JP6812656B2 - Liquid crystal display device - Google Patents

Description

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device in which the occurrence of rainbow-shaped color spots is improved.

The polarizing plate used in the liquid crystal display device (LCD) usually has a structure in which a polarizing element obtained by dyeing iodine on polyvinyl alcohol (PVA) or the like is sandwiched between two polarizing element protective films, and is used as a polarizer protective film. Usually, a triacetyl cellulose (TAC) film is used. In recent years, as LCDs have become thinner, there has been a demand for thinner polarizing plates. However, if the thickness of the TAC film used as the protective film is reduced for this purpose, sufficient mechanical strength cannot be obtained, and there arises a problem that the moisture permeability is deteriorated. 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 iridescent color spots are observed.

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 peculiar to retardation, which is the product of birefringence and thickness of the oriented polyester film. Therefore, if a discontinuous emission spectrum such as a cold-cathode tube or a hot-cathode tube is used as the light source, the transmitted light intensity differs depending on the wavelength, resulting in iridescent color spots (see: Proceedings of the 15th Micro Optical Conference, No. 30-31).

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

In addition, by making the orientation direction of the oriented polyester film perpendicular to or parallel to the polarization direction of the polarizing plate, the linearly polarized light emitted from the polarizer passes through the oriented polyester film while maintaining the polarized state. become. Further, by controlling the birefringence of the oriented polyester film to enhance the uniaxial orientation, light incident from an oblique direction can also pass while maintaining the polarized state. When the oriented polyester film is viewed from an angle, a deviation occurs in the orientation spindle direction as compared with a case where it is viewed from directly above, but when the uniaxial orientation is high, the deviation in the orientation spindle direction when viewed from an angle becomes small. Therefore, it is considered that the deviation between the direction of linearly polarized light and the direction of the main axis of orientation is small, and the change in the 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, and the orientation main axis direction, changes in the polarization state are suppressed, rainbow-shaped color spots do not occur, and visibility is significantly improved. It was thought that.

JP-A-2002-116320 Japanese Unexamined Patent Publication No. 2004-219620 Japanese Unexamined Patent Publication No. 2004-205773 WO2011 / 162198

As a backlight source for liquid crystal display devices, white light emitting diodes (white LEDs) consisting of light emitting elements that combine a blue light emitting diode and an yttrium aluminum garnet yellow phosphor (YAG yellow phosphor) have been widely used in the past. Has been done. The emission spectrum of this white light source has a wide spectrum in the visible light region and is also excellent in luminous efficiency, so that it is widely used as a backlight source. However, a liquid crystal display device using this white LED as a backlight source can reproduce colors only about 20% of the spectrum recognizable by the human eye.

On the other hand, due to the increasing demand for color gamut expansion in recent years, liquid crystal display devices having a clear peak shape in each wavelength region of R (red), G (green), and B (blue) in the emission spectrum of a white light source have been introduced. It is being developed. For example, a white light source using quantum dot technology, a phosphor-type white LED light source using a phosphor having clear emission peaks in the R (red) and G (green) regions due to excitation light, and a blue LED, and three wavelengths. A liquid crystal display device compatible with a wide color range has been developed using various types of light sources such as a white LED light source of the type and a white LED light source combining a red laser. In the case of a liquid crystal display device using a white light source as a backlight source using quantum dot technology, it is said that it is possible to reproduce 60% or more of colors in a spectrum recognizable by the human eye. All of these white light sources have a relatively narrow peak half-value width as compared with a light source composed of a white light emitting diode using a conventional YAG-based yellow phosphor, and an oriented polyester film having retardation is used as a constituent member of the polarizing plate. It was newly found that rainbow spots may occur depending on the type of light source when used as a certain polarizing element protective film.

In the present invention, in a liquid crystal display device using a white light source having a peak top in each wavelength region of R, G, and B and having an emission spectrum having a relatively narrow half-value width of each peak, polarized light, which is a constituent member of a polarizing plate, is used. An object of the present invention is to provide a liquid crystal display device in which the occurrence of iridescent spots is suppressed even when a polyester film is used as a child protective film.

A typical invention is as follows.
Item 1.
A liquid crystal display device having a backlight light source, two polarizing plates, and a liquid crystal cell arranged 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 750 nm or less, and the half width of each peak is 5 nm or more.
At least one of the two polarizing plates has a polyester film laminated on at least one surface of the polarizer.
The polyester film has an easy-adhesion layer on at least one surface.
The difference between the refractive index of the easy-adhesion layer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 0.10 or less.
Liquid crystal display device.
Item 2.
Item 2. The liquid crystal display device according to Item 1, wherein the backlight source is a backlight source including a light source that emits excitation light and quantum dots.
Item 3.
Item 2. The liquid crystal display device according to Item 1 or 2, wherein the polyester film has a retardation of 1500 to 30000 nm.

The liquid crystal display device of the present invention has a wide color gamut, and can ensure good visibility in which the occurrence of rainbow-shaped color spots is significantly suppressed at any observation angle.

(Liquid crystal display device)
Generally, a liquid crystal display device is composed of a rear surface module, a liquid crystal cell, and a front surface module in the order from the side facing the backlight source to the side displaying an image (visual recognition side). The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the surface of the liquid crystal cell side thereof, and a polarizing plate arranged on the opposite side thereof. 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 (visual recognition side) in the front module. The backlight may be configured by an edge light system having a light guide plate, a reflector, or the like as a constituent member, or a direct type system. In addition to the backlight source, the polarizing plate, and the liquid crystal cell, the liquid crystal display device may appropriately have other configurations such as a color filter, a lens film, a diffusion sheet, and an antireflection film. A brightness improving film may be provided between the light source side polarizing plate and the backlight light source. Examples of the brightness improving film include a reflective polarizing plate that transmits one linearly polarized light and reflects the linearly polarized light orthogonal to the linearly polarized light. As the reflective polarizing plate, for example, a brightness improving film of the DBEF (registered trademark) (Dual Brightness Enhancement Film) series manufactured by Sumitomo 3M Ltd. is preferably used. The reflective polarizing plate is usually arranged so that the absorption axis of the reflective polarizing plate and the absorption axis of the light source side polarizing plate are parallel to each other.

(Backlight light source)
The liquid crystal display device of the present invention comprises at least a backlight source and a liquid crystal cell arranged between two polarizing plates as constituent members. The backlight source is a white light source having 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 750 nm or less, and having an emission spectrum in which the half width of each peak is 5 nm or more. preferable.

The wavelength region of 400 nm or more and less than 495 nm is more preferably 430 nm or more and 470 nm or less. The wavelength region of 495 nm or more and less than 600 nm is more preferably 510 nm or more and 560 nm or less. The wavelength region of 600 nm or more and 750 nm or less is more preferably 630 nm or more and 700 nm or less, and even more preferably 630 nm or more and 680 mn or less. If the half width of each peak is less than 5 nm, iridescent color spots are likely to occur, which is not preferable. The preferable lower limit of the half width of each peak is 10 nm or more, more preferably 15 nm or more, and further preferably 20 nm or more. From the viewpoint of ensuring an appropriate color gamut, the upper limit of the half width of each peak is preferably 140 nm or less, preferably 120 nm or less, preferably 100 nm or less, more preferably 80 nm or less, and further preferably. Is 60 nm or less, and more preferably 45 nm or less. Here, the full width at half maximum is the peak width (nm) at half the intensity of the peak intensity at the wavelength of the peak top.

When a plurality of peaks are present in any of the wavelength region of 400 nm or more and less than 495 nm, the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 750 nm or less, it is considered as follows.
When the plurality of peaks are independent peaks, it is preferable that the half width of the peak having the highest peak intensity is in the above range. Further, for other peaks having an intensity of 70% or more of the highest peak intensity, it is more preferable that the half width is similarly in the above range. Here, the independent peak has an intensity region that is halved 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 that is 1/2 of the peak intensity, the plurality of peaks are regarded as one peak as a whole. For one peak having such a shape in which a plurality of peaks are overlapped, the width (nm) of the peak at 1/2 intensity of the highest peak intensity among them is set as the half width.
Of the plurality of peaks, the peak with the highest peak intensity is set as the peak top.
The peak having the highest peak intensity in the wavelength region of 400 nm or more and less than 495 nm, or the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 750 nm or less has an independent relationship with the peaks in other wavelength regions. Is preferable. In particular, the intensity is 600 nm or more and 750 nm or less in the wavelength region between the peak having the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm or the peak having the highest peak intensity in the region of 600 nm or more and 750 nm or less. In terms of color clarity, it is preferable that there is a region that is 1/3 of the peak intensity of the peak having the highest peak intensity in the wavelength region.

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

Specific examples of the above-mentioned backlight source include a light source that emits excitation light and a backlight source that includes at least quantum dots. In addition, a combination of a phosphor with emission peaks in the R (red) and G (green) regions due to excitation light, a phosphor-type white LED light source using a blue LED, a three-wavelength white LED light source, and a red laser. A white LED light source and the like can be exemplified. Among the phosphors, examples of the red phosphor include a nitride-based phosphor having a basic composition of CaAlSiN ₃ : Eu and the like, a sulfide-based phosphor having a basic composition of CaS: Eu and the like, and Ca ₂ SiO ₄ : Eu. Etc. are exemplified as silicate-based phosphors having a basic composition such as. Among the phosphors, as the green phosphor, for example, a sialon-based fluorescent substance having a basic composition of β-SiAlON: Eu or the like, or a silicate-based fluorescent substance having a basic composition of (Ba, Sr) ₂ SiO ₄ : Eu or the like. , Others are exemplified.

The application of quantum dot technology to LCDs is a technology that has been attracting attention due to the growing demand for color gamut expansion in recent years. An LED that uses an ordinary white LED as a backlight source can reproduce colors only about 20% of the spectrum that can be recognized by the human eye. On the other hand, when a backlight source composed of a light source that emits excitation light and a light emitting layer containing quantum dots is used, it is said that 60% or more of colors can be reproduced. Quantum dot technologies that have been put into practical use include QDEF ^TM from Nanosys and Color IQ ^{TM from} QD Vision.

For the quantum dots, for example, a layer containing a large number of quantum dots can be provided, and this can be used as a light emitting layer for the backlight. The light emitting layer containing the quantum dots is formed by including the quantum dots in a resin material such as polystyrene, for example, and is a layer that emits emitted light of each color in pixel units based on the excitation light emitted from the light source. .. This light emitting layer is composed of, for example, a red light emitting layer arranged in red pixels, a green light emitting layer arranged in green pixels, and a blue light emitting layer arranged in blue pixels, and the quantum dots in these multiple color light emitting layers , Emission light of different wavelengths (colors) is generated based on the excitation light.

Examples of such quantum dot materials include CdSe, CdS, ZnS: Mn, InN, InP, CuCl, CuBr, Si, etc., and the particle size (size in one side direction) of these quantum dots is, for example, 2. It is about 20 nm. Among the above-mentioned quantum dot materials, the red light emitting material includes InP, the green light emitting material includes, for example, CdSc, and the blue light emitting material includes, for example, CdS. In such a light emitting layer, it has been confirmed that the emission wavelength changes by changing the size (particle size) of the quantum dots and the composition of the material. The size (particle size) and material of the quantum dots are controlled, mixed with the resin material, and applied separately for each pixel.

A blue LED is used as a light source that emits excitation light, but laser light such as a semiconductor laser may also be used. When the excitation light emitted from the light source passes through the light emitting layer, an emission spectrum having a peak top is generated 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 750 nm or less. At this time, the narrower the half-value width of the peak in each wavelength region, the wider the color range. However, when the half-value width of the peak becomes narrower, the luminous efficiency decreases. Therefore, the shape of the emission spectrum is determined from the balance between the required color gamut and the luminous efficiency. Designed.

(Polarizer)
Of the two polarizing plates arranged in the liquid crystal display device, at least one polarizing plate has a polyester film laminated on at least one surface of a polarizing element obtained by dyeing iodine with polyvinyl alcohol (PVA) or the like. Is. It is preferable that a film having no double refraction such as a TAC film, an acrylic film, or a norbornene-based film is laminated on the other surface of the polarizer (three-layered polarizing plate), but it is not always the same as that of the polarizer. It is not necessary for the film to be laminated on the other surface (two-layer polarizing plate). When a polyester film is used as the protective film on both sides of the polarizer, it is preferable that the slow axes of both polyester films are substantially parallel to each other.

As a result of diligent studies, the present inventions have a liquid crystal having a backlit light source in which the half-value width of each peak of the emission spectrum is relatively narrow, as represented by the above-mentioned light source that emits excitation light and a backlit light source that includes quantum dots. Even when a polarizing plate using a polyester film is used as the polarizer protective film in the display device, a polyester film having an easy-adhesion layer on at least one side is used, and the refractive index of the easy-adhesion layer is parallel to the transmission axis of the polarizer. It was found that if the difference from the refractive index of the polyester film in the above direction is 0.10 or less, rainbow spots can be significantly suppressed. The mechanism by which the occurrence of iridescent color spots is suppressed by the above aspect is considered as follows.

When an oriented polyester film 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. One of the factors that change the polarization state when the linearly polarized light emitted from the backlight unit or the polarizer passes through the oriented polyester film is the difference in the refractive index at the interface between the easy-adhesion layer and the oriented polyester film. I found the possibility of When linearly polarized light incident from an oblique direction passes through each interface, a part of light is reflected due to the difference in refractive index between the interfaces. At this time, it is possible that the polarization state of both the emitted light and the reflected light changes, which is considered to be one of the factors that cause rainbow-shaped color spots. Therefore, by reducing the difference in refractive index between the easy-adhesion layer and the oriented polyester film in the polarization direction (transmission axis direction) of the incident linearly polarized light, reflection at each interface is suppressed, and iridescent color spots are formed. Is thought to be suppressed.

As described above, in the present invention, as represented by a light source that emits excitation light and a backlight source that includes quantum dots, a liquid crystal display device including a backlight source that has a relatively narrow half-value width of each peak of the emission spectrum. Even if a polarizing plate using a polyester film is used as the polarizer protective film, it is possible to have good visibility without generating rainbow-shaped color spots.

The difference between the refractive index of the easy-adhesion layer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is preferably 0.10 or less, preferably 0.09 or less, preferably 0.08 or less. It is preferably 0.07 or less, preferably 0.06 or less. The smaller the difference in refractive index, the more preferable it is because the reflection at the polyester film interface can be suppressed and the rainbow spots can be suppressed. The lower limit is 0.

The difference between the refractive index of the easy-adhesion layer in the direction parallel to the transmission axis of the polarizer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is preferably 0.10 or less. It is preferably 0.09 or less, more preferably 0.08 or less, preferably 0.07 or less, and preferably 0.06 or less. The smaller the difference in refractive index, the more preferable it is because the reflection at the polyester film interface can be suppressed and the rainbow spots can be suppressed. The lower limit is 0.

The method of laminating the polyester film and the polarizer is not particularly limited, and the phase-advancing axis direction of the polyester film and the transmission axis direction of the polarizer are substantially parallel, or the slow-phase axial direction of the polyester film and the transmission of the polarizer are substantially parallel. An arrangement in which the axial directions are substantially parallel is preferable. Careful stacking may be performed so that the difference between the refractive index of the adhesive and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is within a preferable range.

Here, substantially parallel means that the angle formed by the transmission axis of the polarizer and the phase advance axis (or slow phase axis) of the polarizer protective film is preferably -15 ° to 15 °, more preferably -10 °. It means that it is -10 °, more preferably -5 ° to 5 °, even more preferably -3 ° to 3 °, still more preferably -2 ° to 2 °, and particularly preferably -1 ° to 1 °. In one preferred embodiment, substantially parallel is substantially parallel. Here, substantially parallel means that the transmission axis and the phase advance axis (or slow phase axis) are parallel to the extent that the displacement that inevitably occurs when the polarizer and the protective film are bonded to each other is allowed. Means. The direction of the slow-phase axis can be determined by measuring with a molecular orientation meter (for example, MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.).

(Polyester film)
The polyester film used for the polarizer protective film preferably has a retardation of 1500 to 30000 nm. If the retardation is within the above range, iris spots tend to be reduced more easily, which is preferable. The lower limit of the preferred retardation is 3000 nm, the next preferred lower limit is 3500 nm, the more preferred lower limit is 4000 nm, the more preferred lower limit is 6000 nm, and the further preferred lower limit is 8000 nm. The preferable upper limit is 30,000 nm, and a polyester film having a retardation of more than this tends to have a considerably large thickness and a decrease in handleability as an industrial material.

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

The ratio (Re / Rth) of the retardation (Re: in-plane retardation) of the polyester film to the retardation (Rth) in the thickness direction is preferably 0.2 or more, more preferably 0.5 or more, still more preferably 0. 6 or more. The larger the ratio (Re / Rth) of the above retardation to the thickness direction retardation, the more isotropic the action of birefringence, and the less likely it is that iridescent color spots will occur depending on the observation angle. Since the ratio of the above retardation to the thickness direction retardation (Re / Rth) is 2.0 in a completely uniaxial (uniaxially symmetric) film, the ratio of the above retardation to the thickness direction retardation (Re / Rth) The upper limit is preferably 2.0. The phase difference in the thickness direction means the average of the phase differences obtained by multiplying the two birefringences ΔNxz and ΔNyz when the film is viewed from the cross section in the thickness direction by the film thickness d, respectively.

The refractive index of the polyester film in the phase-advancing axis direction is preferably 1.53 or more and 1.62 or less. If the refractive index is less than 1.53, the crystallization of the polyester film becomes insufficient, and the properties obtained by stretching such as dimensional stability, mechanical strength, and chemical resistance become insufficient, which is not preferable. The upper limit of the refractive index of the polyester film in the phase-advancing axis direction is more preferably 1.61 or less, further preferably 1.60 or less, still more preferably 1.59 or less, and particularly preferably 1. It is 58 or less. The lower limit of the refractive index of the polyester film in the phase-advancing axis direction is more preferably 1.54 or more, further preferably 1.55 or more, still more preferably 1.56 or more, and particularly preferably 1. It is 57 or more.
The refractive index of the polyester film in the slow axis direction is preferably 1.67 or more and 1.75 or less. The upper limit of the refractive index of the polyester film in the slow axis direction is more preferably 1.74 or less, further preferably 1.73 or less, still more preferably 1.72 or less, and particularly preferably 1. It is 71 or less. The lower limit of the refractive index of the slow axis of the polyester film is more preferably 1.68 or more. The adjustment of the refractive index can be easily adjusted by a stretching treatment in a film forming step described later.
The difference between the refractive index in the slow axis direction and the refractive index in the phase advance axis direction of the polyester film is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.09 or more.

The polarizer protective film made of the polyester film can be used for both the incident light side (light source side) and the emitted light side (visual recognition side). In the polarizing plate arranged on the incident light side, the polarizer protective film made of the polyester film is arranged on both sides regardless of whether the polarizing element is arranged on the incident light side or the liquid crystal cell side as a starting point. It may be arranged, but it is preferable that it is arranged at least on the incident light side. Regarding the polarizing plate arranged on the emitting light side, the polarizing element protective film made of the polyester film is arranged on both sides regardless of whether it is arranged on the liquid crystal side or the emitting light side with the polarizing element as the starting point. However, it is preferable that the film is arranged at least on the emitted light side.

As the polyester used for the polyester film, polyethylene terephthalate or polyethylene naphthalate can be used, but other copolymerization components may be contained. These resins are excellent in transparency as well as thermal and mechanical properties, and retardation can be easily controlled by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence, and the refractive index in the phase-advancing axis (perpendicular to the slow-phase axis direction) can be suppressed low by stretching the film, and it is relatively easy even if the film is thin. It is the most suitable material because it can obtain a large amount of retardation.

Further, for the purpose of suppressing deterioration of an optically functional dye such as an iodine dye, it is desirable that the polyester film has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration of the optical functional dye due to ultraviolet rays can be suppressed. The transmittance is measured in a method perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

In order to reduce the transmittance of the polyester film at a wavelength of 380 nm to 20% or less, it is desirable to appropriately adjust the type and concentration of the ultraviolet absorber and the thickness of the film. The UV 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, but an organic ultraviolet absorber is preferable from the viewpoint of transparency. Examples of the organic ultraviolet absorber include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and combinations thereof, but are not particularly limited as long as they are within the above-mentioned absorbance range. However, from the viewpoint of durability, benzotoazole-based and cyclic iminoester-based are particularly preferable. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays having different wavelengths can be absorbed at the same time, so that the ultraviolet absorption effect can be further improved.

Examples of benzophenol-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and acrylonitrile-based ultraviolet absorbers include 2- [2'-hydroxy-5'-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2'. -Hydroxy-5'-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2,2'-dihydroxy- 4,4'-Dimethoxybenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, 2,4-di-tert-butyl-6- (5-chlorobenzotriazole-2-yl) phenol, 2- ( 2'-Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (5-chloro (2H) -benzotriazole-2-yl) -4-methyl-6- ( Examples thereof include tert-butyl) phenol and 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-2-yl) phenol. Cyclic iminoester. Examples of the ultraviolet absorbers include 2,2'-(1,4-phenylene) bis (4H-3,1-benzoxadinone-4-one) and 2-methyl-3,1-benzoxazine-4-one. , 2-Butyl-3,1-benzoxazine-4-one, 2-phenyl-3,1-benzoxazine-4-one and the like, but are not particularly limited thereto.

Further, in addition to the ultraviolet absorber, it is also preferable to contain various additives other than the catalyst 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 retardants, flame retardants, heat stabilizers, antioxidants, antigelling agents. , Surfactants and the like. Further, in order to obtain high transparency, it is also preferable that the polyester film contains substantially no particles. "Substantially free of particles" means, for example, in the case of inorganic particles, the content is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less when the inorganic element is quantified by Keiko X-ray analysis. means.

On the surface of the polyester film, which is a polarizing element protective film used in the present invention, various functional layers, that is, a hard coat layer, an antiglare layer, and an antireflection layer, are used for the purpose of preventing reflection, glare, and scratches. It is also preferable to provide a low reflection layer or the like. When providing various functional layers, it is preferable that the polyester film has an easy-adhesion layer on its surface.

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

(Easy adhesive layer)
In the present invention, it is preferable to have an easy-adhesion layer on at least one side of the film of the present invention in order to improve the adhesiveness with the above-mentioned functional layer and the polarizer.

As the easy-adhesion layer, a conventionally known easy-adhesion layer used for an optical film can be used. It is not particularly limited as long as it satisfies the condition of the refractive index difference with the polyester film described above. Among them, it is preferable to have an easy-adhesion layer containing at least one of a polyester resin, a polyurethane resin, a polyacrylic resin or a polyvinyl alcohol-based resin as a main component. Here, the "main component" refers to a component that is 50% by mass or more of the solid components constituting the easy-adhesion layer.
Conventionally known cross-linking agents can be added to these resins. 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, a polyurethane resin and a polyvinyl alcohol-based resin. The polyester resin, polyurethane resin, acrylic resin, and polyvinyl alcohol-based resin may be used alone or in combination of two or more. For example, in order to improve the adhesiveness to the polarizer, a combination of one or more selected from the group consisting of polyester resin, polyurethane resin and acrylic resin and a polyvinyl alcohol-based resin is preferable, and polyester is particularly preferable. It is a combination of a resin and a polyvinyl alcohol-based resin. Examples of these coating liquids include water-soluble or water-dispersible copolymers disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, Japanese Patent No. 4150982, and the like. Examples thereof include a polymerized polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.

Examples of the polyester resin include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, and pyro as acid components. As glycol components such as merit acid, dimer acid, 5-sodium sulfoisophthalic acid, etc., ethylene glycol, dimethylene glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,4 -A copolymer selected from butanediol, neopentyl glycol, xylene glycol, dimethylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) glycol and the like. When these are used as a coating liquid using an aqueous resin, it is preferable to copolymerize a compound containing a carboxylic acid base or a sulfonic acid base in order to facilitate water solubility and improve the adhesiveness of the polyester resin. Examples of the polyurethane resin include those composed of polyols, polyisocyanates, chain extenders, cross-linking agents and the like. The polyol may be obtained by a dehydration reaction between a glycol containing, for example, a polyether such as polyoxyethylene glycol, polyoxypropylene glycol, or polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, or polycaprolactone, and a dicarboxylic acid. Examples thereof include polyester produced, polycarbonate having a carbonate bond, acrylic polyol, castor oil and the like. Examples of the polyisocyanate include tolylene diisocyanate, phenylenediocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate and the like. Examples of the chain extender or cross-linking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, triethylenetetramine, 4,4'-diaminodiphenylmethane, and 4,4'-diamino. Examples thereof include dicyclohexylmethane and water. Examples of the acrylic resin include copolymers selected from methyl methacrylate, ethyl acrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, acrylamide, n-methylol acrylamide, glycidyl methacrylate, acrylic acid and the like. When used as a coating liquid as an aqueous resin, copolymerization with a monomer having a hydrophilic group (acrylic acid, methacrylic acid, acrylamide, vinyl sulfonic acid and a salt thereof, etc.) or emulsion polymerization using a reactive emulsifier or surfactant , Suspension polymerization, soap-free polymerization and other methods can be used. Further, a cross-linking agent or the like may be contained in order to improve the coatability. The cross-linking agent is not particularly limited as long as it is a compound that causes a cross-linking reaction. Coupling agents and the like can be exemplified.

Further, in order to adjust the refractive index of the easy-adhesion layer, high refractive index fine particles, a chelate compound and the like can be added. As the high refractive index fine particles, for example, metal oxide fine particles having a refractive index of 1.60 to 2.80 can be preferably used. Specific examples of the metal oxide fine particles include titanium oxide (TiO ₂ , refractive index: 2.71), zirconium oxide (ZrO ₂ , refractive index: 2.10), tin oxide (SnO ₂ , refractive index). : 2.00), antimony tin oxide (ATO, refractive index: 1.75 to 1.95), cerium oxide (CeO ₂ , refractive index: 2.20), indium tin oxide (ITO, refractive index: 1) .95 to 2.00), phosphotin compound (PTO, refractive index: 1.75 to 1.85), antimony oxide (Sb ₂ O ₅ , refractive index: 2.04), aluminum zinc oxide (AZO, refractive index) Rate: 1.90 to 2.00), Niobide pentoxide (Nb ₂ O ₅ , refractive index: 2.33), gallium zinc oxide (GZO, refractive index: 1.90 to 2.00), tantalum oxide (Tantal oxide) Ta ₂ O ₅ : Refractive index 2.16) and zinc antimonate (ZnSb ₂ O ₆ , refractive index: 1.90 to 2.00) and the like can be listed. The average primary particle size of the high refractive index fine particles is not particularly limited, but is preferably 5 to 100 nm. The content of the high refractive index fine particles is not particularly limited, but the refractive index of the easy-adhesion layer may be adjusted to a desired value. Examples of the chelate compound include a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, and a water-soluble zirconium compound. Examples of the water-soluble titanium chelate compound include isopropoxy (2-ethyl-1,3-hexanediorat) titanium, diisopropoxybis (acetylacetonato) titanium, and diisopropoxybis (triethanolaminato). Examples thereof include titanium, di-n-butoxybis (triethanol aminato) titanium, hydroxybis (lactoto) titanium, hydroxybis (lactoto) titanium ammonium salt, titanium beloxocitrate ammonium salt and the like. In addition, examples of the water-soluble titanium acylate compound include oxotitanium bis (monoammonium oxalate). Examples of the water-soluble zirconium compound include zirconium tetraacetylacetonate and zirconium acetate.

In one embodiment, the refractive index of the easy-adhesion layer is preferably 1.42 to 1.70. It is more preferably 1.42 to 1.65, still more preferably 1.45 to 1.60, even more preferably 1.47 to 1.55, and particularly preferably 1.48 to 1.54.
When the functional layer (or polarizer) is further laminated on the easy-adhesion layer of the polyester film, the refractive index of the easy-adhesion layer is the refractive index of the functional layer (or polarizer) and the refractive index of the polyester film (slow phase). It is preferable to adjust so as to be close to the synergistic average of the refractive index in the axial direction and the refractive index in the phase-advancing axis direction.
Further, in a polarizing plate in which the transmission axis of the polarizer and the slow axis of the polyester film are bonded in parallel, the refractive index of the easy-adhesion layer is the refractive index in the slow axis direction of the polyester film and the functional layer ( Alternatively, it is more preferable that the refractive index of the polarizing element is close to the synergistic average, and in a polarizing plate bonded so that the transmission axis of the polarizer and the phase advance axis of the polyester film are parallel to each other, the refractive index of the easy-adhesion layer is refracted. It is more preferable that the rate is a synergistic average of the refractive index in the phase-advancing axis direction of the polyester film and the refractive index of the functional layer (or the polarizer). A known method can be adopted for adjusting the refractive index of the easy-adhesion layer. For example, it is easy to adjust the copolymerization component of the binder resin or to contain titanium, germanium, or other metal species in the binder resin. Can be adjusted to.

In the above embodiment, there is a relationship of the refractive index of the functional layer (or the polarizer) ≤ the refractive index of the easily adhesive layer ≤ the refractive index of the polyester film, and it is more preferable that the difference in the refractive index at the interface between the layers is small. In a polarizing plate bonded so that the transmission axis of the polarizer and the slow axis of the polyester film are parallel to each other, the refractive index of the functional layer (or the polarizer) ≤ the refractive index of the easy-adhesion layer ≤ the slow phase of the polyester film. It is more preferable that the refractive index difference at the interface between the layers is small because of the relationship of the refractive index in the axial direction. In a polarizing plate bonded so that the transmission axis of the polarizer and the phase advance axis of the polyester film are parallel to each other, the refractive index of the functional layer (or the polarizer) ≤ the refractive index of the easy-adhesion layer ≤ the phase advance of the polyester film. It is even more preferable that the refractive index difference at the interface between the layers is small because of the relationship of the refractive index in the axial direction.

Further, in one embodiment, the refractive index of the easy-adhesion layer preferably satisfies the relationship of the refractive index in the phase-advancing axis direction of the polyester film <the refractive index of the easy-adhesion layer <the refractive index in the slow axial direction of the polyester film. .. When the functional layer is further laminated on the easy-adhesion layer of the polyester film, the relationship of the refractive index in the phase-advancing axis direction of the polyester film <the refractive index of the functional layer <the refractive index in the slow-phase axial direction of the polyester film is satisfied. Is preferable.
Further, in one embodiment, the thickness of the easy-adhesion layer is 3 to 30 nm, and the relationship of the refractive index in the phase-advancing axis direction of the polyester film <the refractive index of the functional layer <the refractive index in the slow-phase axial direction of the polyester film is satisfied. Is preferable. At this time, the refractive index of the easy-adhesion layer is preferably smaller than the refractive index of the polyester film in the phase-advancing axis direction, and the difference between the refractive index of the polyester film in the phase-advancing axis direction and the refractive index of the easy-adhesion layer is 0.05. The following is more preferable. The difference between the refractive index in the phase-advancing axis direction of the polyester film and the refractive index in the functional layer, and the difference between the refractive index in the slow-phase axial direction of the polyester film and the refractive index of the functional layer is 0.025 or more. More preferably.

The easy-adhesion layer can be obtained by applying the coating liquid to one or both sides of a uniaxially stretched film or an unstretched film in the vertical direction, drying at 100 to 150 ° C., and further stretching in the horizontal direction. The thickness of the final easy-adhesion layer is preferably 3 nm or more and 200 nm or less, more preferably 50 nm or more and 150 nm or less, and further preferably 80 nm or more and 130 nm or less. If the thickness is less than 3 nm, the adhesiveness to the functional layer and the polarizer may be insufficient. On the other hand, if the thickness exceeds 200 nm, the blocking resistance may decrease. When the easy-adhesion layers are provided on both sides of the polyester film, the coating amounts of the easy-adhesion layers on both sides may be the same or different, and can be independently set within the above ranges.

It is preferable to add particles to the easy-adhesion layer in order to impart slipperiness. It is preferable to use particles having an average particle size of 2 μm or less. When the average particle size of the particles exceeds 2 μm, the particles are likely to fall off from the coating layer. 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, hectrite, zirconia, tungsten oxide, lithium fluoride, etc. Examples thereof include inorganic particles such as calcium fluoride and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles. These may be added to the easy-adhesion layer alone, or may be added in combination of two or more.

Further, as a method of applying the coating liquid, a known method can be used. For example, the reverse roll coating method, the gravure coating method, the kiss coating method, the roll brush method, the spray coating method, the air knife coating method, the wire bar coating method, the pipe doctor method, etc. can be mentioned, and these methods can be used alone. Alternatively, it can be performed in combination.

The average particle size of the above particles is measured by the following method. The particles are photographed with a scanning electron microscope (SEM), and the maximum diameter of 300 to 500 particles (between the two most distant points) is magnified so that the size of one of the smallest particles is 2 to 5 mm. 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 manufactured according to a general polyester film manufacturing method. For example, a non-oriented polyester obtained by melting a polyester resin and extruding it into a sheet is stretched in the vertical direction at a temperature equal to or higher than the glass transition temperature by utilizing the speed difference of the rolls, and then stretched in the horizontal direction by a tenter. A method of applying 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 the biaxially stretched film is used as a polarizer protective film, it is observed from directly above the film surface. However, rainbow-shaped color spots are not seen, but caution is required because rainbow-shaped color spots may be observed when observed from an oblique direction.

Specifically explaining the film forming conditions of the polyester film, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 135 ° C., more preferably 80 to 130 ° C., 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 stretching ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. The lateral stretching 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 stretching ratio is preferably 2.5 times to 6.0 times, particularly preferably 3.0 to 5.5 times. The transverse stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times.
In order to control the refractive index or retardation of the polyester film in the phase-advancing axis direction within the above range, it is preferable to control the ratio of the longitudinal stretching ratio to the transverse stretching ratio. If the difference between the vertical and horizontal stretching ratios is too small, the refractive index of the polyester film in the phase-advancing axis direction tends to exceed 1.62, and it becomes difficult to increase the retardation, which is not preferable. Further, setting the stretching temperature low is a preferable measure for increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250 ° C, particularly preferably 180 to 245 ° C.

In order to suppress fluctuations 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 influence on the thickness unevenness of the film, it is necessary to optimize the film forming conditions from the viewpoint of the thickness unevenness. In particular, if the longitudinal stretching ratio is lowered in order to increase the retardation, the vertical thickness unevenness may worsen. Since there is a region where the vertical thickness unevenness becomes very poor in a specific range of the draw ratio, it is desirable to set the film forming conditions outside this range.

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

As described above, in order to control the retardation of the polyester film within a specific range, it can be performed by appropriately setting the draw ratio, the draw temperature, and the thickness of the film. 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. On the contrary, the lower the stretching ratio, the higher the stretching 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 appropriately set the film thickness within the range described later. Further, in addition to the control of retardation, it is necessary to set the final film forming conditions in consideration of the physical characteristics required for processing.

The thickness of the polyester film is arbitrary, but is preferably in the range of 15 to 300 μm, more preferably in the range of 15 to 200 μm. In principle, it is possible to obtain retardation of 1500 nm or more even with a film having a thickness of less than 15 μm. However, in that case, the anisotropy of the mechanical properties of the film becomes remarkable, and tearing, tearing, etc. are likely to occur, 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 in the above thickness range, polyethylene sauce phthalate is preferable as the polyester used as the film base material.

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

At this time, the concentration of the ultraviolet absorber in the masterbatch is preferably 5 to 30% by mass in order to uniformly disperse the ultraviolet absorber and to blend it economically. As a condition for producing the masterbatch, it is preferable to use a kneading extruder and extrude the polyester raw material at a temperature equal to or higher than the melting point of the polyester raw material and lower than 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 masterbatch is significantly reduced. If the extrusion temperature is 1 minute or less, 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 needed.

Further, it is preferable that the polyester film has a multilayer structure of at least three layers or more, and an ultraviolet absorber is added to the intermediate layer of the film. Specifically, a film having a three-layer structure containing an ultraviolet absorber in the intermediate layer can be produced as follows. A polyester pellet alone for the outer layer, and a masterbatch containing an ultraviolet absorber for the intermediate layer and polyester pellets are mixed at a predetermined ratio, dried, and then supplied to a known melt lamination extruder to form a slit. It 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 forming both outer layers and a film layer forming an intermediate layer are laminated. A three-layer sheet is extruded from the base and cooled with a casting roll to make an unstretched film. In the present invention, in order to remove foreign substances 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 filter particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. If the size of the filtered particles of the filter medium exceeds 15 μm, the removal of foreign matter of 20 μm or more tends to be insufficient.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples, and is carried out with appropriate modifications to the extent that it can be adapted to the gist of the present invention. It is also possible, all of which are within the technical scope of the invention. The method for evaluating the physical properties in the following examples is as follows.

(1) Refractive coefficient of polyester film Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.), determine the slow axis direction of the film, and the slow axis direction is the long side of the sample for measurement. A rectangle of 4 cm × 2 cm was cut out so as to be parallel to the above, and used as a measurement sample. For this sample, the refractive indexes of the two orthogonal axes (refractive index in the slow axis direction: Ny, refractive index in the phase advance axis (refractive index in the direction orthogonal to the slow axis direction): Nx), and the refractive index in the thickness direction ( Nz) was determined by an Abbe refractive index meter (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm).

(2) Reference (Re)
The retardation is a parameter defined by the product (ΔNxy × d) of the anisotropy of the refractive indexes of the two orthogonal axes on the film (ΔNxy = | Nx−Ny |) and the film thickness d (nm). Yes, it is a scale showing optical isotropic and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.), determine the slow-phase axial direction of the film, and 4 cm so that the slow-phase axial direction is parallel to the long side of the measurement sample. A rectangle of × 2 cm was cut out and used as a measurement sample. For this sample, the refractive index of two orthogonal axes (refractive index in the slow axis direction: Ny, refractive index in the direction orthogonal to the slow axis direction: Nx), and the refractive index in the thickness direction (Nz) are abbe refraction. It was determined by a rate meter (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm), and the absolute value (| Nx-Ny |) of the difference in refractive index between the two axes was defined as the refractive index anisotropy (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D manufactured by Finereuf), 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)
The thickness direction retardation is obtained by multiplying two birefringences ΔNxz (= | Nx−Nz |) and ΔNyz (= | Ny−Nz |) when viewed from a cross section in the film thickness direction by the film thickness d, respectively. It is a parameter indicating the average of the refraction obtained. Nx, Ny, Nz and the film thickness d (nm) are obtained by the same method as the measurement of retardation, and the average value of (ΔNxz × d) and (ΔNyz × d) is calculated to perform thickness direction retardation (Rth). ) Was asked.

(4) Measurement of Emission Spectrum of Backlit Light Source The liquid crystal display device used in each embodiment is a liquid crystal display having a BRAVIA KDL-40W920A manufactured by SONY (a light source that emits excitation light and a backlight source that includes quantum dots). Device) was used. When the emission spectrum of the backlight source of this liquid crystal display device was measured using a multi-channel spectroscope PMA-12 manufactured by Hamamatsu Photonics, emission spectra having peak tops near 450 nm, 528 nm, and 630 nm were observed, and each peak top was observed. The half-value width of was 17 nm to 34 nm. The exposure time for spectrum measurement was 20 msec.

(5) Observation of rainbow spots The liquid crystal display devices obtained in each example were visually observed in a dark place from the front and diagonal directions, and the presence or absence of rainbow spots was determined as follows.

◯: No rainbow spots are observed △: Slight rainbow spots are observed ×: Rainbow spots are observed × ×: Rainbow spots are significantly observed

(6) Refractive Index of Easy Adhesive Layer After applying the adhesive modification coating liquid to the glass plate, it was solidified under predetermined conditions to prepare a coating film of about several μm. The coating film was peeled off from the glass plate, and the refractive index was measured with an Abbe refractometer (NAR-1T SOLID manufactured by Atago Co., Ltd., measurement wavelength 589 nm).

(Production Example 1-Polyester A)
When the temperature of the esterification reaction can reached 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 was used as a catalyst while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Then, the pressure was raised and the pressure esterification reaction was carried out under the conditions of a gauge pressure of 0.34 MPa and 240 ° C., the esterification reaction can 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. Then, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can, and a polycondensation reaction was carried out under reduced pressure at 280 ° C.

After completion of the polycondensation reaction, filtration is performed with a Naslon filter having a 95% cut diameter of 5 μm, extruded into a strand shape from a nozzle, and cooled and solidified using cooling water that has been previously filtered (pore diameter: 1 μm or less). , Cut into pellets. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl / g, and the inert particles and internally precipitated particles were substantially not contained. (Hereafter, it is 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-benzoxadinone-4-one), particle-free PET (A) (intrinsic viscosity) 0.62 dl / g) 90 parts by mass was mixed, and a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter abbreviated as PET (B)).

(Manufacturing Example 3-Adhesive Modification Coating Liquid Adjustment)
The ester exchange reaction and the polycondensation reaction were carried out by a conventional method, and 46 mol% of terephthalic acid, 46 mol% of isophthalic acid and 8 mol% of sodium 5-sulfonatoisophthalate were carried out as dicarboxylic acid components (relative to the entire dicarboxylic acid component). A water-dispersible metal sulfonate metal base-containing copolymer resin having a composition of 50 mol% of ethylene glycol and 50 mol% of neopentyl glycol as the glycol component was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cell solution, and 0.06 parts by mass of a nonionic surfactant are mixed, and then heated and stirred. When the temperature reaches 77 ° C., the above After adding 5 parts by mass of a water-dispersible metal sulfonic acid base-containing copolymerized polyester resin and continuing stirring until the resin clumps disappear, the resin water dispersion is cooled to room temperature to have a solid content concentration of 5.0% by mass. A uniform water-dispersible copolymerized polyester resin solution was obtained. Further, after 3 parts by mass of aggregate silica particles (Syricia 310 manufactured by Fuji Silicia Co., Ltd.) are dispersed in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolymerized polyester resin liquid is added to Syricia 310. 0.54 parts by mass of an aqueous dispersion was added, and 20 parts by mass of water was added with stirring to obtain an adhesive modification coating liquid. The refractive index of the easy-adhesion layer obtained by using this easily-adhesive modified coating liquid was 1.530.

(Polarizer protective film 1)
After 90 parts by mass of PET (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours as raw materials for the base film intermediate layer. , It was supplied to the extruder 2 (for the intermediate layer II layer), and the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, and melted at 285 ° C. .. These two types of polymers are filtered through a stainless steel sintered filter medium (nominal filtration accuracy of 10 μm particles 95% cut), laminated in a two-type three-layer confluence block, extruded into a sheet from the base, and then extruded. An unstretched film was prepared by winding it around a casting drum having a surface temperature of 30 ° C. and cooling and solidifying it using an electrostatic application casting method. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of the I layer, the II layer, and the III layer was 10:80:10.

Next, the adhesive modification coating liquid was applied to both sides of the unstretched PET film by the 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 on which the coating layer was formed was guided to a tenter stretching machine, and while gripping the end of the film with a clip, it was guided to a hot air zone having 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 relaxation treatment of 3.0% in the width direction to obtain a uniaxially stretched PET film having a film thickness of about 100 μm. It was. The Re of the obtained film was 10300 nm, Rth was 12350 nm, Re / Rth was 0.83, Nx = 1.588, and Ny = 1.691.

(Polarizer protective film 2)
A film was formed 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, and a uniaxially stretched PET film having a film thickness of about 80 μm was obtained. The Re of the obtained film was 8080 nm, Rth was 9960 nm, Re / Rth was 0.81, Nx = 1.589, and Ny = 1.690.

(Polarizer protective film 3)
A film was formed 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, to obtain a uniaxially stretched PET film having a film thickness of about 60 μm. The Re of the obtained film was 6060 nm, Rth was 7470 nm, Re / Rth was 0.81, Nx = 1.589, and Ny = 1.690.

(Polarizer protective film 4)
A film was formed 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, to obtain a uniaxially stretched PET film having a film thickness of about 40 μm. The Re of the obtained film was 4160 nm, the Rth was 4920 nm, the Re / Rth was 0.85, Nx = 1.587, and Ny = 1.691.

(Polarizer protective film 5)
The unstretched film produced by the same method as the polarizer protective film 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then 1.5 in the traveling direction in the roll group having a peripheral speed difference. After double-stretching, the film was guided to a hot air zone at a temperature of 130 ° C. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film having a film thickness of about 100 μm in the same manner as in the polarizer protective film 1. The Re of the obtained film was 7820 nm, the Rth was 13890 nm, the Re / Rth was 0.56, Nx = 1.608, and Ny = 1.686.

(Polarizer protective film 6)
The unstretched film produced by the same method as the polarizer protective film 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then 2.0 in the traveling direction in the roll group having a peripheral speed difference. After double stretching, the film was guided to a hot air zone at a temperature of 135 ° C. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film having a film thickness of about 100 μm in the same manner as the polarizer protective film 1. The Re of the obtained film was 6400 nm, Rth was 14600 nm, Re / Rth was 0.44, Nx = 1.617, and Ny = 1.681.

(Polarizer protective film 7)
The unstretched film produced by the same method as the polarizer protective film 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then 2.8 in the traveling direction in the roll group having a peripheral speed difference. After double-stretching, the film was guided to a hot air zone at a temperature of 140 ° C. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film having a film thickness of about 100 μm in the same manner as the polarizer protective film 1. The Re of the obtained film was 5400 nm, Rth was 15900 nm, Re / Rth was 0.34, Nx = 1.631, and Ny = 1.685.

(Polarizer protective film 8)
The unstretched film produced by the same method as the polarizer protective film 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then 3.3 in the traveling direction in the roll group having a peripheral speed difference. After double-stretching, the film was guided to a hot air zone at a temperature of 140 ° C. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film having a film thickness of about 100 μm in the same manner as the polarizer protective film 1. The Re of the obtained film was 4800 nm, Rth was 16700 nm, Re / Rth was 0.29, Nx = 1.640, and Ny = 1.688.

A liquid crystal display device was created using the polarizer protective films 1 to 8 as described later.

(Example 1)
A polarizing element protective film 1 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 1 was prepared by pasting (manufactured by 80 μm in thickness).
The polarizing plate on the visual side of the BRAVIA KDL-40W920A (a liquid crystal display device having a light source that emits excitation light and a backlight light source containing quantum dots) manufactured by SONY is used with the polyester film on the opposite side (distal) to the liquid crystal. A liquid crystal display device was created by replacing the polarizing plate 1 with the above-mentioned polarizing plate 1. 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 the replacement.

(Example 2)
A polarizing element protective film 2 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 2 was prepared by pasting (manufactured by 80 μm in thickness).
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 polarizing element protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 3 was prepared by pasting (manufactured by 80 μm in thickness).
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 polarizing element protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 3 was prepared by pasting (manufactured by 80 μm in thickness).
The polarizing plate on the light source side of BRAVIA KDL-40W920A (a liquid crystal display device having a light source that emits excitation light and a backlight light source including quantum dots) manufactured by SONY is used with a polyester film on the opposite side (distal) to the liquid crystal. A liquid crystal display device was created by replacing the polarizing plate 3 with the above-mentioned polarizing plate 3. The direction of the transmission axis of the polarizing plate 3 was replaced so as to be the same as the direction of the transmission axis of the polarizing plate before replacement.

(Example 5)
A polarizing element protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 3 was prepared by pasting (manufactured by 80 μm in thickness).
The polarizing plate on the visual side and the light source side of the BRAVIA KDL-40W920A (a liquid crystal display device having a light source that emits excitation light and a backlight light source including quantum dots) manufactured by SONY, and the polyester film is on the opposite side (far) from the liquid crystal. A liquid crystal display device was created by replacing the polarizing plate 3 with the above-mentioned polarizing plate 3 so as to be (position). The direction of the transmission axis of the polarizing plate 3 was replaced so as to be the same as the direction of the transmission axis of the polarizing plate before replacement.

(Example 6)
A polarizing element protective film 4 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 4 was prepared by pasting (manufactured by 80 μm in thickness).
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 7)
A polarizing element protective film 5 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. A polarizing plate 5 was prepared by pasting (manufactured by 80 μm in thickness).
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 8)
A polarizing element protective film 6 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. A polarizing plate 6 was prepared by pasting (manufactured by 80 μm in thickness).
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.

(Comparative Example 1)
A polarizing element protective film 1 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are perpendicular to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. A polarizing plate 7 was prepared by pasting (manufactured by 80 μm in thickness).
The polarizing plate on the visual side of the BRAVIA KDL-40W920A (a liquid crystal display device having a light source that emits excitation light and a backlight light source containing quantum dots) manufactured by SONY is used with the polyester film on the opposite side (distal) to the liquid crystal. A liquid crystal display device was created by replacing the polarizing plate 7 with the above-mentioned polarizing plate 7. The direction of the transmission axis of the polarizing plate 7 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 polarizing element protective film 2 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are perpendicular to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. A polarizing plate 8 was prepared by pasting (manufactured by 80 μm in thickness).
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 8.

(Comparative Example 3)
A polarizing element protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are perpendicular to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. A polarizing plate 9 was prepared by pasting (manufactured by 80 μm in thickness).
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 9.

(Comparative Example 4)
A polarizing element protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are perpendicular to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. A polarizing plate 9 was prepared by pasting (manufactured by 80 μm in thickness).
The polarizing plate on the light source side of BRAVIA KDL-40W920A (a liquid crystal display device having a light source that emits excitation light and a backlight light source including quantum dots) manufactured by SONY is used with a polyester film on the opposite side (distal) to the liquid crystal. A liquid crystal display device was created by replacing the polarizing plate 9 with the above-mentioned polarizing plate 9. 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 5)
A polarizing element protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are perpendicular to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. A polarizing plate 9 was prepared by pasting (manufactured by 80 μm in thickness).
The polarizing plate on the visual side and the light source side of the BRAVIA KDL-40W920A (a liquid crystal display device having a light source that emits excitation light and a backlight light source including quantum dots) manufactured by SONY, and the polyester film is on the opposite side (far) from the liquid crystal. A liquid crystal display device was created by replacing the polarizing plate 9 with the above-mentioned polarizing plate 9 so as to be (position). 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 6)
A polarizing element protective film 4 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are perpendicular to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 10 was prepared by pasting (manufactured by 80 μm in thickness).
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 10.

(Comparative Example 7)
A polarizing element protective film 7 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 11 was prepared by pasting (manufactured by 80 μm in thickness).
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 11.

(Comparative Example 8)
A polarizing element protective film 8 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and TAC film (Fuji Film Co., Ltd.) is attached to the opposite surface. The polarizing plate 12 was prepared by pasting (manufactured by 80 μm in thickness).
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 12.

Table 1 below shows the results of measuring rainbow spot observations for the liquid crystal display devices obtained in each example.

The liquid crystal display device and the polarizing plate of the present invention can ensure good visibility in which the occurrence of iridescent color spots is significantly suppressed at any observation angle, and have extremely high industrial applicability. ..

Claims (3)

A liquid crystal display device having a backlight light source, two polarizing plates, and a liquid crystal cell arranged between the two polarizing plates.
The backlight source is 400 nm or more and less than 495 nm, and 495 nm or more and 600 nm.
It has a peak top of the emission spectrum in each wavelength region of less than 600 nm and 600 nm or more and 750 nm or less, and the half width of each peak is 5 nm or more and 120 nm or less .
At least one of the two polarizing plates has a polyester film laminated on the surface of the polarizing element opposite to the liquid crystal cell side .
The retardation of the polyester film is 4000 nm or more, and the retardation is 4000 nm or more.
The polyester film has an easy-adhesion layer on at least one surface.
The difference between the refractive index of the easy-adhesion layer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 0.10 or less.
Liquid crystal display device. The liquid crystal display device according to claim 1, wherein the backlight source is a backlight source including a light source that emits excitation light and quantum dots. The liquid crystal display device according to claim 1 or 2, wherein the polyester film has a retardation of 4000 nm or more and 30,000 nm or less .