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CN-116420101-B - Inspection method

CN116420101BCN 116420101 BCN116420101 BCN 116420101BCN-116420101-B

Abstract

The present invention is a method for inspecting whether or not a film-like object (10) is defective, the object being provided with a circularly polarizing plate (1) comprising a polarizing film (11) and a retardation film (14), and a release film (16 a) comprising a polyethylene terephthalate resin, the release film being laminated on the retardation film (14) side of the circularly polarizing plate (1). A light source (4), a bandpass filter (2) that transmits light of a predetermined wavelength, a first polarizing section (3A), an object (10) to be inspected, and a second polarizing section (3B) are disposed, and the incident angle (theta) of the light to the object (10) to be inspected is changed so that the influence of the phase difference of the release film (16 a) is reduced. The light reflected by the inspected object (10) is observed from the second polarization part (3B) side, thereby judging whether the circular polarization plate (1) has defects.

Inventors

  • SHINJI KOBAYASHI
  • MATSUDA SHUNSUKE
  • Sen Lihui

Assignees

  • 住友化学株式会社

Dates

Publication Date
20260512
Application Date
20211025
Priority Date
20201029

Claims (6)

  1. 1. An inspection method for judging whether or not a film-like object to be inspected, which is a circularly polarizing plate comprising a polarizing film and a retardation film laminated on each other, and a release film comprising a polyethylene terephthalate resin laminated on the retardation film side of the circularly polarizing plate, is defective, A light source, a bandpass filter for transmitting light of a predetermined wavelength, a first polarizing unit, and the object to be inspected having the release film side directed to the first polarizing unit side are sequentially arranged on the optical path of the light emitted from the light source, and a second polarizing unit in a cross nicol state with the first polarizing unit is arranged on the optical path of the light reflected by the object to be inspected, Causing light from the light source to enter the bandpass filter, The incidence angle of the light to the object to be inspected is changed so as to reduce the influence of the phase difference of the peeling film, Observing the light reflected by the inspected object from the second polarization part side, thereby judging whether the circular polarization plate has a defect, Before the said examination is carried out, Preparing a light source and two test pieces having the same circular polarization plate as the circular polarization plate of the inspected object, The two test pieces are arranged such that the two test pieces face each other on the phase difference film side and the angle formed by the slow axes of the phase difference films is an angle other than 90 DEG when viewed from the optical path direction of the light source, The light of various wavelengths is incident from either side of the polarizing film of the test piece so that the optical path passes through the defect-free region on the test piece, and the polarizing film is observed from the other side thereof to determine the wavelength at which the transmitted light amount is smallest, and at least one wavelength of a wavelength 5nm to 50nm larger than the wavelength and a wavelength 5nm to 50nm smaller than the wavelength is determined to be used as the predetermined wavelength.
  2. 2. The inspection method according to claim 1, wherein, After the inspection using the bandpass filter, the inspection is performed using a bandpass filter that transmits light having a wavelength different from that of the light that is most easily transmitted by the bandpass filter.
  3. 3. The inspection method according to claim 1 or 2, wherein, The first polarizing portion and the second polarizing portion are both circularly polarizing plates.
  4. 4. The inspection method according to claim 1 or 2, wherein, The first polarizing portion and the second polarizing portion are formed of a single circular polarizing plate.
  5. 5. The inspection method according to claim 1 or 2, wherein, The first polarizing portion and the second polarizing portion are both linear polarizing plates.
  6. 6. The inspection method according to claim 1 or 2, wherein, The retardation film is composed of a cured product of a polymerizable liquid crystal compound.

Description

Inspection method Technical Field The present invention relates to an inspection method. Background Polarizing plates used in liquid crystal display devices, organic EL display devices, and the like are generally configured by sandwiching a polarizing plate between two protective films. In order to attach the polarizing plate to the display device, an adhesive layer is laminated on one of the protective films, and a release film is further laminated on the adhesive layer. In addition, a release film (surface protective film) for protecting the surface of the other protective film is often bonded to the other protective film. The polarizing plate is transported in a state in which the release film is laminated in this way, and the release film is peeled off when the display device is bonded in the manufacturing process of the display device. However, in the polarizing plate, there are cases where foreign substances are mixed between the polarizing plate and the protective film, bubbles remain, or alignment defects are present inside when the protective film has a function of a retardation film in its manufacturing stage (hereinafter, these foreign substances, bubbles, and alignment defects may be collectively referred to as "defects"). When a defective polarizing plate is attached to a display device, a portion having the defect is visually recognized as a bright point, and an image appears to be distorted at the defective portion. In particular, a defect visually recognized as a bright point is easily visually recognized at the time of black display of the display device. Therefore, in the stage before the polarizing plate is attached to the display device (the polarizing plate in a state of having a release film), inspection for detecting a defect of the polarizing plate is performed. The inspection of the defect is generally an optical inspection using a polarization axis of a polarizing plate. Specifically, as shown in patent document 1, a polarizing filter is provided between a polarizing plate as an object to be inspected and a light source, and then the polarizing plate or the polarizing filter is rotated in a plane direction, whereby the respective polarization axis directions are set to have a specific relationship. When the polarization axis directions are orthogonal to each other (that is, when the arrangement of the cross nicols (japanese) system コ is made), the linearly polarized light that has passed through the polarization filter does not pass through the polarization plate. However, if the polarizing plate has a defect, linearly polarized light is transmitted through the portion, and thus the light is detected, and the presence of the defect is known. On the other hand, when the polarization plate and the polarization filter have polarization axis directions parallel to each other, the linearly polarized light passing through the polarization filter passes through the polarization plate. However, if the polarizing plate has a defect, the linearly polarized light is blocked at that portion, and therefore the light is not detected, and the presence of the defect is known. The presence or absence of the polarizing plate can be inspected by visually detecting light transmitted through the polarizing plate by an inspector or automatically detecting an image analysis processing value obtained by combining a CCD camera and an image processing device. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 9-229817 Disclosure of Invention Problems to be solved by the invention When the polarizing plate is a circular polarizing plate and the release film is made of polyethylene terephthalate resin (PET resin), a phase difference filter (corresponding to the polarizing filter) that matches the wavelength dispersion of the PET resin to a certain extent is used for the inspection of the polarizing plate. Here, in the case where the circularly polarizing plate and the phase difference filter are arranged so as to form a crossed nicols state, the defect is visually recognized as a bright point according to the principle described above, but in some cases, the bright point defect in a region where the phase difference value such as an alignment defect or a pinhole of the phase difference film of the circularly polarizing plate is low is visually recognized as a black point, and in this case, detection and judgment are more difficult than detection as a bright point. In particular, when the circularly polarizing plate includes a retardation film composed of a cured product of a polymerizable liquid crystal compound, this tendency is remarkable. The principle of the inspection method disclosed in patent document 1 is to observe light transmitted through an object to be inspected. In the case where the inspected object has a deformation defect (for example, a wrinkle generated at the time of cutting of the circularly polarizing plate) in this principle, the optical path length h