JP7160127B2 - Liquid crystal display device and polarizing plate - Google Patents

Description

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

A polarizing plate used in a liquid crystal display (LCD) generally has a structure in which a polarizer made of polyvinyl alcohol (PVA) dyed with iodine is sandwiched between two polarizer protective films. usually uses a triacetyl cellulose (TAC) film. In recent years, along with the thinning of LCDs, thinning of polarizing plates is required. However, if the thickness of the TAC film used as the protective film is reduced for this reason, there arises a problem that sufficient mechanical strength cannot be obtained and moisture permeability is deteriorated. In addition, TAC film is very expensive, and polyester film has been proposed as an inexpensive alternative material (Patent Documents 1 to 3), but there is a problem of rainbow-like color spots.

When an oriented polyester film having birefringence is arranged on one side of the polarizer, the polarization state of the linearly polarized light emitted from the backlight unit or the polarizer changes when passing through the polyester film. The transmitted light exhibits an interference color characteristic of the retardation, which is the product of the birefringence and thickness of the oriented polyester film. Therefore, when a discontinuous emission spectrum such as a cold-cathode tube or a hot-cathode tube is used as a light source, the intensity of transmitted light varies depending on the wavelength, resulting in rainbow-like color spots. 30-31).

As a means for solving the above problems, it is possible to use a white light source having a continuous and broad emission spectrum such as a white light emitting diode as a backlight source, and 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 that has passed through the birefringent material, by controlling the retardation of the oriented polyester film, a spectrum similar to the emission spectrum of the light source can be obtained, and the rainbow spots can be suppressed. It is proposed that it is possible.

In addition, by making the orientation direction of the oriented polyester film and the polarization direction of the polarizing plate orthogonal or parallel, the linearly polarized light emitted from the polarizer passes through the oriented polyester film while maintaining its polarization state. become. In addition, by controlling the birefringence of the oriented polyester film to enhance the uniaxial orientation, even light incident from an oblique direction can pass through while maintaining the polarization state. When an oriented polyester film is viewed obliquely, deviation occurs in the direction of the principal axis of orientation compared to when viewed from directly above. For this reason, it is considered that the deviation between the direction of linearly polarized light and the direction of the orientation main axis is reduced, and the change in polarization state is less likely to occur. In this way, by controlling the emission spectrum of the light source, the orientation state of the birefringent material, and the orientation principal axis direction, the change in the polarization state is suppressed, the rainbow-like color spots do not occur, and the visibility is significantly improved. It was thought that

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

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

When industrially producing a liquid crystal display 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 so as to be perpendicular to each other. be done. This is because the polyvinyl alcohol film that is the polarizer is manufactured by longitudinal uniaxial stretching, while the polyester film that is the protective film is manufactured by longitudinally stretching and then laterally stretching. This is because the main axis direction is the horizontal direction, and when a polarizing plate is produced by laminating these elongated objects, the fast axis of the polyester film and the transmission axis of the polarizer are usually perpendicular to each other. In this case, an oriented polyester film having a specific retardation is used as the polyester film, and the backlight source is represented by, for example, a white LED composed of a light-emitting element combining a blue light-emitting diode and an yttrium-aluminum-garnet-based yellow phosphor. , By using a light source having a continuous and broad emission spectrum, the rainbow-like color spots are greatly improved, but 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). We have discovered that when using a backlight source consisting of a white light emitting diode with a spectrum, there is still a new problem of iridescence.

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

A typical present invention is as follows.
Section 1.
A liquid crystal display device comprising a backlight source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,
The backlight source has a peak top of the emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 780 nm or less, and has the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less. A white light emitting diode having an emission spectrum with a peak half width of less than 5 nm,
At least one of the polarizing plates has a polyester film laminated on at least one surface of a polarizer,
The polyester film has a retardation of 1500 to 30000 nm,
An antireflection layer and / or a low reflection layer is laminated on at least one surface of the polyester film,
Liquid crystal display.
Section 2.
The emission spectrum of the backlight light source is
The half width of the peak with the highest peak intensity in the wavelength region of 400 nm or more and less than 495 nm is 5 nm or more,
The half width of the peak with the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm is 5 nm or more.
Item 1. 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 antireflection layer surface has a surface reflectance of 2.0% or less at a wavelength of 550 nm.
Section 4.
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 to 30000 nm, and an antireflection layer and / or a low reflection layer is laminated on at least one surface of the polyester film.
The emission spectrum has a peak top in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 780 nm or less, and 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 is 5 nm. A polarizing plate for a liquid crystal display device having a backlight source comprising a white light emitting diode having an emission spectrum of less than
Item 5.
Item 5. The polarizing plate according to Item 4, wherein the antireflection layer surface has a surface reflectance of 2.0% or less at a wavelength of 550 nm.

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

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

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

In addition to the backlight source, polarizing plate, and liquid crystal cell, the liquid crystal display device may appropriately have other components such as a color filter, lens film, diffusion sheet, antireflection film, and the like. A brightness enhancement film may be provided between the light source side polarizing plate and the backlight source. Examples of the brightness enhancement film include a reflective polarizing plate that transmits one linear polarized light and reflects the orthogonal linear polarized light. As the reflective polarizing plate, for example, brightness enhancement films of the DBEF (registered trademark) (Dual Brightness Enhancement Film) series manufactured by Sumitomo 3M Co., Ltd. are preferably used. Incidentally, the reflective polarizing plate is usually arranged so that the absorption axis of the reflective polarizing plate and the absorption axis of the light source side polarizing plate are parallel to each other.

Of the two polarizing plates placed in the liquid crystal display device, at least one of the polarizing plates is a polarizer in which polyvinyl alcohol (PVA) or the like is dyed with iodine, and a polyester film is laminated on at least one surface of the polarizer. is. In the present invention, from the viewpoint of suppressing rainbow-like color spots, the polyester film has a specific retardation, and an antireflection layer and / or a low reflection layer is laminated on at least one surface of the polyester film. be. 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. It doesn't matter if it's both. Preferably, an antireflection layer and/or a low reflection layer is provided on the surface of the polyester film opposite to the surface on which the polarizer is laminated. When the antireflection layer and/or the low-reflection layer are provided on the surface of the polyester film on which the polarizer is laminated, the antireflection layer and/or the low-reflection layer are preferably provided between the polyester film and the polarizer. In addition, other layers (e.g., easy adhesion layer, hard coat layer, antiglare layer, antistatic layer, antifouling layer, etc.) are present between the antireflection layer and/or low reflection layer and the polyester film. may From the viewpoint of further suppressing rainbow-like color spots, the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is preferably 1.53 to 1.62. On the other surface of the polarizer, it is preferable to laminate a non-birefringent film such as a TAC film, an acrylic film, or a norbornene film (a polarizing plate having a three-layer structure). There is no need to laminate a film on the other side (two-layer polarizer). When polyester films are used as protective films on both sides of the polarizer, the slow axes of both polyester films are preferably substantially parallel to each other.

Any polarizer (polarizing film) used in the art can be appropriately selected and used as the polarizer. Typical polarizers include those obtained by dyeing a polyvinyl alcohol film or the like with a dichroic material such as iodine. can be appropriately selected and used.

Commercially available PVA films can be used. (manufacturer)], etc. Examples of dichroic materials include iodine, diazo compounds, and polymethine dyes.

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

The structure of the backlight may be of an edge light system or a direct type system, in which a light guide plate, a reflector, etc. are used as constituent members. 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 780 nm or less have peak tops of the emission spectrum in each wavelength region, 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 source consisting of white light emitting diodes with an emission spectrum that is less than 5 nm is preferred.
It is known that the peak wavelengths of blue, green, and red defined in the CIE chromaticity diagram are 435.8 nm (blue), 546.1 nm (green), and 700 nm (red), respectively. The wavelength regions of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm correspond to the blue region, the green region, and the red region, respectively.
The upper limit of the half width 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. A peak half width of less than 5 nm is preferable because the color gamut of the liquid crystal display device is widened. Moreover, when the half width of the peak is less than 1 nm, the luminous efficiency may deteriorate. The shape of the emission spectrum is designed from the balance between the required color gamut and luminous efficiency. Here, the half-value width is the peak width (nm) at half the intensity of the peak intensity at the wavelength of the peak top.

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

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

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

A specific example of the white light source having the emission spectrum having the characteristics described above is a phosphor type white light emitting diode in which a blue light emitting diode and a phosphor are combined. Examples of the red phosphor among the phosphors include a fluoride phosphor (also referred to as “KSF”) having a composition formula of K ₂ SiF ₆ :Mn ⁴⁺ and others. The Mn ⁴⁺ -activated fluoride complex phosphor is a phosphor containing Mn ⁴⁺ as an activator and a fluoride complex salt of an alkali metal, an amine or an alkaline earth metal as a base crystal. Fluoride complexes forming host crystals include those with coordination centers of trivalent metals (B, Al, Ga, In, Y, Sc, lanthanide), tetravalent metals (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, At least one selected from Sn, Ti, and Zr), E[MF ₆ ]: Mn (E is at least one selected from Mg, Ca, Sr, Ba, and Zn; M is selected from Ge, Si, Sn, Ti, and Zr. _Ba0.65 , _Zr0.35F2.70 :Mn _{, A3} [ _ZrF7 ]:Mn ₍ A is one or more selected from Li, Na, K, Rb, Cs, and NH4) , A ₂ [MF ₅ ]: Mn (A is at least one selected from Li, Na, K, Rb, Cs and NH ₄ ; M is at least one selected from Al, Ga and In), A ₃ [MF ₆ ] : Mn (A is at least one selected from Li, Na, K, Rb, Cs and NH4 _; M is at least one selected from Al, Ga and _In ), Zn2[ _MF7 ]:Mn (M is Al, one or more selected from Ga and _In ), A[ _In2F7 ]:Mn ₍ A is one or more selected from Li, Na, K, Rb, Cs and NH4), and the like.

One of the preferable Mn ⁴⁺ -activated fluoride complex phosphors is A ₂ MF ₆ :Mn (A is selected from Li, Na, K, Rb, Cs, NH ₄ one or more; M is one or more selected from Ge, Si, Sn, Ti and Zr). Among them, A is one or more selected from K (potassium) or 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 activating element is desirably 100% Mn (manganese), but Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, Al, Ga, B, In, Cr, Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn, Mg, etc. may be included. When M is Si, the proportion of Mn in the sum of Si and Mn is preferably in the range of 0.5 mol % to 10 mol %. Another preferred Mn ⁴⁺ -activated fluoride complex phosphor has the chemical formula A _2+x M _y Mn _z F _n (A is Na and K; M is Si and Al; −1≦x≦1 and 0.9≦y+z≦1 .1 and 0.001≤z≤0.4 and 5≤n≤7).

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

Among the above-described phosphors, the green phosphor may be, for example, a sialon-based phosphor having a basic composition of β-SiAlON:Eu or the like, a silicate-based phosphor having a basic composition of (Ba, Sr) ₂ SiO ₄ :Eu or the like. , and others.

If there are multiple peaks in any one of the wavelength range of 400 nm or more and less than 495 nm, the wavelength range of 495 nm or more and less than 600 nm, or the wavelength range of 600 nm or more and 780 nm or less, consider the following.
When the plurality of peaks are independent peaks, the half width of the peak with the highest peak intensity is preferably within the above range. Furthermore, in a more preferred embodiment, other peaks having an intensity of 70% or more of the highest peak intensity also have half-value widths within the above range.
For one independent peak having a shape in which multiple peaks overlap, if the half-value width of the peak with the highest peak intensity among the plurality of peaks can be measured as it is, that half-value width is used. Here, an independent peak has an intensity region of 1/2 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 of intensity equal to 1/2 of the peak intensity on both sides, the plurality of peaks as a whole is regarded as one peak. For one peak having such a shape in which a plurality of peaks are overlapped, the width (nm) of the peak at half the intensity of the highest peak intensity among them is defined as the half width.
A peak having the highest peak intensity among the plurality of peaks is defined as a peak top.
The peaks 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 are independent of the peaks in other wavelength regions. It is preferable to have a close relationship. In particular, in the wavelength region between the peak with the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm and the peak with the highest peak intensity in the region of 600 nm or more and 780 nm or less, there is a wavelength of 600 nm or more and 780 nm or less. From the standpoint of vividness of color, it is preferable that there is a region in which the peak intensity is ⅓ or less of the peak intensity of the highest peak in the region.

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

As a result of intensive studies by the present inventors, like the backlight light source described above, in each wavelength region of the blue region (400 nm or more and less than 495 nm), the green region (495 nm or more and less than 600 nm), and the red region (600 nm or more and 780 nm or less) As a polarizer protective film in a liquid crystal display device having a backlight source composed of white light emitting diodes each having a peak top of an emission spectrum and having a relatively narrow peak half width of less than 5 nm in the red region (600 nm or more and 780 nm or less). The present inventors have found that a liquid crystal display device and a polarizing plate in which iridescence is suppressed can be provided by using a polyester film having an antireflection layer and/or a low reflection layer and having a specific retardation. The mechanism by which the above-described mode suppresses the occurrence of rainbow-like color spots is thought to be as follows.

When the oriented polyester film is placed on one side of the polarizer, the polarization state of the linearly polarized light emitted from the backlight unit or the polarizer changes when passing through the polyester film. One of the factors that change the polarization state may be the difference in refractive index at the interface between the air layer and the oriented polyester film or the difference in refractive index at the interface between the polarizer and the oriented polyester film. When the linearly polarized light incident on the oriented polyester film passes through each interface, part of the light is reflected due to the refractive index difference between the interfaces. At this time, the polarization states of both the emitted light and the reflected light change, and this is considered to be one of the factors causing the rainbow-like color spots. Therefore, by providing an antireflection layer or a low-reflection layer on the surface of the oriented polyester film to reduce the surface reflection, the reflection at the interface between the air layer and the oriented polyester film is suppressed, resulting in rainbow-like color spots. considered to be suppressed.

As described above, in the present invention, each wavelength region of the blue region (400 nm or more and less than 495 nm), the green region (495 nm or more and less than 600 nm) and the red region (600 nm or more and 780 nm or less) has a peak top of the emission spectrum. In a liquid crystal display device having a backlight source composed of white light emitting diodes with a relatively narrow peak half width of less than 5 nm in the region (600 nm or more and 780 nm or less), a polarizing plate using a polyester film as a polarizer protective film may be used. , it is possible to have good visibility without generating rainbow-like color spots.

The polarizing plate preferably has a polarizer protective film made of a polyester film laminated on at least one surface of the polarizer. The polyester film used for the polarizer protective film preferably has a retardation of 1500-30000 nm. If the retardation is within the above range, the iridescence tends to be more easily reduced, which is preferable. A preferable lower limit of retardation is 3000 nm, a second preferable lower limit is 3500 nm, a more preferable lower limit is 4000 nm, a still more preferable lower limit is 6000 nm, and an even more preferable lower limit is 8000 nm. A preferable upper limit is 30000 nm, and a polyester film having a retardation of 30000 nm or more has a considerably large thickness, and tends to deteriorate in handleability as an industrial material. In this document, retardation means in-plane retardation unless otherwise indicated.

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

The ratio (Re/Rth) of the retardation (Re: in-plane retardation) to the thickness direction retardation (Rth) of the polyester film is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.5. 6 or more. As the ratio of the retardation to the thickness direction retardation (Re/Rth) increases, the birefringence action becomes more isotropic, and rainbow-like color spots tend to be less likely to occur depending on the viewing angle. Since the ratio of the retardation to the thickness direction retardation (Re/Rth) is 2.0 in a perfect uniaxial (uniaxially symmetric) film, the ratio of the retardation to the thickness direction retardation (Re/Rth) The upper limit is preferably 2.0. The thickness direction retardation means the average retardation obtained by multiplying the two birefringences ΔNxz and ΔNyz when the film is viewed from the thickness direction section by the film thickness d.

From the viewpoint of further 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 1.8 or less. 6 or less. Since the NZ coefficient is 1.0 in a perfectly uniaxial (uniaxially symmetrical) film, 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 decrease significantly as the film approaches a perfect uniaxial (uniaxially symmetrical) 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). index), and Nz represents 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 Keisoku Co., Ltd.), and the biaxial refractive indices (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., measuring wavelength 589 nm). The NZ coefficient can be obtained by substituting the value obtained in this way for |Ny-Nz|/|Ny-Nx|.

In addition, from the viewpoint of suppressing rainbow-like color spots, the Ny-Nx value of the polyester film is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.08 or more, and even more preferably. is greater than or equal to 0.09, most preferably greater than or equal to 0.1. The upper limit is not particularly defined, but in the case of polyethylene terephthalate film, the upper limit is preferably about 1.5.

In a more preferred embodiment of the present invention, the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer constituting the polarizing plate is preferably in the range of 1.53 or more and 1.62 or less. This makes it possible to suppress reflection at the interface between the polarizer and the polyester film, and to further suppress rainbow-like color spots. If the refractive index exceeds 1.62, rainbow-like color spots may occur when observed from an oblique direction. The refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is preferably 1.61 or less, more preferably 1.60 or less, still more preferably 1.59 or less, and still more preferably is less than or equal to 1.58.

On the other hand, the lower limit of the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is 1.53. If the refractive index is less than 1.53, the crystallization of the polyester film becomes insufficient, and properties obtained by stretching such as dimensional stability, mechanical strength and chemical resistance become insufficient, which is not preferable. The refractive index is preferably 1.56 or higher, more preferably 1.57 or higher. Any range combining each upper limit and each lower limit of the refractive index noted above is envisioned.

In order to set the refractive index of the polyester film in the range of 1.53 or more and 1.62 or less in the direction parallel to the transmission axis direction of the polarizer, the polarizer has the transmission axis of the polarizer and the fast axis of the polyester film. (the direction perpendicular to the slow axis) is preferably substantially parallel. The polyester film can be adjusted to have a low refractive index of about 1.53 to 1.62 in the fast axis direction, which is the direction perpendicular to the slow axis, by stretching in the film-forming process described later. By making the fast axis direction of the polyester film substantially parallel to the transmission axis direction of the polarizer, the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is set to 1.53 to 1.62. can be done. Here, substantially parallel means that the angle formed by the transmission axis of the polarizer and the fast axis of the polarizer protective film (polyester film) is -15° to 15°, preferably -10° to 10°, more It means preferably -5° to 5°, more preferably -3° to 3°, even more preferably -2° to 2°, still more preferably -1° to 1°. In one preferred embodiment, substantially parallel is substantially parallel. Here, "substantially parallel" means that the transmission axis of the polarizer and the fast axis of the polyester film are parallel to the extent that deviations that inevitably occur when bonding the polarizer and the protective film are allowed. means The direction of the slow axis can be obtained by measuring with a molecular orientation meter (for example, MOA-6004 type molecular orientation meter manufactured by Oji Instruments Co., Ltd.).

That is, the refractive index in the fast axis direction of the polyester film is preferably 1.53 or more and 1.62 or less. The polyester film can have a refractive index of 1.53 or more and 1.62 or less in a direction parallel to the transmission axis of the element.

The polarizer protective film made of the polyester film can be used for both the polarizing plate on the incident light side (light source side) and the emitted light side (viewing side), but at least the polarizing plate on the emitting light side (viewing side) can be used. It is preferably used for protective films.
Regarding the polarizing plate placed on the light output side, the polarizer protective film made of the polyester film is placed on both sides of the polarizer whether it is placed on the liquid crystal cell side or on the light output side. Although it may be arranged, it is preferably arranged at least on the output light side.
Even in the polarizing plate arranged on the incident light side, the polarizer protective film made of the polyester film is placed on the incident light side with the polarizer as the starting point, or on the liquid crystal cell side. However, it is preferable that it is arranged at least on the incident light side. Moreover, the polarizing plate disposed on the incident light side may not use a polarizer protective film made of a polyester film, but may use a polarizer protective film having a low retardation such as a triacetyl cellulose film.

Polyethylene terephthalate and polyethylene naphthalate can be used as the polyester used for the polyester film, but other copolymer components may be included. These resins are excellent in transparency as well as in thermal and mechanical properties, and their retardation can be easily controlled by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence, and by stretching the film, the refractive index in the fast axis direction (perpendicular to the slow axis direction) can be kept low. It is the most suitable material because a large retardation can be obtained at .

For the purpose of suppressing deterioration of optically functional dyes such as iodine dyes, the polyester film preferably has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at 380 nm is more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. If the light transmittance is 20% or less, deterioration of the optical functional dye due to ultraviolet rays can be suppressed. The transmittance is measured perpendicularly to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500).

In order to set 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 absorbent and the thickness of the film. The ultraviolet absorbers used in the present invention are known substances. Examples of the UV absorber include organic UV absorbers and inorganic UV absorbers, but organic UV absorbers are preferred from the viewpoint of transparency. Examples of organic UV absorbers include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and combinations thereof, but are not particularly limited as long as the absorbance is within the range defined by the present invention. However, from the viewpoint of durability, benzotriazole-based and cyclic iminoester-based agents are particularly preferred. When two or more ultraviolet absorbers are used in combination, ultraviolet rays of different wavelengths can be absorbed at the same time, so that the ultraviolet absorption effect can be further improved.

Examples of benzophenone UV absorbers, benzotriazole UV absorbers, and acrylonitrile UV absorbers include 2-[2'-hydroxy-5'-(methacryloyloxymethyl)phenyl]-2H-benzotriazole, 2-[2' -hydroxy-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxypropyl)phenyl]-2H-benzotriazole, 2,2'-dihydroxy- 4,4′-dimethoxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophenone, 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-( 2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole, 2-(5-chloro(2H)-benzotriazol-2-yl)-4-methyl-6-( tert-butyl)phenol, 2,2′-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol, etc. Cyclic iminoesters Examples of UV absorbers include 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one), 2-methyl-3,1-benzoxazin-4-one, Examples include 2-butyl-3,1-benzoxazin-4-one, 2-phenyl-3,1-benzoxazin-4-one, etc. However, it is not particularly limited to these.

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

It is preferable to provide an antireflection layer and/or a low reflection layer on at least one surface of the polyester film which is the polarizer protective film used in the present invention. The surface reflectance of the antireflection layer used in the present invention is preferably 2.0% or less. If it exceeds 2.0%, rainbow-like color spots are likely to be visually recognized. The surface reflectance of the antireflection layer is more preferably 1.6% or less, still more preferably 1.2% or less, and particularly preferably 1.0% or less. Although the lower limit of the surface reflectance of the antireflection layer is not particularly limited, it is, for example, 0.01%. A reflectance of 0% is most preferred. The reflectance can be measured by any method. For example, a spectrophotometer (Shimadzu Corporation, UV-3150) can be used to measure the light reflectance at a wavelength of 550 nm from the antireflection layer side surface.

The antireflection layer may be a single layer or multiple layers, and 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 the plastic film (polyester film) is 1/ of the light wavelength. An anti-reflection effect can be obtained by forming it so as to have four wavelengths or an odd multiple thereof. When the antireflection layer is multi-layered, an antireflection effect can be obtained by alternately forming two or more layers of a low refractive index layer and a high refractive index layer and appropriately controlling the thickness of each layer. Further, if necessary, a hard coat layer can be laminated between the antireflection layers, and an antifouling layer can be formed on the hard coat layer.

Other antireflection layers include those using a moth-eye structure. A moth-eye structure is an uneven structure with a pitch smaller than the wavelength formed on the surface. make it possible to change. Therefore, by forming a moth-eye structure on the surface, light reflection on the surface of the film is reduced. Formation of an antireflection layer using a moth-eye structure can be performed, for example, with reference to Japanese Patent Publication No. 2001-517319.

Methods for forming an antireflection film include, for example, a dry coating method in which an antireflection layer is formed on the substrate (polyester film) surface by vapor deposition or sputtering, and an antireflection coating liquid applied to the substrate surface and dried. A wet coating method for forming an antireflection layer, or a combined method using both of them can be mentioned. The composition and formation method of the antireflection layer are not particularly limited as long as the above characteristics are satisfied.

A known low-reflection layer can be used. For example, it is formed by a method of laminating at least one layer of metal or oxide thin films by vapor deposition or sputtering, or a method of coating one or more layers of organic thin films. As the low-reflection layer, one coated with an organic thin film having a refractive index lower than that of a polyester film or a hard coat layer laminated on a polyester film is preferably used. The surface reflectance of the low-reflection layer is preferably less than 5%, more preferably 4% or less, still more preferably 3% or less, still more preferably 2% or less. Although the lower limit is not particularly limited, it is preferably about 0.8% to 1.0%.

The antireflection layer and/or the low reflection layer may further have an antiglare function. Thereby, iridescence can be further suppressed. That is, it may be a combination of an antireflection layer and an antiglare layer, a combination of a low reflection layer and an antiglare layer, or a combination of an antireflection layer, a low reflection layer and an antiglare layer. Particularly preferred is a combination of a low reflection layer and an antiglare layer. A known antiglare layer can be used as the antiglare layer. For example, from the viewpoint of suppressing the surface reflection of the film, it is preferable to laminate an antireflection layer or a low-reflection layer on the antiglare layer after laminating the antiglare layer on the polyester film.

When providing an antireflection layer or a low-reflection layer, 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 close to the geometric mean of the refractive index of the antireflection layer and the refractive index of the polyester film. The adjustment of the refractive index of the easy-adhesion layer can employ a known method, and can be easily adjusted, for example, by adding titanium, germanium, or other metal species to the binder resin.

The polyester film may be subjected to corona treatment, coating treatment, flame treatment, or the like in order to improve adhesion to the 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 or polyacrylic resin as a main component. is preferred. Here, the "main component" refers to a component that accounts for 50% by mass or more of the solid components that constitute the easy-adhesion layer. The coating liquid used for forming the easy-adhesion layer is preferably an aqueous coating liquid containing at least one of water-soluble or water-dispersible copolyester resins, acrylic resins and polyurethane resins. Examples of these coating liquids include water-soluble or water-dispersible coating liquids disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191 and Japanese Patent No. 4150982. A polymerized polyester resin solution, an acrylic resin solution, a polyurethane resin solution and the like can be used.

The easy-adhesion layer can be obtained by applying the above-described coating liquid to one or both sides of a uniaxially stretched film in the longitudinal direction, drying it at 100 to 150° C., and stretching it in the transverse direction. It is preferable to control the final coating amount of the easy-adhesion layer to 0.05 to 0.20 g/m ² . If the coating amount is less than 0.05 g/m ² , the adhesion to the resulting polarizer may be insufficient. On the other hand, if the coating amount exceeds 0.20 g/m ² , blocking resistance may deteriorate. When the easy-adhesion layer is provided on both sides of the polyester film, the coating amount of the easy-adhesion layer on both sides may be the same or different, and can be independently set within the above range.

Particles are preferably added to the easy-adhesion layer to impart lubricity. It is preferable to use particles having an average particle size of 2 μm or less. When the average particle size of the particles exceeds 2 μm, the particles tend to fall off from the coating layer. 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 particles. These may be added to the easy-adhesion layer singly, or two or more of them may be added in combination.

Moreover, a well-known method can be used as a method of apply|coating a coating liquid. For example, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, etc., and these methods can be used alone. Or it can be performed in combination.

In addition, the measurement of the average particle size of the above particles is performed by the following method. The particles are photographed with a scanning electron microscope (SEM) and the largest diameter of 300-500 particles (between the two furthest Distance) is measured, and the average value is taken as the average particle size.

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

The polyester film used in the present invention may be a uniaxially stretched film or a biaxially stretched film, but when a biaxially stretched film is used as a polarizer protective film, the film is observed from directly above the film surface. Although rainbow-like color spots are not observed even when observed from an oblique direction, it is necessary to pay attention to the fact that rainbow-like color spots may be observed in some cases.

Specifically, the film-forming conditions for the polyester film are preferably 80 to 130°C for the longitudinal stretching temperature and the transverse stretching temperature, and particularly preferably 90 to 120°C. In order to orient the film so that the slow axis is in the TD direction, the longitudinal draw ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. Further, the transverse draw ratio is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times. In order to orient the film so that the slow axis is in the MD direction, the longitudinal draw ratio is preferably 2.5 to 6.0, more preferably 3.0 to 5.5. Further, the transverse draw ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times.
In order to control the refractive index and retardation in the fast axis direction of the polyester film within the above ranges, it is preferable to control the ratio between the longitudinal draw ratio and the transverse draw ratio. If the difference between the longitudinal and transverse draw ratios is too small, the refractive index in the fast axis direction of the polyester film tends to exceed 1.62, and it is difficult to increase the retardation, which is not preferable. Setting the stretching temperature low is also a preferable measure for lowering the refractive index in the fast axis direction of the polyester film and increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably 100-250°C, particularly preferably 180-245°C.

In order to suppress variations in retardation, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio have a great effect on the thickness unevenness of the film, it is preferable to optimize the film-forming conditions from the viewpoint of reducing the thickness unevenness. In particular, if the longitudinal draw ratio is lowered in order to increase the retardation, longitudinal thickness unevenness may increase. Since there is a region in which the thickness unevenness in the machine direction becomes extremely poor within a certain range of the draw ratio, it is desirable to set the film-forming conditions outside this range.

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

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

Although the thickness of the polyester film is arbitrary, it is preferably in the range of 15 to 300 μm, 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 conspicuous, and the film is likely to tear, tear, etc., and the practicality as an industrial material is remarkably lowered. A particularly preferable lower limit of the thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. A particularly preferable upper limit of the thickness is 100 μm, which is equivalent to that of a general TAC film. In order to control the retardation within the range of the present invention even within the above thickness range, polyethylene terephthalate is suitable as the polyester used as the film substrate.

In addition, as a method for blending the ultraviolet absorber with the polyester film, a combination of known methods can be employed. For example, a masterbatch is prepared by blending the dried ultraviolet absorber and the polymer raw material using a kneading extruder in advance. It can be blended by, for example, a method of mixing the predetermined masterbatch and the polymer raw material at the time of film formation after preparation.

At this time, the concentration of the UV absorber in the masterbatch is preferably 5 to 30% by weight in order to uniformly disperse the UV absorber and to blend it economically. As conditions for preparing the masterbatch, a kneading extruder is preferably used, and the extrusion temperature is preferably the melting point of the polyester raw material or higher and 290° C. or lower for 1 to 15 minutes. At 290° C. or higher, the weight loss of the ultraviolet absorber is large, and the viscosity of the masterbatch is greatly lowered. If the extrusion time is less than 1 minute, it becomes 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.

Moreover, it is preferable that the polyester film has a multi-layered structure of at least three layers, and an ultraviolet absorber is added to the intermediate layer of the film. Specifically, a three-layer film containing an ultraviolet absorber in the intermediate layer can be produced as follows. For the outer layer, polyester pellets alone, and for the intermediate layer, a masterbatch containing an ultraviolet absorber and polyester pellets are mixed in a predetermined ratio, dried, then supplied to a known melt lamination extruder, and slit-shaped. A sheet is extruded through a die 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 confluence block (for example, a confluence block having a square confluence portion), the film layers constituting both outer layers and the film layers constituting the intermediate layer are laminated, A three-layer sheet is extruded through a die and cooled on casting rolls to form an unstretched film. In addition, in order to remove foreign matter contained in the raw material polyester, which causes optical defects, it is preferable to perform high-precision filtration at the time of melt extrusion. The filtration particle size (initial filtration efficiency of 95%) of the filter medium used for high-precision filtration of molten resin is preferably 15 μm or less. If the filtration particle size of the filter medium exceeds 15 μm, the removal of foreign matter with a size of 20 μm or more tends to be insufficient.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by the following examples, and can be carried out with appropriate modifications within the scope of the gist of the present invention. Both of them are included in the technical scope of the present invention. Methods for evaluating physical properties in the following examples are as follows.

(1) Refractive index of polyester film A molecular orienter (MOA-6004 type molecular orienter manufactured by Oji Keisoku Co., Ltd.) is used to determine the slow axis direction of the film, and the slow axis direction is parallel to the long side. A rectangle of 4 cm x 2 cm was cut out so as to form a sample for measurement. For this sample, the refractive index in the orthogonal biaxial direction (refractive index in the slow axis direction: Ny, fast axis (refractive index in the direction perpendicular to the slow axis direction): Nx) and the refractive index in the thickness direction ( Nz) was determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., measuring wavelength 589 nm).

(2) Retardation (Re)
Retardation is a parameter defined by the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy=|Nx−Ny|) on the film and the film thickness d (nm). It is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), the slow axis direction of the film was determined, and the slow axis direction was 4 cm so that it was parallel to the long side of the sample for measurement. A 2 cm x 2 cm rectangle was cut out and used as a measurement sample. For this sample, the refractive index in the biaxial direction perpendicular to each other (refractive index in the slow axis direction: Ny, refractive index in the direction perpendicular to the slow axis direction: Nx) and the refractive index in the thickness direction (Nz) were measured by the Abbe refractor. The absolute value of the biaxial refractive index difference (|Nx−Ny|) was defined as the anisotropy of the refractive index (ΔNxy) by using an index meter (NAR-4T, manufactured by Atago Co., measuring wavelength: 589 nm). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Finereuf Co.) and converted into nm. The retardation (Re) was obtained from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

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

(4) NZ Coefficient The values of Ny, Nx, and Nz obtained in (1) above were substituted into NZ=|Ny-Nz|/|Ny-Nx| to obtain the value of 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 multichannel spectrometer PMA-12 manufactured by Hamamatsu Photonics, an emission spectrum having peak tops near 450 nm, 535 nm, and 630 nm was observed. was done. The half-value width of each peak top (the half-value width of the peak having the highest peak intensity in each wavelength region) was 17 nm for the peak at 450 nm, 45 nm for the peak at 535 nm, and 2 nm for the peak at 630 nm. Although this light source had a plurality of peaks in the wavelength region of 600 nm or more and 780 nm or less, the half width was evaluated at the peak near 630 nm, which has the highest peak intensity in this region. The exposure time for spectrum measurement was 20 msec.

(6) Reflectance Using a spectrophotometer (Shimadzu Corporation, UV-3150), the 5-degree reflectance at a wavelength of 550 nm was measured from the antireflection layer side (or low reflection layer side) surface. In addition, after applying black marker on the side opposite to the side of the polyester film provided with the antireflection layer (or low reflection layer), black vinyl tape (Kyowa vinyl tape HF-737 width 50 mm) is attached. I put it on and measured it.

(7) Observation of iris spots The liquid crystal display device obtained in each example was visually observed from the front and oblique directions in a dark place, and the presence or absence of iris spots was determined as follows.
○: No iridescence observed △: Iridescence slightly observed ×: Iridescence observed XX: Iridescence markedly observed

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

After the completion of the polycondensation reaction, it is filtered through a NASLON filter with a 95% cut diameter of 5 μm, extruded from a nozzle in the form of a strand, and cooled and solidified using cooling water that has been previously filtered (pore size: 1 μm or less). , cut into pellets. The resulting polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl/g and contained substantially no inert particles or internal precipitated particles. (Hereinafter abbreviated as PET (A).)

(Production Example 2-Polyester B)
10 parts by mass of dried UV absorber (2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one), particle-free PET (A) (having an intrinsic viscosity of 0.62 dl/g) of 90 parts by mass 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-Adhesion-improving coating liquid preparation)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method to obtain 46 mol % of terephthalic acid, 46 mol % of isophthalic acid and 8 mol % of sodium 5-sulfonatoisophthalate as dicarboxylic acid components (relative to the total dicarboxylic acid components). A water-dispersible sulfonic acid metal group-containing copolymer polyester resin was prepared having a composition of 50 mol % ethylene glycol and 50 mol % neopentyl glycol as the glycol component (relative to the total glycol component). Next, 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 are mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal group-containing copolymerized polyester resin and continuing to stir until the lumps of the resin disappear, the resin aqueous dispersion was cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A homogeneous water-dispersible copolyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (manufactured by Fuji Silysia Co., Ltd., Silysia 310) in 50 parts by mass of water, Silysia 310 was added to 99.46 parts by mass of the water-dispersible copolymer polyester resin liquid. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added while stirring to obtain an adhesion-improving coating liquid.

(Production Example 4-Preparation of high refractive index coating agent)
80 parts by mass of methyl methacrylate, 20 parts by mass of methacrylic acid, 1 part by mass of azoisobutyronitrile, and 200 parts by mass of isopropyl alcohol were charged into a reaction vessel and reacted at 80 ° C. for 7 hours under a nitrogen atmosphere to obtain a weight average molecular weight of 30,000. was obtained as an isopropyl alcohol solution of the polymer. The obtained polymer solution was further diluted with isopropyl alcohol to a solid content of 5% by mass to obtain an acrylic resin solution B. Next, the obtained acrylic resin solution B was mixed as follows to obtain a coating liquid for forming a high refractive index layer.
・Acrylic resin solution B 5 parts by mass ・Bisphenol A diglycidyl ether 0.25 parts by mass ・Titanium oxide particles having an average particle size of 20 nm 0.5 parts by mass ・Triphenylphosphine 0.05 parts by mass ・Isopropyl alcohol 14.25 parts by mass

(Production Example 5-Preparation of low refractive index coating agent)
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), methyl ethyl ketone ( 200 parts by mass) was charged into a reaction vessel and reacted at 80° C. for 7 hours under a nitrogen atmosphere to obtain a methyl ethyl ketone solution of a polymer having a weight average molecular weight of 20,000. 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 coating liquid for forming a low refractive index layer.
・Fluoropolymer solution C 44 parts by mass ・1,10-bis(2,3-epoxypropoxy)-2,2,3,3,4,4,5,5,6,6,7,7,8,8 ,9,9-Hexadecafluorodecane (Kyoeisha Chemical Co., Ltd., Fluorite FE-16) 1 part by mass Triphenylphosphine 0.1 part by mass Methyl ethyl ketone 19 parts by mass

(Preparation Example 6-Preparation of Antiglare Layer Coating Agent-1)
Unsaturated double bond-containing acrylic copolymer Cychromer P ACA-Z250 (manufactured by Daicel Chemical Industries, Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-20 (number average molecular weight 75000) (manufactured by Eastman Chemical Co.) (3 parts by mass), acrylic monomer AYARAD DPHA (manufactured by Nippon Kayaku Co., Ltd.) (49 parts by mass), acrylic-styrene copolymer (average particle size 4.0 μm) (manufactured by Sekisui Plastics Co., Ltd.) (2 parts by mass) , Irgacure 184 (manufactured by BASF) (10 parts by mass) was adjusted to 35% by mass, and a mixed solvent of methyl ethyl ketone:1-butanol=3:1 was added to obtain a coating solution for forming an antiglare layer.

(Preparation Example 7-Preparation of Antiglare Layer Coating Agent-2)
Unsaturated double bond-containing acrylic copolymer Cychromer P ACA-Z250 (manufactured by Daicel Chemical Industries, Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-0.5 (number average molecular weight 25000) (Eastman Chemical Co.) ) (3 parts by mass), acrylic monomer AYARAD DPHA (manufactured by Nippon Kayaku Co., Ltd.) (49 parts by mass), acrylic-styrene copolymer (average particle size 4.0 μm) (manufactured by Sekisui Plastics Co., Ltd.) (4 mass Part), the solid content of Irgacure 184 (manufactured by BASF) (10 parts by mass) was set to 35% by mass, and a mixed solvent of methyl ethyl ketone: 1-butanol = 3: 1 was added to obtain a coating liquid for forming an antiglare layer. .

(Production Example 8-Preparation of Antiglare Layer Coating Agent-3)
Unsaturated double bond-containing acrylic copolymer Cychromer P ACA-Z250 (manufactured by Daicel Chemical Industries, Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-0.2 (number average molecular weight 15000) (Eastman Chemical Co.) ) (3 parts by mass), acrylic monomer AYARAD DPHA (manufactured by Nippon Kayaku Co., Ltd.) (49 parts by mass), acrylic-styrene copolymer (average particle size 4.0 μm) (manufactured by Sekisui Plastics Co., Ltd.) (2 mass Part), the solid content of Irgacure 184 (manufactured by BASF) (10 parts by mass) was set to 35% by mass, and a mixed solvent of methyl ethyl ketone: 1-butanol = 3: 1 was added to obtain a coating liquid for forming an antiglare layer. .

(Polarizer protective film 1)
After drying under reduced pressure (1 Torr) at 135° C. for 6 hours, 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 as raw materials for the base film intermediate layer. , supplied to extruder 2 (for intermediate layer II layer), and PET (A) was dried by a conventional method, supplied to extruder 1 (for outer layer I layer and outer layer III), and melted at 285 ° C. . These two types of polymers are each filtered with a stainless sintered filter material (nominal filtration accuracy: 10 μm, 95% cut of particles), laminated in a two-type, three-layer confluence block, extruded in a sheet form from a nozzle, An unstretched film was produced by winding the film around a casting drum having a surface temperature of 30° C. and solidifying it by cooling using an electrostatic casting method. At this time, the discharge rate 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 adhesion-improving coating solution was applied to both sides of the unstretched PET film by a reverse roll method so that the coating amount after drying was 0.08 g/m ² , and then dried at 80°C for 20 seconds. .

The unstretched film with the coating layer formed thereon was guided to a tenter stretching machine, and while holding the ends of the film with clips, was 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 stretched width in the width direction, it 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 uniaxially stretched PET film with a film thickness of about 100 μm. rice field.

The coating liquid for forming a high refractive index layer obtained by the above method is applied to one coated surface of the uniaxially stretched PET film and dried at 150° C. for 2 minutes to form a high refractive index layer having a thickness of 0.1 μm. did. On this high refractive index layer, the coating liquid for forming a low refractive index layer obtained by the above method is applied and dried at 150° C. for 2 minutes to form a low refractive index layer having a thickness of 0.1 μm, and a reflective layer is formed. A polarizer protective film 1 laminated with an anti-layer was obtained.

(Polarizer protective film 2)
A polarizer protective film 2 having a film thickness of about 80 μm and having a film thickness of about 80 μm was obtained by forming a film in the same manner as the polarizer protective film 1 except that the line speed was changed to change the thickness of the unstretched film. rice field.

(Polarizer protective film 3)
A polarizer protective film 3 having a film thickness of about 60 μm and having an antireflection layer laminated thereon was produced in the same manner as the polarizer protective film 1 except that the line speed was changed to change the thickness of the unstretched film. rice field.

(Polarizer protective film 4)
A polarizer protective film 4 having a film thickness of about 40 μm and having an antireflection layer laminated thereon was produced in the same manner as the polarizer protective film 1 except that the line speed was changed to change the thickness of the unstretched film. rice field.

(Polarizer protective film 5)
Antiglare layer coating agent- 1 was applied and dried in an oven at 80° C. for 60 seconds. Thereafter, an ultraviolet irradiation apparatus (Fusion UV Systems Japan, Light Source H Bulb) was used to irradiate ultraviolet rays at an irradiation dose of 300 mJ/cm ² to laminate an antiglare layer. After that, an antireflection layer was laminated on the antiglare layer in the same manner as the polarizer protective film 1 to obtain a polarizer protective film 5 .

(Polarizer protective film 6)
An antiglare layer and an antireflection layer are formed in the same manner as in polarizer protective film 5 on one coated surface of the polarizer protective film prepared in the same manner as in polarizer protective film 3, except that the antireflection layer is not provided. A polarizer protective film 6 was obtained by lamination.

(Polarizer protective film 7)
An antiglare layer coating agent- 2 was applied and dried in an oven at 80° C. for 60 seconds. Thereafter, an ultraviolet irradiation apparatus (Fusion UV Systems Japan, Light Source H Bulb) was used to irradiate ultraviolet rays at an irradiation dose of 300 mJ/cm ² to laminate an antiglare layer. After that, an antireflection layer was laminated on the antiglare layer in the same manner as the polarizer protective film 1 to obtain a polarizer protective film 7 .

(Polarizer protective film 8)
An unstretched film produced by the same method as the polarizer protective film 1 was heated to 105° C. using a heated roll group and an infrared heater, and then 3.3 degrees in the running direction with a roll group having a peripheral speed difference. After being double-stretched, it is led to a hot air zone at a temperature of 130° C. and stretched 4.0-fold in the width direction. A protective film 8 was obtained.

(Polarizer protective film 9)
A polarizer protective film 9 having a film thickness of about 100 μm was obtained in the same manner as the polarizer protective film 1 except that the antireflection layer was not provided.

(Polarizer protective film 10)
Polarizer protective film 8 was prepared in the same manner as polarizer protective film 8, except that the antireflection layer was not provided. A child protective film 10 was obtained (no antireflection layer was laminated).

(Polarizer protective film 11)
An antiglare layer coating agent- 3 was applied and dried in an oven at 80° C. for 60 seconds. Thereafter, an ultraviolet irradiation device (Fusion UV Systems Japan, Light Source H Bulb) was used to irradiate ultraviolet rays at an irradiation dose of 300 mJ/cm ² to obtain a polarizer protective film 11 laminated with an antiglare layer.

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

(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 is perpendicular to the fast axis of the film, and a TAC film (manufactured by Fuji Film Co., Ltd.) is attached to the other side. (thickness: 80 μm) was adhered to prepare a polarizing plate 1. A polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to prepare a polarizing plate.
A liquid crystal display device was fabricated by replacing the polarizing plate of REGZA 43J10X manufactured by Toshiba Corporation on the viewing side with the polarizing plate 1 so that the polyester film was on the opposite side (distal) to the liquid crystal cell. The direction of the transmission axis of the polarizing plate 1 was replaced so as to be the same as the direction of the transmission axis of the polarizing plate before replacement.

(Example 2)
A polarizer protective film 2 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer is perpendicular to the fast axis of the film, and a TAC film (manufactured by Fuji Film Co., Ltd.) is attached to the other side. (thickness: 80 μm) was adhered to prepare the polarizing plate 2 . A polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to prepare a polarizing plate. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizing plate 1 was changed to the polarizing plate 2 .

(Example 3)
A polarizer protective film 3 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer is perpendicular to the fast axis of the film, and a TAC film (manufactured by Fuji Film Co., Ltd.) is attached to the other side. (thickness: 80 μm) was adhered to prepare the polarizing plate 3 . A polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to prepare a polarizing plate. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizing plate 1 was changed to the polarizing plate 3.

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

(Example 5)
A polarizer protective film 4 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 parallel, and a TAC film (manufactured by Fuji Film Co., Ltd.) is attached to the other side. (thickness: 80 μm) was adhered to prepare the polarizing plate 5 . A polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to prepare a polarizing plate. A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizing plate 1 was changed to the polarizing plate 5 .

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

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

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

(Comparative example 1)
A polarizer protective film 8 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer is perpendicular to the fast axis of the film, and a TAC film (manufactured by Fuji Film Co., Ltd.) is attached to the other side. (thickness: 80 μm) was adhered to prepare a polarizing plate 9 . A polarizer was laminated on the surface of the polarizer protective film on which the antireflection layer was not laminated to prepare a polarizing plate.
A liquid crystal display device was fabricated by replacing the polarizing plate on the visible side of REGZA 43J10X manufactured by Toshiba with the polarizing plate 9 so that the polyester film was on the opposite side (distal) to the liquid crystal cell. The direction of the transmission axis of the polarizing plate 9 was replaced so as to be the same as the direction of the transmission axis of the polarizing plate before replacement.

(Comparative example 2)
A polarizer protective film 9 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer is perpendicular to the fast axis of the film, and a TAC film (manufactured by Fuji Film Co., Ltd.) is attached to the other side. A polarizing plate 10 was prepared by affixing a polarizing plate 10 with a thickness of 80 μm. A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 9 was changed to the polarizing plate 10 .

(Comparative Example 3)
A polarizer protective film 10 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer is perpendicular to the fast axis of the film, and a TAC film (manufactured by FUJIFILM Corporation) is attached to the other side. A polarizing plate 11 was prepared by affixing a film (80 μm thick). A polarizer was laminated on the surface of the polarizer protective film on which the antiglare layer was not laminated to prepare a polarizing plate. A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 9 was changed to the polarizing plate 11 .

(Comparative Example 4)
A polarizer protective film 11 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer is perpendicular to the fast axis of the film, and a TAC film (manufactured by Fuji Film Co., Ltd.) is attached to the other side. (thickness: 80 μm) was attached to prepare the polarizing plate 12 . A polarizer was laminated on the surface of the polarizer protective film on which the antiglare layer was not laminated to prepare a polarizing plate. A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 9 was changed to the polarizing plate 12 .

Table 1 below shows the results of iridescence observation of the liquid crystal display device obtained in each example.

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

Claims (2)

A liquid crystal display device comprising a backlight source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,
The backlight source is a white light emitting diode containing a blue light emitting diode and a fluoride phosphor,
At least one of the polarizing plates has a polyester film laminated on at least one surface of a polarizer,
The polyester film has a retardation of 1500 to 30000 nm,
A liquid crystal display device, wherein an antireflection layer and/or a low reflection layer is laminated on at least one surface of the polyester film. _2. The liquid crystal display device according to claim 1, wherein the fluoride phosphor is _K2SiF6 :Mn4 ⁺ .