JP2009229229A - Double refraction measuring instrument and double refraction measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate retardation Rth in a thickness direction on-line in a film manufacturing process for continuously feeding a sheetlike film to manufacture a film. <P>SOLUTION: The polarization characteristics of the film are measured from the normal line direction of the film by a first polarization characteristic measuring part 11 and the orientation axis azimuth of a sample 16 is calculated on the basis of the measuring result by an axis/retardation calculation means 61. An in-plane azimuth control means 64 performs the azimuth revolution of a second polarization characteristic measuring part 17 so that the oblique incident light of the second polarization characteristic measuring part 17 becomes parallel to the calculated orientation axis azimuth. The sample 16 is fed by a feed roll 21, and the reagent measured by the first polarization characteristic measuring part 11 reaches the measuring position of the polarization characteristic measuring part 17, when measurement is started by the second polarization characteristic measuring part 17. The axis/retardation calculation means 61 calculates the retardation Rth in the thickness direction of the film on the basis of the measuring results of the first and second polarization characteristic measuring parts 11 and 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a birefringence measuring apparatus and a birefringence measuring method, and more particularly to a birefringence measuring apparatus and a birefringence measuring method for accurately measuring the birefringence characteristics of a film in the manufacturing process of a plastic resin film.

  When producing a plastic resin film for use in a liquid crystal display or the like, it is preferable to measure the birefringence characteristics such as the orientation axis and retardation of the film in the production process and control the process conditions based on the measurement result. Thus, by performing feedback on the process conditions, it is possible to stably manufacture a film having a desired performance, and as a result, it is possible to improve the performance and quality of the display.

In Patent Document 1, the measurement range is expanded by using at least two lights having different wavelengths, and the thickness of the sample at the position where the retardation is measured is measured. A retardation measuring device capable of accurately measuring birefringence by capturing a thickness change in the width direction is described. According to the apparatus of Patent Document 1, it is possible to identify retardation fluctuations due to thickness fluctuations, so that it is possible to quickly and accurately grasp process fluctuations.
JP-A-11-326190

  A display is required to satisfy display characteristics such as color and gradation when viewed from various viewing angles. In order to realize such display characteristics, a retardation film used for a liquid crystal display needs to have an appropriate retardation (oblique retardation) with respect to transmitted light in an oblique direction. Appropriate oblique retardation means not only the light transmitted from the backlight in the normal direction of the film but also the property of appropriately converting the polarization state of the light transmitted in the oblique direction to match the liquid crystal display characteristics. .

  Generally, thickness direction retardation (Rth) is used as an index for evaluating the phase difference film. This Rth is calculated from the retardation for the transmitted light in the normal direction of the film (front retardation) and the retardation for the transmitted light in the oblique direction (oblique retardation). Therefore, in order to accurately calculate Rth, it is necessary to determine and measure an in-plane azimuth angle of light transmitted in an oblique direction. Usually, the in-plane azimuth angle is a fast axis viewed from the normal direction of the film. Or, it is the slow axis direction.

  Against this background, in the film manufacturing process, it is desired not only to measure the axial orientation and front retardation, but also to measure oblique retardation and calculate Rth. However, in the apparatus described in Patent Document 1, the in-plane azimuth angle of light transmitted in an oblique direction cannot be aligned with the fast axis direction or the slow axis direction viewed from the film normal direction. There has been a problem that the oblique retardation that is essential for the calculation cannot be measured.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a birefringence measuring apparatus and a birefringence measuring method that accurately calculate a thickness direction retardation by making it possible to accurately measure oblique retardation. And

  In order to achieve the above object, the birefringence measuring apparatus according to claim 1, a first measuring means for measuring a front retardation of the sample to be measured by allowing light to enter the sample to be measured perpendicularly, and the device to be measured A second measuring means for measuring the oblique retardation of the sample to be measured by making light incident on the sample at a predetermined incident angle; and at least the second measurement of the first measuring means and the second measuring means. Direction changing means for changing the incident direction of the light while keeping the incident angle and the incident position of the light of the means constant, and the incident direction of the light is a fast axis direction or a slow axis direction of the sample to be measured. Control means for controlling the azimuth changing means so as to be parallel, and means for calculating a thickness direction retardation of the sample to be measured from the front retardation and the oblique retardation.

  Thereby, since the incident direction of light is changed while keeping the incident angle and incident position of light constant, the oblique retardation can be accurately measured, and the thickness direction retardation can be accurately calculated.

  According to a second aspect of the present invention, in the birefringence measuring device according to the first aspect, the azimuth changing unit includes the first measuring unit and the second measuring unit centering on a normal line at an incident position of the second measuring unit. The incident direction of the light of the second measuring means is changed while keeping the incident angle and the incident position constant by rotating at least the second measuring means among the measuring means. To do.

  Thereby, the incident azimuth can be easily aligned with the orientation axis azimuth.

  According to a third aspect of the present invention, in the birefringence measuring apparatus according to the first or second aspect, the fast axis direction or the slow axis direction of the sample to be measured is calculated based on the measurement result of the first measuring means. And the control means controls the azimuth changing means so that the incident azimuth of the light is parallel to the calculated fast axis azimuth or slow axis azimuth.

  Thereby, even if the orientation axis orientation of the sample varies, the polarization characteristics can be measured according to the orientation axis orientation, so that the thickness direction retardation can be accurately calculated.

  According to a fourth aspect of the present invention, in the birefringence measurement apparatus according to any one of the first to third aspects, the sample to be measured is moved from the incident position of the first measurement unit at a predetermined speed to the second measurement unit. A transport means for transporting to the incident position; and the first measurement means so that the measurement area of the sample to be measured of the first measurement means and the measurement area of the sample to be measured of the second measurement means are the same area. And a control means for controlling the second measuring means.

  Thereby, even when the first measuring unit and the second measuring unit are arranged apart from each other, the front retardation and the oblique retardation can be measured for the same region.

  As shown in claim 5, in the birefringence measuring apparatus according to claim 4, the incident position of the first measuring means and the incident position of the second measuring means are separated by a predetermined distance (L). The first measuring means and the second measuring means are arranged, and the amount by which the sample to be measured is conveyed while the first measuring means performs the measurement, and between the second measuring means performing the measurement. The larger of the amount of the sample to be measured is X, Y is the amount of the sample to be measured while the direction changing means changes the direction, and P is the interval between the measurement points of the sample to be measured. In this case, the relationship X + Y ≦ P ≦ L is satisfied.

  Thereby, even while the sample is being transported, the polarization characteristic can be measured according to the orientation axis direction, so that the thickness direction retardation can be accurately calculated.

  According to a sixth aspect of the present invention, in the birefringence measuring device according to the fourth or fifth aspect, the incident areas of the first measuring means and the second measuring means are within 4 mm.

  Thereby, it is possible to minimize the influence of sample sagging and wrinkles that occur during transportation.

  7. The birefringence measuring apparatus according to claim 4, wherein incident light of the first measuring means and the second measuring means is parallel light. .

  Thereby, the retardation can be measured accurately.

  As shown in claim 8, in the birefringence measuring apparatus according to any one of claims 4 to 7, the control means includes a detecting means for detecting a transport amount of the sample to be measured, the first measuring means, Trigger generating means for starting the measurement of the second measuring means, and the trigger generating means carries the measured sample detected by the detecting means after starting the measurement of the first measuring means. Is equal to the predetermined distance L, the measurement of the second measuring means is started.

  As shown in claim 9, in the birefringence measuring apparatus according to claim 8, the transport means is a transport roll that is rotationally driven, and includes an encoder that outputs a pulse train corresponding to a rotation angle of the transport roll, The detecting means integrates the number of pulses of the pulse train to detect the transport amount of the sample to be measured.

  Thereby, the area measured by the first measuring means can be easily measured by the second measuring means.

  The birefringence measuring device according to any one of claims 1 to 3, wherein the first measuring unit and the second measuring unit are integrated with each other, and the first measuring unit is integrated with the first measuring unit. The first measuring means and the second measuring means are arranged so that the incident position of the measuring means and the incident position of the second measuring means are the same position.

  Thereby, the same position of the sample to be measured can be easily measured, and the incident azimuth can be easily changed.

  In order to achieve the object, the birefringence measurement method according to claim 11 includes a first measurement step of measuring the retardation of the sample to be measured by allowing light to enter the sample to be measured perpendicularly, and the sample to be measured. A second measurement step of measuring the retardation of the sample to be measured by entering light at a predetermined incident angle, and at least the second measurement step of the first measurement step and the second measurement step. An azimuth changing step for changing the incident direction of the light while keeping the incident angle and the incident position of the light constant, and the incident direction of the light is parallel to the fast axis direction or the slow axis direction of the sample to be measured And a control step for controlling the orientation changing step, and a step of calculating a thickness direction retardation of the sample to be measured from the front retardation and the oblique retardation.

  Thereby, since the incident direction of light is changed while keeping the incident angle and incident position of light constant, the oblique retardation can be accurately measured, and the thickness direction retardation can be accurately calculated.

  According to the present invention, in the thickness direction retardation calculation of the sample to be measured, the incident angle of light and the incident position are changed while keeping the incident angle of light constant, so that the oblique retardation can be accurately measured, It is possible to accurately calculate the thickness direction retardation.

  The best mode for carrying out the present invention will be described below.

<First Embodiment>
FIG. 1 is a configuration diagram showing an outline of a first embodiment of a birefringence measuring apparatus 10 according to the present invention.

  As shown in the figure, the birefringence measuring apparatus 10 according to the present embodiment includes a first polarization characteristic measuring unit 11, a second projector 18, and a first projector 12 and a first receiver 14. In addition to the second polarization characteristic measuring unit 17 composed of the second light receiver 19, the transport roll 21 for transporting the sample 16, the axis / retardation calculating means 61, the measurement control means 62, and the in-plane orientation varying means 63. , And in-plane orientation control means 64.

  The first polarization characteristic measuring unit 11 is a measuring unit for calculating the orientation axis direction and retardation of the sample using the rotational analyzer method. FIG. 2 is a configuration diagram of the optical system of the first polarization characteristic measuring unit 11. As shown in FIG. 2, the projector 12 of the first polarization characteristic measuring unit 11 includes a light source 26 and a first plano-convex lens 28. , A spectral filter 32, a pinhole plate 30, a second plano-convex lens 34, a linearly polarizing plate 36, a λ / 4 wavelength plate 38, and an output aperture 40.

  The light source 26 is a light source that generates and emits light including a desired wavelength band, and a monochromatic light source or a white light source can be used.

  The light emitted from the light source 26 passes through the first plano-convex lens 28 and is guided to the spectral filter 32. The spectral filter 32 may extract a light having a desired wavelength from the incident light, or may function to increase the monochromaticity by limiting the wavelength band of the incident light, and a spectroscope such as a diffraction grating may be used. In the present embodiment, an LED having a center wavelength of 630 nm is used as the light source 26, and a metal interference filter having a half-value width of 10 nm is used as the spectral filter 32 to extract light having a desired wavelength.

  The means for guiding the light emitted from the light source 26 to the spectral filter 32 and the means for guiding the light emitted from the spectral filter 32 to the subsequent optical system may use an optical fiber or the like. 26, the spectral filter 32, and the subsequent optical system may be integrated.

  The pinhole of the pinhole plate 30 and the second plano-convex lens 34 function to make the light incident on the sample 16 parallel light. The light emitted from the pinhole of the pinhole plate 30 is regarded as a point light source, and the second planoconvex lens 34 is arranged so that the focal length of the second planoconvex lens 34 matches the pinhole of the pinhole plate 30. Thus, the light emitted from the second plano-convex lens 34 can be made substantially parallel light. In the present embodiment, a lens having a focal length of 40 mm is used as the second plano-convex lens 34 to obtain parallel light having a spot diameter of about 4 mm. Further, the smaller the pinhole diameter of the pinhole plate 30, the higher the parallelism of the parallel light. In this embodiment, a pinhole diameter of φ0.4 mm is used.

The light that has passed through the second plano-convex lens 34 is converted into linearly polarized light along the transmission axis of the linearly polarizing plate 36 by the linearly polarizing plate 36. For the linear polarizing plate 36, an extinction ratio is on the order of 10 ⁻⁶ to 10 ⁻⁵ , and a polymer type using iodine absorption or a prism type using optical crystals is used. In this embodiment, iodine absorption is used. Use polymer type.

  The light polarized into the linearly polarized light is guided to the λ / 4 wavelength plate 38. The λ / 4 wavelength plate 38 is a phase shifter having a phase difference of 90 ° made by combining optical crystals such as quartz having birefringence, and the fast axis is relatively 45 ° with respect to the polarization direction of linearly polarized light. Alternatively, linearly polarized light is converted to circularly polarized light by being arranged at an angle of −45 °. Since it is very difficult to make the λ / 4 wavelength plate 38 with a phase difference of 90 ° accurately in practice, in this embodiment, the fast axis direction of the λ / 4 wavelength plate 38 is 45 °. The incident polarization state (Stokes parameter) is measured in advance and used to calculate the measured value.

  The light that has passed through the λ / 4 wavelength plate 38 is guided to the emission aperture 40, where the beam diameter of the emission light emitted from the projector 12 is determined. In this embodiment, a beam diameter of φ4 mm is used. The light that has passed through the emission aperture 40 passes through the sample 16 and is received by the light receiver 14. In order to make the sample 16 less likely to be affected by sagging of the sample 16 generated during conveyance and deterioration of flatness due to wrinkles, the beam diameter of the exit aperture 40, that is, the diameter of the measurement region of the sample 16 is preferably 4 mm or less.

  As shown in FIG. 2, the light receiver 14 of the first polarization characteristic measuring unit 11 includes a rotary hollow motor 46 with a rotary encoder 44, a linear polarizing plate 48, and a photomultiplier tube (PMT) 50.

  The linear polarizing plate 48 is disposed at the center of the rotary hollow motor 46 and rotates around the optical axis at a predetermined rotation angle. By detecting only the light intensity in the transmission axis direction of the rotating linearly polarizing plate 48 with the PMT 50, the light intensity of polarized light incident on the PMT 50 is detected in all directions. In the present embodiment, an iodine-absorbing polymer type linear polarizing plate 48 is used.

  The rotary hollow motor 46 is a hollow type motor that allows light to pass through the center. The linearly polarizing plate 48 is fixedly held on a hollow rotating body (not shown), and the linearly polarizing plate 48 is rotated 360 °. Is possible. The hollow rotating body has a mechanical coupling portion such as a gear on the outer periphery, and a brushless motor, a stepping motor, or the like is coupled by a belt or a gear. The rotating body and the motor may be separated as a mechanism element or may be integrated. In the present embodiment, a brushless motor is used, and the rotational speed of the rotor is 30 Hz.

  The rotary encoder 44 detects the current angular position of the rotary hollow motor 46 by outputting an angle pulse generated at every predetermined rotation angle pitch, whereby the current transmission axis direction of the linear polarizing plate 48 is detected. Can be detected. In this embodiment, a device that outputs 3000 pulses per rotation is used.

  The photomultiplier tube (PMT) 50 includes a sensitivity adjuster for varying the amplification factor and a current-voltage converter that converts the current signal output from the phototube into a voltage, and converts the light intensity signal into an analog voltage signal. And output. The means for detecting light is not limited to the PMT, and a CCD or the like may be used.

  The first polarization characteristic measuring unit 11 configured as described above is arranged so that the light emitted from the first projector 12 is parallel to the normal line of the sample 16.

  The sample 16 is a sheet-like plastic resin film, which is disposed between the projector 12 and the light receiver 14 and is transported at a predetermined speed by the transport roll 21.

  The second polarization characteristic measurement unit 17 is also a measurement unit for calculating the orientation axis direction and retardation of the sample using the rotational analyzer method. The configuration of the optical system of the second polarization characteristic measurement unit 17 is the same as the configuration of the optical system of the first polarization characteristic measurement unit 11. The second polarization characteristic measurement unit 17 is arranged so that the measurement region thereof is the same as the measurement region of the first polarization property measurement unit 11 in the width direction of the sample 16. That is, the light emitted from the first projector 12 and the light emitted from the second projector 18 are arranged so as to enter the same position in the width direction of the sample 16.

  Further, the second polarization characteristic measuring unit 17 is arranged so that the light emitted from the second projector 18 is incident on the sample 16 in an oblique direction, and the normal of the incident point is obtained by the in-plane orientation varying means 63. Is configured to be capable of turning around. Therefore, the second polarization characteristic measuring unit 17 can change the incident azimuth while keeping the measurement region and the incident angle constant. In the present embodiment, the light emitted from the second projector 18 is arranged so as to have an incident angle of 40 ° from the normal line of the sample 16.

  The first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit 17 are configured so as to be integrated, and the respective measurement areas are the same, that is, the light is emitted from the first projector 12. You may arrange | position so that light and the light radiate | emitted from the 2nd light projector 18 may inject into the same position of the sample 16. FIG. In this case, while maintaining the measurement region and the incident angle of the first polarization property measurement unit 11 and the measurement region and the incidence angle of the second polarization property measurement unit 17, the first polarization property measurement unit 11 and the second polarization property measurement unit 11 are kept constant. And the polarization characteristic measuring unit 17 integrally turn.

  With this configuration, the first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit 17 can easily measure the same region of the sample 16, and can easily change the incident direction. Can do.

  FIG. 3 is a block diagram showing an electrical configuration of the axis / retardation calculation means 61. As shown in the figure, the axis / retardation calculation means 61 includes an AD conversion unit 71 and a calculation unit 72. The AD converter 71 sequentially converts the analog voltage signal output from the rotary encoder 44 into a digital voltage signal. The calculation unit 72 includes a storage unit 73 that stores the output value, calculation result, and the like of the AD conversion unit 71, a Fourier transform processing unit 74 that Fourier transforms the digital data output from the AD conversion unit 71, and an output result of the Fourier transform processing unit 74. The calculation unit 75 calculates the orientation axis orientation and retardation based on the above.

  The storage unit 73 is digital data transmitted from the AD conversion unit 71, result data converted by the Fourier transform processing unit 74, and data in the middle of calculation that occurs in the process of calculating the orientation axis direction and retardation by the calculation unit 75. And data of operation results are stored.

  The Fourier transform processing unit 74 converts digital data corresponding to the rotation angle of the linear polarizing plate 48 stored in the storage unit 73 using a Fourier transform algorithm such as DFT (Discrete Fourier Transform) or FFT (Fast Fourier Transform). The Fourier coefficient of the frequency component at a predetermined rotation angle of the linearly polarizing plate 48 is calculated.

  The AD conversion unit 71 and the calculation unit 72 can be realized by a computer using a predetermined program and a processor (CPU, DSP) that executes the program. In this embodiment, a DSP signal processing board is used.

  The in-plane orientation control means 64 controls the in-plane orientation variable means 63 based on a command from the measurement control means 62.

  The in-plane azimuth changing means 63 is configured to be azimuth variable independently for each of the light projecting side and the light receiving side across the sample 16. A stepping motor is used for the in-plane orientation varying means 63, and the in-plane orientation can be rotated by 0 to 360 °.

  The measurement control unit 62 controls the axis / retardation calculation unit 61 and the in-plane orientation control unit 64 to control the birefringence measurement of the sample 16 in an integrated manner. In this embodiment, a personal computer is used as the measurement control means 62, and the axis / retardation calculation means 61 and the in-plane orientation control means 64 are connected so as to be capable of bidirectional communication.

  With this configuration, the orientation axis direction and the front retardation can be calculated from the measurement result of the first polarization characteristic measurement unit 11, and the alignment axis can be calculated from the measurement result of the second polarization characteristic measurement unit 17. An oblique retardation according to the direction can be calculated. Furthermore, by setting the area to be measured as a spot having a diameter of 4 mm or less, it is possible to make the sample 16 less susceptible to the influence of sagging of the sample 16 generated during conveyance and deterioration of flatness due to wrinkles.

  Next, operation | movement of the birefringence measuring apparatus 10 of this Embodiment is demonstrated.

  When the film orientation axis orientation of the sample 16 is known, the in-plane orientation control means 64 controls the in-plane orientation varying means 63 based on the known orientation axis orientation, and the oblique incident light of the second polarization characteristic measuring unit 17 The second polarization characteristic measurement unit 17 is swiveled so as to be parallel to the known orientation axis azimuth and fixed at the parallel position. Thereafter, the conveyance of the sample 16 by the conveyance roll 21 is started. The first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit 17 respectively pass through the linear polarizing plate 48 on which the light emitted from the projector 12 and the projector 18 rotates about the sample 16 conveyed by the conveyance roll 21. Thus, the light intensity of the polarized light incident on the PMT 50 is detected in all directions.

  The axis / retardation calculation means 61 calculates the front retardation based on the measurement result of the first polarization characteristic measurement unit 11 and the oblique retardation based on the measurement result of the second polarization characteristic measurement unit 17, and is further calculated. Rth is calculated from the front retardation and the oblique retardation.

  As described above, when the film alignment axis direction of the sample 16 is known, the accurate Rth can be obtained by rotating the direction so that the obliquely incident light of the second polarization characteristic measuring unit 17 is parallel to the known alignment axis direction. Can be calculated.

  When the film orientation axis direction of the sample 16 is unknown, the first polarization characteristic measuring unit 11 detects the light intensity of the polarized light of the sample 16 in all directions based on the control of the measurement control unit 62. Based on this measurement result, the axis / retardation calculation means 61 calculates the orientation axis direction of the sample 16. Further, the in-plane azimuth control means 64 controls the in-plane azimuth varying means 63 to measure the second polarization characteristic so that the obliquely incident light of the second polarization characteristic measurement unit 17 is parallel to the calculated orientation axis azimuth. The part 17 is turned and fixed at a parallel position. The subsequent birefringence measurement and Rth calculation are the same as in the case where the orientation axis orientation is known.

  As described above, when the film alignment axis direction of the sample 16 is unknown, the first polarization characteristic measurement unit 11 first measures the polarization characteristic to calculate the alignment axis direction of the sample 16 and the second polarization characteristic measurement. By turning the azimuth so that the obliquely incident light of the portion 17 is parallel to the calculated orientation axis azimuth, it is possible to calculate an accurate Rth.

  Note that the method of measuring the orientation axis direction and retardation is not limited to the rotational analysis method, and a rotational phaser method, an elastic modulation method, or the like may be used.

<Second Embodiment>
FIG. 4 is a block diagram showing an outline of the second embodiment of the birefringence measuring apparatus 10 according to the present invention. In addition, the same code | symbol is attached | subjected to the part which is common in the block diagram shown in FIG. 1, and the detailed description is abbreviate | omitted.

  In the second embodiment, the measurement position of the first polarization characteristic measurement unit 11 and the measurement position of the second polarization characteristic measurement unit 17 are the same position in the width direction of the sample 16 and in the transport direction of the sample 16. It arrange | positions so that only the distance L may leave | separate. The first polarization characteristic measurement unit 11 is fixedly arranged so that the light emitted from the first projector 12 is parallel to the normal line of the sample 16, and the second polarization characteristic measurement unit 17 is a second projector 18. The light emitted from the film 16 is arranged so as to have an incident angle of 40 ° with respect to the sample 16 from the film normal.

  FIG. 5 is a configuration diagram of the second polarization characteristic measuring unit 17 of the present embodiment. The in-plane azimuth varying means 63 is configured to be azimuth variable independently for each of the projector 18 and the light receiver 19, and is controlled by the in-plane azimuth control means 64. A stepping motor is used for the in-plane orientation varying means 63, and the in-plane orientation can be rotated by 0 to 360 °. As described above, the second polarization characteristic measuring unit 17 is configured to turn in the azimuth direction while keeping the incident angle and the measurement region constant by the in-plane azimuth varying means 63.

  Further, the transport position for detecting the transport position of the transport roll 21 so that the measurement region of the sample 16 in the first polarization characteristic measurement unit 11 and the measurement region of the sample 16 in the second polarization characteristic measurement unit 17 are the same. Detection means 65 and trigger generation means 66 are provided.

  The transport position detection means 65 detects the rotation angle of the transport roll 21 that is rotationally driven by an encoder (not shown), and integrates the number of pulses of the encoder pulse train. The trigger generation unit 66 calculates the conveyance amount of the sample 16 based on the detection result of the conveyance position detection unit 65, and based on the calculated conveyance amount, the first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit. A trigger for starting measurement is generated at a desired timing for starting 17 measurements.

  Next, operation | movement of the birefringence measuring apparatus 10 of this Embodiment is demonstrated.

  While the sample 16 is being transported to the transport roll 21 at a predetermined speed, the trigger generating means 66 generates a measurement start trigger. This trigger is input to the measurement control unit 62, and the measurement control unit 62 causes the first polarization characteristic measurement unit 11 to start the polarization characteristic measurement.

  When the polarization property measurement of the first polarization property measurement unit 11 is completed, the axis / retardation calculation unit 61 calculates the orientation axis direction together with the front retardation of the sample 16 based on the measurement result. The in-plane azimuth control unit 64 turns the second polarization characteristic measurement unit 17 so that the obliquely incident light of the second polarization characteristic measurement unit 17 is parallel to the calculated orientation axis azimuth.

  Further, the trigger generation unit 66 calculates the conveyance amount of the sample 16 after generating a measurement start trigger based on the output of the conveyance position detection unit 65. When the calculated transport amount reaches the distance L between the first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit 17, the trigger generating means 66 generates a measurement start trigger again. The measurement control means 62 causes the second polarization characteristic measurement unit 17 to start measurement based on this trigger.

  The second polarization characteristic measurement unit 17 that has been turned in advance to a position parallel to the orientation axis direction of the measurement region of the sample 16 performs polarization characteristic measurement based on a command from the measurement control unit 62. When the polarization property measurement of the second polarization property measurement unit 17 is completed, the axis / retardation calculation means 61 calculates the oblique retardation of the sample 16 based on the measurement result. The axis / retardation calculation means 61 calculates Rth from the calculated front retardation and oblique retardation.

  With this configuration, the measurement areas of the sample 16 in the first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit 17 can be made the same. Further, based on the orientation axis direction calculated by the axis / retardation calculation means from the measurement result of the first polarization characteristic measuring unit 11, the in-plane direction for performing the measurement by turning the second polarization characteristic measuring unit 17 is changed. By doing so, even in the state where the sample 16 is being transported, it is possible to always measure the correct oblique direction retardation.

  In addition, although the 1st polarization characteristic measurement part 11 and the 2nd polarization characteristic measurement part 17 measured the polarization characteristic at the separate timing, it is more preferable to measure simultaneously. That is, while the second polarization characteristic measurement unit 17 is measuring the polarization characteristic, the first polarization characteristic measurement unit 11 performs the polarization characteristic measurement on a new region conveyed by the distance L. By simultaneously measuring in this way, it becomes possible to measure more regions.

  Here, in the first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit 17, the longer one of the conveyance amounts of the sample 16 conveyed per measurement, whichever is longer, X, the second polarization characteristic measurement unit 17 Is set so that X + Y ≦ P ≦ L is satisfied, where Y is the transport amount by which the sample 16 is transported while the azimuth is turned by the in-plane orientation varying means 63 and P is the cycle in the transport direction of the sample 16 for measuring the retardation. , X, Y, L are set.

  By setting in this way, the first polarization characteristic measurement unit 11 and the second polarization characteristic measurement unit 17 perform the polarization characteristic measurement at the same time, and in the same region measured by the first polarization characteristic measurement unit 11, It becomes possible for the polarization characteristic measuring unit 17 to measure.

<Example>
Using the configuration of the second embodiment, the alignment axis direction and Rth were calculated online in the film manufacturing process. The measurement period was set to 100 mm in the length in the film flow direction. The result is shown in FIG. FIG. 6A shows the orientation axis direction of the film at each film transport position, and FIG. 6B shows Rth at each film transport position.

  In this measurement sample, the production conditions are changed during production, and it can be read from the calculation result that the orientation axis direction of the film and Rth have changed since the production conditions were changed. Based on the calculation result, it is possible to further change the manufacturing conditions until a desired film performance is obtained.

  Moreover, the average value of Rth in the conveyance position 27-29m area measured on-line was 215.6 nm. As a result of performing the sampling measurement of N = 4 off-line in this section, the average value of Rth was 215.3 nm, and a result that closely matched the average value of the online measurement result could be obtained. Thus, it was confirmed that Rth can be measured accurately even on-line.

FIG. 1 is a configuration diagram showing an outline of a first embodiment of a birefringence measuring apparatus 10 according to the present invention. FIG. 2 is a configuration diagram of the optical system of the first polarization characteristic measuring unit 11. FIG. 3 is a block diagram showing an electrical configuration of the axis / retardation calculation means 61. FIG. 4 is a block diagram showing an outline of the second embodiment of the birefringence measuring apparatus 10 according to the present invention. FIG. 5 is a configuration diagram of the second polarization characteristic measuring unit 17 of the present embodiment. FIG. 6 is a diagram illustrating measurement results of on-line measurement of orientation axis direction and thickness direction retardation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Birefringence measuring apparatus, 11 ... 1st polarization characteristic measurement part, 12 ... 1st light projection part, 14 ... 1st light-receiving part, 16 ... Sample, 17 ... 2nd polarization characteristic measurement part, 18 ... 2nd light projection part, 19 ... 2nd light-receiving part, 21 ... conveyance roll, 26 ... light source, 28 ... 1st plano-convex lens, 30 ... pinhole plate, 32 ... spectral filter, 34 ... 2nd plano-convex lens , 36: linearly polarizing plate, 38: λ / 4 wavelength plate, 40: emitting aperture, 44: rotary encoder, 46: rotary hollow motor, 48: linearly polarizing plate, 50: photomultiplier tube, 61: axis / retardation calculating means , 62 ... measurement control means, 63 ... in-plane azimuth changing means, 64 ... in-plane azimuth control means, 65 ... transport position detection means, 66 ... trigger generation means, 71 ... AD conversion section, 72 ... calculation section, 73 ... storage Part 74 ... Fourier transform processing part 75 ... calculation

Claims (11)

A first measuring means for measuring the front retardation of the sample to be measured by vertically incident light on the sample to be measured;
Second measuring means for measuring the oblique retardation of the sample to be measured by making light incident on the sample to be measured at a predetermined incident angle;
An azimuth changing means for changing an incident azimuth of the light while keeping an incident angle and an incident position of light of at least the second measuring means out of the first measuring means and the second measuring means;
Control means for controlling the azimuth changing means so that the incident direction of the light is parallel to the fast axis direction or the slow axis direction of the sample to be measured;
Means for calculating a thickness direction retardation of the sample to be measured from the front retardation and the oblique retardation;
A birefringence measuring apparatus comprising:   The azimuth changing means rotates at least the second measuring means among the first measuring means and the second measuring means about the normal line at the incident position of the second measuring means, thereby 2. The birefringence measuring apparatus according to claim 1, wherein the incident direction of the light of the second measuring means is changed while keeping the incident angle and the incident position constant. Means for calculating a fast axis direction or a slow axis direction of the sample to be measured based on a measurement result of the first measuring means;
The said control means controls the said azimuth | direction change means so that the incident azimuth | direction of the said light may become in parallel with the said calculated fast axis azimuth | direction or slow axis azimuth | direction. Birefringence measuring device. Transport means for transporting the sample to be measured from the incident position of the first measuring means to the incident position of the second measuring means at a predetermined speed;
The first measurement unit and the second measurement unit are controlled so that the measurement region of the sample to be measured of the first measurement unit and the measurement region of the sample to be measured of the second measurement unit are the same region. Control means;
The birefringence measuring apparatus according to any one of claims 1 to 3, further comprising: The first measuring means and the second measuring means are arranged so that the incident position of the first measuring means and the incident position of the second measuring means are separated by a predetermined distance (L),
X is the larger of the amount that the sample to be measured is conveyed while the first measuring unit is measuring and the amount that the sample to be measured is conveyed while the second measuring unit is measuring.
The transport amount of the sample to be measured while the azimuth changing means changes the azimuth is Y,
When the interval between the measurement points of the sample to be measured is P,
X + Y ≦ P ≦ L
The birefringence measuring device according to claim 4, wherein the relationship is satisfied.   6. The birefringence measuring apparatus according to claim 4, wherein incident areas of the first measuring means and the second measuring means are within 4 mm.   The birefringence measuring apparatus according to any one of claims 4 to 6, wherein the incident light of the first measuring means and the second measuring means is parallel light. The control means includes
Detecting means for detecting the transport amount of the sample to be measured;
Trigger generation means for starting measurement of the first measurement means and the second measurement means,
The trigger generating means measures the second measuring means when the transport amount of the sample to be measured detected by the detecting means after starting the measurement of the first measuring means becomes equal to the predetermined distance L. The birefringence measuring device according to claim 4, wherein the birefringence measuring device is started. The transport means is a transport roll that is driven to rotate,
An encoder that outputs a pulse train corresponding to the rotation angle of the transport roll;
9. The birefringence measuring apparatus according to claim 8, wherein the detecting unit detects the transport amount of the sample to be measured by integrating the number of pulses of the pulse train.   The first measurement unit and the second measurement unit are configured to be integrated, and the incident position of the first measurement unit and the incident position of the second measurement unit are the same. 4. The birefringence measuring apparatus according to claim 1, wherein one measuring means and the second measuring means are arranged. A first measurement step of measuring the retardation of the sample to be measured by vertically incident light on the sample to be measured;
A second measurement step of measuring the retardation of the sample to be measured by making light incident on the sample to be measured at a predetermined incident angle;
An azimuth changing step of changing an incident azimuth of the light while maintaining an incident angle and an incident position of light of at least the second measuring step out of the first measuring step and the second measuring step;
A control step of controlling the azimuth changing step so that the incident azimuth of the light is parallel to the fast axis azimuth or the slow axis azimuth of the sample to be measured;
Calculating the thickness direction retardation of the sample to be measured from the front retardation and the oblique retardation;
A birefringence measuring method comprising:

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