JP5117759B2 - ND filter, light quantity reduction device using ND filter, and method for manufacturing ND filter - Google Patents

Description

The present invention relates to an ND filter, a light quantity reduction device using the ND filter, and a method for manufacturing the ND filter .

  A light amount diaphragm device mounted on a conventional video camera or the like adjusts the amount of light passing by changing the aperture diameter by a pair of diaphragm blades that open and close on the diaphragm blade support plate. This light amount diaphragm device is provided to control the amount of light incident on a solid-state imaging device such as a CCD, and is narrowed down more when the object field is bright. Therefore, when photographing a clear or high-luminance subject, the aperture becomes a small aperture, which is susceptible to light diffraction by the aperture opening, and there is a problem that image performance is deteriorated.

  As a countermeasure against this problem, for example, a film-like ND filter is attached to the diaphragm blade so that the aperture of the diaphragm is enlarged even if the brightness of the object field is the same. This ND filter is inserted into the optical path when the aperture is reduced to reduce the amount of light, thereby preventing the aperture from becoming too small even during high-intensity shooting.

  Furthermore, for example, Patent Document 1 discloses an ND filter in which the transmittance increases sequentially with the density of the ND filter toward the center of the optical axis. Alternatively, as shown in Patent Document 2, the density of the ND filter is continuously increased toward the center of the optical axis so that the light quantity adjustment function has a density gradient and is moved on the optical axis. There are some which perform further light quantity adjustment.

  Such an ND filter as a light quantity adjusting member is usually a multi-layered film made of a laminated film of a metal film, a metal oxide, a dielectric film, etc. by vacuum deposition or the like on the surface of a transparent synthetic resin substrate in the form of a film. A film is used.

Japanese Patent No. 2592949 JP 2004-117467 A

  However, in the ND filter in which the outermost layer of the laminated film is a metal film, when the ND filter attached to the diaphragm blade slides between the diaphragm blade and the diaphragm blade support plate, the other diaphragm blade and the diaphragm base plate Are rubbed together, and the surface is scratched.

  On the other hand, when the outermost layer of the laminated film is a dielectric film made of an insulator, an effect can be obtained in reducing the occurrence of scratches that occur during sliding compared to the case of using a metal film. However, in this case, another problem arises in that static electricity is generated due to contact between the diaphragm blades and the diaphragm base plate, charging occurs, and surrounding dust is attracted.

  Patent Document 3 discloses an ND filter having scratch resistance and antistatic properties by coating a carbon film on the surface of a laminated film in which light absorption films and dielectric films are alternately laminated. However, it is difficult to ensure sufficient transparency depending on the film thickness of the carbon film, and the extinction coefficient of the carbon film needs to be taken into consideration separately in terms of transmittance characteristics. Moreover, the adhesion of the carbon film to the transparent synthetic resin substrate is not always sufficient.

  Furthermore, when a DLC (diamond-like carbon) film is formed as a carbon film by plasma CVD, sputtering, or the like, an apparatus for forming a DLC film is separately prepared in addition to a vacuum film forming apparatus. There is a problem that it is necessary and disadvantageous in terms of economy.

JP 2006-84994 A

The object of the present invention is to eliminate the above-mentioned problems and to prevent the generation of scratches on the surface when sliding with other members by the opening / closing operation for controlling the amount of transmitted light, and has excellent antistatic properties. In addition, it is an object of the present invention to provide an ND filter excellent in productivity, a light quantity reduction device using the ND filter, and a method for manufacturing the ND filter .

In order to achieve the above object, an ND filter according to the present invention comprises a transparent resin substrate and an ND film on a part of the transparent resin substrate, and the glass transition temperature of the transparent resin substrate is 250 ° C. or higher. The outermost layer including the ND film on the transparent resin substrate is provided with an oxide transparent conductive layer having a thickness of 30 to 50 nm.
Further, the light quantity diaphragm device using the ND filter according to the present invention includes an ND filter that is movably attached to the opening having the diaphragm blades and adjusts the amount of light passing through the opening, and the diaphragm blades. In the light quantity reduction device having a movably supporting member, the ND filter includes a transparent resin substrate and an ND film on the transparent resin substrate, and the glass transition temperature of the transparent resin substrate is 250 ° C. or higher. An oxide transparent conductive layer having a thickness of 30 to 50 nm is provided on the outermost layer on the transparent resin substrate.
Furthermore, the manufacturing method of the ND filter according to the present invention includes a step of forming an ND film on a transparent resin substrate having a glass transition temperature of 250 ° C. or higher, and an oxidation on the outermost layer on the transparent resin substrate including the ND film. The method includes a step of forming a vapor-deposited film using a material conductive material, and a step of heat-treating the vapor-deposited film to form an oxide transparent conductive layer having a thickness of 30 to 50 nm.

  According to the present invention, scratches on the ND filter due to sliding between the ND filter movably attached to the opening and other structural members can be prevented, and dust and dust can be prevented from adhering to the ND filter due to charging. Can be reduced. As a result, it is possible to prevent the ND filter from being scratched or to reduce the resolution of the image that has passed through the light amount restricting device due to the adhesion of dust, and it is possible to cope with higher image quality.

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

  FIG. 1 is a cross-sectional view of a photographing optical system used in a video camera, and FIG. 2 is an exploded perspective view. A solid-state image pickup device 7 including a lens 1, a light amount diaphragm 2, lenses 3 to 5, a low-pass filter 6, a CCD, and the like. They are arranged sequentially. In the light quantity diaphragm device 2, a pair of diaphragm blades 9 a and 9 b for restricting the light amount is movably attached to the diaphragm blade support plate 8. An ND filter 10 for reducing the amount of light passing through the substantially rhombus-shaped opening formed by the diaphragm blades 9a and 9b is bonded to the diaphragm blade 9a. The ND filter 10 may be driven by another member without being attached to the aperture blade 9a.

  FIG. 3 shows a configuration diagram of a chamber of a vacuum evaporation machine for manufacturing the ND filter 10. In the chamber 21, a vapor deposition source 22 and a vapor deposition umbrella 23 that can rotate to face the vapor deposition source 22 are provided. The vapor deposition umbrella 23 is provided with a substrate jig 24 on which a synthetic resin substrate is set in close contact with a mask having an opening at a film formation site where a vapor deposition film is applied. A transparent substrate serving as a substrate of the ND filter 10 is attached to the substrate jig 24, and film formation is performed by rotating around the Z axis together with the vapor deposition umbrella 23.

FIG. 4 shows a configuration diagram of the ND film of the ND filter 10. The first, _third , fifth, seventh, and ninth layers on the transparent resin substrate 31 made of a polyimide resin (Mitsubishi Gas Chemical Neoprim L) having a thickness of 100 μm include an Al ₂ O ₃ film 32 that is an antireflection layer, a _second layer. TiOy films 33 that are light absorption layers are alternately formed on the 4, 6, and 8 layers. Then, an ND film 35 in which an SiO ₂ film 34 is laminated is formed on the tenth TiOy film 33 as an antireflection film.

  The formed ND film 35 is a single concentration film having a uniform concentration on the vapor deposition surface. Specifically, a film having a concentration of 0.6 is formed on both surfaces of the transparent resin substrate 31, respectively. The density is set to 1.2.

  Further, an ITO film 36 is formed on the ND film 35 by a vacuum film formation method such as a vapor deposition method or an ion plating method as an oxide transparent conductive layer as the ND film 35 made of a metal oxide or a dielectric film. It is filmed.

  The transmittance varies depending on the total thickness of the TiOy film 33, and the transmittance decreases as the thickness increases. Further, the neutrality of the transmittance within the wavelength range of 400 to 700 nm varies depending on the numerical value y of the composition of the TiOy film 33, and the transmittance distribution becomes neutral when appropriately selected. A preferable value of y is in the range of 0.5 or more and less than 2, and when y = 1.2 or less, a phenomenon occurs in which the transmittance at a low wavelength is lowered with a wavelength of about 550 nm as a boundary. On the other hand, when y = 1.2 or more, it is inclined to increase the transmittance of low wavelengths. For this reason, it is preferable to make the transmittance neutral by monitoring the transmittance during film formation.

In addition, an Al ₂ O ₃ film 32 is disposed on the first, _third , fifth, seventh, and ninth layers as an antireflection film, and an SiO ₂ film 34 is disposed on the eleventh layer. It is possible to reduce the reflectance by controlling the film thickness.

In addition, the material of the ITO film 36 used in this embodiment is an In ₂ O ₃ —SnO ₂ based material mainly composed of indium oxide and tin oxide, and the composition thereof is, for example, In ₂ O ₃ : SnO ₂ = 84:16 (% by weight) is used. The thickness of the ITO film 36 is not particularly limited. However, since it is necessary to completely cover the surface of the ND film 35 in order to provide at least the entire area of the ND filter 10, the film thickness is preferably 10 to 50 nm. In the embodiment, the thickness is set to 30 nm. In this film thickness range, it is desirable to determine the film thickness according to the required optical characteristics.

  The outermost ITO film 36 formed in this way has a higher hardness than metal oxides, dielectric films, etc., so that it is difficult to be scratched even when it slides on the aperture blade, ground plate, cover plate, etc. . The diaphragm blades 9a and the like contain carbon or the like in order to provide conductivity, and static electricity flows to the camera body through the diaphragm blades 9a. Therefore, the ND filter 10 is difficult to be charged with static electricity and reduces dust adhesion. can do.

  Although some ND filters 10 have the ND film 35 formed on the entire area of the transparent resin substrate 31, the ND film 35 may be formed only on a part thereof, and the transparent resin substrate may be exposed as it is in other parts.

  FIG. 5 is a plan view of the ND filter 10 manufactured by the above-described method, and FIG. 6 is a sectional view. The ND film 35 is formed on one surface of the transparent resin substrate 31 and is not formed on the other surface. For the reason described above, the ITO film 36 is also formed on the portion where the transparent resin substrate 31 on which the ND film 35 is not formed is exposed. That is, by forming the ITO film 36 on the sliding surface of the ND filter 10 including the ND film 35, it is possible to prevent the surface from being scratched or dust from adhering to the static electricity. Yes.

  If the ITO film 36 is heated to 100 ° C. or higher during film formation in a vacuum, an opaque film having a high scattering property may be formed. Therefore, it is desirable to set the substrate temperature to less than 100 ° C. when forming the ITO film 36.

  However, since the ITO film 36 immediately after film formation is brown or brownish gray, the formed ND filter 10 is annealed in the air to make a transparent film having conductivity. As annealing conditions, it is desirable that the temperature is 100 to 240 ° C. for about 120 minutes, preferably 220 to 240 ° C. for about 120 minutes.

  In Example 1, the ND filter 10 was sandwiched between two glass plates and annealed in a heat treatment oven at 240 ° C. for 120 minutes.

  As the transparent substrate used in the first embodiment, a synthetic resin having a high glass transition temperature is used in order to prevent shrinkage deformation and wrinkles due to heat when annealing the ITO film 36 described above. It is desirable to use a sheet. In particular, as an example of a preferable transparent resin substrate 31, an aliphatic polyimide having a tetravalent aliphatic tetracarboxylic acid having a glass transition temperature of 250 ° C. or higher and a divalent diamine, or a material containing the above-described aliphatic polyimide. And a polyimide resin. It is also possible to use other synthetic resin materials such as PET and norbornene resins.

  In these cases, if heat treatment is performed under annealing conditions of about 100 ° C., some absorption of the ITO film 36 occurs, but it is in a practical range for use as the ND filter 10. The thickness of the transparent resin substrate 31 is preferably as thin as possible while maintaining the rigidity of the ND filter 10. Specifically, the thickness is preferably 200 μm or less, and more preferably in the range of 50 to 100 μm.

  In order to confirm the adhesion of dust due to charging of the ND filter 10 manufactured by the above-described method and the strength of the surface, the formed ND filter 10 is punched into a predetermined shape, attached to the diaphragm blade 9a, and the diaphragm blades 9a and 9b. Opening and closing was performed 250,000 times and slid.

  Table 1 shows the sliding test results of Examples 1, 2, and 3 and the comparative example, and almost no dust was observed on the surface of the ND filter 10 in Example 1. Further, no scratches are generated on the film formation surface after the sliding test.

Table 1
Example 1 Comparative Example Example 2 Example 3
Dust adhesion due to electrification No Yes No No Scratch occurrence No No No No

As a comparative example, a polyimide resin (Neoprim L, manufactured by Mitsubishi Gas Chemical Co., Ltd.) having a thickness of 100 μm was prepared as a transparent resin substrate 31 for comparison with the case of using an ND filter that does not form the ITO film 36 on the surface. An ND film 35 having an 11-layer structure as shown in FIG. 7 was formed on both surfaces of the transparent resin substrate 31 by a vacuum deposition method. Since this configuration is a comparative example, the outermost layer is the SiO ₂ film 34 and the ITO film 36 shown in FIG. 4 is not formed. The formed ND film 35 was a single concentration film having a uniform concentration on the vapor deposition surface. Specifically, films having a concentration of 0.6 were formed on both surfaces of the transparent resin substrate 31 so that the concentration after film formation on both surfaces was 1.2.

  Then, in order to confirm the adhesion of dust due to charging of the formed ND filter and the strength of the film formation surface, the ND filter on which the ND film 35 is formed is punched into a predetermined shape, and the diaphragm blade 9a as in the first embodiment. And opened and closed and slid 250,000 times. As shown in Table 1, in the sliding test result of the comparative example, a large number of dust particles were observed due to electrification on the film forming surface of the ND filter, but the film forming surface after the sliding test was scratched. Did not occur.

  In the first embodiment, the ND film 35 is the same single concentration film. However, in the second embodiment, a plurality of regions with different amounts of transmitted light are formed stepwise on the transparent resin substrate 31 similar to the first embodiment. .

  For example, as shown in FIGS. 8 and 9, first, an ND film 35a having an 11-layer configuration similar to that of the first embodiment is vacuum deposited on one surface of the transparent resin substrate 31 so as to have a desired concentration. The ITO film 36a was formed on the entire surface of the ND film 35a so as to have a desired film thickness.

  Next, on the other surface, a mask is arranged for the region A, and after the ND film 35b is formed on the region B so as to have a desired concentration, the mask is removed, and the ITO film 36b is formed on the entire region by a desired value. It forms so that it may become a film thickness.

  Next, the formed ND filter 10 was taken out from the vacuum vapor deposition chamber, sandwiched between two glass plates, and annealed in a heat treatment oven at 240 ° C. for 120 minutes.

  In Example 2, the thickness of the ITO film serving as the outermost layer on each film formation surface was set to 30 nm. Further, the produced ND filter film was a two-stage concentration ND filter 10 in which the concentration of the vapor deposition surface was different between the A region and the B region. Specifically, the deposited ND filter 10 has a region A density of about 0.7 and a region B density of about 1.4.

  In order to confirm adhesion of dust due to charging of the formed ND filter 10 and strength of the film formation surface, the aperture was opened and closed 250,000 times in the same manner as in Example 1. As shown in Table 1, almost no dust was observed on the surface of the ND filter 10 of Example 2. Moreover, it was recognized that the film-forming surface after a sliding test did not generate | occur | produce the damage | wound.

  Thus, it was confirmed that the two-density ND filter 10 having a low density in the region A and a high density in the region B can be manufactured.

  FIG. 10 is a plan view of the ND filter 10 according to the third embodiment, and FIG. 11 is a cross-sectional view. An ND film 35 having a gradation density distribution is formed on the transparent resin substrate 31 as in the first embodiment.

  When forming the ND film 35, a mask having a shielding plate capable of adjusting the angle formed with the mask surface as disclosed in Patent Document 2 is used. By shielding a part of the film material from the vapor deposition surface with this mask, the ND film 35 having a gradation density distribution in which the density continuously changes can be formed on the transparent resin substrate 31. When the outermost ITO film 36 is formed, in order to increase the antistatic property in the entire gradation density, the mask having a shielding plate is not used and the film is formed so as to have a desired film thickness on the entire surface. By doing so, it becomes possible to enhance the antistatic effect on the entire surface of the ND filter 10.

  On the transparent resin substrate 31, an ND filter film having a gradation density where the density sequentially changed from small to large was formed by vacuum deposition. The ITO film 36 as the outermost layer was deposited so as to have a film thickness of 30 nm over the entire area of the ND film 35 without using a mask. Next, it vapor-deposited so that the film thickness of the ITO film | membrane 36 might be set to 30 nm with respect to the whole area | region of the synthetic resin surface in the other surface. Subsequently, the formed ND filter 10 was taken out from the vacuum deposition chamber and sandwiched between two glass plates, and annealed at 240 ° C. for 120 minutes in a heat treatment oven. The concentration of the ND filter film produced in this example was changed sequentially from about 0.4 to about 1.2.

  As in Example 1, the aperture was opened and closed 250,000 times. As shown in Table 1, almost no adhesion of dust was observed on the surface of the ND filter 10 of Example 3, and it was recognized that no scratch was generated on the film formation surface after the sliding test. .

It is sectional drawing of the imaging optical system of Example 1 used for a video camera. It is a disassembled perspective view. It is a block diagram in a chamber. It is a film | membrane structure figure of ND film | membrane. It is a top view of the density distribution example of ND filter. It is sectional drawing of the density distribution example of ND filter. It is a block diagram of the ND film | membrane of a comparative example. 6 is a plan view of a density distribution example of an ND filter according to Embodiment 2. FIG. It is sectional drawing of the density distribution example of ND filter. 6 is a plan view of a density distribution example of an ND filter according to Embodiment 3. FIG. It is sectional drawing of the density distribution example of ND filter.

Explanation of symbols

2 Light quantity diaphragm device 8 Diaphragm blade support plate 9a, 9b Diaphragm blade 10 ND filter 31 Transparent resin substrate 32 Al ₂ O ₃ film 33 TiOy film 34 SiO ₂ film 35 ND film 36 ITO film

Claims (9)

A transparent resin substrate and an ND film on a part of the transparent resin substrate;
The glass transition temperature of the transparent resin substrate is 250 ° C. or higher, and an oxide transparent conductive layer having a thickness of 30 to 50 nm is provided on the outermost layer including the ND film on the transparent resin substrate. ND filter. An ND filter comprising: an ND filter that is movably attached to an opening having an aperture blade and that adjusts an amount of light passing through the aperture; and a member that movably supports the aperture blade. Comprises a transparent resin substrate and an ND film on the transparent resin substrate,
The glass transition temperature of the transparent resin substrate is 250 ° C. or higher, and an oxide transparent conductive layer having a thickness of 30 to 50 nm is provided on the outermost layer including the ND film on the transparent resin substrate. Light quantity diaphragm device. The light quantity diaphragm device according to claim 2 , wherein the transparent resin substrate is a polyimide resin. Aperture diaphragm device according to claim 2 or 3 wherein the transparent conductive oxide layer is characterized by a ITO film composed mainly of indium oxide and tin oxide. The light quantity diaphragm device according to any one of claims 2 to 4, wherein the ND film has a single concentration. The aperture diaphragm device ND film according to any one of claims 2-4, characterized in that it has a different graded concentrations distribution of quantity of transmitted light. The light quantity diaphragm device according to any one of claims 2 to 4, wherein the ND film has continuous density distributions with different amounts of transmitted light. An optical system, a light quantity stop device according to any one of claims 2 to 7 that limits an amount of light that passes through the optical system, and a solid-state imaging device that receives an image formed by the optical system. A camera characterized by that. A step of forming an ND film on a transparent resin substrate having a glass transition temperature of 250 ° C. or higher, a step of forming a deposited film of an oxide conductive material on the outermost layer on the transparent resin substrate including the ND film, And a process of forming an oxide transparent conductive layer having a thickness of 30 to 50 nm by heat-treating the vapor-deposited film.