JP6817020B2 - Infrared transmissive film, optical film, antireflection film, optical components, optical system and imaging device - Google Patents

Description

The present invention relates to an infrared transmissive film, an optical film, an antireflection film, an optical component, an optical system, and an imaging device, and is particularly suitable for an optical system using far infrared rays, an infrared transmissive film, an optical film, an antireflection film, an optical component, Regarding optical systems and imaging devices.

Currently, optical systems that use infrared rays are used in various applications such as surveillance imaging devices, in-vehicle imaging devices, and heat distribution analysis. As these optical systems, a mid-infrared optical system that uses light rays in the mid-infrared wavelength region (2.5 μm to 4 μm) and a far-infrared optical system that uses light rays in the far-infrared wavelength region (8 μm to 14 μm). Is generally known. For example, far-infrared optical systems are mainly used in surveillance imaging devices, in-vehicle imaging devices, and the like. Optical components such as infrared transmissive lenses constituting these optical systems have a lower transmittance of incident light than the optical components constituting the visible light optical system. Therefore, it is particularly important to provide an antireflection film on the incident surface of the optical component to increase the amount of transmitted light of the incident light and prevent insufficient light amount due to surface reflection.

For example, the far-infrared anti-reflection film of the optical components used in optical systems, for example, Patent Document 1, on a Si substrate, Ge film from the substrate side in this order, ZnS film, Ge film, ZnS film, a YF ₃ film A laminated five-layer antireflection film is disclosed. Further, Patent Document 2 discloses an antireflection film having a two-layer structure in which a BiO ₂ film and a YF ₃ film are laminated in order from the substrate side on a chalcogenide glass substrate. As disclosed in these patent documents, by forming the antireflection film into a multilayer structure in which a plurality of infrared transmitting films are laminated, low reflectance is achieved in the entire wavelength range for light rays in a wide wavelength range. Becomes easier. Currently, the following materials including the materials disclosed in Patent Document 1 and Patent Document 2 are known as the layer constituent materials of the antireflection film used in the far infrared wavelength region.

High Refractive Index Material: Ge, Si
Low Refractive Index Materials: YF ₃ , YbF ₃ , NaF, NdF ₃ , LaF ₃ , CaF ₂ , SrF ₂
Intermediate refractive index materials: ZnS, ZnSe, PbTe, Y ₂ O ₃ , CeO ₂ , HfO ₂

By the way, when an antireflection film is provided on the surface of an optical component, a vacuum vapor deposition method in which a raw material is heated and vapor-deposited by electron beam heating or resistance heating is generally adopted. However, considering the expansion of demand for infrared optical systems in the future, it is required to form an antireflection film by a production-efficient method suitable for mass production.

For example, a magnetron sputtering method can be mentioned as a film forming method having higher production efficiency than the vacuum vapor deposition method. However, when the low refractive index material, that is, fluoride is used as a raw material, the fluorine element in the target material is lost in the sputtering process. Therefore, it is difficult to obtain a film having a stoichiometric composition, and it is not possible to obtain an infrared transmissive film that is transparent to light rays in the wavelength range used. The same applies to the above-mentioned intermediate refracting materials ZnS, ZnSe, and PbTe, and it is difficult to obtain a film having a stoichiometric composition by a magnetron sputtering method using these materials.

On the other hand, Ge and Si, which are the high refractive index materials, can be formed into a film by a magnetron sputtering method. As described above, in order to achieve low reflectance in the entire wavelength range for light rays in a wide wavelength range, it is required to use an optical film having a multilayer structure.

Here, since the refractive index of fluoride is too low with respect to Ge or Si, even if the fluoride film is laminated on the Ge film or Si film, good antireflection performance cannot be obtained. Further, as described above, it is difficult to form a fluoride film having a desired composition by the magnetron sputtering method.

Therefore, it is conceivable that the Ge film or Si film and the film made of the intermediate refractive index material are alternately laminated. However, as described above, it is difficult to form a film of ZnS, ZnSe, and PbTe by the magnetron sputtering method. In addition, since these materials are toxic, care must be taken when handling them. Furthermore, since there is concern about the environmental impact of these materials, it is desirable to reduce the amount used. On the other hand, Y ₂ O ₃ , CeO ₂ , and HfO ₂ can be formed by the magnetron sputtering method and are not toxic. However, as compared with other materials, the transparency to light rays in the far infrared region (8 μm to 14 μm) is low, and a film transparent to far infrared rays cannot be obtained.

Further, a monitoring image pickup device, an in-vehicle image pickup device, or the like is often installed and used outdoors. Since the optical film is provided on the surface of these optical components, it is necessary to have high water resistance as well as adhesion to the film-forming surface.

Japanese Unexamined Patent Publication No. 2007-298661 Japanese Unexamined Patent Publication No. 2011-221048

From the above, the subject of the present invention is to provide a novel infrared transmissive film, optical film, antireflection film, optical component, optical system, and image pickup apparatus, which are easy to form and have high water resistance. It is in.

In order to solve the problem of the present invention, the infrared transmissive film according to the present invention is characterized by containing bismuth oxide and a metal oxide having an extinction coefficient of 0.4 or less in the entire wavelength range of 8 μm or more and 14 μm or less. And.

Further, the optical film, the antireflection film, the optical component, and the optical system according to the present invention are each provided with the infrared transmissive film according to the present invention.

Further, the imaging apparatus according to the present invention is characterized by including an optical system including an optical surface provided with the infrared transmissive film according to the present invention.

According to the present invention, it is an infrared transmissive film provided in an optical component used in the far infrared wavelength range, and is a novel infrared transmissive film, an optical film, and an antireflection film which are easy to form and have high water resistance. , Optical components, optical systems and imaging devices can be provided.

It is a scanning electron micrograph of the surface of the sample of Example 9 which concerns on this invention. It is a scanning electron micrograph of the surface of the sample of Example 13 which concerns on this invention.

Hereinafter, embodiments of an infrared transmissive film, an optical film, an antireflection film, an optical component, an optical system, and an imaging device according to the present invention will be described.

1. 1. Infrared Transmissive Film First, an embodiment of the infrared transmissive film according to the present invention will be described. The infrared transmissive film according to the present invention is characterized by containing bismuth oxide and a metal oxide having an extinction coefficient of 0.4 or less in the entire wavelength range of 8 μm or more and 14 μm or less.

1-1. Bismuth oxide Bismuth oxide has an extinction coefficient of less than 0.05 in the entire wavelength range of 8 μm or more and 14 μm or less, that is, the entire far infrared wavelength range, and has high transparency to far infrared rays (light rays having a wavelength of 8 μm or more and 14 μm or less). It is a material.

Further, the refractive index of bismuth oxide with respect to far infrared rays is in the range of 1.5 or more and 2.8 or less, and bismuth oxide is a medium refractive index material in the far infrared wavelength region. Therefore, the infrared transmissive film is also suitable as a constituent material of the antireflection film. For example, by alternately laminating the infrared transmissive film and a Ge film or Si film having a high refractive index in the far infrared wavelength region, reflection having good antireflection performance in the entire far infrared wavelength region is obtained. A protective film can be obtained.

By the way, bismuth oxide is a material that easily crystallizes. Bismuth oxide formed by a physical vapor deposition method such as a vacuum vapor deposition method or a sputtering method has a polycrystalline structure. Therefore, the crystal grain boundaries are easily impregnated with water or the like, and the bismuth oxide film has low water resistance, and it is difficult to satisfy the durability required for practical use. Therefore, the present inventors have found that the water resistance can be improved by forming a film containing bismuth oxide and a predetermined metal oxide as additives. According to the present invention, high water resistance can be realized. Hereinafter, a predetermined metal oxide used together with bismuth oxide in the present invention will be described.

1-2. Metal oxide (1) Extinction coefficient The metal oxide is required to have an extinction coefficient of 0.4 or less in the entire far-infrared wavelength region. When the extinction coefficient in the far-infrared wavelength region exceeds 0.4, the transparency to far-infrared rays decreases. That is, since the transmittance of far infrared rays in the infrared transmitting film is lowered, it becomes difficult to use the infrared transmitting film as an optical film.

Metal oxides having an extinction coefficient of 0.4 or less in the entire far-infrared wavelength region include, for example, zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), chromium oxide (Cr ₂ O ₃ ), and hafnium oxide (HfO ₂ ). ), Yttrium oxide (Y ₂ O ₃ ), copper oxide (CuO), magnesium oxide (MgO) and the like. By forming a film containing bismuth oxide and these metal oxides, the water resistance of the bismuth oxide film can be improved while maintaining the transmittance of the bismuth oxide film with respect to far infrared rays.

Here, from the viewpoint of increasing the transparency of the infrared transmissive film in the wavelength range used, the extinction coefficient of the metal oxide used as an additive is preferably less than 0.4 in the entire wavelength range used, and is 0. It is more preferably less than .2 and even more preferably less than 0.1. An appropriate metal oxide can be appropriately selected from the above-listed metal oxides and the like according to the wavelength range of the infrared transmissive film. The extinction coefficients of each of the metal oxides listed above are shown below. In the following, k (8 μm) represents the extinction coefficient (k) when the wavelength is 8 μm, and k (14 μm) represents the extinction coefficient when the wavelength is 14 μm. The extinction coefficient of bismuth oxide is also shown below.

Zinc oxide: k (8 μm) = 0.004 k (14 μm) = 0.03
Zirconium oxide: k (8 μm) = 0.06 k (14 μm) = 0.35
Chromium oxide: k (8 μm) = 0.007 k (14 μm) = 0.37
Hafnium oxide: k (8 μm) = 0.006 k (14 μm) = 0.4
Bismuth oxide: k (8 μm) = 0.002 k (14 μm) = 0.025
Yttrium oxide: k (8 μm) = 0.00027 k (14 μm) = 0.078
Copper oxide: k (8 μm) = 0.0001 k (14 μm) = 0.04
Magnesium oxide: k (8 μm) = 0.00025 k (14 μm) = 0.014

As shown above, the extinction coefficients of zinc oxide, yttrium oxide, copper oxide and magnesium oxide are smaller than those of zirconium oxide, chromium oxide and hafnium oxide, and are less than 0.1 over the entire far infrared wavelength region. Therefore, from the viewpoint that high transparency can be maintained in the entire far-infrared wavelength region, it is better to use one or more selected from the group consisting of zinc oxide, yttrium oxide, copper oxide and magnesium oxide together with bismuth oxide. preferable. At this time, it goes without saying that one kind of these metal oxides may be used, or one or more of these metal oxides may be mixed and used.

From the viewpoint of improving the water resistance of the bismuth oxide film, a metal oxide having an extinction coefficient outside the above range, such as tantalum oxide (Ta ₂ O ₅ ), can be used as an additive. The extinction coefficient of tantalum oxide is shown below. However, the extinction coefficient of tantalum pentoxide is large as shown below, and when the bismuth oxide film is contained as an additive, the transmittance of the bismuth oxide film with respect to far infrared rays decreases, making it difficult to use as an optical film. Become.
Tantalum oxide: k (8 μm) = 0.028 k (14 μm) = 0.75

(2) Refractive index The refractive index of the metal oxide with respect to light rays in the far-infrared wavelength region is preferably 0.8 or more and 2.5 or less. By using a metal oxide having a refractive index equivalent to that of bismuth oxide, the refractive index of the obtained infrared transmissive film can be set to the same refractive index as bismuth oxide. The refractive index of each of the metal oxides listed above in the far-infrared wavelength range is in the range of 0.8 or more and 2.8 or less. Here, from the viewpoint of not significantly changing the refractive index of bismuth oxide, it is preferable to use a metal oxide having a refractive index more equal to that of bismuth oxide. From this point of view, it is more preferable to form a film containing bismuth oxide and a metal oxide having a refractive index of 1.0 or more and 2.8 or less, and bismuth oxide and a refractive index of 1.5 or more and 2.8 or less. It is more preferable to use a film containing a metal oxide.

1-3. Zinc oxide Here, among the metal oxides listed above, it is particularly preferable to use zinc oxide. Zinc oxide has a small extinction coefficient of 0.004 over the entire wavelength range of 8 μm or more and 14 μm or less, that is, the entire far infrared wavelength range, and has a wavelength of far infrared rays (8 μm or more and 14 μm or less) as compared with yttrium oxide and copper oxide. Higher transparency to light rays).

Further, the refractive index of zinc oxide with respect to far infrared rays is in the range of 1.5 or more and 2.5 or less, and zinc oxide is a medium refractive index material in the far infrared wavelength region. Therefore, the zinc oxide film itself is suitable as a constituent material of the antireflection film as well as the bismuth oxide film. For example, by alternately laminating the infrared transmissive film and a Ge film or Si film having a high refractive index in the far infrared wavelength region, reflection having good antireflection performance in the entire far infrared wavelength region is obtained. A protective film can be obtained.

By the way, zinc oxide is also a material that easily crystallizes like bismuth oxide. The zinc oxide film formed by a physical vapor deposition method such as a vacuum vapor deposition method or a sputtering method has a polycrystalline structure. Therefore, the crystal grain boundaries are easily impregnated with water or the like, and the zinc oxide film has low water resistance, and it is difficult to satisfy the durability required for practical use. However, by using a film containing bismuth oxide and zinc oxide or a film composed of bismuth oxide and zinc oxide, an infrared transmissive film having high transparency and high water resistance in the entire far infrared wavelength range is realized. can do.

(3) Content Next, the content of bismuth oxide and the content of metal oxide in the infrared transmissive film will be described. The infrared transmissive film is preferably composed of bismuth oxide and the metal oxide, and it is preferable that the infrared transmissive film is substantially composed of bismuth oxide and the metal oxide, except for unavoidable impurities. At this time, the bismuth oxide is preferably 10% by mass or more and 90% by mass or less, and the content of other metal oxides is preferably 90% by mass or less and 10% by mass or more. However, the content of other metal oxides referred to here means the total amount of metal oxides other than bismuth oxide contained in the infrared transmissive film. That is, when a plurality of metal oxides are used in addition to bismuth oxide, the total amount is used. Further, in the infrared transmissive film, the main component is preferably bismuth oxide and / or zinc oxide, and more preferably a far infrared transmissive film composed of bismuth oxide and zinc oxide. Bismuth oxide and zinc oxide have high transparency to light rays in the far infrared wavelength region. By using bismuth oxide and / or zinc oxide as the main component of the infrared transmitting film, the transparency of the infrared transmitting film to far infrared rays is increased. Water resistance can be improved while maintaining it. As described above, the bismuth oxide film and the zinc oxide film itself have low water resistance, but by using a mixed film of bismuth oxide and zinc oxide, a far infrared transmissive film having high water resistance can be obtained.

(4) Crystal Structure The infrared transmissive film according to the present invention has the above metal oxide segregated at the grain boundaries of bismuth oxide, or bismuth oxide segregated at the grain boundaries of metal oxides other than bismuth oxide. It is preferable that the product is made. In particular, it is preferable that zinc oxide is segregated at the grain boundaries of bismuth oxide, or bismuth oxide is segregated at the grain boundaries of zinc oxide. Other metal oxides (or bismuth oxide) segregated at the grain boundaries of bismuth oxide (or metal oxides other than bismuth oxide) make it difficult for water to be contained at the grain boundaries, so that the infrared transmissive film is water resistant. The sex becomes good. Further, if a metal oxide (or bismuth oxide) other than bismuth oxide is segregated at the grain boundaries of bismuth oxide (or other metal oxide), crystal growth is suppressed and enlargement of the crystal grains is prevented. As a result, the crystal grains become finer. Therefore, the residual stress in the film becomes small. This is also considered to be one of the factors for improving water resistance. Moreover, since it has a fine crystal structure, the mechanical strength of the film is also high. Further, water resistance and the like are also improved.

That is, in order to improve the water resistance of the bismuth oxide film, it is preferable that the amount of metal oxide other than bismuth oxide and zinc oxide is such that the enlargement of the crystal grains of bismuth oxide (and zinc oxide) can be prevented. .. On the other hand, when zinc oxide is used as the metal oxide other than bismuth oxide, the content of bismuth oxide and the content of zinc oxide may be the same amount (50% by mass each).

(5) Film Density As described above, bismuth oxide is a material that is easier to crystallize than other metal oxides, so there is a problem that the film density is low. On the other hand, an infrared transmissive film containing the above metal oxides other than bismuth oxide and bismuth oxide, particularly an infrared transmissive film containing 10% by mass or more and 90% by mass or less of bismuth oxide, may have a higher film density than the bismuth oxide film. Therefore, the adhesion between the base material and the infrared transmissive film can be improved, and high durability can be realized.

Here, the percentage of the value obtained by dividing the measured value when the film density of the infrared transmissive film is measured by the following formula, that is, the theoretical film density of the infrared transmissive film is referred to as a relative film density.

Relative film density (%) = (measured value of film density / theoretical film density) x 100

The relative film density of the infrared transmissive film according to the present invention is preferably 80% or more. When the relative film density obtained according to the above formula is 80%, the adhesion between the substrate and the infrared transmissive film is good, and a film having excellent durability can be obtained. An infrared transmissive film containing 10% by mass or more and 90% by mass or less of bismuth oxide can have a relative film density of 80% or more.

(6) Film formation method In order to form the infrared transmissive film according to the present invention, for example, sintered ceramics containing bismuth oxide and the above metal oxide other than bismuth oxide in a predetermined content ratio is used as a starting material. The film can be formed by various dry film forming methods such as a vacuum vapor deposition method and a sputtering method. In either method, a sintered body of the mixed oxide can be used as a starting material.

Among various dry film deposition methods, the magnetron sputtering method is particularly simple and has good production efficiency when compared with the vacuum vapor deposition method. Therefore, it is preferable to use the magnetron sputtering method when forming the infrared transmissive film on a mass-produced optical component. At this time, as the discharge mode, direct current, high frequency discharge, or alternating current discharge can be adopted.

When the infrared transmissive film is formed by the magnetron sputtering method, a metal alloy target containing metal bismuth and a metal constituting a metal oxide other than bismuth oxide in a predetermined content ratio can also be used as a starting material. By forming a film in an oxygen gas atmosphere using this metal alloy target, it is possible to obtain an infrared transmissive film according to the present invention containing bismuth oxide and a metal oxide other than bismuth oxide in a predetermined content ratio. it can.

When a bismuth oxide film containing the metal oxide is formed by these physical vapor deposition methods, the metal oxide segregates at the grain boundaries of the bismuth oxide without forming a composite oxide with the bismuth oxide. That is, an infrared transmissive film having a polycrystalline structure of bismuth oxide in which the metal oxide is segregated at the crystal grain boundaries can be obtained.

The infrared transmissive film according to the present invention is not limited to the dry film forming method, but can also be formed by various wet film forming methods such as a chemical vapor phase growth method and a sol-gel method. From each film forming method, an appropriate film forming method can be appropriately selected according to the use of the infrared transmissive film, the material of the base material, and the like.

1-3. Base material The infrared transmissive film according to the present invention is provided on the surface of, for example, an optical component. At this time, the material of the base material such as the optical component is not particularly limited.

The infrared transmissive film according to the present invention has good adhesion to germanium (Ge), silicon (Si), zinc selenide (ZnSe), and zinc sulfide (ZnS), which are transparent to light in the far infrared wavelength region. .. Further, the infrared transmissive film according to the present invention has good adhesion to various chalcogenide glasses containing germanium, arsenic (As), selenium (Se), sulfur (S), antimony (Sb), Ga (gallium) and the like. Has sex. Specific compositions of chalcogenide glass include, for example, As ₂ Se ₃ , CdTe, PbTe, SiSe ₂ , Ga ₂ S ₃ , GeSe ₂ , GeS ₂ , GeAs, CdSe, Ge-As-Se, Ge-Sb-S, Ge-Se-Te, Ge-Se-Sb, Ge-Ga-S, Ga-La-S, As-S-Se, As-S-Te, As-Se-Cu, Ge-Sb-Te, Ga- Ge-As-S, Ge-As-Ga-Sb, As-Se-Sb-Sn, Ga-La-S-Ce, Ge-As-Ga-Se, Ge-As-Ga-Sb-S. Can be done. When various infrared optical components such as an infrared optical lens made of these materials are used as a base material, the infrared transmissive film according to the present invention can be directly provided on the surface of the infrared optical component, and good adhesion can be obtained. it can.

2. 2. Optical film Next, the optical film according to the present invention will be described. In the present invention, the optical film means an antireflection film, an optical filter such as an edge filter and a bandpass filter, and the like. The optical film according to the present invention may be a single-layer film composed of one layer of optical thin films, or may be a multilayer film in which two or more layers of optical thin films are laminated. In any case, the optical film according to the present invention shall include the infrared transmissive film according to the present invention described above. That is, the optical film may be a single-layer film made of the infrared-transmitting film according to the present invention, or may be a multilayer film including at least one layer of infrared-transmitting film.

The infrared transmissive film according to the present invention contains bismuth oxide, which is an intermediate refractive index material, and other metal oxides such as zinc oxide having a refractive index equivalent to that of bismuth oxide. In addition, the infrared transmissive film has good adhesion to the following high-refractive index materials or low-refractive index materials.

High Refractive Index Material: Ge, Si
Low refractive index materials: YF ₃ , YbF ₃ , NaF, NdF ₃ , LaF ₃ , CaF ₂ , SrF ₂

Therefore, using the infrared transmissive film as an intermediate refractive index layer, an optical film having an arbitrary layer structure laminated with a high refractive index layer and / or a low refractive index layer made of the above materials can be appropriately obtained.

3. 3. Antireflection film Next, an embodiment of the antireflection film according to the present invention will be described. The antireflection film according to the present invention is a kind of the above optical film, and is characterized by including the infrared transmissive film according to the present invention. The antireflection film according to the present invention may be a single-layer film composed of one layer of the infrared transmissive film, but it is more preferable to use a multilayer film laminated with the high-refractive index layer and / or the low-refractive index layer. By forming the antireflection film having a multi-layer structure, it becomes easy to realize low reflectance in a wide wavelength range by utilizing the interference action of light due to the interfacial reflected light generated at each interface.

4. Optical component The optical component according to the present invention is characterized by including the infrared transmissive film according to the present invention. Examples of the optical component include various optical components constituting the image pickup optical system or the projection optical system of the image pickup device or the projection device. More specifically, lenses, prisms (color separation prisms, color synthesis prisms, etc.), polarization beam splitters (PBS), cut filters (for long wavelengths, short wavelengths, etc.) and the like can be mentioned. In particular, an infrared lens that constitutes a far-infrared imaging optical system that uses light rays in the far-infrared wavelength region is preferable.

5. Optical System / Imaging Device The optical system according to the present invention is characterized by including the infrared transmissive film according to the present invention. The optical system is preferably an imaging optical system, and particularly preferably a far-infrared imaging optical system that uses light rays in the far-infrared wavelength region. For example, it is preferable that the optical system is an imaging device for monitoring or an imaging device for vehicles. Further, the imaging apparatus according to the present invention is characterized by including an optical system including an optical surface provided with the infrared transmissive film, and a monitoring imaging male value and an in-vehicle imaging equipped with these far-infrared imaging optical systems. It is preferably an apparatus or the like.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

In Example 1, a mixed film of bismuth oxide and zinc oxide was formed on both sides of the base material by the magnetron sputtering method, respectively. Hereinafter, the procedure for film formation will be specifically described.

First, the target, which is a film-forming raw material, and the base material were placed facing each other in the magnetron sputtering apparatus. A zinc oxide sintered body target was used as the film forming raw material. At this time, small pieces of bismuth oxide tablets were evenly arranged on the target so that the content of bismuth oxide in the infrared transmissive film was 4.0% by mass. As a base material, chalcogenide glass (IRG206 manufactured by Hubei Xinhua Gwangbok Information Materials Co., Ltd.) was used.

Next, the entire inside of the device was evacuated to vacuum. Then, when the pressure in the apparatus reached 3 × 10 ^-4 Pa, 20 SCCM (standard cc / min, 1 atm (25 ° C.)) of Ar gas was flowed, and 5 SCCM of oxygen gas was flowed. The exhaust speed was adjusted so that the pressure inside the device at this time was 0.3 Pa.

After that, a high frequency of 13.56 MHz (about 500 W) is applied to the surface of the target, and while rotating the base material in front of the target, infrared rays containing 4% by mass of bismuth oxide and 96% by mass of zinc oxide on the surface of the base material. A permeable film was formed.

In Example 2, the amount of small pieces of bismuth oxide on the zinc oxide sintered target was adjusted so that the content of bismuth oxide in the infrared transmissive film was 0.7% by mass. Similarly, an infrared transmissive film containing 0.7% by mass of bismuth oxide and 99.3% by mass of zinc oxide was formed.

In Example 3, bismuth oxide was 14.7% by mass and zinc oxide was used in the same manner as in Example 1 except that a zinc oxide sintered target having a bismuth oxide content of 14.7% by mass was used. An infrared transmissive film containing 85.3% by mass was formed.

In Example 4, bismuth oxide was 44.7% by mass and zinc oxide was used in the same manner as in Example 1 except that a zinc oxide sintered target having a bismuth oxide content of 44.7% by mass was used. An infrared transmissive film containing 55.3% by mass was formed.

In Example 5, bismuth oxide was 70.0% by mass and zinc oxide was used in the same manner as in Example 1 except that the bismuth oxide sintered target having a zinc oxide content of 30.0% by mass was used. An infrared transmissive film containing 30.0% by mass was formed.

In Example 6, an antireflection film was formed by laminating a Ge film and an infrared transmissive film containing bismuth oxide and a zinc oxide film in this order from the substrate side. When forming a Ge film, germanium is used as a target, and when forming an infrared transmissive film containing bismuth oxide and zinc oxide, zinc oxide having a bismuth oxide content of 2% by mass is baked. Each film was formed in the same manner as in Example 1 using the body-forming target.

In Example 7, a Ge film, an infrared transmissive film containing bismuth oxide and zinc oxide, a Ge film, and an infrared transmissive film containing bismuth oxide and zinc oxide were laminated in this order from the substrate side. At this time, when forming the infrared transmissive film, a zinc oxide sintered target having a bismuth oxide content of 5% by mass was used, and the bismuth oxide content was 5% by mass and the zinc oxide content was 95% by mass. Each film was formed in the same manner as in Example 6 except that.

In Example 8, the substrate side was the same as in Example 6 except that an infrared transmissive film containing 30% by mass and 70% by mass of zinc oxide was used as a film formed by the same method as in Example 5. To obtain an antireflection film in which a Ge film and the infrared transmissive film are laminated in this order.

In Example 9, bismuth oxide was 50.0 in the same manner as in Example 1 except that a sintered target containing 50% by mass each of bismuth oxide and zinc oxide was used as the film forming raw material. An infrared transmissive film containing 50.0% by mass of zinc oxide was formed.

In Example 10, bismuth oxide was set to 38.0% by mass in the same manner as in Example 1 except that a zinc oxide sintered target having a bismuth oxide content of 38.0% by mass was used. An infrared transmissive film containing 62.0% by mass of zinc oxide was formed.

In Example 11, the bismuth oxide was set to 70.0% by mass in the same manner as in Example 1 except that the sintered target of bismuth oxide having a zinc oxide content of 30.0% by mass was used. An infrared transmissive film containing 30.0% by mass of zinc oxide was formed.

In Example 12, 90% by mass of bismuth oxide and 10% by mass of zinc oxide were obtained in the same manner as in Example 1 except that a sintered target of bismuth oxide having a zinc oxide content of 10% by mass was used. An infrared transmissive film containing% was formed.

In Example 13, bismuth oxide was 8% by mass and zinc oxide was 92 by mass, as in Example 1, except that a sintered target of zinc oxide having a bismuth oxide content of 8% by mass was used. An infrared transmissive film containing% by mass was formed.

In Example 14, as in Example 6, an antireflection film was formed by laminating a Ge film and an infrared transmissive film containing bismuth oxide and zinc oxide in this order from the substrate side. When forming a Ge film, germanium is used as a target, and when forming an infrared transmissive film containing bismuth oxide and zinc oxide, zinc oxide having a bismuth oxide content of 38% by mass is baked. An infrared transmissive film containing 38% by mass of bismuth oxide and 62% by mass of zinc oxide was formed in the same manner as in Example 1 except that the body target was used.

In Example 15, an antireflection film was formed by laminating a Si film and an infrared transmissive film containing bismuth oxide and zinc oxide in this order from the substrate side. When forming a Si film, silicon is used as a target, and when forming an infrared transmissive film containing bismuth oxide and zinc oxide, zinc oxide having a bismuth oxide content of 38% by mass is baked. An infrared transmissive film containing 38% by mass of bismuth oxide and 62% by mass of zinc oxide was formed in the same manner as in Example 1 except that the body target was used.

In Example 16, a vacuum vapor deposition material in which bismuth oxide and zinc oxide, which are film-forming raw materials, are mixed on both sides of the substrate by the vacuum vapor deposition method is used, and infrared transmission containing bismuth oxide and zinc oxide in order from the substrate side A three-layer laminated film consisting of a film, an itterbium fluoride film, and an infrared transmissive film containing bismuth oxide and zinc oxide was formed. Hereinafter, the procedure for film formation will be specifically described.

First, the vapor-deposited material, which is a film-forming raw material, and the base material were placed facing each other in the vacuum vapor deposition apparatus. As the film-forming raw material, tablets in which bismuth oxide and zinc oxide were mixed and granules of ytterbium fluoride were used. As a base material, chalcogenide glass (IRG206 manufactured by Hubei Xinhua Gwangbok Information Materials Co., Ltd.) was used.

Next, the entire inside of the device was evacuated to vacuum. The vaporized material was heated in the vapor deposition apparatus and evaporated to vaporize it. When the vapor deposition material was heated and vapor-deposited, tablets in which bismuth oxide and zinc oxide were mixed were vapor-deposited by electron beam heating, and ytterbium fluoride granules were vapor-deposited by resistance heating.

The tablet in which bismuth oxide and zinc oxide were mixed had a bismuth oxide content of 90% by mass and a zinc oxide content of 10% by mass.

In Example 17, in the same manner as in Example 16, an infrared transmissive film containing bismuth oxide and zinc oxide, an itterbium fluoride film, an infrared transmissive film containing bismuth oxide and zinc oxide, and fluoride are used in this order from the substrate side. A five-layer laminated film consisting of an itterbium film and an infrared transmissive film containing bismuth oxide and zinc oxide was formed. As the infrared transmissive film containing bismuth oxide and zinc oxide, each layer of the infrared transmissive film containing 90% by mass of bismuth oxide and 10% by mass of zinc oxide was formed in the same manner as in Example 11.

In Example 18, in the same manner as in Example 16, the Ge film, the infrared transmissive film containing bismuth oxide and zinc oxide, the Ge film, the infrared transmissive film containing bismuth oxide and zinc oxide, and the foot are in this order from the substrate side. A 6-layer laminated film consisting of a chemicalized itterbium film and an infrared transmissive film containing bismuth oxide and zinc oxide was formed. Germanium was deposited by electron beam heating using germanium granules. As the infrared transmissive film containing bismuth oxide and zinc oxide, each layer of the infrared transmissive film containing 90% by mass of bismuth oxide and 10% by mass of zinc oxide was formed in the same manner as in Example 11.

Comparative example

[Comparative Example 1]
In Comparative Example 1, a zinc oxide film was formed in the same manner as in Example 1 except that only a zinc oxide sintered body target was used as a starting material. That is, in Comparative Example 1, a zinc oxide film containing no bismuth oxide was formed.

[Comparative Example 2]
In Comparative Example 2, a film was formed in the same manner as in Example 1 except that a sintered target of bismuth oxide was used as a starting material to obtain a bismuth oxide film. That is, in Comparative Example 2, a zinc oxide film containing no other metal oxide was formed.

[Evaluation]
The film thickness, composition, and average transmittance for far infrared rays of the films formed in Examples 1 to 18, Comparative Example 1 and Comparative Example 2 were measured, and a water resistance test was performed. In addition, a tape test was performed on some of the samples, and the relative film density was determined.

(Film thickness)
The film thickness of each film was measured with a stylus type step meter. The results are shown in Tables 1 to 3. The film thicknesses shown in Tables 1 to 3 are the actual film thicknesses of each film, not the so-called optical film thickness.

(composition)
The composition of each film was analyzed by ICP (inductively coupled plasma emission spectroscopy). The results are shown in Tables 1 to 3.

(Average transmittance)
The average transmittance of the samples obtained in each Example and Comparative Example in the wavelength range of 8 μm to 12 μm and the wavelength range of 8 μm to 14 μm was measured using FT-IR Spectrom 100 Optics manufactured by PerkinElmer. In addition, each sample means a sample which provided each film on both sides of a substrate (hereinafter, the same). The results are shown in Tables 1 to 3.

(Water resistance test)
The samples obtained in each Example and Comparative Example were immersed in pure water. Then, the observation was completed when 24 hours had passed since the sample was immersed in pure water. The results are shown in Tables 1 to 3. However, in Tables 1 to 3, the results of the water resistance test are indicated by "○" and "×". Here, "◯" means that the adhesion between the base material and the film was good even after 24 hours had passed since the sample was immersed in pure water, and no film peeling or the like occurred. In addition, "x" indicates a decrease in adhesion between the substrate and the film, such as the film floating from the substrate or peeling off from the substrate until 24 hours have passed after the sample was immersed in pure water. It means that it was done.

(Tape test) MIL-C-48497A para 4.5.3.1
The samples obtained in Examples 9 to 18 and Comparative Examples 1 and 2 were subjected to a tape test after the water resistance test to evaluate the adhesion between the base material and the coating film. The results are shown in Tables 1 to 3. However, in Tables 1 to 3, the results of the tape test are indicated by "○" and "×". Here, "◯" means that the adhesion between the base material and the coating film was good even when the tape was attached to the sample and peeled off, and no film peeling or the like occurred. Further, "x" means that when the tape was attached to the sample and peeled off, a decrease in adhesion between the base material and the coating film was observed, such as the film floating from the base material or the film peeling off.

(Membrane density)
With respect to the samples obtained in Examples 9 to 18 and Comparative Examples 1 and 2, the film density of the infrared transmissive film was measured by the X-ray reflectivity method (XRR). At this time, as a sample for XRR measurement, a sample having a film thickness of 150 nm was used. This is because the measurement sensitivity on the Si wafer is improved by using a sample having a film thickness of about 150 nm. The percentage of the obtained measured value divided by the theoretical film density for each sample was obtained and used as the relative film density. The results are shown in Tables 1 to 3. Table 4 shows the theoretical film density and the average film density of the samples of Example 9 and Example 13.

(Appearance observation)
With respect to the samples of Example 9 and Example 13, the surface of the infrared transmissive film was observed with a scanning electron microscope (JSM-6500F (manufactured by JEOL Ltd.)) at a magnification of 10,000 times. SEM images for each sample are shown in FIGS. 1 and 2.

As shown in Tables 1 and 2, the samples of Examples 1 to 18 all have good water resistance test results, and even if 24 hours have passed since each sample was immersed in pure water, the substrate No film peeling occurred from the surface. On the other hand, the sample of Comparative Example 1 includes an infrared transmissive film made of zinc oxide. As shown in Table 2, the sample was immersed in pure water and 24 hours later, the film was completely peeled off from the substrate. Therefore, it was confirmed that the mixed film of bismuth oxide and zinc oxide had better water resistance than the zinc oxide film containing no bismuth oxide.

Further, among the samples of Examples 9 to 18 in which the tape test was performed, the samples of Examples 9 to 12 and 14 to 18 did not show any peeling of the film, and the results were good. there were. On the other hand, the sample of Example 13 and the sample of Comparative Example 2 were in a state where the film was peeled off in the tape test after the water resistance test. The sample of Example 13 has a bismuth oxide content of 8% by mass, and the content of bismuth oxide is lower than that of other samples. Moreover, the sample of Comparative Example 2 does not contain zinc oxide.

Here, as shown in Tables 1, 2 and 4, in the samples of Examples 9 to 12 and 14 to 18, the relative film density of each infrared transmissive film is 80.0% or more. More specifically, the relative film density of the sample of Example 13 is less than 80.0%, whereas it is 85.0% or more. Similarly, the relative film densities of the samples of Comparative Example 1 and Comparative Example 2 are less than 80.0%. Further, from FIGS. 1 and 2, it was confirmed from the SEM image that the infrared transmissive film of Example 9 was composed of finer crystal grains than the infrared transmissive film of Example 13 and the film density was improved. .. It was confirmed that the relative film density was changed by changing the mixing ratio of bismuth oxide and zinc oxide, and the content of bismuth oxide in the infrared transmissive film composed of bismuth oxide and other metal oxides (zinc oxide). It was confirmed that the water resistance and adhesion of the bismuth oxide film (or zinc oxide film) can be remarkably improved by setting the content to 10% by mass or more and 90% by mass or less.

Further, as shown in Tables 1 and 2, the samples of Examples 1 to 18 show an average transmittance of 83% or more in the wavelength range of 8 μm to 12 μm, and have high transparency with respect to light rays in these wavelength ranges. Is shown. Therefore, the infrared transmissive film according to the present invention formed in Examples 1 to 18 can be suitably used as an optical film.

On the other hand, as shown in Table 3, the sample of Comparative Example 1 has an average transmittance of 90% or more in a wavelength range of 8 μm to 12 μm, and has optical characteristics suitable for an optical film. However, as described above, since the water resistance and adhesion are low, the durability required for practical use cannot be satisfied. Further, the sample of Comparative Example 2 has an average transmittance of 81% in a wavelength range of 8 μm to 12 μm and has low transparency to far infrared rays, so that it is difficult to use it as an optical film.

According to the present invention, a novel infrared transmissive film which is easy to form a film and has practically sufficient durability such as water resistance, and an optical film, an antireflection film, and an optical component provided with the infrared transmissive film. , Optical systems and imaging devices can be provided.

Claims (6)

An optical component provided with an infrared transmissive film provided on the surface of a substrate made of germanium, silicon, zinc selenide, zinc sulfide, or chalcogenide glass.
The infrared transmissive film contains one or more layers composed of bismuth oxide and zinc oxide having an extinction coefficient of 0.4 or less over the entire wavelength range of 8 μm or more and 14 μm or less, and the thickest layer of these layers is 225 nm or more. An optical component having a wavelength of 1700 nm or less . Optical component according to claim 1 wherein the amount of bismuth oxide is not more than 10 wt% or more and 90 wt% in the infrared transmitting film. When the measured value when measuring the film density of the infrared transmitting film, and the percentage of divided by the theoretical film density of the infrared transmitting film and a relative film density, claim the relative film density is 80% or more 1 or the optical component according to claim 2 . The optical component according to any one of claims 1 to 3, wherein the infrared transmissive film has an average transmittance of 83% or more in a wavelength range of 8 μm to 12 μm. An optical system comprising the optical component according to any one of claims 1 to 4 on an optical surface. An image pickup apparatus comprising the optical component according to any one of claims 1 to 4 .