WO2018159568A1

WO2018159568A1 - Liquid crystal display device

Info

Publication number: WO2018159568A1
Application number: PCT/JP2018/007084
Authority: WO
Inventors: 洋平山口; 章太早川; 村田　浩一; 佐々木　靖; 向山　幸伸
Original assignee: 東洋紡株式会社
Priority date: 2017-02-28
Filing date: 2018-02-27
Publication date: 2018-09-07
Also published as: CN114942541A; JP7464185B2; JP2022180530A; CN110312961B; TWI776857B; CN114942541B; KR20210129252A; JP7184033B2; CN110312961A; JPWO2018159568A1; JP7364001B2; KR20190117562A; KR102315658B1; JP2023171449A; TW201841768A; KR102325038B1

Abstract

According to the present invention, a polarizer protective film comprises a polyester film which has a retardation of 1500-30000 nm and which has an antireflection layer and/or a low reflective layer laminated on at least one surface of the polyester film, wherein the polarizer protective film has a reflectance of 2% or less at a wavelength in a wavelength region between 600 nm and 780 nm, the reflectance being measured from the side on which the antireflection layer and/or the low reflective layer is laminated.

Description

Liquid crystal display

The present invention relates to a polarizer protective film, a polarizing plate, and a liquid crystal display device. Specifically, the present invention relates to a liquid crystal display device in which generation of rainbow-like color spots is improved.

A polarizing plate used in a liquid crystal display device (LCD) is usually configured by sandwiching a polarizer obtained by dyeing iodine in polyvinyl alcohol (PVA) or the like between two polarizer protective films. In general, a triacetyl cellulose (TAC) film is used. In recent years, with the thinning of LCDs, there has been a demand for thinner polarizing plates. However, if the thickness of the TAC film used as the protective film is reduced for this purpose, sufficient mechanical strength cannot be obtained and moisture permeability deteriorates. TAC films are very expensive, and polyester films have been proposed as inexpensive alternative materials (Patent Documents 1 to 3), but there is a problem that rainbow-like color spots occur.

When an oriented polyester film having birefringence is arranged on one side of the polarizer, the polarization state of the linearly polarized light emitted from the backlight unit or the polarizer changes when passing through the polyester film. The transmitted light shows an interference color peculiar to retardation which is a product of birefringence and thickness of the oriented polyester film. Therefore, if a discontinuous emission spectrum such as a cold cathode tube or a hot cathode tube is used as the light source, the transmitted light intensity varies depending on the wavelength, resulting in a rainbow-like color spot (see: Proceedings of the 15th Micro Optical Conference Proceedings, No. 1) 30-31).

As means for solving the above problems, it is possible to use a white light source having a continuous and broad emission spectrum such as a white light emitting diode as a backlight light source, and further using an oriented polyester film having a certain retardation as a polarizer protective film. It has been proposed (Patent Document 4). White light emitting diodes have a continuous and broad emission spectrum in the visible light region. Therefore, focusing on the envelope shape of the interference color spectrum due to the transmitted light transmitted through the birefringent body, 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 rainbow spots.

JP 2002-116320 A JP 2004-219620 A JP 2004-205773 A WO2011 / 162198

Due to the recent increase in color gamut demand for liquid crystal display devices, the emission spectrum peaks in each wavelength region of blue region (400 nm to less than 495 nm), green region (495 nm to less than 600 nm) and red region (600 nm to 780 nm or less). White light-emitting diode (for example, blue light-emitting diode and at least K ₂ SiF ₆ as a phosphor) having a top and having an emission spectrum with a relatively narrow half-width (less than 5 nm) in the red region (600 nm to 780 nm or less) A liquid crystal display device using a backlight source composed of a white light emitting diode having a fluoride phosphor such as Mn ⁴⁺ has been developed.

When industrially producing a liquid crystal display device using a polarizing plate using a polyester film as a polarizer protective film, the transmission axis of the polarizer and the fast axis direction of the polyester film are usually arranged to be perpendicular to each other. Is done. This is because the polyvinyl alcohol film that is a polarizer is manufactured by longitudinal uniaxial stretching, and the polyester film that is the protective film is manufactured by longitudinal stretching and then lateral stretching, so that the polyester film orientation This is because the main axis direction is the horizontal direction, and when these long objects are bonded together to produce a polarizing plate, the fast axis of the polyester film and the transmission axis of the polarizer are usually perpendicular. In this case, an oriented polyester film having a specific retardation is used as the polyester film, and, for example, a white LED composed of a light emitting element in which a blue light emitting diode and a yttrium / aluminum / garnet yellow phosphor are combined is used as a backlight light source. By using a light source having a continuous and broad emission spectrum, the rainbow-like color spot is greatly improved, but the half-width of the peak in the red region (600 nm to 780 nm or less) is relatively narrow (less than 5 nm). It has been found that there is still a new problem that rainbow spots still occur when using a backlight light source consisting of a white light emitting diode having a spectrum.

That is, an object of the present invention is to have a peak top of an emission spectrum in each wavelength region of a blue region (400 nm or more and less than 495 nm), a green region (495 nm or more and less than 600 nm), and a red region (600 nm or more and 780 nm or less). When a polyester film is used as a polarizer protective film in a liquid crystal display device having a backlight light source composed of a white light emitting diode having an emission spectrum having a relatively narrow half-width (less than 5 nm) in the region (600 nm or more and 780 nm or less). Another object is to provide a liquid crystal display device in which rainbow spots are suppressed.

The representative present invention is as follows.
Item 1.
A liquid crystal display device having a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,
The backlight source has a peak top of the emission spectrum in each wavelength region of 400 nm to 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and has the highest peak intensity in the wavelength region of 600 nm to 780 nm. A white light emitting diode having an emission spectrum in which a half width of a peak (the peak with the highest peak top in a wavelength region of 600 nm or more and 780 nm or less) is less than 5 nm;
At least one polarizing plate among the polarizing plates is obtained by laminating a polyester film on at least one surface of a polarizer,
The polyester film has a retardation of 1500 nm or more and 30000 nm or less,
The polyester film has an antireflection layer and / or a low reflection layer laminated on at least one surface,
The antireflection layer and / or the low reflection layer measured from the side where the antireflection layer and / or the low reflection layer are laminated at 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. A liquid crystal display device, wherein the reflectance of the laminated polyester film is 2% or less.
Item 2.
The emission spectrum of the backlight source is
The full width at half maximum 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 full width at half maximum of the peak with the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm is 5 nm or more,
Item 2. A liquid crystal display device according to item 1.
Item 3.
Item 3. The liquid crystal display device according to item 1 or 2, wherein a peak top wavelength of a peak having the highest peak intensity in the wavelength region of 600 nm to 780 nm is in the range of 620 nm to 640 nm.
Item 4.
Item 3. The liquid crystal display device according to Item 1 or 2, wherein the peak top wavelength of the peak having the highest peak intensity in the wavelength region of 600 nm to 780 nm is 630 nm.
Item 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,
A polarizer protective film having a reflectance of 2% or less measured from the side on which the antireflection layer and / or the low reflection layer is laminated in any wavelength of a wavelength region of 600 nm to 780 nm.
Item 6.
Item 6. The polarizer protective film according to Item 5, wherein any one of the wavelengths is from 620 nm to 640 nm.
Item 7.
Item 6. The polarizer protective film according to Item 5, wherein any one of the wavelengths is 630 nm.
Item 8.
A polarizing plate in which the polarizer protective film according to any one of Items 5 to 7 is laminated on at least one surface of the polarizer.

The liquid crystal display device, polarizing plate, and polarizer protective film of the present invention can ensure good visibility in which the occurrence of rainbow-like color spots is significantly suppressed at any observation angle.

Generally, a liquid crystal display device includes a rear module, a liquid crystal cell, and a front module in order from the backlight light source side to the image display side (viewing side). The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface, and a polarizing plate disposed on the opposite side. Here, the polarizing plate is disposed on the backlight source side in the rear module, and is disposed on the image display side (viewing side) in the front module.

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

Further, the liquid crystal display device may appropriately have other components in addition to the backlight source, the polarizing plate, and the liquid crystal cell, such as a color filter, a lens film, a diffusion sheet, and an antireflection film. A brightness enhancement film may be provided between the light source side polarizing plate and the backlight light source. Examples of the brightness enhancement film include a reflective polarizing plate that transmits one linearly polarized light and reflects linearly polarized light orthogonal thereto. As the reflective polarizing plate, for example, a DBEF (Dual Brightness Enhancement Film) series brightness enhancement film manufactured by Sumitomo 3M Limited is preferably used. 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 arranged in the liquid crystal display device, at least one polarizing plate has a polyester film laminated on at least one surface of a polarizer in which iodine is dyed on polyvinyl alcohol (PVA) or the like. It is. In the present invention, from the viewpoint of suppressing rainbow-like color spots, the polyester film has a specific retardation, and an antireflection layer and / or a low reflection layer is laminated on at least one surface of the polyester film. is there. The antireflection layer and / or the low reflection layer may be provided on the surface opposite to the surface on which the polarizer of the polyester film is laminated, or on the surface on which the polarizer of the polyester film is laminated, Both are acceptable. It is preferable to provide an antireflection layer and / or a low reflection layer on the surface of the polyester film opposite to the surface on which the polarizer is laminated. In addition, there are other layers (for example, an easy adhesion layer, a hard coat layer, an antiglare layer, an antistatic layer, an antifouling layer, etc.) between the antireflection layer and / or the low reflection layer and the polyester film. May be. From the viewpoint of suppressing rainbow-like color spots, the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is preferably 1.53 to 1.62. On the other surface of the polarizer, it is preferable that a film having substantially no birefringence (low retardation) as typified by a TAC film, an acrylic film, or a norbornene-based film is laminated (with a three-layer structure). A polarizing plate), a film is not necessarily laminated on the other surface of the polarizer (a polarizing plate having a two-layer structure). In addition, when a polyester film is used as a protective film on both sides of the polarizer, it is preferable that the slow axes of both polyester films are substantially parallel to each other. Here, “substantially parallel” means that the angle formed by the two axes is −15 ° to 15 °, preferably −10 ° to 10 °, more preferably −5 ° to 5 °, and still more preferably −3 ° to It means 3 °, more preferably −2 ° to 2 °, and still more preferably −1 ° to 1 °.

As the polarizer, any polarizer (polarizing film) used in the technical field can be appropriately selected and used. Examples of typical polarizers include those obtained by dyeing a dichroic material such as iodine on a polyvinyl alcohol film or the like. However, the polarizer is not limited to this, and may be a known and later-developed polarizer. Can be appropriately selected and used.

Commercially available products can be used as the PVA film. For example, “Kuraray Vinylon (manufactured by Kuraray Co., Ltd.)”, “Tosero Vinylon (manufactured by Toh Cello Co., Ltd.)”, “Nichigo Vinylon (Nippon Synthetic Chemical Co., Ltd.) The dichroic material includes iodine, a diazo compound, a polymethine dye, and the like.

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

The configuration of the backlight may be an edge light method using a light guide plate, a reflection plate, or the like, or a direct type, but in the present invention, as a backlight light source of a liquid crystal display device, 400 nm or more, less than 495 nm, 495 nm or more, less than 600 nm, and 600 nm or more and 750 nm or less, each having a peak top of the emission spectrum, and the half width of the peak with the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less A backlight light source consisting of a white light emitting diode having an emission spectrum of less than 5 nm is preferred. The upper limit of the full width at half maximum of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less is preferably less than 5 nm, more preferably less than 4 nm, and still more preferably less than 3.5 nm. The lower limit is preferably 1 nm or more, and more preferably 1.5 nm or more. It is preferable that the half width of the peak is less than 5 nm because the color gamut of the liquid crystal display device is widened. In addition, there is no lower limit of the half width of the peak, but it can be set to 1 nm. If the peak half width is less than 1 nm, the light emission efficiency may deteriorate. The shape of the emission spectrum is designed from the balance between the required color gamut and the luminous efficiency. Here, the half width is the peak width (nm) at half the intensity of the peak intensity at the peak top wavelength.

Application of a backlight light source having an emission spectrum having the above-described characteristics to an LCD is a technology that has been attracting attention due to the recent increasing demand for color gamut expansion. Conventionally used white LEDs (for example, light-emitting elements that combine blue light-emitting diodes with yttrium, aluminum, and garnet yellow phosphors) as backlight light sources have a spectrum that can be recognized by the human eye. Only about 20% of colors can be reproduced. On the other hand, when a backlight light source having an emission spectrum having the above-described characteristics is used, it is said that it is possible to reproduce 60% or more of colors.

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 to 780 nm is more preferably 600 nm to 700 nm, and even more preferably 610 nm to 680 mn. A preferred embodiment of the wavelength region of 600 nm to 780 nm is 620 nm to 640 nm, and particularly preferably 630 nm.

The peak half-width at the peak top of each wavelength region of the emission spectrum from 400 nm to less than 495 nm and from 495 nm to less than 600 nm (the half width of the peak having the highest peak intensity in each wavelength region) is not particularly limited, but is from 400 nm to less than 495 nm The half-width of the peak having the highest peak intensity in the wavelength region is preferably 5 nm or more, and the half-width of the peak having the highest peak intensity in the wavelength region of from 495 nm to less than 600 nm is preferably 5 nm or more. From the viewpoint of securing an appropriate color gamut, the upper limit of the peak half width at the peak top of each wavelength region from 400 nm to less than 495 nm and from 495 nm to less than 600 nm (the 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.

Specific examples of a white light source having an emission spectrum having the above-described characteristics include a phosphor type white light emitting diode in which a blue light emitting diode and a phosphor are combined. Examples of the red phosphor among the phosphors include a fluoride phosphor (also referred to as “KSF”) whose composition formula is K ₂ SiF ₆ : Mn ⁴⁺ , and others. The Mn ⁴⁺ activated fluoride complex phosphor is a phosphor having Mn ⁴⁺ as an activator, a fluoride complex salt of an alkali metal, amine, or alkaline earth metal as a base crystal. Fluoride complexes that form host crystals include those whose coordination center is a trivalent metal (B, Al, Ga, In, Y, Sc, lanthanoid), and tetravalent metal (Si, Ge, Sn, Ti, Zr, Re, Hf) and pentavalent metals (V, P, Nb, Ta), and the number of fluorine atoms coordinated around them is 5-7.

Preferable examples of the Mn ⁴⁺ activated fluoride complex phosphor include A ₂ [MF ₆ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, and NH ₄ ; M is Ge, Si , Sn, Ti, and Zr), E [MF ₆ ]: Mn (E is one or more 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 Li, Na, K, Rb, Cs, and NH _4. One or more selected), A ₂ [MF ₅ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, and NH ₄ ; M is one or more selected from Al, Ga, and In) , A ₃ [MF ₆ ]: Mn (A is Li, Na, K, Rb, One or more selected from Cs and NH ₄ ; M is one or more selected from Al, Ga and In), Zn ₂ [MF ₇ ]: Mn (M is one or more selected from Al, Ga and In), A [In ₂ F ₇ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, and NH ₄ ).

One of the preferable Mn ⁴⁺ activated fluoride complex phosphors is A ₂ MF ₆ : Mn (A is selected from Li, Na, K, Rb, Cs, and NH ₄₎ whose base crystal is a hexafluoro complex salt of an alkali metal. M is one or more selected from Ge, Si, Sn, Ti, and Zr). Among them, A is preferably one or more selected from K (potassium) and Na (sodium), and M is Si (silicon) or Ti (titanium). Among them, particularly preferred are those in which A is K (the ratio of K in the total amount of A is 99 mol% or more) and M is Si. The activation element is preferably 100% Mn (manganese), but Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, in a range of less than 10 mol% with respect to the total amount of the activation element. Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn, Mg, and the like may be included. When M is Si, the ratio of Mn in the total of Si and Mn is preferably in the range of 0.5 mol% to 10 mol%. Other preferred Mn ⁴⁺ activated fluoride complex phosphors have the chemical formula A _{2 + x} M _y Mn _z F _n (A is Na and K; M is Si and Al; −1 ≦ x ≦ 1 and 0.9 ≦ y + z ≦ 1) .1 and 0.001 ≦ z ≦ 0.4 and 5 ≦ n ≦ 7).

The backlight light source is preferably a white light emitting diode having a blue light emitting diode and at least a fluoride phosphor as a phosphor, and particularly preferably a fluoride having at least K ₂ SiF ₆ : Mn ⁴⁺ as a blue light emitting diode and a phosphor. A white light emitting diode having a phosphor. For example, commercially available products such as NSSW306FT, which is a white LED manufactured by Nichia Corporation, can be used.

Among the phosphors, as the green phosphor, for example, a sialon phosphor having a basic composition of β-SiAlON: Eu or the like, or a silicate phosphor having a basic composition of (Ba, Sr) ₂ SiO ₄ : Eu or the like. Others are exemplified.

In the case where a plurality of peaks are present in any one 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 780 nm or less, the following is considered.
When a plurality of peaks are independent peaks, it is preferable that the half width of the peak with the highest peak intensity is in the above range. Furthermore, it is a more preferable aspect that the half-value width is similarly in the above range for other peaks having an intensity of 70% or more of the highest peak intensity.
For one independent peak having a shape in which a plurality of peaks are overlapped, the half width of the peak having the highest peak intensity among the plurality of peaks can be used as it is. Here, the independent peak has an intensity region that is ½ of the peak intensity on both the short wavelength side and the long wavelength side of the peak. That is, when a plurality of peaks overlap and each peak does not have a region having an intensity that is ½ of the peak intensity on both sides thereof, the plurality of peaks are regarded as one peak as a whole. In such a peak having a shape in which a plurality of peaks are overlapped, the peak width (nm) at half the intensity of the highest peak intensity is set as the half width.
Of the plurality of peaks, the point with the highest peak intensity is defined as the peak top.
The peak having the highest peak intensity in each 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 780 nm or less is independent from the peaks of other wavelength regions. It is preferable that the relationship is In particular, 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 has a wavelength of 600 nm or more and 780 nm or less. It is preferable in terms 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 in the region.

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

As a result of intensive studies, the present inventors have found that each wavelength region of the blue region (400 nm to less than 495 nm), the green region (495 nm to less than 600 nm), and the red region (600 nm to 780 nm or less), as in the backlight light source described above. In a liquid crystal display device having a backlight source composed of a white light emitting diode each having a peak top of an emission spectrum and a peak half-width in a red region (600 nm or more and 780 nm or less) being relatively narrow, It has been found that if a polyester film having an antireflection layer and / or a low reflection layer having a low reflectance at a wavelength and having a specific retardation is used, it is effective in suppressing rainbow spots. Here, the specific wavelength is a wavelength corresponding to the peak with the highest peak intensity in the wavelength region of 600 nm to 780 nm in the emission spectrum of the backlight light source (the peak top wavelength of the peak with the highest peak intensity). . That is, the present inventors are the side where the antireflection layer and / or the low reflection layer is laminated at the peak top wavelength of the peak with the highest peak intensity in the wavelength region of 600 nm to 780 nm in the emission spectrum of the backlight light source. It was found that when the reflectance of the polyester film on which the antireflection layer and / or the low-reflection layer was laminated was 2% or less, it was particularly effective in suppressing rainbow spots.

When the oriented polyester film is disposed on one side of the polarizer, the polarization state of the linearly polarized light emitted from the backlight unit or the polarizer changes when passing through the polyester film. One of the factors that change the polarization state may be the influence of the refractive index difference at the interface between the air layer and the oriented polyester film or the refractive index difference at the interface between the polarizer and the oriented polyester film. When the linearly polarized light incident on the oriented polyester film passes through each interface, a part of the light is reflected by the difference in refractive index between the interfaces.
The light passing through the polarizer and entering the oriented polyester film is linearly polarized light, and it is considered that there is no transmittance dependency on the wavelength in the state of linearly polarized light. Incident light of linearly polarized light changes to 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 depending on the wavelength λ of light, it is considered that the polarization state when exiting the oriented polyester film differs depending on the wavelength. When emitted from the oriented polyester film to the viewer side, the S-polarized component perpendicular to the P-polarized component parallel to the incident surface is more easily reflected, and this difference (P-polarized light) increases as the viewing angle from the normal increases. The difference between the component and the S-polarized component) tends to increase. Since light of each wavelength having different degrees of polarization has different influences of S-polarized light that is easily reflected, each transmittance changes when passing through the interface. When passing through the interface, the transmittance in a wavelength band with a large amount of S-polarized light component is reduced, which is considered to be one of the factors that cause rainbow-like color spots. In particular, when there is a steep peak in the red region of 600 nm or more and 780 nm or less, color variation tends to occur because the transmittance change due to wavelength is large. Since thin-film interference can be used to suppress interface reflection at any wavelength, the transmittance of the red region is improved by forming a low-reflection layer and / or a low-reflection layer at a steep peak (ie, S It is considered possible to suppress the reflection of the polarization component). In the red region with a steep peak, the transmittance of the S-polarized component is improved, so the change in the transmittance of the emitted light of the oriented polyester film with respect to the incident light that has passed through the polarizer is reduced. Spots can be suppressed.

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 an emission spectrum peak top. In a liquid crystal display device having a backlight light source composed of a white light emitting diode having a relatively narrow half-width of a peak in a region (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, It is possible to have good visibility without causing color spots.

In the polarizing plate of the present invention, a polarizer protective film made of a polyester film is laminated on at least one surface of the polarizer. The polyester film used for the polarizer protective film preferably has a retardation of 1500 nm or more and 30000 nm or less. If the retardation is in the above range, it is preferable because rainbow spots tend to be reduced more easily. The preferred lower limit of retardation is 3000 nm, the next preferred lower limit is 3500 nm, the more preferred lower limit is 4000 nm or 5000 nm, the still more preferred lower limit is 6000 nm or 7000 nm, and the still more preferred lower limit is 8000 nm. A preferable upper limit is 30000 nm, and a polyester film having a retardation larger than this has a considerably large thickness and tends to deteriorate the handleability as an industrial material. A more preferable upper limit is 15000 nm, still more preferably 12000 nm, and still more preferably 11000 nm.

The retardation of the present invention can be obtained by measuring the refractive index and thickness in the biaxial direction, or by using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Scientific Instruments). it can. The refractive index can be obtained by an Abbe refractometer (measurement wavelength: 589 nm).

The ratio (Re / Rth) of the retardation of the polyester film (Re: in-plane retardation) to the retardation in the thickness direction (Rth) is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.8. 6 or more. As the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is larger, the birefringence action is more isotropic, and the occurrence of rainbow-like color spots depending on the observation angle tends to be less likely to occur. In a complete uniaxial (uniaxial symmetry) film, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is 2.0. Therefore, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) The upper limit is preferably 2.0. The thickness direction retardation means an average of retardation obtained by multiplying two birefringences ΔNxz and ΔNyz by the film thickness d when the film is viewed from the cross section in the thickness direction.

From the viewpoint of suppressing rainbow-like color spots, the polyester film preferably has an NZ coefficient of 2.5 or less, more preferably 2.0 or less, still more preferably 1.8 or less, and still more preferably 1. 6 or less. And since a NZ coefficient will be 1.0 in a perfect uniaxial (uniaxial symmetry) film, the minimum of a NZ coefficient is 1.0. However, it should be noted that the mechanical strength in the direction perpendicular to the orientation direction tends to decrease significantly as the film approaches a perfect uniaxial (uniaxial symmetry) film.

The NZ coefficient is represented by | Ny−Nz | / | Ny−Nx |, where Ny is the refractive index in the slow axis direction, and Nx is the refractive index in the direction perpendicular to the slow axis (the refractive index in the fast axis direction). Index) and Nz represent the refractive index in the thickness direction. The orientation axis of the film is obtained using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments Co., Ltd.), and the biaxial refractive index (Ny, Nx, where the orientation axis direction and the direction perpendicular thereto are perpendicular) Ny> Nx) and the refractive index (Nz) in the thickness direction are determined by Abbe's refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm). The value obtained in this manner can be substituted for | Ny−Nz | / | Ny−Nx | to obtain the NZ coefficient.

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

In a more preferred embodiment of the present invention, the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer constituting the polarizing plate is preferably in the range of 1.53 to 1.62. Thereby, reflection at the interface between the polarizer and the polyester film can be suppressed, and rainbow-like color spots can be further suppressed. 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, the crystallization of the polyester film becomes insufficient, and the properties obtained by stretching such as dimensional stability, mechanical strength, and chemical resistance may be 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 the direction parallel to the transmission axis direction of the polarizer in the range of 1.53 or more and 1.62 or less, the polarizing plate has the transmission axis of the polarizer and the fast axis of the polyester film. It is preferable that (the slow axis and the vertical method) are substantially parallel. The refractive index in the fast axis direction, which is the direction perpendicular to the slow axis, can be adjusted to a low value of about 1.53 to 1.62 by stretching the polyester film in the film forming process described later. By setting the fast axis direction of the polyester film and the transmission axis direction of the polarizer to be substantially parallel, the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is set to 1.53 to 1.62. Can do. Here, “substantially parallel” means that the angle formed by 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 °. It means -5 °, more preferably -3 ° to 3 °, still more preferably -2 ° to 2 °, and still more preferably -1 ° to 1 °. In a preferred embodiment, substantially parallel is substantially parallel. Here, “substantially parallel” means that the transmission axis and the fast axis are parallel to such an extent that a deviation inevitably generated when the polarizer and the protective film are bonded to each other is allowed. The direction of the slow axis can be determined by measuring with a molecular orientation meter (for example, MOA-6004 type molecular orientation meter manufactured by Oji Scientific Instruments).

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

The polarizer protective film comprising the polyester film used in the present invention can be used for both the incident light side (light source side) and the outgoing light side (viewing side) polarizing plates, but at least the outgoing light side (viewing side). It is preferable to use for the protective film of this polarizing plate.
About the polarizing plate arranged on the outgoing light side, the polarizer protective film made of the above polyester film is arranged on both sides, whether it is arranged on the liquid crystal side starting from the polarizer or on the outgoing light side. It may be arranged, but it is preferable that it is arranged at least on the outgoing light side.
Even in the polarizing plate arranged on the incident light side, the polarizer protective film made of the polyester film may be disposed on the incident light side from the polarizer, or on the liquid crystal cell side. However, it is preferable that it is disposed at least on the incident light side. Moreover, the polarizing plate arranged on the incident light side does not use a polarizer protective film made of a polyester film, but uses a polarizer protective film that is substantially free of birefringence (low retardation) such as a triacetyl cellulose film. It may be what you did.

Polyester used for the polyester film may be polyethylene terephthalate or polyethylene naphthalate, but may contain other copolymerization components. These resins are excellent in transparency and excellent in thermal and mechanical properties, and the retardation can be easily controlled by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence. By stretching the film, the refractive index in the fast axis direction (perpendicular to the slow axis direction) can be kept low, and it is relatively easy even if the film is thin. Therefore, it is the most suitable material.

Also, for the purpose of suppressing deterioration of optical functional dyes such as iodine dyes, the polyester film preferably has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. If the light transmittance is 20% or less, the optical functional dye can be prevented from being deteriorated by ultraviolet rays. The transmittance is measured by a method perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

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

Examples of benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, and acrylonitrile ultraviolet absorbers include 2- [2'-hydroxy-5 '-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2' -Hydroxy-5 '-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2,2'-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. Examples of cyclic imino ester UV absorbers include 2,2 ′-(1 , 4-phenylene) bis (4H-3,1-benzoxazinon-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazine-4-one ON, 2-phenyl-3,1-benzoxazin-4-one, etc. However, it is not particularly limited thereto.

In addition to the ultraviolet absorber, it is also preferable to include various additives other than the catalyst as long as the effects of the present invention are not hindered. Examples of additives include inorganic particles, heat resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light proofing agents, flame retardants, thermal stabilizers, antioxidants, and antigelling agents. And surfactants. Moreover, in order to show high transparency, it is also preferable that a polyester film does not contain a particle | grain substantially. “Substantially free of particles” means, for example, in the case of inorganic particles, a content that is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less when inorganic elements are quantified by fluorescent X-ray analysis. means.

It is preferable to provide an antireflection layer and / or a low reflection layer on at least one surface of the polyester film that is the polarizer protective film used in the present invention.
The reflectance of the polyester film in which the antireflection layer and / or the low reflection layer is laminated at the peak top wavelength of the peak with the highest peak intensity in the wavelength region of 600 nm to 780 nm of the emission spectrum of the backlight light source is 2%. The following is preferable. The reflectance is measured from the side where the antireflection layer and / or the low reflection layer is laminated. When the reflectance exceeds 2%, it is not preferable because rainbow-like color spots are easily visible. The reflectance is more preferably 1.6% or less, still more preferably 1.2% or less, and particularly preferably 1% or less. The lower limit of the reflectance is not particularly set, but is 0.01%, for example. A reflectance of 0% is most preferable. When laminating an antireflection layer, the upper limit of the reflectance is preferably less than 1%. When laminating a low reflection 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 described later.

The antireflection layer may be a single layer or a multilayer. In the case of a single layer, the thickness of the low refractive index layer made of a material having a lower refractive index than that of the polyester film is set to 1/4 wavelength of the light wavelength or its thickness. If formed so as to be an odd multiple, an antireflection effect can be obtained. When the antireflection layer is a multilayer, an antireflection effect can be obtained by alternately laminating two or more low refractive index layers and high refractive index layers and controlling the thickness of each layer as appropriate. Further, if necessary, a hard coat layer can be laminated between the antireflection layers, and an antifouling layer can be formed on the hard coat layer.

Other antireflection layers include those using a moth-eye structure. The moth-eye structure is a concavo-convex structure with a pitch smaller than the wavelength formed on the surface. With this structure, a sudden and discontinuous refractive index change at the boundary with air is changed into a continuous and gradually changing refractive index change. It is possible to change. Thereby, the light reflection in the surface of a film reduces by forming a moth eye structure in the surface. For example, JP 2001-517319 A can be referred to.

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

A conventionally known low reflection layer can be used. For example, it is formed by a method of laminating at least one metal or oxide thin film by vapor deposition or sputtering, a method of coating one or more organic thin films, or the like. As the low reflection layer, a polyester film or an organic thin film having a lower refractive index than that of a hard coat layer laminated on the polyester film is preferably used.

The antireflection layer and / or the low reflection layer may be further provided with an antiglare function. Thereby, it is possible to further suppress rainbow spots. 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. Particularly preferred is a combination of a low reflection layer and an antiglare layer. As the antiglare layer, a conventionally known antiglare layer can be used. For example, from the viewpoint of suppressing surface reflection of the film, an embodiment in which an antiglare layer is laminated on a polyester film and then an antireflection layer or a low reflection layer is laminated is preferable.

As one method for reducing the reflectance of the polyester film in which the antireflection layer and / or the low reflection layer is laminated at the peak position having the highest peak intensity in the wavelength region of 600 nm to 780 nm in the emission spectrum of the backlight source, For example, the antireflection layer and the low reflection layer may be designed 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 is in the wavelength region of 600 nm to 780 nm. .

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 formula 2nd = λb / 4 is obtained. What is necessary is just to adjust the thickness of an antireflection layer and a low reflection layer so that it may satisfy | fill. 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 antireflection layer and the low reflection layer are multi-layered, the following calculation can be made 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 configuration. An incident medium layer (in) on the side of the first layer opposite to the side in contact with the second layer) In the case of an exit medium layer (out) on the opposite side of the fifth layer that contacts the fourth layer), the refractive index is n, the reflectance is r, and the thickness is Where d is the refractive angle, θ is the wavelength, λ is the wavelength, and Δ is the phase difference, the reflectivity of the lowermost layer (fifth layer) is expressed by the following equation from the equation of thin film interference. The subscript numbers indicate each layer. Further, consecutive suffix numbers indicate the reflectivity between layers.
(5th layer)

Delta _x becomes a phase difference when the a thin film of each layer x back and forth in a V-shape in refraction angle theta _x, it is calculated by the formula of [Expression 2].

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

In general, when calculating the multilayer film reflection, it can be calculated by adding the reflected light from a plurality of boundary surfaces in consideration of the phase. Therefore, the reflectance of each layer can be obtained from the following equation.
(5th to 4th layers)

(5th to 3rd layers)

(5th to 2nd layers)

(5th to 1st layers)
The reflectivity of the entire five layers is obtained by the following formula.

添え Addition of the number attached to the reflectance indicates the total reflectance between the layers. The bottom wavelength can be designed to the target wavelength by adjusting the refractive index n and thickness d of each layer from the above equation.

The wavelength λp of the peak top of the peak with the highest peak intensity in the wavelength region of 600 nm to 780 nm in the emission spectrum of the backlight source, 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. The bottom wavelength of the reflection spectrum is a wavelength at which the reflectance is minimum in the reflection spectrum of 400 nm to 780 nm.

When the antireflection layer or the low reflection layer is provided, the polyester film preferably has an easy adhesion layer on the surface thereof. At this time, from the viewpoint of suppressing interference due to reflected light, it is preferable to adjust the refractive index of the easy-adhesion layer so that it is close to the geometric mean of the refractive index of the antireflection layer or the low reflection layer and the refractive index of the polyester film. The refractive index of the easy-adhesion layer can be adjusted by a known method. For example, the refractive index of the easy-adhesion layer can be easily adjusted by containing a binder resin with titanium, germanium, or other metal species.

The polyester film can be subjected to corona treatment, coating treatment, flame treatment, etc. in order to improve the adhesion with the polarizer.

In the present invention, in order to improve the adhesion to the polarizer, at least one surface of the film of the present invention has an easy-adhesion layer mainly composed of at least one of a polyester resin, a polyurethane resin or a polyacrylic resin. Is preferred. Here, the “main component” refers to a component that is 50% by mass or more of the solid components constituting the easy-adhesion layer. The coating solution used for forming the easy-adhesion layer of the present invention is preferably an aqueous coating solution containing at least one of water-soluble or water-dispersible copolymerized polyester resin, acrylic resin, and polyurethane resin. Examples of these coating solutions include water-soluble or water-dispersible co-polymers disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Examples thereof include a polymerized polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.

The easy-adhesion layer can be obtained by applying the coating solution on one or both sides of an unstretched film or a uniaxially stretched film in the longitudinal direction, drying at 100 to 150 ° C., and further stretching in the transverse direction. The final coating amount of the easy adhesion layer is preferably controlled to 0.05 to 0.2 g / m ² . If the coating amount is less than 0.05 g / m ² , the adhesion with the resulting polarizer may be insufficient. On the other hand, when the coating amount exceeds 0.2 g / m ² , blocking resistance may be lowered. When providing an easily bonding layer on both surfaces of a polyester film, the application quantity of an easily bonding layer on both surfaces may be the same or different, and can be independently set within the above range.

It is preferable to add particles to the easy-adhesion layer in order to impart slipperiness. It is preferable to use particles having an average particle size of 2 μm or less. When the average particle diameter of the particles exceeds 2 μm, the particles easily fall off from the coating layer. As particles to be included in the easy adhesion layer, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, Examples include inorganic particles such as calcium fluoride, and organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone. These may be added alone to the easy-adhesion layer, or may be added in combination of two or more.

Further, as a method for applying the coating solution, a known method can be used. For example, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, etc. can be mentioned. Or it can carry out in combination.

The average particle size of the above particles is measured by the following method. Take a picture of the particles with a scanning electron microscope (SEM) and at a magnification such that the size of one smallest particle is 2-5 mm, the maximum diameter of 300-500 particles (between the two most distant points) Distance) is measured, and the average value is taken as the average particle diameter.

The polyester film used as a polarizer protective film can be manufactured according to a general polyester film manufacturing method. For example, the polyester resin is melted and the non-oriented polyester extruded and formed into a sheet shape is stretched in the longitudinal direction by utilizing the speed difference of the roll at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction by a tenter. The method of performing heat processing is mentioned.

The polyester film used in the present invention may be a uniaxially stretched film or a biaxially stretched film, but when the biaxially stretched film is used as a polarizer protective film, it is observed from directly above the film surface. However, rainbow-like color spots are not seen, but care must be taken because rainbow-like color spots may be observed when observed from an oblique direction.

The film forming conditions of the polyester film will be specifically described. The longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130 ° C, particularly preferably 90 to 120 ° C. In order to orient the film so that the slow axis is in the TD direction, the longitudinal draw ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. The transverse draw ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. In order to orient the film so that the slow axis is in the MD direction, the longitudinal draw ratio is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times. The transverse draw ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times.
In order to control the refractive index and retardation in the fast axis direction of the polyester film within the above range, it is preferable to control the ratio between the longitudinal draw ratio and the transverse draw ratio. In order to increase the retardation, it is preferable to increase the difference between the vertical and horizontal stretch ratios. Setting the stretching temperature low is also a preferable measure for reducing the refractive index in the fast axis direction of the polyester film and increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably from 100 to 250 ° C., particularly preferably from 180 to 245 ° C.

In order to suppress the fluctuation of retardation in the film, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio have a great influence on the thickness unevenness of the film, it is preferable to optimize the film forming conditions from the viewpoint of the thickness unevenness. In particular, if the longitudinal stretching ratio is lowered to increase the retardation, the longitudinal thickness unevenness may be deteriorated. Since there is a region where the vertical thickness unevenness becomes very bad in a specific range of the draw ratio, it is desirable to set the film forming conditions outside this range.

The thickness unevenness 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 described above, in order to control the retardation of the polyester film within a specific range, the stretching ratio, stretching temperature, and film thickness can be appropriately set. For example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the higher the retardation. Conversely, the lower the stretching ratio, the higher the stretching temperature, and the thinner the film, the lower the retardation. However, when the thickness of the film is increased, the thickness direction retardation tends to increase. Therefore, it is desirable to set the film thickness appropriately within the range described below. In addition to controlling the retardation, it is desirable to set final film forming conditions in consideration of physical properties necessary for processing.

The thickness of the polyester film is arbitrary, but is preferably in the range of 15 to 300 μm, more preferably in the range of 15 to 200 μm. Even in the case of a film having a thickness of less than 15 μm, it is possible in principle to obtain a retardation of 1500 nm or more. However, in that case, the anisotropy of the mechanical properties of the film becomes remarkable, and it becomes easy to cause tearing, tearing, etc., and the practicality as an industrial material is remarkably lowered. A particularly preferable lower limit of the thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. A particularly preferable upper limit of the thickness is 100 μm, which is about the same as a general TAC film. Polyethylene terephthalate is preferable as the polyester used as the film substrate in order to control the retardation within the range of the present invention even in the above thickness range.

In addition, as a method of blending the ultraviolet absorber into the polyester film, a known method can be used in combination. For example, a master batch is prepared by blending the dried ultraviolet absorber and the polymer raw material in advance using a kneading extruder. It can be prepared and blended by, for example, a method of mixing a predetermined master batch and a polymer raw material during film formation.

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

It is also preferable that the polyester film has a multilayer structure of at least three layers and an ultraviolet absorber is added to the intermediate layer of the film. A film having a three-layer structure containing an ultraviolet absorber in the intermediate layer can be specifically produced as follows. Polyester pellets alone for the outer layer, master batches containing UV absorbers for the intermediate layer and polyester pellets are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder, which is slit-shaped. Extruded into a sheet form from a die and cooled and solidified on a casting roll to make an unstretched film. That is, using two or more extruders, a three-layer manifold or a merging block (for example, a merging block having a square merging portion), a film layer constituting both outer layers and a film layer constituting an intermediate layer are laminated, An unstretched film is formed by extruding a three-layer sheet from the die and cooling with a casting roll. In the present invention, it is preferable to perform high-precision filtration during melt extrusion in order to remove foreign substances contained in the raw material polyester, which cause optical defects. The filter particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. When the filter particle size of the filter medium exceeds 15 μm, removal of foreign matters of 20 μm or more tends to be insufficient.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention. In addition, the evaluation method of the physical property in the following examples is as follows.

(1) Refractive index of polyester film Using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments), the slow axis direction of the film is obtained, and the slow axis direction is the long side of the sample for measurement. A 4 cm × 2 cm rectangle was cut out so as to be parallel to each other and used as a measurement sample. About this sample, the biaxial refractive index (the refractive index in the slow axis direction: Ny, the fast axis (the refractive index in the direction perpendicular to the slow axis direction): Nx), and the refractive index in the thickness direction ( Nz) was determined by an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm).

(2) Retardation (Re)
Retardation is a parameter defined by the product (ΔNxy × d) of the biaxial refractive index anisotropy (ΔNxy = | Nx−Ny |) on the film and the film thickness d (nm). Yes, it is a scale showing optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments Co., Ltd.), determine the slow axis direction of the film, 4 cm so that the slow axis direction is parallel to the long side of the measurement sample. A rectangle of × 2 cm was cut out and used as a measurement sample. For this sample, Abbe refracts the biaxial refractive index (the refractive index in the slow axis direction: Ny, the refractive index in the direction perpendicular to the slow axis direction: Nx), and the refractive index (Nz) in the thickness direction. The absolute value (| Nx−Ny |) of the biaxial refractive index difference was determined as a refractive index anisotropy (ΔNxy), which was obtained by a refractive index meter (NAGO-4T manufactured by Atago Co., Ltd., measurement wavelength 589 nm). The thickness d (nm) of the film was measured using an electric micrometer (manufactured by Fine Reef, Millitron 1245D), and the unit was converted to nm. Retardation (Re) was determined from the product (ΔNxy × d) of refractive index anisotropy (ΔNxy) and film thickness d (nm).

(3) Thickness direction retardation (Rth)
Thickness direction retardation is obtained by multiplying two birefringences ΔNxz (= | Nx−Nz |) and ΔNyz (= | Ny−Nz |) by film thickness d when viewed from the cross section in the film thickness direction. It is a parameter which shows the average of retardation obtained. Thickness direction retardation (Rth) is obtained by calculating Nx, Ny, Nz and film thickness d (nm) in the same manner as the measurement of retardation, and calculating the average value of (ΔNxz × d) and (ΔNyz × d). )

(4) NZ Coefficient The NZ coefficient was obtained by substituting the values of Ny, Nx, and Nz obtained in (1) above into the formula: NZ = | Ny−Nz | / | Ny−Nx |.

(5) Measurement of emission spectrum of backlight source REGZA 43J10X manufactured by Toshiba was used for the liquid crystal display device used in each example. When the emission spectrum of the backlight source (white light emitting diode) of this liquid crystal display device was measured using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics, an emission spectrum having peak tops in the vicinity of 450 nm, 535 nm, and 630 nm was observed. It was done. The half width of each peak top (the half width of the peak having the highest peak intensity in each wavelength region) was 17 nm for the peak at 450 nm, 45 nm for the peak at 535 nm, and 2 nm for the peak at 630 nm, respectively. This light source had a plurality of peaks in the wavelength region of 600 nm or more and 780 nm or less, and the half-value width was evaluated at a peak near 630 nm having the highest peak intensity in this region. Moreover, the exposure time in the spectrum measurement was 20 msec.

(6) Measurement of reflection spectrum (evaluation of reflectance)
After cutting into A4 size at an arbitrary position from the obtained polarizer protective film, the surface of the substrate opposite to the surface on which the low reflection layer (or antireflection layer) is laminated is uniformly scratched with water-resistant sandpaper, Black magic ink (registered trademark) was applied, and a black tape (Nitto Denko vinyl tape No. 21 black) was applied to prepare a sample in which the reflection of the opposite surface of the low reflection layer (or antireflection layer) was eliminated. For the prepared sample, the reflection spectrum at 400 to 800 nm of the low reflection layer (or antireflection layer) was measured using a spectrophotometer UV-3150 manufactured by Shimadzu Corporation. The reflection spectrum was measured using the Al mirror (part number 202-35988-05) attached as a standard to the specular reflection measuring device (part number 206-14064, manufactured by Shimadzu Corporation) as the standard mirror, and a total luminous flux of 5 °. The measurement was carried out by relative specular reflection at an incident angle of. In addition, the measurement was performed under the conditions of sampling pitch: 1 nm, sample mask opening size :: 5 mmφ. (5) From the measurement result of the emission spectrum of the backlight source, the peak top wavelength of the peak with the highest peak intensity in the wavelength region of 600 to 780 nm of the emission spectrum was 630 nm. The reflectance at was determined. Moreover, the bottom wavelength was also calculated | required about the polarizer protective film 1. FIG.

(Production Example 1-Polyester A)
When the temperature of the esterification reactor was raised to 200 ° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged and 0.017 parts by mass of antimony trioxide as a catalyst while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Next, the pressure was raised and the pressure esterification reaction was carried out under the conditions of gauge pressure 0.34 MPa and 240 ° C., then the esterification reaction can was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and 0.012 mass part of trimethyl phosphate was added. Then, 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 can and subjected to polycondensation reaction at 280 ° C. under reduced pressure.

After completion of the polycondensation reaction, it is filtered through a NASRON filter with a 95% cut diameter of 5 μm, extruded into a strand from a nozzle, and cooled and solidified using cooling water that has been filtered (pore diameter: 1 μm or less) in advance. And cut into pellets. 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. (Hereafter, abbreviated as PET (A).)

(Production Example 2-Polyester B)
10 parts by weight of the dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), and PET (A) containing no particles (inherent 90 parts by mass of a viscosity of 0.62 dl / g) was mixed, and a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter abbreviated as PET (B)).

(Production Example 3-Adjustment of Adhesive Modification Coating Solution)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method, and as a dicarboxylic acid component (based on the total dicarboxylic acid component) 46 mol% terephthalic acid, 46 mol% isophthalic acid and 8 mol% sodium 5-sulfonatoisophthalate, A water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of 50 mol% ethylene glycol and 50 mol% neopentyl glycol as a glycol component (based on the entire glycol component) was prepared. Next, 51.4 parts by weight of water, 38 parts by weight of isopropyl alcohol, 5 parts by weight of n-butyl cellosolve, and 0.06 parts by weight of a nonionic surfactant were mixed and then heated and stirred. After adding 5 parts by mass of the above water-dispersible sulfonic acid metal base-containing copolymer polyester resin and continuing to stir until the resin is no longer agglomerated, the resin aqueous dispersion is cooled to room temperature, and the solid content concentration is 5.0% by mass. A uniform water-dispersible copolymerized polyester resin solution was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silysia Co., Ltd.) in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolyester resin solution was mixed with 99.46 parts by mass of the silicia 310. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added with stirring to obtain an adhesive modified coating solution.

(Production Example 4-Preparation of coating solution for low reflection layer)
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 charged into a reaction vessel and reacted at 80 ° C. for 7 hours under a nitrogen atmosphere to obtain a methyl ethyl ketone solution of a polymer having a weight average molecular weight of 20000. The obtained polymer solution was diluted with methyl ethyl ketone to a solid content concentration of 5% by mass to obtain a fluoropolymer solution C. The obtained fluoropolymer solution C was mixed as follows to obtain a low reflection layer coating solution.

・ 44 parts by mass of fluoropolymer solution C ・ 1,10-bis (2,3-epoxypropoxy)
-2,2,3,3,4,4,5,5,6,6,7,7,
8,8,9,9-hexadecafluorodecane (Kyoeisha Chemicals, Fluorite FE-16) 1 part by mass ・ Triphenylphosphine 0.1 part by mass ・ Methyl ethyl ketone 19 parts by mass

(Production Example 5-Preparation of coating solution for low reflection layer)
An aqueous dispersion (solid content concentration) of vinylidene fluoride / tetrafluoroethylene / chlorotrifluoroethylene copolymer (= 72.1 / 14.9 / 13 (mol%)) as vinylidene fluoride polymer particles. 45.5% by mass) 571.4 g was placed in a 2 L glass separable flask, and 37.1 g of New Coal 707SF (manufactured by Nippon Emulsifier Co., Ltd.) as an emulsifier and 59.3 g of water were added and mixed well to form an aqueous solution. The dispersion was adjusted.

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

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. Further, simultaneously with the addition of the monomer solution, the polymerization proceeded while adding 41.1 g of 1% by mass of ammonium persulfate in 7 portions every 30 minutes. Five hours after the start of the polymerization, the reaction solution was cooled to room temperature to complete the reaction, whereby an aqueous dispersion of acrylic-fluorine composite polymer particles was obtained (solid content concentration 52.0% by mass). The mass ratio of the fluoropolymer portion to the acrylic polymer portion in the obtained acrylic-fluorine composite polymer particles was 50/50.

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

(Production Example 6-Preparation of coating solution for low reflective layer)
An aqueous dispersion (solid content concentration) of vinylidene fluoride / tetrafluoroethylene / chlorotrifluoroethylene copolymer (= 72.1 / 14.9 / 13 (mol%)) as vinylidene fluoride polymer particles. 45.5% by mass) 571.4 g was placed in a 2 L glass separable flask, and 37.1 g of New Coal 707SF (manufactured by Nippon Emulsifier Co., Ltd.) as an emulsifier and 59.3 g of water were added and mixed well to form an aqueous solution. The dispersion was adjusted.

12.12 parts by mass of the acrylic-fluorine composite polymer particle aqueous dispersion, 61.47 parts by mass of water, 20.00 parts by mass of isopropyl alcohol, and 2.80 parts by mass of the oxazoline crosslinking agent WS-700 (Epocross made by Nippon Shokubai Co., Ltd.) Manufactured), 1.75 parts by mass of colloidal silica particle Snowtex ST-ZL (manufactured by Nissan Chemical Industries, Ltd.) and 0.30 parts by mass of a silicon surfactant were added and stirred to obtain a low reflection layer coating solution.

(Polarizer protective film 1)
After drying 90 parts by mass of PET (A) resin pellets containing no particles as a raw material for the base film intermediate layer and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber at 135 ° C. for 6 hours under reduced pressure (1 Torr) , And supplied to the extruder 2 (for the intermediate layer II layer). Also, the PET (A) was dried by an ordinary method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), and dissolved at 285 ° C. . After filtering these two kinds of polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles 95% cut), laminating them in a two-kind / three-layer confluence block, and extruding them into a sheet form from a die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and then cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Next, after applying the adhesive property-modified coating solution of Production Example 3 to 0.08 g / m ² on the opposite side of the surface of the unstretched PET film, which will later form a low reflection layer, by the reverse roll method. And dried at 80 ° C. for 20 seconds.

The unstretched film on which this coating layer was formed was guided to a tenter stretching machine, guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the film was treated at a temperature of 225 ° C. for 10 seconds, and further subjected to a relaxation treatment of 3.0% in the width direction to obtain a PET film having a film thickness of about 100 μm.

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

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

(Polarizer protective film 2)
After drying 90 parts by mass of PET (A) resin pellets containing no particles as a raw material for the base film intermediate layer and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber at 135 ° C. for 6 hours under reduced pressure (1 Torr) , And supplied to the extruder 2 (for the intermediate layer II layer). Also, the PET (A) was dried by an ordinary method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), and dissolved at 285 ° C. . After filtering these two kinds of polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles 95% cut), laminating them in a two-kind / three-layer confluence block, and extruding them into a sheet form from a die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and then cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Subsequently, the low reflective layer was laminated so that the coating amount after drying the coating liquid of Production Example 5 was 0.09 g / m ² on the side on which the low reflective layer of this unstretched PET film was formed by the reverse roll method. On the opposite side of the surface, the adhesion-modified coating solution of Production Example 3 was applied at 0.08 g / m ² and then dried at 80 ° C. for 20 seconds.

The unstretched film on which this coating layer was formed was guided to a tenter stretching machine, guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the film was treated at a temperature of 225 ° C. for 10 seconds, and further subjected to a 3.0% relaxation treatment in the width direction to obtain a polarizer protective film 2 having a film thickness of about 100 μm. Obtained.

The retardation (Re), retardation in the thickness direction (Rth), Re / Rth, and NZ coefficient of the polarizer protective film 2 were the same as those of the polarizer protective film 1.
When the reflection spectrum of the polarizer protective film 2 was measured, the reflectance at a wavelength of 630 nm was 2.11%. The reflectance at a wavelength of 550 nm was 1.96%.

(Polarizer protective film 3)
After drying 90 parts by mass of PET (A) resin pellets containing no particles as a raw material for the base film intermediate layer and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber at 135 ° C. for 6 hours under reduced pressure (1 Torr) , And supplied to the extruder 2 (for the intermediate layer II layer). Also, the PET (A) was dried by an ordinary method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), and dissolved at 285 ° C. . After filtering these two kinds of polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles 95% cut), laminating them in a two-kind / three-layer confluence block, and extruding them into a sheet form from a die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and then cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Next, the low reflective layer is formed so that the coating amount after drying the low reflective layer coating liquid of Production Example 6 is 0.108 g / m ² on the side on which the low reflective layer of the unstretched PET film is formed by the reverse roll method. On the side opposite to the surface on which the film was laminated, the adhesion-modified coating solution of Production Example 3 was applied to 0.080 g / m ² and then dried at 80 ° C. for 20 seconds.

The unstretched film on which this coating 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 being gripped by a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the film was treated at a temperature of 225 ° C. for 10 seconds, and further subjected to a 3.0% relaxation treatment in the width direction to obtain a polarizer protective film 3 having a film thickness of about 100 μm. Obtained.
The polarizer protective film 3 had retardation (Re) of 10300 nm, retardation in the thickness direction (Rth) of 12350 nm, Re / Rth of 0.834, and NZ coefficient of 1.699.
The reflection spectrum of the polarizer protective film 3 had a bottom wavelength of 630 nm and a reflectance at a wavelength of 630 nm of 1.71%.

Example 1
A polarizer protective film 1 is attached to one side of a polarizer composed 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 (Fuji Film Co., Ltd.) Manufactured and having a thickness of 80 μm) to make a polarizing plate. In addition, the polarizer was laminated | stacked on the surface in which the low reflection layer of a polarizer protective film was not laminated | stacked, and the polarizing plate was created.
The polarizing plate on the viewing side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate prepared above so that the polyester film was on the side opposite to the liquid crystal (distal), thereby producing a liquid crystal display device. In addition, it replaced so that the direction of the transmission axis of a polarizing plate might be the same as the direction of the transmission axis of the polarizing plate before replacement.

(Comparative Example 1)
A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizer protective film 2 was used instead of the polarizer protective film 1.

(Example 2)
A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizer protective film 3 was used instead of the polarizer protective film 1.

When the liquid crystal display devices of Examples 1 and 2 and Comparative Example 1 were arranged side by side and the screen was visually observed in a dark place from the front and oblique directions, Examples 1 and 2 were more prone to iridescence than Comparative Example 1. Occurrence was suppressed. Further, in Examples 1 and 2, the liquid crystal display device of Example 1 was more suppressed from generating rainbow spots. Note that rainbow spots here are observed on the screen when the viewer observes the film while moving his head from an oblique direction (when observing while changing the angle from the film normal direction). It is a saddle-shaped rainbow.

In Examples 1 and 2 and Comparative Example 1, the thickness of the polyester film was 100 μm, but this was an 80 μm film (retardation (Re) was 8080 nm, retardation in the thickness direction (Rth) was 9960 nm, Re / A liquid crystal display device of Example 1 ′, Example 2 ′, and Comparative Example 1 ′ was manufactured by replacing Rth with 0.811 and NZ coefficient of 1.733). The generation of rainbow spots was suppressed in the liquid crystal display device of “Acupuncture and Acupuncture Example 2”. In Example 1 'and Vaginal Example 2', rainbow spots were suppressed more in Example 1 'Vaginal. Note that the rainbow spots here are the wrinkles that are observed on the screen when the film is observed from an oblique direction while moving the head (when the angle from the film normal direction is changed). It is a rainbow spot.

In Examples 1 and 2, and Comparative Example 1, the thickness of the polyester film was 100 μm, but this was a 60 μm film (retardation (Re) was 6060 nm, and thickness direction retardation (Rth) was 7470 nm. , Re / Rth was 0.811, and the NZ coefficient was 1.733). The liquid crystal display devices of Example 1 ″, Example 2 ″, and Comparative Example 1 ″ were manufactured. In the liquid crystal display device of Example 1 '' and Example 2 of Example 1 ”, the generation of rainbow spots was suppressed. In Example 1 ″ and Spider Example 2 ″, the iris was more suppressed in Example 1 ″. Note that the rainbow spots here are the wrinkles that are observed on the screen when the film is observed from an oblique direction while moving the head (when the angle from the film normal direction is changed). It is a rainbow spot.

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

Claims

A liquid crystal display device having a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,
The backlight source has a peak top of the emission spectrum in each wavelength region of 400 nm to 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and has the highest peak intensity in the wavelength region of 600 nm to 780 nm. A white light-emitting diode having an emission spectrum with a peak half-width less than 5 nm,
At least one polarizing plate among the polarizing plates is obtained by laminating a polyester film on at least one surface of a polarizer,
The polyester film has a retardation of 1500 nm or more and 30000 nm or less,
The polyester film has an antireflection layer and / or a low reflection layer laminated on at least one surface,
The antireflection layer and / or the low reflection layer measured from the side where the antireflection layer and / or the low reflection layer are laminated at 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. A liquid crystal display device, wherein the reflectance of the laminated polyester film is 2% or less.
The emission spectrum of the backlight source is
The full width at half maximum 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 full width at half maximum of the peak with the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm is 5 nm or more,
The liquid crystal display device according to claim 1.
3. The liquid crystal display device according to claim 1, wherein a peak top wavelength of a peak having the highest peak intensity in the wavelength region of 600 nm to 780 nm is in a region of 620 nm to 640 nm.
3. The liquid crystal display device according to claim 1, wherein a peak top wavelength of a peak having the highest peak intensity in the wavelength region of 600 nm to 780 nm is 630 nm.
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,
A polarizer protective film having a reflectance of 2% or less measured from the side on which the antireflection layer and / or the low reflection layer is laminated in any wavelength of a wavelength region of 600 nm to 780 nm.
The polarizer protective film according to claim 5, wherein any one of the wavelengths is in a region of 620 nm or more and 640 nm or less.
The polarizer protective film according to claim 5, wherein any one of the wavelengths is 630 nm.
A polarizing plate in which the polarizer protective film according to any one of claims 5 to 7 is laminated on at least one surface of the polarizer.