JP6641682B2 - Optical film phase difference measuring method, optical film manufacturing method, optical film phase difference measuring apparatus, and optical film manufacturing apparatus - Google Patents

Description

  The present invention relates to a method for measuring the retardation of an optical film, a method for manufacturing an optical film, an apparatus for measuring an optical film retardation, and an apparatus for manufacturing an optical film.

  When manufacturing an optical film, it is required to precisely control the phase difference over a wide area of the film surface. In the production of optical films, high-speed and continuous production on a production line is required to improve the production efficiency. Therefore, the phase difference of a wide area of the surface of the optical film conveyed at high speed and continuously is accurately and quickly measured in the production line, whereby the measurement result is fed back to the film forming process, or the phase difference is reduced. There is a need for means to remove non-standard parts from the final product.

  In controlling the phase difference, it is often required that the in-plane phase difference Re and the thickness direction phase difference Rth be precisely controlled. As a device for measuring Re and Rth, a phase difference measuring device (for example, Patent Document 1) that measures at a certain point on a film surface has been widely used. When measuring these on the conveyed optical film, such a phase difference measuring device is swung in the TD direction, thereby moving the phase difference measuring device so as to describe a wavy trajectory with respect to the conveyed film. , In the TD direction and in the MD direction, measurement has been widely performed.

  In recent years, a phase difference measuring device for simultaneously measuring an in-plane retardation Re at a plurality of positions on a film surface has been proposed (Patent Document 2).

JP-A-8-201277 JP 2007-263593 A

  When the phase difference measuring device is swung in the production line, undesired objects such as falling of foreign matter from the moving device for moving the phase difference measuring device, occurrence of defects due to contact between the drive portion of the moving device and the film, and obstacles in manufacturing, etc. Phenomena can occur. Further, in the measurement that draws a wavy trajectory with respect to the film to be conveyed, there are a wide range of unmeasured portions on the entire surface of the film, so that a portion having a non-standard phase difference may be overlooked. Such unmeasured portions increase particularly when the film is transported at a high speed.

  On the other hand, when measurement is performed using the phase difference measuring device described in Patent Document 2, Rth cannot be measured simultaneously with Re. In addition, since the measurement is performed in an oblique direction at a location far from the phase difference measuring device on the film surface, there are two measurement locations that are close to the phase difference measuring device and those that are far from the phase difference measuring device on the film surface. In addition, there is a problem that a polar angle which is a reference for measuring the phase difference is different.

An object of the present invention is to precisely control the in-plane retardation Re and the thickness direction retardation Rth at a number of measurement points in a wide area of the film surface without hindering the quality and smoothness of the product in the production of the optical film. It is an object of the present invention to provide a method for measuring the retardation of an optical film and a measuring device for measuring the retardation of an optical film, which can be measured at a time.
A further object of the present invention is to provide an optical film manufacturing method and an optical film manufacturing apparatus capable of smoothly manufacturing a high-quality optical film in which the in-plane retardation Re and the thickness direction retardation Rth are precisely controlled. To provide.

As a result of studying the present invention to solve the above problems, the present invention uses two or more phase difference measuring devices for measuring in-plane retardation Re at the same time at a plurality of positions on the film surface, and based on information obtained therefrom. , Re and Rth can be measured at many points simultaneously, and completed the present invention.
That is, the present invention is as follows.

[1] A method for measuring a phase difference of an optical film conveyed in a conveyance path,
By a plurality of phase difference measuring devices provided apart in the TD direction of the transport path, at each of a plurality of measurement places separated in the TD direction, a plurality of measurements on the surface of the optical film passing through the measurement places A step of measuring a phase difference between points, wherein at each of two or more measurement points, two or more of the phase difference measuring devices measure a phase difference from a plurality of polar angle directions. ), And an in-plane phase difference Re, a thickness direction phase difference Rth, or both of them at each of the measurement points based on the plurality of phase difference values measured in the measurement step (i). Calculation step (ii)
And a measuring method.
[2] In the measurement step (i),
The plurality of phase difference measuring devices are a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device (R) for measuring the other end portion. ),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The measurement of the phase difference at the measurement point (C) is performed by the phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C),
The phase difference at the measurement point (L) is measured by the phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L),
The measurement method according to [1], wherein the measurement of the phase difference at the measurement location (R) is performed by the phase difference measurement device (R) and one or more phase difference measurement devices other than the phase difference measurement device (R). .
[3] A method for producing an optical film,
Step (I) of continuously forming an optical film,
Transporting the optical film formed in step (I) in a transport path, and measuring in-plane retardation Re, thickness-direction retardation Rth, or both of the optical film being transported, and (II), and Based on the in-plane retardation Re measured in the step (II), the in-plane retardation Rth, or both of these values, the conditions for the formation in the step (I) are adjusted, and the in-plane retardation Re is adjusted. Feedback step (III) for adjusting the thickness direction phase difference Rth or both of them to a predetermined value
Including
The step (II) includes:
By a plurality of phase difference measuring devices provided apart in the TD direction of the transport path, at each of a plurality of measurement places separated in the TD direction, a plurality of measurements on the surface of the optical film passing through the measurement places A step of measuring a phase difference between points, wherein at each of two or more measurement points, two or more of the phase difference measuring devices measure a phase difference from a plurality of polar angle directions. ), And an in-plane phase difference Re, a thickness direction phase difference Rth, or both of them at each of the measurement points based on the plurality of phase difference values measured in the measurement step (i). Calculation step (ii)
And a manufacturing method.
[4] In the measurement step (i),
The plurality of phase difference measuring devices are a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device (R) for measuring the other end portion. ),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The measurement of the phase difference at the measurement point (C) is performed by the phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C),
The phase difference at the measurement point (L) is measured by the phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L),
The manufacturing method according to [3], wherein the measurement of the phase difference at the measurement location (R) is performed by the phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R). .
[5] An apparatus for measuring a retardation of an optical film,
A transporter that transports the optical film in a transport path,
A plurality of measurement points provided in the TD direction of the transport path, each measuring a phase difference of a plurality of measurement points on a surface of the optical film passing through the measurement point at each of a plurality of measurement points separated in the TD direction; A phase difference measuring device (i) for measuring a phase difference from a plurality of polar angle directions by two or more of the phase difference measuring devices at each of two or more of the measurement points. And calculating, in each of the measurement points, an in-plane phase difference Re, a thickness direction phase difference Rth, or both of them based on a plurality of phase difference values measured by the phase difference measuring device (i). Calculator (ii)
A measuring device.
[6] The plurality of phase difference measuring devices (i) are a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device (L) for measuring the other end portion. Including a phase difference measuring device (R),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C) are provided to measure a phase difference at the measurement point (C),
The phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L) are provided to measure a phase difference at the measurement location (L).
The phase difference measurement device (R) and one or more phase difference measurement devices other than the phase difference measurement device (R) are provided to measure the phase difference at the measurement location (R). [5] The measuring device as described.
[7] An apparatus for manufacturing an optical film,
Forming device (I) for continuously forming an optical film,
A measuring device (II) for conveying the optical film formed by the forming device (I) in a conveying path and measuring an in-plane retardation Re, a thickness direction retardation Rth, or both of the conveyed optical film; And adjusting the conditions for formation by the forming apparatus (I) based on the in-plane retardation Re and the thickness direction retardation Rth measured by the measuring apparatus (II), or both of the values. A feedback device (III) for adjusting the internal phase difference Re, the thickness direction phase difference Rth, or both of them to a predetermined value.
Including
The measuring device (II) comprises:
A transporter that transports the optical film in a transport path,
A plurality of measurement points provided in the TD direction of the transport path, each measuring a phase difference of a plurality of measurement points on a surface of the optical film passing through the measurement point at each of a plurality of measurement points separated in the TD direction; A phase difference measuring device (i) for measuring a phase difference from a plurality of polar angle directions by two or more of the phase difference measuring devices at each of two or more of the measurement points. And calculating, in each of the measurement points, an in-plane phase difference Re, a thickness direction phase difference Rth, or both of them based on a plurality of phase difference values measured by the phase difference measuring device (i). Calculator (ii)
Manufacturing equipment, including:
[8] The plurality of phase difference measuring devices (i) include a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device (L) for measuring the other end portion. Including a phase difference measuring device (R),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C) are provided to measure a phase difference at the measurement point (C),
The phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L) are provided to measure a phase difference at the measurement location (L).
The phase difference measurement device (R) and one or more phase difference measurement devices other than the phase difference measurement device (R) are provided to measure the phase difference at the measurement location (R). Manufacturing apparatus according to the above.

According to the measuring method and the measuring apparatus of the present invention, the in-plane retardation Re and the thickness are not hindered in the quality of the product in the production of the optical film and the smoothness of the production, and at many measurement points in a wide area of the film surface. The directional phase difference Rth can be accurately measured.
According to the manufacturing method and the manufacturing apparatus of the present invention, a high-quality optical film in which the in-plane retardation Re and the thickness direction retardation Rth are precisely controlled can be smoothly manufactured.

FIG. 1 is a perspective view schematically showing one example of the manufacturing apparatus of the present invention including the measuring apparatus of the present invention. FIG. 2 is a cross-sectional view illustrating the relationship between the phase difference measuring device and the measurement points on the optical film at the measurement points in the measurement device 200 shown in FIG. FIG. 3 is a graph conceptually showing a calculation for obtaining the in-plane phase difference Re and the thickness direction phase difference Rth at the measurement point P1 from the measured value and the measurement angle of the phase difference at the measurement point P1 shown in FIG. . FIG. 4 is a cross-sectional view illustrating a relationship between a phase difference measuring device and a measurement point on an optical film at a measurement location in the measurement device according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view illustrating a relationship between a phase difference measuring device and a measurement point on an optical film at a measurement location in the measurement device according to the third embodiment of the present invention. FIG. 6 is a graph conceptually showing a calculation for obtaining the in-plane retardation Re and the thickness direction retardation Rth at the measurement point P3 from the measured values and the measurement angles of the phase difference at the measurement point P3 shown in FIG. .

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and examples, and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and equivalents thereof.

  In the following description, a “long” film refers to a film having a length of about 5 times or more with respect to the width of the film, preferably having a length of 10 times or more, and Refers to those having a length such that they can be wound into a roll and stored or transported.

  In the following description, unless the element directions are “parallel” and “vertical”, unless otherwise specified, an error in a range that does not impair the effects of the present invention, for example, in a range of ± 5 ° may be included. .

In the following description, the MD direction (machine direction) is a flow direction of a film conveyed on a production line, and usually represents a direction corresponding to a long direction of a long film conveyed. In a long film, a long direction usually corresponds to a longitudinal direction of the film. Further, in the following description, “upstream” or “downstream” means upstream and downstream in the MD direction unless otherwise specified.
The TD direction (traverse direction) is a direction parallel to the surface of the film to be conveyed and a direction perpendicular to the MD direction, and is usually a direction corresponding to the width direction of the long film to be conveyed. Represent. In a long film, the width direction usually corresponds to the lateral direction of the film. Further, in the present application, a direction horizontal to both the MD direction and the TD direction may be referred to as a TH direction.

  In the following description of the specific example, for convenience of explanation, the left and right sides of the edge of the conveyed film in the TD direction are respectively left and right when the horizontally conveyed film is observed from the MD direction upstream side. Is defined as In some of the drawings of the present application, the MD direction, the TD direction, and the TH direction are indicated by coordinate axes assigned with respective signs, and the left TD direction and the right TD direction are denoted by TD (L) and TD (R), respectively. The coordinates are indicated by coordinate axes.

[First embodiment]
FIG. 1 is a perspective view schematically showing one example of the manufacturing apparatus of the present invention including the measuring apparatus of the present invention. Hereinafter, the measuring apparatus and the manufacturing apparatus of the present invention and the measuring method and the manufacturing method of the present invention will be described using this example as a first embodiment.

  1 includes a forming device 100, a measuring device 200, a winding device 300, and a feedback device (not shown). The forming device 100, the measuring device 200, and the winding device 300 are arranged in this order from upstream to downstream on the manufacturing line of the manufacturing device 10.

  In this example, a forming apparatus 100 is an apparatus that continuously forms a long film by melt extrusion molding, and includes a die 101 and a cast roll 102. The molten resin 11 continuously discharged from the die 101 is cooled in the cast roll 102, whereby the optical film 12 is continuously formed. The formed optical film 12 is transported along a horizontal transport path and supplied to the measuring device 200.

  In the present invention, the forming device for performing the forming process of the optical film is not limited to the melt extrusion molding device exemplified in the first embodiment, and may be a device of another method, thereby performing the forming process of another method. May go. The forming step may also include steps such as stretching, heating, and cooling the film, and the forming apparatus may include components for performing such steps.

The measurement device 200 includes a transporter (not shown) that transports the optical film in a transport path, a plurality of phase difference measurement devices, a light source 280, and a calculator 290.
The transporter may be in any form, such as a transporter having a transport roller, a transporter having a gripper for gripping and transporting the film. In this example, in the measuring device 200, the optical film 12 is transported horizontally in the direction indicated by the arrow A1.

  In this example, two phase difference measuring devices 201L and 201R are provided as phase difference measuring devices. The phase difference measuring devices 201L and 201R are provided above the conveyed optical film 12 so as to be separated from the optical film 12 and to be separated from each other. In this example, the phase difference measuring devices 201L and 201R are aligned in the TD direction, the phase difference measuring device 201L is provided at the left end of the optical film 12, and the phase difference measuring device 201R is located at the right end of the optical film 12. Section.

  As the phase difference measuring devices 201L and 201R, a device capable of simultaneously measuring the phase difference at a plurality of locations of the optical film in a certain range of an area can be appropriately selected and used. Specifically, a phase difference measuring device including a polarizer having a pattern in which the direction of transmitted polarized light is different for each region and a light receiving element capable of independently receiving the intensity of light passing through each region is provided. Can be used. More specifically, for example, a measuring device described in Patent Document 2 can be used. More specifically, a photonic crystal polarizer may be provided as such a polarizer, and a light receiving element of a line scan camera or a light receiving element of a two-dimensional camera may be used as a light receiving element.

  The phase difference measuring devices 201L and 201R generally observe the optical film 12 optically, and may specifically observe light transmitted through the optical film 12. In this example, the measurement device 200 includes a light source 280 that illuminates the measurement points Z1 and Z5 at a position on the optical film opposite to the phase difference measurement devices 201L and 201R. By providing a light source 280 and arranging them so that light emitted from the light source 280 and transmitted through the optical film 12 is received and measured by the phase difference measuring devices 201L and 201R, the accuracy of such observation can be increased. . Examples of the light source include a cold cathode tube, an optical fiber illumination, and a flat light source, which can stably emit light having a wavelength necessary for measurement and can uniformly emit light in a region including a measurement point. Known light sources can be used.

  Each of the phase difference measuring devices 201L and 201R includes a plurality of measurement points P1 and P5 on the surface of the optical film 12 passing through the measurement points Z1 and Z5 at the plurality of measurement points Z1 and Z5 separated in the TD direction. Is provided to measure the phase difference of That is, the phase difference measuring device 201L simultaneously measures the phase difference of the optical film 12 in both the measurement locations Z1 and Z5 in a fixed state, and the phase difference measurement device 201R also measures the measurement locations Z1 and Z5 in a fixed state. In both cases, a phase difference of the optical film 12 is measured at the same time.

  FIG. 2 is a cross-sectional view illustrating the relationship between the phase difference measuring device and the measurement points on the optical film at the measurement points in the measurement device 200 shown in FIG. FIG. 2 shows the phase difference measuring devices 201L and 201R in the measuring device 200 and the measuring points P1 and P5 on the optical film 12 at the measuring points Z1 and Z5. In FIG. 2, the optical film 12 is shown as a cross section cut along a plane parallel to the TD direction and the TH direction. In this example, the direction in which the phase difference measuring device 201L observes the measurement points P1 and P2 is inclined in the TD (L) direction with respect to the perpendicular line Ly of the optical film 12, and the phase difference measuring device 201R sets the measurement point P1. And the direction of observing P2 is inclined in the TD (R) direction with respect to the perpendicular Ly of the optical film 12.

  In the measurement of the optical film using the phase difference measuring device described above, when the measurement is performed from a direction perpendicular to the surface of the optical film, the in-plane retardation Re of the optical film can be usually measured. However, when the measurement is performed from a direction that is not perpendicular to the surface of the optical film, a phase difference in an oblique direction observed from the direction is measured. However, when such a measurement of the phase difference in the oblique direction is performed from two or more different directions for a certain measurement point, the in-plane phase difference is calculated based on the measurement angle and the measured value of the two or more phase differences. Re and the thickness direction phase difference Rth can be obtained by calculation. Therefore, the measured values at the respective measurement points by the phase difference measuring devices 201L and 201R are output from the phase difference measuring devices 201L and 201R and input to the calculator 290, and in addition, information of the respective measurement angles is input to the calculator 290. Then, by performing the calculation in the calculator 290, the in-plane retardation Re and the thickness direction retardation Rth at each measurement point can be obtained.

  For example, at the measurement point P1 in the example shown in FIG. 2, the phase difference from the direction inclined by an angle θ1L with respect to the perpendicular Ly is measured by the phase difference measuring device 201L, and the phase difference is measured by the phase difference measuring device 201R. On the other hand, the phase difference from the direction inclined by the angle θ1R is measured. The in-plane phase difference Re and the thickness direction phase difference Rth at the measurement point P1 can be obtained by calculation from the angle θ1L, the angle θ1R, and the respective phase difference values.

  The calculation of the in-plane phase difference Re and the thickness direction phase difference Rth from the measured values and the measurement angles of a plurality of phase differences at a certain measurement point can be performed by solving an elliptic equation. FIG. 3 is a graph conceptually showing a calculation for obtaining the in-plane phase difference Re and the thickness direction phase difference Rth at the measurement point P1 from the measured value and the measurement angle of the phase difference at the measurement point P1 shown in FIG. .

  In the example of the calculation illustrated in FIG. 3, a line segment 32 (R) inclined at an angle θ1R with respect to the y-axis with respect to the coordinate axis and starting at the origin Po, and inclined at an angle θ1L with respect to the y-axis as the starting point. Draw a line segment 32 (L). The lengths of the line segments 32 (R) and 32 (L) are lengths proportional to measured values of the phase difference by the phase difference measuring devices 201R and 201L by a certain proportionality constant, respectively. The equation of the ellipse 31 passing through the end point P (R) of the line segment 32 (R) and the end point P (L) of the line segment 32 (L) is obtained, and the intersection Px between the ellipse and the x axis and the ellipse are calculated. The coordinates of the intersection Py with the y-axis are obtained. The in-plane retardation Re at the measurement point P1 can be obtained based on the distance between Po and Px and the proportionality constant, and the thickness direction retardation Rth at the measurement point P1 is determined by the distance between Po and Py and the proportionality constant. Can be determined based on

  By performing such calculations at the measurement point P1 and other measurement points, the in-plane retardation Re and the thickness direction retardation Rth can be obtained at a plurality of measurement points. Therefore, by repeating such measurement and calculation at the measurement points Z1 and Z5, the surface of the conveyed optical film 12 is measured at a plurality of measurement points separated in the TD direction and aligned in the MD direction. The internal retardation Re and the thickness direction retardation Rth can be measured.

  By increasing the number of measurements per unit time, the distribution of the measurement points in the MD direction can be made denser, and more detailed information on the in-plane retardation Re and the thickness direction retardation Rth can be obtained. it can. As a result, even if the transport speed of the optical film 12 is high, a detailed distribution of the in-plane retardation Re and the thickness direction retardation Rth can be obtained. Specifically, the number of measurements may be preferably at least 3 times / second, more preferably at least 10 times / second. The upper limit of the number of measurements is determined by factors such as the performance of the phase difference measuring device and the calculator, and may be, for example, 100 times / second or less.

  As shown in FIG. 1, in the first embodiment, after performing the measuring method using the measuring device 200, the optical film 12 is wound up by the winding device 300 to form a roll. The calculation result by the calculator 290 can be stored and used, for example, when cutting a product from the obtained optical film 12 in the form of a roll. More specifically, for example, when cutting out a rectangular product having a desired dimension, a portion where the in-plane retardation Re and / or the thickness direction retardation Rth is out of the standard (that is, out of the desired value range). , And high quality products can be obtained. By implementing the measurement method of the present invention, detailed information on the in-plane retardation Re and the thickness direction retardation Rth in which the distribution of measurement points is dense can be obtained. And the exclusion of nonstandard parts can be performed more appropriately.

  Alternatively, the calculation result of the calculator 290 may be transmitted to a feedback device (not shown) in the forming apparatus 100 by the communication unit 291 to execute the manufacturing method of the present invention. For example, the result of the calculation by the computer 290 is fed back to the adjustment of the operation of any of the components that can affect the phase difference in the forming apparatus 100, so that a more uniform optical film 12 can be formed. . For example, the extrusion rate of the resin into the die 101, the interval between the openings of the die 101, the stretching ratio of the film and other stretching conditions, and the degree of operation such as the temperature and temperature distribution of heating and cooling are adjusted. The optical film 12 having the in-plane retardation Re and the thickness direction retardation Rth can be continuously manufactured.

[Second embodiment]
In the above-described first embodiment, only two measurement points Z1 and Z5 are set as measurement points in the measurement device 200, and a row of the measurement points P1 and a row of P5 that are continuous in the MD direction on the optical film 12 are set. Although the measurement was performed only in two rows, the present invention is not limited to this, and the measurement may be performed in three or more measurement points as a more preferable embodiment.

  An embodiment in which the measurement points in the first embodiment are changed will be described below as a second embodiment. FIG. 4 is a cross-sectional view illustrating a relationship between a phase difference measuring device and a measurement point on an optical film at a measurement location in the measurement device according to the second embodiment of the present invention. 4 as in FIG. 2, the optical film 12 is shown as a cross section cut along a plane parallel to the TD direction and the TH direction.

  The second embodiment shown in FIG. 4 is different from the first embodiment in that measurement points Z2 to Z4 are set as measurement points in addition to measurement points Z1 and Z5, and a phase difference is measured at these points. different. By setting the measurement points Z1 to Z5, in addition to the measurement points P1 and P5 on the optical film passing the measurement points Z1 and Z5, the measurement points P2 to P4 on the optical film passing the measurement points Z2 to Z4. The phase difference is also measured, and as a result, on the optical film 12, a row of the measurement points P1 continuous in the MD direction, a row of the measurement points P2 continuous in the MD direction, a row of the measurement points P3 continuous in the MD direction, The measurement is performed in five rows, ie, a row of measurement points P4 continuous in the MD direction and a row of measurement points P5 continuous in the MD direction.

  At each of the measurement points P1 to P5, the phase difference in the oblique direction is measured by both the phase difference measuring device 201L and the phase difference measuring device 201R. The values measured by the phase difference measuring devices 201L and 201R at the respective measurement points are output from the phase difference measuring devices 201L and 201R and input to the calculator. In addition, information of the respective measurement angles is input to the calculator, and the calculator , The in-plane retardation Re and the thickness direction retardation Rth at each measurement point can be obtained.

  As described above, by performing measurement at more measurement points than in the first embodiment, the distribution of measurement points in the TD direction can be made denser, and more detailed in-plane retardation Re and thickness direction retardation Rth can be obtained. Information can be obtained. Further, even in the production of a wide optical film, detailed information on the in-plane retardation Re and the thickness direction retardation Rth can be obtained.

[Third embodiment]
In the first embodiment described above, only two phase difference measuring devices are provided at the left and right ends of the optical film as a phase difference measuring device, but the present invention is not limited to this, and as a more preferable embodiment, Three or more phase difference measuring devices may be provided.

  More specifically, when only two phase difference measuring devices are provided at the left and right ends of the optical film, the elevation angle of both phase difference measuring devices is measured at a measurement location far from both phase difference measuring devices. (Observation angle with the vertical direction being 0 °) increases, and the measurement error may increase. In addition, the in-plane phase difference Re and the thickness direction phase difference Rth can be obtained from only the two measured values by these phase difference measuring devices at the same distance from both the left and right end phase difference measuring devices. There is a singularity that cannot be done. Here, by providing an additional phase difference measuring device between the phase difference measuring devices at the left and right end portions, the measurement error can be reduced, and the in-plane phase difference Re at the singular point. And the thickness direction phase difference Rth.

  An embodiment in which the number of phase difference measuring devices in the second embodiment is changed will be described below as a third embodiment. FIG. 5 is a cross-sectional view illustrating a relationship between a phase difference measuring device and a measurement point on an optical film at a measurement location in the measurement device according to the third embodiment of the present invention. 5 as in FIG. 4, the optical film 12 is shown as a cross section cut along a plane parallel to the TD direction and the TH direction.

  The third embodiment shown in FIG. 5 includes, as a plurality of phase difference measuring devices, a phase difference measuring device 201L for measuring the left end portion and a phase difference measuring device 201R for measuring the right end portion, and a measuring point. The second embodiment differs from the second embodiment in that a phase difference measuring device 201 </ b> C for central portion measurement provided vertically above Z <b> 3 is provided.

  In this example, the phase difference measuring device 201C measures the phase difference at the measurement points Z1 to Z5. Therefore, in this example, at each of the measurement points P1 to P5 on the optical film 12 passing through the measurement points Z1 to Z5, the three phase difference measurement devices 201L, 201C, and 201R determine the oblique direction or The phase difference observed from the vertical direction is measured. The values measured by the three phase difference measuring devices at the respective measurement points are output from the phase difference measuring device and input to the calculator. In addition, information of the respective measurement angles is input to the calculator, and the calculator calculates. Thus, the in-plane retardation Re and the thickness direction retardation Rth at each measurement point can be obtained.

  The calculation for obtaining the in-plane phase difference Re and the thickness direction phase difference Rth from the measured values and the measurement angles of the plurality of phase differences at a certain measurement point is similar to the case of the first embodiment. It can be done by solving. However, in the third embodiment, since the equation of the ellipse can be obtained based on the three coordinates, error correction and the like can be performed, and a more accurate measurement result can be obtained. Further, a measurement result can be obtained even at a singular point where the in-plane retardation Re and the thickness direction retardation Rth cannot be determined only by the measurement value of 2.

  FIG. 6 shows an example of calculation at such a singular point. FIG. 6 is a graph conceptually showing a calculation for obtaining the in-plane retardation Re and the thickness direction retardation Rth at the measurement point P3 from the measured values and the measurement angles of the phase difference at the measurement point P3 shown in FIG. .

  In the calculation example shown in FIG. 6, a line segment 62 (R) having the origin Po as the start point and the angle θ1R with respect to the y-axis, and the origin Po as the start point and the angle θ1L with respect to the y-axis are inclined with respect to the coordinate axes. Draw a line segment 62 (L) and a line segment 62 (C) starting from the origin Po and parallel to the y-axis. The lengths of the line segments 62 (R), 62 (C), and 62 (L) are lengths proportional to the measured values of the phase difference by the phase difference measuring devices 201R, 201C, and 201L, respectively, by a certain proportionality constant.

  In this example, the measurement point P3 is a singular point at a distance equal to both of the measuring devices 201L and 201R. Therefore, in the graph shown in FIG. 6, the line segment 62 (R) and the line segment 62 (L) are: It becomes line-symmetric about the y-axis. In such a case, based on only the end point P (R) of the line segment 62 (R) and the end point P (L) of the line segment 62 (L), the equation of the ellipse passing through them is obtained. In addition to the above, other ellipses such as the ellipse 63 are also obtained, so that the solution is not fixed to one. Here, when the information of the end point P (C) of the line segment 62 (C) is further added, the ellipse 61 is determined, whereby the in-plane phase difference Re and the thickness direction phase difference Rth at the measurement point P3 can be obtained. .

[Optical film]
The optical film to be measured by the measuring device and the measuring method of the present invention, and the optical film that can be manufactured by the manufacturing device and the manufacturing method of the present invention are not particularly limited, and may be optical films used for various applications. Specifically, the film may be required to have a controlled retardation in some form.

  The optical film may be a single-layer film or a multilayer film having a plurality of layers. The optical film may also be a stretched film or an unstretched film.

  The optical film preferably has a total light transmittance of 85% to 100%, more preferably 90% to 100%. The light transmittance can be measured using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible-near-infrared spectrophotometer “V-570”) in accordance with JIS K0115.

  The thickness of the optical film is preferably 1 μm or more, more preferably 5 μm or more, further preferably 10 μm or more, while preferably 300 μm or less, more preferably 200 μm or less, and still more preferably 100 μm or less.

  The in-plane retardation Re of the optical film is a value represented by (nx−ny) × d. The thickness direction phase difference Rth is a value represented by {((nx + ny) / 2) −nz} × d. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the film and in a direction giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the film and in a direction perpendicular to the direction of nx. nz represents the refractive index in the thickness direction of the film. d represents the thickness of the film.

  Whether or not the phase difference measured by the measuring method of the present invention is a value effectively measured is determined by a known phase difference measuring device (for example, “KOBRA-21ADH” manufactured by Oji Scientific Instruments, Photonic Lattice) Manufactured by "WPA-micro") or the Senarmont method by separately measuring the retardation of the optical film. Further, the measurement wavelength of the phase difference can be set to an arbitrary wavelength according to the use of the optical film, but can be usually 550 nm.

[Modification]
The measuring device and the manufacturing device of the present invention and the measuring method and the manufacturing method of the present invention are not limited to those according to the above-described first to third embodiments, and for example, even if these embodiments are further modified. Good. In the following, a description will be given with an example of such a modification.

  In the third embodiment, three phase difference measuring devices 201L, 201C, and 201R are used to measure all five of the set measurement points Z1 to Z5. The present invention is not limited to the mode in which the measuring device measures all measurement points. For example, three phase difference measuring devices may be used, and measurement may be performed by only two phase difference measuring devices at some or all of the measurement points.

  Specifically, by performing a measurement using one phase difference measuring device close to the measurement location and one or more other phase difference measurement devices at a certain measurement location, two or more measurement results at the measurement location are obtained. Can be obtained. As a more specific example, the plurality of phase difference measuring devices include a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device (L) for measuring the other end portion. And a phase difference measuring device (R) for measuring the position of the phase difference measuring device (C) at the center, the measuring position (L) at the end on the side where the phase difference measuring device (L) is located, and the phase difference measuring device The measurement of the phase difference at the measurement location (C) includes the measurement location (R) at the end on the side where the (R) is located, and measures the phase difference at the measurement location (C) and the phase difference measurement instrument (C). The above-described phase difference measuring device is used, and the measurement of the phase difference at the measurement point (L) is performed using the phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L). The measurement of the phase difference at the point (R) is performed by using a phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R). Manner of performing the like. In this way, at each measurement point, by appropriately selecting the phase difference measuring device to be used, it is possible to perform a calculation based on data based on the measurement from the measurement point with a relatively small error, and as a result, More accurate in-plane retardation Re and thickness direction retardation Rth can be obtained.

  In the third embodiment, the phase difference measuring device 201C for measuring the center portion is located at the same position from both the phase difference measuring device 201L for measuring the left end portion and the phase difference measuring device 201R for measuring the right end portion. However, the present invention is not limited to this, and the phase difference measuring device for measuring the center portion is more centered than the phase difference measuring device for measuring the left end portion and the phase difference measuring device for measuring the right end portion. It can be provided at any position near the part. For example, the phase difference measuring device for measuring the central portion may be arranged at a position closer to one of the phase difference measuring device for measuring the left end portion and the phase difference measuring device for measuring the right end portion. .

  In the first to third embodiments, the plurality of phase difference measuring devices are provided in a manner separated from each other in the TD direction and aligned in the TD direction. However, the present invention is not limited to this. May be located upstream or downstream of another phase difference measuring device. More specifically, for example, the phase difference measuring device 201L at the left end of the optical film 12 may be located relatively downstream as compared with the phase difference measuring device 201R at the right end. In this case, a certain measuring point on the conveyed optical film may pass through a measuring point by the phase difference measuring device 201R, and then pass through a measuring point by the phase difference measuring device 201L. In this case, based on the information on the transport speed of the film, the time lag of the measurement by the phase difference measuring devices 201R and 201L is offset by the computer 290, so that at a certain measurement point, the measurement result by the phase difference measuring device 201L and The information of the measurement result by the phase difference measuring device 201R can be obtained. By locating one phase difference measuring device upstream or downstream of another phase difference measuring device, it is possible to freely optimize the measurement conditions of each phase difference measuring device.

In the first to third embodiments, the number of phase difference measurement devices in the measurement device 200 is two or three, and the number of measurement points is two or five. However, the present invention is not limited to this. Four or more phase difference measuring devices may be provided in one measuring device, and the number of measuring points may be an arbitrary number such as three, four, six or more. For example, a large number of measurement points can be provided in the TD direction using a high-resolution phase difference measuring device. By providing a large number of measurement points and shortening the intervals between the measurement points, the distribution of the measurement points in the TD direction can be made even denser, and more detailed in-plane phase difference Re and thickness direction phase difference Rth can be obtained. Information can be obtained. The distance between the measurement points in the TD direction may be preferably 100 mm or less, more preferably 25 mm or less.
Further, for example, the number and position of the phase difference measuring devices in the TD direction can be appropriately adjusted in accordance with the width of the optical film. When three or more phase difference measuring devices are provided, the intervals may be equal or may be unequal. The narrower the interval of the phase difference measuring device in the TD direction, the more precise the measurement can be made. Specifically, the interval in the TD direction of the phase difference measuring device can be preferably 1000 mm or less, more preferably 500 mm or less. Further, it is preferable that the distance between the phase difference measuring device and the optical film is substantially equal to the distance in the TD direction of the phase difference measuring device from the viewpoint of performing accurate measurement efficiently. More preferably, it can be 500 mm or less.

  In the first to third embodiments, the phase difference measuring device measures only the phase difference, and acquires only the in-plane phase difference Re and the thickness direction phase difference Rth based on the phase difference. However, the present invention is not limited to this. For example, by using a phase difference measuring device, in addition to the phase difference, other optical information such as the azimuth of the optical axis of the optical film is also measured, and this is calculated by a computer. The information may be corrected and acquired as information.

  In the first to third embodiments, the form in which a long optical film is manufactured and measured is exemplified. However, the present invention is not limited to this. For example, a manufacturing line that continuously manufactures and transports a sheet-like film. It can also be applied to

  In the first to third embodiments, the calculation step was performed by the computer 290, but the measurement method and the manufacturing method of the present invention are not limited to this, and the operator can use the information output from the phase difference measuring device. May be manually calculated by the operator based on the. In the first to third embodiments, the feedback step is performed by transmitting the calculation result by the computer 290 to the feedback device via the communication unit 291. However, the manufacturing method of the present invention is not limited to this. The present invention is not limited thereto, and the operator may manually perform the feedback step based on the calculation result by the computer or the calculation result by the operator.

10: Manufacturing apparatus 100: Forming apparatus 200: Measuring apparatus 300: Winding apparatus 101: Die 102: Cast roll 11: Molten resin 12: Optical film 280: Light source 290: Calculator 201L, 201C, 201R: Phase difference measuring instrument Z1 To Z5: measurement points in the measurement device P1 to P5: measurement points on the optical film Ly: perpendicular line Po: origin 32 (R): line segment 32 (L): line segment 31: ellipse Px: intersection of ellipse and x-axis Py: intersection of ellipse and y axis 62 (R): line segment 62 (L): line segment 62 (C): line segment 61: ellipse 63: ellipse

Claims (4)

A method for measuring a phase difference of an optical film conveyed in a conveyance path,
By a plurality of phase difference measuring devices provided apart in the TD direction of the transport path, at each of a plurality of measurement places separated in the TD direction, a plurality of measurements on the surface of the optical film passing through the measurement places Measuring a phase difference of a point, at each of two or more of the measurement points, measuring a phase difference from a plurality of non-perpendicular polar angle directions by two or more of the phase difference measuring devices. Step (i), and at each of the measurement points, the in-plane retardation Re, the thickness direction retardation Rth, or both at each of the measurement points based on the plurality of phase difference values measured in the measurement step (i). Calculation step (ii) of calculating
Including
The TD direction is a direction parallel to the film plane of the optical film to be conveyed, and, Ri perpendicular der in the flow direction of the optical film to be conveyed,
In the measurement step (i),
The plurality of phase difference measuring devices are a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device (R) for measuring the other end portion. ),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The measurement of the phase difference at the measurement point (C) is performed by the phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C),
The phase difference at the measurement point (L) is measured by the phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L),
A measurement method in which the measurement of the phase difference at the measurement location (R) is performed by the phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R) . A method for producing an optical film, comprising:
Step (I) of continuously forming an optical film,
Transporting the optical film formed in step (I) in a transport path, and measuring in-plane retardation Re, thickness-direction retardation Rth, or both of the optical film being transported, and (II), and Based on the in-plane retardation Re measured in the step (II), the in-plane retardation Rth, or both of these values, the conditions for the formation in the step (I) are adjusted, and the in-plane retardation Re is adjusted. Feedback step (III) for adjusting the thickness direction phase difference Rth or both of them to a predetermined value
Including
The step (II) includes:
By a plurality of phase difference measuring devices provided apart in the TD direction of the transport path, at each of a plurality of measurement places separated in the TD direction, a plurality of measurements on the surface of the optical film passing through the measurement places Measuring a phase difference of a point, at each of two or more of the measurement points, measuring a phase difference from a plurality of non-perpendicular polar angle directions by two or more of the phase difference measuring devices. Step (i), and at each of the measurement points, the in-plane retardation Re, the thickness direction retardation Rth, or both at each of the measurement points based on the plurality of phase difference values measured in the measurement step (i). Calculation step (ii) of calculating
Including
The TD direction is a direction parallel to the film plane of the optical film to be conveyed, and, Ri perpendicular der in the flow direction of the optical film to be conveyed,
In the measurement step (i),
The plurality of phase difference measuring devices are a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device (R) for measuring the other end portion. ),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The measurement of the phase difference at the measurement point (C) is performed by the phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C),
The phase difference at the measurement point (L) is measured by the phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L),
A method for measuring the phase difference at the measurement location (R) using the phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R) . An optical film retardation measuring device,
A transporter that transports the optical film in a transport path,
A plurality of measurement points provided in the TD direction of the transport path, each measuring a phase difference of a plurality of measurement points on a surface of the optical film passing through the measurement point at each of a plurality of measurement points separated in the TD direction; A phase difference measuring device, wherein at each of two or more measurement points, two or more of the phase difference measuring devices measure a phase difference from a plurality of non-perpendicular polar angle directions. (I), and at each of the measurement points, an in-plane retardation Re, a thickness direction retardation Rth, or a phase retardation at each of the measurement points based on a plurality of phase difference values measured by the phase difference measuring device (i). Calculator for calculating both (ii)
Including
The TD direction is a direction parallel to the film plane of the optical film to be conveyed, and, Ri perpendicular der in the flow direction of the optical film to be conveyed,
The plurality of phase difference measuring devices (i) are a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device for measuring the other end portion. Vessel (R),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C) are provided to measure a phase difference at the measurement point (C),
The phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L) are provided to measure a phase difference at the measurement location (L).
A measuring device provided with the phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R) for measuring a phase difference at the measurement point (R) . An apparatus for manufacturing an optical film,
Forming device (I) for continuously forming an optical film,
A measuring device (II) for conveying the optical film formed by the forming device (I) in a conveying path and measuring an in-plane retardation Re, a thickness direction retardation Rth, or both of the conveyed optical film; And adjusting the conditions for formation by the forming apparatus (I) based on the in-plane retardation Re and the thickness direction retardation Rth measured by the measuring apparatus (II), or both of the values. A feedback device (III) for adjusting the internal phase difference Re, the thickness direction phase difference Rth, or both of them to a predetermined value.
Including
The measuring device (II) comprises:
A transporter that transports the optical film in a transport path,
A plurality of measurement points provided in the TD direction of the transport path, each measuring a phase difference of a plurality of measurement points on a surface of the optical film passing through the measurement point at each of a plurality of measurement points separated in the TD direction; A phase difference measuring device, wherein at each of two or more measurement points, two or more of the phase difference measuring devices measure a phase difference from a plurality of non-perpendicular polar angle directions. (I), and at each of the measurement points, an in-plane retardation Re, a thickness direction retardation Rth, or a phase retardation at each of the measurement points based on a plurality of phase difference values measured by the phase difference measuring device (i). Calculator for calculating both (ii)
Including
The TD direction is a direction parallel to the film plane of the optical film to be conveyed, and, Ri perpendicular der in the flow direction of the optical film to be conveyed,
The plurality of phase difference measuring devices (i) are a phase difference measuring device (C) for measuring a central portion, a phase difference measuring device (L) for measuring one end portion, and a phase difference measuring device for measuring the other end portion. Vessel (R),
The measurement point is a central measurement point (C), an end measurement point (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measuring device (R) is located. Part of the measurement point (R),
The phase difference measuring device (C) and one or more phase difference measuring devices other than the phase difference measuring device (C) are provided to measure a phase difference at the measurement point (C),
The phase difference measuring device (L) and one or more phase difference measuring devices other than the phase difference measuring device (L) are provided to measure a phase difference at the measurement location (L).
A manufacturing apparatus provided with the phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R) for measuring a phase difference at the measurement location (R) .

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