JP2016080473A - Phase difference measuring method for optical films, optical film manufacturing method, phase difference measuring device for optical films, and optical film manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference measuring method for optical films and related techniques that enable the in-plane phase difference Re and the thickness direction phase difference Rth to be accurately measured at many measuring points in large areas of film faces without sacrificing the product quality and manufacturing smoothness in the manufacture of optical films.SOLUTION: A phase difference measuring method for optical films carried along a carriage route comprises a step of measuring phase differences at a plurality of measuring points on the faces of the optical films passing measuring positions at each of multiple measuring positions separated from one another in a TD direction with a plurality of phase difference measuring tools separated from one another in the TD direction of the carriage route and measuring phase differences in a plurality of polar angle directions at two or more of the measuring points with two or more of the phase difference measuring tools.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical film retardation measurement method, an optical film manufacturing method, an optical film retardation measurement device, and an optical film manufacturing device.

  When manufacturing an optical film, it is required to precisely control the retardation in a wide area of the film surface. In manufacturing an optical film, it is also required to perform high-speed and continuous manufacturing on a manufacturing line in order to improve the manufacturing efficiency. Therefore, the phase difference of a wide area of the surface of the optical film transported at high speed and continuously can be measured accurately and quickly on the production line, and the measurement result can be fed back to the film forming process. 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 are precisely controlled. As an apparatus 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 transported optical film, such a phase difference measuring device is swung in the TD direction, thereby moving the phase difference measuring device so as to draw a wavy trajectory with respect to the conveyed film. Measurements in a measurement range having a spread in the TD direction and the MD direction have been widely performed so far.

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

JP-A-8-2012277 JP 2007-263593 A

  When the phase difference measuring device is swung in the production line, it is undesirable to drop foreign matter from the moving device that moves the phase difference measuring device, and to generate defects due to contact between the driving unit of the moving device and the film, or to obstruct manufacturing. May occur. Further, in the measurement of drawing a wavy trajectory with respect to the film to be conveyed, there are a wide range of portions that are not measured on the entire surface of the film, thereby overlooking a portion having a phase difference outside the standard. Such a part which is not measured increases especially when a film is conveyed at high speed.

  On the other hand, when the measurement using the phase difference measuring device described in Patent Document 2 is performed, 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, the measurement location near the phase difference measuring device on the film surface and the measurement location far from the phase difference measurement device. There is a problem that polar angles serving as a reference for phase difference measurement are different.

The object of the present invention is to prevent in-plane retardation Re and thickness direction retardation Rth at many measurement points in a wide area of the film surface without impeding product quality and manufacturing smoothness in optical film production. An object of the present invention is to provide an optical film retardation measuring method and an optical film retardation measuring apparatus that can be measured in the following manner.
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. It is to provide.

As a result of studies to solve the above-mentioned problems, the present inventors have used a combination of two or more phase difference measuring devices that measure the in-plane phase difference Re at a plurality of positions on the film surface, and based on information obtained from them. , Re and Rth can be measured at a number of points simultaneously, and the present invention has been completed.
That is, the present invention is as follows.

[1] A method for measuring a retardation of an optical film conveyed in a conveyance path,
A plurality of measurements on the surface of the optical film passing through the measurement location in each of a plurality of measurement locations separated in the TD direction by a plurality of phase difference measuring devices provided separately in the TD direction of the transport path. A step of measuring a phase difference between points, wherein at each of the two or more measurement points, the phase difference is measured from a plurality of polar angle directions by two or more of the phase difference measuring devices. ), And in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points based on a plurality of phase difference values measured in measurement step (i). Calculation step (ii)
Including a measuring method.
[2] In the measurement step (i),
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 (R) for measuring the other end portion. )
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
Measurement of the phase difference at the measurement location (C) is performed by one or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C),
Measurement of the phase difference at the measurement location (L) is performed by one or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L),
The measurement method according to [1], wherein the phase difference at the measurement location (R) is measured by one or more phase difference measuring devices other than the phase difference measuring device (R) and the phase difference measuring device (R). .
[3] A method for producing an optical film,
Step (I) of continuously forming an optical film,
A step (II) of measuring the in-plane retardation Re, the thickness direction retardation Rth, or both of the optical film conveyed in the conveyance path by conveying the optical film formed in the step (I); and Based on the values of the in-plane retardation Re, the thickness direction retardation Rth, or both measured in the step (II), the formation conditions in the step (I) are adjusted, and the in-plane retardation Re , Thickness direction phase difference Rth, or both of them are adjusted to a predetermined value (III)
Including
The step (II)
A plurality of measurements on the surface of the optical film passing through the measurement location in each of a plurality of measurement locations separated in the TD direction by a plurality of phase difference measuring devices provided separately in the TD direction of the transport path. A step of measuring a phase difference between points, wherein at each of the two or more measurement points, the phase difference is measured from a plurality of polar angle directions by two or more of the phase difference measuring devices. ), And in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points based on a plurality of phase difference values measured in measurement step (i). Calculation step (ii)
Manufacturing method.
[4] In the measurement step (i),
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 (R) for measuring the other end portion. )
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
Measurement of the phase difference at the measurement location (C) is performed by one or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C),
Measurement of the phase difference at the measurement location (L) is performed by one or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L),
The phase difference measurement 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). .
[5] An optical film retardation measuring device,
A transporter for transporting the optical film in the transport path;
A plurality of measurement points which are provided separately in the TD direction of the transport path and measure the phase differences of a plurality of measurement points on the surface of the optical film passing through the measurement point in each of the plurality of measurement points spaced in the TD direction. A phase difference measuring device (i) that measures 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. Based on a plurality of phase difference values measured by the phase difference measuring device (i), in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points. Calculator (ii)
Including a measuring device.
[6] The plurality of phase difference measuring devices (i) include a phase difference measuring device (C) for measuring the central portion, a phase difference measuring device (L) for measuring one end portion, and a device for measuring the other end portion. Including a phase difference measuring device (R),
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
One or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C) are provided to measure the phase difference at the measurement location (C),
One or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L) are provided to measure the phase difference at the measurement location (L),
One or more phase difference measuring devices other than the phase difference measuring device (R) and the phase difference measuring device (R) are provided to measure the phase difference at the measurement location (R). The measuring device described.
[7] An optical film manufacturing apparatus,
Forming apparatus (I) for continuously forming an optical film,
Measuring device (II) for measuring the in-plane retardation Re, the thickness direction retardation Rth, or both of the optical film conveyed by the forming device (I) in the conveying path. And adjusting the conditions of formation by the forming device (I) based on the in-plane retardation Re, the thickness direction retardation Rth, or both values measured by the measuring device (II), 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)
A transporter for transporting the optical film in the transport path;
A plurality of measurement points which are provided separately in the TD direction of the transport path and measure the phase differences of a plurality of measurement points on the surface of the optical film passing through the measurement point in each of the plurality of measurement points spaced in the TD direction. A phase difference measuring device (i) that measures 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. Based on a plurality of phase difference values measured by the phase difference measuring device (i), in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points. Calculator (ii)
Including manufacturing equipment.
[8] The plurality of phase difference measuring devices (i) include a phase difference measuring device (C) for measuring the central portion, a phase difference measuring device (L) for measuring one end portion, and a device for measuring the other end portion. Including a phase difference measuring device (R),
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
One or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C) are provided to measure the phase difference at the measurement location (C),
One or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L) are provided to measure the phase difference at the measurement location (L),
The phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R) are provided to measure the phase difference at the measurement location (R). The manufacturing apparatus as described.

According to the measurement method and the measurement apparatus of the present invention, the in-plane retardation Re and the thickness are not disturbed at many measurement points in a wide region of the film surface without impeding the quality and smoothness of the product in the production of the optical film. The direction phase difference Rth can be accurately measured.
According to the production method and production 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 produced smoothly.

FIG. 1 is a perspective view schematically showing an 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 instrument and the measurement points on the optical film at the measurement location in the measurement apparatus 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 measurement 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 the relationship between the phase difference measuring device and the measurement points on the optical film at the measurement location in the measurement apparatus of the second embodiment of the present invention. FIG. 5 is a cross-sectional view illustrating the relationship between the phase difference measuring instrument and the measurement points on the optical film at the measurement location in the measurement apparatus of the third embodiment of the present invention. FIG. 6 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 P3 from the measurement value and measurement angle 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 exemplifications, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

  In the following description, the “long” film refers to a film having a length of about 5 times or more, preferably 10 times or more of the film width. Refers to those having a length that is wound in a roll and stored or transported.

  In the following description, the directions of the elements “parallel” and “vertical” may include errors within a range that does not impair the effect of the present invention, for example, ± 5 °, unless otherwise specified. .

In the following description, an MD direction (machine direction) is a flow direction of a film conveyed in a production line, and usually represents a direction corresponding to a long direction of a long film to be conveyed. In the long film, the long direction usually coincides with the vertical direction of the film. Furthermore, in the following description, “upstream” or “downstream” refers to upstream and downstream in the MD direction unless otherwise specified.
The TD direction (traverse direction) is a direction parallel to the film surface to be transported and is perpendicular to the MD direction, and is usually a direction corresponding to the width direction of the long film to be transported. Represent. In the long film, the width direction usually coincides with the lateral direction of the film. Furthermore, 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 description of the specific examples below, for convenience of explanation, the left side and the right side of the end portion in the TD direction of the film to be transported are the left side and the right side when the horizontally transported film is observed from the upstream side in the MD direction, respectively. It is prescribed that In a part of the drawings of the present application, the MD direction, the TD direction, and the TH direction are indicated by coordinate axes with respective signs, and the leftward TD direction and the rightward TD direction are indicated by TD (L) and TD (R), respectively. This is indicated by the coordinate axis with the symbol.

[First embodiment]
FIG. 1 is a perspective view schematically showing an example of the manufacturing apparatus of the present invention including the measuring apparatus of the present invention. Below, this example is made into 1st embodiment, and the measuring apparatus and manufacturing apparatus of this invention, and the measuring method and manufacturing method of this invention are demonstrated.

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

  In this example, the forming apparatus 100 is an apparatus that continuously forms a long film by melt extrusion, and includes a die 101 and a cast roll 102. The molten resin 11 continuously discharged from the die 101 is cooled by 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 apparatus 200.

  In the present invention, the forming apparatus for performing the optical film forming process is not limited to the melt extrusion molding apparatus exemplified in the first embodiment, and may be an apparatus by another method, thereby forming the forming process of another method. You 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 measuring apparatus 200 includes a transporter (not shown) that transports the optical film in the transport path, a plurality of phase difference measuring devices, a light source 280, and a calculator 290.
A conveyance machine can be made into arbitrary forms, such as a conveyance machine provided with a conveyance roller, and a conveyance machine provided with a grasping tool which grasps and conveys a film. In this example, in the measuring apparatus 200, the optical film 12 is conveyed 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 201 </ b> L and 201 </ b> R are provided on the upper side of the conveyed optical film 12 so as to be separated from the optical film 12 and 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 the right end of the optical film 12. Provided in the section.

  As the phase difference measuring devices 201L and 201R, an apparatus capable of simultaneously measuring the phase difference at a plurality of locations on the optical film in a certain range 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 that can independently receive the intensity of light that has passed through each region. Can be used. More specifically, for example, a measuring device described in Patent Document 2 can be used. More specifically, a photonic crystal polarizer can be used as such a polarizer, and a light receiving element using a light receiving element of a line scan camera or a light receiving element of a two-dimensional camera can be used.

  The phase difference measuring devices 201 </ b> L and 201 </ b> R are usually for optically observing the optical film 12, and specifically, can observe light transmitted through the optical film 12. In this example, the measuring apparatus 200 includes a light source 280 that illuminates the measurement points Z1 and Z5 at a position of the optical film opposite to the phase difference measuring devices 201L and 201R. By providing the light source 280 and arranging such that the 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 the observation can be improved. . As a light source, it is possible to stably emit light having a wavelength necessary for measurement, and perform uniform light emission in a region including a measurement location, such as a cold cathode tube, an optical fiber illumination, a planar light source, etc. 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 that passes through the measurement points Z1 and Z5 in each of the plurality of measurement points Z1 and Z5 that are separated in the TD direction. It is provided to measure the phase difference. That is, the phase difference measuring device 201L simultaneously measures the phase difference of the optical film 12 at both the measurement points Z1 and Z5 in a fixed state, and the phase difference measuring device 201R is also fixed at the measurement points Z1 and Z5. In both cases, the phase difference of the optical film 12 is measured simultaneously.

  FIG. 2 is a cross-sectional view illustrating the relationship between the phase difference measuring instrument and the measurement points on the optical film at the measurement location in the measurement apparatus 200 shown in FIG. In FIG. 2, phase difference measuring devices 201L and 201R in the measuring apparatus 200 and measurement points P1 and P5 on the optical film 12 at the measurement locations Z1 and Z5 are shown. In FIG. 2, the optical film 12 is shown as a cross section cut by 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 normal line Ly of the optical film 12, and the phase difference measuring device 201R is measured at the measurement point P1. And the direction of observing P2 is inclined in the TD (R) direction with respect to the normal line Ly of the optical film 12.

  In the measurement of an optical film using the retardation 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 measurement is performed from a direction non-perpendicular to the surface of the optical film, an oblique phase difference observed from the direction is measured. However, when the measurement of the phase difference in the oblique direction at one measurement point is performed from two or more different directions, the in-plane phase difference is calculated based on the measurement angle and the measured two or more phase difference values. Re and thickness direction retardation Rth can be obtained by calculation. Therefore, the measurement values obtained 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 290. In addition, information on the respective measurement angles is input to the calculator 290. Then, by performing the calculation in the calculator 290, the in-plane phase difference Re and the thickness direction phase difference 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 the angle θ1L with respect to the perpendicular Ly is measured by the phase difference measuring device 201L, and the perpendicular difference Ly is obtained by the phase difference measuring device 201R. The phase difference from the direction inclined by the angle θ1R is measured. From the angle θ1L, the angle θ1R, and the respective phase difference values, the in-plane phase difference Re and the thickness direction phase difference Rth at the measurement point P1 can be obtained by calculation.

  The calculation for obtaining the in-plane phase difference Re and the thickness direction phase difference Rth from the measurement values and measurement angles of a plurality of phase differences at one 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 measurement value and the measurement angle of the phase difference at the measurement point P1 shown in FIG. .

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

  By performing such calculation at the measurement point P1 and other measurement points, the in-plane phase difference Re and the thickness direction phase difference Rth can be obtained at a plurality of measurement points. Therefore, by repeatedly performing such measurement and calculation at the measurement points Z1 and Z5, the surface is measured at a plurality of measurement points that are separated in the TD direction and separated in the MD direction. The internal phase difference Re and the thickness direction phase difference Rth can be measured.

  By increasing the number of times of measurement 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 phase difference Re and the thickness direction phase difference Rth can be obtained. it can. As a result, even if the conveyance 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 can be preferably 3 times / second or more, more preferably 10 times / second or more. The upper limit of the number of times of measurement is determined by factors such as the performance of the phase difference measuring device and the calculator, and can 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 be a roll. The calculation result by the calculator 290 can be stored and used, for example, when a product is cut out from the obtained roll-shaped optical film 12. More specifically, for example, when cutting out a rectangular product having a desired size, the in-plane phase difference Re and / or the thickness direction phase difference Rth are out of specification (that is, outside the desired value range). Can be used to obtain a high-quality product. By carrying out the measurement method of the present invention, it is possible to obtain detailed information on the in-plane phase difference Re and the thickness direction phase difference Rth with a dense distribution of measurement points, thereby reducing oversight of non-standard locations. Therefore, it is possible to more appropriately execute the exclusion of the nonstandard part.

  Alternatively, the calculation result by the calculator 290 can be transmitted to the feedback device (not shown) in the forming apparatus 100 by the communication means 291 to implement the manufacturing method of the present invention. For example, the calculation result by the computer 290 can be fed back to the adjustment of the operation of any component that can affect the phase difference in the forming apparatus 100, thereby forming a more uniform optical film 12. . For example, the degree of operation such as the extrusion speed of the resin to the die 101, the gap between the openings of the die 101, the stretching ratio of the film and other stretching conditions, and the heating and cooling temperature and temperature distribution can be adjusted accordingly. The optical film 12 having the in-plane retardation Re and the thickness direction retardation Rth can be continuously produced.

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

  Embodiment which changed the measurement location in 1st embodiment is described below as 2nd embodiment. FIG. 4 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 location in the measurement apparatus of the second embodiment of the present invention. 4 as well as 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, in addition to the measurement points Z1 and Z5, measurement points Z2 to Z4 are set as measurement points, and the 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 through the measurement points Z1 and Z5, the measurement points P2 to P4 on the optical film passing through the measurement points Z2 to Z4. The phase difference is also measured, and as a result, on the optical film 12, a row of measurement points P1 continuous in the MD direction, a row of measurement points P2 continuous in the MD direction, a row of measurement points P3 continuous in the MD direction, Measurement is performed in five rows, that is, 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. Measurement values obtained 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, and in addition, information on the respective measurement angles is input to the computer. By performing the calculation in, the in-plane phase difference Re and the thickness direction phase difference Rth at each measurement point can be obtained.

  Thus, 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 phase difference Re and thickness direction phase difference Rth. 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 the two phase difference measuring devices are provided at the left and right end portions of the optical film as the phase difference measuring device, but the present invention is not limited to this, and as a more preferable aspect, 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 end portions of the optical film, the elevation angle of both phase difference measuring devices at a measurement point far from both phase difference measuring devices. (Observation angle with the vertical direction being 0 °) increases, and measurement errors can increase. In addition, the in-plane phase difference Re and the thickness direction phase difference Rth are obtained at the same distance from both of the left and right side phase difference measuring devices by using only two measured values by these phase difference measuring devices. There are singularities 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 can be achieved. In addition, the thickness direction retardation Rth can be obtained.

  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 the relationship between the phase difference measuring instrument and the measurement points on the optical film at the measurement location in the measurement apparatus of the third embodiment of the present invention. 5 as well as FIG. 4, the optical film 12 is shown as a cross section cut by a plane parallel to the TD direction and the TH direction.

  In the third embodiment shown in FIG. 5, as a plurality of phase difference measuring devices, in addition to the phase difference measuring device 201 </ b> L for measuring the left end and the phase difference measuring device 201 </ b> R for measuring the right end, The second embodiment is different from the second embodiment in that it includes a phase difference measuring device 201C for measuring the central portion, which is provided vertically above Z3.

  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 are used in an oblique direction or The phase difference observed from the vertical direction is measured. The measurement values obtained by the three phase difference measuring devices at each measurement point are output from the phase difference measuring device and input to the calculator. In addition, information on each measurement angle is input to the computer, and the calculation is performed by the calculator. 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 measurement values and measurement angles of a plurality of phase differences at a certain measurement point is performed using the elliptic equation as in the case of the first embodiment. It can be done by solving. However, in the third embodiment, an elliptic equation can be obtained based on the three coordinates, so that an error can be corrected and a more accurate measurement result can be obtained. Further, the measurement result can be obtained even at a singular point where the in-plane phase difference Re and the thickness direction phase difference Rth cannot be obtained only by the measured value of 2.

  An example of calculation at such a singular point is shown in FIG. FIG. 6 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 P3 from the measurement value and measurement angle of the phase difference at the measurement point P3 shown in FIG. .

  In the example of the calculation shown in FIG. 6, the line segment 62 (R) tilted at 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 as the start point on the coordinate axis. A line segment 62 (L) and a line segment 62 (C) starting from the origin Po and parallel to the y-axis are drawn. The lengths of the line segments 62 (R), 62 (C), and 62 (L) are proportional to the measured values of the phase difference by the phase difference measuring devices 201R, 201C, and 201L, respectively, with a certain proportional constant.

  In this example, the measurement point P3 is a singular point at a distance equal to both of the measuring instruments 201L and 201R. Therefore, in the graph shown in FIG. 6, the line segment 62 (R) and the line segment 62 (L) are Axisymmetric with respect to 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), an ellipse equation 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 information on the end point P (C) of the line segment 62 (C) is further added, an 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 apparatus and measuring method of the present invention and the optical film that can be manufactured by the manufacturing apparatus and manufacturing method of the present invention are not particularly limited, and may be an optical film used for various applications. Specifically, it may be a film that is 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, UV-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, and preferably 300 μm or less, more preferably 200 μm or less, and even 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 giving the maximum refractive index. ny represents a refractive index in the in-plane direction of the film and in a direction perpendicular to the nx direction. 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 measurement method of the present invention is a value measured effectively is determined by a known phase difference measurement device (for example, “KOBRA-21ADH” manufactured by Oji Scientific Instruments, Photonic Lattice Co., Ltd.) Manufactured, “WPA-micro”) or by measuring the retardation of the optical film separately using the Senarmon method. Moreover, although the measurement wavelength of a phase difference can be set to arbitrary wavelengths according to the use of an optical film, it can usually be 550 nm.

[Modification]
The measuring apparatus and the manufacturing apparatus of the present invention and the measuring method and the manufacturing method of the present invention are not limited to those according to the first to third embodiments described above. For example, these embodiments may be further modified. Good. Hereinafter, an example of such a modification will be described.

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

  Specifically, two or more measurement results at the measurement location are obtained by performing measurement with one phase difference measurement device close to the measurement location and one or more other phase difference measurement devices at a measurement location. Can be obtained. As a more specific example, a plurality of phase difference measuring devices include a phase difference measuring device (C) for measuring the central portion, a phase difference measuring device (L) for measuring one end portion, and the other end measuring portion. A phase difference measuring device (R) for measurement, the measurement location is the measurement location (C) at the center, the measurement location (L) at the end where the phase difference measurement device (L) is located, and the phase difference measurement device The measurement of the phase difference at the measurement location (C), including the measurement location (R) at the end on the side where (R) is located, is performed by measuring the phase difference other than the phase measurement device (C) and the phase difference measurement device (C). Measurement is performed with the above phase difference measuring device, and measurement of the phase difference at the measurement location (L) is performed with one or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L). The phase difference is measured at the location (R) by measuring one or more phase differences other than the phase difference measuring device (R) and the phase difference measuring device (R). Manner of performing the like. Thus, in each measurement location, by appropriately selecting the phase difference measuring device to be used, it is possible to perform a calculation based on the data based on the measurement from the measurement location with a relatively small error, 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 central portion is equal in position from both the phase 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 central portion is more central 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 close to the part. For example, the phase difference measuring instrument for measuring the central part may be arranged at a position closer to either one of the phase difference measuring instrument for measuring the left end part and the phase difference measuring instrument for measuring the right end part. .

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

In the first to third embodiments, the number of phase difference measuring devices in the measuring apparatus 200 is two or three, and the number of measurement points is two or five. However, the present invention is not limited to this, for example, Four or more phase difference measuring devices may be provided in one measuring apparatus, and the number of measurement points may be any number such as three, four, six or more. For example, a high-resolution phase difference measuring device can be used and a large number of measurement locations can be provided in the TD direction. By providing a large number of measurement points and shortening the interval 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 interval in the TD direction of the measurement locations can be preferably 100 mm or less, more preferably 25 mm or less.
Further, for example, the number and position of the phase difference measuring device in the TD direction can be appropriately adjusted according to the width of the optical film. When three or more phase difference measuring devices are provided, the intervals may be equal intervals, but may be non-uniform intervals. As the interval in the TD direction of the phase difference measuring device is narrower, more detailed measurement can be accurately performed. 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. In addition, the distance between the phase difference measuring device and the optical film is preferably about the same as the interval in the TD direction of the phase difference measuring device from the viewpoint of efficiently performing accurate measurement, and therefore preferably 1000 mm or less, More preferably, it may 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 measuring device. However, the present invention is not limited to this. For example, in addition to the phase difference, other optical information such as the azimuth of the optical axis of the optical film is measured together with the phase difference measuring device, and this is calculated by a computer, and the deviation due to the elevation angle in the measurement direction is measured. It may be corrected and acquired as information.

  In 1st-3rd embodiment, although the form which manufactures and measures a long optical film was illustrated, this invention is not restricted to this, For example, the manufacturing line which manufactures and conveys a sheet-like film continuously It can also be applied to.

  In the first to third embodiments, the calculation process is performed by the computer 290. However, the measurement method of the present invention and the manufacturing method of the present invention are not limited to this, and the operator outputs information output from the phase difference measuring device. Based on the above, the operator may perform the calculation manually. 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 feedback process may be manually performed by the operator based on the calculation result by the computer or the manual calculation result by the operator.

DESCRIPTION OF SYMBOLS 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 -Z5: Measurement points in the measuring device P1-P5: Measurement points on the optical film Ly: Vertical 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 (8)

A method for measuring a retardation of an optical film conveyed in a conveyance path,
A plurality of measurements on the surface of the optical film passing through the measurement location in each of a plurality of measurement locations separated in the TD direction by a plurality of phase difference measuring devices provided separately in the TD direction of the transport path. A step of measuring a phase difference between points, wherein at each of the two or more measurement points, the phase difference is measured from a plurality of polar angle directions by two or more of the phase difference measuring devices. ), And in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points based on a plurality of phase difference values measured in measurement step (i). Calculation step (ii)
Including a measuring method. In the measurement step (i),
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 (R) for measuring the other end portion. )
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
Measurement of the phase difference at the measurement location (C) is performed by one or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C),
Measurement of the phase difference at the measurement location (L) is performed by one or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L),
The measurement method according to claim 1, wherein the measurement of the phase difference at the measurement location (R) is performed by one or more phase difference measuring devices other than the phase difference measuring device (R) and the phase difference measuring device (R). . An optical film manufacturing method comprising:
Step (I) of continuously forming an optical film,
A step (II) of measuring the in-plane retardation Re, the thickness direction retardation Rth, or both of the optical film conveyed in the conveyance path by conveying the optical film formed in the step (I); and Based on the values of the in-plane retardation Re, the thickness direction retardation Rth, or both measured in the step (II), the formation conditions in the step (I) are adjusted, and the in-plane retardation Re , Thickness direction phase difference Rth, or both of them are adjusted to a predetermined value (III)
Including
The step (II)
A plurality of measurements on the surface of the optical film passing through the measurement location in each of a plurality of measurement locations separated in the TD direction by a plurality of phase difference measuring devices provided separately in the TD direction of the transport path. A step of measuring a phase difference between points, wherein at each of the two or more measurement points, the phase difference is measured from a plurality of polar angle directions by two or more of the phase difference measuring devices. ), And in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points based on a plurality of phase difference values measured in measurement step (i). Calculation step (ii)
Manufacturing method. In the measurement step (i),
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 (R) for measuring the other end portion. )
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
Measurement of the phase difference at the measurement location (C) is performed by one or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C),
Measurement of the phase difference at the measurement location (L) is performed by one or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L),
The manufacturing method according to claim 3, wherein the phase difference is measured at the measurement location (R) by one or more phase difference measuring devices other than the phase difference measuring device (R) and the phase difference measuring device (R). . A device for measuring the retardation of an optical film,
A transporter for transporting the optical film in the transport path;
A plurality of measurement points which are provided separately in the TD direction of the transport path and measure the phase differences of a plurality of measurement points on the surface of the optical film passing through the measurement point in each of the plurality of measurement points spaced in the TD direction. A phase difference measuring device (i) that measures 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. Based on a plurality of phase difference values measured by the phase difference measuring device (i), in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points. Calculator (ii)
Including a measuring device. 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 for measuring the other end portion. Including vessel (R),
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
One or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C) are provided to measure the phase difference at the measurement location (C),
One or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L) are provided to measure the phase difference at the measurement location (L),
The phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R) are provided to measure the phase difference at the measurement location (R). The measuring device described. An optical film manufacturing apparatus,
Forming apparatus (I) for continuously forming an optical film,
Measuring device (II) for measuring the in-plane retardation Re, the thickness direction retardation Rth, or both of the optical film conveyed by the forming device (I) in the conveying path. And adjusting the conditions of formation by the forming device (I) based on the in-plane retardation Re, the thickness direction retardation Rth, or both values measured by the measuring device (II), 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)
A transporter for transporting the optical film in the transport path;
A plurality of measurement points which are provided separately in the TD direction of the transport path and measure the phase differences of a plurality of measurement points on the surface of the optical film passing through the measurement point in each of the plurality of measurement points spaced in the TD direction. A phase difference measuring device (i) that measures 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. Based on a plurality of phase difference values measured by the phase difference measuring device (i), in-plane phase difference Re, thickness direction phase difference Rth, or both are calculated at each of the measurement points. Calculator (ii)
Including manufacturing equipment. 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 for measuring the other end portion. Including vessel (R),
The measurement location is a measurement location (C) at the center, an end measurement location (L) on the side where the phase difference measuring device (L) is located, and an end on the side where the phase difference measurement device (R) is located. Including the measurement point (R) of the part,
One or more phase difference measuring devices other than the phase difference measuring device (C) and the phase difference measuring device (C) are provided to measure the phase difference at the measurement location (C),
One or more phase difference measuring devices other than the phase difference measuring device (L) and the phase difference measuring device (L) are provided to measure the phase difference at the measurement location (L),
The phase difference measuring device (R) and one or more phase difference measuring devices other than the phase difference measuring device (R) are provided to measure the phase difference at the measurement location (R). The manufacturing apparatus as described.

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