Optical element and optical apparatus

Abstract

[Problem] To provide an optical element and an optical apparatus, and to provide a technique which facilitates the realization of an optical element having high environmental durability. [Solution] An optical element is provided with a substrate and a laminate having a plurality of layers disposed on the substrate. The laminate has a surface layer of an optical element containing a metal fluoride, a base layer, and an intermediate layer disposed between the surface layer and the base layer. The base layer has a layer containing an oxide. The intermediate layer contains a metal compound and an OH group bonded to a metal of the metal compound.

Description

Technical Field

[0001] This disclosure relates to optical components and optical devices. Background Technology

[0002] On the surface of the substrate of optical elements such as lenses and mirrors, for example, to achieve low or high reflectivity, a laminate composed of a high-refractive-index layer and a low-refractive-index layer is disposed. To improve the function of the optical element, the high-refractive-index layer is typically made of an oxide material, and the low-refractive-index layer is typically made of a fluoride material. However, in the case of a laminate of oxide and fluoride layers, a mixed layer formed by the reaction of the two substances is formed at the boundary between the two layers, which may result in light absorption. As a result, the performance of the optical element may be degraded.

[0003] In contrast, Patent Document 1 discloses that an intermediate refractive index layer of Al2O3 or MgO is disposed between a low refractive index material layer containing fluoride and a high refractive index material layer containing oxide.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 7-244201 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, even if the intermediate layer disclosed in Patent Document 1 is disposed between the surface layer and the base layer, peeling may still occur between the surface layer and the base layer depending on the usage environment of the optical element.

[0009] Methods for solving problems

[0010] One aspect of this disclosure provides a technique that facilitates the realization of optical components with high environmental durability.

[0011] One aspect of this disclosure is an optical element characterized by comprising a substrate and a multilayer stack disposed on the substrate, the multilayer stack comprising: a surface layer of the optical element containing a metal fluoride; a base layer; and an intermediate layer disposed between the surface layer and the base layer, the base layer having an oxide layer, and the intermediate layer containing a metal compound and OH groups metal-bonded to the metal compound. Attached Figure Description

[0012] Figure 1 This is a schematic cross-section of the optical element in the embodiment.

[0013] Figure 2This is a schematic diagram of the film-forming apparatus used in the fabrication of the optical element according to the embodiment.

[0014] Figure 3 This is an explanatory diagram of an exposure apparatus, which is an example of an optical device used in an implementation.

[0015] Figure 4 This is an explanatory diagram of a camera according to another embodiment.

[0016] Figure 5 The figure shows the experimental results of Examples 1-7 and Comparative Examples 1-2.

[0017] Figure 6 This is a diagram showing the waveform of the O1s spectrum in the embodiment.

[0018] Figure 7 (a) is an explanatory diagram of the configuration of the optical elements of Example 8 and Comparative Example 3. Figure 7 (b) is a graph showing the evaluation results of the environmental durability of the laminates of Example 8 and Comparative Example 3, as well as the results of light transmittance. Figure 7 (c) is a graph representing the characteristics of light transmittance of the laminate of Example 8.

[0019] Figure 8 (a) is an explanatory diagram of the configuration of the optical elements of Example 9 and Comparative Example 4. Figure 8 (b) is a graph showing the evaluation results of the environmental durability of the laminates of Example 9 and Comparative Example 4, as well as the results of light transmittance. Figure 8 (c) is a graph representing the light transmittance characteristics of the laminate of Example 5.

[0020] Figure 9 (a) is an explanatory diagram of the configuration of the optical elements of Example 10 and Comparative Example 5. Figure 9 (b) is a graph showing the evaluation results of the environmental durability of the laminates of Example 10 and Comparative Example 5, as well as the results of light transmittance. Figure 9 (c) is a graph representing the light transmittance characteristics of the laminate of Example 10.

[0021] Explanation of reference numerals in the attached figures

[0022] 100…Optical element, 101…Substrate, 102…Laminated structure, 102a…High refractive index layer, 102b…Low refractive index layer, 102c…Surface layer, 102d…Intermediate layer, 103…Base layer Detailed Implementation

[0023] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0024] (Optical components)

[0025] Figure 1 This is a schematic cross-sectional view of the optical element 100 according to the embodiment. The optical element 100 is an optical element such as a lens, filter, mirror, prism, imaging element (image sensor), or display element (display). Furthermore, the optical element 100 is used in optical devices such as exposure apparatus, cameras, and interchangeable lenses.

[0026] The optical element 100 includes a substrate 101 and a laminate 102 disposed on the substrate 101. The laminate 102 is composed of multiple layers. The laminate 102 includes: a base layer 103 disposed on the substrate 101, a surface layer 102c of the optical element 100, and an intermediate layer 102d disposed between the surface layer 102c and the base layer 103.

[0027] The substrate 101 can be made of optical glass such as quartz glass, calcium fluoride crystal, BK7 (borosilicate crown glass), or resin. In addition, the substrate 101 can be made of various shapes, such as planar or curved, depending on the application of the optical element.

[0028] The substrate 103 is a single layer of high refractive index layer 102a, or two or more layers of alternating high refractive index layer 102a and low refractive index layer 102b. In this embodiment, it is two or more layers of alternating high refractive index layer 102a and low refractive index layer 102b.

[0029] In the substrate 103, the layer closest to the intermediate layer 102d (i.e., the layer farthest from the substrate 101) can be either the high-refractive-index layer 102a or the low-refractive-index layer 102b, such as Figure 1 As shown, it can be a high refractive index layer 102a. The outermost layer 102c is the outermost layer of the laminate 102, and can be a low refractive index layer.

[0030] In some embodiments, the laminate 102 of the optical element 100 is made of a material that absorbs little light in the wavelength region intended for use in the optical device, and also of a material that absorbs little light at the boundaries between the layers of the laminate 102. Therefore, the laminate 102 is configured according to the wavelength of the light used. For example, in the case of an exposure apparatus, light with wavelengths shorter than i-rays or deep ultraviolet light is used; in the case of a camera or interchangeable lens, light with wavelengths of visible light is used.

[0031] In this embodiment, a high refractive index layer refers to a layer with a refractive index of 1.8 or higher at a wavelength of 280 nm, and a low refractive index layer refers to a layer with a refractive index of 1.6 or lower at a wavelength of 280 nm.

[0032] The high-refractive-index layer 102a of the base layer 103 contains an oxide as the main component. The oxide can be a metal oxide. For example, the metal oxide can be at least one of HfO2 (hafnium oxide), Ta2O5 (tantalum pentoxide), Sm2O3 (samarium oxide), and Nb2O5 (niobium pentoxide). That is, the metal oxide can contain one material of HfO2, Ta2O5, Sm2O3, and Nb2O5, or it can be a mixture or compound containing two or more materials of HfO2, Ta2O5, Sm2O3, and Nb2O5.

[0033] The low-refractive-index layer 102b of the substrate 103 may contain oxides or fluorides as the main components. The oxide may contain one material selected from SiO2 (silicon dioxide) and Al2O3 (aluminum oxide), or a mixture or compound containing two of these materials. The fluoride may be a metal fluoride. The metal fluoride may be at least one of MgF2 (magnesium fluoride), AlF3 (aluminum fluoride), CaF2 (calcium fluoride), and Na3AlF6 (sodium hexafluoroaluminate). That is, the metal fluoride may contain one material selected from MgF2, AlF3, CaF2, and Na3AlF6, or a mixture or compound containing two or more of these materials.

[0034] The surface layer 102c, serving as a low-refractive-index layer, comprises a metal fluoride as its main component. The metal fluoride can be at least one of MgF2 (magnesium fluoride), Na3AlF6 (sodium hexafluoroaluminate), LiF (lithium fluoride), BaF2 (barium fluoride), SrF2 (strontium fluoride), CaF2 (calcium fluoride), NaF (sodium fluoride), and AlF3 (aluminum fluoride). That is, the metal fluoride can contain one material selected from MgF2, Na3AlF6, LiF, BaF2, SrF2, CaF2, NaF, and AlF3, or it can be a mixture or compound containing two or more materials selected from MgF2, Na3AlF6, LiF, BaF2, SrF2, CaF2, NaF, and AlF3. The material of the surface layer 102c can be MgF2 (magnesium fluoride) from these materials.

[0035] In this embodiment, in order to suppress the formation of a light-absorbing mixed layer between the surface layer 102c and the base layer 103, an intermediate layer 102d is disposed between the surface layer 102c and the high refractive index layer 102a. The intermediate layer 102d contains a metal compound (a compound of a metallic material).

[0036] Furthermore, in this embodiment, in order to suppress peeling between the surface layer 102c and the intermediate layer 102d, or to suppress peeling between the intermediate layer 102d and the base layer 103, OH groups that are metal-bonded to the metal compound are included. In this embodiment, the intermediate layer 102d is composed of a single layer. It should be noted that the case where the intermediate layer 102d is composed of a single layer containing a metal compound and OH groups that are metal-bonded to the metal compound is described, but it is not limited to this. For example, the intermediate layer may also be composed of multiple layers, and at least one of the multiple layers is a layer containing a metal compound and OH groups that are metal-bonded to the metal compound.

[0037] The metal compound can be a metal oxide, such as MgO (magnesium oxide) or Al2O3 (aluminum oxide). That is, the metal in the metal compound can be, for example, Mg (magnesium) or Al (aluminum).

[0038] According to this embodiment, even with prolonged continuous use, the optical element 100 can suppress film peeling and maintain good optical performance. In other words, a technology that facilitates the achievement of high environmental durability in the optical element 100 can be provided. Particularly in high-temperature and high-humidity environments, film peeling can be effectively suppressed.

[0039] (Film-forming method)

[0040] The method for fabricating the optical element 100 of this embodiment will be described. It should be noted that known film formation methods can be used for the high refractive index layer 102a, the low refractive index layer 102b, and the surface layer 102c, so the description is omitted.

[0041] The fabrication method of the intermediate layer 102d is described below. In this embodiment, sputtering is used as an example, but the method is not limited to this film formation method. For example, the intermediate layer 102d can also be fabricated by known physical vapor deposition methods such as vacuum evaporation and ALD or chemical vapor deposition methods.

[0042] Figure 2 This is a schematic diagram of a film-forming apparatus 200 used in the fabrication of the optical element 100 according to the embodiment. The film-forming apparatus 200 includes a vacuum chamber 201 serving as an airtight container and an exhaust system 202 for venting exhaust gas from the vacuum chamber 201. Furthermore, the film-forming apparatus 200 includes an argon gas inlet port 203, an oxygen gas inlet port 204, and a hydrogen gas inlet port 205 for introducing gases required for film formation into the vacuum chamber 201. The argon gas inlet port 203 is the port for introducing argon gas into the vacuum chamber 201. The oxygen gas inlet port 204 is the port for introducing oxygen gas into the vacuum chamber 201. The hydrogen gas inlet port 205 is the port for introducing hydrogen gas into the vacuum chamber 201.

[0043] In this embodiment, hydrogen gas is introduced into the vacuum chamber 201 to contain OH groups in the intermediate layer 102d. It should be noted that water can also be introduced into the vacuum chamber 201 instead of hydrogen.

[0044] A sputtering target 206, a backplate 207, a magnet mechanism 208, and a substrate holding mechanism 210 are disposed within a vacuum chamber 201. A substrate 101, to which the substrate layer 103 is formed, is held in the substrate holding mechanism 210, and power is applied from a power source 209, thereby performing film formation by reactive sputtering. The substrate 101 is, for example, made of quartz glass and processed into a predetermined shape.

[0045] First, a magnesium oxide layer is formed on the substrate 103 by reactive sputtering in the following order. The substrate 101 is placed in the substrate holding mechanism 210. The sputtering target 206 is set to 7 inches of magnesium (99.9 wt%). The vertical distance between the sputtering target 206 and the substrate 101 is, for example, 200 mm. Evacuation is performed through the evacuation system 202 until the pressure inside the vacuum chamber 201 reaches 10. -5 A vacuum level at the Pa level is achieved. Under these conditions, argon is introduced into the vacuum chamber 201 through argon inlet port 203, oxygen through oxygen inlet port 204, and hydrogen through hydrogen inlet port 205, while an electric current is applied to the sputtering target 206 to generate plasma discharge. Alternatively, as described above, water can be introduced into the vacuum chamber 201 instead of hydrogen. The thickness of the magnesium oxide layer can be adjusted by regulating the duration of the electric current application.

[0046] Next, the surface layer 102c is formed into a film, becoming a laminate 102. As mentioned above, the film formation method for each layer is not limited to sputtering, and can be appropriately selected from known film formation methods.

[0047] Figure 3 This is an explanatory diagram of an exposure apparatus 300, which is an example of an optical device used in an embodiment. The exposure apparatus 300 is, for example, an exposure apparatus for a flat panel display.

[0048] The exposure apparatus 300 includes a housing 310, and a light source 301, an illumination optical system 302, a reflector 303, and a projection optical system 305 disposed inside the housing 310. In the projection optical system 305, exposure light 309 emanating from the light source 301 is focused along with the pattern of a mask 304 and projected onto a substrate 306 on a stage 307. A photoresist is coated on the substrate 306, and the photoresist is exposed by the exposure light 309. The substrate 306 is, for example, a glass substrate for a flat panel display, but is not limited thereto; when the exposure apparatus 300 is a semiconductor exposure apparatus, the substrate 306 may also be a semiconductor wafer. The wavelength of the exposure light 309 can be appropriately selected according to the object or product.

[0049] Figure 1 The optical element 100 shown is used, for example, as an optical element (lens) in an illumination optical system 302 or a projection optical system 305. Furthermore, the laminate 102 of the optical element 100 functions, for example, as an anti-reflective film. Compared to conventional optical elements, the laminate 102 of such an optical element 100 can suppress film peeling even with prolonged continuous use, maintaining good optical performance, such as good anti-reflective function.

[0050] Figure 4 This is an explanatory diagram of a camera 400 according to another embodiment. The camera 400 includes a camera body 401 and a lens unit 402, which is detachable from the camera body 401 and serves as an interchangeable lens. Examples of cameras 400 include single-lens reflex cameras, mirrorless cameras, and broadcast cameras. The camera body 401 and the lens unit 402 can each be optical devices.

[0051] Multiple optical elements (lenses) are arranged inside the housing 410 of the lens unit 402. Light is focused by the multiple optical elements and imaged on the imaging element 403 included in the camera body 401.

[0052] exist Figure 4 Of the 400 cameras shown, Figure 1 The optical element 100 shown is employed by at least one of a plurality of optical elements included in the lens unit 402. The laminate 102 of the optical element 100 functions, for example, as an anti-reflective film. The film composition and thickness of the laminate 102 can be appropriately varied according to the required performance of the optical element. Compared with the conventional type, such a laminate 102 of the optical element 100 can suppress film peeling even with prolonged continuous use, maintaining good optical performance, such as good anti-reflective function.

[0053] It should be noted that in the above description, the camera body 401 and the lens unit 402 are separate units, but this is not the only possibility. For example, in optical devices where the camera body and the lens unit are integrated, this method can also be applied. Figure 1 The optical element 100 shown.

[0054] [Example]

[0055] Hereinafter, Examples 1 to 7 and Comparative Examples 1 to 2 will be described. Examples 1 to 7 are optical elements having a three-layer stack having a high-refractive-index layer, an intermediate layer, and a low-refractive-index layer arranged sequentially from the substrate side. Comparative Example 1 is an optical element having a three-layer stack having a high-refractive-index layer, an intermediate layer, and a low-refractive-index layer (surface layer) arranged sequentially from the substrate side. Comparative Example 2 is an optical element having a two-layer stack having a high-refractive-index layer and a low-refractive-index layer arranged sequentially from the substrate side.

[0056] The high-refractive-index layer was set as HfO2, and the low-refractive-index layer as the surface layer was set as MgF2. In addition, the thickness of the HfO2 layer as the high-refractive-index layer was set to about 70 nm, and the thickness of the MgF2 layer as the low-refractive-index layer was set to about 40 nm.

[0057] Figure 5 The figure shows the experimental results of Examples 1-7 and Comparative Examples 1-2. In Examples 1-7 and Comparative Example 1, Ar gas was introduced from Ar gas inlet port 203 at a flow rate of 400 sccm and O2 gas was introduced from O2 gas inlet port 204 at a flow rate of 300 sccm while the intermediate layer was formed.

[0058] In Examples 1-7, the amount of hydrogen introduced and the thickness of the intermediate layer were different to form an intermediate layer. The thickness of the intermediate layer was adjusted appropriately according to the film formation time. In Comparative Example 1, no hydrogen was introduced during the formation of the intermediate layer. In Comparative Example 2, no intermediate layer was formed.

[0059] Next, the evaluation method for the fabricated optical element will be explained. Regarding the light absorption rate, immediately after the laminate is formed, a spectrophotometer is used to measure the light transmittance and reflectance in the wavelength range of 200nm to 500nm, at an angle of incidence of 5 degrees relative to a line perpendicular to the surface of the optical element. The light absorption rate is calculated using the following formula.

[0060] Ab(%)=100-T(%)-R(%)

[0061] Where Ab (%) represents the light absorption rate, T (%) represents the light transmittance, and R (%) represents the light reflectance.

[0062] As an evaluation criterion, since the wavelength range of light used varies depending on the application, the evaluation is conducted at three wavelengths of light: 280nm, 365nm, and 450nm. Cases where the light absorption rate in the laminate is less than 0.3% are denoted as "A", and cases where it is greater than 0.3% are denoted as "C".

[0063] The content of OH groups in the intermediate layer was evaluated using spectra obtained by analyzing the intermediate layer using X-ray photoelectron spectroscopy (XPS, QuanteraII / ULVAC-PHI Co., Ltd.). To analyze the intermediate layer, ion sputtering was used in combination to perform depth-direction analysis from the surface of the laminate formed on the optical element, thus evaluating the intermediate layer.

[0064] In the O1s binding energy spectrum obtained by analyzing the intermediate layer using XPS (O1s spectrum), waveforms of the binding energy originating from the Mg-O bond (Mg-O bond) with a peak near 529 eV and the binding energy originating from the Mg-OH bond (Mg-OH bond) with a peak near 531 eV were separated (using software: MultiPak / ULVAC-PHI Co., Ltd.).

[0065] Figure 6 This is a diagram showing the waveform of the O1s spectrum in the embodiment. Figure 6 The waveform W0 of the O1s spectrum of Example 4 is illustrated illustratively. Figure 6 In this diagram, the waveform representing the binding energy originating from the Mg-O bond is denoted as W1, and the waveform representing the binding energy originating from the Mg-OH bond is denoted as W2. Waveform W0 is separated into waveforms W1 and W2. The area enclosed by waveform W1 is expressed as the peak area of ​​Mg-O, and the area enclosed by waveform W2 is expressed as the peak area of ​​Mg-OH. The peak area of ​​Mg-O represents the intensity of the binding energy originating from the Mg-O bond. Similarly, the peak area of ​​Mg-OH represents the intensity of the binding energy originating from the Mg-OH bond. The intensity ratio of the binding energy originating from the Mg-OH bond to the binding energy originating from the Mg-O bond is expressed as (peak area of ​​Mg-OH) / (peak area of ​​Mg-O). The intensity ratios were calculated for Examples 1-7 and Comparative Example 1 to evaluate the content of OH groups. Furthermore, regarding the waveform separation properties, the peak area of ​​Mg-OH can be calculated using a Gaussian function even in the absence of OH groups. Therefore, when the intensity ratio is below 0.2, it is evaluated as not containing OH groups. Figure 5 In the example of Embodiment 4 shown, the strength ratio is 0.67.

[0066] In addition, constant temperature and humidity tests were conducted to evaluate environmental durability. Environmental durability was evaluated under two conditions: a temperature of 50°C and a humidity of 80%, with holding times of 20 hours and 100 hours. After each holding time, the laminate was visually inspected or microscopically to confirm the presence or absence of film peeling. As an evaluation criterion, cases where no film peeling was detected even after a holding time of 100 hours were recorded as "A"; cases where no film peeling was detected after a holding time of 24 hours but film peeling was detected after a holding time of 100 hours were recorded as "B"; and cases where film peeling was detected after a holding time of 24 hours were recorded as "C". The evaluation results of Examples 1-7 and Comparative Examples 1-2 are as follows: Figure 5 As shown.

[0067] Regarding Example 1, during the formation of the magnesium oxide layer as the intermediate layer, the hydrogen introduction rate was set to 10 sccm. At this time, the intensity ratio of (Mg-OH peak area) / (Mg-O peak area) was 0.23. Furthermore, the physical film thickness of the intermediate layer was 3.2 nm. The light absorption rate was 0.23% at 280 nm, 0.07% at 365 nm, and 0.03% at 450 nm, exhibiting good optical properties at all wavelengths. Regarding environmental durability, no film peeling was observed at 24 hours during the constant temperature and humidity test, but peeling occurred at 100 hours.

[0068] Regarding Example 2, during the formation of the magnesium oxide layer as the intermediate layer, the hydrogen introduction rate was set to 30 sccm. At this time, the intensity ratio of (Mg-OH peak area) / (Mg-O peak area) was 0.46. Furthermore, the physical film thickness of the intermediate layer was 3.0 nm. The light absorption rate was 0.20% at 280 nm, 0.07% at 365 nm, and 0.06% at 450 nm, exhibiting good optical properties at all wavelengths. Regarding environmental durability, no film peeling was observed up to 100 hours during the constant temperature and humidity test.

[0069] Regarding Example 3, during the formation of the magnesium oxide layer as the intermediate layer, the hydrogen introduction rate was set to 50 sccm. At this time, the intensity ratio of (Mg-OH peak area) / (Mg-O peak area) was 0.55. Furthermore, the physical film thickness of the intermediate layer was 1.0 nm. The light absorption rate was 0.75% at 280 nm, 0.44% at 365 nm, and 0.18% at 450 nm, exhibiting good optical properties in the visible wavelength range. Regarding environmental durability, no film peeling was observed up to 100 hours during the constant temperature and humidity test.

[0070] Regarding Example 4, during the formation of the magnesium oxide layer as the intermediate layer, the hydrogen introduction rate was set to 50 sccm. At this time, the intensity ratio of (Mg-OH peak area) / (Mg-O peak area) was 0.67. Furthermore, the physical film thickness of the intermediate layer was 12.0 nm. The light absorption rate was 0.27% at 280 nm, 0.07% at 365 nm, and 0.03% at 450 nm, exhibiting good optical properties at all wavelengths. Regarding environmental durability, no film peeling was observed up to 100 hours during the constant temperature and humidity test.

[0071] Regarding Example 5, during the formation of the magnesium oxide layer as the intermediate layer, the hydrogen introduction rate was set to 50 sccm. At this time, the intensity ratio of (Mg-OH peak area) / (Mg-O peak area) was 0.70. Furthermore, the physical film thickness of the intermediate layer was 13.8 nm. The light absorption rate was 0.26% at 280 nm, 0.07% at 365 nm, and 0.03% at 450 nm, exhibiting good optical properties at all wavelengths. Regarding environmental durability, no film peeling was observed at 24 hours during the constant temperature and humidity test, but peeling occurred at 100 hours.

[0072] Regarding Example 6, during the formation of the magnesium oxide layer as the intermediate layer, the hydrogen introduction rate was set to 100 sccm. At this time, the intensity ratio of (Mg-OH peak area) to (Mg-O peak area) was 2.55. Furthermore, the physical film thickness of the intermediate layer was 6.2 nm. The light absorption rate was 0.23% at 280 nm, 0.05% at 365 nm, and 0.03% at 450 nm, exhibiting good optical properties at all wavelengths. Regarding environmental durability, no film peeling was observed up to 100 hours during the constant temperature and humidity test.

[0073] Regarding Example 7, during the formation of the magnesium oxide layer as the intermediate layer, the hydrogen introduction rate was set to 120 sccm. At this time, the intensity ratio of (Mg-OH peak area) to (Mg-O peak area) was 3.35. Furthermore, the physical film thickness of the intermediate layer was 6.7 nm. The light absorption rate was 0.18% at 280 nm, 0.07% at 365 nm, and 0.02% at 450 nm, exhibiting good optical properties at all wavelengths. Regarding environmental durability, no film peeling was observed up to 100 hours during the constant temperature and humidity test.

[0074] Regarding Comparative Example 1, the magnesium oxide layer, serving as the intermediate layer, was formed without introducing hydrogen gas. The intensity ratio of (Mg-OH peak area) to (Mg-O peak area) was less than 0.2, confirming that the intermediate layer did not contain OH groups. Furthermore, the physical film thickness of the intermediate layer was 4.5 nm. The light absorption rate was 0.20% at 280 nm, 0.06% at 365 nm, and 0.03% at 450 nm, exhibiting good optical properties at all wavelengths. However, regarding environmental durability, film peeling occurred after 24 hours in the constant temperature and humidity test.

[0075] Regarding Comparative Example 2, the magnesium oxide layer without film formation served as the intermediate layer. The light absorption rate was 1.46% at 280 nm, 1.01% at 365 nm, and 0.58% at 450 nm, confirming light absorption at all wavelengths and a decrease in optical properties. Regarding environmental durability, no film peeling was observed up to 100 hours during the constant temperature and humidity test.

[0076] When comparing Examples 1-7 with Comparative Example 1, the environmental durability of Examples 1-7 is improved compared to Comparative Example 1. Furthermore, in Comparative Example 2, although no intermediate layer was provided, it exhibited high performance in terms of environmental durability. The rationale for this is explained below through the envisioned mechanism.

[0077] First, when comparing the light absorption rates of Comparative Example 1 and Comparative Example 2, in Comparative Example 1, which has a magnesium oxide layer as an intermediate layer, a film with low light absorption rate at any wavelength was obtained. However, in Comparative Example 2, a film with high light absorption rate at any wavelength was obtained. This confirms that by using a magnesium oxide layer without OH groups as an intermediate layer, it is also possible to suppress light absorption at the boundary between metal oxides and metal fluorides.

[0078] On the other hand, regarding environmental durability, when no magnesium oxide layer is provided, as in Comparative Example 2, no film peeling occurs. However, when a magnesium oxide layer without OH groups is provided as an intermediate layer, as in Comparative Example 1, environmental durability decreases, and film peeling occurs. That is, the decrease in environmental durability can be attributed to the magnesium oxide layer without OH groups. Furthermore, when a magnesium oxide layer with OH groups is provided as an intermediate layer, as in Examples 1-7, environmental durability is significantly improved, and film peeling is less likely to occur.

[0079] The mechanism of membrane delamination is believed to be the hygroscopicity of magnesium oxide. Magnesium oxide is known to be highly hygroscopic, reacting with moisture in the air even under normal conditions. This hygroscopicity causes a chemical change in MgO, transforming it into Mg(OH)₂. As a result, the magnesium oxide layer can expand to more than twice its original volume. It is thought that by incorporating layers containing other materials on top of the magnesium oxide layer during lamination, the highly hygroscopic magnesium oxide layer expands compared to the other material layers, thus causing membrane delamination.

[0080] Therefore, the inventors discovered that by pre-compromising a portion of the magnesium oxide layer with OH groups, the effects of volume expansion can be mitigated, resulting in optical components with high environmental durability. Furthermore, based on XPS analysis, the inventors found that if the intensity ratio of (Mg-OH peak area) to (Mg-O peak area) is 0.23 or higher, environmental durability is further improved. Additionally, the inventors found that if the intensity ratio of (Mg-OH peak area) to (Mg-O peak area) is 0.46 or higher, even higher environmental durability is achieved. Furthermore, the inventors found that if the intensity ratio of (Mg-OH peak area) to (Mg-O peak area) is 3.35 or lower, even higher environmental durability is achieved.

[0081] While it was confirmed that the intermediate layer improves environmental durability regardless of thickness, it was also confirmed that optical elements with even higher environmental durability can be obtained when the thickness of the intermediate layer is above 1 nm and below 12 nm.

[0082] Next, Example 8 and Comparative Example 3 will be described. As optical elements of Example 8 and Comparative Example 3, the case in which a laminate having anti-reflective properties for light in the wavelength region of ultraviolet light is provided on the main surface of the substrate will be described.

[0083] Optical elements with anti-reflective properties in the ultraviolet wavelength region, such as optical devices used in exposure apparatuses for lamps utilizing ultraviolet wavelengths, for example... Figure 3 The exposure apparatus 300 shown. As Example 8, a laminate was fabricated in which a magnesium oxide layer is disposed as an intermediate layer on a substrate layer consisting of three alternately stacked layers: a hafnium oxide layer as a high-refractive-index layer and a silicon oxide layer as a low-refractive-index layer, and a magnesium fluoride layer is disposed as a surface layer on the intermediate layer. This laminate is equivalent to... Figure 1 The structure of the laminate 102 shown.

[0084] The magnesium oxide layer in Example 8 used a magnesium oxide layer with an XPS intensity ratio of (Mg-OH peak area) / (Mg-O peak area) of 0.67. Additionally, as Comparative Example 3, a magnesium oxide layer without OH groups was disposed on the substrate layer as an intermediate layer. The other film structures were the same as in Example 8.

[0085] Both Example 8 and Comparative Example 3 maximized anti-reflective properties in the 280nm-380nm wavelength region. The structure of the laminate was determined by optimizing the physical film thickness of each layer based on the materials (refractive index) used in each layer. The refractive index and physical film thickness of each layer in Example 8 and Comparative Example 3 are as follows: Figure 7 As shown in (a).

[0086] The substrate is a quartz substrate with a thickness of 2 mm. After forming a laminate with anti-reflective properties on both sides of the substrate, the laminate is evaluated.

[0087] Figure 7 (b) is a graph showing the evaluation results of the environmental durability of the laminates of Example 8 and Comparative Example 3, as well as the results of light transmittance. Figure 7 (c) is a graph representing the characteristics of light transmittance of the laminate of Example 8.

[0088] An isothermal and humidity test was conducted on the optical components to evaluate the environmental durability of the optical component laminate. The isothermal and humidity test was carried out in an environment with a temperature of 50°C and a humidity of 80%, and the temperature and humidity were maintained for 100 hours.

[0089] After a 100-hour holding period, the laminate was visually inspected or microscopically to confirm the presence or absence of film peeling. As an evaluation criterion, cases where no film peeling was detected after 100 hours were marked as "A," and cases where film peeling was detected were marked as "C." Additionally, after evaluating environmental durability, a spectrophotometer was used to measure light transmittance at an angle of 5 degrees to a line perpendicular to the surface of the optical element, thus evaluating light transmittance.

[0090] In Example 8, no film peeling was observed during a constant temperature and humidity test with a holding time of 100 hours, but film peeling was observed in Comparative Example 3. Furthermore, in Example 8, where no film peeling was observed, light transmittance was evaluated, and a high transmittance of 99.6% with an average wavelength of 280 nm to 380 nm was obtained.

[0091] Next, Example 9 and Comparative Example 4 will be described. As optical elements of Example 9 and Comparative Example 4, the case in which a laminate having anti-reflective properties against i-ray wavelength (365 nm) light is provided on the main surface of the substrate will be described.

[0092] Optical elements with anti-reflective properties for i-ray wavelengths (365 nm) are used, for example, in exposure apparatuses that utilize i-ray light from lasers. As Example 9, a laminate was fabricated in which a magnesium oxide layer is disposed as an intermediate layer on a substrate layer consisting of three alternating layers: a tantalum pentoxide layer as a high-refractive-index layer and a silicon oxide layer as a low-refractive-index layer, and a magnesium fluoride layer is disposed as a surface layer on the intermediate layer. This laminate is equivalent to... Figure 1 The structure of the laminate 102 shown.

[0093] The magnesium oxide layer in Example 9 used a magnesium oxide layer with an XPS intensity ratio of (Mg-OH peak area) / (Mg-O peak area) of 0.67. Additionally, as Comparative Example 4, a magnesium oxide layer without OH groups was disposed on the substrate layer as an intermediate layer. The other film structures were the same as in Example 9.

[0094] In both Example 9 and Comparative Example 4, the anti-reflective properties of light were maximized at a wavelength of 365 nm. The physical film thickness of each layer was optimized based on the material (refractive index) used in each layer to determine the structure of the laminate. The refractive index and physical film thickness of each layer in Example 9 and Comparative Example 4 are as follows: Figure 8 As shown in (a).

[0095] The substrate is a quartz substrate with a thickness of 2 mm. After forming a laminate with anti-reflective properties on both sides of the substrate, the laminate is evaluated.

[0096] Figure 8 (b) is a graph showing the evaluation results of the environmental durability of the laminates of Example 9 and Comparative Example 4, as well as the results of light transmittance. Figure 8 (c) is a graph representing the light transmittance characteristics of the laminate of Example 5.

[0097] An isothermal and humidity test was conducted on the optical components to evaluate the environmental durability of the optical component laminate. The isothermal and humidity test was carried out in an environment with a temperature of 50°C and a humidity of 80%, and the temperature and humidity were maintained for 100 hours.

[0098] After a 100-hour holding period, the laminate was visually inspected or microscopically to confirm the presence or absence of film peeling. As an evaluation criterion, cases where no film peeling was detected after 100 hours were marked as "A," and cases where film peeling was detected were marked as "C." Additionally, after evaluating environmental durability, a spectrophotometer was used to measure light transmittance at an angle of 5 degrees to a line perpendicular to the surface of the optical element, thus evaluating light transmittance.

[0099] In Example 9, no film peeling was observed during a constant temperature and humidity test with a holding time of 100 hours, but film peeling was observed in Comparative Example 4. Furthermore, in Example 9, where no film peeling was observed, light transmittance was evaluated, and a high transmittance of 99.9% was obtained at a wavelength of 365 nm.

[0100] Next, Example 10 and Comparative Example 5 will be described. As optical elements of Example 10 and Comparative Example 5, the case in which a laminate with anti-reflective properties for visible light is provided on the main surface of the substrate will be described.

[0101] Optical components that have anti-reflective properties for visible light, such as those used in cameras and interchangeable lenses, are examples of such components. Figure 4 The camera 400 shown. As Example 9, a laminate was fabricated in which a magnesium oxide layer is disposed as an intermediate layer on a substrate layer consisting of seven layers, on which niobium pentoxide layers (high refractive index layers) and silicon oxide layers (low refractive index layers) are alternately stacked, and a magnesium fluoride layer is disposed as a surface layer on the intermediate layers. This laminate is equivalent to... Figure 1 The structure of the laminate 102 shown.

[0102] The magnesium oxide layer in Example 10 used a magnesium oxide layer with an XPS intensity ratio of (Mg-OH peak area) / (Mg-O peak area) of 0.67. Additionally, as Comparative Example 5, a magnesium oxide layer without OH groups was disposed on the substrate layer as an intermediate layer. The other film structures were the same as in Example 10.

[0103] In both Example 10 and Comparative Example 5, the anti-reflective properties of light were maximized in the wavelength region of 400 nm to 650 nm. The structure of the laminate was determined by optimizing the physical film thickness of each layer based on the materials (refractive index) used in each layer. The refractive index and physical film thickness of each layer in Example 10 and Comparative Example 5 are as follows: Figure 9 As shown in (a).

[0104] The substrate is a quartz substrate with a thickness of 2 mm. After forming a laminate with anti-reflective properties on both sides of the substrate, the laminate is evaluated.

[0105] Figure 9 (b) is a graph showing the evaluation results of the environmental durability of the laminates of Example 10 and Comparative Example 5, as well as the results of light transmittance. Figure 9 (c) is a graph representing the light transmittance characteristics of the laminate of Example 10.

[0106] An isothermal and humidity test was conducted on the optical components to evaluate the environmental durability of the optical component laminate. The isothermal and humidity test was carried out in an environment with a temperature of 50°C and a humidity of 80%, and the temperature and humidity were maintained for 100 hours.

[0107] After a 100-hour holding period, the laminate was visually inspected or microscopically to confirm the presence or absence of film peeling. As an evaluation criterion, cases where no film peeling was detected after 100 hours were marked as "A," and cases where film peeling was detected were marked as "C." Additionally, after evaluating environmental durability, a spectrophotometer was used to measure light transmittance at an angle of 5 degrees to a line perpendicular to the surface of the optical element, thus evaluating light transmittance.

[0108] In Example 10, no film peeling was observed during a constant temperature and humidity test with a holding time of 100 hours, but film peeling was observed in Comparative Example 5. Furthermore, in Example 10, where no film peeling was observed, light transmittance was evaluated, and a high transmittance of 99.5% with an average wavelength of 380 nm to 650 nm was obtained.

[0109] [Other variations]

[0110] This invention is not limited to the embodiments described above, and various modifications can be made within the scope of the technical concept disclosed herein. Furthermore, the effects described in the above embodiments are merely examples of the most suitable effects produced by the embodiments of this disclosure, and the effects of this invention are not limited to those described in the above embodiments.

[0111] Based on the above disclosure, technologies that facilitate the realization of optical components with high environmental durability can be provided.

Claims

1. An optical element, characterized in that, It comprises: a matrix; and a laminate having multiple layers disposed on said matrix. The laminate has: The surface of the optical element contains a metal fluoride. basal layer; as well as An intermediate layer configured between the surface layer and the base layer, The base layer has a layer containing oxides. The intermediate layer contains a metal compound and OH groups that are metal-bonded to the metal compound.

2. The optical element according to claim 1, characterized in that, The metal compound is MgO or Al2O3.

3. The optical element according to claim 1, characterized in that, The metal fluoride is at least one of MgF2, Na3AlF6, LiF, BaF2, SrF2, CaF2, NaF, and AlF3.

4. The optical element according to claim 1, characterized in that, The base layer has two or more layers. Of the two or more layers, at least the layer closest to the intermediate layer is the oxide-containing layer.

5. The optical element according to claim 4, characterized in that, The two or more layers have alternating layers of high refractive index layers and low refractive index layers.

6. The optical element according to claim 5, characterized in that, The layer closest to the intermediate layer is the high refractive index layer.

7. The optical element according to claim 5, characterized in that, The high refractive index layer is a layer with a refractive index of 1.8 or higher at a wavelength of 280 nm.

8. The optical element according to claim 5, characterized in that, The high refractive index layer is the oxide-containing layer. The oxide of the high refractive index layer is at least one of HfO2, Ta2O5, Sm2O3 and Nb2O5.

9. The optical element according to claim 5, characterized in that, The low refractive index layer is a layer with a refractive index of less than 1.6 at a wavelength of 280 nm.

10. The optical element according to claim 5, characterized in that, The low refractive index layer is the oxide-containing layer. The oxide of the low refractive index layer is at least one of SiO2 and Al2O3.

11. The optical element according to claim 5, characterized in that, The low-refractive-index layer is a fluoride-containing layer. The fluoride in the low refractive index layer is at least one of MgF2, AlF3, CaF2, and Na3AlF6.

12. The optical element according to any one of claims 1 to 11, characterized in that, The metal compound is MgO. In the O1s spectrum obtained by analyzing the intermediate layer using X-ray photoelectron spectroscopy, the intensity ratio of the binding energy originating from the Mg-OH bond to the binding energy originating from the Mg-O bond is 0.23 or higher.

13. The optical element according to any one of claims 1 to 11, characterized in that, The metal compound is MgO. In the O1s spectrum obtained by analyzing the intermediate layer using X-ray photoelectron spectroscopy, the intensity ratio of the binding energy originating from the Mg-OH bond to the binding energy originating from the Mg-O bond is 0.46 or higher.

14. The optical element according to any one of claims 1 to 11, characterized in that, The metal compound is MgO. In the O1s spectrum obtained by analyzing the intermediate layer using X-ray photoelectron spectroscopy, the intensity ratio of the binding energy originating from the Mg-OH bond to the binding energy originating from the Mg-O bond is less than 3.

35.

15. The optical element according to any one of claims 1 to 11, characterized in that, The physical film thickness of the intermediate layer is greater than 1 nm and less than 12 nm.

16. An optical device, characterized in that, have: The outer casing; and The optical element according to any one of claims 1 to 15 is disposed inside the housing.

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