JP2017058444A - Polarizing plate and liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate which can prevent the warpage of a thin liquid crystal cell while achieving high-definition display quality.SOLUTION: A polarizing plate 100 comprises a polarizer 10, and a protection film 20 disposed on the polarizer 10. The polarizer 10 has a thickness of 10 μm or less, the polarizing plate 100 has a degree of polarization of 99.98% or more, and the polarizing plate 100 has a total light transmittance of 42% or more.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, a liquid crystal panel in which polarizing plates are bonded to both surfaces of a liquid crystal cell is known.

JP 2012-58381 A

  In recent years, liquid crystal panels have been increased in size, and from the viewpoint of design, liquid crystal cells have been made thinner in order to make the liquid crystal panel thinner. There is also a need for further improvement in the display quality of liquid crystal panels.

  The inventors have examined that a liquid crystal cell may be warped when a polarizing plate having a high transmittance and degree of polarization is attached to a large thin liquid crystal cell for the purpose of improving brightness and improving black display quality. I found.

  The present invention has been made in view of the above problems, and an object thereof is to provide a polarizing plate and the like that can suppress warpage of a thin liquid crystal cell while realizing a bright and high-quality black display.

  The polarizing plate which concerns on this invention is equipped with a polarizer and the protective film arrange | positioned on the said polarizer. And the thickness of the said polarizer is 10 micrometers or less, the polarization degree of the said polarizing plate is 99.98% or more, and the total light transmittance of the said polarizing plate is 42% or more.

  According to the present invention, the brightness of the liquid crystal panel and the quality of black display are improved by the high total light transmittance and the degree of polarization. Further, in such a polarizing plate having a high total light transmittance and a high degree of polarization, shrinkage is likely to occur, and warping is likely to occur in a thin liquid crystal cell. However, in the present invention, since the polarizer is thin, warping of the liquid crystal cell is also suppressed. .

  Here, the outer shape of the polarizing plate may be a rectangle having a long side of 660 mm or more and a short side of 370 mm or more. Such a large polarizing plate is more likely to be warped, but since the thickness of the polarizer is thin, the warpage of the liquid crystal cell is suppressed.

  Moreover, it can be for liquid crystal cells having a thickness of 3 mm or less. A thin liquid crystal cell is highly effective because it is easily warped.

Moreover, it can be used for a liquid crystal cell having a pixel area of 0.5 mm ² or less. When applied to such a liquid crystal cell, the high-definition characteristics of the liquid crystal cell can be sufficiently extracted.

  Further, the total value (%) of transmitted image definition (%) for optical combs having four types of widths of 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm can be 200 or more. If the transmitted light image clarity is high in addition to the high total light transmittance and the degree of polarization, it is possible to display a higher-definition image.

  The liquid crystal panel according to the present invention includes a liquid crystal cell and a pair of the above-described polarizing plates attached to both surfaces of the liquid crystal cell.

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

The pixel area of the liquid crystal cell may be 0.5 mm ² or less.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate etc. which can suppress the curvature of a thin liquid crystal cell, implement | achieving bright and high quality black display quality are 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. The protective film 20 is disposed on the liquid crystal cell side, and the protective film 30 is disposed on the opposite side of the liquid crystal cell. A functional layer 26 can be provided on the protective film 30. Moreover, the adhesive layer 28 can be provided under the protective film 20, and is attached to the liquid crystal cell via the adhesive layer 28, for example. 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.

  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

  The polarizing plate 100 may have a total light transmittance of 42% or more and 42.5 or more as shown in JISK 7361-1: 1997. The upper limit of the total light transmittance may be 50%, but may be 45% or less and may be 44.5% or less.

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 makes the light that has passed through the slit parallel light and incident vertically from the opposite side (from the side opposite to the liquid crystal cell) of the protective film 30 (from the side of the protective film 20 in FIG. 1). It comprises an optical device that detects transmitted light through an optical comb that moves, and a measurement system device that records fluctuations 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 treatment layer or an antireflection layer having a small surface roughness may be provided on the outermost layer such as a protective film.

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 it is preferably thicker than 2 μm from the viewpoint that a high degree of polarization is easily obtained, a defect is hardly generated, and handling is easy.

(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.

  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. When the thickness of the protective films 20 and 30 is less than 10 μm, handling tends to be difficult, and 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. If the protective film 20 is not provided and the pressure-sensitive adhesive layer 28 is provided directly on the polarizer 10, the distance between the polarizer 10 and the liquid crystal cell is reduced, which is preferable in that a black display can be realized.

  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 a layer having other functions such as an antireflection layer and an antiglare layer instead of the hard coat layer. These functional layers may be a layer having one type of function, or may be a layer combining a plurality of layers having one type of function, and one layer exhibits two or more types of functions. May be. 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.

(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. Solventless adhesives do not contain a significant amount of solvent, and are curable compounds (monomers or oligomers) that are reactively cured by heating or irradiation with active energy rays (for example, ultraviolet rays, visible light, electron beams, X-rays, etc.) ), And the adhesive layer is formed by curing of the curable compound, typically a curable compound that is reactively cured by heating or irradiation of 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 more preferable that it exists in the range of 1-20 micrometers, and also 2-10 micrometers.

(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. 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.

  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 pixel 42 is not particularly limited, but may be, for example, 0.5 mm ² or less, and may be 0.3 mm ² or less.

According to the polarizing plate 100 and the liquid crystal panel 200 according to the present embodiment, brightness and black display quality are improved due to high total light transmittance and degree of polarization. Further, in such a polarizing plate having a high total light transmittance and a high degree of polarization, warpage is likely to occur in a thin liquid crystal cell. However, in the present invention, since the polarizer is thin, warpage of the liquid crystal cell is also prevented. That is, since the polarizer is uniaxially stretched, the manufactured polarizer and polarizing plate tend to contract in the stretching direction. The pair of polarizers are attached to the liquid crystal cell so that the polarizers are crossed Nicols, that is, the extension axes of the polarizers are perpendicular to each other. Can not. Further, since the liquid crystal panel is more easily bent in the longitudinal direction, the liquid crystal cell is likely to warp toward the side where the absorption axis of the polarizer comes in a direction parallel to the longitudinal direction of the liquid crystal panel. In particular, when the polarizing plate is exposed to a high temperature atmosphere, the warpage becomes significant. However, in this embodiment, since the polarizer is thin, the contraction stress exerted on the liquid crystal cell by the polarizing plate is suppressed, and the warpage of the liquid crystal cell is suppressed.
Furthermore, a large liquid crystal panel is usually used in a vertical orientation, and the large liquid crystal panel is not affected by its own weight. .

  Further, since the contraction force becomes stronger as the polarizing plate becomes larger, the warpage of the large liquid crystal cell tends to be remarkable. Therefore, the effect is particularly high when the outer 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.

  Further, since the warpage tends to become remarkable even if the liquid crystal cell becomes thin, the effect is high even for a liquid crystal cell having a thickness of 3 mm or less, and the effect is further high if it is 2 mm or less, particularly 1.3 mm or less. In the case of the liquid crystal cell, the effect is particularly high.

Further, when the total value T _c (%) of the transmitted image clarity of the polarizing plate is 200 or more, further 250 or more, particularly 300 or more, the image is less likely to be blurred, and the visibility of the image is further improved and the visibility is further improved. To do.

  From another point of view, in recent years, screen definition has been increased, for example, high definition such as a change from the 4k standard to the 8k standard has progressed, and the black matrix area tends to increase and the aperture ratio tends to decrease. Therefore, in order to maintain the brightness of the screen, the polarizing plate is required to have a high total light transmittance of 42% or more, further 42.5% or more. Also, when the transmittance of the polarizing plate is increased, the degree of polarization of the polarizing plate tends to decrease relatively. When the degree of polarization decreases, the transmittance during black display increases, and the contrast (white luminance / black luminance) increases. It will decline. Therefore, in addition to a high total light transmittance, a high degree of polarization of 99.98% or even 99.99% or more is required for the polarizing plate. In particular, in the VA mode of a large TV, a decrease in the degree of polarization is visually recognized and the dark portion is not tightened, so that the effect of increasing the definition of the display device is reduced. While the VA mode is characterized by a higher contrast than the IPS mode, a slight decrease in the degree of polarization appears remarkably. In order to obtain a polarizing plate having a high transmittance and a high degree of polarization, the PVA is highly oriented by increasing the draw ratio in the absorption axis direction of the polarizer to 5.2 times or more, and further to 5.5 times or more. It is necessary to make the minimum necessary staining. However, when the draw ratio is increased, the thermal shrinkage in that direction usually increases, and thus the warpage of the liquid crystal cell becomes large because the cell is easily bent in a large and thin liquid crystal cell. Therefore, even with a high transmittance and a high degree of polarization, if the polarizer is thinned, the contraction force is lowered and the warpage is reduced. This provides a polarizing plate that can suppress the warpage of a thin liquid crystal cell while realizing bright and high-quality black display.

(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. The chromatic dye is adsorbed and oriented on the resin layer. Subsequently, if necessary, the resin layer on which the dichroic dye is adsorbed and oriented is treated with an aqueous boric acid solution, and a washing step of washing off the aqueous boric acid solution is performed. 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.

  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. In order to obtain a high transmittance and a high degree of polarization, the draw ratio is 5 times or more, preferably 5.2 times or more, and particularly preferably 5.5 times or more. The upper limit of the draw ratio is not particularly limited, but is preferably 8 times or less from the viewpoint of suppressing breakage and the like.

  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.

  In order to sufficiently increase the total light transmittance and the degree of polarization of the polarizing plate while making the thickness of the polarizer 10 μm or less, the production is 5 times or more, preferably 5.2 times or more, particularly preferably 5.5 times or more. It is preferable to perform sufficient dyeing and cross-linking while keeping the draw ratio to a minimum so that washing is minimized. Further, by providing a surface treatment layer having a low reflectance on the outside of the protective film 30, or providing a brightness enhancement film as the outside of the protective film 30 on the backlight side or as the protective film 30, high transmission and high degree of polarization can be achieved. It becomes possible.

  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. The shape of the polarizing plate may be other than a rectangle.

  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.). It mixed and it was set as the adhesive agent aqueous solution.

(7) Bonding of Polarizer and Protective Film Next, the polyvinyl alcohol-coated surface of the obtained polarizing laminate film and a protective film (6 μm antireflection layer provided on 40 μm triacetyl cellulose)) 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.
From the obtained long polarizing plate, a polarizing plate having a first size of 150 mm × 150 mm and a polarizing plate having a second size of 1780 mm × 1000 mm were obtained. The thickness of the polarizer was 5 μm.

(Example 2)
The same procedure as in Example 1 was performed except that a protective film having an antiglare layer of 8 μm laminated on 40 μm of triacetyl cellulose was used.

(Comparative Example 1)
The same procedure as in Example 2 was performed except that the polyvinyl alcohol-based resin layer was formed thicker on the support film. The thickness of the obtained polarizer was 25 μm.

(Comparative Example 2)
A polyvinyl alcohol-based resin layer is formed thicker (thinner than Comparative Example 1) on the support film to obtain a stretched film with a final MD magnification of 0.40 and a final TD magnification of 4.3 times. Example 2 was the same as in Example 2. The thickness of the obtained polarizer was 25 μm.

(Evaluation of polarizing plate)
The optical properties of the polarizing plates of Examples 1 to 3 and Comparative Examples 1 and 2 were as shown in the table.

(Visibility evaluation 1: White display evaluation)
Liquid crystal display (Liquid crystal television manufactured by Sharp Corporation, model: NEXT “80XU30”, liquid crystal panel screen size: 80 inches, liquid crystal cell thickness 1.1 mm, VA mode, pixel area: about 0.21 mm ² ) After removing the panel (referred to as the liquid crystal cell A) and first removing the 150 mm × 150 mm optical film placed on the viewing side of the liquid crystal panel, the glass surface of the obtained liquid crystal cell was wiped with water and alcohol-soaked ben Wipe 3 times with cotton to remove foreign material and adhesive. The liquid crystal panel was obtained by bonding the first size polarizing plate obtained in Examples 1 and 2 and Comparative Examples 1 and 2 to the glass substrate of this liquid crystal cell via an acrylic adhesive (thickness: 20 μm). Is made. The viewing-side polarizing plate is configured such that the absorption axis direction of the polarizing plate is substantially parallel to the long side direction of the liquid crystal cell. In this state, a white screen is displayed on the liquid crystal panel, and a person visually evaluates the appearance of the image. As an evaluation, a white light whose brightness is hardly changed from the surroundings (original polarizing plate) is evaluated as ◯, and a darker one than the surroundings is evaluated as ×.

(Visibility evaluation 2: Black display evaluation)
Next, after removing all the optical film arranged on the viewing side of the liquid crystal panel, wipe the glass surface of the obtained liquid crystal cell with water and wipe it with Bencotton soaked in alcohol three times to remove foreign matter and adhesive. . The liquid crystal panel is obtained by bonding the polarizing plate having the second size obtained in Examples 1 and 2 and Comparative Examples 1 and 2 to the glass substrate of the liquid crystal cell via an acrylic adhesive (thickness: 20 μm). Is made. In this state, an image of fireworks is displayed on the liquid crystal panel, and a person visually evaluates the appearance of the image. As an evaluation, a case where a firework image is clearly seen in a bright indoor environment is evaluated as ◯, and a case where a fireworks image is blurred is evaluated as ×.

(Visibility evaluation 3: definition evaluation)
Furthermore, forest images are displayed on a liquid crystal panel, and humans visually evaluate the appearance of the images. The one that looks fine in the details of the leaves of the trees is marked with ◯, and the one where the details are blurred is marked with ×.

(Evaluation of warpage)
Regarding the warpage, the liquid crystal panel is kept in a furnace at 80 ° C. for 250 hours, and then the warpage amount of the liquid crystal panel immediately after being taken out from the furnace is measured. The case where the amount of warpage is 5 mm or less is marked as ◯, and the case where the amount of warpage is larger than 5 mm is marked as x.

The polarizing plate of Example 1 is also evaluated in another liquid crystal cell (referred to as liquid crystal cell B). Specifically, the liquid crystal display device is a liquid crystal television manufactured by Samsung, model: UN55D7000LF, liquid crystal panel screen size: 55 inches, liquid crystal cell thickness 1.1 mm, VA mode, pixel area: about 0.40 mm ² ) Except for changing, the evaluation is performed in the same manner as described above.

  The results up to the above are shown in Table 1.

  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 polarizer has a thickness of 10 μm or less,
The polarization degree of the polarizing plate is 99.98% or more,
A polarizing plate, wherein the polarizing plate has a total light transmittance of 42% or more.   The polarizing plate according to claim 1, wherein 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 according to claim 1 or 2, which is for a liquid crystal cell having a thickness of 3 mm or less. The polarizing plate as described in any one of Claims 1-3 which is an object for liquid crystal cells whose area of a pixel is 0.5 mm < ² > or less.   The total value (%) of transmitted image clarity (%) for optical combs having four types of widths of 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm is 200 or more. The polarizing plate as described in any one of these.   A liquid crystal panel provided with a liquid crystal cell and a pair of polarizing plates as described in any one of Claims 1-5 affixed on both surfaces of the said liquid crystal cell.   The liquid crystal panel according to claim 6, wherein the liquid crystal cell has a thickness of 3 mm or less. The liquid crystal panel according to claim 6 or 7, wherein an area of a pixel of the liquid crystal cell is 0.5 mm ² or less.

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