JP3336276B2 - Fiber orientation measurement device and orientation measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for measuring the degree of molecular orientation of a fiber.

[0002]

2. Description of the Related Art Conventional methods for measuring the degree of molecular orientation of fibers include an X-ray diffraction method, an infrared two-color method, a magnetic anisotropy method, etc., all of which are complicated and expensive. The measuring method is also difficult and not practical. As a relatively practical method, there is a birefringence index measuring method using optical means. The birefringence measurement method includes an interference fringe counting method, a parallel Nicol rotation method, a step compensator method, and the like. The interference fringe counting method is a method in which a fiber is cut obliquely in advance, irradiated with monochromatic light of a reference wavelength, the number of interference fringes appearing on the cut surface is counted, and the degree of orientation is obtained. The parallel Nicol rotation method is
As disclosed in Japanese Patent Application Laid-Open No. 10-82697, a method of irradiating monochromatic light, taking a wave plate into and out of an optical path, measuring the intensity of transmitted light, and obtaining the degree of orientation of a sample having a uniform thickness. It is. As disclosed in Japanese Patent Application Laid-Open No. 10-78389, the step compensator method compensates for the optical path difference stepwise while observing interference colors, develops black interference fringes, and measures the intervals between the interference fringes. Is a method for obtaining the degree of orientation by

[0003]

However, in the above-described interference fringe counting method, it is necessary to cut an extremely fine fiber (usually on the order of microns) obliquely and linearly in advance, which makes the preparation work extremely difficult. . Further, it is necessary to make the cut surface upward for observation from above, but when the fiber is placed on the microscope, the fiber is often inclined and it is difficult to place the fiber. Furthermore, when the optical path difference between the fibers is large, the number of interference fringes is large, and the higher-order interference fringes are lightened, which may cause erroneous counting. Although there are a Senarmon compensator and a Berek compensator as auxiliary measures for measurement, they are not suitable for measurement of a fiber having a large optical path difference due to a small compensation range of the optical path difference. As another auxiliary measure for the measurement, there is a babinet compensator or the like, but it is only for roughly measuring the optical path difference, and thus is not suitable for measuring the degree of orientation of the fiber, which requires high accuracy. The parallel Nicol rotation method is a method for determining the degree of orientation of a sample having a sheet-like uniform thickness, and is not suitable for measuring the degree of orientation of a fiber having a circular cross section or an arbitrary cross section. In addition, a mechanism for integrally rotating the polarizer and the analyzer around the optical axis, a filter attachment / detachment mechanism for sequentially changing the wavelength of monochromatic light, and a wavelength plate position control mechanism for moving the wavelength plate into and out of the optical path. Requires a complicated structure. The step compensator method is a method of compensating for the optical path difference stepwise using a plurality of wavelength plates (for example, ４λ, λλ, 1λ, 3λ, 5λ) having different optical path differences. It is not suitable for compensating for differences (less than 1 / 4λ). In the case of fibers with an arbitrary cross section, a pair of black interference fringes does not appear,
It is not suitable for measuring the degree of orientation of fibers having an arbitrary cross section. Further, undrawn yarn, ultrafine yarn and the like have an extremely small optical path difference (1/100
λ or less), it is necessary to prepare a large number of wave plates having a small optical path difference for measurement with a wave plate, which is inefficient. Therefore, in the step compensator method,
The fiber to be measured is a fiber having a circular cross-section, and the optical path difference is limited to a somewhat large (１ ／ λ or more) fiber. Therefore, the present invention has been made in view of the above-described circumstances, and has as its object to provide a measuring apparatus and a measuring method suitable for measuring the degree of orientation of a fiber.

[0004]

In order to achieve this object, an orientation measuring device according to the present invention comprises a light source mechanism for irradiating a fiber to be measured with white light, and an observation mechanism for observing the illuminated light. And a step compensation mechanism disposed between the light source mechanism and the fiber, and a continuous compensation mechanism disposed between the observation mechanism and the fiber, wherein the step compensation mechanism is a fixed polarizing plate. And a plurality of wave plates having different optical path difference compensation values, and an addition / subtraction cutout portion in which the wave plate can be mounted by changing the direction by 90 degrees, wherein the continuous compensation mechanism converts elliptically polarized light into linearly polarized light. And a rotating polarizer that is rotatable in forward and reverse directions.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 3, an orientation measuring apparatus (1) according to the present invention comprises a light source mechanism (2) for irradiating a synthetic fiber filament (F) to be measured with white light. An observation mechanism (3) for observing transmitted light of the synthetic fiber filament (F), and a step compensation mechanism (4) disposed between the light source mechanism (2) and the synthetic fiber filament (F).
And a continuous compensating mechanism (5) disposed between the observation mechanism (3) and the synthetic fiber filament (F). The step compensating mechanism (4) comprises a fixed polarizing plate (41) and an optical path. It comprises a plurality of wave plates (42) having different difference compensation values, and an addition / subtraction notch (43) on which the wave plate can be mounted by changing its direction by 90 degrees. And a rotating polarizer (52) rotatable in forward and reverse directions.

Here, a description will be given of the positional relationship of the respective constituent mechanisms based on the synthetic fiber filament (F) in the orientation measuring device (1) according to the present invention. A direction parallel to the thickness of the synthetic fiber filament (F) will be described as an X-axis direction, and a direction parallel to the length will be described as a Y-axis direction. First, the polarization directions of the reference points of the fixed polarizing plate (41) and the rotating polarizing plate (52) are orthogonal (90 degrees), forming orthogonal Nicols. The fixed polarizing plate (41) is disposed at 45 degrees with respect to the X-axis direction. Further, the fast-moving direction of the wave plate (42) is arranged parallel to the X axis or the Y axis. This direction corresponds to the wave plate (4
2) is a direction in which the optical path difference of the synthetic fiber filament (F) is added or subtracted. The phase advance direction of the conversion mechanism (51) is disposed at 45 degrees with respect to the X axis. This direction is determined by the conversion mechanism (5).
1) is a direction in which elliptically polarized light transmitted through the synthetic fiber filament (F) is converted into linearly polarized light.

The light source mechanism (2) is a light source device incorporating a known halogen lamp and a white light generation filter,
It is installed at a position where the transmitted light of the synthetic fiber filament (F) enters the observation mechanism (3).

The observation mechanism (3) includes an optical microscope (31)
And an imaging camera (33) connected to the optical microscope (31), and an image processing device (36) and an image display device (37) connected to the imaging camera (33).

The step compensation mechanism (4) includes a fixed polarizing plate (41) having a fixed polarization direction, a plurality of wavelength plates (42) having different optical path difference compensation values, and mounting the wavelength plate by changing its direction by 90 degrees. A possible addition / subtraction notch (43).
3) is configured as an integral structure above the fixed polarizing plate (41). Since the step compensation mechanism has such an integral structure of (4), it can be easily mounted and used on the light source lens (21) of the optical microscope (31). Further, the wave plates (42a) and (42b)
As shown in (2), it is held by a wave plate holding holder (42c). The holding holder (42c) has a notch 1 formed by cutting a hollow cylinder or prism having a diameter substantially equal to the polarizing plate diameter in the X direction indicated by the width of the wave plate (42b).
(42c1) and a cutout 2 (42c2) cut out in the Y direction indicated by the width of the wavelength plate (42a). The notches 1 (42c1) and the notches 2 (42c2) are designed to have different depths. Also, its depth is
The depth of each of the notch 1 and the notch 2 is designed so that a plurality of wave plates can be inserted. As shown in FIG.
When the wave plate (42a) is placed in the arrow Y direction, the optical path difference compensation value is added, and when the wave plate (42b) is placed in the arrow X direction, the optical path difference compensation value is subtracted. .

The continuous compensating mechanism (5) comprises a conversion mechanism (51) for converting elliptically polarized light into linearly polarized light, and a rotating polarizer (52) which rotates freely in forward and reverse directions. Continuous compensation mechanism (5)
Is to continuously and completely compensate for the residual optical path difference that cannot be completely compensated by the above-mentioned step compensation mechanism (4). Since light having a residual optical path difference is generally elliptically polarized light, it has an optical path difference of λλ, and is converted into linearly polarized light by the conversion mechanism (51) arranged in the above-described direction. The polarization direction of the linearly polarized light thus converted is shifted from the reference point of the rotating polarizer (52) by θ degrees. Therefore, by rotating the rotating polarizing plate (52) by θ degrees, the polarization directions are orthogonal to each other and the residual optical path difference is compensated.

Next, a description will be given of a method of measuring the degree of orientation using the measuring apparatus having the above configuration. First, a measuring method for a fiber having a circular cross section will be described, and then a fiber having an arbitrary cross section will be described.

First, the degree of orientation of a synthetic fiber filament is defined as the difference between the refractive index in the length direction and the thickness direction of the fiber (hereinafter, referred to as birefringence). A description will be given of transforming the definition formula into a format that can be measured by the above.

As shown in FIG. 4, in the synthetic fiber filament (F), the molecular chains (M) are selectively oriented by the stress applied to the polymer chains (M) constituting the fibers during operations such as spinning and drawing. Then, the orientation birefringence based on the frozen state occurs. Quantitatively measuring the birefringence occurs, birefringence is the difference between the refractive index N _X of the refractive index N _Y direction perpendicular to the fiber axis (X-axis direction) of the fiber axis (Y-axis direction) .DELTA.N Is defined as the degree of fiber orientation by the following formula 1. Equation 1 is
It is a commonly used one.

[0015] Equation _{1 ΔN = N y -N x ΔN} : birefringence = fiber orientation index N _y: fiber axis direction of the refractive index N _x: refractive index in the direction perpendicular to the fiber axis

Further, by using the speed of light v ₀ , Δ
N can be represented by the following equation (2).

Equation 2 ΔN = (v ₀ / v _y ) − (v ₀ / v _x ) v ₀ : speed of light in the atmosphere v _x : speed of light in the X-axis direction in the material v _y : speed of light in the Y-axis direction in the material speed of light

If the passing distance of the substance is t ₀ , Δ
N can be represented by Equation 3 below.

Equation 3 ΔN = (v ₀ / t ₀ ) × (t ₀ / v _y −t ₀ / v _x ) t ₀ : the passage distance of the substance

When T _x and T _y are transit times in a substance, ΔN can be expressed by the following equation (4).

Equation 4 ΔN = (1 / t ₀ ) × v ₀ (T _y −T _x ) = (1 / t ₀ ) × R T _x : X-direction transit time in the material T _y : Y direction in the material Transit time R = v ₀ (T _y −T _x ): optical path difference of transmitted light

For a normal fiber, _Ty > _Tx , and the transmitted light of the fiber causes a delay in the light in the Y direction as shown in FIGS. 5 (a) and 5 (b), and this delay is caused by the optical path difference R (the retardation). )is called. When the synthetic fiber filament (F) having the optical path difference R is irradiated with white light, the image of the transmitted light of the synthetic fiber filament (F) has an interference color (rainbow color composed of multiple colors).
Is expressed. While observing the interference color with the observation mechanism (3),
By adjusting the wavelength plate (42) of the step compensation mechanism (4) and the rotating polarizing plate (52) of the continuous compensation mechanism (5) and increasing the optical path difference compensation value R ′, the interference color gradually becomes lower ( (The direction of the dark area). The optical path difference compensation value R ′ has a function of advancing the delay R in the Y-axis direction of the synthetic fiber filament (F) by R ′, and when compensation is made so that R = R ′, FIG.
As shown in (d), the light in the X-axis direction and the light in the Y-axis direction have the same phase. Since the light having the same phase cannot pass through the rotating polarizing plate (52), when the light in this state is observed, the light becomes dark and a pair of black interference fringes appears.
In this state, the birefringence index ΔN can be determined by using the fiber thickness t ₀ .

That is, in a synthetic fiber filament, the birefringence index ΔN defined as the degree of fiber orientation is represented by a value obtained by dividing the optical path difference R of transmitted light by the thickness t ₀ . Here, since the synthetic fiber filament is not a flat plate having a certain thickness, but is approximated by a circular cross section, the fiber diameter cannot be used as the thickness t ₀ of the measurement target, and a representative alternative It is necessary to determine the thickness t.

Therefore, in the case of a synthetic fiber filament whose cross-sectional shape is approximated by a circle, if the two values of the representative thickness t and the optical path difference R of the transmitted light can be calculated, the birefringence ΔN defined as the degree of orientation can be obtained. Can be done.

As described above, the transformation of the definition formula has been described. Next, using the measuring apparatus of the present invention,
A method for obtaining the degree of fiber orientation from Equation 4 will be described.

What is the inclination of each component mechanism with the direction parallel to the thickness of the synthetic fiber filament (F) to be measured as the X-axis direction and the direction parallel to the length as the Y-axis direction? As described above, by arranging in such an orientation, the function of converting elliptically polarized light into linearly polarized light and supplying the linearly polarized light to the rotating polarizing plate is realized. That is, by setting each component mechanism to a predetermined orientation, the interference color of the synthetic fiber filament (F) is developed, and the stepwise compensation by the wave plate (42) and the continuous compensation by the rotating polarizing plate (52) are performed. It becomes possible. Using this two-stage compensation, the fiber orientation degree is determined.

Next, when the fiber is placed on a microscope, the periphery of the fiber is filled with a liquid having a refractive index substantially equal to the refractive index in the thickness direction of the fiber. Accordingly, since the fiber is not in direct contact with the atmosphere, complicated refraction of light at the end of the fiber is avoided, and accurate measurement of the degree of orientation can be performed. In addition, it is preferable that the direction of placing the fiber with respect to the microscope be the longitudinal direction of the fiber (Y-axis direction) as the longitudinal direction of the microscope.
This facilitates the alignment of the fiber under the objective lens and the observation of the interference phenomenon, and also facilitates the alignment with the coordinate axes in an image processing device or the like.

Next, the synthetic fiber filament (F) is irradiated with white light by the light source mechanism (2). By using white light, a rainbow interference color can be expressed in the image of the fiber. By expressing the rainbow interference color, when compensating for the optical path difference using the wave plate, the determination of whether to add or subtract the wave plate becomes clear. Further, only the position where the optical path difference is completely compensated is darkened only, so that the determination of the completion of the optical path difference compensation becomes clear.

Next, the optical path difference of the fiber is compensated by using a plurality of wave plates having different optical path difference compensation values. As the optical path difference compensation value of the wavelength plate, for example, 1λ, 3λ, 9λ, or the like is used. 1λ is a reference wavelength, and is not particularly limited. However, it is preferable to use 546 nm from the viewpoint of periodicity of an interference color generated due to an optical path difference and physiological wavelength sensitivity.
The wave plate is mounted and used in the addition / subtraction notch in the X-axis direction or the Y-axis direction. Y-axis direction is addition,
When the X-axis direction is a subtraction, for example, when 3λ is placed in the Y-axis direction and 1λ is placed in the X-axis direction, the optical path difference compensation value is (3λ−1λ).
Becomes When 1λ, 3λ, and 9λ are used, 1λ to 13λ can be realized at a 1λ pitch. Wave plate of less than 1λ, for example,
If 1 / 9λ and 1 / 3λ are added, 1 / 9λ ~ (13+
4 / 9λ) can be realized with a 1 / 9λ pitch.

In order to make the combination of the wave plates most efficient, the optical path difference compensation value of the wave plate = 3 ^m × λ (m = 0, ± 1,
± 2, ...). m = -2, -1,
In the case of 0, 1, 2, 1 / 9λ, 1 / 3λ, 1λ, 3λ,
A 9λ wavelength plate will be prepared. This means that there is no overlap between combinations of wave plates, and a wide range of compensation values can be realized with the minimum necessary wave plates.

When the interference color is observed by the observation mechanism (3) and the optical path difference compensation value of the wave plate is increased, the interference color gradually shifts to a lower order side (toward a dark portion). The wave plate is a fiber Y
There is a function to advance the axial light delay R by R ', and R = R'
When the adjustment is made such that, the delay of light in the Y-axis direction is compensated (canceled), and the state shown in FIGS. 5C and 5D is obtained. Observing the light in this state, it looks dark. In the case of a fiber having a circular cross section, a pair of black interference fringes (S) as shown in FIG. The birefringence is determined from the following equation by analyzing this image with the image processing device (36).

Formula 5 ΔN = nλ / SQR (D ² −W ² ) ΔN: birefringence of fiber n: value of wave plate λ: reference wavelength D: diameter of fiber of circular cross section W: pair of black of fiber of circular cross section Interference fringe spacing

In this manner, the degree of orientation can be measured for ordinary fibers having a circular cross section only by adjusting the wavelength plate. However, since the wave plate compensates for the optical path difference step by step, there is a limit to the minimum compensation value of the wave plate. Certain fibers (undrawn yarns and ultrafine fibers) have a very small optical path difference (1 / 100λ or less), so that it is necessary to prepare a large number of wavelength plates with an extremely small optical path difference for measurement with a wavelength plate. Inefficient and uneconomical.

In the case of a fiber having an arbitrary cross section, a pair of black interference fringes does not appear, so that Equation 4 cannot be applied. In such a case, the compensation by the wave plate is limited to the coarse adjustment, and the optical path difference is compensated by the following operation.

By rotating the rotating polarizing plate (52) in the forward or reverse direction and finely adjusting it while continuously compensating for the optical path difference, the optical path difference is completely compensated and a dark portion is developed. Light that cannot be completely compensated for by a wavelength plate and has a small optical path difference generally becomes elliptically polarized light. The conversion mechanism (51) has an optical path difference of ４λ, and has an action of converting elliptically polarized light to linearly polarized light by being disposed in the above-described direction. This principle is
This can be explained by a Poincare sphere described in a literature or the like relating to polarization, but detailed description is omitted here. The light transmitted through the conversion mechanism is linearly polarized light, but the polarization direction is shifted by θ.

The relationship between the residual optical path difference R and the polarization direction θ is R
= Θ / 180 · λ. Then, when the rotating polarizing plate is rotated by θ, the polarization directions are orthogonal to each other, and a dark portion appears. In the case of a fiber having a circular cross section, a pair of black interference fringes as shown in FIG. By analyzing this image with an image processing device, the birefringence can be determined from the following equation.

Equation 6 ΔN = {n + (θ / 180)} λ / {SQR (D ² −W ² )} ΔN: birefringence of fiber n: value of wave plate θ: from reference point of rotating polarizer Rotation angle λ: Reference wavelength D: Diameter of circular cross-section fiber W: Distance between a pair of black interference fringes of circular cross-section fiber

In the case of a fiber having an arbitrary cross section, the rotating polarizing plate (52) is rotated so that a dark portion appears at an appropriate position (a position where the thickness of the fiber is easily measured). The birefringence can be determined from the following equation by analyzing this image with the image processing device (36).

Equation 7 ΔN = {n + (θ / 180)} λ / T ΔN: birefringence of fiber n: value of wave plate θ: rotation angle from reference point of rotating polarizing plate λ: reference wavelength T: arbitrary Thickness of dark section of cross-section fiber

The thickness T of the fiber is determined in advance by another means (such as a known thickness measuring device). In addition, the thickness T of a sheet-like film or the like is usually known in many cases. Some types of fibers have an optical path difference of almost zero or have a negative optical path difference. The birefringence can be measured by reversely rotating the plate to make θ negative.

Some fibers have a refractive index dispersion, and the dark portion at the position where the optical path difference is compensated may be slightly colored and observed. However, in this case, the order K of the interference color can be verified by the following procedure. The order K is the optical path difference R
= Nλ = nλ. If the thickness of the fiber at the position of the n-th interference fringe is T _n and the thickness of the fiber at the position of the (n + 1) -th interference fringe is T _{n + 1} , the order K of the n-th interference fringe can be verified from Expression 8. The method of measuring T _n and T _{n + 1} can be measured by drawing an auxiliary line having a circular cross section with an image processing device in the case of a fiber having a circular cross section. In the case of a fiber having an arbitrary cross section, it can be determined by a known thickness measuring instrument.

Equation 8 K = T _n / (T _{n + 1} −T _n )

[0043]

As described in detail above, according to the first aspect of the present invention, it is possible to provide an inexpensive measurement apparatus for the degree of orientation in which measurement preparation work and measurement work are easy. According to the second aspect of the present invention, in the measurement of the degree of orientation, it is possible to perform high-accuracy measurement without the possibility of erroneous counting of the developed interference fringes. Further, it becomes possible to measure the degree of orientation of the fiber including the sample in the form of a sheet. It is possible to measure the degree of orientation of various fibers regardless of the difference in optical path and the cross-sectional shape. Further, it becomes possible to measure the degree of orientation of a fiber having a zero optical path difference or a fiber having a negative value.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a measuring apparatus.

FIG. 2 is a configuration diagram showing a polarization mechanism and an optical path difference compensation mechanism.

FIG. 3 is a configuration diagram showing a step compensation mechanism.

FIG. 4 is a diagram showing fiber orientation.

FIG. 5 is a diagram showing an optical path difference.

FIG. 6 is an observation diagram

[Explanation of symbols]

 Reference Signs List 1 orientation degree measuring device 2 light source mechanism 3 observation mechanism 4 step compensation mechanism 5 continuous compensation mechanism F synthetic fiber filament

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 G01J 3/00-3/52 G01J 4 / 00-4/04 G01J 9/00-9/04 Practical file (PATOLIS) Patent file (PATOLIS)

Claims (1)

(57) [Claims] An apparatus for measuring the degree of orientation of a fiber, comprising:
A light source mechanism for irradiating the fiber to be measured with white light, an observation mechanism for observing the irradiation light, a step compensation mechanism disposed between the light source mechanism and the fiber, and between the observation mechanism and the fiber The step compensation mechanism comprises a fixed polarization plate, a plurality of wavelength plates having different optical path difference compensation values, and the wavelength plate can be mounted by changing the direction by 90 degrees. A measuring device comprising an addition / subtraction notch, wherein the continuous compensating mechanism comprises a conversion mechanism for converting elliptically polarized light into linearly polarized light, and a rotating polarizer capable of rotating forward and backward.