JP2017161948A - Polarizing plate and liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate and the like that can achieve a large-sized liquid crystal panel with excellent visibility.SOLUTION: A polarizing plate 100 comprises a polarizer 10 and a protective film 20. The outer shape of the polarizing plate 100 is a rectangle having long sides with a length of 660 mm or more and short sides with a length of 370 mm or more. The average degree of polarization of the polarizing plate 100 is 99.98% or more. The number of defective parts having a degree of polarization of less than 99% and a maximum diameter of 30 μm or more is 10/mor less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate and a liquid crystal panel.

  Conventionally, a polarizing plate for a liquid crystal panel having a polarizer and a transparent protective film is known.

JP 2012-58381 A

  Recently, as the size of liquid crystal panels has increased, the definition has also increased, and the number of scenes that stare at fine details, such as medical monitors, has increased. Is required.

  This invention is made | formed in view of the said subject, and it aims at providing the polarizing plate etc. which can implement | achieve the large sized liquid crystal panel excellent in visibility.

  As a result of investigations by the present inventors, the inventors have found that a defect portion of a small polarizer, which has been ignored in the past, greatly affects the visibility of a large liquid crystal panel.

The polarizing plate which concerns on this invention is equipped with a polarizer and the protective film arrange | positioned on the said polarizer. The outer shape of the polarizing plate is a rectangle having a long side of 660 mm or more and a short side of 370 mm or more. The average degree of polarization of the polarizing plate is 99.98% or more, and the degree of polarization is less than 99% and the maximum. The number of defect portions having a diameter of 30 μm or more is 10 pieces / m ² or less.

  According to the present invention, since the number of defect portions that have been ignored in the past is controlled to be small, visibility can be improved in a large liquid crystal panel.

  Here, the outer shape of the polarizing plate may be a rectangle having a long side of 800 mm or more and a short side of 450 mm or more. This is suitable for application to a larger liquid crystal panel.

  The polarizer may have a thickness of 10 μm or less.

  If the polarizer is thin, the deformed part tends to be relatively large in the case of a defect due to the inclusion of foreign matter between the polarizer and the protective film as compared with the case where the polarizer is thick, and it has also adhered to the roll. Even in the case of a defect due to a dent caused by a foreign substance, the deformation of the polarizer is likely to remain as compared with the case where the polarizer is thick, so the effect of the present invention is enhanced.

The polarizing plate may have a degree of polarization of less than 99% and a number of defect portions having a maximum diameter of 20 μm or more of 20 pieces / m ² or less. Thereby, visibility improves further.

The polarizing plate is preferably for attaching to a liquid crystal cell having a subpixel area of 0.1 mm ² or less. In a liquid crystal panel having a large screen and a small subpixel area, the effect is high.

  The polarizing plate has a total value (%) of transmitted image clarity (%) of 200 or more for optical combs having four widths of 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm. Can do. In a high-definition display, in order to take advantage of high definition, a polarizing plate with high transmission definition is often combined, and an image is not easily blurred, so that a defect of the polarizing plate is likely to be clearly seen. However, according to the present invention, a high-definition liquid crystal panel can be realized without causing defects to be noticeable.

  The liquid crystal panel according to the present invention can include a liquid crystal cell and a pair of polarizing plates attached to both surfaces of the liquid crystal cell. One of the polarizing plates is the polarizing plate of the present invention, and the other polarizing plate. Can also be the polarizing plate of the present invention.

  Here, the thickness of the liquid crystal cell may be 3 mm or less.

The subpixel area of the liquid crystal cell may be 0.1 mm ² or less.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate which can implement | achieve the large sized liquid crystal panel excellent in visibility is provided.

FIG. 1 is a cross-sectional view of a polarizing plate according to one embodiment of the present invention. FIG. 2 is a view as seen from a direction perpendicular to the main surface of the polarizing plate of FIG. FIG. 3 is a side view of a liquid crystal panel according to an embodiment of the present invention. FIG. 4 is an enlarged plan view of a pixel of the liquid crystal panel of FIG.

An embodiment of the present invention will be described with reference to the drawings.
(Polarizer)
FIG. 1 is a schematic cross-sectional view showing an example of a basic layer configuration of a polarizing plate 100 according to an embodiment of the present invention. The polarizing plate 100 has an adhesive layer on one surface of the polarizer 10 and the polarizer 10. 5 and a protective film 20 attached to the other surface of the polarizer 10 via an adhesive layer 5. Further, the polarizing plate 100 is usually attached to the liquid crystal cell on the surface opposite to the adhesive layer 5 of the protective film 20 via, for example, an adhesive layer 28. Alternatively, although not shown, the protective film 20 is not used, and a layer (such as an easy-adhesion layer, an antistatic layer, or an overcoat layer) is provided directly on the surface opposite to the protective film 30 of the polarizer 10 or another layer. It is also possible to provide an adhesive layer 28 via the adhesive layer 28 and attach it to the liquid crystal cell via the adhesive layer 28. By not providing the protective film 20 as described above, it is possible to prevent the occurrence of defects due to the protective film 20.

  FIG. 2 is a view of the polarizing plate 100 as viewed from a direction perpendicular to the main surface. The outer shape of the polarizing plate 100 is a rectangle. This rectangle has a long side A of 660 mm or more and a short side B of 370 mm or more (corresponding to a 32-inch screen). This rectangular shape can have a long side A of 800 mm or more and a short side B of 450 mm or more (corresponding to a 40-inch screen), and has a long side A of 1000 mm or more and a short side B of 550 mm or more (50 inches). It can also have a long side A of 1300 mm or more and a short side B of 700 mm or more (corresponding to a 60-inch type screen).

  In the present specification, the rectangular shape includes those in which about 5 mm on both sides of the corner C are rounded or rounded. The rectangle includes a square.

  There is no particular upper limit on the size of the rectangle, but for example, the size of the long side A can be 3000 mm or less.

  The average degree of polarization of the polarizing plate 100 (based on Japan Electronics and Information Technology Industries Association (JEITA) ED-2521B) is 99.980% or more, preferably 99.985% or more, and 99.990% or more. It is more preferable that

In the polarizing plate 100, the number of first defect portions d1 having a degree of polarization of less than 99% and a maximum diameter of 30 μm or more is 10 pieces / m ² or less. The number of first defect portions d1 is preferably 5 / m ² or less, and more preferably 3 / m ² or less. Such defects include defects having a low degree of polarization and a degree of polarization of less than 99%, as well as defects having a degree of polarization of 0%.
In the polarizing plate 100, the number of the second defect portions d2 having a degree of polarization of less than 99% and a maximum diameter of 20 μm or more can be 20 pieces / m ² or less, and can be 10 pieces / m ² or less. / M ² or less. Since the first defect portion d1 satisfies the requirements for the second defect portion d2, the number of the second defect portions d2 includes the number of the first defect portions d1.

The polarizing plate 100 is an optical comb having four types of widths of 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm in a transmission image definition measurement test defined in JIS K 7374 (2007). The total value T _c (%) of the transmitted image definition C _n (%) can be 200 or more, and can be 300 or more.
In the transmitted image definition measurement test, the amount of light transmitted through the polarizing plate is measured through an optical comb having a width n (mm) that is perpendicular to the optical axis of the transmitted light and moves at a speed of 10 mm / min. Specifically, the measurement is performed using a image clarity measuring device (manufactured by Suga Test Instruments Co., Ltd.). The image clarity measuring device uses the light transmitted through the slit as a parallel light beam and is perpendicular to the polarizing plate 100 from the side opposite to the protective film 30 on the outside (opposite side to the liquid crystal cell) (from the protective film 20 side in FIG. 1). An optical apparatus that detects the incident light and transmits the transmitted light through an optical comb, and a measurement system apparatus that records a change in the detected light quantity as a waveform. In the optical comb, the ratio of the width of the bright part to the dark part is 1: 1, the width n (mm) is four types of 0.125, 0.5, 1, and 2, and the moving speed is 10 mm / min. .

Transmission image clarity C _{n (%)} is the highest value of the amount of transmitted light when the rays shaft is transmitted portion of the optical comb (bright portion) M _n, optical comb on light axis in the transmission image clarity measured test When the minimum value of the amount of transmitted light when there is a light-shielding part (dark part) is _mn , it is calculated by the following equation.
C _n = {(M _n −m _n ) / (M _n + m _n )} × 100

The total value T _c (%) is the four transmitted image clarity C _0.125 (%) and C when the optical comb width n (mm) is _0.125 , 0.5, 1, and 2, respectively. It is the total value of _0.5 (%), C ₁ (%), and C ₂ (%). Therefore, the maximum value that can be taken is 400%.
In order to increase the transmitted image definition, for example, a functional layer 26 (details will be described later) such as an antiglare layer or an antireflection layer having a small surface roughness may be provided on the outermost layer such as the protective film 30.

  The total light transmittance shown in JISK 7361-1: 1997 can be 42 to 45%, and it is preferable that the polarizing plate 100 is 42.5 to 44.5%.

Subsequently, each layer will be described.
(Polarizer)
The polarizer 10 includes a resin and a dichroic dye. The dichroic dye is oriented in the resin, thereby exhibiting polarization characteristics. Examples of dichroic dyes are iodine and dichroic organic dyes.

  An example of the resin is a polyvinyl alcohol resin. The polyvinyl alcohol-based resin is a saponified product of a polyvinyl acetate-based resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like can be used.

  Specific examples of the polarizer 10 include an iodine polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol resin film, and a dye polarizing film in which a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol resin film.

  Although the thickness of the polarizer 10 is not specifically limited, it can be 10 micrometers or less, can also be 8 micrometers or less, and can also be 5 micrometers or less. The lower limit of the thickness is not particularly limited, but can be 0.5 μm or more, for example.

(Protective film)
The protective films 20 and 30 are not particularly limited as long as they are transparent resin films in visible light. The protective films 20 and 30 may be films of the same material or may be films of different materials. Either one may not be present. Since the protective film 20 is closer to the liquid crystal cell than the polarizer 10, the defects of the protective film 20 are easily noticeable, but the absence of the protective film 20 can prevent defects caused by this, It is preferable that the pressure-sensitive adhesive layer 28 is in direct contact with the polarizer 10 without the protective film 20.

  Examples of the protective films 20 and 30 are acrylic resin films, acrylic resins such as methyl methacrylate resins (including methacrylic resins and acrylic resins), olefin resins, polyvinyl chloride resins, cellulose resins, Styrene resin, acrylonitrile / butadiene / styrene copolymer resin, acrylonitrile / styrene copolymer resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether Resin, polybutylene terephthalate resin, polyester resin represented by polyethylene terephthalate resin, polysulfone resin, polyethersulfone resin, polyarylate resin, polyamideimide resin, polyimide resin, epoxy Shea based resins, and oxetane-based resin.

  The protective films 20 and 30 may be films that have been stretched. For example, the protective films 20 and 30 may be uniaxially stretched products or biaxially stretched products that are stretched in two directions such as two directions perpendicular to each other.

  Said polyethylene terephthalate-type resin means the resin in which 80 mol% or more of a repeating unit is comprised with ethylene terephthalate, and may contain the structural unit derived from another copolymerization component. Other copolymer components include isophthalic acid, p-β-oxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid, 1,4-dicarboxycyclohexane; propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, bisphenol A ethylene oxide adduct, polyethylene glycol, Examples of the diol component include polypropylene glycol and polytetramethylene glycol. These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. It is also possible to use an oxycarboxylic acid such as p-oxybenzoic acid in combination with the carboxylic acid component or diol component. As other copolymerization component, a dicarboxylic acid component and / or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be used.

  The above cellulose-based resin means that some or all of the hydrogen atoms in the hydroxyl group of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, conifer pulp) are acetyl group, propionyl group and / or butyryl group. It refers to a substituted cellulose organic acid ester or cellulose mixed organic acid ester. Examples include cellulose acetates, propionic acid esters, butyric acid esters, and mixed esters thereof. Among these, a triacetyl cellulose film, a diacetyl cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, and the like are preferable.

  The above-mentioned olefin resin is, for example, a cyclic olefin resin obtained by polymerizing cyclic olefin monomers such as norbornene and other cyclopentadiene derivatives using a polymerization catalyst, or a chain olefin monomer such as ethylene and propylene. Representative is a chain olefin resin polymerized using a catalyst.

  The above cyclic olefin-based resin is, for example, a resin obtained by performing ring-opening metathesis polymerization using norbornene or its derivative obtained from cyclopentadiene and olefins by Diels-Alder reaction as a monomer, followed by hydrogenation, dicyclopentadiene Ring-opening metathesis polymerization using tetracyclododecene or its derivative obtained from olefins or methacrylic acid esters by Diels-Alder reaction as a monomer, followed by hydrogenation resin, norbornene, tetracyclododecene, etc. Similarly, a ring-opening metathesis copolymerization using two or more of these derivatives or other cyclic olefin monomers, followed by hydrogenation, a resin obtained by hydrogenation, norbornene, tetracyclododecene, or the like. Luo derivatives, such as resins obtained by addition copolymerization of an aromatic compound having a vinyl group.

  Examples of the chain olefin resin include polyethylene or the above polypropylene resin.

  The thickness of the protective films 20 and 30 is 10-200 micrometers normally, Preferably it is 20-120 micrometers, More preferably, it is 50 micrometers or less. When the thickness of the protective films 20 and 30 is increased, the effect of giving a defect to the display image is increased. In particular, when the thickness is less than 10 μm, handling tends to be difficult. Moreover, when the thickness exceeds 200 μm, the polarizing plate tends to be thick. The thickness of the protective films 20 and 30 may be the same as or different from each other.

  The protective films 20 and 30 are preferably excellent in transparency. Specifically, the protective film preferably has a total haze value measured in accordance with JIS K 7136: 2000 of 10% or less, and more preferably 7% or less. If the total haze value is larger than 10%, the white luminance is lowered and the screen may be darkened.

  The protective film 20 disposed on the liquid crystal cell side is particularly excellent in transparency and preferably does not cause internal scattering. Specifically, the protective film 20 has an internal haze value measured according to JIS K 7136: 2000 after the surface haze (external haze) is filled with a solution having a refractive index of the same level, an adhesive, or the like. Is preferably 0.5% or less, and more preferably 0.2% or less. If the inner haze value is larger than 0.2%, the black luminance is lowered, the screen is brightened during black display, and the contrast is greatly lowered. Furthermore, it is preferable not to include the protective film 20.

  A functional layer 26 may be provided on the surface of the protective film 30 disposed on the side opposite to the liquid crystal cell. The functional layer 26 may be a hard coat layer, for example, from the viewpoint of preventing scratches in an assembly process of a liquid crystal display device. The material for forming the hard coat layer (hard coat material) is preferably a material that is cured by heat or light. For example, organic hard such as organic silicone, melamine, epoxy, acrylic, urethane acrylate, etc. Coating materials; inorganic hard coat materials such as silicon dioxide; and the like. Among these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferable from the viewpoint of good adhesive strength and excellent productivity.

  The functional layer 26 may be other functional layers such as an antireflection layer and an antiglare layer instead of the hard coat layer. The functional layer 26 may be a layer having one type of function, a layer obtained by combining a plurality of layers having one type of function, or one layer may exhibit two or more types of functions. These functional layers may contain various fillers for the purpose of adjusting the refractive index, improving the flexural modulus, stabilizing the volume shrinkage, and improving heat resistance, antistatic properties, and antiglare properties, as desired. Can be contained. The functional layer 26 can contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent. In particular, by containing an antistatic agent, it is possible to prevent electrification that occurs when the film roll is unwound and friction due to friction with the roll during the transporting or laminating process, which is preferable from the viewpoint of reducing adhered foreign matter.

  By containing and / or applying an antistatic agent or an antistatic layer on the surface of the protective film 30 or in the resin, charging occurs when the film roll is unwound, or charging due to friction with the roll during the transporting or bonding process. This is preferable from the viewpoint of reducing adhered foreign matter.

(Adhesive layer)
As the adhesive layer 5, an adhesive having an epoxy resin, a urethane resin, a cyanoacrylate resin, an acrylamide resin, or the like as an adhesive component can be used. One of the adhesives preferably used in the present invention is a solventless adhesive. Solvent-free adhesives do not contain a significant amount of solvent, and contain curable compounds (such as monomers or oligomers) that are reactively cured by heating or irradiation with active energy rays (for example, ultraviolet rays, electron beams, X-rays, etc.). The adhesive layer is formed by curing the curable compound, and typically a curable compound that is reactively cured by heating or irradiation with active energy rays and a polymerization initiator (cationic polymerization initiator, anionic polymerization). Initiator, radical polymerization initiator). Among the solventless adhesives, those that are cured by cationic polymerization are preferable from the viewpoint of reactivity. Particularly, the solventless epoxy adhesive having an epoxy compound as a curable compound includes a polarizing film and an acrylic type. Since it is excellent in the adhesiveness with a resin film, and the adhesiveness with the protective film which consists of resin films other than a polarizing film and acrylic resin, it is more preferable.

  Moreover, as an adhesive agent of the adhesive bond layer 5, the water-system adhesive agent, ie, what melt | dissolved the adhesive component in water, or what disperse | distributed this to water can be mentioned. When a water-based adhesive is used, the thickness of the adhesive layer can be further reduced. Examples of the water-based adhesive include those containing a water-soluble crosslinkable epoxy resin or a hydrophilic urethane-based resin as an adhesive component.

  As a specific example of the above-described adhesive, an adhesive disclosed in JP-A-2015-38631 can be used.

  The thickness of the adhesive layer is usually 0.1 to 50 μm, preferably 0.5 μm or more, more preferably 1 μm or more. Moreover, it is preferable that it is 10 micrometers or less. If the adhesive layer is 0.5 μm or more, especially 1 μm or more, even if a foreign substance is mixed between the polarizing film and the protective film, the deformation applied to the polarizer can be suppressed and concealed so that it is not recognized as a defect by humans. This is preferable because it can be performed. If the thickness is too thick, the reaction does not proceed sufficiently, and there is a possibility that problems such as peeling will occur in the durability test.

  Application of the adhesive to the polarizer and / or the protective layer (protective film) bonded thereto can be performed by a known method, for example, casting method, Mayer bar coating method, gravure coating method, comma A coater method, a doctor blade method, a die coating method, a dip coating method, a spraying method, or the like can be used. The casting method is a method of spreading and spreading an adhesive on the surface of a film to be coated while moving it in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two. After apply | coating an adhesive agent, a polarizing film and the protective layer bonded by this are piled up, and it bonds by a nip roll etc. and bonds a film. Film bonding using nip rolls is, for example, a method in which an adhesive is applied and then pressurized with a roll or the like to spread uniformly, and after applying an adhesive, it is passed between the rolls and pressed. A method of spreading out can be employed. In this case, the material of the roll to be used may be metal or rubber. Moreover, when a film is passed between a plurality of rolls and pushed out, the plurality of rolls may be made of the same material or different materials.

  Note that surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment may be appropriately performed on the adhesion surface between the polarizer and the protective layer in order to improve adhesion. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide. Corona treatment is preferred for improving adhesion. After the corona treatment, it is preferable to include a step of static elimination before the step of applying a pressure such as a nip roll. Since the film is easily charged when the corona treatment is performed, the static elimination is performed immediately after the corona treatment. Is preferable because environmental foreign matter such as foreign matter attached on the metal roll in the process of transporting the film can be prevented and defects can be reduced.

(Other configurations)
The polarizing plate 100 can have the pressure-sensitive adhesive layer 28 on the protective film 20 directly or via another layer (such as an easy-adhesion layer, an antistatic layer, or an overcoat layer), and the protective film 20 exists. If not, the pressure-sensitive adhesive layer 28 can be provided on the polarizer 10 directly or via another layer (such as an easy-adhesion layer, an antistatic layer, or an overcoat layer). It becomes easy to attach to a cell or the like. An example of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 28 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2015-38631.

  The thickness of the pressure-sensitive adhesive layer can be about 3 to 50 μm. When the pressure-sensitive adhesive layer 28 is applied to the polarizing plate 100, the surface of the protective film 20 of the polarizing plate 100 may be subjected to a surface treatment such as a corona treatment. After the corona treatment, it is preferable to include a step of static elimination before the step of applying a pressure such as a nip roll.Because the corona treatment facilitates charging of the film, the static elimination is performed immediately after the corona treatment. It is preferable to perform this because it is possible to prevent adhesion of environmental foreign matters such as foreign matters attached on the metal roll in the process of transporting the film and to reduce defects. When the pressure-sensitive adhesive layer 28 is formed, it is usual to cover the surface of the pressure-sensitive adhesive layer 28 with a release film or the like.

(LCD panel)
FIG. 3 is a side view showing an example of a basic configuration of the liquid crystal panel 200 according to one embodiment of the present invention. A liquid crystal panel 200 shown in FIG. 3 includes a liquid crystal cell 40 and a pair of polarizing plates 100A and 100B disposed on both surfaces thereof. The polarizing plate 100B is disposed on the surface of the liquid crystal cell 40 on the backlight BL side. On the other hand, the polarizing plate 100A is disposed on the surface of the liquid crystal cell 40 opposite to the backlight BL, that is, on the viewing side. In the present embodiment, the polarizing plate 100 </ b> A on the viewing side has the functional layer 26, but the polarizing plate 100 </ b> B on the backlight side does not have the functional layer 26. The pressure-sensitive adhesive layer 28 of each polarizing plate 100A, 100B is in contact with the liquid crystal cell 40. Although not shown, the liquid crystal cell 40 has, for example, a layer structure of electrode substrate / liquid crystal layer / electrode substrate with a color filter.

  The pressure-sensitive adhesive layer 28 may be provided in advance on the polarizing plate or may be provided in advance on the surface of the liquid crystal cell. The polarization axes of the pair of polarizing plates 100 are usually crossed Nicols.

  The size of the main surface of the liquid crystal cell 40 is preferably a rectangular shape (corresponding to a 32-inch type) having a long side of 660 mm or more and a short side of 370 mm or more, and has a long side of 800 mm or more and a short side of 450 mm or more. The rectangular shape (equivalent to a 40 inch type) is preferable. Further, the size of the main surface of the liquid crystal cell 40 is preferably a rectangular shape (corresponding to a 50 inch type) having a long side of 1000 mm or more and a short side of 550 mm or more, and a long side of 1300 mm or more and a short side of 700 mm or more. A rectangular shape having a side (equivalent to a 60-inch type) is preferable.

  The thickness of the liquid crystal cell 40 is not particularly limited, but may be 3 mm or less, may be 2 mm or less, and may be 1.3 mm or less. When the thickness of the liquid crystal cell is reduced, foreign matter in the polarizing plate 100 disposed on the backlight side (back side) among the polarizing plates 100 disposed on both surfaces of the liquid crystal cell 40 becomes easy to visually recognize. Becomes prominent.

  4A and 4B are enlarged plan views of the electrode substrate with a color filter of the liquid crystal cell 40. FIG. The color filter of the liquid crystal cell 40 has a large number of pixels 42 arranged in a matrix. In FIG. 4A, each pixel 42 has a red subpixel 42r, a green subpixel 42g, and a blue subpixel 42b. As shown in FIG. 4B, each pixel 42 may have a red subpixel 42r, a green subpixel 42g, a blue subpixel 42b, and a yellow subpixel 42y.

The area of the subpixel is not particularly limited, but may be, for example, 0.1 mm ² or less, and may be 0.05 mm ² or less.

  The driving method of the liquid crystal cell 40 is not particularly limited, and examples thereof include a TN mode, a VA mode, an IPS mode, and an OCB mode. In particular, in the VA mode, since the contrast ratio is high and the black display is displayed darker and darker, a defect with white light omission caused by a defect under crossed Nicols is more noticeable. A polarizing plate is preferred. In the case of the IPS mode, since the white display becomes bright, if there is a defect accompanied by a decrease in the degree of polarization, the portion becomes darker and more conspicuous than the surroundings, so the polarizing plate of the present invention is suitable. It is.

  The polarizing plate 100 according to the present embodiment has a rectangular shape having a long side of 660 mm or more and a short side of 370 mm or more, and is therefore suitable as a polarizing plate for a liquid crystal panel having a large liquid crystal cell of 32 inches or more type. Available.

In addition, the polarizing plate according to this embodiment has an average degree of polarization of 99.98% or more, and the number of first defect portions d1 having a degree of polarization of less than 99% and a maximum diameter of 30 μm or more. 10 pieces / m ² or less. Conventionally, such a small polarizer defect has not been a problem in large liquid crystal panels. Therefore, the conventional large polarizing plate for a liquid crystal panel has a considerably large number of first defect portions d1. However, the present inventors, as 4K televisions, 8K televisions, and the like have advanced in high definition, in a large-sized liquid crystal display such as a 32-inch type or larger, the area of the subpixel is small even though the screen is large ( for example, 0.1 mm ² or less) becomes Therefore, conventionally it has found that defects of small polarizer being ignored largely affects visibility. This is particularly noticeable in scenes such as medical monitors where the user is staring at fine details. Then, by controlling the number of small defective portions to be low, visibility can be increased in a high-definition large-sized liquid crystal display device.

  Further, the defect of the polarizer is mainly that when the polarizer and the protective film are bonded, a minute foreign matter is sandwiched between them, and the laminate of the polarizer and the protective film is bonded at the time of bonding. It may be caused by the fact that foreign particles may adhere to the surface of the roll to be pressed, resulting in deformation or cracking of the polarizer. This phenomenon is considered to be particularly remarkable when the thickness of the polarizer is 10 μm or less. Therefore, the effect is particularly high when the thickness of the polarizer is 10 μm or less.

Further, when the total value T _c (%) of the transmitted image definition of the polarizing plate is 200 or more, the image is less likely to be blurred and the image definition becomes high. As a result, the defect of the polarizer is easily noticeable. Since the number of defects is low in the form, both the sharpness and the visibility are highly compatible.

(Production method of polarizing plate)
Then, an example of the manufacturing method of such a polarizing plate is demonstrated. First, a polarizer film is manufactured. Specifically, first, a base film is prepared, a resin solution such as a polyvinyl alcohol resin is applied on the base film, and the solvent is dried to form a resin layer on the base film. A primer layer can be formed in advance on the surface of the base film on which the resin layer is formed. As the substrate film, a resin film such as PET can be used. An example of the material of the primer layer is a resin obtained by crosslinking a hydrophilic resin used for a polarizer.

  Subsequently, if necessary, the amount of solvent such as moisture in the resin layer is adjusted, and then the base film and the resin layer are uniaxially stretched, and then the resin layer is dyed with a dichroic dye such as iodine. A dyeing process for adsorbing and orienting the chromatic dye to the resin layer is performed. In the dyeing step, the dichroic dye is adsorbed and oriented by immersing the resin layer in an aqueous solution of the dichroic dye. Subsequently, if necessary, a boric acid treatment step is performed in which the resin layer on which the dichroic dye is adsorbed and oriented is treated with an aqueous boric acid solution. The boric acid treatment step is performed by contacting or immersing the resin layer in a boric acid aqueous solution. Thereafter, a washing step of washing off the boric acid aqueous solution is performed. In particular, it is preferable that the cleaning here is sufficiently performed so that the foreign matters are washed away. Thereafter, a step of draining after washing (removal of water adhering to the film surface) is performed. As a draining method, an air knife, an air blower, a nip by a roll, contact with a draining bar or the like is performed. Also in this step, it is possible to remove foreign matters that adhere to or deposit on the surface. Thus, a resin layer in which the dichroic dye is adsorbed and oriented, that is, a polarizer film is manufactured. A known method can be adopted for each step.

  Furthermore, it is preferable to use the dichroic dye aqueous solution in the dyeing step, the boric acid aqueous solution in the boric acid treatment step, and the cleaning solution in the washing step while filtering out foreign substances contained in these solutions. As an example of this method, a part of the liquid is taken out from each liquid tank, the polyvinyl alcohol resin eluted from the resin layer in the liquid is precipitated by cooling, and the polyvinyl alcohol resin precipitated by filtration is collected. There is a method of returning to each tank later. Thereby, it becomes possible to prevent adhesion of foreign substances derived from the eluted polyvinyl alcohol resin.

  Uniaxial stretching of the base film and the resin layer may be performed before dyeing, may be performed during dyeing, or may be performed during boric acid treatment after dyeing. You may uniaxially stretch in each of these several steps. The base film and the resin layer may be uniaxially stretched in the MD direction (film transport direction). In that case, the base film and the resin layer may be uniaxially stretched between rolls with different peripheral speeds, or uniaxially stretched using a hot roll. May be. Moreover, you may uniaxially stretch a base film and a resin layer in TD direction (direction perpendicular | vertical to a film conveyance direction), In that case, what is called a tenter method can be used. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 4 to 8 times.

  Subsequently, a protective film is bonded to the surface of the polarizer using an adhesive. Specifically, first, a polarizer and a protective film are overlapped with each other through an adhesive layer, and the adhesive is cured or dried by a known method to obtain a base film, a polarizer, and A laminate of protective films is obtained. Thereafter, the base film is peeled from the laminate, and another protective film may be bonded to the other surface of the exposed polarizer in the same manner using an adhesive. When laminating a plurality of films via an adhesive, these layers are usually pressed with a pair of rolls so as to be brought into close contact with each other so that bubbles and the like do not enter. Preferably, each film is transported while removing electricity and bonded while removing electricity.

  When the present inventors examined, when a particulate foreign material is pinched | interposed between a polarizer and a protective film in the bonding process of a polarizer and a protective film, these laminated | multilayer film will be pressurized with a pair of roll. It has been found that the polarizer is deformed or cracked by a foreign substance to cause a defect in polarization characteristics. In the bonding step, for example, when a laminate of the support film / polarizer / adhesive / protective film is pressed with a pair of rolls, if a foreign matter such as fine particles adheres to the roller surface, the protective film It was also found that a relatively thin and soft polarizer deformed greatly during the roll even when it was covered with a support film or the like, resulting in defects in polarization characteristics.

  Therefore, in order to obtain a polarizing plate having a large polarizer with few defects as described above, the number of suspended particles in the ambient air in the bonding process of the polarizer and the protective film should be made sufficiently smaller than before. preferable. Specifically, the polarizing plate manufacturing process including the manufacturing of the polarizer is usually performed in a clean room, but a clean room dedicated to the bonding process is further provided in the clean room, and the bonding process is performed therein. Is preferred. The air cleanliness in the clean room in the bonding process is preferably ISO class 6 or higher (class 1000 or higher in the FED standard), more preferably ISO class 5 or higher (class 100 or higher in the FED standard), ISO. More preferably, it is class 4 or higher (class 10 or higher in the FED standard).

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, as described above, in the above embodiment, the protective film is provided on both surfaces of the polarizer, but the protective film may be provided only on one side. Moreover, you may have other layers other than a polarizer and a protective film.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples. In Examples,% and parts representing the content or amount used are based on weight unless otherwise specified.

Example 1
(1) Manufacture of base film A base material having a three-layer structure in which resin layers made of “Sumitomo Noblen FLX80E4” made by Sumitomo Chemical Co., Ltd. are arranged on both sides of a resin layer made of “Sumitomo Noblen W151” made by Sumitomo Chemical Co., Ltd. The film was formed by coextrusion using a multilayer extrusion molding machine to obtain a base film having a thickness ratio of 3/4/3 and a total thickness of 100 μm.

(2) Primer coating Polyvinyl alcohol (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 3 wt% aqueous solution with a solid content of 6 parts by weight as a crosslinking agent (Taoka Chemical Co., Ltd. “Smiles” 5 parts by weight of Resin 650 ") was mixed. The obtained mixed aqueous solution is coated on the corona-treated surface of the base film subjected to the corona treatment using a gravure coater and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm. did.

(3) Formation of a polyvinyl alcohol-based resin layer Polyvinyl alcohol (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0-99.0 mol%) is dissolved in 95 ° C. hot water, A polyvinyl alcohol aqueous solution having a concentration of 8% by weight was prepared. The obtained aqueous solution is coated on the primer layer using a comma coater and dried at 80 ° C. for 5 minutes, whereby a laminated film having a three-layer structure consisting of a base film / primer layer / polyvinyl alcohol resin layer is formed. Was made. The thickness of the polyvinyl alcohol-based resin layer was 10.5 μm.

(4) Stretching Step The above laminated film was stretched in the TD direction (direction perpendicular to the film transport direction) while shrinking in the MD direction (film transport direction) under hot air at 160 ° C. While controlling the MD magnification and TD magnification during the stretching process, a stretched film having a final MD magnification of 0.40 and a final TD magnification of 5.8 was obtained. In the middle of the stretching process, MD magnification is 0.71 when TD magnification is 1.6, MD magnification is 0.63 when TD magnification is 2.0, MD magnification is 0.52 when TD magnification is 3.0, and TD magnification is 4. Stretching was performed so that the MD magnification was 0.45 when 0 and the MD magnification was 0.41 when TD magnification was 5.0. Finally, a stretched film having a TD magnification of 5.8 and an MD magnification of 0.40 was produced.

(5) Dyeing process About the laminated | multilayer film which extended | stretched, the polarizing stretched film was produced in the following procedure. First, the stretched film is immersed in a dyeing solution at 30 ° C., which is an aqueous solution containing iodine and potassium iodide, for 48 seconds to dye the polyvinyl alcohol resin layer, and then an excess iodine solution is added with 10 ° C. pure water. Washed away. Next, it was immersed for 600 seconds in a 72 degreeC crosslinking solution which is the aqueous solution containing a boric acid and potassium iodide. Thereafter, it was washed with pure water at 9 ° C. for 4 seconds, and finally dried at 80 ° C. for 5 minutes to obtain a polarizing laminated film.

(6) Preparation of adhesive The polarizing plate was produced in the following procedure using the polarizing laminated film. First, 1 part by weight of a crosslinking agent (“Smiles Resin 650” manufactured by Taoka Chemical Co., Ltd.) with respect to 2 parts by weight of the solid content of a 3% by weight aqueous solution of polyvinyl alcohol (“KL-318” manufactured by Kuraray Co., Ltd.). Mixed to form an adhesive solution.

(7) Bonding of polarizer and protective film Next, a polyvinyl alcohol coated surface of the obtained polarizing laminate film and a protective film (6 μm antireflection layer provided on a 40 μm triacetyl cellulose film) The laminate in which the above-mentioned adhesive aqueous solution was interposed was introduced between a pair of rolls and pressed, and then dried at 80 ° C. for 5 minutes. Thereafter, another protective film (23 μm cycloolefin polymer) was similarly bonded to the exposed surface of the polarizer after peeling the substrate film from the laminate to obtain a polarizing plate.

The process from the base film to the bonding of the polarizer and the protective film is performed in a clean room CR1 of ISO class 6 (Class 1000 in the FED standard), and the bonding of the polarizer and the protective film is Further, it was performed in a clean room CR2 of ISO class 5 (class 100 in the FED standard) provided in the clean room CR1.
From the obtained long polarizing plate, a polarizing plate having a first size of 1215 mm × 685 mm and a polarizing plate having a second size of 1780 mm × 1000 mm were obtained. The thickness of the polarizer was 5 μm.

(Comparative Example 1)
Example 1 was performed except that the clean room CR2 was not provided and the bonding was performed in the clean room CR1. The thickness of the polarizer was 5 μm.

(Evaluation of polarizing plate)
When the average polarization degree of the polarizing plate of Example 1 and Comparative Example 1 was evaluated, it was 99.990%. When the total light transmittance of the polarizing plate was evaluated, it was 42.51%. The total value T _c (%) of the transmitted image definition was 390.

  The defect inspection of the polarizing plate of Example 1 and Comparative Example 1 was performed. A halogen lamp was used as a light source and a CCD camera was used as a camera. A polarizing plate for reference was arranged in front of the camera so as to be crossed with a polarizing plate to be inspected. An Optics image processing appearance inspection apparatus (manufactured by Kubotec Co., Ltd.) was used as the signal processing apparatus.

  In the signal processing apparatus, the brightness serving as a baseline indicating a normal polarization region was set to 0, and 32768 gradations were set on the brighter white side. Preliminary experiments show that the first defect portion having a degree of polarization of less than 99% and a maximum diameter of 30 μm or more has a gradation peak of 14000 or more, and the second defect portion having a polarization degree of less than 99% and a maximum diameter of 20 μm or more. It was confirmed that the tone peak of 12,000 or more. Then, the number density of the first defect portion and the second defect portion was determined based on the number density of the region having a peak of 14000 gradations or more and the number density of the region having a peak of 12000 gradations or more, respectively.

  In addition, although the part which has the defect (1st defect part) of the gradation peak 14225 was not able to be confirmed with the naked eye, when observed with the microscope, the elliptical defect of 32 micrometers of major axes and 25 micrometers of minor axes could be confirmed. The portion having the gradation peak 12131 (second defect portion) having a defect could not be confirmed with the naked eye, but when observed with a microscope, a polygonal defect having a major axis of 21 μ and a minor axis of 19 μ could be confirmed.

The results are shown in Table 1.

(Visibility evaluation)
(Liquid crystal panels A and B)
From a liquid crystal display device (Sony liquid crystal television, model: BRAVIA KD-55X8500, A liquid crystal panel screen size: 55 inches, VA mode, liquid crystal cell thickness: 1.1 mm, subpixel area: 0.02 mm ² ) After removing the liquid crystal panel and removing all the optical film disposed on the viewing side of the liquid crystal panel, the exposed glass surface of the liquid crystal cell was wiped with water and wiped three times with Ben cotton soaked in alcohol. The polarizing plate of the 1st magnitude | size obtained in Example 1 was bonded together through the acrylic adhesive (thickness: 20 micrometers) on the glass surface of the visual recognition side of this liquid crystal cell, and the liquid crystal panel A was produced. The polarizing plate was such that the absorption axis direction of the polarizing plate was substantially parallel to the long side direction of the liquid crystal cell. Similarly, a liquid crystal panel B was prepared using the first size polarizing plate prepared in Comparative Example 1.

(Liquid crystal panels C and D)
Using a liquid crystal display device (sharp liquid crystal television, model: NEXT “80XU30”, liquid crystal panel screen size: 80 inches, VA mode, liquid crystal cell thickness 1.1 mm, subpixel area: 0.03 mm ² ) The liquid crystal panels C and D were evaluated by bonding the polarizing plates of the second size obtained in Example 1 and Comparative Example 1 in the same manner.

(Evaluation)
Visibility was evaluated about obtained liquid crystal panel AD. In the evaluation of visibility, a video with many relatively dark images was used, and humans visually evaluated the appearance of the images. The case where the image was clearly observed was rated as ◯, the case where white light omission was observed for a while, Δ, and the case where white light loss was observed as x. The results are shown in Table 2.

  DESCRIPTION OF SYMBOLS 5 ... Adhesive layer, 10 ... Polarizer, 20, 30 ... Protective film, 40 ... Liquid crystal cell, 100 ... Polarizing plate, 200 ... Liquid crystal panel.

Claims (8)

A polarizing plate comprising a polarizer and a protective film disposed on the polarizer,
The outer shape of the polarizing plate is a rectangle having a long side of 660 mm or more and a short side of 370 mm or more,
The average polarization degree of the polarizing plate is 99.98% or more,
A polarizing plate having a degree of polarization of less than 99% and a maximum number of defective portions of 30 μm or more of 10 / m ² or less.   The polarizing plate according to claim 1, wherein an outer shape of the polarizing plate is a rectangle having a long side of 800 mm or more and a short side of 450 mm or more.   The polarizing plate according to claim 1, wherein the polarizer has a thickness of 10 μm or less. The polarizing plate according to any one of claims 1 to 3, wherein the number of defective portions having a degree of polarization of less than 99% and a maximum diameter of 20 µm or more is 20 pieces / m ² or less. The polarizing plate as described in any one of Claims 1-4 which is an object for liquid crystal cells whose area of a sub pixel is 0.1 mm < ² > or less.   The total value (%) of transmitted image clarity (%) for four types of optical combs having a width of 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm is 200 or more. The polarizing plate of any one.   A liquid crystal cell and a pair of polarizing plates attached to both surfaces of the liquid crystal cell are provided. One polarizing plate is also the polarizing plate according to any one of claims 1 to 6, and the other polarizing plate is also used. Item 7. A liquid crystal panel, which is the polarizing plate according to any one of items 1 to 6.   The liquid crystal panel according to claim 7, wherein a thickness of the liquid crystal cell is 3 mm or less.

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