JP2016501386A - Polarizing plate and liquid crystal display device including the same - Google Patents

Abstract

The present invention relates to a polarizing plate and a liquid crystal display device including the same, and more specifically, a first protective film, a polarizer, a second protective film, and an adhesive layer are laminated in this order, and the at least one protective film has an MD direction (Machine). (Direction) is uniaxially stretched, and the front retardation value (RO) is more than 100 nm to less than 300 nm, and the polarizing plate satisfies the following formula. The protective film used in the above polarizing plate has a low cost and high phase difference compared to the conventional film, so it not only has excellent price competitiveness, but also suppresses the occurrence of rainbow unevenness and maintains image quality (such as securing the viewing angle). ) Has a possible effect. (Wherein RO is the front phase difference value and NZ is the refractive index ratio). [Selection] Figure 1

Description

  The present invention relates to a polarizing plate capable of suppressing rainbow unevenness generated by using a protective film having a high retardation, and a liquid crystal display device including the same.

  The liquid crystal display (LCD) replaces a cathode-ray tube (CRT), which currently has the highest market share among flat panel displays and the most popular among image display devices. Yes.

  Liquid crystal display devices have improved various technical disadvantages during the initial development stage, and are now making efforts to increase market competitiveness by increasing price competitiveness. For this reason, efforts have been made to improve the polarizing plate, which is the core component of the liquid crystal display device.

  A typical method for improving the price competitiveness of a polarizing plate is to use an inexpensive polarizer protective film.

  The main purpose of the polarizer protective film is to protect a mechanically weak polarizer. Recently, in the case of a protective film laminated on the side surface of a liquid crystal panel of a polarizer, a function of adding an appropriate retardation through stretching to compensate the viewing angle has been added. Among these, in the case of a protective film laminated on the other side of the liquid crystal panel with a polarizer, it is common for engineers in the field that the retardation value does not affect the optical characteristics.

  As such a protective film, triacetyl cellulose (TAC) or the like is typically used. Triacetyl cellulose (TAC) is usually produced by a casting method, and the solvent is volatilized to form a negative C plate. Such triacetyl cellulose (TAC) is much more expensive than a general plastic film.

  For this reason, an attempt to use a plastic film having a low unit price as a polarizer protective film instead of triacetyl cellulose (TAC) has been underway.

  However, inexpensive plastic films are generally stretched at a high magnification in order to increase the yield and have a large phase difference, and the liquid crystal display device including this has the disadvantage that rainbow unevenness occurs and the image quality is degraded. is there.

  In addition, as a method for suppressing rainbow unevenness generated by a film stretched at a high magnification, the surface of the film stretched at a high magnification is treated with a diffusing agent, or the film stretched at a high magnification is used. A method of adding a diffusing agent to was proposed. However, in this case as well, there is a problem that the image quality is deteriorated or the manufacturing cost is increased.

  The objective of this invention is providing the polarizing plate which can apply the film which has an inexpensive type and a high phase difference with the protective film of a polarizer, without the quality degradation of an image.

  Another object of the present invention is to provide a liquid crystal display device having the polarizing plate.

（式中、ＲＯは正面位相差値であり、ＮＺは屈折率比である）。 In order to achieve the above object, the present invention is laminated in the order of a first protective film, a polarizer, a second protective film, and an adhesive layer, the at least one protective film is uniaxially stretched in the MD direction (Machine Direction), Provided is a polarizing plate having a front retardation value (RO) of more than 100 nm and less than 300 nm and satisfying the following formula 1.

(In the formula, RO is a front phase difference value, and NZ is a refractive index ratio).

  Preferably, the NZ may be NZ> 1.

  Preferably, the NZ may be NZ <0.

  The at least one protective film may be a first protective film and a second protective film.

  The second protective film includes cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate. It may be at least one selected from the group consisting of (PMMA).

  The first protective film includes cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate. It may be at least one selected from the group consisting of (PMMA).

  The first protective film may include a surface treatment layer on a surface opposite to a surface to be bonded to the polarizer.

  Moreover, this invention provides the liquid crystal display device containing the said polarizing plate.

  The liquid crystal display device may include a polarization backlight.

  The polarizing plate of the present invention is excellent in price competitiveness because a low-cost film having a high retardation can be applied as a protective film for a polarizer, and a polarizing plate including a conventionally inexpensive film having a high retardation is included. When applied to a liquid crystal display device, there is an advantage that rainbow unevenness generated by a high phase difference of a film can be suppressed and image quality can be maintained (viewing angle secured, etc.).

1 is a vertical sectional view of a polarizing plate according to the present invention. It is a figure which shows the structure of the liquid crystal display device of Example 1 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 1 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 2 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 3 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 4 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 5 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 6 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 7 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 8 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 9 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 10 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 11 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 12 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 13 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 14 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of Example 16 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of the comparative example 1 which concerns on this invention. It is a figure which shows the omnidirectional rainbow nonuniformity generation | occurrence | production degree at the time of the voltage application of the liquid crystal display device of the comparative example 2 which concerns on this invention.

  The present invention relates to a polarizing plate capable of suppressing rainbow unevenness generated by using a protective film having a high retardation, and a liquid crystal display device including the same.

  Rainbow unevenness is a phenomenon that occurs when polarized light passes through the phase difference layer, because the phase difference value varies greatly depending on the incident angle, and the difference in phase difference value varies depending on the wavelength.

  Since the high retardation film is usually produced by high-stretch stretching, the retardation value is large, and the change of the retardation value due to the incident angle is large. Therefore, if the polarized light passes, rainbow unevenness is generated. Furthermore, since most films have positive wavelength dispersion, the change in retardation value with wavelength is even greater.

  In the present invention, a high retardation film is applied as a protective film for a polarizing plate, but the stretching method and the refractive index ratio of the high retardation film are controlled within a specific range to suppress the occurrence of rainbow unevenness. In the present invention, the occurrence of rainbow unevenness due to the high retardation film is referred to as high retardation unevenness.

・・・（１）
（式中、ＲＯは正面位相差値であり、ＮＺは屈折率比である）。 The present invention will be described in detail below.
The polarizing plate of the present invention is laminated in the order of the first protective film, the polarizer, the second protective film and the pressure-sensitive adhesive layer, and the at least one protective film is uniaxially stretched in the MD direction (Machine Direction) and has a front retardation value. (RO) is more than 100 nm to less than 300 nm and satisfies the following formula.

... (1)
(In the formula, RO is a front phase difference value, and NZ is a refractive index ratio).

  In the mathematical formula (1), NZ preferably satisfies NZ> 1 or NZ <0.

  In general, when NZ is 0 or 1, the optical axis is positioned in the plane and the effect of eliminating rainbow unevenness is obtained, and it is recognized that it is obvious to those skilled in the art. Even if this is removed, the range where the effect is excellent is presented as preferable.

  When the liquid crystal cell is in the VA mode, the polarizing plate preferably uses a first protective film that satisfies the above conditions.

  In addition, the polarizing plate has a second protective film alone or the same first protective film when the liquid crystal cell is in a mode in which the liquid crystal rotates in a plane such as IPS mode, FFS mode, PLS mode, and ADS mode. It is preferable to use a second protective film that satisfies the above conditions. More preferably, the same first protective film and second protective film are used.

  Usually, a film is manufactured in a stretching process, and as the stretching proceeds, the retardation value increases and the unit cost per unit area of the film decreases. If the triacetyl cellulose (TAC), which is a conventional representative protective film, is not stretched, the front retardation value (RO) is 10 nm or less and the thickness direction retardation value (Rth) is 30 to 50 nm. appear. Such optical properties are in a significantly lower retardation range than common plastic films that are often found.

  The following mathematical formulas (2) to (4) are a front retardation value (RO), a thickness direction retardation value (Rth) and a refractive index ratio (NZ) which are optical characteristics of the first protective film and the second protective film. Is defined. At this time, the optical characteristics are for all wavelengths in the visible light region.

・・・（２）
（ここで、Ｎｘ、Ｎｙは面内屈折率であってＮｘ≧Ｎｙであり、ｄはフィルムの厚さを表す）

... (2)
(Here, Nx and Ny are in-plane refractive indexes, Nx ≧ Ny, and d represents the thickness of the film)

・・・（３）
（ここで、Ｎｘ、Ｎｙは面内屈折率であってＮｘ≧Ｎｙであり、Ｎｚはフィルムの厚さ方向屈折率、ｄはフィルムの厚さを表す）

... (3)
(Here, Nx and Ny are in-plane refractive indexes and Nx ≧ Ny, Nz is the refractive index in the thickness direction of the film, and d is the thickness of the film.)

・・・（４）
（ここで、Ｎｘ、Ｎｙは面内屈折率であってＮｘ≧Ｎｙであり、Ｎｚはフィルムの厚さ方向屈折率を表す）

... (4)
(Nx and Ny are in-plane refractive indexes where Nx ≧ Ny, and Nz represents the refractive index in the thickness direction of the film)

  The present invention is characterized in that a highly stretched film is used as a protective film for a polarizer instead of a protective film whose retardation value is limited to a specific range in consideration of optical properties such as rainbow unevenness. is there.

  A highly stretched film has a front retardation value (RO) of more than 100 nm to less than 300 nm, is stretched at a high magnification, and has a low product unit price per unit area.

  The protective film applied to the present invention must be uniaxially stretched in the MD direction (Machine Direction). The MD direction means a direction in which a film existing in a roll (ROll) state can be unwound or wound before being bonded to a polarizer, and uniaxial stretching means stretching and orientation in only one direction. Means film.

  If the film is uniaxially stretched in the MD direction, the extension line of the optical axis will be present in the plane without going out of the film surface, so that high retardation unevenness will not occur.

  High phase difference unevenness occurs at a viewing angle in which the phase difference change due to the viewing angle is severe. Although the light passing through the optical axis has no phase difference, the change in the phase difference due to the viewing angle is large at the viewing angle around the optical axis, and thus high phase difference unevenness is often observed at the viewing angle around the optical axis.

  In addition, the protective film of the present invention has a front retardation value (RO) of more than 100 nm to less than 300 nm and satisfies the above mathematical formula 1. When the refractive index ratio is out of the range of the mathematical formula 1, there arises a problem that the viewing angle is narrowed. The refractive index ratio (NZ) of the protective film is preferably 0 or 1.

  Specifically, if the liquid crystal cell is in the VA mode, a film in which the front retardation value (RO) and the refractive index ratio (NZ) are specified in the scope of the present invention is used as the first protective film, and the second protective film. As such, a film not limited to the scope of the present invention can be used.

  Further, if the liquid crystal cell is IPS mode, FFS mode, PLS mode and ADS mode, a film in which the front retardation value (RO) and the refractive index ratio (NZ) are specified as the second protective film within the scope of the present invention. A film that is not limited to the scope of the present invention can be used as the first protective film.

  Moreover, the film which specified the front phase difference value (RO) and refractive index ratio (NZ) in the range of this invention as a 1st protective film and a 2nd protective film can be used.

  Since the polarizer is mechanically weak, the first and second protective films of the present invention are polarizer protective films for protecting the polarizer. Further, the second protective film can have a retardation compensation function.

  The first and second protective films have different moisture permeability depending on the type of resin, and can be selected and used depending on transparency, mechanical strength, thermal stability, water barrier properties, isotropic properties, and the like.

  Specifically, as the first and second protective films, cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polysulfone ( At least one selected from the group consisting of PSF) and polymethyl methacrylate (PMMA) can be used.

  The thickness of the first and second protective films is not particularly limited. However, if the thickness is too thin, the strength and workability deteriorate, and if it is too thick, the transparency decreases, or the curing time increases after being laminated on the polarizer. is there. The thickness of each protective film is 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm.

  A polarizer is an optical film that serves to change incident natural light into a desired single polarization state (linear polarization state), and uses a film made of a polyvinyl alcohol resin and adsorbed and oriented with a dichroic dye. be able to.

  The polyvinyl alcohol resin constituting the polarizer can be produced by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers with other monomers copolymerizable with vinyl acetate. Specific examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and acrylamides having an ammonium group. The polyvinyl alcohol-based resin may be modified, but for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100% by mole, preferably 98% by mole or more. Moreover, the polymerization degree of polyvinyl alcohol-type resin is 1,000-10,000 normally, Preferably it is 1,500-5,000.

  Such a polyvinyl alcohol resin is formed into a film and used in a polarizer. The film forming method of the polyvinyl alcohol resin is not particularly limited, and various known methods can be used. The film thickness of a polyvinyl alcohol-type resin is not specifically limited, For example, it can be 3-150 micrometers.

  The polarizer is usually produced through a process of uniaxially stretching the polyvinyl alcohol film as described above, a process of dyeing and adsorbing with a dichroic dye, a process of treating with an aqueous boric acid solution, and a process of washing and drying.

  The step of uniaxially stretching the polyvinyl alcohol film can be performed before dyeing and at the same time as dyeing or after dyeing. When uniaxial stretching is performed after dyeing, it can also be performed before or during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in a plurality of stages combining these. Uniaxial stretching can use rolls or heat rolls having different peripheral speeds, and can be dry stretching that stretches in the air, or can be wet stretching that stretches in a state swollen with a solvent. The draw ratio is usually 3 to 8 times.

  The process of dye | staining the stretched polyvinyl alcohol-type film with a dichroic dye can use the method of immersing a polyvinyl alcohol-type film in the aqueous solution containing a dichroic dye, for example. As a specific example of the dichroic dye, iodine or a dichroic organic dye is used. Moreover, it is preferable to swell a polyvinyl alcohol-type film by previously immersing in water before dyeing | staining.

  When iodine is used as the dichroic dye, a method of dyeing by immersing a polyvinyl alcohol film in an aqueous dyeing solution containing iodine and potassium iodide can be usually used. Usually, the iodine content in the dyeing aqueous solution is 0.01 to 1 part by weight with respect to 100 parts by weight of water (distilled water), and the potassium iodide content is 0.5 to 20 with respect to 100 parts by weight of water. Parts by weight. The temperature of the aqueous dyeing solution is usually 20 to 40 ° C., and the immersion time, for example, the dyeing time is usually 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of dyeing by immersing a polyvinyl alcohol film in an aqueous dyeing solution usually containing a water-soluble dichroic organic dye can be used. The content of the dichroic organic dye in the aqueous dyeing solution is usually 1 × 10 ⁻⁴ to 10 parts by weight, preferably 1 × 10 ⁻³ to 1 part by weight with respect to 100 parts by weight of water. The aqueous dyeing solution may further contain an inorganic salt such as sodium sulfate as a dyeing auxiliary. The temperature of the aqueous dyeing solution is usually 20 to 80 ° C., and the immersion time, for example, the dyeing time is usually 10 to 1,800 seconds.

  The step of treating the dyed polyvinyl alcohol film with boric acid can be performed by immersing it in a boric acid-containing aqueous solution. Usually, the boric acid content in the boric acid-containing aqueous solution is 2 to 15 parts by weight, preferably 5 to 12 parts by weight with respect to 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide, and its content is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight based on 100 parts by weight of water. Good part. The temperature of the boric acid-containing aqueous solution is 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C., and the immersion time is 60 to 1,200 seconds, preferably 150 to 600 seconds, more preferably. Is preferably 200 to 400 seconds.

  After the boric acid treatment, the polyvinyl alcohol film is washed with water and dried. The washing treatment can be performed by immersing the boric acid-treated polyvinyl alcohol film in water, the temperature of the water during the washing treatment is 5 to 40 ° C., and the dipping time is 1 to 120 seconds. A polarizer is obtained by drying after washing. The drying treatment can usually be performed using a hot air dryer or a far infrared heater, the drying treatment temperature is usually 30 to 100 ° C., preferably 50 to 80 ° C., and the drying time is usually 60 to 600 seconds, preferably It is good for 120 to 600 seconds.

  The thickness of the polarizer can be 3 to 40 μm.

  An adhesive layer is formed between the polarizer and the first protective film and between the polarizer and the second protective film. For example, a water-based adhesive or a UV curable adhesive can be used for the adhesive layer.

  The adhesive is not particularly limited as long as it can sufficiently bond the polarizer and the protective film, has excellent optical transparency, and does not change over time, such as yellowing. A water-based adhesive composition containing a resin and a crosslinking agent is exemplified.

  Examples of the polyvinyl alcohol resin contained in the aqueous adhesive composition include a polyvinyl alcohol resin or a polyvinyl alcohol resin having an acetoacetyl group. Among these, a polyvinyl alcohol resin having an acetoacetyl group is a highly reactive functional group. As the polyvinyl alcohol-based adhesive having the above, it is preferable in that the durability of the polarizing plate is improved.

  The resin contained in the UV curable adhesive composition is generally used in this field, and an epoxy resin, an acrylic resin, or the like can be used.

  In addition, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, or saponification treatment is appropriately applied to the surface of the polarizer to be bonded to the protective film. It can be carried out.

  As a method of bonding the protective film to the polarizer with an adhesive, a method commonly known in the art can be used, for example, a softening method, a wire bar coating method, a gravure coating method, a die coating method, or a spraying method. The method of apply | coating an adhesive agent to a polarizer, a protective film, or all these bonding surfaces by the method etc., and bonding these is mentioned. Here, the softening method means that the adhesive or the protective film, which is an object to be coated, is allowed to flow down on the surface of the object to be coated while moving the polarizer or the protective film in a substantially vertical direction, a substantially horizontal direction, or an inclination direction therebetween. It is a method of spreading. After apply | coating an adhesive agent, a polarizer and a protective film are pinched | interposed on a bonding roll etc., and are bonded.

  The pressure-sensitive adhesive layer is a layer for laminating with a liquid crystal cell, and can be formed of a pressure-sensitive adhesive composition commonly used in this field, which contains a pressure-sensitive adhesive resin and a crosslinking agent.

  As the pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition, acrylic, silicone, rubber, urethane, polyester, or epoxy copolymers can be used, and an acrylic copolymer is preferably used. The pressure-sensitive adhesive composition can also contain known antistatic agents such as alkali metal salts, ionic compounds, conductive polymers, metal oxides, and CNTs. Among these, it is more preferable that an ionic compound is included.

  The method of laminating the pressure-sensitive adhesive layer on the polarizing plate is not particularly limited as long as it is a method usually used in this field. For example, the pressure-sensitive adhesive composition can be applied on the antistatic coating layer formed on the polarizer protective film using the same method as the application method of the antistatic coating liquid composition, and dried and laminated. Moreover, after forming an adhesive layer on the silicone-coated release film by the same application method as described above, an adhesive sheet was produced, and then this was formed on the polarizer protective film using a roll pressing device. It can also be laminated on the protective coating layer. At this time, when the pressure-sensitive adhesive composition contains an ultraviolet curable compound as a cross-linking agent, it is preferable to irradiate with ultraviolet light after the pressure-sensitive adhesive composition is applied or laminated using a roll pressing device.

  The thickness of the pressure-sensitive adhesive layer can be adjusted by its adhesive strength, and is usually preferably 3 to 100 μm, more preferably 10 to 100 μm.

  The liquid crystal display device of the present invention can include any of the upper plate, the lower plate, and the upper / lower plate with the polarizing plate. When the polarizing plate is provided on the upper plate or the lower plate, the other polarizing plate is generally used in the art, and uses a form in which protective films are bonded to both sides of the polarizer. be able to.

  Hereinafter, preferred embodiments will be presented for the understanding of the present invention. However, the following embodiments are merely illustrative of the present invention, and various changes and modifications can be made within the scope and technical spirit of the present invention. It will be obvious to those skilled in the art, and such variations and modifications are, of course, within the scope of the claims.

Example 1
Each optical film according to the present invention and actual measurement data such as a liquid crystal cell and a backlight were laminated on a TECH WIZ LCD with a structure as shown in FIG. A liquid crystal cell of a 55-inch PS-VA mode liquid crystal display device was parameterized and stacked on a TECH WIZ LCD.

  The liquid crystal display device was composed of a polarizing backlight, a lower plate polarizing plate PS-VA mode liquid crystal cell, and an upper plate polarizing plate. The upper plate and the lower plate polarizing plate were laminated in the order of the pressure-sensitive adhesive layer, the second protective film, the adhesive layer, the polarizer, the adhesive layer, and the first protective film from the liquid crystal cell side.

  The polarizer imparts a polarizer function to the PVA through stretching and dyeing, and the absorption axis of the backlight side polarizer is stacked vertically when viewed from the viewing side, and the absorption axis of the viewing side polarizer is arranged in the horizontal direction. did.

とするとき、下記数学式（５）〜（９）により定義される。

・・・（５）

・・・（６）

・・・（７）

・・・（８）

・・・（９） The polarizing performance of such a polarizer was a visibility polarization degree of 99.9% or more and a visibility single transmittance of 41% or more in the visible light range of 370 to 780 nm. Visibility polarization degree and visibility single transmittance: the transmission axis transmission factor by wavelength is TD (λ), the absorption axis transmission factor by wavelength is MD (λ), and visibility correction defined in JIS Z 8701: 1999 The value

Is defined by the following mathematical formulas (5) to (9).

... (5)

... (6)

... (7)

... (8)

... (9)

  Each first protective film of the upper and lower plates is uniaxially stretched in the MD direction, has a light source of 589 nm, a front phase difference value (RO) of 250 nm, and a refractive index ratio (NZ) of 1, polyethylene terephthalate (PET) Films were laminated. The first protective films were laminated so that the absorption axis and slow axis directions of adjacent polarizers were perpendicular to each other.

  Each of the second protective films of the upper plate and the lower plate is a protective film having a retardation compensation function, and has a light source of 589 nm, a front retardation value (RO) of 50 nm, and a thickness direction retardation value (Rth). A 125 nm cycloolefin polymer (COP) film was laminated.

  The upper polarizer and the lower polarizer each formed an acrylic adhesive layer between the protective films on both sides.

  FIG. 3 is a result of calculating rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and specifically showing the hues in all directions in a contour map (on Color Control Map). It was confirmed that no rainbow unevenness occurred.

(Example 2: VA mode)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 250 nm with a light source of 589 nm, and refractive index ratio ( A modified polystyrene (PS) film in which (NZ) is 0 was laminated.

  FIG. 4 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred at all.

(Example 3: VA mode)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 150 nm with 589 nm of light sources, and refractive index ratio ( A polyethylene terephthalate (PET) film in which (NZ) is 1 was laminated.

  FIG. 5 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 4: VA mode)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 150 nm with 589 nm of light sources, and refractive index ratio ( A modified polystyrene (PS) film in which (NZ) is 0 was laminated.

  FIG. 6 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 5: VA mode)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 200 nm with 589 nm of light sources, and refractive index ratio ( A polyethylene terephthalate (PET) film in which (NZ) is 2 was laminated.

  FIG. 7 shows the result of calculating rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 6: VA mode)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 290 nm with a light source of 589 nm, and refractive index ratio ( A polyethylene terephthalate (PET) film having a (NZ) of 1.5 was laminated.

  FIG. 8 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 7: VA mode)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 110 nm with 589 nm of light sources, and refractive index ratio ( A modified polystyrene (PS) film in which (NZ) is -3 was laminated.

  FIG. 9 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 8: VA mode)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 250 nm with a light source of 589 nm, and refractive index ratio ( A modified polystyrene (PS) film in which (NZ) is -1 was laminated.

  FIG. 10 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred at all.

(Example 9: IPS mode)
Although it carries out similarly to the said Example 1, each 1st and 2nd protective film of an upper board and a lower board is uniaxially stretched in MD direction on a 42-inch IPS mode liquid crystal cell, a front phase difference value ( RO) was 250 nm, and a polyethylene terephthalate (PET) film having a refractive index ratio (NZ) of 1 was laminated.

  FIG. 11 shows the result of calculating rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 10: IPS mode (only the second protective film is used))
Although it carries out similarly to the said Example 9, each 2nd protective film of an upper board and a lower board is uniaxially stretched in MD direction, a front phase difference value (RO) is 250 nm with a light source of 589 nm, and refractive index ratio ( A modified polystyrene (PS) film in which (NZ) is 0 was laminated.

  Each 1st protective film of an upper board and a lower board laminated | stacked NRT (Japan) which is a TAC series isotropic film.

  FIG. 12 shows the result of calculating rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 11: IPS mode (only the second protective film is used))
Although it carries out similarly to the said Example 9, each 2nd protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 150 nm with 589 nm of light sources, and refractive index ratio ( A polyethylene terephthalate (PET) film in which (NZ) is 1 was laminated.

  Each 1st protective film of an upper board and a lower board laminated | stacked NRT (Japan) which is a TAC series isotropic film.

  FIG. 13 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred at all.

(Example 12: IPS mode)
Although it carries out similarly to the said Example 9, each 1st and 2nd protective film of an upper board and a lower board is uniaxially stretched in MD direction, a front phase difference value (RO) is 150 nm with a light source of 589 nm, it is refractive A modified polystyrene (PS) film having a rate ratio (NZ) of 0 was laminated.

  FIG. 14 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 13: IPS mode)
Although it carries out similarly to the said Example 9, each 1st and 2nd protective film of an upper board and a lower board is uniaxially stretched in MD direction, a front phase difference value (RO) is 200 nm with a light source of 589 nm, it is refracting A modified polystyrene (PS) film having a rate ratio (NZ) of −2 was laminated.

  FIG. 15 shows the result of calculating rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 14: IPS mode)
Although it carries out similarly to the said Example 9, each 1st and 2nd protective film of an upper board and a lower board is uniaxially stretched in MD direction, front phase difference value (RO) is 290 nm with a light source of 589 nm, it is refracting A modified polystyrene (PS) film having a rate ratio (NZ) of -0.2 was laminated.

  FIG. 16 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Example 15: IPS mode)
Although it carries out similarly to the said Example 9, each 1st and 2nd protective film of an upper board and a lower board is uniaxially stretched in MD direction, a front phase difference value (RO) is 250 nm with a light source of 589 nm, it is refracting A polyethylene terephthalate (PET) film having a rate ratio (NZ) of 2 was laminated.

  FIG. 17 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that no rainbow unevenness occurred.

(Comparative Example 1)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is uniaxially stretched in TD direction, front phase difference value (RO) is 2,000 nm with a light source of 589 nm, and refractive index Those having a ratio (NZ) of 1.9 were laminated.

  FIG. 18 shows the result of calculating the rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that the rainbow unevenness occurred.

(Comparative Example 2)
Although it carries out similarly to the said Example 1, each 1st protective film of an upper board and a lower board is biaxially stretched, a front phase difference value (RO) is 2,000 nm with a light source of 589 nm, and refractive index ratio ( (NZ) is 3 laminated.

FIG. 19 shows the result of calculating rainbow unevenness in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, and it was confirmed that many rainbow unevenness occurred.

Claims (11)

The first protective film, the polarizer, the second protective film and the pressure-sensitive adhesive layer are laminated in this order,
The at least one protective film is uniaxially stretched in the MD direction (Machine Direction), and has a front phase difference value (RO) of more than 100 nm to less than 300 nm,
Polarizing plate satisfying the following formula:

(In the formula, RO is a front phase difference value, and NZ is a refractive index ratio).   The polarizing plate according to claim 1, wherein the NZ is NZ> 1.   The polarizing plate according to claim 1, wherein the NZ is NZ <0.   The polarizing plate according to claim 1, wherein the at least one protective film is a first protective film.   The polarizing plate according to claim 1, wherein the at least one protective film is a second protective film.   The polarizing plate according to claim 1, wherein the at least one protective film is a first protective film and a second protective film.   The second protective film includes cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate. The polarizing plate according to claim 5 or 6, wherein the polarizing plate is at least one selected from the group consisting of (PMMA).   The first protective film includes cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate. The polarizing plate according to claim 4 or 6, which is at least one selected from the group consisting of (PMMA).   The polarizing plate according to claim 1, wherein the first protective film includes a surface treatment layer on a surface opposite to a surface to be bonded to the polarizer.   The liquid crystal display device containing the polarizing plate as described in any one of Claims 1-6.   The liquid crystal display device according to claim 10, wherein the liquid crystal display device includes a polarization backlight.

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