JPH06229912A - Orientation measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform on-line measurement for orientation of film having large anisotropy by detecting the transmission degrees for three or more kinds of the polarized lights having the different polarizing directions. CONSTITUTION:Polarizers 41, 42... and analyzers 51, 52... are assembled at the positions corresponding to the optical axes of holding plates 40 and 50 of a polarizing part 4 and an analyzing part 5. The polarizing directions of the polarizers of the polarizing part 4 are shifted by, e.g. 30 degrees. The polarizing direction is imparted for each polarizer of the polarizing part 4 so as to obtain the relation of parallel Nicol. A sheet S to be measured is made to run between the polarizing part 4 and the analyzing part 5. The intensities of the transmitted lights through the polarizers 41, 42..., the sample S and the analyzers 51, 52... with respect to the light having the specified wavelength transmitted through the filter 3 from the light source 2 are detected with detecting elements 61, 62... of a detecting part 6. The orientation degree and the direction of the main refractive index of the sheet S to be measured are computed based on the bearing and intensity of each transmitted light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orientation measuring device, particularly to a film or sheet made of a polymer material, which has a large anisotropy such as after a longitudinal stretching process such as a biaxially stretched film. The present invention relates to an apparatus, and in particular, it is suitable for on-line measurement and control in the manufacturing process of a film or sheet, because the measurement takes a short time.

[0002]

2. Description of the Related Art Birefringence measurement is often used as a method for determining the optical anisotropy of a transparent or semitransparent material.
Conventionally, on-line birefringence measurement of a sheet-shaped material is performed by three or more pairs of polarizers and analyzers arranged in a constant polarization azimuth relationship (parallel Nicol state), for example, as in Japanese Patent Application No. 318229 of 1991. In some cases, the retardation and the main refractive index direction of the measured sheet are obtained by measuring the transmitted light intensity of each analyzer when the polarizer is irradiated with a single wavelength light flux while passing through the measured sheet.

This method is effective when the retardation of the sheet to be measured is a few thousand nm or less and has a relatively small anisotropy, but it is anisotropic such as after the longitudinal stretching step of a biaxially stretched film. When the film is large and the film thickness is large, the retardation also increases to 10,000 nm or more,
It is difficult to accurately measure the retardation by the method that requires the specification of the optical order as in the above method.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to provide an orientation measuring apparatus capable of on-line measurement of orientation during the manufacturing process of a polymer film or sheet having large anisotropy.

[0005]

According to the present invention, three or more pairs of polarizers and analyzers placed in a parallel Nicol state are arranged with their polarization directions shifted from each other, and between the polarizers and the analyzers. Running the measured sheet, a means for detecting the transmitted light intensity of the polarizer, the sample and the analyzer for light of a specific wavelength, and the azimuth and intensity of the polarization of each transmitted light, the degree of orientation of the measured sheet and And a means for calculating the direction of the main refractive index.

The present invention also stores means for detecting the transmittances of three or more kinds of polarized light having different polarization directions, means for sampling the detection outputs of these detecting means according to a predetermined program, and storing the sampled data. It also has a means, a means for calculating the value of the polarization degree value and the main refractive index direction from the sampling data, and a means for displaying the angular distribution of the polarization transmission degree online.

The present invention further comprises means for monitoring the various operations of the device, including an optical path for the monitor light flux.

[0008]

As a specific example of the present invention, a case will be described in which three or more pairs of polarizers and analyzers in the parallel Nicol state and having different polarization directions are used. At this time, the analyzer transmitted light intensity I (θ) is expressed by the following equation. I (θ _i ) = A ² (α ² cos ⁴ (θ _i −φ) + sin ⁴ (θ _i −φ) + 1/2 · C · α · sin ² 2 (θ _i −φ)} ... (1 ) C≡cos (2πR / λ) (2) where R: Retardation of the sample A: Amplitude of linearly polarized light incident on the sample α: Linearly polarized waves in the two main refractive index directions of the sample Amplitude transmittance ratio (this is also referred to as “polarization degree” in the present invention.) Λ: wavelength of measurement light θ _i : azimuth angle of polarizer and analyzer with respect to sample reference direction (MD direction) φ: sample Azimuth angle of main refractive index i: Number of pairs of polarizer and analyzer.

The distribution of the refractive ellipticity and I (θ _i ) generally has the relationship shown in FIG. Both sides of equation (1)
Partial differentiation with A, C and α is as follows. ∂I / ∂A = 2A {α ² cos ⁴ (θ ₁ -φ) + sin ⁴ (θ -φ) + 1/2 · C · α · sin ² 2 (θ ₁ -φ)} ... (3) ∂ I / ∂C = 1/2 ・ A ²・ α ・ sin ² 2 (θ ₁ -φ) ・ ・ ・ (4) ∂I / ∂α = A ² {2 ・ α ・ cos ⁴ (θ ₁ -φ) + 1/2 · C · sin ² 2 (θ ₁ −φ) (5) Considering the function matrix B as in the following equation,

[0010]

[Equation 1]

Given an appropriate initial value for P = (A ₀ + C ₀ + α ₀ ), and letting the residual matrix be S, e =-(B ^t B) ^-1 B ^t S (7) is calculated. , Next, P = P + e (8) is set, P + e is set as a new initial value, the same calculation is performed again, and the calculation is repeated until the convergence condition is satisfied.

At this time, although the value of φ is not known in the equation (1), φ is treated as a known value when the convergent values A, C and α are obtained by the above numerical calculation. Specifically, using the first sampling value I (θi),
When calculating A, C, and α, for example, the value of φ is -90.
The above calculation is performed by changing from 1 ° to 90 ° in 1 ° steps, and the values of A, C, and α corresponding to φ in 1 ° steps are obtained.
A method is adopted in which the value φ ₀ of φ when the sum of squares of the residuals of the sampled value and the calculated value is the minimum is the optimum value of φ. This φ
The value of α corresponding to ₀ is taken as the degree of orientation.

When obtaining φ and α from the second and subsequent sampling values I (θ _i ), the range of φ is changed within a range of ± 5 ° around φ ₀ obtained from the previous sampling value. Then, if φ and α are obtained by the same procedure, the calculation time is shortened, and it is possible to accurately obtain the temporal changes of φ and α in the film manufacturing process.

[0014]

FIG. 1 is a schematic configuration diagram of an embodiment of the orientation measuring apparatus of the present invention. (S) is a measurement sample, (1) is a sample portion through which the measurement sample passes, and (2) is a light source. , (3) is a filter section, (4) is a polarization section, (5) is an analysis section, and (6) is a photodetector for photoelectrically converting the transmitted light intensity of the analyzer.

The light source unit (2) includes a plurality of required light sources (21), such as about 5 to 6 small light sources (21) for the holding disk (20). (2
2) ... Are provided on the same circumference at substantially equal angular intervals, and as shown in the plan view of FIG. 2A, a parallel light flux (L1 ), (L
2), ... (L6) are irradiated in the downward direction of FIG. A disc-shaped light source or a ring-shaped light source is used instead of an individual light source, and a plurality of parallel light beams as described above are taken out by a condensing system such as a condensing lens (or condensing mirror) and a diaphragm hole (or slit). You may Alternatively, the light from one light source may be converted into a light beam having an appropriate diameter by a condensing system, and then the required number of the parallel light beams may be extracted by an appropriate number of optical fibers.

The filter section (3) may be composed of a single filter plate or may be composed by incorporating a filter element at a position corresponding to each light flux of the holding plate. Further, it may be arranged in place of another position on the optical path from the light source section (2) to the detection section (6). The polarizing unit (4) and the light detecting unit (5) are shown in FIG.
As shown in plan views in (b) and (c) respectively, the polarizers (41), (42), ..., At the positions corresponding to the optical axes of the holding plates (40) and (50), respectively. Analyzer (5
1), (52), ... Are incorporated, and the polarization directions of the polarization elements of the polarization section (4) are shifted by 30 degrees. For example, if the polarizer (41) is oriented at 0 °, the polarizer (4
2) ··· (46) counterclockwise + 30 °, +
Elements having polarization directions of 60 °, + 90 °, + 120 °, and + 150 ° are arranged. The respective polarizers of the light detecting section (5) are arranged so that those on the same optical axis have a predetermined polarization direction relationship, for example, a parallel Nicol relationship, with respect to the respective polarizers of the polarization section (3). Is given.

The sample portion (1) is provided with a measuring space (not shown) having a narrow gap for passing a sheet-like sample continuously sent out from the production line. This measurement space may be closed at both ends in the width direction with a narrow width measurement sheet, but setting work of the photometry unit on the measurement sheet, setting of the photometry unit at an arbitrary position in the width direction of the measurement sheet, width direction It is preferable that one side of the measurement space in the width direction is formed as an open type in terms of the scanning of the photometric portion (measurement point) in FIG. To this end, when the photometric unit is formed as one unit, the light projecting unit from the light source unit to the polarizing unit and the light receiving unit of the light detecting unit and the detecting unit are provided outside one side end of the sample sheet. Cantilever supported by "(U-shaped")
It is preferable to provide a system-type holding mechanism.

Alternatively, it is possible to perform the measurement while synchronously scanning the light projecting unit and the light receiving unit in the width direction of the measurement sheet.

In addition, the sample portion is placed at a position corresponding to a measurement point on the measurement sheet (corresponding to the measurement point) at every constant distance movement of the measurement sheet, at every constant time, or at the sampling timing of the measurement data. A marking mechanism such as an inkjet method that attaches a measurement position identification mark is provided on the side edge of the sheet to be measured, or on a measurement point, etc., and the sampling data of the detection signal is also identified according to the code attached to the sheet. Data may be processed by attaching a code. It can be appropriately used for tabulating measurement results, extracting and processing arbitrary data from measured / stored data, rechecking measured data, and so on.

The detection section (6) includes a detection element (61),
, (62) are arranged on the holding plate (60) in correspondence with the respective optical axis positions. A photoelectric conversion element such as a solar cell, a photodiode, or a CCD element is used as the detection element. The multi-beam photometric unit including the light source unit, the filter unit, the polarizing unit, the sample unit, the light detecting unit, and the detecting unit may be formed as a single unit with a space for passing the measurement sheet. it can. As a result, the entire photometry unit can be made compact, the design and production of each element of each unit of the photometry unit, the assembly, adjustment, inspection, etc. of the photometry unit can be standardized, and accuracy and production efficiency can be improved. Also, the unitization allows the photometric unit to be handled as a single detection end, so it can be installed in the production line, especially for instrumentation work and scanning of the measurement point (and therefore the photometric unit) in the width direction of the measurement sheet, and the site. Exterior and other protective instrumentation of the photometry unit against environmental temperature and atmosphere,
It is possible to improve efficiency in installation work, installation of a scanning mechanism for measuring points in the width direction of the measurement sheet, and the like.

The size of the measurement point of this photometric unit (the required total polarized light flux in each direction) is, for example, several mm to 10 m.
Although it may be formed into a circle having a diameter (φ) of around m, or a rectangular shape of the same size, for coarse online measurement of a long sheet, for example, a diameter of 2 to 3 cm or a square may be used.
The following parts are the data processing part and control part, and the main part can be installed in a place apart from the site environment separately from the photometric part, and the transmission of measurement data, control commands, etc. with the photometric part is In addition to wired or wireless electric signals, optical communication means such as optical fibers can be used.

Reference numeral (7) is an input signal processing section for amplifying each detection output of the detection section (6), A / D converting, etc., and introducing this to the data processing section. These elements and the transmitter are
It may be appropriately provided at the position of the detection end according to the system configuration of the entire measuring apparatus. (B) is a data bus line of the data processing / control unit, and (8) is a CPU. (9) is a ROM,
A program storage unit that is composed of fixed (or semi-fixed) memory such as EPROM and that stores various control / calculation programs, and (91) is a storage area for control programs that control the operation of the entire device. In addition to such a control program, a separate program for providing a measurement position identification mark on the measurement sheet, operating a filter, or the like may be provided. , (92) is a storage area of a sampling program for instructing the sampling of data from the detection output, and (93) is the above-mentioned various necessary calculations from measurement data stored in a memory (10) described later. The storage area of the arithmetic program for (94) is the storage area of the output program for outputting the processed data to the CRT (11), the printer (12) and the like.

The above-mentioned sampling program is a method of sampling data at a predetermined moving distance or a predetermined time of a continuous sheet-like sample coming out of a production line, or a specific point on the sample (regardless of whether the sample is stationary or moving, for example, Various other methods such as a method of sampling data of marking points, etc. are considered, and the detection output of each detection element is input processing unit (7) according to the selected sampling program.
The data is sampled at, and stored in the memory (10) together with the information of the number of the detecting element (hence the polarization direction) and the information of the measurement position on the sample.

The calculation program described above uses the basic data and the measurement data stored in the memory (10) to determine the polarization degree,
It performs various necessary calculations including a calculation calculation of the main refractive index direction. The above output program is a CRT of measurement results.
Display, print output, and other output control are processed, but each time the detector output is sampled and stored in the memory (10), an angle distribution map of the polarized light transmission intensity is displayed to show the flow direction of the measured sheet. It is also possible to perform processing such as continuously displaying changes in the orientation characteristics (or birefringence characteristics) online.

The memory (10) is a memory having variable storage contents, which is formed of, for example, a RAM, and an input buffer memory (101) for temporarily storing the measurement data and the like introduced from the input processing unit (7). , Storage area for arithmetic processing data (102) for storing processed data, basic data storage area (103) for storing basic data necessary for data processing, mathematical formulas, etc., data for CRT display, print output, etc. Has an area such as an output buffer memory (104) for storing (14) is a keyboard input device.

FIG. 3 is a schematic system configuration diagram of an orientation measuring apparatus according to another embodiment of the present invention, which basically has the same configuration as that of FIG. 3 and common elements are denoted by the same numbers or reference numerals. Has been done. 3 is different from the configuration of FIG. 1 in that the center of an assembly of optical axes (L1), (L2), ... (L6) for measuring the transmittance of polarized light beams with different polarization directions. Is provided with a monitor optical path (optical axis L7).

That is, the light source section (2) is provided with a light source (27), and the polarizing section (4) and the light detecting section (5) have through holes (47) at the centers of the holding disks (40) and (50). , (57) are provided, and further, in the detection section (6), a photodetection element (67) is provided at the center of the holding disk (60). These respective elements (27), (47), (57) and (67) are located on the optical axis. The position of this optical axis (L7) is preferably the center of each optical axis (L1) to (L6),
Its position is not exact.

The light projected from the light source section (2) does not have to be a divided light beam, and may be a surface light source which generates a parallel light beam having a wide cross section. The detecting section (6) also transmits light through each optical path. 2D CCs for detecting the
It may be configured by a surface detector such as a D detection element. The detection output of the detection element (67) is introduced into the data processing control unit via the input processing unit (7) and stored in the control program storage unit, similarly to the polarization transmission detection outputs of (61) to (66). The monitoring program (95) is used to monitor various device operating states.

For example, the lamp life can be judged by checking whether the light quantity of the light source lamp is equal to or more than the reference value by the output of the detecting element (67) without the sheet to be measured. This confirmation may be automatically performed every certain device usage time, or may be performed at any time. Further, when the measurement sheet is scanned in the width direction for measurement, the edge of the sheet can be detected by the fluctuation of the detection output of the detection element (67), and it can be used, for example, in the control of the width direction scanning. Further, when the sheet to be measured has a seam or dirt, the light amount change of (67) becomes large in the vicinity of this portion. Therefore, by detecting this, the orientation degree and the direction of the main refractive index are calculated from the sampling data. In this case, it is possible to prevent the value from greatly changing and adversely affecting the subsequent measurement. The through holes (47) and (57) are respectively (41)
To (47), ((51) to ((57), the same polarizer,
Provide an analyzer and other polarizers. If a polarization direction different from that of the analyzer pair is given, it can be used for calculation of the main refractive index direction and orientation degree. In this case, as shown in FIG. 4, the three elements including the polarizer (47) and the analyzer (57) are arranged in a straight line (for example, (41), (457), (44) and (61). ), (67), (67)) and the linear arrangement direction are made to coincide with the sheet flow direction or the sheet width direction, the measurement point area can be made smaller.

FIG. 4 shows another example of the specific structure of a part of the photometric section, the light source section (2), the polarizing section (4), the light detecting section (5), and the detecting section (6) of the apparatus shown in FIG. Shown, rectangular holding plate 20A),
Elements (40A), (50A), and (60A) are arranged on the circumference and at the center thereof, and through holes (h1) for positioning each optical axis are provided at the four corners of each holding plate. Is provided. Furthermore, the holding plates (50A), (60A)
Through holes (h2) for assembling the both together are provided at the four corners, so that they can be easily and compactly combined and separated from each other.

(Experimental Example) (Experimental Example 1) According to this measurement method, the same film at 12.5 GHz was used for the same film as the result of measuring the main refractive index direction φ and the orientation degree α using unstretched and uniaxially stretched films. Difference between the maximum and minimum values of the dielectric constant in the film plane using microwaves Δ
Table 1 below shows a comparison with ε '.

[0032]

[Table 1]

Looking at the correlation between α and Δε'at this time,
The correlation coefficient was -0.987. Therefore, if the correlation between the birefringence ΔN obtained from the refractometer and the α value according to this measurement method is obtained in advance for the same sample, the conversion into the birefringence can be easily performed.

[0034]

【The invention's effect】

1) Since it is not necessary to determine the optical order, the anisotropy is large and the measurement of a thick sample is easy. 2) The degree of orientation and the main refractive index direction can be effectively obtained by a numerical calculation in a short calculation time. The birefringence value can also be easily converted from the degree of orientation. 3) The measurement data necessary for calculating the orientation degree can be immediately obtained at any time point, and the on-line measurement of birefringence becomes possible. Therefore, in a film production line or the like, it is possible to finely know the change in the characteristics of the measured sheet in the flow direction.

4) It is possible to simultaneously obtain the degree of orientation and the direction of the main refractive index. 5) The memory capacity required for data storage can be kept within an appropriate value while ensuring sufficient measurement accuracy. 6) Since the angle distribution of the polarized light transmission intensity can be immediately known, it is possible to continuously display this and visually monitor the degree of anisotropy of the sample arbitrarily.

7) By providing the monitor optical path, it is possible to easily monitor various operating states of the apparatus.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an orientation measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a detailed diagram of a polarizer and an analyzer in the configuration of FIG.

FIG. 3 is a schematic configuration diagram of an orientation measuring apparatus according to another embodiment of the present invention.

FIG. 4 is a diagram showing an example of a specific configuration of a part of a photometric unit of the apparatus shown in FIG.

FIG. 5 is a diagram for explaining the operation of the device of the present invention.

FIG. 6 is a diagram showing an example of the correlation with the measurement result of the orientation degree by the device of the present invention.

[Explanation of symbols]

 1 sample part 2 light source part 3 filter part 4 polarizing part 5 light detecting part 6 detecting part 7 input processing part 8 CPU 9 program storing part 10 data storing part 11 CRT display device. 12 Printer 13 Keyboard Input Device 20, 40, 50, 60 Holding Board 21-26 Light Source 41-46 Polarizer 51-56 Analyzer 61-66 Detection Element 91 Control Program Storage 92 Sampling Program Storage 93 Calculation Program Storage 94 Output program storage unit 101 Input buffer memory 102 Arithmetic processing data storage area 103 Basic data storage area 104 Output buffer memory B Data bus lines L1 to L6 Optical axis S Measurement sample

Claims (5)

[Claims] 1. A set of three or more pairs of polarizers and analyzers placed in a parallel Nicol state are arranged with their polarization directions displaced from each other,
A sheet to be measured is interposed between a polarizer and an analyzer, a means for detecting the intensity of light transmitted through a polarizer, a sample and an analyzer for light of a specific wavelength, and a direction of polarization of each transmitted light. An orientation measuring apparatus comprising: means for calculating the degree of orientation of a measured sheet and the direction of the main refractive index from the strength. 2. An orientation measuring apparatus according to claim 1, wherein the polarizer, the analyzer and the light receiving means constituting the transmittance detecting means are arranged on substantially the same circumference. 3. The orientation measuring apparatus according to claim 2, wherein an optical path for a monitor light beam is provided at a substantially central portion of the circumference. 4. A means for respectively detecting the transmittances of three or more kinds of polarized light having different polarization directions, a means for sampling the detection outputs of these detecting means according to a predetermined program, and a means for storing the sampled data. A means for calculating the polarization degree and the main refractive index direction from the sampling data is provided.
The orientation measuring device described. 5. The orientation measuring apparatus according to claim 1, 2, 3 or 4, wherein a photometric section including a light source section, a polarizing section, a light detecting section and a detecting section is formed as a unit.