Hydrophilic film, antireflective film, camera, and film formation method

Abstract

The present technology relates to: a hydrophilic film used for, for example, a hydrophilic coating of an optical component; an antireflective film; a camera; and a film formation method. The purpose of the present technology is to provide: a hydrophilic film that has excellent optical transparency and abrasion resistance and that can be reversibly hydrophilized; an antireflective film; a camera; and a film formation method. A hydrophilic film according to the present technology comprises a substance in which a silicon oxide and a metal oxide having a structure represented by M2O3 are compounded, wherein M is a metal element. In the hydrophilic film according to the present technology, polarization occurs between oxygen atoms and atoms of the metal element, and the atoms of the metal element are negatively charged.

Description

Hydrophilic film, anti-reflection film, camera and film forming method

[0001] The present technology relates to a hydrophilic film used for hydrophilic coating of optical components, an anti-reflection film, a camera, and a film forming method.

[0002] In-vehicle cameras are used in systems such as automatic braking, autonomous driving, and rearview mirror replacement, and are becoming increasingly standard equipment. The number of security surveillance cameras installed is also increasing, and higher performance is required. When used outdoors, these cameras can experience a significant reduction in the quality of their visual information due to water droplets and dirt, preventing them from performing to their full potential. In automotive applications, abrasion resistance is also required to prevent the adhesion of sand and dust, or to prevent them from being removed by cleaning. Furthermore, the basic characteristics of camera optical systems require high light transmittance and low light reflectance.

[0003] Water droplets are a common occurrence on glass due to rain, fog, and condensation, and reducing their impact is essential. The hydrophilicity of ordinary glass changes over time and with the adhesion of organic matter, causing the water droplets to degrade the image quality of captured images. To prevent this degradation, hydrophilic coatings that reduce the contact angle of water droplets and water-repellent coatings that prevent water droplets from adhering have been developed. However, hydrophilic coatings tend to lose their surface hydrophilic groups (such as hydroxyl groups), while water-repellent coatings tend to lose their performance due to wear and the influence of adhering substances.

[0004] The hydrophilicity of a hydrophilic coating is generally determined by the amount of hydroxyl groups on the surface, so the greater the amount of hydroxyl groups, the better the hydrophilic coating. Outdoor camera lenses are made of silicon oxide-based materials, taking into consideration transparency and weather resistance. However, because the electronegativity of oxygen, silicon, and hydrogen is "silicon < hydrogen < oxygen," silicon bonds more easily with oxygen than hydrogen, and hydroxyl groups decrease over time or with exposure to high temperatures. Moreover, this is usually irreversible degradation. To solve this problem, a method utilizing the photocatalytic properties of titanium oxide has been put into practical use (see, for example, Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2008-161777

[0006] However, titanium oxide, a photocatalyst, has the following problems. First, its high refractive index results in low light transmittance and high light reflectance. It also has low abrasion resistance. Furthermore, it becomes hydrophobic in environments without light (ultraviolet rays). Additionally, it becomes inactivated by the silicone contained in automobile coatings.

[0007] In view of the above circumstances, an object of the present technology is to provide a hydrophilic film, an anti-reflection film, a camera, and a film-forming method that have excellent light transmittance and abrasion resistance and can be reversibly hydrophilized.

[0008] In order to achieve the above object, the hydrophilic membrane according to one embodiment of the present technology comprises: ２ O ３ The compound is a compound of a metal oxide and silicon oxide having a structure represented by the formula: where M is any of the metal elements.

[0009] Polarization may occur between the atom of the metal element and the oxygen atom, and the atom of the metal element may be negatively charged.

[0010] The metal element may be one or more of aluminum, gallium, indium, and yttrium.

[0011] The metal oxide may be aluminum oxide.

[0012] The Si / M atomic ratio of the metal element to the silicon may be 4 or more.

[0013] In order to achieve the above object, a hydrophilic film according to an embodiment of the present technology includes a low refractive index layer and a high refractive index layer. ２ O ３ where M is any metal element. The high refractive index layers are alternately stacked with the low refractive index layers and are made of a material having a higher refractive index than the material.

[0014] In order to achieve the above object, a camera according to an embodiment of the present technology includes a lens and an image sensor. ２ O ３The surface is coated with a hydrophilic film, which is made of a compound of metal oxide and silicon oxide and has a structure represented by the formula: where M is any metal element. The imaging element captures an image of the light collected by the lens.

[0015] In order to achieve the above object, a film forming method according to an embodiment of the present technology includes: ２ O ３ The hydrophilic film is formed from a compound of a metal oxide and silicon oxide having a structure represented by the formula: where M is one of the metal elements.

[0016] In the film forming method, the hydrophilic film may be formed by sputtering using a target made of a mixture of the metal element and silicon oxide.

[0017] In the film forming method, the hydrophilic film may be formed by sputtering using a target made of a mixture of the metal oxide and the silicon oxide.

[0018] In the film forming method, the hydrophilic film may be formed by sputtering using a target made of a sintered body obtained by mixing the metal oxide and the silicon oxide and sintering the mixture.

[0019] In the film forming method, the hydrophilic film may be formed by sputtering using a target made of a material in which elemental silicon is doped with the metal oxide.

[0020] The sputtering may be RF (Radio Frequency) sputtering.

[0021] 1 is a schematic diagram of a component provided with a hydrophilic film according to an embodiment of the present technology; FIG. 2 is a chemical formula of a substance constituting the hydrophilic film; FIG. 3 is a chemical formula of the substance when the element M is aluminum; FIG. 4 is a chemical formula of a general hydrophilic material made of silicon oxide; FIG. 5 is a schematic diagram of a component provided with an anti-reflection film according to an embodiment of the present technology; FIG. 6 is a photograph of a state in which water is dropped onto a glass substrate on which a hydrophilic film according to Example 1 is formed; FIG. 7 is a photograph of a state in which water is dropped onto a glass substrate on which a conventional hydrophilic film is formed; FIG. 8 is a measurement result of the hydrophilic film according to Example 1 by D-SIMS; FIG. 9 is a measurement result of the hydrophilic film according to Example 1 by GD-OES; and FIG. 10 is an enlarged view of FIG. 9. FIG. 11 is a graph showing the relationship between the contact angle measured for the hydrophilic film of each thickness according to Example 2 and the elapsed time from film formation. FIG. 12 is a graph showing the contact angle increase rate calculated for the hydrophilic film of each thickness according to Example 2. FIG. 13 is a graph showing the change in contact angle when the hydrophilic film according to Example 2 and the hydrophilic film according to the comparative example are maintained in a general environment. 16 is a graph showing the change in contact angle when the hydrophilic film according to Example 2 and the hydrophilic film according to the comparative example are held in a clean booth. This is the result of analyzing deposits on the hydrophilic film according to Example 2 held in a general environment by TOF-SIMS. This is the result of analyzing deposits on the hydrophilic film according to Example 2 held in a clean booth by TOF-SIMS. This is a graph comparing the analysis results shown in FIGS. 15 and 16. This is a photograph of the state in which the surface of the hydrophilic film according to Example 2 has been cleaned and water has been dropped on the surface. This is a graph showing the simulation results of the light reflectance for each wavelength of the anti-reflection film according to Example 3. This is a graph showing the results of an abrasion resistance test of the hydrophilic film according to Example 3. This is an image taken by a camera on which the anti-reflection film according to the comparative example is formed. This is an image taken by a camera on which the anti-reflection film according to Example 3 is formed. This is an image taken by a camera on which the anti-reflection film according to Example 3 is formed, with a large amount of water sprayed. ２ This is a photograph of the sputtering target (SiO + Al mixture) and the hydrophilic film formed by the sputtering target (SiO + Al mixture) with water dropped onto the film. ２ +Al ２ O ３ This is a photograph of the sputtering target (SiO mixture) and the hydrophilic film formed by the sputtering target (SiO ２ +Al２ O ３ This is a photograph of the sputtering target (Si with Al) and the hydrophilic film formed on it with water dropped on it. ２ O ３ The photographs show the state of the formed hydrophilic film after doping and the state of water being dropped onto the film.

[0022] [Configuration of Hydrophilic Film] A hydrophilic film according to an embodiment of the present technology will be described. Fig. 1 is a schematic diagram of a component 100 according to this embodiment. As shown in the figure, the component 100 includes a substrate 110 and a hydrophilic film 120. The substrate 110 is not particularly limited, but may be a camera lens, an automobile mirror, or the like.

[0023] The hydrophilic film 120 is formed on the surface of the substrate 110. The hydrophilic film 120 is ２ O ３ and silicon oxide (SiO ２ M is any metal element, for example, any one or more of aluminum (Al), gallium (Ga), indium (In), and yttrium (Y). ２ O ３ is aluminum oxide (Al ２ O ３ ), gallium oxide (Ga ２ O ３ ), indium oxide (In ２ O ３ ) and yttrium oxide (Y ２ O ３ Hereinafter, the substance constituting the hydrophilic film 120 will be referred to as "substance S", and the element indicated by M will be referred to as "element M".

[0024] In substance S, polarization occurs between element M and oxygen atoms (O), causing element M to be negatively charged. Figure 2 is the chemical formula of substance S. As shown in the figure, substance S has a structure in which four oxygen atoms (O) are bonded to element M, each oxygen atom (O) is bonded to a silicon atom (Si), and each silicon atom (Si) is bonded to three oxygen atoms (O). Polarization occurs between the oxygen atoms (O) bonded to element M and element M, causing element M to be negatively charged.

[0025] This charged element M is surrounded by a water molecule (H ２ Since the charged M atoms are adsorbed onto the surface of the substance S, the substance S has hydrophilicity. A typical hydrophilic material has hydrophilicity due to the presence of hydroxyl groups (OH groups), but the substance S has hydrophilicity due to the charged M atoms, not the hydroxyl groups (OH groups).

[0026] The atomic ratio of element M to silicon (Si / M atomic ratio) in substance S is preferably 4 or more, and more preferably 4 to 50. In substance S, if elements M are adjacent to each other, polarization does not occur and hydrophilicity does not occur, but by setting the Si / M atomic ratio to 4 or more, it is possible to prevent elements M from being adjacent to each other and to generate hydrophilicity.

[0027] The polarization in the substance S will be described in detail below. Table 1 below shows the physical properties of each element.

[0028]

[0029] As shown in Table 1, element M forms three chemical bonds with oxygen (O). Silicon (Si) forms four chemical bonds with oxygen (O). Titanium (Ti) and zirconium (Zr), shown for comparison, also form four chemical bonds with oxygen (O).

[0030] Here, the electronegativity of each element has the following magnitude relationship: Oxygen (O) > Hydrogen (H) > Silicon (Si) > Element M Therefore, the bond strength (electronegativity difference) between each element has the following magnitude relationship: Oxygen-element M (O-M) > Oxygen-silicon (O-Si) > Oxygen-hydrogen (O-H) In other words, due to the electronegativity difference, oxygen (O) is more likely to bond with element M than silicon (Si).

[0031] For this reason, M ２ O ３ and silicon oxide (SiO ２In substance S, which is a mixture of element M and element M, oxygen (O) is attracted to element M, which has a small number of bonds with oxygen (O), and oxygen (O) forms a half bond on the element M side. As a result, polarization occurs between element M and oxygen (O) as shown in Figure 2, and element M becomes negatively charged. On the other hand, elements such as titanium (Ti) and zirconium (Zr) have four bonds with oxygen (O) from the beginning, so no half bond is formed with oxygen (O), and no polarization occurs. Therefore, M ２ O ３ In order to generate polarization in the material S, it is necessary to use a metal oxide having a structure represented by the following formula:

[0032] An example will be described in which the element M is aluminum (Al). Figure 3 shows the chemical formula of the substance S when the element M is aluminum (Al). Tables 2 and 3 below show the physical properties of each element.

[0033]

[0034]

[0035] As shown in Table 2, the electronegativity of each element has the following magnitude relationship: Oxygen (O) > Hydrogen (H) > Silicon (Si) > Aluminum (Al) > Titanium (Ti) > Zirconium (Zr) Therefore, the bond strength (electronegativity difference) between each element has the following magnitude relationship: Oxygen-zirconium (O-Zr) > Oxygen-titanium (O-Ti) > Oxygen-aluminum (O-Al) > Oxygen-silicon (O-Si) > Oxygen-hydrogen (O-H) In other words, due to the difference in electronegativity, oxygen (O) is more likely to bond with aluminum (Al) than with silicon (Si).

[0036] Therefore, the substance S is aluminum oxide (Al ２ O ３ ) and silicon oxide (SiO ２In the case of a substance containing a mixture of oxygen (O), oxygen (O) is attracted to aluminum (Al) which has a smaller number of bonds with oxygen (O), and oxygen (O) forms a semi-bond on the aluminum (Al) side. This causes polarization between aluminum (Al) and oxygen (O), as shown in FIG. 3, and aluminum (Al) becomes negatively charged. For the same reason, when element M is gallium (Ga), indium (In), or yttrium (Y), these elements also become negatively charged.

[0037] Although the thickness D of the hydrophilic film 120 (see FIG. 1) is not particularly limited, a thicker film is advantageous for maintaining long-term hydrophilicity because it stabilizes crystallinity. Specifically, when the element M is aluminum (Al), a thickness of 79 nm or more allows hydrophilicity to be maintained for three months or more (see Examples).

[0038] [Effects of Hydrophilic Film] The effects of the hydrophilic film 120 will be described. As described above, the hydrophilic film 120 exhibits hydrophilicity by generating polarization in the substance S and negatively charging the element M. On the other hand, conventional hydrophilic films do not allow water molecules (H ２ However, due to the difference in electronegativity between the elements, oxygen (O) bonds more easily with silicon (Si) than with hydrogen (H), so the number of hydroxyl groups (OH groups) gradually decreases in conventional hydrophilic films.

[0039] Figure 4 shows the chemical formula of a typical hydrophilic material made of silicon oxide. As time passes or when heated, the hydroxyl groups (OH groups) in this material gradually decrease, as shown by Q1 to Q4 in the figure. This causes a gradual decline in hydrophilicity. To restore the hydrophilicity, a treatment involving exposure to high-temperature steam is required, which is not easy to perform on hydrophilic films installed on automobiles, cameras, etc.

[0040] On the other hand, the hydrophilicity of substance S is not generated by hydroxyl groups (OH groups). Although its hydrophilicity is reduced by the adsorption of substances contained in the air (such as alkylammonium), the hydrophilicity can be restored by removing the adsorbed substances with a dry wipe (see Examples). In other words, the hydrophilic film 120 has reversible hydrophilicity. Furthermore, substance S has excellent abrasion resistance and light transmittance, making it suitable for use as a hydrophilic coating on cameras, mirrors, etc.

[0041] [Configuration of Anti-Reflection Film] An anti-reflection film according to an embodiment of the present technology will be described. Fig. 5 is a schematic diagram of a component 150 according to this embodiment. As shown in the figure, the component 150 includes a substrate 110 and an anti-reflection film 160. As described above, the substrate 110 is a camera lens, an automobile mirror, or the like.

[0042] The anti-reflection film 160 is configured by alternately stacking low refractive index layers 161 and high refractive index layers 162. The number of layers is not particularly limited. The outermost surface of the anti-reflection film 160 is configured by the low refractive index layer 161. The low refractive index layer 161 is made of the above-mentioned substance S, i.e., M ２ O ３ and silicon oxide (SiO ２ The high refractive index layer 162 is made of a material having a higher refractive index than the material S. Specifically, the high refractive index layer 162 is made of niobium pentoxide (Nb ２ O ５ ) etc.

[0043] In the anti-reflection coating 160, light reflected at the interfaces of each layer interferes, thereby suppressing the light reflectance. By using substance S as the material for the low refractive index layer 161, it is possible to make the outermost surface of the anti-reflection coating 160 reversibly hydrophilic, thereby realizing an anti-reflection coating 160 with excellent abrasion resistance.

[0044] [Configuration of Camera] A camera according to an embodiment of the present technology will be described. The camera according to this embodiment includes a lens and an image sensor. The lens corresponds to the substrate 110 shown in FIG. 1. A hydrophilic coating is applied to the surface of the optical component, and the hydrophilic coating corresponds to the hydrophilic film 120 shown in FIG. 1. The image sensor is a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, and captures an image of light collected by the lens.

[0045] By applying a hydrophilic coating made of hydrophilic film 120 to the lens, water adhering to the hydrophilic coating spreads, thereby suppressing the influence of water droplets on the captured image. Note that an anti-reflection film 160 may be used instead of hydrophilic film 120 as the hydrophilic coating on the lens surface.

[0046] [Method for forming hydrophilic film] A method for forming a hydrophilic film according to an embodiment of the present disclosure will be described. The hydrophilic film 120 can be formed by sputtering using a specific target. The target may be any target capable of forming a film made of substance S.

[0047] Specifically, a simple substance of element M and silicon oxide (SiO ２ A target consisting of a mixture of M and M can be used. The element M is oxidized during sputtering, and M ２ O ３ becomes silicon oxide (SiO ２ For example, when the element M is aluminum (Al), a film is formed with aluminum (Al) and silicon oxide (SiO ２ ) can be used as a target.

[0048] Also, M ２ O ３ and silicon oxide (SiO ２ A target made of a mixture of the above metal oxide powder and silicon oxide (SiO ２) powder in a liquid, and then dried and solidified to form a target (see JP 2014-101545 A). ２ For example, when the element M is aluminum (Al), a target containing aluminum oxide (Al ２ O ３ ) and silicon oxide (SiO ２ ) can be used as a target.

[0049] Also, M ２ O ３ and silicon oxide (SiO ２ For example, when the element M is aluminum (Al), aluminum oxide (Al ２ O ３ ) and silicon oxide (SiO ２ A target made of a sintered body obtained by mixing and sintering the above-mentioned materials can be used.

[0050] Furthermore, M is added to the silicon (Si) element. ２ O ３ It is also possible to use a target made of a material doped with a metal oxide having a structure represented by the following formula: Silicon (Si) is oxidized during sputtering to form silicon oxide (SiO ２ ) and is formed into a film together with the metal oxide. For example, when the element M is aluminum (Al), aluminum oxide (Al) is formed on silicon (Si). ２ O ３ ) may also be used as a target.

[0051] Although RF (Radio Frequency) sputtering can be used for sputtering the target, other sputtering methods may also be used. The hydrophilic film 120 can also be formed by a film formation method other than sputtering.

[0052] [About the present disclosure] The effects described in this disclosure are merely examples and are not limiting, and other effects may also be present. The description of multiple effects does not necessarily mean that these effects are exhibited simultaneously. It means that at least one of the effects described above can be obtained depending on the conditions, etc., and effects not described in this disclosure may also be exhibited. Furthermore, it is possible to combine at least two of the characteristic features described in this disclosure.

[0053] [Example 1] A silicon oxide (SiO ２ Two 2 mm diameter aluminum wires cut to 2 cm lengths were placed on a target consisting of a tungsten carbide (TTA) and a glass substrate fixed to the upper surface. A hydrophilic film according to the present technology was formed by RF sputtering on the substrate. The thickness of the hydrophilic film was approximately 1 μm. Figure 6 is a photograph of the glass substrate on which the hydrophilic film was formed, with water dropped onto it. The contact angle of this hydrophilic film was measured to be 4.3°. Furthermore, when this thin film was held at 90° for 24 hours (equivalent to 3 months at 25°) to accelerate thermal degradation, the contact angle was 6.5°, demonstrating high hydrophilicity.

[0054] For comparison, Figure 7 shows a photograph of a glass substrate coated with a conventional hydrophilic film, with water dropped on it. This hydrophilic film was formed by RF sputtering using a sintered shirasu (volcanic ash) target. The contact angle of this hydrophilic film was measured to be 13.8°. Furthermore, when this thin film was held at 90° for 24 hours to accelerate thermal degradation, the contact angle was 66.4°, indicating that the hydrophilicity had been lost.

[0055] The composition of the hydrophilic film according to the present technology was measured using D-SIMS (Dynamic SIMS (Secondary Ion Mass Spectrometry)) and GD-OES (Glow Discharge Optical Emission Spectrometry). FIG. 8 shows the results of the D-SIMS measurement. FIGS. 9 and 10 show the results of the GD-OES measurement, with FIG. 10 being an enlarged view of FIG. 9. As shown in FIG. 10, the hydrophilic film contained 0.8 atomic% aluminum (Al). This corresponds to a state in which the central silicon atom of one of the ten tetrahedra is replaced with an aluminum atom, assuming that four silicon atoms surround one aluminum atom with an oxygen atom sandwiched between them. When aluminum atoms are adjacent to each other, polarization utilizing the difference in electronegativity and the number of bonds with oxygen, which is the mechanism of the present technology, does not occur, and therefore this content is considered to be reasonable.

[0056] [Example 2] Silicon oxide (SiO ２ ) and aluminum oxide (Al ２ O ３ ) were mixed and sintered, and using the resulting target, hydrophilic films according to the present technology were formed at thicknesses ranging from 87 nm to 866 nm. The contact angle was measured for each hydrophilic film thickness, and the relationship between the time elapsed since film formation and the contact angle was plotted. Figure 11 shows this graph. Furthermore, the contact angle increase rate was calculated and plotted for each hydrophilic film thickness. Figure 12 shows this graph. From the approximation formula for the relationship between film thickness and contact angle increase rate, it was found that a film thickness of 79 nm is required to achieve a contact angle of less than 40° within three months, which is the target for initial inspection after vehicle delivery.

[0057] Furthermore, Figure 13 is a graph showing the change in contact angle when the hydrophilic film according to the present technology and the hydrophilic film according to the comparative example are maintained in a general environment. Figure 14 is a graph showing the change in contact angle when the hydrophilic film according to the technology and the hydrophilic film according to the comparative example are maintained in a clean booth (hereinafter referred to as CR). In Figures 13 and 14, "Sample 1" and "Sample 2" are hydrophilic films according to the present technology. "SKZ function" is a conventional anti-reflection film that is thickened to prioritize hydrophilicity, while "SKZ optics" is a conventional anti-reflection film that is thinned to prioritize optical performance.

[0058] Figure 15 shows the results of a TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) analysis of deposits on a hydrophilic film (see Figure 13) held in a general environment. Figure 16 shows the results of a TOF-SIMS analysis of a hydrophilic film (see Figure 14) held in CR. Figure 17 is a graph comparing the analysis results of Figures 15 and 16. The results of Figures 15 to 17 show that the increase in contact angle over time is due to the adhesion of alkyl quaternary ammonium contained in detergents and fabric softeners that are suspended in the air.

[0059] Figure 18 shows a photograph of a water droplet on the surface of a hydrophilic film. As shown in Figure 18(a), the hydrophilic film exhibited high hydrophilicity immediately after deposition, but the contact angle was too small to measure. As shown in Figure 18(b), after 24 hours at 90°, the contact angle increased to 40.4°. After 50 days at room temperature, the contact angle increased to 67.0°, as shown in Figure 18(c). However, when the surface of the hydrophilic film was subsequently cleaned by wiping it dry with a cotton swab, the contact angle decreased to 26.1°, as shown in Figure 18(d), restoring hydrophilicity. This is thought to be due to the removal of the attached alkyl quaternary ammonium when the surface of the hydrophilic film is cleaned. Thus, the hydrophilicity of the hydrophilic film produced by this technology decreases over time, but this is a reversible change, not an irreversible change as in conventional methods.

[0060] [Example 3] Hydrophilic films according to the present technology were formed with a thickness of 100 nm and a thickness of 1000 nm, with the aluminum atom content being varied from 0.8 to 5.7 atomic %. In addition, low refractive index layers (SiO ２ -Al ２ O ３ ) and niobium oxide (Nb ２ O ５ The anti-reflection film according to the present technology was formed by alternately laminating high refractive index layers made of a fluorine-containing compound (F2) and a fluorine-containing compound (F3). Table 4 below shows the configuration of this anti-reflection film.

[0061]

[0062] FIG. 19 shows the antireflection film shown in Table 4, which has a low refractive index layer (SiO ２ -Al ２ O ３ 1 is a graph showing the results of a simulation of the light reflectance at each wavelength of an anti-reflection film having an atomic ratio (Si:Al) of silicon (Si) to aluminum (Al) of 20:1 in a sample of 1000 nm. The light reflectance of this anti-reflection film was 1.5% or less at wavelengths of 450-550 nm, 1.2% or less at wavelengths of 650-750 nm, and 4% or less at a wavelength of 850 nm, demonstrating that a sufficient anti-reflection effect was obtained.

[0063] The following Tables 5 and 6 show the results of measuring the contact angles of the hydrophilic film and the anti-reflection film. In these tables, "target" refers to silicon oxide (SiO ２ ) and aluminum oxide (Al ２ O ３ The atomic ratio (Si:Al) of silicon (Si) to aluminum (Al) in the target consisting of a mixture of silicon (Si) and aluminum (Al), i.e., the same atomic ratio (Si:Al) in the hydrophilic film and the low refractive index layer. The retention of the contact angle was compared for each hydrophilic film and each anti-reflection film when maintained at 125° for up to 300 hours.

[0064]

[0065] At 125°, 3.1 atomic % (SiO ２ :Al ２O ３ The hydrophilic film and anti-reflection film with a ratio of 20:1 showed the best retention. As the aluminum (Al) content increases, the refractive index increases. ２ :Al ２ O ３ It has been confirmed that it is possible to design an anti-reflection film even with a configuration where the ratio is 20:1 (see FIG. 19).

[0066] Abrasion resistance tests were conducted using a suspension of Kanto loam mud for hydrophilic films with thicknesses of 100 nm and 1000 nm. Figure 20 is a graph showing the results of the abrasion resistance test. As shown in the figure, the hydrophilic films (each sample) according to this technology retained their hydrophilicity even after the abrasion resistance test, confirming that a strong hydrophilic film was formed from the material and film formation method.

[0067] Furthermore, water was sprayed onto a rearview camera for automobiles having an anti-reflection coating according to the present technology and a comparative example formed on the lens surface, and images were taken. FIG. 21 shows an image taken by a camera having an anti-reflection coating (water-repellent) according to the comparative example formed thereon. FIGS. 22 and 23 show images taken by a camera having an anti-reflection coating according to the present technology formed thereon, with a larger amount of water sprayed in FIG. 23. Image distortion due to water droplets was observed with the conventional anti-reflection coating shown in FIG. 21. On the other hand, slight image distortion due to water droplets was observed with the anti-reflection coating according to the present technology shown in FIGS. 22 and 23, but it was not so severe that the subject was mistakenly recognized, and no reduction in the effective field of view area was observed.

[0068] [Example 4] In order to confirm that the hydrophilicity of the hydrophilic film according to the present technology does not depend on the sputtering target, but that the ratio of silicon (Si) to aluminum (Al) is important, hydrophilic films were formed by RF (Radio Frequency) sputtering using various targets, and the hydrophilicity was evaluated. Figures 24 to 27 show various targets ((a) in each figure) and photographs ((b) in each figure) of the hydrophilic films formed using those targets with water dropped onto them.

[0069] FIG. 24 shows silicon oxide (SiO ２ ) and metallic aluminum (Al) mixture (SiO ２The target consisted of silicon oxide (SiO + 2×Al) and when the target was used for 3 hours of film formation at 100 W, a hydrophilic film with a film thickness of 862.2 nm was formed. The contact angle immediately after film formation was not measurable, but after 24 hours at 90°, the contact angle was 3.9°. ２ ) and powdered aluminum oxide (Al ２ O ３ ) in a liquid, dried, and solidified to form a target (Si:Al = 82:1). When film formation was performed for 3 hours at 100 W, a hydrophilic film with a film thickness of 935.6 nm was formed. The contact angle immediately after film formation was unmeasurable, but the contact angle after 24 hours at 90° was 7.3°.

[0070] FIG. 26 shows the silicon oxide (SiO ２ ) and metallic aluminum (Al ２ O ３ The target was a sintered body of silicon (Si) and aluminum oxide (Al) (Si:Al = 80:1). When the target was deposited for 3 hours at 100 W, a hydrophilic film with a thickness of 816.4 nm was deposited. The contact angle immediately after deposition was unmeasurable, but after 24 hours at 90°, the contact angle was 11.4°. ２ O ３ The target is made of a material doped with argon (Ar) and oxygen (O ２ ) in a mixed gas (Ar / O ２ When the film was formed at 100 W for 3 hours, a hydrophilic film with a thickness of 1.306 μm was formed. The contact angle immediately after film formation was not measurable, but the contact angle after 24 hours at 90° was 12.3°.

[0071] Thus, the contact angle of the hydrophilic films formed using either target was less than 20° after 24 hours at 90° (corresponding to 3 months at 25°), indicating that a highly hydrophilic film could be formed.

[0072] The present technology can also be configured as follows.

[0073] (1) M ２ O ３(2) The hydrophilic film according to (1) above, which is the hydrophilic film according to claim 1, wherein polarization occurs between atoms of the metal element and oxygen atoms, and the atoms of the metal element are negatively charged. (3) The hydrophilic film according to (2) above, wherein the metal element is one or more of aluminum, gallium, indium, and yttrium. (4) The hydrophilic film according to (3) above, wherein the metal oxide is aluminum oxide. (5) The hydrophilic film according to (3) above, which is the hydrophilic film according to any one of (1) to (4) above, wherein the Si / M atomic ratio of the metal element to the silicon is 4 or more. (6) M ２ O ３ (7) An anti-reflection film comprising: low refractive index layers made of a compound substance of a metal oxide and silicon oxide having a structure represented by the formula: where M is any metal element; and high refractive index layers alternately stacked with the low refractive index layers and made of a material having a higher refractive index than the substance. ２ O ３ (8) A camera comprising: a lens whose surface is coated with a hydrophilic film made of a compound substance of a metal oxide and silicon oxide having a structure represented by the following formula: and M is any of the metal elements; and an image pickup element that picks up an image of light collected by the lens. ２ O ３(9) A film formation method for forming a hydrophilic film made of a compound substance of a metal oxide and silicon oxide having a structure represented by the following formula: where M is any metal element. (9) The film formation method according to (8) above, wherein the hydrophilic film is formed by sputtering using a target made of a mixture of the metal element and the silicon oxide. (10) The film formation method according to (8) above, wherein the hydrophilic film is formed by sputtering using a target made of a mixture of the metal oxide and the silicon oxide. (11) The film formation method according to (8) above, wherein the hydrophilic film is formed by sputtering using a target made of a sintered body obtained by mixing the metal oxide and the silicon oxide and sintering it. (12) The film formation method according to (8) above, wherein the hydrophilic film is formed by sputtering using a target made of a material obtained by doping elemental silicon with the metal oxide. (13) The film deposition method according to any one of (9) to (12) above, wherein the sputtering is RF (Radio Frequency) sputtering.

[0074] 100, 150... Component 110... Substrate 120... Hydrophilic film 160... Anti-reflection film

Claims

1. M ２ O ３ A hydrophilic membrane comprising a compound of a metal oxide and silicon oxide having a structure represented by the formula: wherein M is any one of the metal elements.

2. The hydrophilic film according to claim 1, wherein polarization occurs between the atoms of the metal element and oxygen atoms, and the atoms of the metal element are negatively charged.

3. The hydrophilic film according to claim 2, wherein the metal element is one or more of aluminum, gallium, indium, and yttrium.

4. The hydrophilic membrane according to claim 3, wherein the metal oxide is aluminum oxide.

5. The hydrophilic film according to claim 1, wherein the Si / M atomic ratio of said metal element to said silicon is 4 or more.

6. M ２ O ３ wherein M is any metal element; and high refractive index layers alternately stacked with the low refractive index layers and made of a material having a higher refractive index than the low refractive index layers.

7. M ２ O ３ and an imaging element that captures the light collected by the lens.

8. On the object to be coated, ２ O ３ A method for forming a hydrophilic film comprising a compound substance of a metal oxide and silicon oxide having a structure represented by the formula: wherein M is any one of the metal elements.

9. A method for forming a hydrophilic film according to claim 8, wherein the hydrophilic film is formed by sputtering using a target made of a mixture of the metal element and silicon oxide.

10. A method for forming a hydrophilic film according to claim 8, wherein the hydrophilic film is formed by sputtering using a target made of a mixture of the metal oxide and the silicon oxide.

11. A method for forming a hydrophilic film according to claim 8, wherein the hydrophilic film is formed by sputtering using a target made of a sintered body obtained by mixing and sintering the metal oxide and silicon oxide.

12. A method for forming a hydrophilic film according to claim 8, wherein the hydrophilic film is formed by sputtering using a target made of a material in which simple silicon is doped with the metal oxide.

13. A film deposition method according to any one of claims 9 to 12, wherein the sputtering is RF (Radio Frequency) sputtering.

Images