JP5067149B2 - Absorption-type multilayer ND filter - Google Patents

Description

  The present invention relates to an absorptive multilayer ND filter (Neutral Density Filter) comprising a substrate, an optical multilayer film layer that attenuates the amount of transmitted light on the substrate, and a protective film layer formed thereon. The present invention relates to an improvement of an absorption-type multilayer ND filter that is less likely to be scratched by sliding friction, has flat transmittance spectral characteristics with good reproducibility, and is excellent in mass productivity.

  An ND filter is an optical filter having a non-selective transmittance that transmits each wavelength in the visible spectrum of light almost evenly, and is used by attaching it to a lens such as a digital camera in order to attenuate the amount of transmitted light. It is done. For example, if the lens is overexposed even under a high light condition such as under a clear sky, if you want to limit the light quantity so that the shutter can be released at a lower speed, or if you want to open the diaphragm, It is generally used to limit the amount of light so that the aperture can be opened when overexposure occurs even when the maximum is set.

  By the way, an inexpensive ND filter includes a glass filter in which a light absorbing material is added to glass. However, these glass filters have a problem that spectral characteristics are not uniform over the entire visible range.

An absorption type multilayer ND filter is known as a solution to such a problem. For example, as a conventional technique in which an optical multilayer film composed of a dielectric film and a metal film is used and the respective types of materials are referred to, Patent Document 1 discloses an Nb metal film and a SiO ₂ dielectric film alternately. A laminated thin film type ND filter is disclosed.

Further, as a conventional technique using only a light-absorbing dielectric film without using a metal film, Patent Document 2 discloses that the number of layers is about seven and titanium oxides such as TiO and Ti ₂ O ₃ . A thin film type ND filter having a multilayer structure using a light-absorbing metal oxide layer is disclosed.

Further, as a result of examining the constituent materials of many absorption multilayer ND filters in Patent Document 3, the inventor is an optical multilayer film layer in which a substrate, a metal film, and a dielectric film are alternately stacked. The metal film is a metal film containing nickel (Ni) as a main component, the dielectric film is a dielectric film made of silicon oxide or aluminum oxide, and absorption using an optical multilayer film layer that attenuates the amount of transmitted light Type multilayer ND filter is proposed.
JP 2002-350610 A JP 7-63915 A JP 2006-58854 A

The outermost layer of the thin-film ND filter is provided with an SiO ₂ film or an Al ₂ O ₃ film known as an inorganic hard film, but it is not always sufficient in terms of resistance to scratches and abrasion. That is, even when the inorganic hard film is used, the surface of the light amount diaphragm device is scratched by the sliding friction that repeatedly occurs between the ND filter and the blade portion of the diaphragm device and the blade support plate each time the light amount is reduced. There was a problem.

  The present invention has been made paying attention to such problems, and the subject of the present invention is, in particular, that scratches due to sliding friction are not easily scratched, flat transmittance spectral characteristics can be obtained with good reproducibility, and mass production. An object of the present invention is to provide an absorption type multilayer ND filter having excellent properties.

  In order to solve such problems, the present inventors have studied many constituent materials of the absorption multilayer ND filter, and as a result, the transmitted light amount is attenuated by alternately laminating the substrate, the metal film, and the dielectric film. In the absorption multilayer ND filter comprising the optical multilayer film layer to be formed and the protective film layer formed on the optical multilayer film layer, the metal film of the optical multilayer film layer is mainly composed of nickel (Ni), Preferably, it is made of a nickel-based alloy material to which one or more elements selected from titanium (Ti), aluminum (Al), vanadium (V), tungsten (W), tantalum (Ta), and silicon (Si) are added. It is a metal film, the dielectric film of the optical multilayer film layer is a dielectric film made of silicon oxide or aluminum oxide, and a protective film layer made of a diamond-like carbon film is formed And in the unlikely scratches due to sliding friction, and flat transmittance spectral characteristics with good reproducibility is obtained, moreover the absorption type multi-layer film ND filter having excellent mass productivity came to find that obtained. The present invention has been completed based on such technical findings.

That is, the first invention of the present invention is a substrate, an optical multilayer film layer in which a metal film and a dielectric film are alternately laminated to attenuate the amount of transmitted light, and a protection formed on the optical multilayer film layer. in absorption type multi-layer film ND filter comprising a membrane layer, a metal film composed mainly of optical multilayer film layer of the metal film crab nickel (Ni), the optical multilayer film layer dielectric film of silicon oxide or aluminum oxide There is provided an absorptive multilayer ND filter, wherein the protective film layer is formed of a diamond-like carbon film having a thickness of 1 nm to 10 nm formed by sputtering .

According to a second aspect of the present invention, the diamond-like carbon film has a hardness of Hv = 2500 or more, and a ratio sp ³ / sp ^{2 of} sp ³ hybrid orbitals to sp ² hybrid orbitals is 0.1 or more. An absorption-type multilayer ND filter according to the first invention is provided.

  According to a third aspect of the present invention, there is provided the absorptive multilayer ND filter according to the first or second aspect, wherein the friction coefficient is 0.2 or less.

  According to a fourth aspect of the present invention, a metal film containing nickel (Ni) as a main component is titanium (Ti), aluminum (Al), vanadium (V), tungsten (W), tantalum (Ta), silicon (Si). 1) An absorptive multilayer ND filter according to any one of the first to third inventions, characterized in that it is a metal film made of a nickel (Ni) alloy material to which one or more elements selected from To do.

According to a fifth aspect of the present invention, when a metal film containing nickel (Ni) as a main component adds one of the above elements, the addition ratio of titanium (Ti) element is 5 to 15% by weight, aluminum (Al ) Addition ratio of element is 3-8 wt%, Addition ratio of vanadium (V) element is 3-9 wt%, Addition ratio of tungsten (W) element is 18-32 wt%, Addition ratio of tantalum (Ta) element Is provided in the range of 22 to 48% by weight, and the addition ratio of silicon (Si) element is set in the range of 2 to 6% by weight. .

  According to a sixth aspect of the present invention, there is provided the absorptive multilayer ND filter according to any one of the first to fifth aspects, wherein the substrate is made of a resin plate or a resin film.

  According to a seventh aspect of the present invention, the resin plate or resin film is made of a resin material of polyethylene terephthalate (PET), polyether sulfone (PES), polyarylate (PAR), polycarbonate (PC), polyolefin (PO), and norbornene. Or a composite of a resin plate or resin film selected from the above resin materials and an acrylic organic film covering at least one side of the single resin. An absorptive multilayer ND filter according to the sixth invention is provided.

The absorption-type multilayer ND filter according to the present invention is formed on a substrate, an optical multilayer film in which a metal film and a dielectric film are alternately laminated to attenuate a transmitted light amount, and the optical multilayer film layer. In the absorption multilayer ND filter comprising a protective film layer, the metal film of the optical multilayer film layer is mainly composed of nickel (Ni), preferably titanium (Ti), aluminum (Al), vanadium (V), A metal film made of a nickel-based alloy material to which one or more elements selected from tungsten (W), tantalum (Ta), and silicon (Si) are added, and the dielectric film of the optical multilayer film layer is silicon oxide or oxide It is a dielectric film made of aluminum and a diamond-like carbon film as a protective film layer, and it is possible to make it difficult to be damaged by sliding friction. The diamond-like carbon film has an extremely high hardness of Hv = 2500 or more, whereas the SiO ₂ or Al ₂ O ₃ film, which is known as an inorganic hard film, has a hardness of about Hv = 1000 to 2000, and has a sliding friction. Excellent resistance to. Therefore, by using it as the outermost layer of the absorption multilayer ND filter, it is possible to remarkably improve the resistance to scratches and wear.

  Hereinafter, the absorption multilayer ND filter of the present invention will be described in detail with reference to the drawings.

  First, an absorptive multilayer ND filter according to the present invention includes an optical multilayer film layer in which metal films and dielectric films are alternately laminated on a substrate, and an optical multilayer film layer that attenuates the amount of transmitted light, on the optical multilayer film layer. In the absorption multilayer ND filter comprising the formed protective film layer, the metal film of the optical multilayer film layer is a metal film mainly composed of nickel (Ni), and the dielectric film of the optical multilayer film layer is oxidized. It is a dielectric film made of silicon or aluminum oxide, and the protective film layer is made of a diamond-like carbon film.

  The metal film containing nickel (Ni) as a main component is at least one selected from titanium (Ti), aluminum (Al), vanadium (V), tungsten (W), tantalum (Ta), and silicon (Si). A metal film made of a nickel (Ni) -based alloy material to which an element is added is preferable. When one kind of the elements is added, the addition ratio of titanium (Ti) is 5 to 15% by weight, the addition ratio of aluminum (Al) element is 3 to 8% by weight, and vanadium (V ) 3 to 9% by weight for the addition ratio of elements, 18 to 32% by weight for the addition ratio of tungsten (W) element, 22 to 48% by weight for the addition ratio of tantalum (Ta) element, silicon ( If it is the addition ratio of the Si) element, it is preferably set in the range of 2 to 6% by weight.

  FIG. 1 shows a specific example of an absorption type multilayer ND filter according to the present invention. The absorption multilayer ND filter shown in FIG. 1 is obtained by providing an optical multilayer film layer 10 and a protective film layer 20 on a substrate 1.

  FIG. 2 shows a specific example of the optical multilayer film layer 10. The optical multilayer film layer 10 is provided on the substrate 1 to attenuate the amount of transmitted light. For example, the metal film layers 11 and the dielectric film layers 12 having an arbitrary number of layers are alternately stacked. In this case, the metal film 11 is a metal film containing nickel (Ni) as a main component. The metal film 11 is formed by, for example, a DC magnetron sputtering method.

  The dielectric film 12 is preferably a low refractive index silicon oxide or aluminum oxide film. The dielectric film is formed by, for example, an RF magnetron sputtering method.

  The protective film layer 20 needs to be a diamond-like carbon film. The diamond-like carbon film is preferably formed by sputtering using a target made of graphite.

  Sputtering is superior to other deposition processes, such as vapor deposition, in terms of adhesion between the film and the substrate or different types of film, film surface smoothness, film denseness, and the like. In addition, it is very advantageous in the overall production of ND filters. In particular, it is a thin film formation technique that is effective when a film is formed on a substrate using a material having a low vapor pressure or when precise film thickness control is required. Has been used.

  In general, under an argon gas pressure of about 10 Pa or less, the substrate is an anode, the film source target is a cathode, glow discharge is caused between them to generate argon plasma, and This is a technique in which an argon cation collides with a cathode target to repel particles of a target component, and deposits the particles on a substrate to form a film.

  The above sputtering methods are classified according to the method of generating argon plasma. Those using high frequency plasma are called radio frequency (RF) sputtering methods, and those using direct current plasma are called direct current (DC) sputtering methods. A method of forming a film by arranging a magnet on the back side of the target and concentrating argon plasma directly on the target and increasing the collision efficiency of argon ions even at a low gas pressure is called a magnetron sputtering method.

  And the diamond-like carbon film used as the protective film layer according to the present invention is formed, for example, by DC magnetron sputtering using a graphite target in an Ar atmosphere.

  The thickness of the diamond-like carbon film is preferably in the range of 1 nm to 10 nm. This is because if the thickness is less than 1 nm, sufficient resistance to scratches and wear may not be obtained. On the other hand, if the thickness exceeds 10 nm, the transmittance decreases, and flat optical characteristics may not be obtained in the visible light region. And when the tolerance with respect to said flaw and abrasion, an optical characteristic, etc. are considered, it is more preferable that the thickness of the protective film layer 20 is about 2 nm.

The diamond-like carbon film preferably has a friction coefficient of 0.2 or less. If it is 0.2 or less, sufficient slidability can be obtained. Further, the hardness of the film is preferably Hv = 2500 or more in order to obtain sufficient resistance against scratches and wear caused by sliding friction. A diamond-like carbon film is composed of a σ bond component represented by sp ³ hybrid orbitals and a π bond component represented by sp ² hybrid orbitals, and the hardness of the film depends on the ratio of both components sp ³ / sp ^2. To do. In order to obtain a diamond-like carbon film having high hardness, the sp ³ / sp ² ratio is preferably 0.1 or more.

  The material of the substrate 1 is not particularly limited, but is preferably transparent, and when considering mass productivity, is preferably a flexible substrate that can be formed by a roll coating method. A flexible substrate is superior in that it is cheaper, lighter, and more deformable than a conventional glass substrate. In particular, a resin plate or a resin film is preferable as such a substrate.

  Specific examples of the substrate include a resin plate or resin selected from polyethylene terephthalate (PET), polyethersulfone (PES), polyarylate (PAR), polycarbonate (PC), polyolefin (PO), and norbornene resin materials. Examples thereof include a single film, or a composite of a resin plate or resin film selected from the above resin materials and an acrylic organic film covering one or both surfaces of this single material. In particular, as for norbornene resin materials, representative examples include ZEONOR (registered trademark) of Nippon Zeon Co., Ltd. and Arton (registered trademark) of JSR Corporation.

  Moreover, the said board | substrate 1 may be what the hard-coat layer was coated as needed and the board | substrate intensity | strength was improved. For example, an acrylic resin is used for the hard coat layer, and the hard coat layer is formed on the substrate with a thickness of, for example, 5 μm.

  The absorptive multilayer ND filter as described above can also be formed by a roll coating method using a roll-type roll coater on a film-like substrate. This method enables efficient mass production.

  By adopting the above-described configuration for the optical multilayer film layer, the absorption multilayer film having a reflectance of 5% or less and a transmittance fluctuation width of 10% or less in the entire visible range of 400 to 800 nm. An ND filter can be provided.

  Next, specific examples of the present invention will be described.

Example 1
Optical multilayer film composed of a total of four layers in which metal layers and silicon oxide layers composed of nickel (Ni) -based materials containing 7.5% by weight of titanium (Ti) are alternately laminated, and protection composed of a diamond-like carbon film An absorption multilayer ND filter having the structure shown in Table 1 in which the film layer was formed on the substrate was produced.

  The nickel-based material target used was a nickel alloy target containing 7.5% by weight of titanium (manufactured by Sumitomo Metal Mining Co., Ltd.). This nickel target containing 7.5% by weight of Ti could be stably discharged even when placed on the nonmagnetic cathode. For the formation of the diamond-like carbon film, a graphite target [manufactured by Kojundo Chemical Laboratory Co., Ltd.] was used.

  Specifically, the films (2) to (6) in Table 1 were sequentially formed on a 100 μm-thick PET film [manufactured by Toyobo Co., Ltd.] using a sputtering apparatus (manufactured by ULVAC). The absorptive multilayer ND filter shown was produced.

  The transmittance and reflectance of the obtained absorption-type multilayer ND filter were measured using a self-recording spectrophotometer device [U-4000, manufactured by Hitachi, Ltd.]. The measurement results are shown in FIG.

  From the data shown in FIG. 3, the transmittance in the visible region (wavelength 400 to 800 nm) is 18 to 22%, and the transmittance characteristic is excellent in flatness with respect to the wavelength. confirmed. Further, the reflectance in the visible range was 3% or less, and the antireflection effect was also good.

  Next, in order to confirm the strength of the surface of the ND filter, it was actually attached to a light quantity diaphragm device and slid by opening and closing the diaphragm 250,000 times. As a result, it was confirmed that no scratch was generated on the surface of the protective film made of the diamond-like carbon film of the ND filter.

  The friction test was performed using a micro scratch tester MST (manufactured by CSM Instruments). The friction coefficient was obtained from the load value and the friction force. As a result, the obtained coefficient of friction was 0.15, and it was confirmed that the coefficient of friction was sufficiently low.

The diamond-like carbon film was measured with a Raman spectrophotometer (HoloLab-5000, manufactured by Shimadzu Corporation), and the sp ³ / sp ² ratio was determined from the area ratio, and was confirmed to be 0.1 or more.

(Example 2)
The films (2) to (6) in Table 1 were sequentially formed under the same conditions as in Example 1 except that the film thickness of the protective film layer made of (6) diamond-like carbon film in the above table was changed to 5 nm. An absorption multilayer ND filter shown in FIG. 1 was produced.

  The measurement results of the transmittance and the reflectance of the absorption multilayer ND filter according to Example 2 are shown in FIG. From the data shown in FIG. 3, it is confirmed that the transmittance in the visible range is 17 to 21%, exhibiting a transmittance characteristic with excellent flatness with respect to the wavelength, and the reflection in the visible range. The rate was 3% or less, and the antireflection effect was also good.

In the same manner as in Example 1, the ND filter was attached to the light quantity diaphragm and the surface strength was confirmed. As a result, it was confirmed that the surface of the protective film of the ND filter was not damaged by sliding.
The coefficient of friction was measured by the same method as in Example 1. As a result, the coefficient of friction was 0.20, and it was confirmed that the coefficient of friction was sufficiently low.
As in Example 1, when the sp ³ / sp ² ratio of the diamond-like carbon film was determined from the area ratio by measurement with a Raman spectrophotometer, it was confirmed to be 0.1 or more.

(Comparative Example 1)
Films (2) to (5) in Table 1 were sequentially formed under the same conditions as in Example 1 except that the protective film layer made of (6) diamond-like carbon film in Table 1 was not formed. An absorptive multilayer ND filter having no protective film layer 20 was produced.
FIG. 4 shows the measurement results of the transmittance and reflectance of the absorption multilayer ND filter according to Comparative Example 1. From the data shown in FIG. 4, it is confirmed that the transmittance in the visible range is 18 to 22%, and shows a transmittance characteristic excellent in flatness with respect to the wavelength, and the reflection in the visible range. The rate was 3% or less, and the antireflection effect was also good.

  However, when the ND filter was attached to the light quantity diaphragm device and the strength of the surface was confirmed by the same method as in Example 1, a large scratch due to sliding occurred on the contact track between the diaphragm blade and the ND filter. It was confirmed.

  The coefficient of friction was measured from the surface of the film (5) silicon oxide film in Table 1 in the same manner as in Example 1. As a result, the friction coefficient was 0.50. It was confirmed that it had a large coefficient of friction compared to the examples.

(Comparative Example 2)
The films (2) to (6) in Table 1 were formed in order under the same conditions as in Example 1 except that the film thickness of the protective film layer made of (6) diamond-like carbon film in the above table was changed to 15 nm. An absorption multilayer ND filter shown in FIG. 1 was produced.

  The measurement results of the transmittance and the reflectance of the absorption multilayer ND filter according to Comparative Example 2 are shown in FIG. From the data shown in FIG. 4, it was confirmed that the transmittance in the visible range was 11 to 19%, and the flatness with respect to the wavelength, which is the transmittance characteristic necessary for the ND filter, was impaired. Further, the reflectance in the visible range was 5% or more, and the antireflection effect was inferior.

  The coefficient of friction was measured by the same method as in Example 1. As a result, the coefficient of friction was a sufficiently low value of 0.12.

As in Example 1, when the sp ³ / sp ² ratio of the diamond-like carbon film was determined from the area ratio by measurement with a Raman spectrophotometer, it was confirmed to be 0.1 or more. It was confirmed that the film can be evaluated as a high hardness film.

It is a schematic sectional drawing which shows the laminated structure of the absorption type multilayer ND filter which concerns on this invention. It is a schematic sectional drawing which shows the laminated structure of the optical multilayer film layer 10 of the absorption type multilayer ND filter which concerns on this invention. It is a figure which shows the result of having measured the transmittance | permeability and reflectance of the absorption type multilayer ND filter of Example 1 and Example 2 of this invention using the self-recording spectrophotometer apparatus. It is a figure which shows the result of having measured the transmittance | permeability and reflectance of the absorption multilayer film ND filter of the comparative example 1 using the self-recording spectrophotometer apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 10 Optical multilayer film layer 11 Metal layer 12 Dielectric film layer 20 Protective film layer

Claims (7)

Absorption type multilayer film ND filter comprising a substrate, an optical multilayer film layer that attenuates the amount of transmitted light, and a protective film layer formed on the optical multilayer film layer, in which metal films and dielectric films are alternately laminated in a metal film composed mainly of metal film crab nickel optical multilayer film (Ni), a dielectric film dielectric layer of the optical multilayer film is made of silicon oxide or aluminum oxide, the protective layer An absorptive multilayer ND filter comprising a diamond-like carbon film having a film thickness of 1 nm or more and 10 nm or less formed by a sputtering method . ^2. The absorption according to claim 1, wherein the diamond-like carbon film has a hardness of Hv = 2500 or more, and a ratio sp ³ / sp ^{2 of} sp ³ hybrid orbitals to sp ² hybrid orbitals is 0.1 or more. Type multilayer ND filter.   The absorption multilayer ND filter according to claim 1 or 2, wherein a friction coefficient is 0.2 or less.   The metal film containing nickel (Ni) as a main component is at least one selected from titanium (Ti), aluminum (Al), vanadium (V), tungsten (W), tantalum (Ta), and silicon (Si). The absorptive multilayer ND filter according to any one of claims 1 to 3, which is a metal film made of a nickel (Ni) -based alloy material to which an element is added. When a metal film mainly composed of nickel (Ni) adds one of the above elements, the addition ratio of titanium (Ti) element is 5 to 15% by weight and the addition ratio of aluminum (Al) element is 3 to 8%. %, The addition ratio of vanadium (V) element is 3 to 9% by weight, the addition ratio of tungsten (W) element is 18 to 32% by weight, the addition ratio of tantalum (Ta) element is 22 to 48% by weight, silicon ( The absorption multilayer ND filter according to claim 4, wherein the addition ratio of Si) element is set in the range of 2 to 6% by weight.   6. The absorptive multilayer ND filter according to claim 1, wherein the substrate is made of a resin plate or a resin film.   The resin plate or resin film is selected from the resin materials of polyethylene terephthalate (PET), polyethersulfone (PES), polyarylate (PAR), polycarbonate (PC), polyolefin (PO) and norbornene. Or a composite of a resin plate or resin film selected from the resin materials and an acrylic organic film covering at least one surface of the single body. Item 7. The absorption multilayer ND filter according to Item 6.

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