JP6964435B2 - Optical film manufacturing method - Google Patents

Description

The present invention relates to a method for producing an optical film having a multilayer optical thin film on a film substrate.

Functional optical films such as antireflection films, transparent conductive films, electromagnetic wave shielding films, and solar radiation adjusting films include a laminate of a plurality of optical thin films having different refractive coefficients (multilayer optical thin films) on a film base material. Examples of the material of the optical thin film include various oxides such as silicon oxide and metal oxide, and various metal materials.

The sputtering method is widely used for forming a multilayer optical thin film on a film substrate. By using a roll-to-roll sputtering device that can arrange multiple targets along the transport path of the film substrate, a multilayer optical thin film can be formed on the film substrate in one pass, thus improving the production efficiency of the optical film. Can be improved.

The multilayer optical thin film uses multiple reflection interference to adjust the light reflection / transmission characteristics and realize the desired optical characteristics. In order to exhibit these characteristics, it is necessary to adjust the film quality (particularly the refractive index) and the film thickness of each optical thin film constituting the multilayer film within a predetermined range. In particular, optical films for displays such as antireflection films are required to have a high degree of uniformity in the film quality and film thickness of the optical thin film. Therefore, in the production of multilayer optical thin films, the film formation conditions are strictly controlled so that the film quality and film thickness of each optical thin film are constant, and the film quality and film thickness fluctuate in the width direction and the length direction. Need to be suppressed.

As a method of keeping the film quality and film thickness of a thin film constant, a method of detecting the plasma emission intensity of a sputtering discharge and feeding it back to the amount of gas introduced (plasma emission monitor (PEM) control) is known. For example, in reactive sputtering using a metal target and an oxidizing gas such as oxygen, the control value (set point; SP) of the emission intensity is set in a predetermined range, and oxygen is introduced so that the emission intensity is within this range. By adjusting the amount, the film quality and film thickness of the oxide thin film can be kept constant.

By combining the control of the gas introduction amount by PEM control and the control based on the measurement result of the optical characteristics of the thin film in-line, the uniformity of the optical thin film can be further improved. For example, in Patent Document 1, in the formation of an optical thin film by sputtering, in addition to controlling the oxygen flow rate so that the plasma emission intensity is within the set range (PEM control), the spectral reflectance after forming the optical thin film is formed. Is measured in-line, and continuous film formation is performed while changing the setting range of the emission intensity of PEM so that the spectral reflectance is within a predetermined range.

By combining PEM control and control based on in-line optical measurement, even if a slight environmental change occurs due to erosion of the target during film formation, the film formation conditions can be finely adjusted to correspond to this. Therefore, an optical thin film having excellent uniformity of optical characteristics in the longitudinal direction and the width direction can be obtained.

In this film formation carried out to obtain a product, the uniformity of optical characteristics can be maintained by applying the above control. On the other hand, in order to form a multilayer optical thin film having the target optical characteristics, it is important to set the initial film formation conditions at the start of the film formation. In the film formation of an optical thin film by roll-to-roll sputtering, a preliminary film formation is performed before the start of the main film formation for the purpose of setting conditions for the main film formation and the like. For example, Patent Document 2 discloses a multilayer optical thin film in which a high-refractive-index transparent thin film and a metal conductor thin film are alternately laminated. It is described that the film was formed, the film formation rate was calculated, and the roll temperature was adjusted.

WO2011 / 046050 Pamphlet Japanese Unexamined Patent Publication No. 2001-249221

In the pre-deposition of the multilayer optical thin film, the method of sequentially adjusting the film forming conditions of the single-layer thin film increases the number of adjustments as the number of laminated thin films increases. Therefore, the time required for the preliminary film formation becomes long, which causes an increase in material loss and a decrease in productivity. In particular, when adjusting the film forming conditions at a plurality of locations in the width direction in order to make the film thickness in the width direction uniform, it takes a lot of time to set the initial conditions because there are many parameters to be adjusted. Further, when the adjustment accuracy in the preliminary film formation is low, it takes time to finely adjust the film formation conditions in the main film formation, which may lead to a further increase in material loss and a decrease in productivity. In view of these problems, it is an object of the present invention to improve the efficiency of adjusting the film forming conditions in the preliminary film formation of the multilayer optical thin film, and to improve the productivity and the uniformity of the optical characteristics of the optical film including the multilayer optical thin film. And.

The present invention relates to a method for producing an optical film including a multilayer optical thin film composed of a plurality of thin films on a film substrate. Examples of the optical film include an antireflection film including a multilayer optical thin film (antireflection layer) composed of a plurality of oxide thin films.

In the present invention, a multilayer optical thin film composed of a plurality of thin films is continuously conveyed on a film substrate in a sputtering film forming apparatus provided with a plurality of sputtering chambers along the conveying direction of the film substrate. (Main film formation) is performed. In the preliminary film formation performed before the main film formation, a plurality of sputtering chambers are simultaneously energized to form two or more thin films having different refractive indexes on the film substrate. The optical characteristics of a laminate in which a plurality of thin films are formed on a film substrate are measured in-line, and the film thickness of each thin film is calculated based on the measurement results. The film thickness conditions of each thin film are adjusted based on the film thickness calculation result. It is preferable that the film forming conditions are adjusted until the optical characteristics obtained by the optical measuring unit or the film thicknesses of the plurality of thin films calculated from the optical characteristics are within a predetermined range.

In the adjustment step, it is preferable that the optical measuring unit measures the reflection spectrum of the laminate in which the plurality of thin films are formed on the film substrate, and the film thickness of the plurality of thin films is calculated from the reflection spectrum. In this case, until the measured values of the film thicknesses of the plurality of thin films are within the predetermined range, or the difference between the reflection spectrum obtained by the measurement by the optical measuring unit and the target reflection spectrum is within the predetermined range. It is preferable that the membrane conditions are adjusted.

The optical measurement in the adjustment step is preferably performed at a plurality of locations in the width direction of the film substrate, and the film thickness conditions are adjusted based on the measurement results at the plurality of locations in the width direction to adjust the film thickness in the width direction. It is preferable to reduce the film thickness distribution.

In one embodiment, at least one of the plurality of thin films constituting the multilayer optical thin film is a laminated film of a plurality of sub-thin films formed in two or more sputtering chambers. It is preferable that the film forming conditions of the plurality of sub-thin films constituting one laminated film are adjusted in different adjustment steps. In the preliminary film formation, it is preferable that the transfer speed of the film substrate in the adjustment steps performed a plurality of times is the same.

The film substrate used for the preliminary film formation may be the same as or different from the film substrate used for the main film formation. For example, in order to reduce backside reflection and improve the measurement accuracy of the film thickness and the adjustment accuracy of the film formation conditions, a light-absorbing film base material or the like may be used in the preliminary film formation. In at least one of the preliminary film formation and the main film formation, a laminate in which a light absorbing member is detachably attached to the thin film non-forming surface side of the transparent film via an adhesive layer is used as the film base material. May be done. In order to improve the production efficiency, it is preferable that the same film base material is used for the preliminary film formation and the main film formation. Above all, after the preliminary film formation, it is preferable to continuously carry out the main film formation in a state where the energization of the sputter chamber is continued.

In the production method of the present invention, in the preliminary film formation for determining the film forming conditions of the multilayer optical thin film, a laminate composed of a plurality of thin films is formed on the film substrate, and the plurality of thin films are measured by in-line optical measurement. The film formation conditions are adjusted while measuring each film thickness. Since the film formation conditions of a plurality of thin films are adjusted in one adjustment step, the number of adjustment steps in the pre-deposition can be reduced and the time required for the pre-deposition can be shortened.

It is a schematic cross-sectional view which shows the laminated structure example of the antireflection film. It is a schematic diagram which shows the structural example of the sputtering film formation apparatus used for manufacturing a multilayer optical thin film. It is a construct diagram of a sputter chamber. It is a figure which shows the outline of the adjustment method of the film formation condition in the preliminary film formation of the prior art. It is a flowchart which shows an example of the adjustment method of the film formation condition in the preliminary film formation. It is a figure which shows the outline of the adjustment method of the film forming condition in the preliminary film formation of the manufacturing method of this invention. It is a figure which shows the outline of the adjustment method of the film forming condition in the preliminary film formation of the manufacturing method of this invention. It is a reflection spectrum of 23 points in the width direction before and after the film formation condition adjustment by the first adjustment step S151. It is a reflection spectrum of 23 points in the width direction before and after the film formation condition adjustment by the second adjustment step S152. It is a reflection spectrum of 23 points in the width direction before and after the film formation condition adjustment by the third adjustment step S153. It is a reflection spectrum of 23 points in the width direction before and after the film formation condition adjustment by the 4th adjustment step S154. It is the reflection spectrum of 23 places in the width direction of the antireflection film which formed the film formation at the same substrate transport speed as this film formation after adjusting the film formation conditions by steps S151 to S154.

The present invention relates to a method for producing an optical film including a multilayer optical thin film composed of a laminate of a plurality of optical thin films having different refractive coefficients on a film substrate. Specifically, the present invention relates to a method for producing a multilayer optical thin film on a film substrate. The present invention relates to a forming method and a preliminary forming method for adjusting the forming conditions of a multilayer optical thin film.

[Optical film]
An antireflection film is mentioned as an example of an optical film having a multilayer optical thin film on a film substrate. The antireflection film includes an antireflection layer made of a multilayer optical thin film on a film base material such as a transparent film or a polarizing plate. In the antireflection film, a wide band of visible light is formed by setting the optical film thickness (product of refractive index and thickness) of the thin film constituting the antireflection layer so that the inverted phases of the incident light and the reflected light cancel each other out. The reflectance can be reduced in the wavelength range of.

FIG. 1 is a cross-sectional view schematically showing a laminated configuration example of an antireflection film. The antireflection film 100 of FIG. 1 includes an antireflection layer 50 made of a multilayer optical thin film on a film base material 20 via an adhesion improving layer 30. In FIG. 1, an antireflection layer 50 composed of a laminated body of four thin films 51, 52, 53, 54 is shown.

As the film base material 20, a transparent film, a polarizing plate, or the like is used. Examples of the resin material constituting the transparent film include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose; polymethyl methacrylate and the like. Acrylic polymers; styrene-based polymers such as polystyrene and acrylonitrile-styrene copolymers; cyclic polyolefins such as polynorbornene; polycarbonate and the like. The thickness of the film base material 20 is about 5 to 300 μm. A hard coat layer, an anti-glare layer, or the like may be provided on the antireflection layer 50 forming surface side of the film base material 20.

By providing the adhesion improving layer 30 between the film base material 20 and the antireflection layer 50, the adhesion between the film base material which is an organic material and the antireflection layer which is an inorganic material can be improved. The film thickness of the adhesion improving layer 30 is, for example, about 1 to 30 nm. The thin film provided in contact with the film base material 20 in the multilayer optical thin film may have a function as an adhesion improving layer. For example, by providing an oxide layer having an oxygen content smaller than that of the stoichiometric composition as the adhesion improving layer 30 on the film base material 20, both high transparency and adhesion to the antireflection layer can be achieved at the same time. The amount of oxygen in the adhesion improving layer 30 is preferably about 60 to 95% of the stoichiometric composition. For example, when a silicon oxide (SiO _x ) layer is formed as the adhesion improving layer 30, x is preferably about 1.2 to 1.9.

Examples of the material of the thin film constituting the antireflection layer 50 include metal oxides, nitrides, and fluorides. For example, silicon oxide, magnesium fluoride and the like can be mentioned as low refractive index materials having a refractive index of 1.6 or less at a wavelength of 550 nm. Examples of high-refractive-index materials having a refractive index of 1.9 or more at a wavelength of 550 nm include titanium oxide, niobium oxide, zirconium oxide, tin-doped indium oxide (ITO), and antimony-doped tin oxide (ATO). In addition to the low refractive index layer and the high refractive index layer, as a medium refractive index layer having a refractive index of about 1.50 to 1.85, for example, a thin film made of titanium oxide or a mixture of the low refractive index material and the high refractive index material. May be formed.

The laminated structure of the antireflection layer 50 is a two-layer structure consisting of a high refractive index layer having an optical film thickness of about 240 nm to 260 nm and a low refractive index layer having an optical film thickness of about 120 nm to 140 nm from the film substrate 20 side; A three-layer structure consisting of a medium refractive index layer having a film thickness of 170 nm to 180 nm, a high refractive index layer having an optical film thickness of 60 nm to 70 nm, and a low refractive index layer having an optical film thickness of 135 nm to 145 nm; an optical film thickness of 25 nm to A high refractive index layer having an optical thickness of about 55 nm, a low refractive index layer having an optical film thickness of about 35 nm to 70 nm, a high refractive index layer having an optical film thickness of about 60 nm to 250 nm, and a low refractive index layer having an optical film thickness of about 100 nm to 180 nm. A low refractive index layer having an optical film thickness of about 15 nm to 30 nm, a high refractive index layer having an optical film thickness of about 20 nm to 40 nm, a low refractive index layer having an optical film thickness of about 20 nm to 40 nm, and an optical film thickness. Examples thereof include a five-layer structure consisting of a high refractive index layer having an optical thickness of about 240 nm to 290 nm and a low refractive index layer having an optical film thickness of about 100 nm to 200 nm. The range of the refractive index and the film thickness of the thin film constituting the antireflection layer is not limited to the above examples. Further, the antireflection layer 50 may be a laminated body of six or more thin films. In order to reduce reflection at the air interface, the thin film 54 provided as the outermost surface layer of the antireflection layer is preferably a low refractive index layer.

The optical film that is the subject of the present invention is not limited to the antireflection film, and may be any film base material provided with a multilayer optical thin film. For example, an electromagnetic wave shielding film or a solar radiation adjusting film has both a shielding property against electromagnetic waves of a specific wavelength and a transmission of visible light by laminating a metal thin film that reflects electromagnetic waves and infrared rays and a metal oxide thin film. There is. In the transparent conductive film, by laminating one or more dielectric thin films and a transparent electrode layer made of ITO or the like on a transparent film base material, the dielectric thin film plays a role as an optical adjustment layer, and transmitted visible light or The hue of reflected visible light can be neutralized.

As described above, the functional optical film provided with the multilayer optical thin film on the film substrate adjusts the light reflection / transmission characteristics by utilizing the multiple reflection interference of the multilayer optical thin film. Therefore, in order to obtain an optical film having the desired characteristics, it is necessary to appropriately control the (optical) film thickness of each optical thin film constituting the multilayer optical thin film. If there is a distribution in the film thickness of the optical thin film in the plane of the optical film, unevenness in reflectance and transmittance occurs, and these are visually recognized as color unevenness. In particular, in optical films for displays such as antireflection films, the reflected light characteristics affect the image quality and visibility of the display, so that strict control of the thickness of the optical thin film is required.

[Membrane film]
A roll-to-roll sputter film forming apparatus is used to form a multilayer optical thin film on a film substrate. In the roll-to-roll method, film formation is performed while continuously conveying the film substrate in a sputtering apparatus in which a plurality of sputtering targets are arranged along the conveying direction of the film substrate. Therefore, a plurality of thin films can be formed in one pass from unwinding to winding of the film base material.

FIG. 2 is a conceptual diagram showing a configuration example of a sputtering film forming apparatus. The film forming apparatus of FIG. 2 unwinds the film base material from the unwinding roll 211 in the unwinding chamber 210 and supplies it onto the film forming rolls 221, 222 in the film forming chamber 220 to form a thin film. The base material (optical film 100) is wound by a winding roll 291 in the winding chamber 290.

The film forming chamber 220 is connected to a vacuum pump and can be adjusted to a predetermined degree of vacuum. A first film forming roll 221 and a second film forming roll 222 are provided in the film forming chamber 220. Sputter chambers 1 to 5 separated by partition walls are provided along the circumferential direction of the first film forming roll 221, and the sputtering chambers 6 separated by partition walls along the circumferential direction of the second film forming roll 222. 10 are provided. Cathodes 251 to 260 are provided in each of the sputtering chambers 1 to 10, and a target is arranged on each cathode so as to face the film forming roll.

Between the second film forming roll 222 and the take-up roll 291, an optical measuring unit 280 for measuring optical characteristics such as reflectance and transmittance of the optical film is provided, and an optical measuring unit 280 is provided on the film substrate. It is possible to measure optical characteristics such as transmittance and reflectance of a laminated body provided with a thin film. The optical measurement unit 280 is used not only for monitoring the optical characteristics of the product in the main film formation, but also for measuring the film thickness in the preliminary film formation. A reflective optical system is suitable for measuring the film thickness.

The reflected light detected by the photodetector 293 is converted into an electric signal by the light receiving element, and the calculation unit 273 performs the calculation as necessary. In the calculation unit, the spectrum of the detected reflected light is calculated, converted to a specific color system (for example, XYZ color system, L ^* a ^* b ^* color system, Yab color system), and the film thickness is changed. Calculation etc. are performed.

The optical measuring unit 280 is preferably configured so that it can measure the optical characteristics of a plurality of locations in the width direction of the film. Examples of the method for measuring the optical characteristics at a plurality of locations in the width direction include a method in which a plurality of photodetectors are provided in the width direction, a method in which a measurement head provided with the photodetectors is configured to be movable in the width direction, and the like.

<Spatter room>
Examples of the sputtering method in the sputtering chamber include a two-pole sputtering method, a three-pole sputtering method, and a magnetron sputtering method. Since the film formation rate is high, the magnetron sputtering method is preferable. Above all, the dual magnetron sputtering method is suitable for forming a dielectric thin film. The power source for applying the voltage to the target may be either direct current or alternating current. Since the film formation rate is high, it is preferable to use a DC power supply.

The sputter film formation of the oxide thin film can be carried out by either a method using an oxide target or a reactive sputtering using a metal target. Reactive sputtering using a metal target is suitable for forming a dielectric thin film such as silicon oxide because it can be formed at a high rate. In reactive sputtering, an inert gas such as argon and a reactive gas such as oxygen are introduced into the sputtering chamber, and the amount of the reactive gas introduced is controlled so as to be an intermediate transition region between the metal region and the oxide region. This makes it possible to form an oxide thin film at a high rate.

In the reactive sputtering, it is preferable to control the amount of the reactive gas introduced such as oxygen by controlling the plasma emission monitor (PEM). In the PEM control, the plasma emission intensity of the sputtering film formation is detected, and the amount of the reactive gas introduced is adjusted so that the emission intensity becomes a predetermined control value (set point; SP). By automatically adjusting the gas introduction amount so that the plasma emission intensity becomes constant, in addition to being able to maintain the transition region and form a film at a high rate, the film formation rate can be kept constant. However, if film formation is continuously performed for a long time, the film formation rate changes due to the influence of target erosion and the like even if the plasma emission intensity is the same. Therefore, when continuous film formation is carried out for a long time as in the present film formation, it is preferable to appropriately adjust the SP of PEM based on the measurement results of in-line optical characteristics and the like.

FIG. 3 is a conceptual diagram of the structure of the sputter chamber. A pair of targets 251a and 251b are installed on the cathode in the sputtering chamber. Gas introduction pipes 310 and 320 for sharing an inert gas such as argon and a reactive gas such as oxygen are connected to the sputtering chamber. The reactive gas introduction pipe 310 is branched in the middle, and mass flow controllers 31 to 314 are provided in each branch pipe. The inert gas introduction pipe 320 is also branched in the middle, and mass flow controllers 321 to 324 are provided in each branch pipe.

Each mass flow controller is connected to a control unit 370 and controls the flow rate of the gas introduced into the sputtering chamber. With this configuration, it is possible to individually adjust the amount of gas introduced at a plurality of locations in the width direction. The branch pipe is further branched on the downstream side of the mass flow controller, and gas is introduced into the sputter chamber from gas ejection nozzles 319 and 329 provided side by side in the width direction around the target. Although FIG. 3 shows a mode in which the reactive gas and the inert gas are individually introduced into the sputter chamber from the gas ejection nozzles 319 and 329, the reactive gas and the inert gas are mixed in advance. Therefore, it may be introduced into the sputter chamber from the same gas ejection nozzle.

A plurality of PEMs 341 to 344 for detecting the plasma emission intensity of the sputtering discharge are provided in the vicinity of the target in the sputtering chamber along the width direction. PEM341-344 are connected to the control unit 370.

In order to control the state of sputter film formation in each sputtering chamber, the plasma emission intensity is constantly monitored by PEM, and the gas into the sputtering chamber is based on the emission intensity control value (set point; SP) set in a predetermined range. The introduction amount is feedback controlled. A set point can be set independently for each of a plurality of PEMs provided in the width direction, and a uniform film thickness in the width direction is adjusted by adjusting the balance of the gas flow rate introduced at the position in the width direction corresponding to the PEM. Can form a thin film having.

[Manufacturing method of optical film]
In the present invention, as described above, the multilayer optical thin film is formed on the film substrate by using the roll-to-roll sputtering apparatus provided with the optical measuring unit on the upstream side of the take-up roll. The production method of the present invention is based on a pre-deposition step for setting the film-forming conditions of the thin film formed on the film substrate and the film-forming conditions set in the pre-deposition step, on the film substrate. It has a main film forming step of forming a multilayer optical thin film to obtain an optical film.

In the pre-deposition step, at least one adjustment step is carried out as a sub step. In one adjustment step, the presence or absence of discharge in the sputter chamber to be energized is maintained. After completing one adjustment step, the sputter chamber to be energized is changed and the next adjustment step is carried out. In the present invention, in at least one adjustment step in the preliminary film formation, two or more sputtering chambers are simultaneously energized, and two or more thin films of different materials are sputtered and formed on the film substrate. The optical characteristics of the film substrate on which two or more thin films are sputter-deposited are measured by the optical measuring unit 280 before being wound by the winding roll 291. The film thickness of two or more thin films is calculated based on the optical measurement results, and the film forming conditions in the two or more sputtering film forming chambers are adjusted based on the calculation results.

In this way, in the adjustment step, the film thickness is formed by sputter film formation while conveying the film substrate, and the film thickness is repeated by repeating optical measurement, film thickness calculation, and adjustment of film thickness conditions while the film thickness is continued. Is adjusted within the set range. After performing this adjustment step for all the sputtering chambers and setting the sputtering film formation conditions for the main film formation, the main film formation is performed.

Hereinafter, a method of setting the film forming conditions in the preliminary film formation will be described in more detail with reference to the production example of the antireflection film 100 shown in FIG. _{The antireflection film 100 of FIG. 1 has a SiO x} adhesion improving layer 30 (x <2) having a film _{thickness of 3.5 nm and an Nb 2} O ₅ height of 12 nm on the film substrate 20 by roll-to-roll sputtering. By forming a refractive index layer 51, a SiO ₂ low refractive index layer 52 having _{a film thickness of 28 nm, an Nb 2} O ₅ high refractive index layer 53 having _{a film thickness of 102 nm, and a SiO 2} low refractive index layer 54 having a film thickness of 84 nm in this order. can get.

First, the main film forming process in the method for producing this antireflection film will be described. _{In the sputter chamber 1, the SiO x} adhesion improving layer 30 is formed while introducing argon and oxygen using a Si target. _{In the sputter chamber 2, the Nb 2} O ₅ layer 51 is formed by using the Nb target while introducing argon and oxygen. _{In the sputter chamber 3, the SiO 2} layer 52 is formed by using a Si target while introducing argon and oxygen. In the sputter chambers 4 to 7, the Nb ₂ O ₅ layer 53 is formed by introducing argon and oxygen using the Nb target. Since the Nb ₂ O ₅ layer 53 has a _{larger film thickness than the SiO 2} layer 52 and the Nb ₂ O ₅ layer 51, in the present embodiment, the four sub-thin films 53a, 53b, 53c, in the sputtering chambers 4 to 7, 53d is formed. That is, the Nb ₂ O ₅ layer 53 is a laminated film of sub-thin films 53a, 53b, 53c and 53d formed in four sputtering chambers. Similarly, the SiO ₂ layer 54 is a laminated film of sub-thin films 54a, 54b, 54c, and film formation is performed in three sputtering chambers 8 to 10.

In the pre-deposition step performed before the main film formation, the film formation conditions (deposition conditions of the sputtering chambers 2 to 10) of the four thin films 51 to 54 constituting the antireflection layer 50 are adjusted. The adhesion improving layer 30 formed in the sputter chamber 1 does not necessarily have to adjust the film forming conditions. Therefore, it is not always necessary to form the adhesion improving layer in the preliminary film formation. Table 1 shows a list of the relationship between the layer structure of the thin film in the present embodiment and the sputtering chamber used for forming the film of each sub-thin film. The numbers of the thin films in Table 1 correspond to the reference numerals in FIG. 1, and the numbers of the sputtering chambers in Table 1 correspond to the reference numerals in FIG.

<Conventional pre-deposition method>
First, a conventional pre-deposition method of forming a single-layer thin film and adjusting the film thickness and film formation conditions will be described. FIG. 4 shows the state (presence / absence of energization) of the sputtering chamber at each adjustment step of the film thickness adjusting method in the preliminary film formation of the prior art. The preliminary film formation step of FIG. 4A comprises five substeps of steps S611 to S615. In the adjustment steps S611 to S614, the single-layer thin film is formed and the film forming conditions are adjusted, and in step S615, the film forming conditions of all the thin films are adjusted as necessary.

In the first adjustment step S611, the niobium oxide layer 51 is sputter-deposited on the film substrate by energizing only the sputter chamber 2 while continuously transporting the film substrate at a speed v611. The film thickness of the niobium oxide layer in the laminate in which the niobium oxide layer 51 is formed on the film substrate is calculated based on the measurement result of the optical measuring unit. For example, the reflection spectrum is measured in the optical measurement unit, and the optical film thickness of the niobium oxide layer 51 is calculated based on the peak wavelength of the reflectance. The calculation of the film thickness based on the reflection spectrum utilizes the fact that the thin film having an optical film thickness of nd has a reflectance peak at a wavelength of λ = 2nd / m (m is an integer of 1 or more, n is the refractive index). , D is the physical film thickness).

Even if the film substrate is conveyed at the same transfer rate V as in this film formation to form a niobium oxide thin film with a film thickness of 12 nm (refractive index n = 2.33, optical film thickness 28 nm), the wavelength is higher than 56 nm. The peak of reflectance does not appear at long wavelengths. Therefore, in order to obtain the film thickness of the niobium oxide thin film in the adjustment step S611, 1/8 of the transport speed V of the film substrate in this film formation so that the reflected peak wavelength of the niobium oxide thin film appears in the visible light region. It is necessary to transport the film base material at a transport speed v611 of about or less to increase the film thickness.

When the transport speed v611 in the first adjustment step is 1/8 of the transport speed V in the main film formation, if the film formation conditions are appropriate, the niobium oxide thin film has an optical film thickness of about 224 nm, so that the wavelength is around 448 nm. The peak wavelength of reflectance is observed. If the peak wavelength of reflectance measured by the optical measuring unit is out of this range, the film formation conditions can be adjusted by changing the voltage applied to the target, the amount of oxygen introduced into the sputtering chamber, etc. Will be done. Optical measurement, film thickness calculation (confirmation of reflectance peak wavelength), and adjustment of film formation conditions are repeated, and the film thickness in the entire width direction is within the set range (for example, the reflectance peak wavelength is within ± 15 nm of the set value). When it becomes, the first adjustment step S611 is finished and the energization of the sputter chamber is turned off.

In the second adjustment step S612, while the film substrate is continuously conveyed at a speed v612, the sputtering chamber 3 is energized to sputter-deposit the silicon oxide layer 52, and optical measurement, film thickness calculation, and film-forming conditions. Is repeated until the entire film thickness in the width direction is within the set range. The silicon oxide layer 52 and the niobium oxide layer 51 have different optical film thicknesses. Therefore, in the second adjustment step S612, the silicon oxide layer is formed while transporting the film substrate at a transport speed v612 different from that of the first adjustment step so that the silicon oxide layer has a reflectance peak in the visible light region. The conditions are adjusted.

After the end of the second adjustment step S612, the energization of the sputter chamber 3 is turned off, the sputter chambers 5, 6, 7, and 8 are energized, and the third adjustment step S613 is performed. In the adjustment step S613, the film forming conditions of the sub-thin films 53a, 53b, 53c, and 53d are adjusted until the film thickness of the niobium oxide layer 53 is within the set range while the film substrate is conveyed at the transfer speed v613. ..

It is not possible to calculate the individual film thicknesses of the sub-thin films 53a, 53b, 53c, and 53d only by measuring the reflection peak wavelength. Therefore, in the third adjustment step S613, the film forming conditions of the sputtering chambers 4 to 7 are adjusted at the same time, and the conditions are adjusted so that the total film thickness of the four sub-thin films is within the set range. Alternatively, as in the adjustment step S623 of FIG. 4B, the film formation condition of any one of the sputter chambers 4 to 7 is adjusted, and the other three sputter chambers continue the film formation under a constant condition, whereby the total film thickness is formed. Is adjusted so that is within the set range.

After that, the energization of the sputter chambers 4 to 7 is turned off, the sputter chambers 8 to 10 are energized, and the fourth adjustment step S614 is performed. In the adjustment step S614, the film forming conditions of the sub-thin films 54a, 54b, and 54c are adjusted until the film thickness of the silicon oxide layer 54 is within the set range while the film substrate is conveyed at the transfer speed v614.

As described above, in the adjustment steps S611 to 614, the film forming conditions are adjusted for each of the thin films 51 to 54 made of a single material. After that, in step S615, all of the sputter chambers 1 to 10 are energized, the film substrate is conveyed at the same transfer speed v615 as the transfer speed V in the main film formation, and the reflection made of the multilayer optical thin film is transferred onto the film substrate. Form a protective layer. The reflection spectrum is measured by the optical measuring unit, and if there is a deviation from the set value in the spectrum shape (reflection bottom wavelength) or hue, the film formation conditions are further adjusted to obtain the spectrum of the desired antireflection layer. After confirming, the main film formation for obtaining the product is carried out.

In the modes shown in FIGS. 4A and 4B, the film formation conditions of the single-layer thin film are adjusted in each of the four adjustment steps, and then the film formation conditions of the multilayer optical thin film are adjusted in the fifth adjustment step. In this method, it is necessary to reduce the transport speed of the film substrate in the adjustment step of the preliminary film formation so that the single-layer thin film has the peak wavelength of the reflection spectrum in the visible light region. Further, since the optical film thickness of the single-layer thin film to be adjusted for the film forming conditions differs depending on the adjustment step, it is necessary to change the transport speed of the film substrate for each adjustment step.

In steps S613 and S614 in FIG. 4A (and steps S623 and S624 in FIG. 4B), only the film thickness conditions are adjusted based on the total film thickness of the plurality of sub-thin films, and the film thickness of each sub-thin film is individually adjusted. Is not done. Therefore, it may take a long time to set the conditions for making the film thickness in the width direction uniform. Further, even if the total film thickness of the plurality of sub-thin films is uniform in the width direction, each sub-thin film may have a film thickness distribution in the width direction. If the sub-thin film has a film thickness distribution in the width direction, the film thickness distribution in the width direction may become large due to a slight change in the film formation environment. Therefore, when all the sputtering chambers are energized to form a film, it becomes difficult to correct the film thickness deviation, and it takes time to adjust the conditions in the adjustment step S615 (or S625), or in the main film formation. The film thickness distribution in the width direction becomes large, which may cause defective products with non-standard quality.

As shown in FIG. 4C, if the film formation conditions are adjusted so that the film thickness of each sub-thin film is within a predetermined range in the adjustment steps S631 to S639, the problem of non-uniform film thickness of the sub-thin films can be solved. can. However, in the form shown in FIG. 4C, the number of adjustment steps increases. Further, in order to set the film thickness of the sub-thin film so as to have the reflected peak wavelength in the visible light region, the film is more than the case where a plurality of sub-thin films are formed as a single-layer thin film as shown in FIGS. 4A and 4B. It is necessary to further reduce the transfer speed v631 to v639 of the base material. Therefore, the time required for the preliminary film formation becomes longer, which causes a decrease in productivity.

<Preliminary film formation method of the present invention>
As described above, in the conventional preliminary film formation, the film thickness is adjusted based on the peak (bottom) wavelength of the reflection spectrum of the single-layer thin film. On the other hand, in the present invention, a laminate of thin films of two or more different materials is sputter-deposited on a film substrate, and the film thicknesses of the plurality of thin films are calculated based on the optical measurement results. Based on this calculation result, the film forming conditions of a plurality of thin films are adjusted in one adjustment step.

The dissimilar material is specifically a material having a different refractive index, preferably a film formed from different target materials. For example, niobium oxide (refractive index 2.33) formed using an Nb target and silicon oxide (refractive index 1.46) formed using a Si target are different materials.

FIG. 5 is a flowchart of an example of a method (adjustment step) of adjusting the film forming conditions in the preliminary film formation of the present invention. In this embodiment, each layer is such that the difference between the in-line reflection spectrum of the film substrate on which the m-layer optical thin film (m is an integer of 2 or more) and the target reflection spectrum is within a predetermined range. The film formation conditions are adjusted. Specifically, based on the measurement result of the line of the reflection spectrum, the film thickness d _i of the respective thin film optical thin film composed of m layers _(i is an integer of 1 to m) is calculated by adjusting the deposition conditions by changing the thickness d _i, closer to the reflection spectrum to target line of the reflection spectrum.

As a method of calculating the film thickness of a plurality of thin films based on the reflection spectrum, a known method such as a curve fitting method or a Fourier transform method can be adopted. The curve fitting method is suitable for measuring the film thickness of a multilayer optical thin film including a thin film on the order of nanometers.

In the curve fitting method, _{the difference between the reflection spectrum R (λ) cal} obtained from the optical calculation model and the actually measured reflection spectrum R (λ) obtained by the in-line measurement is obtained as the evaluation function F (R, R _cal ). Iterative calculation is performed by changing the combination of film thicknesses in the optical calculation, and the combination of film thicknesses (d ₁ , d ₂ , ..., _Dm ) that minimizes the evaluation function is output as the calculated film thickness value (measured value). do.

_{As a method of obtaining the reflection spectrum R (λ) cal} of the multilayer optical thin film by the optical calculation model, the thin film interference formula is repeatedly applied to each interface of the thin film, and all the multiple reflected waves are added together; A method of calculating the reflection spectrum by a transfer matrix in consideration of the boundary condition of the Maxwell equation is known. In the present invention, the reflection spectrum may be obtained by any calculation method.

Generally, in the optical calculation model of the multilayer optical thin film, the reflection at the interface between the film substrate 20 and the multilayer optical thin film and the reflection at the surface (air interface) of the multilayer optical thin film are taken into consideration at the time of calculation. Reflection at the air interface on the back surface side (thin film non-forming surface side) is not considered. Therefore, when the film base material 20 is a transparent film such as triacetyl cellulose or polyethylene terephthalate, it is necessary to add the back surface reflected light component of the film base material to the reflectance obtained by the optical calculation of the multilayer optical thin film. .. The back surface reflected light component R _b is represented by the following formula.

上記式において、Ｔ_ｆｆは基材裏面における透過率、Ｔ_ｉは基材の内部透過率、Ｒ_０は基材裏面と空気との界面における反射率、Ｒ_{ｒｅｍｅｎ}は基材と多層光学薄膜との界面における反射率である。

In the above formula, T _ff the transmittance at the substrate rear surface, T _i is the internal transmittance of the substrate, R ₀ is reflectance at the interface between the substrate back surface and the air, R _REMEN the substrate and the multilayer optical thin film The reflectance at the interface.

When adjusting the film formation conditions of each layer, first, the target reflection spectrum R (λ) _int is obtained by an optical calculation model (S10, S11). _{In calculating the target reflection spectrum, the set value Di} and the refractive index n (λ) _i of the film thickness of each of the thin films of the m layer are used. If the material is known, the refractive index n (λ) is known, so for each thin film, n (λ) _i stored in the database may be read. Instead of calculating the target spectrum R _{(λ) int} the thickness of the set value _{D i,} may calculate the set value _{D i} of thickness by optical calculation from the known R _{(λ) int.}

(Calculation of film thickness from reflection spectrum)
The film formation conditions of each layer are adjusted so that the actually measured reflection spectrum obtained by the in-line measurement approaches the target spectrum obtained by the optical calculation model. By evaluating the difference between the measured value of the film thickness and the target value for each of the plurality of thin films, the film forming conditions of the plurality of thin films can be efficiently adjusted. The measured value of the film thickness here refers to a value calculated by an optical calculation model of the film thickness of each layer from the actually measured reflection spectrum obtained by the in-line measurement.

First, the initial calculation spectrum calculated by optical calculation from an arbitrary film thickness of each layer is set. In the present embodiment, the target reflectance spectrum R _{(λ) int} calculated from each of the set thickness _{D i,} is used as an initial calculation spectrum (S12).

The difference between the actually measured reflection spectrum R (λ) obtained by the in-line measurement and the reflection spectrum R (λ) _cal obtained by optical calculation is calculated as the evaluation function F (R, R _cal ) (S23). The evaluation function is calculated as, for example, the distance between the actually measured spectrum R (λ) and the calculated spectrum R (λ) _{cal by optical calculation.} The distance between the two spectra is determined by dividing the evaluation wavelength range into M wavelength regions and calculating _{the reflectance R (λ k ) of the measured spectrum in each wavelength region λ k} (k is an integer of 1 to M). It can be calculated by obtaining the sum of squares of the difference from the reflectance R (λ _k ) _{cal of the calculated spectrum.}

In addition, there may be a difference between the measured value and the calculated value of the reflectance due to the in-line optical measurement environment and other factors. Therefore, when calculating the evaluation function, the sum of squares may be used by subtracting the predetermined correction function β (λ) from the simple difference between _{R (λ) and R (λ) cal as shown in the following equation.}

In the optical calculation, the reflection spectrum R (λ) _cal may be obtained in consideration of the correction function. The evaluation function is not limited to the above, and any function can be used as long as it can determine the magnitude of the difference between the two spectra. It should be adopted.

After calculating the evaluation function based on the reflection spectrum R (λ) _cal by optical calculation and the actually measured reflection spectrum, the film thickness _di and cal are changed (S26), and based on the _{changed film thickness di and cal,} The reflection spectrum R (λ) _cal is recalculated (S27). _{The evaluation function F (R, R cal} ) is calculated based on the recalculated reflection spectrum R (λ) _cal and the actually measured reflection spectrum R (λ). Contrast with the evaluation function of. Based on the amount of change in the evaluation function, determines the thickness _{d i, cal} amount of change [Delta] d _i, the thickness _{d i,} change the _cal (S26), the thickness _{d i} of the _changed based on the _cal, reflecting The spectrum R (λ) _cal is recalculated (S27). This is repeated, and when it is determined that the evaluation function F (R, R _cal ) has converged, the calculation ends.

The method for calculating the film thickness is not limited to the above, and the film thickness may be calculated using a general-purpose optical simulation program or a film thickness calculation program.

(Adjustment of film formation conditions)
Thickness of the thin film, which is calculated based on the reflection spectrum of the in-line measurement d _i, and outputs the _cal as film measured value d _i of the thickness of the i layer (S30). The measured value d _i of the thickness of each layer, calculates a difference between the thickness D _i of each layer corresponding to the target reflectance spectrum _{R (λ) int (S31)} , if the difference is within the allowable range, the i The film thickness conditions (PEM set point, voltage, etc.) of the layer are stored as the film thickness conditions for the main film formation (S40), and the adjustment is completed. Instead of using the difference in film thickness as a criterion for determining the end of adjustment, the difference between the actually measured reflection spectrum R (λ) obtained by in-line measurement and the target spectrum R (λ) _int may be used as the criterion. The difference in the reflection spectrum may be evaluated based on, for example, the above-mentioned evaluation function.

If the difference between the set thickness D _i and the thickness d _i (or differences in reflection spectrum) is out of range, by changing the film forming conditions, to adjust the film thickness. The adjustment is repeated until the difference in film thickness (or the difference in reflection spectrum) of each layer after changing the film forming conditions is within the permissible range. In order to eliminate the variation in the film thickness in the width direction, the film thickness distribution may be adjusted at the plurality of locations in the width direction in consideration of the film thickness distribution obtained from the measurement results of the reflection spectra at the plurality of locations in the width direction.

The operator may manually adjust these film forming conditions, or the film forming conditions may be adjusted by automatic adjustment. For example, when adopting PEM control that adjusts the amount of reactive gas introduced so that the emission intensity of a plurality of plasma emission monitors 341 to 344 provided along the width direction is within a predetermined range, the measured value and the set value ( The film formation conditions are adjusted by changing the PEM control value (set point; SP) so that the difference from the target value) becomes small.

As described above, in the method of the present invention, by individually calculating the film thicknesses of the plurality of thin films constituting the multilayer thin film, the film thickness conditions of the plurality of thin films can be adjusted at the same time in one adjustment step. The number of adjustment steps in film formation can be reduced. By reducing the number of adjustment steps, not only the time required for adjusting the film forming conditions can be shortened, but also the time required for switching the adjustment steps can be shortened. In particular, in sputter film formation, the discharge tends to become unstable immediately after the start of energization, and it is necessary to wait for the film thickness measurement and the adjustment of the film formation conditions until the discharge stabilizes. As the number of adjustment steps is reduced, the number of times the energization is turned on and off in each sputter chamber during pre-deposition is also reduced, so that the reduction in the number of adjustment steps greatly contributes to shortening the pre-deposition time. Further, in the method of the present invention, the film forming conditions are adjusted so that the measured spectrum and the film thickness approach the target value by using the optical measurement data such as the reflection spectrum, so that the variation in the optical characteristics can be reduced. It's easy.

<Specific example of adjustment step>
FIG. 6 is a diagram for explaining an embodiment of the preliminary film formation in the present invention, and shows the state of each sputter chamber in the adjustment step. In the embodiment shown in FIG. 6A, in one adjustment step S101, all the sputtering chambers are energized, and all the film forming conditions of the four thin films constituting the antireflection layer are adjusted. In the adjustment step S101, while continuously transporting the film base material at a speed v101, all of the sputter chambers 1 to 10 are energized, and the adhesion improving layer 30, niobium oxide layer 51, and silicon oxide are placed on the film base material. Five film thicknesses of the layer 52, the niobium oxide layer 53, and the silicon oxide layer 54 are formed. The optical measuring unit measures the reflection spectrum of the laminate in which the multilayer optical thin film is formed on the film substrate, and based on the reflectance spectrum, the four-layer thin films 51 to 54 constituting the antireflection layer 50 are formed. The thickness of each of the above is calculated.

The film thickness of the thin films 51, 52, 53, 54 calculated from the reflection spectrum is compared with the set value of the film thickness, and the film formation conditions of the sputtering chamber corresponding to the thin film having the difference in film thickness are adjusted. Therefore, the film thickness conditions of all the thin films can be adjusted in one adjustment step. At this time, by measuring the reflection spectrum at a plurality of points in the width direction and adjusting the SP of the PEM at a plurality of points in the width direction according to the film thickness distribution, the film thickness distribution in the width direction is reduced and the uniformity is achieved. Can be improved.

The transport speed v101 of the film base material in the adjustment step S101 may be the same as or different from the transport speed V of the film base material in the present film formation. When the two are different, the set value of the film thickness in the adjustment step may be determined according to the transport speed ratio (V / v101).

After the adjustment of the film forming conditions is completed, the main film forming for product acquisition is carried out. If the transport speed v101 of the film base material in the pre-film formation adjustment step S101 is different from the transport speed V in the main film formation, the transport speed of the film base material is changed after the adjustment of the film formation conditions is completed. The membrane may be started. After changing the transport speed, the reflection spectrum of the optical film (antireflection film) may be confirmed, and if necessary, the film formation conditions may be finely adjusted before the main film formation (product acquisition) may be started.

In the embodiment shown in FIG. 6A, the sputter chamber 1 is energized to form the adhesion improving layer at the time of the preliminary film formation, but as in the embodiment shown in FIG. 6B, the adhesion is formed in the preliminary film formation. It is not necessary to form the property improving layer. Further, as in the embodiment shown in FIG. 6C, the adhesion improving layer is not formed in the adjustment steps S121 to S126 of the preliminary film formation, and in step S127 before the start of the main film formation after adjusting the film formation conditions in the adjustment step. An adhesion improving layer may be formed.

The film base material used for the preliminary film formation may be the same as or different from the film base material used for the main film formation. When the same film base material is used for the preliminary film formation and the main film formation, the main film formation can be performed following the preliminary film formation while maintaining the energization of the sputter chamber, so that the production efficiency can be improved. When different film substrates are used for the preliminary film formation and the main film formation, after adjusting the film formation conditions in the adjustment step S101, the film substrate is switched to the main film formation and the energization is restarted to perform the main film formation. Just do it.

FIG. 6B is a diagram relating to another embodiment of the preliminary film formation. In the embodiment shown in FIG. 6B, the number of sputter chambers to be energized is increased for each adjustment step, and the film formation conditions of the sputter chambers newly started to be energized are adjusted to change the film formation conditions of all the sputter chambers. Set individually.

First, in the adjustment step S111, the sputtering chambers 2, 3 and 4 are energized, the film forming conditions of the niobium oxide layer 51 in the sputtering chamber 2, the film forming conditions of the silicon oxide layer 52 in the sputtering chamber 3, and the sputtering chamber 4. The film forming conditions of the niobium oxide layer 53a in the above are adjusted. The niobium oxide layer 51 and the niobium oxide layer 53a have the same refractive index, but since a silicon oxide layer 52 having a different refractive index is formed between them, these 3 are based on the in-line reflection spectrum measurement results. The thickness of one thin film can be calculated individually.

The film thicknesses of the thin films 51, 52, and 53a calculated from the reflection spectrum are compared with the set value of the film thickness, and the film forming conditions of the sputtering chamber corresponding to the thin film in which the film thickness is deviated are adjusted. When the film thicknesses of the plurality of thin films in the thin films 51, 52 and 53a deviate from the set values, the film forming conditions of the plurality of sputtering chambers corresponding to these may be adjusted at the same time. After the film formation conditions have been set, the film formation conditions in another sputtering chamber may be adjusted. The transport speed v111 of the film base material in the adjustment step S111 may be the same as or different from the transport speed V of the film base material in the present film formation.

The optical film thickness of the niobium oxide layer 51 (2.33 × 12 = 28 nm), the optical film thickness of the silicon oxide layer 52 (1.46 × 28 = 41 nm), and the optical film thickness of the niobium sub-thin film 53a (2.33 ×). Since the total of 102/4 = 59 nm) is 128 nm, neither the single-layer film nor the laminated film can be calculated from the peak wavelength of the visible light reflection spectrum.

On the other hand, if the film thickness is calculated from the waveform of the spectrum (the function of the reflectance with respect to the wavelength), the film thicknesses of a plurality of thin films are formed even when the peak wavelength or the bottom wavelength does not exist in the measurement wavelength region (visible light region). Can be calculated individually. Therefore, in the method of the present invention, the film base material may be conveyed at the same transfer speed v111 as the transfer speed V of the film substrate in the present film formation in the adjustment step S111. Even when the transfer speed v111 in the adjustment step S111 is different from the transfer speed V in the main film formation, it is not necessary to consider the peak wavelength of the reflection spectrum and the like. Therefore, in the method of the present invention, the substrate transfer speed in the preliminary film formation is selected. The degree of freedom is high.

After adjusting the film forming conditions of the sputtering chambers 2, 3 and 4 in the adjustment step S111, in the adjustment step S112, the energization of the sputtering chamber 5 is started while maintaining the energization of these sputtering chambers. In the adjustment step S112, the film forming conditions of the niobium oxide layer 53b in the sputter chamber 5 newly started to be energized are adjusted.

The in-line reflection spectrum measurement calculates the film thicknesses of the niobium oxide layer 51, the silicon oxide layer 52, and the niobium oxide layer (a laminated film of the sub-thin film 53a and the sub-thin film 53b). In the film thickness measurement based on the reflection spectrum, the film thickness of the niobium oxide layer (the total film thickness of the sub-thin films 53a and 53b) is calculated, and the film thickness of the sub-thin films 53b cannot be obtained individually. On the other hand, in the previous adjustment step S111, the film thickness of the niobium oxide layer 51, the silicon oxide layer 52, and the niobium sub-thin film 53a oxide is adjusted so that the film thickness becomes a set value. The thickness is known. Since the film thickness of the niobium sub-thin film 53a is known, the film thickness of the niobium oxide thin film 53b can be calculated from the difference between the film thickness of the niobium oxide layer and the film thickness of the sub-thin film 53a.

In this way, the film formation conditions of the thin film whose film formation conditions were adjusted in the previous adjustment step are fixed, and the film thickness measurement of the newly started thin film and the adjustment of the film formation conditions are performed. As a result, the film forming conditions of the plurality of sub-thin films 53a and 53b can be individually adjusted, and the film thickness in the width direction can be made uniform not only for the total film thickness of the laminated films but also for each sub-thin film.

The transport speed v112 of the film base material in the adjustment step S112 may be the same as or different from the transport speed v111 of the film base material in the previous adjustment step S111. Since the film thickness value in the previous adjustment step can be used as it is and the change in the film forming environment due to the change in the transfer speed can be suppressed, the transfer speeds v111 and v112 of the film substrate in the adjustment steps S111 and S112 are the same. Is preferable. It is preferable that the transport speeds v113 to v116 in the adjustment steps S113 to S116 performed after the adjustment step S112 are also the same as v111 and v112.

In the adjustment step S113, the energization of the sputter chamber 6 is newly started while the energization of the sputter chambers 2 to 5 is maintained, and the film forming conditions of the niobium oxide layer 53c are adjusted.

In the adjustment step S114, the energization of the sputter chambers 7 and 8 is newly started while the energization of the sputter chambers 2 to 6 is maintained, and the film forming conditions of the niobium oxide layer 53d and the silicon oxide layer 54a are adjusted. After that, in the adjustment steps S115 and S116, energization of the sputtering chamber 9 and the sputtering chamber 10 is started, and the film forming conditions of the silicon oxide layers (sub-thin films) 54b and 54c are adjusted.

As described above, in the present embodiment, the film forming conditions of the nine sputter chambers can be individually adjusted by six adjustment steps. By individually adjusting the film thickness of each sub-thin film, it is possible to form a multilayer optical thin film having excellent film thickness uniformity. In the prior art, in order to individually adjust the film forming conditions of the nine sputter chambers, nine adjustment steps, which are the same as the number of sputter chambers, are required as shown in FIG. 4C. On the other hand, in the method of the present invention, since the film forming conditions of a plurality of thin films are adjusted in one adjustment step, the number of adjustment steps in the preliminary film formation can be reduced.

In the present invention, it is sufficient that the film forming conditions of the plurality of thin films are adjusted in any one of the adjustment steps in the preliminary film formation, and the film forming conditions of the plurality of thin films can be adjusted in all the adjusting steps. Not always necessary. For example, as in steps S112, S113, and S115 of FIG. 6B, a step of adjusting the film thickness of one thin film may be included.

After adjusting the film forming conditions of all the sputter chambers, in step S117, the film substrate is conveyed at the same transfer rate V as in the main film formation, and the reflected light is deviated from the set values (design values) of the spectral shape and hue. Check for the presence of. If there is a discrepancy between the set value and the measured value, further adjust the film forming conditions, confirm that the desired antireflection layer spectrum can be obtained, and then form the adhesion improving layer. The sputter chamber 1 is energized to carry out the main film formation for obtaining a product.

In the embodiment shown in FIG. 6B, energization of the sputtering chamber to be adjusted for film formation conditions is started in the next adjustment step while maintaining energization of the sputtering chamber after adjusting the film forming conditions in the previous adjustment step. In another embodiment, the adjustment step is performed in a state where the energization of the sputtering chamber after adjusting the film forming conditions is turned off and only the sputtering chamber for which the film forming conditions are adjusted is energized.

For example, in the embodiment shown in FIG. 6C, in the first adjustment step S121, the sputtering chambers 2 to 4 to be adjusted are energized to adjust the film forming conditions of these sputtering chambers. In the next adjustment step S122, the energization of the sputter chambers 2 to 4 is turned off, and only the sputter chamber 5 is energized to adjust the film forming conditions. In the subsequent adjustment step S123, only the sputter chamber 6 is energized to adjust the film forming conditions. In the adjustment step S124, the film formation conditions are adjusted by inheriting the sputtering chambers 7 and 8, and in the adjustment steps S125 and S126, the sputtering chambers 9 and 10 are energized to adjust the film formation conditions, respectively.

In this way, after individually adjusting the film forming conditions of the nine sputter chambers by the six adjustment steps, in step S127, the film substrate is conveyed at the same transfer rate V as the main film formation, and the sputter chambers 1 to 1 10 is energized, and the presence or absence of deviation from the set value (design value) of the spectral shape and hue of the reflected light is confirmed. If there is a discrepancy between the set value and the measured value, further adjust the film formation conditions, confirm that the desired antireflection layer spectrum can be obtained, and then perform the main film formation to obtain the product. do.

In this embodiment, in the adjustment steps S121 to S126, since the sputtering chamber that is not the object of adjusting the film formation condition (film thickness) is not energized, the consumption of the target material in the preliminary film formation can be reduced. On the other hand, as in the embodiment shown in FIG. 6B, if the next adjustment step is performed while maintaining the energization of the sputtering chamber after adjusting the film forming conditions in the previous adjustment step, the stable state of the sputtering discharge can be maintained. .. Further, since step S117 of the embodiment shown in FIG. 6B is continuously performed with the adjustment step S116 before that, the discharge state and the distribution of the gas concentration are stable. Therefore, the film thickness is less likely to deviate, and the time required for final adjustment of the film thickness conditions can be shortened, leading to improvement in production efficiency.

In FIGS. 6B and 6C, energization is started in order from the sputtering chamber on the upstream side to adjust the sputtering conditions, but the adjustment order is not particularly limited. For example, as in the adjustment steps S131 to S136 of the embodiment shown in FIG. 6D, the film forming conditions may be adjusted in order from the sputtering chamber on the downstream side.

In the embodiment shown in FIGS. 6B, 6C and 6D, the film forming conditions of the nine sputter chambers are individually adjusted by six adjustment steps, but the number of adjustment steps can be further reduced. .. Specifically, the number of adjustment steps can be reduced to the maximum number of sub-thin films contained in one thin film. In the embodiment of the antireflection film 100 shown in FIG. 1 (Table 1), the niobium oxide layer 53 contains four sub-thin films, which is the maximum number of sub-thin films contained in one thin film. Therefore, it is possible to reduce the number of adjustment steps in the preliminary film formation for producing this antireflection film to four.

FIG. 7A shows an example of an embodiment in which the film forming conditions of the nine sputter chambers are individually adjusted by four adjustment steps. In this embodiment, each of the four adjustment steps S141 to 144 is assigned to the adjustment of the film forming conditions of the sputtering chambers 7 to 10 for forming the four sub-thin films 53a, 53b, 534c, 53d. As described above, by assigning the adjustment steps S141 to S141 to the adjustment of the film forming conditions of each sub-thin film of the niobium oxide layer 53 including the largest number of sub-thin films, the number of adjustment steps can be reduced.

The adjustment of the film forming conditions of the sputtering chamber for forming the thin film other than the niobium oxide layer 53 can be appropriately assigned. In the embodiment shown in FIG. 7A, the film forming conditions of the four sputter chambers 2, 3, 4, and 8 are adjusted in the first adjustment step S141, whereas in the embodiment shown in FIG. 7B, the first adjustment step is performed. In S151, the film forming conditions of the three sputter chambers 2, 3 and 4 are adjusted, and the number of sputter chambers adjusted in one adjustment step is reduced. In this way, by dispersing the sputtering chambers to be adjusted in a plurality of adjustment steps and reducing the number of sputtering chambers to be adjusted in one adjustment step, the complexity of adjustment can be reduced.

In the embodiment shown in FIGS. 7A and 7B, the film forming conditions of the niobium oxide layer 51 and the silicon oxide layer 52 in the sputtering chamber 2 and the sputtering chamber 3 are adjusted in the first adjustment step, whereas the embodiment shown in FIG. 7C is shown. As in the embodiment, the film forming conditions of the niobium oxide layer 51 and the film forming conditions of the silicon oxide layer 52 may be adjusted in two different adjustment steps.

As described above, in the present invention, the film thicknesses of the plurality of thin films are calculated based on the waveform of the reflection spectrum (the function of the reflectance with respect to the wavelength), and the film forming conditions of the plurality of sputter chambers are adjusted based on the calculation. .. Therefore, the number of adjustment steps in the preliminary film formation can be reduced and the production efficiency can be improved as compared with the case where the film thickness of the single-layer thin film is calculated based on the peak wavelength of the reflection spectrum. Further, since the film forming conditions in the preliminary film forming step are adjusted based on the waveform of the reflection spectrum, more precise adjustment is possible, and a multilayer optical thin film having a small film thickness distribution can be formed.

In this film formation, the film formation is carried out with the film formation conditions obtained in the preliminary film formation as the initial conditions, and the film formation conditions are readjusted as necessary while the reflection spectrum is measured by the optical measuring unit. If the film formation conditions are adjusted so that the film thickness of each sub-thin film becomes uniform in the preliminary film formation, it is easy to adjust the film formation conditions even if the reflectance is distributed in the width direction. .. Therefore, a high-quality antireflection film having excellent reflectance and uniformity of reflected light hue can be obtained.

A typical application of the antireflection film is a polarizing plate with an antireflection layer having an antireflection layer on the surface of the polarizing plate. The polarizing plate has a structure in which transparent films are laminated on both sides of the polarizing element, and the polarizing plate with an antireflection layer includes an antireflection layer on the surface of the transparent film laminated on the visible side of the polarizing element.

As a method for producing such a polarizing plate with an antireflection layer, a method of forming an antireflection layer on the surface of a polarizing plate in which a transparent film is laminated on the surface of a polarizing element, and a transparent method in which an antireflection layer is formed on the surface. A method of laminating a film with a polarizer to form a polarizing plate can be mentioned.

<Base film used for preliminary film formation>
Since the polarizing plate is more expensive than a single transparent film, if a polarizing plate is used as the film base material for the preliminary film formation, the cost increase due to the loss of the base material during the preliminary film formation becomes remarkable. Therefore, when the antireflection layer is formed on the surface of the polarizing plate in the present film formation, it is preferable to perform the preliminary film formation using another film base material.

As described above, from the viewpoint of improving productivity, it is preferable to use the same film base material for the preliminary film formation and the main film formation. Therefore, from the viewpoint of reducing the manufacturing cost and improving the productivity, an antireflection film is produced by forming an antireflection layer on the transparent film, and the antireflection film and the polarizing plate are bonded to each other to form a polarizing plate with an antireflection layer. Is preferred. Further, when sputter film formation is carried out on a polarizing plate, the polarizer may be deteriorated due to exposure to a high temperature environment or high output plasma. Therefore, from the viewpoint of suppressing deterioration of the polarizer, it is preferable to carry out sputter film formation on the transparent film substrate in both the preliminary film formation and the main film formation.

On the other hand, when a transparent film base material is used, it is necessary to consider the _{back surface reflected light component R b in the measurement of the reflection spectrum as described above.} Generally, the antireflection film is designed so that the visible light reflectance of the antireflection layer forming surface is 1% or less, whereas the antireflection film is visible on the back surface side of the transparent film (the interface between the transparent film and air). The light reflectance is about 4%. Therefore, most of the reflected light detected by the in-line optical measurement becomes the reflected light from the back surface, and it becomes difficult to accurately evaluate the reflected spectrum on the thin film forming surface. Along with this, the film thickness measurement accuracy of the thin film at the time of preliminary film formation may decrease, and the film thickness conditions may not be adjusted appropriately.

Therefore, when forming a thin film on a transparent film, it is preferable to form a film base material so that the influence of backside reflection can be eliminated in both the preliminary film formation and the main film formation. For example, backside reflection can be reduced by laminating a light-scattering member that scatters visible light or a light-absorbing member that absorbs visible light on the back surface side (thin film non-forming surface side) of the transparent film.

The light absorbing member preferably has a visible light transmittance of 40% or less, and examples thereof include a black film. Examples of the light scattering member include a diffusion adhesive layer having a haze of 40% or more. Above all, it is preferable to eliminate the influence of backside reflection by detachably attaching the light absorbing film to the back side of the transparent film via the adhesive layer.

By attaching a light-absorbing film having a visible light transmittance of 40% or less, the back surface reflectance can be reduced to less than 1%. As the material of the light absorbing film, polyesters, cellulose-based polymers, acrylic-based polymers, styrene-based polymers, amide-based polymers, polyolefins, cyclic polyolefins, polycarbonates and the like are used. A light-absorbing film can be obtained by adding a black pigment such as carbon black to these resin materials or by providing a colored layer with black ink or the like on the surface of the base film. From the viewpoint of handleability of the film substrate during sputter film formation, the thickness of the light absorbing film is preferably 5 μm to 200 μm, more preferably 10 μm to 130 μm, and even more preferably 15 μm to 110 μm.

In order to detachably attach the light-absorbing film to the back surface side of the transparent film, it is preferable to attach the two to each other via an adhesive. As the pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, or the like can be used. Of these, an acrylic pressure-sensitive adhesive containing an acrylic polymer as a main component is preferably used.

By using a laminated film base material in which a light-absorbing film with low visible light transmittance is laminated on the back surface of the transparent film, _{the influence of the back-reflective light component R b} is ignored, and the reflection spectrum is measured and the film based on the light-absorbing spectrum is measured. Since the thickness can be calculated, the accuracy of adjusting the film forming conditions in the preliminary film formation can be improved. Further, by using this laminated film base material in both the preliminary film formation and the main film formation, the preliminary film formation and the main film formation can be continuously performed without replacing the film base material, so that the antireflection film is used. It is possible to improve the productivity of optical films such as.

The light-absorbing film is peeled off from the antireflection film (a laminate of a transparent film on which an antireflection layer is formed and a light-absorbing film) obtained by this film formation, and the transparent film and a polarizing element are bonded together. As a result, a polarizing plate with an antireflection layer can be obtained.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

A black PET film (1300 mm width) having a thickness of 100 μm, a visible light transmittance of 0.01%, and a refractive index of 1.65 was set on the unwinding roll of the roll-to-roll sputtering apparatus, and the adjustment steps S151 to S154 shown in FIG. 7B were carried out. Then, the film forming conditions of the antireflection layer were adjusted. The transport speed of the base material in the adjustment steps S151 to S154 was 0.7 m / min.

A Si target was used for film formation of silicon oxide, and an Nb target was used for film formation of niobium oxide. Each thin film was formed by PEM control at four points in the width direction while introducing argon and oxygen into the sputtering chamber.

The in-line reflection spectrum was measured at 23 points in the width direction, and the film thickness at 23 points in the width direction was calculated based on the obtained reflection spectrum, so that the film thickness was uniform in the width direction. The set value (SP) of the emission intensity was changed. The calculation of the film thickness and the change of SP were repeated until the film thickness distribution in the width direction became within the allowable range. The reflection spectra at 23 locations in the width direction before and after adjusting the film forming conditions in the adjustment steps S151 to S154 are shown in FIGS. 8 to 11. In FIGS. 8 to 11, the left side is the reflection spectrum before adjustment, and the right side is the reflection spectrum after adjustment.

In the first adjustment step S151 (FIG. 8), the peak wavelength does not appear in the reflection spectrum. Therefore, in the method of adjusting the film forming conditions based on the peak wavelength of the reflectance, it is necessary to change the transfer speed of the base material so that the peak of the reflectance appears. On the other hand, in this embodiment, the film thickness is measured based on the waveform of the reflection spectrum, and the film formation conditions are adjusted based on the film thickness. It can be seen that the variation in the reflection spectrum in the width direction can be significantly reduced without changing.

In step S152 (FIG. 9), the minimum reflectance was confirmed in the vicinity of the wavelength of 480 nm in the reflection spectra of all 23 locations in the width direction before the film formation conditions were adjusted. In the method of adjusting the film forming conditions based on the peak wavelength of the reflectance, no further condition adjustment is performed when the minimum peak wavelengths are aligned. On the other hand, in this embodiment in which the film thickness is measured based on the waveform of the reflection spectrum, the reflection having a wavelength longer than 500 nm is reflected while maintaining the minimum peak wavelength (around 480 nm) by adjusting the film forming conditions. The variation in the width direction of the rate is reduced. It can be seen that also in step 153 (FIG. 10) and step 154 (FIG. 11), the waveform of the reflection spectrum is approximated by more precise adjustment of the film forming conditions than the adjustment based on the peak wavelength.

In FIG. 12, after adjusting the film forming conditions (FIG. 11) in the preliminary film forming adjustment step S154, the transfer rate of the substrate is set to the same substrate transfer rate (1.4 m / min) as in the main film formation. It is a reflection spectrum changed and measured at 23 points in the width direction. It can be seen that there is almost no variation in the reflection spectrum in the width direction, the uniformity of the reflected light characteristics is high, and a high-quality antireflection layer is obtained. Further, after the adjustment of the film forming conditions of each sputter chamber in the adjustment step is completed, only the transfer speed is changed, and the film forming is continuously performed without adjusting the film forming conditions. , The desired reflection spectrum has been obtained. From this result, it can be seen that the production method of the present invention can reduce the number of adjustment steps in the preliminary film formation and improve the productivity of the antireflection film.

20 Film base material 30 Adhesion improvement layer 50 Multilayer optical thin film (antireflection layer)
51, 52, 53, 54 Thin film 100 Anti-reflection film 1-10 Sputtering chamber 221,222 Film formation roll 251-260 Cone 290 Optical measuring unit 310 Reactive gas introduction tube 320 Inert gas introduction tube 31 to 314 Mass flow controller 319, 329 Gas ejection nozzle 341-344 Plasma emission monitor (PEM)

Claims (14)

A multilayer optical thin film composed of a plurality of thin films is formed on the film base material while continuously transporting the film base material in a sputter film forming apparatus provided with a plurality of sputter chambers along the transport direction of the film base material. This is a method for manufacturing optical films.
The sputtering film forming apparatus includes an optical measuring unit for measuring the optical characteristics of a laminate in which a thin film is formed on a film substrate.
After performing a preliminary film formation in which the film forming conditions are adjusted while forming a thin film on the film substrate in the sputter film forming apparatus, the main film forming for forming the multilayer optical thin film on the film substrate is performed.
In the preliminary film formation, the film thickness of the thin film is calculated from the optical characteristics obtained by the optical measuring unit while forming at least one thin film on the film substrate, and the film thickness is formed based on the calculation result of the film thickness. The adjustment step of adjusting the conditions is performed at least once.
At least once in the adjustment step
By energizing a plurality of sputtering chambers at the same time, a laminate of thin films of two or more different materials is formed on the film substrate.
The thickness of a plurality of thin films is calculated from the optical characteristics obtained by the optical measuring unit, and until the optical characteristics obtained by the optical measuring unit or the thicknesses of the plurality of thin films calculated from the optical characteristics are within a predetermined range. , The film formation conditions of each thin film are adjusted.
A method for manufacturing an optical film. At least one of the plurality of thin films constituting the multilayer optical thin film is a laminated film of a plurality of sub-thin films formed in two or more sputtering chambers.
In the pre-deposition, the adjustment step is performed at least twice.
The method for producing an optical film according to claim 1, wherein the film forming conditions of the plurality of sub-thin films are adjusted in different adjustment steps. In the adjustment step, the optical measuring unit measures the reflection spectrum of the laminate in which the thin film is formed on the film substrate.
The method for producing an optical film according to claim 1 or 2, wherein the film thicknesses of the plurality of thin films are calculated from the reflection spectrum at least once in the adjustment step. In the adjustment step, the film thickness conditions of the respective thin films are adjusted based on the measured values of the film thicknesses of the plurality of thin films calculated from the reflection spectra.
The method for producing an optical film according to claim 3, wherein the film forming conditions of each thin film are adjusted until the measured values of the film thicknesses of the plurality of thin films are within a predetermined range. In the adjustment step, the film thickness conditions of the respective thin films are adjusted based on the measured values of the film thicknesses of the plurality of thin films calculated from the reflection spectra.
The optical according to claim 3, wherein the film forming conditions of each thin film are adjusted until the difference between the reflection spectrum obtained by the measurement by the optical measuring unit and the target reflection spectrum is within a predetermined range. Film manufacturing method. In the pre-deposition, the adjustment step is performed at least twice.
The method for producing an optical film according to any one of claims 1 to 5, wherein the transport speed of the film substrate in the plurality of adjustment steps is the same. In the adjustment step, the optical measuring unit measures the optical characteristics at a plurality of locations in the width direction, and the film thickness at the plurality of locations in the width direction is calculated from the obtained optical characteristics.
The method for producing an optical film according to any one of claims 1 to 6, wherein the film thickness distribution in the width direction of the thin film is reduced by adjusting the film forming conditions at a plurality of locations in the width direction. The sputtering film forming apparatus is provided with a plasma emission monitor for detecting the plasma emission intensity of the sputtering film forming in the sputtering chamber.
The method for producing an optical film according to any one of claims 1 to 7, wherein the flow rate of the gas introduced into the sputtering chamber is adjusted so that the plasma emission intensity detected by the plasma emission monitor is within the set range. .. The sputtering film forming apparatus is provided with the plasma emission monitors at a plurality of locations along the width direction in the sputtering chamber.
Multiple plasma emission monitors can set plasma emission intensity settings independently.
The method for manufacturing an optical film according to claim 8, wherein the flow rate of the gas introduced at the corresponding width direction is adjusted so that the emission intensity detected by each plasma emission monitor is within the set range. The method for producing an optical film according to claim 8 or 9, wherein the film forming conditions in the adjustment step are adjusted by changing the set value of the plasma emission intensity of the plasma emission monitor. In at least one of the preliminary film formation and the main film formation, a laminate in which a light absorbing member is detachably attached to a thin film non-forming surface side of a transparent film as a film base material via an adhesive layer. The method for producing an optical film according to any one of claims 1 to 10, wherein is used. The method for producing an optical film according to any one of claims 1 to 11, wherein the same film base material is used for the preliminary film formation and the main film formation. The method for producing an optical film according to claim 12, wherein after the pre-deposition, the main film formation is continuously carried out in a state where the energization of the sputter chamber is continued. The method for producing an optical film according to any one of claims 1 to 13, wherein the multilayer optical thin film is an antireflection layer composed of a plurality of oxide thin films.

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