JPWO2018159568A1 - Liquid crystal display - Google Patents

Abstract

A polarizer protective film comprising a polyester film having a retardation of 1500 nm or more and 30000 nm or less, and an antireflection layer and / or a low reflection layer laminated on at least one surface, and in any one of a wavelength region of 600 nm or more and 780 nm or less. A polarizer protective film having a reflectance of 2% or less at that wavelength, as measured from the side on which the antireflection layer and / or the low reflection layer is laminated.

Description

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

  A polarizing plate used for a liquid crystal display device (LCD) is a structure in which a polarizer obtained by dyeing iodine on polyvinyl alcohol (PVA) or the like is sandwiched between two polarizer protective films. Usually uses a triacetyl cellulose (TAC) film. In recent years, as LCDs have become thinner, a thinner polarizing plate has been required. However, if the thickness of the TAC film used as the protective film is reduced, sufficient mechanical strength cannot be obtained, and moisture permeability deteriorates. Further, the TAC film is very expensive, and a polyester film has been proposed as an inexpensive alternative material (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 linearly polarized light emitted from the backlight unit or the polarizer changes its polarization state when passing through the polyester film. The transmitted light shows an interference color unique to retardation, which is the product of the birefringence and the thickness of the oriented polyester film. Therefore, when a discontinuous emission spectrum such as a cold cathode tube or a hot cathode tube is used as a light source, the transmitted light intensity varies depending on the wavelength, resulting in a rainbow-like color spot (see: Proceedings of the 15th Micro Optical Conference, 30-31).

  As means for solving the above problems, it is possible to use a white light source having a continuous and wide emission spectrum such as a white light emitting diode as a backlight light source, and to use an oriented polyester film having a certain retardation as a polarizer protective film. It has been proposed (Patent Document 4). A white light emitting diode has 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 is possible to obtain a spectrum similar to the light emission spectrum of the light source by controlling the retardation of the oriented polyester film. It has become possible to suppress rainbow spots.

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

Due to the increasing demands for color gamut expansion of liquid crystal display devices in recent years, the peaks of the emission spectrums respectively in the blue region (400 nm or more and less than 495 nm), the green region (495 nm or more and less than 600 nm) and the red region (600 nm or more and 780 nm or less) A white light-emitting diode (eg, a blue light-emitting diode and at least K ₂ SiF ₆ as a phosphor) having a top and having an emission spectrum in which a half width of a peak in a red region (600 nm or more and 780 nm or less) is relatively narrow (less than 5 nm): Liquid crystal display devices using a backlight light source composed of a white light emitting diode having a fluoride phosphor such as Mn ⁴⁺ ) have been developed.

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

  That is, an object of the present invention is to provide 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) in each wavelength region. In the case where 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 in which a half width of a peak in a region (600 nm or more and 780 nm or less) is relatively narrow (less than 5 nm). Another object is to provide a liquid crystal display device in which rainbow spots are suppressed.

A typical 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 light source has a peak top of an emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or less and less than 600 nm, and 600 nm or more and 780 nm or less, and has the highest peak intensity in a wavelength region of 600 nm or more and 780 nm or less. A white light emitting diode having an emission spectrum in which the half width of the peak (the peak having the highest peak top in the wavelength region of 600 nm or more and 780 nm or less) is less than 5 nm;
At least one of the polarizing plates is a polarizing plate in which a polyester film is laminated 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 anti-reflection layer and / or the low-reflection layer measured from the side where the anti-reflection 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 light source,
A half-width of a peak having the highest peak intensity in a wavelength region of 400 nm or more and less than 495 nm is 5 nm or more;
A half-value width of a peak having the highest peak intensity in a wavelength region of 495 nm or more and less than 600 nm is 5 nm or more;
Item 2. The liquid crystal display device according to item 1.
Item 3.
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 620 nm to 640 nm.
Item 4.
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 or more and 780 nm or less 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 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 at any wavelength in the wavelength range of 600 nm or more and 780 nm or less as measured from the side where the antireflection layer and / or the low reflection layer is laminated.
Item 6.
Item 6. The polarizer protective film according to Item 5, wherein any one of the wavelengths is 620 nm or more and 640 nm or less.
Item 7.
Item 6. The polarizer protective film according to item 5, wherein any one of the wavelengths is 630 nm.
Item 8.
Item 7. 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, the polarizing plate, and the polarizer protective film of the present invention can ensure good visibility in which occurrence of rainbow-like color spots is significantly suppressed at any viewing angle.

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

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

  Further, the liquid crystal display device may appropriately have other components, such as a color filter, a lens film, a diffusion sheet, an antireflection film, etc., in addition to the backlight light source, the polarizing plate, and the liquid crystal cell. A brightness enhancement film may be provided between the light source side polarizing plate and the backlight light source. As the brightness enhancement film, for example, a reflective polarizing plate that transmits one linearly polarized light and reflects a linearly polarized light that is orthogonal to the linearly polarized light is exemplified. As the reflective polarizing plate, for example, a brightness enhancement film of the DBEF (registered trademark) (Dual Brightness Enhancement Film) series manufactured by Sumitomo 3M Limited is suitably used. The reflective polarizing plate is usually arranged such that the absorption axis of the reflective polarizing plate is parallel to the absorption axis of the light source side polarizing plate.

  At least one of the two polarizers disposed in the liquid crystal display device is a polarizer obtained by dyeing iodine on polyvinyl alcohol (PVA) or the like and a polyester film laminated on at least one surface of a polarizer. It is. In the present invention, from the viewpoint of suppressing rainbow-like color spots, the polyester film has a specific retardation, and at least one surface of the polyester film is laminated with an antireflection layer and / or a low reflection layer. is there. The antireflection layer and / or the low reflection layer may be provided on the surface of the polyester film opposite to the surface on which the polarizer is laminated, or may be provided on the surface of the polyester film on which the polarizer is laminated, Both may be used. 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. Further, another layer (for example, an easy-adhesion layer, a hard coat layer, an antiglare layer, an antistatic layer, and an antifouling layer) exists between the antireflection layer and / or the low reflection layer and the polyester film. You may. From the viewpoint of suppressing rainbow-like color spots, the refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is preferably from 1.53 to 1.62. It is preferable that a film having substantially no birefringence (low retardation), such as a TAC film, an acrylic film, or a norbornene-based film, is laminated on the other surface of the polarizer (three-layer structure). Polarizing plate), it is not always necessary to laminate a film on the other surface of the polarizer (two-layer polarizing plate). When a polyester film is used as the protective film on both sides of the polarizer, the slow axes of both polyester films are preferably substantially parallel to each other. Here, being 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 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. Representative polarizers include those obtained by dyeing a dichroic material such as iodine on a polyvinyl alcohol film or the like, but are not limited thereto, and are known and will be developed in the future. Can be appropriately selected and used.

  As the PVA film, a commercially available product can be used. For example, "Kuraray Vinylon (manufactured by Kuraray Co., Ltd.)", "Tocellovinylon (manufactured by Tosero Co., Ltd.)", "Nichigo Vinylon (Nippon Gohsei 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, uniaxially stretching a PVA film dyed with a dichroic material in a boric acid aqueous solution, and washing and drying while maintaining the stretched state Can be obtained by The stretching ratio of the uniaxial stretching is usually about 4 to 8 times, but is not particularly limited. Other manufacturing conditions and the like can be appropriately set according to a known method.

  The configuration of the backlight may be an edge light type using a light guide plate or a reflection plate as a constituent member, or may be a direct type, but in the present invention, as a backlight light source of a liquid crystal display device, 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and each having a peak top of the emission spectrum in each wavelength region of 600 nm or more and 750 nm or less, 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 even more preferably less than 3.5 nm. The lower limit is preferably 1 nm or more, more preferably 1.5 nm or more. When the half width of the peak is less than 5 nm, the color gamut of the liquid crystal display device is preferably widened. There is no particular lower limit for the half width of the peak, but it can be set to 1 nm. When the peak half width is less than 1 nm, the luminous efficiency may be deteriorated. The shape of the emission spectrum is designed from the balance between the required color gamut and the emission efficiency. Here, the half width means the peak width (nm) at half the intensity of the peak intensity at the peak top wavelength.

  The application of a backlight light source having an emission spectrum having the above-described characteristics to an LCD is a technique that has attracted attention in recent years due to a growing demand for color gamut expansion. An LED that uses a conventionally used white LED (for example, a light emitting element in which a blue light emitting diode and a yttrium aluminum garnet-based yellow phosphor are combined) as a backlight light source has a spectrum with a human eye recognizable. Only about 20% of colors can be reproduced. On the other hand, it is said that when a backlight light source having an emission spectrum having the above-mentioned characteristics is used, 60% or more of colors can be reproduced.

  The wavelength region from 400 nm to less than 495 nm is more preferably from 430 nm to 470 nm. The wavelength range from 495 nm to less than 600 nm is more preferably from 510 nm to 560 nm. The wavelength region from 600 nm to 780 nm is more preferably from 600 nm to 700 nm, and even more preferably from 610 nm to 680 nm. One preferred embodiment of the wavelength region of 600 nm or more and 780 nm or less is 620 nm or more and 640 nm or less, particularly preferably 630 nm.

  The peak half width (peak half width of the peak having the highest peak intensity in each wavelength region) at the peak top of each wavelength region of 400 nm to less than 495 nm and 495 nm to less than 600 nm of the emission spectrum is not particularly limited, but is 400 nm or more and 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 495 nm or more and 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-value width (half-width of the peak having the highest peak intensity in each wavelength region) at the peak top of each wavelength region of 400 nm to less than 495 nm and 495 nm to less than 600 nm is: It is preferably 140 nm or less, preferably 120 nm or less, preferably 100 nm or less, more preferably 80 nm or less, further preferably 60 nm or less, and still more preferably 50 nm or less.

Specifically, as a white light source having an emission spectrum having the above-described characteristics, for example, a phosphor-type white light-emitting diode in which a blue light-emitting diode and a phosphor are combined is exemplified. Examples of the red phosphor among the phosphors include a fluoride phosphor (also referred to as “KSF”) having a composition formula of K ₂ SiF ₆ : Mn ⁴⁺ and others. The Mn ⁴⁺ activated fluoride complex phosphor is a phosphor having Mn ⁴⁺ as an activator and a fluoride complex salt of an alkali metal, an amine or an alkaline earth metal as a host crystal. The fluoride complex forming the host crystal includes 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 therearound is 5-7.

Preferred 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 at least one selected from Mg, Ca, Sr, Ba, and Zn; M is Ge, Si, Sn, Ti, and one or more 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 the NH ₄ one or more _{selected), A 2 [MF 5]} : Mn (A is Li, Na, K, Rb, Cs, and one or more selected from NH _4; M is Al, Ga, and one or more selected from in) , A ₃ [MF ₆ ]: Mn (A is Li, Na, K, Rb, At least one selected from Cs and NH ₄ ; M is at least one selected from Al, Ga, and In), Zn ₂ [MF ₇ ]: Mn (M is at least one selected from Al, Ga, and In); A [In ₂ F ₇ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, and NH ₄ ) and the like.

One preferred Mn ⁴⁺ activated fluoride complex phosphor is A ₂ MF ₆ : Mn (where A is selected from Li, Na, K, Rb, Cs, and NH _{4) using} an alkali metal hexafluoro complex salt as a host crystal. M is at least one selected from Ge, Si, Sn, Ti, and Zr). Of these, A is preferably one or more selected from K (potassium) and Na (sodium), and M is Si (silicon) or Ti (titanium). Among them, it is particularly preferable that A is K (the ratio of K to the total amount of A is 99 mol% or more) and M is Si. The activator element is desirably 100% Mn (manganese), but Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn, Mg and the like may be contained. 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 phosphor, the 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 which is at least K ₂ SiF ₆ : Mn ⁴⁺ as a blue light emitting diode and a phosphor. It is 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, the green phosphor is, 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. , Etc. are exemplified.

In the case where a plurality of peaks exist in any one of a wavelength region of 400 nm or more and less than 495 nm, a wavelength region of 495 nm or more and less than 600 nm, or a wavelength region of 600 nm or more and 780 nm or less, the following is considered.
When the plurality of peaks are independent peaks, the half width of the peak having the highest peak intensity is preferably in the above range. Further, it is more preferable that the half width of the other peak having an intensity of 70% or more of the highest peak intensity is also in the above range.
For one independent peak having a shape in which a plurality of peaks overlap, if the half width of the peak having the highest peak intensity among the plurality of peaks can be directly measured, the half width is used. Here, the independent peak has a region where the peak intensity is １ ／ 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 on each side of which the intensity is の of the peak intensity, the plurality of peaks are regarded as one peak as a whole. In such a single peak having a shape in which a plurality of peaks are overlapped, the half width of the peak (nm) at half the intensity of the highest peak intensity is set.
Note that a point having the highest peak intensity among a plurality of peaks is defined as a peak top.
Note that 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 of the peaks in other wavelength regions. It is preferable that they have the following relationship. 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 from the viewpoint of color clarity that a region having a peak intensity of 1/3 or less of the peak having the highest peak intensity is present.

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

  As a result of the inventor's intensive studies, as in the above-described backlight light source, each of the wavelength regions 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). In a liquid crystal display device having a backlight light source consisting of a white light emitting diode having a peak top of an emission spectrum and a half width of a peak in a red region (600 nm or more and 780 nm or less) being relatively narrow, a specific polarizer protective film is used. It has been found that using 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 effective in suppressing rainbow spots. Here, the specific wavelength is a wavelength corresponding to the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less (the peak top wavelength of the peak having the highest peak intensity) in the emission spectrum of the backlight light source. . In other words, the present inventors have found that, 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 in the emission spectrum of the backlight light source, the side on which the antireflection layer and / or the low reflection layer is laminated It has been found that when the reflectance of the polyester film on which the antireflection layer and / or the low-reflection layer is measured is 2% or less, it is particularly effective in controlling the iris.

When an 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 possible cause of the change in the polarization state is that the difference in the refractive index at the interface between the air layer and the oriented polyester film or the difference in the refractive index at the interface between the polarizer and the oriented polyester film may be affected. 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 the refractive index between the interfaces.
Light passing through the polarizer and entering the oriented polyester film is linearly polarized light, and it is considered that there is no transmittance dependence on wavelength in the state of linearly polarized light. The linearly polarized incident light changes into elliptically polarized light or circularly polarized light by passing through the oriented polyester film. The phase difference δ is represented by δ = 2π × Re / λ (Re: retardation, λ: wavelength), and the phase difference δ differs 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 upon exiting the oriented polyester film differs depending on the wavelength. When emitted from the oriented polyester film to the viewing side, the S-polarized component perpendicular to the plane of incidence is more likely to be reflected than the P-polarized component, and this difference (P-polarized light) increases as the viewing angle from the normal increases. Component and the S-polarized component) tend to be large. Light of each wavelength having a different degree of polarization has a different effect of S-polarized light, which is easily reflected, so that each transmittance changes when passing through the interface. When the light passes through the interface, the transmittance in the wavelength band containing a large amount of S-polarized light component is reduced, and this is considered to be one of the factors that cause rainbow-like color spots. In particular, when there is a steep peak in a red region of 600 nm or more and 780 nm or less, a change in transmittance depending on the wavelength is large, and color spots are likely to appear. Since the interface reflection at an arbitrary wavelength can be suppressed by using the thin film interference, the transmittance in the red region is improved by forming an antireflection layer and / or a low reflection layer having a low reflectance at a sharp peak (that is, S). It is considered that the reflection of the polarized light component can be suppressed). In the red region having a steep peak, since the transmittance of the S-polarized light component is improved, 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, so that a rainbow-like color is obtained. Spots can be suppressed.

  As described above, in the present invention, each 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 the peak top of the emission spectrum, and the red In a liquid crystal display device having a backlight light source composed of a white light emitting diode having a relatively narrow half-value 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 as a polarizer protective film is used, a rainbow-like shape is obtained. 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. It is preferable that the retardation be in the above-mentioned range since the iris tends to be more easily reduced. A preferred lower limit of the retardation is 3000 nm, a next preferred lower limit is 3500 nm, a more preferred lower limit is 4000 nm or 5000 nm, a still more preferred lower limit is 6000 nm or 7000 nm, and a still more preferred lower limit is 8000 nm. A preferred upper limit is 30,000 nm, and a polyester film having a retardation of more than 30000 nm has a considerably large thickness and tends to have low handleability as an industrial material. A more preferred upper limit is 15000 nm, further preferably 12000 nm, and still more preferably 11000 nm.

  In addition, 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. Note that the refractive index can be determined by an Abbe refractometer (measuring wavelength 589 nm).

  The ratio (Re / Rth) of the retardation (Re: in-plane retardation) of the polyester film to the retardation in the thickness direction (Rth) is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.5 or more. 6 or more. As the ratio of the retardation to the thickness direction retardation (Re / Rth) is larger, the effect of birefringence is more isotropic, and the occurrence of rainbow-like color spots depending on the observation angle tends to be less likely to occur. Since the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is 2.0 in a perfect uniaxial (uniaxially symmetric) film, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is 2.0. The upper limit is preferably 2.0. The retardation in the thickness direction means an average of retardations 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 NZ coefficient of the polyester film is preferably 2.5 or less, more preferably 2.0 or less, still more preferably 1.8 or less, and even more preferably 1. 6 or less. And since a perfect uniaxial (uniaxially symmetric) film has an NZ coefficient of 1.0, the lower limit of the NZ coefficient is 1.0. However, it should be noted that the mechanical strength in the direction perpendicular to the orientation direction tends to be significantly reduced as the film approaches a completely uniaxial (uniaxially symmetric) 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 orthogonal to the slow axis (refraction in the fast axis direction). ) 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), and the biaxial refractive index (Ny, Nx, where Ny> Nx), and the refractive index (Nz) in the thickness direction are determined by an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd., measurement wavelength: 589 nm). The value thus obtained is substituted into | Ny−Nz | / | Ny−Nx | to obtain the NZ coefficient.

  In addition, from the viewpoint of suppressing rainbow-like color spots, the value of Ny-Nx of the polyester film is preferably equal to or greater than 0.05, more preferably equal to or greater than 0.07, and still more preferably equal to or greater than 0.08. Is 0.09 or more, most preferably 0.1 or more. There is no particular upper limit, but in the case of a polyethylene terephthalate film, the upper limit is preferably about 1.5.

  In a more preferred embodiment in the present invention, the refractive index of the polyester film in a direction parallel to the transmission axis direction of the polarizer constituting the polarizing plate is preferably in a range from 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. It is preferably 1.61 or less, more preferably 1.60 or less, further preferably 1.59 or less, and still more preferably 1.58 or less.

  On the other hand, the lower limit of the refractive index is preferably 1.53. When the refractive index is less than 1.53, crystallization of the polyester film becomes insufficient, and properties obtained by stretching, such as dimensional stability, mechanical strength, and chemical resistance, may be insufficient. It is preferably at least 1.56, more preferably at least 1.57.

  In order to set the refractive index of the polyester film in a direction parallel to the transmission axis direction of the polarizer to a range of 1.53 or more and 1.62 or less, the polarizing plate includes a transmission axis of the polarizer and a fast axis of the polyester film. (Slow axis and perpendicular direction) are preferably substantially parallel. The refractive index of the polyester film 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 a stretching treatment in a film forming step described later. By setting the fast axis direction of the polyester film and the transmission axis direction of the polarizer to be substantially parallel, the refractive index of the polyester film in a direction parallel to the transmission axis direction of the polarizer is set to 1.53 to 1.62. Can be. Here, being substantially parallel means that the angle between the transmission axis of the polarizer and the fast axis of the polarizer protective film is −15 ° to 15 °, preferably −10 ° to 10 °, and more preferably −5 °. -5 °, more preferably -3 ° -3 °, even more preferably -2 ° -2 °, and even more preferably -1 ° -1 °. In one 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 shift inevitably occurred when the polarizer and the protective film are bonded to each other. 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, and the polarizer is laminated so that the transmission axis of the polarizer and the fast axis of the polyester film are substantially parallel to each other. 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 made of the polyester film used in the present invention can be used for both the polarizing plate on the incident light side (light source side) and the emitting light side (viewing side), but at least on the emitting light side (viewing side). It is preferable to use it for the protective film of the polarizing plate.
Regarding the polarizing plate disposed on the output light side, the polarizer protective film made of the polyester film is disposed on the liquid crystal side with the polarizer as a starting point, disposed on the output light side, or disposed on both sides. However, it is preferable to be arranged at least on the outgoing light side.
Even in the polarizing plate disposed on the incident light side, the polarizer protective film made of the polyester film may be disposed on the incident light side with the polarizer as a starting point, or disposed on the liquid crystal cell side, on both sides. However, in a preferred embodiment, it is arranged at least on the incident light side. In addition, the polarizer disposed on the incident light side does not use a polarizer protective film made of a polyester film, and uses a polarizer protective film having substantially no birefringence (low retardation) such as a triacetyl cellulose film. May be done.

  As the polyester used for the polyester film, polyethylene terephthalate or polyethylene naphthalate can be used, but may contain other copolymer components. These resins have excellent transparency and thermal and mechanical properties, and can easily control retardation by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence, so that the refractive index in the fast axis direction (perpendicular to the slow axis direction) can be suppressed low by stretching the film, and it is relatively easy even if the film thickness is small. It is the most suitable material because it can provide a large retardation.

  For the purpose of suppressing the deterioration of the optical functional dye such as the iodine dye, the polyester film desirably has a light transmittance at a wavelength of 380 nm of 20% or less. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration of the optical functional dye due to ultraviolet light can be suppressed. 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).

  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 and concentration of the ultraviolet absorber and the thickness of the film. 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 a benzotriazole type, a benzophenone type, a cyclic imino ester type and the like, and a combination thereof, but are not particularly limited as long as the absorbance is within the range specified by the present invention. From the viewpoint of durability, benzotriazoles and cyclic iminoesters are particularly preferred. When two or more ultraviolet absorbers are used in combination, ultraviolet rays of different wavelengths can be simultaneously absorbed, so that the ultraviolet absorbing effect can be further improved.

  Examples of the benzophenone-based UV absorber, benzotriazole-based UV absorber, and acrylonitrile-based UV absorber include 2- [2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl] -2H-benzotriazole and 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'-me Tylphenyl) -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 the cyclic iminoester ultraviolet absorber include 2,2 ′-(1,4 -Phenylene) bis (4H-3,1-benzoxazinone-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, Examples include 2-phenyl-3,1-benzoxazin-4-one, but are not particularly limited thereto.

  It is also a preferable embodiment that various additives other than the catalyst are contained in addition to the ultraviolet absorber as long as the effects of the present invention are not impaired. As additives, for example, inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light stabilizers, flame retardants, heat stabilizers, antioxidants, anti-gelling agents And a surfactant. It is also preferable that the polyester film contains substantially no particles in order to exhibit high transparency. "Substantially not containing particles" means, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescent X-ray analysis, the content is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less. means.

It is preferable to provide an antireflection layer and / or a low reflection layer on at least one surface of the polyester film which is the polarizer protective film used in the present invention.
The reflectance of the polyester film on which 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 of the emission spectrum of the backlight light source is 2%. The following is preferred. The reflectivity is measured from the side where the antireflection layer and / or the low reflection layer are laminated. If the reflectance exceeds 2%, it is not preferable because rainbow-like color spots are easily recognized. The reflectance is more preferably 1.6% or less, further preferably 1.2% or less, and particularly preferably 1% or less. The lower limit of the reflectance is not particularly set, but is, for example, 0.01%. A reflectance of 0% is most preferred. When an antireflection layer is laminated, the upper limit of the reflectance is preferably less than 1%. When a low reflection layer is laminated, 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 measurement of the reflectance can be performed by a 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 を 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, the antireflection effect can be obtained by alternately forming two or more low-refractive-index layers and high-refractive-index layers and controlling the thickness of each layer as appropriate. If necessary, a hard coat layer may be laminated between the antireflection layers, and an antifouling layer may be formed on the hard coat layer.

  Other examples of the antireflection layer 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, and this structure converts a sudden and discontinuous refractive index change at the boundary with air into a continuous and gradually changing refractive index change. It allows you to change. Thus, by forming a moth-eye structure on the surface, light reflection on the surface of the film is reduced. For example, JP-T-2001-517319 can be referred to.

  As a method of forming an anti-reflection film, a dry coating method of forming an anti-reflection layer on a substrate surface by vapor deposition or sputtering, or an anti-reflection coating solution is applied to a substrate surface and dried to form an anti-reflection layer Examples include a wet coating method or a method using both of them. In the present invention, the composition of the antireflection layer and the method for forming the same are not particularly limited as long as the above characteristics are satisfied.

  As the low reflection layer, a conventionally known one can be used. For example, it is formed by a method of laminating at least one layer of a metal or oxide thin film by a vapor deposition method or a sputtering method, or a method of coating one or more organic thin films. As the low reflective layer, a polyester film or a layer coated with 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 further have an antiglare function. Thereby, the rainbow spot can be further suppressed. That is, a combination of an antireflection layer and an antiglare layer, a combination of a low reflection layer and an antiglare layer, and a combination of an antireflection layer, 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 or a low reflection layer is laminated after laminating an antiglare layer on a polyester film is preferable.

In the emission spectrum of the backlight light source, at one of the highest peak positions in the wavelength region of 600 nm or more and 780 nm or less, as one method for reducing the reflectance of the polyester film on which the antireflection layer and / or the low reflection layer are laminated, For example, designing the anti-reflection layer and the low-reflection layer so that the bottom wavelength of the reflection spectrum of the polyester film on which the anti-reflection layer and / or the low-reflection layer are laminated is in a wavelength region of 600 nm or more and 780 nm or less. .

  In order to set the bottom wavelength of the reflection spectrum of the antireflection layer and / or the low reflection layer to 600 nm or more and 780 nm or less, for example, when the antireflection layer or the low reflection layer is a single layer, the expression 2nd = λb / 4 is used. What is necessary is just to adjust the thickness of an antireflection layer and a low reflection layer so that it may be satisfied. 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 multilayered, 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 having a five-layer structure. The incident medium layer (in) is provided on the side opposite to the side of the first layer in contact with the second layer). In the case of an exit medium layer (out) on the side of the fifth layer opposite to the side in contact with the fourth layer), the refractive index is n, the reflectance is r, the thickness is Where d is the refraction angle, λ is the wavelength, and Δ is the phase difference, the reflectance of the lowermost layer (fifth layer) is expressed by the following equation from the equation of thin-film interference. Subscripts indicate each layer. Further, consecutive numbers attached to the reflectivity indicate the reflectivity between the respective 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, is calculated by the formula of [Expression 2].

θ _x is calculated by Expression 3 by continuously using Snell's law.

In general, when calculating the multilayer film reflection, the reflection can be calculated by adding the reflected lights from a plurality of boundary surfaces while taking the phases into consideration, so that the reflectance of each layer is obtained from the following equation.
(5th to 4th layers)

(5th to 3rd layer)

(5th layer to 2nd layer)

(5th to 1st layer)
The reflectivity of all five layers is obtained by the following equation.

  The sum of the subscripts of the reflectivity indicates the total reflectivity between the respective layers. By adjusting the refractive index n and the thickness d of each layer from the above equation, the bottom wavelength can be designed to a target wavelength.

  In the emission spectrum of the backlight light source, the peak wavelength λp of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less, and the bottom of the reflection spectrum of the polyester film on 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 more preferably 5 nm or less. In addition, the bottom wavelength of the reflection spectrum is a wavelength at which the reflectance becomes 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 its surface. At that 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 as to be near the geometric mean of the refractive index of the antireflection layer or the low reflection layer and the refractive index of the polyester film. A known method can be used to adjust the refractive index of the easy-adhesion layer. For example, the refractive index can be easily adjusted by adding titanium, germanium, or other metal species to the binder resin.

  The polyester film may be subjected to a corona treatment, a coating treatment, a flame treatment, or the like in order to improve the adhesion to 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 containing at least one of polyester resin, polyurethane resin and polyacryl resin as a main component. 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 liquid used for forming the easy-adhesion layer of the present invention is preferably an aqueous coating liquid containing at least one of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin and a polyurethane resin. These coating solutions include, for example, water-soluble or water-dispersible compounds disclosed in Japanese Patent No. 3,567,927, Japanese Patent No. 3,589,232, Japanese Patent No. 3,589,233, Japanese Patent No. 3,900,191, and Japanese Patent No. 4,150,982. Examples 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. It is preferable to control the final coating amount of the easy-adhesion layer to 0.05 to 0.2 g / m ² . When the coating amount is less than 0.05 g / m ² , the adhesiveness to the obtained polarizer may be insufficient. On the other hand, if the coating amount exceeds 0.2 g / m ² , the blocking resistance may decrease. When the easy-adhesion layers are provided on both surfaces of the polyester film, the application amounts of the easy-adhesion layers 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 lubricity. It is preferable to use particles having an average particle diameter 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. Examples of the particles contained in the easy-adhesion layer include, 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 two or more of them may be added in combination.

  In addition, as a method of applying the coating liquid, a known method can be used. For example, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, a spray coating method, an air knife coating method, a wire bar coating method, a pipe doctor method, and the like, and these methods are used alone. Alternatively, they can be performed in combination.

  The measurement of the average particle diameter of the above particles is performed by the following method. The particles are photographed 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 furthest points) Distance), and the average value is defined as the average particle size.

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

  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. Even though rainbow-like color spots are not seen, attention should be paid to the fact that rainbow-like color spots may be observed when obliquely observed.

When the film forming conditions of the polyester film are specifically described, the longitudinal stretching temperature and the transverse stretching temperature are preferably from 80 to 130 ° C, particularly preferably from 90 to 120 ° C. In order to orient the film so that the slow axis is in the TD direction, the longitudinal stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. Further, the transverse stretching 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 stretching ratio is preferably 2.5 times to 6.0 times, and particularly preferably 3.0 times to 5.5 times. Further, the transverse stretching ratio is preferably from 1.0 to 3.5 times, particularly preferably from 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 ranges, it is preferable to control the ratio between the longitudinal stretching ratio and the transverse stretching ratio. In order to increase the retardation, it is preferable to increase the difference between the vertical and horizontal stretch ratios. Also, setting the stretching temperature low is 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 250C, particularly preferably from 180 to 245C.

  In order to suppress the variation of the retardation in the film, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio greatly affect the thickness unevenness of the film, it is preferable to optimize the film forming conditions also from the viewpoint of the thickness unevenness. In particular, when the longitudinal stretching ratio is reduced to increase the retardation, the unevenness in the vertical thickness may be deteriorated. Since there is a region where the unevenness in the vertical thickness becomes extremely bad in a specific range of the stretching ratio, it is desirable to set the film forming conditions outside this range.

  The unevenness in thickness 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, the retardation of the polyester film can be controlled to a specific range by appropriately setting the stretching ratio, the stretching temperature, and the film thickness. For example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the easier it is to obtain high retardation. Conversely, the lower the draw ratio, the higher the draw temperature, and the thinner the film, the easier it is to obtain low retardation. However, when the thickness of the film is increased, the phase difference in the thickness direction tends to increase. Therefore, it is desirable to set the film thickness appropriately in the range described below. In addition to the control of the retardation, it is desirable to set the final film forming conditions in consideration of physical properties and the like required for processing.

  The thickness of the polyester film is arbitrary, but is preferably in the range of 15 to 300 μm, and more preferably in the range of 15 to 200 μm. In principle, it is possible to obtain a retardation of 1500 nm or more even with a film having a thickness of less than 15 μm. However, in this case, the anisotropy of the mechanical properties of the film becomes remarkable, so that the film is liable to be torn, torn or the like, and the practicality as an industrial material is significantly reduced. A particularly preferred 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 large, 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 that of a general TAC film. In order to control the retardation within the range of the present invention even in the above thickness range, polyethylene terephthalate is preferred as the polyester used as the film substrate.

  In addition, as a method of blending the UV absorber into the polyester film, a known method may be used in combination.For example, using a kneading extruder, the dried UV absorber and the polymer raw material are blended to form a master batch. It can be prepared and blended by a method of mixing the master batch and the polymer raw material at the time of film formation.

  At this time, the concentration of the ultraviolet absorber in the master batch is preferably 5 to 30% by mass in order to uniformly disperse the ultraviolet absorber and to mix it economically. It is preferable to use a kneading extruder as a condition for preparing a master batch, and to extrude at a temperature of from the melting point of the polyester raw material to 290 ° C. for 1 to 15 minutes. At 290 ° C. or higher, the amount of the ultraviolet absorber is greatly reduced, and the viscosity of the master batch is greatly reduced. If the extrusion temperature is 1 minute or less, it is difficult to uniformly mix the ultraviolet absorber. At this time, a stabilizer, a color tone adjusting agent, and an antistatic agent may be added as necessary.

  Further, it is preferable that the polyester film has a multilayer structure of at least three layers and an ultraviolet absorber is added to an intermediate layer of the film. The three-layer film including the ultraviolet absorbent in the intermediate layer can be specifically produced as follows. Polyester pellets alone for the outer layer, a master batch containing an ultraviolet absorber and polyester pellets for the intermediate layer are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder to form a slit. The sheet is extruded from a die into a sheet, and cooled and solidified on a casting roll to form 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, The three-layer sheet is extruded from a die and cooled with a casting roll to form an unstretched film. 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 filtration 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 filtration particle size of the filter medium exceeds 15 μm, the removal of foreign substances of 20 μm or more tends to be insufficient.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and the present invention is practiced with appropriate modifications within a range that is compatible with the gist of the present invention. And they are all included in the technical scope of the present invention. In addition, the evaluation method of the physical property in the following Examples is as follows.

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

(2) Retardation (Re)
The retardation is a parameter defined by a product (の Nxy × d) of anisotropy (△ Nxy = | Nx−Ny |) of a biaxial refractive index on a film and a film thickness d (nm). Yes, a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (△ Nxy) was determined by the following method. The slow axis direction of the film was determined using a molecular orientation meter (manufactured by Oji Scientific Instruments, MOA-6004 type molecular orientation meter), and 4 cm was set so that the slow axis direction was parallel to the long side of the sample for measurement. A rectangle of 2 cm was cut out and used as a measurement sample. For this sample, the Abbe refraction is the refractive index of two orthogonal axes (the refractive index in the slow axis direction: Ny, the refractive index in the direction orthogonal to the slow axis direction: Nx), and the refractive index (Nz) in the thickness direction. The absolute value of the biaxial refractive index difference (| Nx-Ny |) was determined as the anisotropy of the refractive index (屈折 Nxy) using a rate meter (NAR-4T, manufactured by Atago Co., Ltd., measurement wavelength: 589 nm). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Fineleuf Co.), and the unit was converted to nm. The retardation (Re) was determined from the product (ΔNxy × d) of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film.

(3) Thickness direction retardation (Rth)
Thickness direction retardation is defined by multiplying two birefringences △ Nxz (= | Nx-Nz |) and △ Nyz (= | Ny-Nz |) by the film thickness d when viewed from the cross section in the film thickness direction. It is a parameter indicating the average of the retardation obtained by the above. Nx, Ny, Nz and film thickness d (nm) are obtained in the same manner as in the measurement of the retardation, and the average value of (△ Nxz × d) and (△ Nyz × d) is calculated to obtain the retardation in the thickness direction (Rth ).

(4) NZ coefficient The values of Ny, Nx and Nz obtained in the above (1) were substituted into the equation: NZ = | Ny-Nz | / | Ny-Nx | to determine the NZ coefficient.

(5) Measurement of emission spectrum of backlight light source REGZA 43J10X manufactured by Toshiba Corporation was used as a liquid crystal display device used in each example. When the emission spectrum of the backlight light source (white light emitting diode) of this liquid crystal display device was measured using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics, emission spectra having peak tops near 450 nm, 535 nm and 630 nm were observed. Was done. The half width at the top of each peak (half width of the peak having the highest peak intensity in each wavelength region) was 17 nm for the 450 nm peak, 45 nm for the 535 nm peak, and 2 nm for the 630 nm peak. Note that 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 where the peak intensity was highest in this region. The exposure time at the time of spectrum measurement was 20 msec.

(6) Measurement of reflection spectrum (evaluation of reflectance)
A4 size cut out from the obtained polarizer protective film at an arbitrary position, after evenly scratching the substrate surface opposite to the surface on which the low reflection layer (or the antireflection layer) is laminated with water-resistant sandpaper, A sample was prepared by applying black magic ink (registered trademark) and further applying black tape (Nitto Denko vinyl tape No. 21 black) to eliminate reflection on the opposite surface of the low reflection layer (or antireflection layer). The reflection spectrum at 400 to 800 nm of the low reflection layer (or antireflection layer) of the produced sample was measured using a spectrophotometer UV-3150 manufactured by Shimadzu Corporation. The reflection spectrum measurement conditions were as follows: an Al-deposited mirror (part number 202-35988-05) attached as a standard to a specular reflection measurement device (manufactured by Shimadzu Corporation, part number 206-14064) was used as a reference mirror, and the total luminous flux was 5 °. Was performed with relative specular reflection at an incident angle of. In addition, the measurement was performed under the conditions of a sampling pitch of 1 nm and an opening size of the sample mask of 5 mmφ. (5) From the measurement result of the emission spectrum of the backlight light source, the peak top wavelength of the peak having the highest peak intensity in the wavelength region from 600 nm to 780 nm of the emission spectrum was 630 nm. Was determined. The bottom wavelength of the polarizer protective film 1 was also determined.

(Production Example 1-Polyester A)
When the temperature of the esterification reactor reached 200 ° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged, and while stirring, 0.017 parts by mass of antimony trioxide as a catalyst was added. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Subsequently, the temperature was increased under pressure to perform a pressure esterification reaction under the conditions of a gauge pressure of 0.34 MPa and 240 ° C. Then, the esterification reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Further, the temperature was raised to 260 ° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Next, after 15 minutes, a dispersion treatment was performed with a high-pressure disperser. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction vessel, and a polycondensation reaction was performed at 280 ° C. under reduced pressure.

  After the completion of the polycondensation reaction, the mixture is filtered through a NASLON filter having a 95% cut diameter of 5 μm, extruded from a nozzle into a strand, and cooled and solidified using cooling water that has been filtered (pore diameter: 1 μm or less) in advance. , And cut into pellets. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl / g, and substantially no inert particles or internally precipitated particles were contained. (Hereinafter abbreviated as PET (A))

(Production Example 2-Polyester B)
10 parts by mass of a dried ultraviolet absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinone-4-one) and PET (A) containing no particles (specifically 90 parts by mass (viscosity: 0.62 dl / g) were mixed and a kneading extruder was used to obtain a polyethylene terephthalate resin (B) containing an ultraviolet absorber (hereinafter abbreviated as PET (B)).

(Production Example 3-Preparation of Adhesion Modification Coating Solution)
A transesterification reaction and a polycondensation reaction are carried out by a conventional method, and as a dicarboxylic acid component, 46 mol% of terephthalic acid (46 mol% of isophthalic acid) and 8 mol% of sodium 5-sulfonatoisophthalate are used. A water-dispersible sulfonic acid metal base-containing copolymerized polyester resin having a composition of 50 mol% of ethylene glycol and 50 mol% of neopentyl glycol as a glycol component (based on the whole glycol component) was prepared. Next, after mixing 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant, the mixture was heated and stirred. After adding 5 parts by mass of the above water-dispersible sulfonic acid metal base-containing copolymerized polyester resin and continuing to stir until the resin no longer solidifies, the aqueous resin dispersion is cooled to room temperature, and the solid content concentration is 5.0% by mass. To obtain a uniform water-dispersible copolymerized polyester resin liquid. Further, after dispersing 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silysia K.K.) in 50 parts by mass of water, 99.46 parts by mass of the above water-dispersible copolymerized polyester resin solution was added to 99.46 parts by mass of thyricia 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 adhesion-modified coating solution.

(Production Example 4-Preparation of coating liquid 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 in a nitrogen atmosphere to obtain a solution of a polymer having a weight average molecular weight of 20,000 in methyl ethyl ketone. 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.

-Fluoropolymer solution C 44 parts by mass-1,10-bis (2,3-epoxypropoxy)
-2,2,3,3,4,4,5,5,6,6,7,7,
8,8,9,9-Hexadecafluorodecane (Kyoeisha Chemical, 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 low reflection layer coating solution)
As the vinylidene fluoride-based polymer particles, an aqueous dispersion (solid content concentration) of particles of vinylidene fluoride / tetrafluoroethylene / chlorotrifluoroethylene copolymer (= 72.1 / 14.9 / 13 (mol%)) (45.5 mass%) 571.4 g was placed in a 2 L glass separable flask, 37.1 g of Newcol 707SF (manufactured by Nippon Emulsifier Co., Ltd.) as an emulsifier and 59.3 g of water were added, and the mixture was thoroughly mixed. The dispersion was prepared.

  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 vinylidene fluoride / tetrafluoroethylene / chlorotrifluoroethylene copolymer particles over 3 hours. At the same time as the addition of the monomer solution, 41.1 g of 1% by mass of ammonium persulfate was added in seven portions every 30 minutes to carry out the polymerization. Five hours after the start of the polymerization, the reaction solution was cooled to room temperature to terminate the reaction, and 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 aqueous dispersion of acrylic-fluorine composite polymer particles, 61.47 parts by mass of water, 20.00 parts by mass of isopropyl alcohol, and 8.40 parts by mass of oxazoline crosslinking agent WS-700 (Nippon Shokubai Co., Ltd. Co., Ltd.), 1.75 parts by mass of colloidal silica particles Snowtex ST-ZL (manufactured by Nissan Chemical Industries, Ltd.), and 0.30 part by mass of a silicon surfactant were added and stirred to obtain a low reflection layer coating solution.

(Production Example 6-Preparation of coating liquid for low reflection layer)
As the vinylidene fluoride-based polymer particles, an aqueous dispersion (solid content concentration) of particles of vinylidene fluoride / tetrafluoroethylene / chlorotrifluoroethylene copolymer (= 72.1 / 14.9 / 13 (mol%)) (45.5% by mass) in a 2 L glass separable flask, 37.1 g of Newcol 707SF (manufactured by Nippon Emulsifier Co., Ltd.) as an emulsifier and 59.3 g of water were added, and the mixture was thoroughly mixed. The dispersion was prepared.

  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 vinylidene fluoride / tetrafluoroethylene / chlorotrifluoroethylene copolymer particles over 3 hours. At the same time as the addition of the monomer solution, 41.1 g of 1% by mass of ammonium persulfate was added in seven portions every 30 minutes to carry out the polymerization. Five hours after the start of the polymerization, the reaction solution was cooled to room temperature to terminate the reaction, and 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.

  12.12 parts by mass of the aqueous dispersion of acrylic-fluorine composite polymer particles, 61.47 parts by mass of water, 20.00 parts by mass of isopropyl alcohol, and 2.80 parts by mass of oxazoline crosslinking agent WS-700 (Nippon Shokubai Co., Ltd. Co., Ltd.), 1.75 parts by mass of colloidal silica particles Snowtex ST-ZL (manufactured by Nissan Chemical Industries, Ltd.), and 0.30 part 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 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) as raw materials for a base film intermediate layer, To the extruder 2 (for the intermediate layer II), and dried PET (A) by a conventional method, and then supplied to the extruder 1 (for the outer layer I and the outer layer III) to be melted at 285 ° C. . Each of these two types of polymers was filtered through a stainless sintered compact filter medium (nominal filtration accuracy: 10 μm, particles cut by 95%), laminated by a two-type three-layer merging block, extruded into a sheet from a die, and extruded. It was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and cooled and solidified to form 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.

Then, the unmodified PET film was coated with the adhesion-modified coating solution of Production Example 3 at a rate of 0.08 g / m ² on the side opposite to the surface on which the low-reflection layer is to be formed later by a reverse roll method. And dried at 80 ° C. for 20 seconds.

  The unstretched film having the coating layer formed thereon was guided to a tenter stretching machine, and while holding the end of the film with a clip, guided to a hot air zone at a temperature of 125 ° C. 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 PET film having a film thickness of about 100 μm.

  The coating liquid of Production Example 4 was applied to the coating surface of the PET film on which the low reflection layer was formed, and dried at 150 ° C. for 2 minutes to form a 0.1 μm-thick low reflection layer. 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%. Note that the bottom wavelength of the reflection spectrum was also 630 nm. Further, 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 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) as raw materials for a base film intermediate layer, To the extruder 2 (for the intermediate layer II), and dried PET (A) by a conventional method, and then supplied to the extruder 1 (for the outer layer I and the outer layer III) to be melted at 285 ° C. . Each of these two types of polymers was filtered through a stainless sintered compact filter medium (nominal filtration accuracy: 10 μm, particles cut by 95%), laminated by a two-type three-layer merging block, extruded into a sheet from a die, and extruded. It was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and cooled and solidified to form 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, a low-reflection layer was laminated on the side on which the low-reflection layer of the unstretched PET film was to be formed by a reverse roll method so that the coating amount after drying the coating solution of Production Example 5 was 0.09 g / m ² . After applying the adhesiveness-modified coating solution of Production Example 3 to the opposite side to 0.08 g / m ² , it was dried at 80 ° C. for 20 seconds.

  The unstretched film having the coating layer formed thereon was guided to a tenter stretching machine, and while holding the end of the film with a clip, guided to a hot air zone at a temperature of 125 ° C. and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the film is 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 polarizer protective film 2 having a film thickness of about 100 μm. Obtained.

The retardation (Re), the retardation in the thickness direction (Rth), the Re / Rth, and the 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 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) as raw materials for a base film intermediate layer, To the extruder 2 (for the intermediate layer II), and dried PET (A) by a conventional method, and then supplied to the extruder 1 (for the outer layer I and the outer layer III) to be melted at 285 ° C. . Each of these two types of polymers was filtered through a stainless sintered compact filter medium (nominal filtration accuracy: 10 μm, particles cut by 95%), laminated by a two-type three-layer merging block, extruded into a sheet from a die, and extruded. It was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and cooled and solidified to form 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-reflection layer was coated on the non-stretched PET film by the reverse roll method such that the coating amount after drying the low-reflection layer coating solution of Production Example 6 was 0.108 g / m ^2. Was applied on the side opposite to the surface on which the was laminated, so that the adhesion-modified coating solution of Production Example 3 was 0.080 g / m ^2, and dried at 80 ° C. for 20 seconds.

The unstretched film having the coating layer formed thereon was guided to a tenter stretching machine, and while holding the end of the film with a clip, guided to a hot air zone at a temperature of 125 ° C. and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the film is 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 polarizer protective film 3 having a film thickness of about 100 μm. Obtained.
In the polarizer protective film 3, the retardation (Re) was 10300 nm, the retardation (Rth) in the thickness direction was 12350 nm, the Re / Rth was 0.834, and the NZ coefficient was 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 made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (Fuji Film Co., Ltd.) And a thickness of 80 μm) were pasted to form a polarizing plate. A polarizer was formed by laminating a polarizer on the surface of the polarizer protective film on which the low reflection layer was not laminated.
A liquid crystal display device was prepared by replacing the polarizing plate on the viewing side of REGZA 43J10X manufactured by Toshiba with the polarizing plate prepared above so that the polyester film was on the opposite side (distal) to the liquid crystal. Note that the polarizing plate was replaced so that the direction of the transmission axis of the polarizing plate was the same as the direction of the transmission axis of the polarizing plate before replacement.

(Comparative Example 1)
A liquid crystal display device was prepared 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 prepared 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 had more rainbow spots than Comparative Example 1. The occurrence was suppressed. In Examples 1 and 2, the occurrence of rainbow spots was more suppressed in the liquid crystal display device of Example 1. The rainbow spot here is observed on the screen when the viewer observes the film from an oblique direction while moving his or her head (when observing while changing the angle from the normal direction of the film). It is a hazy rainbow spot.

  In all of Examples 1 and 2, and Comparative Example 1, the thickness of the polyester film was 100 μm, but this was changed to an 80 μm film (retardation (Re): 8080 nm, retardation (Rth) in the thickness direction: 9960 nm, Re / The liquid crystal display devices of Example 1 ′, Example 2 ′, and Comparative Example 1 ′ were manufactured by replacing Rth with 0.811 and the NZ coefficient with 1.733). In the liquid crystal display devices of 'and Example 2', the occurrence of rainbow spots was suppressed. In Example 1 'and Example 2', the iris was more suppressed in Example 1 '. Here, the rainbow spot is a mist-like shape observed on the screen when observing the film from an oblique direction while moving the head (when observing while changing the angle from the normal direction of the film). It is a rainbow spot.

  In Examples 1 and 2, and Comparative Example 1, the thickness of the polyester film was 100 μm, but the thickness of the polyester film was 60 μm (the retardation (Re) was 6060 nm, and the retardation (Rth) in the thickness direction 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. The occurrence of rainbow spots was more suppressed in the liquid crystal display devices of Example 1 '' and Example 2 '' than in ''. In Example 1 '' and Example 2 '', the iris was more suppressed in Example 1 ''. Here, the rainbow spot is a mist-like shape observed on the screen when observing the film from an oblique direction while moving the head (when observing while changing the angle from the normal direction of the film). It is a rainbow spot.

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

Claims (8)

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 light source has a peak top of an emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or less and less than 600 nm, and 600 nm or more and 780 nm or less, and has the highest peak intensity in a wavelength region of 600 nm or more and 780 nm or less. A white light emitting diode having an emission spectrum having a peak half width of less than 5 nm,
At least one of the polarizing plates is a polarizing plate in which a polyester film is laminated 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 anti-reflection layer and / or the low-reflection layer, measured from the side where the anti-reflection layer and / or the low-reflection layer is 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 light source,
A half-width of a peak having the highest peak intensity in a wavelength region of 400 nm or more and less than 495 nm is 5 nm or more;
A half-value width of a peak having the highest peak intensity in a 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 a highest peak intensity in the wavelength region of 600 nm to 780 nm is in a region of 620 nm to 640 nm. 4.   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 or more and 780 nm or less is 630 nm. 4. A polarizer protective film comprising a polyester film having a retardation of 1500 nm or more and 30000 nm or less, and 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 at any wavelength in the wavelength range of 600 nm or more and 780 nm or less as measured from the side where the antireflection layer and / or the low reflection layer is laminated.   The polarizer protective film according to claim 5, wherein any one of the wavelengths is in a range from 620 nm to 640 nm.   The polarizer protective film according to claim 5, wherein any one of the wavelengths is 630 nm.   A polarizing plate comprising the polarizer protective film according to any one of claims 5 to 7 laminated on at least one surface of the polarizer.