lenses under high-temperature conditions. Film cracks are more likely to occur when tensile stress is high. Therefore, an effective measure to prevent cracking in such anti-reflective coatings is to control the overall stress so that it does not become tensile stress, that is, to keep the overall film stress at zero or close to compressive stress.

[0101] However, controlling the film stress of an anti-reflective coating is difficult because the range of film stress is determined by the deposition material. For example, MgF2 has a lower refractive index compared to other low refractive index materials such as SiO2, and is therefore widely used as a low refractive index material for the outermost layer. However, it has strong tensile stress, and it is difficult to find conditions under which cracks do not occur. As a result, there are almost no examples of it being used in plastic lenses for automotive applications where high heat resistance is required. Generally, it is known that the lower the refractive index of the outermost layer of an anti-reflective coating, the lower the reflectivity. Therefore, anti-reflective coatings that do not use MgF2 perform worse than anti-reflective coatings that use MgF2 on a glass substrate.

[0102] Furthermore, in conventional methods, as mentioned above, film stress is adjusted by adjusting various conditions such as the lamination combination of film materials, deposition conditions, or film thickness. However, considering mechanical or optical properties other than stress, there are limits to the controllable range. Even when adjusting film stress to improve heat resistance, the overall film thickness may increase, resulting in insufficient anti-reflective performance.

[0103] Thus, in conventional technology, when anti-reflective coatings require not only optical performance but also environmental resistance, heat resistance is ensured by selecting a material that allows for easy stress adjustment from existing film-forming materials and limiting the film thickness. Therefore, even with optically useful materials such as MgF2, it is difficult to use materials in which the film has high tensile stress, and consequently, the reflectivity tends to be higher compared to anti-reflective coatings using MgF2.

[0104] Specifically, focusing on the countermeasures described in the aforementioned patent documents, for example, Patent Document 1 addresses the main issue of improving high-temperature durability, but it does not provide specific numerical values, and the examples do not mention MgF2. Therefore, it can be inferred that it is difficult to introduce MgF2 using the technology described in Patent Document 1.

[0105] Furthermore, the technology described in Patent Document 2 is equivalent to stress control, and the text states that MgF2 may be used. However, there are no examples in the examples where MgF2 was used. Therefore, it is presumed that the use of MgF2 is difficult even with the technology described in Patent Document 2. In addition, the thickness ratio of the innermost layer described in the claims of Patent Document 2 (30-70%) is considered to have a low degree of freedom in thin film design. In fact, the thickness ratio of the innermost layer in the three examples remains at 45-50%.

[0106] Furthermore, the technology described in Patent Document 3 is considered to be synonymous with stress control, just like the technology in Patent Document 2. However, Patent Document 3 does not mention the use of MgF2. Also, in the examples in Patent Document 3, the total film thickness is 600 nm or more for examples with heat resistance of 120°C or higher, and the reflectivity is high, indicating a trade-off between high heat resistance and anti-reflective performance.

[0107] Furthermore, Patent Document 4 specifies that the low refractive index material used is of the SiO2 type, and does not mention MgF2.

[0108] Anti-reflective coatings often consist of a lamination of two or more film materials with different refractive indices. These materials are generally single metal oxides or mixtures or compounds of two or more metal oxides. While film stress can be adjusted by the combination of film materials or film thickness, MgF2 exhibits particularly strong tensile stress. Even with such adjustments, MgF2 films crack at high temperatures, making them unsuitable for use on plastic lenses at high temperatures.

[0109] On the other hand, in the embodiment of the present invention, a composite film is formed by simultaneously depositing an organosilicon compound via CVD (Chemical Vapor Deposition) at the same time as conventional MgF2 deposition. By replacing the MgF2 layer, which has tensile stress, with an MO-containing layer with organic components in this way, the inherent stress of the film itself can be changed, allowing for the setting of a wider range of arbitrary internal stresses. As a result, the compressive stress of the entire film is increased, and crack formation can be suppressed even in high-temperature environments. Furthermore, since MgF2 can also be used, the reflectivity is also more advantageous compared to conventional methods.

[0110] As is clear from the above description, the first aspect of the present invention is an optical thin film comprising one or more MO mixed layers (11) in which organometallic compounds are mixed within a layer formed by physical deposition of magnesium fluoride. According to the first aspect, a novel optical thin film can be realized that achieves the expression of desired optical properties and the suppression of crack generation.

[0111] A second aspect of the present invention is a multilayer film in which an optical thin film is laminated with two or more dielectric layers having different refractive indices, and at least one of the dielectric layers includes an MO mixed layer. The second aspect is even more effective from the viewpoint of improving optical properties such as anti-reflective properties in the optical thin film.

[0112] A third aspect of the present invention is that, in the first or second aspect, the dielectric layer is a layer of oxide, oxynitride, or nitride of a dielectric material comprising one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce, formed by physical vapor deposition. The third aspect is even more effective in terms of achieving desired optical properties of the optical thin film.

[0113] A fourth aspect of the present invention is that, in any of the first to third aspects, the dielectric layer includes a DO mixed layer in which an organometallic compound is mixed within a layer of oxide, oxynitride, or nitride of a dielectric material, which is a dielectric material containing one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce, by physical vapor deposition of the dielectric material. The fourth aspect is even more effective in terms of further improving optical properties such as anti-reflective properties in optical thin films and further optimizing the film stress of optical thin films.

[0114] A fifth aspect of the present invention is an organic compound in which, in any of the first to fourth aspects, the organometallic compound contains one or more elements selected from the group consisting of Si, Al, Ti, Hf, and Mg. The fifth aspect is even more effective in terms of achieving desired anti-reflective properties in a multilayer optical thin film.

[0115] A sixth aspect of the present invention includes an MO-containing layer as the optical outermost layer in any of the first to fifth aspects. The sixth aspect is even more effective in suppressing damage to the optical functional layer.

[0116] A seventh aspect of the present invention is that, in any of the first to sixth aspects, when the tensile stress is positive and the compressive stress is negative, the optical thin film has a film stress of +200 to -1000 MPa. The seventh aspect is even more effective in preventing crack formation at high temperatures.

[0117] An eighth aspect of the present invention is that, in any of the first to seventh aspects, the reflectance of the optical thin film for light with wavelengths of 450 to 600 nm is 0.5% or less, or the reflectance of light with wavelengths of 400 to 850 nm is 1.5% or less. The eighth aspect is even more effective in terms of achieving desired optical properties according to a specific application of the optical thin film.

[0118] A ninth aspect of the present invention is an optical element comprising a substrate and an optical thin film according to any of the first to eighth aspects supported thereon. According to the ninth aspect, a highly reliable optical element can be realized using a novel optical thin film that achieves desired optical properties and suppresses crack formation.

[0119] A tenth aspect of the present invention, in the ninth aspect, further comprises an adhesion layer (14) interposed between the substrate and the optical thin film. The tenth aspect is even more effective in terms of improving the adhesion between the substrate and the optical thin film.

[0120] An eleventh aspect of the present invention is that, in the ninth or tenth aspect, the optical thin film further has a protective film with a thickness of 50 nm or less on its surface. The eleventh aspect is even more effective in terms of suppressing damage to the surface of the optical thin film and improving the reliability of the optical element.

[0121] In the twelfth aspect of the present invention, the substrate is made of plastic resin, in any of the ninth to eleventh aspects. The twelfth aspect is even more effective in terms of further improving the reliability of the optical element in the temperature environment.

[0122] A thirteenth aspect of the present invention is an optical device having an optical element according to any of the ninth to twelfth aspects. According to the thirteenth aspect, it is possible to realize a highly reliable optical device using a new optical thin film that achieves desired optical properties and suppresses crack formation.

[0123] A fourteenth aspect of the present invention is a method for manufacturing an optical thin film, comprising the step of forming a mixed layer in which an organometallic compound is mixed within a layer of oxide, oxynitride, or nitride of the dielectric material by physical deposition in an atmosphere containing an organometallic compound and a reactive gas, wherein the step of forming the mixed layer comprises the step of forming an MO mixed layer in which an organometallic compound is mixed within a layer formed by physical deposition of magnesium fluoride using magnesium fluoride as the dielectric material. According to the fourteenth aspect, a novel optical thin film can be provided that achieves the expression of desired optical properties and the suppression of crack generation.

[0124] One aspect of the present invention provides an optical thin film that combines both the optical properties of magnesium fluoride and film stress resistance suitable for heat use, while also offering a high degree of freedom in film design. The present invention, with its such effects, is expected to contribute to achieving, for example, United Nations Sustainable Development Goal (SDG) 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0125] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Examples]

[0126] An embodiment of the present invention is described below. This embodiment is an anti-reflective coating for lenses, primarily intended for use in high-temperature environments such as automotive applications. In this embodiment, unless otherwise specified, an optical thin film is formed on a cycloolefin copolymer lens.

[0127] [Example 1] Simultaneous deposition of magnesium fluoride and an organosilicon compound was performed. A manufacturing apparatus was prepared, as shown in Figure 2, which included a PVD deposition mechanism by vacuum deposition and a precursor gas supply mechanism. Granular magnesium fluoride was packed into the crucible of the PVD deposition mechanism, and the precursor gas supply mechanism was prepared to supply gas of a siloxane compound. Argon gas for discharge and oxygen gas as a reactive gas were also prepared to be supplied to the chamber of the vacuum deposition apparatus. Mixed deposition was performed by PVD deposition of magnesium fluoride with a siloxane gas flow rate of 10 sccm, and an optical thin film 1 was obtained consisting of a single layer of MO mixed layer in which an organometallic compound was mixed within a layer formed by physical deposition of magnesium fluoride.

[0128] [Examples 2-4] Optical thin film 2 was obtained in the same manner as in Example 1, except that the flow rate of siloxane gas was set to 30 sccm. Optical thin film 3 was obtained in the same manner as in Example 1, except that the flow rate of siloxane gas was set to 50 sccm. Furthermore, optical thin film 4 was obtained in the same manner as in Example 1, except that the flow rate of siloxane gas was set to 80 sccm.

[0129] [Comparative Example 1] A single-layer optical thin film C1 made of MgF2 was obtained in the same manner as in Example 1, except that the flow rate of siloxane gas was set to 0 sccm.

[0130] Table 1 shows the deposition conditions for optical thin films 1, 2, and C1.

[0131] [Table 1]

[0132] [Evaluation (monolayer film)] [Optical constants, film thickness] For each of the optical thin films 1-4 and C1, spectral reflectance and transmittance measurements were performed at a wavelength of 550 nm using a Hitachi High-Technologies U-4100 spectrophotometer, and the optical constants (refractive index at a wavelength of 550 nm) of the optical thin film were calculated from the results.

[0133] [Membrane stress] The film stresses of optical thin films 1-4 and C1 were determined using the substrate curvature method. During film deposition, a 0.15 mm thick cover glass was placed in the deposition dome, and the amount of warpage (height from the reference surface) of the cover glass before and after film deposition was measured using a laser displacement meter. The displacement of this warpage before and after film deposition was then determined, and the film stress (tensile stress) was calculated using Stoney's formula below. The meaning of each letter in the formula below is as follows: In film stress, a positive value represents the magnitude of tensile stress, and a negative value represents the magnitude of compressive stress. Es: Young's modulus of the cover glass ν: Poisson's ratio of the cover glass b: Cover glass thickness L: Length of the cover glass d: Thickness of optical thin film (layer) δ: amount of warp displacement

[0134]

number

[0135] [composition] For each of the optical thin films 1, 2, and C1, spectral analysis was performed by irradiating the sample with an electron beam at an acceleration voltage of 10 kV using a JEOL scanning electron microscope JSM-6500F and an EDAX energy-dispersive X-ray analyzer Genesis. The ratios of various elements in the optical thin films were determined by the ZAF method. The Si element ratio is the ratio of the amount of Si element to the total amount of Si and Mg elements in the film. In this evaluation, an Al plate substrate was used as a substrate that does not interfere with either Mg or Si in the composition measurement, and each optical thin film was deposited on this substrate to ensure that the substrate does not affect the quantification of elements. In addition, a Pt coating was applied to the sample using a sputtering apparatus as a pretreatment to prevent static charge buildup during analysis. For optical thin films 3 and 4, the Si element ratio of each optical thin film was calculated based on the correlation relationship (represented by a calibration curve) obtained from the measured values ​​of optical thin films 1, 2, and C1.

[0136] [Indentation hardness, Young's modulus] For each of the optical thin films 1, 2, and C1, the film hardness (indentation hardness) and Young's modulus were measured using an Elionix nanoindenter. The measurement load was set to 0.1 mN. Measurements were taken at nine specific points on each optical thin film, and the average value of these measurements was calculated and used as the indentation hardness and Young's modulus for each optical thin film. For optical thin films 3 and 4, the indentation hardness and Young's modulus for each optical thin film were calculated based on the correlation (represented by a calibration curve) obtained from the measured values ​​of optical thin films 1, 2, and C1.

[0137] Table 2 shows the evaluation results for optical thin films 1-4 and C1. Figure 8 shows the detection results for various elements in optical thin films 1 and 2.

[0138] [Table 2]

[0139] [Abrasion test] For each of the optical thin films 1 and C1, methanol was impregnated into a wiper (Ozu Sangyo, Dasper® K4), and the optical thin film on the resin lens surface was wiped 10 times back and forth with a load of approximately 200g. After that, the wiped surface was visually observed. For visual inspection, the optical thin film was observed by changing the angle of the illumination light shining on it.

[0140] As a result, while white streaky patterns were observed on optical thin film 1 depending on how the illumination light was applied, these patterns were not observed at all at times, confirming that these patterns were not scratches but rather wiping marks. Thus, no scratches were observed on the surface of optical thin film 1.

[0141] On the other hand, in optical thin film C1, white streaky patterns were observed regardless of how the illumination light was applied, confirming that these patterns were scratches. Thus, scratches were observed in optical thin film C1 due to this test.

[0142] [Measurement of friction coefficient] Measurements were performed on optical thin films 1 and C1 using a surface properties measuring instrument TYPE:14FW manufactured by Shinto Chemical Co., Ltd., under the conditions of a load of 200g, a travel speed of 100mm / sec, and a travel distance of 30mm. A φ10 cylindrical SUS indenter was used as the contactor for the test specimen. The contact portion of the contactor with the test specimen was the flat surface of the cylinder. The static friction coefficient was then determined from the measured values. As a result, the static friction coefficient of optical thin film 1 was 0.74, and the static friction coefficient of optical thin film C1 was 1.38.

[0143] [Discussion (monolayer film)] As shown in Tables 1 and 2, the tensile stress of the film decreased as the flow rate of the organosilicon compound increased. Furthermore, the indentation hardness and Young's modulus decreased as the amount of organosilicon compound in the optical thin film increased. This is presumed to be due to the presence of an organic framework within the film.

[0144] Based on the results described above, it is believed that by using the MO-containing layer in the present invention in a multilayer film, it is possible to suppress the tensile stress of the entire film stress and control it to the compressive side, thereby enabling the production of an anti-reflective film that is low reflectivity and less prone to cracking at high temperatures.

[0145] Furthermore, according to the friction coefficient measurement results described above, the MO-mixed layer in the present invention exhibits a lower static friction coefficient compared to conventional MgF2 films, indicating a surface that is less prone to wear than ordinary MgF2 films. This is thought to be because the inclusion of an organic skeleton in the film reduces the brittleness characteristic of MgF2 films, while still exhibiting the strength characteristic of MgF2 films. Therefore, it is clear that adopting the MO-mixed layer in the present invention as the surface layer in a multilayer film is expected to improve the wear resistance of the multilayer film.

[0146] Next, an example of a multilayer film containing an MO mixed layer in the present invention is shown.

[0147] [Example 5] The optical thin film 5 has eight layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of silicon dioxide is formed as the second layer on the first layer by PVD deposition of silicon dioxide. Next, a layer of titanium dioxide is formed as the third layer on the second layer by PVD deposition of titanium dioxide. Then, the formation of the silicon dioxide PVD layer and the titanium dioxide PVD layer is repeated two more times to form the fourth to seventh layers. Next, a mixed layer of magnesium fluoride and organic SiO2 is formed as the eighth layer on the seventh layer with a siloxane gas flow rate of 30 sccm.

[0148] [Example 6] The optical thin film 6 has eight layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of silicon dioxide is formed on the first layer as the second layer by PVD deposition of silicon dioxide. Next, a mixed DO layer of titanium dioxide and organic SiO2 is formed on the second layer as the third layer. Then, the formation of the silicon dioxide PVD layer and the mixed DO layer of titanium dioxide and organic SiO2 is repeated two more times to form the fourth to seventh layers. Next, a mixed MO layer of magnesium fluoride and organic SiO2 is formed on the seventh layer as the eighth layer with a siloxane gas flow rate of 10 sccm.

[0149] [Example 7] The optical thin film 7 has twelve layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, layers of silicon dioxide and titanium dioxide are fabricated five times by PVD deposition, producing layers from the second to the eleventh layer. Then, with a siloxane gas flow rate of 30 sccm, a mixed layer of magnesium fluoride and organic SiO2 is fabricated on the eleventh layer as the twelfth layer.

[0150] [Example 8] The optical thin film 8 has twelve layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, the fabrication of a layer of silicon dioxide by PVD and a mixed layer of titanium dioxide and organic SiO2 is repeated five times to produce layers from the second to the eleventh layer. Then, with a siloxane gas flow rate of 30 sccm, a mixed layer of magnesium fluoride and organic SiO2 is fabricated on the eleventh layer as the twelfth layer.

[0151] [Example 9] The optical thin film 9 has six layers and is manufactured as follows. First, the first to fourth layers are fabricated on the substrate by repeating the process of fabricating a silicon dioxide PVD layer and a mixed DO layer of titanium dioxide and organic SiO2 twice. Next, a mixed MO layer of magnesium fluoride and organic SiO2 is fabricated as the fifth layer on the fourth layer with a siloxane gas flow rate of 10 sccm. Then, a silicon dioxide PVD layer is fabricated as the sixth layer on the fifth layer.

[0152] [Example 10] The optical thin film 10 has six layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of a mixed compound of silicon dioxide and aluminum oxide is formed as the second layer on the first layer by PVD deposition. Next, a mixed DO layer of titanium dioxide and organic SiO2 is formed as the third layer on the second layer. Next, the formation of the PVD layer of the mixed compound of silicon dioxide and aluminum oxide and the mixed DO layer of titanium dioxide and organic SiO2 is repeated once more to form the fourth and fifth layers. Next, a mixed MO layer of magnesium fluoride and organic SiO2 is formed as the sixth layer on the fifth layer with a siloxane gas flow rate of 30 sccm.

[0153] [Example 11] The optical thin film 11 has eight layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of a mixed compound of silicon dioxide and aluminum oxide is formed as the second layer on the first layer by PVD deposition. Next, a layer of a mixed compound of titanium dioxide and niobium oxide is formed as the third layer on the second layer by PVD deposition. Then, the formation of the layers of the mixed compound of silicon dioxide and aluminum oxide and the mixed compound of titanium dioxide and niobium oxide by PVD deposition is repeated two more times to form the fourth to seventh layers. Next, a mixed layer of magnesium fluoride and organic SiO2 is formed as the eighth layer on the seventh layer with a siloxane gas flow rate of 10 sccm.

[0154] [Example 12] The optical thin film 12 has seven layers and is manufactured as follows: Layers of silicon dioxide and aluminum oxide mixed compound and layers of titanium dioxide mixed compound are fabricated three times, creating the first to sixth layers on the substrate. Then, with a siloxane gas flow rate of 10 sccm, a mixed MO layer of magnesium fluoride and organic SiO2 is fabricated as the seventh layer on the sixth layer.

[0155] [Example 13] The optical thin film 13 has eight layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of silicon dioxide is formed on the first layer as the second layer by PVD deposition of silicon dioxide. Next, a mixed DO layer of titanium dioxide and organic SiO2 is formed on the second layer as the third layer. Next, a mixed MO layer of magnesium fluoride and organic SiO2 is formed on the third layer as the fourth layer with a siloxane gas flow rate of 30 sccm. Next, the formation of the mixed DO layer of titanium dioxide and organic SiO2 and the above mixed MO layer of magnesium fluoride and organic SiO2 is repeated two more times to produce the fifth to eighth layers.

[0156] [Example 14] The optical thin film 14 has ten layers and is manufactured as follows. First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of a mixed compound of silicon dioxide and aluminum oxide is formed as the second layer on the first layer by PVD deposition. Next, a layer of titanium dioxide is formed as the third layer on the second layer by PVD deposition. Then, the formation of layers of the mixed compound of silicon dioxide and aluminum oxide by PVD deposition and the layer of titanium dioxide by PVD deposition is repeated three times to form layers four through ninth on the substrate. Next, a mixed layer of magnesium fluoride and organic SiO2 (MO) is formed as the tenth layer on the ninth layer with a siloxane gas flow rate of 30 sccm.

[0157] [Comparative Example 2] Optical thin film C2 is constructed in the same manner as optical thin film 3 described above, except that the eighth layer is made of magnesium fluoride. Optical thin film C2 is fabricated in the same manner as optical thin film 3 described above, except that the eighth layer is made of magnesium fluoride PVD on top of the seventh layer.

[0158] [Comparative Example 3] The optical thin film C3 has eight layers and is manufactured as follows: First, a layer of organic SiO2 is fabricated on the substrate as the first layer by CVD deposition of siloxane. Next, layers of silicon dioxide and aluminum oxide mixed compound and layers of titanium dioxide PVD are fabricated three times to create the second to seventh layers. Then, a layer of magnesium fluoride PVD is fabricated on the seventh layer as the eighth layer.

[0159] [Comparative Example 4] The optical thin film C4 has eight layers and is manufactured as follows: First, a layer of organic SiO2 is formed on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of silicon dioxide is formed as the second layer on the first layer by PVD deposition of silicon dioxide. Next, a layer of titanium dioxide is formed as the third layer on the second layer by PVD deposition of titanium dioxide. Then, the formation of the silicon dioxide PVD layer and the titanium dioxide PVD layer is repeated two more times to produce the fourth to seventh layers. Next, a layer of silicon dioxide PVD is formed as the eighth layer on the seventh layer.

[0160] Tables 3 to 5 show the layer structure and overall film stress of the multilayer optical thin films 5-14 and C2-C4.

[0161] [Table 3]

[0162] [Table 4]

[0163] [Table 5]

[0164] [Evaluation (Multilayer Film)] [Membrane stress] The total film stress of optical thin films 5-14 and C2-C4 was calculated by summing the film stresses of the single layers of each film. The film stress values ​​of the single layers used in this calculation are shown in Table 6. The film stress values ​​listed in Table 6 are per unit area (1 m²). 2 This is the value of the membrane stress per unit area.

[0165] [Table 6]

[0166] [Spectral reflectance] For each of the optical thin films 5-14 and C2-C4, the spectral reflectance at the center of each surface of the resin lens was measured using an Olympus USPM-RU-W microspectrometer.

[0167] For each optical thin film, the maximum and average reflectance values ​​for light with wavelengths of 450-600 nm were determined, and the acceptable value for the reflectance of light with wavelengths of 450-600 nm was set to less than 0.5%, which is considered acceptable for practical use, and evaluated according to the following criteria. In addition, for each optical thin film, the maximum and average reflectance values ​​for light with wavelengths of 400-850 nm were also determined, and the acceptable value for the reflectance of light with wavelengths of 400-850 nm was set to less than 1.5%, which is considered acceptable for practical use, and evaluated according to the following criteria. ○: Both the maximum and average values ​​are within the acceptable range. △: Either the maximum value or the average value is within the acceptable range. ×: Both the maximum and average values ​​exceed the acceptable limits.

[0168] [Reliability testing] <High-temperature test and high-temperature / high-humidity test> High-temperature tests and high-temperature / high-humidity tests were conducted on optical thin films 5-14 and C2-C4, respectively. The high-temperature test involved leaving each optical thin film in an ESPEC constant-temperature chamber set at 110°C for 500 hours. The high-temperature / high-humidity test involved leaving each optical thin film in a constant-temperature chamber set at 85°C and 85% relative humidity for 500 hours. After each test, the surface of the optical thin films was observed with an optical microscope and evaluated according to the following criteria. ○: No wrinkles or cracks are observed on the surface. ×: Wrinkles or cracks are observed on the surface.

[0169] <Abrasion Test> For each of the optical thin films 5-14 and C2-C4, methanol was impregnated into a wiper (Ozu Sangyo, Dasper K4), and the optical thin film on the resin lens surface was wiped 10 times back and forth with a load of approximately 200g. After that, the wiped surface was visually observed and evaluated according to the following criteria. ◎: No changes are observed on the surface, including scratches. ○: No scratches were observed on the surface, so there are no practical problems.

[0170] Table 7 shows the results of the film stress, spectral reflectance, high-temperature test, high-temperature high-humidity test, and abrasion test for optical thin films 5-14 and C2-C4, respectively. Tables 8-20 show the layer structure, film thickness of each layer, and overall film stress for optical thin films 5-14 and C2-C4, respectively. Figures 9-21 show graphs of the reflectance of light at wavelengths of 350-750 nm for optical thin films 5-14 and C2-C4, respectively.

[0171] [Table 7]

[0172] [Table 8]

[0173] [Table 9]

[0174] [Table 10]

[0175] [Table 11]

[0176] [Table 12]

[0177] [Table 13]

[0178] [Table 14]

[0179] [Table 15]

[0180] [Table 16]

[0181] [Table 17]

[0182] [Table 18]

[0183] [Table 19]

[0184] [Table 20]

[0185] [Consideration (multilayer film)] As is clear from the above explanation, optical thin films 5-14 offer a high degree of design flexibility. Therefore, it is clear that the optical thin films of the multilayer film of the present invention can be configured into various multilayer films with various layer configurations by changing the number of layers and the film material used.

[0186] Furthermore, no cracks or wrinkles occurred in optical thin films 5-14 in either the high-temperature test or the high-temperature, high-humidity test. Optical thin films 5-13 all exhibited low reflectivity of less than 0.5% at wavelengths of 450-600 nm. In particular, optical thin films 5, 6, 9, and 11-13 exhibited low reflectivity with an average value of less than 1.5% at wavelengths of 400-850 nm. In addition, optical thin film 14 exhibited low reflectivity, with both the maximum value and average value below 1.5% at wavelengths of 450-600 nm, although its maximum value exceeded 0.5% at wavelengths of 400-850 nm.

[0187] The results above demonstrate that by using a MgF2 film fabricated by PVD+CVD mixed deposition as a multilayer film, it is possible to create a plastic lens coating that is low-reflectivity and has high-temperature reliability.

[0188] On the other hand, cracks occurred in optical thin films C2 and C3 during high-temperature testing. Based on these results, it can be inferred that the crack initiation threshold is between 70 MPa in compressive stress and 150 MPa in tensile stress (-70 to 150 MPa). Furthermore, based on the above results, it is thought that in optical thin films 5 to 14, which are embodiments of the present invention, the MgF2 layer is replaced with a mixed film of MgF2 and organosilicon compounds (MO), which increases the compressive stress of the entire multilayer film and leads to crack suppression. Moreover, the film stress of the multilayer film in the embodiments of the present invention can be adjusted to the desired film stress by changing the mixing ratio of the precursor gas.

[0189] Furthermore, in the optical thin film C4, the maximum spectral reflectance exceeds the allowable value in both the 450-600 nm and 400-850 nm wavelength ranges. This demonstrates that improving reliability in conventional optical thin films reduces anti-reflective performance (there is a trade-off between reliability and anti-reflective performance). [Industrial applicability]

[0190] This invention is expected to have potential applications in all technical fields involving coating substrates that expand and contract relatively large with heat with thin films that expand and contract relatively little with heat, and is also expected to contribute to the further development of this technical field. [Explanation of Symbols]

[0191] 10 Base material 11 MO mixed layer 12 Low refractive index layer 13 High refractive index layer 14. Contact layer 21 Optical thin film 200, 300, 400, 500, 600 manufacturing equipment 210, 610 chambers 220 Evaporation Dome 230 Vapor deposition source 240 First Gas Inlet 250 Plasma Gun 260 Second gas inlet 350 Ion Gun 450 High frequency power supply 530 Sputtering source 620 stages 650 Plasma Radical Sources

Claims

1. An optical thin film containing one or more MO-mixed layers in which organometallic compounds are mixed within a layer formed by the physical deposition of magnesium fluoride.

2. The optical thin film according to claim 1, which is a multilayer film comprising two or more dielectric layers having different refractive indices, and which includes the MO mixed layer as at least one of the dielectric layers.

3. The optical thin film according to claim 2, wherein the dielectric layer is a layer of oxide, oxynitride, or nitride of a dielectric material comprising one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce, formed by physical vapor deposition of the dielectric material.

4. The optical thin film according to claim 2, wherein the dielectric layer includes a DO mixed layer in which an organometallic compound is mixed within a layer of oxide, oxynitride, or nitride of the dielectric material, which is a dielectric material containing one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce, formed by physical vapor deposition of the dielectric material.

5. The optical thin film according to claim 1, wherein the organometallic compound is an organic compound containing one or more elements selected from the group consisting of Si, Al, Ti, Hf, and Mg.

6. The optical thin film according to claim 1, comprising the MO mixed layer as the optical outermost layer.

7. The optical thin film according to claim 1, having a film stress of +200 to -1000 MPa when the tensile stress is positive and the compressive stress is negative.

8. The optical thin film according to claim 1, wherein the reflectance of light with a wavelength of 450 to 600 nm is 0.5% or less, or the reflectance of light with a wavelength of 400 to 850 nm is 1.5% or less.

9. An optical element comprising a substrate and an optical thin film according to any one of claims 1 to 8 supported thereon.

10. The optical element according to claim 9, further comprising an adhesion layer interposed between the substrate and the optical thin film.

11. The optical element according to claim 9, further comprising a protective film with a thickness of 50 nm or less on the surface of the optical thin film.

12. The optical element according to claim 9, wherein the substrate is made of plastic resin.

13. An optical device having the optical element described in claim 9.

14. The process includes generating a layer of dielectric material on a substrate by physical deposition in an atmosphere containing an organometallic compound and a reactive gas, thereby forming a mixed layer in which the organometallic compound is mixed within the layer of oxide, oxynitride, or nitride of the dielectric material. A method for manufacturing an optical thin film, wherein the step of forming the mixed layer includes a step of using magnesium fluoride as the dielectric material to form an MO mixed layer in which the organometallic compound is mixed within a layer formed by physical deposition of magnesium fluoride.

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