WO2012056697A1 - Inspection method for polyimide film, polyimide film manufacturing process using same, and polyimide film manufacturing equipment - Google Patents

Abstract

The purpose of the present invention is to provide an inspection method by which the scale of linear expansion coefficient anisotropy of a polyimide film can be determined speedily, easily and nondestructively. In order to achieve the purpose, this inspection method for polyimide film includes: a step (A) of measuring optically the in-plane retardation (Re) of a polyimide film; a step (B) of measuring the scales (S₁) of linear expansion coefficient anisotropy of film specimens consisting of a polyimide having the same composition as that of the polyimide film; a step (C) of grasping the correlation between in-plane retardation (Re) and scale (S₁) of linear expansion coefficient anisotropy; and a step (D) of estimating the scale (S₂) of linear expansion coefficient anisotropy of the polyimide film on the basis of the grasped correlation from the in-plane retardation (Re).

Description

Polyimide film inspection method, polyimide film manufacturing method using the same, and polyimide film manufacturing apparatus

The present invention relates to a polyimide film inspection method, a polyimide film manufacturing method using the same, and a polyimide film manufacturing apparatus.

In recent years, as electronic devices have become smaller and more portable, flexible circuit boards have become thinner and denser. Furthermore, since the proportion of lead-free solder used in component mounting is increasing, the temperature during component mounting or repair may become high. For this reason, the flexible circuit board is also required to have high heat resistance. With the demands for thinning flexible circuit boards, high-density wiring, and high heat resistance, demands for thinning, high dimensional stability, and high heat resistance are increasing for polyimide metal laminates as circuit board materials. .

As a polyimide metal laminate as a circuit board material, a flexible circuit board obtained by laminating a copper foil and a polyimide film is known (for example, see Patent Document 1). Such a polyimide metal laminate is obtained by laminating a metal foil on a polyimide film by a laminating method or the like.

In order to produce a polyimide film, in the film-forming process, the film is heated in a state where both ends of the film are sandwiched between clip tenters or pin tenters, and dried or imidized. For this reason, the film may be temporarily softened and stretched to cause orientation anisotropy. In particular, when a so-called bowing phenomenon or the like occurs in which the end portion of the film is strongly molecularly oriented, a remarkable orientation anisotropy may occur at the end portion of the obtained polyimide film.

It is known that the linear expansion coefficient of a polyimide film is closely related to the degree of orientation of polyimide molecular chains (for example, see Non-Patent Document 1). For this reason, when orientation anisotropy arises in a film, linear expansion coefficient anisotropy will also arise simultaneously.

When a polyimide film with a large linear expansion coefficient anisotropy or anisotropic distribution is used as the base film of a flexible printed circuit board (FPC), warping occurs due to the difference in the linear expansion coefficient with the copper foil, or wiring formation Problems such as distortion and thermal stress are likely to occur during the heating of the process. For this reason, for the polyimide film used as the base film for FPC, the linear expansion coefficient is generally the same as that of the copper foil, and the anisotropy and anisotropic distribution of the linear expansion coefficient are small in the entire width direction. Required.

It is possible to estimate the anisotropy of the linear expansion coefficient of the polyimide film by examining the degree of molecular orientation and the direction of molecular orientation based on the relationship between the linear expansion coefficient and the degree of orientation of the polyimide molecular chain. However, while a general method for measuring the degree of molecular orientation is highly accurate, it cannot be said to be a simple method. Therefore, a method for estimating the linear expansion coefficient anisotropy by measuring physical property values depending on the degree of molecular orientation such as ultrasonic wave propagation speed or microwave absorption has been proposed in order to make the operation easier. (For example, see Patent Documents 2 to 4).

Also, a method for estimating the thermal expansion anisotropy by measuring the dichroic ratio of the polyimide film has been proposed (Patent Document 5). Furthermore, a method has also been proposed in which the retardation of a specific wavelength of a thermoplastic resin film is measured with monochromatic light and the production conditions of the thermoplastic resin film are adjusted (for example, Patent Document 6).

JP 2001-270037 A Japanese Patent No. 3006752 Japanese Patent No. 3202935 JP 2002-154168 A Japanese Patent Application Laid-Open No. 07-63611 JP-A-9-218307

However, according to the methods proposed in Patent Documents 2 to 4 and the like, an operation such as cutting a polyimide film to be measured into a predetermined size is required. For this reason, it was extremely difficult to inspect the anisotropy of the linear expansion coefficient of the polyimide film in-line during the production process of the polyimide film.

Also, in the method proposed in Patent Document 5, since the absorbance is measured, the sensitivity is very low and it is not practical. Furthermore, since the phase difference is measured with monochromatic light in the method proposed in Patent Document 6, it cannot be applied to a thermoplastic resin film that can have a phase difference in a wide range.

The linear expansion coefficient of the polyimide film is generally determined by a thermomechanical analysis (TMA) test at a temperature rising rate of 10 ° C./min or less (preferably 5 ° C./min or less) in a temperature range of 100 to 200 ° C. Measured in In order to measure the anisotropy of the linear expansion coefficient, it is necessary to perform a TMA test at at least two measurement points. Therefore, when the anisotropic distribution of the linear expansion coefficient is examined across the width direction and the flow direction of the film, it is necessary to measure the linear expansion coefficient a number of times. In order to solve such problems, it is required to develop a method for evaluating the orientation anisotropy of a polyimide film quickly and with high accuracy. Furthermore, it is required to produce a polyimide film in which the orientation anisotropy is evaluated in-line during the production process of the polyimide film and the distribution of molecular orientation is controlled.

The present invention has been made in view of such problems of the prior art, and the problem is that the magnitude of anisotropy of the linear expansion coefficient of the polyimide film can be quickly and easily nondestructive. An object of the present invention is to provide an inspection method that can be measured. Another object of the present invention is to provide a method capable of producing a polyimide film while controlling the occurrence of anisotropy of the linear expansion coefficient, and further to provide a production apparatus therefor.

As a result of intensive studies to achieve the above problems, the present inventor has found that a high correlation exists between the in-plane retardation of the polyimide film and the magnitude of anisotropy of the linear expansion coefficient. And by measuring the in-plane retardation of the polyimide film optically with white light, it is possible to quickly and easily predict the anisotropy of the linear expansion coefficient of the polyimide film in a nondestructive manner. The present inventors have found that it is possible to achieve the problem and have completed the present invention.

That is, according to the present invention, the following polyimide film inspection method, polyimide film manufacturing method, and polyimide film manufacturing apparatus are provided.

[1] A step of setting an in-plane retardation threshold allowable for the polyimide film to be inspected from the relationship between the anisotropy of the linear expansion coefficient of the polyimide film and the in-plane retardation of the polyimide film ( A), in-plane retardation Re measured spectroscopically with white light in the in-plane retardation Re of the polyimide film to be inspected, the threshold, and the in-plane retardation measured in the step (B) A method for inspecting a polyimide film, comprising comparing (Re) and determining whether the degree of anisotropy of the linear expansion coefficient of the polyimide film to be inspected is within a standard range.

[2] Step (A) in which the in-plane retardation of the polyimide film test piece is measured spectroscopically with white light, and the anisotropy of the linear expansion coefficient of the polyimide film test piece a step of measuring the size S ₁ (b), and step to grasp the correlation between the size S ₁ of the in-plane retardation of the specimen anisotropy (c), a polyimide film to be inspected A step of setting a threshold value of an in-plane retardation that is allowable for the polyimide film to be inspected based on the anisotropy size S _{2 of} the allowable linear expansion coefficient and the correlation grasped in the step (c) ( The inspection method of the polyimide film as described in [1] containing d).

[3] A polyimide film in which the method for inspecting a polyimide film according to [1] or [2] is performed in a polyimide film forming process, and the polyimide film to be inspected is a polyimide film in the film forming process. A method for producing a film.
[4] The method for producing a polyimide film according to [3], wherein the orientation angle of the polyimide film to be inspected is also calculated in the step (B).
[5] The polyimide film according to [3] or [4], wherein in the step (B), the in-plane retardation Re is measured at a plurality of locations in the flow direction and the width direction of the roll film-like polyimide film. Production method.

[6] The method for producing a polyimide film according to [3] or [4], wherein the polyimide film to be inspected is a roll film or a cut film.
[7] The method for producing a polyimide film according to any one of [3] to [6], wherein the spectroscopic measurement in the step (B) is performed with white light having a wavelength range of 500 to 800 nm.
[8] The spectroscopic measurement in the step (B) includes the transmittance spectrum measurement of white light, the transmittance spectrum of the polyimide film to be inspected is measured in advance, and the transmittance measured in the step (B) is measured. The method for producing a polyimide film according to any one of [3] to [7], wherein the rate spectrum is corrected.
[9] In any one of [3] to [8], including the step (D) of feeding back the result determined in the step (C) to the manufacturing process of the polyimide film and adjusting the manufacturing conditions of the polyimide film The manufacturing method of the polyimide film of description.

[10] A storage mechanism for storing a threshold value of an in-plane retardation allowable for the polyimide film to be inspected, a transport mechanism for transporting the polyimide film in a certain direction, and a measurement for measuring the in-plane retardation Re of the polyimide film A polyimide film manufacturing apparatus having a mechanism.
[11] The in-plane retardation Re measured by the measurement mechanism is compared with the threshold value stored in the storage mechanism, and the degree of anisotropy of the linear expansion coefficient of the polyimide film to be inspected is determined according to the standard. The polyimide film manufacturing apparatus according to [10], further including a determination mechanism for determining whether the value is within the range of [10].
[12] The polyimide film manufacturing apparatus according to [11], which includes a control mechanism that controls manufacturing conditions of the polyimide film based on a result determined by the determination mechanism.
[13] The manufacturing conditions controlled by the control mechanism are the tension applied to the polyimide film or its precursor, the draw ratio of the polyimide film or its precursor, the heating temperature of the polyimide film or its precursor, the polyimide [2], which is at least one selected from the group consisting of a heating speed of the film or its precursor, an air volume of dry air sprayed on the polyimide film or its precursor, and a transport speed of the polyimide film or its precursor. The polyimide film manufacturing apparatus of description.

[14] The measurement system according to any one of [10] to [13], wherein the measurement mechanism includes a plurality of optical system phase difference measurement devices arranged in a direction perpendicular to a conveyance direction of the polyimide film by the conveyance mechanism. Polyimide film manufacturing equipment.
[15] The polyimide according to any one of [10] to [13], wherein the measurement mechanism includes an optical phase difference measuring device capable of scanning in a direction perpendicular to a conveyance direction of the polyimide film by the conveyance mechanism. Film manufacturing equipment.

According to the polyimide film inspection method of the present invention, the anisotropy of the linear expansion coefficient of the polyimide film can be measured quickly and easily in a nondestructive manner. Since the anisotropic magnitude | size of the linear expansion coefficient of a polyimide film can be test | inspected nondestructively, the test | inspection method of this invention can be integrated in the manufacturing process of a polyimide film. Thereby, since an inspection result can be immediately fed back to a manufacturing process, the polyimide film by which generation | occurrence | production of the anisotropy of the linear expansion coefficient was suppressed can be manufactured efficiently.

FIG. 1 is a flowchart showing an example of a threshold value determining step of the polyimide film inspection method of the present invention. Figure 2 is a schematic diagram showing in measuring the size S ₁ of the anisotropy of the linear expansion coefficient of the polyimide film specimen, an example of a sample cut method. FIG. 3 is a first diagram showing a linear expansion coefficient ellipsoid of the film test piece 1. FIG. 4 is a second diagram showing a linear expansion coefficient ellipsoid of the film test piece 1. FIG. 5 is a graph showing the relationship between an in-plane retardation Re measured by a spectroscopic method and ΔCTE calculated by linear expansion coefficient measurement for a polyimide film test piece. FIG. 6 is a graph showing the relationship between the orientation angle calculated by the spectroscopic method and the orientation angle calculated by measuring the linear expansion coefficient for the polyimide film test piece. FIG. 7 is a schematic diagram showing an example of a method for measuring the in-plane retardation Re of the polyimide film. FIG. 8 is a graph showing the waveform of the transmittance spectrum when the in-plane phase difference Re is 100 nm and the waveform of the transmittance spectrum when the in-plane phase difference Re is 700 nm. 9A to 9C are process diagrams showing an example of a technique for measuring in-plane retardation Re of a polyimide film to be inspected in-line. FIG. 10 is a schematic diagram illustrating another example of a method for measuring in-plane retardation Re of a polyimide film to be inspected in-line. FIG. 11 is a schematic diagram showing another example of a method for measuring in-plane retardation Re of a polyimide film to be inspected in-line.

A. Method for Inspecting Polyimide Film and Method for Producing Polyimide Film The method for inspecting a polyimide film of the present invention includes the step (A) of setting a threshold value of an in-plane retardation Re that is acceptable for the polyimide film to be inspected, and the polyimide to be inspected The step (B) of measuring the in-plane retardation Re of the film spectroscopically with white light, the threshold value, and the in-plane retardation Re measured in the step (B) are compared and inspected. (C) which determines whether the magnitude | size of the anisotropy of the linear expansion coefficient of the object polyimide film is in the range of a specification.

The above inspection method can be incorporated in the polyimide film manufacturing process, and in this case, the inspection object can be a polyimide film in the film forming process. The said inspection method is performed at the time of the manufacturing condition setting of a polyimide film, for example, Various manufacturing conditions of a polyimide film with low anisotropy of a linear expansion coefficient can be determined by adjusting manufacturing conditions based on this result. Moreover, it is also possible to perform the said test | inspection in the production line of a polyimide film for the purpose of performing quality control of the polyimide film under manufacture.

The polyimide film that can be inspected by the inspection method of the present invention is not particularly limited as long as the in-plane retardation can be measured spectroscopically with white light. For example, a film made of only polyimide, or a polyimide and a filler Or a film containing additives and the like.

The kind of polyimide contained in the polyimide film is not particularly limited, and examples thereof include wholly aromatic polyimides, aliphatic polyimides, alicyclic polyimides, and blended, copolymerized, and block-based polyimides combining these. It is done. Among these, amorphous polyimide is preferable from the viewpoint of measurement accuracy of in-plane retardation Re, and specifically, pyromellitic dianhydride and 4,4′-diaminodiphenyl ether known as DuPont Kapton are preferable. And a polyimide composed of 3,3,4,4-biphenyltetracarboxylic acid anhydride and p-phenylenediamine, which are known as Upilex of Ube Industries, Ltd. are preferred.

In addition, the fillers or additives that can be included in the polyimide film include wear resistance improvers such as graphite, carborundum, silica stone powder, molybdenum disulfide, and fluorine-based resins; antimony trioxide, magnesium carbonate, calcium carbonate, and the like. Flammability improvers; Electrical property improvers such as clay and mica; Tracking resistance improvers such as asbestos, silica and graphite; Acid resistance improvers such as barium sulfate, silica and calcium metasilicate; Iron powder, zinc powder and aluminum Examples thereof include heat conductivity improvers such as powder and copper powder; glass beads, glass spheres, talc, diatomaceous earth, alumina, shirasu balun, hydrated alumina, metal oxides, colorants and pigments. These fillers or additives may be used alone or in combination of two or more.

The content of the filler or additive relative to 100 parts by weight of polyimide is preferably 10 parts by weight or less, more preferably 5 parts by weight or less. When the content of the filler or additive is excessive, the transparency of the film is lowered and light scattering occurs, which may make it difficult to measure the in-plane retardation Re spectroscopically.

The overall shape of the polyimide film to be inspected is not particularly limited. According to the inspection method of the present application, since a polyimide film can be measured nondestructively, a polyimide film having a product shape such as a roll film or a cut film can be used.
The thickness of the polyimide film to be inspected may be, for example, the thickness of a polyimide film used as a general FPC base film, and is preferably about 12.5 to 150 μm.

(Process (A))
In step (A), an in-plane retardation threshold allowable for the polyimide film to be inspected is set based on the relationship between the anisotropy of the linear expansion coefficient of the polyimide film and the in-plane retardation of the polyimide film. . As described above, there is a high correlation between the anisotropy of the linear expansion coefficient of the polyimide film and the in-plane retardation of the polyimide film.
Therefore, for example, from the polyimide film test piece having the same composition as the polyimide film to be inspected, the correlation between the magnitude of anisotropy of the linear expansion coefficient and the in-plane retardation is grasped, and this correlation and the target Based on the anisotropy of the linear expansion coefficient, an in-plane retardation threshold allowable for the polyimide film to be inspected is set. Since the in-plane phase difference has wavelength dependence, a threshold is set for the in-plane phase difference at a specific wavelength.

FIG. 1 shows a flowchart up to the setting of the in-plane phase difference threshold. However, this is an embodiment and the present invention is not limited to this.
As shown in FIG. 1, the process (process (a)) which measures the in-plane phase difference of a polyimide film test piece previously, and the process of measuring the anisotropic magnitude | size of the linear expansion coefficient of the said film test piece ( Step (b)) is performed. A calibration curve or the like is created from these measurement results, and the correlation between the in-plane phase difference and the anisotropy of the linear expansion coefficient is grasped (step (c)). The calibration curve, and based on the size S ₂ of the acceptable linear expansion coefficient inspected to calculate the threshold value of the in-plane retardation that is acceptable to the polyimide film to be inspected (step (d)). Note that either step (a) or step (b) may be performed first. That is, the order of step (a) → step (b) may be used, and the order of step (b) → step (a) may be used.

In the step (a) and the step (b), the number of test pieces for measuring the in-plane retardation and the anisotropy of the linear expansion coefficient is not particularly limited, but the correlation in the step (c) The number is preferably a number that can be grasped, that is, a number that allows creation of a calibration curve or the like. Specifically, 2 or more is preferable, 5 or more is more preferable, and 10 or more is more preferable.

In addition, when the in-plane retardation threshold that can make the anisotropy of the linear expansion coefficient anisotropy of the polyimide film to be inspected within an allowable range based on past measurement data or the like is known, the above process It is not always necessary to perform (a) to (d), and a known value may be set as the threshold value.

・ Process (a)
A polyimide film test piece having the same composition as the polyimide film to be inspected is prepared, and the in-plane retardation of the test piece is measured. The same composition means that both of its constituent components and component ratios are the same. The test piece is not particularly limited as long as it has a size and shape capable of measuring the in-plane retardation and the anisotropy of the linear expansion coefficient, and may be a cut film, for example. Moreover, the thickness of the test piece may be the same as or different from the polyimide film to be inspected. The in-plane retardation is proportional to the thickness of the film. For this reason, even when a test piece having a thickness different from that of the polyimide film to be inspected is used, the thickness is corrected in the step (d), and the threshold value of the in-plane retardation allowed for the polyimide film to be inspected is set. It is possible to calculate.

The in-plane retardation measurement of the test piece can be performed by an arbitrary method. For example, the in-plane retardation may be measured by a spectroscopic technique with white light in the same manner as the in-plane retardation Re of the polyimide film to be inspected. Further, the in-plane phase difference may be measured by a method of reading an interference color using a Belek type compensator or the like, or the Senarmon method. The method of measuring the in-plane phase difference spectroscopically with white light will be described in detail in the step (B) described later.

The temperature and humidity when measuring the in-plane retardation of the test piece may be different from the temperature and humidity when measuring the in-plane retardation Re of the polyimide film to be inspected. Since they may change depending on the temperature and humidity at the time of measurement, it is more preferable to make them equal.

・ Process (b)
For polyimide film specimen of the same test piece for measuring the in-plane retardation, as well as measuring the linear expansion coefficient, measuring the size S ₁ of the anisotropy of the linear expansion coefficient.
In order to measure the linear expansion coefficient of the test piece, a plurality of measurement samples are cut out from the test piece. FIG. 2 is a schematic diagram illustrating an example of a method of cutting a sample from a film test piece. FIG. 2 shows a state in which six strip-shaped measurement samples 12 are cut out from the square test piece 14. In the method shown in FIG. 2, the MD direction axis of the test piece 14 is assumed to be 0 °, and the 0 ° sample 12 is cut into a strip shape. Next, the sample 12 is cut out at every angle inclined by 15 to 45 ° from the MD direction axis. At this time, it is preferable to cut out the sample 12 over a range of 90 ° to 180 °.

Then, a TMA test is performed on these measurement samples using a thermomechanical analysis (TMA) apparatus or the like, and a linear expansion coefficient (CTE) is measured. The TMA test can be performed, for example, under a nitrogen stream, under conditions of a temperature increase rate of 5 to 10 ° C./min and a temperature range of 25 to 300 ° C.

The linear expansion coefficient ellipsoids 20 and 30 as shown in FIGS. 3 and 4 are created by plotting the linear expansion coefficient (CTE) values (measurement points 25 and 35) measured for each measurement sample according to a standard method (plotting). ) Then, as shown in FIG. 4, the value of ΔCTE represented by the difference (ba) between the major axis radius b and the minor axis radius a of the linear expansion coefficient ellipsoid 30 is expressed as “difference in linear expansion coefficient of film test piece”. It can be calculated as the magnitude of isotropic S ₁ (ppm / K). The inclination θ (that is, the inclination of the ellipse) of the short axis of the linear expansion coefficient ellipsoid 30 with respect to the MD direction axis can be calculated as “orientation angle (°) of film test piece”.

Steps (c) and (d)
In step (c), to understand the process and the in-plane phase difference calculated in (a), the anisotropy of the calculated coefficient of linear expansion in step (b) the correlation between the size S _1. There is a high correlation between the in-plane retardation calculated in step (a) and the anisotropy magnitude S ₁ (ΔCTE) of the linear expansion coefficient calculated in step (b). A calibration curve showing the relationship between the phase difference and the anisotropy magnitude S ₁ of the linear expansion coefficient can be created. FIG. 5 is a graph in which ΔCTE calculated by measuring the linear expansion coefficient in the step (b) is plotted against the in-plane retardation measured spectroscopically in the step (a).

In step (d), from a correlation grasped, it inspected and made anisotropic in linear expansion coefficient that is acceptable to the polyimide film size S ₂ Metropolitan in step (c), the surface of the polyimide film to be inspected Sets a threshold value for the internal phase difference. That is, a calibration curve prepared in step (c), based on the size S ₂ of the anisotropy of the linear expansion coefficient that is acceptable to the polyimide film to be inspected, acceptable plane polyimide film to be inspected The value of the phase difference can be calculated and the threshold value can be set.

FIG. 6 is a graph plotting the orientation angle of the test piece calculated by the spectroscopic technique in step (a) and the orientation angle calculated by measuring the linear expansion coefficient in step (b). As shown in FIG. 6, it can be seen that the orientation angle of the film measured and calculated by the spectroscopic technique and the orientation angle of the film calculated by measuring the linear expansion coefficient are almost the same. This indicates that the orientation angle can also be obtained by a spectroscopic technique at the same time when the in-plane retardation Re of the polyimide film to be inspected is measured in the step (B) described later.

(Process (B))
In the step (B), the in-plane retardation Re of the polyimide film to be inspected is measured spectroscopically with white light.
Examples of the method for spectroscopically measuring the in-plane retardation Re of the polyimide film to be inspected with white light include a parallel Nicol rotation method and a crossed Nicol rotation method. Examples of commercially available measuring devices for in-plane retardation Re employing these measurement methods include the product name “KOBRA” series manufactured by Oji Scientific Instruments, the product name “RETS” series manufactured by Otsuka Electronics Co., Ltd. Name “MCPD” series and the like. Among them, the product name “KOBRA” series manufactured by Oji Scientific Instruments and the product name “RETS” series manufactured by Otsuka Electronics Co., Ltd. are in-line in the flow direction (length direction) and width direction (perpendicular to the flow direction) of the roll film. This is preferable because the apparatus can measure the in-plane retardation Re at a plurality of locations.

Hereinafter, a method for measuring the transmittance spectrum of white light by the orthogonal Nicol rotation method and calculating the in-plane retardation Re of the polyimide film will be described as an example. FIG. 7 is a schematic diagram showing a technique for measuring a transmittance spectrum by the orthogonal Nicol rotation method. As shown in FIG. 7, the polarizer 2 and the analyzer 8 are arranged in crossed Nicols, and a polyimide film 4 to be inspected and optionally a phase difference plate 6 are arranged therebetween. In this state, the white light 10 is irradiated from the polarizer 2 side to the analyzer 8 side, and the transmittance spectrum is measured with a spectroscope (not shown) or the like installed on the analyzer 8 side. By analyzing the waveform of the transmittance spectrum, the in-plane retardation Re of the polyimide film can be specified.

In general, the in-plane retardation Re is often specified by measuring the transmitted light intensity of monochromatic light. However, in the present invention, as described above, white light is irradiated and the in-plane retardation Re is spectroscopically specified. This is because the in-plane retardation Re of the polyimide film can take a relatively wide range. When specifying the in-plane phase difference Re with monochromatic light (measurement wavelength λ), the relationship between the measurement wavelength (λ), the in-plane phase difference Re, and the transmitted light intensity I is expressed by the following equation. I ₀ indicates the incident light intensity.
I = I ₀ sin ² (πRe / λ)
Therefore, if the range that the in-plane phase difference Re can take is large, the same transmitted light intensity I is observed in different orders, and it is difficult to specify the in-plane phase difference Re accurately. Even when the value of the in-plane retardation Re is about n / 2 (n is an integer) times the measurement wavelength λ, it is difficult to specify the in-plane retardation Re.

The present inventor has found that the in-plane retardation Re is approximately 300 nm or more in a portion having a large linear expansion coefficient anisotropy of a polyimide film having a thickness of about 20 μm. Therefore, in the present invention, the in-plane phase difference Re is specified spectroscopically using white light that is not monochromatic light. If white light is used, the specific in-plane phase difference Re can be specified without being influenced by the order or the like. Especially for polyimide films that absorb light with a wavelength of 500 nm or less, such as films made of wholly aromatic polyimide (colored polyimide film), the in-plane retardation Re is measured by irradiating light in the wavelength range of 500 to 800 nm. It is preferable to do.

The type of the white light source is not particularly limited, and examples thereof include a halogen lamp, a xenon lamp, a deuterium lamp, a laser beam, and a combination thereof.

In the present invention, the retardation plate 6 is disposed between the polarizer 2 and the analyzer 8 so that the optical principal axis is inclined by 45 ° with respect to the transmission axes of the polarizer 2 and the analyzer 8. Is preferred. FIG. 8 shows a transmittance spectrum of a polyimide film having an in-plane retardation Re of 100 nm at a wavelength of 600 nm and a transmittance spectrum of a polyimide film having an in-plane retardation Re of 700 nm at a wavelength of 600 nm. As shown in FIG. 8, when the in-plane phase difference Re is small, there is little change in transmittance due to wavelength change, and it is difficult to analyze the in-plane phase difference Re from the spectrum waveform. Therefore, by arranging the phase difference plate 6, the observed in-plane phase difference Re shifts to the phase difference of the phase difference plate, the higher wavelength side, and wavelength analysis becomes easy.
In the case of measuring the transmittance spectrum by arranging a retardation plate, the waveform of the transmittance spectrum is analyzed to obtain a temporary in-plane retardation Re, and then the retardation of the retardation plate is further calculated. To determine the true in-plane phase difference Re.

The retardation of the retardation plate is suitably 400 nm or more, but more preferably a retardation plate of 500 nm to 750 nm used as a sensitive color plate. Further, the measurement may be performed using a retardation plate of 750 nm or more in which both the minimum value and the maximum value of transmittance appear.

The transmittance spectrum can be measured by (i) rotating the polyimide film 4 to be inspected relative to the polarizer 2, the analyzer 8, and the phase difference plate 6, or (ii) the polarizer 2, the detector. The photon 8 and the phase difference plate 6 are performed a plurality of times while being rotated relative to the polyimide film 4 to be inspected. That is, the transmittance spectrum is measured a plurality of times while changing the angle formed by the slow axis of the polyimide film 4 and the transmission axis of the polarizer 2.

When the inspection object is a roll film, the transmittance spectrum can be measured in the film forming process (in-line) of the polyimide film while rotating the set of the polarizer 2, the analyzer 8, and the phase difference plate 6. preferable. On the other hand, when the inspection object is a cut film, the transmittance spectrum may be measured while rotating the polyimide film 4 to be inspected, and the set of the polarizer 2, the analyzer 8, and the retardation plate 6 is rotated. However, the transmittance spectrum may be measured.

A technique for measuring the in-plane retardation Re in-line with respect to the roll film will be described with reference to FIG. As shown in FIG. 9A, the transmission axis of the polarizer 2 is parallel to the transport direction of the polyimide film 4 (hereinafter also referred to as “MD direction”), and the transmission axis of the analyzer 8 is vertical. Thus, the polarizer 2 and the analyzer 8 are arranged. Further, the phase difference plate 6 is arranged so that an angle formed by the optical principal axis of the phase difference plate 6 and the transmission axis of the polarizer 2 is 45 °. In this state, white light is irradiated from the light source 9 installed on the polarizer side, and the transmittance spectrum is measured by the spectroscope 11 installed on the analyzer 8 side.

Next, the above relationship was maintained for the polarizer 2, the phase difference plate 6, and the analyzer 8 so that the angle formed by the MD direction of the polyimide film 4 and the transmission axis of the polarizer 2 was 30 °. The transmittance spectrum is measured by rotating the material as it is (FIG. 9B). Similarly, the polarizer 2, the phase difference plate 6, and the analyzer 8 so that the angles formed by the MD direction of the polyimide film 4 and the transmission axis of the polarizer 2 are 60 °, 90 °, 120 °, and 150 °. The transmittance spectrum is measured by rotating while maintaining the above relationship (FIG. 9C). Waveform analysis of the obtained transmittance spectrum is performed, and the phase difference value having the largest value is set as the in-plane retardation Re of the polyimide film.

When the phase difference is observed to be the highest; that is, when the slow axis of the polyimide film 4 and the optical principal axis of the retardation plate 6 are parallel, the MD direction of the polyimide film 4 and the optical property of the retardation plate 6 The angle formed by the main axis is the orientation angle of the polyimide film.

In the above description, the transmittance spectrum is measured by rotating the polarizer 2 and the like by 30 °, but the rotation angle is not limited to the above angle. However, in order to accurately measure the in-plane retardation Re and specify the orientation angle, it is preferable to perform the measurement every 10 to 30 °.

In the embodiment shown in FIG. 9, the set of the polarizer 2, the phase difference plate 6, and the analyzer 8 is rotated with respect to the polyimide film roll film 4. For example, as shown in FIGS. 10 and 11. A set of a plurality of polarizers 2, a phase difference plate 6, and an analyzer 8 whose angles with respect to the MD direction are changed may be arranged along the flow direction.

In the present application, it is preferable to measure the in-plane retardation Re (transmittance) at a plurality of locations in the TD direction (in the width direction) of the polyimide film. That is, for example, as shown in FIG. 10, it is preferable to measure a plurality of in-plane retardation Re (transmittance spectrum) in the TD direction.

As a method of measuring a plurality of in-plane phase differences Re (transmittance spectra) in the TD direction, for example, as shown in FIG. 10, a plurality of light sources 9 and a plurality of spectroscopes 11 corresponding thereto are arranged in the width direction. Alternatively, for example, as shown in FIG. 11, a set of the light source 9 and the spectroscope 11 may be scanned in the width direction.

In the present invention, for example, the light source 9 and the spectroscope 11 are disposed only in a portion where the anisotropy of the linear expansion coefficient is likely to be high at the time of polyimide film production, such as an end portion of the polyimide film, and the in-plane retardation Re is set. You may measure.

Furthermore, in this inspection method, it is preferable to measure the in-plane retardation Re (transmittance spectrum) for every several meters, for example, for a polyimide roll film flowing on the line.

The in-plane phase difference Re may change with temperature and humidity. Therefore, the measurement of the in-plane retardation Re is preferably performed at a temperature of 15 to 40 ° C., and preferably 20 to 30 ° C. The humidity during measurement is preferably 10 to 85% Rh, more preferably 30 to 65% Rh.

In addition, for example, when the polyimide film is colored, the transmittance spectrum of the polyimide film to be inspected is measured before or after the present step, and the measurement is performed by the above method based on the result. You may correct | amend the value of the transmittance | permeability spectrum. The transmittance spectrum can be measured with the above-described spectroscope or the like.

The in-plane phase difference Re is obtained by analyzing the waveform of the transmittance spectrum measured as described above by the following method. The transmittance T (λ) at each wavelength when observing a polyimide film using a white light source with crossed Nicols is expressed by the following formula (1), and the transmitted light intensity I _⊥ (λ) is expressed by the following formula (2). It is represented by

In the above formulas (1) and (2), λ represents the wavelength of light, I ₀ (λ) represents the incident light intensity, and χ represents the polarizer transmission axis and the slow axis of the sample (polyimide film). Indicates a corner.
When the phase difference is calculated based on the above formulas (2) to (4), the phase difference becomes maximum when the angle χ formed by the polarizer transmission axis and the slow axis of the polyimide film is 45 °. . As described above, the value when the phase difference becomes maximum is defined as the in-plane phase difference Re.

It is known that the in-plane phase difference Re increases as the wavelength decreases. Therefore, considering the chromatic dispersion of the in-plane retardation Re according to the Cauchy dispersion formula, the equation (1) can be rewritten as the following equation (5). Then, by analyzing A ′ and B ′ in the following formula (5) as fitting parameters, the in-plane retardation Re at each wavelength of the polyimide film represented by the following formula (6) can be calculated.

In the above, the method of calculating the in-plane phase difference Re by observation with orthogonal Nicols has been described, but the present invention is not limited to this. For example, the transmitted light intensities I _強度 (λ) and I _∥ (λ) can be measured with orthogonal Nicols and parallel Nicols, and the in-plane phase difference Re can be calculated. Transmitted light intensities I _⊥ (λ) and I _∥ (λ) when the light transmittance of the polyimide film using a white light source is observed with crossed Nicols and parallel Nicols are expressed by the following formula (7).

Accordingly, I ₀ and δ are obtained by measuring I _⊥ (λ) and I _∥ (λ) at an appropriate angle such as χ = π / 4, and the above formula (7) and the above formula (2) to The in-plane phase difference Re may be calculated based on (4).

Further, by arranging the retardation film 6 and the polyimide film 4 to be inspected between the polarizer 2 and the analyzer 8 arranged in the crossed Nicols, and examining the shift amount of the wavelength showing the minimum value or the maximum value, The in-plane phase difference Re can also be calculated. In this method, first, only the phase difference plate 6 is disposed between the polarizer 2 and the analyzer 8 that are arranged in crossed Nicols, and the transmittance is measured. For example, when only the 550 nm phase difference plate 6 is disposed at the above position, the transmittance shows a minimum value at a wavelength of 550 nm. Next, the polyimide film 4 and the phase difference plate 6 are arrange | positioned between the polarizer 2 and the analyzer 8, and a transmittance | permeability spectrum is measured. At this time, when the orientation angle of the polyimide film 4 and the slow axis of the phase difference plate 6 are parallel, the wavelength showing the minimum value is shifted to the higher wavelength side by the in-plane retardation Re of the polyimide film 4. Further, when the orientation angle of the polyimide film 4 is perpendicular to the slow axis of the retardation plate 6, the wavelength showing the minimum value is shifted to the lower wavelength side by the in-plane retardation Re of the polyimide film 4. Based on this, the shift amount of the wavelength exhibiting the minimum value can be examined, and the shift amount when the shift amount becomes the maximum can be calculated as the in-plane phase difference Re.

(Process (C) and process (D))
In the step (C), the in-plane phase difference threshold set in the step (A) is compared with the in-plane phase difference Re measured in the step (B). If the in-plane retardation Re measured in the step (B) exceeds the threshold value, it indicates that the anisotropy of the linear expansion coefficient of the polyimide film to be inspected is not within the allowable range. Therefore, this result is fed back to the production process of the polyimide film, and this result is fed back, and the process (D) of adjusting the production condition of the polyimide film; the production condition causing the anisotropy of the linear expansion coefficient in the polyimide film is performed. It is preferable.

The polyimide film may have anisotropy in linear expansion coefficient due to various factors during the production process. Therefore, taking into consideration the result detected in step (C), by immediately adjusting to the manufacturing conditions such that the anisotropy of the linear expansion coefficient does not occur in step (D), the anisotropy of the linear expansion coefficient is generated. Can be produced with high yield.

The production conditions to be adjusted based on the result calculated in the step (C) are, for example, (i) tension applied to the polyimide film or its precursor (polyamic acid) at the time of drying or imidization, and (ii) Stretch ratio of polyimide film or its precursor (polyamic acid), (iii) heating temperature of polyimide film or its precursor (polyamic acid), (iv) heating rate of polyimide film or its precursor (polyamic acid), (v ) The amount of dry air blown onto the polyimide film or its precursor (polyamide acid), (vi) the conveyance speed of the polyimide film or its precursor (polyamide acid), and the like. Two or more manufacturing conditions may be adjusted simultaneously.

The manufacturing method of the polyimide film of the present invention is in accordance with the conventional manufacturing method of polyimide film (dry film) except that the above-described inspection method is incorporated in the film forming process. Hereinafter, the flow of the manufacturing method of a polyimide film is demonstrated, giving an example.

A polyimide film can be obtained by, for example, applying a polyamic acid solution (polyamic acid varnish) as a polyimide precursor on a substrate, removing the solvent and imidizing, and then peeling the obtained film from the substrate. it can. Solvent removal and imidation of the polyamic acid varnish are not particularly limited, but are preferably performed under reduced pressure or in an inert atmosphere such as nitrogen, helium, or argon. Solvent removal and imidization of the polyamic acid varnish are performed by passing the polyimide acid varnish coating film through a drying furnace at a constant speed.

The heating temperature at the time of desolvation and imidization of the polyamic acid varnish may be a temperature at which the imidization reaction proceeds while being not lower than the boiling point of the solvent. For example, in the case of a polyamic acid synthesized in an aprotic amide solvent, the heating temperature for desolvation and imidization may be about 100 to 300 ° C., and the heating time is not particularly limited, Usually, it may be about 3 minutes to 12 hours. Examples of the substrate on which the polyamic acid varnish is applied include a metal foil, an inorganic substrate such as glass, and various resin films. The thickness of the coating film of the polyamic acid varnish is preferably adjusted so that the film thickness after solvent removal and imidization is 1 mm or less, although it depends on the solid content concentration of the polyamic acid varnish.

Examples of means for applying the polyamic acid varnish include general application means such as a roll coater, a die coater, a gravure coater, a dip coater, a spray coater, a comma coater, a curtain coater, and a bar coater. These application means are appropriately selected according to the viscosity and the coating film thickness of the polyamic acid varnish.

Examples of the means for drying the polyamic acid varnish include an electrically heated or oil heated hot air, a roll support using infrared rays as a heat source, an air float type drying furnace, and the like. In order to prevent deterioration of the polyimide resin, discoloration due to oxidation of the metal foil, and the like, the dry atmosphere may be replaced with a gas other than air, such as nitrogen, argon, or hydrogen. The polyamic acid varnish is conveyed in the drying furnace in a state in which both ends of the film are sandwiched between clip tenters or pin tenters and tension is applied. Moreover, you may extend | stretch with respect to the obtained imide film. The produced film is usually wound up on a roll or the like.

In addition, it is preferable to perform the measurement of the in-plane retardation Re (the above-described step (B)) with respect to the polyimide film before winding, which is taken out from the drying furnace and cooled to a predetermined temperature. In particular, it is preferable to perform the in-plane retardation Re immediately before winding from the viewpoint of the reliability of the measured in-plane retardation Re.

In the present invention, in-plane retardation measurement may be performed in the process of heating and stretching the polyimide film, that is, inside the drying furnace. In this case, the orientation state of the polyimide film in the drying furnace can be evaluated in real time.

B. Polyimide film manufacturing apparatus The polyimide film manufacturing apparatus of the present invention includes a storage mechanism that stores a threshold value of the in-plane retardation Re that is acceptable for the polyimide film to be inspected, and a transport mechanism that transports the polyimide film to be inspected in a certain direction. And at least a measurement mechanism for measuring the in-plane retardation Re of the polyimide film, and if necessary, determines whether the degree of anisotropy of the linear expansion coefficient of the polyimide film is within a standard range And a control mechanism for controlling the manufacturing conditions of the polyimide film based on the determination mechanism and the result determined by the determination mechanism.

In the polyimide film manufacturing apparatus of the present invention, the in-plane retardation Re of the polyimide film is measured by the measurement mechanism while the polyimide film is conveyed in a certain direction by the conveyance mechanism. By comparing the in-plane retardation Re measured by the measurement mechanism with the in-plane retardation threshold stored in the storage mechanism, the anisotropy of the linear expansion coefficient of the polyimide film being manufactured can be quickly determined. This result can be fed back to the manufacturing conditions. Therefore, a polyimide film in which the occurrence of anisotropy of the linear expansion coefficient is suppressed can be efficiently produced.

(Memory mechanism)
The memory | storage mechanism arrange | positioned at the polyimide film manufacturing apparatus of this invention is a mechanism which memorize | stores the threshold value of the in-plane phase difference Re of the polyimide film which is a test object. For example, the storage mechanism may include an input unit for inputting a threshold value and a storage unit for storing the threshold value. The storage unit can be any data readable medium such as a magnetic disk, a hard disk, a CD-ROM or the like.

The threshold value stored in the memory mechanism is based on the method described in the polyimide film inspection method described above, that is, the correlation between the anisotropy of the linear expansion coefficient of the polyimide film and the in-plane retardation Re of the polyimide film. The value calculated from the correlation and the anisotropy of the linear expansion coefficient acceptable for the polyimide film to be inspected is preferable.

(Transport mechanism)
The transport mechanism disposed in the polyimide film manufacturing apparatus is not particularly limited as long as it is a mechanism capable of moving the polyimide film in a constant direction at a constant speed, and may be a general roll film transport mechanism, for example.
The transport mechanism may be provided with a heating unit for drying the solvent of the polyamic acid varnish and imidizing the polyamic acid during the transport, a discharge unit for discharging the drying air, and the like. Moreover, the mechanism etc. which convey a polyimide film in a specific direction may be sufficient.

(Measuring mechanism)
The measurement mechanism is a mechanism for measuring the in-plane retardation Re of the polyimide film. The type of equipment of the measurement mechanism is appropriately selected depending on the inspection method. For example, a general optical system phase difference measuring device of an in-plane phase difference Re measuring device employing a parallel Nicol rotation method, an orthogonal Nicol rotation method, or the like can be used.

The measuring mechanism is preferably arranged so as to measure the in-plane retardation Re in-line when the polyimide film is transported by the transport mechanism. Further, for example, as shown in FIG. 10, the measurement mechanism has a plurality of optical phase difference measuring devices in the direction perpendicular to the polyimide film conveyance direction by the conveyance mechanism (the width direction of the film), or in FIG. As shown, it is preferable to have an optical phase difference measuring device capable of scanning in the vertical direction with respect to the conveyance direction of the polyimide film by the conveyance mechanism.

(Judgment mechanism)
The determination mechanism is a mechanism that reads the threshold value of the in-plane phase difference stored in the storage mechanism and performs a comparison operation with the in-plane phase difference Re measured by the measurement mechanism described above. For example, the result of the comparison operation is output to the outside. It is preferable to have a means to do. As an output method to the outside, for example, a method of outputting a comparison calculation result to a monitor or the like, and an output method of generating an error sound when the in-plane phase difference Re exceeds a threshold value are exemplified.

(Manufacturing condition control mechanism)
The manufacturing condition control mechanism may be a mechanism that controls various manufacturing conditions of the polyimide film based on the result of the comparison operation by the determination mechanism. Various production conditions include (i) tension applied to the polyimide film or its precursor (polyamic acid) during drying or imidization, (ii) stretch ratio of the polyimide film or its precursor (polyamic acid), (iii) ) Heating temperature of polyimide film or its precursor (polyamic acid), (iv) Heating speed of polyimide film or its precursor (polyamic acid), (v) Dry air sprayed onto polyimide film or its precursor (polyamic acid) The air volume, (vi) the conveyance speed of the polyimide film or its precursor (polyamic acid), etc. are mentioned.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(Example 1) (1) Spectroscopic measurement of in-plane retardation and orientation angle of test piece As shown in FIG. 7, a polyimide film is disposed between a polarizer 2 and an analyzer 8 arranged in a crossed Nicol state. The test piece 4 and the phase difference plate 6 (530 nm) were arranged, and the transmittance spectrum was measured. In addition, as the polyimide film test piece 4, six Kapton EN films (fully aromatic polyimide films) manufactured by Toray DuPont having different lot numbers were used. A halogen lamp was used as a light source, and an optical fiber and a multi-channel spectrometer were used as detectors.

The white light was irradiated with a measurement wavelength range of 450 to 750 nm, and the transmittance spectrum was measured while rotating the test piece 4 around the light transmission axis 10 as the rotation center. The measured transmittance spectrum waveform was fitted by the above equation (5), and the in-plane phase difference of each test piece 4 was calculated. Moreover, the MD direction of the polyimide film was set to 0 °, and the orientation angle of the polyimide film was calculated from the rotation angle when the phase difference reached the maximum value.

Before the measurement, calibration is performed with the film test piece 4 placed in front of the polarizer 2, that is, the light source, the film test piece 4, the polarizer 2, the analyzer 8, and the detector arranged in this order. The contribution of coloring of the polyimide film test piece 4 was considered.

(2) Measurement of ΔCTE and orientation angle of film test piece About the same film test piece (10 cm × 10 cm) 14 as the polyimide film used in the above (1), as shown in FIG. Six strip-shaped measurement samples 12 (36 in total) were cut out. The measurement sample 12 was cut in a range of −30 to 120 ° in total, with the MD direction axis of the film test piece 14 set to 0 °, tilted by 30 ° therefrom. Using a thermomechanical analyzer (trade name “TMA” series, manufactured by Shimadzu Corporation), TMA was measured for each measurement sample under the conditions of a temperature increase rate of 5 ° C./min and a temperature range of room temperature to 300 ° C. under a nitrogen stream. A test was conducted, and the coefficient of linear expansion (CTE) in the range of 100 to 200 ° C. was measured.

The linear expansion coefficient ellipsoids 20 and 30 shown in FIGS. 3 and 4 were plotted by plotting the linear expansion coefficient (CTE) values (measurement points 25 and 35) measured for each measurement sample for each test piece. . Thereafter, ΔCTE represented by the difference (ba) between the major axis radius b and the minor axis radius a of the linear expansion coefficient ellipsoid 30 shown in FIG. 4 was calculated. The calculated ΔCTE corresponds to “the degree of anisotropy S ₁ of the linear expansion coefficient of the film test piece”. The inclination θ of the short axis of the linear expansion coefficient ellipsoid 30 with respect to the MD direction axis was calculated as the orientation angle of the film test piece.

Table 1 shows the in-plane retardation and orientation angle at a wavelength of 600 nm calculated by spectroscopic techniques, and ΔCTE and orientation angle measurement results calculated by measuring the linear expansion coefficient for the above test pieces.

(3) Preparation of calibration curve For each test piece, a graph (calibration curve) was plotted in which ΔCTE calculated by linear expansion coefficient measurement was plotted against the in-plane phase difference calculated by the spectroscopic technique. The prepared calibration curve is shown in FIG. Also, The correlation coefficient R using the following equation ^(7), was R 2 = 0.9188.
R ² = σ _tR ² / σ _t σ _R (7)
(Σ _t represents the variance of the major axis radius and minor axis radius (ΔCTE) in the linear expansion coefficient ellipsoid, σ _R represents the in-plane phase difference variance, and σ _tR represents the covariance between ΔCTE and the orientation angle Indicates)

For each test piece, a graph (calibration curve) was prepared by plotting the orientation angle calculated by measuring the linear expansion coefficient with respect to the orientation angle calculated by the spectroscopic technique. The prepared calibration curve is shown in FIG. Also, The correlation coefficient R using the following equation ^(8), were R 2 = 0.9197.
R ² = σ _Ao ² / σ _A σ _o (8)
(Σ _A indicates the dispersion of the orientation angle of the film specimen, σ _o indicates the dispersion of the orientation angle of the polyimide film, and σ _Ao indicates the covariance of the orientation angle of the film specimen and the orientation angle of the polyimide film)

As shown in FIG. 5, for each test piece, there is a high correlation between the in-plane phase difference calculated by the spectroscopic method and the anisotropy magnitude S ₁ (ΔCTE) of the linear expansion coefficient. It is clear that it exists. Thus, it is clear that the anisotropy of the linear expansion coefficient of the polyimide film can be predicted by optically measuring the in-plane retardation of the polyimide film.

Further, as shown in FIG. 6, it is clear that the orientation angle of the film measured and calculated by the optical technique and the orientation angle of the film measured and calculated by the TMA test are in good agreement.

If the polyimide film inspection method of the present invention is used, the anisotropy of the linear expansion coefficient of the polyimide film can be measured quickly and easily in a nondestructive manner. For this reason, it becomes possible to manufacture efficiently the polyimide film by which generation | occurrence | production of the anisotropy of the linear expansion coefficient was suppressed by incorporating this test | inspection method in the manufacturing process of a polyimide film. Moreover, according to the method for producing a polyimide film of the present invention, a polyimide film having an extremely small linear expansion coefficient anisotropy can be obtained by a simple technique. If a copper foil is laminated on the polyimide film thus obtained, a copper-clad laminate is obtained that is less likely to suffer from problems such as warping and that is less susceptible to problems such as distortion and thermal stress during heating in the wiring formation process. Can do.

2 Polarizer 4 Polyimide film 6 Phase difference plate 8 Analyzer 9 Light source 10 Light transmission axis 11 Spectrometer 12 Sample for measurement 14 Film specimen 20, 30 Linear expansion coefficient ellipsoid 25, 35 Measurement point

Claims (15)

1. From the relationship between the anisotropy of the linear expansion coefficient of the polyimide film and the in-plane retardation of the polyimide film, a step (A) for setting a threshold value of the in-plane retardation acceptable for the polyimide film to be inspected; ,
   Step (B) of measuring the in-plane retardation Re of the polyimide film to be inspected spectroscopically with white light;
   The threshold value is compared with the in-plane retardation Re measured in the step (B) to determine whether the anisotropy of the linear expansion coefficient of the polyimide film to be inspected is within a standard range. A method for inspecting a polyimide film, comprising the step (C).
2. The step (A)
   A step (a) for spectroscopically measuring the in-plane retardation of the polyimide film test piece with white light; and
   And step (b) measuring the size S ₁ of the anisotropy of the linear expansion coefficient of the polyimide film specimen,
   And step (c) to ascertain the correlation between the size S ₁ of the anisotropic in-plane retardation of the test piece,
   Based on the anisotropy size S ₂ of the linear expansion coefficient acceptable for the polyimide film to be inspected and the correlation grasped in the step (c), the in-plane retardation acceptable for the polyimide film to be inspected The inspection method of the polyimide film of Claim 1 including the process (d) which sets a threshold value.
3. The method for inspecting a polyimide film according to claim 1 is performed in the process of forming a polyimide film,
   The method for producing a polyimide film, wherein the polyimide film to be inspected is a polyimide film in a film forming process.
4. The method for producing a polyimide film according to claim 3, wherein the orientation angle of the polyimide film to be inspected is also calculated in the step (B).
5. The method for producing a polyimide film according to claim 3, wherein in the step (B), the in-plane retardation Re is measured at a plurality of locations in the flow direction and the width direction of the roll-film-like polyimide film.
6. The method for producing a polyimide film according to claim 3, wherein the polyimide film to be inspected is a roll film or a cut film.
7. The method for producing a polyimide film according to claim 3, wherein the spectroscopic measurement in the step (B) is performed with white light in a wavelength range of 500 to 800 nm.
8. The spectroscopic measurement of the step (B) includes white light transmittance spectrum measurement,
   The manufacturing method of the polyimide film of Claim 3 which measures the transmittance | permeability spectrum of the polyimide film of test object previously, and correct | amends the transmittance | permeability spectrum measured by the said process (B).
9. The method for producing a polyimide film according to claim 3, comprising a step (D) of feeding back a result determined in the step (C) to a production process of the polyimide film and adjusting a production condition of the polyimide film.
10. A storage mechanism for storing a threshold value of an in-plane retardation acceptable to the polyimide film to be inspected;
    A transport mechanism for transporting the polyimide film in a certain direction;
    A polyimide film manufacturing apparatus having a measurement mechanism for measuring an in-plane retardation Re of the polyimide film.
11. The in-plane retardation Re measured by the measurement mechanism is compared with the threshold value stored in the storage mechanism, and the anisotropy of the linear expansion coefficient of the polyimide film to be inspected is within the standard range. The polyimide film manufacturing apparatus of Claim 10 which has the determination mechanism which determines whether it is.
12. The polyimide film manufacturing apparatus according to claim 11, further comprising a control mechanism for controlling manufacturing conditions of the polyimide film based on the result determined by the determination mechanism.
13. The manufacturing conditions controlled by the control mechanism are the tension applied to the polyimide film or its precursor, the draw ratio of the polyimide film or its precursor, the heating temperature of the polyimide film or its precursor, the polyimide film or its The polyimide according to claim 12, which is at least one selected from the group consisting of a heating rate of a precursor, an amount of dry air blown onto the polyimide film or its precursor, and a transport speed of the polyimide film or its precursor. Film manufacturing equipment.
14. The polyimide film manufacturing apparatus according to claim 10, wherein the measurement mechanism includes a plurality of optical phase difference measurement devices arranged in a direction perpendicular to a conveyance direction of the polyimide film by the conveyance mechanism.
15. The polyimide film manufacturing apparatus according to claim 10, wherein the measurement mechanism includes an optical phase difference measurement device that can scan in a direction perpendicular to a conveyance direction of the polyimide film by the conveyance mechanism.
    

Images