JP5223847B2 - Method for manufacturing absorption multilayer ND filter chip - Google Patents

Description

  The present invention relates to a method for manufacturing an absorption multilayer ND filter chip that attenuates transmitted light in the visible light region, and more particularly to a method for manufacturing an absorption multilayer ND filter chip using a resin film as a substrate by pressing. .

  An ND filter (Neutral Density Filter) is an optical filter having a non-selective transmittance which transmits each wavelength in the visible spectral range of light almost evenly, and a lens such as a digital camera for the purpose of attenuating the amount of transmitted light. Used by attaching to.

  For example, if the lens is overexposed even when the lens is squeezed under high light conditions, such as under a clear sky, you can limit the amount of light so that the shutter can be released at a lower speed, or you want to open the aperture, but you want to open the shutter. An ND filter 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.

  As such an ND filter, a reflection type ND filter that reflects and attenuates incident light and an absorption type ND filter that absorbs and attenuates incident light are known. When an ND filter is incorporated in a lens optical system in which reflected light is a problem, an absorption ND filter is generally used. The absorption type ND filter includes a type in which an absorbing substance is mixed in the substrate itself (colored glass ND filter) and a type in which the substrate itself does not absorb and the thin film formed on the surface has absorption.

  In the case of the latter absorptive ND filter, by forming the thin film with an absorptive multilayer film in order to prevent reflection on the surface of the thin film, it is possible to have an antireflection effect as well as a function of attenuating transmitted light. Note that an absorption multilayer ND filter used in a small and thin digital camera or the like has a small installation space, so that it is necessary to thin the substrate itself, and a very thin glass plate or resin film is used as the substrate.

Regarding the above-described absorption multilayer ND filter, Patent Document 1 discloses a configuration of an absorption multilayer film in which dielectric film layers and absorption film layers are alternately stacked. Examples of the material constituting the absorption film layer include metals such as Ti, and examples of the material constituting the dielectric film layer include SiO ₂ and MgF ₂ . Further, as described in Patent Document 2, an ND filter that adopts a metal oxide film such as TiOx or Ta ₂ Ox that intentionally introduces oxygen when forming an absorption film layer and absorbs oxygen deficiency. Is also known. Furthermore, Patent Document 3 describes a multilayer film in which a dielectric film layer and a niobium film layer are combined.

Here, when the metal film constituting the absorption film layer and the metal oxide film are compared, the metal film such as Ti has the same extinction coefficient as compared with the metal oxide film such as TiOx and Ta ₂ Ox. In order to obtain an extinction coefficient, the thickness of the absorption film layer can be reduced by using a metal film. In addition, when an absorption multilayer film is formed on a flexible resin film substrate, considering the warpage of the resin film substrate, film cracking, film formation time, etc., the film thickness is thinner than the metal oxide film. It is advantageous to adopt a metal film that can be set. Therefore, in an absorption type multilayer ND filter used for a digital camera or the like, a metal film is mainly used as an absorption film layer.

  Further, a photographing optical system of a digital camera provided with an ND filter is exemplified in Patent Document 4. For example, as shown in FIG. 1, component lenses L1, L2, L3, and L4 constituting the imaging optical system 16 and a low-pass A filter 14 and a solid-state imaging device 15 such as a CCD are provided. Further, 11 to 13 are light quantity diaphragms, 11 is an ND filter, 12a and 12b are diaphragm blades, 13 is a diaphragm blade support plate, and one ND filter 11 is bonded to the diaphragm blade 12a.

  In general, in a light quantity diaphragm device (light quantity adjusting device), a passing light quantity is adjusted by changing an aperture diameter with a pair of diaphragm blades that open and close on a 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 the light field is narrowed down as the object field becomes brighter. Therefore, in normal cases, for example, when shooting a clear or high-luminance subject, the aperture becomes a small aperture, which is susceptible to light diffraction by the aperture opening, and image performance deteriorates.

  As a countermeasure, an ND filter is installed in a light amount diaphragm device such as a digital camera. The ND filter functions to prevent the aperture from becoming extremely small even during high-luminance shooting by reducing the amount of light by being positioned in the optical path when the aperture is reduced. In this way, in a digital camera or the like with a film-like ND filter attached to the aperture blade, the brightness of the object field is the same so that image performance does not deteriorate when the subject is photographed in fine weather or with high brightness. Even so, the aperture of the diaphragm becomes large.

  In general, diaphragm blades and filters for adjusting the amount of light are often made of a plastic material. For example, the diaphragm blade is formed into a blade shape by press-processing or the like by applying PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) or the like to a black sheet, molding the sheet into a sheet, and applying a matte coating to the surface. Also, ordinary filters include organic dyes or pigments mixed with TAC (triacetylcellulose) or the like to give optical filter characteristics, and after forming into a sheet shape, the filter shape is formed by pressing, and PET Alternatively, PEN may be formed into a transparent sheet, an inorganic film is formed on the surface by a vapor deposition method to provide optical filter characteristics, and then a filter is formed by pressing.

  In the case of the above-described absorption-type multilayer ND filter, the multilayer obtained by forming the absorption-type multilayer film by alternately laminating dielectric film layers and absorption film layers on a resin film or resin plate serving as a substrate. The film ND filter sheet is pressed to produce an absorption multilayer ND filter chip 20 having a complicated chip shape with a size of several mm as shown in FIG. However, it is known that a thin whisker-like defect 21 occurs in the cut portion of the absorption multilayer ND filter chip 20 obtained by pressing as shown in an enlarged view in FIG. The whisker-like defect 21 is a residue of sheared resin stretched by pressing.

  If a beard-like defect exists in the absorption type multilayer ND filter chip, the beard-like defect may interfere with the operation of the filter or may rub the surface of the part due to contact with other parts. . Further, the whisker-like defect may be detached from the resin film substrate during operation and adhere to other parts to hinder the operation, or may remain in the optical path and affect the photographed image.

  A method for removing the whisker-like defects generated in the ND filter chip is not known. In addition, as a method applicable to the removal of beard-like defects, Patent Document 5 discloses that generation of whiskers and cutting powders by cutting with a cutting blade heated to a predetermined temperature when cutting a general resin plate. A method of preventing this is disclosed. Further, Patent Document 6 discloses a method in which the outer peripheral portion of the thermoplastic resin sheet after cutting is subjected to a heating roll process to remove sharp edges, burrs, whiskers, etc. generated on the outer peripheral portion. Yes.

Japanese Patent Application Laid-Open No. 5-93811 JP 7-63915 A JP 2002-350610 A JP 2007-65109 A JP-A-5-69391 Japanese Patent Laid-Open No. 7-41033

  As described above, in the field of press processing of normal resin plates and resin sheets, as a method of preventing or removing the occurrence of defects such as whiskers and burrs, a method of heating a resin to be pressed or a resin after press processing There is known a method of bringing a heating roll into contact therewith. However, these methods have never been performed on an absorption multilayer ND filter chip having a small size of several millimeters and a complicated film configuration.

  This is because the absorption type multilayer ND filter chip is a composite material composed of a resin film substrate and an oxide dielectric film layer and an absorption film layer laminated on the substrate. The thermal expansion of the film material and the thermal contraction of the resin film cause cracks in the absorption multilayer film, undulation is generated, the entire absorption multilayer film ND filter chip is distorted, or bubbles are generated inside the resin film, etc. Because we know that there is a danger. Furthermore, if heat treatment is performed on a high-precision optical component combined with a CCD or CMOS, optical characteristics such as transparency and scattering characteristics may be affected.

  The present invention has been made in view of such conventional problems, and the absorption multilayer obtained when the absorption multilayer ND filter sheet is pressed into an absorption multilayer ND filter chip. Provided is a method of manufacturing an absorption type multilayer ND filter chip that can remove only the whisker-like defects generated in the film ND filter chip and that maintains the original optical characteristics without affecting the optical path portion. For the purpose.

  To achieve the above object, the present invention provides an absorption multilayer ND filter chip manufacturing method, that is, an oxide dielectric film layer and an absorption film layer are alternately laminated on at least one surface of a substrate made of a resin film. The method for manufacturing an absorption type multilayer ND filter chip having the absorption type multilayer film is obtained by alternately laminating an oxide dielectric film layer and an absorption film layer on at least one surface of a resin film. A step of producing a sheet, a pressing process of pressing the obtained absorption multilayer ND filter sheet to obtain an absorption multilayer ND filter chip, and a cut surface of the absorption multilayer ND filter chip. And a heat treatment step for removing the whisker-like defects of the resin film by heating.

  In the method for manufacturing an absorption type multilayer ND filter chip according to the present invention, the heat treatment step is a flame treatment in which the absorption type multilayer film ND filter chip is passed through a flame, or an absorption type multilayer ND filter chip in a heating atmosphere of an infrared lamp. Infrared lamp treatment that passes through a membrane ND filter chip is preferred. In addition, the heat treatment is performed by heating the whisker-like defects to a temperature equal to or higher than the melting point of the resin film within a treatment time until the optical path portion of the absorption multilayer ND filter chip reaches the glass transition temperature of the resin film. It is characterized by removing.

  According to the present invention, only the whisker-like defects generated from the resin film at the time of pressing the absorption multilayer ND filter sheet can be easily removed by heat treatment. In addition, there is no cracking or overall distortion of the absorption multilayer film or generation of bubbles inside the resin film even by heat treatment, so there is no effect on the optical characteristics or transmitted light, and there are defects in the optical path part. Absorptive multilayer multilayer ND filter chips can be provided.

  Therefore, the absorption-type multilayer ND filter chip obtained by the present invention has a problem that the whisker-like defect of the resin film generated during the press processing interferes with the operation due to contact with other parts or rubs the surface of the parts. Further, it is possible to solve the problem that the beard-like defect is detached from the resin film of the substrate and adheres to other components to hinder the operation or stay in the optical path and affect the photographed image. Therefore, the absorption multilayer ND filter chip of the present invention is extremely useful for a small and thin digital camera that requires long-term reliability in a harsh environment.

  In addition, the frequency of occurrence of whisker-like defects in the absorption-type multilayer ND filter chip due to press working is closely related to the mold clearance, and the frequency of occurrence of whisker-like defects may increase with long-term use of the die. Are known. However, according to the present invention, it is possible to easily melt and remove the whisker-like defects of the resin film generated by the press working, so that the life of the mold and the maintenance interval can be extended, and the productivity is improved and the production is improved. Cost can be reduced.

It is a schematic explanatory drawing which shows the imaging optical system of the digital camera provided with the ND filter. It is a schematic plan view showing an absorption type multilayer ND filter chip. It is a schematic plan view which expands and shows the beard-like defect of an absorption type multilayer ND filter chip. It is a graph which shows the spectral transmission characteristic of the absorption type multilayer ND filter chip concerning this invention.

  The manufacturing method of the absorption type multilayer ND filter chip of the present invention is a process for producing an absorption type multilayer ND filter sheet by alternately laminating an oxide dielectric film layer and an absorption film layer on at least one surface of a resin film. A pressing process of pressing the absorption multilayer ND filter sheet to obtain an absorption multilayer ND filter chip, and a beard-like shape of the resin film generated on the cut surface of the obtained absorption multilayer ND filter chip And a heat treatment step for removing the defects by heating.

First, in the step of producing the above-described absorption-type multilayer ND filter sheet, an oxide dielectric film layer and an absorption film layer are alternately laminated on at least one surface of a resin film to be a substrate in accordance with a conventional method. . The oxide dielectric film layer and the absorption film layer may be conventionally known. For example, the dielectric film layer includes SiO ₂ and MgF ₂ , and the absorption film layer includes Ni, Ni alloy, Ti, or the like. In addition to these metals, it is also possible to employ a metal oxide film such as TiOx that absorbs oxygen deficiency by intentionally introducing oxygen during film formation.

  Each film thickness of the oxide dielectric film layer is preferably 10 nm to 200 nm. This is because if the thickness of each oxide dielectric film layer is less than 10 nm, the interference effect as a multilayer film may be reduced, whereas if it exceeds 200 nm, film cracking is likely to occur. Moreover, it is desirable that each film thickness of the absorption film layer is 2 nm to 20 nm. If the film thickness of each absorption film layer is less than 2 nm, the film formation time may be short, so that desired film formation may be difficult. Conversely, if the film thickness exceeds 20 nm, the transmittance may be less than 1%. is there.

In the absorption-type multilayer ND filter sheet of the present invention, Ni simple substance or Ni alloy is preferable as the absorption film layer, and SiOx (where 1.5 <x <2) is particularly preferable as the oxide dielectric film layer. . The reason why the oxide dielectric film having oxygen vacancies indicated by SiOx is used is that the absorption multilayer ND filter composed of a transparent SiO ₂ film and a Ni film has a transmittance on the short wavelength side in the visible wavelength region. Therefore, in order to improve the flatness of the spectral transmission characteristic represented by (maximum transmittance−minimum transmittance) / average transmittance, the transmittance on the shorter wavelength side than the longer wavelength side in the visible wavelength region. This is because it is preferable to use a SiOx film having a low (that is, a high absorption rate).

  The Ni film or Ni alloy film constituting the absorption film layer is formed by physical vapor deposition using a target of Ni simple substance or Ni alloy. The SiOx film constituting the oxide dielectric film is formed by physical vapor deposition using a Si target, for example, a target made of Si single crystal, Si polycrystal, SiC ceramic, or a mixture thereof. Be filmed. Note that when SiC ceramics is used as a target, carbon (C) is almost exhausted and is therefore hardly included in the film.

  The SiOx film is formed by using a target containing Si or SiC as a main component and controlling the amount of oxygen gas introduced. In addition, in the formation of an absorption film layer, characteristics such as refractive index and absorption coefficient may vary greatly depending on the additive and impurities of the film material, the residual gas during film formation, the gas released from the substrate and the film formation speed. Therefore, it is desirable that these conditions are selected as appropriate and set so as to obtain desired absorption multilayer ND filter characteristics. Examples of the physical vapor deposition method include a vacuum deposition method, an ion beam sputtering method, a magnetron sputtering method, and an ion plating method.

  More specifically, when the SiOx film is formed, the oxygen introduction amount at the time of forming the SiOx film is controlled by the oxygen introduction valve so that the impedance between the cathodes becomes a set value. When the impedance setting value is high, the amount of oxygen introduced is reduced, and a colored SiOx film having a large extinction coefficient is obtained. On the other hand, when the impedance setting value is lowered, the amount of oxygen introduced is increased and a transparent SiOx film having a small extinction coefficient is obtained.

  In film formation of Ni or Ni alloy film combined with the SiOx film, depending on the film formation conditions (sputtering power, Ar introduction amount, film formation speed, residual gas, film thickness, etc.), the optical constant (refraction of the Ni or Ni film obtained) is obtained. Rate, extinction number). Therefore, it is necessary to form an absorption multilayer film using the impedance setting value as a parameter, repeat the process of measuring spectral transmission characteristics and obtaining flatness, and obtain an impedance setting value with excellent flatness.

  Further, in order to suppress oxidation of the absorption film layer, the outermost layer of the absorption multilayer film composed of the laminated oxide dielectric film layer and absorption film layer is made of hard SiOx (provided that 1.5 < Preferably, the oxide dielectric film layer is composed of an oxide dielectric film layer composed of x <2), and the oxide dielectric film composed of the above-mentioned SiOx in order to improve the adhesion of the film in contact with the resin film substrate of the absorption type multilayer film. It is preferable to comprise in layers.

  Although the material of the resin film which comprises a board | substrate is not specifically limited, What is transparent is preferable. In particular, in consideration of mass productivity, a substrate made of a flexible resin film is preferable so that dry sputtering roll coating described later can be performed. A substrate made of a flexible resin film is superior in that it is cheaper, lighter and more deformable than a conventional glass substrate.

  Specific examples of the resin film include a single resin film selected from polyethylene terephthalate (PET), polyethersulfone (PES), polyarylate (PAR), polycarbonate (PC), polyolefin (PO), and norbornene resin materials. Alternatively, a composite of a resin film selected from the above resin materials and an acrylic organic film covering one or both sides of the single can be mentioned. Representative examples of the norbornene resin material include ZEONOR (trade name) manufactured by Nippon Zeon Co., Ltd. and Arton (trade name) manufactured by JSR Corporation.

  Next, the manufacturing method of the absorption multilayer ND filter chip of the present invention will be specifically described. First, in the step of producing the absorption multilayer ND filter sheet, before forming the absorption multilayer film, at least the surface of the resin film on which the absorption multilayer film is formed is subjected to plasma treatment or ion beam treatment, It is preferable to heat shrink the resin film. In addition, there is no restriction | limiting in particular about plasma processing and ion beam processing, Argon gas single-piece | unit or the gas which mixed oxygen or nitrogen with argon gas can be used for introduction gas.

  In general, since a resin film is produced by stretching in a biaxial direction, it has stress in the stretching direction, and a shrinkage phenomenon occurs due to heating or humidity. It is also known that the thermal shrinkage differs in the longitudinal direction (length direction) and the transverse direction (width direction) because the amount of stretching differs, and the thermal shrinkage rate in the longitudinal direction is greater than in the transverse direction. On the other hand, in the film formation of the absorption-type multilayer film using a roll coater, the film is formed while winding it while applying tension in the longitudinal direction of the resin film. Therefore, the thermal shrinkage rate of the resin film by plasma treatment or ion beam treatment may be measured in the longitudinal direction (length direction) of the resin film. In addition, the thermal contraction rate of a resin film can be calculated | required from the dimensional change which measured the film length marked on the resin film before a process before and after a process.

  In the plasma treatment or ion beam treatment, it is desirable to heat shrink the resin film by 0.2% or more. This is because if the heat shrinkage of the resin film is less than 0.2%, it is difficult to obtain an effect of preventing cracking of the absorption multilayer film in a high temperature and high humidity environment. However, when the thermal shrinkage of the resin film is 0.5% or more, the resin film surface is deteriorated, so that the adhesive strength of the absorption multilayer film tends to be lowered. Therefore, it is preferable to adjust the conditions for plasma treatment or ion beam treatment so that the thermal shrinkage of the resin film is 0.2% or more and less than 0.5%.

  An oxide dielectric film layer and an absorption film layer constituting an absorption multilayer film are alternately formed on one surface or both surfaces of the resin film subjected to the plasma treatment or the ion beam treatment. For example, when an absorption multilayer film is formed on both sides A and B of the PET film with an easy adhesion layer, first, plasma treatment voltage or ion beam treatment is performed on the A surface, and then the absorption multilayer film is formed on the A surface. Form a film. Thereafter, plasma treatment or ion beam treatment may be performed on the B surface in the same manner as the A surface, and then an absorption multilayer film may be formed on the B surface.

  As a preferable method for forming the absorption multilayer film, there is a method of forming a film using a roll coater on a long resin film wound in a roll shape. The method using this roll coater is excellent in that the productivity is higher than the batch method because the film forming area that can be processed at one time is large. However, since it is extremely difficult to overlay a mask on a moving long resin film, after forming an absorption multilayer film on the entire surface of the resin film without using a mask, In general, at least one of the absorption multilayer films at the portion to be joined to the diaphragm blade material is removed by laser scribing or the like.

  In the roll coater, film formation can be performed while the resin film is in close contact with the water-cooled can roll. Therefore, in the case of sputtering, since the resin film is cooled by a water-cooled can roll, the heat load can be reduced, so that a large amount of power can be input to the sputtering target, and the deposition rate can be improved. . In addition, since it is possible to obtain a time-stable film thickness in the direction of conveyance (length direction) of the resin film, the film thickness distribution in the width direction of the resin film can be improved with a film thickness correction plate or the like on the entire surface. A uniform film thickness distribution can be obtained, whereby uniform optical characteristics can be obtained.

  In the film formation by the roll coater, as a pretreatment for increasing the adhesion between the absorption multilayer film and the resin film, a surface treatment by plasma or ion beam is performed before starting the film formation while the resin film is conveyed. It is preferable. In addition, this pre-processing can also serve as the pre-processing aiming at the heat shrink of the resin film mentioned above.

  As a specific method for forming the absorption multilayer film, for example, after the first oxide dielectric film layer is formed on the surface of the resin film, the transport direction of the resin film is reversed and the second layer is formed. This absorption film layer is formed, and this operation is repeated several times to form an absorption multilayer film. Next, the resin film is turned over, and an absorptive multilayer film is formed on the back surface of the resin film in the same manner as described above. It is also possible to appropriately control the differential exhaust of the film formation chamber and the film formation speed, and to form two layers of oxide dielectric film layer and absorption film layer in one transport. It is also possible to arrange two can rolls and to form an absorption multilayer film on the front and back surfaces simultaneously.

  Here, as an example of the absorption multilayer ND filter according to the present invention (from a chip obtained by cutting the absorption multilayer ND filter sheet produced as described above into a predetermined shape), the average transmittance is 6.3%. The film structure of the absorption multilayer ND filter is shown in Table 1 below, and its spectral transmission characteristics are shown in FIG. The oxide dielectric film layer of the absorption type multilayer ND filter is a SiOx (where 1.5 <x <2) film, and uses a target mainly composed of SiC and controls the amount of oxygen gas introduced. The film was formed by the magnetron sputtering method. The absorption film layer is a Ni film formed by magnetron sputtering.

  As described above, the absorption multilayer film ND filter sheet produced by alternately laminating the oxide dielectric film layer and the absorption film layer on the resin film surface is then cut into a predetermined shape by pressing and absorbed. Type multilayer ND filter chip. There is a method of using a Thomson blade, a pinnacle blade, and a compound die for press processing of the absorption multilayer ND filter sheet. However, the absorption multilayer ND filter chip having a complicated shape including a curve is pressed with high dimensional accuracy. For this purpose, a compound mold is optimal.

  However, when the absorption multilayer ND filter sheet is pressed with a compound mold, thin beard-like defects 21 are likely to occur in the cut portion of the resulting absorption multilayer ND filter chip 20 as shown in FIG. The occurrence position of the beard-like defect may be presumed to occur easily due to the relationship with the mold clearance, but is basically generated randomly. In particular, when the number of punches in the mold increases, the clearance of the mold increases, so that beard-like defects tend to increase. For example, when the resin film is a PET film, it is known that the size of the whisker-like defect generated by press working is often 20 to 200 μm in length and several μm in thickness.

  The whisker-like defects generated by the press working are made of a resin of a resin film that constitutes the substrate of the absorption multilayer ND filter sheet. In the present invention, in order to remove the beard-like defects made of the resin film, the beard-like defects remaining on the cut surface of the absorption multilayer ND filter chip obtained by pressing are melted by the heat treatment described below. Remove.

  First, in order to melt and remove the beard-like defects generated in the absorption multilayer ND filter chip, it is necessary to heat the beard-like defects to the melting point of the resin film or higher. Thus, when examining the thermal characteristics of a commercially available resin film for an absorption type multilayer ND filter, the most common PET film has a slight difference, but the glass transition temperature is 85 ° C., and the usable temperature is -70-150 degreeC, heat shrink start temperature is 100-150 degreeC, heat shrink limit temperature (melting | fusing point) is 260 degreeC, ignition temperature is 390 degreeC, and ignition temperature is 485 degreeC. Therefore, from these thermal characteristics, for example, when the resin film is a PET film, the whisker-like defects can be melted and removed by heating to 260 ° C. or higher, which is the melting point of the PET film.

  However, when melting and removing beard-like defects by heat treatment, only the beard-like defects are selectively heated and removed by melting, and the main body of the absorption type multilayer ND filter chip, that is, the optical path portion through which light passes is affected. You must avoid it. When the temperature of the resin film of the absorption-type multilayer ND filter chip exceeds the heat shrinkage start temperature (100 to 150 ° C for PET film) or exceeds the glass transition temperature (80 to 85 ° C for PET film) at which the volume change becomes large This is because cracks may occur in the absorption multilayer film on the resin film.

On the other hand, the material constituting the absorptive multilayer film has a melting point of Ni of 1453 ° C. and a phase displacement temperature from the α phase to the β phase of SiO ₂ of 573 ° C. Not easily affected. The outermost surface of the absorption multilayer ND filter chip is covered with a SiOx (where 1.5 <x <2) film, and thus has high heat resistance.

  Therefore, in consideration of the heat treatment conditions based on the thermal characteristics of the material constituting the absorption multilayer ND filter chip described above, the heat treatment method for melting and removing the whisker-like defects according to the present invention has an optical path portion made of resin. Any method can be used as long as the whisker-like defects can be heated to a melting point or higher of the resin film within the treatment time until the glass transition temperature of the film is reached.

  More specifically, the size of the absorption multilayer ND filter chip is as small as several millimeters. Therefore, it is technically difficult to selectively heat only the whisker-like defects, and a temperature sensor such as a thermocouple is used. Taking into account the fact that it is difficult to directly measure the temperature of the whisker-like defect and the optical path portion, it is possible to perform flame treatment in which an absorption type multilayer ND filter chip is passed through the flame, or absorption in the heating atmosphere of the infrared lamp. Infrared lamp treatment that passes through a mold multilayer ND filter chip is suitable.

  That is, according to the flame treatment or the infrared lamp treatment, the small absorption multilayer ND filter chip can be exposed to the atmosphere above the melting point of the resin film (260 ° C. with PET film) for a very short time. Inside, the thin whiskers have a small heat capacity, so that they reach the melting point and are removed by melting. On the other hand, the optical path portion of the absorption-type multilayer ND filter chip is a SiOx film (where 1.5 <x <2) where the heat capacity is much larger than that of the beard-like defect, and the outermost surface is preferably heat resistant. Since it is covered, it does not reach the glass transition temperature (80 to 85 ° C. with PET film) within an extremely short time, and the influence of heat can be avoided.

  Note that it is difficult to hold a small absorption multilayer ND filter chip so that it does not bend or fly by wind pressure in a heating method that applies wind such as hot air treatment. In addition, when a jig or the like that is pressed when heat-treating the absorption multilayer ND filter chip is used, heat is accumulated and the temperature rises by repeating the heat treatment. Therefore, it is necessary to cool the holding jig or the like for each heat treatment to prevent the temperature from rising above the glass transition temperature.

  In the case of the infrared lamp treatment, since the temperature of the atmosphere heated by infrared rays varies depending on the distance from the infrared lamp, the region where the ambient temperature is equal to or higher than the melting point of the resin film and the passage time (treatment time) are obtained in advance. It is necessary to keep. The transit time of the absorption type multilayer ND filter chip depends on the temperature of the atmosphere heated by infrared rays, but can be appropriately set in consideration of the melting and removal of only the whiskers and the presence or absence of thermal damage in the optical path portion. Good.

  In particular, an infrared lamp with a reflecting mirror for condensing infrared rays has an ambient temperature of about 400 ° C. to 500 ° C. in the vicinity of the condensed light. By passing, the whisker-like defects can be melted and removed in a very short time. For example, when a 200 W infrared lamp with a reflecting mirror is used, it is sufficient that the passage time (processing time) of the absorption multilayer ND filter chip in the infrared condensing region is up to 0.1 second.

  In the case of the above-mentioned flame treatment, the whisker-like defects can be melted and removed by passing the absorption multilayer ND filter chip through a flame such as city gas or LP gas. The temperature of the flame varies depending on the position, and it is difficult to measure the temperature. Therefore, the passage position and the passage time (processing time) into the flame can melt and remove the whisker-like defects of the absorption multilayer ND filter chip, and there is no thermal damage in the optical path portion, and the kind and passage of the flame. It is necessary to obtain it appropriately according to the position. For example, when using a flame like a gas lighter and passing through the center of the flame, only the whisker-like defects can be melted and removed in a passage time of less than 0.1 seconds.

  In particular, when the resin film is a polyethylene terephthalate (PET) film, the optical path is obtained by passing the absorption multilayer film ND filter chip through the flame or the heating atmosphere of the infrared lamp using the flame treatment or the infrared lamp treatment. Within a very short processing time until the part reaches 80 to 85 ° C., only the whisker-like defects can be heated to a temperature of 260 ° C. or higher and melted away.

  The absorption-type multilayer ND filter chip obtained by the present invention operates because the whisker-like defects of the resin film generated during press processing are melted and removed by the above heat treatment, so that the whisker-like defects touch other parts. It will not interfere with or scratch the surface of other parts. Furthermore, it is possible to eliminate a beard-like defect from falling off the resin film as a substrate and adhering to other components to hinder the operation, or staying in the optical path and affecting the photographed image.

  Further, if the method for manufacturing an absorption-type multilayer ND filter chip of the present invention is used, it is possible to easily melt and remove only the whisker-like defects of the resin film generated by the press working. It is no longer necessary to strictly manage the mold, the maintenance interval of the mold can be lengthened, and the life can be extended, so that the productivity can be improved and the production cost can be reduced.

  Next, a diaphragm blade for a small thin digital camera will be described as an example of use of the absorption multilayer ND filter chip. The diaphragm blade is generally made of a black resin film that does not transmit light, and has an opening or a notch for attaching an absorption multilayer ND filter chip to the optical axis portion. In addition, the black resin film for the diaphragm blades is obtained by mixing the pigment into the resin to make a black resin film, and by applying a black paint on the surface of the transparent resin film or forming a black film to perform black treatment. There is a method.

  The diaphragm blade has two types of structures. One of them is the function of continuously attenuating the amount of light by blocking the luminous flux due to the shape of the diaphragm blades, but when this function alone cannot attenuate the amount of light, the absorption multilayer ND filter chip is placed on the optical axis. The structure to be inserted. The other structure has no function of continuously attenuating the amount of light on the diaphragm blade itself to which the absorption type multilayer ND filter chip is bonded, and it functions only as a frame of the absorption type multilayer ND filter chip, and the amount of light is continuous. This structure is combined with another diaphragm that can be attenuated automatically.

  The absorption multilayer ND filter chip obtained by the present invention is joined to the aperture or notch of the diaphragm blade. As a method for joining the absorption type multilayer ND filter chip and the diaphragm blade, there are a laser welding method, an ultrasonic welding method, and a method using an adhesive. The absorptive multilayer film ND filter chip to be joined is previously removed so as to have a shape suitable for each joining method.

  For example, in the case of joining by laser welding, the spot diameter of the laser is about 0.5 to 1.5 mm, so the joining portion with the diaphragm blade of the absorption type multilayer ND filter chip should be removed slightly larger than the above size. Is desirable. In the case of bonding with an adhesive, it is only necessary to remove only the absorption multilayer film on the bonding surface side with the diaphragm blade. In the case of joining by laser welding, it is desirable to remove the absorption multilayer film on both sides as well as on one side. If only the absorption multilayer film on the joint surface side with the diaphragm blade is removed and laser welding is performed from the opposite side of the joint surface, the remaining absorption multilayer film absorbs the laser energy without being removed. is there.

[Example 1]
Using a sputtering roll coater device equipped with a DC plasma processing mechanism as a film forming device, SiOx (however, each having a 100 μm thick PET film with an easy adhesion layer (manufactured by Toyobo Co., Ltd.)) 1.5 <x <2) A film having an average transmittance of 6.3% and a film structure as shown in Table 1 above, in which oxide dielectric film layers and Ni absorption film layers are alternately laminated. An absorption multilayer ND filter sheet was produced.

  Specifically, Ar gas was introduced into the apparatus at 100 sccm, the Ar gas pressure was reduced to 3 Pa by lowering the number of revolutions of the turbo pump, and then the surface of the plasma was transferred while the PET film was transferred at a transfer speed of 1 m / min. Processed. Subsequently, using a target composed mainly of SiC (manufactured by Sumitomo Metal Mining Co., Ltd.) on one side of the PET film, the amount of oxygen gas introduced was controlled by an impedance monitor by a dual magnetron sputtering method in which Ar gas was introduced. Then, a SiOx (where 1.5 <x <2) film was formed. Furthermore, using a Ni target (manufactured by Sumitomo Metal Mining Co., Ltd.), a Ni film was formed by a DC magnetron sputtering method in which Ar gas was introduced.

  After repeating the above film formation and alternately laminating an oxide dielectric film layer made of SiOx film and an absorption film layer made of Ni film on one side of the PET film, plasma treatment is similarly performed on the other side of the PET film. Subsequently, an absorption type multilayer ND filter sheet was obtained by alternately laminating SiOx films and Ni films.

  The obtained absorption-type multilayer ND filter sheet was pressed using a compound mold (manufactured by Sumitomo Metal Mining Co., Ltd.) to produce an absorption-type multilayer ND filter chip. An absorption multilayer ND filter chip manufactured by press working using a compound mold was observed with a stereomicroscope at a magnification of 64 times to select a sample having a beard-like defect.

  Heat treatment is performed by passing the selected absorption-type multilayer ND filter chip sample with a beard-like defect through an atmosphere of a region where the luminous flux of the infrared lamp is condensed using a 200 W infrared lamp with a reflector. did. Note that the ambient temperature in the region where the luminous flux of the infrared lamp converges reached 400 ° C.

  By changing the time (processing time) during which the absorption type multilayer film ND filter chip passes through the atmosphere of the region where the light beam is condensed, the state of the beard-like defect and the thermal damage of the optical path portion were observed. The obtained results are shown in Table 2 below. As can be seen from the results in Table 2, in order to remove only the beard-like defects, the processing time may be an extremely short time from 0.05 seconds to 0.1 seconds. Damage has occurred.

  The absorption multilayer ND filter chip from which the beard-like defects have been removed in the above embodiment and the absorption multilayer ND filter chip from which the beard-like defects have not been removed are incorporated into an experimental mechanism close to an actual shutter unit, respectively. The operation was performed continuously. As a result, no change was observed in the absorption-type multilayer ND filter chip from which the beard-like defects were removed even after 10,000 operation tests.

  On the other hand, in the absorption-type multilayer ND filter chip from which the beard-like defects have not been removed, a locus in which the beard-like defects were rubbed with the black PET film in contact with the chip was attached from around 2000 operations. When the operation was further continued, the whisker-like defect was cut off in the vicinity of the operation of about 6000 times and detached from the absorption type multilayer ND filter chip. If it is in an actual camera module, the detached beard-like defect may adhere to the surface of another lens unit and interfere with the optical path, or may enter a driving mechanism such as a shutter unit and cause a malfunction. .

[Example 2]
In the same manner as in Example 1, an absorption-type multilayer ND filter sheet was prepared and pressed using a compound mold to manufacture an absorption-type multilayer ND filter chip. An absorption multilayer ND filter chip sample with a beard-like defect selected from the obtained absorption multilayer ND filter chip was heat-treated using a flame.

  That is, the LP gas supplied to the nozzle having an inner diameter of 3 mm was ignited to generate a flame having a length of about 1.5 cm. The temperature in the vicinity of the flame front end reached 1700 ° C. By passing the absorption multilayer ND filter chip sample through the center of the flame and changing the time (processing time) for the absorption multilayer ND filter chip sample to pass through the flame, the state of the beard-like defect and the optical path portion Thermal damage was observed. As a result, it was confirmed that the flame treatment with an extremely short time from 0.05 seconds to 0.1 seconds has no thermal damage in the optical path portion and can remove beard-like defects.

L1, L2, L3, L4 Component lenses constituting the imaging optical system 11 ND filter 12a, 12b Aperture blade 13 Aperture blade support plate 14 Low-pass filter 16 Imaging optical system 20 Absorbing multilayer ND filter chip 21 Beard defect

Claims (3)

On at least one surface of a substrate made of a resin film, an oxide dielectric film layer composed of a SiOx (where 1.5 <x <2) film and an absorption film layer composed of a Ni film or a Ni alloy film are alternately arranged. A method of manufacturing an absorptive multilayer ND filter chip having an absorptive multilayer film laminated on the outermost layer, and the outermost layer of the absorptive multilayer film is a SiOx (where 1.5 <x <2) film ,
A process of producing an absorption multilayer ND filter sheet by alternately laminating an oxide dielectric film layer and an absorption film layer on at least one surface of a resin film, and pressing the resulting absorption multilayer ND filter sheet The press processing step of obtaining the absorption multilayer ND filter chip , and the beard-like defects of the resin film generated on the cut surface of the absorption multilayer ND filter chip, the optical path portion of the absorption multilayer ND filter chip is And a heat treatment step in which the resin film is heated to a temperature equal to or higher than the melting point of the resin film within a treatment time until the glass transition temperature of the resin film is reached. .   The heat treatment step is a flame treatment in which an absorption multilayer ND filter chip is passed through a flame or an infrared lamp treatment in which an absorption multilayer ND filter chip is passed in a heating atmosphere of an infrared lamp. The manufacturing method of the absorption type multilayer ND filter chip according to claim 1. The method for producing an absorptive multilayer ND filter chip according to claim 1 or 2, wherein the resin film is a polyethylene terephthalate film .

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