A dielectric multilayer film-coated substrate and a method for manufacturing the same, and a method for manufacturing an optical multilayer film-coated substrate.

Abstract

This invention provides a dielectric multilayer film substrate in which dirt on the film-forming surface can be easily removed even by cleaning with a weak alkali, and in which deterioration of optical properties is less likely to occur. [Solution] A dielectric multilayer film substrate 1 comprising a substrate 2, a multilayer film 3 provided on the substrate 2 having a portion in which a high refractive index film 5 with a relatively high refractive index and a low refractive index film 6 with a relatively low refractive index are alternately stacked, and a sacrificial film 4 provided on the multilayer film 3 and containing silicon oxide and aluminum oxide.

Description

Technical Field

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

Background Art

[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 optical functional film such as an antireflection film, an infrared reflection film, a band-pass filter, and a mirror. For example, the dielectric multilayer film is used as an antireflection film for a cover glass used in an image sensor.

[0003] Patent Document 1 below discloses an optical multilayer film filter used as a band-pass filter or a mirror. As the above-mentioned optical multilayer film filter, a substrate with a dielectric multilayer film is used, which includes a glass substrate and a dielectric multilayer film formed by alternately laminating a high refractive index material layer and a low refractive index material layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the film deposition surface of a dielectric multilayer film substrate is sometimes subjected to alkaline cleaning to remove dirt and other contaminants. In this case, the outermost layer of the dielectric multilayer film may have a sacrificial film that is removed along with the dirt during alkaline cleaning, acting as a protective layer. However, such sacrificial films cannot be easily removed with weak alkaline cleaning, posing a problem in that it is difficult to reliably remove dirt from the film deposition surface. Therefore, to reliably remove the sacrificial film, strong alkaline cleaning is required, which is problematic from a safety standpoint. Furthermore, strong alkaline cleaning can dissolve not only the sacrificial film but also the dielectric multilayer film directly beneath it, reducing the thickness of the dielectric multilayer film and potentially degrading its optical properties.

[0006] The object of the present invention is to provide a dielectric multilayer film-coated substrate that can easily remove dirt from the film-forming surface even by cleaning with a weak alkali, and that is less prone to deterioration of optical properties, 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. [Means for solving the problem]

[0007] The following describes various aspects of a dielectric multilayer film substrate that solves the above problems, a method for manufacturing the dielectric multilayer film substrate, and a method for manufacturing an optical multilayer film substrate using the dielectric multilayer film substrate.

[0008] A dielectric multilayer film substrate according to Embodiment 1 of the present invention is characterized by comprising a substrate, a multilayer film provided on the substrate having a portion in which a high refractive index film having a relatively high refractive index and a low refractive index film having a relatively low refractive index are alternately laminated, and a sacrificial film provided on the multilayer film containing silicon oxide and aluminum oxide.

[0009] In the dielectric multilayer film substrate according to Embodiment 2, it is preferable that the film provided directly beneath the sacrificial film in the multilayer film of Embodiment 1 is the low refractive index film.

[0010] In the dielectric multilayer film substrate according to Embodiment 3, it is preferable that the ratio of the content of aluminum oxide to silicon oxide (aluminum oxide / silicon oxide) in the sacrificial film of Embodiment 1 or Embodiment 2 is 0.02 or more and 99 or less by mass ratio.

[0011] In the dielectric multilayer film substrate according to Embodiment 4, it is preferable that the low refractive index film in the multilayer film of any one of Embodiments 1 to 3 contains silicon dioxide.

[0012] In the dielectric multilayer film substrate according to Embodiment 5, it is preferable that in the multilayer film of any one embodiment from Embodiments 1 to 4, the high refractive index film includes 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.

[0013] A method for manufacturing a dielectric multilayer film substrate according to aspect 6 of the present invention is characterized by comprising the steps of: forming a multilayer film on a substrate having a portion in which a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index are alternately laminated; and forming a sacrificial film containing silicon oxide and aluminum oxide on the multilayer film.

[0014] A method for manufacturing an optical multilayer film substrate according to aspect 7 of the present invention is characterized by comprising the steps of preparing a dielectric multilayer film substrate according to any one of aspects 1 to 5, and subjecting the dielectric multilayer film substrate to alkaline cleaning to remove the sacrificial film.

[0015] In the method for manufacturing an optical multilayer film substrate according to embodiment 8 of the present invention, in embodiment 7, it is preferable that the pH of the cleaning solution used for alkaline cleaning is 11.0 to 13.9. [Effects of the Invention]

[0016] According to the present invention, it is possible to easily remove the dirt on the film-forming surface even by washing with a weak alkali, and it is possible to provide a substrate with a dielectric multilayer film, a method for manufacturing the substrate with a dielectric multilayer film, and a method for manufacturing an optical multilayer film substrate using the substrate with a dielectric multilayer film, in which deterioration of optical properties hardly occurs.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a substrate with a dielectric multilayer film according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an optical multilayer film substrate according to an embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing the light transmittance measurement results of the optical multilayer film substrates obtained in Examples 1 and 2.

Modes for Carrying Out the Invention

[0018] Hereinafter, preferred embodiments of the present invention will be described. However, the following embodiments are merely illustrative, and the present invention is not limited to the following embodiments. Also, in each drawing, members having substantially the same function may be referred to by the same reference numerals.

[0019] [Substrate with Dielectric Multilayer Film] FIG. 1 is a schematic cross-sectional view showing a substrate with a dielectric multilayer film according to an embodiment of the present invention.

[0020] As shown in FIG. 1, the substrate 1 with a dielectric multilayer film includes a substrate 2, a multilayer film 3, and a sacrificial film 4.

[0021] In the present embodiment, the substrate 2 has a substantially rectangular plate shape. However, the substrate 2 may have a substantially disc shape, and the shape is not particularly limited.

[0022] In this embodiment, the substrate 2 is preferably a substrate that is transparent in the wavelength range of use of the substrate 1 with a dielectric multilayer film. For example, when the substrate 1 with a dielectric multilayer film is used as a cover glass for a display, the thickness of the substrate 2 can be set to 0.4 mm, and the light transmittance at a wavelength of 350 nm to 800 nm can be set to 80% or more and 94% or less.

[0023] The substrate 2 has a first main surface 2a and a second main surface 2b facing each other. A multilayer film 3 is provided on the first main surface 2a of the substrate 2.

[0024] In this embodiment, the multilayer film 3 is formed by alternately laminating a high refractive index film 5 with a relatively high refractive index and a low refractive index film 6 with a relatively low refractive index in this order. However, the multilayer film 3 only needs to have a portion where a high refractive index film 5 with a relatively high refractive index and a low refractive index film 6 with a relatively low refractive index are alternately laminated in this order, and may include other layers. Also, in the multilayer film 3, the lamination order of the high refractive index film 5 and the low refractive index film 6 is not particularly limited.

[0025] A sacrificial film 4 is provided on the multilayer film 3. The sacrificial film 4 is provided on the main surface 3a of the multilayer film 3 on the side opposite to the substrate 2.

[0026] The sacrificial film 4 is a film that protects the surface of the multilayer film 3 from dirt and the like and is a film that is removed by alkali cleaning or the like. The sacrificial film 4 can be, for example, a film that elutes about 4 nm in 1 minute when immersed in an aqueous sodium hydroxide solution with a concentration of 3.0 mass%. However, the sacrificial film 4 only needs to be a film that is removed by alkali cleaning or the like, and its elution amount can be appropriately determined and is not particularly limited.

[0027] When using the dielectric multilayer substrate 1, the sacrificial film 4 is removed, for example, by alkaline cleaning. When using the dielectric multilayer substrate 1, it is desirable that the sacrificial film 4 be completely removed, but a portion of the sacrificial film 4 may remain on the dielectric multilayer substrate 1. Alternatively, the dielectric multilayer substrate 1 may be used with the sacrificial film 4 completely remaining without removal, and is not particularly limited.

[0028] The sacrificial film 4 contains silicon oxide and aluminum oxide. Preferably, the sacrificial film 4 is a film whose main component is at least one of silicon oxide and aluminum oxide.

[0029] In this specification, the term "main component membrane" refers to a membrane containing 50% or more of that component by mass, preferably 80% or more by mass, and more preferably 90% or more by mass. Naturally, it is preferable that the membrane is composed solely of that component, with impurities removed.

[0030] Since the dielectric multilayer film substrate 1 of this embodiment has the above configuration, dirt on the film-forming surface can be easily removed even by cleaning with a weak alkali, and deterioration of optical properties is less likely to occur.

[0031] Conventionally, the outermost layer of dielectric multilayer films sometimes included a sacrificial film as a protective layer during alkaline cleaning, which was removed along with the dirt during the cleaning process. However, such sacrificial films could not be easily removed with weak alkaline cleaning, making it difficult to reliably remove dirt from the film surface. Therefore, to reliably remove the sacrificial film, strong alkaline cleaning was required, which posed a safety concern. Furthermore, strong alkaline cleaning could dissolve not only the sacrificial film but also the dielectric multilayer film directly beneath it, reducing the thickness of the dielectric multilayer film and potentially degrading its optical properties.

[0032] In response to this, the present inventors focused on the composition of the sacrificial film 4 and found that by providing a sacrificial film 4 containing silicon oxide and aluminum oxide on the outermost layer of the dielectric multilayer film substrate 1, the sacrificial film 4 can be easily removed even by alkaline cleaning with a weak alkali.

[0033] Thus, in the dielectric multilayer film substrate 1 of this embodiment, alkaline cleaning with a weak alkali is possible, which makes it less likely for the multilayer film 3 located directly beneath the sacrificial film 4 to dissolve, and as a result, it is less likely for the optical properties of the dielectric multilayer film substrate 1 to deteriorate.

[0034] Conventionally, when a silicon oxide film is provided as a low refractive index film directly beneath the sacrificial film, a problem arises in that the silicon oxide film is easily dissolved by alkaline cleaning with a strong alkali. In contrast, with the dielectric multilayer film substrate 1 of this embodiment, alkaline cleaning with a weak alkali is possible, so even when a silicon oxide film is provided as a low refractive index film 6 directly beneath the sacrificial film 4, the dissolution of the silicon oxide film can be made less likely, and as a result, the deterioration of the optical properties of the dielectric multilayer film substrate 1 can be made less likely.

[0035] Therefore, in the dielectric multilayer substrate 1 of this embodiment, even when a low refractive index film 6 such as a silicon oxide film is provided directly beneath the sacrificial film 4, it is possible to make it less likely for the optical properties of the dielectric multilayer substrate 1 to deteriorate due to alkaline cleaning.

[0036] Furthermore, as in this embodiment, when a silicon oxide film is provided as a low refractive index film 6 directly beneath the sacrificial film 4, the oxidation resistance, sulfidation resistance, and weather resistance of the multilayer film 3 after alkaline cleaning can be further improved. In addition, compared to the case where a high refractive index film 5 is provided directly beneath the sacrificial film 4, it becomes easier to design a film with high transmittance in the wavelength range of 450 nm to 700 nm.

[0037] The following describes in more detail each layer that makes up the dielectric multilayer substrate 1.

[0038] (substrate) Examples of materials for substrate 2 include glass and resin. Alternatively, if the wavelength range used is in the infrared region, the substrate 2 material may also be Si or Ge. Examples of glass include soda-lime glass, borosilicate glass, alkali-free glass, crystallized glass, quartz glass, and fluoride glass. Aluminosilicate glass, used as tempered glass, may also be used.

[0039] The thickness of substrate 2 is not particularly limited. The thickness of substrate 2 can be set appropriately according to the light transmittance, etc. For example, the thickness of substrate 2 can be about 0.05 mm to 1.2 mm.

[0040] (Multilayer film) The multilayer film 3 is a dielectric multilayer film having a high refractive index film 5 and a low refractive index film 6.

[0041] The material of the high refractive index film 5 is not particularly limited as long as it is a material with a relatively high refractive index. Examples of materials for the high refractive index film 5 include niobium oxide, titanium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silicon nitride, aluminum oxide, or aluminum nitride. These materials for the high refractive index film 5 may be used individually or in combination of multiple types. The high refractive index film 5 is preferably a film mainly composed of 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 mainly composed of niobium oxide.

[0042] The material of the low refractive index film 6 is not particularly limited as long as it is a material with a relatively low refractive index. Examples of materials for the low refractive index film 6 include silicon oxide or aluminum oxide. These materials for the low refractive index film 6 may be used individually or in combination of multiple types. The low refractive index film 6 is preferably a film mainly composed of at least one of silicon oxide or aluminum oxide, and more preferably a film mainly composed of silicon oxide.

[0043] The number of layers of the high refractive index film 5 is not particularly limited, but is preferably 2 or more layers, more preferably 5 or more layers, even more preferably 7 or more layers, preferably 26 or fewer layers, more preferably 23 or fewer layers, and even more preferably 20 or fewer layers.

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

[0045] The total number of layers in the multilayer film 3 is not particularly limited, but is preferably 10 or more layers, more preferably 20 or more layers, preferably 50 or fewer layers, more preferably 35 or fewer layers, and even more preferably 25 or fewer layers.

[0046] The thickness of each layer of the high refractive index film 5 is not particularly limited, but is preferably 1 nm or more, more preferably 2 nm or more, preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less.

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

[0048] The overall thickness of the multilayer film 3 is not particularly limited, but is preferably 100 nm or more, more preferably 300 nm or more, even more preferably 500 nm or more, preferably 2000 nm or less, more preferably 1500 nm or less, and even more preferably 1000 nm or less.

[0049] (Sacrificial membrane) In the sacrificial film 4, the ratio of aluminum oxide content to silicon oxide content (aluminum oxide / silicon oxide) is preferably 0.02 or more, more preferably 0.25 or more, even more preferably 0.54 or more, particularly preferably 0.82 or more, preferably 99 or less, more preferably 5.7 or less, even more preferably 2.4 or less, and particularly preferably 1.5 or less, in terms of mass ratio. When the above content ratio (aluminum oxide / silicon oxide) is above the lower limit, dirt on the film-forming surface of the dielectric multilayer film substrate 1 can be removed more easily even by cleaning with a weak alkali. When the above content ratio (aluminum oxide / silicon oxide) is below the upper limit, the thickness of the sacrificial film 4 can be designed to be thinner, thereby further improving the productivity of the dielectric multilayer film substrate 1. In addition, the oxidation resistance, sulfurization resistance, and weather resistance of the sacrificial film 4 are improved, and the deterioration of the multilayer film 3 before alkaline cleaning can be prevented more effectively.

[0050] The aluminum oxide content in the sacrificial film 4 is preferably 1.0% by mass or more, more preferably 23% by mass or more, even more preferably 45% by mass or more, preferably 99% by mass or less, more preferably 80% by mass or less, and even more preferably 60% by mass or less. When the aluminum oxide content is above the lower limit, dirt on the film-forming surface of the dielectric multilayer film substrate 1 can be removed more easily even by cleaning with a weak alkali. Furthermore, when the aluminum oxide content is below the upper limit, the thickness of the sacrificial film 4 can be designed to be thinner, thereby further improving the productivity of the dielectric multilayer film substrate 1. In addition, the oxidation resistance, sulfidation resistance, and weather resistance of the sacrificial film 4 are further improved, and the deterioration of the multilayer film 3 before alkaline cleaning can be more effectively prevented.

[0051] The silicon dioxide content in the sacrificial film 4 is preferably 1.0% by mass or more, more preferably 20% by mass or more, even more preferably 40% by mass or more, preferably 99% by mass or less, more preferably 77% by mass or less, and even more preferably 55% by mass or less. When the silicon dioxide content is above the lower limit, the thickness of the sacrificial film 4 can be designed to be thinner, thereby further improving the productivity of the dielectric multilayer film substrate 1. In addition, the oxidation resistance, sulfurization resistance, and weather resistance of the sacrificial film 4 are further improved, and the deterioration of the multilayer film 3 before alkaline cleaning can be more effectively prevented. When the silicon dioxide content is below the upper limit, dirt on the film surface of the dielectric multilayer film substrate 1 can be removed more easily even by cleaning with a weak alkali.

[0052] The proportion of each component in the film can be measured using a scanning transmission electron microscope (TEM-EDX, manufactured by Hitachi High-Tech Corporation, model number "HD-2700").

[0053] The refractive index of the sacrificial film 4 at a wavelength of 550 nm is preferably 1.48 or higher, more preferably 1.51 or higher, even more preferably 1.54 or higher, preferably 1.66 or lower, more preferably 1.63 or lower, and even more preferably 1.60 or lower. When the refractive index of the sacrificial film 4 at a wavelength of 550 nm is within the above range, the light transmittance of the sacrificial film 4 can be further improved.

[0054] The refractive index can be measured using molecular ellipsometry (for example, the M-2000 from JA Woollam Japan).

[0055] The thickness of the sacrificial film 4 can be appropriately set according to the planned degree of alkaline cleaning, preferably 1.0 nm or more, more preferably 2.0 nm or more, even more preferably 4.0 nm or more, preferably 30.0 nm or less, more preferably 20.0 nm or less, and even more preferably 10.0 nm or less.

[0056] (Substrate with dielectric multilayer film) The dielectric multilayer film-coated substrate 1 has a light transmittance of preferably 95% or more, more preferably 97% or more, even more preferably 99% or more, and particularly preferably 99.5% or more in the wavelength range of 350 nm to 800 nm.

[0057] In the dielectric multilayer substrate 1, the multilayer film 3 and sacrificial film 4 are provided on the entire surface of the first main surface 2a of the substrate 2. However, in the present invention, the multilayer film 3 and sacrificial film 4 may be provided only partially on the first main surface 2a of the substrate 2. In addition, other films may be provided between the first main surface 2a of the substrate 2 and the multilayer film 3, or between the multilayer film 3 and the sacrificial film 4, etc.

[0058] Furthermore, in the dielectric multilayer substrate 1, the multilayer film 3 and sacrificial film 4 are provided only on the first main surface 2a of the substrate 2. However, in the present invention, the multilayer film 3 and sacrificial film 4 may also be provided on the second main surface 2b of the substrate 2.

[0059] The following describes a manufacturing method for a dielectric multilayer film substrate 1 as an example.

[0060] (Manufacturing method for substrates with dielectric multilayer films) First, prepare substrate 2. Next, deposit the multilayer film 3 and sacrificial film 4 onto substrate 2 in that order. The multilayer film 3 and sacrificial film 4 can be deposited by sputtering, vapor deposition, or pulsed laser deposition (PLD), etc. The following describes how to deposit the multilayer film 3 and sacrificial film 4 using the sputtering method.

[0061] In the sputtering method, first, the substrate 2 is placed in the sputtering apparatus. Next, a multilayer film 3 is formed on the first main surface 2a of the substrate 2 by alternately stacking a high refractive index film 5 and a low refractive index film 6 in that order.

[0062] The high refractive index film 5 can be deposited, for example, using a target made of the material constituting the high refractive index film 5, and can be carried out using an inert gas such as argon gas and oxygen gas as carrier gases. In this case, the flow rate of argon gas can be, for example, 500 sccm or more and 2000 sccm or less. The flow rate of 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, and the pressure inside the apparatus can be, for example, 0.1 Pa or more and 0.6 Pa or less. If the high refractive index film 5 is a nitride such as silicon nitride or aluminum nitride, nitrogen gas can be used as the carrier gas instead of oxygen gas. In this case, the flow rate of nitrogen gas can be, for example, 150 sccm or more and 600 sccm or less.

[0063] The low refractive index film 6 can be deposited, for example, using a target made of the material constituting the low refractive index film 6, and can be carried out using an inert gas such as argon gas and oxygen gas as carrier gases. In this case, the flow rate of argon gas can be, for example, 500 sccm or more and 2000 sccm or less. The flow rate of oxygen gas can be, for example, 150 sccm or more and 600 sccm or less. Furthermore, the power applied during sputtering can be, for example, 5 kW or more and 15 kW or less, and the pressure inside the apparatus can be, for example, 0.1 Pa or more and 0.6 Pa or less.

[0064] Next, a sacrificial film 4 is deposited on the main surface 3a of the multilayer film 3. The sacrificial film 4 can be deposited using both a silicon target and an aluminum target. In this case, an inert gas such as argon gas and oxygen gas can be used as the carrier gas. 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 pressure inside the apparatus during sputtering can be, for example, 0.1 Pa or more and 0.6 Pa or less. The ratio of aluminum oxide content to silicon oxide content (aluminum oxide / silicon oxide) in the resulting sacrificial film 4 can be adjusted, for example, by the ratio of the applied power to the aluminum target and the applied power to the silicon target.

[0065] The applied power (deposition power) to the silicon target is preferably 1.0 kW or more, more preferably 2.0 kW or more, preferably 5.5 kW or less, and more preferably 5.0 kW or less. The deposition rate during film formation using the silicon target is preferably 0.05 nm / s or more, more preferably 0.1 nm / s or more, preferably 0.25 nm / s or less, and more preferably 0.2 nm / s or less.

[0066] The applied power (film deposition power) to the aluminum target is preferably 1.0 kW or more, more preferably 2.0 kW or more, preferably 4.0 kW or less, and more preferably 3.5 kW or less. The film deposition rate when forming a film with the aluminum target is preferably 0.001 nm / s or more, more preferably 0.004 nm / s or more, preferably 0.2 nm / s or less, and more preferably 0.15 nm / s or less.

[0067] In the manufacturing method of this embodiment, a sacrificial film 4 containing silicon oxide and aluminum oxide is formed on the outermost layer of the multilayer film 3. Therefore, even by cleaning with a weak alkali, dirt on the film surface can be easily removed, and a dielectric multilayer film-coated substrate 1 can be obtained that is less prone to deterioration of optical properties.

[0068] [Substrate with optical multilayer film] Figure 2 is a schematic cross-sectional view showing a substrate with an optical multilayer film according to one embodiment of the present invention. As shown in Figure 2, in the substrate 10 with an optical multilayer film, the sacrificial film 4 of the dielectric multilayer film substrate 1 shown in Figure 1 has been removed.

[0069] The optical multilayer film-coated substrate 10 can be manufactured by performing alkaline cleaning on the dielectric multilayer film-coated substrate 1 to remove the sacrificial film 4. Alkaline cleaning can be performed, for example, by immersing the dielectric multilayer film-coated substrate 1 in an alkaline cleaning solution. It is preferable to use a weakly alkaline cleaning solution. In this case, the pH of the alkaline cleaning solution is preferably 11.0 or higher, more preferably 11.5 or higher, preferably 13.9 or lower, and more preferably 13.5 or lower. By having the pH of the alkaline cleaning solution within the above range, it is possible to more reliably remove only the sacrificial film 4 during alkaline cleaning and reduce the possibility that the multilayer film 3 will be affected by alkaline cleaning.

[0070] As the alkaline cleaning solution, for example, an aqueous sodium hydroxide solution can be used. In this case, 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 substrate 1 in the aqueous sodium hydroxide solution can be, for example, 1 minute or more and 20 minutes or less.

[0071] In this specification, weakly alkaline cleaning conditions refer to conditions in which the amount of film eluted per unit time is small when compared to the amount of film eluted per unit time at 60°C with a 3.0% by mass sodium hydroxide aqueous solution.

[0072] Since the optical multilayer film substrate 10 is obtained by removing the sacrificial film 4 from the dielectric multilayer film substrate 1, the desired optical properties can be obtained.

[0073] For example, in the optical multilayer film substrate 10, the light transmittance at a thickness of 0.4 mm and a wavelength of 350 nm to 800 nm can be set to 97% or more and 99.5% or less.

[0074] The present invention will be described in more detail below based on specific examples and reference examples. The present invention is not limited in any way to the following examples, and can be implemented with appropriate modifications without changing its essence.

[0075] (Reference examples 1~4) First, a glass substrate (manufactured by Nippon Electric Glass Co., Ltd., OA-10G, 1.1 mm thick) was prepared as the substrate.

[0076] Next, a film containing silicon oxide (SiO2) and / or aluminum oxide (Al2O3) was deposited on the substrate by sputtering. During this process, argon gas and oxygen gas were used as carrier gases, and the silicon target and the aluminum target were sputtered. The flow rate of the argon gas was set to 1000 sccm, the flow rate of the oxygen gas to 420 sccm, and the pressure inside the apparatus was set to 0.3 Pa.

[0077] The applied power (deposition power) to the silicon and aluminum targets, as well as the deposition rates for silicon and aluminum, were set as shown in Table 1 below when depositing the films for each reference example. Furthermore, the SiO2 content (unit: mass%), Al2O3 content (unit: mass%), Al2O3 / SiO2 (ratio of Al2O3 content (unit: mass%) to SiO2 content (unit: mass%) (mass ratio)), refractive index at 550 nm, film thickness, amount of film dissolved after alkaline cleaning (1 min), and film dissolution rate during alkaline cleaning are as shown in Table 1 below. Conditions 1 and 2 will be described later. The SiO2 and Al2O3 content in the films were measured using a scanning transmission electron microscope (TEM-EDX, Hitachi High-Tech Corporation, model number "HD-2700"). Furthermore, the refractive index of the film at a wavelength of 550 nm was measured using molecular ellipsometry (JA Woollam Japan, M-2000).

[0078] (Examples 1 and 2 and Comparative Examples 1 and 2) First, a glass substrate (manufactured by Nippon Electric Glass Co., Ltd., OA-10G, 1.1 mm thick) was prepared as the substrate. Next, a multilayer film was deposited on one main surface of the prepared substrate by sputtering. Specifically, first, the substrate was placed in the sputtering apparatus. Next, using argon gas and oxygen gas as carrier gases, a niobium target was sputtered to deposit a niobium oxide film (Nb2O5 film) on one main surface of the substrate. At this time, the flow rate of argon gas was set to 1000 sccm, the flow rate of oxygen gas to 420 sccm, the target applied power (deposition power) to 10 kW, and the pressure inside the apparatus to 0.3 Pa. Next, using argon gas and oxygen gas as carrier gases, a silicon target was sputtered to deposit a silicon oxide film (SiO2 film) on top of the Nb2O5 film. In this process, the argon gas flow rate was set to 1000 sccm, the oxygen gas flow rate to 420 sccm, the target applied power (film deposition power) to 8 kW, and the pressure inside the apparatus to 0.3 Pa. By repeating this operation, a total of 24 multilayer films (the outermost layer being an 83.3 nm thick SiO2 film) were formed on one main surface of the substrate, with Nb2O5 films and SiO2 films alternately stacked one layer at a time. The film structure is shown in Table 2. The multilayer film structure is the same in Examples 1 and 2 and Comparative Examples 1 and 2.

[0079] Next, a sacrificial film containing silicon oxide (SiO2) and aluminum oxide (Al2O3) was deposited on the main surface opposite to the multilayer substrate by sputtering to obtain a dielectric multilayer substrate. In this process, argon gas and oxygen gas were used as carrier gases, and the silicon target and aluminum target were sputtered to deposit the sacrificial film on the main surface of the multilayer. The flow rate of argon gas was set to 1000 sccm, the flow rate of oxygen gas to 420 sccm, and the pressure inside the apparatus was set to 0.3 Pa.

[0080] In addition, when forming the sacrificial films for each example and comparative example, the applied power (deposition power) to the silicon and aluminum targets, and the deposition rates during silicon and aluminum film formation were set as shown in Table 3 below. Furthermore, the composition of the sacrificial films obtained in each example and comparative example, the SiO2 content (unit: mass%), the Al2O3 content (unit: mass%), the thickness of the sacrificial films, and the results of confirming the adhesion of surface contaminants after alkaline immersion are shown in Table 3 below.

[0081] [evaluation] Alkaline immersion tests were performed on the dielectric multilayer film-coated substrates obtained in each reference example. In the alkaline immersion test, the obtained dielectric multilayer film-coated substrates were immersed for 1 minute in a 3.0 mass% sodium hydroxide aqueous solution (pH: 13.9) at 40°C (Condition 1), and the amount of film dissolved and the film dissolution rate after immersion were determined. For Reference Examples 1 and 2, two samples were prepared each, and alkaline immersion tests were also performed in a 3.0 mass% sodium hydroxide aqueous solution (pH: 13.9) at 60°C (Condition 2). The results are shown in Table 1.

[0082] Table 1 shows that the amount of film eluted (dissolved) under condition 1 is less than the amount of film eluted (dissolved) under condition 2. In other words, when the temperature of the sodium hydroxide aqueous solution decreases, the alkaline cleaning power is relatively weaker compared to when the temperature is higher.

[0083] An alkaline immersion test was performed on the dielectric multilayer film-coated substrates obtained in each example and comparative example. In the alkaline immersion test, the obtained dielectric multilayer film-coated substrates were immersed for 1 minute in a 3.0% by mass sodium hydroxide aqueous solution (pH: 13.9) at 40°C. Surface contamination after the alkaline immersion test was marked "×" if contamination was visually observed, and "○" if no contamination was observed. The results are shown in Table 3.

[0084] Next, for the dielectric multilayer film substrates (optical multilayer film substrates) obtained in Examples 1 and 2 and Comparative Example 1, the light transmission spectra in the wavelength range of 350 nm to 850 nm were measured using a spectrophotometer (Hitachi High-Tech Corporation, U-4000) with an incident angle of 0°.

[0085] Figure 3 shows the light transmission spectra of the dielectric multilayer film-coated substrates (optical multilayer film-coated substrates) obtained in Examples 1 and 2 after alkaline cleaning.

[0086] As shown in Figure 3, the optical multilayer film substrates obtained in Examples 1 and 2 exhibit high transmittance exceeding 99% in the wavelength range of 450 nm to 700 nm. In Comparative Example 1, a reliable optical transmission spectrum could not be obtained due to the influence of surface contamination.

[0087] [Table 1]

[0088] [Table 2]

[0089] [Table 3]

[0090] Based on these results, it can be seen that the dielectric multilayer film substrates of Examples 1 and 2 can be easily cleaned of contaminants on the film deposition surface, along with the sacrificial film, even by cleaning with a weak alkali. Furthermore, in the dielectric multilayer film substrates of Examples 1 and 2, the amount of SiO2 film dissolved directly beneath the sacrificial film can be suppressed, resulting in good optical properties. [Explanation of symbols]

[0091] 1… Dielectric multilayer substrate 2… Circuit board 2a...First main surface 2b...Second principal surface 3…Multilayer film 3a…main surface 4…Sacrificial membrane 5…High refractive index film 6…Low refractive index film 10…Substrate with optical multilayer film

Claims

1. circuit board and A multilayer film provided on the substrate, having a portion in which a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index are alternately stacked, A sacrificial film is provided on the aforementioned multilayer film, and contains silicon oxide and aluminum oxide. A substrate with a dielectric multilayer film, comprising the above features.

2. The dielectric multilayer film substrate according to claim 1, wherein the film provided directly beneath the sacrificial film in the multilayer film is the low refractive index film.

3. The dielectric multilayer film substrate according to claim 2, wherein in the sacrificial film, the ratio of the content of aluminum oxide to silicon oxide (aluminum oxide / silicon oxide) is 0.02 or more and 99 or less by mass ratio.

4. A dielectric multilayer film substrate according to any one of claims 1 to 3, wherein the low refractive index film in the multilayer film contains silicon oxide.

5. A dielectric multilayer film substrate according to any one of claims 1 to 3, wherein the multilayer 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.

6. A step of forming a multilayer film on a substrate, having a portion in which a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index are alternately stacked. The process involves forming a sacrificial film containing silicon oxide and aluminum oxide on the multilayer film, A method for manufacturing a dielectric multilayer film substrate, comprising the features described above.

7. A step of preparing a dielectric multilayer film substrate according to any one of claims 1 to 3, The process involves alkaline cleaning the dielectric multilayer film-coated substrate to remove the sacrificial film, A method for manufacturing a substrate with an optical multilayer film, comprising the features described above.

8. The method for manufacturing an optical multilayer film substrate according to claim 7, wherein the pH of the cleaning solution used for the alkaline cleaning is 11.0 to 13.9.

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