KR20180054642A - Polarizer plate and liquid crystal panel - Google Patents

Abstract

A polarizing plate or the like capable of realizing a large liquid crystal panel having excellent visibility is provided. The polarizing plate 100 includes a polarizer 10 and a protective film 20. The external shape of the polarizing plate 100 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 100 is 99.98% or more. The number of defects having a degree of polarization of less than 99% and a maximum diameter of 30 mu m or more is 10 / m < 2 >

Description

Polarizer plate and liquid crystal panel

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

BACKGROUND ART A polarizing plate for a liquid crystal panel having a polarizer and a transparent protective film has heretofore been known.

Patent Document 1: JP-A-2012-58381

In recent years, the liquid crystal panel has been enlarged, high definition has been advanced, and particularly, the number of cases where the liquid crystal panel gazes at a fine place such as a medical monitor has been increased. Therefore, it is required to further improve the visibility of the liquid crystal panel.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarizing plate or the like capable of realizing a large liquid crystal panel having excellent visibility.

The inventors of the present invention have discovered that a defective portion of a small polarizer, which has been neglected in the past, greatly affects the visibility of a large liquid crystal panel, and has reached the present invention.

A polarizing plate according to the present invention comprises 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 polarizing plate has an average degree of polarization of 99.98% or more, a degree of polarization of less than 99%, and a number of defects having a maximum diameter of 30 탆 or more 10 pieces / m 2 or less.

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

Here, the outer shape of the polarizer may be a rectangle having a long side of 800 mm or more and a short side of 450 mm or more. This is preferable because it can be applied to a liquid crystal panel of a larger size.

Further, the thickness of the polarizer may be 10 占 퐉 or less.

When the polarizer is thin, the deformation portion is liable to become relatively large in the case of defects due to the foreign matter being mixed between the polarizer and the protective film as compared with the case where the polarizer is thick, and also, In the case of defects, the deformation of the polarizer is liable to remain as compared with the case where the polarizer is thick, so that the effect of the present invention is enhanced.

The polarizing plate may have a degree of polarization of less than 99%, and the number of defects having a maximum diameter of 20 탆 or more may be 20 / m 2 or less. This further improves the visibility.

It is preferable that the polarizing plate is adhered to a liquid crystal cell having an area of sub pixels of 0.1 mm 2 or less. The effect is enhanced in a liquid crystal panel having a large screen and a small sub pixel area.

The polarizing plate may have a total combined value (%) of transmission phase clarity (%) of four types of optical combs of 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm of 200 or more. In a high-definition display, in many cases, a polarizing plate having a high transparency sharpness is combined to take advantage of high definition, and defects of the polarizing plate are likely to appear clearly because an image is not easily blurred. However, according to the present invention, it is possible to realize a liquid crystal panel in which defects are not conspicuous and high definition.

The liquid crystal panel according to the present invention may include a liquid crystal cell and a pair of polarizers bonded to both surfaces of the liquid crystal cell. One of the polarizers is the polarizer of the present invention, and the other polarizer is also the Polarizer.

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

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

According to the present invention, a polarizing plate capable of realizing a large liquid crystal panel having excellent visibility is provided.

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

An embodiment of the present invention will be described with reference to the drawings.

(Polarizer)

1 is a schematic sectional view showing an example of a basic layer structure of a polarizing plate 100 according to an embodiment of the present invention. The polarizing plate 100 includes a polarizer 10, an adhesive layer 5 on one side of the polarizer 10 And a protective film 30 adhered to the other side of the polarizer 10 through an adhesive layer 5. The protective film 20 is bonded to the other side of the polarizer 10 through the adhesive layer 5, The polarizing plate 100 is usually adhered to the liquid crystal cell through a pressure-sensitive adhesive layer 28, for example, on the side opposite to the adhesive layer 5 of the protective film 20. An adhesive layer, an antistatic layer, an overcoat layer, or the like may be formed directly on the surface opposite to the protective film 30 of the polarizer 10 without using the protective film 20, The pressure sensitive adhesive layer 28 may be formed through the pressure sensitive adhesive layer 28 and adhered to the liquid crystal cell through the pressure sensitive adhesive layer 28. By not forming the protective film 20 in this manner, it is possible to prevent the occurrence of defects attributable to the protective film 20. [

2 is a view of the polarizing plate 100 viewed in a direction perpendicular to its principal surface. The outer shape of the polarizing plate 100 is rectangular. 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 type screen). This rectangle may have a long side A of 800 mm or more and a short side B of 450 mm or more (equivalent to a 40-inch screen), and a long side A of 1000 mm or more and a short side B of 550 mm or more, (Corresponding to a 50-inch type screen), and may have a longer side A of 1300 mm or more and a shorter side B of 700 mm or more (equivalent to a 60-inch type screen).

In the present specification, the rectangle includes those having R chamfer or C chamfer about 5 mm on both sides of the corner (C). Further, the rectangle includes a square.

The upper limit of the size of the rectangle is not particularly limited, but the size of the long side A may be 3000 mm or less.

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

The number of the first defects d1 in the polarizing plate 100 having a degree of polarization of less than 99% and a maximum diameter of 30 mu m or more is 10 / m < 2 > The number of first defects d1 is preferably 5 / m 2 or less, more preferably 3 / m 2 or less. Such a defect may be a defect showing a value of the degree of polarization of less than 99% due to a low degree of polarization, and a degree of 0% as a degree of polarization.

The number of the second defects d2 having a degree of polarization of less than 99% and a maximum diameter of 20 m or more may be 20 / m 2 or less, 10 m 2 / m 2 or less and 5 m 2 / m 2 or less in the polarizing plate 100 . Since the first defective portion d1 satisfies the requirements of the second defective portion d2, the number of the second defective portions d2 includes the number of the first defective portions d1.

The polarizing plate 100 has a transmittance sharpness measurement C _{n (n)} in each of four types of optical combs of 0.125 mm, 0.5 mm, 1.0 mm and 2.0 mm in the transmission phase sharpness measurement test prescribed in JIS K 7374 total conformity of the (%) T _c (%) is 200 or more may be, may be 300 or more.

The transmission phase clarity measurement test measures the light amount of the transmitted light of the polarizing plate through an optical comb having a width n (mm) perpendicular to the light ray axis of the transmitted light and moving at a speed of 10 mm / min. Specifically, the measurement is carried out using a mismatch measuring instrument (manufactured by Suga Test Instruments Co., Ltd.). The mismatch measuring device is a device in which the light transmitted through the slit is made to be a parallel light beam and is incident on the polarizing plate 100 from the side opposite to the protective film 30 (on the side opposite to the liquid crystal cell) An optical device for vertically incident light, an optical device for detecting the transmitted light through a moving optical comb, and a measuring device for recording fluctuation of the detected light quantity as a waveform. In the optical comb, the ratio of the width of the name portion to the width of the dark portion is 1: 1, and the width n (mm) is set to 0.125, 0.5, 1, and 2, and the moving speed is 10 mm / min.

The transmittance sharpness C _n (%) is defined as M _n , where M _n is the maximum value of the transmitted light when the transmission portion (list portion) of the optical comb is present on the optical axis in the transmission phase sharpness measurement test, When the minimum value of the amount of transmitted light when there is a dark portion is m _n , it is calculated by the following expression.

C _n = {(M _n -m _n ) / (M _n + m _n )} × 100

Total conformity T _c (%) is, of an optical comb width of n (mm) is each of 0.125, 0.5, 1, four transmission image clarity C _0.125 (%), C _0.5 in the case of _{2 (%), C 1 (} % ) And C ₂ (%), so the maximum value that can be taken is 400%.

In order to enhance the clarity of the transmitted image, for example, a functional layer 26 (described later in detail) such as an antiglare layer or antireflection layer having a small surface roughness may be formed on the outermost layer of the protective film 30 or the like.

The polarizing plate 100 preferably has a total light transmittance of 42 to 45% as shown in JIS K 7361-1: 1997, and is preferably 42.5 to 44.5%.

Next, 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-based resin. The polyvinyl alcohol resin is a saponified polyvinyl acetate resin. Examples of the polyvinyl acetate-based 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, unsaturated sulfonic acids, and the like. In addition, the polyvinyl alcohol resin may be modified, and for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral and the like may be used.

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

The thickness of the polarizer 10 is not particularly limited, but may be 10 占 퐉 or less, 8 占 퐉 or less, or 5 占 퐉 or less. The lower limit of the thickness is not particularly limited, but may be 0.5 mu m 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. Also, either one may be unnecessary. Since the protective film 20 is closer to the liquid crystal cell side than the polarizer 10, defects of the protective film 20 become conspicuous. However, the absence of the protective film 20 prevents defects caused by the protective film 20 It is preferable that the protective film 20 is not provided and that the pressure sensitive adhesive layer 28 is in direct contact with the polarizer 10. [

Examples of the protective films 20 and 30 include an acrylic resin film (including a methacrylic resin and an acrylic resin) such as an acrylic resin film and a methyl methacrylate resin, an olefin resin, a polyvinyl chloride resin, a cellulose resin , Styrene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyamide resin, polyacetal resin, polycarbonate Based resin, polyether sulfone-based resin, polyarylate-based resin, polyamide-based resin, polyamide-based resin, polyamide-based resin, polyamide- Based resin, a mid-based resin, a polyimide-based resin, an epoxy-based resin and an oxetane-based resin.

The protective films 20 and 30 may be films subjected to stretching treatment. For example, the protective films 20 and 30 may be uniaxially stretched or two-directionally stretched biaxially stretched in two directions perpendicular to each other.

The polyethylene terephthalate resin means a resin in which 80 mol% or more of the repeating units are composed of ethylene terephthalate, and may contain a constituent unit derived from another copolymerizable component. Examples of other copolymerization components include isophthalic acid, p-β-oxyethoxybenzoic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4- , Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid and 1,4-dicarboxycyclohexane; Diol components such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acid components and diol components may be used in combination of two or more as necessary. It is also possible to use an oxycarboxylic acid such as p-oxybenzoic acid together with the carboxylic acid component or the diol component. As the 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-mentioned cellulose resin is a resin in which a part or all of the hydrogen atoms in the hydroxyl group of cellulose obtained from the raw cellulose such as cotton linters and wood pulp (hardwood pulp, softwood pulp) and the like are substituted with an acetyl group, a propionyl group and / or a butyryl group , A cellulose organic acid ester, or a cellulose mixed organic acid ester. Examples thereof include acetate esters of cellulose, propionic acid esters, butyric acid esters, and mixed esters thereof. Among them, triacetylcellulose film, diacetylcellulose film, cellulose acetate propionate film and cellulose acetate butyrate film are preferable.

The olefin-based resin can be produced, for example, by reacting a cyclic olefin-based resin obtained by polymerizing a cyclic olefin monomer such as norbornene and other cyclopentadiene derivatives with a polymerization catalyst, or a chain-like olefin monomer such as ethylene and propylene, Chain olefin-based resin obtained by polymerization using a polyolefin-based catalyst.

The cyclic olefin-based resin is, for example, a resin obtained by ring-opening metathesis polymerization using norbornene or a derivative thereof obtained by a Diels-Alder reaction from cyclopentadiene and olefins as monomers, followed by hydrogenation, Ring-opening metathesis polymerization is carried out using dicyclopentadiene, tetracyclododecene or a derivative thereof obtained from a diester-alder reaction from olefins or methacrylic acid esters as a monomer, and a resin obtained by subsequent hydrogenation, A ring-opening metathesis copolymerization is carried out by using two or more kinds of cyclic olefin monomers such as boron, tetracyclododecene, derivatives thereof, or other cyclic olefin monomers, followed by hydrogenation of the resin, norbornene and tetracyclo Dodecene, or derivatives thereof, with a vinyl group Include resins obtained by addition-copolymerizing an aromatic compound and the like.

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

The thickness of the protective films 20 and 30 is usually 10 to 200 占 퐉, preferably 20 to 120 占 퐉, more preferably 50 占 퐉 or less. If the thickness of the protective films 20 and 30 is increased, the influence of the defects on the display image is increased. Particularly, when the protective films 20 and 30 are less than 10 탆, the protective films 20 and 30 tend to be difficult to handle. When the thickness exceeds 200 占 퐉, the polarizing plate tends to be thickened. The thicknesses of the protective films 20 and 30 may be the same or different.

The protective films 20 and 30 are preferably excellent in transparency. Specifically, the total haze value of the protective film measured in accordance with JIS K 7136: 2000 is preferably 10% or less, more preferably 7% or less. If the total haze value is larger than 10%, the white luminance may be lowered and the screen may become dark, which is not preferable.

It is preferable that the protective film 20 disposed on the liquid crystal cell side has excellent transparency and does not cause internal scattering. Specifically, the protective film 20 is formed by filling a surface haze (external haze) with a solution having a refractive index of the same level, a pressure-sensitive adhesive or the like, and then measuring an internal haze value measured according to JIS K 7136: 2000 of 0.5% , More preferably 0.2% or less. When the internal haze value is larger than 0.2%, the black luminance is lowered and the screen brightens at the time of black display, and the contrast is greatly lowered, which is not preferable. Further, it is preferable that no protective film 20 is provided.

The functional layer 26 may be formed on the surface of the protective film 30 disposed on the opposite side of the liquid crystal cell. The functional layer 26 may be a hard coat layer, for example, from the viewpoint of prevention of scratching in a process of assembling a liquid crystal display device or the like. The material (hard coat material) for forming the hard coat layer is preferably a material which is cured by heat or light, and examples thereof include organic hard coat materials such as organosilicone type, melamine type, epoxy type, acrylic type and urethane acrylate type; Inorganic hard coat materials such as silicon dioxide; And the like. Of these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferable from the viewpoint of good adhesion and high productivity.

The functional layer 26 may be not a hard coat layer but may be another functional layer such as an antireflection layer or an antiglare layer. The functional layer 26 may be a layer having one function or a layer in which a plurality of layers having one function are combined, and one layer may exhibit two or more functions. These functional layers may contain various fillers for the purpose of adjusting the refractive index, improving the bending elastic modulus, stabilizing the volume shrinkage ratio, and improving heat resistance, antistatic property, and antistatic property. The functional layer 26 may 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 the charging caused by the coarsening of the film roll, the charging caused by the friction between the rolls during the conveying or bonding process, and is preferable from the viewpoint of reducing adhering foreign matter.

By containing and / or applying an antistatic agent or an antistatic layer in the surface or the resin of the protective film 30, it is possible to prevent the charging caused by the coarsening of the film roll or the charging caused by the friction with the roll during the conveying or bonding process And is preferable from the viewpoint of reducing adhering foreign matter.

(Adhesive layer)

As the adhesive layer 5, an adhesive containing 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 an adhesive for a solventless formulation. The adhesive for the non-solvent formulation includes a curing compound (such as a monomer or oligomer) that does not contain a significant amount of solvent but reacts and cures by heating or irradiation of an active energy ray (for example, ultraviolet ray, electron beam or X- (Curing polymerization initiator, anion polymerization initiator, and radical polymerization initiator) which is cured by heating or irradiation of an active energy ray, and a polymerization initiator, . Among the adhesives of the solventless form, it is preferable to cure by cationic polymerization from the viewpoint of reactivity, and in particular, the epoxy-based adhesive of the solventless form containing an epoxy compound as a curable compound is excellent in adhesiveness between a polarizing film and an acrylic resin film, Because the film is excellent in adhesion of a protective film made of a resin film other than acrylic resin.

As an adhesive for the adhesive layer 5, an aqueous adhesive, that is, an adhesive component may be dissolved in water, or the adhesive may be dispersed in water. By using an aqueous adhesive, 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 specific examples of the above-mentioned adhesives, the adhesives disclosed in JP-A-2015-38631 can be used.

The thickness of the adhesive layer is usually 0.1 to 50 占 퐉, preferably 0.5 占 퐉 or more, and more preferably 1 占 퐉 or more. Further, it is preferably 10 m or less. If the adhesive layer is 0.5 占 퐉 or more, particularly 1 占 퐉 or more, deformation to be imparted to the polarizer can be suppressed even if a foreign matter is mixed between the polarizing film and the protective film, desirable. If the thickness is excessively large, the reaction does not proceed sufficiently, and there is a possibility that problems such as peeling may occur in the durability test.

The application of the adhesive to the polarizer and / or the protective layer (protective film) bonded to the polarizer can be carried out by a known method. For example, a softening method, a Meyer bar coating method, a gravure coating method, a comma coater method, , A die coating method, a dip coating method, a spraying method, and the like. The flexible method is a method in which a film to be coated is moved in a substantially vertical direction, in a substantially horizontal direction, or in an inclined direction therebetween, and an adhesive is caused to flow down on the surface of the film to be spread. After the adhesive is applied, the polarizing film and the protective layer bonded to the polarizing film are polymerized, and the film is sandwiched by a nip roll or the like. The bonding of the film using the nip roll can be carried out by, for example, a method of spreading an adhesive and then spreading it uniformly with a roll or the like, a method of spreading the adhesive by spreading it between a roll and a roll, can do. In this case, the material of the roll used may be metal or rubber. Further, when the film is spread between a plurality of rolls so as to spread, the plurality of rolls may be the same material or different materials.

The surface of adhesion between the polarizer and the protective layer may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, frame (flame) treatment, saponification treatment, etc., in order to improve adhesion. As the saponification treatment, there may be mentioned a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide. Corona treatment is preferred for the improvement of the adhesion. After the corona treatment, it is preferable to include a step of removing static electricity before the step of applying pressure such as a nip roll. When the corona treatment is carried out, the film is liable to be charged. Therefore, the removal of the environmental foreign matter such as the foreign matter adhered on the metal roll during the process of transporting the film is carried out immediately after the corona treatment, It is preferable.

(Other configurations)

The polarizing plate 100 can have the pressure-sensitive adhesive layer 28 directly on the protective film 20 or through a separate layer (the adhesive layer, the antistatic layer, the overcoat layer, etc.) It is possible to have the pressure sensitive adhesive layer 28 directly on the polarizer 10 or through a separate layer (the adhesive layer, the antistatic layer, the overcoat layer, etc.), and in this case, the polarizing plate 100 is bonded to the liquid crystal cell or the like . Examples of the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer 28 are disclosed in, for example, Japanese Patent Application Laid-Open No. 2015-38631.

The thickness of the pressure-sensitive adhesive layer may be about 3 to 50 mu m. 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 surface treatment such as corona treatment. After the corona treatment, it is preferable to include a step of discharging before the step of applying the pressure such as the nip roll. Since the film is easily charged by the corona treatment, the discharge is immediately performed after the corona treatment , Adherence of environmental foreign matter such as foreign matter adhered on the metal roll in the process of transporting the film is prevented, and defects can be reduced. In the case of forming the pressure-sensitive adhesive layer 28, the surface of the pressure-sensitive adhesive layer 28 is usually covered with a peeling film or the like.

(Liquid crystal panel)

3 is a side view showing an example of the basic configuration of the liquid crystal panel 200 according to the embodiment of the present invention. The liquid crystal panel 200 shown in Fig. 3 has a liquid crystal cell 40 and a pair of polarizers 100A and 100B arranged on both sides thereof. The polarizing plate 100B is disposed on the backlight BL side of the liquid crystal cell 40. [ On the other hand, the polarizing plate 100A is disposed on the side of the liquid crystal cell 40 opposite to the backlight BL, that is, on the side of the viewer side. In the present embodiment, the polarizing plate 100A on the viewing side has the functional layer 26, but the polarizing plate 100B on the backlight side does not have the functional layer 26. [ The pressure sensitive adhesive layer 28 of each of the polarizers 100A and 100B is in contact with the liquid crystal cell 40. [ Although not shown, the liquid crystal cell 40 has a layer structure of an electrode substrate / liquid crystal layer / electrode substrate with a color filter.

The pressure-sensitive adhesive layer 28 may be previously formed on the polarizing plate or on the surface of the liquid crystal cell. The polarization axis of the pair of polarizing plates 100 is usually Cross-Nicol.

The size of the main surface of the liquid crystal cell 40 is preferably a rectangular shape (equivalent to a 32-inch shape) having a long side of 660 mm or more and a short side of 370 mm or more, and a rectangular shape having a long side of 800 mm or more and a short side of 450 mm or more 40 inches). The size of the main surface of the liquid crystal cell 40 is preferably a rectangular shape (equivalent to 50 inches) having a long side of at least 1000 mm and a short side of at least 550 mm, and a long side of at least 1,300 mm and a short side of at least 700 mm (Equivalent to a 60-inch type).

The thickness of the liquid crystal cell 40 is not particularly limited, but may be 3 mm or less, 2 mm or less, or 1.3 mm or less. When the thickness of the liquid crystal cell is reduced, foreign substances in the polarizing plate 100 disposed on the backlight side (back side) of the polarizing plate 100 disposed on both sides of the liquid crystal cell 40 are easily visible, It becomes.

4 (a) and 4 (b) are enlarged plan views of a color filter-equipped electrode substrate of the liquid crystal cell 40. Fig. The color filter of the liquid crystal cell 40 has a plurality of pixels 42 arranged in a matrix form. In Figure 4 (a), each pixel 42 has a red subpixel 42r, a green subpixel 42g, and a blue subpixel 42b. Each pixel 42 may have a red subpixel 42r, a green subpixel 42g, a blue subpixel 42b, and a yellow subpixel 42y, as shown in FIG. 4 (b).

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. Among them, in the VA mode, since the contrast ratio is high and the black display is displayed more darkly and densely, it is more noticeable if there are some defects accompanied by white light leakage caused by defects under Cross Nicol, Is suitable. Further, in the case of the IPS mode, since the white display is brighter, if there is a defect accompanied by a decrease in the degree of polarization, the portion becomes darker and becomes more noticeable as compared with the surroundings, so that the polarizing plate of the present invention is suitable.

According to the polarizing plate 100 of the present embodiment, since it has a long side of 660 mm or more and a short side of 370 mm or more, it can be suitably used as a polarizing plate of a liquid crystal panel having a large liquid crystal cell of 32 inches or more.

The polarizing plate according to the present embodiment has a number of first defects d1 having an average degree of polarization of 99.98% or more and a degree of polarization of less than 99% and a maximum diameter of 30 m or more of 10 / m 2 or less. Conventionally, defects of such a small polarizer have not been a problem in a large liquid crystal panel. Therefore, in the conventional polarizing plate for a large liquid crystal panel, the number of the first defects d1 is considerably large. However, the inventors of the present invention have found that, in the case of a large-sized liquid crystal display such as a 4-inch TV or an 8K television and the like, the area of the subpixel is small (for example, 0.1 mm 2 or less) It has been found that defects of small polarizers, which had conventionally been ignored, have a great influence on visibility. This is particularly noticeable when the image is looked up to a fine spot such as a medical monitor. By controlling the number of these small defects to be low, the visibility of a high-definition large-size liquid crystal display device can be increased.

The defects of the polarizer are mainly caused by the fact that minute foreign substances enter between the polarizer and the protective film when they are bonded together and that foreign substances adhere to the surface of the roll which presses the laminate of the polarizer and the protective film at the time of bonding It is considered that the polarizer is deformed or cracked. 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.

If the total combined value T _c (%) of the transmission image clarity of the polarizing plate is 200 or more, the image becomes difficult to be blurred and the sharpness of the image becomes high. As a result, the defects of the polarizer are also conspicuous. In this embodiment, Because it is low, sharpness and visibility are highly compatible.

(Production method of polarizing plate)

Next, an example of a method for producing such a polarizing plate will be described. First, a polarizer film is produced. Specifically, first, a base film is prepared, a solution of a resin such as polyvinyl alcohol resin is coated on the base film, and the solvent is dried to form a resin layer on the base film. A primer layer may be formed on the surface of the base film on which the resin layer is formed. As the base 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, the amount of a solvent such as water in the resin layer is adjusted as required. Thereafter, the base film and the resin layer are uniaxially stretched. Then, the resin layer is dyed with a dichroic dye such as iodine to obtain a dichroic dye And a dyeing step of adsorbing orientation to the resin layer is performed. In the dyeing step, the resin layer is immersed in an aqueous solution of a dichroic dye to adsorb and align the dichroic dye. Subsequently, a boric acid treatment step is carried out in which a resin layer in which a dichroic dye is adsorbed and oriented, if necessary, is treated with an aqueous solution of boric acid. The boric acid treatment step is carried out by contacting or immersing the resin layer in an aqueous solution of boric acid. Thereafter, a cleaning step for washing the aqueous solution of boric acid is carried out. Particularly, it is preferable that the cleaning is performed sufficiently to wash the foreign matter. Thereafter, dehydration (removal of water adhering to the surface of the film) after cleaning is performed. The dehydration method is performed by an air knife, an air blower, a nip by a roll, a dehydration bar contact, or the like. In this process, it is also possible to remove foreign substances adhered to or deposited on the surface. Thus, a film of a resin layer in which a dichroic dye is adsorbed and oriented, that is, a polarizer, is produced. A known method can be adopted for each step.

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 liquid in the cleaning step while filtering the foreign matters contained in these liquids by filtration. 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, the polyvinyl alcohol resin precipitated by filtration is collected, There is a way to return to the group. This makes it possible to prevent the foreign matter derived from the eluted polyvinyl alcohol-based resin from adhering.

The uniaxial stretching of the base film and the resin layer may be performed before dyeing, during dyeing, or during boric acid treatment after dyeing. And may be uniaxially stretched in each of these plural steps. The base film and the resin layer may be uniaxially stretched in the MD direction (film transport direction). In this case, uniaxial stretching may be performed between rolls different in the main speed, or uniaxially stretching may be performed using a heat roll. Further, the base film and the resin layer may be uniaxially stretched in the TD direction (direction perpendicular to the film transport direction), and in that case, the so-called tenter method can be used. In addition, dry stretching may be performed in the atmosphere, or wet stretching may be performed in a state of being swollen with a solvent. The stretching magnification is usually about 4 to 8 times.

Subsequently, a protective film is bonded to the surface of the polarizer using an adhesive. Specifically, a polarizer and a protective film are first polymerized through a layer of an adhesive, and the adhesive is cured or dried by a known method to obtain a laminate of a base film, a polarizer and a protective film. Thereafter, the base film is peeled from the laminate, and another protective film is bonded to the other surface of the exposed polarizer using an adhesive. When a plurality of films are to be polymerized through an adhesive, these layers are usually pressed together by a pair of rolls so that bubbles or the like are prevented from entering. Preferably, each film is transported while discharging, and is bonded while discharging.

As a result of investigations made by the present inventors, it has been found that, when a particle type foreign substance is sandwiched between a polarizer and a protective film in a process of bonding a polarizer and a protective film, when the laminated film is pressed by a pair of rolls, , And found that defects in the polarization characteristics occur. Further, in the joining step, for example, when a layered product of the support film / polarizer / adhesive / protective film is pressed with a pair of rollers, if foreign substances such as minute particles adhere to the roller surface, , It has been found that a relatively thin and soft polarizer is largely deformed at the time of pressing the roll, resulting in defects in the polarization characteristics.

Therefore, in order to obtain a polarizing plate having a polarizer having a large size and a small defect as described above, it is preferable that the number of suspended particles in the environmental air in the process of bonding the polarizer and the protective film is sufficiently smaller than in the prior art. Concretely, normally, the production process of the polarizing plate including the production of the polarizer is performed in the clean room, but it is preferable to further provide a clean room dedicated for the bonding process in the clean room, and perform the bonding process therein. The cleanliness of 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 Class 4 Or more (Class 10 or higher in the FED standard).

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, as described above, in the above embodiment, the protective film is formed on both surfaces of the polarizer, but a protective film may be formed only on one side. Further, it may have layers other than the polarizer and the protective film.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In the examples,% and parts indicating the content or amount are based on weight unless otherwise specified.

(Example 1)

(1) Production of base film

Layer structure in which a resin layer made of " Sumitomonoblen FLX80E4 " manufactured by Sumitomo Chemical Co., Ltd. was arranged on both sides of a resin layer made of " Sumitomonoblen W151 ", manufactured by Sumitomo Chemical Co., To form a base film having a total layer thickness ratio of 3/4/3 and a total thickness of 100 占 퐉.

(2) Primer coating

5 parts by weight ("Sumirejin 650" manufactured by Daoka Chemical Industrial Co., Ltd.) was added as a crosslinking agent to 6 parts by weight of a solid content of 3% by weight aqueous solution of polyvinyl alcohol ("Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Mixed well. The resulting mixed aqueous solution was coated on the corona-treated surface of the substrate film subjected to the corona treatment using a gravure coater and dried at 80 DEG C for 10 minutes to form a primer layer having a thickness of 0.2 mu m.

(3) Formation of a polyvinyl alcohol-based resin layer

A polyvinyl alcohol aqueous solution having a concentration of 8% by weight was prepared by dissolving polyvinyl alcohol ("PVA124" manufactured by Kuraray Co., Ltd., average degree of polymerization: 2400, average saponification degree: 98.0 to 99.0 mol%) in hot water at 95 ° C. The obtained aqueous solution was coated on the primer layer using a comma coater and dried at 80 ° C for 5 minutes to produce a laminated film having a three-layer structure composed of a base film / primer layer / polyvinyl alcohol resin layer. The thickness of the polyvinyl alcohol-based resin layer was 10.5 占 퐉.

(4) Drawing process

The 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 캜. A stretched film having a final MD magnification of 0.40 and a final TD magnification of 5.8 was obtained while controlling the MD magnification and the TD magnification during the drawing process. When the TD magnification was 1.6, the MD magnification was 0.71. When the TD magnification was 2.0, the MD magnification was 0.63. When the TD magnification was 3.0, the MD magnification was 0.52. When the TD magnification was 4.0, the MD magnification was 0.45. When the TD magnification was 5.0, , And finally a stretched film having a TD magnification of 5.8 and an MD magnification of 0.40 was produced.

(5) Dyeing process

With respect to the stretched laminated film, a polarizing stretched film was produced in the following order. First, the stretched film was dipped in a dyeing solution at 30 占 폚, which is an aqueous solution containing iodine and potassium iodide, for 48 seconds to dye the polyvinyl alcohol-based resin layer, and then the excess iodine solution was washed with pure water at 10 占 폚. Next, the substrate was immersed in a crosslinking solution at 72 DEG C for 600 seconds as an aqueous solution containing boric acid and potassium iodide. Thereafter, the film was washed with pure water at 9 占 폚 for 4 seconds, and finally dried at 80 占 폚 for 5 minutes to obtain a polarizing laminated film.

(6) Preparation of adhesive

Using a polarizing laminated film, a polarizing plate was produced in the following order. First, 1 part by weight of a crosslinking agent (" Sumirejin 650 ", manufactured by Daoka Chemical Industry Co., Ltd.) was added to 2 parts by weight of a solid content of a 3% by weight aqueous solution of polyvinyl alcohol (KL- And mixed to prepare an adhesive solution.

(7) Bonding of polarizer to protective film

Next, a layered product obtained by interposing the above-described aqueous adhesive solution between the obtained polyvinyl alcohol coated surface of the obtained polarizing laminated film and a protective film (one having a 6 占 퐉 antireflection layer provided on a 40 占 퐉 triacetylcellulose film) Was introduced between a pair of rolls and pressed, and then dried at 80 DEG C for 5 minutes. Thereafter, the base film was peeled from the laminate, and another protective film (cycloolefin polymer of 23 mu m) was similarly bonded to the surface of the polarizer exposed to obtain a polarizing plate.

The process from the base film to the bonding of the polarizer and the protective film is carried out 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 in the clean room (Class 2 in the FED standard) in the clean room CR2 installed in the CR1.

A polarizing plate of a first size of 1215 mm x 685 mm and a polarizing plate of a second size of 1780 mm x 1000 mm were obtained from the obtained long polarizing plate. The thickness of the polarizer was 5 탆.

(Comparative Example 1)

The same procedure as in Example 1 was carried out except that the clean room CR2 was not provided and bonding was performed in the clean room CR1. The thickness of the polarizer was 5 탆.

(Evaluation of Polarizer)

The average polarization degree of the polarizing plate of Example 1 and Comparative Example 1 was evaluated and found to be 99.990%. The total light transmittance of the polarizing plate was evaluated to be 42.51%. The total combined T _c (%) of the transmission image clarity was 390.

The polarizers of Example 1 and Comparative Example 1 were inspected for defects. A halogen lamp as a light source and a CCD camera as a camera were used, and a polarizing plate for inspection and a polarizing plate for reference were arranged in front of the camera so as to be cross-nicol. As a signal processing apparatus, an Optics image processing visual inspection apparatus (KUBOTEC CO., LTD.) Was used.

In the signal processing apparatus, the brightness which becomes the baseline indicating the normal polarizing region is set to 0, and the 32768 gradations are set on the bright side of the base. A preliminary experiment has revealed that the gradation peak of the first defect portion having a degree of polarization of less than 99% and a maximum diameter of 30 占 퐉 or more becomes 14000 gradations or more, a gradation peak of the second defect portion having a degree of polarization of less than 99% and a maximum diameter of 20 占 퐉 or more, Or more. The densities of the first defective portion and the second defective portion were respectively determined on the basis of the density of the number of regions having a peak of 14000 gradations or more and the number density of regions having peaks of 12000 gradations or more.

In addition, the portion having the defect (first defect) of the gray scale peak 14225 could not be visually confirmed, but when observed under a microscope, it was confirmed that the elliptical defect having a long diameter of 32 mu and a short diameter of 25 mu was confirmed. The defective portion of the gray scale peak 12131 (the second defect portion) could not be visually confirmed, but when observed under a microscope, it was confirmed that a defect of a polygon having a long diameter of 21 mu and a short diameter of 19 mu was confirmed.

The results are shown in Table 1.

(Evaluation of visibility)

(Liquid crystal panels A and B)

The liquid crystal panel was removed from the liquid crystal display device (liquid crystal television manufactured by Sony Corporation: format: BRAVIA KD-55X8500, screen size of A liquid crystal panel: 55 inches, VA mode, thickness of liquid crystal cell: 1.1 mm, area of sub pixel: 0.02 mm & After all of the optical films disposed on the viewer's side of the liquid crystal panel were removed, the glass surface of the exposed liquid crystal cell was wiped with water, and wiped three times with benzocotte immersed in alcohol. The polarizing plate of the first size obtained in Example 1 was bonded to the glass surface on the viewing side of this liquid crystal cell through an acrylic pressure-sensitive adhesive (thickness: 20 占 퐉) to prepare liquid crystal panel A. In the polarizing plate, the absorption axis direction of the polarizing plate is substantially parallel to the longitudinal direction of the liquid crystal cell. Similarly, the liquid crystal panel B was produced by using the polarizer of the first size prepared in Comparative Example 1.

(Liquid crystal panels C and D)

The same procedure was carried out using a liquid crystal display device (liquid crystal television manufactured by Sharp Corporation, format: NEXT "80XU30", screen size of liquid crystal panel: 80 inches, VA mode, thickness of liquid crystal cell: 1.1 mm, subpixel area: 0.03 mm 2) And 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 to each other.

(evaluation)

The obtained liquid crystal panels A to D were evaluated for visibility. In the evaluation of the visibility, an image with a relatively dark image was used, and the human was able to visually recognize the image. The image was observed clearly when the image was observed clearly, the case where the white light leakage was slightly observed, and the case where the white light leakage was observed a large amount was evaluated as & cir & The results are shown in Table 2.

5: adhesive layer, 10: polarizer, 20, 30: protective film, 40: liquid crystal cell, 100: polarizer, 200: liquid crystal panel.

Claims (9)

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,
The number of defects having a degree of polarization of less than 99% and a maximum diameter of 30 mu m or more is 10 / m < 2 > or less. The polarizing plate according to claim 1, wherein the outer shape of the polarizing plate is a rectangular shape 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 or 2, wherein the thickness of the polarizer is 10 占 퐉 or less. The polarizer according to any one of claims 1 to 3, wherein the number of defects having a degree of polarization of less than 99% and having a maximum diameter of 20 탆 or more is 20 / m 2 or less. The polarizer according to any one of claims 1 to 4, wherein the area of the subpixel is 0.1 mm 2 or less. 6. The optical fiber according to any one of claims 1 to 5, wherein the total combined value (%) of the transmission image clarity (%) for four types of optical combs of 0.125 mm, 0.5 mm, 1.0 mm and 2.0 mm Polarizer. And a pair of polarizing plates bonded to both surfaces of the liquid crystal cell, wherein one of the polarizing plates is the polarizing plate according to any one of claims 1 to 6, and the other polarizing plate is a polarizing plate 7. A liquid crystal panel as claimed in any one of claims 1 to 6. The liquid crystal panel according to claim 7, wherein the liquid crystal cell has a thickness of 3 mm or less. The liquid crystal panel according to claim 7 or 8, wherein an area of the subpixel of the liquid crystal cell is 0.1 mm 2 or less.

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