JP4706859B2 - Method for manufacturing absorption multilayer ND filter - Google Patents

Description

  The present invention relates to a method of manufacturing an absorptive multilayer ND filter for attenuating transmitted light in the visible range by using a roll-to-roll process type gas phase film forming method, and in particular, an absorptive multilayer having excellent optical characteristics. The present invention relates to a method for manufacturing an absorption-type multilayer ND filter that can stably manufacture a film ND filter.

  As this type of ND (Neutral Density Filter) 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. In this absorption ND filter, an absorbing substance is mixed in the substrate itself (color glass ND filter). ) Or a type in which an absorbing material is applied, and a type in which a thin film formed on the surface of the substrate does not absorb but has absorption. In the latter case, in order to prevent reflection on the surface of the thin film, the thin film is formed of a multilayer film, and an effect of preventing reflection as well as a function of attenuating transmitted light is performed.

  In addition, the absorption multilayer ND filter used for small and thin digital cameras has a small mounting space, so it is necessary to make the substrate itself thin, so the resin film is the optimal substrate, and the thin film is composed of a multilayer film. Patent Document 1 discloses an ND filter composed of an oxide dielectric film and a metal absorption film as an absorption type multilayer ND filter.

  When an absorption multilayer ND filter is manufactured using a vapor phase film formation method, it can be continuously formed on the surface of a belt-shaped resin film, although there is a drawback that the film formation time is extremely long compared to the batch method. A roll-to-roll process method is suitable. The manufacturing method of the absorption type multilayer ND filter using the roll-to-roll process vapor phase film forming method is as follows: a first roll for unwinding a strip-shaped resin film into the film forming chamber of the vapor phase film forming apparatus; A second roll that winds up the strip-shaped resin film, and is absorbed by at least one surface of the strip-shaped resin film unwound from the first roll in the film formation region provided in the conveyance path between the first roll and the second roll. Absorbing film or dielectric film of strip-shaped resin film which is collected by the second roll while forming a film or dielectric film, then reverses the rotation direction of each roll and is unwound from the second roll in the film forming region The film is collected by the first roll while forming a dielectric film or absorption film thereon, and thereafter, the above process is repeated as necessary to have an absorption multilayer film composed of the absorption film and the dielectric film. It is intended to produce a mold multilayer ND filter.

  By the way, the absorption multilayer film ND filter including the oxide dielectric film and the metal absorption film has a metal film thickness of only about 10 nm as an absorption film. Even with a film thickness error of several nm, the transmittance changes greatly. For this reason, when manufacturing an absorption-type multilayer ND filter by the vapor-phase film formation method of the roll-to-roll process method in which the film formation time becomes extremely long, it is necessary to control the film thickness of the multilayer film to be formed with high accuracy. was there.

  As a method for controlling the film thickness of a single layer or a multilayer film, Patent Document 2 discloses an optical system for measuring the film thickness of a thin film deposited on a continuous film-like substrate at a position before reaching the end point of the vapor deposition zone. A method has been proposed in which a film thickness measuring means is arranged and the film thickness of a thin film finally formed is controlled from the measured value.

However, in the above method in which the film thickness measurement (monitoring) means of the optical system is incorporated into the roll-to-roll process type gas phase film forming apparatus, the transmittance of the multilayer film obtained by the deterioration of the monitoring accuracy over time is the target value. Therefore, there is a problem that it is difficult to stably manufacture an absorption type multilayer ND filter having excellent optical characteristics.
JP 2006-178395 A Japanese Patent Laid-Open No. 08-225940

  The present invention has been made paying attention to such problems, and the problem is that an absorption-type multilayer ND filter having excellent optical characteristics using a vapor-phase film forming method of a roll-to-roll process method. Is to provide a method for producing an absorption-type multilayer ND filter.

  Therefore, the present inventor examined a transmittance monitor whose monitoring accuracy is less likely to deteriorate over time even when incorporated in a roll-to-roll process type vapor deposition apparatus, and an absorption type using this transmittance monitor. An attempt was made to develop a method for producing a multilayer ND filter.

  The absorption multilayer ND filter having an average transmittance of 12.5% having a film structure shown in Table 1 below has spectral transmission characteristics as shown in the graph of FIG. The metal film which is an absorption film has a thickness of only 7 nm. Even with a film thickness error of several nm, the transmittance changes greatly. Therefore, the roll-to-roll process type vapor deposition method requires a film thickness (transmittance) monitor for accurately monitoring the film thickness (transmittance) of the metal film.

ところで、表１に示す膜構造の吸収型多層膜ＮＤフィルターについて、バッチ方式の気相成膜装置に取り付けられた膜厚モニターによりその成膜中の透過率変化（片面５層分）を測定すると、図２のグラフ図に示すような変化になる。

By the way, with respect to the absorption multilayer ND filter having the film structure shown in Table 1, the transmittance change (for 5 layers on one side) during the film formation is measured by the film thickness monitor attached to the batch type vapor deposition apparatus. The change is as shown in the graph of FIG.

  However, when a film thickness monitor is attached to a roll-to-roll process type vapor deposition apparatus, the resin film itself as a deposition substrate moves in the deposition chamber. Thus, it is impossible to measure the change in the amount of light during film formation. For this reason, there is no choice but to measure the light quantity of the single layer or the multilayer film after the film formation, and the transmitted light quantity of the multilayer film immediately after the film formation must be measured as described in Patent Document 2.

  Table 2 shows the transmittance at a wavelength of 532 nm after the film formation of each layer in the absorption multilayer ND filter having the film structure shown in Table 1. The transmittance is 100% when light is transmitted through the film from the film transmittance measuring light projecting portion of the optical monitor and directly incident on the film transmittance measuring light receiving portion. The gain may be adjusted so that the transmittance at the start of film formation is equal to the theoretical transmittance. Since the PET film of the substrate has a thickness of 50 μm to 100 μm, it is not necessary to consider interference. After film formation on the A side of the PET film, when the film is turned over and the B film is formed on the PET film, the gain can be adjusted to the same transmittance as at the time of film formation on the A surface. In this way, an ND filter having a transmittance of 12.3% (= 35.1% × 35.1%) at a wavelength of 532 nm is completed.

そして、各層の成膜後に、それぞれ目標の透過率になるように成膜条件（例えば、スパッタリング電力、フィルム搬送速度等）を調整すれば、目標とする吸収型多層膜ＮＤフィルターの分光光学特性を得ることができる。

Then, after film formation of each layer, if the film formation conditions (for example, sputtering power, film conveyance speed, etc.) are adjusted so as to achieve the target transmittance, the spectral optical characteristics of the target absorption multilayer ND filter can be obtained. Obtainable.

  However, the roll-to-roll process type vapor deposition method is extremely long as compared with the batch-type vapor deposition method as described above, and therefore, the film formation chamber or the like during film formation is extremely long. It is likely that the time variation of the light source light amount in the optical monitor is likely to occur due to misalignment caused by thermal expansion, etc., and the monitoring accuracy has been reduced over time due to this light amount variation. That is, when the film formation chamber or the like is thermally expanded, the relative distance between the resin film transported in the film formation chamber and the light source of the optical monitor changes, or an optical fiber that guides light from the light source to the vicinity of the resin film surface A phenomenon in which the amount of light source irradiated to the resin film slightly fluctuates due to, for example, a change in the relative distance to the resin film is confirmed.

  Therefore, the time change of the light source light amount in the optical monitor is measured during the vapor-phase film formation of the roll-to-roll process method, and the transmittance of the multilayer film measured corresponding to the change of the light source light amount is corrected. When film formation conditions are controlled in consideration of the difference between the transmittance and the target transmittance, the film thickness can be continuously controlled with high accuracy, and as a result, an absorption multilayer film having excellent optical characteristics. It has been found that stable production of ND filters becomes possible. The present invention has been completed based on such technical examination and discovery.

That is, the invention according to claim 1
A first roll for unwinding the strip-shaped resin film and a second roll for winding the unrolled strip-shaped resin film in the film forming chamber of the vapor phase film deposition apparatus are provided in the conveyance path between the first roll and the second roll. In the formed film formation region, after collecting by the second roll while forming an absorption film or a dielectric film on at least one side of the belt-shaped resin film unwound from the first roll, the rotation direction of each roll is reversed and The film is collected by the first roll while forming a dielectric film or absorption film on the absorption film or dielectric film of the belt-shaped resin film unwound from the second roll in the film formation region, and then the above steps as necessary. On the premise of a method of manufacturing an absorptive multilayer ND filter having an absorptive multilayer film composed of an absorptive film and a dielectric film,
A white light source, a first branched optical fiber in which light from the light source is distributed into three optical paths and at least two first and second optical fibers constituting the two optical paths are introduced into the film forming chamber, and the film forming chamber The front end of the first optical fiber introduced into the belt is disposed in the vicinity of the surface of the belt-shaped resin film transported from the film formation region to the second roll side, and is disposed on the opposite side of the belt-shaped resin film. The first light receiving fiber to which the white light transmitted through and the tip of the second optical fiber introduced into the film forming chamber are located in the vicinity of the belt-shaped resin film surface conveyed from the film forming region to the first roll side. A second light-receiving fiber that is disposed and is disposed on the opposite side of the belt-shaped resin film through which the white light transmitted through the belt-shaped resin film is incident, and each end and the remaining one of the first light-receiving fiber and the second light-receiving fiber A measuring light switch connected to the outside of the film forming chamber, a first light receiving fiber provided in the measuring light switch and connected to the measuring light switch, a second light receiving fiber, Integrating the three optical paths including the light receiving rotary mask and the light receiving rotary mask for allowing the white light emitted from the third optical fiber to sequentially enter the corresponding three light receiving portions through a certain time interval. A second branch optical fiber, a spectroscope that separates monochromatic light of a specific wavelength from white light incident from the end of the integrated optical fiber, and a light quantity measurement that measures the light quantity when the separated monochromatic light is incident A single- or multi-layer film formed during normal rotation based on monochromatic light passing through the first light-receiving fiber and the measuring light switch. Measure rate In addition, the transmittance of the multilayer film formed during reverse conveyance is measured based on the monochromatic light that has passed through the second light receiving fiber and the measuring light switch, and the monochromatic light that has passed through the third optical fiber and the measuring light switch. The light source light quantity is measured based on the light source, the transmittance is corrected based on the measured light source light quantity, and the correction value of each transmittance is compared with the target value to control the film forming conditions in the vapor deposition apparatus. It is characterized by.

Next, the invention according to claim 2
Based on the manufacturing method of the absorption multilayer ND filter according to the invention of claim 1,
The first branching optical fiber is composed of an optical fiber in which fibers are randomly bundled before branching, and the first, second and third optical fibers after branching distribute at least two fiber bundles. It is an optical fiber,
The invention according to claim 3
Based on the manufacturing method of the absorption multilayer ND filter according to the invention of claim 1 or 2,
A diffusion plate is disposed between the white light source and the first branch optical fiber,
The invention according to claim 4
Based on the manufacturing method of the absorption-type multilayer ND filter according to the invention of claim 1, 2, or 3,
The stability of the transmittance measurement value is within ± 0.05% / 10 hours.

According to the manufacturing method of the absorption multilayer ND filter according to the present invention,
A white light source, a first branched optical fiber in which light from the light source is distributed into three optical paths and at least two first and second optical fibers constituting the two optical paths are introduced into the film forming chamber, and the film forming chamber The front end of the first optical fiber introduced into the belt is disposed in the vicinity of the surface of the belt-shaped resin film transported from the film formation region to the second roll side, and is disposed on the opposite side of the belt-shaped resin film. The first light receiving fiber to which the white light transmitted through and the tip of the second optical fiber introduced into the film forming chamber are located in the vicinity of the belt-shaped resin film surface conveyed from the film forming region to the first roll side. A second light-receiving fiber that is disposed and is disposed on the opposite side of the belt-shaped resin film through which the white light transmitted through the belt-shaped resin film is incident, and each end and the remaining one of the first light-receiving fiber and the second light-receiving fiber A measuring light switch connected to the outside of the film forming chamber, a first light receiving fiber provided in the measuring light switch and connected to the measuring light switch, a second light receiving fiber, Integrating the three optical paths including the light receiving rotary mask and the light receiving rotary mask for allowing the white light emitted from the third optical fiber to sequentially enter the corresponding three light receiving portions through a certain time interval. A second branch optical fiber, a spectroscope that separates monochromatic light of a specific wavelength from white light incident from the end of the integrated optical fiber, and a light quantity measurement that measures the light quantity when the separated monochromatic light is incident A single- or multi-layer film formed during normal rotation based on monochromatic light passing through the first light-receiving fiber and the measuring light switch. Measure Measures the transmittance of the multilayer film formed during reverse conveyance based on the monochromatic light passing through the second light receiving fiber and the measuring light switch, and based on the monochromatic light passing through the third optical fiber and the measuring light switch. The light source light quantity is measured, the respective transmittances are corrected based on the measured light source light quantity, and the film thickness conditions in the vapor deposition apparatus are controlled by comparing the correction values of the respective transmittances with the target values.

  Therefore, even if the transmittance monitor is incorporated into the vapor-phase film formation method of the roll-to-roll process method in which the film formation time becomes extremely long, the measurement error due to the time fluctuation of the light source light amount is avoided, so the formed multilayer film As a result, it is possible to stably manufacture an absorption multilayer ND filter having excellent optical characteristics. It becomes possible.

  Hereinafter, embodiments of the present invention will be described in detail.

  First, as shown in FIG. 3, the vapor phase film forming (sputtering) apparatus includes a film forming chamber (vacuum chamber) 1 and a first roll (unwinding roll) that is housed in the vacuum chamber 1 and unwinds the belt-shaped resin film 100. ) 5 and a second roll (winding roll) 6 for winding the unrolled belt-shaped resin film 100, and the belt-shaped resin film 100 provided in the conveyance path between the unwinding roll 5 and the winding roll 6 is wound. The main part is comprised by the water-cooled can roll 2 and the film-forming area | region 101 provided along the outer peripheral surface of this can roll 2, and the Si sputtering target 9 and the Ni sputtering target 10 are each arrange | positioned.

  Further, the transmittance monitor incorporated in this vapor deposition (sputtering) apparatus distributes the white (halogen) light source 11 and the optical path from the light source 11 into three optical paths as shown in FIG. The first optical fiber 121 and the second optical fiber 122 constituting the first branched optical fiber 12 are introduced into the vacuum chamber 1 and the tip (light projecting part) 14 of the first optical fiber 121 is the above-mentioned. It is disposed in the vicinity of the surface of the strip-shaped resin film 100 conveyed from the film formation region 101 to the second roll (winding roll) 6 side, and is disposed on the opposite side of the strip-shaped resin film 100 so as to pass through the strip-shaped resin film 100. The first light receiving fiber 201 into which the white light that has entered is incident on the tip (light receiving portion) 16 and the tip (light projecting portion) 13 of the second optical fiber 122 are moved from the film formation region 101 to the first roll. Unwinding roll) White light that is disposed in the vicinity of the surface of the strip-shaped resin film 100 conveyed to the 5 side and is disposed on the opposite side of the strip-shaped resin film 100 and transmitted through the strip-shaped resin film 100 is the front end (light receiving portion). 15, the second light receiving fiber 202 incident on the first light receiving fiber 201, the end (outgoing part) 20 of the first light receiving fiber 201, the end (outgoing part) 19 of the second light receiving fiber 202, and the remaining third optical fiber 123. Measuring light switch 17 connected to the outside of the vacuum chamber 1 and a first light receiving fiber 201 provided in the measuring light switch 17 and connected to the measuring light switch 17. The white light emitted from the second light receiving fiber 202 and the third optical fiber 123 is sequentially passed at regular time intervals to the corresponding three light receiving units 21, 22, and 23. A rotating mask 24 for switching light to be incident, a second branch optical fiber 26 that integrates the three optical paths including the light receiving portions 21, 22, and 23, and an integrated second branch optical fiber 26. The main part is composed of a spectroscope 27 that separates monochromatic light of a specific wavelength from white light incident from the end, and a light amount measuring device 28 that receives the separated monochromatic light and measures the amount of light. .

  In the transmittance monitor incorporated in the vapor deposition (sputtering) apparatus, a single or multilayer film formed during normal rotation based on monochromatic light passing through the first light receiving fiber 201 and the measurement light switch 17 is used. The transmittance of the film is measured, and the transmittance of the multilayer film formed during reverse conveyance is measured based on the monochromatic light that has passed through the second light receiving fiber 202 and the measuring light switch 17, and the third optical fiber 123 The light source light amount is measured based on the monochromatic light that has passed through the measuring light switch 17 and the above-described transmittances are corrected based on the measured light source light amount.

  Therefore, even if the transmittance monitor is incorporated into the vapor-phase film formation method of the roll-to-roll process method in which the film formation time becomes extremely long, the measurement error due to the time fluctuation of the light source light amount is avoided, so the formed multilayer film The transmittance can be continuously monitored with high accuracy in spite of its simple structure and low cost, which makes it possible to stably produce an absorption type multilayer ND filter having excellent optical characteristics. It becomes.

  In this vapor phase film formation (sputtering) apparatus, the normal rotation conveyance means that the belt-shaped resin film 100 is conveyed from the first roll (unwinding roll) 5 to the second roll (winding roll) 6 side. The reverse conveyance means that the belt-shaped resin film 100 is conveyed from the second roll (winding roll) 6 to the first roll (unwinding roll) 5 side.

  Hereinafter, the vapor phase film deposition (sputtering) apparatus and the transmittance monitor according to the present invention will be described in more detail.

  A roll-to-roll process type vapor deposition apparatus, that is, a sputtering roll coater according to the present invention, includes a winding roll 5 and a winding roll 6 in a vacuum chamber 1, and includes a water-cooled can roll 2 and feed rolls 3, 4. The belt-shaped resin film 100 is conveyed by driving. Then, as described above, the direction in which the film 100 is conveyed from the unwinding roll 5 to the winding roll 6 is defined as the forward rotation direction, and the opposite direction is defined as the reverse rotation direction. The unwinding roll 5 and the winding roll 6 balance the tension of the film.

  As an example, in this embodiment, the Si sputtering target 9 and the Ni sputtering target 10 are arranged on both sides of the can roll 2, and Si sputtering is performed by forward conveyance and Ni sputtering is performed by reverse conveyance. Further, since there is a large difference in the film thicknesses of Si and Ni in the absorption multilayer ND filter, it is extremely difficult to form films simultaneously.

  Between the feed roll 4 and the free roll 8, there are a light projecting section 14 of the first optical fiber 121 and a light receiving section 16 of the first light receiving fiber 201 as a transmittance monitor used during Si sputtering during normal rotation conveyance. Between the feed roll 3 and the free roll 7, the light projecting unit 13 of the second optical fiber 122 and the light receiving unit 15 of the second light receiving fiber 202 used during Ni sputtering at the time of reverse conveyance are disposed.

  As described above, the first branch optical fiber 12 is connected to the halogen light source 11 stabilized by the stabilized power source, and the third optical fiber 123 for correcting the temporal change in the light source light amount, and during normal rotation conveyance The first optical fiber 121 for monitoring and the second optical fiber 122 for monitoring during reverse conveyance are branched.

  The end face of the first branch optical fiber 12 connected to the halogen light source 11 is preferably formed by randomly bundling the fibers and distributing the fiber bundle into at least two, thereby positioning the halogen light source. The strength unevenness due to is minimized. Further, a diffusion plate may be disposed between the first branch optical fiber 12 and the halogen light source 11.

  When the above-mentioned collecting multilayer ND filter is formed by a roll-to-roll process type vapor phase film forming method, that is, a roll coater, white (halogen) is used as described above in order to eliminate the influence of each light receiving system in the transmittance monitor. ) The optical path from the light source 11 is divided into three optical paths, and the two first optical fibers 121 and the second optical fiber 122 constituting the two optical paths are introduced into the vacuum chamber 1, and the strip-shaped resin film is introduced from the first optical fiber 121. The white light projected toward 100 is received by the corresponding first light receiving fiber 201 and guided to the measuring light switch 17 side, and is projected from the second optical fiber 122 toward the belt-shaped resin film 100. The white light received by the corresponding second light receiving fiber 202 is guided to the measuring light switch 17 side, and the remaining one third of the first branch optical fiber 12 is third. Through the fiber 123 has a light from the white (halogen) light source 11 so as to guide directly into the measuring light switch 17 side. In the measurement light switch 17, a disc-shaped light switching rotary mask 24 having an opening 25 is attached as shown in FIGS. 3 and 4, and the first light beam connected to the measurement light switch 17 is connected. White light emitted from the end portions (emission portions) 18, 19, and 20 of the one light receiving fiber 201, the second light receiving fiber 202, and the third optical fiber 123 is sequentially passed at regular time intervals to correspond to the corresponding three types. It is made to inject into the light-receiving parts 21, 22, and 23, respectively. In order to reduce measurement noise, a method of chopping light from the white (halogen) light source 11 with a chopper and performing signal processing with a lock-in amplifier may be used in combination.

  The light-switching rotary mask 24 is controlled to rotate, for example, 120 degrees every 5 seconds, and when forwardly transported, the opening 25 is formed at the position of 0 degrees as shown in FIG. The opening 25 is arranged between the end (emission part) 20 of the first light receiving fiber 201 and the light receiving part 23 at a position of 120 degrees. It is like that. Therefore, as shown in FIG. 5, white light that has passed through the third optical fiber 123 and the light switching rotary mask 24 is incident on the spectroscope 27 to separate the monochromatic light of a specific wavelength, and the separated monochromatic light is emitted. The light is incident on the measuring device 28 and the amount of light from the light source is measured, and the white light passing through the first light receiving fiber 201 and the light switching rotary mask 24 is incident on the spectroscope 27 to similarly separate the monochromatic light having a specific wavelength. In addition, the separated monochromatic light is incident on the light quantity measuring device 28 and the transmitted light quantity at the time of forward conveyance is measured. Further, at the time of reverse conveyance, as shown in FIG. 4, the opening 25 is disposed between the end (emission part) 18 of the third optical fiber 123 and the light receiving part 21 at a position of 0 degrees, and at a position of 240 degrees. The opening 25 is arranged between the end portion (outgoing portion) 19 of the second light receiving fiber 202 and the light receiving portion 22. Therefore, as shown in FIG. 6, white light that has passed through the third optical fiber 123 and the light switching rotary mask 24 is incident on the spectroscope 27 to separate the monochromatic light of a specific wavelength, and the separated monochromatic light is emitted. The light is incident on the measuring device 28 and the amount of light from the light source is measured, and white light that has passed through the second light receiving fiber 202 and the light switching rotary mask 24 is incident on the spectroscope 27 to similarly separate monochromatic light having a specific wavelength. The separated monochromatic light is incident on the light quantity measuring device 28 and the transmitted light quantity during reverse conveyance is measured.

During forward rotation, the light source light amount measured before the transmitted light amount measurement based on the monochromatic light passing through the third optical fiber 123 and the light switching rotary mask 24 is S1, the first light receiving fiber 201 and the light switching rotation. The transmitted light quantity of the single or multilayer film measured based on the monochromatic light passing through the mask 24 is T1, and the light source measured after the transmitted light quantity measurement based on the monochromatic light passed through the third optical fiber 123 and the light switching rotary mask 24. In the case where the light amount is S2, in order to correct the transmitted light amount T1 accompanying the temporal variation of the light source light amount, as the light source light amount S0 at the start,
T1 ′ = T1 / [(S1 / S0 + S2 / S0) / 2]
Or
T1 ′ = T1 / (S1 / S0), T1 ′ = T1 / (S2 / S0)
The correction value (T1 ′) can be obtained from the relational expression, and the transmittance corrected based on the correction value (T1 ′) can be obtained.

Similarly, during reverse conveyance, the light source light amount measured before the transmitted light amount measurement based on the monochromatic light passing through the third optical fiber 123 and the light switching rotary mask 24 is S1, the second light receiving fiber 202 and the light switching rotation. The transmitted light amount of the multilayer film measured based on the monochromatic light passing through the mask 24 is T1, and the light source light amount measured after the transmitted light amount measurement based on the monochromatic light passing through the third optical fiber 123 and the light switching rotary mask 24 is S2. In order to correct the transmitted light amount T1 with time variation of the light source light amount, as the light source light amount S0 at the start,
T1 ′ = T1 / [(S1 / S0 + S2 / S0) / 2]
Or
T1 ′ = T1 / (S1 / S0), T1 ′ = T1 / (S2 / S0)
The correction value (T1 ′) can be obtained from the relational expression, and the transmittance corrected based on the correction value (T1 ′) can be obtained.

  Of course, it is also possible to use a moving average of the designated number of measurement light quantities in consideration of noise at the time of measurement.

  Using such a monitor system, the transmittance immediately after film formation of each layer is accurately measured and compared with a target value, and film formation conditions (for example, sputtering power, film conveyance speed, etc.) according to the deviation from the target value ) Can be obtained, the spectral optical characteristics of the target absorption multilayer ND filter can be obtained.

  And according to the manufacturing method of the absorption type multilayer ND filter according to the present invention, the light quantity of the light source is measured by the built-in transmittance monitor, and the film transmittance during the film formation of the entire multilayer film is corrected based on the light quantity of the light source. Therefore, the stability of the transmittance measurement value can be reduced to about ± 0.05% / 10 hours or less even in the vapor-phase film formation method of the roll-to-roll process method in which the film formation time becomes extremely long. Become.

  Further, in the film configuration of the absorption multilayer ND filter shown in Table 1, the light quantity error of the optical film thickness monitor is ± 1%, ± 0.2%, ± 0.1%, ± 0.05 by theoretical analysis. %, The transmission error of each absorption multilayer ND filter is about ± 1.3%, about ± 0.3%, about ± 0.15%, and about ± 0.07%.

  Therefore, by controlling the film forming conditions such as sputtering power appropriately using the above transmittance monitor capable of reducing the stability of the transmittance measurement value to about ± 0.05% / 10 hours or less, the roll toe can be controlled. An absorption multilayer ND filter having a transmittance error within about ± 0.07% can be stably manufactured by a roll process type vapor deposition method.

  Examples of the present invention will be specifically described below.

  First, a film structure (shown in Table 1 above) of an absorption multilayer ND filter having a spectral transmission characteristic with an average transmittance of 12.5% was designed.

  For film formation, a roll-to-roll process type vapor deposition method, that is, a sputtering roll coater of FIG. 3 equipped with a transmittance monitor was used.

Further, a Ni alloy target [manufactured by Sumitomo Metal Mining Co., Ltd.] is used as a target for forming a metal absorption film, and a Si target is used as a target for forming SiO ₂ that is an oxide dielectric film. [Sumitomo Metal Mining Co., Ltd.] was used. The Ni alloy target is formed by DC magnetron sputtering in which Ar gas is introduced, the Si target is subjected to dual magnetron sputtering in which Ar gas is introduced, and an impedance monitor (plasma manufactured by Bon Ardennes) is used to form SiO ₂ from Si. The amount of oxygen introduced was controlled by an emission monitor.

  The monitor wavelength (monochromatic light) in the transmittance monitor is 532 nm, the light switching rotary mask 24 rotates 120 degrees every 5 seconds, and the white light and the second light received via the third optical fiber 123 and the light switching rotary mask 24. White light that has passed through the fiber 202 and the light switching rotary mask 24 and white light that has passed through the first light receiving fiber 201 and the light switching rotary mask 24 are sequentially incident on the spectrometer 27 at regular time intervals. ing.

  Moreover, the PET film with an easily bonding layer (made by Toyobo Co., Ltd.) having a thickness of 100 μm and a length of 50 m was used as the belt-shaped resin film.

Since SiO ₂ is formed during normal conveyance (from 0 m to 50 m) of the belt-shaped resin film 100, its transmittance is measured based on the monitor wavelength via the first light receiving fiber 201 and the light switching rotary mask 24. Since the film was formed during reverse conveyance (from 50 m to 0 m) of the belt-shaped resin film 100, the transmittance was measured based on the monitor wavelength via the second light receiving fiber 202 and the light switching rotary mask 24. The spectral transmission characteristics of the completed ND filter were measured using a self-recording spectrophotometer (V570 manufactured by JASCO Corporation).

First, the conveyance speed of the belt-shaped resin film 100 is fixed, and the sputtering power is adjusted so that the transmittances of the SiO ₂ film and the Ni film to be formed become the target set values. The change in transmittance between 50 m in 50 m) and in reverse conveyance (from 50 m to 0 m) was measured. The results are shown in Table 3 below.

次に、帯状樹脂フィルム１００の搬送速度を固定し、成膜されるＳｉＯ_２膜とＮｉ膜の透過率が目標設定値になるようにスパッタ電力を調整し、かつ、正転搬送（０ｍから５０ｍへ）および逆転搬送（５０ｍから０ｍへ）における５０ｍ間の透過率変化を測定すると共に、透過率変化を測定する際に目標設定値とのズレ分を考慮して１０ｍ毎に目標設定値になるようにスパッタ電力を再調整した。この結果を表４に示す。

Next, the conveyance speed of the belt-shaped resin film 100 is fixed, the sputtering power is adjusted so that the transmittance of the formed SiO ₂ film and the Ni film becomes a target set value, and the normal rotation conveyance (from 0 m to 50 m). ) And reverse transmission (from 50 m to 0 m), the change in transmittance between 50 m is measured, and when the change in transmittance is measured, the deviation from the target set value is taken into account and the target set value is set every 10 m. The sputtering power was readjusted as follows. The results are shown in Table 4.

表４に示された結果から明らかなように、例えば、１層目のＳｉＯ_２膜においてはその目標透過率が９４．８％（開始成膜条件であるスパッタ電力は５００３Ｗ）であるのに対し、帯状樹脂フィルム１００を１０ｍ搬送した時点における透過率が９４．７％（監視後の成膜条件であるスパッタ電力は５００９Ｗ）、２０ｍ搬送した時点における透過率が９４．８％（監視後の成膜条件であるスパッタ電力は５０１３Ｗ）、３０ｍ搬送した時点における透過率が９４．７％（監視後の成膜条件であるスパッタ電力は５０１６Ｗ）、４０ｍ搬送した時点における透過率が９４．８％（監視後の成膜条件であるスパッタ電力は５０２３Ｗ）、および、５０ｍ搬送した時点における透過率が９４．８％（監視後の成膜条件であるスパッタ電力は５０２７Ｗ）であり、目標設定値とのズレ分が極めて少ないことが確認される。

As is apparent from the results shown in Table 4, for example, in the first SiO ₂ film, the target transmittance is 94.8% (the sputtering power as the starting film formation condition is 5003 W). When the belt-shaped resin film 100 is transported for 10 m, the transmittance is 94.7% (sputtering power, which is a film forming condition after monitoring is 5009 W), and when the belt-shaped resin film 100 is transported for 20 m, the transmittance is 94.8% (after monitoring). Sputtering power, which is a film condition, is 5013 W), and the transmittance when transported for 30 m is 94.7% (sputtering power, which is a filming condition after monitoring is 5016 W), and the transmittance when transported for 40 m is 94.8% ( The sputter power, which is the film formation condition after monitoring, is 5023 W), and the transmittance at the time when the film is transported by 50 m is 94.8% (sputter power, which is the film formation condition after monitoring is 502). 7W), and it is confirmed that there is very little deviation from the target set value.

  Similarly, the target transmittance up to the fifth layer is 35.1% (sputtering power, which is the starting film formation condition, is 5005 W), whereas the transmittance at the time when the belt-shaped resin film 100 is conveyed by 10 m is 34.9. % (Sputtering power, which is a film forming condition after monitoring is 5009 W), and the transmittance at the time of 20 m transfer is 35.0% (sputtering power, which is the film forming condition after monitoring is 5015 W). Is 35.1% (sputtering power, which is a film formation condition after monitoring is 5021 W), and the transmittance at the time of 40 m conveyance is 35.1% (sputtering power, which is a film formation condition after monitoring is 5024 W), and 50 m The transmittance at the time of conveyance is 35.1% (sputtering power, which is a film forming condition after monitoring, is 5031 W), and there is very little deviation from the target set value.

  As described above, according to the method for manufacturing an absorptive multilayer ND filter according to the present invention, the light amount of the light source is measured with the built-in transmittance monitor, and the transmittance during the film formation of the entire multilayer film is corrected based on the light amount of the light source. Therefore, stable production of an absorptive multilayer ND filter with excellent spectral transmittance reproducibility by appropriately controlling film formation conditions (sputtering power, film transport speed, etc.) based on the correction value of transmittance. Is possible.

  The material of the belt-like resin film is not limited. Specific examples include polyethylene terephthalate (PET), polyethersulfone (PES), polyarylate (PAR), polycarbonate (PC), polyolefin (PO), and norbornene. Examples thereof include a single resin film selected from resin materials, or a composite of a single resin film selected from the above resin materials and an acrylic organic film covering one or both surfaces of this single material. 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.

  In this embodiment, since the transmittance is measured over the entire length of the roll formed by the roll coater, there is an advantage in quality control. Furthermore, it is possible to increase the measurement accuracy by setting the monitor wavelength of the spectroscope to two or more wavelengths, or to measure the spectral transmission spectrum in the visible range with the spectroscope by temporarily stopping film conveyance.

  According to the method for manufacturing an absorption-type multilayer ND filter according to the present invention, it is possible to measure the light amount of the light source with the built-in transmittance monitor and correct the transmittance during film formation of the entire multilayer film based on the light amount of the light source. Therefore, it is possible to stably manufacture an absorption-type multilayer ND filter with excellent spectral transmittance reproducibility by appropriately controlling the film formation conditions (sputtering power, film transport speed, etc.) based on the transmittance correction value. Become. Therefore, the manufactured absorption multilayer ND filter has industrial applicability to be mounted on a small and thin digital camera.

The graph which shows the spectral transmission characteristic of the absorption type multilayer ND filter of average transmittance | permeability 12.5%. The graph which shows the transmittance | permeability change (for 5 layers on one side) of the multilayer film during the film-forming measured by the film thickness monitor attached to the batch type vapor phase film-forming apparatus. Explanatory drawing of the sputtering roll coater equipped with the transmittance | permeability monitor which concerns on this invention. The schematic front view of the rotation mask for light switching provided in the measurement light switch of the transmittance | permeability monitor which concerns on this invention. The graph which shows the relationship between the operation | movement of the rotation mask for light switching at the time of forward conveyance of a strip | belt-shaped resin film, and a measurement light quantity. The graph figure which shows the relationship between the operation | movement of the rotation mask for light switching at the time of reverse conveyance of a strip | belt-shaped resin film, and measured light quantity.

Explanation of symbols

1 Deposition chamber (vacuum chamber)
2 Water-cooled can roll 3 Feed roll 4 Feed roll 5 First roll (unwinding roll)
6 Second roll (winding roll)
7 Free Roll 8 Free Roll 9 Si Sputtering Target 10 Ni Sputtering Target 11 White (Halogen) Light Source 12 First Branched Optical Fiber 13 Tip of Second Optical Fiber 122 (Light Projecting Unit)
14 Tip of first optical fiber 121 (light projecting part)
15 End of second light receiving fiber 202 (light receiving portion)
16 Tip of first light receiving fiber 201 (light receiving portion)
17 Measuring light switch 18 End part (outgoing part) of third optical fiber 123
19 End (outgoing part) of the second light receiving fiber 202
20 End part (outgoing part) of the first light receiving fiber 201
DESCRIPTION OF SYMBOLS 21 Light-receiving part 22 Light-receiving part 23 Light-receiving part 24 Light-switching rotation mask 25 Aperture 26 Second branch optical fiber 27 Spectrometer 28 Light quantity measuring device 100 Band-shaped resin film 101 Deposition region 121 First optical fiber 122 Second optical fiber 123 First Three optical fibers 201 First light receiving fiber 202 Second light receiving fiber

Claims (4)

A first roll for unwinding the strip-shaped resin film and a second roll for winding the unrolled strip-shaped resin film in the film forming chamber of the vapor phase film deposition apparatus are provided in the conveyance path between the first roll and the second roll. In the formed film formation region, after collecting by the second roll while forming an absorption film or a dielectric film on at least one side of the belt-shaped resin film unwound from the first roll, the rotation direction of each roll is reversed and The film is collected by the first roll while forming a dielectric film or absorption film on the absorption film or dielectric film of the belt-shaped resin film unwound from the second roll in the film formation region, and then the above steps as necessary. In the method of manufacturing an absorption multilayer ND filter having an absorption multilayer film composed of an absorption film and a dielectric film by repeating
A white light source, a first branched optical fiber in which light from the light source is distributed into three optical paths and at least two first and second optical fibers constituting the two optical paths are introduced into the film forming chamber, and the film forming chamber The front end of the first optical fiber introduced into the belt is disposed in the vicinity of the surface of the belt-shaped resin film transported from the film formation region to the second roll side, and is disposed on the opposite side of the belt-shaped resin film. The first light receiving fiber to which the white light transmitted through and the tip of the second optical fiber introduced into the film forming chamber are located in the vicinity of the belt-shaped resin film surface conveyed from the film forming region to the first roll side. A second light-receiving fiber that is disposed and is disposed on the opposite side of the belt-shaped resin film through which the white light transmitted through the belt-shaped resin film is incident, and each end and the remaining one of the first light-receiving fiber and the second light-receiving fiber A measuring light switch connected to the outside of the film forming chamber, a first light receiving fiber provided in the measuring light switch and connected to the measuring light switch, a second light receiving fiber, Integrating the three optical paths including the light receiving rotary mask and the light receiving rotary mask for allowing the white light emitted from the third optical fiber to sequentially enter the corresponding three light receiving portions through a certain time interval. A second branch optical fiber, a spectroscope that separates monochromatic light of a specific wavelength from white light incident from the end of the integrated optical fiber, and a light quantity measurement that measures the light quantity when the separated monochromatic light is incident A single- or multi-layer film formed during normal rotation based on monochromatic light passing through the first light-receiving fiber and the measuring light switch. Measure rate In addition, the transmittance of the multilayer film formed during reverse conveyance is measured based on the monochromatic light that has passed through the second light receiving fiber and the measuring light switch, and the monochromatic light that has passed through the third optical fiber and the measuring light switch. The light source light quantity is measured based on the light source, the transmittance is corrected based on the measured light source light quantity, and the correction value of each transmittance is compared with the target value to control the film forming conditions in the vapor deposition apparatus. A manufacturing method of an absorption type multilayer ND filter characterized by the above.   The first branching optical fiber is composed of an optical fiber in which fibers are randomly bundled before branching, and the first, second and third optical fibers after branching distribute at least two fiber bundles. 2. The method of manufacturing an absorptive multilayer ND filter according to claim 1, wherein the method is an optical fiber.   3. The method for producing an absorption multilayer ND filter according to claim 1, wherein a diffusion plate is disposed between the white light source and the first branch optical fiber.   4. The method for producing an absorptive multilayer ND filter according to claim 1, wherein stability of the measured transmittance is within ± 0.05% / 10 hours.

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