KR102325038B1 - Liquid crystal display device - Google Patents

Abstract

The present invention is a polarizer protective film composed of a polyester film having a retardation of 1500 nm or more and 30000 nm or less and having an antireflection layer and/or a low reflection layer laminated on at least one surface thereof, at any wavelength in a wavelength range of 600 nm or more and 780 nm or less. It is a polarizer protective film whose reflectance measured from the side where the antireflection layer and/or the low reflection layer in in was laminated|stacked is 2 % or less.

Description

Liquid crystal display device {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a polarizer protective film, a polarizing plate, and a liquid crystal display device. Specifically, it relates to the liquid crystal display device in which generation|occurrence|production of the rainbow-like color unevenness was improved.

A polarizing plate used in a liquid crystal display device (LCD) has a configuration in which a polarizer obtained by dyeing iodine in polyvinyl alcohol (PVA) or the like is usually sandwiched between two polarizer protective films, and the polarizer protective film is usually a triacetyl cellulose (TAC) film. this is being used In recent years, with thinning of LCD, thinning of a polarizing plate is calculated|required. However, for this reason, when the thickness of the TAC film used as a protective film is made thin, sufficient mechanical strength cannot be obtained and the problem that moisture permeability deteriorates will arise. Moreover, a TAC film is very expensive, and although the polyester film was proposed as an inexpensive substitute material (patent documents 1-3), there existed a problem that rainbow-like color unevenness generate|occur|produced.

When the oriented polyester film which has birefringence is arrange|positioned on one side of a polarizer, a polarization state changes when linearly polarized light radiate|emitted from a backlight unit or a polarizer passes through a polyester film. The transmitted light exhibits a characteristic interference color through retardation, which is the product of the birefringence and 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, transmitted light intensity differs depending on wavelength, resulting in rainbow-like color irregularities (refer to the 15th Microoptical Conference Notice, Paragraphs 30 to 31) ).

As a means to solve the above problem, it is proposed 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 to use an oriented polyester film having constant retardation as a polarizer protective film. There is (Patent Document 4). A white light emitting diode has a continuous and broad emission spectrum in the visible region. Therefore, if attention is paid to the envelope shape of the interference color spectrum by the transmitted light passing through the birefringent, it becomes possible to obtain a spectrum similar to the emission spectrum of the light source by controlling the retardation of the oriented polyester film. It has become possible to suppress

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

Due to the recent rise in demand for expanding the color gamut of liquid crystal display devices, light is emitted in each wavelength region of the blue region (400 nm or more and less than 495 nm), the green region (495 nm or more and less than 600 nm), and the red region (600 nm or more and 780 nm or less). A white light emitting diode (for example, a blue light emitting diode and a phosphor) having a peak top of the spectrum and having a relatively narrow (less than 5 nm) emission spectrum with a peak at half maximum width in the red region (600 nm or more and 780 nm or less) A liquid crystal display device using a backlight light source composed of at least _{a white light emitting diode having a fluoride phosphor such as K 2 SiF 6} :Mn ^{4+ or the like) has been developed.}

When a liquid crystal display device is industrially produced using a polarizing plate using a polyester film as a polarizer protective film, the direction of the transmission axis of the polarizer and the fast axis of the polyester film is usually arranged so as to be perpendicular to each other. do. This is because the polyvinyl alcohol film, which is a polarizer, is produced by longitudinal uniaxial stretching, and the polyester film, which is the protective film, is produced by longitudinal stretching and then transverse stretching, so the polyester film orientation main axis direction is horizontal. It becomes a direction, and when a polarizing plate is manufactured by bonding these elongate objects, it is because the fast axis of a polyester film and the transmission axis of a polarizer will become a perpendicular direction normally. In this case, an oriented polyester film having a specific retardation is used as the polyester film, and as a backlight light source, for example, a white LED comprising a light emitting element in which a blue light emitting diode and a yttrium/aluminum/garnet system yellow phosphor are combined. By using a light source having a continuous and broad emission spectrum represented by When a backlight light source made of a white light emitting diode having

That is, the subject of the present invention has a peak top of the emission spectrum in each wavelength region of the blue region (400 nm or more and less than 495 nm), the green region (495 nm or more and less than 600 nm), and the red region (600 nm or more and 780 nm or less), respectively, in the red region In the liquid crystal display device having a backlight light source comprising a white light emitting diode having a relatively narrow (less than 5 nm) emission spectrum with a peak at half maximum width (600 nm or more and 780 nm or less), even when a polyester film is used as a polarizer protective film, It is to provide the liquid crystal display device in which the rainbow_pattern|erythema was suppressed.

Representative of the present invention is as follows.

Section 1.

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

The backlight light source has a peak top 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, and has the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less. It is a white light emitting diode having an emission spectrum with a half maximum width of a peak (a peak with the highest peak in the wavelength region of 600 nm or more and 780 nm or less) less than 5 nm,

At least one of the polarizing plates is a polyester film laminated on at least one surface of the polarizer,

The polyester film has a retardation of 1500 nm or more and 30000 nm or less,

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

The anti-reflection layer and/or low-reflection layer is laminated, measured from the side where the anti-reflection layer and/or the low-reflection layer are laminated, in the wavelength of the peak peak of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less. The reflectance of the used polyester film is 2 % or less, The liquid crystal display device characterized by the above-mentioned.

Section 2.

The emission spectrum of the backlight light source is,

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

The liquid crystal display device according to item 1, wherein 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 5 nm or more.

Section 3.

The liquid crystal display device according to item 1 or 2, wherein the wavelength of the peak top of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less is in the region of 620 nm or more and 640 nm or less.

Section 4.

The liquid crystal display device according to item 1 or 2, wherein the wavelength of the peak top of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less is 630 nm.

Section 5.

A polarizer protective film comprising a polyester film having a retardation of 1500 nm or more and 30000 nm or less and having an antireflection layer and/or a low reflection layer laminated on at least one surface thereof,

The polarizer protective film whose reflectance measured from the side on which the antireflection layer and/or the low reflection layer in any wavelength in a wavelength range of 600 nm or more and 780 nm or less was laminated|stacked is 2 % or less.

Section 6.

The polarizer protective film according to item 5, wherein any of the wavelengths are 620 nm or more and 640 nm or less.

Section 7.

The polarizer protective film according to item 5, wherein any of the above wavelengths is 630 nm.

Section 8.

The polarizing plate in which the polarizer protective film in any one of Claims 5-7 was laminated|stacked on at least one surface of a polarizer.

The liquid crystal display device of this invention, a polarizing plate, and a polarizer protective film can ensure favorable visibility by which generation|occurrence|production of the rainbow-like color unevenness was suppressed significantly also in any observation angle.

In general, a liquid crystal display device is composed of a rear module, a liquid crystal cell, and a front module in the order from the backlight light source side toward the image display side (viewer side). The rear module and the front module are generally constituted by a transparent substrate, a transparent conductive film formed on a surface of the liquid crystal cell side thereof, and a polarizing plate disposed on the opposite side thereof. Here, in the rear module, the polarizing plate is arranged on the backlight light source side, and in the front module, it is arranged on the image display side (viewing side).

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

Moreover, a liquid crystal display device may have suitably other structures other than a backlight light source, a polarizing plate, and a liquid crystal cell, for example, a color filter, a lens film, a diffusion sheet, an antireflection film, etc. suitably. You may provide a brightness improvement film between a light source side polarizing plate and a backlight light source. As a brightness improving film, the reflection type polarizing plate which transmits one linearly polarized light and reflects the linearly polarized light orthogonal to it is mentioned, for example. As a reflection type polarizing plate, the brightness improving film of the DBEF (trademark) (Dual Brightness Enhancement Film) series by Sumitomo 3M Corporation is used suitably, for example. In addition, the reflective polarizing plate is usually arranged so that the absorption axis of the reflective polarizing plate and the absorption axis of the light source-side polarizing plate are parallel to each other.

Of the two polarizing plates disposed in the liquid crystal display device, at least one of the polarizing plates has a polyester film laminated on at least one surface of the polarizer in which iodine is dyed with polyvinyl alcohol (PVA) or the like. In this invention, from a viewpoint of suppressing rainbow-like color unevenness, a polyester film has specific retardation, and the antireflection layer and/or a low reflection layer are laminated|stacked on at least one surface of a polyester film. An antireflection layer and/or a low reflection layer may be provided in the surface on the opposite side to the surface on which the polarizer of a polyester film is laminated|stacked, and may be provided in the surface on which the polarizer of a polyester film is laminated|stacked, and both are not cared about. It is preferable to provide an antireflection layer and/or a low reflection layer on the surface on the opposite side to the surface on which the polarizer of a polyester film is laminated|stacked. In addition, between the antireflection layer and/or the low reflection layer and the polyester film, other layers (for example, an easily adhesive layer, a hard coat layer, an antiglare layer, an antistatic layer, an antifouling layer, etc.) may exist. . It is preferable that the refractive index of the said polyester film of the direction parallel to the transmission axis of a polarizer from a viewpoint of suppressing more rainbow-like color nonuniformity is 1.53-1.62. On the other side of the polarizer, a film having substantially no birefringence (low retardation) such as typified by a TAC film, an acrylic film, or a norbornene-based film is preferably laminated (a polarizing plate having a three-layer configuration), but must be It is not necessary that the film be laminated on the other side of the polarizer (polarizing plate having a two-layer configuration). Moreover, when a polyester film is used as a protective film on both sides of a polarizer, it is preferable that the slow axes of both polyester films are mutually substantially parallel. The substantially parallel here means that the angle formed by the two axes is -15° to 15°, preferably -10° to 10°, more preferably -5° to 5°, still more preferably -3°. -3°, even more preferably -2° to 2°, still more preferably -1° to 1°.

A polarizer can select suitably arbitrary polarizers (polarizing film) used in the said technical field, and can be used. A representative polarizer includes, but is not limited to, a polyvinyl alcohol film obtained by dyeing a dichroic material such as iodine. have.

A commercial item can be used for a PVA film, For example, "Kuraray vinylon (manufactured by Kuraray Co., Ltd.)", "Tosero vinylon (manufactured by Tosero Corporation)", "Nichigo vinylon (Nippon Kose Kaga)" KU Co., Ltd.)" etc. can be used. Examples of the dichroic material include iodine, diazo compounds, and polymethine dyes.

A polarizer can be obtained by arbitrary methods, for example, uniaxially stretching what dyed the PVA film with a dichroic material in boric-acid aqueous solution, It can obtain by washing|cleaning and drying, maintaining an extending|stretching state. Although the draw ratio of uniaxial stretching is about 4 to 8 times normally, it is not restrict|limited in particular. Other manufacturing conditions, etc. can be set suitably according to a well-known method.

The configuration of the backlight may be an edge light system or a direct system in which a light guide plate or a reflecting plate is used as a constituent member, but in the present invention, 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and A white light emitting diode having a peak top of the emission spectrum in each wavelength region of 600 nm or more and 780 nm or less, and an emission spectrum having the highest peak intensity peak in the wavelength region of 600 nm or more and 780 nm or less and less than 5 nm. A backlight light source is preferred. As for the upper limit of the half maximum width of the peak which has the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less, less than 5 nm is preferable, More preferably, it is less than 4 nm, More preferably, it is less than 3.5 nm. The lower limit is preferably 1 nm or more, more preferably 1.5 nm or more. Since the color gamut of a liquid crystal display device becomes it that the full width at half maximum of a peak is less than 5 nm, it is preferable. In addition, although there is no particular lower limit of the half width of the peak, it can be set to 1 nm. When the peak half width is less than 1 nm, there is a possibility that the luminous efficiency is deteriorated. The shape of the emission spectrum is designed from the balance between the required color gamut and the luminous efficiency. In addition, here, a half width is a peak width (nm) in the intensity|strength of 1/2 of the peak intensity in the wavelength of a peak top.

Application of a backlight light source having an emission spectrum having the above-described characteristics to an LCD is a technology that is attracting attention from the recent increase in demand for color gamut expansion. In LEDs using conventionally used white LEDs (e.g., a light emitting element combining a blue light emitting diode and a yttrium/aluminum/garnet-based yellow phosphor) as a backlight light source, only about 20% of the spectrum that the human eye can recognize Color cannot be reproduced. On the other hand, when a backlight light source having an emission spectrum having the above characteristics is used, it is said that 60% or more of colors can be reproduced.

The wavelength region of 400 nm or more and less than 495 nm is more preferably 430 nm or more and 470 nm or less. The wavelength region of 495 nm or more and less than 600 nm is more preferably 510 nm or more and 560 nm or less. 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. A preferable aspect of the wavelength range of 600 nm or more and 780 nm or less is 620 nm or more and 640 nm or less, and particularly preferably 630 nm.

The peak half-width at the peak top of each wavelength region of 400 nm or more and less than 495 nm and 495 nm or more and less than 600 nm of the emission spectrum (the half-maximum width of the peak having the highest peak intensity in each wavelength region) is not particularly limited, but 400 nm or more It is preferable that the half-width of the peak having the highest peak intensity in the wavelength region of less than 495 nm is 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 an appropriate color gamut, the upper limit of the peak half-width at the peak top of each wavelength region of 400 nm or more and less than 495 nm and 495 nm or more and less than 600 nm (the peak half-width of the peak having the highest peak intensity in each wavelength region) is, Preferably it is 140 nm or less, Preferably it is 120 nm or less, Preferably it is 100 nm or less, More preferably, it is 80 nm or less, More preferably, it is 60 nm or less, More preferably, it is 50 nm or less.

As a white light source which has the emission spectrum which has the above-mentioned characteristic, specifically, for example, the fluorescent substance type white light emitting diode which combined a blue light emitting diode and a fluorescent substance is mentioned. Examples of the red phosphor among the phosphors include a _{fluoride phosphor having a composition formula of K 2} SiF ₆ :Mn ⁴⁺ (also referred to as “KSF”), and others. The Mn ⁴⁺ activated fluoride complex phosphor is a phosphor in which Mn ⁴⁺ is an activator and a fluoride complex salt of an alkali metal, amine or alkaline earth metal is used as a matrix crystal. Examples of the fluoride complex forming the parent crystal include those whose coordination centers are trivalent metals (B, Al, Ga, In, Y, Sc, lanthanoids), tetravalent metals (Si, Ge, Sn, Ti, Zr, Re, Hf) and pentavalent metals (V, P, Nb, Ta) exist, and the number of fluorine atoms coordinated around them is 5-7.

Suitable examples of the Mn ⁴⁺ activated fluoride complex phosphor include A ₂ [MF ₆ ]:Mn (A is at least one selected from Li, Na, K, Rb, Cs, and NH ₄ ; M is Ge, Si, At least one selected from Sn, Ti, and Zr), E[MF ₆ ]:Mn (E is at least one selected from Mg, Ca, Sr, Ba, and Zn; M is Ge, Si, Sn, Ti , and at least one selected from Zr), Ba _0.65 , Zr _0.35 F _2.70 :Mn, A ₃ [ZrF ₇ ]:Mn (A is at least one selected from Li, Na, K, Rb, Cs, and NH _{4 )} or more), A ₂ [MF ₅ ]:Mn (A is at least one selected from Li, Na, K, Rb, Cs, and NH ₄ ; M is at least one selected from Al, Ga, and In), A ₃ [MF ₆ ]:Mn (A is 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 ]:Mn (M is at least one selected from Al, Ga, and In), A[In ₂ F ₇ ]:Mn (A is selected from Li, Na, K, Rb, Cs, and NH _{4 )} 1 or more), etc.

One of the preferred Mn ⁴⁺ _{activated fluoride complex phosphors is A 2} MF ₆ :Mn (A is selected from Li, Na, K, Rb, Cs, and NH _{4 )} in which a hexafluoro complex salt of an alkali metal is used as a parent crystal. at least one; M is at least one selected from Ge, Si, Sn, Ti, and Zr). Among them, preferably, A is at least one selected from K (potassium) and Na (sodium), and M is Si (silicon) or Ti (titanium). Among them, it is preferable that A is K (the ratio of K to the total amount of A is 99 mol% or more) and M is Si. The activator element preferably contains 100% Mn (manganese), but Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn, Mg, etc. may be contained. When M is Si, it is preferable that the ratio of Mn in the sum total of Si and Mn exists in the range of 0.5 mol% - 10 mol%. As another preferred Mn ⁴⁺ activated fluoride complex phosphor, Formula A _2+x M _y Mn _z F _n (A is Na and K; M is Si and Al; -1≤x≤1 Also 0.9≤y+z≤1.1 Also 0.001 ≤ z ≤ 0.4 and 5 ≤ n ≤ 7).

The backlight light source is preferably a blue light emitting diode and a white light emitting diode having at least a fluoride phosphor as a phosphor, particularly preferably, a blue light emitting diode and a white light emitting diode having a fluoride phosphor having _{at least K 2} SiF ₆ :Mn ^{4+ as the phosphor.} am. For example, commercial items, such as NSSW306FT which is a Nichia Chemical Industry Co., Ltd. product white LED, can be used.

In addition, among the above-mentioned phosphors, green phosphors include, for example, a sialon-based phosphor having a basic composition such as β-SiAlON:Eu, a silicate-based phosphor having a basic composition such as _{(Ba,Sr) 2} SiO _{4 :Eu, and the like;} outside is exemplified.

In addition, the case where a plurality of peaks exist in any of the wavelength region 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 less than 780 nm is considered as follows.

When a plurality of peaks are independent peaks, it is preferable that the half width of the peak having the highest peak intensity is within the above range. Moreover, also about the other peak which has intensity|strength of 70% or more of the highest peak intensity, it is a more preferable aspect that a half width becomes the said range similarly.

With respect to one independent peak having a shape in which a plurality of peaks overlapped, the half maximum width of the peak having the highest peak intensity among the plurality of peaks can be measured as it is, the half maximum width is used. Here, an independent peak has an intensity|region which becomes 1/2 of a peak intensity on both the short-wavelength side and the long-wavelength side of a peak. That is, when a plurality of peaks overlap and each peak does not have a region having an intensity equal to 1/2 of the peak intensity on both sides thereof, the plurality of peaks are regarded as one peak as a whole. In the case of one peak having such a shape in which a plurality of peaks overlapped, the width (nm) of the peak at half the intensity of the highest peak intensity among them is taken as the half width.

In addition, let the point with the highest peak intensity among several peaks be a peak top.

In addition, the peak having the highest peak intensity in each wavelength region of a wavelength region of 400 nm or more and less than 495 nm, a wavelength region of 495 nm or more and less than 600 nm, or a wavelength region of 600 nm or more and less than 780 nm is different from the peaks of other wavelength regions. It is desirable to be in an independent relationship. In particular, 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, the intensity is in the wavelength 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 that is 1/3 or less of the peak intensity of the peak having the highest peak intensity of .

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 present inventors, like the above-described backlight light source, each wavelength region of the blue region (400 nm or more and less than 495 nm), the green region (495 nm or more and less than 600 nm) and the red region (600 nm or more and 780 nm or less) of the emission spectrum, respectively. In the liquid crystal display device having a backlight light source comprising a white light emitting diode having a peak top and having a peak at half width relatively narrow in the red region (600 nm or more and 780 nm or less), as a polarizer protective film, the reflectance at a specific wavelength is It has a low antireflection layer and/or a low reflection layer, and when the polyester film which has specific retardation was used, it discovered that it was effective in suppression of rainbow_pattern|erythema. Here, the specific wavelength is the wavelength corresponding to the peak with the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less in the emission spectrum of the backlight light source (the wavelength of the peak top of the peak with the highest peak intensity). . That is, the present inventors measured from the side where the antireflection layer and/or the low reflection layer were laminated in the peak top wavelength of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less in the emission spectrum of the backlight light source. As long as the reflectance of the polyester film on which the antireflection layer and/or the low reflection layer were laminated|stacked was 2 % or less, it discovered that there was especially an effect in rainbow_pattern|erythema suppression.

When an orientation polyester film is arrange|positioned on one side of a polarizer, when linearly polarized light radiate|emitted from a backlight unit or a polarizer passes a polyester film, a polarization state changes. As one of the factors to which a polarization state changes, the possibility that the refractive index difference of the interface of an air layer and an oriented polyester film or the refractive index difference of the interface of a polarizer and an oriented polyester film is having an influence is considered. When the linearly polarized light which injected into the orientation polyester film passes through each interface, a part of light is reflected by the refractive index difference between interfaces.

The light which passes through a polarizer and injects into an orientation polyester film is linearly polarized light, and it is thought that there is no transmittance|permeability dependence with respect to a wavelength in the state of linearly polarized light. The incident light of linearly polarized light changes into elliptically polarized light or circularly polarized light by passing through the oriented polyester film. The phase difference δ is expressed by δ=2π×Re/λ (Re: retardation, λ: wavelength), and the phase difference δ varies depending on the wavelength λ. That is, since the change cycle of linearly polarized light, elliptically polarized light, and circularly polarized light differs with the wavelength λ of light, it is thought that the polarization state at the time of radiating|emitting an oriented polyester film differs with wavelength. When exiting from the oriented polyester film to the viewing side, the S-polarized component perpendicular to the P-polarized component parallel to the incident surface is more likely to be reflected, and as the viewing angle from the normal increases, the difference (P-polarized component and S-polarized component) ) tends to increase. Since the influence of S-polarized light, which is easily reflected, is different for each wavelength of light having a different degree of polarization, each transmittance changes when passing through the interface. When passing through the interface, the transmittance of a wavelength band with many S-polarized components is lowered, and this is considered to be one of the factors causing the rainbow-like color unevenness. In particular, when it has a steep peak in the red region of 600 nm or more and 780 nm or less, the transmittance change according to the wavelength is large, so color unevenness tends to appear. Since the interfacial reflection of arbitrary wavelengths can be suppressed by using thin film interference, the transmittance of the red region is improved by forming an antireflection layer and/or a low reflection layer with low reflectance at steep peaks (i.e., the reflection of S-polarized components is reduced). suppression) is thought to be possible. In the red region having a steep peak, since the transmittance of the S-polarized light component is improved, the change in transmittance of the emitted light of the oriented polyester film with respect to the incident light passing through the polarizer decreases, thereby suppressing rainbow-like color unevenness.

As described above, in the present invention, each wavelength region of the blue region (400 nm or more and less than 495 nm), the green region (495 nm or more and less than 600 nm) and the red region (600 nm or more and 780 nm or less) has a peak top of the emission spectrum, respectively, and the red region ( In a liquid crystal display device having a backlight light source comprising a white light emitting diode having a relatively narrow half-width of the peak at 600 nm or more and 780 nm or less), even if a polarizing plate using a polyester film is used as a polarizer protective film, rainbow-like color unevenness does not occur. , it becomes possible to have good visibility.

On the polarizing plate of this invention, the polarizer protective film which consists of a polyester film is laminated|stacked on at least one surface of a polarizer. It is preferable that the polyester film used for a polarizer protective film has retardation of 1500 nm or more and 30000 nm or less. When retardation exists in the said range, it is preferable in the tendency which becomes easy to reduce a rainbow_pattern|erythema. A preferable lower limit of the retardation is 3000 nm, a next preferable lower limit is 3500 nm, a more preferable lower limit is 4000 nm or 5000 nm, a more preferable lower limit is 6000 nm or 7000 nm, and a still more preferable lower limit is 8000 nm. A preferable upper limit is 30000 nm, and in the polyester film which has retardation more than this, thickness becomes large considerably, and it exists in the tendency for the handleability as an industrial material to fall. A more preferable upper limit is 15000 nm, more preferably 12000 nm, still more preferably 11000 nm.

In addition, the retardation of this invention can be calculated|required by measuring the refractive index and thickness of the biaxial direction, and can also be calculated|required using a commercially available automatic birefringence measuring apparatus like KOBRA-21ADH (Oji Keisoku Instruments Co., Ltd.). In addition, the refractive index can be calculated|required with Abbe's refractometer (measurement wavelength 589 nm).

Ratio (Re/Rth) of retardation (Re: in-plane retardation) of a polyester film and retardation (Rth) of thickness direction becomes like this. Preferably it is 0.2 or more, More preferably, it is 0.5 or more, More preferably, it is 0.6 or more. am. The larger the ratio (Re/Rth) of the retardation to the thickness direction retardation is, the higher the birefringence effect is, the more difficult it is to generate rainbow-like color unevenness depending on the observation angle. In a perfectly uniaxial (uniaxially symmetric) film, the ratio (Re/Rth) of the retardation to the thickness direction retardation is 2.0, so the upper limit of the ratio (Re/Rth) of the retardation to the thickness direction retardation is 2.0 is preferred. In addition, the thickness direction retardation means the average of the retardation obtained by multiplying the film thickness d by two birefringence (DELTA)Nxz, (DELTA)Nyz when the film is seen from the cross section in the thickness direction, respectively.

It is preferable that the NZ coefficient of a polyester film is 2.5 or less from a viewpoint of suppressing more rainbow-like color unevenness, More preferably, it is 2.0 or less, More preferably, it is 1.8 or less, More preferably, it is 1.6 or less. And in a perfect uniaxial (uniaxially symmetric) film, since NZ coefficient becomes 1.0, the lower limit of NZ coefficient is 1.0. However, it is necessary to note that the mechanical strength in the direction orthogonal to the orientation direction tends to decrease remarkably as the film approaches a perfect uniaxial (uniaxially symmetric) film.

The NZ coefficient is expressed by |Ny-Nz|/|Ny-Nx|, where Ny is the refractive index in the slow axis direction, Nx is the refractive index in the direction orthogonal to the slow axis (the refractive index in the fast axis direction), and Nz is the thickness It indicates the refractive index of the direction. The orientation axis of the film is determined using a molecular orientation meter (manufactured by Oji Keisoku Instruments Co., Ltd., MOA-6004 type molecular orientation meter), and the refractive indices of the orientation axis direction and the biaxial direction orthogonal thereto (Ny, Nx, except Ny) >Nx) and the refractive index (Nz) of the thickness direction are calculated|required with Abbe's refractive index meter (The Atago company make, NAR-4T, measurement wavelength 589nm). The NZ coefficient can be calculated|required by substituting the value calculated|required in this way into |Ny-Nz|/|Ny-Nx|.

Moreover, as for the value of Ny-Nx of a polyester film from a viewpoint of suppressing more rainbow-like color unevenness, 0.05 or more are preferable, More preferably, it is 0.07 or more, More preferably, it is 0.08 or more, More preferably, it is 0.09 or more. , most preferably 0.1 or more. Although the upper limit is not particularly set, in the case of a polyethylene terephthalate-based film, the upper limit is preferably about 1.5.

As a more preferable aspect in this invention, it is preferable to make the refractive index of the polyester film of the direction parallel to the transmission axis direction of the polarizer which comprises a polarizing plate into the range of 1.53 or more and 1.62 or less. Thereby, the reflection in the interface of a polarizer and a polyester film is suppressed, and it becomes possible to suppress more rainbow-like color unevenness. Preferably it is 1.61 or less, More preferably, it is 1.60 or less, More preferably, it is 1.59 or less, More preferably, it is 1.58 or less.

On the other hand, the lower limit of the refractive index is preferably 1.53. When the refractive index is less than 1.53, crystallization of the polyester film becomes insufficient, and there is a possibility that the properties obtained by stretching, such as dimensional stability, mechanical strength, and chemical resistance, become insufficient. Preferably it is 1.56 or more, More preferably, it is 1.57 or more.

In order to set the refractive index of the polyester film in a direction parallel to the direction of the transmission axis of the polarizer in the range of 1.53 or more and 1.62 or less, in the polarizing plate, the transmission axis of the polarizer and the fast axis (vertical direction to the slow axis) of the polyester film are approximately It is preferable to be parallel. A polyester film can adjust the refractive index of the fast axis direction which is a direction perpendicular|vertical to a slow axis low to about 1.53-1.62 by the extending|stretching process in the film forming process mentioned later. By making the fast axis direction of a polyester film and the transmission axis direction of a polarizer substantially parallel, the refractive index of the polyester film of the direction parallel to the transmission axis direction of a polarizer can be set to 1.53-1.62. The substantially parallel here means that the angle between the transmission axis of the polarizer and the fast axis of the polarizer protective film is -15° to 15°, preferably -10° to 10°, more preferably -5° to 5°, It means more preferably -3° to 3°, still more preferably -2° to 2°, still more preferably -1° to 1°. In one preferred embodiment, approximately parallel is substantially parallel. The term "substantially parallel" here means that the transmission axis and the fast axis are parallel to the extent to which a shift that inevitably occurs when the polarizer and the protective film are interlocked. The direction of the slow axis can be measured and calculated|required with a molecular orientation meter (For example, the Oji Keisoku Instruments Co., Ltd. make, MOA-6004 type molecular orientation meter).

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

The polarizer protective film made of the polyester film used in the present invention can be used for both polarizing plates on the incident light side (light source side) and outgoing light side (viewer side), but at least on the protective film of the polarizing plate on the outgoing light side (viewer side). It is preferable to use

Regarding the polarizing plate disposed on the outgoing light side, the polarizer protective film made of the polyester film may be disposed on the liquid crystal side with the polarizer as a starting point, may be disposed on the outgoing light side, or may be disposed on both sides, but at least It is preferably arranged on the light side.

Also in the polarizing plate disposed on the incident light side, the polarizer protective film made of the polyester film may be disposed on the incident light side with the polarizer as a starting point, may be disposed on the liquid crystal cell side, or may be disposed on both sides, but at least It is a preferable aspect that it is arrange|positioned on the side of the incident light. The polarizing plate disposed on the incident light side may use a polarizer protective film substantially free of birefringence (low retardation), such as a triacetyl cellulose film, without using a polarizer protective film made of a polyester film.

Although a polyethylene terephthalate and a polyethylene naphthalate can be used for polyester used for a polyester film, it does not matter even if another copolymerization component is included. These resins are excellent in transparency and also excellent in thermal and mechanical properties, and retardation can be easily controlled by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence, and by stretching the film, the refractive index in the fast axis (perpendicular to the slow axis direction) direction can be suppressed to be low, and large retardation can be obtained relatively easily even if the thickness of the film is thin. In this respect, it is the most suitable material.

Moreover, it is preferable that the light transmittance of wavelength 380nm of a polyester film is 20 % or less for the purpose of suppressing deterioration of optically functional dyes, such as an iodine dye. The light transmittance of 380 nm is more preferably 15% or less, still more preferably 10% or less, and particularly preferably 5% or less. If the said light transmittance is 20 % or less, the quality change by the ultraviolet-ray of an optically functional dye can be suppressed. In addition, the transmittance|permeability is what is measured in the perpendicular|vertical direction with respect to the plane of a film, and can be measured using the spectrophotometer (For example, Hitachi U-3500 type|mold).

In order to make the transmittance|permeability of wavelength 380nm of a polyester film 20 % or less, it is preferable to adjust the kind of ultraviolet absorber, a density|concentration, and the thickness of a film suitably. The ultraviolet absorber used in the present invention is a known substance. Although an organic type ultraviolet absorber and an inorganic type ultraviolet absorber are mentioned as a ultraviolet absorber, From a transparency viewpoint, an organic type ultraviolet absorber is preferable. Although a benzotriazole type, a benzophenone type, a cyclic iminoester type, etc. are mentioned as an organic type ultraviolet absorber, If it is the range of the absorbance prescribed|regulated by this invention, it will not specifically limit. From a durable viewpoint, a benzotriazole type and a cyclic iminoester type are especially preferable. When two or more types of ultraviolet absorbers are used together, since the ultraviolet-ray of each wavelength can be absorbed simultaneously, the ultraviolet-ray absorption effect can be improved more.

Examples of the benzophenone-based UV absorber, the benzotriazole-based UV absorber and the acrylonitrile-based UV absorber include 2-[2'-hydroxy-5'-(methacryloyloxymethyl)phenyl]-2H-benzo Triazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxy) Propyl) phenyl] -2H-benzotriazole, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',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, 2,2'-methylenebis (4- (1,1,3, 3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol etc. As a cyclic iminoester type|system|group ultraviolet absorber, for example, 2,2'-(1,4- Phenylene)bis(4H-3,1-benzoxazin-4-one), 2-methyl-3,1-benzooxazin-4-one, 2-butyl-3,1-benzoxazin-4- one, 2-phenyl-3,1-benzooxazin-4-one, etc. However, it is not particularly limited thereto.

Moreover, it is also a preferable aspect to contain various additives other than a catalyst in the range which does not impair the effect of this invention other than a ultraviolet absorber. Examples of the additive include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light resistance agents, flame retardants, heat stabilizers, antioxidants, anti-gelling agents, surfactants, and the like. . Moreover, in order to exhibit high transparency, it is also preferable not to contain particle|grains substantially in a polyester film. "Substantially does not contain particles" means, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescence X-ray analysis, the content is 50 ppm or less, preferably 10 ppm or less, particularly preferably the content below the detection limit. means

It is preferable to provide an antireflection layer and/or a low reflection layer in at least one surface of the polyester film which is a polarizer protective film used for this invention.

The reflectance of the polyester film on which the antireflection layer and/or the low reflection layer was laminated|stacked in the wavelength of the peak top of the peak with the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less of the emission spectrum of the said backlight light source is 2% It is preferable that it is below. In addition, the reflectance is measured from the side where the antireflection layer and/or the low reflection layer were laminated|stacked. When a reflectance exceeds 2 %, it is unpreferable at the point which becomes easy to visually recognize the color nonuniformity of a rainbow shape. A reflectance becomes like this. More preferably, it is 1.6 % or less, More preferably, it is 1.2 % or less, Especially preferably, it is 1 % or less. Although the lower limit in particular of a reflectance is not set, it is 0.01 %, for example. A reflectance of 0% is most preferred. When laminating an antireflection layer, the upper limit of the reflectance is preferably less than 1%. When laminating a low reflective layer, the upper limit of the reflectance is preferably 2% or less, more preferably less than 2%, and the lower limit is preferably about 1%. The reflectance can be measured by the method described in Examples to be described later.

The antireflection layer may be a single layer or multiple layers, and in the case of a single layer, if the thickness of the low refractive index layer made of a material having a lower refractive index than that of the polyester film is formed to be 1/4 wavelength of the light wavelength or an odd multiple thereof, an antireflection effect is obtained. Moreover, when the antireflection layer is multilayered, the low-refractive-index layer and the high-refractive-index layer are alternately two or more layers, and the thickness of each layer is appropriately controlled and laminated to obtain an antireflection effect. Moreover, it is also possible to laminate|stack a hard-coat layer between reflection prevention layers as needed, and to form an antifouling|stain-resistant layer on a hard-coat layer.

As an antireflection layer, what used a moth-eye structure is mentioned other than that. The moth-eye structure is a concave-convex structure with a pitch smaller than the wavelength formed on the surface, and by this structure, it is possible to change the abrupt and discontinuous refractive index change at the interface with air into a continuous and gradually transitioning refractive index change. will be. Thereby, by forming a moth-eye structure on the surface, the light reflection in the surface of a film reduces. For example, reference can be made to Japanese Patent Application Laid-Open No. 2001-517319.

As a method for forming an antireflection film, a dry coating method in which an antireflection layer is formed on the surface of a substrate by vapor deposition or sputtering method, 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 method or the method of using both together is mentioned. In the present invention, the composition of the antireflection layer and the formation method thereof will not be particularly limited as long as the above characteristics are satisfied.

A conventionally well-known thing can be used for a low reflection layer. For example, it is formed by a method of laminating at least one layer or more of a metal or oxide thin film by vapor deposition or sputtering, or a method of coating an organic thin film in one or multiple layers. As a low-reflection layer, what coated the organic thin film whose refractive index is lower than the hard-coat layer laminated|stacked on a polyester film or a polyester film further is used preferably.

An anti-glare function may be further provided to the antireflection layer and/or the low reflection layer. Thereby, rainbow_pattern|erythema can be suppressed further. That is, a combination of an antireflection layer and an antiglare layer, a combination of a low reflection layer and an antiglare layer, or a combination of an antireflection layer, a low reflection layer and an antiglare layer may be used. Especially preferably, it is a combination of a low reflection layer and a glare-proof layer. As the anti-glare layer, a conventionally known anti-glare layer can be used. For example, from a viewpoint of suppressing the surface reflection of a film, after laminating|stacking a glare-proof layer on a polyester film, the aspect which laminates|stacks an antireflection layer or a low-reflection layer is preferable.

As one method of reducing the reflectance of the polyester film in which the antireflection layer and/or the low reflection layer are laminated at the peak position with the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less in the emission spectrum of the backlight light source, For example, designing the antireflection layer and the low reflection layer so that the bottom wavelength of the reflection spectrum of the polyester film on which the antireflection layer and/or the low reflection layer is laminated becomes a wavelength range of 600 nm or more and 780 nm or less.

In order to set the bottom wavelength of the reflection spectrum of the antireflection layer and/or the low reflection layer to 600 nm or more and 780 nm or less, for example, when the antireflection layer or the low reflection layer is a single layer, the expression 2nd = λb/4 is satisfied. , the thickness of the low reflection layer may be adjusted. Here, n is the refractive index of the antireflection layer or the refractive index of the low reflection layer, d is the thickness of the antireflection layer or the thickness of the low reflection layer, and λb is the bottom wavelength of the reflection spectrum.

Even when the anti-reflection layer and the low-reflection layer are multi-layered, it can be calculated as follows from the principle of thin-film interference. For example, five layers (a first layer, a second layer, a third layer, a fourth layer, and a fifth layer) )(in) exists, and the emission medium layer (out) exists on the side opposite to the side in contact with the fourth layer of the fifth layer), the refractive index is n, the reflectance is r, and the thickness is When d, the refraction angle is θ, the wavelength is λ, and the phase difference is Δ, the reflectance of the lowest layer (fifth layer) is expressed by the following equation from the thin film interference equation. The appended (添) number indicates each floor. In addition, successive appended numbers of the reflectance indicate the reflectance between each layer.

(5th floor)

[Equation 1]

Δ _x is, there is a phase difference when the inside of each layer x thin film have a round trip to the V-shaped angle of refraction θ _x, is calculated by the formula of Equation (2).

[Equation 2]

θ _x is calculated by the formula of [Equation 3] by continuously using Snell's law.

[Equation 3]

In general, when calculating the multilayer film reflection, the reflectance of each layer is obtained from the following equation, since it can be calculated by adding the reflected light from a plurality of boundary surfaces while considering the phases.

(5th to 4th floor)

[Equation 4]

(5th to 3rd floor)

[Equation 5]

(5th floor - 2nd floor)

[Equation 6]

(5th to 1st floor)

The reflectance in all five layers is obtained by the following formula.

[Equation 7]

The addition of the suffix of the reflectance represents the reflectance of the summation between each layer. By adjusting the refractive index n and thickness d of each layer from the said formula, a bottom wavelength can be designed as a target wavelength.

In the emission spectrum of the backlight light source, the wavelength λp of the peak top of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less, and the bottom of the reflection spectrum of the polyester film in which the antireflection layer and/or the low reflection layer are laminated As for the wavelength λb, the absolute value of the difference between λp and λb is preferably 30 nm or less, preferably 20 nm or less, preferably 10 nm or less, and preferably 5 nm or less. In addition, the bottom wavelength of a reflection spectrum is a wavelength at which a reflectance becomes the minimum in the reflection spectrum of 400 nm - 780 nm.

When providing an antireflection layer or a low reflection layer, it is preferable that a polyester film has an easily adhesive layer on the surface. In that case, from a viewpoint of suppressing the interference by reflected light, it is preferable to adjust the refractive index of an easily adhesive layer so that it may become near a rising average of the refractive index of a reflection prevention layer or a low reflection layer, and the refractive index of a polyester film. A well-known method can be employ|adopted for adjustment of the refractive index of an easily bonding layer, For example, it can adjust easily by containing titanium, germanium, and another metal species in binder resin.

In order to make adhesiveness with a polarizer favorable to a polyester film, it is also possible to give a corona treatment, a coating process, a flame treatment, etc.

In the present invention, in order to improve the adhesiveness with the polarizer, it is preferable to have an easily adhesive layer mainly composed of at least one of a polyester resin, a polyurethane resin, or a polyacrylic resin on at least one side of the film of the present invention. . Here, a "main component" means a component 50 mass % or more among the solid components which comprise an easily bonding layer. As for the coating liquid used for formation of the easily bonding layer of this invention, the aqueous coating liquid containing at least 1 sort(s) among a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin is preferable. As these coating liquids, for example, Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, etc. and the disclosed water-soluble or water-dispersible co-polyester resin solution, acrylic resin solution, polyurethane resin solution, and the like.

After apply|coating the said coating liquid on one side or both surfaces of an unstretched film or a longitudinal uniaxially stretched film, an easily adhesive layer can be obtained by drying at 100-150 degreeC, and also extending|stretching transversely. It is preferable to manage the application amount of the final easily bonding layer to 0.05-0.2 g/m<2>. Adhesiveness with the polarizer obtained as an application amount is less than 0.05 g/m<2> may become inadequate. On the other hand, when an application amount exceeds 0.2 g/m<2>, blocking resistance may fall. When providing an easily bonding layer on both surfaces of a polyester film, the application quantity of the easily bonding layer of both surfaces may be same or different, and can be set within the said range independently, respectively.

It is preferable to add particle|grains in order to provide easy activity to an easily adhesive layer. The average particle diameter of the fine particles is preferably 2 µm or less. When the average particle diameter of the particles exceeds 2 µm, the particles easily fall off from the coating layer. Examples of particles to be contained in the easily adhesive layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride. , inorganic particles such as calcium fluoride, and organic polymer particles such as styrene, acrylic, melamine, benzoguanamine and silicone particles. These may be independently added to an easily bonding layer, and may be added in combination of 2 or more type.

Moreover, as a method of apply|coating a coating liquid, a well-known method can be used. For example, the reverse roll coating method, the gravure coating method, the kiss coating method, the roll brush method, the spray coating method, the air knife coating method, the wire bar coating method, the pipe doctor method, etc. are mentioned, These methods are It can be performed individually or in combination.

In addition, the measurement of the average particle diameter of said particle|grains is performed by the following method. The particles are photographed with a scanning electron microscope (SEM), and the maximum diameter (distance between the two most distant points) of 300 to 500 particles is measured at a magnification such that the size of one smallest particle is 2 to 5 mm. , the average value is taken as the average particle diameter.

The polyester film used as a polarizer protective film can be manufactured according to the manufacturing method of a general polyester film. For example, after the polyester resin is melted, extruded into a sheet, and molded unoriented polyester is stretched in the longitudinal direction using the speed difference of the rolls at a temperature above the glass transition temperature, and then in a tenter. The method of extending|stretching in a transverse direction and heat-processing is mentioned.

Although the polyester film used in the present invention may be a uniaxially stretched film or a biaxially stretched film, when the biaxially stretched film is used as a polarizer protective film, rainbow-like color unevenness is not observed even when observed from directly above the film surface, but When observed from the direction, it is necessary to be careful because rainbow-like color unevenness may be observed.

When the film forming conditions of a polyester film are demonstrated concretely, 80-130 degreeC is preferable and, as for longitudinal stretch temperature and lateral stretch temperature, it is 90-120 degreeC especially preferably. In order to orientate a film so that a slow axis may become a TD direction, 1.0-3.5 times are preferable and, as for a longitudinal stretch ratio, 1.0 times - 3.0 times are especially preferable. Moreover, as for the lateral draw ratio, 2.5 to 6.0 times are preferable, Especially preferably, it is 3.0 to 5.5 times. In order to orientate a film so that a slow axis may become MD direction, as for a longitudinal stretch ratio, 2.5 times - 6.0 times are preferable, Especially preferably, they are 3.0 - 5.5 times. Moreover, 1.0 times - 3.5 times are preferable and, as for the lateral stretch magnification, especially preferably, they are 1.0 times - 3.0 times.

In order to control the refractive index and retardation of the fast axis direction of a polyester film in the said range, it is preferable to control the ratio of a longitudinal stretch ratio and a horizontal stretch ratio. In order to raise retardation, it is preferable to enlarge the difference of the draw ratio of length and breadth. Moreover, setting extending|stretching temperature low also lowers|hangs the refractive index of the fast-axis direction of a polyester film, and when raising retardation, it is a preferable correspondence. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250°C, particularly preferably 180 to 245°C.

In order to suppress the fluctuation|variation of retardation in a film, it is preferable that the thickness dispersion|variation of a film is small. Since extending|stretching temperature and a draw ratio have a large influence on the thickness variation of a film, it is preferable to optimize film forming conditions also from a viewpoint of thickness variation. In particular, when a longitudinal draw ratio is lowered|hung in order to raise retardation, longitudinal thickness dispersion|variation may worsen. Since there is a region where the vertical thickness variation becomes very bad within a certain specific range of the draw ratio, it is preferable to set the film forming conditions outside this range.

The thickness variation of the polyester film is preferably 5% or less, more preferably 4.5% or less, still more preferably 4% or less, and particularly preferably 3% or less.

As mentioned above, in order to control retardation of a polyester film in a specific range, it can carry out by setting a draw ratio, extending|stretching temperature, and the thickness of a film suitably. For example, it becomes easy to obtain high retardation, so that a draw ratio is high, so that extending|stretching temperature is low, and the thickness of a film is thick. Conversely, it becomes easy to obtain low retardation, so that a draw ratio is low, so that a extending|stretching temperature is high, and the thickness of a film is thin. However, when the thickness of a film is made thick, thickness direction retardation becomes large easily. Therefore, it is preferable to set film thickness suitably in the range mentioned later. Moreover, in addition to retardation control, it is preferable to set the final film forming conditions in consideration of the physical property etc. required for a process.

Although the thickness of a polyester film is arbitrary, The range of 15-300 micrometers is preferable, More preferably, it is the range of 15-200 micrometers. Even if it is a film with a thickness of less than 15 micrometers, in principle, it is possible to obtain retardation of 1500 nm or more. However, in that case, the anisotropy of the mechanical property of a film becomes remarkable, it becomes easy to generate|occur|produce a crack, a tear, etc., and practicality as an industrial material falls remarkably. A particularly preferable lower limit of the thickness is 25 µm. On the other hand, when the upper limit of the thickness of a polarizer protective film exceeds 300 micrometers, the thickness of a polarizing plate will become thick too much, and it is unpreferable. As for the upper limit of thickness from a practical viewpoint as a polarizer protective film, 200 micrometers is preferable. A particularly preferable upper limit of the thickness is 100 µm, which is equivalent to that of a general TAC film. In order to control retardation within the range of this invention also in the said thickness range, polyethylene terephthalate is suitable as polyester used as a film base material.

In addition, as a method of blending the UV absorber with the polyester film, a combination of known methods can be employed. For example, a master batch is prepared by blending the dried UV absorber with a polymer raw material using a kneading extruder in advance. In addition, it can mix|blend by the method of mixing this predetermined masterbatch and a polymer raw material at the time of film forming, etc.

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 mix it economically. As conditions for producing a master batch, a kneading extruder is used, and the extrusion temperature is preferably higher than the melting point of the polyester raw material and extruded at a temperature of 290°C or lower for 1 to 15 minutes. At 290°C or higher, the loss of the ultraviolet absorber is large, and the decrease in the viscosity of the masterbatch is large. If the extrusion temperature is 1 minute or less, uniform mixing of the ultraviolet absorber becomes difficult. At this time, you may add a stabilizer, a color tone adjuster, and an antistatic agent as needed.

Moreover, it is preferable to make a polyester film into a multilayer structure of at least 3 layers or more, and to add a ultraviolet absorber to the intermediate|middle layer of a film. A film having a three-layer structure including an ultraviolet absorber in the intermediate layer can be specifically produced as follows. For the outer layer, polyester pellets alone, for the intermediate layer, the master batch containing the ultraviolet absorber and polyester pellets are mixed in a predetermined ratio, dried, fed to a known melt lamination extruder, and a sheet from a slit die It is extruded onto the top and cooled and solidified on a casting roll to make an unstretched film. That is, by using two or more extruders, a three-layer manifold or a merging block (for example, a merging block having a square confluence), the film layers constituting both outer layers and the film layers constituting the intermediate layer are laminated. Then, a three-layer sheet is extruded from a nozzle and cooled on a casting roll to form an unstretched film. Moreover, in this invention, in order to remove the foreign material contained in the polyester of a raw material which becomes a cause of an optical defect, it is preferable to perform high-precision filtration at the time of melt extrusion. As for the filter particle size (95% of initial stage filtration efficiency) of the filter medium used for high-precision filtration of molten resin, 15 micrometers or less are preferable. When the filter particle size of the filter medium exceeds 15 µm, the removal of foreign substances of 20 µm or more tends to be insufficient.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples, and may be implemented with appropriate modifications within a range suitable for the spirit of the present invention. and they are all included in the technical scope of the present invention. In addition, the evaluation method of the physical property in a following example is as follows.

(1) Refractive index of polyester film

Using a molecular orientation meter (manufactured by Oji Keisoku Instruments Co., Ltd., MOA-6004 type molecular orientation meter), the direction of the slow axis of the film is determined, and the slow axis direction is parallel to the long side of the sample for measurement, 4 cm x 2 cm A rectangle was cut out and it was set as the sample for a measurement. For this sample, the refractive index of the biaxial orthogonal axes (refractive index in the slow axis direction: Ny, fast axis (refractive index in the direction orthogonal to the slow axis direction): Nx) and the refractive index (Nz) in the thickness direction were measured using an Abbe refractometer (Ata). It calculated|required by the Kosa company make, NAR-4T, measurement wavelength 589 nm).

(2) Retardation (Re)

Retardation is a parameter defined by the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy=|Nx-Ny|) of the biaxial orthogonal refractive index on the film and the film thickness d (nm), indicating optical isotropy and anisotropy is a measure The biaxial anisotropy (ΔNxy) of the refractive index was determined by the following method. Using a molecular orientation meter (manufactured by Oji Keisoku Instruments Co., Ltd., MOA-6004 type molecular orientation meter), the direction of the slow axis of the film is determined, and the slow axis direction is parallel to the long side of the sample for measurement, 4 cm x 2 cm A rectangle was cut out and it was set as the sample for a measurement. For this sample, the refractive index of the biaxial orthogonal axis (refractive index in the slow axis direction: Ny, the refractive index in the direction orthogonal to the slow axis direction: Nx) and the refractive index in the thickness direction (Nz) were measured with an Abbe refractometer (manufactured by Atago Corporation, NAR). -4T, measurement wavelength 589 nm), and the absolute value (|Nx-Ny|) of the refractive index difference of the said biaxial was made into the anisotropy of refractive index ((DELTA)Nxy). The thickness d (nm) of the film was measured using an electric micrometer (made by Fine Lup Co., Ltd., Millitron 1245D), and the unit was converted into nm. The retardation (Re) was calculated|required from the product (ΔNxy×d) of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film.

(3) Retardation in thickness direction (Rth)

The thickness direction retardation is an average of the retardation obtained by multiplying the film thickness d by two birefringence ΔNxz (=|Nx-Nz|) and ΔNyz (=|Ny-Nz|) when viewed from a cross section in the thickness direction of the film, respectively. is a parameter representing The thickness direction retardation (Rth) is calculated by calculating Nx, Ny, Nz and the film thickness d (nm) in the same manner as the retardation measurement, and calculating the average of (ΔNxz × d) and (ΔNyz × d). saved

(4) NZ coefficient

The values of Ny, Nx, and Nz obtained by the above (1) were substituted into the formula: NZ=|Ny-Nz|/|Ny-Nx|, and the NZ coefficient was calculated|required.

(5) Measurement of emission spectrum of backlight light source

REGZA 43J10X by Toshiba Corporation was used for the liquid crystal display device used in each Example. The emission spectrum of the backlight light source (white light emitting diode) of this liquid crystal display device was measured using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics, and emission spectra having peak tops around 450 nm, 535 nm and 630 nm were observed. As for the half-width of each peak top (the half-width of the peak having the highest peak intensity in each wavelength region), the peak of 450 nm was 17 nm, the peak of 535 nm was 45 nm, and the peak of 630 nm was 2 nm, respectively. In addition, although this light source had a plurality of peaks in a wavelength region of 600 nm or more and 780 nm or less, the half width was evaluated at a peak near 630 nm with the highest peak intensity in this region. In addition, the exposure time at the time of a spectrum measurement was set to 20 msec.

(6) Measurement of reflection spectrum (evaluation of reflectance)

The obtained polarizer protective film was cut into A4 size at an arbitrary position, and the surface of the substrate opposite to the surface on which the low-reflection layer (or anti-reflection layer) was laminated was uniformly scratched with water-resistant sandpaper, and then black magic ink (registered trademark) was applied. A sample in which reflection on the opposite surface of the low-reflection layer (or anti-reflection layer) was eliminated was produced by applying a black tape (vinyl tape No. 21 black manufactured by Nitto Denko). The produced sample measured the reflection spectrum in 400-800 nm of a low reflection layer (or antireflection layer) using the spectrophotometer UV-3150 by Shimadzu Corporation. Reflection spectrum measurement conditions were conducted using an Al deposition mirror (part number 202-35988-05) attached as a standard to a specular reflection measurement device (Shimadzu Seisakusho Co., Ltd. part number 206-14064) as a reference mirror, and the total luminous flux (Full light) It implemented by relative specular reflection with an incident angle of 5 degrees. In addition, it measured on the conditions of sampling pitch: 1 nm, and the opening dimension of a sample mask: 5 mm(phi). (5) From the measurement result of the emission spectrum of the backlight light source, the wavelength of the peak top of the peak with the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less of the emission spectrum was 630 nm, so the reflectance at 630 nm from the obtained reflection spectrum saved Moreover, about the polarizer protective film 1, the bottom wavelength was also calculated|required.

(Production Example 1-Polyester A)

When the temperature of the esterification reaction tube was raised to 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added, and while stirring, 0.017 parts by mass of antimony trioxide as a catalyst and 0.064 parts by mass of magnesium acetate tetrahydrate , and 0.16 parts by mass of triethylamine were put therein. Then, after pressurizing temperature rise and performing pressurization esterification on the conditions of 0.34 MPa of gauge pressure and 240 degreeC, the esterification reaction tube was returned to normal pressure, and 0.014 mass parts of phosphoric acid was added. Furthermore, it heated up at 260 degreeC over 15 minutes, and added 0.012 mass part of trimethyl phosphates. Subsequently, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tube, and polycondensation reaction was performed at 280°C under reduced pressure.

After completion of the polycondensation reaction, filtration is performed with a filter manufactured by Naslon with a 95% cut diameter of 5 µm, extruded from the nozzle into a strand shape, and cooled using cooling water previously subjected to filtration (pore diameter: 1 µm or less); It solidified and cut into pellet form. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl/g, and contained substantially no inert particles and internally precipitated particles. (hereinafter abbreviated as PET (A).)

(Preparation Example 2-Polyester B)

10 parts by mass of dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzooxazin-4-one), and particle-free PET (A) (native A viscosity of 0.62 dl/g) was mixed with 90 parts by mass, and using a kneading extruder, a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained. (hereinafter abbreviated as PET (B).)

(Preparation Example 3 - Preparation of adhesive modifying coating solution)

Transesterification reaction and polycondensation reaction are performed by a conventional method, and as a dicarboxylic acid component (with respect to the whole dicarboxylic acid component), 46 mol% of terephthalic acid, 46 mol% of isophthalic acid, and sodium 5-sulfonatoisophthalate 8 A water-dispersible sulfonic acid metal base-containing copolymerized polyester resin having a composition of 50 mol% of ethylene glycol and 50 mol% of neopentyl glycol (relative to the total glycol component) as a mol% and glycol component was prepared. Next, after mixing 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, the mixture is heated and stirred, and when it reaches 77°C, the water dispersibility After adding 5 parts by mass of a sulfonic acid metal base-containing copolymerized polyester resin, stirring is continued until the lumps of the resin disappear, the aqueous resin dispersion is cooled to room temperature, and a uniform water-dispersible copolymerized polyester resin having a solid content concentration of 5.0 mass% got the liquid. Further, after dispersing 3 parts by mass of aggregated silica particles (Fuji Silicia Co., Ltd., Silicia 310) in 50 parts by mass of water, 0.54 parts by mass of the aqueous dispersion of Silicia 310 in 99.46 parts by mass of the water-dispersible co-polyester resin solution A mass part was added, 20 mass parts of water was added, stirring, and the adhesiveness modification coating liquid was obtained.

(Preparation Example 4 - Preparation of low-reflection layer coating solution)

2,2,2-trifluoroethyl acrylate (45 parts by mass), perfluorooctylethyl acrylate (45 parts by mass), acrylic acid (10 parts by mass), azoisobutyronitrile (1.5 parts by mass), and Methyl ethyl ketone (200 parts by mass) was put into a reaction vessel, and it was made to react at 80 degreeC in nitrogen atmosphere for 7 hours, and the methyl ethyl ketone solution which is a polymer with a weight average molecular weight of 20000 was obtained. 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 obtained fluoropolymer solution C was mixed as follows, and the low reflection layer coating liquid was obtained.

・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 (manufactured by Kyoeisha Chemical, Fluorite FE-16) 1 part by mass

・Triphenylphosphine 　　　　　　　　　　0.1 parts by mass

・Methyl ethyl ketone 　　　　　　　　　　　19 parts by mass

(Preparation Example 5-Preparation of low-reflection layer coating liquid)

As the vinylidene fluoride-based polymer particles, an aqueous dispersion of particles of a vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer (=72.1/14.9/13 (mol%)) (solid content concentration 45.5 mass%) 571.4 g was put into a 2L glass separable flask, 37.1 g of Nucol 707SF (manufactured by Nippon Nyukazai Co., Ltd.) as an emulsifier and 59.3 g of water were added and thoroughly mixed to prepare an aqueous dispersion.

Next, 208.1 g of methyl methacrylate, 44.9 g of n-butyl acrylate, and 7.0 g of acrylic acid were added to the 1 L glass flask, and the monomer solution was prepared.

The internal temperature of the separable flask was raised to 80°C, and the entire amount of the monomer solution was added to the aqueous dispersion of the vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer particles over 3 hours. Moreover, polymerization was progressed while adding 41.1 g of 1 mass % ammonium persulfate dividedly and adding 7 times every 30 minutes simultaneously with addition of a monomer solution. After 5 hours from the start of polymerization, the reaction solution was cooled to room temperature to complete the reaction, and an aqueous dispersion of acryl-fluorine composite polymer particles was obtained (solid content concentration: 52.0 mass%). The mass ratio of the fluoropolymer part and the acrylic polymer part in the obtained acrylic-fluorine composite polymer particle was 50/50.

8.08 parts by mass of the acryl-fluorine composite polymer particle aqueous dispersion, 61.47 parts by mass of water, 20.00 parts by mass of isopropyl alcohol, 8.40 parts by mass of oxazoline crosslinking agent WS-700 (manufactured by Epocross manufactured by Nippon Shokubai), colloidal silica particles 1.75 parts by mass of Snowtex ST-ZL (manufactured by Nissan Chemical Industry Co., Ltd.) and 0.30 parts by mass of silicone-based surfactant were added and stirred to obtain a low-reflection layer coating liquid.

(Preparation Example 6-Preparation of low-reflection layer coating solution)

As the vinylidene fluoride-based polymer particles, an aqueous dispersion of particles of a vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer (=72.1/14.9/13 (mol%)) (solid content concentration 45.5 mass%) 571.4 g was put into a 2L glass separable flask, 37.1 g of Nucol 707SF (manufactured by Nippon Nyukazai Co., Ltd.) as an emulsifier and 59.3 g of water were added and thoroughly mixed to prepare an aqueous dispersion.

Next, 208.1 g of methyl methacrylate, 44.9 g of n-butyl acrylate, and 7.0 g of acrylic acid were added to the 1 L glass flask, and the monomer solution was prepared.

The internal temperature of the separable flask was raised to 80°C, and the entire amount of the monomer solution was added to the aqueous dispersion of the vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer particles over 3 hours. Moreover, polymerization was progressed while adding 41.1 g of 1 mass % ammonium persulfate dividedly and adding 7 times every 30 minutes simultaneously with addition of a monomer solution. After 5 hours from the start of polymerization, the reaction solution was cooled to room temperature to complete the reaction, and an aqueous dispersion of acryl-fluorine composite polymer particles was obtained (solid content concentration: 52.0 mass%). The mass ratio of the fluoropolymer part and the acrylic polymer part in the obtained acrylic-fluorine composite polymer particle was 50/50.

12.12 parts by mass of the acryl-fluorine composite polymer particle aqueous dispersion, 61.47 parts by mass of water, 20.00 parts by mass of isopropyl alcohol, 2.80 parts by mass of oxazoline crosslinking agent WS-700 (manufactured by Epocuros manufactured by Nippon Shokubai), colloidal silica particles 1.75 parts by mass of Snowtex ST-ZL (manufactured by Nissan Chemical Industry Co., Ltd.) and 0.30 parts by mass of silicone-based surfactant were added and stirred to obtain a low-reflection layer coating liquid.

(Polarizer Protective Film 1)

After drying under reduced pressure (1 Torr) at 135°C for 6 hours at 135°C for 6 hours, extruder 2 (for the intermediate layer II layer), and further, the PET (A) was dried according to the conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III layer), respectively, and melted at 285°C. These two types of polymers are each filtered with a stainless steel sintered filter medium (nominal filtration precision of 10 µm particle 95% cut), laminated with 2 types and 3 layer merging blocks, extruded from a nozzle into a sheet form, and then subjected to electrostatic application (印加) It was wound around a casting drum with a surface temperature of 30 degreeC using the casting method, it cooled and solidified, and the unstretched film was made. At this time, the discharge amount of each extruder was adjusted so that ratio of the thickness of the I-layer, II-layer, and III-layer might be set to 10:80:10.

Next, the adhesive modifying coating solution of Preparation Example 3 was applied to the opposite side of the unstretched PET film to the side opposite to the surface on which the low-reflection layer is formed later by the reverse roll method so as to be 0.08 g/m 2 , and then dried at 80° C. for 20 seconds. did.

The unstretched film in which this application layer was formed was guide|guided|guided|guided|derived to the tenter drawing machine, it guide|induced to the hot air zone with a temperature of 125 degreeC, holding the edge part of the film with a clip, and it extended|stretched 4.0 times in the width direction. Next, while maintaining the width|variety extended|stretched in the width direction, it processed for 10 second at the temperature of 225 degreeC, the 3.0% relaxation process was further performed in the width direction, and the PET film with a film thickness of about 100 micrometers was obtained.

The coating liquid of Production Example 4 was applied to the coated surface of the PET film on the side on which the low reflection layer is formed, and dried at 150° C. for 2 minutes to form a low reflection layer having a film thickness of 0.1 μm to obtain a polarizer protective film 1.

When the reflection spectrum of the polarizer protective film 1 was measured, the reflectance in wavelength 630 nm was 1.00 %. In addition, the bottom wavelength of the reflection spectrum was also 630 nm. Moreover, retardation (Re) of 10300 nm and thickness direction of the polarizer protective film 1 was 12350 nm, Re/Rth was 0.834, and NZ coefficient was 1.699.

(Polarizer Protective Film 2)

After drying under reduced pressure (1 Torr) at 135°C for 6 hours at 135°C for 6 hours, extruder 2 (for the intermediate layer II layer), and further, the PET (A) was dried according to the conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III layer), respectively, and melted at 285°C. Each of these two polymers is filtered with a stainless steel sintered filter medium (nominal filtration precision of 10 µm particle 95% cut), laminated with two types and three layer merging blocks, extruded from a nozzle into a sheet form, and then electrostatically applied and cast Using the method, it was wound around a casting drum having a surface temperature of 30° C. and cooled and solidified to form an unstretched film. At this time, the discharge amount of each extruder was adjusted so that ratio of the thickness of the I-layer, II-layer, and III-layer might be set to 10:80:10.

Next, by the reverse roll method, the coating solution of Production Example 5 was applied to the side on which the low reflection layer of the unstretched PET film was formed so that the application amount after drying was 0.09 g/m 2 Production Example 3 on the opposite side to the side on which the low reflection layer was laminated After applying the adhesive modifying coating solution of 0.08 g/m 2 , it was dried at 80° C. for 20 seconds.

The unstretched film in which this application layer was formed was guided to a tenter stretching machine, and the film was guided to a hot air zone at a temperature of 125°C while gripping the edge of the film with a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width|variety extended|stretched in the width direction, the temperature 225 degreeC and 10 second process were performed, the 3.0% relaxation process was further performed in the width direction, and the polarizer protective film 2 with a film thickness of about 100 micrometers was obtained.

The retardation (Re) of the polarizer protective film 2, the retardation (Rth) of the thickness direction, Re/Rth, and NZ coefficient were the same as that of the polarizer protective film 1.

When the reflection spectrum of the polarizer protective film 2 was measured, the reflectance in wavelength 630nm was 2.11 %. The reflectance in wavelength 550nm was 1.96 %.

(Polarizer Protective Film 3)

After drying under reduced pressure (1 Torr) at 135°C for 6 hours at 135°C for 6 hours, extruder 2 (for the intermediate layer II layer), and further, the PET (A) was dried according to the conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III layer), respectively, and melted at 285°C. Each of these two polymers is filtered with a stainless steel sintered filter medium (nominal filtration precision of 10 µm particle 95% cut), laminated with two types and three layer merging blocks, extruded from a nozzle into a sheet form, and then electrostatically applied and cast Using the method, it was wound around a casting drum having a surface temperature of 30° C. and cooled and solidified to form an unstretched film. At this time, the discharge amount of each extruder was adjusted so that ratio of the thickness of the I-layer, II-layer, and III-layer might be set to 10:80:10.

Next, the low reflective layer coating solution of Production Example 6 was applied on the side on which the low reflective layer of this unstretched PET film was formed by the reverse roll method so that the application amount after drying was 0.108 g/m2. The adhesive modifying coating solution of Example 3 was applied so as to be 0.080 g/m 2 , and then dried at 80° C. for 20 seconds.

The unstretched film in which this application layer was formed was guided to a tenter stretching machine, and the film was guided to a hot air zone at a temperature of 125°C while gripping the edge of the film with a clip, and stretched 4.0 times in the width direction. Next, maintaining the width|variety extended|stretched in the width direction, the temperature 225 degreeC and 10 second process were performed, the 3.0% relaxation process was further performed in the width direction, and the polarizer protective film 3 with a film thickness of about 100 micrometers was obtained.

As for the polarizer protective film 3, retardation (Re) was 10300 nm, retardation (Rth) of thickness direction was 12350 nm, Re/Rth was 0.834, and NZ coefficient was 1.699.

Moreover, as for the reflection spectrum of the polarizer protective film 3, a bottom wavelength was 630 nm, and the reflectance in wavelength 630 nm was 1.71 %.

(Example 1)

A polarizer protective film 1 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 μm) is attached to the opposite side. was attached to prepare a polarizing plate. Moreover, the polarizer was laminated|stacked on the surface on which the low reflection layer of the polarizer protective film is not laminated|stacked, and the polarizing plate was created.

The polarizing plate by the side of the visual recognition of REGZA 43J10X by Toshiba Corporation was substituted by the polarizing plate created above so that a polyester film might become the opposite side (far position) to a liquid crystal, and the liquid crystal display device was created. Moreover, it substituted so that the direction of the transmission axis of a polarizing plate might become the same as the direction of the transmission axis of the polarizing plate before substitution.

(Comparative Example 1)

In Example 1, instead of the polarizer protective film 1, except having used the polarizer protective film 2, it carried out similarly, and created the liquid crystal display device.

(Example 2)

In Example 1, instead of the polarizer protective film 1, except having used the polarizer protective film 3, it carried out similarly, and created the liquid crystal display device.

When the liquid crystal display devices of Examples 1 and 2 and Comparative Example 1 were arranged and the screen was visually observed in a dark place from the front and the oblique direction, in Examples 1 and 2, more than Comparative Example 1, iridescence was generated. this was suppressed. Moreover, in Examples 1 and 2, the generation|occurrence|production of the rainbow_pattern|erythema was suppressed in the direction of the liquid crystal display device of Example 1. In addition, when the film is observed while the viewer moves his head in the oblique direction (when observed while changing the angle from the film normal direction), the rainbow_pattern|erythema is a fog-like rainbow_pattern|erythema observed on a screen.

In Examples 1 and 2, and Comparative Example 1, the polyester film had a thickness of 100 µm, but this was an 80 µm film (retardation (Re) was 8080 nm, retardation in the thickness direction (Rth) was 9960 nm, Re/ Rth is 0.811, NZ coefficient is 1.733), and the liquid crystal display devices of Examples 1', 2', and Comparative Example 1' were manufactured. Similarly, Example 1' or Example 2' rather than Comparative Example 1' In the liquid crystal display device, generation|occurrence|production of rainbow_pattern|erythema was suppressed. In Example 1' and Example 2', the rainbow color was suppressed more in Example 1'. In addition, when the film is observed while moving the head from an oblique direction (when observed while changing the angle from the film normal direction), the rainbow_pattern|erythema said here is a fog-like rainbow_pattern|erythema observed on a screen.

Moreover, in Example 1, 2, and Comparative Example 1, although the thickness of a polyester film was 100 micrometers in all, this is a film of 60 micrometers (retardation (Re) is 6060 nm, retardation (Rth) of thickness direction is 7470 nm) , Re/Rth is 0.811, and NZ coefficient is 1.733) to prepare liquid crystal display devices of Example 1'', Example 2'', and Comparative Example 1''. Similarly, Example 1 rather than Comparative Example 1'' In the liquid crystal display device of ''and Example 2'', generation|occurrence|production of rainbow_pattern|erythema was suppressed. In Example 1'' and Example 2'', the rainbow color was suppressed more in Example 1''. In addition, when the film is observed while moving the head from the oblique direction (when observed while changing the angle from the film normal direction), the rainbow_pattern|erythema referred to here is a fog-like rainbow_pattern|erythema observed on a screen.

Industrial Applicability

The liquid crystal display device and the polarizing plate of this invention can ensure the favorable visibility by which generation|occurrence|production of the rainbow-like color unevenness was suppressed significantly also in any angle, and the contribution to the industrial world is large.

Claims (7)

A liquid crystal display having a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates, the liquid crystal display comprising:
The backlight light source has a peak top 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, and has the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less. It is a white light source having an emission spectrum with a peak half width less than 5 nm,
At least one of the polarizing plates is a polyester film laminated on at least one surface of the polarizer,
The polyester film has a retardation of 1500 nm or more and 30000 nm or less,
In the polyester film, an antireflection layer and/or a low reflection layer are laminated on at least one surface,
The anti-reflection layer and/or low-reflection layer is laminated, measured from the side where the anti-reflection layer and/or the low-reflection layer are laminated, in the wavelength of the peak peak of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less. The reflectance of the used polyester film is 2 % or less, The liquid crystal display device characterized by the above-mentioned. The method of claim 1,
The emission spectrum of the backlight light source is,
The half width of the peak with the highest peak intensity in the wavelength region of 400 nm or more and less than 495 nm is 5 nm or more,
A liquid crystal display device having a peak at half maximum width of 5 nm or more with the highest peak intensity in a wavelength region of 495 nm or more and less than 600 nm. 3. The method according to claim 1 or 2,
The liquid crystal display device in which the wavelength of the peak top of the peak with the highest peak intensity in the said wavelength range of 600 nm or more and 780 nm or less exists in the area|region of 620 nm or more and 640 nm or less. 3. The method according to claim 1 or 2,
The liquid crystal display device whose wavelength of the peak top of the peak with the highest peak intensity in the said 600 nm or more and 780 nm or less wavelength range is 630 nm. 3. The method according to claim 1 or 2,
The liquid crystal display device of claim 1, wherein the backlight light source includes a fluoride phosphor. 3. The method according to claim 1 or 2,
The liquid crystal display device whose retardation (Re) of a polyester film is 6000 nm or more, 15000 nm or less, the value of Ny-Nx is 0.100 or more, and NZ coefficient is 1.0 or more and 1.699 or less. 3. The method according to claim 1 or 2,
The liquid crystal display device whose retardation (Re) of a polyester film is 8000 nm or more, 15000 nm or less, and NZ coefficient is 1.0 or more and 1.699 or less.