JP2021012392A - Method and device for inspecting polarizing plate - Google Patents

Abstract

To provide a method of appropriately inspecting appearance of an elongate polarizing plate having non-polarizing sections arranged at a predetermined interval in a longitudinal direction.SOLUTION: A method is provided of inspecting appearance of an elongate polarizing plate having non-polarizing sections arranged at a predetermined interval in a longitudinal direction while the polarizing plate is being conveyed in the longitudinal direction, the method comprising steps of; photographing the polarizing plate to acquire image data; analyzing the image data and extracting defect candidate sections; determining whether the sizes of the defect candidate sections are equal to or less than a reference value; and detecting defects based on the sizes of the defect candidate sections.SELECTED DRAWING: Figure 4

Description

The present invention relates to an inspection method and an inspection apparatus for a polarizing plate having a non-polarizing portion. Typically, the present invention relates to an inspection method and an inspection apparatus for a polarizing plate including a polarizer having a non-polarizing portion.

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, with the rapid spread of smartphones and touch panel type information processing devices, further improvement in camera performance and the like is desired. Further, in order to cope with the diversification and high functionality of the shape of the image display device, a polarizing plate having a partial polarization performance is required. In order to realize these demands industrially and commercially, it is desired to manufacture an image display device and / or its parts at an acceptable cost, and various studies are made to establish such a technique. Matters are left.

Japanese Unexamined Patent Publication No. 2011-81315 Japanese Unexamined Patent Publication No. 2007-241314 U.S. Patent Application Publication No. 2004/0212555 Korean Publication No. 10-2012-0118205 Korean Patent No. 10-1293210 Japanese Unexamined Patent Publication No. 2012-137738 U.S. Patent Application Publication No. 2014/0118826

The present inventors prepared a polarizing plate using a polarizing element having a non-polarizing portion as a polarizing plate having a partially polarized light performance, and subjected the obtained polarizing plate to an appearance inspection. As a result, the non-polarizing portion was found. Faced with the problem of being mistakenly detected as a defect. The present invention has been made to solve the problem, and a main object thereof is a long length including a polarizing element having a non-polarizing part and having non-polarizing parts arranged at predetermined intervals in a long direction. An object of the present invention is to provide a method for preferably inspecting the appearance of a shaped polarizing plate.

According to the present invention, there is provided a method for inspecting the appearance of a long polarizing plate having non-polarizing portions arranged at predetermined intervals in the long direction while transporting the long polarizing plate in the long direction. The inspection method includes a step of capturing an image of the polarizing plate to acquire image data, a step of analyzing the image data to extract a defect candidate portion, and whether or not the defect candidate portion has a size equal to or less than a reference value. The process includes a step of determining whether or not the defect is detected, and a step of detecting the defect based on the size of the defect candidate portion.
In one embodiment, the polarizing plate has non-polarized portions arranged at predetermined intervals in the longitudinal direction and the width direction.
In one embodiment, the acquisition of the image data is based on the continuous imaging of the polarizing plate.
In one embodiment, the defect candidate portion is extracted based on the luminance information of the image data.
In one embodiment, the step of determining whether or not the defect candidate portion has periodicity in the long direction is further included, and the step of detecting the defect is the size and periodicity of the defect candidate portion. This is a process of detecting defects based on the presence or absence.
In one embodiment, it is determined whether or not the defect candidate portion having a size exceeding the reference value has periodicity in the long direction.
In one embodiment, the determination of the presence or absence of periodicity of the defect candidate portion is performed based on the position coordinates of the defect candidate portion in the longitudinal direction.
In one embodiment, the determination of the presence or absence of periodicity of the defect candidate portion is determined by determining the distance between the defect candidate portion to be determined and the non-polarizing portion existing on the upstream side in the transport direction in the long direction. It is done based on whether it is a distance or not.
According to another aspect of the present invention, there is provided a method for producing a polarizing plate. The manufacturing method includes inspecting the polarizing plate by the above inspection method.
According to yet another aspect of the present invention, there is provided an appearance inspection device for a long polarizing plate. The visual inspection device includes an imaging device that obtains image data by imaging a long polarizing plate having non-polarizing portions arranged at predetermined intervals in the long direction, and an imaging device that analyzes the image data to obtain the polarized light. It is provided with an image analysis device for detecting defects in the plate. The image analysis device extracts a defect candidate unit based on the image data, a defect candidate unit extraction unit, a size determination unit that determines whether or not the defect candidate unit has a size equal to or less than a reference value, and a defect candidate unit. Defect detection that detects defects based on the periodicity determination unit that determines whether or not the image has periodicity in the long direction and the size of the defect candidate unit, or the size of the defect candidate unit and the presence or absence of periodicity. It has a part and.

According to the inspection method of the present invention, it is possible to avoid erroneously detecting the non-polarized portion as a defect. Therefore, the non-polarized portion including the polarizing element having the non-polarized portion and arranged at predetermined intervals in the long direction. The appearance of the elongated polarizing plate having the above can be suitably inspected.

It is the schematic sectional drawing of the polarizing plate which can be used for the inspection method of this invention. It is a schematic plan view explaining an example of the arrangement pattern of a non-polarized part. It is the schematic plan view explaining another example of the arrangement pattern of a non-polarized part. It is the schematic plan view explaining still another example of the arrangement pattern of a non-polarized part. It is the schematic explaining the inspection apparatus which can be used in the inspection method of this invention. It is a flowchart explaining the specific procedure of defect detection in one Embodiment of this invention. It is a flowchart explaining the specific procedure of defect detection in another embodiment of this invention. It is a schematic diagram explaining the specific procedure of defect detection in the embodiment shown in FIG.

[A. Inspection method and inspection equipment]
The present invention provides a method for inspecting the appearance of a long polarizing plate having non-polarizing portions arranged at predetermined intervals in the long direction while transporting the long polarizing plate in the long direction. The inspection method of the present invention includes a step of acquiring image data by imaging a polarizing plate having a non-polarizing portion, a step of analyzing the image data to extract a defect candidate portion, and a defect candidate portion having a defect candidate portion of a reference value or less. It includes a step of determining whether or not the defect has a size and a step of detecting a 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 the reference value can be recognized and distinguished as a non-polarized portion, and a defect candidate portion having a size equal to or less 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 in the longitudinal direction. In this case, in the step of detecting the defect, the defect is detected based on the size of the defect candidate portion and the presence or absence of periodicity. More specifically, a defect candidate portion having a size equal to or less than a reference value is detected as a defect, and a defect candidate portion having no periodicity is also detected as a defect. The inspection accuracy can be improved by evaluating the defect candidate portion from the two aspects of size and periodicity. From the viewpoint of inspection efficiency, it is preferable to determine the presence or absence of periodicity only for the defect candidate portion having a size exceeding the reference value. In this case, all defect candidate portions having a size equal to or less than the reference value are detected as defects, and only those having no periodicity are detected as defects from the defect candidate portions having a size exceeding the reference value.

A-1. Polarizing plate The polarizing plate used in the inspection method of the present invention is long and has non-polarized parts arranged at predetermined intervals in the long direction. The unpolarized portion is typically caused by the non-polarized portion formed on the polarizer. In addition, in this specification, "long-shaped" means an elongated shape having a length sufficiently long with respect to a width, and for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to a width. Including shape.

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 has a polarizer 10 having a non-polarizing portion, and protective films 11 and 12 arranged on both sides of the polarizing element 10. In the illustrated example, the protective films are arranged on both sides of the polarizer, but the protective films may be arranged on only one side. Alternatively, the polarizing plate may be composed of only a polarizer (that is, the polarizing plate may be a polarizer).

The polarizer 10 is typically composed of a resin film containing a dichroic substance. Since the polarizing plate 30 has a long shape, the polarizer 10 also has a long shape. The polarizer 10 has non-polarizing portions arranged at predetermined intervals in the longitudinal direction. In one embodiment, the polarizer 10 has non-polarizing portions arranged at predetermined intervals in the longitudinal direction and the width direction. The arrangement pattern of the non-polarized portion can be appropriately set according to the purpose. Typically, the non-polarized portion is said to be cut to a predetermined size (for example, cut or punched in a long direction and / or a width direction) in order to attach a polarizer to an image display device of a predetermined size. It may be arranged at a position corresponding to the camera unit of the image display device. In one embodiment, the non-polarized portions are arranged at substantially equal intervals in both the longitudinal and width directions. In addition, "substantially evenly spaced in both the long direction and the width direction" means that the intervals in the long direction are evenly spaced and the intervals in the width direction are evenly spaced. The spacing in the shaku direction and the spacing in the width direction do not have to be equal. In another embodiment, the non-polarized portions may be arranged at substantially equal intervals in the longitudinal direction and at different intervals in the width direction. When the non-polarized parts are arranged at different intervals in the width direction, the intervals of the adjacent non-polarized parts may be all different, or only a part (the interval of a specific adjacent non-polarized part) may be different. .. Further, a plurality of regions may be defined in the elongated direction of the polarizer, and the spacing between the non-polarized portions in the elongated direction and / or the width direction may be set for each region.

2A to 2C are schematic plan views for explaining an example of the arrangement pattern of the non-polarizing portion in the polarizer 10, respectively. In one embodiment, in the non-polarized portion 10a, as shown in FIG. 2A, a straight line connecting adjacent non-polarized portions in the elongated direction is substantially parallel to the elongated direction and has a width. The straight lines connecting the non-polarized parts adjacent to each other in the direction are arranged so as to be substantially parallel to the width direction.

As the plan view shape of the non-polarized portion, any appropriate shape may be adopted depending on the purpose. For example, as the plan view shape of the non-polarizing portion, any appropriate shape can be adopted as long as it does not adversely affect the camera performance of the image display device in which the polarizer is used. The non-polarized portion of the illustrated example is circular, but may be formed in, for example, an ellipse, a square, a rectangle, a rhombus, or the like.

The transmittance of the non-polarized portion (for example, the transmittance measured with light having a wavelength of 550 nm at 23 ° C.) is preferably 50% or more, more preferably 60% or more, still more preferably 75% or more. Particularly preferably, it is 90% or more. With such a transmittance, it is possible to prevent an adverse effect on the shooting performance of the camera, for example, when the polarizer is arranged so that the non-polarizing portion corresponds to the camera portion of the image display device.

The non-polarized portion can be in any suitable form. In one embodiment, the non-polarized portion is a partially decolorized decolorized portion. The decolorized portion is formed by, for example, laser irradiation or chemical treatment. In another embodiment, the non-polarized portion is a through hole. Through holes are formed, for example, by mechanical punching (eg punching, Thomson blade punching, plotters, water jets) or removal of predetermined portions (eg 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, (meth) acrylic resins, cycloolefin resins, olefin resins such as polypropylene, and polyethylene terephthalate resins. Examples thereof include ester-based resins, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. One of the protective films 11 and 12 may be omitted depending on the purpose and the desired configuration.

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

Practically, the polarizing plate 30 has an adhesive layer 13 as the outermost layer. The pressure-sensitive adhesive layer 13 is typically the outermost layer on the image display device side. A separator 14 is temporarily attached to the pressure-sensitive adhesive layer 13 so as to be peelable, which protects the pressure-sensitive adhesive layer until actual use and enables roll formation.

The polarizing plate 30 may further have an arbitrary suitable optical functional layer depending on 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 may be placed between the protective film 12 and the pressure-sensitive adhesive layer 13 (not shown). The optical characteristics of the retardation film (for example, refractive index ellipsoid, in-plane retardation, thickness direction retardation) can be appropriately set according to the purpose, the characteristics of the image display device, and the like.

The surface treatment layer may be arranged on the outside of 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 treatment layer is preferably a layer having low moisture permeability for the purpose of improving the humidification durability of the polarizer, for example. 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 device FIG. 3 is a schematic view illustrating an inspection device that can be used in the inspection method of the present invention. In the illustrated embodiment, the elongated polarizing plate 30 is conveyed to the inspection device 100 to perform a visual inspection. The inspection device 100 includes an image pickup device 50 that captures an image of the polarizing plate 30 and acquires image data, and an image analysis device 80 that analyzes the obtained image data and detects defects in the polarizing plate 30. The image analysis device 80 includes a defect candidate unit extraction unit 82 that extracts defect candidate units based on the obtained image data, and a size determination unit 84 that determines whether or not the defect candidate unit has a size equal to or less than a reference value. , Defects are determined based on the periodicity determination unit 86 that determines whether or not the defect candidate portion has periodicity in the longitudinal direction, the size of the defect candidate portion, or the size of the defect candidate portion and the presence or absence of periodicity. It has a defect detection unit 88 for detection.

A-3. Step of acquiring image data (1)
The step (1) can be performed by using the image pickup apparatus 50 to image the polarizing plate having the non-polarizing portion to obtain image data. The image pickup apparatus 50 typically includes an illumination unit 52 and an image pickup unit 54.

The illumination unit 52 can be configured using any suitable 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, halogen lamps, metal halide lamps, LEDs and the like.

The image pickup unit 54 is typically a camera configured by using a lens and an image sensor. The imaging unit is preferably provided with one or more so that the entire width of the polarizing plate can be imaged. Further, the imaging unit is preferably capable of capturing continuous images in the long direction. In one embodiment, the imaging unit is a line sensor camera.

In the embodiment shown in FIG. 3, the illumination unit 52 arranged on one side of the polarizing plate irradiates the polarizing plate 30 with light so that the other side of the polarizing plate 30 faces the illumination unit 52. The light transmitted through the polarizing plate 30 is imaged by the imaging unit 54 arranged in. By imaging the transmitted light, it is possible to obtain an image in which the brightness of the region corresponding to the non-polarized portion is higher than the brightness of the region corresponding to the other portion.

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

In yet another embodiment (not shown), the illumination unit and the imaging unit are arranged on one side of the polarizing plate so that the optical axis of the camera of the imaging unit and the optical axis of the irradiation light coincide with each other. The light is irradiated perpendicularly to the polarizing plate, and the reflected light is imaged.

By selecting an appropriate imaging method according to the form of the non-polarized part (bleached part, through hole, etc.), the configuration of the polarizing plate, and imaging the polarizing plate, the brightness of the region corresponding to the non-polarized part and other factors can be obtained. An image having a large difference from the brightness of the region corresponding to the portion (as a result, a large contrast ratio) can be obtained. Imaging of the polarizing plate may be performed according to any one of the above embodiments, or may be performed by combining two or more embodiments.

Preferably, imaging is performed while transporting a long polarizing plate in the long direction. By performing imaging while transporting, it is possible to avoid a stoppage of the production line and maintain production efficiency.

A-4. Step of extracting defect candidate part (2)
The image data obtained by the image pickup device 50 is transmitted to the image analysis device 80 as an electric signal. The transmitted image data is analyzed by the defect candidate unit extraction unit 82, whereby the defect candidate unit is extracted.

In one embodiment, the defect candidate portion is extracted based on the luminance information of the image data. Specifically, a normal polarizing plate is imaged in advance to set a brightness standard to be determined to be normal, and a defect candidate portion is extracted based on the standard. For example, a high-luminance portion exceeding the upper limit of the brightness determined to be normal, a low-luminance portion exceeding the lower limit of the brightness determined to be normal, and the like can be determined as defect candidate portions. Defects that cause poor appearance such as foreign matter, air bubbles, and pinholes are usually extracted as defect candidate parts according to the above-mentioned luminance criteria because the transmittance, reflectance, etc. are different from the normal region of the polarizing plate. To. On the other hand, in the obtained image data, the region corresponding to the non-polarized portion can also be extracted as a defect candidate portion because the transmittance, reflectance and the like are different from the region corresponding to the other portion.

The defect candidate extraction unit 82 preferably stores the position information of the defect candidate unit (for example, the position coordinates (X, Y) in the long direction and the width direction in the continuous image in the long direction), and the periodicity determination unit 86 Send to.

A-5. Step of determining whether or not the defect candidate portion has a size smaller than the reference value (3)
When the defect candidate unit is extracted by the defect candidate unit extraction unit 82, the size determination unit 84 determines the size of each extracted defect candidate unit, and further, whether or not the size is equal to or less than the reference value. To judge.

Determining the size of the defect candidate can be done by any suitable method. For example, the size can be determined based on the number of pixels, diameter, area, and the like of the defect candidate portion in the image data. The diameter of the defect candidate portion can be typically determined with the length of the longest straight line connecting any two points on the outer circumference of the defect candidate portion as the diameter in the image data. The area can be calculated based on the number of pixels or diameter.

The reference value can be determined by any suitable method. For example, the reference value can be determined based on the size of the non-polarized 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-polarized portion (theoretical value) is calculated based on the shape and dimensions of the non-polarized portion in design, or the diameter of the non-polarized portion actually formed on the polarizer (measured value) is measured. However, for example, 90%, preferably 95%, of the diameter of the obtained non-polarized portion can be used as a reference value. Further, for example, when the average size of the defect is sufficiently smaller than the size of the non-polarized portion (for example, when the average diameter of the defect is 1/8 or less of the diameter of the non-polarized portion), the above reference value is not set. The value can be 1/4 to 1/2 of the diameter of the polarizing portion. As a specific example, when the diameter of the non-polarized portion is about 2800 μm and the average diameter of the defects is 150 μm to 300 μm, the reference value can be set to about 1000 μm.

A-6. Step of determining whether or not the defect candidate portion has periodicity in the long direction (4)
The periodicity determination unit 86 may use all of the extracted defect candidate units as periodicity determination targets, and only the defect candidate units confirmed by the size determination unit 84 to have a size exceeding the reference value as a determination target. May be good. Preferably, only the defect candidate portion confirmed by the size determination unit 84 to have a size exceeding the reference value is set as the determination target.

In one embodiment, when three 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-polarized parts are arranged at least at predetermined intervals in the long direction, the periodicity can be determined based on the distance between the non-polarized parts in the long 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 screening those existing at the above-mentioned predetermined intervals.

In one embodiment, the determination of the presence or absence of periodicity of the defect candidate portion is performed based on the position coordinates of the defect candidate portion (for example, the position coordinates in the longitudinal direction). For example, the position coordinates of the defect candidate part (for example, two or more, preferably three or more adjacent defect candidate parts in the longitudinal direction) transmitted from the defect candidate part extraction unit are set as a design (theoretical) non-polarized part. If the position coordinates match with each other, it can be determined that the defect candidate portion has periodicity. Further, for example, based on the position coordinates in the long direction of the defect candidate portion transmitted from the defect candidate portion extraction unit, the defect candidate portion to be determined and the non-polarized portion (not a defect) existing on the upstream side in the transport direction thereof. The distance in the long direction from the defect candidate portion that has been determined to be) is obtained, and the distance is determined based on whether or not the distance is a predetermined distance. The distance may be, for example, an arrangement interval of non-polarized parts in the long direction (that is, a predetermined distance in the long direction), or a distance obtained by multiplying the predetermined distance by an integer.

A-7. Step of detecting defects (5)
The defect detection unit 88 detects a defect based on the size of the defect candidate unit, or the size of the defect candidate unit and the presence or absence of periodicity. Specifically, the defect detection unit 88 detects a defect candidate unit determined by the size determination unit 84 to have a size equal to or less than a reference value as a defect. The defect detection unit 88 further recognizes the defect candidate unit determined to have periodicity by the periodicity determination unit 86 as a non-polarized part, distinguishes it from the defect candidate unit, and detects the remaining defect candidate unit as a defect. Can be done. In other words, the defect detection unit 88 can detect the defect candidate unit determined to have a size equal to or less than the reference value and the defect candidate unit determined to have no periodicity as defects.

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

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

A-8. Marking process (6)
The inspection device 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 detecting unit) detects a defect, the marking device transmits the 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 removed as a defective polarizing plate after cutting. Examples of the marking include marking using a marker pen and laser marking.

[B. Method for manufacturing polarizing plate]
The method for producing a long polarizing plate including a polarizing element having a non-polarizing portion of the present invention is to form a non-polarizing portion on the long polarizing element, and to form a long polarizing element having the non-polarizing portion. It includes producing a polarizing plate using the above-mentioned inspection method and inspecting the appearance of the polarizing plate by the above-mentioned inspection method.

B-1. Polarizer Polarizer is typically composed of a resin film containing a dichroic substance. Examples of the dichroic substance include iodine and organic dyes. These can be used alone or in combination of two or more. Iodine is preferably used.

Any suitable resin can be used as the resin for forming the resin film. Preferably, a polyvinyl alcohol-based resin is used. Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponification of polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer.

The polarizer (excluding the non-polarizing portion) preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizer (excluding the non-polarizing portion) is preferably 39% or more, more preferably 39.5% or more, still more preferably 40% or more, and particularly preferably 40.5% or more. The theoretical upper limit of the single transmittance is 50%, and the practical upper limit is 46%. The single transmittance is a Y value measured by a JIS Z8701 double field of view (C light source) and corrected for luminosity factor. For example, it is measured using a microspectroscopy system (manufactured by Lambdavision, LVmicro). Can be done. The degree of polarization of the polarizer (excluding the non-polarized portion) is preferably 99.9% or more, more preferably 99.93% or more, still more preferably 99.95% or more.

The thickness of the polarizer can be set to any suitable 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, more preferably 1 μm or more.

The absorption axis of the polarizer can be set in any suitable direction depending on the purpose. The direction of the absorption axis may be, for example, a long direction or a width direction. A polarizer having an absorption axis in the long direction has an advantage that, for example, it is excellent in manufacturing efficiency. A polarizer having an absorption axis in the width direction has an advantage that it can be laminated with, for example, a retardation film having a slow phase axis in the long direction by roll-to-roll. In one embodiment, the absorption shaft is substantially parallel in the longitudinal or width direction, and both ends of the polarizer in the width direction are slitted parallel to the longitudinal direction. According to such a configuration, it is possible to easily manufacture a plurality of polarizers which can be cut with reference to the end edge of the polarizer, have a non-polarizing portion at a desired position, and have an absorption axis in an appropriate direction. Can be done. The absorption axis of the polarizer can correspond to the stretching direction in the stretching treatment described later.

The polarizer is typically obtained by subjecting the resin film to various treatments such as swelling treatment, stretching treatment, dyeing treatment with the dichroic substance, cross-linking treatment, cleaning treatment, and drying treatment. When performing various treatments, the resin film may be a resin layer formed on the base material. The formation of the non-polarizing portion can also be performed during the process of manufacturing the polarizer.

B-2. Formation of non-polarized portion Preferably, the non-polarized portion is a decolorized portion. According to such a configuration, cracks and delaminations are formed as compared with the case where a through hole is formed mechanically (for example, by a method of mechanically punching out using a Thomson blade punch, a plotter, a water jet, etc.). Quality problems such as (delamination) and glue squeeze out are avoided. The decolorized portion is preferably formed by bringing a basic solution into contact with a desired position of a polarizer (a resin film containing a dichroic substance). The non-polarized portion formed by such a method can be a low-concentration portion having a lower content of the dichroic substance than other portions (non-contact portions). Since the content of the dichroic substance itself is low in the low-concentration part, the transparency of the non-polarized part is maintained better than in the case where the dichroic substance is decomposed by laser light or the like to form the decolorized part. Will be done.

The content of the dichroic substance in the low concentration portion is preferably 1.0% by weight or less, more preferably 0.5% by weight or less, still more preferably 0.2% by weight or less. The lower limit of the content of the dichroic substance in the low concentration portion is usually below 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, more preferably 1% by weight or more. When iodine is used as the dichroic substance, the iodine content is determined, for example, from the X-ray intensity measured by fluorescent X-ray analysis by a calibration curve prepared in advance using a standard sample.

Any suitable compound can be used as the basic compound contained in the basic solution. Examples of the basic compound include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, and inorganic alkali metal salts such as sodium carbonate. , Organic alkali metal salts such as sodium acetate, aqueous ammonia and the like. Among these, 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 substance 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.

Water and alcohol are preferably used as the solvent for the basic solution. The concentration of the basic solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, and more preferably 0.1N to 2.5N. The temperature of the basic solution is, for example, 20 ° C to 50 ° C. The contact time of the basic solution can be set according to the thickness of the polarizer and the type and concentration of the basic compound contained in the basic solution. The contact time is, for example, 5 seconds to 30 minutes, preferably 5 seconds to 5 minutes.

Any suitable method can be adopted as the contact method for the basic solution. For example, a method of dropping, coating, and spraying a basic solution on a polarizer, and a method of immersing the polarizer in the basic solution can be mentioned. Upon contact with the basic solution, the polarizer may be protected with any suitable protective material so that the basic solution does not come into contact with any part other than the desired site. As such a protective material, for example, a protective film and a surface protective film are used. The protective film can be used as it is as a protective film for the polarizer. The surface protective film is temporarily used during the manufacture of the polarizer. Since the surface protective film is removed from the polarizer at an arbitrary appropriate timing, it is typically attached to the polarizer via an adhesive layer. Another specific example of the protective material is a photoresist or the like. Further, the base material used in the above-mentioned process of producing the polarizer can also be used as a protective material.

Preferably, the surface of the polarizer is coated with a surface protective film so that at least a part thereof is exposed upon contact with the basic solution. A polarizer having a non-polarized portion arrangement pattern as shown in the illustrated example is a surface protective film having a small circular through hole formed at a position corresponding to the arrangement pattern and a small circular through hole corresponding to a desired non-polarized portion size. A polarizing film laminate is prepared by laminating it on one side of the surface, and a basic solution is brought into contact with the polarizing film laminate. At that time, it is preferable that the other side of the polarizer (the side on which the surface protective film (first protective film) having through holes is not arranged) is also protected. The protective film and the surface protective film are preferably bonded by roll-to-roll. As used herein, the term "roll-to-roll" refers to laminating roll-shaped films while transporting them so that their longitudinal directions are aligned with each other.

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

The first surface protective film has through holes arranged in a predetermined pattern. The position of the through hole corresponds to the position where the unpolarized portion is formed. The shape of the through hole corresponds to the shape of the desired non-polarized portion. Through holes are formed, for example, by mechanical punching (eg punching, Thomson blade punching, plotters, water jets) or removal of certain parts of the film (eg laser ablation or chemical dissolution).

In one embodiment, the basic solution is removed from the polarizer by any suitable means after contact with the polarizer. According to such an embodiment, for example, it is possible to more reliably prevent a decrease in the transmittance of the non-polarized portion due to the use of the polarizer. Specific examples of the method for removing the basic solution include washing, wiping removal with a waste cloth, suction removal, natural drying, heat drying, blast drying, vacuum drying and the like. Preferably, the basic 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 washings is not particularly limited and may be performed a plurality of times. When the basic solution is removed by drying, the drying temperature is, for example, 20 ° C to 100 ° C.

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

By contacting with a basic solution, hydroxides of alkali metals and / or alkaline earth metals may remain at the contacts. Further, by contacting with a basic solution, a metal salt of an alkali metal and / or an alkaline earth metal (for example, borate) can be formed at the contact portion. These can generate hydroxide ions, and the generated hydroxide ions act (decompose / reduce) on a dichroic substance (for example, iodine complex) existing around the contact portion to widen the non-polarized region. obtain. Therefore, it is considered that by reducing the alkali metal and / or alkaline earth metal salt, it is possible to suppress the expansion of the non-polarized region over time and maintain the desired non-polarized portion shape.

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

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

Any suitable acidic compound can be used as the acidic compound contained in the acidic solution. 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.

Water and alcohol are preferably used as the solvent for the acidic solution. 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 ° C to 50 ° C. The contact time of the acidic solution is, for example, 5 seconds to 5 minutes. As the contact method for the acidic solution, the same method as the contact method for the basic solution can be adopted. Also, the acidic solution can be removed from the polarizer. As the method for removing the acidic solution, the same method as the method for removing the basic solution can be adopted.

Typically, after the non-polarized portion is formed as described above (preferably after reduction of alkali metals and / or alkaline earth metals), the surface protective film can be stripped and removed.

B-3. Fabrication of Polarizing Plate A long-shaped polarizer having a non-polarizing portion obtained as described above typically constitutes a laminate of a polarizer / protective film. While the laminate can be used as a polarizing plate as it is, by laminating other constituent members such as a protective film on the laminate according to the purpose or the like, any appropriate configuration as a final product can be obtained. A polarizing plate having a polarizing plate can be obtained. Similarly, when a polarizing element made of a single resin film can be obtained, an arbitrary final product can be obtained by laminating other constituent members such as a protective film on one side or both sides thereof depending on the intended use. A polarizing plate having an appropriate configuration can be obtained. The other constituent members to be laminated are as described in Section A-1.

Lamination of the other constituent members can be performed by so-called roll-to-roll.

B-4. Appearance inspection of polarizing plate The polarizing plate obtained as described above is subjected to the inspection method according to Item A. By inspecting the appearance of the polarizing plate having the non-polarized part by the inspection method described in Item A, the target defect (foreign matter, air bubbles, pinholes, etc.) can be inspected without erroneously detecting the non-polarized part as a defect. Can be detected, so that inspection efficiency and inspection accuracy can be compatible with each other at a high level. As a result, a high quality polarizing plate can be obtained with excellent production efficiency.

B-5. Cutting a Polarizing Plate The method for producing a polarizing plate of the present invention may further include a step of cutting a long polarizing plate into a desired size. Cutting can be done by cutting, punching, etc. The elongated polarizing plate is preferably cut so as to have a size corresponding to the attached image display device and to have a non-polarizing portion at a position corresponding to the camera portion when attached to the image display device. To.

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

The inspection method of the present invention is suitably used for manufacturing a polarizing plate provided in an image display device (liquid crystal display device, organic EL device) with a camera such as a mobile phone such as a smartphone, a notebook PC, or a tablet PC. Be done.

10 Polarizer 10a Non-polarizing part 30 Polarizing plate 50 Imaging device 80 Image analysis device 82 Defect candidate part Extraction part 84 Size judgment part 86 Periodic judgment part 88 Defect detection part 100 Inspection device

Claims (8)

Forming non-polarizing portions arranged at predetermined intervals in the long direction on a long polarizing element, and producing a long polarizing plate using a long polarizing element having the non-polarizing portion. A method for manufacturing a polarizing plate, which comprises inspecting the appearance of the long-shaped polarizing plate while transporting it in the long direction.
Inspecting the appearance of the elongated polarizing plate
The process of imaging the polarizing plate and acquiring image data,
A process of analyzing the image data and extracting a defect candidate portion,
The process of determining whether the defect candidate part has a size smaller than the reference value, and
Only for the defect candidate portion having a size exceeding the reference value, a step of determining whether or not the defect candidate portion has periodicity in the longitudinal direction, and
The process of detecting defects and
Including
The step of detecting the defect includes detecting a defect candidate portion having a size equal to or less than a reference value and a defect candidate portion having a size exceeding the reference value and having no periodicity as a defect. Manufacturing method. The method for manufacturing a polarizing plate according to claim 1, wherein non-polarizing portions arranged at predetermined intervals in the elongated direction and the width direction are formed on the elongated polarizing element. The method for manufacturing a polarizing plate according to claim 1 or 2, wherein the acquisition of the image data is performed based on continuous imaging of the polarizing plate. The method for manufacturing a polarizing plate according to any one of claims 1 to 3, wherein the defect candidate portion is extracted based on the luminance information of the image data. The method for manufacturing a polarizing plate according to any one of claims 1 to 4, wherein the presence or absence of periodicity of the defect candidate portion is determined based on the position coordinates of the defect candidate portion in the longitudinal direction. The determination of the presence or absence of periodicity of the defect candidate portion is made by determining that the distance between the defect candidate portion to be determined and the non-polarizing portion existing on the upstream side in the transport direction in the long direction is the distance of the non-polarizing portion in the long direction. The method for manufacturing a polarizing plate according to any one of claims 1 to 4, which is performed based on the arrangement interval or a distance obtained by multiplying the interval by an integral number. The method for producing a polarizing plate according to any one of claims 1 to 6, further comprising cutting the elongated polarizing plate to a desired size after inspecting the appearance. The method for producing a polarizing plate according to any one of claims 1 to 7, wherein the non-polarized portion is formed on the elongated polarizer by contact with a basic solution.