Substrate with dielectric multilayer film, method for manufacturing same, and method for manufacturing substrate with optical multilayer film

Abstract

To provide a method for manufacturing a substrate with a dielectric multilayer film whose optical characteristics are hardly deteriorated even when alkali cleaning is performed.SOLUTION: A method for manufacturing a substrate 1 with an attached dielectric multilayer film including a substrate 2 and a dielectric multilayer film 3 provided on the substrate 2, the method including a step of disposing the substrate 2 in a vacuum deposition apparatus, and a step of depositing the dielectric multilayer film 3 on the substrate 2 in the vacuum deposition apparatus, wherein the step of depositing the dielectric multilayer film 3 includes a step of depositing a dielectric film 5 as an outermost layer, the step of forming the dielectric film 5 as the outermost layer includes a low-pressure film-forming step of forming a film by setting the inside of a vacuum film-forming apparatus to a relatively low pressure, and a high-pressure film-forming step of forming a film by setting the inside of the vacuum film-forming apparatus to a relatively high pressure after the low-pressure film-forming step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a substrate with a dielectric multilayer film, a method for manufacturing the substrate with the dielectric multilayer film, and a method for manufacturing a substrate with an optical multilayer film using the substrate with the dielectric multilayer film. [Background technology]

[0002] Conventionally, a substrate with a dielectric multilayer film, in which a dielectric multilayer film is provided on a glass substrate, has been used. The dielectric multilayer film is used as an optically functional film such as an anti-reflection film, an infrared reflective film, a band-pass filter, and a mirror. For example, the dielectric multilayer film is used as an anti-reflection film for a cover glass used in an image sensor.

[0003] The film-forming surface of a substrate with a dielectric multilayer film may be subjected to alkaline cleaning in order to remove dirt, etc. In this case, a silicon oxide layer may be formed on the outermost layer of the dielectric multilayer film, which also serves as a protective layer during alkaline cleaning (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6702078 Summary of the Invention [Problem to be solved by the invention]

[0005] As in Patent Document 1, when a protective layer (sacrificial film) for alkaline cleaning is formed on the outermost layer of a dielectric multilayer film, only the sacrificial film is dissolved during alkaline cleaning, protecting the rest of the dielectric multilayer film from the alkaline solution. However, it is difficult to selectively dissolve only the sacrificial film by alkaline cleaning. In particular, when the outermost layer of the dielectric multilayer film below the sacrificial film is made of a material that is easily dissolved by alkaline cleaning, such as a silicon oxide film, the silicon oxide film below the sacrificial film may be dissolved in addition to the sacrificial film, resulting in a thin silicon oxide film in the outermost layer. As a result, the optical properties of the resulting dielectric multilayer film-coated substrate may be degraded.

[0006] The object of the present invention is to provide a dielectric multilayer substrate whose optical properties are resistant to deterioration even when subjected to alkaline cleaning, a method for manufacturing the dielectric multilayer substrate, and a method for manufacturing an optical multilayer substrate using the dielectric multilayer substrate. [Means for solving the problem]

[0007] Hereinafter, various embodiments of a dielectric multilayer film-coated substrate that solves the above problems, a method for manufacturing the dielectric multilayer film-coated substrate, and a method for manufacturing an optical multilayer film-coated substrate using the dielectric multilayer film-coated substrate will be described.

[0008] A method for manufacturing a substrate with a dielectric multilayer film according to aspect 1 of the present invention is a method for manufacturing a substrate with a dielectric multilayer film, comprising a substrate and a dielectric multilayer film provided on the substrate, and comprising the steps of placing the substrate in a vacuum film-forming apparatus and forming a dielectric multilayer film on the substrate in the vacuum film-forming apparatus, wherein the step of forming the dielectric multilayer film includes a step of forming an outermost dielectric film, and the step of forming the outermost dielectric film includes a low-pressure film-forming step in which the vacuum film-forming apparatus is set to a relatively low pressure for film formation, and a high-pressure film-forming step in which the vacuum film-forming apparatus is set to a relatively high pressure for film formation after the low-pressure film-forming step.

[0009] In the method for manufacturing a substrate with a dielectric multilayer film according to aspect 2, in aspect 1, it is preferable that the difference between the pressure inside the vacuum film-forming apparatus in the high-pressure film-forming process and the pressure inside the vacuum film-forming apparatus in the low-pressure film-forming process is 0.10 Pa or more and 0.30 Pa or less.

[0010] In the method for manufacturing a substrate with a dielectric multilayer film according to aspect 3, in aspect 1 or aspect 2, it is preferable that the pressure inside the vacuum film-forming apparatus in the low-pressure film-forming process is 0.05 Pa or more and 0.15 Pa or less, and the pressure inside the vacuum film-forming apparatus in the high-pressure film-forming process is 0.25 Pa or more and 0.35 Pa or less.

[0011] The method for manufacturing a substrate with a dielectric multilayer film according to aspect 4 is any one of aspects 1 to 3, wherein the step of forming the dielectric multilayer film includes a multilayer film forming step of forming a multilayer film other than the outermost dielectric film, and it is preferable that the pressure in the vacuum film forming apparatus in the multilayer film forming step is the same as that in the high-pressure film forming step.

[0012] A fifth aspect of the method for producing a dielectric multilayer film-coated substrate is preferably the same as the fourth aspect, in that the multilayer film includes a high refractive index film made of niobium oxide and a low refractive index film made of silicon oxide.

[0013] In the method for manufacturing a substrate with a dielectric multilayer film according to aspect 6, in any one of aspects 1 to 5, it is preferable that the pressure within the vacuum film-forming apparatus in the low-pressure film-forming process is the lowest pressure in the process of forming the dielectric multilayer film.

[0014] In the method for producing a dielectric multilayer substrate according to aspect 7, in any one of aspects 1 to 6, the outermost dielectric film preferably contains silicon oxide.

[0015] In the method for producing a dielectric multilayer film-coated substrate according to aspect 8, in any one of aspects 1 to 7, the vacuum film-forming apparatus is preferably a sputtering apparatus.

[0016] A substrate with a dielectric multilayer film according to aspect 9 is a substrate with a dielectric multilayer film comprising a substrate and a dielectric multilayer film provided on the substrate, characterized in that when the substrate with a dielectric multilayer film is immersed in an aqueous sodium hydroxide solution having a concentration of 3 mass % and a temperature of 60°C, the dissolution rate of the outermost dielectric film in the dielectric multilayer film slows down midway through the dissolution.

[0017] A substrate with a dielectric multilayer film according to aspect 10 is the same as that of aspect 9, and preferably has a portion in which high-refractive-index films with a relatively high refractive index and low-refractive-index films with a relatively low refractive index are alternately stacked, and the outermost dielectric film in the dielectric multilayer film is the low-refractive-index film.

[0018] In the dielectric multilayer film-coated substrate according to aspect 11, in accordance with aspect 10, the low refractive index film preferably contains silicon oxide.

[0019] In the dielectric multilayer film-coated substrate of aspect 12, in aspect 10 or aspect 11, it is preferable that the high refractive index film contains at least one selected from the group consisting of niobium oxide, titanium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silicon nitride, aluminum oxide, and aluminum nitride.

[0020] A method for manufacturing an optical multilayer substrate according to aspect 13 of the present invention is characterized by comprising the steps of preparing a dielectric multilayer substrate according to any one of aspects 9 to 12, and performing alkaline cleaning to remove a portion of the outermost dielectric film. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a dielectric multilayer film-coated substrate whose optical properties are resistant to deterioration even when subjected to alkaline cleaning, a method for manufacturing the dielectric multilayer film-coated substrate, and a method for manufacturing an optical multilayer film-coated substrate using the dielectric multilayer film-coated substrate. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a dielectric multilayer film-coated substrate according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an optical multilayer film-coated substrate according to one embodiment of the present invention. [Figure 3] FIG. 3 shows the optical transmission spectra of the dielectric multilayer film-coated substrates obtained in Example 1, Comparative Example 1, and Reference Example 1. [Figure 4] FIG. 4 is a graph showing the results of an alkali immersion test of the dielectric multilayer film-coated substrate obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0023] Preferred embodiments of the present invention will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0024] [Substrate with dielectric multilayer film] FIG. 1 is a schematic cross-sectional view showing a dielectric multilayer film-coated substrate according to one embodiment of the present invention.

[0025] 1, the dielectric multilayer film-coated substrate 1 includes a substrate 2 and a dielectric multilayer film 3. The dielectric multilayer film 3 has a multilayer film 4 and a dielectric film 5 as an outermost layer.

[0026] In this embodiment, the substrate 2 has a substantially rectangular plate shape, but the shape of the substrate 2 is not particularly limited and may be a substantially circular plate shape.

[0027] In this embodiment, the substrate 2 is preferably a substrate that is transparent in the wavelength range used by the dielectric multilayer film-coated substrate 1. For example, when the dielectric multilayer film-coated substrate 1 is used as a cover glass for a display, the substrate 2 can have a thickness of 0.4 mm and a light transmittance of 80% or more and 92% or less at wavelengths of 350 nm to 800 nm.

[0028] The substrate 2 has a first main surface 2a and a second main surface 2b that face each other. A multilayer film 4 is provided on the first main surface 2a of the substrate 2.

[0029] The dielectric multilayer film 3 can be used as an optically functional film such as an anti-reflection film, an infrared reflective film, a band-pass filter, a mirror, etc. For example, the dielectric multilayer film 3 can be used as an anti-reflection film for a cover glass used in an image sensor.

[0030] In this embodiment, the multilayer film 4 is configured by alternately stacking high-refractive-index films 6 having a relatively high refractive index and low-refractive-index films 7 having a relatively low refractive index in this order. However, the multilayer film 4 may include other layers as long as it has a portion where the high-refractive-index films 6 having a relatively high refractive index and the low-refractive-index films 7 having a relatively low refractive index are alternately stacked in this order. Furthermore, the stacking order of the high-refractive-index films 6 and the low-refractive-index films 7 in the multilayer film 4 is not particularly limited.

[0031] An outermost dielectric film 5 is provided on the multilayer film 4. The outermost dielectric film 5 is provided on a main surface 4a of the multilayer film 4 opposite to the substrate 2. The material of the outermost dielectric film 5 is not particularly limited, but in this embodiment it is silicon oxide.

[0032] When the dielectric multilayer film-coated substrate 1 of this embodiment is immersed in a sodium hydroxide aqueous solution having a concentration of 3 mass % and a temperature of 60°C, the dissolution rate of the outermost dielectric film 5 of the dielectric multilayer film 3 slows down midway through the dissolution.

[0033] The dielectric multilayer film-coated substrate 1 of this embodiment has the above-described configuration, and therefore its optical properties are less likely to deteriorate even when subjected to alkaline cleaning.

[0034] Conventionally, when a sacrificial film is formed on the outermost layer of a dielectric multilayer film substrate during alkaline cleaning, the substrate has been designed so that only the sacrificial film is dissolved during alkaline cleaning. However, it is difficult to selectively dissolve only the sacrificial film. In particular, when the outermost layer of the dielectric multilayer film below the sacrificial film is formed of a material that is easily dissolved by alkaline cleaning, such as a silicon oxide film, the silicon oxide film below the sacrificial film is dissolved in addition to the sacrificial film, which can result in a thin silicon oxide film in the outermost layer. As a result, the optical properties of the resulting dielectric multilayer film substrate can be deteriorated.

[0035] In contrast, when the dielectric multilayer film-coated substrate 1 of this embodiment is immersed in a sodium hydroxide aqueous solution with a concentration of 3 mass % at a temperature of 60°C, the dissolution rate of the outermost dielectric film 5 in the dielectric multilayer film 3 slows down midway through the dissolution. Therefore, the portion of the outermost dielectric film 5 that serves as a sacrificial film (the portion before the dissolution rate slows down) is selectively dissolved, while the portion of the dielectric multilayer film 3 that contributes to the optical properties (the portion after the dissolution rate slows down) is selectively left. Therefore, the optical properties of the dielectric multilayer film-coated substrate 1 are less likely to deteriorate even when subjected to alkaline cleaning.

[0036] When the dielectric multilayer film-coated substrate 1 of this embodiment is immersed in a sodium hydroxide aqueous solution having a concentration of 3% by mass and a temperature of 60°C, the ratio (Va / Vb) of the dissolution rate Va before the dissolution rate slows to the dissolution rate Vb after the dissolution rate slows is preferably 1.2 or more, more preferably 1.5 or more. When the ratio (Va / Vb) is equal to or greater than the above-mentioned lower limit, contamination on the surface 3a of the dielectric multilayer film 3 can be more reliably removed by alkaline cleaning, while further reducing the deterioration of the optical properties of the dielectric multilayer film-coated substrate 1. There is no particular upper limit to the ratio (Va / Vb), but in practice it is 10 or less.

[0037] Furthermore, in the dielectric multilayer film-coated substrate 1, the change point in the dissolution rate when immersed in the sodium hydroxide aqueous solution is preferably at a depth of 4 nm or more and 24 nm or less from the surface 3a of the dielectric multilayer film 3, more preferably at a depth of 7 nm or more and 21 nm or less from the surface 3a of the dielectric multilayer film 3, and even more preferably at a depth of 10 nm or more and 18 nm or less from the surface 3a of the dielectric multilayer film 3. In this case, contamination on the surface 3a of the dielectric multilayer film 3 can be more reliably removed by alkaline cleaning, while the optical properties of the dielectric multilayer film-coated substrate 1 can be made even less susceptible to deterioration.

[0038] Furthermore, the immersion time of the dielectric multilayer film-coated substrate 1 until the change in dissolution rate when immersed in the sodium hydroxide aqueous solution is preferably 3 minutes or more, more preferably 5 minutes or more, and preferably 20 minutes or less, more preferably 15 minutes or less. In this case, contamination on the surface 3a of the dielectric multilayer film 3 can be more reliably removed by alkaline cleaning, while the optical properties of the dielectric multilayer film-coated substrate 1 can be made even less susceptible to deterioration.

[0039] Each layer constituting the dielectric multilayer film-coated substrate 1 will be described in more detail below.

[0040] (substrate) Examples of materials for the substrate 2 include glass and resin. Furthermore, the material for the substrate 2 may be Si, Ge, or the like, as long as the wavelength range used for the dielectric multilayer film-coated substrate 1 is in the infrared range. Examples of glass include soda-lime glass, borosilicate glass, alkali-free glass, crystallized glass, quartz glass, and fluoride glass. Furthermore, aluminosilicate glass, which is used as tempered glass, may also be used.

[0041] There is no particular limitation on the thickness of the substrate 2. The thickness of the substrate 2 can be set appropriately depending on the light transmittance, etc. The thickness of the substrate 2 can be, for example, about 40 μm to 1200 μm.

[0042] (Multilayer film) The multilayer film 4 includes a high-refractive-index film 6 and a low-refractive-index film 7. The high-refractive-index film 6 is preferably a film containing, as a main component, at least one selected from the group consisting of niobium oxide, titanium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silicon nitride, aluminum oxide, and aluminum nitride, and more preferably a film containing niobium oxide as a main component, as in this embodiment. The low-refractive-index film 7 is preferably a film containing silicon oxide as a main component.

[0043] In this specification, a film containing a component as a main component means a film containing that component in an amount of 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. Naturally, a film composed only of that material, excluding impurities, is particularly preferred.

[0044] The number of layers in the high refractive index film 6 is not particularly limited, and is preferably 2 or more, more preferably 5 or more, even more preferably 7 or more, and preferably 26 or less, more preferably 23 or less, even more preferably 20 or less.

[0045] The number of layers in the low refractive index film 7 is not particularly limited, and is preferably 1 layer or more, more preferably 4 layers or more, even more preferably 6 layers or more, and preferably 26 layers or less, more preferably 23 layers or less, even more preferably 20 layers or less.

[0046] The total number of layers in the multilayer film 4 is not particularly limited, but is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and is preferably 45 or less, more preferably 40 or less, even more preferably 35 or less.

[0047] The thickness of each layer of the high refractive index film 6 is not particularly limited, but is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 3 nm or more, and is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less.

[0048] The thickness of each layer of the low refractive index film 7 is not particularly limited, but is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 3 nm or more, and is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less.

[0049] The total thickness of the multilayer film 4 is not particularly limited, and the lower limit is preferably 100 nm or more, more preferably 300 nm or more, and even more preferably 500 nm or more, and the upper limit is preferably 2000 nm or less, more preferably 1500 nm or less, and even more preferably 1200 nm or less.

[0050] (Outermost dielectric film) The outermost dielectric film 5 is preferably a film containing silicon oxide as a main component. The thickness of the outermost dielectric film 5 can be appropriately set depending on the intended degree of alkaline cleaning, and is preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more, and is preferably 200 nm or less, more preferably 170 nm or less, and even more preferably 140 nm or less.

[0051] (Substrate with dielectric multilayer film) The dielectric multilayer film-coated substrate 1 has a thickness of 0.4 mm and a light transmittance at wavelengths of 350 nm to 800 nm of preferably 95% or more, more preferably 97% or more, even more preferably 99% or more, and most preferably 99.5% or more.

[0052] In the dielectric multilayer film-coated substrate 1, the dielectric multilayer film 3 is provided on the entire first main surface 2a of the substrate 2. However, in the present invention, the dielectric multilayer film 3 may be provided partially on the first main surface 2a of the substrate 2. Furthermore, another film may be provided between the first main surface 2a of the substrate 2 and the dielectric multilayer film 3.

[0053] In the dielectric multilayer film-coated substrate 1, the dielectric multilayer film 3 is provided only on the first main surface 2a of the substrate 2. However, in the present invention, the dielectric multilayer film 3 may also be provided on the second main surface 2b of the substrate 2.

[0054] An example of a manufacturing method for the dielectric multilayer film-coated substrate 1 will now be described.

[0055] (Method of manufacturing a substrate with a dielectric multilayer film) First, prepare the substrate 2. Next, place the prepared substrate 2 in a vacuum film-forming apparatus. The vacuum film-forming apparatus is not particularly limited, and examples thereof include a sputtering apparatus and a vacuum deposition apparatus.

[0056] Next, in a vacuum film-forming apparatus, a dielectric multilayer film 3 is formed on the first main surface 2a of the substrate 2. The dielectric multilayer film 3 can be formed by sputtering, evaporation, pulsed laser deposition (PLD), or the like. A method for forming the dielectric multilayer film 3 using sputtering will be described below.

[0057] In the process of forming the dielectric multilayer film 3, first, the multilayer film 4 is formed on the first main surface 2a of the substrate 2. The multilayer film 4 can be formed by alternately laminating high refractive index films 6 and low refractive index films 7 in this order.

[0058] The high-refractive-index film 6 can be formed, for example, using a target made of the material constituting the high-refractive-index film 6 and an inert gas such as argon gas and oxygen gas as carrier gases. The flow rate of the argon gas can be, for example, 500 sccm or more and 2000 sccm or less. The flow rate of the oxygen gas can be, for example, 150 sccm or more and 600 sccm or less. The power applied during sputtering can be, for example, 5 kW or more and 15 kW or less. When the high-refractive-index film 6 is made of a nitride such as silicon nitride or aluminum nitride, nitrogen gas can be used instead of oxygen gas as a carrier gas. The flow rate of the nitrogen gas can be, for example, 150 sccm or more and 600 sccm or less.

[0059] The low refractive index film 7 can be formed, for example, using a target made of the material constituting the low refractive index film 7 and an inert gas such as argon gas and oxygen gas as carrier gases. In this case, the flow rate of the argon gas can be set to, for example, 500 sccm or more and 2000 sccm or less. The flow rate of the oxygen gas can be set to, for example, 150 sccm or more and 600 sccm or less. The power applied during sputtering can be set to, for example, 5 kW or more and 15 kW or less.

[0060] In the step of forming the dielectric multilayer film 3, next, an outermost dielectric film 5 is formed on the main surface 4a of the multilayer film 4. Thereby, a substrate 1 with a dielectric multilayer film, in which the dielectric multilayer film 3 is provided on the substrate 2, can be obtained.

[0061] The outermost dielectric film 5 can be formed using, for example, a target made of a low refractive index material and an inert gas such as argon gas and oxygen gas as carrier gases. The flow rate of the argon gas can be set to, for example, 500 sccm or more and 2000 sccm or less. The flow rate of the oxygen gas can be set to, for example, 150 sccm or more and 600 sccm or less. The power applied during sputtering can be set to, for example, 5 kW or more and 15 kW or less.

[0062] In the manufacturing method of the dielectric multilayer substrate 1 of this embodiment, the process of forming the outermost dielectric film 5 includes a low-pressure film formation process in which the inside of the vacuum film formation apparatus is set to a relatively low pressure, and a high-pressure film formation process in which the inside of the vacuum film formation apparatus is set to a relatively high pressure after the low-pressure film formation process. When forming the outermost dielectric film 5, the low-pressure film formation process can form a dense film, which makes it difficult to dissolve in alkaline cleaning. On the other hand, the high-pressure film formation process can form a film that is easily dissolved in alkaline cleaning.

[0063] Therefore, in the dielectric multilayer film-coated substrate 1 obtained by the manufacturing method of this embodiment, it is possible to selectively dissolve the portion of the outermost dielectric film 5 that serves as a sacrificial film (the portion formed in the high-pressure film-forming step), while selectively leaving the portion that contributes to the optical properties (the portion formed in the low-pressure film-forming step) in the dielectric multilayer film 3. Therefore, according to the manufacturing method of this embodiment, it is possible to obtain a dielectric multilayer film-coated substrate 1 whose optical properties are resistant to deterioration even when subjected to alkaline cleaning.

[0064] The pressure inside the vacuum film-forming apparatus in the high-pressure film-forming step is preferably the same as that in the step of forming the multilayer film 4. In this case, the productivity of the dielectric multilayer film-coated substrate 1 can be further improved.

[0065] Furthermore, the pressure inside the vacuum film-forming apparatus in the low-pressure film-forming step is preferably the lowest in the step of forming the dielectric multilayer film 3. In this case, the deterioration of optical properties of the obtained dielectric multilayer film-coated substrate 1 due to alkaline cleaning can be further suppressed.

[0066] In this embodiment, the difference between the pressure inside the vacuum film-forming apparatus in the high-pressure film-forming step and the pressure inside the vacuum film-forming apparatus in the low-pressure film-forming step is preferably 0.10 Pa or more, more preferably 0.15 Pa or more, and preferably 0.30 Pa or less, more preferably 0.25 Pa or less. In this case, in the obtained dielectric multilayer film-coated substrate 1, contamination on the surface 3a of the dielectric multilayer film 3 can be more reliably removed by alkaline cleaning, while the optical properties can be made less susceptible to deterioration.

[0067] In this embodiment, the pressure inside the vacuum film-forming apparatus in the low-pressure film-forming step is preferably 0.0.5 Pa or more, more preferably 0.07 Pa or more, even more preferably 0.09 Pa or more, and is preferably 0.15 Pa or less, more preferably 0.13 Pa or less, even more preferably 0.11 Pa or less. In this case, the deterioration of optical properties of the obtained dielectric multilayer film-coated substrate 1 due to alkaline cleaning can be further suppressed.

[0068] In this embodiment, the pressure inside the vacuum film-forming apparatus in the high-pressure film-forming step is preferably 0.25 Pa or more, more preferably 0.27 Pa or more, even more preferably 0.29 Pa or more, and is preferably 0.35 Pa or less, more preferably 0.33 Pa or less, even more preferably 0.31 Pa or less. In this case, in the obtained dielectric multilayer film-coated substrate 1, contamination on the surface 3a of the dielectric multilayer film 3 can be more reliably removed by alkaline cleaning.

[0069] [Optical multilayer film substrate] Fig. 2 is a schematic cross-sectional view showing an optical multilayer-coated substrate according to one embodiment of the present invention. As shown in Fig. 2, an optical multilayer-coated substrate 10 has an outermost dielectric film 5A formed by removing a portion of the outermost dielectric film 5 of the dielectric multilayer-coated substrate 1 shown in Fig. 1.

[0070] The optical multilayer film-coated substrate 10 can be produced by alkaline cleaning the dielectric multilayer film-coated substrate 1 and removing a portion of the outermost dielectric film 5. The alkaline cleaning can be performed by immersing the dielectric multilayer film-coated substrate 1 in an aqueous sodium hydroxide solution. The concentration of the aqueous sodium hydroxide solution can be, for example, 2% by mass or more and 5% by mass or less. The temperature of the aqueous sodium hydroxide solution can be, for example, 40°C or more and 80°C or less. The immersion time of the dielectric multilayer film-coated substrate 1 in the aqueous sodium hydroxide solution can be, for example, 5 minutes or more and 20 minutes or less.

[0071] The optical multilayer-coated substrate 10 is resistant to deterioration in optical properties because the outermost dielectric film 5A obtained by removing a portion of the outermost dielectric film 5 from the dielectric multilayer-coated substrate 1 has excellent alkali resistance, and therefore the optical properties of the optical multilayer-coated substrate 10 can be obtained as desired.

[0072] For example, the optical multilayer film-coated substrate 10 can have a light transmittance of 97% or more and 99.5% or less at a thickness of 0.4 mm and a wavelength of 350 nm to 800 nm.

[0073] The present invention will be described in more detail below with reference to specific examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the present invention.

[0074] Example 1 First, a glass substrate (OA-10G, manufactured by Nippon Electric Glass Co., Ltd., thickness 1.1 mm) was prepared as a substrate. Next, a dielectric multilayer film was formed on one main surface of the prepared substrate by sputtering. Specifically, the substrate was first placed in a sputtering apparatus (vacuum film forming apparatus) and heated at a pressure of 4.0 × 10 ―4 The pressure was reduced to 100 Pa. Next, a niobium target was sputtered using argon gas and oxygen gas as carrier gases to form a niobium oxide film (Nb2O5 film) on one main surface of the substrate. The argon gas flow rate was 1000 sccm, the oxygen gas flow rate was 420 sccm, the target power (film formation power) was 10 kW, and the pressure inside the sputtering chamber was 0.30 Pa. Next, a silicon target was sputtered using argon gas and oxygen gas as carrier gases to form a silicon oxide film (SiO2 film) on the Nb2O5 film. The argon gas flow rate was 1000 sccm, the oxygen gas flow rate was 420 sccm, the target power (film formation power) was 8 kW, and the pressure inside the sputtering chamber was 0.30 Pa. By repeating this process, a multilayer film having a total of 23 layers of Nb2O5 and SiO2 films was formed on one main surface of the substrate. The thickness of each layer is as shown in Table 1 below.

[0075] [Table 1]

[0076] Next, an outermost dielectric film (the 24th layer in Table 1) was formed on the main surface of the multilayer film opposite the substrate. Argon gas and oxygen gas were used as carrier gases to sputter a silicon target, forming a silicon oxide (SiO2) film on the main surface of the multilayer film. The argon gas flow rate was 1000 sccm, and the oxygen gas flow rate was 420 sccm. The pressure inside the apparatus was set to a low pressure of 0.10 Pa at the start of deposition of the outermost dielectric film, and the film was deposited for 438 seconds. The pressure inside the apparatus was then increased to a high pressure of 0.30 Pa, and the film was deposited for 73 seconds. The same procedure was repeated on the main surface opposite the substrate to form a multilayer film and an outermost dielectric film, forming a dielectric multilayer film. The dielectric multilayer film was then subjected to alkaline cleaning. The alkaline cleaning was performed by immersing the substrate with the dielectric multilayer film in a sodium hydroxide solution with a concentration of 3% by mass and a temperature of 60°C for 30 minutes. The thickness of the obtained outermost dielectric film was 83.3 nm.

[0077] (Comparative Example 1) A substrate with a dielectric multilayer film was obtained in the same manner as in Example 1, except that the outermost dielectric film was formed while maintaining a constant pressure inside the apparatus at 0.30 Pa. The thickness of the obtained outermost dielectric film was 52.3 nm.

[0078] [evaluation] (light transmittance) For the dielectric multilayer film-coated substrates obtained in Example 1 and Comparative Example 1, optical transmission spectra were measured in the wavelength range of 350 nm to 850 nm using a spectrophotometer (Hitachi High-Tech Corporation, model number U-4000) at an incident angle of 0°. For comparison, the dielectric multilayer film-coated substrate obtained in Comparative Example 1 was used as is without being subjected to alkaline cleaning to form a dielectric multilayer film-coated substrate of Reference Example 1, and optical transmission spectra were measured for this substrate. The thickness of the outermost dielectric film in Reference Example 1 was 97.3 nm.

[0079] FIG. 3 shows the optical transmission spectra of the dielectric multilayer film-coated substrates obtained in Example 1, Comparative Example 1, and Reference Example 1.

[0080] 3, the dielectric multilayer substrate of Example 1, in which the pressure inside the apparatus was changed during deposition of the outermost dielectric film, exhibited high transmittance in the wavelength range of 450 nm to 700 nm. On the other hand, the dielectric multilayer substrate of Comparative Example 1, in which the pressure inside the apparatus was kept constant during deposition of the outermost dielectric film, did not exhibit sufficient light transmittance in the wavelength range of 450 nm to 700 nm.

[0081] (Alkaline immersion test) The substrate with the dielectric multilayer film obtained in Example 1 was immersed in an alkaline solution for a predetermined time, and the relationship between the immersion time and the amount of elution of the outermost dielectric film was measured. The alkaline solution used was an aqueous sodium hydroxide solution with a concentration of 3% by mass and a temperature of 60°C. The results are shown in Figure 4.

[0082] 4, it can be seen that the dissolution rate slows down during the dissolution of the outermost dielectric film in the dielectric multilayer substrate obtained in Example 1. In Example 1, the ratio (Va / Vb) of the dissolution rate Va before the dissolution rate slows down to the dissolution rate Vb after the dissolution rate slows down was 1.28. [Explanation of symbols]

[0083] 1...Substrate with dielectric multilayer film 2...Substrate 2a...first principal surface 2b...Second main surface 3...Dielectric multilayer film 3a…Surface 4...Multilayer film 4a...Main surface 5,5A...Outermost dielectric film 6...High refractive index film 7...Low refractive index film 10...Substrate with optical multilayer film

Claims

1. A method for manufacturing a substrate with a dielectric multilayer film, the method comprising: placing the substrate in a vacuum deposition apparatus; forming a dielectric multilayer film on the substrate in the vacuum film forming apparatus; Equipped with the step of forming the dielectric multilayer film includes a step of forming an outermost dielectric film, The method for manufacturing a substrate with a dielectric multilayer film includes a low-pressure film-forming process in which the outermost dielectric film is formed by setting the pressure inside the vacuum film-forming apparatus to a relatively low level, and a high-pressure film-forming process in which the pressure inside the vacuum film-forming apparatus is set to a relatively high level after the low-pressure film-forming process.

2. 2. The method for manufacturing a substrate with a dielectric multilayer film according to claim 1, wherein the difference between the pressure inside the vacuum film-forming apparatus in the high-pressure film-forming process and the pressure inside the vacuum film-forming apparatus in the low-pressure film-forming process is 0.10 Pa or more and 0.30 Pa or less.

3. a pressure in the vacuum film-forming apparatus in the low-pressure film-forming step is 0.05 Pa or more and 0.15 Pa or less; 3. The method for manufacturing a substrate with a dielectric multilayer film according to claim 1, wherein the pressure inside the vacuum film-forming apparatus in the high-pressure film-forming step is 0.25 Pa or more and 0.35 Pa or less.

4. the step of forming the dielectric multilayer film includes a multilayer film forming step of forming a multilayer film other than the outermost dielectric film, 3. The method for manufacturing a substrate with a dielectric multilayer film according to claim 1, wherein the pressure inside the vacuum film-forming apparatus in the multilayer film-forming step is the same as that in the high-pressure film-forming step.

5. 5. The method for producing a substrate with a dielectric multilayer film according to claim 4, wherein the multilayer film comprises a high refractive index film made of niobium oxide and a low refractive index film made of silicon oxide.

6. 3. The method for manufacturing a substrate with a dielectric multilayer film according to claim 1, wherein the pressure inside the vacuum film-forming apparatus in the low-pressure film-forming step is the lowest pressure in the step of forming the dielectric multilayer film.

7. The method for producing a substrate with a dielectric multilayer film according to claim 1 or 2, wherein the outermost dielectric film contains silicon oxide.

8. 3. The method for manufacturing a substrate with a dielectric multilayer film according to claim 1, wherein the vacuum film-forming device is a sputtering device.

9. A substrate with a dielectric multilayer film, comprising: a substrate; and a dielectric multilayer film provided on the substrate, A substrate with a dielectric multilayer film, wherein when the substrate with the dielectric multilayer film is immersed in an aqueous sodium hydroxide solution having a concentration of 3 mass % and a temperature of 60°C, the dissolution rate of the outermost dielectric film in the dielectric multilayer film slows down midway through the dissolution.

10. the dielectric multilayer film has a portion in which high-refractive-index films having a relatively high refractive index and low-refractive-index films having a relatively low refractive index are alternately laminated, 10. The substrate with a dielectric multilayer film according to claim 9, wherein the outermost dielectric film in the dielectric multilayer film is the low refractive index film.

11. The dielectric multilayer film-coated substrate according to claim 10 , wherein the low refractive index film contains silicon oxide.

12. 12. The substrate with a dielectric multilayer film according to claim 10, wherein the high refractive index film comprises at least one selected from the group consisting of niobium oxide, titanium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silicon nitride, aluminum oxide, and aluminum nitride.

13. A step of preparing a substrate with a dielectric multilayer film according to any one of claims 9 to 11; a step of removing a part of the outermost dielectric film by alkaline cleaning; A method for manufacturing a substrate with an optical multilayer film, comprising:

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