CN113741099A - Polarizing plate - Google Patents

Abstract

The present invention relates to a polarizing plate having a polyester film laminated on at least one surface of the polarizing plate, the polyester film having a retardation of 8000 to 10300 nm, and the NZ coefficient of the polyester film being 1.0 or more and 1.733 Hereinafter, an anti-reflection layer and/or a low-reflection layer are laminated on the opposite side of the polyester film to the side on which the polarizer is laminated, and the NZ coefficient is represented by |Ny‑Nz|/|Ny‑Nx|, Here, Ny represents the refractive index in the slow axis direction, Nx represents the refractive index in the direction orthogonal to the slow axis, that is, the refractive index in the fast axis direction, and Nz represents the refractive index in the thickness direction.

Description

Polarizing plate

The present application is a divisional application filed on 2016 under the name of 2016800594454, having a filing date of "liquid crystal display device and polarizing plate".

Technical Field

The present invention relates to a liquid crystal display device and a polarizing plate. More particularly, the present invention relates to a liquid crystal display device and a polarizing plate capable of reducing generation of iridescent stains.

Background

A polarizing plate used in a Liquid Crystal Display (LCD) is generally configured by sandwiching a polarizing plate obtained by dyeing iodine on polyvinyl alcohol (PVA) or the like with 2 sheets of a polarizing plate protective film, and a cellulose Triacetate (TAC) film is generally used as the polarizing plate protective film. In recent years, with the thinning of LCDs, the polarizing plate is required to be thin. However, if the thickness of the TAC film used as the protective film is reduced for this purpose, a sufficient mechanical strength cannot be obtained, and the moisture permeability deteriorates. In addition, TAC films are very expensive, and polyester films have been proposed as an inexpensive alternative material (patent documents 1to 3), but have a problem of iridescent unevenness.

When an oriented polyester film having birefringence is disposed on one side of a polarizing plate, the polarization state of linearly polarized light emitted from a backlight unit or the polarizing plate changes when the linearly polarized light passes through the polyester film. The transmitted light exhibits a characteristic interference color depending on the retardation amount, which is the product of the birefringence and the thickness of the oriented polyester film. Therefore, when a discontinuous emission spectrum such as a cold cathode tube or a hot cathode tube is used as a light source, it shows different transmitted light intensities depending on the wavelength and forms rainbow-like color spots (see the 15 th Microoptics Commission, items 30 to 31).

As a method for solving the above-mentioned problems, it has been proposed to use a white light source having a continuous and wide emission spectrum, such as a white light emitting diode, as a backlight light source, and further use an oriented polyester film having a certain retardation amount as a polarizer protective film (patent document 4). For a white light emitting diode, there is a continuous and wide light emission spectrum in the visible light region. Therefore, it is proposed that when focusing on the shape of the envelope of the interference color spectrum of transmitted light transmitted through a birefringent body, a spectrum similar to the emission spectrum of a light source can be obtained by controlling the retardation amount of an oriented polyester film, and iridescence can be suppressed.

Further, by making the orientation direction of the oriented polyester film orthogonal or parallel to the polarization direction of the polarizing plate, the linearly polarized light emitted from the polarizing plate passes through the oriented polyester film while maintaining the polarization state. Further, the uniaxial orientation is improved by controlling the birefringence of the oriented polyester film, and light incident from an oblique direction also passes through the oriented polyester film while maintaining the polarization state. When the oriented polyester film is observed from an oblique direction, a shift occurs in the orientation main axis direction as compared with the case of observation from directly above, but when the uniaxial orientation is high, the shift in the orientation main axis direction when observed from an oblique direction becomes small. Therefore, it is considered that the deviation between the direction of the linearly polarized light and the orientation main axis direction is small, and the change of the polarization state is less likely to occur. As described above, it is considered that by controlling the emission spectrum of the light source, the orientation state of the birefringent body, and the orientation main axis direction, the change in the polarization state can be suppressed, and the visibility can be remarkably improved without generating rainbow-like color spots.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2002-116320

Patent document 2: japanese patent laid-open publication No. 2004-219620

Patent document 3: japanese patent laid-open publication No. 2004-205773

Patent document 4: WO2011/162198

Disclosure of Invention

Problems to be solved by the invention

In recent years, liquid crystal display devices have been required to expand the color gamut, and therefore white light emitting diodes (for example, blue light emitting diodes and at least K as a phosphor) have been developed₂SiF₆：Mn⁴⁺White light emitting diode of isofluro phosphor, etc.) having the following emission spectrum: a blue region (400nm or more and less than 495nm), and a green region (4)95nm or more and less than 600nm) and a red region (600nm or more and 780nm or less) have a peak top of an emission spectrum, respectively, and the half-value width of the peak in the red region (600nm or more and 780nm or less) is narrow (less than 5 nm).

In the case of industrially producing a liquid crystal display device using a polarizing plate using a polyester film as a polarizer protective film, the transmission axis of the polarizing plate and the fast axis direction of the polyester film are generally arranged so as to be perpendicular to each other. This is because a polyvinyl alcohol film as a polarizing plate is produced by uniaxially stretching in the longitudinal direction, and a polyester film as a protective film thereof is produced by stretching in the longitudinal direction and then stretching in the transverse direction, and therefore, when a polarizing plate is produced by laminating these long articles with the orientation main axis of the polyester film being in the transverse direction, the fast axis of the polyester film and the transmission axis of the polarizing plate are generally perpendicular to each other. In the above-described case, the iridescent color spots were greatly improved by using an oriented polyester film having a specific retardation as the polyester film and using, as the backlight light source, for example, a light source having a continuous and broad emission spectrum represented by a white LED formed by a light emitting element obtained by combining a blue light emitting diode and an yttrium-aluminum-garnet-based yellow phosphor, but it was found that: when a backlight light source is used which is formed of a white light emitting diode having an emission spectrum in which the half-value width of the peak in the red region (600nm or more and 780nm or less) is narrow (less than 5nm), there is a new problem that the rainbow unevenness still occurs.

That is, an object of the present invention is to provide a liquid crystal display device and a polarizing plate, which can suppress rainbow unevenness even when a polyester film is used as a polarizer protective film in a liquid crystal display device having a backlight light source formed of a white light emitting diode having an emission spectrum as follows: each of the wavelength regions of the blue region (400nm or more and less than 495nm), the green region (495nm or more and less than 600nm), and the red region (600nm or more and 780nm or less) has a peak top of an emission spectrum, and the half-value width of the peak in the red region (600nm or more and 780nm or less) is narrow (less than 5 nm).

For solving the problemsScheme(s)

Representative invention is described below.

Item 1.

A liquid crystal display device has: a backlight source, 2 polarizing plates, and a liquid crystal cell disposed between the 2 polarizing plates,

the backlight light source is a white light emitting diode with the following light emitting spectrum: has a peak top of an emission spectrum in each wavelength region of 400nm or more and less than 495nm, 495nm or more and less than 600nm, and 600nm or more and 780nm or less, and has a half-value width of a peak having the highest peak intensity in a wavelength region of 600nm or more and 780nm or less of less than 5nm,

at least one of the polarizing plates is obtained by laminating a polyester film on at least one surface of a polarizing plate,

the polyester film has a retardation of 1500 to 30000nm,

an antireflection layer and/or a low reflection layer is laminated on at least one surface of the polyester film.

Item 2.

The liquid crystal display device according to item 1, wherein, in the light emission spectrum of the backlight light source,

the half-value width of the peak having the highest peak intensity in a wavelength region of 400nm or more and less than 495nm is 5nm or more,

the half-value width of the peak having the highest peak intensity in a wavelength region of 495nm or more and less than 600nm is 5nm or more.

Item 3.

The liquid crystal display device according to item 1 or 2, wherein a surface reflectance of the surface of the antireflection layer at a wavelength of 550nm is 2.0% or less.

Item 4.

A polarizing plate for a liquid crystal display device having a backlight source comprising a white light emitting diode, which is obtained by laminating a polyester film on at least one surface of a polarizing plate,

the polyester film has a retardation of 1500 to 30000nm, and an antireflection layer and/or a low reflection layer is laminated on at least one surface of the polyester film,

the white light emitting diode has the following light emission spectrum: the emission spectrum has a peak top in each wavelength region of 400nm or more and less than 495nm, 495nm or more and less than 600nm, and 600nm or more and 780nm or less, and the half-value width of the peak having the highest peak intensity in the wavelength region of 600nm or more and 780nm or less is less than 5 nm.

Item 5.

The polarizing plate according to item 4, wherein a surface reflectance at a wavelength of 550nm of the surface of the antireflection layer is 2.0% or less.

ADVANTAGEOUS EFFECTS OF INVENTION

The liquid crystal display device and the polarizing plate of the present invention can ensure good visibility with generation of rainbow color spots significantly suppressed at any observation angle.

Detailed Description

Generally, a liquid crystal display device is configured by a rear module, a liquid crystal cell, and a front module in this order from a side facing a backlight light source to a side (visible side) where an image is displayed. The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface, and a polarizing plate disposed on the opposite side. Here, the polarizing plate is disposed on the side facing the backlight light source in the rear module, and on the side (visible side) displaying an image in the front module.

The liquid crystal display device of the present invention has at least a backlight source and a liquid crystal cell disposed between 2 polarizing plates as constituent members.

The liquid crystal display device may preferably have a configuration other than the backlight source, the polarizing plate, and the liquid crystal cell, for example, a color filter, a lens film, a diffusion sheet, an antireflection film, or the like. A luminance improving film may be provided between the light source side polarizing plate and the backlight light source. As the luminance improving film, for example, a reflection type polarizing plate which transmits one linearly polarized light and reflects a linearly polarized light orthogonal thereto is exemplified. As the reflective polarizing plate, for example, a DBEF (registered trademark) series Brightness Enhancement Film manufactured by Sumitomo 3M Limited can be suitably used. In general, a reflective polarizing plate is arranged such that the absorption axis of the reflective polarizing plate is parallel to the absorption axis of the light source side polarizing plate.

At least one of the 2 polarizing plates disposed in the liquid crystal display device is obtained by laminating a polyester film on at least one surface of a polarizing plate dyed with iodine such as polyvinyl alcohol (PVA). In the present invention, the polyester film has a specific retardation amount from the viewpoint of suppressing the iridescent unevenness, and an antireflection layer and/or a low reflection layer is laminated on at least one surface of the polyester film. The antireflection layer and/or the low reflection layer may be provided on the surface of the polyester film opposite to the surface of the laminated polarizing plate, or may be provided on both surfaces. Preferably, an antireflection layer and/or a low reflection layer is provided on a surface of the polyester film opposite to the surface on which the polarizing plate is laminated. When an antireflection layer and/or a low reflection layer is provided on one surface of the polyester film laminated polarizer, the antireflection layer and/or the low reflection layer is preferably provided between the polyester film and the polarizer. Further, other layers (for example, an easy adhesion layer, a hard coat layer, an antiglare layer, an antistatic layer, an antifouling layer, and the like) may be present between the antireflection layer and/or the low reflection layer and the polyester film. From the viewpoint of further suppressing the rainbow-like color spots, the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizing plate is preferably 1.53 to 1.62. A film (a polarizing plate comprising 3 layers) having no birefringence, such as a TAC film, an acrylic film, or a norbornene film, is preferably laminated on the other surface of the polarizer, but a film (a polarizing plate comprising 2 layers) is not necessarily laminated on the other surface of the polarizer. In the case of using polyester films as the protective films on both sides of the polarizing plate, the slow axes of the two polyester films are preferably substantially parallel to each other.

The polarizing plate may be any one of those used in the art (polarizing film) and may be selected as appropriate. A typical polarizing plate is a polarizing plate obtained by dyeing a dichroic material such as iodine on a polyvinyl alcohol film or the like, but the polarizing plate is not limited thereto, and a known polarizing plate or a polarizing plate that can be developed in the future can be appropriately selected and used.

As the PVA film, commercially available products can be used, and examples thereof include "Kuraray vinyl on (manufactured by Kuraray Co., Ltd.)," Tohcello vinyl on (manufactured by Tohcello Co., Ltd.), "Nikkilvinyl on (manufactured by Nippon synthetic chemical Co., Ltd.)" and the like. Examples of the dichroic material include iodine, diazo compounds, and polymethine dyes.

The polarizing plate can be obtained by any method, for example, as follows: the PVA film dyed with the dichroic material is uniaxially stretched in an aqueous boric acid solution, and washed and dried while maintaining the stretched state, thereby obtaining the PVA film. The stretching ratio of the uniaxial stretching is usually about 4 to 8 times, but is not particularly limited. Other production conditions and the like may be appropriately set according to a known method.

The backlight may be of a side light type having a light guide plate, a reflection plate, or the like as a constituent member, or of a direct type, and in the present invention, as the backlight light source of the liquid crystal display device, a backlight light source formed of a white light emitting diode having the following emission spectrum is preferable: the emission spectrum has a peak top in each of wavelength regions of 400nm or more and less than 495nm, 495nm or more and less than 600nm, and 600nm or more and 780nm or less, and the half-value width of the peak having the highest peak intensity in the wavelength region of 600nm or more and 780nm or less is less than 5 nm.

The respective peak wavelengths of blue, green and red defined in the CIE chromaticity diagram are known to be 435.8nm (blue), 546.1nm (green) and 700nm (red), respectively. The wavelength regions of 400nm or more and less than 495nm, 495nm or more and less than 600nm, and 600nm or more and 780nm or less correspond to a blue region, a green region, and a red region, respectively.

The upper limit of the half-value width of the peak having the highest peak intensity in the wavelength region of 600nm or more and 780nm or less is preferably less than 5nm, more preferably less than 4nm, and further preferably less than 3.5 nm. The lower limit is preferably 1nm or more, more preferably 1.5nm or more. When the half width of the peak is less than 5nm, the color gamut of the liquid crystal display device is enlarged, which is preferable. In addition, when the half-value width of the peak is less than 1nm, the light emission efficiency may be deteriorated. The shape of the emission spectrum is designed from the viewpoint of the balance between the required color gamut and the emission efficiency. Here, the half-value width refers to a peak width (nm) of 1/2 intensity of the peak intensity at the wavelength of the peak top.

The application of the backlight light source having the emission spectrum having the above characteristics to the LCD is a technology that has attracted attention due to the recent increase in the demand for color gamut expansion. In an LED using a conventionally used white LED (for example, a light-emitting element obtained by combining a blue light-emitting diode and an yttrium-aluminum garnet-based yellow phosphor) as a backlight light source, only about 20% of a spectrum recognizable to human eyes can be reproduced. On the other hand, when a backlight light source having an emission spectrum having the above characteristics is used, it can be said that 60% or more of colors can be reproduced.

The wavelength region of 400nm or more and less than 495nm is more preferably 430nm or more and 470nm or less. The wavelength region of 495nm or more and less than 600nm is more preferably 510nm or more and 560nm or less. The wavelength region of 600nm to 780nm is more preferably 600nm to 700nm, and still more preferably 610nm to 680 mn.

The half width of the peak at the peak top in each wavelength region of 400nm or more and less than 495nm, 495nm or more and less than 600nm in the emission spectrum (the half width of the peak having the highest peak intensity in each wavelength region) is not particularly limited, and the half width of the peak having the highest peak intensity in the wavelength region of 400nm or more and less than 495nm is preferably 5nm or more, and the half width of the peak having the highest peak intensity in the wavelength region of 495nm or more and less than 600nm is preferably 5nm or more. From the viewpoint of ensuring an appropriate color gamut, the upper limit of the peak half-value width in the peak top of each wavelength region of 400nm or more and less than 495nm, 495nm or more and less than 600nm (the half-value width of the peak having the highest peak intensity in each wavelength region) is preferably 140nm or less, preferably 120nm or less, preferably 100nm or less, more preferably 80nm or less, further preferably 60nm or less, and still further preferably 50nm or less.

Specific examples of the white light source having an emission spectrum having the above characteristics include a fluorescent light source obtained by combining a blue light-emitting diode and a fluorescent materialA white light emitting diode of a phosphor system. Among the above phosphors, red phosphor having a composition formula of K is exemplified₂SiF₆：Mn⁴⁺Fluoride phosphor (also referred to as "KSF") of (ii), and the like. Mn⁴⁺The phosphor of the activated fluoride complex is Mn⁴⁺A phosphor which is an activator and has a fluoride complex salt of an alkali metal, an amine or an alkaline earth metal as a host crystal. The fluoride complex forming the matrix crystal includes a substance having a coordination center of a 3-valent metal (B, Al, Ga, In, Y, Sc, lanthanide), a substance having a 4-valent metal (Si, Ge, Sn, Ti, Zr, Re, Hf), and a substance having a 5-valent metal (V, P, Nb, Ta), and the number of fluorine atoms coordinated around the substance is 5 to 7.

As Mn⁴⁺Suitable examples of the activated fluoride complex phosphor include: a. the₂[MF₆]: mn (A is selected from Li, Na, K, Rb, Cs, NH₄One or more of (1); m is at least one selected from Ge, Si, Sn, Ti and Zr), and E [ MF₆]: mn (E is more than one selected from Mg, Ca, Sr, Ba and Zn; M is more than one selected from Ge, Si, Sn, Ti and Zr), Ba_0.65、Zr_0.35F_2.70：Mn、A₃[ZrF₇]: mn (A is selected from Li, Na, K, Rb, Cs, NH₄One or more of) A) and₂[MF₅]: mn (A is selected from Li, Na, K, Rb, Cs, NH₄One or more of (1); m is more than one selected from Al, Ga and In), A₃[MF₆]: mn (A is selected from Li, Na, K, Rb, Cs, NH₄One or more of (1); m is more than one selected from Al, Ga and In), Zn₂[MF₇]: mn (M is more than one selected from Al, Ga and In), A [ In₂F₇]: mn (A is selected from Li, Na, K, Rb, Cs, NH₄One or more of) and the like.

Preferred Mn⁴⁺One of the activated fluoride complex phosphors is A having a hexafluoro complex salt of an alkali metal as a matrix crystal₂MF₆: mn (A is selected from Li, Na, K, Rb, Cs, NH₄One or more of (1); m is at least one selected from Ge, Si, Sn, Ti and Zr). Wherein, the preferred example is that A is selected from K (potassium) or Na (sodium) and M is Si (silicon) or Ti (titanium). Among them, a substance in which a is K (the ratio of K to the total amount of a is 99 mol% or more) and M is Si is particularly preferable. The activating element is desirably 100% Mn (manganese), and Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn, Mg, and the like may be included In a range of less than 10 mol% with respect to the total amount of the activating element. When M is Si, the ratio of Mn in the total of Si and Mn is desirably in the range of 0.5 mol% to 10 mol%. As other preferable Mn⁴⁺The activated fluoride complex phosphor may be represented by the formula A_2+xM_yMn_zF_n(A is Na and K; M is Si and Al; x is not less than 1 and not more than 1, y + z is not less than 0.9 and not more than 1.1, z is not less than 0.001 and not more than 0.4, and n is not less than 5 and not more than 7).

Among the backlight sources, a white light-emitting diode having a blue light-emitting diode and at least a fluoride phosphor as a phosphor is preferable, and a blue light-emitting diode and at least K as a phosphor are particularly preferable₂SiF₆：Mn⁴⁺The fluoride phosphor of (3) in the above range. For example, commercially available products such as NSSW306FT, which is a white LED manufactured by Nissan chemical industries, Ltd.

In addition, examples of the green phosphor among the above phosphors include those represented by β -SiAlON: eu, etc. as basic composition sialon phosphor, and (Ba, Sr)₂SiO₄: eu, etc. as a basic composition.

When a plurality of peaks are present in any wavelength region of a wavelength region of 400nm or more and less than 495nm, a wavelength region of 495nm or more and less than 600nm, or a wavelength region of 600nm or more and 780nm or less, the following is considered.

When a plurality of peaks are independent peaks, the half-value width of the peak having the highest peak intensity is preferably in the above range. Further, it is more preferable that the half-value width of the other peaks having an intensity of 70% or more of the maximum peak intensity is within the above range.

In the case where the half-value width of the peak having the highest peak intensity among the plurality of peaks can be directly measured for one independent peak having a shape in which the plurality of peaks overlap, the half-value width is used. Here, the independent peak means a peak having a region of 1/2 intensity reaching the peak intensity on both the short wavelength side and the long wavelength side of the peak. That is, when a plurality of peaks overlap and each peak does not have a region of 1/2 intensity on both sides of the peak, the plurality of peaks are regarded as one peak as a whole. For such a peak having a shape in which a plurality of peaks overlap, the width (nm) of the peak at the intensity of 1/2, which is the highest peak intensity among them, is taken as the half-value width.

Among the plurality of peaks, the peak having the highest peak intensity was defined as the peak top.

In each wavelength region of the wavelength region of 400nm or more and less than 495nm, the wavelength region of 495nm or more and less than 600nm, or the wavelength region of 600nm or more and 780nm or less, a peak having the highest peak intensity and peaks in other wavelength regions are preferably in a mutually independent relationship. In particular, in terms of color clarity, it is preferable that a region having an intensity equal to or higher than 1/3 or less than the peak intensity of the peak having the highest peak intensity in the wavelength region of 600nm or higher and 780nm or lower exists in the wavelength region between the peak having the highest peak intensity in the wavelength region of 495nm or higher and lower than 600nm and the peak having the highest peak intensity in the wavelength region of 600nm or higher and 780nm or lower.

The emission spectrum of the backlight source can be measured by using a spectrometer such as a multichannel spectrometer PMA-12 manufactured by Hamamatsu Photonics K.K.

The present inventors have conducted intensive studies and, as a result, have found that: in a liquid crystal display device having a backlight source formed of a white light-emitting diode having a peak top of an emission spectrum and a half-value width of a peak in a red region (600nm or more and 780nm or less) that are narrow and less than 5nm in each wavelength region of a blue region (400nm or more and less than 495nm), a green region (495nm or more and less than 600nm) and a red region (600nm or more and less than 780 nm), a liquid crystal display device in which an iridescence spot is suppressed and a polarizing plate are provided if a polyester film having an antireflection layer and/or a low-reflection layer as a polarizer protective film and having a specific retardation is used. The mechanism of suppressing generation of iridescent stains by the above-described means is considered as follows.

When an oriented polyester film is disposed on one side of a polarizing plate, the polarization state changes when linearly polarized light emitted from a backlight unit or the polarizing plate passes through the polyester film. One of the factors that cause the change in the polarization state is considered to be the possibility of the influence of the difference in refractive index at the interface between the air layer and the oriented polyester film or the difference in refractive index at the interface between the polarizing plate and the oriented polyester film. When linearly polarized light incident on the oriented polyester film passes through each interface, a part of the light is reflected by a refractive index difference between the interfaces. At this time, the polarization state of both the emitted light and the reflected light changes, which is considered to be one of the main causes of the occurrence of the rainbow-like color spots. Therefore, it is considered that by providing an antireflection layer or a low reflection layer on the surface of the oriented polyester film to reduce the surface reflection, the reflection at the interface between the air layer and the oriented polyester film is suppressed, and the rainbow-like unevenness is suppressed.

As described above, in the present invention, in a liquid crystal display device having a backlight source formed of a white light emitting diode having a peak top of an emission spectrum in each wavelength region of a blue region (400nm or more and less than 495nm), a green region (495nm or more and less than 600nm) and a red region (600nm or more and less than 780 nm), and having a narrow half-value width of a peak in the red region (600nm or more and 780nm or less), a rainbow-like color spot is not generated and excellent visibility can be obtained even when a polarizing plate using a polyester film as a polarizer protective film is used.

In the polarizing plate, a polarizer protective film made of a polyester film is preferably laminated on at least one surface of the polarizer. The polyester film used for the polarizer protective film preferably has a retardation of 1500 to 30000 nm. When the retardation amount is within the above range, the amount of rainbow unevenness tends to be further reduced, and the retardation amount is preferably. The lower limit of the retardation is preferably 3000nm, and the lower limit thereof is preferably 3500nm, more preferably 4000nm, still more preferably 6000nm, and still more preferably 8000 nm. The preferable upper limit is 30000nm, and in the polyester film having a retardation of not less than this, the thickness tends to be considerably large, and the workability as an industrial material tends to be lowered. In the present specification, the retardation amount refers to an in-plane retardation amount unless otherwise specified.

The retardation may be determined by measuring the refractive index and the thickness in the biaxial direction, or may be determined by using a commercially available automatic birefringence measurement device such as KOBRA-21ADH (Oji Scientific Instruments co., Ltd.). The refractive index can be determined by an abbe refractometer (measurement wavelength 589 nm).

The ratio (Re/Rth) of the retardation (Re: in-plane retardation) of the polyester film to the retardation (Rth) in the thickness direction is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.6 or more. As the ratio (Re/Rth) of the retardation to the retardation in the thickness direction is larger, the birefringence action becomes more isotropic, and the occurrence of rainbow-like color spots due to the observation angle tends to be less likely to occur. In a completely uniaxial (1-axis symmetric) film, the ratio of the retardation to the retardation in the thickness direction (Re/Rth) is 2.0, and therefore the upper limit of the ratio of the retardation to the retardation in the thickness direction (Re/Rth) is preferably 2.0. The thickness direction retardation is an average of the retardation obtained by multiplying each of the 2 birefringence Δ Nxz and Δ Nyz when the film is observed from a cross section in the thickness direction by the film thickness d.

From the viewpoint of further suppressing the rainbow-like color spots, the NZ coefficient of the polyester film is preferably 2.5 or less, more preferably 2.0 or less, further preferably 1.8 or less, and further preferably 1.6 or less. Further, in a completely uniaxial (one-axis symmetric) film, the NZ coefficient is 1.0, and therefore the lower limit of the NZ coefficient is 1.0. However, as the film approaches a perfect uniaxial (one-axis symmetric) film, the mechanical strength in the direction perpendicular to the orientation direction tends to be significantly reduced, and therefore, attention is required.

The NZ coefficient is represented by | Ny-Nz |/| Ny-Nx |, where Ny represents the refractive index in the slow axis direction, Nx represents the refractive index in the direction perpendicular to the slow axis (the refractive index in the fast axis direction), and NZ represents the refractive index in the thickness direction. An orientation axis of the film was determined using a molecular orientation meter (an Oji Scientific Instruments Co., Ltd., MOA-6004 type molecular orientation meter), and refractive indices (Ny, Nx, wherein Ny > Nx) in the orientation axis direction and a direction perpendicular thereto and a refractive index (Nz) in the thickness direction were determined using an Abbe refractometer (ATAGO CO., LTD, NAR-4T, measurement wavelength 589 nm). The value thus obtained can be substituted into | Ny-Nz |/| Ny-Nx | to obtain the Nz coefficient.

From the viewpoint of further suppressing the rainbow-like color spots, the value of Ny-Nx of the polyester film is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.08 or more, still more preferably 0.09 or more, and most preferably 0.1 or more. The upper limit is not particularly limited, and in the case of a polyethylene terephthalate film, the upper limit is preferably about 1.5.

In the present invention, it is preferable that the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer constituting the polarizing plate is in the range of 1.53 to 1.62. This can suppress reflection at the interface between the polarizing plate and the polyester film, and further suppress rainbow unevenness. When the refractive index exceeds 1.62, rainbow-like color unevenness may occur when viewed from an oblique direction. The refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizing plate is preferably 1.61 or less, more preferably 1.60 or less, still more preferably 1.59 or less, and still more preferably 1.58 or less.

On the other hand, the lower limit of the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizing plate was 1.53. If the refractive index is less than 1.53, the crystallization of the polyester film becomes insufficient, and the properties obtained by stretching, such as dimensional stability, mechanical strength, and chemical resistance, become insufficient, which is not preferable. The refractive index is preferably 1.56 or more, more preferably 1.57 or more. Any range in which the upper limits and the lower limits of the refractive index are combined is assumed.

In order to set the refractive index of the polyester film in the range of 1.53 to 1.62 in the direction parallel to the transmission axis direction of the polarizer, the transmission axis of the polarizer is preferably substantially parallel to the fast axis (direction perpendicular to the slow axis) of the polyester film. The polyester film can be adjusted to have a refractive index as low as about 1.53 to 1.62 in the fast axis direction, which is a direction perpendicular to the slow axis, by stretching in a film forming step to be described later. The refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizing plate can be set to 1.53 to 1.62 by making the fast axis direction of the polyester film substantially parallel to the transmission axis direction of the polarizing plate. Here, the substantially parallel means that the angle formed by the transmission axis of the polarizing plate and the fast axis of the polarizing plate protective film (polyester film) is-15 ° to 15 °, preferably-10 ° to 10 °, more preferably-5 ° to 5 °, further preferably-3 ° to 3 °, further preferably-2 ° to 2 °, and further preferably-1 ° to 1 °. In a preferred embodiment, substantially parallel means substantially parallel. The term "substantially parallel" as used herein means that the transmission axis of the polarizing plate is parallel to the fast axis of the polyester film to the extent that the inevitable variations are allowed when the polarizing plate and the protective film are bonded. The direction of the slow axis can be determined by measurement with a molecular orientation meter (for example, an Oji Scientific Instruments Co., Ltd., manufactured by Ltd., MOA-6004 type molecular orientation meter).

That is, the refractive index of the polyester film in the fast axis direction is preferably 1.53 or more and 1.62 or less, and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizing plate can be 1.53 or more and 1.62 or less by laminating the polarizing plate and the fast axis of the polyester film so as to be substantially parallel to each other.

The polarizer protective film formed of the polyester film can be used for a polarizing plate on both the incident light side (light source side) and the outgoing light side (visible side), and is preferably used at least as a protective film for a polarizing plate on the outgoing light side (visible side).

The polarizing plate disposed on the light-emitting side may be a polarizer protective film formed of the polyester film, disposed on the liquid crystal cell side from the polarizer as a starting point, disposed on the light-emitting side, disposed on both sides, and preferably disposed at least on the light-emitting side.

In the polarizing plate disposed on the incident light side, the polarizer protective film formed of the polyester film may be disposed on the incident light side from the polarizer as a starting point, may be disposed on the liquid crystal cell side, may be disposed on both sides, or may be disposed at least on the incident light side. In addition, a polarizer protective film having a low retardation such as a triacetylcellulose film may be used instead of the polarizer protective film formed of a polyester film for the polarizing plate disposed on the incident light side.

The polyester used in the polyester film may be polyethylene terephthalate or polyethylene naphthalate, or may contain other copolymerizable components. These resins are excellent in transparency, thermal properties and mechanical properties, and the retardation can be easily controlled by stretching. In particular, polyethylene terephthalate is an optimum material because it has a large intrinsic birefringence, can suppress the refractive index in the fast axis (direction perpendicular to the slow axis) to a low level by stretching the film, and can easily obtain a large retardation even when the film is thin.

In order to suppress deterioration of an optically functional dye such as an iodine dye, it is desirable that the polyester film has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at 380nm is more preferably 15% or less, still more preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, the deterioration of the optically functional dye by ultraviolet rays can be suppressed. The transmittance is measured in a direction perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, hitachi U-3500 type).

In order to make the transmittance of the polyester film at a wavelength of 380nm 20% or less, it is desirable to appropriately adjust the type and concentration of the ultraviolet absorber and the thickness of the film. The ultraviolet absorber used in the present invention is a known one. Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, and from the viewpoint of transparency, an organic ultraviolet absorber is preferable. Examples of the organic ultraviolet absorber include benzotriazole-based, benzophenone-based, cyclic imino ester-based, and combinations thereof, and the range of absorbance defined in the present invention is not particularly limited. However, benzotriazole and cyclic imino ester are particularly preferable from the viewpoint of durability. When 2 or more ultraviolet absorbers are used in combination, ultraviolet rays of respective wavelengths can be absorbed simultaneously, and thus the ultraviolet absorption effect can be further improved.

Examples of benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and acrylonitrile-based ultraviolet absorbers include: 2- [2 ' -hydroxy-5 ' - (methacryloyloxymethyl) phenyl ] -2H-benzotriazole, 2- [2 ' -hydroxy-5 ' - (methacryloyloxyethyl) phenyl ] -2H-benzotriazole, 2- [2 ' -hydroxy-5 ' - (methacryloyloxypropyl) phenyl ] -2H-benzotriazole, 2 ' -dihydroxy-4, 4 ' -dimethoxybenzophenone, 2 ', 4,4 ' -tetrahydroxybenzophenone, 2, 4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2- (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) -5-chlorobenzotriazole, 2- (5-chloro (2H) -benzotriazol-2-yl) -4-methyl-6- (tert-butyl) phenol, 2' -methylenebis (4- (1,1,3, 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, etc. As cyclic imino ester ultraviolet absorbers, examples thereof include: 2, 2' - (1, 4-phenylene) bis (4H-3, 1-benzoxazin-4-one), 2-methyl-3, 1-benzoxazin-4-one, 2-butyl-3, 1-benzoxazin-4-one, 2-phenyl-3, 1-benzoxazin-4-one, and the like, but is not particularly limited thereto.

In addition, it is also a preferable embodiment to contain various additives other than the catalyst in addition to the ultraviolet absorber within a range not to impair the effects of the present invention. Examples of the additives include: inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light-resistant agents, flame retardants, heat stabilizers, antioxidants, antigelling agents, surfactants, and the like. In order to exhibit high transparency, it is also preferable that the polyester film contains substantially no particles. "substantially free of particles" means: for example, in the case of inorganic particles, the content of the inorganic element is 50ppm or less, preferably 10ppm or less, particularly preferably the detection limit or less when the inorganic element is quantitatively determined by fluorescent X-ray analysis.

It is preferable that an antireflection layer and/or a low reflection layer is provided on at least one surface of the polyester film as the polarizer protective film used in the present invention. The surface reflectance of the antireflection layer used in the present invention is preferably 2.0% or less. When the content exceeds 2.0%, iridescent stains are easily visualized. The surface reflectance of the antireflection layer is more preferably 1.6% or less, still more preferably 1.2% or less, and particularly preferably 1.0% or less. The lower limit of the surface reflectance of the antireflection layer is not particularly limited, and is, for example, 0.01%. The reflectance is most preferably 0%. The reflectance can be measured by any method, and for example, the reflectance of light at a wavelength of 550nm can be measured from the surface on the side of the anti-reflection layer using a spectrophotometer (Shimadzu corporation, UV-3150).

The antireflection layer may be a single layer or a plurality of layers, and in the case of a single layer, if the thickness of the low refractive index layer formed of a material having a lower refractive index than the plastic film (polyester film) is formed so as to be 1/4 wavelength or an odd multiple thereof as the wavelength of light, the antireflection effect can be obtained. When the antireflection layer is a multilayer, if the low refractive index layer and the high refractive index layer are alternately formed in 2 or more layers and the thickness of each layer is appropriately controlled and laminated, an antireflection effect can be obtained. Further, if necessary, a hard coat layer may be laminated between the antireflection layers, and an antifouling layer may be formed on the hard coat layer.

As the antireflection layer, in addition to this, an antireflection layer using a moth-eye structure can be given. The moth-eye structure is an uneven structure formed on a surface at a pitch smaller than a wavelength, and is capable of changing a sharp and discontinuous change in refractive index at a boundary portion with air into a continuous and gradually changing change in refractive index. Thus, by forming the moth-eye structure on the surface, light reflection on the surface of the film is reduced. The formation of the antireflection layer using the moth-eye structure can be performed, for example, with reference to japanese patent application laid-open No. 2001-517319.

Examples of the method for forming the antireflection film include: a dry coating method of forming an antireflection layer on the surface of a base material (polyester film) by vapor deposition or sputtering; a wet coating method in which an antireflection coating liquid is applied to the surface of a substrate and dried to form an antireflection layer; alternatively, a combination of these two methods may be used. The composition of the antireflection layer and the method for forming the antireflection layer are not particularly limited as long as the above properties are satisfied.

The low reflection layer may be formed using a known material. For example, by the following method or the like: a method of laminating at least 1 or more thin films of a metal or an oxide by an evaporation method or a sputtering method; a method of coating one or more organic thin films. As the low reflection layer, a layer obtained by coating an organic film having a lower refractive index than a polyester film, a hard coat layer laminated on a polyester film, or the like is preferably used. The surface reflectance of the low reflection layer is preferably less than 5%, more preferably 4% or less, further preferably 3% or less, and further preferably 2% or less. The lower limit is not particularly limited, but is preferably about 0.8% to 1.0%.

The antireflection layer and/or the low reflection layer may be further imparted with an antiglare function. This can further suppress the rainbow unevenness. That is, a combination of an antireflection layer and an antiglare layer, a combination of a low-reflection layer and an antiglare layer, and a combination of an antireflection layer and a low-reflection layer and an antiglare layer may be used. Particularly preferred is a combination of a low reflection layer and an antiglare layer. As the antiglare layer, a known antiglare layer can be used. For example, from the viewpoint of suppressing the surface reflection of the film, it is preferable to laminate an antiglare layer on a polyester film and then laminate an antireflection layer or a low reflection layer on the antiglare layer.

When the antireflection layer or the low reflection layer is provided, the polyester film preferably has an easy-adhesion layer on the surface thereof. In this case, from the viewpoint of suppressing interference due to reflected light, it is preferable to adjust the refractive index of the easy-adhesion layer to be in the vicinity of the geometric average of the refractive index of the anti-reflection layer and the refractive index of the polyester film. The refractive index of the easy-adhesion layer can be adjusted by a known method, and can be easily adjusted by, for example, adding titanium, germanium, or another metal species to the binder resin.

The polyester film may be subjected to corona treatment, coating treatment, flame treatment, or the like in order to improve adhesion to the polarizing plate.

In the present invention, in order to improve the adhesiveness to the polarizing plate, the film of the present invention preferably has an easy-adhesion layer containing at least 1 of a polyester resin, a polyurethane resin, or a polyacrylic resin as a main component on at least one surface thereof. Here, the "main component" means a component of 50 mass% or more of the solid components constituting the easy adhesion layer. The coating liquid used for forming the easy adhesion layer is preferably an aqueous coating liquid containing at least 1 of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin. Examples of these coating liquids include: water-soluble or water-dispersible copolyester resin solutions, acrylic resin solutions, urethane resin solutions, and the like disclosed in japanese patent No. 3567927, japanese patent No. 3589232, japanese patent No. 3589233, japanese patent No. 3900191, and japanese patent No. 4150982.

The easy-adhesion layer can be obtained by applying the coating liquid to one or both surfaces of a uniaxially stretched film in the longitudinal direction, drying the film at 100 to 150 ℃, and stretching the film in the transverse direction. The coating weight of the final easy-bonding layer is preferably controlled to be 0.05-0.20 g/m². If the coating weight is less than 0.05g/m²The adhesiveness to the obtained polarizing plate may be insufficient. On the other hand, if the coating amount exceeds 0.20g/m²Sometimes the blocking resistance is reduced. When the easy-adhesion layers are provided on both sides of the polyester film, the coating amounts of the easy-adhesion layers on both sides may be the same or different, and may be set within the above ranges independently.

In order to impart slidability, it is preferable to add particles to the easy-adhesion layer. It is preferable to use particles having an average particle diameter of 2 μm or less. If the average particle diameter of the particles exceeds 2 μm, the particles are easily detached from the coating layer. Examples of the particles contained in the easy adhesion layer include: inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconium oxide, tungsten oxide, lithium fluoride, and calcium fluoride, and organic polymer-based particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. These may be added alone to the easy-adhesion layer or in combination of 2 or more.

As a method for applying the coating liquid, a known method can be used. Examples thereof include: the reverse roll coating method, gravure coating method, kiss coating method, roll brushing method, spray coating method, air knife coating method, wire bar coating method, and tube blade method, and the like, which may be performed alone or in combination.

The average particle size of the particles was measured by the following method. The particles were photographed by a Scanning Electron Microscope (SEM), and the maximum diameter (distance between 2 points farthest apart) of 300 to 500 particles was measured at a magnification of 2 to 5mm for 1 smallest particle, and the average value was defined as the average particle diameter.

The polyester film used as the polarizer protective film can be produced by a method for producing a usual polyester film. For example, the following methods may be mentioned: a non-oriented polyester, which is obtained by melting a polyester resin and extrusion-molding the same into a sheet, is stretched in the longitudinal direction at a temperature not lower than the glass transition temperature by the speed difference of rolls, then stretched in the transverse direction by a tenter, and subjected to a heat treatment.

The polyester film used in the present invention may be a uniaxially stretched film or a biaxially stretched film, and when the biaxially stretched film is used as a polarizer protective film, no rainbow-like unevenness is observed even from the right above the film surface, but rainbow-like unevenness is observed in an oblique view, and therefore, attention is required.

Specifically, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130 ℃, and particularly preferably 90 to 120 ℃. When the film is oriented so that the slow axis is in the TD direction, the longitudinal stretching magnification is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. The transverse stretching magnification is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. When the film is oriented so that the slow axis is in the MD direction, the longitudinal stretching magnification is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. The stretching magnification in the transverse direction is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times.

In order to control the refractive index and retardation in the fast axis direction of the polyester film to the above ranges, it is preferable to control the ratio of the longitudinal stretching magnification to the transverse stretching magnification. If the difference in longitudinal and lateral draw ratios is too small, the refractive index of the polyester film in the fast axis direction tends to exceed 1.62, and it is difficult to increase the retardation, which is not preferable. In addition, when the stretching temperature is set to be low, it is also preferable to lower the refractive index in the fast axis direction of the polyester film and to increase the retardation. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250 ℃, particularly preferably 180 to 245 ℃.

In order to suppress variation in retardation amount, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and stretching ratio greatly affect the thickness unevenness of the film, it is preferable to optimize the film forming conditions from the viewpoint of reducing the thickness unevenness. In particular, when the longitudinal stretching magnification is reduced in order to increase the retardation, the longitudinal thickness unevenness may become large. Since the thickness variation in the machine direction has a region in which the thickness variation becomes very poor in a certain specific range of the stretch ratio, it is preferable to set film forming conditions so as to deviate from this range.

The thickness variation of the polyester film is preferably 5.0% or less, more preferably 4.5% or less, further preferably 4.0% or less, and particularly preferably 3.0% or less.

As described above, the retardation of the polyester film can be controlled to a specific range by appropriately setting the stretching ratio, the stretching temperature, and the film thickness. For example, a higher stretching ratio, a lower stretching temperature, and a thicker film thickness make it easier to obtain a higher retardation. Conversely, the lower the stretch ratio, the higher the stretching temperature, and the thinner the film thickness, the more easily a low retardation can be obtained. However, when the thickness of the film is increased, the retardation in the thickness direction tends to be increased. Therefore, it is desirable that the film thickness is appropriately set in the range described later. Further, it is preferable to set the final film forming conditions by examining physical properties and the like required for processing while controlling the retardation amount.

The thickness of the polyester film is arbitrary, and is preferably in the range of 15 to 300 μm, and more preferably in the range of 15 to 200 μm. Even a thin film having a thickness of less than 15 μm can in principle obtain a retardation of 1500nm or more. However, in this case, the anisotropy of the mechanical properties of the film becomes remarkable, and cracks, breakage, and the like are likely to occur, and the practicability as an industrial material is remarkably lowered. The lower limit of the thickness is particularly preferably 25 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizer becomes too thick, which is not preferable. From the viewpoint of practical use as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. The upper limit of the thickness is particularly preferably 100 μm which is equivalent to that of a typical TAC film. In order to control the retardation to the range of the present invention within the above thickness range, the polyester used as the film base material is preferably polyethylene terephthalate.

The method of blending the ultraviolet absorber into the polyester film may be combined with a known method, and may be, for example, blended by the following method: the dried ultraviolet absorber and the polymer material are mixed in advance using a kneading extruder to prepare a master batch, and a predetermined master batch and the polymer material are mixed at the time of film formation.

In this case, the concentration of the ultraviolet absorber in the masterbatch is preferably 5 to 30 mass% in order to uniformly disperse the ultraviolet absorber and to economically blend the ultraviolet absorber. The master batch is preferably prepared by extrusion using a kneading extruder at an extrusion temperature of not less than the melting point of the polyester raw material and not more than 290 ℃ for 1to 15 minutes. When the temperature is 290 ℃ or higher, the weight loss of the ultraviolet absorber increases, and the viscosity of the master batch decreases greatly. When the extrusion time is 1 minute or less, it becomes difficult to uniformly mix the ultraviolet absorber. In this case, a stabilizer, a color tone adjuster, and an antistatic agent may be added as needed.

Further, it is preferable that the polyester film is formed into a multilayer structure having at least 3 layers or more, and an ultraviolet absorber is added to an intermediate layer of the film. Specifically, a 3-layer film having an ultraviolet absorber in the intermediate layer can be produced as follows. Pellets of the polyester for the outer layer were individually mixed and dried, and a master batch containing an ultraviolet absorber for the intermediate layer and pellets of the polyester were mixed at a predetermined ratio and dried, and then supplied to a known melt-laminating extruder, extruded into a sheet form through a slit-shaped die, and cooled and solidified on a casting roll to produce an unstretched film. That is, using 2 or more extruders and a 3-layer manifold or confluence block (for example, confluence block having a rectangular confluence part), film layers constituting the two outer layers and a film layer constituting the intermediate layer were laminated, and 3-layer sheets were extruded from a pipe head and cooled by a casting roll to produce an unstretched film. In order to remove foreign matters contained in the raw material polyester, which cause optical defects, it is preferable to perform high-precision filtration during melt extrusion. The filter medium used for high-precision filtration of the molten resin preferably has a filter particle size (initial filtration efficiency 95%) of 15 μm or less. If the filter medium has a filter particle size of more than 15 μm, removal of foreign matter of 20 μm or more tends to be insufficient.

Examples

The present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples described below, and can be carried out by appropriately changing the examples within a range that can be adapted to the gist of the present invention, and these examples are included in the scope of protection of the present invention. The physical properties in the following examples were evaluated as follows.

(1) Refractive index of polyester film

The slow axis direction of the film was determined using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments co., ltd.) and a rectangle of 4cm × 2cm was cut out so that the slow axis direction was parallel to the long side to obtain a sample for measurement. For this sample, the refractive index (refractive index in the slow axis direction: Ny, refractive index in the fast axis direction (refractive index in the direction orthogonal to the slow axis direction: Nx) and refractive index in the thickness direction (Nz) of the orthogonal biaxial axes were obtained by using an Abbe refractometer (NAR-4T, manufactured by LTD, Inc.) at a measurement wavelength of 589 nm.

(2) Retardation (Re)

The retardation is a parameter defined by the product (Δ Nxy × d) of the refractive index anisotropy (Δ Nxy ═ Nx-Ny |) of the orthogonal biaxial refractive indices on the film and the film thickness d (nm), and is a standard indicating optical isotropy and anisotropy. The biaxial refractive index anisotropy (Δ Nxy) is obtained by the following method. The slow axis direction of the film was determined using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments co., ltd.) and a rectangle of 4cm × 2cm was cut out as a measurement sample so that the slow axis direction was parallel to the long side of the measurement sample. For this sample, refractive indices (refractive index in the slow axis direction: Ny, refractive index in the direction orthogonal to the slow axis direction: Nx) and refractive index in the thickness direction (Nz) of the orthogonal biaxial axes were obtained by an Abbe refractometer (manufactured by ATAGO CO., LTD, NAR-4T, measurement wavelength 589nm), and the absolute value of the difference in refractive indices (i Nx-Ny i) of the biaxial axes was used as the anisotropy of refractive index (Δ Nxy). The thickness D (nm) of the film was measured by using an electrical micrometer (Fine Liu off Co., Ltd., Miritoron 1245D), and the unit was converted to nm. The retardation (Re) is determined from the product (Δ Nxy × d) of the anisotropy of the refractive index (Δ Nxy) and the thickness d (nm) of the thin film.

(3) Retardation in thickness direction (Rth)

The retardation in the thickness direction is a parameter representing an average of the 2 birefringence Δ Nxz (═ Nx-Nz |), (| Ny-Nz |) and Δ Nyz (═ Ny-Nz |) obtained by multiplying the respective retardation values by the film thickness d when viewed from a cross section in the film thickness direction. Nx, Ny, Nz and the film thickness d (nm) were obtained by the same method as the measurement of the retardation amount, and the average value of (Δ Nxz × d) and (Δ Nyz × d) was calculated to obtain the retardation amount in the thickness direction (Rth).

(4) Coefficient of NZ

The values of Ny, Nx, and Nz obtained in (1) above are substituted into Nz | Ny-Nz |/| Ny-Nx | to obtain the value of the Nz coefficient.

(5) Measurement of emission spectrum of backlight light source

The liquid crystal display device used in each example was manufactured by REGZA43J10X manufactured by toshiba corporation. The emission spectrum of the backlight light source (white light emitting diode) of the liquid crystal display device was measured by using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics k.k., and emission spectra having peaks were observed at around 450nm, 535nm, and 630 nm. Regarding the half width of each peak top (half width of the peak having the highest peak intensity in each wavelength region), the peak at 450nm was 17nm, the peak at 535nm was 45nm, and the peak at 630nm was 2nm, respectively. In this light source, although a plurality of peaks are present in a wavelength region of 600nm to 780nm, the half-value width is evaluated as a peak near 630nm where the peak intensity is highest in this region. The exposure time during the spectrometry was set to 20 msec.

(6) Reflectivity of light

The 5-degree reflectance at a wavelength of 550nm was measured from the surface on the side of the anti-reflection layer (or on the side of the low-reflection layer) using a spectrophotometer (UV-3150, manufactured by Shimadzu corporation). After coating a black marker on the surface of the polyester film opposite to the side provided with the antireflection layer (or low reflection layer), a black polyvinyl chloride insulating Tape (Kyowa co., Ltd, Vinyl Tape HF-737, 50mm wide) was attached and measured.

(7) Iridescent speckle Observation

The liquid crystal display devices obtained in the respective examples were visually observed in a dark place from the front and in the oblique direction, and the presence or absence of occurrence of rainbow unevenness was determined as follows.

O: no iridescent plaques were observed

And (delta): slight iridescent spotting was observed

X: iridescent plaques were observed

X: obvious rainbow spots were observed

Production example 1 polyester A

The esterification reaction tank was heated, and when the temperature reached 200 ℃, 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added, and 0.017 parts by mass of antimony trioxide as a catalyst, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were added while stirring. Subsequently, the esterification reaction was carried out under a pressure and temperature rise condition, and after the pressure esterification reaction was carried out under a gage pressure of 0.34MPa at 240 ℃, the esterification reaction tank was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Further, the temperature was raised to 260 ℃ over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, the resulting mixture was dispersed by a high-pressure disperser, and after 15 minutes, the esterification reaction product was transferred to a polycondensation reaction tank and subjected to polycondensation reaction at 280 ℃ under reduced pressure.

After the completion of the polycondensation reaction, the reaction mixture was filtered through a NASLON filter having a 95% cutoff diameter of 5 μm, extruded from a nozzle into a strand form, cooled and solidified with cooling water having been subjected to a filtration treatment (pore diameter: 1 μm or less), and cut into pellets. The resulting polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62dl/g and was substantially free of inactive particles and internally precipitated particles. (hereinafter abbreviated as PET (A))

Production example 2 polyester B

10 parts by mass of a dried ultraviolet absorber (2, 2' - (1, 4-phenylene) bis (4H-3, 1-benzoxazin-4-one) and 90 parts by mass of a pellet-free PET (A) (intrinsic viscosity: 0.62dl/g) were mixed together, and a kneading extruder was used to obtain a polyethylene terephthalate resin (B) containing an ultraviolet absorber.

(hereinafter abbreviated as PET (B))

Production example 3 preparation of coating liquid for adhesive Property modification

The ester exchange reaction and the polycondensation reaction were carried out by a conventional method to prepare a water-dispersible metal sulfonate group-containing copolyester resin having a composition of a dicarboxylic acid component (with respect to the whole dicarboxylic acid component) 46 mol% of terephthalic acid, 46 mol% of isophthalic acid, and 8 mol% of sodium 5-sulfoisophthalate, and a diol component (with respect to the whole diol component) 50 mol% of ethylene glycol, and 50 mol% of neopentyl glycol. Subsequently, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 part by mass of a nonionic surfactant were mixed, and then heated and stirred to 77 ℃. Further, after 3 parts by mass of aggregate silica particles (SILYSIA 310, manufactured by FUJI SILYSIA CHEMICAL ltd.) were dispersed in 50 parts by mass of water, 0.54 part by mass of an aqueous dispersion of SILYSIA 310 was added to 99.46 parts by mass of the water-dispersible copolyester resin solution, and 20 parts by mass of water was added thereto with stirring to obtain an adhesion-modifying coating solution.

Production example 4 preparation of high refractive index coating agent

In a reaction vessel, 80 parts by mass of methyl methacrylate, 20 parts by mass of methacrylic acid, 1 part by mass of azobisisobutyronitrile and 200 parts by mass of isopropyl alcohol were charged and reacted at 80 ℃ for 7 hours under a nitrogen atmosphere to obtain an isopropyl alcohol solution of a polymer having a weight average molecular weight of 30000. The obtained polymer solution was further diluted with isopropyl alcohol until the solid content became 5% by mass, to obtain an acrylic resin solution B. Next, the obtained acrylic resin solution B was mixed as follows to obtain a coating liquid for forming a high refractive index layer.

Preparation example 5 preparation of Low refractive index coating agent

2,2, 2-trifluoroethyl acrylate (45 parts by mass), perfluorooctyl ethyl acrylate (45 parts by mass), acrylic acid (10 parts by mass), azobisisobutyronitrile (1.5 parts by mass), and methyl ethyl ketone (200 parts by mass) were charged into a reaction vessel, and reacted at 80 ℃ for 7 hours under a nitrogen atmosphere to obtain a methyl ethyl ketone solution of a polymer having a weight average molecular weight of 20000. The obtained polymer solution was diluted with methyl ethyl ketone until the solid content concentration became 5% by mass, to obtain a fluoropolymer solution C. The obtained fluoropolymer solution C was mixed as follows to obtain a low refractive index layer forming coating liquid.

Production example 6 preparation of anti-glare layer coating agent-1

An unsaturated double bond-containing acrylic copolymer Cyclomer P ACA-Z250 (manufactured by Daicel Chemical corporation) (49 parts by mass), cellulose acetate propionate CAP482-20 (number average molecular weight 75000) (manufactured by Eastman Chemical Company) (3 parts by mass), an acrylic monomer AYARAD DPHA (manufactured by nippon Chemical corporation) (49 parts by mass), an acrylic-styrene copolymer (average particle diameter 4.0 μm) (manufactured by water Chemical corporation) (2 parts by mass), and IRGACURE 184 (manufactured by BASF corporation) (10 parts by mass) were mixed so that the solid content became 35% by mass, and methyl ethyl ketone was added: 1-butanol ═ 3: 1to obtain an antiglare layer-forming coating liquid.

Production example 7 production of anti-glare layer coating agent-2

An unsaturated double bond-containing acrylic copolymer CYCLOMER P ACA-Z250 (manufactured by Daicel Chemical Co., Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-0.5 (number average molecular weight 25000) (manufactured by Eastman Chemical Company) (3 parts by mass), an acrylic monomer AYARAD DPHA (manufactured by Nippon Chemical Co., Ltd.) (49 parts by mass), an acrylic-styrene copolymer (average particle diameter 4.0 μm) (manufactured by Water Chemical Co., Ltd.) (4 parts by mass), and IRGACURE 184 (manufactured by BASF Co., Ltd.) (10 parts by mass) were allowed to stand at a solid content of 35% by mass, and methyl ethyl ketone was added: 1-butanol ═ 3: 1to obtain an antiglare layer-forming coating liquid.

Production example 8 production of anti-glare layer coating agent-3

An unsaturated double bond-containing acrylic copolymer CYCLOMER P ACA-Z250 (manufactured by Daicel Chemical Co., Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-0.2 (number average molecular weight 15000) (manufactured by Eastman Chemical Company) (3 parts by mass), an acrylic monomer AYARAD DPHA (manufactured by Nippon Chemical Co., Ltd.) (49 parts by mass), an acrylic-styrene copolymer (average particle diameter 4.0 μm) (manufactured by Water Chemical Co., Ltd.) (2 parts by mass), and IRGACURE 184 (manufactured by BASF Co., Ltd.) (10 parts by mass) were allowed to stand at a solid content of 35% by mass, and methyl ethyl ketone was added: 1-butanol ═ 3: 1to obtain an antiglare layer-forming coating liquid.

(polarizer protective film 1)

After 90 parts by mass of pellet-free pet (a) resin pellets and 10 parts by mass of uv absorber-containing pet (b) resin pellets as raw materials for the intermediate layer of the base film were dried under reduced pressure (1Torr) at 135 ℃ for 6 hours, they were supplied to the extruder 2 (for the intermediate layer II), and further, pet (a) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I and the outer layer III), respectively, and melted at 285 ℃. The 2 polymers were each filtered with a filter medium of a stainless steel sintered body (nominal filtration accuracy 10 μm particle 95% cutoff), laminated with 2 kinds of 3-layer flow blocks, extruded from a pipe head into a sheet shape, wound around a casting drum (casting drum) having a surface temperature of 30 ℃ by an electrostatic casting method, cooled and solidified, and an unstretched film was produced. In this case, the ratio of the thicknesses of the layers I, II, and III is 10: 80: the discharge amount of each extruder was adjusted in the manner of 10.

Then, the coating weight after drying was set to 0.08g/m by the reverse roll method²The coating liquid for modifying adhesiveness was applied to both surfaces of the non-stretched PET film, and then dried at 80 ℃ for 20 seconds.

The unstretched film on which the coating layer was formed was introduced into a tenter stretcher, while holding the end of the film with clips, the film was introduced into a hot air zone at 125 ℃ and stretched 4.0 times in the width direction. Subsequently, the film was treated at 225 ℃ for 10 seconds while maintaining the stretching width in the width direction, and further subjected to a relaxation treatment of 3.0% in the width direction to obtain a uniaxially stretched PET film having a film thickness of about 100 μm.

The coating liquid for forming a high refractive index layer obtained by the above method was applied to one coated surface of the uniaxially stretched PET film, and dried at 150 ℃ for 2 minutes to form a high refractive index layer having a thickness of 0.1. mu.m. The coating liquid for forming a low refractive index layer obtained by the above method was applied on the high refractive index layer, and dried at 150 ℃ for 2 minutes to form a low refractive index layer having a film thickness of 0.1 μm, thereby obtaining a polarizer protective film 1 in which an antireflection layer was laminated.

(polarizer protective film 2)

Film formation was performed in the same manner as for the polarizing plate protective film 1 except that the linear velocity was changed and the thickness of the unstretched film was changed, to obtain a polarizing plate protective film 2 having a film thickness of about 80 μm in which an antireflection layer was laminated.

(polarizer protective film 3)

Film formation was performed in the same manner as for the polarizing plate protective film 1 except that the linear velocity was changed and the thickness of the unstretched film was changed, to obtain a polarizing plate protective film 3 having a film thickness of about 60 μm in which an antireflection layer was laminated.

(polarizer protective film 4)

A polarizing plate protective film 4 having a film thickness of about 40 μm and an antireflection layer laminated thereon was obtained by film formation in the same manner as the polarizing plate protective film 1 except that the linear speed was changed and the thickness of the unstretched film was changed.

(polarizing plate protective film 5)

An anti-glare layer coating agent 1 was applied to one coated surface of a polarizer protective film produced in the same manner as the polarizer protective film 2, except that no anti-reflection layer was provided, so that the cured film thickness became 8 μm, and the coating was dried in an oven at 80 ℃ for 60 seconds. Then, an ultraviolet irradiation apparatus (FUSION UV SYSTEMS JAPAN, light source H bulb) was used to irradiate the sample with a radiation amount of 300mJ/cm²Irradiating ultraviolet rays and laminating an anti-glare layer. Then, an antireflection layer was laminated on the antiglare layer in the same manner as in the polarizing plate protection film 1, to obtain a polarizing plate protection film 5.

(polarizing plate protective film 6)

An antiglare layer and an antireflection layer were laminated on one coated surface of a polarizer protective film produced by the same method as that of the polarizer protective film 3 in the same method as that of the polarizer protective film 5, except that no antireflection layer was provided, to obtain a polarizer protective film 6.

(polarizing plate protective film 7)

An anti-glare layer coating agent 2 was applied to one coated surface of a polarizer protective film prepared in the same manner as the polarizer protective film 4 so that the cured film thickness became 8 μm, and the coating was dried in an oven at 80 ℃ for 60 seconds, except that no anti-reflection layer was provided. Then, an ultraviolet irradiation apparatus (FUSION UV SYSTEMS JAPAN, light source H bulb) was used to irradiate the sample with a radiation amount of 300mJ/cm²Irradiating ultraviolet rays and laminating an anti-glare layer. Then, an antireflection layer was laminated on the antiglare layer in the same manner as in the polarizer protective film 1to obtain a polarizer protective film 7.

(polarizing plate protective film 8)

An unstretched film produced in the same manner as the polarizer protective film 1 was heated to 105 ℃ using a heated roll set and an infrared heater, stretched 3.3 times in the advancing direction using a roll set having a peripheral speed difference, introduced into a hot air zone having a temperature of 130 ℃ and stretched 4.0 times in the width direction, and a polarizer protective film 8 having an antireflection layer laminated thereon and having a film thickness of about 30 μm was obtained in the same manner as the polarizer protective film 1.

(polarizer protective film 9)

A polarizing plate protective film 9 having a film thickness of about 100 μm was obtained by the same method as the polarizing plate protective film 1 except that no antireflection layer was provided.

(polarizer protective film 10)

An antiglare layer was laminated on one coated surface of a polarizer protective film produced by the same method as the polarizer protective film 8 in the same method as the polarizer protective film 5, to obtain a polarizer protective film 10 (no antireflection layer was laminated) except that no antireflection layer was provided.

(polarizing plate protective film 11)

An anti-glare layer coating agent 3 was applied to one coated surface of a polarizer protective film produced in the same manner as the polarizer protective film 1, except that no anti-reflection layer was provided, so that the cured film thickness became 8 μm, and the coating was dried in an oven at 80 ℃ for 60 seconds. Then, an ultraviolet irradiation apparatus (FUSION UV SYSTEMS JAPAN, light source H bulb) was used to irradiate the sample with a radiation amount of 300mJ/cm²The polarizing plate protective film 11 on which the antiglare layer was laminated was obtained by irradiation with ultraviolet rays.

The liquid crystal display device is manufactured as described below using the polarizer protective films 1to 11.

(example 1)

A polarizer protective film 1 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to prepare a polarizing plate 1. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antireflection layer was not laminated.

The polarizing plate on the viewing side of REGZA43J10X manufactured by toshiba corporation was replaced with the above polarizing plate 1 so that the polyester film and the liquid crystal cell were on the opposite side (distal end), to produce a liquid crystal display device. Note that the direction of the light transmission axis of the polarizing plate 1 is replaced in the same manner as the direction of the light transmission axis of the polarizing plate before replacement.

(example 2)

A polarizer protective film 2 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to prepare a polarizing plate 2. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antireflection layer was not laminated. A liquid crystal display device was produced in the same manner as in example 1, except that the polarizing plate 1 was changed to the polarizing plate 2.

(example 3)

A polarizer protective film 3 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to prepare a polarizing plate 3. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antireflection layer was not laminated. A liquid crystal display device was produced in the same manner as in example 1, except that the polarizing plate 1 was changed to the polarizing plate 3.

(example 4)

A polarizer protective film 4 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to obtain a polarizing plate 4. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antireflection layer was not laminated. A liquid crystal display device was produced in the same manner as in example 1, except that the polarizing plate 1 was changed to the polarizing plate 4.

(example 5)

A polarizer protective film 4 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was parallel to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness: 80 μm) was attached to the opposite side to prepare a polarizing plate 5. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antireflection layer was not laminated. A liquid crystal display device was produced in the same manner as in example 1, except that the polarizing plate 1 was changed to the polarizing plate 5.

(example 6)

A polarizer protective film 5 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to prepare a polarizing plate 6. A polarizing plate was produced by laminating a polarizing plate on the side of the polarizer protective film on which the antireflection layer and the antiglare layer were not laminated. A liquid crystal display device was produced in the same manner as in example 1, except that the polarizing plate 1 was changed to the polarizing plate 6.

(example 7)

A polarizer protective film 6 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to form a polarizing plate 7. A polarizing plate was produced by laminating a polarizing plate on the side of the polarizer protective film on which the antireflection layer and the antiglare layer were not laminated. A liquid crystal display device was produced in the same manner as in example 1, except that the polarizing plate 1 was changed to the polarizing plate 7.

(example 8)

A polarizer protective film 7 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to prepare a polarizing plate 8. A polarizing plate was produced by laminating a polarizing plate on the side of the polarizer protective film on which the antireflection layer and the antiglare layer were not laminated. A liquid crystal display device was produced in the same manner as in example 1, except that the polarizing plate 1 was changed to the polarizing plate 8.

Comparative example 1

A polarizer protective film 8 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to obtain a polarizing plate 9. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antireflection layer was not laminated.

The polarizing plate on the viewing side of REGZA43J10X manufactured by toshiba corporation was replaced with the above polarizing plate 9 so that the polyester film and the liquid crystal cell were on the opposite side (distal end), to produce a liquid crystal display device. Note that the direction of the light transmission axis of the polarizing plate 9 is replaced in the same manner as the direction of the light transmission axis of the polarizing plate before replacement.

Comparative example 2

A polarizer protective film 9 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to prepare a polarizing plate 10. A liquid crystal display device was produced in the same manner as in comparative example 1, except that the polarizing plate 9 was changed to the polarizing plate 10.

Comparative example 3

A polarizer protective film 10 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to prepare a polarizing plate 11. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antiglare layer was not laminated. A liquid crystal display device was produced in the same manner as in comparative example 1, except that the polarizing plate 9 was changed to the polarizing plate 11.

Comparative example 4

A polarizer protective film 11 was attached to one side of a polarizer containing PVA and iodine so that the transmission axis of the polarizer was perpendicular to the fast axis of the film, and a TAC film (manufactured by Fujifilm Corporation, thickness 80 μm) was attached to the opposite side to obtain a polarizing plate 12. A polarizing plate was produced by laminating a polarizing plate on the surface of the polarizer protective film on which the antiglare layer was not laminated. A liquid crystal display device was produced in the same manner as in comparative example 1, except that the polarizing plate 9 was changed to the polarizing plate 12.

The results of observing the liquid crystal display devices obtained in the respective examples by measuring the rainbow unevenness are shown in table 1 below.

[ Table 1]

Industrial applicability

The liquid crystal display device and the polarizing plate of the present invention can ensure good visibility in which the occurrence of rainbow-like color unevenness is significantly suppressed at any angle, and contribute greatly to the industry.

Claims (13)

1. A polarizing plate, which is laminated with a polyester film on at least one side of the polarizing plate, The polyester film has a retardation of 8000 to 10300 nm, the NZ coefficient of the polyester film is 1.0 or more and 1.733 or less, An anti-reflection layer and/or a low-reflection layer are laminated on the opposite side of the polyester film to the side on which the polarizer is laminated, The NZ coefficient is represented by |Ny-Nz|/|Ny-Nx|, where Ny represents the refractive index in the slow axis direction, Nx represents the refractive index in the direction orthogonal to the slow axis, that is, the refractive index in the fast axis direction, and Nz Indicates the refractive index in the thickness direction. 2 . The polarizing plate according to claim 1 , wherein a ratio Re/Rth of the in-plane retardation Re of the polyester film to the retardation Rth in the thickness direction is 0.811 or more and 2.0 or less. 3 . 3. The polarizing plate according to claim 1 or 2, wherein the polyester used in the polyester film is polyethylene terephthalate. 4. The polarizing plate according to claim 1 or 2, wherein the value of Ny-Nx of the polyester film is 0.09 or more and 1.5 or less, Here, Ny represents the refractive index in the slow axis direction, and Nx represents the refractive index in the direction orthogonal to the slow axis, that is, the refractive index in the fast axis direction. 5 . The polarizing plate according to claim 1 , wherein the surface reflectance of the surface of the antireflection layer at a wavelength of 550 nm is 2.0% or less. 6 . 6. The polarizing plate according to claim 1 or 2, wherein another layer is provided between the anti-reflection layer and/or the low-reflection layer and the polyester film. 7. The polarizing plate of claim 6, wherein the other layer is an anti-glare layer. 8. The polarizing plate of claim 6, wherein the other layer is a hard coat layer. 9 . The polarizing plate according to claim 1 or 2 , wherein the surface of the polyester film on the side where the antireflection layer and/or the low reflection layer is provided has an easy-adhesion layer. 10 . 10. The polarizing plate according to claim 1 or 2, wherein at least one side of the polyester film has at least one of polyester resin, urethane resin, or polyacrylic resin as a main component for An easy-adhesion layer that improves adhesion to polarizers. 11. The polarizing plate according to claim 1 or 2, wherein the polarizing plate is used in a liquid crystal display device having a backlight light source having an emission spectrum of the following characteristics: The backlight light source is a white light source having the following emission spectrum: the peaks of the emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 780 nm or less, respectively, and 600 nm or more and The half-value width of the peak with the highest peak intensity in the wavelength region of 780 nm or less is less than 5 nm. 12 . The polarizing plate of claim 11 , wherein the backlight light source has a Mn ⁴⁺ activated fluoride complex phosphor as a red phosphor. 13 . 13. The polarizing plate of claim 11, wherein the backlight light source is a white light emitting diode.