CN112817083A

CN112817083A - Method for manufacturing polarizing plate

Info

Publication number: CN112817083A
Application number: CN202110204125.6A
Authority: CN
Inventors: 古泽修也; 杉脇正晃; 八重樫将宽; 木村真规子
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2015-09-30
Filing date: 2016-09-29
Publication date: 2021-05-18
Anticipated expiration: 2036-09-29
Also published as: JP2021012393A; KR102386369B1; KR20170038727A; CN112817083B; KR20210124118A; CN106940320A; JP6784540B2; CN112782798A; JP6967131B2; JP2021012392A; CN112782798B; JP6801142B1; JP2017068244A; CN106940320B

Abstract

The invention provides a method for inspecting a vertically long polarizing plate, a method for manufacturing the same, and an appearance inspection apparatus. In this inspection method, the appearance of a vertically long polarizing plate having non-polarizing sections arranged at predetermined intervals along the longitudinal direction is appropriately inspected. A method for inspecting the appearance of a vertically long polarizing plate having non-polarizing sections arranged at predetermined intervals in the longitudinal direction while conveying the polarizing plate in the longitudinal direction, the method comprising: a step of acquiring image data by imaging the polarizing plate; analyzing the image data to extract a defect candidate portion; a step of determining whether or not the defect candidate portion has a size equal to or smaller than a reference value; and a step of detecting the defect based on the size of the defect candidate portion.

Description

Method for manufacturing polarizing plate

The present application is a divisional application entitled "method for inspecting a polarizing plate having a longitudinal shape, method for manufacturing the polarizing plate, and appearance inspection apparatus", filed as 2016.09.29, filed as 201610868195.0.

Technical Field

The present invention relates to a method for inspecting a vertically long polarizing plate having an unpolarized portion, a method for manufacturing the polarizing plate, and an appearance inspection apparatus. Typically, the present invention relates to a method of inspecting a polarizing plate including a polarizer having a non-polarizing portion, and an appearance inspection apparatus.

Background

Some image display devices such as mobile phones and notebook Personal Computers (PCs) are equipped with internal electronic components such as cameras. Various studies have been made for the purpose of improving the camera performance of such an image display device (for example, patent documents 1 to 7). However, due to the rapid spread of smart phones and touch panel type information processing apparatuses, further improvement in camera performance and the like is desired. In order to cope with the diversification of the shape and the high functionality of the image display device, a polarizing plate having a polarizing performance locally is required. In order to industrially and commercially realize these desires, it is desirable to manufacture the image display device and/or parts thereof at an allowable cost, and as a result, various research matters remain in order to identify such a technique.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-81315

Patent document 2: japanese patent laid-open publication No. 2007-241314

Patent document 3: U.S. patent application publication No. 2004/0212555 specification

Patent document 4: korean laid-open patent No. 10-2012-0118205

Patent document 5: korean patent No. 10-1293210

Patent document 6: japanese laid-open patent publication No. 2012-137738

Patent document 7: U.S. patent application publication No. 2014/0118826 specification

Disclosure of Invention

Problems to be solved by the invention

The inventor waits for the following problems: as a polarizing plate having a local polarizing performance, a polarizing plate was produced using a polarizing plate having a non-polarizing portion, and the obtained polarizing plate was subjected to an appearance inspection to erroneously detect the non-polarizing portion as a defect. The present invention has been made to solve the above-mentioned problems, and a main object thereof is to provide a method for appropriately inspecting the appearance of a polarizing plate having a longitudinal shape which includes a polarizing plate having a non-polarizing portion and which has the non-polarizing portion arranged at a predetermined interval along the longitudinal direction.

Means for solving the problems

According to the present invention, there can be provided a method of inspecting the appearance of a vertically long polarizing plate having non-polarizing portions arranged at predetermined intervals in the longitudinal direction while conveying the vertically long polarizing plate in the longitudinal direction. The inspection method comprises the following steps: a step of acquiring image data by imaging the polarizing plate; analyzing the image data to extract a defect candidate portion; determining whether the defect candidate portion has a size equal to or smaller than a reference value; and detecting the defect based on the size of the defect candidate portion.

In 1 aspect, the polarizing plate includes non-polarizing portions arranged at predetermined intervals in a longitudinal direction and a width direction.

In 1 embodiment, the image data is acquired based on continuous shooting of the polarizing plate.

In 1 aspect, the extraction of the defect candidate portion is performed based on luminance information of the image data.

In the 1 st aspect, the method further includes a step of determining whether or not the defect candidate portion has periodicity along the longitudinal direction, and the step of detecting the defect is a step of detecting the defect based on the size of the defect candidate portion and the presence or absence of the periodicity.

In the 1 aspect, it is determined whether only the defect candidate portion having a size exceeding the reference value has periodicity along the longitudinal direction.

In 1 aspect, the periodic presence or absence of the defect candidate portion is determined based on position coordinates in a longitudinal direction of the defect candidate portion.

In 1 aspect, the periodic presence or absence of the defect candidate portion is determined based on whether or not a longitudinal distance between the defect candidate portion to be determined and a non-polarizing portion existing on an upstream side in a transport direction of the defect candidate portion is a predetermined distance.

According to another aspect of the present invention, a method for manufacturing a polarizing plate can be provided. The manufacturing method includes inspecting the polarizing plate by the above inspection method.

According to still another aspect of the present invention, an appearance inspection apparatus for a longitudinally long polarizing plate can be provided. The appearance inspection device includes: an imaging device for imaging a vertically long polarizing plate having non-polarizing sections arranged at predetermined intervals along a longitudinal direction thereof to acquire image data; and an image analysis device for analyzing the image data to detect defects of the polarizing plate. The image analysis device includes: a defect candidate extraction unit that extracts a defect candidate based on the image data; a size determination unit that determines whether or not the defect candidate portion has a size equal to or smaller than a reference value; a periodicity judging unit that judges whether or not the defect candidate unit has periodicity along the longitudinal direction; and a defect detecting unit that detects a defect based on the size of the defect candidate unit or based on the size of the defect candidate unit and the presence or absence of periodicity of the defect.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the inspection method of the present invention, since erroneous detection of the non-polarizing portion as a defect can be avoided, it is possible to appropriately inspect the appearance of a vertically long polarizing plate including a polarizing plate having a non-polarizing portion and having non-polarizing portions arranged at predetermined intervals along the longitudinal direction.

Drawings

Fig. 1 is a schematic cross-sectional view of a polarizing plate that can be used in the inspection method of the present invention.

Fig. 2A is a schematic plan view illustrating an example of the arrangement pattern of the non-polarizing portion.

Fig. 2B is a schematic plan view illustrating another example of the arrangement pattern of the non-polarizing portion.

Fig. 2C is a schematic plan view illustrating another example of the arrangement pattern of the non-polarizing portion.

Fig. 3 is a schematic diagram illustrating an inspection apparatus that can be used in the inspection method of the present invention.

Fig. 4 is a flowchart illustrating a specific procedure of defect detection in 1 embodiment of the present invention.

Fig. 5 is a flowchart illustrating a specific procedure of defect detection in another embodiment of the present invention.

Fig. 6 is a schematic diagram illustrating a specific procedure of defect detection in the embodiment shown in fig. 5.

Description of the reference numerals

10. A polarizing plate; 10a, a non-polarizing portion; 30. a polarizing plate; 50. a photographing device; 80. an image analysis device; 82. a defect candidate extraction unit; 84. a size determination unit; 86. a periodicity judging section; 88. a defect detection unit; 100. and (6) checking the device.

Detailed Description

[ A. inspection method and inspection apparatus ]

The invention provides a method for inspecting the appearance of a vertically long polarizing plate having non-polarizing sections arranged at predetermined intervals along the longitudinal direction while conveying the polarizing plate along the longitudinal direction. The inspection method of the present invention includes: a step of acquiring image data by imaging a polarizing plate having a non-polarizing section; analyzing the image data to extract a defect candidate portion; a step of determining whether or not the defect candidate portion has a size equal to or smaller than a reference value; and a step of detecting the defect based on the size of the defect candidate portion. In the step of detecting a defect, for example, a defect candidate portion having a size exceeding a reference value can be identified and distinguished as a non-polarized portion, and a defect candidate portion having a size equal to or smaller than the reference value can be detected as a defect.

The inspection method of the present invention may further include a step of determining whether or not the defect candidate portion has periodicity along the longitudinal direction. In this case, in the step of detecting the defect, the defect is detected based on the size and the periodicity of the defect candidate portion. More specifically, a defect candidate portion having a size equal to or smaller than a reference value is detected as a defect, and a defect candidate portion having no periodicity is also detected as a defect. By evaluating the defect candidates from both sides of the size and periodicity, inspection accuracy can be improved. From the viewpoint of inspection efficiency, it is preferable to determine the presence or absence of periodicity only for defect candidate portions having a size exceeding a reference value. In this case, all the defect candidate portions having a size equal to or smaller than the reference value are detected as defects, and for the defect candidate portions having a size exceeding the reference value, only the defect candidate portions having no periodicity therein are detected as defects.

A-1. Polarizing plate

The polarizing plate used in the inspection method of the present invention is vertically long and has non-polarizing portions arranged at predetermined intervals along the longitudinal direction. Typically, the non-polarizing portion is derived from a non-polarizing portion formed in the polarizing plate. In the present specification, the term "elongated shape" refers to an elongated shape having a length sufficiently long with respect to a width, and includes, for example, an elongated shape having a length 10 times or more, preferably 20 times or more, as long as the width.

Fig. 1 is a schematic cross-sectional view of a polarizing plate that can be used in the inspection method of the present invention. The polarizing plate 30 includes: a polarizing plate 10 having a non-polarizing portion;

protective films

11 and 12 disposed on both sides of the polarizing plate 10. In the illustrated example, the protective films are disposed on both sides of the polarizing plate, but the protective film may be disposed only on one side. Alternatively, the polarizing plate may be constituted by only a polarizing plate (that is, the polarizing plate may be a polarizing plate).

Typically, the polarizing plate 10 is made of a resin film containing a dichroic material. The polarizing plate 30 is vertically long, and therefore, the polarizer 10 is also vertically long. The polarizing plate 10 has non-polarizing portions arranged at predetermined intervals along the longitudinal direction. In embodiment 1, the polarizing plate 10 has unpolarized sections arranged at predetermined intervals in the longitudinal direction and the width direction. The arrangement pattern of the non-polarizing portion can be appropriately set according to the purpose. Typically, the non-polarizing portion may be disposed at a position corresponding to a camera portion of an image display device when the polarizing plate is cut to a predetermined size (for example, cut or punched in a longitudinal direction and/or a width direction) in order to attach the polarizing plate to the image display device having the predetermined size. In 1 embodiment, the non-polarizing portions are arranged at substantially equal intervals in both the longitudinal direction and the width direction. The phrase "substantially equally spaced in both the longitudinal direction and the width direction" means that the intervals in the longitudinal direction are equally spaced and the intervals in the width direction are equally spaced, and the intervals in the longitudinal direction and the intervals in the width direction do not need to be equal. In another embodiment, the non-polarizing portions may be arranged at substantially equal intervals along the longitudinal direction and at different intervals along the width direction. When the unpolarized sections are arranged at different intervals in the width direction, the intervals between adjacent unpolarized sections may be different entirely or only partially (the interval between specific adjacent unpolarized sections). Further, a plurality of regions may be defined along the longitudinal direction of the polarizing plate, and the interval of the non-polarizing portion in the longitudinal direction and/or the width direction may be set for each region.

Fig. 2A to 2C are schematic plan views each illustrating an example of the arrangement pattern of the non-polarizing portions in the polarizing plate 10. In the 1 embodiment, as shown in fig. 2A, the unpolarized sections 10a are arranged such that a straight line connecting the unpolarized sections adjacent in the longitudinal direction is substantially parallel to the longitudinal direction, and a straight line connecting the unpolarized sections adjacent in the width direction is substantially parallel to the width direction.

The shape of the non-polarizing portion in plan view may be any appropriate shape according to the purpose. For example, the planar shape of the non-polarizing portion may be any appropriate shape as long as it does not adversely affect the camera performance of the image display device using the polarizing plate. The non-polarizing portion illustrated in the figure is circular, but may be formed in, for example, an oval shape, a square shape, a rectangular shape, a diamond shape, or the like.

The transmittance of the non-polarizing portion (for example, the transmittance measured by light having a wavelength of 550nm at 23 ℃) is preferably 50% or more, more preferably 60% or more, still more preferably 75% or more, and particularly preferably 90% or more. If the transmittance is such, for example, when the polarizing plate is disposed so that the non-polarizing portion corresponds to the camera portion of the image display device, adverse effects on the imaging performance of the camera can be prevented.

The unpolarized section may have any suitable form. In 1 embodiment, the unpolarized portion is a decolored portion which is partially decolored. The discolored portion is formed by, for example, laser irradiation or chemical treatment. In another embodiment, the non-polarizing portion is a through hole. The through-holes are formed by, for example, mechanical blanking (e.g., punch, thomson knife blanking, cutter (japanese: プロッター), water jet cutting) or removal of a predetermined portion (e.g., laser ablation or chemical dissolution).

Examples of the material for forming the

protective films

11 and 12 include cellulose resins such as diacetyl cellulose and triacetyl cellulose, olefin resins such as methacrylic resins, cycloolefin resins and polypropylene, resin resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. Depending on the purpose and desired structure, one of the

protective films

11 and 12 may be omitted.

The thickness of the protective film is typically 10 μm to 100 μm. Typically, the protective film is laminated on the polarizing plate via an adhesive layer (specifically, an adhesive layer). The adhesive layer is typically formed of a PVA adhesive or an active energy ray-curable adhesive. The adhesive layer is typically formed of an acrylic adhesive.

In practical applications, polarizing plate 30 has adhesive layer 13 as the outermost layer. Typically, the adhesive layer 13 is an outermost layer on the image display device side. The separator 14 is temporarily fixed to the pressure-sensitive adhesive layer 13 so as to be peelable, and the pressure-sensitive adhesive layer can be protected until the pressure-sensitive adhesive layer is actually used and can be formed into a roll.

The polarizing plate 30 may further have any appropriate optical function layer according to the purpose. Typical examples of the optical functional layer include a retardation film (optical compensation film) and a surface treatment layer. For example, a retardation film (not shown) may be disposed between the protective film 12 and the adhesive layer 13. The optical properties (for example, refractive index ellipsoid, in-plane retardation, thickness direction retardation) of the retardation film can be appropriately set according to the purpose, the characteristics of the image display device, and the like.

The surface treatment layer may be disposed outside the protective film 11 (not shown). Typical examples of the surface treatment layer include a hard coat layer, an antireflection layer, and an antiglare layer. The surface-treated layer is preferably a layer having a low moisture permeability for the purpose of, for example, improving the humidification durability of the polarizing plate. Instead of providing the surface treatment layer, the surface of the protective film 11 may be subjected to the same surface treatment.

A-2. Inspection apparatus

Fig. 3 is a schematic diagram illustrating an inspection apparatus that can be used in the inspection method of the present invention. In the illustrated embodiment, the polarizing plate 30 having a long length is transported to the inspection apparatus 100 to be subjected to an appearance inspection. The inspection apparatus 100 includes an imaging apparatus 50 that images the polarizing plate 30 to obtain image data, and an image analysis apparatus 80 that analyzes the obtained image data to detect defects in the polarizing plate 30. The image analysis device 80 includes: a defect candidate extraction unit 82 that extracts a defect candidate based on the obtained image data; a size determination unit 84 that determines whether or not the defect candidate portion has a size equal to or smaller than a reference value; a periodicity judging unit 86 that judges whether or not the defect candidate portion has periodicity along the longitudinal direction; and a defect detecting unit 88 for detecting a defect based on the size of the defect candidate portion or based on the size of the defect candidate portion and the presence or absence of periodicity of the defect.

A-3. Step (1) of acquiring image data

The step (1) can be performed by obtaining image data by imaging the polarizing plate having the non-polarizing portion by using the imaging device 50. Typically, the imaging device 50 includes an illumination unit 52 and an imaging unit 54.

The illumination unit 52 may be configured using any appropriate light source. The light source may be a white light source or a monochromatic light source. Specific examples of the light source include fluorescent lamps, tungsten halogen lamps, metal halide lamps, and LEDs.

The imaging unit 54 is typically a camera configured using a lens and an image sensor. Preferably, the number of the imaging units is 1 or more so that the entire width of the polarizing plate can be imaged. Further, the imaging unit is preferably capable of imaging images that are continuous along the longitudinal direction. In 1 embodiment, the imaging section is a line sensor camera.

In the embodiment shown in fig. 3, light is irradiated from the illumination section 52 disposed on one side of the polarizing plate to the polarizing plate 30, and the light transmitted through the polarizing plate 30 is imaged by the imaging section 54 disposed on the other side of the polarizing plate 30 so as to face the illumination section 52. By imaging the transmitted light, an image having a higher luminance in a region corresponding to the unpolarized portion than in a region corresponding to another portion can be obtained.

In another embodiment (not shown), an illumination unit and an imaging unit are disposed on one side of the polarizing plate, light is irradiated from the illumination unit to the polarizing plate from an oblique direction, and light reflected by the polarizing plate is imaged by the imaging unit disposed on the same side as the illumination unit.

In still another embodiment (not shown), an illumination unit and an imaging unit are disposed on one side of the polarizing plate, and light is irradiated perpendicularly to the polarizing plate so that the optical axis of a camera of the imaging unit coincides with the optical axis of the irradiated light, and the reflected light of the light is imaged.

By selecting an appropriate imaging method and imaging the polarizing plate according to the form of the non-polarizing portion (the decoloring portion, the through hole, and the like), the structure of the polarizing plate, and the like, an image having a large difference (as a result, a relatively large contrast) between the luminance of the region corresponding to the non-polarizing portion and the luminance of the region corresponding to the other portion can be obtained. The imaging of the polarizing plate may be performed in any 1 of the above embodiments, or may be performed by combining two or more embodiments.

Preferably, the image is taken while the longitudinal polarizing plate is transported in the longitudinal direction. By performing imaging while conveying, the stop of the manufacturing line can be avoided and the manufacturing efficiency can be maintained.

A-4. Step (2) of extracting Defect candidate portions

The image data obtained by the photographing device 50 is transmitted as an electric signal to the image analysis device 80. The transmitted image data is analyzed by the defect candidate extraction section 82, whereby a defect candidate can be extracted.

In 1 embodiment, the defect candidate portion is extracted based on the luminance information of the image data. Specifically, a luminance standard determined to be normal is set by imaging a normal polarizing plate in advance, and a defect candidate portion is extracted based on the standard. For example, a high luminance portion exceeding the upper limit of the luminance determined to be normal, a low luminance portion exceeding the lower limit of the luminance determined to be normal, and the like may be determined as the defect candidate portion. Since a defective portion that causes an appearance defect such as a foreign substance, air bubble, or pin hole generally has a transmittance, reflectance, or the like different from those of a normal region of a polarizing plate, it can be extracted as a defect candidate portion by using the luminance standard as described above. On the other hand, in the obtained image data, since the transmittance, reflectance, and the like of the region corresponding to the non-polarizing portion are also different from those of the regions corresponding to the other portions, it is possible to extract the region as a defect candidate portion.

The defect candidate extracting unit 82 preferably stores position information of the defect candidate unit (for example, position coordinates (X, Y) in the longitudinal direction and the width direction in images continuing in the longitudinal direction) and transmits the position information to the periodicity judging unit 86.

A-5. A step (3) of determining whether or not the defect candidate portion has a size equal to or smaller than a reference value

When the defect candidate portion is extracted by the defect candidate portion extraction unit 82, the size determination unit 84 determines the size of each extracted defect candidate portion, and further determines whether the size is equal to or smaller than a reference value.

The size of the defect candidate may be determined by any appropriate method. The size can be determined based on, for example, the number of pixels, the diameter, the area, and the like of the defect candidate portion in the image data. As a representative example of the diameter of the defect candidate portion, the longest length of a straight line connecting two arbitrary points on the outer periphery of the defect candidate portion in the image data may be determined as the diameter. The area may be calculated based on the number of pixels or the diameter.

The reference value may be determined by any appropriate method. For example, the reference value may be determined based on the size of the non-polarizing portion. For example, when the size is determined by the diameter, the reference value (reference value of the diameter) can be determined as follows. That is, the diameter of the non-polarizing portion (theoretical value) is calculated based on the shape and size of the non-polarizing portion in design, or the diameter of the non-polarizing portion actually formed in the polarizing plate (actual measurement value) is measured, and for example, 90%, preferably 95%, of the obtained diameter of the non-polarizing portion can be used as a reference value. For example, when the average size of the defect is sufficiently smaller than the size of the non-polarizing portion (for example, when the average diameter of the defect is not more than 1/8 of the diameter of the non-polarizing portion), the reference value may be 1/4 to 1/2 of the diameter of the non-polarizing portion. Specifically, when the diameter of the unpolarized portion is about 2800 μm and the average diameter of the defects is 150 to 300 μm, the reference value can be about 1000 μm.

A-6. A step (4) of determining whether or not the defect candidate portion has periodicity along the longitudinal direction

The periodicity judging unit 86 may judge all of the extracted defect candidate portions as periodicity, or may judge only defect candidate portions for which the size judging unit 84 confirms that the defect candidate portions have a size exceeding the reference value. Preferably, only the defect candidate portions for which the size determination unit 84 confirms that the defect candidate portion has a size exceeding the reference value are to be determined.

In 1 embodiment, when 3 or more defect candidate portions are present at equal intervals on a straight line extending in an arbitrary direction, it can be determined that these defect candidate portions have periodicity.

In the polarizing plate to be inspected, since the non-polarizing portions are arranged at predetermined intervals at least along the longitudinal direction, the periodicity can be determined based on the intervals between the non-polarizing portions in the longitudinal direction. Therefore, the presence or absence of periodicity can be efficiently determined by determining the position of the defect candidate portion to be determined on the surface of the polarizing plate and performing screening or the like on the non-polarizing portions existing at the predetermined intervals.

In 1 embodiment, the periodic presence or absence of the defect candidate portion is determined based on the position coordinates (for example, position coordinates in the longitudinal direction) of the defect candidate portion. For example, the position coordinates of the defect candidate portions (for example, two or more, preferably 3 or more adjacent defect candidate portions along the longitudinal direction) transmitted from the defect candidate portion extracting portion are compared with the position coordinates of the non-polarized portion in design (theoretically), and when the position coordinates coincide, it can be determined that the defect candidate portions have periodicity. Further, for example, the longitudinal distance between the defect candidate portion to be determined and the unpolarized portion (which may be a defect candidate portion determined not to be a defect) present on the upstream side in the transport direction of the defect candidate portion to be determined is obtained based on the longitudinal position coordinates of the defect candidate portion transmitted from the defect candidate portion extraction unit, and the presence or absence of periodicity of the defect candidate portion is determined based on whether or not the distance is a predetermined distance. The distance may be, for example, the arrangement interval of the unpolarized sections in the longitudinal direction (that is, the predetermined interval in the longitudinal direction) or a distance that is an integral multiple of the predetermined interval.

A-7. Procedure for detecting Defect (5)

The defect detecting section 88 detects a defect based on the size of the defect candidate section, or detects a defect based on the size of the defect candidate section and the presence or absence of periodicity. Specifically, the defect detecting unit 88 detects a defect candidate determined to have a size equal to or smaller than the reference value by the size determining unit 84 as a defect. The defect detecting unit 88 may also identify the defect candidate determined to have periodicity by the periodicity determining unit 86 as a non-polarized portion and distinguish it from the defect candidate, and detect the remaining defect candidate as a defect. In other words, the defect detecting section 88 can detect as defects a defect candidate portion determined to have a size equal to or smaller than the reference value and a defect candidate portion determined to have no periodicity.

Fig. 4 is a flowchart illustrating a specific procedure of defect detection in 1 embodiment of the present invention. In the embodiment shown in fig. 4, first, image data of the polarizing plate is acquired (step (1) described above). Next, a defect candidate portion is extracted based on the image data (step (2) described above). Next, it is determined whether or not the defect candidate portion has a size equal to or smaller than a reference value (step (3) described above), the defect candidate portion having a size larger than the reference value is determined as a non-polarized portion, and the defect candidate portion having a size equal to or smaller than the reference value is detected as a defect (step (5) described above).

Fig. 5 is a flowchart illustrating a specific procedure of defect detection in another embodiment of the present invention. In the embodiment shown in fig. 5, first, image data of the polarizing plate is acquired (step (1) described above). Next, a defect candidate portion is extracted based on the image data (step (2) described above). Next, it is determined whether or not the defect candidate portion has a size equal to or smaller than a reference value (step (3) described above), and whether or not the periodicity is present is determined for the defect candidate portion having a size larger than the reference value (step (4) described above). Based on the obtained results, the defect candidate portions having a size equal to or smaller than the reference value and the defect candidate portions having a size exceeding the reference value but having no periodicity are detected as defects (step (5) described above). The white circles in fig. 6 (a) indicate all the defect candidate portions extracted in step (2) in this embodiment, the white circles in fig. 6 (b) indicate defect candidate portions that have a size exceeding a reference value and are to be determined as being periodic, the black circles in fig. 6 (c) indicate defect candidate portions determined as being periodic (non-polarized portions), the white circles indicate defect candidate portions determined as not having periodicity (defects), and the white circles in fig. 6 (d) indicate finally detected defects.

A-8. Marking process (6)

The inspection apparatus 100 may further include a marking device (not shown). The marking device is connected to the image processing device, and when the image processing device (substantially the defect detection unit) detects a defect, the marking device transmits position information of the defect to the marking device. The marking device marks the defective portion based on the position information. The marked region can be easily eliminated as a defective polarizing plate after cutting. Examples of the marking include marking with a marking pen and laser marking.

[ method for producing polarizing plate ]

The method for manufacturing a vertically long polarizing plate having a polarizer having a non-polarizing portion according to the present invention includes: forming a non-polarizing portion in the vertically long polarizing plate; a polarizing plate is produced using a long polarizing plate having the non-polarizing portion; and inspecting the appearance of the polarizing plate by the inspection method.

B-1. Polarizing plate

The polarizing plate is typically made of a resin film containing a dichroic material. Examples of the dichroic substance include iodine and an organic dye. These may be used alone or in combination of two or more. Iodine is preferably used.

As the resin forming the resin film, any appropriate resin can be used. Preferably, a polyvinyl alcohol resin can be used. Examples of the polyvinyl alcohol resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer.

In the polarizing plate (except for the non-polarizing portion), it is preferable that absorption dichroism is exhibited at any one of wavelengths of 380nm to 780 nm. The monomer transmittance of the polarizing plate (excluding the non-polarizing portion) is preferably 39% or more, more preferably 39.5% or more, further preferably 40% or more, and particularly preferably 40.5% or more. Further, the theoretical upper limit of the monomer transmittance is 50%, and the practical upper limit is 46%. The monomer transmittance is a Y value obtained by measuring the value with a 2-degree field of view (C light source) according to JIS Z8701 and correcting visibility, and can be measured using, for example, a micro-spectroscopic system (LVmicro, manufactured by Lambda Vision inc.). The degree of polarization of the polarizing plate (excluding the non-polarizing portion) is preferably 99.9% or more, more preferably 99.93% or more, and still more preferably 99.95% or more.

The thickness of the polarizing plate can be set to any appropriate value. The thickness is preferably 30 μm or less, more preferably 25 μm or less, still more preferably 20 μm or less, and particularly preferably 10 μm or less. On the other hand, the thickness is preferably 0.5 μm or more, and more preferably 1 μm or more.

The absorption axis of the polarizing plate may be set in any appropriate direction according to the purpose. The direction of the absorption axis may be, for example, the longitudinal direction or the width direction. A polarizing plate having an absorption axis in the longitudinal direction has advantages such as excellent manufacturing efficiency. A polarizing plate having an absorption axis in the width direction has an advantage that it can be laminated with a retardation film having a slow axis in the longitudinal direction by roll-to-roll, for example. In 1 embodiment, the absorption axis is substantially parallel to the longitudinal direction or the width direction, and both ends in the width direction of the polarizing plate are divided and processed parallel to the longitudinal direction. According to such a configuration, the polarizing plates can be cut with the edge sides thereof as references, and a plurality of polarizing plates having non-polarizing portions at desired positions and having absorption axes in appropriate directions can be easily manufactured. Further, the absorption axis of the polarizing plate may correspond to the extending direction in the extending process described later.

Typically, the polarizing plate is obtained by subjecting the resin film to various treatments such as swelling treatment, stretching treatment, dyeing treatment with the dichroic substance, crosslinking treatment, washing treatment, and drying treatment. When various treatments are performed, the resin film may be a resin layer formed on the substrate. The formation of the non-polarizing portion may be performed during the process of producing the polarizing plate.

B-2. Formation of unpolarized portions

Preferably, the non-polarizing portion is a decoloring portion. With such a configuration, quality problems such as cracking, delamination (interlayer peeling), and paste overflow are avoided as compared with a case where the through-hole is formed mechanically (by a method of mechanically blanking using, for example, thomson knife punching, a cutter, or water jet cutting). The discolored part is preferably formed by bringing an alkaline solution into contact with a desired position of a polarizing plate (resin film containing a dichroic substance). The non-polarizing portion formed by such a method may be a low-concentration portion in which the content of the dichroic material is lower than the content of the dichroic material in other portions (non-contact portions). Since the content of the low-concentration portion of the dichroic material itself is low, the transparency of the non-polarizing portion is maintained more favorably than the case where the dichroic material is decomposed by a laser or the like to form a discolored portion.

The content of the dichroic substance in the low-concentration portion is preferably 1.0 wt% or less, more preferably 0.5 wt% or less, and still more preferably 0.2 wt% or less. The lower limit of the content of the dichroic substance in the low concentration portion is generally equal to or lower than the detection limit. The difference between the content of the dichroic substance in the other portion and the content of the dichroic substance in the low concentration portion is preferably 0.5% by weight or more, and more preferably 1% by weight or more. In the case of using iodine as the dichroic material, the iodine content is determined from the X-ray intensity measured by, for example, fluorescent X-ray analysis using a calibration curve prepared in advance using a standard sample.

As the basic compound contained in the basic solution, any appropriate compound can be used. Examples of the basic compound include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide, hydroxides of alkaline earth metals such as calcium hydroxide, inorganic alkali metal salts such as sodium carbonate, organic alkali metal salts such as sodium acetate, and aqueous ammonia. Among them, hydroxides of alkali metals and/or alkaline earth metals are preferably used, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are more preferably used. The dichroic material can be efficiently ionized, and the decolorized portion can be formed more easily. These basic compounds may be used alone or in combination of two or more.

As the solvent of the alkaline solution, water or alcohol is preferably used. The concentration of the alkaline solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, and more preferably 0.1N to 2.5N. The liquid temperature of the alkaline solution is, for example, 20 ℃ to 50 ℃. The contact time of the alkaline solution can be set according to the thickness of the polarizing plate, the kind and concentration of the alkaline compound contained in the alkaline solution. The contact time is, for example, 5 seconds to 30 minutes, preferably 5 seconds to 5 minutes.

As the method of contacting the alkaline solution, any appropriate method can be used. Examples thereof include a method of dropping, coating, and spraying an alkaline solution to the polarizing plate, and a method of immersing the polarizing plate in an alkaline solution. When the polarizing plate is contacted with the alkaline solution, the polarizing plate may be protected with an arbitrary appropriate protective material so that the alkaline solution does not contact with a portion other than the desired portion. As such a protective material, for example, a protective film or a surface protective film can be used. The protective film can be directly used as a protective film for a polarizing plate. The surface protective film may be temporarily used in the manufacture of the polarizing plate. The surface protective film is removed from the polarizing plate at any appropriate timing, and is thus typically attached to the polarizing plate via an adhesive layer. Another specific example of the protective material is a photoresist. In addition, the base material used in the above-described polarizing plate production process may be used as a protective material.

Preferably, the surface of the polarizing plate is covered with a surface protective film so that at least a part of the surface of the polarizing plate is exposed when the polarizing plate is contacted with an alkaline solution. A polarizing plate having an arrangement pattern of non-polarizing sections as shown in the drawing was manufactured by preparing a polarizing film laminate by bonding a surface protective film, in which small circular through holes corresponding to a desired size of the non-polarizing section were formed at positions corresponding to the arrangement pattern, to one side of the polarizing plate, and bringing the polarizing film laminate into contact with an alkaline solution. In this case, the other side of the polarizing plate (the side where the surface protective film (1 st protective film) having the through-hole is not disposed) is preferably also protected. Preferably, the protective film and the surface protective film are bonded by a roll-to-roll method. In the present specification, "roll-to-roll" means that films are stacked while being aligned in the longitudinal direction while being conveyed in a roll.

Examples of the material for forming the surface protective film include resin-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polyethylene and polypropylene, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. The resin is preferably a resin (particularly, a polyethylene terephthalate resin). This is because the elastic modulus is sufficiently high, and even if tension is applied during transportation and/or bonding, for example, deformation of the through-hole is less likely to occur. The thickness of the surface protective film is typically 20 μm to 250 μm, and preferably 30 μm to 150 μm.

The No. 1 surface protection film has through holes arranged in a predetermined pattern. The position of the through hole corresponds to the position where the non-polarizing portion is to be formed. The shape of the through-hole corresponds to the shape of the desired non-polarizing portion. The through-holes are formed by, for example, mechanical blanking (e.g., punch, thomson knife blanking, cutter, water jet cutting) or removal of a predetermined portion of the film (e.g., laser ablation or chemical dissolution).

In 1 embodiment, the alkaline solution may be removed from the polarizer by any suitable method after contacting the polarizer. According to such an embodiment, for example, the transmittance of the non-polarizing portion can be more reliably prevented from decreasing with the use of the polarizing plate. Specific examples of the method for removing the alkaline solution include washing, wiping off waste cotton yarn ends, suction removal, natural drying, heat drying, air drying, and reduced-pressure drying. Preferably, the alkaline solution is washed. Examples of the cleaning liquid used for cleaning include water (pure water), alcohols such as methanol and ethanol, and mixed solvents thereof. Preferably, water is used. The number of washing times is not particularly limited, and may be performed plural times. In the case where the alkaline solution is removed by drying, the drying temperature thereof is, for example, 20 ℃ to 100 ℃.

Preferably, the alkali metal and/or alkaline earth metal contained in the resin film is reduced in the contact portion with the alkaline solution after the contact with the alkaline solution. By reducing the amount of alkali metal and/or alkaline earth metal, a non-polarizing portion having excellent dimensional stability can be obtained. Specifically, even in a humidified environment, the shape of the non-polarizing portion formed by contact with the alkaline solution can be maintained at all times.

By contacting with the alkaline solution, a hydroxide of an alkali metal and/or an alkaline earth metal remains at the contact portion. Further, by contacting with the alkaline solution, a metal salt (for example, borate) of an alkali metal and/or an alkaline earth metal can be generated at the contact portion. These metal salts can generate hydroxide ions, and the generated hydroxide ions act (decompose and reduce) on a dichroic material (for example, an iodine complex) present around the contact portion, thereby enlarging the non-polarizing region. Thus, it is believed that: by reducing the amount of the alkali metal and/or alkaline earth metal salt, the non-polarizing region is suppressed from expanding over time, and a desired shape of the non-polarizing portion can be maintained.

The content of the alkali metal and/or the alkaline earth metal in the non-polarizing portion is preferably 3.6 wt% or less, more preferably 2.5 wt% or less, still more preferably 1.0 wt% or less, and particularly preferably 0.5 wt% or less. The content of the alkali metal and/or the alkaline earth metal can be determined from the X-ray intensity measured by fluorescence X-ray analysis and a calibration curve prepared in advance using a standard sample, for example.

As the method for reducing the alkali metal and/or the alkaline earth metal, a method of bringing an acidic solution into contact with a contact portion with an alkaline solution is preferably used. According to such a method, the alkali metal and/or the alkaline earth metal can be efficiently transferred to the acidic solution, and the content thereof can be reduced. The contact with the acidic solution may be performed after the removal of the alkaline solution or without removing the alkaline solution.

As the acidic compound contained in the acidic solution, any appropriate acidic compound can be used. Examples of the acidic compound include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and hydrogen fluoride, and organic acids such as formic acid, oxalic acid, citric acid, acetic acid, and benzoic acid. Among these, the acidic compound contained in the acidic solution is preferably an inorganic acid, and more preferably hydrochloric acid, sulfuric acid, or nitric acid. These acidic compounds may be used alone or in combination of two or more.

As the solvent of the acidic solution, water or alcohol can be preferably used. The concentration of the acidic solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, and more preferably 0.1N to 2.5N. The liquid temperature of the acidic solution is, for example, 20 ℃ to 50 ℃. The contact time of the acidic solution is, for example, 5 seconds to 5 minutes. In addition, as the method of contacting the acidic solution, the same method as the method of contacting the basic solution described above can be employed. In addition, the acidic solution may be removed from the polarizer. As the method for removing the acidic solution, the same method as the method for removing the basic solution described above can be used.

Typically, the surface protective film may be peeled off and removed after the non-polarizing portion is formed as described above (preferably, after the alkali metal and/or the alkaline earth metal is reduced).

B-3. Fabrication of polarizing plates

Typically, the longitudinally long polarizing plate having the unpolarized section obtained as described above constitutes a polarizing plate/protective film laminate. The laminate can be used as a polarizing plate as it is, and a polarizing plate having an arbitrary appropriate structure as a final product can be obtained by laminating other constituent members such as a protective film on the laminate according to the purpose or the like. In addition, similarly to the case of obtaining a polarizing plate formed of a single resin film, by laminating other constituent members such as a protective film on one side or both sides thereof depending on the application or the like, a polarizing plate having an arbitrary appropriate structure as a final product can be obtained. The other laminated structural members are as described in the section A-1.

The lamination of the other constituent members may be performed by a so-called roll-to-roll method.

B-4. Appearance inspection of polarizing plate

The polarizing plate obtained as described above was subjected to the inspection method described in item a. In the inspection method described in item a, by inspecting the appearance of the polarizing plate having the non-polarizing portion, the target defect (foreign matter, air bubbles, pinholes, or the like) can be detected without erroneously detecting the non-polarizing portion as a defect, and therefore, both the inspection efficiency and the inspection accuracy can be achieved at a high level. As a result, a high-quality polarizing plate can be obtained with excellent production efficiency.

B-5. Cutting of polarizing plate

The method for manufacturing a polarizing plate of the present invention may further include a step of cutting the polarizing plate in a longitudinal shape into a desired size. Cutting can be performed by cutting, punching, or the like. The polarizing plate in the longitudinal shape is preferably cut so as to have a size corresponding to the image display device to be mounted, and to have a non-polarizing portion at a position corresponding to a camera portion of the image display device when mounted on the image display device.

Since the defective portion is preferably marked on the cut polarizing plate, defective polarizing plates can be easily removed based on the mark after cutting.

Industrial applicability

The inspection method of the present invention can be suitably used in manufacturing a polarizing plate included in a camera-equipped image display device (liquid crystal display device, organic EL device) such as a mobile phone such as a smartphone, a notebook PC, or a tablet PC.

Claims

1. A method of manufacturing a polarizing plate, comprising: forming a non-polarizing portion in the vertically long polarizing plate; a polarizing plate having a longitudinal shape is manufactured by using a longitudinal polarizing plate having the non-polarizing section; and inspecting the appearance of the polarizing plate while conveying the polarizing plate in a longitudinal direction, wherein,

the polarizing plate has non-polarizing sections arranged at predetermined intervals along the longitudinal direction,

the inspecting the appearance of the vertically long polarizing plate includes:

a step of acquiring image data by imaging the polarizing plate;

analyzing the image data to extract a defect candidate portion;

a step of determining whether or not the defect candidate portion has a size equal to or smaller than a reference value;

determining whether or not the defect candidate portion has periodicity along the longitudinal direction only for the defect candidate portion having a size exceeding the reference value; and

a step of detecting the defects,

the step of detecting the defect includes detecting a defect candidate portion having a size equal to or smaller than a reference value and a defect candidate portion having a size exceeding the reference value but not having periodicity as the defect,

the extraction of the defect candidate portion is performed based on luminance information of the image data.

2. The method for manufacturing a polarizing plate according to claim 1,

the polarizing plate has non-polarizing sections arranged at predetermined intervals along the longitudinal direction and the width direction.

3. The method for manufacturing a polarizing plate according to claim 1 or 2,

the image data is acquired based on continuous shooting of the polarizing plate.

4. The method for manufacturing a polarizing plate according to claim 1 or 2,

the periodic presence or absence of the defect candidate portion is determined based on position coordinates in the longitudinal direction of the defect candidate portion.

5. The method for manufacturing a polarizing plate according to claim 1 or 2,

the periodic presence or absence of the defect candidate portion is determined based on whether or not the longitudinal distance between the defect candidate portion to be determined and the unpolarized portion present on the upstream side in the transport direction of the defect candidate portion to be determined is the longitudinal distance or an integral multiple of the longitudinal distance of the unpolarized portion.

6. The method for manufacturing a polarizing plate according to claim 1 or 2,

further, the method includes cutting the longitudinal polarizing plate into a desired size after checking the appearance.

7. The method for manufacturing a polarizing plate according to claim 1 or 2,

the non-polarizing portion is formed on the polarizing plate having a longitudinal shape by contacting with an alkaline solution.