JP2009092746A - Antireflection coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance antireflection coating having functions such as water repellency, oil repellency, pollution prevention property or the like. <P>SOLUTION: An inorganic oxide film 2 is formed as a first layer on a glass substrate 1. An inorganic oxide film 3 is formed as a second layer on the inorganic oxide film 2. A MgF<SB>2</SB>film formed by a fluoride compound in an inorganic coating 4 is formed as a third layer on the inorganic oxide film 3. In addition, an organic coating 5 formed by a fluoride-containing organic compound is formed as a fourth layer positioned on the most outside air side of the outermost surface layer to form a multilayer film 6 constituted by a four layer structure. as the outermost surface layer. The high performance antireflection coating having functions such as water repellency, oil repellency, pollution prevention property or the like can be formed by depositing the fluoride-containing organic compound as an organic coating 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antireflection film used for an optical member such as a camera.

Conventionally, an antireflection film for increasing the amount of transmitted light and avoiding ghost and flare due to unnecessary light has been formed on both surfaces or one surface of an optical member such as a photographic lens of a TV camera, a video camera, or a photographic camera. These anti-reflective coatings are composed of alternating high-refractive-index and low-refractive-index inorganic dielectric materials, and the outermost layer has a low-refractive-index inorganic dielectric material to improve the anti-reflection effect. Is used. Further, MgF ₂ (magnesium fluoride) or SiO ₂ (silicon dioxide) is used as an inorganic dielectric material having a low refractive index.

  For example, when the camera is always installed outdoors, such as a surveillance camera used in the rain or a weather camera, the surface of the optical member is exposed to water droplets and dust. The antireflective performance of the protective film is likely to deteriorate. In such a case, there is known a method of removing the contamination by wiping the contaminated portion with a cloth or paper or providing a wiper mechanism.

  However, the dielectric film that makes up the antireflection film has a high frictional resistance on the surface, so it is extremely difficult to completely remove the contamination. Have the problem of being lost.

  Therefore, an antireflection film capable of easily removing dirt and water droplets has been required, and functions such as water repellency, oil repellency, and antifouling properties have been conventionally formed by forming an organic coating on an inorganic dielectric film. It is widely known to improve.

In Patent Document 1, as a method for producing an antifouling optical component, it is disclosed that the antireflection film on the outermost surface of the substrate on which the antifouling layer is formed is a layer containing SiO ₂ as a main component.

Patent Document 2 discloses that in the surface treatment method for forming an organic coating on an inorganic coating film, the outermost layer of the inorganic coating layer is an antireflection film made of SiO ₂ .

Japanese Patent Laid-Open No. 2005-301208 JP-A-6-340966

When an SiO ₂ film is used as the lower layer film of the organic coating as described in Patent Documents 1 and 2, performance that is not particularly problematic as an antireflection effect of an eyeglass lens or the like can be obtained.

  However, as an antireflection film used for a photographing lens, the effect of antireflection is insufficient, causing ghost and flare, and satisfactory performance cannot be obtained.

  An object of the present invention is to solve the above-described problems and provide an antireflection film having functions such as high performance water repellency, oil repellency and antifouling properties.

  In order to achieve the above object, the technical feature of the antireflection film according to the present invention is that the antireflection film in which two or more kinds of materials having different refractive indexes are formed in two or more layers on the substrate is the most external side. The layer to be formed is an organic film, and the second layer from the outside air is an inorganic film made of a fluorinated compound.

  According to the present invention, an antireflection film having a high amount of transmitted light can be realized while having functions such as water repellency, oil repellency, and antifouling properties.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 shows a film configuration diagram of an antireflection film in Example 1. First, on a substrate 1 made of glass having a d-line refractive index of 1.52, the first layer has a d-line refractive index of 1.63. An inorganic oxide film 2 having an optical film thickness of 113 nm is formed. As the second layer on the inorganic oxide film 2, an inorganic oxide film 3 having a d-line refractive index of 2.10 and an optical film thickness of 243 nm is formed.

As the fluorinated compound of the inorganic coating 4, an MgF ₂ film having a d-line refractive index of 1.38 and an optical film thickness of 115 nm is formed as the third layer on the inorganic oxide film 3. Further, the fourth layer located on the outermost surface side of the outermost layer is formed by forming a fluorine-containing organic compound having a d-line refractive index of 1.36 and an optical film thickness of 10 nm as the organic coating 5. A multilayer film 6 having a structure is formed.

  The difference in refractive index between the fluorinated compound of the inorganic coating 4 and the refractive index of the organic coating 5 is 0.02. If the refractive index of the organic coating 5 is higher than the refractive index of the fluorinated compound of the inorganic coating 4, the antireflection performance is deteriorated, so that the refractive index difference is preferably 0.1 or less. If the organic coating 5 is too thick, the surface becomes cloudy and its function is impaired, so a thickness of about 10 nm is desirable.

  As the fluorine-containing organic compound, halogenated silane compounds such as dimethyldichlorosilane, diethyldichlorosilane, and diphenylvinyldichlorosilane described in Patent Document 3 are applicable. Further, alkoxysilane compounds such as dimethyldiethoxysilane and dimethoxymethyl-3,3,3-trifluoropropylsilane described in Patent Document 4 are also applicable. Further, aminosilane compounds such as bis (dimethylamino) methylsilane, hexamethyldisilazane, 1,1,3,3,5,5,7,7-octylmethylcyclotetrasilazane described in Patent Document 5 are also applicable. It is. Moreover, the fluorine-containing aminosilane compound described in Patent Document 6 is also applicable. These fluorine-containing organic compounds are not particularly limited as long as they can provide functions such as water repellency, oil repellency, and dust resistance.

JP 63-169102 A JP 62-178903 A JP 62-247302 A JP-A 62-296002

  The inorganic oxide films 2 and 3 and the inorganic coating film 4 were formed by using a vacuum deposition method at a film formation temperature of 200 ° C. or higher, and the fluorine-containing organic layer 5 of the outermost organic coating film 5 was formed. The compound is formed at a low temperature of 100 ° C. or lower.

  FIG. 2 is a graph showing the reflection characteristics of the antireflection film formed by the above-described method. A high-performance antireflection film having a spectral reflectance of 0.2% or less is realized in the wavelength band of 430 to 630 nm. I was able to confirm that it was possible.

  In this embodiment, the range of the antireflection characteristic is set to 430 to 630 nm. However, it is not limited to this band, and can be moved to the short wavelength side or the long wavelength side by changing the optical film thickness described above. Therefore, the same degree of antireflection effect can be obtained.

  In this embodiment, the multilayer film 6 that is an antireflection film is formed of four types of materials having different refractive indexes in four layers, but is not limited to four layers, and is formed in four or more layers. It is also possible to do.

  Then, by forming a fluorine-containing organic compound as the organic coating 5 on the outermost layer, functions such as water repellency, oil repellency, antifouling properties, such as a contact angle with water of 90 degrees or more, and a sliding angle of 28 A high-performance antireflection film having a function of less than 1 degree can be obtained.

  FIG. 3 shows a film configuration diagram of the antireflection film in the second embodiment. In this embodiment, first, an inorganic oxide film 12 having a d-line refractive index of 1.63 and an optical film thickness of 246 nm is formed on a substrate 11 such as a glass lens having a d-line refractive index of 1.80. Form a film. In the second layer on the inorganic oxide film 12, an inorganic oxide film 13 having a d-line refractive index of 2.10 and an optical film thickness of 247 nm is formed.

Then, an MgF ₂ film having a d-line refractive index of 1.38 and an optical film thickness of 121 nm is formed as the fluorinated compound of the inorganic coating 14 in the third layer on the inorganic oxide film 13. Further, the fourth layer located on the outermost air side of the outermost layer is formed by forming a fluorine-containing organic compound having a d-line refractive index of 1.36 and an optical film thickness of 10 nm as the organic coating 15. A multilayer film 16 having a structure is formed. The film formation method and film formation temperature of the inorganic oxide films 12 and 13, the inorganic coating film 14, and the organic coating film 15 are the same as those in the first embodiment.

  FIG. 4 is a graph showing the reflection characteristics of the antireflection film formed by the above-described method. A high-performance antireflection film having a spectral reflectance of 0.2% or less in the wavelength band of 420 to 650 nm can be realized. .

  Also in this embodiment, the range of the antireflection characteristic can be moved to the short wavelength side or the long wavelength side. The multilayer film 16 which is an antireflection film is not limited to four layers.

FIG. 5 shows a film configuration diagram of an antireflection film in Example 3. In this embodiment, the optical film thickness is d38 with a d-line refractive index of 1.38 on a substrate 21 such as a glass lens having a d-line refractive index of 1.52 as the fluorinated compound of the inorganic coating 22 as the first layer. Is a 120 nm thick MgF ₂ film. Then, a two-layer structure is formed by forming a fluorine-containing organic compound having a d-line refractive index of 1.36 and an optical film thickness of 10 nm as a second organic coating 23 on the inorganic coating 22. A multilayer film 24 is formed.

MgF ₂ which is the inorganic coating 22 is formed at a film forming temperature of 200 ° C. or higher in the vacuum deposition method, and the fluorine-containing organic compound of the organic coating 23 is formed at a low temperature condition of 100 ° C. or lower.

  FIG. 6 is a graph showing the reflection characteristics of the antireflection film formed by the above-described method. The spectral reflectance is 2.0% or less in the wavelength range of 400 to 700 nm, and 1.3 in the wavelength band of 520 nm. % Or less, an excellent antireflection film is obtained. In this embodiment, the wavelength band with the least reflection is set to about 520 nm. However, the minimum reflectance wavelength region can be changed by changing the optical film thickness as described above. Furthermore, the multilayer film 24 which is an antireflection film is not limited to a two-layer structure, and can be obtained by laminating two or more materials into two or more layers.

FIG. 7 shows a film configuration diagram of an antireflection film in Example 4. In this example, an optical film thickness with a d-line refractive index of 1.38 is used as a fluorinated compound of the first inorganic coating 32 on a substrate 31 such as a glass lens having a d-line refractive index of 1.81. Is a 120 nm thick MgF ₂ film. Then, a multilayer organic film having a two-layer structure is formed by forming a fluorine-containing organic compound having a d-line refractive index of 1.36 and an optical film thickness of 10 nm as a second organic film 33 on the inorganic film 32. A film 34 is formed.

  FIG. 8 is a graph showing the reflection characteristics of the antireflection film formed by the above-described method. In the wavelength band of 520 nm, a good antireflection film having a spectral reflectance of 0.1% or less is obtained. .

  In the present embodiment, the wavelength band with the least reflection is set to about 520 nm, but the minimum reflectance wavelength region can be changed by changing the optical film thickness described above.

  FIG. 9 is a front view of a photographing system having a pan / tilt mechanism such as a weather camera used outdoors. The taking lens 41 includes a protective glass 42 as an optical member, and the surface of the protective glass 42 is provided with the antireflection film according to the above-described embodiment. Further, the wiper 43 operates on the protective glass 42 as a water droplet removing mechanism.

  In this embodiment, when water drops adhere to the surface of the protective glass 42 due to rain or when dust or the like adheres, the wiper 43 is activated by remote operation from the outside to remove water drops and dirt. can do.

  In the case where an inorganic coating is formed on the outermost layer as in the conventional example, since the surface frictional resistance is large, even with the wiper 43, water droplets and dirt cannot be completely removed. Further, the blade of the wiper 43 is worn, the antireflection film is peeled off, and not only the antireflection performance is lowered but also the optical performance is affected.

  In this example, by applying the antireflection film of Examples 1 to 4 as a filter to the outermost layer on the outside air side of the protective glass 42, the contact angle of water is increased to, for example, 90 degrees or more, and the falling angle is increased. For example, since it becomes 28 degrees or less, it becomes difficult for water droplets to adhere. Furthermore, since the adhesion of dirt is reduced and the frictional resistance of the surface is also reduced, water droplets and dirt can be easily removed by the wiper 43.

  Further, since the frictional force with respect to the wiper 43 is weakened, the antireflection film is not peeled off and not only the good optical performance can be maintained, but also the driving mechanism of the wiper 43 can be simplified and the power consumption of the motor can be reduced. There is.

  FIG. 10 shows a partial cross-sectional view of the taking lens barrel. A lens 52 is incorporated as an optical member in the lens barrel 51, and the lens 52 is held on the lens barrel 51 by a screw-shaped holding ring 53. At this time, if the contact resistance between the lens barrel 51 and the lens surface is large, the lens 52 may be decentered or the lens surface may be distorted, and the optical performance may be deteriorated.

  When the antireflection film 54 of Examples 1 to 4 is formed on the surface of the lens 52 on the outside air side, even if dust or dirt adheres to the lens 52 during installation, the lens cleaning paper can be easily wiped with a solvent. Dust and the like can be removed.

  Conventionally, when the frictional resistance of the surface of the lens 52 is large, wiping unevenness remains and the dirt cannot be completely removed. However, according to the sixth embodiment, not only unevenness in removing dirt during assembly is prevented, but also because the frictional resistance is small, the eccentricity and distortion of the lens can be reduced, and high optical performance can be maintained. Is possible.

  It can be used to improve antifouling durability for an optical system having an antireflection function.

2 is a film configuration diagram of an antireflection film of Example 1. FIG. 3 is a graph of spectral reflection characteristics of Example 1. FIG. 6 is a film configuration diagram of an antireflection film of Example 2. FIG. 6 is a graph of spectral reflection characteristics of Example 2. FIG. 4 is a film configuration diagram of an antireflection film of Example 3. FIG. 6 is a graph of spectral reflection characteristics of Example 3. FIG. 6 is a film configuration diagram of an antireflection film of Example 4. FIG. 6 is a graph of spectral reflection characteristics of Example 4. FIG. It is a front view of an imaging system. It is a fragmentary sectional view of the lens barrel of a photographic lens.

Explanation of symbols

1, 11, 21, 31 Substrate 2, 3, 12, 13 Inorganic oxide film 4, 14, 22, 32 Inorganic film 5, 15, 23, 33 Organic film 6, 16, 24, 34 Multilayer film 41 Lens 42 Protective glass 43 Wiper 51 Lens barrel 52 Lens 53 Retaining ring 54 Antireflection film

Claims (5)

  In an antireflection film in which two or more kinds of materials having different refractive indexes are formed on a substrate in two or more layers, the layer that is formed most on the outside air side is an organic film, and the film is formed on the second layer from the outside air side. An antireflection film characterized in that the layer is an inorganic film made of a fluorinated compound.   2. The antireflection film according to claim 1, wherein in the wavelength band of 430 to 630 nm, the spectral reflectance is 0.2% or less, and the antireflection film is composed of four or more layers. The antireflection film according to claim 1, wherein the fluorinated compound is made of MgF ₂ .   The antireflection film according to claim 1, wherein the organic coating is a fluorine-containing organic compound.   A photographic lens, wherein the antireflection film according to any one of claims 1 to 6 is provided on the surface of the optical member closest to the outside air.

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