KR20180071250A - Liquid crystal display and polarizer - Google Patents

Abstract

The liquid crystal display of the present invention comprises a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates, wherein the backlight light source has an angle of not less than 400 nm and less than 495 nm, less than 495 nm and less than 600 nm, Wherein the white light emitting diode is a white light emitting diode having an emission spectrum having peak tops of luminescence spectrums in the wavelength region and a half width of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less less than 5 nm, Is a polyester film laminated on at least one side of a polarizer, and the polyester film has a retardation of 1500 to 30000 nm, and an antireflection layer and / or a low reflection layer are laminated on at least one surface of the polyester film have.

Description

Liquid crystal display and polarizer

The present invention relates to a liquid crystal display and a polarizing plate. More particularly, the present invention relates to a liquid crystal display and a polarizing plate in which occurrence of irregular color on a rainbow is reduced.

A polarizing plate used in a liquid crystal display (LCD) is generally composed of two polarizer protective films sandwiching a polarizer obtained by dyed iodine in polyvinyl alcohol (PVA) or the like, and triacetylcellulose (TAC) . In recent years, along with the thinning of the LCD, a thin polarizing plate has been required. However, when the thickness of the TAC film used as the protective film is reduced, sufficient mechanical strength can not be obtained and the moisture permeability is deteriorated. In addition, although a polyester film has been proposed as a substitute material which is very expensive and inexpensive (Patent Literatures 1 to 3), the TAC film has a problem of irregular color on a rainbow.

When the oriented polyester film having birefringence is disposed on one side of the polarizer, the linearly polarized light emitted from the backlight unit or the polarizer changes its polarization state when passing through the polyester film. The transmitted light exhibits an interference color peculiar to retardation, which is a 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, the transmitted light intensity differs depending on the wavelength, resulting in a color irregularity on a rainbow (see 15th Micro Optical Conference, ).

As means for solving the above problems, it is preferable to use a white light source having a continuous and broad emission spectrum such as a white light emitting diode as a backlight light source and further to use an oriented polyester film having a certain retardation as the polarizer protective film (Patent Document 4). In a white light emitting diode, it has a continuous and broad emission spectrum in the visible light region. Therefore, when attention is paid to the envelope shape of the interference color spectrum by the transmitted light transmitted through the birefringent body, the retardation of the oriented polyester film is controlled to obtain a spectrum similar to the emission spectrum of the light source, Has been proposed.

In addition, by making the alignment direction of the oriented polyester film orthogonal or parallel to the polarizing direction of the polarizing plate, the linearly polarized light emitted from the polarizer passes through the oriented polyester film while maintaining the polarization state. Further, by controlling the birefringence of the oriented polyester film to increase the uniaxial orientation, the light passes through while maintaining the incident light polarization state from the oblique direction. When the oriented polyester film is observed from the oblique direction, the deviation in the direction of the alignment main axis is generated as compared with that observed from above. However, if the uniaxial alignment property is high, the deviation in the direction of the alignment main axis when viewed from the oblique direction is small. As a result, the deviation between the direction of the linearly polarized light and the direction of the main alignment axis is reduced, and it is considered that the change of the polarization state is difficult to occur. Thus, by controlling the light emission spectrum of the light source, the orientation state of the birefringent body, and the direction of the main alignment axis of alignment, changes in the polarization state are suppressed, color irregularities on the iridescence are not generated, and visibility is remarkably improved.

Japanese Patent Application Laid-Open No. 2002-116320 Japanese Patent Application Laid-Open No. 2004-219620 Japanese Patent Application Laid-Open No. 2004-205773 WO2011 / 162198

In recent years, due to the increase in the demand for enlargement of the color gamut of a liquid crystal display device, it has become possible to provide a red (blue) has a peak top, the half width of the peak in the red region (600nm or more than 780nm) is relatively narrow (5nm less than) a white light-emitting diode (for example, having an emission spectrum example, a blue LED, and at least a phosphor K ₂ SiF ₆ : A white light emitting diode having a fluorophosphor such as Mn ^{4 +} , etc.) has been developed.

When a liquid crystal display device is industrially produced by using a polarizing plate using a polyester film as a polarizer protective film, the transmission axis of the polarizer and the direction of the fast axis of the polyester film are usually arranged to be perpendicular to each other. This is because the polyvinyl alcohol film which is a polarizer is produced by vertical uniaxial stretching, and the polyester film as the protective film is produced by transversely stretching after longitudinal stretching, And when the polarizing plate is produced by joining these long objects, the fast axis of the polyester film and the transmission axis of the polarizer are usually in the vertical direction. In this case, a white LED including a light emitting element in which a blue light emitting diode and a yttrium aluminum garnet yellow phosphor are combined as a backlight light source is used as the polyester film, for example, by using an oriented polyester film having a specific retardation By using a light source having a continuous and broad luminescence spectrum, which is representative, the color unevenness on the iridescence is greatly improved, but the luminescence spectrum in which the half width of the peak in the red region (600 nm or more and 780 nm or less) is relatively narrow In the case of using a backlight source including a white light emitting diode having a white light emitting diode, there is still a new problem that rainbow stains still occur.

That is, a problem to be solved by the present invention is to provide a light emitting device having peak tops of emission spectrum in each wavelength region of a blue region (less than 400 nm and less than 495 nm), a green region (less than 495 nm and less than 600 nm) Even when a polyester film is used as the polarizer protective film in a liquid crystal display device having a backlight light source including a white light emitting diode having a relatively narrow half width (less than 5 nm) of peak at a peak wavelength (600 nm or more and 780 nm or less) , A liquid crystal display device in which iridescence is suppressed, and a polarizing plate.

The representative present invention is as follows.

Section 1.

A backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,

Wherein the backlight light source has peak peaks of luminescence spectra in each wavelength region of not less than 400 nm and less than 495 nm, not less than 495 nm and less than 600 nm, and not less than 600 nm and not more than 780 nm, and half of a peak having the highest peak intensity in a wavelength region of not less than 600 nm and not more than 780 nm A white light emitting diode having an emission spectrum with a width of less than 5 nm,

Wherein at least one of the polarizers is formed by laminating a polyester film on at least one surface of the polarizer,

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

Wherein an antireflection layer and / or a low reflection layer are laminated on at least one surface of the polyester film,

Liquid crystal display device.

Section 2.

The light emission spectrum of the backlight light source is,

The half width of the peak having the highest peak intensity in the wavelength range of 400 nm or more and less than 495 nm is 5 nm or more,

A half peak width of the peak having the highest peak intensity in a wavelength range of 495 nm or more and less than 600 nm is 5 nm or more,

A liquid crystal display device according to item 1.

Section 3.

Wherein a surface reflectance of the surface of the antireflection layer at a wavelength of 550 nm is 2.0% or less.

Section 4.

A polarizing plate in which a polyester film is laminated on at least one surface of a polarizer,

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

A peak having an emission spectrum peak in each of wavelength regions 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, and a peak having the highest peak intensity in a wavelength region of 600 nm or more and 780 nm or less is less than 5 nm A polarizer for a liquid crystal display having a backlight source including a white light emitting diode having an emission spectrum.

Item 5.

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

The liquid crystal display device and the polarizing plate of the present invention can ensure good visibility in which occurrence of color irregularity on the rainbow is significantly suppressed at any observation angle.

Generally, a liquid crystal display device is composed of a rear surface module, a liquid crystal cell, and a front panel module in the order from the side facing the backlight source to the side displaying the image (viewer side). The rear surface module and the front surface module generally comprise a transparent substrate, a transparent conductive film formed on the surface of the liquid crystal cell, 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 surface module, and on the side (on the viewer side) displaying the image in the front surface module.

The liquid crystal display device of the present invention comprises at least a backlight light source and a liquid crystal cell disposed between the two polarizing plates.

In addition, the liquid crystal display device may have other configurations other than the backlight light source, the polarizing plate, and the liquid crystal cell, for example, a color filter, a lens film, a diffusion sheet, an anti- A brightness enhancement film may be provided between the light source-side polarizing plate and the backlight light source. Examples of the brightness enhancement film include a reflection type polarizing plate that transmits linearly polarized light of one side and reflects linearly polarized light orthogonal thereto. As the reflection type polarizing plate, for example, a brightness enhancement film of a DBEF (registered trademark) (Dual Brightness Enhancement Film) series manufactured by Sumitomo 3M Ltd. is suitably used. Further, the reflection type polarizing plate is usually arranged such that the absorption axis of the reflection type polarizing plate and the absorption axis of the light source side polarizing plate are parallel to each other.

At least one of the two polarizing plates disposed in the liquid crystal display device is a polarizing plate formed by laminating a polyester film on at least one surface of polarizers obtained by dyes of iodine in polyvinyl alcohol (PVA) or the like. In the present invention, the polyester film has a specific retardation, and the antireflection layer and / or the low reflection layer are laminated on at least one side of the polyester film from the viewpoint of suppressing irregular color on the rainbow. The antireflection layer and / or the low reflection layer may be provided on the surface opposite to the surface on which the polarizer of the polyester film is laminated, or may be provided on the surface on which the polarizer of the polyester film is laminated, or both. Preferably, the antireflection layer and / or the low reflection layer is formed on the surface of the polyester film opposite to the surface on which the polarizer is laminated. When the antireflection layer and / or the low reflection layer is provided on the surface of the polyester film on which the polarizer is laminated, it is preferable that the antireflection layer and / or the low reflection layer is provided between the polyester film and the polarizer. Further, another layer (for example, an adhesion facilitating layer, a hard coating layer, an antiglare layer, an antistatic layer, an antifouling layer, or the like) may be present between the antireflection layer and / or the low reflection layer and the polyester film. It is preferable that the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 1.53 to 1.62 from the viewpoint of suppressing color unevenness on the rainbow. On the other side of the polarizer, it is preferable that films without birefringence such as those represented by TAC films, acrylic films and norbornene films are laminated (polarizing plate having a three-layer structure), but a film is necessarily laminated on the other side of the polarizer (Two-layer polarizer). Further, when a polyester film is used as the protective film on both sides of the polarizer, it is preferable that both of the polyester film slow axes are substantially parallel to each other.

As the polarizer, any polarizer (polarizing film) used in this technical field can be appropriately selected and used. Representative examples of the polarizer include a polyvinyl alcohol film in which a dichromatic material such as iodine is dyed. However, the present invention is not limited thereto, and a known and later-developed polarizer can be appropriately selected and used.

As the PVA film, commercially available products can be used. Examples of the PVA film include "Kurarabinylon (Kuraray Co., Ltd.)", "Torarovinylon (manufactured by Toserol Corporation)", "Nichogovinylon Ltd.)] may be used. Examples of the dichroic material include iodine, diazo compounds, and polymethine dyes.

The polarizer can be obtained by any method, for example, by uniaxially stretching a PVA film dyed with a dichroic material in an aqueous solution of boric acid, and washing and drying while maintaining the stretched state. The draw ratio of the uniaxial stretching is usually about 4 to 8 times, but is not particularly limited. Other manufacturing conditions and the like can be appropriately set according to known methods.

The backlight may be either an edge light system using a light guide plate, a reflector, or the like as a constituent member, or a direct type system. In the present invention, a backlight light source of a liquid crystal display device A white light emitting diode including a white light emitting diode having a peak of emission spectrum in each wavelength region of 780 nm or less and an emission spectrum having a half peak width of peak having the highest peak intensity in a wavelength region of 600 nm to 780 nm is less than 5 nm, .

It is known that the peak wavelengths of blue, green and red defined in the CIE chromaticity diagram are 435.8 nm (blue), 546.1 nm (green) and 700 nm (red), respectively. Each of the wavelength ranges 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 corresponds to a blue region, a green region, and a red region, respectively.

The upper limit of the half width of the peak having the highest peak intensity in the wavelength range of 600 nm or more and 780 nm or less is preferably less than 5 nm, more preferably less than 4 nm, still more preferably less than 3.5 nm. The lower limit is preferably 1 nm or more, and more preferably 1.5 nm or more. When the half width of the peak is less than 5 nm, the color gamut of the liquid crystal display device is widened. If the half width of the peak is less than 1 nm, the light emitting efficiency may be deteriorated. The shape of the emission spectrum is designed from the balance of the required color gamut and the luminous efficiency. Here, the half-value width is the peak width (nm) at an intensity of 1/2 of the peak intensity at the peak top wavelength.

The application of a backlight light source having an emission spectrum having the above-described characteristics to an LCD has attracted attention due to the increase in demand for color gamut expansion in recent years. In an LED using a conventionally used white LED (for example, a light emitting element in which a blue light emitting diode is combined with a yttrium aluminum garnet yellow phosphor) as a backlight light source, only about 20% of the human eye recognizable spectrum The color can not be reproduced. In contrast, when a backlight source having an emission spectrum having the above-described characteristics is used, it is said that it is possible to reproduce a color of 60% or more.

The wavelength range of 400 nm or more and less than 495 nm is more preferably 430 nm or more and 470 nm or less. The wavelength range of not less than 495 nm and not more than 600 nm is more preferably not less than 510 nm and not more than 560 nm. The wavelength region of 600 nm or more and 780 nm or less is more preferably 600 nm or more and 700 nm or less, and still more preferably 610 nm or more and 680 nm or less.

The peak half width (half width of the peak having the highest peak intensity in each wavelength region) in the peak top of each wavelength range of 400 nm or more and less than 495 nm and 495 nm or more and 600 nm or less of the luminescence spectrum is not particularly limited, The half width of the peak having the highest peak intensity in the wavelength region of less than 495 nm and less than 600 nm is preferably 5 nm or more and the half width of the peak having the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm is preferably 5 nm or more. From the viewpoint of ensuring a proper color region, the upper limit of the peak half width (half width of the peak having the highest peak intensity in each wavelength region) in the peak top of each wavelength region of from 400 nm to less than 495 nm and from 495 nm to less than 600 nm , Preferably not more than 140 nm, preferably not more than 120 nm, preferably not more than 100 nm, more preferably not more than 80 nm, more preferably not more than 60 nm, still more preferably not more than 50 nm.

As a white light source having an emission spectrum having the above-described characteristics, for example, a white light emitting diode of a phosphor system in which a blue light emitting diode and a phosphor are combined is exemplified. As the red phosphor among the above-mentioned phosphors, for example, a fluoride phosphor (KSF) having a composition formula of K ₂ SiF ₆ : Mn ⁴⁺ and others are exemplified. The Mn ^{4 +} activated fluoride complex phosphor is a phosphor in which Mn ^{4 +} is a host crystal of a fluoride complex salt of an activator, an alkali metal, an amine or an alkaline earth metal. Ge, Sn, Ti, Zr, Re, and the like) of a trivalent metal (B, Al, Ga, In, Y, Sc, lanthanoids) Hf), a pentavalent metal (V, P, Nb, Ta), and the number of fluorine atoms coordinating to the periphery thereof is 5 to 7.

Mn ^{4 +} active fluoride examples suitable for complex _{phosphor, A 2 [MF 6]:} Mn (A is Li, Na, K, Rb, Cs, at least one member selected from NH _4; M is Ge, Si, Sn, Ti , And Zr), E [MF ₆ ]: Mn (E is at least one element selected from Mg, Ca, Sr, Ba and Zn, and M is at least one element selected from Ge, Si, Sn, Ti and Zr one or _{more), Ba 0 .65, Zr 0} .35 F 2.70: Mn, A 3 [ZrF 7]: Mn (A is Li, Na, K, Rb, Cs, at least one member selected from NH _{4), A 2 [MF 5]: Mn} (A is Li, Na, K, Rb, Cs, at least one member selected from NH _4; M is at least one selected from Al, Ga, In), A 3 [MF 6 ]: Mn (at least one selected from Li, Na, K, Rb, Cs and NH ₄ , M is at least one selected from Al, Ga and In), Zn ₂ [MF ₇ ] is at least one selected from Al, Ga, In), a [In 2 F 7]: and the like Mn (a is Li, Na, K, Rb, Cs, at least one member selected from NH _4).

Preferred Mn ^{4 +} one active fluoride complex phosphor, the complex salt hexafluorophosphate of an alkali metal A ₂ MF ₆ to the host crystal: Mn (A is Li, Na, K, Rb, Cs, is selected from 1 NH ₄ And M is at least one species selected from Ge, Si, Sn, Ti, and Zr). Among them, it is preferable that A is at least one element selected from K (potassium) or Na (sodium), and M is Si (silicon) or Ti (titanium). Especially, it is preferable that A is K (the proportion of K in all the A is 99 mol% or more), and M is Si. But it is preferable that Mn (manganese) is 100% as an activating element, but Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn, Mg, and the like. When M is Si, the ratio of Mn in the total of Si and Mn is preferably within a range of 0.5 mol% to 10 mol%. In another preferred Mn ^{+ 4} activated fluoride complex phosphor, the formula _{A 2+ x M y Mn z F} n (A is Na and K; M is Si and Al; also -1≤x≤1 also 0.9≤y + z≤1.1 0.001? Z? 0.4 and 5? N? 7).

As the backlight light source, a blue light emitting diode and a white light emitting diode having at least a fluorophosphor phosphor as a fluorescent material are preferable, and a white light emitting diode having a blue light emitting diode and a fluorophosphor phosphor at least K ₂ SiF ₆ : Mn ^{4 +} to be. For example, commercially available products such as NSSW306FT, which is a white LED manufactured by Nichia Kagaku Kogyo Co., Ltd., can be used.

As the green phosphor among the above-mentioned phosphors, for example, a sialon-based phosphor having a basic composition of? -SiAlON: Eu or the like, a silicate-based phosphor having a basic composition of (Ba, Sr) ₂ SiO ₄ : .

In the case where a plurality of peaks are present in any of the wavelength regions of 400 nm or more and less than 495 nm, the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 780 nm or less,

When the plurality of peaks are independent peaks, the half width of the peak having the highest peak intensity is preferably in the above range. It is more preferable for the other peaks having the intensity of 70% or more of the highest peak intensity to have the same half-value width in the above range.

For one independent peak having a plurality of overlapping peaks, the half width of the peak having the highest peak intensity among the plurality of peaks can be measured as it is. Here, the independent peaks are regions having an intensity that is half of the peak intensity on both the short wavelength side and the long wavelength side of the peak. That is, when a plurality of peaks are overlapped and each peak does not have an intensity region where the peak intensity is half of the peak intensity on both sides, the plurality of peaks are regarded as one peak as a whole. One peak having a shape in which a plurality of peaks are overlapped has a half width of the peak width (nm) of the peak at the intensity of 1/2 of the highest peak intensity.

Further, among the plurality of peaks, the peak having the highest peak intensity is regarded as the peak top.

The peak having the highest peak intensity in the wavelength range of 400 nm or more and less than 495 nm, the wavelength range of 495 nm or more and less than 600 nm, or the wavelength range of 600 nm or more and 780 nm or less is different from the peaks of other wavelength ranges It is preferable that the relationship be established. Particularly, in the wavelength region between the peak having the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm and the peak having the highest peak intensity in the region of 600 nm or more and 780 nm or less, It is preferable from the viewpoint of color clarity that there is a region which is 1/3 or less of the peak intensity of the peak having a high peak intensity.

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

As a result of intensive studies, the inventors of the present invention have found that the above-described backlight light source can emit light having a luminescence spectrum in each wavelength region of a blue region (less than 400 nm and less than 495 nm), a green region (less than 495 nm and less than 600 nm) In a liquid crystal display device having a backlight light source having a peak top and including a white light emitting diode having a relatively narrow peak having a half width of less than 5 nm in a red region (600 nm to 780 nm), the antireflection layer and / It has been found that a liquid crystal display device and a polarizing plate each having a low reflection layer and using a polyester film having a specific retardation suppress rainbow stains can be provided. As a mechanism by which the occurrence of color unevenness on the rainbow is suppressed by the above-described form, the following is considered.

When the oriented polyester film is disposed on one side of the polarizer, the linearly polarized light emitted from the backlight unit or the polarizer changes its polarization state when it passes through the polyester film. It is conceivable that the refractive index difference between the interface between the air layer and the oriented polyester film or the refractive index difference between the interface between the polarizer and the oriented polyester film is influential as one of the factors for changing the polarization state. When the linearly polarized light incident on the oriented polyester film passes through each interface, a part of the light is reflected by the difference in refractive index between the interfaces. At this time, the outgoing light and the reflected light also change in polarization state, which is considered to be one of the factors causing color irregularity on the rainbow. Thus, it is considered that the reflection of the interface between the air layer and the oriented polyester film is suppressed by suppressing the surface reflection by adding an antireflection layer or a low reflection layer to the surface of the oriented polyester film, thereby suppressing color irregularities on the iridescence.

As described above, in the present invention, each of the wavelength regions of the blue region (400 nm or more and less than 495 nm), the green region (less than 495 nm and less than 600 nm), and the red region (600 nm or more and 780 nm or less) Even when a polarizing plate using a polyester film is used as a polarizer protective film in a liquid crystal display device having a backlight light source including a white light emitting diode having a relatively narrow half width of a peak in a range of from 600 nm to 780 nm It is possible to obtain good visibility without occurrence of unevenness.

It is preferable that a polarizer protective film including a polyester film is 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 is in the above range, the iridescence tends to be more easily reduced, which is preferable. The lower limit of the retardation is preferably 3000 nm, the lower limit is preferably 3500 nm, more preferably lower limit is 4000 nm, still more preferably lower limit is 6000 nm, still more preferably lower limit is 8000 nm. The preferred upper limit is 30000 nm, and the polyester film having the retardation of not less than 30 nm has a considerably large thickness, and the handling property as an industrial material tends to be lowered. In this document, retardation refers to in-plane retardation, except when a separate mark is given.

The retardation can be obtained by measuring the refractive index and thickness in the biaxial direction, or can be obtained by using a commercially available automatic birefringence measuring device called KOBRA-21ADH (Oji Keisoku Kikai K.K.). The refractive index can be determined by Abbe's refractive index meter (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, Or more. The larger the ratio of retardation to retardation in the thickness direction (Re / Rth), the more the action of birefringence increases the isotropy, and the irregular color on the rainbow tends to be less likely to occur due to the observation angle. In the complete uniaxial (uniaxial) film, the ratio of the retardation to the thickness direction retardation (Re / Rth) is 2.0, and the upper limit of the retardation to thickness direction retardation ratio (Re / Rth) is 2.0 . The retardation in the thickness direction means an average of retardation obtained by multiplying two birefringence angles? Nxz and? Nyz by the film thickness d, respectively, when the film is viewed from the thickness direction end face.

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, still more preferably 1.6 or less, from the viewpoint of suppressing color irregularities on the rainbow. Since the NZ coefficient is 1.0 in a complete uniaxial (uniaxial) film, the lower limit of the NZ coefficient is 1.0. However, as the film is closer to the complete uniaxial (uniaxial) film, the mechanical strength in the direction perpendicular to the alignment direction tends to be significantly lowered.

Nz is the index of refraction in the direction of the slow axis, Nx is the index of refraction in the direction perpendicular to the slow axis (refractive index in the fast axis direction), and Nz is the thickness Directional refractive index. The orientation axis of the film was determined using a molecular orientation system (MOA-6004 type molecular alignment system, manufactured by Oji Scientific Co., Ltd.) to determine the orientation axis direction and the biaxial refractive indexes Ny, Nx, Ny > Nx) and a refractive index (Nz) in the thickness direction are determined by Abbe's refractive index meter (manufactured by 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.

Further, from the viewpoint of suppressing color irregularity on the rainbow, the value of Ny-Nx of the polyester film is preferably 0.05 or more, more preferably 0.07 or more, further preferably 0.08 or more, still more preferably 0.09 Or more, particularly preferably 0.1 or more. The upper limit is not particularly defined, but in the case of a polyethylene terephthalate film, the upper limit is preferably about 1.5.

In a preferred embodiment of the present invention, the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer constituting the polarizing plate is preferably in the range of 1.53 to 1.62. Thereby, reflection at the interface between the polarizer and the polyester film can be suppressed, and color irregularity on the rainbow can be further suppressed. When the refractive index exceeds 1.62, color irregularities on the iridescence may occur when observed from the oblique direction. The refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is preferably 1.61 or less, more preferably 1.60 or less, still more preferably 1.59 or less, still more preferably 1.58 or less.

On the other hand, the lower limit value of the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is 1.53. When the refractive index is less than 1.53, the crystallization of the polyester film becomes insufficient, and the characteristics obtained by stretching such as dimensional stability, mechanical strength, chemical resistance and the like become insufficient. The refractive index is preferably 1.56 or more, and more preferably 1.57 or more. An arbitrary range combining the upper limit and the lower limit of the refractive index mentioned above is assumed.

In order to set the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer to be in the range of 1.53 to 1.62, the polarizing plate is formed such that the transmission axis of the polarizer and the fast axis (vertical direction to the slow axis) Parallel. The refractive index of the polyester film in the direction of the fast axis, which is the direction perpendicular to the slow axis, can be controlled to be as low as about 1.53 to 1.62 by the stretching treatment in the film forming step described later. By setting the fast axis direction of the polyester film and the transmission axis direction of the polarizer to be substantially parallel, the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer can be set to 1.53 to 1.62. Here, the term "substantially parallel" means that the angle formed by the transmission axis of the polarizer and the fast axis of the polarizer protective film (polyester film) is -15 ° to 15 °, preferably -10 ° to 10 °, more preferably -5 ° ° to 5 °, more preferably -3 ° to 3 °, even more preferably -2 ° to 2 °, and still more preferably -1 ° to 1 °. In a preferred embodiment, the substantially parallel is substantially parallel. Here, substantially parallel means that the transmission axis of the polarizer and the fast axis of the polyester film are parallel to each other to such an extent as to permit a shift that is unavoidably caused when the polarizer and the protective film are bonded. The direction of the slow axis can be determined by measuring with a molecular orientation system (for example, MOA-6004 type molecular alignment system, manufactured by Oji Paper Co., Ltd.).

That is, the refractive index in the fast axis direction of the polyester film is preferably 1.53 or more and 1.62 or less. By laminating the transmission axis of the polarizer and the fast axis of the polyester film so as to be approximately parallel, The refractive index of the film can be 1.53 or more and 1.62 or less.

The polarizer protective film comprising the polyester film can be used for both the polarizers of the incident light side (light source side) and the emergent light side (viewer side), but at least it is used for the protective film of the polarizer of the emergent light side desirable.

With respect to the polarizing plate disposed on the outgoing light side, the polarizing plate protective film comprising the polyester film may be disposed on the side of the liquid crystal cell, on the side of the outgoing light, or on both sides thereof, Or the like.

In the polarizing plate disposed on the incident light side, the polarizer protective film comprising the polyester film may be disposed on the side of the incident light, the side of the liquid crystal cell, or on both sides with the polarizer as a starting point. As shown in Fig. The polarizing plate disposed on the side of the incident light may be a polarizing plate having a low retardation such as a triacetyl cellulose film without using a polarizing protective film including a polyester film.

The polyester used in the polyester film may be polyethylene terephthalate or polyethylene naphthalate, but may contain other copolymerizable components. These resins have excellent transparency, excellent thermal and mechanical properties, and can easily control retardation by stretching. Particularly, polyethylene terephthalate has a large intrinsic birefringence and is capable of suppressing the refractive index in the direction of the fast axis (perpendicular to the slow axis direction) to a low level by stretching the film, and that the retardation can be relatively easily obtained even if the film thickness is thin , It is the most suitable material.

Further, for the purpose of suppressing deterioration of an optically functional dye such as iodine dye, it is preferable that the polyester film has a light transmittance of not more than 20% at a wavelength of 380 nm. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration due to ultraviolet rays of the optically functional dye can be suppressed. The transmittance is measured by a perpendicular method to the plane of the film and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

In order to reduce the transmittance at a wavelength of 380 nm of the polyester film to 20% or less, it is preferable to appropriately adjust the type, concentration and film thickness of the ultraviolet absorbent. The ultraviolet absorber used in the present invention is a known substance. As the ultraviolet absorber, an organic ultraviolet absorber and an inorganic ultraviolet absorber can be mentioned, but from the viewpoint of transparency, an organic ultraviolet absorber is preferable. Examples of the organic ultraviolet absorber include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and the like, and combinations thereof, but are not particularly limited as long as they are within the range of the absorbance as defined by the present invention. However, from the viewpoint of durability, benzotriazole-based cyclic imino ester-based ones are particularly preferable. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays of respective wavelengths can be simultaneously absorbed, so that the ultraviolet absorption effect can be further improved.

Examples of the benzophenone-based ultraviolet absorber, benzotriazole-based ultraviolet absorber and acrylonitrile-based ultraviolet absorber include 2- [2'-hydroxy-5 '- (methacryloyloxymethyl) phenyl] -2H-benzotriazole , 2- [2'-hydroxy-5 '- (methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [ Phenyl] -2H-benzotriazole, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 2,4- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2 Methyl-6- (tert-butyl) phenol, 2,2'-methylenebis (4- (1,1,3,3- (2H-benzotriazol-2-yl) phenol, and the like. Examples of the cyclic imino ester-based ultraviolet absorber include 2,2 '- (1,4-phenylene) bis (4H-3,1-benzoxazin-4-one), 2-methyl-3,1-benzo 2-butyl-3,1-benzoxazine-4-one, 2-phenyl-3,1-benzoxazine-4-one and the like. no.

In addition to the ultraviolet absorber, it is also preferable to add various additives other than the catalyst in the range not hindering the effect of the present invention. Examples of the additive include inorganic particles, heat resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light stabilizers, flame retardants, heat stabilizers, antioxidants, antigelling agents and surfactants. Further, in order to exhibit high transparency, it is also preferable that the polyester film contains substantially no particles. The phrase " substantially not containing particles " means that, for example, in the case of inorganic particles, a content of not more than 50 ppm, preferably not more than 10 ppm, particularly preferably not more than a detection limit when the inorganic element is quantified by fluorescent X- .

It is preferable to form an antireflection layer and / or a low reflection layer 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. If it exceeds 2.0%, color irregularities on the rainbow tend to become visible. The surface reflectance of the antireflection layer is more preferably 1.6% or less, still more preferably 1.2% or less, particularly preferably 1.0% or less. The lower limit of the surface reflectance of the antireflection layer is not particularly limited, but is, for example, 0.01%. The reflectance of 0% is most preferred. The reflectance can be measured by an arbitrary method. For example, a light reflectance at a wavelength of 550 nm can be measured from the surface of the antireflection layer side using a spectrophotometer (Shimadzu Corporation, UV-3150).

If the thickness of the low refractive index layer including a material having a lower refractive index than that of the plastic film (polyester film) is 1/4 wavelength of the light wavelength or an odd multiple thereof, Prevention effect can be obtained. When the antireflection layer has a multilayer structure, the antireflection effect can be obtained by alternately arranging the low refractive index layer and the high refractive index layer in two or more layers and appropriately controlling the thickness of each layer. In addition, a hard coat layer may be laminated between the antireflection layers, if necessary, or an antifouling layer may be formed on the hard coat layer.

As the antireflection layer, there may be mentioned a structure using a moss eye structure. The moth eye structure is a concavo-convex structure having a pitch smaller than the wavelength formed on the surface, and this structure makes it possible to change the abrupt and discontinuous refractive index change at the boundary with air to a continuous and gradually changing refractive index variation. Thus, by forming a morphi structure on the surface, light reflection on the surface of the film is reduced. The formation of the antireflection layer using a moth eye structure can be performed, for example, by referring to Japanese Patent Application Laid-Open No. 2001-517319.

Examples of the method for forming the antireflection film include a dry coating method in which an antireflection layer is formed on the surface of a base material (polyester film) by vapor deposition or sputtering, a method in which an antireflection coating liquid is applied to the surface of a base material and dried to form an antireflection layer A wet coating method in which both of them are used together, and the like. The composition and the formation method of the antireflection layer are not particularly limited as long as the above characteristics are satisfied.

As the low reflection layer, a known one can be used. For example, at least one layer of a metal or oxide thin film is deposited by a vapor deposition method or a sputtering method, or a method of coating one or more layers of an organic thin film. As the low reflection layer, it is preferable to further coat an organic thin film having a lower refractive index than a hard coat layer or the like to be laminated on a polyester film or a polyester film. The surface reflectance of the low reflection layer is preferably less than 5%, more preferably not more than 4%, further preferably not more than 3%, further preferably not more than 2%. 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 provided with an antiglare function. Thereby, it is possible to further suppress rainbow stains. That is, the combination of the antireflection layer and the antiglare layer, the combination of the low reflection layer and the antiglare layer, and the combination of the antireflection layer, the low reflection layer and the antiglare layer. Particularly preferably, it 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 that the antireflection layer is laminated on the polyester film, and then the antireflection layer or the low reflection layer is laminated on the antiglare layer.

When forming the antireflection layer or the low reflection layer, it is preferable that the polyester film has an easy adhesion layer on its surface. At this time, from the viewpoint of suppressing the interference by the reflected light, it is preferable to adjust the refractive index of the easy-adhesion layer so as to be close to the rising average of the refractive index of the antireflection layer and the refractive index of the polyester film. The adjustment of the refractive index of the easy-to-adhere layer can be carried out by a known method, and can easily be adjusted, for example, by containing titanium, germanium or other metal species in the binder resin.

The polyester film may be subjected to a corona treatment, a coating treatment, a flame treatment, or the like in order to improve the adhesiveness with the polarizer.

In the present invention, it is preferable that the film of the present invention has an easy-to-adhere layer mainly composed of at least one of a polyester resin, a polyurethane resin and a polyacrylic resin on at least one surface thereof in order to improve the adhesiveness with the polarizer Do. Here, the " main component " refers to a component that is at least 50 mass% of the solid components constituting the adhesion facilitating layer. The coating liquid used for forming the adhesion facilitating layer is preferably an aqueous coating liquid containing at least one of a water-soluble or water-dispersible copolymer polyester resin, an acrylic resin and a polyurethane resin. Examples of the coating liquids include water-soluble or water-dispersible copolymers disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, A polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.

The adhesion facilitating layer can be obtained by applying the coating liquid on one side or both sides of the uniaxially stretched film in the longitudinal direction, followed by drying at 100 to 150 占 폚 and subsequent stretching in the transverse direction. The final coating amount of the easy-adhesion layer is preferably controlled to 0.05 to 0.20 g / m 2. If the application amount is less than 0.05 g / m 2, the adhesiveness with the obtained polarizer may become insufficient. On the other hand, if the applied amount exceeds 0.20 g / m 2, the blocking resistance may be lowered. In the case of providing an easy-to-adhere layer on both sides of the polyester film, the application amount of the easy-to-adhere layer on both sides may be the same or different and can be independently set within the above range.

It is preferable to add particles for imparting inverse activity to the easy-adhesion layer. Particles having an average particle size of 2 mu m or less are preferably used. If the average particle diameter of the particles exceeds 2 탆, the particles tend to fall off from the coating layer. Examples of the particles to be contained in the adhesion facilitating layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, Inorganic particles such as calcium fluoride, and organic polymerization system particles such as styrene type, acrylic type, melamine type, benzoguanamine type and silicone type. These may be added to the easy-to-adhere layer alone, or two or more of them may be added in combination.

As a method of applying the coating liquid, a known method can be used. For example, there can be mentioned a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brush method, a spray coating method, an air knife coating method, a wire bar coating method and a pipe doctor method. Alone or in combination.

The average particle diameter of the particles is measured by the following method. The particles were photographed with a scanning electron microscope (SEM) and the maximum diameter (distance between the two most distant points) of 300 to 500 particles was measured at the same magnification as that of the smallest particle of 2 to 5 mm in size , And the average value is taken as the average particle diameter.

The polyester film used as the polarizer protective film can be produced by a general method for producing a polyester film. For example, after the polyester resin is molten and the non-oriented polyester extruded into a sheet is stretched in the longitudinal direction at a temperature not lower than the glass transition temperature using the speed difference of the roll, stretched in the transverse direction by a tenter, And a heat treatment is carried out.

The polyester film used in the present invention may be either a uniaxially stretched film or a biaxially stretched film. However, when a biaxially stretched film is used as a polarizer protective film, color irregularities on a rainbow are not seen even when viewed from directly above the film surface, Care should be taken because there is a case where irregular color unevenness is observed when observed from the oblique direction.

The film-forming conditions of the polyester film will be specifically described. The longitudinal stretching temperature and transverse stretching temperature are preferably 80 to 130 占 폚, and particularly preferably 90 to 120 占 폚. In order to align the film so that the slow axis is in the TD direction, the longitudinal stretching magnification is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. The transverse stretching magnification is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times. In order to align the film so that the slow axis is in the MD direction, the longitudinal stretching magnification is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times. The transverse stretching magnification is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times.

In order to control the refractive index and the retardation in the fast axis direction of the polyester film to the above range, it is preferable to control the ratio of the longitudinal stretching magnification and the transverse stretching magnification. When the difference in longitudinal and lateral stretching 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. Setting the stretching temperature to a lower value is also a preferable countermeasure for lowering the refractive index in the fast axis direction of the polyester film and increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250 占 폚, particularly preferably 180 to 245 占 폚.

In order to suppress the fluctuation of the retardation, it is preferable that the thickness irregularity of the film is small. Since the stretching temperature and stretching ratio greatly influence the thickness irregularity of the film, it is preferable to optimize the film forming conditions from the viewpoint of reducing the thickness unevenness. Particularly, when the vertical stretching magnification is lowered in order to increase the retardation, there is a case where the longitudinal thickness unevenness becomes large. The thickness unevenness in the longitudinal direction is preferably set at a position outside this range because there is a region in which the stretching magnification is extremely deteriorated in a certain range.

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

As described above, in order to control the retardation of the polyester film to a specific range, it can be performed by appropriately setting the stretching magnification, stretching temperature, and film thickness. For example, the higher the stretching magnification, the lower the stretching temperature, and the thicker the film, the easier it is to obtain a higher retardation. Conversely, the lower the stretching ratio, the higher the stretching temperature, and the thinner the film, the easier to obtain a lower retardation. However, if the thickness of the film is increased, the retardation in the thickness direction tends to increase. Therefore, it is preferable to set the film thickness appropriately within the range described later. In addition to the control of the retardation, it is preferable to set the final film forming conditions in consideration of the physical properties required for processing and the like.

The thickness of the polyester film is arbitrary, but is preferably in the range of 15 to 300 mu m, more preferably in the range of 15 to 200 mu m. Even in the case of a film having a thickness of less than 15 占 퐉, it is possible to obtain a retardation of 1500 nm or more in principle. However, in that case, the anisotropy of the mechanical properties of the film becomes remarkable, and it tends to cause bursting, tearing, and the like, and practicality as an industrial material is remarkably lowered. A particularly preferable lower limit of the thickness is 25 占 퐉. On the other hand, when the upper limit of the thickness of the polarizer protective film exceeds 300 탆, the thickness of the polarizer becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 mu m. An upper limit of a particularly preferable thickness is 100 mu m, which is equivalent to that of a general TAC film. In order to control the retardation within the range of the present invention even in the above-mentioned thickness range, polyethylene terephthalate is suitable as the polyester used as the film base.

As a method of blending an ultraviolet absorber with a polyester film, known methods may be used in combination. For example, a master batch is prepared by blending a dry ultraviolet absorber and a polymer raw material in advance using a kneading extruder Or may be blended by a method of mixing a predetermined master batch with a polymer raw material at the time of film formation.

At this time, the concentration of the ultraviolet absorber in the master batch is preferably 5 to 30% by mass in order to uniformly disperse the ultraviolet absorber and to economically blend it. As a condition for producing the master batch, it is preferable to use a kneading extruder to extrude the extruding temperature at a temperature not lower than the melting point of the polyester raw material and not higher than 290 캜 for 1 to 15 minutes. Above 290 占 폚, the weight loss of the ultraviolet absorber is large, and the viscosity drop of the master batch is large. When the extrusion time is 1 minute or less, uniform mixing of the ultraviolet absorber becomes difficult. At this time, a stabilizer, a color tone adjusting agent and an antistatic agent may be added as necessary.

It is also preferable that the polyester film has a multilayer structure of at least three layers, and an ultraviolet absorbent is added to the intermediate layer of the film. The three-layer structure film containing the ultraviolet absorber in the intermediate layer can be specifically prepared as follows. A master batch containing polyester as the outer layer alone and a master batch containing the ultraviolet absorbent as the middle layer and the polyester pellets were mixed at a predetermined ratio and then dried and fed to a known extruder for melt lamination to form a sheet And cooled and solidified on a casting roll to form an unstretched film. That is, by using two or more extruders, a three-layer manifold, or a joining block (for example, a joining block having a rectangular joining portion), a film layer constituting both outer layers and a film layer constituting the intermediate layer are laminated, The three-layer sheet is extruded and cooled with a casting roll to form an unstretched film. Further, in order to remove foreign matters contained in the polyester of the raw material, which causes optical defects, it is preferable to perform high-precision filtration at the time of melt extrusion. The filtration particle size (initial filtration efficiency: 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 탆 or less. If the filtration particle size of the filter medium exceeds 15 탆, foreign matter of 20 탆 or more tends to become insufficient.

Example

Hereinafter, the present invention will be described more concretely with reference to Examples, but the present invention is not limited by the following Examples, and it is possible to carry out the present invention by appropriately modifying it within the range that is suitable for the purpose of the present invention , All of which are included in the technical scope of the present invention. The evaluation methods of physical properties in the following examples are as follows.

(1) Refractive index of polyester film

Using the molecular orientation system (MOJ-6004 type molecular alignment system, manufactured by Oji Paper Co., Ltd.), the slow axis direction of the film was determined, and a rectangle of 4 cm x 2 cm was formed so as to be parallel to the long side And cut into samples for measurement. (Refractive index in the slow axis direction: Ny, refractive index in the direction orthogonal to the slow axis direction) and refractive index in the thickness direction (Nz) of the orthogonal two axes were measured with an Abbe's refractive index meter , NAR-4T, measurement wavelength: 589 nm).

(2) Retardation (Re)

The retardation is a parameter defined by a product (DELTA Nxy x d) of a refractive index anisotropy (DELTA Nxy = | Nx-Ny |) of two orthogonal axes on a film and a film thickness d (nm) to be. The refractive index anisotropy (DELTA Nxy) of biaxial is obtained by the following method. The direction of the slow axis of the film was determined using a molecular orientation system (MOA-6004 type molecular alignment system, manufactured by Oji Paper Co., Ltd.), and the direction of the slow axis was parallel to the long side of the measurement sample. Was cut out as a sample for measurement. (Refractive index in the slow axis direction: Ny, refractive index in the direction perpendicular to the slow axis direction: Nx) and refractive index (Nz) in the thickness direction of the sample were measured with Abbe's refractive index meter (NAR-4T , Measurement wavelength: 589 nm), and the absolute value (| Nx-Ny |) of the refractive index difference of the biaxial axis was defined as anisotropy (? Nxy) of the refractive index. The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Paleo Pure Chemical Industries, Ltd.), and the unit was converted to nm. The retardation (Re) was determined from the product (Nxy x d) of the anisotropy of the refractive index (DELTA Nxy) and the thickness of the film d (nm).

(3) Thickness direction retardation (Rth)

The retardation in the thickness direction means the retardation obtained by multiplying the birefringence ΔNxz (= | Nx-Nz |) and ΔNyz (= | Ny-Nz |) by the film thickness d respectively as seen from the cross- . Nx, Ny, and Nz and the film thickness d (nm) were obtained in the same manner as in the measurement of the retardation, and the average value of (DELTA Nxzxd) and (DELTA Nyzxd) was calculated to calculate the thickness direction retardation (Rth) Respectively.

(4) NZ coefficient

Ny, Nx, and Nz values obtained by the above (1) were substituted into NZ = | Ny-Nz | / | Ny-Nx |

(5) Measurement of luminescence spectrum of backlight source

REGZA 43J10X manufactured by Toshiba Corporation was used for the liquid crystal display device used in each of the embodiments. The luminescence spectrum of the backlight source (white light-emitting diode) of the liquid crystal display device was measured using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics to find an emission spectrum having peaks at 450 nm, 535 nm and 630 nm . The half width of each peak top (half width of the peak having the highest peak intensity in each wavelength range) was 17 nm for the 450 nm peak, 45 nm for the 535 nm peak, and 2 nm for the 630 nm peak. In this light source, the half width was evaluated at a peak near 630 nm, which had a plurality of peaks in a wavelength range of 600 nm or more and 780 nm or less, but the peak intensity was the highest in this range. The exposure time in spectral measurement was 20 msec.

(6) Reflectance

A 5-degree reflectance at a wavelength of 550 nm was measured from the surface of the antireflection layer side (or the low reflection layer side) using a spectrophotometer (Shimadzu Corporation, UV-3150). The surface of the polyester film opposite to the side on which the antireflection layer (or the low reflection layer) was provided was coated with black magic and then measured with a black vinyl tape (Kyodo's vinyl tape HF-737, width 50 mm) .

(7) Rainbow spot observation

The liquid crystal display device obtained in each of the examples was visually observed from a dark place in the front and oblique directions, and the presence / absence of rainbow stains was judged as follows.

○: No rainbow stains observed

△: Rainbow stain slightly observed

X: Irregular stain observed

××: Significantly observed rainbow stains

(Production Example 1-Polyester A)

After the temperature of the esterification reaction vessel was elevated to 200 占 폚, 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were fed and 0.017 part by mass of antimony trioxide, 0.064 parts by mass of magnesium acetate tetrahydrate, And 0.16 parts by mass of ethylamine. Subsequently, the mixture was subjected to pressure esterification at a gauge pressure of 0.34 MPa and at 240 占 폚, and then the esterification reaction vessel was returned to atmospheric pressure and 0.014 parts by mass of phosphoric acid was added. Then, the temperature was raised to 260 DEG C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Subsequently, after 15 minutes, dispersion treatment was carried out with a high-pressure disperser. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can and subjected to a polycondensation reaction under reduced pressure at 280 占 폚.

After completion of the polycondensation reaction, filtration treatment was carried out with a nylon filter having a cut-off diameter of 5 탆 of 95%, extruded from the nozzle onto a strand, and cooled using cooling water previously subjected to filtration treatment (pore diameter: , Solidified and cut into pellets. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl / g and substantially no inactive particles and no internal 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), PET (A) Of 0.62 dl / g) were mixed and a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained (hereinafter abbreviated as PET (B)) by using a kneading extruder.

(Preparation Example 3 -Adjustment of Adhesive Modification Coating Liquid)

Ester exchange reaction and polycondensation reaction were carried out according to a conventional method to obtain a mixture of 46 mol% of terephthalic acid, 46 mol% of isophthalic acid and 5 mol% of sodium 5-sulfonate isophthalate (relative to the entire dicarboxylic acid component) as a dicarboxylic acid component And 50% by mole of ethylene glycol and 50% by mole of neopentyl glycol as glycol components (relative to the entire glycol component). 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 parts by mass of a nonionic surfactant were mixed with heating and stirred at 77 占 폚, And 5 parts by mass of a metal base-containing copolymerizable polyester resin were added and stirred until the lump of the resin disappeared. Thereafter, the resin aqueous dispersion was cooled to room temperature to obtain a water dispersible copolymer polyester resin having a solid content concentration of 5.0% Solution. Further, 3 parts by mass of agglomerated silica particles (Siacia 310, manufactured by Fuji Silysia Co., Ltd.) were dispersed in 50 parts by mass of water, and then 0.54 parts by mass of an aqueous dispersion of Si010310 in water (99.46 parts by mass) And 20 parts by mass of water was added with stirring to obtain an adhesive modified coating liquid.

(Production Example 4 - Production of high refractive index coating agent)

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

· Acrylic resin solution B 5 parts by mass

· Bisphenol A diglycidyl ether 0.25 parts by mass

Titanium oxide particles having an average particle diameter of 20 nm 0.5 parts by mass

· Triphenylphosphine 0.05 parts by mass

· Isopropyl alcohol 14.25 parts by mass

(Production Example 5 - Production of low refractive index coating agent)

Acrylic acid (10 parts by mass), azoisobutyronitrile (1.5 parts by mass), methyl (2-ethylhexyl) acrylate, Ethyl ketone (200 parts by mass) was charged into a reaction vessel and reacted at 80 占 폚 under a nitrogen atmosphere for 7 hours to obtain a polymer methyl ethyl ketone solution having a weight average molecular weight of 20,000. The obtained polymer solution was diluted with methyl ethyl ketone to a solid content concentration of 5 mass% to obtain a fluoropolymer solution C. [ The resulting fluoropolymer solution C was mixed as follows to obtain a coating liquid for forming a low refractive index layer.

Fluoropolymer solution C 44 parts by mass

· 1,10-bis (2,3-epoxypropoxy) -2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadeca Fluorodecane

(Fluorite FE-16, available from Kyoeisha Chemical Co., Ltd.) 1 part by mass

· Triphenylphosphine 0.1 parts by mass

· Methyl ethyl ketone 19 parts by mass

(Preparation Example 6-Adjustment of Antigloss Layer Coating Agent-1)

(49 parts by mass), acrylic acetate propionate CAP482-20 (number average molecular weight: 75,000) (manufactured by Eastman Chemical Co., Ltd.) (3 parts by mass Styrene copolymer (average particle diameter 4.0 占 퐉) (2 parts by mass, manufactured by Sekisui Chemical Co., Ltd.), IRGACURE 184 (BASF, trade name, manufactured by Nippon Kayaku Co., Ltd.), 49 parts by mass of acrylic monomer AYARAD DPHA (10 parts by mass) was added in an amount of 35% by mass and a mixed solvent of methyl ethyl ketone: 1-butanol = 3: 1 to obtain an antiglare layer-forming coating liquid.

(Preparation Example 7-Adjustment of Antiglare Layer Coating Agent-2)

(49 parts by mass), acrylic acetate propionate CAP482-0.5 (number average molecular weight: 25,000) (manufactured by Eastman Chemical Co., Ltd.) (3 parts by mass Styrene copolymer (average particle diameter 4.0 mu m) (manufactured by Sekisui Chemical Co., Ltd.) (4 parts by mass), IRGACURE 184 (BASF) (trade name, manufactured by Nippon Kayaku Co., Ltd.), 49 parts by mass of acrylic monomer AYARAD DPHA (10 parts by mass) was added in an amount of 35% by mass and a mixed solvent of methyl ethyl ketone: 1-butanol = 3: 1 to obtain an antiglare layer-forming coating liquid.

(Preparation Example 8 - Adjustment of the antiglare layer coating agent-3)

(49 parts by mass), acrylic acetate propionate CAP482-0.2 (number average molecular weight: 15,000) (manufactured by Eastman Chemical Co., Ltd.) (3 parts by mass Styrene copolymer (average particle diameter 4.0 占 퐉) (2 parts by mass, manufactured by Sekisui Chemical Co., Ltd.), IRGACURE 184 (BASF, trade name, manufactured by Nippon Kayaku Co., Ltd.), 49 parts by mass of acrylic monomer AYARAD DPHA (10 parts by mass) was added in an amount of 35% by mass and a mixed solvent of methyl ethyl ketone: 1-butanol = 3: 1 to obtain an antiglare layer-forming coating liquid.

(Polarizer Protective Film 1)

90 parts by mass of PET (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber were dried at 135 ° C for 6 hours under reduced pressure (1 Torr) as raw materials for the base film intermediate layer raw material, (For the intermediate layer II layer), and the PET (A) was dried by a usual method and supplied to the extruder 1 (for the outer layer I and outer layer III), respectively, and dissolved at 285 deg. These two kinds of polymers were respectively filtered with a filter material of a stainless steel sintered body (nominal filtration accuracy of 10 탆 and a particle size of 95% cut) and laminated with a two-kind three-layer confluence block. Casting drum having a surface temperature of 30 DEG C using a casting method, and then cooled and solidified to prepare an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio of the I layer, the II layer and the III layer was 10:80:10.

Subsequently, the adhesive modifying coating liquid was applied on both sides of the unstretched PET film by a reverse roll method so that the coating amount after drying was 0.08 g / m < 2 >, followed by drying at 80 DEG C for 20 seconds.

The unstretched film having the coated layer formed thereon was led to a tenter stretching machine and led to a hot air zone at a temperature of 125 캜 while grasping the end of the film with a clip and stretched 4.0 times in the width direction. Subsequently, the film was treated at a temperature of 225 DEG C for 10 seconds while maintaining the stretched width in the width direction, and subsequently subjected to a relaxation treatment of 3.0% in the width direction to obtain a monoaxially stretched PET film having a film thickness of about 100 mu m.

The coating liquid for forming a high refractive index layer obtained by the above method was applied to one side of the uniaxially stretched PET film and dried at 150 DEG C 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 onto the high refractive index layer and dried at 150 DEG C for 2 minutes to form a low refractive index layer having a thickness of 0.1 mu m, 1.

(Polarizer protective film 2)

Film formation was carried out in the same manner as in the case of the polarizer protective film 1 except that the line speed was changed to change the thickness of the unstretched film to obtain a polarizer protective film 2 having a film thickness of about 80 탆 and laminated with the antireflection layer.

(Polarizer Protective Film 3)

A film was formed in the same manner as in the case of the polarizer protective film 1 except that the line speed was changed to change the thickness of the unstretched film to obtain a polarizer protective film 3 having a film thickness of about 60 탆 laminated with the antireflection layer.

(Polarizer Protective Film 4)

Film formation was carried out in the same manner as in the case of the polarizer protective film 1 except that the line speed was changed to change the thickness of the unstretched film to obtain a polarizer protective film 4 having a film thickness of about 40 탆 laminated with the antireflection layer.

(Polarizer protective film 5)

The antiglare layer coating agent-1 was applied to one side of the polarizer protective film produced by the same method as that of the polarizer protective film 2 so as to have a film thickness after curing of 8 탆, Dry in oven for 60 seconds. Thereafter, the antiglare layer was laminated by irradiating ultraviolet rays at an irradiation dose of 300 mJ / cm 2 using an ultraviolet irradiation device (Fusion UV Systems Japan, light source H valve). Thereafter, an antireflection layer was laminated on the antiglare layer in the same manner as the polarizer protective film 1 to obtain a polarizer protective film 5.

(Polarizer protective film 6)

The antiglare layer and the antireflection layer were laminated on one coating side of the polarizer protective film produced by the same method as that of the polarizer protective film 3 except that the antireflection layer was not provided, .

(Polarizer protective film 7)

An antiglare layer coating agent-2 was applied on one side of a polarizer protective film produced by the same method as that of the polarizer protective film 4 so as to have a film thickness after curing of 8 탆, Dry in oven for 60 seconds. Thereafter, the antiglare layer was laminated by irradiating ultraviolet rays at an irradiation dose of 300 mJ / cm 2 using an ultraviolet irradiation device (Fusion UV Systems Japan, light source H valve). Thereafter, an antireflection layer was laminated on the antiglare layer in the same manner as the polarizer protective film 1 to obtain a polarizer protective film 7.

(Polarizer protective film 8)

The unstretched film produced by the same method as the polarizer protective film 1 was heated to 105 DEG C by using a heated roll group and an infrared heater and then stretched 3.3 times in the traveling direction in a group of rolls having a peripheral speed, And the film was stretched 4.0 times in the width direction to obtain a polarizer protective film 8 having a film thickness of about 30 占 퐉 laminated with an antireflection layer in the same manner as in the case of the polarizer protective film 1. [

(Polarizer protective film 9)

A polarizer protective film 9 having a film thickness of about 100 占 퐉 was obtained in the same manner as in the polarizer protective film 1 except that no antireflection layer was provided.

(Polarizer protective film 10)

A polarizer protective film 10 was obtained by laminating an antiglare layer in the same manner as in the case of the polarizer protective film 5 on one coating side of the polarizer protective film produced by the same method as the polarizer protective film 8 except that the antireflection layer was not provided The anti-blocking layer is not laminated).

(Polarizer protective film 11)

An antiglare layer coating agent-3 was coated on one side of a polarizer protective film produced by the same method as that of the polarizer protective film 1 so as to have a film thickness after curing of 8 탆, Dry in oven for 60 seconds. Thereafter, ultraviolet rays were irradiated at an irradiation dose of 300 mJ / cm 2 using an ultraviolet irradiator (Fusion UV Systems Japan, light source H valve) to obtain a polarizer protective film 11 in which an antiglare layer was laminated.

Using the polarizer protective films 1 to 11, a liquid crystal display device was produced as described later.

(Example 1)

The polarizer protective film 1 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other, and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 1. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to produce a polarizing plate.

The polarizing plate on the viewer side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate 1 so that the polyester film was located on the opposite side (distal side) from the liquid crystal cell, thereby producing a liquid crystal display device. The transmission axis direction of the polarizing plate 1 was changed to be the same as the transmission axis direction of the polarizing plate before the replacement.

(Example 2)

The polarizer protective film 2 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 2. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to produce a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Example 1 except that the polarizing plate 1 was replaced with the polarizing plate 2.

(Example 3)

The polarizer protective film 3 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 3. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to produce a polarizing plate. A liquid crystal display was produced in the same manner as in Example 1 except that the polarizing plate 1 was replaced with the polarizing plate 3.

(Example 4)

The polarizer protective film 4 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 4. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to produce a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 4.

(Example 5)

The polarizer protective film 4 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were parallel to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 5. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to produce a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 5.

(Example 6)

The polarizer protective film 5 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 6. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer and the antiglare layer were not laminated to produce a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 6.

(Example 7)

The polarizer protective film 6 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 7. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer and the antiglare layer were not laminated to produce a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 7.

(Example 8)

The polarizer protective film 7 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 8. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer and the antiglare layer were not laminated to produce a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 8.

(Comparative Example 1)

The polarizer protective film 8 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 9. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to produce a polarizing plate.

A polarizing plate on the viewer side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate 9 so that the polyester film was on the opposite side (distal side) from the liquid crystal cell, thereby producing a liquid crystal display device. The transmission axis direction of the polarizing plate 9 was replaced with the transmission axis direction of the polarizing plate before replacement.

(Comparative Example 2)

The polarizer protective film 9 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 10. A liquid crystal display device was fabricated in the same manner as in Comparative Example 1 except that the polarizing plate 9 was replaced by the polarizing plate 10.

(Comparative Example 3)

The polarizer protective film 10 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other, and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 11. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antiglare layer was not laminated to prepare a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Comparative Example 1 except that the polarizing plate 9 was replaced with the polarizing plate 11.

(Comparative Example 4)

The polarizer protective film 11 was attached to one side of the polarizer including PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film were perpendicular to each other and a TAC film (80 μm in thickness, manufactured by Fuji Film Co., Ltd.) To prepare a polarizing plate 12. Further, a polarizer was laminated on the surface of the polarizer protective film on which the antiglare layer was not laminated to prepare a polarizing plate. A liquid crystal display device was fabricated in the same manner as in Comparative Example 1 except that the polarizing plate 9 was replaced with the polarizing plate 12.

Table 1 below shows the results of measurement of rainbow stain on the liquid crystal display device obtained in each example.

The liquid crystal display device and the polarizing plate of the present invention can ensure good visibility with which occurrence of irregular color irregularity is significantly suppressed at any angle, and contribution to the industry is great.

Claims (5)

A backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,
Wherein the backlight light source has peak peaks of luminescence spectra in each wavelength region of not less than 400 nm and less than 495 nm, not less than 495 nm and less than 600 nm, and not less than 600 nm and not more than 780 nm, and half of a peak having the highest peak intensity in a wavelength region of not less than 600 nm and not more than 780 nm A white light emitting diode having an emission spectrum with a width of less than 5 nm,
Wherein at least one of the polarizers is formed by laminating a polyester film on at least one surface of the polarizer,
Wherein the polyester film has a retardation of 1500 to 30000 nm and an antireflection layer and / or a low reflection layer are laminated on at least one surface of the polyester film. The backlight unit according to claim 1,
The half width of the peak having the highest peak intensity in the wavelength range of 400 nm or more and less than 495 nm is 5 nm or more,
A half peak width of the peak having the highest peak intensity in a wavelength range of 495 nm or more and less than 600 nm is 5 nm or more,
Liquid crystal display device. The liquid crystal display device according to any one of claims 1 to 2, wherein the surface reflectance of the surface of the antireflection layer at a wavelength of 550 nm is 2.0% or less. A polarizing plate in which a polyester film is laminated on at least one surface of a polarizer,
Wherein the polyester film has retardation of 1500 to 30000 nm and an antireflection layer and / or a low reflection layer are laminated on at least one surface of the polyester film,
A peak having an emission spectrum peak in each of wavelength regions 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, and a peak having the highest peak intensity in a wavelength region of 600 nm or more and 780 nm or less is less than 5 nm A polarizer for a liquid crystal display having a backlight source including a white light emitting diode having an emission spectrum. The polarizing plate according to claim 4, wherein the surface reflectance of the surface of the antireflection layer at a wavelength of 550 nm is 2.0% or less.