JP5262612B2 - Moisture content measuring method and moisture content measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture content measuring method suitable for measuring accurately the amount of moisture included in a resin film F under conveyance in a processing device applying a processing onto the surface of the resin film F. <P>SOLUTION: This moisture content measuring device 50 includes an irradiation part 80 for irradiating measuring light L1 having a first wavelength and reference light L2 having a second wavelength onto the resin film F, and a light receiving part 90 for receiving the measuring light L1 and the reference light K2 transmitted through the resin film F. The moisture content measuring device 50 also includes a reflecting mirror unit 60 for allowing transmission through the resin film F, of the measuring light L1 and the reference light L2 irradiated onto the resin film F; and a computing unit 100 for operating the amount of moisture included in the resin film F based on absorbances of both the measuring light L1 and the reference light L2 received by the light receiving part 90. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a moisture content measuring method and a moisture content measuring device for measuring the amount of moisture contained in a resin film.

  The long resin film has flexibility (flexibility) and can be easily processed, and thus is widely used in the industrial fields such as electronic parts, optical parts, and packaging materials. An example of a resin film used in the industry is a polyimide film. A polyimide film is a material having electrical insulation and heat resistance, and is widely used in the electrical and electronic fields for flexible printed wiring boards, COF (Chip on Film), TAB tape, and the like. Rolled polyimide film is a flexible printed circuit board in which a thin film of metal such as chrome or copper is vacuum-deposited using a vacuum film-formation device and then subjected to processing such as chemical etching to form a wiring pattern. , COF, TAB tape, etc.

  By the way, since polyimide has an affinity for water, there is a problem that dimensional change due to moisture absorption cannot be ignored when a polyimide film that has absorbed moisture is applied to a fine wiring or the like. Moisture-absorbing polyimide film causes moisture to evaporate by heating, such as when mounting gold-tin eutectic bonds, causing the so-called popcorn phenomenon, creating pinholes in metal thin films and reducing connection reliability. There is also. The polyimide film that has absorbed moisture also has a problem that voids are generated in the sealing plate resin and the reliability is lowered. In addition, there may be a problem in the long-term reliability of adhesion between the moisture-absorbed polyimide film and the metal. As a technique for improving these reliability, a technique for removing moisture from a moisture-absorbed polyimide film is known (for example, see Patent Document 1).

  However, Patent Document 1 discloses a technique for removing moisture from a moisture-absorbed polyimide film, but does not disclose a technique for measuring how much the polyimide film has absorbed moisture. Moreover, the polyimide film wound in a roll shape not only has a different moisture content in the roll-shaped outer portion and the inner portion, but also the moisture content of the entire polyimide film wound in a roll shape varies depending on the season. Therefore, in order to control the moisture absorption state of the polyimide film, it is necessary to measure the moisture content of the polyimide film. It is possible to measure the moisture content of the atmosphere by measuring the atmosphere of a drying apparatus, which is an example of a treatment apparatus for treating a polyimide film, with a quadrupole mass spectrometer. However, this measurement is a measurement of the moisture content of the atmosphere in the drying apparatus, and does not measure the moisture content of the polyimide film itself. In addition, it is possible to measure the moisture content of the polyimide film by chemical analysis or thermal analysis, but in this measurement the analysis result cannot be obtained unless the polyimide film is destroyed, and the analysis result can be timely transferred to the drying conditions ( There is a problem that cannot be fed back quickly). Since the moisture content of the polyimide film cannot be measured in a timely manner by a processing device such as a drying device or a vacuum film-forming device, a metal thin film may be vacuum-deposited on a polyimide film that is insufficiently dried. There is a risk that the reliability of COF, TAB tape, etc. may be reduced. For this reason, the problem of the yield reduction of an electronic component may arise.

A technique that utilizes infrared absorption of water molecules is known as a method for measuring the moisture content of a sample in a non-destructive manner in response to the above-described problem (see, for example, Patent Document 2). Patent Document 2 discloses an invention of an infrared moisture measuring device that utilizes reflection of infrared rays irradiated on a sample. However, this measuring device is not suitable for moisture measurement of a sample that transmits light like a polyimide film. Furthermore, it is difficult to install a known infrared moisture measuring device in a processing apparatus for processing the surface of a polyimide film, such as a vacuum film forming apparatus or a vacuum drying apparatus, due to restrictions on dimensions and the like. When the amount of moisture contained in the polyimide film in the processing apparatus is measured with an infrared moisture measuring device, it is measured through a viewing window. In this case, since it is difficult to adjust the optical path of infrared rays, the water content cannot be measured with high accuracy. In addition, when the amount of moisture contained in the film is small, the absorption intensity becomes low, the resolution becomes less than the resolution, and the problem that it becomes difficult to determine the absorption peak due to the influence of interference due to multiple reflection in the film occurs. The prior art cannot avoid this problem.
JP-A-5-106021 Japanese Patent Laid-Open No. 9-250982

  In view of the above circumstances, the present invention provides a moisture content measuring method and moisture suitable for accurately measuring the amount of trace moisture contained in a resin film that is being transported through a treatment apparatus that treats the surface of the resin film. An object is to provide a quantity measuring device.

In order to achieve the above object, the moisture content measuring method of the present invention comprises measuring light that is infrared light having a first wavelength absorbed by water molecules and infrared light having a second wavelength that is not absorbed by water molecules. A moisture content measuring method for irradiating a resin film with a certain reference light and measuring the amount of moisture contained in the resin film,
The measurement light and the reference light are passed through substantially the same optical path, irradiated and transmitted to the resin film in transit, and then reflected by the reflecting mirror and irradiated again and transmitted through the resin film a plurality of times. In this case, in order to reduce the interference caused by reflection near the absorption peak wavelength of the first wavelength of the measurement light, the measurement light is transmitted through the resin film a plurality of times with different angles of incidence. The transmittance of each wavelength after including the absorption peak of the first wavelength and within the wavelength range of twice or more of the half-value width after the measurement light and the reference light are transmitted through the resin film a plurality of times. The incident angle is determined so that the sum of squared deviations of
The amount of moisture contained in the resin film is measured based on the absorbance of both the measurement light and the reference light transmitted through the resin film.

Furthermore,
The pre-Symbol measurement light and the reference light, by way of the irradiation reflected cylinder mirror is formed on the inner wall surface irradiating the resin film,
The measurement light and the reference light that have been transmitted through the resin film may be received through a light-receiving reflection tube having a mirror formed on the inner wall surface.

Furthermore,
Spectrally pre Symbol the measurement light and the reference light to the resin film was finished transmitting, even by measuring the amount of water contained in the said resin film on the basis of the spectral was the measurement light and the reference light both absorbance Good.

Furthermore,
Before SL give absorbance intensity of the both measuring light and the reference light has finished passing through the resin film by Fourier transform, on the basis of the absorbance, the resin film may measure the amount of moisture contained.

In order to achieve the above object, the water content measuring apparatus of the present invention includes a measuring light that is infrared light having a first wavelength absorbed by water molecules and an infrared light having a second wavelength that is not absorbed by water molecules. A moisture measuring device that irradiates a resin film with a reference light that is light and measures the amount of moisture contained in the resin film,
Irradiation means for irradiating the resin film being conveyed through the measurement light and the reference light through substantially the same optical path;
A mirror unit that transmits the measurement light and the reference light through the resin film a plurality of times through substantially the same optical path;
A light receiving means for receiving the measurement light and the reference light transmitted through the resin film;
Calculating means for calculating the amount of moisture contained in the resin film based on the absorbance of both the measurement light and the reference light received by the light receiving means;
The mirror unit includes a plurality of reflecting mirrors that repeat a plurality of times that the measurement light and the reference light that are irradiated and transmitted through the resin film are reflected, and the resin film is irradiated and transmitted again. Is arranged so that all the incident angles of the measurement light to the resin film are different from each other, and in order to reduce interference due to reflection near the absorption peak wavelength of the first wavelength of the measurement light, the measurement light of the measurement light The square of the deviation of the transmittance of each wavelength after including the absorption peak of the first wavelength and within the wavelength range of twice or more of the half-value width after the measurement light and the reference light are transmitted through the resin film a plurality of times The incident angle is arranged so that the sum becomes a minimum value .

Furthermore,
Before Symbol the measurement light and the reference light irradiated from the irradiation means passes before reaching the resin film, and irradiating the reflective cylinder mirror is formed on the inner wall surface,
Pass before the resin film the measurement light and the reference light has finished transmitting a reaches the light receiving means may be a light receiving reflecting cylinder mirror is formed on the inner wall surface.

Furthermore,
Before Symbol receiving means, it disperses the measurement light and the reference light received may be one to obtain the spectral and the measurement light and the intensity of the reference light both have.

Furthermore,
The intensity of the measuring light and the reference light both obtained in the previous SL light receiving means to a Fourier transform comprises a Fourier transform means for obtaining the absorbance of the resin film,
Before SL calculating means, on the basis of the absorbance, the resin film may be one that calculates the amount of moisture contained.

  Examples of the resin film used in the present invention include a polyimide film, a polyamide film, a polyester film, a polytetrafluoroethylene film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a liquid crystal polymer film. . In addition to the resin film, the present invention can be applied to a glass epoxy substrate, other resin boards, and the like. The present invention can be applied regardless of whether the resin film is conveyed by roll-to-roll or a single wafer type.

  The first wavelength absorbed by water molecules refers to the wavelength region of electromagnetic waves having energy equivalent to the energy for water molecules to vibrate. However, the rate at which the measurement light having the first wavelength is absorbed depends on the amount of water molecules. The second wavelength that is not absorbed by water molecules refers to a wavelength region of electromagnetic waves having energy different from energy for molecular vibration of water molecules. However, the reference light having the second wavelength is not completely absorbed by water molecules, but is slightly absorbed.

  The optical path in which the measurement light and the reference light are substantially the same means that the measurement is the same to the extent that no error occurs in the measurement of the moisture content, and includes exactly the same, but is not limited thereto.

  Here, the full width at half maximum refers to a wavelength (wave number) range at an absorbance that is 1/2 of the absorbance peak. The reason why the absorption peak is included in the wavelength range that determines the incident angle is to eliminate interference of the measurement light near the absorption peak on the resin film. The wavelength range is preferably not less than 2 times the half width of the absorption peak and not more than 4 times. The reason for defining the wavelength range is that it is impossible to specify absorption when the wavelength range is narrow, and it is difficult to suppress interference over a wide range.

  According to the present invention, since the moisture amount is measured by irradiating and transmitting the measurement light and the reference light to the resin film F through substantially the same optical path, the light is not reflected on the resin film. Therefore, the moisture content of the resin film can be accurately measured. Further, even if the resin film is being transported, the moisture content can be detected by transmitting the measurement light and the reference light through the resin film, so that the moisture content contained in the resin film being transported can be accurately measured. Therefore, conventionally, due to dimensional restrictions in the processing apparatus such as a vacuum film forming apparatus, the moisture absorption state (moisture content) of the resin film (for example, polyimide film) in the processing apparatus could not be accurately measured. By attaching the moisture content measuring device of the present invention to a vacuum film forming device or the like, the moisture content of the resin film can be measured, and the moisture content of the polyimide film or the like can be accurately known. As a result, it becomes possible to ensure the reliability of the flexible printed circuit board.

  The present invention has been realized in a moisture content measuring method for measuring the amount of moisture contained in a resin film being conveyed.

  With reference to FIG. 1, the roll-to-roll vacuum film-forming apparatus to which an example of the moisture content measuring apparatus of this invention was attached is demonstrated. FIG. 1 is a front view schematically showing a roll-to-roll vacuum film forming apparatus to which an example of the moisture content measuring apparatus of the present invention is attached.

The vacuum processing apparatus 10 includes a rectangular parallelepiped decompression container 12 in which most of the components are stored. The decompression vessel 12 may be cylindrical and may have any shape as long as the decompression vessel 12 can maintain a decompressed state in a range of 10 ⁻⁴ Pa to 1 Pa. The vacuum processing apparatus 10 is for heat-drying a long resin film F in a vacuum container 12 and subsequently performing sputtering film formation. When a polyimide film is used as the resin film F, the polyimide film adsorbs (absorbs) water (moisture), and thus a component for removing water by heat drying is required. In addition, a moisture amount measuring device 50 that measures the amount of moisture contained in the resin film F is attached to the vacuum processing apparatus 10. The components of the vacuum processing apparatus 10 including these components will be described.

  The vacuum processing apparatus 10 includes components (members) such as various rolls arranged inside the decompression vessel 12, and a resin film F (polyimide film here) before processing (before film formation) is an unwinding roll. 14 is wound into a roll. The resin film F drawn out from the unwinding roll 14 is subjected to various processes while being conveyed in the arrow X direction (conveyance direction, delivery direction). The unwinding roll 14 is a roll having a driving force (a driving roll and connected to a driving source such as a motor). Following the unwinding roll 14, from the upstream side in the transport direction of the resin film F. In order, a pair of heaters 16 for heating and drying the resin film F, the first guide roll 18, the mirror unit 60, which is one part of the moisture content measuring device 50, and the second guide roll 20 are arranged. The first guide roll 18 and the second guide roll 20 are driven rollers for guiding the resin film F in the arrow X direction, do not have a driving force, and rotate by friction with the resin film F being conveyed.

  When the resin film F passes through the space between the pair of heaters 16 in the conveyance path of the resin film F, the resin film F is dried by heating, and thereby moisture absorbed by the resin film F is removed. As will be described later, when the resin film F from which moisture has been removed passes through the mirror unit 60, the amount of moisture contained therein is measured. A can roll 22 is disposed downstream of the second guide roll 20 in the transport direction. The resin film F is guided by the second guide roll 20 and is conveyed while being cooled by contacting the outer peripheral surface of the can roll 22 with a predetermined pressure. Three sputtering cathodes 24, 26, and 28 are arranged facing the portion of the outer peripheral surface of the can roll 22 that is in contact with the resin film F. A predetermined thin film is formed on the surface of the resin film F by the sputtering cathodes 24, 26 and 28.

  A coolant such as water or an organic solvent circulates inside the can roll 22 to cool the resin film F during sputtering. The can roll 22 is a drive roller that includes a rotary joint (not shown) and also has power. The conveyance speed of the resin film F is determined by the rotation speed of the unwinding roll 14, the can roll 22, and a winding roll 34 described later. The sputtering cathodes 24, 26, and 28 are of a magnetron type and include a sputtering target. The material of the sputtering target is appropriately selected according to the film to be formed on the long resin film F. The resin film F that has passed through the can roll 22 is guided by the third guide roll 30 and the fourth guide roll 32 and is taken up by the take-up roll 34 having a driving force.

  With reference to FIG. 2, the moisture content measuring method of the present invention will be described. FIG. 2A is a schematic diagram illustrating an example of a measurement method in which the measurement light and the reference light are transmitted through the resin film F only once. FIG. 2B is a schematic view illustrating the measurement light and the reference light through the resin film F a plurality of times. It is a schematic diagram which shows an example of the measuring method which permeate | transmits (six times in a figure).

  In the present invention, measurement light having a first wavelength that is absorbed by water molecules and reference light having a second wavelength that is not absorbed by water molecules are applied to an apparatus such as a vacuum film forming apparatus or a drying apparatus (for example, the vacuum processing apparatus 10). ), The resin film F being conveyed is irradiated and transmitted, and the amount of moisture contained in the resin film F is measured based on the absorbance of both the measurement light and the reference light that have been transmitted through the resin film F. Is the method. Specifically, the measurement light L1 and the reference light L2 irradiated from the irradiation unit 80 (which is an example of the irradiation means according to the present invention) pass through the resin film F via the substantially same optical path LW, and pass through the resin film F. The intensity of both the measurement light L1 and the reference light L2 that are guided to the light receiving unit 90 (which is an example of a light receiving unit in the present invention) and received by the light receiving unit 90 are measured. The optical paths LW of the measurement light L1 and the reference light L2 are the same (substantially the same). According to the moisture content measurement method of the present embodiment, the absorbance of the resin film F is measured based on the intensity of the measurement light L1 received by the light receiving unit 90 and the reference light L2 (the intensity is calculated as the absorbance). There is no contact with the resin film F, and the resin film F is not destroyed. Further, the incident angle when the measurement light L1 and the reference light L2 are incident on the resin film F is preferably in the range of 0 ° to 80 ° (0 ° to 80 °). The absorbance of the resin film F = −log (transmittance of the resin film F), that is, in the moisture content measuring apparatus of the present invention, the absorbance of the resin film F = −log (received by the light receiving unit 90 when there is a resin film). Intensity / intensity received by the light receiving unit 90 when there is no resin film).

  When set as described above, the measurement light L1 and the reference light L2 irradiated on the resin film F follow the same optical path LW and enter the resin film F at an incident angle within a range of 0 ° to 80 ° and transmit therethrough. Then, the light is guided to the light receiving unit 90 and the intensity thereof is measured. Since the optical paths of the measurement light L1 and the reference light L2 are the same, the influence of the difference (difference) between these optical paths LW on the measurement light L1 and the reference light L2 can be eliminated. Moreover, the reason for setting the incident angle to the resin film F within the range of 0 ° to 80 ° is that when the incident angle exceeds 80 °, the transmittance is lowered and the measurement sensitivity is lowered. In addition, an incident angle means the angle which the normal line of the resin film F, the measurement light L1, and the reference light L2 comprise.

  In the example shown in FIG. 2A, the measurement light L1 and the reference light L2 are transmitted only once through the resin film F, and the measurement light L1 and the reference light K2 irradiated from the irradiation unit 80 are converted into the mirror unit 60. Is reflected by the reflecting mirror 62 and irradiated onto the resin film F. The measurement light L1 and the reference light L2 are reflected by the reflecting mirror 62 so as to be incident on the resin film F within an incident angle range of 0 ° to 80 °. 2A, the reflecting mirror 62 is used. However, depending on the position of the irradiation unit 80, an incident angle of 0 ° to 80 ° can be realized without the reflecting mirror 62. That is, the resin is adjusted so that the measurement light L1 and the reference light L2 are within the range of incident angles of 0 ° to 80 ° by appropriately selecting either the adjustment or selection of the attachment position of the irradiation unit 80 or the reflecting mirror 62. The film F may be irradiated. The measurement light L1 and the reference light L2 that have passed through the resin film F are reflected by the reflecting mirror 64 and guided to the light receiving unit 90.

  In the example shown in FIG. 2B, the measurement light L1 and the reference light L2 are transmitted through the resin film F six times. The measurement light L1 and the reference light L2 emitted from the irradiation unit 80 are transmitted through the resin film F (first transmission), reflected by the reflecting mirror 66, and transmitted through the resin film F again (second transmission). And reflected by the reflecting mirror 68, transmitted again through the resin film F (third transmission), reflected by the reflecting mirror 70, transmitted again through the resin film F (fourth transmission), and reflected by the reflecting mirror 72. Then, the resin film F is transmitted again (fifth transmission) and reflected by the reflecting mirror 74, and the resin film F is transmitted again (sixth transmission) and guided to the light receiving unit 90. Even in the case where the light is transmitted a plurality of times in this way, the reflecting mirrors 66, 68, 70, 72, 74 so that the measurement light L1 and the reference light L2 are incident on the resin film within an incident angle range of 0 ° to 80 °. Place. In the above example, the number of times of transmission through the resin film F is six, but it may be less or more, and the number of transmission is appropriately determined according to the material of the resin film F and the like. The reflecting mirrors 62, 64, 66, 68, 70, 72, 74 are configured such that a glass plate is coated with a metal film, and the measurement light and the reference light are reflected by the metal film. As the metal film, a metal film such as gold having a high reflectance in the infrared region is preferable. The reflecting mirrors 66, 68, 70, 72, and 74 are made by, for example, coating an aluminum film on a glass plate, and the measurement light L1 and the reference light L2 are reflected by the aluminum film. The reflecting mirrors 62, 64, 66, 68, 70, 72, and 74 may be plane mirrors or concave mirrors, and can be appropriately selected in terms of the design of the optical path LW of the measurement light L1 and the reference light L2. In the schematic diagram of the optical path LW in FIGS. 2A and 2B, plane mirrors are used as the reflecting mirrors 62, 64, 66, 68, 70, 72, and 74. However, the concave mirror can be formed by appropriately designing the optical path. It may be used.

  When the measurement light L1 and the reference light L2 are transmitted through the resin film F a plurality of times (repeatedly transmitted) as in the example of FIG. 2B, even if the amount of moisture contained in the resin film F is very small, Since the absorption amount of the first wavelength by water molecules can be amplified, measurement sensitivity can be improved. Furthermore, it is possible to detect a minute amount of moisture by increasing the moisture absorption intensity by transmitting the film a number of times and reducing the interference due to the multiple reflection within the film by optimizing the incident angle a number of times.

  Examples of the measurement light L1 include infrared light having a first wavelength that changes the absorbance of the resin film F by being absorbed by water molecules. The first wavelength is a wavelength that is characteristically absorbed by water molecules. When using a polyimide film as the resin film F, when using a light source within a wavelength range of 1800 nm to 2000 nm, the wavelength (first wavelength) of the measurement light L1 can be 1910 nm. Further, when a light source in the wavelength range of 2600 nm to 3300 nm is used, the measurement light L1 having a wavelength (first wavelength) of 2740 nm or 2870 nm can be obtained.

  Examples of the reference light L2 include infrared light having a wavelength that is not absorbed by water molecules and does not substantially change the absorbance of the resin film F. When a polyimide film is used for the resin film F, the wavelength that the polyimide film absorbs characteristically can be obtained without characteristically absorbing water molecules. When a light source having a wavelength in the range of 2600 nm to 3300 nm is used, the reference light L2 having a wavelength (second wavelength) of 3250 nm can be obtained. The wavelength 3250 nm is a characteristic absorption wavelength of polyimide, and hardly changes with moisture contained in the polyimide film.

  By measuring the intensities of the measurement light L1 and the reference light L2 received by the light receiving unit 90 and calculating the difference or ratio of the absorbance between them, it is possible to know the change in absorbance due to water contained in the polyimide film. . The above difference or ratio of absorbance can be appropriately selected according to the calculation of the water content. In particular, the transmittance is calculated from the intensities of the measurement light L1 and the reference light L2, and the absorbance of the measurement light L1 = −log (the transmittance of the measurement light L1) and the absorbance of the reference light L2 = −log (reference light L2). ) (Absorbance of the measurement light L1−background at the first wavelength of the measurement light L1) / (absorbance of the reference light L2−background of the second wavelength of the reference light L2) ) To calculate the amount of water. The transmittance of the wavelength λ is transmittance (λ) = the intensity of the wavelength λ received by the light receiving unit 90 when there is a resin film / the intensity of the wavelength λ received by the light receiving unit 90 when there is no resin film. . Furthermore, the background refers to a flat portion that appears in the immediate vicinity of a certain wavelength peak in the absorbance spectrum. By calculating the ratio of the absorbance of the measurement light L1 and the reference light L2, it is possible to compensate for variations in the optical path through which the measurement light L1 and the reference light L2 pass. For example, when the moisture content is measured while transporting the resin film F by the roll-to-roll method, the resin film F is set in the apparatus by calculating the ratio of the intensity of the measurement light L1 and the reference light L2. This eliminates the need for fine adjustment of the optical path of the reflecting mirror and correction of deterioration of the light source.

  If the optical path LW of the schematic diagram shown in FIG. 2 is used, the moisture content of the resin film F can be measured only by the measurement light L1. However, as described above, when the difference or ratio between the absorbances of the measurement light L1 and the reference light L2 is not obtained, fine adjustment of the optical path LW or the light source may be necessary, and the measurement result of the moisture amount becomes unstable. .

  The irradiation unit and the light receiving unit will be described with reference to FIGS. 3 and 4. FIG. 3 is a side view showing a schematic configuration of the irradiating unit and the light receiving unit, and is a view of the irradiating unit, the light receiving unit, and the mirror unit from the direction of arrow A in FIG. FIG. 4 is a block diagram showing a calculator that calculates the amount of water based on the intensity of the measurement light and the reference light. In FIG. 3, the resin film F is conveyed from the front side to the back side of the paper surface (that is, the direction from the front side to the back side of the paper surface in FIG. 3 is the direction of arrow A in FIG. 1). In FIG. 3 and FIG. 4, the same components as those shown in FIG. 1 and FIG.

  The water content measuring device 50 for measuring the amount of water contained in the resin film F being conveyed (passing through) the inside of the mirror unit 60 incorporated in the vacuum processing apparatus 10 (see FIG. 1) is the first wavelength. Irradiating unit 80 for irradiating the resin film F with the measurement light L1 having the above and the reference light L2 having the second wavelength, and the light reception by which the measurement light L1 and the reference light K2 having been transmitted through the resin film F are received. Part 90. In addition, the moisture content measuring device 50 includes a mirror unit 60 that transmits the measurement light L1 and the reference light L2 irradiated to the resin film F to the resin film F, and both the measurement light L1 and the reference light L2 received by the light receiving unit 90. A computing unit 100 (which is an example of computing means in the present invention) that computes the amount of moisture contained in the resin film F based on the strength is provided. On the side wall of the mirror unit 60, an opening 61 for introducing the resin film F being conveyed and an opening (not shown) are formed.

  The measurement light L1 and the reflected light L2 irradiated from the light source 82 of the irradiation unit 80 enter the mirror unit 60 through the irradiation reflector 86 described later, and as described with reference to FIG. F is transmitted through and reflected by the reflecting mirror 66, transmitted through the resin film F again, reflected by the reflecting mirror 68, transmitted through the resin film F again, reflected by the reflecting mirror 70, and transmitted through the resin film F again. Reflected by the reflecting mirror 72, transmitted again through the resin film F and reflected by the reflecting mirror 74, transmitted through the resin film F again, exits the mirror unit 60, passes through a light receiving reflecting cylinder 92, which will be described later, and receives the light receiving unit 90. Led to.

  Inside the mirror unit 60, the reflecting mirrors 66, 68, 70, 72, and 74 are arranged so that the measurement light L1 and the reflected light L2 have the same optical path. Further, in the roll-to-roll vacuum film forming apparatus 10, the atmosphere in the mirror unit 60 is maintained in a reduced pressure state of less than 1 Pa. On the other hand, the irradiation unit 80, the light receiving unit 90, the irradiation reflecting tube 86, and the light receiving reflecting tube 92 are arranged under normal pressure. Although the inside of the roll-to-roll vacuum film forming apparatus 10 is kept in a reduced pressure state, the atmospheric pressure inside the mirror unit 60 can be appropriately selected according to the use situation.

  An irradiation window 88 through which the measurement light L1 from the light source 82 and the reference light L2 pass is attached to the irradiation unit 80. The irradiation window 88 corresponds to the entrance of the irradiation reflector 86 and is arranged at the boundary between the main body of the irradiation unit 80 and the irradiation reflector 86. The inside of the irradiation unit 80 appropriately guides the measurement light L1 and the reference light L2 from the light source 82 to the irradiation window 88 by a known mirror or the like (not shown). The light source 82 may be a single light source that can emit the measurement light L1 and the reference light L2, or may be a dedicated light source for the measurement light L1 and the reference light L2. That is, for the light source 82, for example, a light source that emits light having a continuous wavelength in a wavelength range of 1800 nm to 2000 nm or a wavelength range of 2600 nm to 3300 nm, or the measurement light L1 and the reference light L2 can be separate light sources. When the measurement light L1 and the reference light L2 are emitted as a continuous light from one light source, or when the measurement light L1 and the reference light L2 are simultaneously emitted by separate light sources, as will be described later, the light receiving unit 90 has an inside. A spectroscopic unit may be arranged, or the interferometer 84 may be arranged inside the irradiation unit 80. In this case, the measurement light L1 and the reference light L2 can be optically separated.

The measurement light L1 and the reference light L2 emitted from the irradiation unit 80 pass through the entrance-side window 60a of the mirror unit 60, pass through the exit-side window 60b of the mirror unit 60 and the light-receiving window 94 via the mirror unit 60. To reach the light receiving unit 90. The irradiation window 88, the entrance side window 60a of the mirror unit 60, the exit side window 60b, and the light receiving window 94 are all made of optical calcium fluoride (CaF ₂ ). The light receiving unit 90 includes a known mirror (not shown) that guides the received measurement light L1 and reference light L2 to the detector 96, and a detector 96 (not shown) that detects the intensity of the measurement light L1 and the reference light L2. Z) and are arranged.

  The irradiation reflecting tube 86 and the light receiving reflecting tube 92 will be described.

  A gap (space) may be formed between the roll-to-roll vacuum film forming apparatus 10 and the irradiation unit 80 and the light receiving unit 90 due to restrictions such as the size of each device. In this case, the gap passes through the gap. The measurement light L1 and the reference light L2 are attenuated by scattering or diffusion. By disposing the irradiation reflecting tube 86 and the light receiving reflecting tube 92 in the gap, the measurement light L1 and the reference light L2 between the irradiation unit 80 and the mirror unit 60 and between the mirror unit 60 and the light receiving unit 90 are transmitted. Attenuation due to scattering and diffusion can be suppressed. In order to improve the measurement sensitivity, it is desirable to provide an irradiation reflecting tube 86 and a light receiving reflecting tube 92. Irradiation reflecting tube 86 and light receiving reflecting tube 92 may be of any shape as long as all of the inner wall surface is formed of a mirror, and may be a cylinder or a tube having a square or hexagonal cross section. The mirror surface can be formed by known electropolishing.

  An optical fiber may be used instead of the irradiation reflecting tube 86 and the light receiving reflecting tube 92. When using an optical fiber, a chalcogenite-based optical fiber is used. However, since the wavelength region of the chalcogenite-based optical fiber is limited, it is necessary to pay attention to the selection of the wavelengths of the measurement light L1 and the reference light L2, and depending on the selected wavelength, measurement is possible. In some cases, improvement in accuracy cannot be expected. When considering the precautions of wavelength selection when using an optical fiber, the use of the anti-irradiation reflecting tube 86 and the light receiving reflecting tube 92 increases the degree of freedom in wavelength selection and leads to improved measurement accuracy.

  The configuration of the light receiving unit 90 will be described.

  The light receiving unit 90 may include a spectroscopic unit (not shown) that separates the measurement light and the reference light transmitted through the resin film F a plurality of times for each wavelength by spectroscopy. As the spectroscopic means, a known spectroscopic means such as a prism or a diffraction grating can be used. Furthermore, the optical path guided from the light receiving window 94 to the detector 96 may be provided with known optical means such as a slit or a mirror. Instead of the interferometer 84 of the irradiation unit 80, a so-called dispersive spectrophotometer may be configured by a light receiving unit provided with spectroscopic means. By using the mirror unit 60 which is a feature of the present embodiment, it is possible to measure the moisture content of the resin film with high accuracy using the irradiation unit and the light receiving unit of a commercially available spectrophotometer.

  Further, in order to separate the measurement light L1 and the reference light L2 from the infrared component emitted from the resin film F, so-called chopping may be performed. Specifically, the detector 96 includes means for periodically and mechanically shielding the measurement light L1 and the reference light L2, and performs signal processing for synchronizing the light shielding period, the intensity of the measurement light L1, and the intensity of the reference light L2. Do. In order to synchronize both signals, a known electrical signal converting means can be used.

  A method for obtaining the absorbance of the resin film F from the intensities of the measurement light L1 and the reference light L2 detected by the detector 96 (a method calculated by Fourier transforming the detected intensity) will be described.

  As shown in FIG. 4, the irradiation unit 80 includes an interferometer 84 that interferes with the light emitted from the light source 82, and the light receiving unit 90 includes a detector 96 that detects the intensity of the light transmitted through the resin film F. The absorbance of the resin film F may be measured by a Fourier transformer 98 that Fourier-transforms the intensity detected by the detector 96 and the interferogram obtained from the interferometer 84. A commercially available Fourier transform spectrophotometer irradiation unit 80, a mirror unit 60 instead of the sample chamber, a light receiving unit 90, a Fourier transformer 98, and the like constitute a moisture content measuring apparatus. That is, the moisture content of the resin film F is measured with high accuracy by using an irradiation part and a light receiving part of a commercially available Fourier spectrophotometer (for example, a Fourier transform infrared spectrophotometer, hereinafter referred to as FT-IR). be able to. The Fourier transformer 98 is composed of an electronic computer, and a known one can be used. As the interferometer 84, a known interferometer such as a Michelson interferometer can be used. Further, in the case of performing Fourier transform, the infrared component emitted from the resin film F itself does not change during the measurement time (about 1 second) and becomes a direct current component in the detector 96 and is removed by Fourier transform. This chopping process becomes unnecessary.

  Calculation of the amount of moisture contained in the resin film F will be described.

  As described above, the moisture content of the resin film F is calculated based on the difference or ratio in absorbance calculated from the intensities of the measurement light L1 and the reference light L2. If a calibration curve for the absorbance of a resin film with a known moisture content is obtained, the moisture content can be calculated from the absorbance of the resin film with an unknown moisture content by referring to this calibration curve. A calibration curve may be created for each type (including brand) and thickness of the resin film. If the water content measuring apparatus 50 includes an electronic computer (for example, the water content calculator 102 shown in FIG. 4), a calibration curve is stored in the electronic computer, and the water content is calculated from the obtained absorbance. A program should be organized. Of course, a calibration curve is created for each type of resin film, but it is also desirable to create a calibration curve for each brand. This is because, for example, in polyimide films, the degree of polymerization may differ among film manufacturers, and the chart of absorption wavelengths may differ.

  The background correction of the water content measuring device 50 will be described.

  When the resin film F is not set in the mirror unit 60 (the resin film F is not allowed to pass), the background measurement of the moisture content measuring device 50 is possible. The background measurement result may be stored in an electronic computer (water content calculator 102) or the like to correct the absorbance.

  Interference due to reflection in the resin film F will be described.

The light incident on the resin film F is partially reflected into the resin film F when it exits the surface of the resin film F. This reflection is generated many times in the resin film F, and as a result, the transmitted light is a combination of light having one transmission in the resin film F, three lights, and five lights. Interference due to the superposition of light occurs and the intensity of the light increases or decreases. As a result, the absorbance of the resin film F has a peak and valley depending on the light wavelength. If these peaks and valleys coincide with the absorption wavelength of a trace amount of water, the measured value is affected. If the resin film F is transmitted only once, this interference cannot be removed. However, if the resin film F is transmitted many times, the interference can be reduced although it is within a limited wavelength range. It becomes possible. In addition to the refractive index and thickness of the resin film F, the wavelength of the peaks and valleys due to interference depends on the incident angle. Even if the incident angle changes with each transmission, the wavelength-dependent peaks and valleys due to superposition can be reduced. This is due to the fact that the optical path length in the resin film F changes depending on the incident angle, and as a result, the wavelength dependence of the valleys changes. Utilizing this, the position of the peaks and valleys of interference in each transmission is changed by changing the incident angle when transmitting the resin film F a plurality of times, and as a result, the height of the peaks and valleys in the transmission a plurality of times is reduced. Can do.
The outline of the calculation is described below. The electrolysis E incident on the resin film F is reflected many times in the resin film F, and the transmitted electric field strength E ′ is given by the following equation.

ここに、ｎ＝樹脂フィルムＦ内の多重反射の回数、λ＝光の空気中における波長、δ＝２π２ｄｃｏｓβｍ／λ、α＝膜伝播中の減衰係数＝ｅｘｐ（−ａ ｄ／ｃｏｓβ） ａ＝吸収係数（ｃｍ−１） ｐ＝空気から樹脂フィルムＦへの透過係数 、ｑ＝樹脂フィルムＦから空気への透過係数、ｒ＝樹脂フィルムＦから空気への反射係数、ｄ＝薄膜の厚さ、ｍ＝薄膜の屈折率、θ＝入射角、β＝反射角 （ ｓｉｎβ＝ｓｉｎθ／ｍ）である。

Here, n = number of multiple reflections in the resin film F, λ = wavelength of light in air, δ = 2π2 dcos βm / λ, α = attenuation coefficient during film propagation = exp (−ad / cosβ) a = absorption Coefficient (cm-1) p = Transmission coefficient from air to resin film F, q = Transmission coefficient from resin film F to air, r = Reflection coefficient from resin film F to air, d = Thickness of thin film, m = Refractive index of thin film, θ = incident angle, β = reflection angle (sin β = sin θ / m).

The transmittance or absorbance of the resin film F once transmitted can be calculated from the equation (1), and the value is defined as f (θi, λ). Absorbance F in the case of multiple transmissions of resin film F is given as a function of incident angle θi and wavelength λ.
F (λ) = Σf (θi, λ) i = 1, 2,... Number of transmissions The incident angle θi in each transmission is determined by the angle of the reflecting mirror in FIG. Therefore, the λ dependency of F (λ) can be reduced by appropriately selecting the angle of the reflecting mirror. Actually, since the wavelength (λ) dependence cannot be eliminated at all wavelengths, the reflector angle should be set so as to reduce the wavelength (λ) dependence around the wavelength to be measured, that is, the absorption of water molecules. Set (that is, set θi). In actual calculation, an optimum value of the angle of the reflecting mirror is obtained within the device designable range so that the sum of squared deviations transmitted at each wavelength a plurality of times in the designated wavelength range is minimized. That is, it is only necessary to obtain θi so that the sum of deviation squares of the two absorbances is minimized for each wavelength λx in the designated wavelength range. As a result, the angle of the other reflector can be defined by designating the angle (incident angle) of any one reflector.
In summary, the effect of interference can be reduced by allowing the resin film F to pass through a plurality of times as compared with a single pass, and the absorption by moisture can be increased, so that the moisture content can be increased with high sensitivity. It becomes possible to measure. In the case where the wavelength of the resin film F itself is not affected by the moisture is 3195 cm ⁻¹ (3129 nm), the wavelength absorbed by the moisture is 3597 cm ⁻¹ (2780 nm), and the resin film F is transmitted six times, interference occurs at a wavelength near the moisture absorption. FIG. 8 shows an example in which the conditions for reducing the above are simulated. FIG. 8 shows an angle of the reflecting mirror that does not consider interference, that is, a normal angle (as shown in FIG. 3, the reflecting mirror angle is 22.5 ° with respect to the resin film F surface, the reflecting mirror 66 is 22.5 °. 68, 70, 72 are 0 ° and the reflecting mirror 74 is 22.5 °), and the condition where the interference is the smallest in the vicinity of the absorption by moisture (the angle of the reflecting mirror is the above-mentioned normal). With respect to the angle, the reflecting mirror 66 is 22.5 ° + 1.1 °, the reflecting mirror 68 is 0 ° -1.4 °, the reflecting mirror 70 is 0 ° + 0.7 °, and the reflecting mirror 72 is 0 ° + 1. .3 ° and the reflection mirror 74 is 22.5 ° + 5.7 °).

  Of course, the moisture content measuring apparatus 50 of the present embodiment can be attached to a roll-to-roll drying apparatus or a surface treatment apparatus for various resin films F in addition to a roll-to-roll vacuum film forming apparatus. Moreover, it is also possible to control the drying conditions of the resin film F from the measurement result of the moisture content measuring method of the resin film F of this example. The moisture content is measured before (and / or after) drying of the resin film F to control the drying conditions. That is, the moisture content of the resin film F before drying is measured, the drying conditions (drying temperature and drying time) are controlled so as to obtain a desired dry body, and the moisture content of the polyimide resin film F after drying is measured. By doing so, it is possible to feed back to the drying conditions. Feeding back the measured moisture content to the drying conditions can suppress subsequent drying defects and prevent the poorly dried polyimide resin film F from flowing out to the next step. As a heat source for heat drying, a known heat source such as an electric heater or electromagnetic waves (including infrared rays) can be used. Furthermore, the moisture content measuring method of this embodiment can be carried out regardless of whether it is in a vacuum or in the atmosphere. There is no need to separate the vacuum level between the drying mechanism and the film forming mechanism.

An experimental example in which the amount of moisture contained in the resin film F is actually measured will be described with reference to FIGS. FIG. 5 was obtained using Kapton (registered trademark) manufactured by Toray-DuPont Co., Ltd. as the resin film F using the roll-to-roll vacuum film forming apparatus 10 and the water content measuring apparatus 50 shown in FIG. It is a graph which shows a calibration curve. FIG. 6 is a reference graph showing the relationship between the wavelength and absorbance of Kapton (polyimide resin film F) in which the amount of water was changed (the drying time was changed) in a reduced-pressure atmosphere using the roll-to-roll vacuum film forming apparatus 10. It is. FIG. 7 shows a calibration curve obtained using the Upilex (registered trademark) Ube Industries) as the resin film F using the roll-to-roll vacuum film forming apparatus 10 and the water content measuring apparatus 50 shown in FIG. It is a graph which shows.
(Experimental example 1)

Without operating the heater 16 and the sputtering cathodes 24, 26, and 28 of the roll-to-roll vacuum film forming apparatus 10 shown in FIG. A calibration curve was created for The polyimide resin film F having a known moisture content was produced by changing the drying time of the polyimide resin film F. The moisture content of the polyimide resin film F was measured by a weight method. The correlation coefficient of this calibration curve was 0.96. The wavelength of the measurement light L1 was 2748 nm (3639 cm ⁻¹ ), and the wavelength of the reference light L2 was 2868 nm (3487 cm ⁻¹ ).

  When creating the reference graph shown in FIG. 6, the light source 82 and the Michelson interferometer 84 including light having a wavelength of 2600 nm to 3300 nm are incorporated in the irradiation unit 80, and the configuration and optical path of the reflector unit 60 are as shown in FIG. This light was transmitted through the resin film F six times. The angle of each mirror is the same as in Experimental Example 3 described later. In addition, a Fourier transformer 98 (see FIG. 4) that Fourier-transforms the signal detected by the light receiving unit 90, and a moisture amount calculator 102 that stores a calibration curve and stores a program for calculating a moisture amount according to the calibration curve. And an electronic computer 100 (which is an example of a computing means according to the present invention). Further, two reflecting cylinders 86 and 92 (see FIG. 3) were also used.

A sample Kapton (registered trademark, manufactured by Toray-DuPont Co., Ltd.) having an unknown moisture content is set in the roll-to-roll vacuum film forming apparatus 10, and the sample Kapton is not operated without operating the heater 16, the sputtering cathodes 24, 26, and 28. The water content was measured from the absorbance, and it was 0.38% by mass. For comparison, the water content of the sample was measured by TG-DTA (Thermogravimetry-Diferential Thermal Analysis) at 250 ° C. for 30 minutes, and the water content was measured from the weight reduction to be 0.41% by mass. There is no difference between the amount of water measured by absorbance and the amount of water measured by TG-DTA. Furthermore, when the above-described sample Kapton resin film F having an unknown moisture content is dried in a roll-to-roll film forming apparatus 10 under a reduced pressure atmosphere by operating the heater 16 and drying at a temperature of 150 ° C., the moisture content is measured. According to the calibration curve, it was 0.15% by mass.
(Experimental example 2)

  A calibration curve (FIG. 7) was prepared in the same manner as in Experimental Example 1 except that the polyimide resin film F (Upilex (registered trademark) Ube Industries) was used as the resin film F. The correlation coefficient of the calibration curve was 0.94.

When the moisture content of the sample Iupilex with unknown moisture content was measured from the absorbance, it was 0.12% by mass. The sample was held at 250 ° C. for 30 minutes with TG-DTA, and the water content was measured from the weight loss. There is no difference between the amount of water measured by absorbance and the amount of water measured by TG-DTA. Further, when the moisture content was measured by drying the sample at a temperature of 300 ° C. in a reduced pressure atmosphere using the roll-to-roll film forming apparatus 10, it was 0.03% by mass according to the calibration curve of FIG. It was. The angle of each mirror is the same as in Experimental Example 3 described later.
(Experimental example 3)

  An example in which interference is reduced by using the five reflecting mirrors in the atmosphere and transmitting the resin film F six times will be described with reference to FIGS. FIG. 8 is a graph showing a pattern of interference in the resin film F when light is transmitted through the resin film F six times. FIG. 9 is a graph showing the absorbance when the incident angle is optimized to reduce interference when light is transmitted through the resin film F. FIG. In FIG. 9, the solid line indicates the case where the incident angle is not optimized, and the broken line indicates the case where the incident angle is optimized. The angles of the reflecting mirrors with respect to the surface of the resin film F in FIG. 3 are 22.5 ° for the reflecting mirror 66, 0 ° for the reflecting mirrors 68, 70, and 72, and 22.2 for the reflecting mirror 74 when the incident angle is not optimized. When the incident angle is optimized, the reflecting mirror 66 is 23.6 °, the reflecting mirror 68 is −1.4 °, the reflecting mirror 70 is + 0.7 °, the reflecting mirror 72 is + 1.3 °, The reflecting mirror 74 was 28.2 °.

  As for the optimum angle, first, the absorbance was measured by FTIR in accordance with the above-mentioned value, and the angle of the reflecting mirror was adjusted so as to minimize the interference pattern. It can be seen that when the angle of incidence on the resin film F is optimized, the peaks and valleys of interference are reduced. By incorporating the reflecting mirror optical system unit adjusted in the air in this way into the vacuum apparatus, it is possible to perform measurement under the same interference reduction conditions.

  As described above, according to the present invention, the resin film F is not taken out from the processing apparatus such as the roll-to-roll film forming apparatus 10 (see FIG. 1), and the resin film F is not destroyed. Furthermore, since the moisture content of the resin film F can be accurately measured during the operation of the processing apparatus, the industrial applicability is extremely high.

It is a front view which shows typically the roll-to-roll vacuum film-forming apparatus to which an example of the moisture content measuring apparatus of this invention was attached. (A) is a schematic diagram which shows an example of the measuring method which permeate | transmits measurement light and reference light to the resin film F only once, (b) is measurement light and reference light to the resin film F several times (FIG. (6 times) is a schematic diagram showing an example of a measurement method for transmission. It is a side view which shows schematic structure of an irradiation part and a light-receiving part, and is the figure which looked at the irradiation part, the light-receiving part, and the reflective mirror unit from the arrow A direction of FIG. It is a block diagram which shows the computing unit which calculates a moisture content based on the intensity | strength of measurement light and reference light. The calibration curve obtained using the Kapton (registered trademark) Toray DuPont Co., Ltd. as the resin film F using the roll-to-roll vacuum film forming apparatus 10 and the water content measuring apparatus 50 shown in FIG. It is a graph. 3 is a reference graph showing the relationship between the wavelength and absorbance of Kapton (polyimide resin film F) whose water content was changed (changed in drying time) under a reduced pressure atmosphere using the roll-to-roll vacuum film forming apparatus 10. 1 is a graph showing a calibration curve obtained by using the roll-to-roll vacuum film forming apparatus 10 and the water content measuring apparatus 50 shown in FIG. 1 and using the Upilex (registered trademark) Ube Industries) as the resin film F. is there. It is a graph which shows a pattern in the resin film F when light is permeate | transmitted the resin film F 6 times. It is a graph which shows the light absorbency when an incident angle is optimized and interference is reduced when transmitting light to the resin film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 50 Moisture content measuring apparatus 60 Reflector unit 80 Irradiation part 82 Light source 86 Irradiation reflection cylinder 90 Light reception part 92 Light reception reflection cylinder 100 Calculator F Resin film F
L1 Measurement light L2 Reference light

Claims (8)

The resin film is irradiated with measurement light that is infrared light having a first wavelength absorbed by water molecules and reference light that is infrared light having a second wavelength that is not absorbed by water molecules. A moisture content measuring method for measuring the amount of moisture contained,
The measurement light and the reference light are passed through substantially the same optical path, irradiated and transmitted to the resin film in transit, and then reflected by the reflecting mirror and irradiated again and transmitted through the resin film a plurality of times. In this case, in order to reduce the interference caused by reflection near the absorption peak wavelength of the first wavelength of the measurement light, the measurement light is transmitted through the resin film a plurality of times with different angles of incidence. The transmittance of each wavelength after including the absorption peak of the first wavelength and within the wavelength range of twice or more of the half-value width after the measurement light and the reference light are transmitted through the resin film a plurality of times. The incident angle is determined so that the sum of squared deviations of
A method for measuring moisture content, comprising measuring the amount of moisture contained in the resin film based on the absorbance of both the measurement light and the reference light transmitted through the resin film. Irradiating the measurement light and the reference light to the resin film via an irradiation reflector having a mirror formed on the inner wall surface,
2. The method of measuring moisture content according to claim 1 , wherein the measurement light and the reference light that have been transmitted through the resin film are received via a light-receiving reflection tube having a mirror formed on an inner wall surface. . The measurement light and the reference light that have been transmitted through the resin film are dispersed, and the amount of moisture contained in the resin film is measured based on the intensities of both of the measured measurement light and the reference light. The water content measuring method according to claim 1 or 2 . The intensity of both the measurement light and the reference light that have been transmitted through the resin film is Fourier-transformed to obtain absorbance, and based on this absorbance, the amount of moisture contained in the resin film is measured. The moisture content measuring method according to claim 1 or 2 . The resin film is irradiated with measurement light that is infrared light having a first wavelength absorbed by water molecules and reference light that is infrared light having a second wavelength that is not absorbed by water molecules. A moisture content measuring device for measuring the amount of moisture contained,
Irradiation means for irradiating the resin film being conveyed through the measurement light and the reference light through substantially the same optical path;
A mirror unit that transmits the measurement light and the reference light through the resin film a plurality of times through substantially the same optical path;
A light receiving means for receiving the measurement light and the reference light transmitted through the resin film;
Calculating means for calculating the amount of moisture contained in the resin film based on the absorbance of both the measurement light and the reference light received by the light receiving means;
The mirror unit includes a plurality of reflecting mirrors that repeat a plurality of times that the measurement light and the reference light that are irradiated and transmitted through the resin film are reflected, and the resin film is irradiated and transmitted again. Is arranged so that all the incident angles of the measurement light to the resin film are different from each other, and in order to reduce interference due to reflection near the absorption peak wavelength of the first wavelength of the measurement light, the measurement light of the measurement light The square of the deviation of the transmittance of each wavelength after including the absorption peak of the first wavelength and within the wavelength range of twice or more of the half-value width after the measurement light and the reference light are transmitted through the resin film a plurality of times The moisture content measuring apparatus , wherein the incident angle is arranged so that the sum is a minimum value . A reflection cylinder for irradiation in which a mirror is formed on an inner wall surface, through which the measurement light and the reference light irradiated from the irradiation means pass before reaching the resin film;
Claims, characterized in that the measuring light and the reference light has finished transmitting the resin film passes before reaching the light receiving unit, and a light receiving reflecting cylinder mirror is formed on the inner wall surface 5. The water content measuring apparatus according to 5. The light receiving means is
The water content measuring apparatus according to claim 5 or 6 , wherein the measurement light and the reference light received are split to obtain the intensities of both the split measurement light and the reference light. Fourier transform means for obtaining the absorbance of the resin film by Fourier transforming the intensity of both the measurement light and the reference light obtained by the light receiving means,
The moisture content measuring apparatus according to claim 5 or 6 , wherein the computing means computes the amount of moisture contained in the resin film based on the absorbance.

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