JP7361587B2 - Inspection method, inspection device, and inspection system - Google Patents

Description

The present invention relates to an inspection method, an inspection device, and an inspection system.

A retardation film can convert linearly polarized light into circularly or elliptically polarized light, or conversely, convert circularly or elliptically polarized light into linearly polarized light, so this retardation film and a linearly polarized plate are combined (elliptical). Circularly polarizing plates are applied to organic EL display devices and reflective liquid crystal display devices. Among retardation films, the retardation film obtained by aligning and curing a polymerizable liquid crystal compound is an extremely thin film, and has been attracting attention for manufacturing thin display devices (for example, Patent Document (see 1).

The method for producing such a retardation film is usually to form a thin film by coating a liquid composition containing a polymerizable liquid crystal compound on a long base film, and then to form a thin film by applying a liquid composition containing a polymerizable liquid crystal compound to a long substrate film. After oriented in a desired direction, active energy rays are irradiated. As a result, the oriented polymerizable liquid crystal compound is cured and becomes a retardation film. In order to orient the polymerizable liquid crystal compound, an alignment film may be formed on the base film before coating the liquid composition on the base film.

Japanese Patent Application Publication No. 2006-58546

In this manufacturing method, if there is dust or the like on the base film or in the form of an alignment film, the orientation of the polymerizable liquid crystal compound may be disturbed at the dusty portion, resulting in defects. If the base film has an in-plane retardation, it is likely to be difficult to inspect the presence or absence of defects in the retardation film formed on the base film using an optical method. Since base films that are inexpensively available on the market are generally produced by stretching, the reality is that inexpensive base films are difficult to use for inspecting retardation films produced by the above method.

SUMMARY OF THE INVENTION Therefore, the present invention provides an inspection method, an inspection device, and an inspection method capable of inspecting a retardation film made of a cured product of a polymerizable liquid crystal compound for defects while suppressing the influence of the in-plane retardation of the base film. The purpose is to provide an inspection system.

The present invention provides a film-like coating comprising a base film having an in-plane retardation value of 50 nm or more at a wavelength of 550 nm, and a retardation film made of a cured product of a polymerizable liquid crystal compound formed on one side of the base film. An inspection method for determining the presence or absence of a defect in a retardation film by injecting light into an object to be inspected, the method comprising: a first linearly polarizing plate, an object to be inspected, a retardation filter, a second linearly polarizing plate; are arranged in this order, and the surface of the test object facing the base film side faces the first linear polarizing plate, and the slow axis of the base film and the first linear polarizing plate or the first linear polarizing plate are aligned. The polarization axes of the linear polarizing plates No. 2 and 2 are substantially orthogonal to each other or substantially parallel to each other, and the slow axes of the retardation film and the slow axis of the retardation filter are substantially parallel to each other. The in-plane retardation value at a wavelength of 550 nm is 300 nm or less, and the sum of the in-plane retardation value at a wavelength of 550 nm of the retardation film and the in-plane retardation value at a wavelength of 550 nm of the retardation filter is 520 nm to 600 nm. Yes, the first linear polarizing plate and the second linear polarizing plate form a crossed nicol structure, and the optical axis is directed from either the first linear polarizing plate side or the second linear polarizing plate side. An inspection method is provided in which light is incident on an object to be inspected so as to pass through a predetermined inspection area, and a second linearly polarizing plate or a first linearly polarizing plate is observed from the other side.

In this inspection method, the polarization axes of the first linear polarizing plate or the second linear polarizing plate are arranged so as to be substantially orthogonal to each other or substantially parallel to the slow axis of the base film having a retardation. Therefore, the polarization state of the light that has passed through the linearly polarizing plate is not disturbed by the base film. That is, the assembled optical system functions as intended, and if there is a defect in the retardation film, the defect can be appropriately recognized in the observation field. In addition, in this inspection method, the sum of the in-plane retardation value at a wavelength of 550 nm of the retardation film and the in-plane retardation value at a wavelength of 550 nm of the retardation filter is 520 nm to 600 nm. The linearly polarized light that has passed through the phase difference filter will have a phase difference of approximately λ before and after it. This increases the brightness difference between the normal part and the defective part of the retardation film in the observation field. Therefore, according to this inspection method, it is possible to easily determine the presence or absence of a defect in the retardation film while suppressing the influence of the in-plane retardation that the base film has.

Further, in this inspection method, the first linearly polarizing plate and the second linearly polarizing plate form a crossed nicol. In this case, the entire observation field can be made darkest, so that the defective portion of the retardation film observed as a bright spot stands out most in the observation field. Therefore, it is possible to more easily determine whether there is a defect in the retardation film.

This inspection method may include a step of determining in advance the direction of the slow axis of the base film using an orientation angle measuring device for the base film before the retardation film is formed. If the direction of the slow axis of the base film is unknown, by determining this in advance, the polarization axis of the first linear polarizing plate or the second linear polarizing plate can be aligned with the slow axis of the base film. They can be arranged substantially orthogonally or substantially parallel to each other.

At this time, after determining the slow axis of the base film using an orientation angle measuring device, a liquid composition containing a polymerizable liquid crystal compound is coated on one side of the base film and polymerized onto the surface of the base film. The method may include a step of forming a coating film containing a polymerizable liquid crystal compound, and aligning and curing the polymerizable liquid crystal compound contained in the coating film to form a retardation film. This improves the efficiency of manufacturing the retardation film.

Furthermore, in the inspection method of the present invention, the inspection is performed continuously in the length direction while the inspection target is conveyed in the length direction of the inspection target between the first linear polarizing plate and the phase difference filter. It's okay. This makes the inspection of the inspection object more efficient.

Furthermore, in the inspection method of the present invention, a plurality of inspection areas may be provided in the width direction of the object to be inspected. Since the base film is generally manufactured by stretching in at least one direction, the slow axes often have different directions in the width direction. Therefore, by dividing the inspection area across the width of the object to be inspected and performing the inspection in each inspection area, it is possible to conduct an inspection that suppresses the influence of the in-plane retardation of the base film in each part in the width direction. It can be carried out.

Light is applied to a film-like test object comprising a base film having an in-plane retardation value of 50 nm or more at a wavelength of 550 nm, and a retardation film made of a cured product of a polymerizable liquid crystal compound formed on one side of the base film. An inspection device that determines the presence or absence of a defect in a retardation film by inputting a first linear polarizing plate and a retardation filter arranged to sandwich a place where an object to be inspected, and the retardation filter. The second linearly polarizing plate is placed in an area opposite to the place where the object to be inspected is placed, and the place where the object to be inspected is placed with respect to the first linearly polarizing plate or the second linearly polarizing plate. a light source disposed in an opposite region, and the first linearly polarizing plate or the second linearly polarizing plate is arranged such that its polarization axis is substantially orthogonal to or substantially parallel to the slow axis of the base film. The phase difference filter is arranged so that its slow axis is substantially parallel to the slow axis of the phase difference film, and the in-plane phase difference at a wavelength of 550 nm of the phase difference filter is The value is a value such that the sum of the in-plane retardation value at a wavelength of 550 nm of the retardation film is 520 nm to 600 nm, and the first linear polarizing plate and the second linear polarizing plate form a crossed nicol. , the light source is arranged at a position where a first linearly polarizing plate, a predetermined inspection area on the object to be inspected, a phase difference filter, and a second linearly polarizing plate are lined up on its optical axis.

In this inspection device, the polarization axes of the first linear polarizing plate or the second linear polarizing plate are arranged so as to be substantially orthogonal to each other or substantially parallel to the slow axis of the base film having a retardation. Therefore, the polarization state of the light that has passed through the linearly polarizing plate is not disturbed by the base film. That is, the assembled optical system functions as intended, and if there is a defect in the retardation film, the defect can be appropriately recognized in the observation field. In addition, in this inspection device, since the sum of the in-plane retardation value of the retardation film at a wavelength of 550 nm and the in-plane retardation value of the retardation filter at a wavelength of 550 nm is 520 nm to 600 nm, the retardation film and the The linearly polarized light that has passed through the phase difference filter will have a phase difference of approximately λ before and after it. This increases the brightness difference between the normal part and the defective part of the retardation film in the observation field. Therefore, according to this inspection device, it is possible to easily determine whether there is a defect in the retardation film while suppressing the influence of the in-plane retardation that the base film has.

Further, in this inspection device, the first linearly polarizing plate and the second linearly polarizing plate constitute a crossed nicol. In this case, the entire observation field can be made darkest, so that the defective portion of the retardation film observed as a bright spot stands out most in the observation field. Therefore, it is possible to more easily determine whether there is a defect in the retardation film.

The present invention also provides the above inspection device, an orientation angle measuring device for determining the slow axis of the base film before a retardation film is formed, and a slow phase axis of the base film determined by the orientation angle measuring device. An inspection system is provided that includes an angle adjustment mechanism that adjusts the angle of the first linear polarizing plate so that the axis and the polarization axis of the first linear polarizing plate are substantially orthogonal to each other or substantially parallel to each other. If the direction of the slow axis of the base film is unknown, by determining this in advance, the polarization axis of the first linear polarizing plate or the second linear polarizing plate can be aligned with the slow axis of the base film. They can be arranged substantially orthogonally or substantially parallel to each other. Furthermore, by providing an angle adjustment mechanism, the angle adjustment can be automated.

According to the present invention, an inspection method and an inspection apparatus are capable of inspecting the presence or absence of defects in a retardation film made of a cured product of a polymerizable liquid crystal compound while suppressing the influence of in-plane retardation of a base film. and an inspection system.

FIG. 1 is a diagram showing an inspection device according to a first embodiment. FIG. 1 is a diagram showing an inspection system according to a first embodiment. It is a partial perspective view showing arrangement of a plurality of inspection devices in an inspection system of a 1st embodiment. FIG. 3 is a plan view showing the state of the slow axis of the base film. It is a figure showing the inspection device of a 2nd embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same parts or corresponding parts are given the same reference numerals, and overlapping explanations will be omitted.

(Definition of terms and symbols)
Definitions of terms and symbols used herein are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction), "ny" is the in-plane direction perpendicular to the slow axis, and "nz" is the refractive index in the thickness direction. It is the refractive index.
(2) In-plane retardation value The in-plane retardation value (Re(λ)) refers to the in-plane retardation value of the film at 23° C. and wavelength λ (nm). Re(λ) is determined by Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the film.
(3) Retardation value in the thickness direction The retardation value in the thickness direction (Rth (λ)) refers to the retardation value in the thickness direction of the film at 23° C. and wavelength λ (nm). Rth(λ) is determined by Rth(λ)=((nx+ny)/2−nz)×d, where d (nm) is the thickness of the film.

<First embodiment>
(Inspection equipment and inspected object)
The inspection device of this embodiment inspects the presence or absence of optical defects in a retardation film. As shown in FIG. 1, the inspection device 1A includes a light source 2, a first linear polarizing plate 3, a phase difference filter 4, a second linear polarizing plate 5, and a camera (detection means) 6 arranged in this order. It is something that has been done. In the inspection apparatus 1A, a place is prepared between the first linear polarizing plate 3 and the phase difference filter 4 to place the object 10 to be inspected, and in FIG. It depicts how it is placed.

First, the film-shaped inspection object 10 to be inspected will be explained. The inspection object 10 includes a retardation film 7A, which is the main body of the inspection object, and a base film 8A on which the retardation film 7A is laminated on one side. One example of the retardation film 7A is one used as a circularly polarizing plate in a display device, such as a liquid crystal display device or an organic EL display device, in combination with a linearly polarizing plate. Note that in this specification, the term "circularly polarizing plate" includes a circularly polarizing plate and an elliptically polarizing plate. Furthermore, "circularly polarized light" includes circularly polarized light and elliptically polarized light.

The retardation film 7A has an in-plane retardation value of 300 nm or less at a wavelength of 550 nm, and for example, the retardation film 7A is a λ/4 plate. In this embodiment, the retardation film 7A is made of a cured product of a polymerizable liquid crystal compound. The retardation film 7A made of a cured product of a polymerizable liquid crystal compound is usually thin, about 0.2 μm to 10 μm, and if it contains foreign matter, the retardation value tends to decrease in that part.

Polymerizable liquid crystal compounds that can form the retardation film 7A are described in, for example, JP2009-173893A, JP2010-31223A, WO2012/147904, WO2014/10325, and WO2017-43438. Those disclosed can be mentioned. The polymerizable liquid crystal compounds described in these publications can form a retardation film having so-called reverse wavelength dispersion, which is capable of uniform polarization conversion in a wide wavelength range.

As a method for forming the retardation film 7A, a solution containing the polymerizable liquid crystal compound (polymerizable liquid crystal compound solution; liquid composition) is applied (coated) onto the base film 8A to form a coated film. By photopolymerizing the material, extremely thin materials can be formed as described above. The base film 8A may be provided with an alignment film for aligning the polymerizable liquid crystal compound. The alignment film may be one that is optically aligned by polarized light irradiation or one that is mechanically aligned by rubbing treatment. In addition, as a specific example of such an alignment film, those described in the above-mentioned publication can be used. The thus formed retardation film 7A is pasted together with the base film 8A to another film, and then the base film 8A is peeled off to transfer the retardation film 7A onto the other film. can do.

When forming the retardation film 7A, if there are foreign substances or the like on the base film 8A to which the polymerizable liquid crystal compound solution is applied, or if there are scratches or the like on the base film 8A itself, the polymerizable liquid crystal compound solution may be applied. Defects may occur in the coating film itself obtained by coating. Furthermore, when the alignment film is subjected to a rubbing treatment, scraps of the rubbing cloth remain on the alignment film, which may cause defects in the coating film of the polymerizable liquid crystal compound solution (composition for forming a cured liquid crystal film). In this way, when forming a retardation film from a polymerizable liquid crystal compound, it is possible to form an extremely thin retardation film, but the above-mentioned debris and scratches can cause optical defects in the retardation film. It may be a factor.

Since the base film 8A to which the polymerizable liquid crystal compound solution is applied is in a laminated state with the retardation film 7A during defect inspection of the retardation film 7A, it is desirable that the retardation value is small. However, in this embodiment, the base film 8A has an in-plane retardation value of 50 nm or more at a wavelength of 550 nm. The in-plane retardation value may be 100 nm or more, 500 nm or more, 1000 nm or more, 2000 nm or more, 5000 nm or more, 8000 nm or more. It may be. Even if the base film 8A has such a retardation, the inspection device of this embodiment can detect defects in the retardation film 7A without being affected by the retardation of the base film 8A. The presence or absence can be easily determined.

Materials constituting the base film 8A include those described in the above-mentioned publications, and among them, polyethylene terephthalate (PET) is preferred. The thickness of the base film 8A may be 10 to 500 μm, 30 to 300 μm, 50 to 200 μm, or 80 to 150 μm.

In the inspection device 1A, the first linearly polarizing plate 3 is a film that converts the light incident from the light source 2 into linearly polarized light, and is formed by pasting a protective film on at least one surface of the polarizing film. Examples of polarizing films include polyvinyl alcohol films with iodine and dichroic dyes adsorbed and oriented, and polymerizable liquid crystal compounds oriented and polymerized with dichroic dyes adsorbed and oriented. It will be done. The retardation of the protective film used in the linearly polarizing plate is preferably small; for example, for Re(550), the retardation is preferably 10 nm or less, particularly preferably 5 nm or less.

The protective film here is for protecting the polarizing film. As the protective film, those commonly used in the technical field of polarizing plates are used for the purpose of obtaining a polarizing plate having appropriate mechanical strength. Typically, cellulose ester films such as triacetyl cellulose (TAC) films; cyclic olefin films; polyester films such as polyethylene terephthalate (PET) films; (meth)acrylic films such as polymethyl methacrylate (PMMA) films; Film, etc. Further, additives commonly used in the technical field of polarizing plates may be included in the protective film.

Although various commercially available products can be used as the light source 2, it is advantageous to use a straight light beam (including one that approximates a straight light beam) such as a laser beam, for example. The light emitted by the light source 2 is unpolarized, passes through the first linear polarizing plate 3 to become polarized light in a predetermined direction, and further passes through the retardation film 7A to become circularly polarized light. That is, unpolarized light becomes circularly polarized light by passing through the first linear polarizing plate 3 and the retardation film 7A.

The phase difference filter 4 includes a phase difference film 7B. The phase difference filter 4 used is one in which the sum of the in-plane retardation value at a wavelength of 550 nm and the in-plane retardation value at a wavelength of 550 nm of the retardation film 7A to be inspected is 520 nm to 600 nm. This total is preferably 530 nm to 590 nm, more preferably 540 nm to 580 nm, and even more preferably λ itself. Here, "λ" is the measurement wavelength (here, 550 nm). The phase difference filter 4 may be constructed by laminating a plurality of retardation films each having an in-plane retardation value of about 100 to 200 nm. When determining optical defects based on luminance (brightness) information ΔL*, it is preferable that the phase difference filter 4 uses a film having the same configuration as the inspected object 10. Further, when determining an optical defect based on color difference information ΔE*, it is preferable to use a film having a wavelength dispersion property opposite to that of the object to be inspected 10 as the phase difference filter 4. Further, the direction in which the phase difference filter 4 is arranged is such that the slow axis of the phase difference film 7A and the slow axis of the phase difference filter 4 are parallel to each other. That is, when the object to be inspected 10 is inspected, the direction of the phase difference filter 4 is adjusted so that the polarization axis of the linearly polarized light is always rotated in the same direction as the retardation film 7A in the object to be inspected 10. be done. Preferably, the retardation film 7A and the retardation filter 4 act as a λ plate. For example, when the phase difference of the phase difference film 7A is λ/4, the phase difference of the phase difference filter 4 is set to 3λ/4. In this case, the phase difference filter 4 may be composed of one 3λ/4 plate or may be composed of three λ/4 plates stacked together.

Further, the phase difference filter 4 may further include a positive C plate. The positive C plate may be provided on the surface facing the retardation film 7A, or may be provided on the surface opposite thereto. By using a positive C plate, the inspection area can be expanded. The retardation value (Rth(550)) of the positive C plate in the thickness direction may be appropriately selected depending on the retardation value in the thickness direction of the retardation film 7A to be inspected. For example, if the retardation film 7A is a λ/4 plate In this case, the effect is likely to be obtained by using a material with a thickness direction retardation value (Rth(550)) of -50 nm to -300 nm.

The retardation filter 4 may include a retardation film 7B and a base film 8B on which the retardation film 7B is laminated. The base film 8B has an in-plane retardation value (Re(550)) of substantially zero so as not to impair the optical properties of the retardation film 7B. Here, the in-plane retardation being substantially zero means that the in-plane retardation value (Re(550)) is 3 nm or less.

Here, how to obtain the in-plane retardation value (Re(550)) and the thickness direction retardation value (Rth(550)) at a wavelength of 550 nm will be described. As described above, pieces of, for example, about 40 mm x 40 mm are separated from the film to be measured (eg, separated from a long film using an appropriate cutting tool). The Re(550) of this piece is measured three times and the average value of Re(550) is determined. The Re(550) of the piece can be measured at room temperature (23° C.) using a phase difference measuring device KOBRA-WPR (manufactured by Oji Scientific Instruments Co., Ltd.).

The second linearly polarizing plate 5 is a film on which the light that has passed through the phase difference filter 4 is incident, and its structure and material are the same as those of the first linearly polarizing plate 3. In the inspection apparatus 1A, the second linearly polarizing plate 5 is arranged so as to form a crossed nicol with the first linearly polarizing plate 3.

Furthermore, in order to enlarge the inspection area, a positive C plate may be placed between the first linear polarizing plate 3 and the base film 8A. The retardation value (Rth(550)) in the thickness direction of the positive C plate may be appropriately selected depending on the retardation value in the thickness direction of the base film 8A. The effect can be easily obtained by setting the retardation value in the thickness direction to about 1/3 to 2/3 of (Rth(550)).

In the inspection apparatus 1A of this embodiment, in order to observe the light that has passed through the first linear polarizing plate 3, the object to be inspected 10, the phase difference filter 4, and the second linear polarizing plate 5, , and a camera (detection means) 6 is disposed on the opposite side of the phase difference filter 4 from the side where the light source 2 is located. The camera 6 is, for example, a CCD camera, and in this case, the object to be inspected 10 can be inspected by automatically detecting it by image processing analysis using a combination of a CCD camera and an image processing device. Alternatively, the detection means may be a human visually observing the second linear polarizing plate 5 instead of the camera 6.

(Inspection method)
The inspection method using the inspection device 1A is as follows. First, the object to be inspected 10 is placed between the first linear polarizing plate 3 and the phase difference filter 4 inside the inspection apparatus 1A. At this time, the inspected object 10 has its base film 8A side facing the first linearly polarizing plate 3 side, and the slow axis of the base film 8A and the polarizing axis of the first linearly polarizing plate 3. (transmission axes) are arranged so that they are substantially perpendicular or substantially parallel to each other. Then, the slow axis of the retardation film 7A and the slow axis of the retardation filter 4 are made parallel to each other, and furthermore, the first linear polarizing plate 3 and the second linear polarizing plate 5 are arranged in a crossed nicol state. Arrange to configure.

Light is irradiated from the light source 2 toward the first linear polarizing plate 3. The light emitted by the light source 2 enters the first linearly polarizing plate 3, where the unpolarized light is converted into linearly polarized light. Then, the linearly polarized light enters the object to be inspected 10 from the base film 8A side. The linearly polarized light that has passed through the base film 8A passes through the retardation film 7A and becomes circularly polarized light. This circularly polarized light enters the phase difference filter 4 from the phase difference film 7B side. Here, the slow axis of the retardation film 7A and the slow axis of the retardation filter 4 are substantially parallel to each other, and the in-plane retardation value at a wavelength of 550 nm of the retardation film 7A and the phase difference Since the sum of the in-plane phase difference value at the wavelength of 550 nm of the filter 4 is 520 nm to 600 nm, the light passing through the phase difference filter 4 becomes linearly polarized light, and the linearly polarized light is This means that there is a phase difference of approximately λ compared to the linearly polarized light. Therefore, the light that has passed through the phase difference filter 4 and returned to linearly polarized light enters the second linearly polarized plate 5 with its polarization axis substantially coinciding with the polarization axis of the original linearly polarized light. The second linear polarizing plate 5 and the first linear polarizing plate 3 are arranged in a crossed nicol configuration, that is, the transmission axis of the first linear polarizing plate 3 and the absorption axis of the second linear polarizing plate 5 are Since they are parallel, the light that has passed through the phase difference filter 4 and returned to linearly polarized light is blocked by the second linearly polarizing plate 5. In this inspection, if there is no defect in the retardation film 7A in the inspection object 10, the front surface of the second linear polarizing plate 5 appears uniformly black when observed with the camera 6. On the other hand, if there is a defect in the retardation film 7A in the object to be inspected 10, the light that has passed through this defective part will not become the expected circularly polarized light (elliptically polarized light) and will reach the retardation filter 4. incident. Then, when the circularly polarized light (elliptically polarized light) passes through the phase difference filter 4, it cannot return to normal linearly polarized light and becomes elliptically polarized light. Therefore, the second linear polarizing plate 5 cannot properly block the light and leaks light, and when observed by the camera 6, the defective portion is observed as a bright spot.

Here, since the base film 8A has a retardation with an in-plane retardation value of 50 nm or more at a wavelength of 550 nm, the polarization state of the light that has passed through the first linear polarizing plate 3 is the same as that of the base film 8A. can be disturbed by However, in the inspection method of the present embodiment, the polarization axes of the first linear polarizing plate 3 are arranged so as to be substantially orthogonal to each other or substantially parallel to the slow axis of the base film 8A having a retardation. Therefore, the polarization state of the light that has passed through the first linearly polarizing plate 3 is not disturbed by the base film 8A. That is, the assembled optical system functions as intended, and if there is a defect in the retardation film 7A, the defect can be appropriately recognized in the observation field of view. Conventionally, when the in-plane retardation value of the base film 8A is 50 nm or more, the light passing through the first linear polarizing plate 3 is converted into circularly polarized light (elliptically polarized light) due to the retardation of the base film 8A. As a result, a large amount of light leaks from the second linear polarizing plate 5, which becomes an obstacle to inspection. Therefore, according to the inspection method of this embodiment, it is possible to easily determine whether there is a defect in the retardation film while suppressing the influence of the in-plane retardation that the base film 8A has.

(Continuous inspection method)
As shown in FIG. 2, the inspection method of this embodiment can be carried out continuously on the same production line in conjunction with the step of continuously forming the retardation film 7A on the base film 8A. can. In addition to the above-mentioned inspection device 1A, the inspection system 100 shown in FIG. 12, and a first straight line so that the slow axis of the base film 8A determined by the orientation angle measuring device 12 and the polarization axis of the first linear polarizing plate 3 are substantially orthogonal to each other or substantially parallel to each other. It is equipped with an angle adjustment mechanism 14 that adjusts the angle of the polarizing plate 3, and inspects the object 10 to be inspected in-line. Here, the object to be inspected 10 passes through the optical axis 9 of the inspection apparatus 1A while being conveyed, and is inspected for the presence or absence of defects. The inspected object 10 that has been inspected is then wound up. Note that the width of the base film 8A may be, for example, 0.5 to 2.0 m, or 1.0 to 1.5 m.

As shown in FIG. 3, in the inspection system 100, a plurality of inspection devices 1A are arranged across the width direction of the object 10 to be inspected (direction perpendicular to the transport direction). It is preferable that the inspection devices 1A are arranged at 5 to 20 locations across the width of the object 10 to be inspected. In FIG. 3, five inspection devices 1A are arranged.

In the production line shown in FIG. 2, the orientation angle measuring device 12 measures the direction of the slow axis of the base film 8A while conveying the long base film 8A. At this time, when the base film 8A is manufactured by stretching, the direction of the slow axis changes in the width direction as shown in FIG. In FIG. 4, the arrow represents the direction of the slow axis in that portion. Therefore, measurements by the orientation angle measuring device 12 are performed at a plurality of locations across the width direction of the base film 8A. The orientation angle measuring device 12 provides information on the measured slow axis to the angle adjustment mechanism 14 . Thereafter, while conveying the base film 8A, a polymerizable liquid crystal compound solution is applied onto the base film 8A using a coating machine 16 to form a coating film 7a. The coating film 7a is dried in step 18. Here, the coated polymerizable liquid crystal compound is oriented on the base film 8A, and is cured by drying and polymerization to form the retardation film 7A. The dried film is the object to be inspected 10, and is subjected to inspection by an inspection device 1A disposed on the downstream side of the conveyance.

The angle adjustment mechanism 14 rotates the first linear polarizing plate 3 based on the information about the slow axis direction of the base film 8A provided from the orientation angle measuring device 12, and changes the polarization of the first linear polarizing plate 3. The axis is made to be approximately perpendicular or approximately parallel to the slow axis of the base film 8A. At the same time, the phase difference filter 4 and the second linear polarizing plate 5 are also rotated so as to have the above-mentioned predetermined relationship. The plurality of inspection devices 1A arranged in the width direction of the object to be inspected 10 are each assigned an inspection area A (see FIG. 3), and the object to be inspected 10 is inspected over the entire area in the width direction. . In the inspection, the angle adjustment mechanism 14 orients the polarization axis of the first linear polarizing plate 3 for each inspection area A according to the fact that the slow axis of the base film 8A changes in the width direction. It will take a different direction. In addition, the inspection area A shown in FIG. 4 has shown the part corresponding to the inspection area A shown in FIG. 3 on the base film 8A.

By using the inspection system 100, the formation and inspection of the retardation film 7A can be carried out continuously and efficiently over the transport direction of the base film 8A, so that the production and inspection of the inspection object 10 can be made more efficient. be done. In addition, since the inspection system 100 has a plurality of inspection devices 1A arranged in the width direction of the inspected object 10, even if the slow axis direction of the base film 8A is different in the width direction, the individual inspection devices The relationship between the polarization axis of the first linearly polarizing plate 3 in 1A and the slow axis of the base film 8A in its inspection area A can be adjusted to a predetermined relationship. That is, it is possible to conduct an inspection in which the influence of the in-plane retardation of the base film 8A is suppressed at all locations in the width direction of the base film 8A.

<Second embodiment>
A second embodiment of the present invention will be described. The inspection apparatus 1B shown in FIG. 5 as the second embodiment differs from the inspection apparatus 1A of the first embodiment in that the positions of the light source 2 and the detection means are reversed. That is, the inspection device 1B includes a camera (detection means) 6, a first linear polarizing plate 3, a phase difference filter 4, a second linear polarizing plate 5, and a light source 2 arranged in this order. FIG. 5 depicts a state in which an object to be inspected 10 is placed between the first linearly polarizing plate 3 and the phase difference filter 4. As shown in FIG. Here, regarding the arrangement of the inspected object 10 and the second linear polarizing plate 5, the slow axis of the base film 8A and the polarization axis of the second linear polarizing plate 5 are arranged so that they are substantially orthogonal to each other or substantially parallel to each other. Arrange it so that

In the inspection of the inspection object 10 using this inspection apparatus 1B, the presence or absence of defects in the retardation film 7A can be easily inspected based on the same principle as in the first embodiment.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

INDUSTRIAL APPLICATION This invention can be utilized for the inspection which determines the presence or absence of a defect of a retardation film.

1A, 1B... Inspection device, 2... Light source, 3... First linear polarizing plate, 4... Phase difference filter, 5... Second linear polarizing plate, 6... Camera (detection means), 7A, 7B... Phase difference film , 7a... Coating film, 8A, 8B... Base film, 9... Optical axis, 10... Test object, 12... Orientation angle measuring device, 14... Angle adjustment mechanism, 16... Coating machine, 18... Dryer, 100...Inspection system, A...Inspection area.

Claims (7)

A film-like test object comprising a base film having an in-plane retardation value of 50 nm or more at a wavelength of 550 nm, and a retardation film made of a cured product of a polymerizable liquid crystal compound formed on one side of the base film. An inspection method for determining the presence or absence of defects in the retardation film by incident light, the method comprising:
a first linear polarizing plate;
The object to be inspected;
a phase difference filter;
a second linearly polarizing plate, arranged in this order,
The object to be inspected has a surface on the base film side facing the first linear polarizing plate,
The slow axis of the base film and the polarization axis of the first linearly polarizing plate or the second linearly polarizing plate are substantially orthogonal to each other or substantially parallel to each other,
The slow axis of the phase difference film and the slow axis of the phase difference filter are substantially parallel to each other,
The in-plane retardation value of the retardation film at a wavelength of 550 nm is 300 nm or less,
The sum of the in-plane retardation value of the retardation film at a wavelength of 550 nm and the in-plane retardation value of the retardation filter at a wavelength of 550 nm is 520 nm to 600 nm,
The first linearly polarizing plate and the second linearly polarizing plate constitute a crossed nicol,
Injecting light from either the first linearly polarizing plate side or the second linearly polarizing plate side such that the optical axis passes through a predetermined inspection area on the object to be inspected, and the other side. An inspection method of observing the second linearly polarizing plate or the first linearly polarizing plate from. 2. The inspection method according to claim 1, further comprising the step of determining in advance the direction of the slow axis of the base film using an orientation angle measuring device, with respect to the base film before the retardation film is formed. After determining the slow axis of the base film using the orientation angle measuring device, a liquid composition containing a polymerizable liquid crystal compound is coated on one side of the base film so that the slow axis of the base film is coated on the surface of the base film. 3. The inspection method according to claim 2, comprising the steps of forming a coating film containing a polymerizable liquid crystal compound, and aligning and curing the polymerizable liquid crystal compound contained in the coating film to form the retardation film. 1 . The inspection target is continuously inspected in the longitudinal direction while the inspection target is conveyed in the longitudinal direction between the first linear polarizing plate and the phase difference filter. - The inspection method described in any one of 3. 5. The inspection method according to claim 1, wherein the inspection area is provided at a plurality of locations in the width direction of the object to be inspected. A film-like test object comprising a base film having an in-plane retardation value of 50 nm or more at a wavelength of 550 nm, and a retardation film made of a cured product of a polymerizable liquid crystal compound formed on one side of the base film. An inspection device that determines the presence or absence of defects in the retardation film by inputting light,
A first linear polarizing plate and a phase difference filter are arranged to sandwich the place where the object to be inspected is placed, and a first linear polarizing plate and a phase difference filter are arranged in a region opposite to the place where the object to be inspected is placed with respect to the phase difference filter. a second linearly polarizing plate, and a light source disposed in an area opposite to a location where the object to be inspected is placed with respect to the first linearly polarizing plate or the second linearly polarizing plate,
The first linearly polarizing plate or the second linearly polarizing plate is arranged so that its polarization axis is substantially perpendicular to or substantially parallel to the slow axis of the base film,
The phase difference filter is arranged such that its slow axis is substantially parallel to the slow axis of the phase difference film,
The in-plane retardation value of the phase difference filter at a wavelength of 550 nm is a value such that the sum of the in-plane retardation value of the retardation film at a wavelength of 550 nm is 520 nm to 600 nm,
The first linearly polarizing plate and the second linearly polarizing plate constitute a crossed nicol,
The light source is arranged at a position where the first linearly polarizing plate, a predetermined inspection area on the object to be inspected, the phase difference filter, and the second linearly polarizing plate are lined up on its optical axis. , inspection equipment. The inspection device according to claim 6,
an orientation angle measuring device for determining the slow axis of the base film before the retardation film is formed;
The first linearly polarizing plate is arranged so that the slow axis of the base film determined by the orientation angle measuring device and the polarization axis of the first linearly polarizing plate are substantially perpendicular to each other or substantially parallel to each other. An inspection system comprising an angle adjustment mechanism that adjusts the angle of the.

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