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

Abstract

To provide an optical thin film in which crack formation is suppressed regardless of the material. [Solution] The optical thin film includes a layer structure formed by physical deposition of a dielectric material, and also includes one or more mixed layers in which one or more compounds consisting of an organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed.

Description

[Technical Field]

[0001] The present invention relates to an optical thin film, a method for manufacturing the same, an optical element having the optical thin film, and an optical device having the optical element. [Background technology]

[0002] In recent years, with the demand for lighter and more cost-effective lenses for automotive applications and other applications, there has been research into replacing glass lenses with resin lenses. However, when optical multilayer coatings such as anti-reflective coatings and IR-cut filters, which were conventionally applied to glass lenses, are applied to resin lenses, the difference in thermal expansion between the substrate and the optical thin film, such as the anti-reflective coating, can easily cause cracks or film delamination (observed as wrinkles, for example) in high-temperature environments.

[0003] Techniques for suppressing crack formation in optical thin films covering such resin lenses include a multilayer film consisting of a layer formed using a high refractive index dielectric material and a layer formed using a low refractive index dielectric material, in which the range of compressive stress or Young's modulus of each layer is defined (see, for example, Patent Document 1). Furthermore, techniques for defining the total thickness and stress range of the multilayer film are known (see, for example, Patent Document 2). In addition, techniques for manufacturing a multilayer film with adjusted stress by defining the vacuum level and materials during film formation are known (see, for example, Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-21893 [Patent Document 2] Japanese Patent Publication No. 2019-66600 [Patent Document 3] Japanese Patent Publication No. 2006-251760 [Overview of the project] [Problems that the invention aims to solve]

[0005] The materials used for the layers constituting multilayer optical thin films typically include high refractive index dielectric materials such as TiO2 or Ta2O5. Additionally, MgF2 is sometimes used as the surface layer material for anti-reflective films to reduce reflectivity. In such cases, the design of the optical thin film involves determining the film thickness to the sub-nanometer order using this material combination to obtain the desired spectral characteristics.

[0006] However, layers formed using TiO2, Ta2O5, or MgF2 exhibit tensile stress. Thus, the physical properties of the film are largely determined by the material.

[0007] Therefore, simply adjusting the deposition conditions or film thickness makes it difficult to adjust the properties of a multilayer film to differ significantly from the intrinsic properties of the material. In other words, if a material useful for obtaining the desired optical properties has high tensile stress, such as MgF2, even if the deposition conditions or film thickness are adjusted to obtain compressive stress in the multilayer film, it is difficult to satisfy the desired optical properties. Consequently, the use of such useful materials may be rejected from a stress perspective, or the design flexibility of the film thickness may be lost.

[0008] Recently, methods involving sintering and mixing materials to control their physical properties have been considered. However, this method makes it extremely difficult to uniformly mix materials, and there are limitations on the amount that can be mixed. Furthermore, it has drawbacks such as difficulty in forming films by vapor deposition due to the use of materials with different boiling points, or changes in refractive index during film formation.

[0009] Thus, the conventional techniques described above still have challenges in suppressing the occurrence of cracks in optical thin films, regardless of the material.

[0010] One aspect of the present invention aims to provide an optical thin film in which crack formation is suppressed regardless of the material. [Means for solving the problem]

[0011] To solve the above problems, an optical thin film according to one aspect of the present invention includes a layer structure formed by physical vapor deposition (hereinafter also referred to as "PVD") of a dielectric material, and includes one or more mixed layers in which one or more compounds consisting of an organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed.

[0012] Furthermore, in order to solve the above problems, an optical element according to one aspect of the present invention comprises a substrate and the optical thin film formed on the surface of the substrate.

[0013] 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.

[0014] Furthermore, 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 synchronously performing PVD of a dielectric material and chemical vapor deposition (hereinafter also referred to as "CVD") of the organometallic compound in an atmosphere containing an organometallic compound gas and a reactive gas, thereby forming a mixed layer on a substrate in which one or more compounds consisting of the organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed within the PVD layer of the dielectric material. [Effects of the Invention]

[0015] According to one aspect of the present invention, it is possible to provide an optical thin film in which crack formation is suppressed regardless of the material. [Brief explanation of the drawing]

[0016] [Figure 1] This diagram schematically shows the configuration of an optical thin film relating to one embodiment of the present invention. [Figure 2] This figure schematically shows the configuration of the first example of an optical thin film manufacturing apparatus according to one embodiment of the present invention. [Figure 3] This diagram schematically shows the configuration of a second example of an optical thin film manufacturing apparatus according to one embodiment of the present invention. [Figure 4]It is a diagram schematically showing a configuration of a third 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 a configuration of a fourth 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 a configuration of a fifth example in an apparatus for manufacturing an optical thin film according to an embodiment of the present invention. [Figure 7] It is a diagram showing a graph of the elemental ratios of optical thin film 1 and optical thin film 2 in an example of the present invention. [Figure 8] It is a diagram showing a graph of the spectral reflectance (calculated value) of optical thin film 3 at wavelengths of 400 to 700 nm in Example 3 of the present invention. [Figure 9] It is a diagram showing a graph of the spectral reflectance (calculated value) of optical thin film 4 at wavelengths of 400 to 700 nm in Example 4 of the present invention. [Figure 10] It is a diagram showing a graph of the spectral reflectance (calculated value) of optical thin film 5 at wavelengths of 400 to 700 nm in Example 5 of the present invention. [Figure 11] It is a diagram showing a graph of the spectral reflectance (calculated value) of optical thin film 6 at wavelengths of 400 to 700 nm in Example 6 of the present invention. [Figure 12] It is a diagram showing a graph of the spectral reflectance (calculated value) of optical thin film C3 at wavelengths of 400 to 700 nm in Comparative Example 3 of the present invention. [Figure 13] It is a diagram showing a graph of the spectral reflectance (calculated value and measured value) of optical thin film 3 at wavelengths of 400 to 700 nm in Example 3 of the present invention.

Mode for Carrying Out the Invention

[0017] The present invention relates to an optical thin film suitable for an antireflection film for plastic lenses in a market where high environmental resistance is required, such as in-vehicle lenses or lenses for surveillance cameras. The optical thin film is suitable for obtaining an antireflection film having compressive stress. Hereinafter, an embodiment of the present invention will be described in detail.

[0018] [Optical thin film] An optical thin film according to an embodiment of the present invention includes a layer structure made of a dielectric material by PVD, and also includes one or more mixed layers in which one or more compounds (hereinafter also referred to as "organometallic material compounds") consisting of an organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed. Including a mixed layer in the optical thin film is effective from the viewpoint of suppressing the occurrence of cracks in the optical thin film, regardless of the dielectric material.

[0019] The mixed layer includes a layer formed by PVD of the dielectric material. The structure of this layer is the portion of the mixed layer that has substantially the same structure as the layer formed by PVD of the dielectric material. In this embodiment, the structure of this layer corresponds to the portion of the mixed layer other than the organometallic material compound. For example, if the mixed layer has a sea-island structure of a dielectric material and an organometallic material compound, then one side of the sea-island is the dielectric material and the other side is the organometallic material compound.

[0020] The dielectric material is the material that constructs the above layer structure and can be the main component in the mixed layer. The dielectric material is a material that can form layers, for example by PVD, and more specifically, can be the material that constitutes each layer in a conventional multilayer anti-reflective film. The dielectric material is not particularly limited, but examples include oxides, oxynitrides, fluorides, or nitrides containing one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, Zn, and Ce. More specifically, examples of dielectric materials include TiO2, ZrO2, ZrO2+TiO2, La2O3, La2O3+TiO2, Nb2O5, Hf2O3, Al2O3, SiO2, Pr2O3, SiO x N y It is preferable that it also contains CeO2. The "+" above indicates a mixture or its compound.

[0021] Among the dielectric materials mentioned above, it is preferable that the dielectric material contains Ti and is an oxide, oxynitride, or nitride thereof in order to achieve the anti-reflective properties required by optical properties and physical properties. In a single mixed layer, the dielectric material may be one or more of the materials shown in the example.

[0022] The compounds mixed in the mixed layer, which includes a dielectric material layer, are one or more compounds (organometallic material compounds) consisting of organometallic compounds, their oxidation reaction products, their oxynitrides, and their nitrides. These organometallic material compounds may be minor components constituting the mixed layer, or trace components in the mixed layer. 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 the desired anti-reflective properties of a multilayer anti-reflective film. More specifically, examples of organometallic material compounds include organic SiO2, organic TiO2, organic Al2O3, organic Hf2O3, and organic MgF2. In a single mixed layer, there may be one or more organometallic material compounds.

[0023] The content of organometallic material compounds in the mixed layer can be appropriately determined according to the desired film properties, such as the compressive stress of the optical thin film, and the optical properties, such as reflectance, depending on the application of the optical thin film. The content of dielectric material in the mixed layer is expressed by the amount of metal elements contained in the dielectric material, and the content of organometallic material compounds in the mixed layer is indicated by the content of metal elements contained in the organometallic material compounds. The content of organometallic material compounds in the mixed layer can be, for example, 1 to 90% by mass.

[0024] The optical thin film may consist only of mixed layers, or it may include mixed layers and other layers. For example, the optical thin film may include a configuration (multilayer film) in which a first layer, which includes a PVD layer of a first dielectric material, and a second layer, which includes a PVD layer of a second dielectric material and has a different refractive index than the first layer, are alternately stacked, and at least one of the first and second layers may be a mixed layer. An optical thin film as a single layer of mixed layers is suitable, for example, as a surface protective layer for an optical element. An optical thin film as a multilayer film including mixed layers 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). Both the first dielectric material and the second dielectric material can be selected from the dielectric materials described above.

[0025] The first layer and the second layer may be either a mixed layer or both may be separate mixed layers. If one layer is a mixed layer, the other layer may be a PVD layer of a dielectric material. Thus, 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 a configuration in which mixed layers and PVD layers of a dielectric material are alternately stacked.

[0026] Furthermore, in this embodiment, the optical thin film may include other layers besides the mixed layer described above, to the extent that the effects of the present invention can be obtained. Examples of such other layers include the layer formed by PVD of the dielectric material described above, as well as the layer composed of the organometallic material compound described above. The layer composed of the organometallic material compound can be fabricated, for example, by CVD of the organometallic compound described above.

[0027] Layers composed of such organometallic material compounds exhibit higher adhesion to resin materials compared to PVD-formed dielectric material layers and mixed layers, making them suitable as adhesion layers. Therefore, it is preferable for an optical thin film to have such a layer at one end in the overlapping direction of the first and second layers from the viewpoint of improving the adhesion of the optical thin film to the surface of the resin substrate material.

[0028] Figure 1 schematically shows the structure of an optical thin film according to one embodiment of the present invention. As shown in Figure 1, the optical thin film 1 is formed on a substrate 100. The substrate 100 is a plate-shaped substrate and is a carrier on which the optical thin film 1 is supported on its surface. The substrate 100 is, for example, a resin optical element such as a resin lens.

[0029] The optical thin film 1 is composed of an adhesion layer 11, a mixed layer 12, a high refractive index layer 13, and a surface layer 14. More specifically, the optical thin film 1 is a multilayer film having an adhesion layer 11 and a surface layer 14, and is composed of an adhesion layer 11 formed on a substrate 100, a multilayer film of a mixed layer 12 and a high refractive index layer 13 arranged on the adhesion layer 11, and a surface layer 14 formed on the multilayer film.

[0030] The adhesion layer 11 is a layer composed of, for example, an organometallic material compound. When the substrate 100 is made of resin, the adhesion layer 11 has good adhesion to both the substrate 100 and the mixed layer 12 or the high refractive index layer 13. Furthermore, the adhesion layer 11 has compressive stress depending on the type of organometallic material compound.

[0031] The multilayer film is composed of alternating layers of mixed layers 12 and high refractive index layers 13. The mixed layers 12 are composed of a PVD layer of a first dielectric material, such as SiO2, which exhibits a relatively low refractive index, with an organometallic material compound, such as an oxide of an organosilicon compound, mixed within it. The mixed layers 12 are low refractive index layers that exhibit a lower refractive index than the high refractive index layers 13, and also have compressive stress mainly corresponding to the type of first dielectric material, the type of organometallic material compound, and their respective ratios.

[0032] The high refractive index layer 13 is a layer formed by PVD deposition of a second dielectric material such as TiO2, which has a higher refractive index than the first dielectric material. The high refractive index layer 13 has tensile stress mainly depending on the type of second dielectric material.

[0033] In this specification, the first dielectric material may be any dielectric material having a lower refractive index than the second dielectric material constituting the high refractive index layer 13. The first dielectric material includes dielectric materials generally called low refractive index dielectric materials, as well as substances such as Al2O3, which are generally called intermediate refractive index dielectric materials.

[0034] The surface layer 14 is a layer formed by PVD deposition of a dielectric material other than the first dielectric material and the second dielectric material in the above-described laminated structure, for example, MgF2.

[0035] Furthermore, the mixed layer 12 has higher adhesion to the resin substrate 100 compared to the high refractive index layer 13. Therefore, the mixed layer 12 may be formed directly on the substrate 100 instead of the adhesion layer 11. Such a configuration is also preferable from the viewpoint of achieving sufficiently high adhesion to the substrate 100 in the optical thin film of this embodiment.

[0036] Alternatively, the first dielectric material layer may be a PVD-deposited layer, while the second dielectric material layer, which has a higher refractive power, may be a mixed layer (including the mixing of organometallic material compounds). With such a configuration, the entire optical thin film can have compressive stress, and it is possible to obtain the desired optical constants.

[0037] In this embodiment, the mixed layer contains an organometallic material compound within a PVD-coated dielectric material layer. While PVD-coated dielectric material layers generally exhibit tensile stress, the mixed layer as a whole can exhibit compressive stress. This is thought to be due to the presence of the organometallic material compound. Therefore, not only optical thin films consisting solely of the mixed layer, but also optical thin films containing the mixed layer within a multilayer film can exhibit compressive stress as a whole.

[0038] If the compressive stress of an optical thin film is too low, the tensile stress from the PVD-deposited layer of the dielectric material becomes stronger, which can cause cracks to form due to the thermal expansion of the substrate. Conversely, if the compressive stress of the optical thin film is too high, the force that peels the optical thin film away from the substrate becomes stronger due to thermal contraction, which can cause the optical thin film to delaminate. The compressive stress of an optical thin film can be appropriately determined depending on the physical properties of the substrate or the application of the optical thin film.

[0039] For example, if an optical thin film is placed on a resin substrate and the optical thin film is used in a temperature environment of 110°C (e.g., in resin automotive lenses), the compressive stress of the optical thin film is preferably 100 MPa or more, more preferably 150 MPa or more, and even more preferably 200 MPa or more, from the viewpoint of preventing cracks due to thermal expansion. Furthermore, in the above case, the compressive stress of the optical thin film is preferably 1000 MPa or less, more preferably 700 MPa or less, and even more preferably 500 MPa or less, from the viewpoint of preventing film delamination. By adjusting the compressive stress to such an appropriate range, it is possible to prevent cracks or film delamination of the optical thin film at high temperatures.

[0040] The mechanisms by which defects occur in optical thin films include cracks or film delamination as described above, but film delamination also depends on the balance between the stress of each layer in the optical thin film and the adhesion force between the film and the substrate. It is preferable to appropriately determine the compressive stress of the optical thin film by further considering such mechanisms or balances from the viewpoint of preventing the above-mentioned defects in optical thin films. The above numerical range for the compressive stress of the optical thin film is a typical range for preventing defects in optical thin films, and it is possible to prevent the aforementioned defects in optical thin films even outside the above range by appropriately setting various conditions in the optical thin film (such as the type of substrate or film formation conditions).

[0041] The compressive stress of an optical thin film can be adjusted by the number of mixed layers in the optical thin film or by the amount of organometallic material compound in the mixed layers. A larger number of mixed layers in an optical thin film increases its compressive stress. Furthermore, a larger amount of organometallic material compound in the mixed layers increases the compressive stress of the mixed layers, and consequently, the compressive stress of the optical thin film can be increased.

[0042] Furthermore, multilayer optical thin films function as anti-reflective coatings by adjusting their film thickness, and the reflectivity of the optical thin film is appropriately determined according to its intended use as an anti-reflective coating. Generally, when attempting to design with the same thin film material and the same number of layers, the broader the desired anti-reflective wavelength band, the higher the reflectivity tends to be. For example, for visible light lenses used for viewing, it is preferable that the reflectivity of the optical thin film for light with wavelengths of 400 to 700 nm be 1% or less, while for sensing applications such as surveillance lenses and automotive lenses, which include observation of near-infrared light, it is preferable that the reflectivity of the optical thin film for light with wavelengths of 400 to 950 nm be 2% or less.

[0043] Conventional techniques have attempted to prevent cracks in optical thin films by enhancing the influence of layers with compressive stress. For example, in multilayer optical thin films, there is a technique to achieve the desired compressive stress by increasing the thickness of the PVD layer made of a low-refractive index material that has compressive stress. However, with such conventional techniques, the reflectivity of the optical thin film can become too high, making it impossible to achieve the desired optical properties.

[0044] In contrast, in this embodiment, as shown in the examples described later, it is possible to generate the desired compressive stress within a range that achieves the desired optical properties.

[0045] [Method for manufacturing optical thin films] The optical thin film according to this embodiment can be manufactured by the following method. Specifically, the method for manufacturing the optical thin film according to this embodiment includes a step of generating a dielectric material layer on the surface of a substrate by PVD of the dielectric material, and a step of generating an organometallic compound film on the surface of a substrate using CVD, in which an organometallic compound gas (precursor gas) or reactive gas is introduced and reacted in sync with the step of generating a dielectric material layer on the surface of a substrate, and preferably the optical thin film is obtained by depositing the mixed layer thus generated.

[0046] Thus, in this embodiment, the aforementioned mixed layer can be fabricated by synchronizing the PVD film deposition process using the aforementioned dielectric material with the CVD of the aforementioned organometallic compound. The organometallic compound is mixed into the mixed layer by CVD of the organometallic compound under the PVD film deposition conditions for the dielectric material.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The substrate is an optical component that is coated with the optical thin film in the method for manufacturing 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.

[0052] 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.

[0053] The conditions for the film formation process by PVD can be appropriately determined according to the material of the layer or the substrate, etc. For example, when a layer of MgF2 is produced by PVD, from the viewpoint of enhancing the scratch resistance of the layer, the film formation temperature on a substrate such as high-temperature-resistant glass is preferably 200 °C or higher. Further, for example, when a mixed layer is produced 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.

[0054] [Manufacturing equipment] The manufacturing method employs equipment capable of performing both PVD (photovoltaic deposition) of dielectric materials and CVD (chemical vapor deposition) of organometallic compounds. A schematic example of the configuration of the manufacturing equipment used in this method is shown in Figure 2.

[0055] <First example of manufacturing equipment> As shown in Figure 2, the manufacturing apparatus 20 is equipped with a deposition dome 22 at the top of the chamber 21. A deposition source 23 and a plasma gun 25 are positioned opposite the deposition dome 22 within the chamber 21. The chamber 21 also has a first gas inlet 24 for supplying reactive gas to the space between the deposition dome 22 and the deposition source 23 and plasma gun 25, and a second gas inlet 26 for supplying precursor gas.

[0056] Chamber 21 is configured to be depressurized. Evaporation dome 22 is configured to accommodate multiple substrates, which will be described later. Evaporation source 23 includes, for example, a crucible and an electron gun that irradiates the crucible with an electron beam. Plasma gun 25 is a plasma source in which the plasma strength can be varied by changing parameters such as discharge voltage. First gas inlet 24 is connected to a source of reactive gases such as oxygen (e.g., a cylinder) and is configured to supply these gases into chamber 21 at a desired flow rate. Second gas inlet 26 is connected to a source of precursor gas (e.g., a cylinder) and is configured to supply this gas into chamber 21 at a desired flow rate.

[0057] Thus, the manufacturing apparatus 20 is equipped with a PVD film deposition mechanism by vacuum deposition, and further includes a precursor gas supply mechanism. Such a manufacturing apparatus 20 can be constructed, for example, by adding a precursor gas supply device to an existing PVD film deposition apparatus.

[0058] In the manufacturing of optical thin films, a substrate such as a resin lens is placed in the deposition dome 22. Then, a dielectric material such as titanium oxide is filled into the crucible of the deposition source 23. In addition, a supply source for reactive gas and inert gas for discharge is connected to the first gas inlet 24, and a cylinder of precursor gas is connected to the second gas inlet 26.

[0059] A precursor gas is supplied into the chamber 21 from the second gas inlet 26, and a reactive gas and an inert gas for discharge, such as argon gas, are supplied from the first gas inlet 24. The chamber 21 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 21. Next, an electron beam is irradiated from the electron gun onto the crucible of the deposition source 23. At the same time, for example, argon plasma is released into the chamber 21 from the plasma gun 25.

[0060] The dielectric material in the crucible is deposited on the surface of the substrate inside the deposition dome 22 by plasma-assisted vacuum deposition, forming a layer. Meanwhile, the precursor gas supplied into the chamber 21 from the second gas inlet 26 reacts with the reactive gas from the first gas inlet 24 in the presence of argon plasma from the plasma gun 25, and is deposited on the surface of the substrate inside the deposition dome 22. In this way, a mixed layer is created on the substrate in which reactants of organometallic compounds are mixed in with the PVD layer of dielectric material.

[0061] When the operation of the deposition source 23 is stopped, only the reactants of the organometallic compound are deposited on the substrate, creating the aforementioned adhesion layer. When the supply of precursor gas from the second gas inlet 26 is stopped, only the film derived from the dielectric material of the PVD is deposited on the substrate, creating the aforementioned high refractive index layer or low refractive index layer. By appropriately controlling the operation of the manufacturing apparatus 20 in this way, the aforementioned adhesion layer and multilayer film can be formed on the surface of the substrate.

[0062] 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.

[0063] 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 mixed layer and the high refractive index layer that has tensile stress, the optical thin film of this embodiment can have compressive stress as a whole.

[0064] 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.

[0065] This makes it possible to obtain a multilayer optical thin film that has equivalent reflectivity to conventional multilayer films of high refractive index layers 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, even when MgF2, which has high tensile stress and is prone to cracking, is used in the optical thin film for plastic lenses, a highly durable (crack-free) optical thin film can be obtained.

[0066] <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, the same reference numerals will be used for components having the same function as those described in the previously mentioned examples, and their descriptions will not be repeated.

[0067] Figure 3 schematically shows the configuration of a second example of the optical thin film manufacturing apparatus of this embodiment. As shown in Figure 3, the manufacturing apparatus 30 has the same configuration as the manufacturing apparatus 20 described above, except that it has an ion gun 35 instead of a plasma gun 25.

[0068] The ion gun 35 injects, for example, cations derived from argon gas toward the substrate in the deposition dome 22. The dielectric material in the crucible is deposited on the surface of the substrate inside the deposition dome 22 by ion-assisted vacuum deposition, forming a layer. The precursor gas supplied into the chamber 21 from the second gas inlet 26 reacts with the reactive gas from the first gas inlet 24 in the presence of ions from the ion gun 35, and is deposited on the surface of the substrate inside the deposition dome 22.

[0069] The manufacturing apparatus 30 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 20 described above. The manufacturing apparatus 30 is advantageous in terms of increasing the density of the produced layer.

[0070] <Third example of manufacturing equipment> Figure 4 schematically shows the configuration of a third example of the optical thin film manufacturing apparatus according to this embodiment. As shown in Figure 4, the manufacturing apparatus 40 has the same configuration as the manufacturing apparatus 20 described above, except that it has a high-frequency power supply 45 instead of a plasma gun 25.

[0071] The high-frequency power supply 45 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 21 from the second gas inlet 26 reacts with the reactive gas from the first gas inlet 24 in the presence of plasma caused by the voltage applied to the substrate by the high-frequency power supply 45, and deposits on the surface of the substrate within the deposition dome 22.

[0072] The manufacturing apparatus 40 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 20 described above. The manufacturing apparatus 40 is advantageous in terms of improving the adhesion of the produced layer to the substrate.

[0073] <Fourth example of manufacturing equipment> Figure 5 schematically shows the configuration of a fourth example of the optical thin film manufacturing apparatus according to this embodiment. As shown in Figure 5, the manufacturing apparatus 50 has the same configuration as the manufacturing apparatus 20 described above, except that it has a sputtering source 53 instead of an evaporation source 23.

[0074] The sputtering source 53 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 25, 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.

[0075] The manufacturing apparatus 50 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 20 described above. The manufacturing apparatus 50 is advantageous in terms of increasing the adhesion of the produced layer to the substrate.

[0076] <Fifth example of manufacturing equipment> Figure 6 schematically shows the configuration of a fifth example of the optical thin film manufacturing apparatus according to this embodiment. The manufacturing apparatus 60 includes a chamber 61, a stage 62, a sputtering source 53, a first gas inlet 24, a plasma radical source 65, and a second gas inlet 26.

[0077] Chamber 61 has a first chamber where a sputtering source 53 is located and a second chamber where a plasma radical source 65 is located. The first and second chambers are in communication with each other. Stage 62 is a component that holds a substrate on its surface. Stage 62 is positioned across the first and second chambers and is located within Chamber 61 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 65 generates, for example, argon plasma and also generates radicals of reactive gases.

[0078] When the substrate on stage 62 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 62 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 the plasma.

[0079] The manufacturing apparatus 60 can produce the mixed layer of this embodiment in the same way as the manufacturing apparatus 20 described above. The manufacturing apparatus 60 is advantageous in terms of forming a thinner layer.

[0080] <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.

[0081] 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.

[0082] Furthermore, the high-frequency power supply 45 of the manufacturing apparatus 40 may be other power sources 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 sources.

[0083] [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.

[0084] The substrate material is typically a light-transmitting material, including 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 achieving a more pronounced effect in preventing cracks due to thermal deformation, it is preferable and more beneficial in this embodiment for the substrate to be made of plastic resin.

[0085] 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, cyclic polyolefin 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.

[0086] 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.

[0087] [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.

[0088] 〔summary〕 Generally, the coefficient of thermal expansion of plastic resins is about 10 times that of inorganic thin films. Therefore, at high or low temperatures, the inorganic layer may fail to keep up with the expansion or contraction of the plastic resin substrate, leading to defects in appearance.

[0089] Furthermore, the effect of heat on substrate deformation differs depending on the material of the inorganic layer. Even among inorganic layers made by PVD, a layer made of SiO2 PVD has strong compressive stress and is more responsive to deformation in the expansion direction due to high temperatures. In contrast, a layer made of MgF2 PVD has strong tensile stress. Therefore, if a layer made of MgF2 PVD is used in an optical thin film, the substrate expands in the opposite direction to the force applied to the thin film, which can significantly reduce the crack resistance of the optical thin film. For example, this tendency becomes even more pronounced when a MgF2 layer is used instead of an SiO2 layer.

[0090] In contrast, the present invention includes the aforementioned mixed layer in the optical thin film, as described above. Such a configuration can be achieved by performing CVD film deposition of organometallic compounds in substantially synchronization with conventional PVD such as vapor deposition. Furthermore, according to the present invention, it is possible to change the stress in the layer of dielectric material exhibiting a high refractive index (such as TiO2, Nb2O5, and Ta2O5) from tensile stress to compressive stress. As a result, even when an optical thin film is deposited on a plastic resin substrate, it is possible to suppress the occurrence of cracks in high-temperature tests (95°C or higher), and optical thin films, optical elements, and optical devices with high reliability against temperature changes can be provided.

[0091] As is clear from the above description, the first aspect of the present invention is an optical thin film comprising a PVD layer of a dielectric material, and one or more mixed layers in which one or more compounds consisting of an organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed. According to the first aspect, it is possible to provide an optical thin film in which crack generation is suppressed regardless of the material.

[0092] A second aspect of the present invention includes, in the first aspect, a configuration in which a first layer comprising a PVD layer of a first dielectric material and a second layer comprising a PVD layer of a second dielectric material having a different refractive index from the first layer are alternately stacked, and at least one of the first layer and the second layer is a mixed layer. The second aspect is even more effective from the viewpoint of improving the anti-reflective properties of the optical thin film.

[0093] A third aspect of the present invention, in the second aspect, further comprises a layer at one end in the overlapping direction of the first and second layers, composed of one or more compounds consisting of an organometallic compound, its oxidation reaction product, its oxynitride, and its nitride. The third aspect is even more effective in terms of improving the adhesion of the optical thin film to or to the substrate supporting the optical thin film.

[0094] A fourth aspect of the present invention is that, in any of the first to third aspects, the dielectric material is an oxide, oxynitride, fluoride, or nitride containing one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce. The fourth aspect is even more effective in terms of realizing desired optical properties of an optical thin film, such as anti-reflective properties when used in a multilayer film.

[0095] A fifth aspect of the present invention is, in the fourth aspect, that the dielectric material is an oxide, oxynitride, or nitride containing Ti. The fifth aspect is even more effective in terms of realizing desired optical properties of an optical thin film, such as anti-reflective properties when it is formed as a multilayer film.

[0096] A sixth aspect of the present invention is an organic compound in which, in any of the first to fifth aspects, the organometallic compound contains one or more elements selected from the group consisting of Si, Al, Ti, Hf, and Mg. The sixth aspect is even more effective in terms of realizing desired optical properties of an optical thin film, such as anti-reflective properties when formed as a multilayer film.

[0097] A seventh aspect of the present invention is that, in any of the first to sixth aspects, the compressive stress of the optical thin film is 100 to 1000 MPa. The seventh aspect is even more effective in terms of suppressing the occurrence of cracks due to temperature changes and improving reliability against temperature changes.

[0098] An eighth aspect of the present invention is that, in any of the first to seventh aspects, the reflectance of light with a wavelength of 400 to 700 nm is 1% or less, or the reflectance of light with a wavelength of 400 to 950 nm is 2% 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.

[0099] A ninth aspect of the present invention is an optical element comprising a substrate and an optical thin film formed on the surface of the substrate according to any of the first to eighth aspects. According to the ninth aspect, crack generation is suppressed in the optical thin film regardless of the material, and an optical element with high reliability in a temperature environment can be provided.

[0100] A tenth aspect of the present invention is that, in the ninth aspect, the substrate is made of plastic resin. The tenth aspect is even more effective in terms of further improving the reliability of the optical element in the temperature environment.

[0101] An eleventh aspect of the present invention is an optical device having an optical element according to the ninth or tenth aspect. According to the eleventh aspect, an optical device with high reliability in temperature environments can be provided.

[0102] A twelfth aspect of the present invention is a method for manufacturing an optical thin film, comprising the step of synchronously performing PVD of a dielectric material in an atmosphere containing an organometallic compound precursor gas and a reactive gas, and CVD of the precursor gas, thereby forming a mixed layer on a substrate in which one or more compounds consisting of an organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed within a PVD layer of the dielectric material. According to the twelfth aspect, similar to the first aspect, it is possible to provide an optical thin film in which crack generation is suppressed regardless of the material.

[0103] A thirteenth aspect of the present invention, in the twelfth aspect, involves generating a layer of dielectric material on the surface of a substrate by irradiation with an electron beam from an electron gun, sputtering, or resistance heating, while generating plasma, ions, or heat in an atmosphere. The thirteenth aspect is even more effective in that it allows for appropriate adjustment of the magnitude of compressive stress and anti-reflective properties of the optical thin film.

[0104] A fourteenth aspect of the present invention is, in the thirteenth aspect, a plasma, ions, or heat is generated in an atmosphere to react the precursor gas and the reactive gas. The fourteenth aspect is even more effective in terms of stabilizing the composition of the mixed layer and the layer formation process.

[0105] One aspect of the present invention provides an optical thin film with high reliability against temperature changes by applying compressive stress to an existing dielectric material layer formed by PVD without significantly affecting its optical properties. The present invention, which achieves 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."

[0106] 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]

[0107] 〔overview〕 The following are embodiments of the present invention. These embodiments mainly concern anti-reflective coatings for optical elements intended for use in high-temperature environments such as automotive applications, and optical thin films that can constitute layers within anti-reflective coatings. In the following embodiments and comparative examples, a cycloolefin copolymer resin lens is used as a substrate, and an optical thin film or anti-reflective coating is formed on the substrate.

[0108] In this embodiment, a vacuum deposition apparatus capable of parallel plasma-assisted and CVD is used, as shown in Figure 2. The apparatus is equipped with a plasma gun and is configured to supply argon gas to the chamber as the plasma discharge gas, and is also configured to allow adjustment of the vacuum level. The apparatus is also connected to a supply unit for organometallic compound gas (precursor gas), which is the material gas for CVD. With this apparatus, plasma-assisted vacuum deposition (PVD) can be performed while the precursor gas flows through the chamber. The apparatus is also equipped with a reactive gas supply unit and is configured to supply reactive gases (such as O2 or N2) to the chamber.

[0109] In a vacuum deposition apparatus, dielectric materials are deposited onto a substrate by irradiating the deposition material packed in a crucible with an electron beam. Meanwhile, in a precursor gas supply system, any desired precursor gas can be supplied by appropriately switching between the precursor gas tanks. Furthermore, by supplying reactive gases into the chamber from a reactive gas supply device, it is possible to fabricate any oxide, nitride, or oxynitride layer in organometallic compounds.

[0110] In this embodiment, by introducing an organosilicon compound gas (precursor gas) as the gas of the organometallic compound into the chamber, the precursor gas reacts with the reactive gas to form an organosilicon material compound, which is deposited on the substrate, creating a mixed layer in which the dielectric material layer is doped with the organosilicon material compound. Irradiating the atmosphere inside the chamber with plasma (or ions) accelerates the above reaction. Applying an RF bias to the substrate side is also effective in accelerating the reaction.

[0111] In this example, the following materials are used. Dielectric materials: Titanium oxide (TiO2), silicon oxide (SiO2), aluminum oxide (Al2O3) Organometallic compounds (organosilicon compounds): Siloxane compounds Organometallic material compounds: Organic silicon dioxide (organic SiO2) Magnesium fluoride: MgF2

[0112] [Example 1] Titanium oxide is placed in the crucible of the vacuum deposition apparatus, and the precursor gas supply unit is prepared to supply a siloxane compound gas as the precursor gas. In addition, argon gas for discharge and oxygen gas as a reactive gas are prepared to be supplied to the chamber of the vacuum deposition apparatus.

[0113] The flow rate of siloxane gas was set to 10 sccm, the flow rate of the reactive gas, oxygen gas, to 60 sccm, and the flow rate of argon gas to 16 sccm. The discharge voltage (Vd) of the plasma gun was set to 100 V, and the discharge current (Id) of the plasma gun was set to 20 A. The film deposition rate was set to 4 Å / second, and a layer of titanium dioxide was fabricated by plasma-assisted vacuum deposition, while a mixed layer containing the oxidation reaction product (organic SiO2) of siloxane by CVD was fabricated on the substrate. This is referred to as optical thin film 1.

[0114] [Example 2] A mixed layer of titanium dioxide and silicon dioxide was prepared on a substrate in the same manner as in Example 1, except that the flow rate of siloxane gas was set to 30 sccm. This was designated as optical thin film 2.

[0115] [Comparative Examples 1 and 2] A layer of titanium dioxide was fabricated on a substrate by PVD in the same manner as in Example 1, except that CVD was not performed, i.e., siloxane gas was not supplied. This was designated as optical thin film C1. Furthermore, a layer of siloxane gas was fabricated on a substrate by CVD in the same manner as in Example 1, except that vacuum deposition of titanium dioxide was not performed, i.e., the crucible was not irradiated with an electron beam, and the oxygen gas flow rate was changed to 10 sccm. This was designated as optical thin film C2.

[0116] [Rating 1] [1-1 Composition] The elemental ratios of optical thin film 1 and optical thin film 2 were determined using a scanning electron microscope and an energy-dispersive X-ray spectrometer (SEM-EDX). More specifically, the elemental ratios in the layers were determined using the ZAF method with an acceleration voltage of 5 kV. In addition, the ratio of Si to the total amount of Si and Ti elements in the layers was calculated to determine the proportion of Si in the layers (Si element ratio).

[0117] [1-2 Membrane stress] The film stresses of optical thin film 1, optical thin film 2, optical thin film C1, and optical thin film C2 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 was calculated using stoney's formula below. The meaning of each letter in the formula below is as follows. 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

[0118]

number

[0119] [1-3 Optical properties and film thickness] The spectral reflectance and transmittance of optical thin film 1 and optical thin film 2 were measured using a Hitachi High-Technologies U-4100. From these results, the optical constants of optical thin film 1 and optical thin film 2, namely the refractive index and film thickness at a wavelength of 550 nm, were calculated.

[0120] Table 1 shows the fabrication conditions for optical thin film 1, optical thin film 2, optical thin film C1, and optical thin film C2. Table 2 shows the evaluation results for optical thin film 1, optical thin film 2, optical thin film C1, and optical thin film C2. Furthermore, Figure 7 shows graphs of the elemental ratios obtained by SEM-EDX analysis of optical thin film 1 and optical thin film 2. Note that the Pt element in Figure 7 originates from the Pt coating applied as a pretreatment to the analysis sample to prevent charge buildup during analysis.

[0121] [Table 1]

[0122] [Table 2]

[0123] [Consideration 1] As is clear from Table 2, optical thin film C1, which does not undergo parallel CVD of siloxane, has a tensile stress of approximately 200 MPa. On the other hand, optical thin films 1 and 2, which are mixed layers of titanium oxide and organic SiO2, both have compressive stresses of 200 MPa or more. Thus, optical thin films 1 and 2 have higher compressive stresses compared to optical thin film C1.

[0124] Furthermore, it can be seen that as the flow rate of siloxane gas during film formation increases, the Si element ratio in the formed layer increases, the compressive stress of the layer increases, and the refractive index of the layer decreases.

[0125] [Example 3] A layer of organic SiO2 was fabricated on the substrate as the first layer by CVD deposition of siloxane. Next, a layer of silicon dioxide was fabricated on the first layer as the second layer by PVD deposition of silicon dioxide. Then, a mixed layer of titanium dioxide and organic SiO2 was fabricated on the second layer as the third layer.

[0126] Next, the process of fabricating layers of silicon dioxide using PVD and mixed layers of titanium dioxide and organic SiO2 was repeated two more times to produce layers four through seven. Then, a layer of silicon dioxide using PVD was fabricated as the eighth layer on top of the seventh layer. In this way, an optical thin film 3 consisting of eight layers laminated on a substrate was obtained.

[0127] [Example 4] A six-layer optical thin film 4 was fabricated in the same manner as in Example 3, except that the number of repetitions for fabricating the silicon dioxide PVD layer from the fourth layer onwards and the mixed layer of titanium dioxide and organic SiO2 was changed from two to one.

[0128] [Example 5] A siloxane CVD layer was fabricated on the substrate as the first layer in the same manner as in Example 3. Then, a mixed layer of aluminum oxide and organic SiO2 was fabricated on the first layer as the second layer by performing PVD using aluminum oxide and CVD using siloxane. Next, a titanium oxide PVD layer was fabricated on the second layer as the third layer.

[0129] Next, the fabrication of a mixed layer of aluminum oxide and organic SiO2 and a layer of titanium oxide by PVD was repeated two more times to create layers four through seven. Then, a layer of silicon oxide by PVD was fabricated as the eighth layer on top of the seventh layer. In this way, an optical thin film 5 consisting of eight layers laminated on a substrate was obtained.

[0130] [Example 6] A first layer was fabricated on the substrate in the same manner as in Example 5, and a second layer was fabricated on the first layer. Next, a mixed layer of titanium oxide and organic SiO2 was fabricated on the second layer as the third layer. Then, the fabrication of a mixed layer of aluminum oxide and organic SiO2 and a mixed layer of titanium oxide and organic SiO2 was repeated one more time to fabricate a mixed layer of aluminum oxide and organic SiO2 as the fourth layer, and a mixed layer of titanium oxide and organic SiO2 as the fifth layer. Next, a PVD layer of magnesium fluoride was fabricated on the fifth layer as the sixth layer by performing PVD using magnesium fluoride as the material and without plasma assistance. In this way, an optical thin film 6 consisting of six layers laminated on the substrate was obtained.

[0131] [Comparative Example 3] In Example 3, instead of the mixed layer of titanium dioxide and organic SiO2, a layer of titanium dioxide was fabricated using PVD, thereby creating an eight-layer optical thin film C3 on a substrate with a layered structure of silicon dioxide and titanium dioxide.

[0132] [Rating 2] [2-1 Membrane stress] The film stresses of optical thin films 3-6 and optical thin film C3 were calculated. For optical thin films 3-6 and optical thin film C3, the film stress of each layer from the first to the sixth or eighth layer was converted to a stress relative to the thickness of that layer, and the sum of the stresses of each layer was taken as the film stress of each optical thin film.

[0133] Table 3 shows a list of the materials, layer configurations, and film stresses of each layer in optical thin films 3-6 and optical thin film C3. Table 4 shows the composition and film stress values ​​of each layer. The presence or absence of "Plasma Assist" in Table 4 indicates whether the layers derived from the materials in the table were fabricated under plasma-assisted conditions. Furthermore, Tables 5-9 show the composition and thickness of each layer in optical thin films 3-6 and optical thin film C3, respectively.

[0134] [Table 3]

[0135] [Table 4]

[0136] [Table 5]

[0137] [Table 6]

[0138] [Table 7]

[0139] [Table 8]

[0140] [Table 9]

[0141] [2-2 Optical properties] (1) Spectral reflectance (calculated value) The spectral reflectance of optical thin films 3-6 and optical thin film C3 at wavelengths of 400-700 nm was calculated. Graphs of these calculated spectral reflectance values ​​are shown in Figures 8-12. If the spectral reflectance in the wavelength range of 400-700 nm is 1% or less, it can be judged that the optical thin films are practically acceptable for use in automotive lenses.

[0142] (2) Spectral reflectance (measured value) Optical thin films 3 were fabricated on both sides of a resin lens, and both sides were coated with the optical thin films 3. The spectral reflectance at the center of the lens was measured on each surface of the resin lens using an Olympus USPM-RU-W microspectrometer. The results are shown in Figure 13. In Figure 13, the solid line represents the calculated spectral reflectance of the optical thin film 3, the dashed line represents the measured spectral reflectance of the optical thin film 3 on the first principal surface of the lens, and the dotted line represents the measured spectral reflectance of the optical thin film 3 on the second principal surface of the lens. The results show that although the shape of the spectral reflectance spectrum changes slightly depending on the lens surface, the measured values ​​are generally equivalent to the calculated values. It was also confirmed that the reflectance in the wavelength range of 400 to 700 nm is 1% or less.

[0143] [2-3 Reliability Testing] High-temperature tests and high-temperature / high-humidity tests were performed on optical thin films 3-6 and optical thin film C3, respectively. The high-temperature test involved leaving each optical thin film in an ESPEC constant-temperature chamber set at 110°C for 1000 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 1000 hours.

[0144] The surface of the optical thin film after each test was observed using an optical microscope and evaluated according to the following criteria. The evaluation results are shown in Table 10. ○: No wrinkles or cracks are observed on the surface. ×: Wrinkles or cracks are observed on the surface.

[0145] [Table 10]

[0146] [Consideration 2] As is clear from Figures 8-12, optical thin films 3-6 all have a spectral reflectance of 1% or less in the wavelength range of 400-700 nm, and possess optical properties equivalent to or better than optical thin film C3, which is a conventional anti-reflective coating for multilayer films.

[0147] Furthermore, as is clear from Table 10, optical thin films 3 to 6 do not develop wrinkles or cracks on their surfaces even in high-temperature and high-temperature, high-humidity environments. As is clear from Tables 3 to 9, optical thin films 3 to 6 have higher compressive stress than optical thin film C3. Therefore, it is considered that optical thin films 3 to 6 can adequately follow the thermal expansion of the plastic lens substrate even in high-temperature environments where optical thin film C3 would crack, thus preventing defects in appearance.

[0148] Furthermore, as is clear from Table 3, organosilicon compounds exhibit sufficiently high optical properties and reliability, as shown, whether doped into a PVD layer of a high refractive index dielectric material or a PVD layer of a low refractive index dielectric material. Moreover, even when a layer of MgF2 with strong tensile stress is used as the surface layer of the optical thin film, it exhibits similarly sufficiently high optical properties and reliability. From this, it can be seen from Examples 3 to 6 above that in multilayer optical thin films with the above-mentioned excellent optical properties and reliability, it is possible to vary the number of layers and the materials used, resulting in a high degree of design freedom and the ability to fabricate multilayer films with diverse configurations.

[0149] Thus, according to the present invention, by mixing an organometallic material compound during the PVD fabrication of the dielectric material constituting the optical thin film, it is possible to adjust the film stress of the entire optical thin film to compressive stress. This makes it possible to realize an optical thin film that has sufficient optical properties and prevents cracking at high temperatures. The amount of organometallic material compound to be mixed should be determined according to the design value of the refractive index of the mixed layer. For example, from the viewpoint of achieving a refractive index that is sufficiently high for optical advantage, a flow rate of around 10 sccm is considered appropriate for an organosilicon compound.

[0150] Furthermore, since optical thin film C3 developed cracks in the high-temperature test described above, the results of the reliability test suggest that it is preferable for the compressive stress of the optical thin film to be sufficiently high. According to Examples 3 to 6 and Comparative Example 3 described above, 100 MPa is given as an example of a compressive stress threshold that can prevent cracking.

[0151] According to the above embodiment, by using a film formed by overlapping timing of a dielectric material by PVD and an organometallic material compound by CVD in some or all of the layers of a multilayer film, an anti-reflective film with low reflectivity and compressive stress appropriately adjusted to the substrate can be obtained. Therefore, it is clear that this is a useful technique for preventing cracks at high temperatures in plastic lens coatings. [Industrial applicability]

[0152] This invention is expected to have potential applications in all technical fields involving coating substrates that exhibit relatively large thermal expansion and contraction with thin films that exhibit relatively small thermal expansion and contraction, and is also expected to contribute to the further development of this technical field. [Explanation of Symbols]

[0153] 1 Optical thin film 11. Contact layer 12 Mixed layer 13 High refractive index layer 14 Surface layer 20, 30, 40, 50, 60 manufacturing equipment 21, 61 Chambers 22 Evaporated domes 23 Vapor deposition source 24 First gas inlet 25 Plasma gun 26 Second gas inlet 35 Ion Gun 45 High frequency power supply 53 Sputtering source 62 stages 65 Plasma Radical Sources 100 circuit boards

Claims

1. An optical thin film comprising a layer formed by physical deposition of a dielectric material, and further comprising one or more mixed layers in which one or more compounds consisting of an organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed within the layer.

2. The configuration includes a first layer comprising a layer formed by physical deposition of the first dielectric material, and a second layer comprising a layer formed by physical deposition of the second dielectric material and having a different refractive index than the first layer, which are alternately stacked. The optical thin film according to claim 1, wherein at least one of the first layer and the second layer is the mixed layer.

3. The optical thin film according to claim 2, further comprising a layer at one end in the overlapping direction of the first layer and the second layer, composed of one or more compounds comprising the organometallic compound, its oxidation reaction product, its oxynitride, and its nitride.

4. The optical thin film according to claim 1, wherein the dielectric material is an oxide, oxynitride, fluoride, or nitride containing one or more elements selected from the group consisting of Ti, Zr, Ta, La, Nb, Hf, Al, Si, Pr, Y, and Ce.

5. The optical thin film according to claim 1, wherein the dielectric material is an oxide, oxynitride, or nitride containing Ti.

6. 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.

7. The optical thin film according to claim 1, wherein the compressive stress is 100 to 1000 MPa.

8. The optical thin film according to claim 1, wherein the reflectance of light with a wavelength of 400 to 700 nm is 1% or less, or the reflectance of light with a wavelength of 400 to 950 nm is 2% or less.

9. An optical element comprising a substrate and an optical thin film according to any one of claims 1 to 8 formed on the surface of the substrate.

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

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

12. A method for manufacturing an optical thin film, comprising the steps of synchronously performing physical deposition of a dielectric material and chemical deposition of the organometallic compound in an atmosphere containing an organometallic compound and a reactive gas, thereby forming a mixed layer on a substrate in which one or more compounds consisting of the organometallic compound, its oxidation reaction product, its oxynitride, and its nitride are mixed within the layer formed by the physical deposition of the dielectric material.

13. A method for manufacturing an optical thin film according to claim 12, wherein a layer of the dielectric material is formed on the surface of the substrate by irradiating the dielectric material with an electron beam from an electron gun, sputtering, or resistance heating, while generating plasma, ions, or heat in the atmosphere.

14. A method for producing an optical thin film according to claim 13, comprising generating plasma, ions, or heat in the atmosphere to react the organometallic compound and the reactive gas.

Images