Multilayer film, optical member, and multilayer film manufacturing method

Abstract

To provide a multilayer film that fully exhibits a self-purification function by a photocatalytic reaction on a surface, even in a case where a film thickness of a low refractive index layer of a surface is made equal to or more than a specific thickness for reducing a reflection rate of light, and can maintain hydrophilicity over a long period in a dark place.SOLUTION: In a multilayer film, a layer containing cerium oxide contains cerium oxide that includes a cubic system polycrystalline structure and a columnar structure, and a film thickness of the layer containing the cerium oxide is equal to or more than 85 nm and less than 800 nm, let the layer as a whole containing the cerium oxide be an area (A), and let an oxygen vacancy rate of the cerium oxide in the area (A) be an oxygen vacancy rate (VA), the oxygen vacancy rate (VA) is equal to or more than 0.05% and less than 10%, a film thickness of a layer containing silicon oxide or a layer containing magnesium fluoride is equal to or more than 50 nm and less than 240 nm, and a refractive index of a layer containing a low refractive index layer with respect to light of a wavelength 500 nm is equal to or less than 1.65.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure relates to a multilayer film excellent in self-cleaning property and hydrophilicity, an optical member having the multilayer film, and a method for producing the multilayer film.

Background Art

[0002] Optical members such as optical lenses, mirrors, and optical filters have a film formed of an inorganic material in order to increase or decrease the transmittance or reflectance of light. Since the film formed of an inorganic material generally has a high surface free energy immediately after film formation, it has high hydrophilicity. However, due to self-reaction or adhesion of dirt derived from humans or the environment, the surface free energy decreases and the hydrophilicity decreases in a relatively short time.

[0003] For example, when water droplets adhere to the surface of an optical product used outdoors such as an optical product for automobiles, a security camera, or a spectacle lens, or a protective cover thereof, and the hydrophilicity of the surface is reduced, the visibility may deteriorate, and the functions of the optical product and the protective cover may not be fully exhibited.

[0004] As a means for solving the above problems, a hydrophilic film in which a silicon dioxide thin film is formed on a crystalline titanium dioxide thin film is used (Patent Document 1, Patent Document 2, Non-Patent Document 1). When near-ultraviolet light is irradiated on the surface of crystalline titanium dioxide, active oxygen is generated by the photocatalytic function, and the generated active oxygen decomposes the organic matter on the surface of the hydrophilic film. As a result, the hydrophilicity of the hydrophilic film is restored, the dirt is washed away by rainfall, and self-cleaning is achieved. In addition, by disposing silicon dioxide on titanium dioxide, even when the light irradiation is stopped, it does not become hydrophobic in a short time like a thin film of only titanium dioxide, and it is known that the hydrophilicity continues for about 1 to 2 weeks even in the dark.

[0005] However, as described in Table 2 of Patent Document 1, when the silicon dioxide thin film formed on the crystalline titanium dioxide thin film is less than 50 nm, since the refractive index of titanium dioxide is large, there is a problem that the reflectance increases and the transmittance decreases. Therefore, even if it can be applied to in-vehicle door mirrors and the like where an increase in reflectance does not cause a problem, there is a problem that it is not suitable for optical members such as lenses provided with an antireflection film. In addition, when the silicon dioxide thin film on the surface formed on the crystalline titanium dioxide thin film is 50 nm or more, there is a problem that the self-cleaning function by the photocatalytic reaction is not sufficiently exhibited. In addition, although the hydrophilicity maintenance performance in a dark place is improved compared to the case of only crystalline titanium dioxide, there is a problem that it is not sufficient.

[0006] Further, as described in the examples of Patent Document 2 and Non-Patent Document 1, when a crystalline titanium dioxide layer is used as a photocatalyst, in order to crystallize a thin film made of titanium dioxide, it may be necessary to heat the thin film or the substrate provided thereon to a high temperature, and there is a problem that a resin substrate with low heat resistance cannot be used. The formation of a titanium dioxide film by some wet processes does not require high-temperature heating. However, when using a wet process, it is difficult to control the film thickness in units of 1 nm, form a thin film with a uniform film thickness, and form a film on a substrate other than a substrate with a simple shape such as a flat plate. There are also specific problems such as a short storage period of the coating solution.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Considering the application to optical members, a multilayer film is desired in which the self-cleaning function by photocatalytic reaction is sufficiently exhibited even when the film thickness of the low refractive index layer on the surface of the optical member is increased so that the low refractive index layer on the surface can be designed as an antireflection film. Also, a multilayer film is desired in which the hydrophilic property is maintained for a longer period in a dark place.

[0010] An object of the present disclosure is made in view of the above problems, and in order to reduce the reflectance of light, even when the film thickness of the low refractive index layer on the surface is made equal to or greater than a specific thickness, the self-cleaning function by photocatalytic reaction is sufficiently exhibited on the surface, and also to provide a multilayer film that can maintain hydrophilicity for a long time in a dark place. An object of the present disclosure is to provide an optical member having the above multilayer film. Also, an object of the present disclosure is to provide a method for manufacturing the above multilayer film.

Means for Solving the Problems

[0011] In order to solve the above problems, the present disclosure has a layer containing cerium oxide and, directly or via another layer, a low refractive index layer on the layer containing cerium oxide, the low refractive index layer has a layer containing silicon oxide or a layer containing magnesium fluoride, the layer containing cerium oxide contains cerium oxide including a cubic polycrystalline structure and a columnar structure, the film thickness of the layer containing cerium oxide is 85 nm or more and 800 nm or less, when the entire layer containing cerium oxide is defined as region (A) and the oxygen deficiency rate of cerium oxide in the region (A) is defined as the oxygen deficiency rate (V A )), the oxygen deficiency rate (V A) is 0.05% or more and 10% or less, the film thickness of the low refractive index layer is 50 nm or more and 240 nm or less, the refractive index of the low refractive index layer with respect to light having a wavelength of 500 nm is 1.65 or less, and the multilayer film is characterized by this.

[0012] Further, the present disclosure is an optical member having the above multilayer film.

[0013] Further, the present disclosure step (A) of forming a layer containing cerium oxide by a vacuum deposition method directly on a substrate or via another layer, step (B) of forming a low refractive index layer by a vacuum deposition method directly on the layer containing cerium oxide or via another layer and the low refractive index layer has a layer containing silicon oxide or a layer containing magnesium fluoride, the layer containing cerium oxide contains cerium oxide including a cubic polycrystalline structure and a columnar structure, the film thickness of the layer containing cerium oxide is 85 nm or more and 800 nm or less, the entire layer containing cerium oxide is defined as region (A), and when the oxygen deficiency rate of cerium oxide in the region (A) is defined as the oxygen deficiency rate (V A ), A the oxygen deficiency rate (V ) is 0.5% or more and 10% or less, The film thickness of the low refractive index layer is 50 nm or more and 240 nm or less, and this is a method for manufacturing a multilayer film.

[0014] According to one aspect of the present disclosure, in order to reduce the reflectance of light, even when the film thickness of the low refractive index layer on the surface is made to be a specific thickness or more, the self - purification function by a photocatalytic reaction is sufficiently exhibited on the surface, and also, a multilayer film capable of maintaining hydrophilicity for a long period even in a dark place, an optical member having the above multilayer film, and a method for manufacturing the above multilayer film can be obtained.

Brief Description of the Drawings

[0015]

Fig. 1A

Fig. 1B

Fig. 2

Fig. 3

Fig. 4

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of a multilayer film, an optical member having the multilayer film, and a method for forming the multilayer film according to the present disclosure will be described by way of preferred embodiments. Also, the present disclosure is not necessarily limited to the following embodiments. Also, in the present disclosure, the description of [XX or more and YY or less] or [XX to YY] representing a numerical range means a numerical range including the lower limit and the upper limit which are endpoints, unless otherwise specified. Further, when the numerical ranges are described stepwise, the upper limit and the lower limit of each numerical range can be arbitrarily combined.

[0017] In the present disclosure, the [multilayer film] refers to a configuration including two or more layers formed on the surface of a substrate. The multilayer film according to the present disclosure can be provided directly on the substrate or via another layer. Hereinafter, the layers constituting the multilayer film may also be referred to as films or thin films.

[0018] In the present disclosure, the [substrate] is a solid as an article.

[0019] In the present disclosure, the [optical member] is an optical member provided with the above multilayer film. Examples of the optical member include an optical filter, an optical lens, a light collecting lens, an optical film, an optical prism, spectacle lenses, photographic lenses, a cover for a surveillance camera, a cover for an in-vehicle camera, a cover for an in-vehicle sensor, a vehicle door mirror, a sensor for a home door, a cover for a light collecting lens, plate glass, a condenser lens, a cover glass for a display, a touch panel, and various films.

[0020] Prior to specifically describing the multilayer film according to the present disclosure, for the understanding of the present disclosure, first, the estimation of the mechanism by which the effect is achieved will be described below. However, the following description is merely a hypothesis and the present disclosure is not limited by any of the following hypotheses.

[0021] The inventor has arranged a layer containing cerium oxide having a cubic polycrystalline structure with specific oxygen vacancies directly on a substrate or via another layer, and further, a layer containing magnesium fluoride or silicon oxide with a specific film thickness is arranged directly on the layer containing cerium oxide or via another layer. In this case, it has been found that the recovery function of hydrophilicity due to the self-cleaning property by a photocatalyst is exhibited, and the ability to maintain hydrophilicity in a dark place is dramatically improved. Regarding the above mechanism, the following contents are conceivable.

[0022] When near-ultraviolet light is irradiated on a photocatalyst film that responds to near-ultraviolet light, electrons and holes are generated by photoexcitation. When the generated electrons and holes reach the surface of the film, a chemical reaction occurs, and the recovery function of hydrophilicity due to the self-cleaning property is exhibited. The cerium oxide in the layer containing cerium oxide of the present disclosure has an appropriate amount of oxygen vacancies. Since the oxygen vacancies are not excessive, the recombination of holes and electrons generated by photoexcitation is suppressed. As a result, the photocatalytic activity is enhanced. Further, a decrease in the mobility of electrons and holes generated by photoexcitation due to a shortage of oxygen vacancies is suppressed. As a result, a decrease in the self-cleaning function by the photocatalyst is suppressed.

[0023] Furthermore, due to the presence of oxygen vacancies, water molecules (H2O) and oxygen molecules (O2) from the thin film or the environment are captured by the oxygen vacancies, and active species are generated even in an environment without ultraviolet light, contributing to the maintenance of surface hydrophilicity in the dark. In addition, in the cerium oxide-containing layer of the present disclosure, oxygen vacancies are present particularly at the polycrystalline interfaces. As a result, the electrical conductivity is improved, so that the separation of electrons and holes generated by photoexcitation is promoted, and the electrons and holes move smoothly along the interface and easily reach the surface. As a result, it is considered that the hydrophilicity recovery function due to the photocatalytic self-cleaning property is exhibited, and the hydrophilicity maintenance ability in the dark is remarkably improved.

[0024] ≪First Embodiment≫ The first embodiment relates to a multilayer film. The multilayer film of the present disclosure has a cerium oxide-containing layer and, directly or via another layer, on top of the cerium oxide-containing layer, a low refractive index layer, wherein the low refractive index layer has a silicon oxide-containing layer or a magnesium fluoride-containing layer, the cerium oxide-containing layer contains cerium oxide including a cubic polycrystalline structure and a columnar structure, the film thickness of the cerium oxide-containing layer is 85 nm or more and 800 nm or less, when the entire cerium oxide-containing layer is defined as region (A) and the oxygen deficiency rate of cerium oxide in region (A) is defined as oxygen deficiency rate (V A ), the oxygen deficiency rate (V A ) is 0.05% or more and 10% or less, the film thickness of the low refractive index layer is 50 nm or more and 240 nm or less, and the refractive index of the low refractive index layer with respect to light having a wavelength of 500 nm is 1.65 or less.

[0025] The multilayer film of the present disclosure has a cerium oxide-containing layer and a low refractive index layer directly on the cerium oxide-containing layer or via another layer, and the low refractive index layer has a silicon oxide-containing layer or a magnesium fluoride-containing layer. FIG. 1A is a schematic cross-sectional view showing a first embodiment of the multilayer film of the present disclosure provided on a substrate. In FIG. 1A, a cerium oxide-containing layer 13 of the present disclosure is formed as a low refractive index layer on a substrate 11, and a magnesium fluoride-containing layer 14 is further formed on the cerium oxide-containing layer 13. A configuration example is shown. In FIG. 1A (and FIG. 1B described later), instead of the magnesium fluoride-containing layer 14, a silicon oxide-containing layer 15 may be formed on the cerium oxide-containing layer 13. Note that FIGS. 1A, 1B, and 2 schematically show the configuration of the multilayer film in the present disclosure. Therefore, the area and film thickness of each layer are not represented at an accurate ratio.

[0026] The substrate 11 will be described. The substrate 11 may be any substrate on which other layers 12 and the cerium oxide-containing layer 13 of the present disclosure can be laminated, and glass, ceramics, resin, metal, etc. can be used. The shape of the substrate is not limited, and for example, it may be planar, curved, concave, convex, or film-shaped. Further, the substrate 11 may have a hard coat layer or a barrier layer. In addition, the size and thickness of the substrate 11 are not particularly limited, and can be appropriately set according to the application and the like.

[0027] The cerium oxide-containing layer 13 according to the present disclosure will be described. The multilayer film of the present disclosure sets the entire cerium oxide-containing layer as region (A), and when the oxygen deficiency rate of cerium oxide in region (A) is the oxygen deficiency rate (V A ) and the oxygen deficiency rate (V A ) is 0.05% or more and 10% or less. When the oxygen deficiency rate is less than 0.05%, the mobility of electrons and holes excited by light decreases, and the self-purification function by the photocatalyst decreases. When it exceeds 10%, electrons and holes excited by light are likely to recombine, and the self-purification function by the photocatalyst decreases.

[0028] As the definition of [oxygen deficiency rate] in the present disclosure, when the oxygen content of cerium oxide is A and the theoretically oxygen content of CeO2 is B, the oxygen deficiency rate can be expressed as (B - A) / B × 100 (%). For example, the oxygen deficiency rate of CeO2 with a stoichiometric composition is 0%, and the oxygen deficiency rate is 100% when it is assumed that all oxygen atoms of CeO2 are absent (when it is Ce).

[0029] In the multilayer film of the present disclosure, the oxygen deficiency rate (V A ) of cerium oxide in the region (A) of the layer 13 containing cerium oxide is preferably 0.05% or more and 0.6% or less. When the oxygen deficiency rate is 0.05% or more, the self-purifying ability and the ability to maintain hydrophilicity are further enhanced.

[0030] In the multilayer film of the present disclosure, the oxygen deficiency rate (V A ) of cerium oxide in the region (A) of the layer 13 containing cerium oxide is more preferably 0.1% or more and 0.3% or less. When the oxygen deficiency rate is within this range, the self-purifying ability and the ability to maintain hydrophilicity are further enhanced.

[0031] The multilayer film of the present disclosure contains cerium oxide (CeO x ) containing a cubic polycrystalline structure in the layer 13 containing cerium oxide. In a layer made of single-crystalline cerium oxide, cracks are likely to occur in the film. When it is a layer made of amorphous cerium oxide, the self-purifying function by photocatalyst and the ability to maintain hydrophilicity in the dark are significantly reduced.

[0032] In addition, as the definition of [polycrystalline structure] in the present disclosure, it means that peaks specific to cerium oxide appear in the X-ray diffraction (XRD) measurement of the film after film formation.

[0033] In the multilayer film of the present disclosure, the film thickness of the cerium oxide-containing layer 13 is 85 nm or more and 800 nm or less. When the film thickness of the cerium oxide-containing layer 13 is less than 85 nm, the self-cleaning function by the photocatalyst and the ability to maintain hydrophilicity in the dark are significantly reduced. Further, when the film thickness of the cerium oxide-containing layer 13 exceeds 800 nm, cracks are likely to occur, and light scattering due to inhomogeneity, surface roughness, and crystal interfaces of polycrystals may become too large, which may have an adverse effect on optical properties.

[0034] The multilayer film of the present disclosure contains cerium oxide in which the cerium oxide-containing layer 13 has a columnar structure. By having a columnar structure, the separation of electrons and holes excited by light is promoted, and electrons and holes easily reach the surface. As a result, the self-cleaning function by the photocatalyst is enhanced.

[0035] Here, the [columnar structure] in the present disclosure is defined. The columnar structure means that the film contains polycrystals such as a cylindrical structure, a prismatic structure, a frustum-shaped structure, a rod-shaped structure, and a fibrous column in the film. It may be solid or hollow. The longitudinal direction of the column generally grows from the base material side of the film toward the outside air side of the film, and includes those that extend straight in the vertical direction, those that extend obliquely, those that extend while curving, those that branch and extend in a dendritic shape, and those in which a plurality of columnar crystals fuse during growth.

[0036] The cerium oxide-containing layer 13 of the present disclosure may be directly disposed on the base material 11 or may be disposed via another layer 12 described later.

[0037] In the multilayer film of the present disclosure, it is preferable that the film thickness of the low refractive index layer is 50 nm or more and 240 nm or less. In the multilayer film of the present disclosure, it is preferable that the refractive index of the low refractive index layer with respect to light having a wavelength of 500 nm is 1.65 or less.

[0038] The layer 14 containing magnesium fluoride according to the present disclosure will be described. In the multilayer film of the present disclosure, the film thickness of the layer 14 containing magnesium fluoride is 50 nm or more and 240 nm or less. If the film thickness of the layer 14 containing magnesium fluoride is less than 50 nm, the reflectance of the multilayer film may become too high. On the other hand, if the film thickness of the layer 14 containing magnesium fluoride exceeds 240 nm, the self-cleaning function by the photocatalyst may not be exhibited on the surface of the multilayer film. Further, in the multilayer film of the present disclosure, the refractive index of the layer 14 containing magnesium fluoride with respect to light having a wavelength of 500 nm is 1.65 or less. If the refractive index of the layer 14 containing magnesium fluoride exceeds 1.65, the reflectance of the multilayer film may become too high.

[0039] As shown in FIG. 1B, in the multilayer film of the present disclosure, the region of the layer 13 containing cerium oxide located at a position of 8 nm or less from the interface between the layer 13 containing cerium oxide and the layer 14 containing magnesium fluoride is defined as region (B), and when the oxygen deficiency rate of cerium oxide in region (B) is defined as the oxygen deficiency rate (V B ), it is preferable that the oxygen deficiency rate (V B ) is 0.5% or more and 30% or less. In the multilayer film of the present disclosure, the region excluding region (B) from region (A) is defined as region (C), and when the oxygen deficiency rate of cerium oxide in region (C) is defined as the oxygen deficiency rate (V C ), it is preferable that the oxygen deficiency rate (V C ) is 0% or more and 10% or less. In the multilayer film of the present disclosure, it is preferable that the oxygen deficiency rate (V B ) is larger than the oxygen deficiency rate (V C ).

[0040] The content ratio of magnesium fluoride in the total amount of the substances constituting the layer 14 containing magnesium fluoride is preferably 65% by mass or more. Within the above range, the hydrophilicity maintaining ability in the dark place is further enhanced.

[0041] As described above, in FIGS. 1A and 1B, instead of the layer 14 containing magnesium fluoride, a layer 15 containing silicon oxide may be disposed. Hereinafter, the layer 15 containing silicon oxide according to the present disclosure will be described.

[0042] In the multilayer film of the present disclosure, the refractive index of the layer 15 containing silicon oxide with respect to light having a wavelength of 500 nm is 1.65 or less. If the refractive index of the layer 15 containing silicon oxide exceeds 1.65, the reflectance of the multilayer film may become too high. In the multilayer film of the present disclosure, the layer 15 containing silicon oxide is 50 nm or more and 240 nm or less. If the film thickness of the layer 15 containing silicon oxide is less than 50 nm, the reflectance of the multilayer film may become too high. On the other hand, if the film thickness of the layer 15 containing silicon oxide exceeds 240 nm, the self-cleaning function by the photocatalyst may not be exhibited on the surface of the multilayer film.

[0043] As shown in FIG. 1B, in the multilayer film of the present disclosure, a region of the layer 13 containing cerium oxide located at a position of 8 nm or less from the interface between the layer 13 containing cerium oxide and the layer 15 containing silicon oxide is defined as region (B), and the oxygen deficiency rate of cerium oxide in region (B) is defined as the oxygen deficiency rate (V B ) When, then, the oxygen deficiency rate (V B ) is preferably 0.5% or more and 30% or less. In the multilayer film of the present disclosure, a region excluding region (B) from region (A) is defined as region (C), and the oxygen deficiency rate of cerium oxide in region (C) is defined as the oxygen deficiency rate (V C ) When, the oxygen deficiency rate (V C ) is preferably 0% or more and 10% or less. In the multilayer film of the present disclosure, it is preferable that the oxygen deficiency rate (V B ) is larger than the oxygen deficiency rate (V C ).

[0044] The layer 15 containing silicon oxide is silicon oxide (SiO xIt is a layer containing

[0045] The layer 15 containing silicon oxide has a silicon oxide content ratio preferably of 65% by mass or more with respect to the entire layer 15 containing silicon oxide. If the silicon oxide content ratio in the layer 15 containing silicon oxide is within the above range, the hydrophilicity maintaining ability in the dark is further enhanced. x It is, and x is preferably 1.5 or more and 2.0 or less. If the value of x in the silicon oxide composition SiO x is within the above range, the refractive index of the layer 15 containing silicon oxide can be made 1.65 or less. Also, a more transparent film can be obtained in the wavelength range from visible light to near-infrared light.

[0046] The layer 15 containing silicon oxide may contain aluminum oxide in addition to silicon oxide (SiO x ). At this time, the content ratio of aluminum oxide in the layer 15 containing silicon oxide is preferably 0.1% by mass or more and 10% by mass or less with respect to the entire layer 15 containing silicon oxide. When the layer 15 containing silicon oxide contains 0.1 to 10% by mass of aluminum oxide, the durability of the multilayer film such as scratch resistance and moisture resistance can be enhanced while maintaining the photocatalytic self-cleaning function and the hydrophilicity maintaining ability in the dark of the multilayer film.

[0047] The layer 15 containing silicon oxide may contain cerium oxide in addition to silicon oxide (SiO x ). At this time, the content ratio of cerium oxide in the layer 15 containing silicon oxide is preferably 0.1% by mass or more and 10% by mass or less with respect to the entire layer 15 containing silicon oxide. When the layer 15 containing silicon oxide contains 0.1% by mass or more and 10% by mass or less of cerium oxide, the photocatalytic self-cleaning function can be enhanced while maintaining the hydrophilicity maintaining ability of the multilayer film.

[0048] <<Second Embodiment>> The second embodiment relates to a multilayer film. The multilayer film of the second embodiment is different from the multilayer film of the first embodiment in that it is provided on another layer 12 provided on the base material 11. Since the other parts except for the other layer 12 are as described above, the description thereof is omitted. FIG. 2 is a schematic cross-sectional view showing a second embodiment in the multilayer film of the present disclosure. In FIG. 2, the multilayer film according to the present disclosure is provided on another layer 12 provided on the base material 11. That is, in the second embodiment, another layer 12 is formed on the base material 11, and further, a layer 13 containing cerium oxide of the present disclosure is formed on the other layer 12. In addition, a layer 15 containing silicon oxide is formed as a low refractive index layer on the layer 13 containing cerium oxide, showing a configuration example.

[0049] The base material 11 and the layer 13 containing cerium oxide of the present disclosure are as described in the first embodiment above.

[0050] In FIG. 2, for all or part of the layer 15 containing silicon oxide, the layer 14 containing magnesium fluoride described in the first embodiment may be arranged instead. Further, the layer 13 containing cerium oxide of the present disclosure may be directly arranged on the base material 11 without passing through the other layer 12.

[0051] As the other layer 12, a layer containing a metal, a fluoride, an oxide, a carbide, a sulfide, a halide, a nitride, and a composite anion compound (such as an oxynitride, an oxysulfide, an oxyhalide, an oxyfluoride, an oxynitride, etc.) can be arranged. Specifically, as the other layer 12, a metal layer containing elements such as aluminum (Al), chromium (Cr), gold (Au), silver (Ag), copper (Cu), silicon (Si), germanium (Ge), titanium (Ti), nickel (Ni), or a layer containing a fluoride such as magnesium fluoride (MgF2) or calcium fluoride (CaF2), silicon oxide (SiO x )), aluminum oxide (Al2O x ), yttrium oxide (Y2O x ), zirconium oxide (ZrO x ), hafnium oxide (HfOx ) Zinc oxide (ZnO x ) Tantalum oxide (Ta2O x ) Niobium oxide (Nb2O x ) Indium oxide (In2O x ) Tin oxide (SnO x ) Tungsten oxide (WO x ) Cerium oxide (CeO x ) Titanium oxide (TiO x ) Lanthanum titanate (La x Ti y O z ) Aluminum titanate (La x Al y O z ) Layers containing oxides such as silicon dioxide with alumina added (SiO2+Al2O3), layers containing sulfides such as ZnS, silicon nitride (Si x N y ) Layers containing nitrides such as gallium nitride (GaN), layers containing carbides such as tungsten carbide (WC), silicon oxynitride (SiO x N y ) Composite anion compounds such as lead titanate oxyfluoride (Pb w Ti x O y F z ) can be used. The other layer 12 may be a single layer or a multilayer of two or more layers. When the other layer 12 is a multilayer of two or more layers, the other layer 12 may be constituted by combining a plurality of types of the layers exemplified above. Further, the other layer 12 may also be a layer containing a mixture composed of two or more of the compounds contained in the layers exemplified above.

[0052] The method for forming the other layer 12 is not particularly limited. For the method for forming the other layer 12, for example, dry film-forming methods such as sputtering method, vacuum evaporation method, and ion plating method, or wet film-forming methods such as dipping method, coating method, spraying method, spin coating method, bar coating method, printing method, and flow coating method can be applied.

[0053] By making the other layer 12 have a composition, refractive index, film thickness, number of layers, etc. according to the purpose and function, it is possible to form a multilayer film with specific functions such as an antireflection layer, a half mirror layer, a light absorption layer, an alkali diffusion prevention layer, an adhesion layer, an antistatic layer, a heater layer, and the like.

[0054] ≪Application Example≫ The application example of the present disclosure is about an optical member. The optical member of the present disclosure is characterized by having the multilayer film described above. FIG. 3 and FIG. 4 are schematic views showing the configuration in one embodiment of the optical member of the present disclosure. FIG. 3 is a lens cover for a surveillance camera, in which the multilayer film of the present disclosure is formed on the surface of a dome-shaped resin base material 21. Further, FIG. 4 is glasses, which is composed of a spectacle lens 31 and a spectacle frame 32, which are one embodiment of the optical member of the present disclosure. The multilayer film of the present disclosure is formed on both surfaces of the spectacle lens 31.

[0055] The multilayer film of the present disclosure can be used as an optical thin film such as an antireflection film, various optical filter multilayer films, and optical mirror multilayer films. Further, it can be used for optical members such as optical filters, optical lenses, light collecting lenses, optical films, optical prisms, spectacle lenses, photographic lenses, covers for surveillance cameras, covers for in-vehicle cameras, covers for in-vehicle sensors, vehicle door mirrors, plate glass, condenser lenses, cover glasses for displays, touch panels, and various films, and covers for protecting the optical members. Further, by coating a layer having a composition, refractive index, film thickness, number of layers, etc. according to the purpose and function on the surface of the base material 11 other than the surface provided with each of the above-described layers, an optical member with specific functions such as a mirror layer, a half mirror layer, a light absorption layer, a transparent heater layer, and an antireflection layer can be formed.

[0056] ≪Third Embodiment≫ The third embodiment is about a method for manufacturing a multilayer film. The method for manufacturing the multilayer film of the present disclosure is a step (A) of forming a layer containing cerium oxide by a vacuum evaporation method directly on a base material or via another layer, Step (B) of forming a low refractive index layer by a vacuum deposition method directly on the layer containing cerium oxide or via another layer including The low refractive index layer has a layer containing silicon oxide or a layer containing magnesium fluoride, The layer containing cerium oxide contains cerium oxide including a cubic polycrystalline structure and a columnar structure, The film thickness of the layer containing cerium oxide is 85 nm or more and 800 nm or less, Taking the entire layer containing cerium oxide as region (A) and the oxygen deficiency rate of cerium oxide in the region (A) as the oxygen deficiency rate (V A ), when the oxygen deficiency rate (V A ) is 0.05% or more and 10% or less, The film thickness of the low refractive index layer is 50 nm or more and 240 nm or less, which is characterized by this. The explanation will be given below. Regarding the multilayer film, since it is as described above, the explanation will be partially omitted.

[0057] The layer 13 containing cerium oxide formed in the above step (A) contains cerium oxide having a cubic polycrystalline structure with a specific oxygen deficiency rate, and the film thickness of the layer 13 containing cerium oxide formed in the above step (A) is 85 nm or more and 800 nm or less. Also, the film thickness of the layer 14 containing silicon oxide or the layer 15 containing magnesium fluoride formed in the above step (B) is 50 nm or more and 240 nm or less. The refractive index of the layer 14 containing silicon oxide and the layer 15 containing magnesium fluoride formed in the above step (B) with respect to light with a wavelength of 500 nm is 1.65 or less.

[0058] The method for manufacturing a multilayer film of the present disclosure includes a step (A) of forming a layer containing cerium oxide on a substrate directly or via another layer by a vacuum evaporation method, and a step (B) of forming a layer containing silicon oxide or a layer containing magnesium fluoride on the layer containing cerium oxide directly or via another layer by a vacuum evaporation method. The temperature of the substrate during vacuum evaporation is preferably the temperature at which cerium oxide crystallizes. Although it depends on the heat-resistant temperature of the substrate to be used and other film-forming conditions, the temperature can usually be selected in the range of 0°C or higher and 500°C or lower.

[0059] The evaporation method in vacuum evaporation is not limited as long as it is a method by which the film-forming material evaporates. For example, as the evaporation method, evaporation means such as an electron gun, resistance heating, or a laser can be applied. Further, ion assist, plasma assist, etc. can be used in combination with the above evaporation means as necessary.

[0060] In the method for manufacturing a multilayer film of the present disclosure, before step (A), the total value of the partial pressure of water molecules (H2O) and the partial pressure of oxygen molecules (O2) in the atmosphere is preferably 2×10 -2 Pa or less, and more preferably 5.9×10 -4 Pa or less. Further, the total value of the partial pressure of water molecules (H2O) and the partial pressure of oxygen species (in the present invention, oxygen species refer to oxygen atoms, oxygen molecules, and oxygen ions) during film formation in region (B) is preferably 2×10 -2 Pa or less on average, and more preferably 7.8×10 -3 Pa or less on average.

[0061] The degree of vacuum in the evaporation apparatus is the same (for example, a degree of vacuum of 7×10 -4Even when the conditions are the same as in (Pa), if the conditions inside the vapor deposition apparatus are different, for example, in cases of different degrees of contamination, the presence of minute vacuum leaks, and almost no leaks, the partial pressure ratio of the gas remaining in the vacuum atmosphere changes significantly depending on the implementation of pre-baking or the like. As a result, since the gas partial pressures before and during the formation of the layer containing cerium oxide change, the characteristics of the obtained layer 13 containing cerium oxide may be affected. For example, the partial pressure of water molecules can be reduced by performing cleaning so that the adsorbed substances (such as water molecules) around the evaporation source and on the wall surface inside the apparatus are reduced before film formation.

[0062] Regarding the film-forming material formed by an electron gun, when using the most commonly used pure copper hearth liner, due to its high thermal and electrical conductivity, the energy loss is large, and it will not evaporate unless the electron gun output is increased, so the temperature around the evaporation source becomes higher. Therefore, the amount of adsorbed gas (such as water molecules) desorbing may become larger. By using a hearth liner made of molybdenum or tantalum instead of pure copper, the electron gun output during film formation can be reduced. Also, molybdenum and the like have the feature of having less gas content than ordinary oxygen-free copper.

[0063] When installing a cryochiller in addition to a rotary pump and a diffusion pump in the vacuum evacuation apparatus, the partial pressure of water molecules in the atmosphere tends to decrease. Also, when heating the vicinity of the wall surface of the vacuum vapor deposition apparatus with a heater (wall heater) or performing pre-baking, the partial pressure of water molecules in the atmosphere tends to decrease.

[0064] Before starting the film-forming process, if it is confirmed that there is almost no leak in the film-forming apparatus, the oxygen partial pressure inside the apparatus can be stabilized. This is because even a minute leak allows air around the apparatus to flow into the apparatus, increasing the oxygen partial pressure in the atmosphere and potentially affecting the characteristics of the obtained layer containing cerium oxide.

[0065] When heating the substrate, there is a time lag until the actual temperature of the substrate reaches the same temperature as the measured temperature by the thermocouple. Depending on the substrate heat setting temperature, the material of the substrate holder, the thickness of the substrate, etc., after the temperature of the thermocouple reaches the set temperature, it is necessary to wait for about 10 to 20 minutes. In addition, since the substrate adsorbs a certain amount of moisture, etc., by heating the substrate sufficiently, more moisture adsorbed on the substrate before film formation can be desorbed. During film formation, energy from radiant heat from the evaporation source is also added, so it becomes easier for moisture to desorb from the substrate. Therefore, when heating the substrate, after 15 minutes or more have elapsed since the thermocouple for measuring the substrate temperature indicates the set temperature ±2°C, the film formation process is started.

[0066] When installing the substrate in the vapor deposition apparatus, a jig such as a normal holder or a yatoi is usually used to set the substrate in the apparatus. Regarding this jig, using a cleaned and clean one and a material with little gas adsorption and desorption such as SUS316LN can reduce the amount of gas released such as moisture desorbing during film formation. On the other hand, a dirty jig, a porous material, a jig made of brass or synthetic resin, or a zinc-plated jig has a large gas release amount, so gas components such as moisture and oxygen are likely to desorb from the jig during film formation.

[0067] The reasons for performing these such as inner wall surface cleaning, installation of a cryochiller, leak confirmation, control of substrate heating time, selection of jig material, etc. are that when forming the layer 13 containing cerium oxide, even under the same gas introduction conditions (for example, when no gas is introduced at all or when the oxygen introduction amount is set to 1×10 -2 Pa), the partial pressures of oxygen molecules and water molecules in the atmosphere are different. Therefore, it may affect the oxygen deficiency rate of the obtained layer containing cerium oxide. Therefore, if these are not performed, even if other film formation conditions, etc. are the same as those in the examples of the present application, a multilayer film including the layer 13 containing cerium oxide of the present disclosure may not be obtained.

[0068] The method for manufacturing the multilayer film of the present disclosure sets the entire layer containing cerium oxide as region (A), and the oxygen deficiency rate of cerium oxide in region (A) is the oxygen deficiency rate (V AWhen it is set as (oxygen deficiency rate V A ), the oxygen deficiency rate is 0.05% or more and 10% or less. Further, as shown in FIG. 1B, in the method for manufacturing the multilayer film of the present disclosure, the region of the cerium oxide-containing layer located at a position of 8 nm or less from the interface between the cerium oxide-containing layer and the low refractive index layer (the layer containing magnesium fluoride or the layer containing silicon oxide) is defined as region (B), and when the oxygen deficiency rate of cerium oxide in region (B) is defined as oxygen deficiency rate V B ), the oxygen deficiency rate V B ) is 0.5% or more and 30% or less. In region (A), the region excluding region (B) is defined as region (C), and when the oxygen deficiency rate of cerium oxide in region (C) is defined as oxygen deficiency rate V C ), the oxygen deficiency rate V C ) is 0% or more and 10% or less, and it is preferable that the oxygen deficiency rate V B ) is larger than the oxygen deficiency rate V C ).

[0069] The multilayer film of the present disclosure can be suitably manufactured by the above method.

Example

[0070] Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to the following examples at all.

[0071] The materials used for manufacturing and evaluating the multilayer film in the examples are described below.

[0072] (Substrate) Flat plates of the following materials were used as substrates. When the substrate temperature during vapor deposition was 100°C or higher, substrates other than resin substrates were used. In other cases of substrate temperature, all the following substrates were used. Note that the silicon and sodium chloride substrates were used for analyzing the oxygen deficiency rate and measuring the film thickness by an electron microscope. · Borosilicate glass: thickness 3 mm · Synthetic quartz: thickness 3 mm · Polycarbonate resin: thickness 2 mm · Polymethyl methacrylate resin: thickness 2 mm · Silicon: thickness 1 mm · Sodium chloride: thickness 2 mm (Film-forming material) The following materials were used. · Ce: granular, purity 99.9% · CeO2: cylindrical, purity 99.9% · La2O3: cylindrical, purity 99.9% · Sm2O3: cylindrical, purity 99.9% · SiO: granular, purity 99.9% · SiO2: granular, purity 99.9% · Al2O3: granular, purity 99.95% · MgF2: granular, purity 99.9% · Ti3O5: granular, purity 99.9% · TaO: granular, purity 99.9% · Cr: granular, purity 99.9% (Gas for ion-assisted film formation) · O2: gas, purity 99.999% · Ar: gas, purity 99.999% (Gas for vacuum leak check) · He: gas, purity 99.9999% (Etching gas during measurement) · Ar: gas, purity 99.9999% (Reagents, etc.) · Pure water: JIS K0557 A4 · Stearic acid: JIS K8585 special grade, purity 99.9% · Heptane: JIS K9701 special grade, purity 99.9%

[0073] (Fabrication of multilayer film) The common film-forming methods and conditions for the examples and comparative examples in the fabrication of the multilayer film are described. A vacuum evaporation apparatus (dome diameter Φ1300 mm, evaporation distance 1100 mm) was used as the film-forming apparatus. The temperature distribution, the film formation rate of the film forming material, the incident ion distribution of the ion assist, etc. were adjusted to be the same for all the substrates installed in the evaporation device so that the same multilayer film could be obtained. For this adjustment, measurements using a Faraday cup, a thermocouple, a film thickness measuring device, etc., and corrections, the arrangement of correction plates and sheathed heaters, and the optimization of the heater output were repeated. Before film formation, the periphery of the evaporation source, the dome, and the wall surface inside the device were polished and wiped clean with an organic solvent (isohexane).

[0074] Subsequently, the above-mentioned film forming material and various clean substrates were set in the vacuum evaporation device. For the evaporation material to be formed into a film by an electron gun, it was placed on a molybdenum hearth liner that had been cleaned and degassed and evaporated. As the substrate holder, one made of SUS316LN that had been cleaned and degassed was used. Since it may be difficult to perform analysis and analytical evaluation when the obtained test piece is only a multilayer film, various substrates were set in a mechanism that can replace the substrate for each layer so that not only multilayer films but also single-layer films for analysis and analytical evaluation can be obtained simultaneously.

[0075] After that, the degree of vacuum at which film formation was to be started was evacuated until the partial pressures of water molecules and oxygen molecules were reached. In addition to a rotary pump and a diffusion pump, a cryochiller (PFC-1102HC, manufactured by Polycold) was used in combination with the vacuum evacuation device. Before starting the film formation process, He gas for leak detection and a quadrupole mass spectrometer (Qulee with YTP-H, manufactured by ULVAC) were used as a leak detector to confirm that there was almost no leak in the vacuum evaporation device. As the confirmation items, it was confirmed that the mass spectrometer did not detect He gas for leak detection and that the ratio of nitrogen molecules (mass number 28) to oxygen molecules (mass number 32) was clearly different from the ratio in the atmosphere (N2:O2 = 79%:21%).

[0076] Before the start of film formation of layer 13 containing cerium oxide, the partial pressures of water molecules and oxygen molecules in the atmosphere were measured and calculated using an ionization vacuum gauge and a quadrupole mass spectrometer. Also, during the formation of the region (B) of the cerium oxide-containing layer 13, the partial pressure of water molecules and the partial pressure of oxygen species (oxygen atoms, oxygen molecules, oxygen ions) were measured and calculated every second using an ionization vacuum gauge and a quadrupole mass spectrometer. These partial pressures were summed and averaged to calculate the average partial pressure during the formation of the region (B). The substrate temperature during film formation was -15°C or higher and 600°C or lower. Since 15 minutes or more had elapsed after the substrate temperature reached the set temperature ±2°C, the film formation process was started.

[0077] Thereafter, a film-forming material was vacuum-deposited on the set substrate to form a multilayer film as listed in Tables 1-1 to 1-4, and a test piece was obtained. Unless otherwise specified, the cerium oxide-containing layer was deposited at a film formation rate of 0.5 nm / s. The dome rotation speed during the formation of each layer was 20 rpm. Films composed of two components such as CeO2 + Al2O3 and SiO2 + Al2O3 were formed by a binary evaporation method in which two types of film-forming materials were installed in two heating sources respectively and evaporated simultaneously. When using MgF2 and SiO as film-forming materials, a tantalum boat and resistance heating were used as the heating sources.

[0078] In addition, in each of Examples 1 to 66 and Comparative Examples 1 to 22, since there was no substantial difference between the multilayer films obtained by changing the type of substrate, only one example was described in Tables 1-1 to 1-4. Also, "crystalline" in Tables 1-1 to 1-4 means that the cerium oxide-containing layer contains cerium oxide having a cubic polycrystalline structure, and "amorphous" means that the cerium oxide-containing layer does not contain cerium oxide having a cubic polycrystalline structure. "Columnar" in Tables 1-1 to 1-4 means that the cerium oxide-containing layer contains cerium oxide having a columnar structure, and "non-columnar" means that the cerium oxide-containing layer does not contain cerium oxide having a columnar structure.

[0079] Hereinafter, the individual conditions of each example and comparative example in the production of the multilayer film will be described. [Example 1] The substrate temperature of the vacuum evaporation apparatus was set at 400 °C, the wall heater was set at 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.53×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide (the region of the layer containing cerium oxide located at a position of 8 nm or less from the interface between the layer containing cerium oxide and the layer containing silicon oxide or the layer containing magnesium fluoride) was, on average, 3.11×10 -3 Pa. Other film formation conditions were as described in (Production of Multilayer Film).

[0080] [Example 2] The substrate temperature of the vacuum evaporation apparatus was set at 400 °C, the wall heater was set at 105 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.50×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide was, on average, 3.06×10 -3 Pa. Other film formation conditions were as described in (Production of Multilayer Film).

[0081] [Example 3] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, the wall heater was set to 110 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.50×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to fabricate a multilayer film. Note that the average total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was 3.05×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0082] [Example 4] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, the wall heater was set to 115 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.49×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. Note that the average total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was 3.03×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0083] [Example 5] The substrate temperature of the vacuum deposition apparatus was set at 400 °C, the wall heater was set at 140 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed since the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.48×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.00×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0084] [Example 6] The substrate temperature of the vacuum deposition apparatus was set at 400 °C, the wall heater was set at 120 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed since the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.47×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as film-forming materials to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.98×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0085] [Example 7] The substrate temperature of the vacuum deposition apparatus was set at 400 °C, the wall heater was set at 125 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed since the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.45×10-4 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.96×10 -3 It was Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0086] [Example 8] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 130 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.45×10 -4 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.94×10 -3 It was Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0087] [Example 9] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 135 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.44×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 2.92×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0088] [Example 10] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 140 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.39×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 2.84×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0089] [Example 11] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 145 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.38×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.80×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0090] [Example 12] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 150 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.37×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as film-forming materials to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.78×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0091] [Example 13] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 155 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.34×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 2.73×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0092] [Example 14] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 160 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.33×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 2.71×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0093] [Example 15] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 165 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.26×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.57×10 -3 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0094] [Example 16] The substrate temperature of the vacuum deposition apparatus was set to 400 °C, and the wall heater was set to 150 °C for vacuum evacuation. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.71×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material at a film formation rate of 0.7 nm / s. Subsequently, a MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 4.89×10 -3 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0095] [Example 17] The substrate temperature of the vacuum deposition apparatus was set to 400 °C, and the wall heater was set to 175 °C for vacuum evacuation. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.78×10 -4It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 1.0 nm / s using CeO2 as the film formation material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as the film formation material to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 7.23×10 -3 It was Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0096] [Example 18] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 180 °C, followed by vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.96×10 -4 It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 1.5 nm / s using CeO2 as the film formation material. Subsequently, an SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as the film formation materials to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 1.20×10 -2 It was Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0097] [Example 19] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 100 °C, followed by vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 2.87×10 -4It was Pa. Subsequently, a cerium oxide-containing layer was formed on various substrates using Ce and CeO2 as film-forming materials. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. During the film formation of the outermost surface side 8 nm (region (B)) of the cerium oxide-containing layer, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 5.84×10 -3 It was Pa. The other film formation conditions were as described in (Production of Multilayer Film).

[0098] [Example 20] The substrate temperature of the vacuum deposition apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the cerium oxide-containing layer, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 2.83×10 -4 It was Pa. Subsequently, a cerium oxide-containing layer was formed on various substrates using Ce and CeO2 as film-forming materials. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to produce a multilayer film. During the film formation of the outermost surface side 8 nm (region (B)) of the cerium oxide-containing layer, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 5.76×10 -3 It was Pa. The other film formation conditions were as described in (Production of Multilayer Film).

[0099] [Example 21] The substrate temperature of the vacuum deposition apparatus was set to 400 °C and the wall heater was set to 200 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the cerium oxide-containing layer, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.03×10 -4It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 0.65 nm / s using Sm2O3 and CeO2 as film formation materials. Subsequently, an SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film formation materials to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.71×10 -3 It was Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0100] [Example 22] The substrate temperature of the vacuum deposition apparatus was set to 400 °C, and the wall heater was set to 100 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 2.84×10 -4 It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed using Ce and CeO2 as film formation materials. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film formation material to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 5.76×10 -3 It was Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0101] [Example 23] The substrate temperature of the vacuum deposition apparatus was set to 250 °C, and the wall heater was set to 100 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 250 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.51×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. When forming the layer containing cerium oxide, ion assist was performed using an RF ion source. The conditions for ion assist were an acceleration voltage value of 700 V, an acceleration current value of 700 mA, and an O2 gas flow rate of 60 sscm. Also, when forming the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, film formation was carried out with the ion gun and gas introduction stopped. When forming the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, film formation was carried out with the ion gun and gas introduction stopped. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. Note that the total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 3.08×10 -3 It was Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0102] [Example 24] The substrate temperature of the vacuum deposition apparatus was set to 350 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 350 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.49×10 -4 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. When forming the layer containing cerium oxide, oxygen introduction was performed by Auto Pressure Control (APC). The introduction amount of oxygen gas was 1.9×10 -2 It was Pa. Also, when forming the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, film formation was carried out 1 minute after stopping the oxygen gas introduction. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. Note that the total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 3.03×10 -3It was Pa. Other film-forming conditions are as described in (Fabrication of Multilayer Films).

[0103] [Example 25] The substrate temperature of the vacuum evaporation apparatus was set to 300 °C, the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 300 ± 2 °C and before starting the film-forming process of the cerium oxide-containing layer, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.45×10 -4 Pa. Thereafter, a cerium oxide-containing layer was formed on various substrates using CeO2 as a film-forming material. When forming the cerium oxide-containing layer, ion assist was performed using an RF ion source. The conditions for ion assist were an acceleration voltage value of 700 V, an acceleration current value of 700 mA, an O2 gas flow rate of 35 sscm, and an Ar gas flow rate of 7 sccm. Also, when forming the outermost 8 nm (region (B)) of the cerium oxide-containing layer, film formation was performed with the ion gun and gas introduction stopped. Subsequently, a SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO2 and Al2O3 as film-forming materials to fabricate a multilayer film. Note that the average total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the outermost 8 nm (region (B)) of the cerium oxide-containing layer was 2.95×10 -3 Pa. Other film-forming conditions are as described in (Fabrication of Multilayer Films).

[0104] [Example 26] The substrate temperature of the vacuum evaporation apparatus was set to 300 °C, the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 300 ± 2 °C and before starting the film-forming process of the cerium oxide-containing layer, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.39×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. When forming the layer containing cerium oxide, ion assist was performed by an RF ion source. The conditions for ion assist were an acceleration voltage value of 700 V, an acceleration current value of 700 mA, an O2 gas flow rate of 30 sscm, and an Ar gas flow rate of 10 sccm. Also, when forming the 8-nm (region (B)) on the surface layer side of the layer containing cerium oxide, film formation was carried out with the ion gun and gas introduction stopped. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8-nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 2.83×10 -3 It was Pa. The other film-forming conditions were as described in (fabrication of multilayer film).

[0105] [Example 27] The substrate temperature of the vacuum deposition apparatus was set to 400 °C, and the wall heater was set to 100 °C, followed by vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 2.45×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material at a film formation rate of 2.0 nm / s. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8-nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 1.99×10 -2 It was Pa. The other film-forming conditions were as described in (fabrication of multilayer film).

[0106] [Example 28] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, the wall heater was set to 100 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 2.87×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using Ce and CeO2 as film forming materials. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film forming material to fabricate a multilayer film. Incidentally, the average total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide was 5.84×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0107] [Example 29] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, the wall heater was set to 100 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.51×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as a film forming material. Subsequently, a MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film forming material to fabricate a multilayer film. Incidentally, the average total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide was 3.08×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0108] [Example 30] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, the wall heater was set to 100 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.51×10-4 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.08×10 -3 It was Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0109] [Example 31] The substrate temperature of the vacuum deposition apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.50×10 -4 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.05×10 -3 It was Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0110] [Example 32] The substrate temperature of the vacuum deposition apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.47×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 2.98×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0111] [Example 33] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.45×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was, on average, 2.95×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0112] [Example 34] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.42×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as film-forming materials to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.89×10 -3 It was Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0113] [Example 35] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.38×10 -4 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.80×10 -3 It was Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0114] [Example 36] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.37×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.80×10 -3 Pa. The other film-forming conditions were as described in (Fabrication of Multilayer Film).

[0115] [Example 37] The substrate temperature of the vacuum evaporation apparatus was set to 400°C, and the wall heater was set to 100°C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.31×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.66×10 -3 Pa. The other film-forming conditions were as described in (Fabrication of Multilayer Film).

[0116] [Example 38] The substrate temperature of the vacuum evaporation apparatus was set to 400°C, and the wall heater was set to 200°C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 9.84×10 -5It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 0.7 nm / s using La2O3 and CeO2 as film formation materials. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film formation material to produce a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.80×10 -3 It was Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0117] [Example 39] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 160 °C, followed by vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 2.87×10 -4 It was Pa. On various substrates, a layer containing cerium oxide was formed using Ce and CeO2 as film formation materials. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film formation material to produce a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 5.84×10 -3 It was Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0118] [Example 40] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 160 °C, followed by vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.27×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO₂ as a film-forming material. Subsequently, a SiO₂ + CeO₂ film (low refractive index layer) was formed thereon using SiO and CeO₂ as film-forming materials to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.59×10 -3 Pa. The other film-forming conditions were as described in (Fabrication of Multilayer Film).

[0119] [Example 41] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 100 °C for vacuum evacuation. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film-forming process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.51×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO₂ as a film-forming material. Subsequently, a SiO₂ film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.08×10 -3 Pa. The other film-forming conditions were as described in (Fabrication of Multilayer Film).

[0120] [Example 42] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 100 °C for vacuum evacuation. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film-forming process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.37×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as film-forming materials to produce a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.79×10 -3 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0121] [Example 43] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 100 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.51×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.08×10 -3 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0122] [Example 44] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 160 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.45×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.94×10 -3 Pa. The other film formation conditions were as described in (Production of Multilayer Film).

[0123] [Example 45] The substrate temperature of the vacuum deposition apparatus was set to 400°C and the wall heater was set to 160°C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.51×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.08×10 -3 Pa. The other film formation conditions were as described in (Production of Multilayer Film).

[0124] [Example 46] The substrate temperature of the vacuum deposition apparatus was set to 400°C and the wall heater was set to 160°C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.45×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.95×10 -3 Pa. The other film-forming conditions were as described in (fabrication of multilayer film).

[0125] [Example 47] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.51×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.07×10 -3 Pa. The other film-forming conditions were as described in (fabrication of multilayer film).

[0126] [Example 48] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.41×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, on top of that, a SiO2 + CeO2 film (low refractive index layer) was formed using SiO and CeO2 as film-forming materials to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.87×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0127] [Example 49] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.51×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, on top of that, a MgF2 film (low refractive index layer) was formed using MgF2 as a film-forming material to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.07×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0128] [Example 50] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.37×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.78×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0129] [Example 51] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.51×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, a SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO2 and Al2O3 as film-forming materials to fabricate a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.08×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0130] [Example 52] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.45×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.95×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0131] [Example 53] The substrate temperature of the vacuum evaporation apparatus was set to 400°C, and the wall heater was set to 160°C, followed by vacuum evacuation. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.50×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO2 as a film-forming material to produce a multilayer film. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.05×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0132] [Example 54] The substrate temperature of the vacuum evaporation apparatus was set to 400°C, and the wall heater was set to 160°C, followed by vacuum evacuation. When 15 minutes or more had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.44×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO2 and CeO2 as film-forming materials to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.94×10 -3 It was Pa. Other film-forming conditions were as described in (Fabrication of Multilayer Film).

[0133] [Example 55] The substrate temperature of the vacuum evaporation apparatus was set to 400°C and the wall heater was set to 160°C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.37×10 -4 It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.79×10 -3 It was Pa. Other film-forming conditions were as described in (Fabrication of Multilayer Film).

[0134] [Example 56] The substrate temperature of the vacuum evaporation apparatus was set to 400°C and the wall heater was set to 160°C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2°C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.22×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to produce a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.49×10 -3 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0135] [Example 57] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 2.08×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed at a film formation rate of 3.0 nm / s using CeO2 as a film-forming material. Subsequently, a SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to produce a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.54×10 -2 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0136] [Example 58] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 160 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 2.87×10 -4It was Pa. On various substrates, a layer containing cerium oxide was formed using Ce and CeO2 as film-forming materials. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.51×10 -2 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0137] [Example 59] The substrate heating of the vacuum deposition apparatus was turned off, the wall heater was set to 50 °C, and vacuum evacuation was performed. The substrate temperature before film formation was 28 °C. When the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed before starting the film formation process of the layer containing cerium oxide, it was 1.22×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.48×10 -3 Pa. The other film formation conditions were as described in (fabrication of multilayer film).

[0138] [Example 60] The substrate heating of the vacuum deposition apparatus was turned off, the wall heater was set to 50 °C, and vacuum evacuation was performed. The substrate temperature before film formation was 31 °C. When the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed before starting the film formation process of the layer containing cerium oxide, it was 1.45×10 -4 Pa. On various substrates, a layer containing cerium oxide was formed using CeO2 as a film-forming material. Subsequently, an SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as film-forming materials to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.95×10-3 It was Pa. Other film formation conditions were as described in (Fabrication of Multilayer Films).

[0139] [Example 61] The substrate temperature of the vacuum evaporation apparatus was set to 100 °C, and the wall heater was set to 100 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 100 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 9.54×10 -5 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as the film-forming material. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as the film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the average total value of the partial pressure of water molecules and the partial pressure of oxygen species was 1.94×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Films).

[0140] [Example 62] The substrate temperature of the vacuum evaporation apparatus was set to 100 °C, and the wall heater was set to 100 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 100 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.36×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as the film-forming material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as the film-forming material to fabricate a multilayer film. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the average total value of the partial pressure of water molecules and the partial pressure of oxygen species was 2.78×10 -3 Pa. Other film formation conditions were as described in (Fabrication of Multilayer Films).

[0141] [Example 63] The substrate temperature of the vacuum evaporation apparatus was set to 270 °C and the wall heater was set to 100 °C, and then vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 270 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 2.87×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using Ce and CeO2 as film-forming materials. Subsequently, an SiO2 + Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to produce a multilayer film. Incidentally, the average total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was 5.84×10 -3 Pa. Other film formation conditions were as described in (fabrication of multilayer film).

[0142] [Example 64] The substrate temperature of the vacuum evaporation apparatus was set to 270 °C and the wall heater was set to 100 °C, and then vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 270 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.84×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material at a film formation rate of 1.0 nm / s. Subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. Incidentally, the average total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide was 7.50×10 -3 Pa. Other film formation conditions were as described in (fabrication of multilayer film).

[0143] [Example 65] The substrate temperature of the vacuum evaporation apparatus was set to 500 °C, the wall heater was set to 200 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 500 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.37×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a SiO2 film (low refractive index layer) was formed thereon using SiO as a film-forming material to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 2.79×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0144] [Example 66] The substrate temperature of the vacuum evaporation apparatus was set to 500 °C, the wall heater was set to 200 °C, and vacuum evacuation was performed. When 15 minutes or more had elapsed after the substrate temperature reached 500 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 2.87×10 -4 Pa. Thereafter, a layer containing cerium oxide was formed on various substrates using Y2O3 and CeO2 as film-forming materials at a film formation rate of 0.7 nm / s. Subsequently, a SiO2 + CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as film-forming materials to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 8.18×10 -3 Pa. The other film formation conditions were as described in (Fabrication of Multilayer Film).

[0145] [Comparative Example 1] The substrate temperature of the vacuum evaporation apparatus was set to 300 °C, the wall heater was set to 50 °C, and vacuum evacuation was performed. Before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 8.20×10 -3It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates at a film formation rate of 0.2 nm / s using CeO2 as the film formation material. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO2 as the film formation material to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 6.68×10 -2 It was Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0146] [Comparative Example 2] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 6.15×10 -3 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates at a film formation rate of 0.2 nm / s using CeO2 as the film formation material. Subsequently, an SiO2+CeO2 film (low refractive index layer) was formed thereon using SiO2 and CeO2 as the film formation materials to fabricate a multilayer film. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 5.01×10 -2 It was Pa. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0147] [Comparative Example 3] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 1.53×10 -4 It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates at a film formation rate of 0.2 nm / s using CeO2 as the film formation material. When forming the layer containing cerium oxide, the degree of vacuum was 1.8×10 by an Auto Pressure Control (APC) device -2O2 gas was introduced to achieve Pa. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 1.80×10 -2 Pa. Subsequently, an MgF2 film (low refractive index layer) was formed on top of it using MgF2 as the film-forming material to fabricate a multilayer film. Other film formation conditions were as described in (fabrication of multilayer film).

[0148] [Comparative Example 4] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 1.53×10 -4 Pa. Thereafter, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 0.2 nm / s using CeO2 as the film-forming material. When forming the outermost 8 nm (region (B)) of the layer containing cerium oxide, ion assist was performed using an RF ion source. The conditions for ion assist were an acceleration voltage value of 700 V, an acceleration current value of 700 mA, and an O2 gas flow rate of 50 sscm. During the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.11×10 -3 Pa. Subsequently, an SiO2 film (low refractive index layer) was formed on top of it using SiO as the film-forming material to fabricate a multilayer film. Other film formation conditions were as described in (fabrication of multilayer film).

[0149] [Comparative Example 5] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 150 °C, and vacuum evacuation was performed. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 2.91×10 -4It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 0.9 nm / s using Ce and CeO2 as film formation materials. When forming the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the film formation rate was changed to 0.1 nm / s for film formation. During the film formation of the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 1.07×10 -2 Pa. Subsequently, on top of it, a SiO2+Al2O3 film (low refractive index layer) was formed using SiO and Al2O3 as film formation materials to fabricate a multilayer film. Other film formation conditions were as described in (fabrication of multilayer film).

[0150] [Comparative Example 6] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 150 °C for vacuum evacuation. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 2.87×10 -4 Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 1.0 nm / s using Ce and CeO2 as film formation materials. When forming the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the film formation rate was changed to 0.1 nm / s for film formation. During the film formation of the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 1.17×10 -2 Pa. Subsequently, on top of it, a MgF2 film (low refractive index layer) was formed using MgF2 as film formation material to fabricate a multilayer film. Other film formation conditions were as described in (fabrication of multilayer film).

[0151] [Comparative Example 7] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 150 °C for vacuum evacuation. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 2.83×10 -4It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 1.1 nm / s using Ce and CeO2 as film formation materials. When forming the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the film formation rate was changed to 0.1 nm / s for film formation. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 1.27×10 -2 Pa. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO as a film formation material to fabricate a multilayer film. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0152] [Comparative Example 8] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 150 °C for vacuum evacuation. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 2.79×10 -4 Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 1.2 nm / s using Ce and CeO2 as film formation materials. When forming the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the film formation rate was changed to 0.1 nm / s for film formation. During the film formation of the 8 nm on the surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 1.36×10 -2 Pa. Subsequently, an SiO2+CeO2 film (low refractive index layer) was formed thereon using SiO and CeO2 as film formation materials to fabricate a multilayer film. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0153] [Comparative Example 9] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 150 °C for vacuum evacuation. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 2.75×10 -4It was Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed at a film formation rate of 1.4 nm / s using Ce and CeO2 as film formation materials. When forming the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the film formation rate was changed to 0.1 nm / s for film formation. During the film formation of the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 1.57×10 -2 Pa. Subsequently, on top of it, a MgF2 film (low refractive index layer) was formed using MgF2 as a film formation material to fabricate a multilayer film. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0154] [Comparative Example 10] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C and the wall heater was set to 100 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.53×10 -4 Pa. Subsequently, on various substrates, a layer containing cerium oxide was formed using CeO2 as a film formation material. When forming the layer containing cerium oxide, oxygen was introduced by APC. The introduction amount of oxygen gas was 5.0×10 -2 Pa. During the film formation of the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 5.00×10 -2 Pa. Subsequently, on top of it, a SiO2 film (low refractive index layer) was formed using SiO as a film formation material to fabricate a multilayer film. Other film formation conditions were as described in (Fabrication of Multilayer Film).

[0155] [Comparative Example 11] The substrate temperature of the vacuum evaporation apparatus was set to 250 °C and the wall heater was set to 100 °C for vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 250 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.52×10 -4It was Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. When forming the layer containing cerium oxide, ion assist was performed by an RF ion source. The conditions for ion assist were an acceleration voltage value of 700 V, an acceleration current value of 700 mA, and an O2 gas flow rate of 80 sscm. During the film formation of the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.09×10 -2 Pa. Subsequently, an SiO2+Al2O3 film (low refractive index layer) was formed thereon using SiO and Al2O3 as film-forming materials to produce a multilayer film. Other film formation conditions were as described in (fabrication of multilayer film).

[0156] [Comparative Example 12] The substrate temperature of the vacuum deposition apparatus was set to 250 °C and the wall heater was set to 100 °C, and vacuum evacuation was performed. When more than 15 minutes had elapsed after the substrate temperature reached 250 ± 2 °C and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed to be 1.52×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. When forming the layer containing cerium oxide, ion assist was performed by an RF ion source. The conditions for ion assist were an acceleration voltage value of 700 V, an acceleration current value of 700 mA, and an O2 gas flow rate of 70 sscm. During the film formation of the 8-nm surface layer side (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.02×10 -2 Pa. Also, subsequently, an MgF2 film (low refractive index layer) was formed thereon using MgF2 as a film-forming material to produce a multilayer film. Other film formation conditions were as described in (fabrication of multilayer film).

[0157] [Comparative Example 13] Instead of the layer containing cerium oxide having the columnar structure of Example 34, the substrate temperature was changed to 600 °C so that a layer containing cerium oxide having a non-columnar structure was obtained. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 1.51×10 -4 Pa. For film formation of the layer containing cerium oxide, ion assist was performed using an RF ion source. The conditions for ion assist were an acceleration voltage value of 900 V, an acceleration current value of 1000 mA, an O2 gas flow rate of 6 sscm, and an Ar gas flow rate of 34 sscm. Also, when forming the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the O2 gas flow rate of the ion source was changed to 2 sscm and the Ar gas flow rate was changed to 38 sscm for film formation. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.08×10 -3 Pa. Otherwise, the multilayer film was produced in the same manner as in Example 34.

[0158] [Comparative Example 14] Instead of the layer containing cerium oxide having the columnar structure of Example 36, the substrate temperature was changed to 600 °C so that a layer containing cerium oxide having a non-columnar structure was obtained. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 1.51×10 -4 Pa. For film formation of the layer containing cerium oxide, ion assist was performed using an RF ion source. The conditions for ion assist were an acceleration voltage value of 1000 V, an acceleration current value of 1000 mA, an O2 gas flow rate of 3 sscm, and an Ar gas flow rate of 37 sscm. Also, when forming the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the O2 gas flow rate of the ion source was changed to 0 sscm and the Ar gas flow rate was changed to 40 sscm for film formation. During the film formation of the 8 nm (region (B)) on the surface layer side of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was, on average, 3.07×10 -3 Pa. Otherwise, the multilayer film was produced in the same manner as in Example 36.

[0159] [Comparative Example 15] Instead of the cubic polycrystalline CeO2 layer of Example 19, the substrate temperature was changed to -18 °C so that an amorphous CeO2 layer could be obtained. In addition, after turning off the wall heater, the chamber was evacuated and film formation was carried out. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 2.38×10 -5 Pa. Also, during the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was on average 4.84×10 -4 Pa. Otherwise, the multilayer film was fabricated in the same manner as in Example 19.

[0160] [Comparative Example 16] Instead of the cubic polycrystalline CeO2 layer of Example 20, the substrate temperature was changed to -18 °C so that an amorphous CeO2 layer could be obtained. In addition, after turning off the wall heater, the chamber was evacuated and film formation was carried out. Before starting the film formation process of the layer containing cerium oxide, when the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, it was 2.87×10 -4 Pa. Also, during the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen species was on average 5.84×10 -3 Pa. Otherwise, the multilayer film was fabricated in the same manner as in Example 20.

[0161] [Comparative Example 17] Instead of forming the SiO2 film of Example 24, an SiO film was formed at a film formation rate of 1.3 nm / s using SiO. Since the SiO film had a high refractive index and a large amount of optical loss due to light absorption, it was unsuitable as an optical thin film.

[0162] [Comparative Example 18] The substrate temperature of the vacuum evaporation apparatus was set to 400 °C, and the wall heater was set to 180 °C, followed by vacuum evacuation. When more than 15 minutes had elapsed after the substrate temperature reached 400 ± 2 °C, and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 2.87×10 -4 Pa. Subsequently, a layer containing cerium oxide was formed on various substrates using CeO2 as a film-forming material. Subsequently, a Y2O3 film was formed thereon using Y2O3 as a film-forming material to produce a multilayer film. Incidentally, during the film formation of the outermost 8 nm (region (B)) of the layer containing cerium oxide, the average total value of the partial pressure of water molecules and the partial pressure of oxygen species was 5.84×10 -3 Pa. The other film formation conditions were as described in (fabrication of multilayer film). Since the refractive index was higher than that of the Y2O3 film, it was unsuitable as an optical member.

[0163] (Evaluation of oxygen deficiency rate) A test piece of the obtained multilayer film was introduced into an X-ray photoelectron spectrometer (ESCA-300 manufactured by Scienta) and evacuated until a high vacuum was achieved. The thin film above the layer 13 containing cerium oxide of the multilayer film was removed by argon ion etching. Subsequently, XPS spectrum measurement of the Ce 3d orbital and argon ion etching were repeated. A total of three locations were analyzed by changing the analysis area of the multilayer film. From the obtained results, the oxygen deficiency rates (V A ), oxygen deficiency rates (V B ), and oxygen deficiency rates (V C ) of the layer containing cerium oxide (13) were calculated.

[0164] For the oxygen deficiency rate below the quantification limit of X-ray photoelectron spectroscopy, observation, projection, and measurement of oxygen vacancies were performed using a scanning transmission electron microscope (HF5000, manufactured by Hitachi High-Technologies Corporation). As pretreatment of the multilayer film to be measured, any one or a combination of the following operations (1) to (3) was carried out: (1) cutting the obtained multilayer film together with the substrate and exposing the cross section, (2) processing by focused ion beam (FIB), and (3) etching in the vertical direction by ion beam. The measurement site was sampled and microfabricated. Also, during the processing, in order to minimize the change in oxygen vacancies, it was carried out immediately after film formation in an atmosphere combining low temperature, argon gas, and a vacuum pump.

[0165] Thereafter, under the condition of an acceleration voltage of 200 kV, HAADF-STEM images and ABF-STEM images that can show the presence or absence of oxygen atoms in the layer containing cerium oxide were obtained step by step in the depth direction of the film thickness. In order to assist the observation of light elements such as oxygen and oxygen vacancies, LAADF-STEM images of the same area were also obtained. A total of 5 images were obtained by changing the analysis area of the layer film. Each of the obtained images was processed by software and converted into a mapping image, and the number of oxygen sites and the number of oxygen vacancies were counted to obtain the oxygen deficiency rate (V A ) of the layer containing cerium oxide, (V B ) of the layer containing cerium oxide, (V C ) of the layer containing cerium oxide.

[0166] For the multilayer films obtained in Examples 19 to 22, 28, 38, 39, and Comparative Examples 5 to 9, measurement of the oxygen deficiency rate (V A ) was also carried out by X-ray absorption fine structure method (XAFS). CeO2 and Ce(NO3)3·6H2O were used as standard samples, the measurement absorption edge was the Ce-L3 absorption edge (5723.0 eV), and the measurement was carried out by the fluorescence yield method using a multi-element silicon drift detector. The oxygen deficiency rate was calculated from the fitting results of the obtained XANES spectra. There was almost no difference from the oxygen deficiency rate values measured by X-ray photoelectron spectroscopy and electron microscopy, and it was confirmed that the measurement of the oxygen deficiency rate was reasonable.

[0167] (Measurement of thickness (film thickness) and refractive index) The thickness and refractive index of each layer of the multilayer films in the examples and comparative examples were determined using spectroscopic ellipsometry (ESM300 manufactured by JA WOOLLAM). The wavelength of the light source was set from 192 nm to 1000 nm, and the incident angle was measured every 5° in the range of 45° to 65°. Also, in order to improve the accuracy of the analysis, the transmittance was measured as well. The obtained reflection and transmittance data were analyzed by combining models such as Cauchy, Gaussian, Tauc-Lorentz, and effective medium approximation (surface roughness) to determine the film thickness and refractive index. Since it is a multilayer film, the number of layers and film thickness are complex, and the analysis may be difficult. In such cases, a single-layer film separately obtained in the same batch of film formation was measured and analyzed, and the analysis was carried out using the data such as the obtained refractive index.

[0168] (Measurement of Composition) The composition of the two-component layers such as SiO2 + CeO2 and SiO2 + Al2O3 in the multilayer films of the examples and comparative examples was measured and determined by a wavelength-dispersive X-ray fluorescence spectrometer (ZSX PrimusII manufactured by Rigaku Corporation). When quantitative analysis for each layer was difficult, measurement was performed on a single-layer film separately obtained in the same batch of film formation.

[0169] (Confirmation of Structure) The multilayer film formed on the Si substrate was observed for the reflected electron image and secondary electron image using a cross-sectional ultra-high resolution field emission scanning electron microscope (JSM-IT800, manufactured by JEOL Ltd.). It was confirmed whether the obtained image had a columnar structure or other structures (non-columnar). At that time, the film thickness of each layer was also confirmed. There was almost no difference from the film thickness value obtained by the ellipsometer, and it was confirmed that the film thickness measurement by the ellipsometer was reasonable. Also, the composition of each layer was measured by energy-dispersive X-ray spectroscopy (EDX), and there was almost no difference from the value obtained in the above (Measurement of Composition), and it was confirmed that the above measurement of the composition was reasonable.

[0170] (Measurement of Crystallinity) The multilayer films of the examples and comparative examples were measured by the focusing method using an XRD diffractometer (Smart Lab, manufactured by Rigaku Corporation) in the range of 2θ = 20° to 100° at a step of 0.01° and a speed of 5° / min. The layers were identified and the crystallinity was confirmed based on the diffraction line intensity and the like. Since they were multilayer films, the diffraction intensities of MgF2, SiO2 + CeO2, etc. might interfere with the analysis. In such cases, the single-layer films separately obtained in the same batch of film formation were also measured and analyzed together. Multilayer films with diffraction peaks attributed to the cerium oxide-containing layer were judged to be crystalline, and multilayer films without diffraction peaks attributed to the cerium oxide-containing layer were judged to be amorphous.

[0171] (Hydrophilicity maintenance evaluation) The multilayer films of the examples and comparative examples were left in the dark (temperature 23 ± 2°C, humidity 60 ± 15%RH) for 60 days, and then the contact angle with water was measured. After the above measurement, the substrate was left in the dark for another 240 days, and after being left in the dark for a total of 300 days, the contact angle with water was measured. A CA-X150 type manufactured by Kyowa Interface Science Co., Ltd. was used as the contact angle meter. 2.5 mL of pure water was dropped onto the test piece from a microsyringe, and the contact angle 5 seconds after dropping was determined by the θ / 2 method. The hydrophilicity of the surface can be quantified by the contact angle with water. Generally, a case where the contact angle is less than 20° is called hydrophilic, and a case where it is less than 10° is called superhydrophilic. Following this, when the contact angle was less than 10°, the evaluation was [A], when the contact angle was 10° or more and less than 20°, the evaluation was [B], and when the contact angle was 20° or more, the evaluation was [C].

[0172] (Self-cleaning performance evaluation) To the multilayer films of the examples and comparative examples, stearic acid was applied using a heptane solution (0.3% by mass) of stearic acid in accordance with JIS R1753-1, and dried at 70 °C for 30 minutes using a dryer. Thereafter, the contact angle of the test piece coated with stearic acid was measured in the same manner as the method described in (Evaluation of hydrophilicity maintenance), and it was confirmed that the contact angle was 20° or more. When the contact angle was less than 20°, the application, drying, and contact angle measurement of stearic acid were repeated until the contact angle became 20° or more. Thereafter, the multilayer film coated with stearic acid was irradiated with ultraviolet rays for 2 hours and 30 hours, and then the contact angle was measured again to obtain the water contact angle after ultraviolet irradiation. A black light blue fluorescent lamp (FL20SBL-B manufactured by Hotarux Co., Ltd.) was used as the ultraviolet light source. The ultraviolet rays were irradiated onto the test piece so that the illuminance was 2.0 mw / cm 2 became. In the same manner as the evaluation in the above (Evaluation of hydrophilicity maintenance), when the contact angle was less than 10°, the evaluation was [A], when the contact angle was 10° or more and less than 20°, the evaluation was [B], and when the contact angle was 20° or more, the evaluation was [C].

[0173] The results obtained in (Evaluation of hydrophilicity maintenance) and (Self-cleaning performance evaluation) are shown in Tables 1-1 to 1-4. In each example and comparative example, the evaluation results were the same regardless of the type of substrate.

[0174] (Evaluation of optical properties) The transmittance and reflectance at an incident angle of 5° of the multilayer films of the examples and comparative examples were measured. An ultraviolet-visible near-infrared spectrophotometer (UH4150 manufactured by Hitachi High-Tech) was used as the measuring device, and the measurement wavelength range of 450 nm to 1200 nm was measured every 1 nm. The average values of the transmittance (%) and reflectance (%) for each obtained wavelength were obtained to obtain the average transmittance (%) and average reflectance (%). The average value of the light loss was obtained by subtracting the average transmittance (%) and average reflectance (%) from 100%. When the average value of the light loss was less than 1%, the evaluation was [A], and when it was 1% or more, the evaluation was [C].

[0175]

Table 1-1

[0176] [Table 1-2]

[0177] [Table 1-3]

[0178] [Table 1-4]

[0179] [Comparative Example 23] Instead of forming the cerium oxide-containing layer of Example 23, a TiO2 film was formed. At that time, Ti3O5 was used as the film-forming material. For other film-forming conditions, a multilayer film was formed under the same conditions as in Example 23. As a result of evaluating the crystallinity of the TiO2 layer, it was an anatase-type polycrystal. Also, as a result of evaluating the structure, it had a columnar structure. As a result of evaluating the hydrophilicity maintenance performance, the water contact angle after 60 days was 58.7°, and the water contact angle after 300 days was 63.4°. As a result of evaluating the self-cleaning performance, the water contact angle after 2 hours of irradiation was 77.5°, and the water contact angle after 30 hours of irradiation was 72.5°.

[0180] [Comparative Example 24] Instead of forming the cerium oxide-containing layer of Example 24, a TiO2 film was formed. At that time, Ti3O5 was used as the film-forming material. For other film-forming conditions, a multilayer film was formed under the same conditions as in Example 24. As a result of evaluating the crystallinity of the TiO2 layer, it was a polycrystal with the main component being anatase-type crystals and a small amount of rutile-type crystals present. Also, as a result of evaluating the structure, it had a columnar structure. As a result of evaluating the hydrophilicity maintenance performance, the water contact angle after 60 days was 39.4°, and the water contact angle after 300 days was 61.6°. As a result of evaluating the self-cleaning performance, the water contact angle after 2 hours of irradiation was 72.3°, and the water contact angle after 30 hours of irradiation was 63.4°.

[0181] [Comparative Example 25] Various substrates were set on brass and 99.5% pure aluminum holders, the substrate heating of the vacuum deposition apparatus was turned off, the wall heater was set to off, and the pressure was evacuated to 1.3×10 -3 Pa or less. The substrate temperature before film formation was 24°C. A Cr layer (1 nm) was formed as the first layer on various substrates. Using an oxygen-free copper hearth liner and CeO2 as the film-forming material, a layer containing cerium oxide was formed. Before starting the film-forming process of the layer containing cerium oxide, when the total partial pressure of water molecules and oxygen molecules was confirmed, it was 8.94×10 -4 Pa. Subsequently, an SiO2 film (low refractive index layer) was formed thereon using SiO2 as the film-forming material to fabricate a multilayer film. Note that the total partial pressure of water molecules and oxygen species during film formation in the 8 nm on the surface side of the layer containing cerium oxide (region (B): the region of the layer containing cerium oxide located at a position of 8 nm or less from the interface between the layer containing cerium oxide and the layer containing silicon oxide or the layer containing magnesium fluoride) was on average 8.03×10 -3 Pa. Regarding the obtained multilayer film, similar to the multilayer films of Examples 1 to 68, evaluation was performed on crystallinity, structure, optical properties, and oxygen deficiency rate. As a result of the evaluation, the layer containing cerium oxide had a crystalline columnar structure, and the oxygen deficiency rate was such that V A was 0.02%, V B was 0.01%, and V C was 0.02%. The refractive index of the SiO2 layer was 1.46. The light loss of the multilayer film was 1.4%, and the optical properties were evaluated as [C].

[0182] [Example 67] The flat glass having the multilayer film obtained in Example 3 was processed and attached to the outside of a commercially available vehicle's near-infrared sensor to serve as a protective cover for the sensor.

[0183] [Example 68] As the base material to be used, a dome-shaped transparent base material made of polymethyl methacrylate resin (Acrylite (registered trademark) manufactured by Mitsubishi Chemical Corporation) with an acrylic hard coat was used. The base material temperature of the vacuum deposition apparatus was set to 50°C and the wall heater was set to 50°C, and then vacuum evacuation was performed. When more than 15 minutes had elapsed after the base material temperature reached 50 ± 2°C, and before starting the film formation process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.49×10 -4 Pa. As the film-forming material, SiO was used to form a SiO2 film (200 nm) in the first layer at a deposition rate of 0.3 nm / s.

[0184] Next, as the film-forming material, TaO was used to form a Ta2O5 film (14 nm) in the second layer at a deposition rate of 0.2 nm / s. In the third layer, as the film-forming material, SiO2 was used to form a SiO2 film (35 nm) in the first layer at a deposition rate of 0.7 nm / s. In the fourth layer, as the film-forming material, Ce and CeO2 were used to form a layer containing cerium oxide (256 nm) at a deposition rate of 0.3 nm / s. In the fifth layer, as the film-forming material, SiO and CeO2 were used to form a SiO2 (95%) + CeO2 (5%) film (79 nm, refractive index 1.52) at a deposition rate of 0.5 nm / s. In the last sixth layer, as the film-forming material, SiO2 was used to form a SiO2 film (10 nm, refractive index 1.46) to fabricate a multilayer film. During film formation, the multilayer film was fabricated while rotating the base material in a planetary motion.

[0185] Also, during the film formation on the 1st, 2nd, and 4th layers, ion assist was performed using an RF ion source. At that time, for the 1st layer, ion assist was performed under the conditions of an acceleration voltage value of 280 V, an acceleration current value of 280 mA, and an O2 gas flow rate of 40 sccm. For the 2nd layer, ion assist was performed under the conditions of an acceleration voltage value of 500 V, an acceleration current value of 500 mA, and an O2 gas flow rate of 60 sccm. For the 5th layer, ion assist was performed under the conditions of an acceleration voltage value of 500 V, an acceleration current value of 500 mA, and an O2 gas flow rate of 40 sccm. When forming the 8 nm on the surface layer side of the 5th layer, the film formation rate was changed to 0.5 nm / s, and further, the O2 gas flow rate of the ion source was changed to 0 sccm and the Ar gas flow rate was changed to 40 sccm for film formation.

[0186] Regarding the obtained dome-shaped resin substrate with a multilayer film and various substrates formed simultaneously, similar to the multilayer films in Examples 1 to 68, evaluations were performed on the composition, crystallinity, structure, oxygen deficiency rate, and optical properties of the thin film. As a result of the evaluation, the composition of the SiO2 + CeO2 layer was SiO2 (95%) + CeO2 (5%), the film thickness was 79 nm, and the refractive index was 1.52. The refractive index of the SiO2 layer was 1.46. Also, the layer containing cerium oxide had a crystalline columnar structure, and the oxygen deficiency rates were V A at 0.05%, V B at 0.52%, V C at 0.03%, and the light loss was less than 1.5%. Subsequently, the obtained dome-shaped resin substrate with a multilayer film was attached to a surveillance camera for use as a surveillance camera cover.

[0187] The surveillance camera equipped with the fabricated cover was stored in a commercial makeup box, which is a dark place, for 4 months. Then, it was installed outdoors during a rainy night. Even when water adhered due to rainfall, the water droplets spread wet on the cover, maintaining good visibility. Also, after the moisture dried, no water marks remained, maintaining good visibility. Furthermore, even during a rainy day 8 months after the outdoor installation, the water droplets spread wet on the cover, maintaining good visibility.

[0188] [Example 69] The base material to be used was a resin base material (MR-8 manufactured by Mitsui Chemicals) with a silicon-based hard coat. The base material temperature of the vacuum deposition apparatus was set to 80°C, and the wall heater was set to 80°C, followed by vacuum evacuation. When more than 15 minutes had elapsed after the base material temperature reached 80 ± 2°C and before starting the film-forming process of the layer containing cerium oxide, the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules was confirmed, and it was 1.52×10 -4 Pa. Using Al2O3 as the film-forming material, an Al2O3 film (82 nm) was formed as the first layer of the multilayer film. For the second layer, using Ce and CeO2 as the film-forming materials, a CeO2 film (252 nm) was formed. For the third layer, using SiO2 and Al2O3 as the film-forming materials, a SiO2(95%) + CeO2(5%) film (75 nm, refractive index 1.52) was formed. For the last fourth layer, using SiO2 for the film-forming material, a SiO2 film (15 nm, refractive index 1.46) was formed to fabricate a multilayer film. During film formation, the multilayer film was fabricated at a deposition rate of 0.5 nm / s. The obtained resin base material with the multilayer film was processed and attached to a frame for glasses to fabricate glasses.

[0189] Regarding the obtained spectacle lens base material with the multilayer film and various substrates formed simultaneously, similar to the multilayer films of Examples 1 to 68, evaluations were carried out on crystallinity, structure, oxygen deficiency rate, and optical properties. As a result of the evaluation, the layer containing cerium oxide had a crystalline columnar structure, and the oxygen deficiency rates were V A was 0.05%, V B was 0.53%, V C was 0.03%, and the light loss was less than 1.5%. Subsequently, the fabricated glasses were stored in an aluminum glasses case in a dark place for 3 months. After that, when water droplets were attached to the lens, the water droplets spread wet on the lens, maintaining good visibility. The contact angle of water at that time was 4.7°. Also, no water marks remained after the moisture dried, maintaining good visibility.

Industrial Applicability

[0190] The multilayer film of the present disclosure can be used for optical members such as optical filters, optical lenses, light collecting lenses, optical films, optical prisms, spectacle lenses, photographic lenses, vehicle door mirrors, plate glass, condenser lenses, cover glass for displays, touch panels, and various films, and covers for protecting optical members such as covers for surveillance cameras, in-vehicle cameras, and in-vehicle sensor covers.

[0191] In addition, the optical member of the present disclosure can be used as optical devices such as digital cameras, digital video cameras, action cameras, endoscopes, lens barrels, glasses, sensors, binoculars, telescopes, surveillance cameras, in-vehicle cameras, smartphones, tablet PCs, weather cameras, live cameras, protective goggles, underwater glasses, head-mounted displays, sunglasses, smart glasses, face shields, helmet shields, vehicle mirrors, and bathroom mirrors, and covers for protecting them.

[0192] The present disclosure includes the following embodiments. (1) It has a cerium oxide-containing layer and a low refractive index layer directly or via another layer on the cerium oxide-containing layer. The low refractive index layer has a silicon oxide-containing layer or a magnesium fluoride-containing layer. The cerium oxide-containing layer contains cerium oxide including a cubic polycrystalline structure and a columnar structure. The film thickness of the cerium oxide-containing layer is 85 nm or more and 800 nm or less. Taking the entire cerium oxide-containing layer as region (A) and the oxygen deficiency rate of cerium oxide in the region (A) as the oxygen deficiency rate (V A ), when the oxygen deficiency rate (V A ) is 0.05% or more and 10% or less. The film thickness of the low refractive index layer is 50 nm or more and 240 nm or less. A multilayer film characterized in that the refractive index of the low refractive index layer with respect to light having a wavelength of 500 nm is 1.65 or less. (2) The oxygen deficiency rate (V A ) is 0.05% or more and 0.6% or less, and the multilayer film according to (1). (3) The oxygen deficiency rate (V A ) is 0.1% or more and 0.3% or less, and the multilayer film according to (1). (4) The region of the cerium oxide-containing layer within a range of 8 nm or less from the interface between the cerium oxide-containing layer and the low refractive index layer is defined as region (B). When the oxygen deficiency rate of cerium oxide in region (B) is defined as the oxygen deficiency rate (V B ), the oxygen deficiency rate (V B ) is 0.5% or more and 30% or less, and the multilayer film according to any one of (1) to (3). (5) The oxygen deficiency rate (V A ) is 0.05% or more and 10% or less, and The oxygen deficiency rate (V B ) is 0.5% or more and 30% or less, and Among the region (A), the region excluding the region (B) is defined as region (C). When the oxygen deficiency rate of cerium oxide in region (C) is defined as the oxygen deficiency rate (V C ), the oxygen deficiency rate (V C ) is 0% or more and 10% or less, and The oxygen deficiency rate (V B ) is greater than the oxygen deficiency rate (V C ), and the multilayer film according to any one of (1) to (4). (6) An optical member having the multilayer film according to any one of (1) to (5). (7) Step (A) of forming a cerium oxide-containing layer by a vacuum deposition method directly on a substrate or via another layer, and Step (B) of forming a low refractive index layer by a vacuum deposition method directly on the cerium oxide-containing layer or via another layer are included, The low refractive index layer has a silicon oxide-containing layer or a magnesium fluoride-containing layer, The layer containing cerium oxide contains cerium oxide having a cubic polycrystalline structure and a columnar structure, the film thickness of the layer containing cerium oxide is 85 nm or more and 800 nm or less, the entire layer containing cerium oxide is defined as region (A), and when the oxygen deficiency rate of cerium oxide in the region (A) is defined as oxygen deficiency rate (V A ), the oxygen deficiency rate (V A ) is 0.05% or more and 10% or less, the film thickness of the low refractive index layer is 50 nm or more and 240 nm or less, which is a method for manufacturing a multilayer film. (8) From the interface between the layer containing cerium oxide and the low refractive index layer, the region of the layer containing cerium oxide within a range of 8 nm or less is defined as region (B), and when the oxygen deficiency rate of cerium oxide in the region (B) is defined as oxygen deficiency rate (V B ), the oxygen deficiency rate (V B ) is 0.5% or more and 30% or less, in the region (A), the region excluding the region (B) is defined as region (C), and when the oxygen deficiency rate of cerium oxide in the region (C) is defined as oxygen deficiency rate (V C ), the oxygen deficiency rate (V C ) is 0% or more and 10% or less, the oxygen deficiency rate (V B ) is greater than the oxygen deficiency rate (V C ), the method for manufacturing a multilayer film according to (7). (9) Before the step (A), the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules in the atmosphere is 2×10 -2 Pa or less, the total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation of the region (B) is 2×10 -2 Pa or less on average, the method for manufacturing a multilayer film according to (7) or (8).

Explanation of symbols

[0193] 11 Substrate 12 Other layer 13 Layer containing cerium oxide Layer containing magnesium fluoride Layer containing silicon oxide Layer containing silicon dioxide 21 Dome-shaped resin substrate 31 Eyeglass lens 32 Eyeglass frame

Claims

1. It has a layer containing cerium oxide and a low refractive index layer directly on the layer containing cerium oxide or via another layer, The low refractive index layer has a layer containing silicon oxide or a layer containing magnesium fluoride, The layer containing cerium oxide contains cerium oxide including a cubic polycrystalline structure and a columnar structure, The film thickness of the layer containing cerium oxide is 85 nm or more and 800 nm or less, The entire layer containing cerium oxide is defined as region (A), and when the oxygen deficiency rate of cerium oxide in the region (A) is defined as oxygen deficiency rate (V Ａ ), when the oxygen deficiency rate (V Ａ ) is 0.05% or more and 10% or less, The film thickness of the low refractive index layer is 50 nm or more and 240 nm or less, The refractive index of the low refractive index layer with respect to light having a wavelength of 500 nm is 1.65 or less. A multilayer film characterized by this.

2. The oxygen deficiency rate (V Ａ ), which is 0.05% or more and 0.6% or less, of the multilayer film according to claim 1.

3. The oxygen deficiency rate (V Ａ ), which is 0.1% or more and 0.3% or less, of the multilayer film according to claim 1.

4. The region of the cerium oxide-containing layer within a range of 8 nm or less from the interface between the cerium oxide-containing layer and the low refractive index layer is defined as region (B). When the oxygen deficiency rate of cerium oxide in the region (B) is defined as the oxygen deficiency rate (V Ｂ ), the multilayer film according to claim 1, wherein the oxygen deficiency rate (V Ｂ ) is 0.5% or more and 30% or less.

5. The oxygen deficiency rate (V Ａ ) is 0.05% or more and 10% or less, and The oxygen deficiency rate (V Ｂ ) is 0.5% or more and 30% or less, and Of the said region (A), the region excluding the said region (B) is defined as region (C), and when the oxygen deficiency rate of cerium oxide in the said region (C) is defined as oxygen deficiency rate (V Ｃ ), when the said oxygen deficiency rate (V Ｃ ) is 0% or more and 10% or less, The oxygen deficiency rate (V Ｂ ) is greater than the oxygen deficiency rate (V Ｃ ), the multilayer film according to claim 4.

6. An optical member having the multilayer film according to any one of Claims 1 to 5.

7. A step (A) of forming a layer containing cerium oxide by a vacuum deposition method directly on a substrate or via another layer, A step (B) of forming a low refractive index layer by a vacuum deposition method directly on the layer containing cerium oxide or via another layer including, The low refractive index layer has a layer containing silicon oxide or a layer containing magnesium fluoride, The layer containing cerium oxide contains cerium oxide including a cubic polycrystalline structure and a columnar structure, The film thickness of the layer containing cerium oxide is set to 85 nm or more and 800 nm or less, Taking the entire layer containing cerium oxide as region (A), when the oxygen deficiency rate of cerium oxide in the region (A) is defined as the oxygen deficiency rate (V Ａ ), when the oxygen deficiency rate (V Ａ ) is 0.05% or more and 10% or less, The film thickness of the low refractive index layer is 50 nm or more and 240 nm or less. A method for manufacturing a multilayer film characterized by this.

8. From the interface between the layer containing cerium oxide and the low refractive index layer, the region of the layer containing cerium oxide within the range of 8 nm or less is defined as region (B), and when the oxygen deficiency rate of cerium oxide in the region (B) is defined as the oxygen deficiency rate (V Ｂ ), the oxygen deficiency rate (V Ｂ ) is 0.5% or more and 30% or less, Of the said region (A), the region excluding the said region (B) is defined as region (C), and when the oxygen deficiency rate of cerium oxide in the said region (C) is defined as oxygen deficiency rate (V Ｃ ), when the said oxygen deficiency rate (V Ｃ ) is 0% or more and 10% or less, The oxygen deficiency rate (V Ｂ ) is greater than the oxygen deficiency rate (V Ｃ ), the method for manufacturing a multilayer film according to claim 7.

9. Before the step (A), the total value of the partial pressure of water molecules and the partial pressure of oxygen molecules in the atmosphere is 2×10 －２ Pa or less, The total value of the partial pressure of water molecules and the partial pressure of oxygen species during the film formation in the region (B) is, on average, 2×10 －２ Pa or less. The method for manufacturing a multilayer film according to claim 7 or 8.

Images