TWI777916B - Liquid crystal display device and use of polarizing plate in liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal display device, which can suppress rainbow spots even when a polyester film is used as a polarizer protective film in a liquid crystal display device having a light source for emitting excitation light and a backlight light source for quantum dots.

The liquid crystal display device is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers. The backlight source includes a light source for emitting excitation light and quantum dots, and at least one of the polarizers One of the polarizers is a polarizer with a polyester film laminated on at least one side of the polarizer. The polyester film has a retardation of 1500-30000 nm, and an anti-reflection layer and/or low reflection are laminated on at least one side of the polyester film. Floor.

Description

Liquid crystal display device and use of polarizing plate in liquid crystal display device

The present invention relates to a liquid crystal display device and a polarizing plate. In detail, it is about a liquid crystal display device and a polarizing plate in which the occurrence of rainbow-like color irregularities is reduced.

The polarizing plate used in the liquid crystal display device (LCD) is usually composed of two polarizer protective films sandwiched by a polarizer such as polyvinyl alcohol (PVA) dyed with iodine. Triacetyl cellulose (TAC) films may be used in some cases. In recent years, with thinning of LCDs, thinning of polarizing plates is required. However, when the thickness of the TAC thin film used as a protective film is reduced for this reason, sufficient mechanical strength cannot be obtained, and the problem of deterioration in moisture permeability occurs. In addition, since TAC films are very expensive, polyester films have been proposed as inexpensive alternatives (Patent Documents 1 to 3), but there is a problem that rainbow-like color spots are observed.

When an oriented polyester film having birefringence is arranged on one side of the polarizer, the linearly polarized light emitted from the backlight unit or the polarizer passes through the polyester film, and the polarization state changes. The transmitted light exhibits a characteristic interference color on the retardation of 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 The intensity of the transmitted light varies depending on the wavelength, forming a rainbow-like color spot (refer to: The 15th Micro-Optics Conference Proceedings, Items 30~31).

As a means to solve the above problems, it is proposed to use a white light source with a continuous and broad emission spectrum, such as a white light emitting diode, as a backlight source, and further use an oriented polyester film with a certain retardation as a polarizer protective film ( Patent Document 4). The white light-emitting diode system has a continuous and broad emission spectrum in the visible light region. Therefore, there is a proposal to focus on the envelope shape of the interference color spectrum caused by the transmitted light passing through the birefringent body, and to obtain a spectrum similar to the emission spectrum of the light source by controlling the hysteresis of the oriented polyester film, which can suppress the rainbow spot.

By making the alignment direction of the alignment polyester film and the polarizing direction of the polarizing plate orthogonal or parallel to each other, the linearly polarized light emitted from the polarizer passes through the alignment polyester film while maintaining the polarized state and passing through. In addition, by controlling the birefringence of the oriented polyester film, the uniaxial orientation is improved, and the light incident from the oblique direction also passes through while maintaining the polarized state. When the oriented polyester film is viewed obliquely, the deviation in the direction of the main axis of the alignment occurs when viewed from directly above, but when the one-axis orientation is high, the deviation in the direction of the main axis of the alignment when viewed obliquely becomes smaller. Therefore, it is considered that the deviation between the direction of the linearly polarized light and the direction of the main axis of the alignment becomes small, and the change of the polarization state becomes less likely to occur. It is considered that by controlling the emission spectrum of the light source, the alignment state of the birefringent body, and the direction of the main axis of alignment as described above, changes in the polarization state can be suppressed, rainbow-like color spots are not generated, and visibility is remarkably improved.

[Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2002-116320

Patent Document 2: Japanese Patent Laid-Open No. 2004-219620

Patent Document 3: Japanese Patent Laid-Open No. 2004-205773

Patent Document 4: WO2011/162198

When industrially producing a liquid crystal display device using a polarizer with a polyester film as a polarizer protective film, the transmission axis of the polarizer and the fast axis of the polyester film are generally arranged to be perpendicular to each other. This is based on the following events. The polyvinyl alcohol film of the polarizer can be produced by being uniaxially stretched in the longitudinal direction. Therefore, the polyvinyl alcohol film used as a polarizer is generally a long film in the extending direction. On the other hand, since the polyester film of this protective film is produced by extending in the vertical direction and then extending in the horizontal direction, the orientation main axis direction of the polyester film becomes the horizontal direction. That is, the orientation principal axis of the polyester film used as the polarizer protective film and the longitudinal direction of the film are substantially perpendicular to each other. These films are usually bonded together so that their longitudinal directions are parallel to each other to manufacture a polarizing plate. In this way, the phase advance axis of the polyester film and the transmission axis of the polarizer are usually perpendicular to each other. In this case, by using an oriented polyester film with a specific retardation as the polyester film, and using a light source with a continuous and broad emission spectrum such as a white LED as a backlight light source, the iridescent color spot is greatly improved. However, when the backlight light source is composed of a light source emitting excitation light and a light-emitting layer containing quantum dots, a new problem of occurrence of rainbow spots is still found.

Due to the increasing demand for color gamut expansion in recent years, in addition to the white light source using quantum dot technology, the emission spectrum of the white light source has been developed in each wavelength region of R (red), G (green) and B (blue). Each of the liquid crystal display devices has a clear peak of relative luminous intensity. For example, a liquid crystal display device corresponding to a wide color gamut using various light sources has been developed: a phosphor having clear emission peaks in the (red) and G (green) regions due to excitation light, and a blue LED White LED light source of phosphor method, white LED light source of 3-wavelength method, white LED light source combined with red laser, etc. Compared with the conventional light sources composed of white light-emitting diodes using YAG-based yellow phosphors, the half-value widths of the peaks of these white light sources are all narrower. In these white light sources, when a polyester film having retardation is used as a polarizer protective film for a constituent member of a polarizer, it has been found that there is a backlight composed of a light source for emitting excitation light and a light-emitting layer containing quantum dots as described above. The same problem occurs in the case of the liquid crystal display device of the light source.

That is, one of the problems of the present invention is to provide a liquid crystal display device and a polarizing plate, which have a comparison of the half-value widths of each peak in the emission spectrum, such as a light source including a light source for emitting excitation light and a backlight light source of quantum dots. In a liquid crystal display device with a narrow backlight source, when a polyester film is used as a polarizer protective film, rainbow spots can also be suppressed.

Representative aspects of the present invention are described below.

Invention 1.

A liquid crystal display device, which is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers, The aforementioned backlight source includes a light source for emitting excitation light and quantum dots, at least one of the aforementioned polarizers is laminated with a polyester film on at least one side of the polarizer, and the aforementioned polyester film has a hysteresis of 1500-30000 nm, and An anti-reflection layer and/or a low-reflection layer are laminated on at least one side of the polyester film.

Invention 2.

A liquid crystal display device, which is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers, wherein the backlight source emits more than 400nm and less than 495nm, more than 495nm and less than 600nm , and each wavelength region above 600nm and below 780nm each has a peak of the emission spectrum, and the half-value width of each peak is light of 5nm or more, and at least one of the above-mentioned polarizing plates is attached to at least one side of the polarizer. A polyester film is laminated on the surface, the polyester film has a retardation of 1500-30000 nm, and an antireflection layer and/or a low reflection layer is laminated on at least one side of the polyester film.

Invention 3.

The liquid crystal display device according to claim 2, wherein the backlight light source has a peak top of an emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 750 nm or less, and the half value of each peak is The width is 5 nm or more.

Invention 4.

The liquid crystal display device according to any one of Inventions 1 to 3, wherein The surface reflectance of the surface of the antireflection layer at a wavelength of 550 nm is 2.0% or less.

Invention 5.

A polarizing plate for a liquid crystal display device, which is a polarizing plate with a polyester film laminated on at least one side of a polarizer, the polyester film having a retardation of 1500-30000 nm, and a polyester film laminated on at least one side of the polyester film. The reflection layer and/or the low reflection layer has a backlight source including a light source for emitting excitation light and quantum dots.

Invention 6.

A polarizing plate for a liquid crystal display device, which is a polarizing plate with a polyester film laminated on at least one side of a polarizer, the polyester film having a retardation of 1500-30000 nm, and a polyester film laminated on at least one side of the polyester film. The reflective layer and/or the low-reflection layer has a backlight source, which 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-value width of each peak is Light emission spectrum above 5nm.

Invention 7.

The polarizing plate according to invention 5 or 6, wherein the surface reflectance of the surface of the antireflection layer at a wavelength of 550 nm is 2.0% or less.

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 deliberately suppressed at any viewing angle.

Fig. 1 shows an example when plural peaks exist in a single wavelength region.

Fig. 2 shows an example when plural peaks exist in a single wavelength region.

Fig. 3 shows an example when plural peaks exist in a single wavelength region.

Fig. 4 shows an example when plural peaks exist in a single wavelength region.

[Form of implementing the invention]

Generally speaking, a liquid crystal display device has a rear module, a liquid crystal cell, and a front module in sequence from the side where the backlight light source (also referred to as the "backlight unit") is disposed toward the side (visual recognition side) where the image is displayed. The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the side surface of the liquid crystal cell, and a polarizer arranged on the opposite side. That is, the polarizing plate is arranged on the side opposite to the backlight light source in the rear module, and is arranged on the side (visual recognition side) where the image is displayed in the front module.

The liquid crystal display device of the present invention includes at least a backlight light source and a liquid crystal cell arranged between two polarizing plates as constituent members. The backlight light source preferably 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 has an emission spectrum in which the half width of each peak is 5 nm or more. The peak wavelengths of blue, green, and red defined by the CIE chromaticity diagram are known to be 435.8 nm (blue), 546.1 nm (green), and 700 nm (red), respectively. The wavelength regions 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 correspond to the blue region, the green region, and the red region, respectively. Examples of the light source having the above-mentioned emission spectrum include at least a light source for emitting excitation light and a backlight light source for quantum dots. In addition, there can be exemplified a white LED light source of a phosphor method combining a phosphor having emission peaks in the R (red) and G (green) regions due to excitation light and a blue LED, and a white LED light source of the three-wavelength method. LED light source, white LED light source combined with red laser, etc. As the red phosphor among the aforementioned phosphors, for example, a nitride-based phosphor having CaAlSiN ₃ : Eu or the like as a basic composition, a sulfide-based phosphor having CaS: Eu or the like as a basic composition, a Ca ₂ SiO ₄ : a silicate-based phosphor or the like whose basic composition is Eu or the like. In addition, as a green phosphor among the aforementioned phosphors, for example, a Sialon-based phosphor having β-SiAlON:Eu or the like as its basic composition, a (Ba,Sr) ₂ SiO ₄ :Eu or the like can be exemplified. Silicate phosphor as the basic composition.

The liquid crystal display device may suitably have other structures such as a color filter, a lens film, a diffuser, an anti-reflection film, and the like in addition to a backlight source, a polarizing plate, and a liquid crystal cell. A brightness enhancement film can also be arranged between the light source side polarizing plate and the backlight light source. As a brightness enhancement film, for example, a reflective polarizing plate that transmits one linearly polarized light and reflects the linearly polarized light orthogonal to the same is mentioned. As the reflective polarizing plate, for example, a DBEF (registered trademark) (Dual Brightness Enhancement Film) series brightness enhancement film manufactured by Sumitomo 3M Co., Ltd. is preferably used. In addition, the reflective polarizer is usually arranged so that the absorption axis of the reflective polarizer and the absorption axis of the light source side polarizer are parallel.

烯系薄膜為代表之無雙折射的薄膜(3層構成的偏光板)，但在偏光鏡的另一側之面上未必需要積層薄膜(2層構成的偏光板)。再者，使用聚酯薄膜作為偏光鏡的兩側之保護膜時，兩側的聚酯薄膜之遲相軸(slow axis)較佳為互相大致平行。 Among the two polarizers arranged in the liquid crystal display device, at least one of the polarizers is preferably laminated with polyester on at least one side of a polarizer such as polyvinyl alcohol (PVA) dyed with iodine. film. From the viewpoint of suppressing rainbow-like color irregularities, it is preferable that the polyester film has a specific retardation, and an antireflection layer and/or a low reflection layer are laminated on at least one side of the polyester film. The anti-reflection layer and/or the low-reflection layer may be provided on the surface of the polyester film opposite to the surface of the laminated polarizer, or may be provided on the surface of the polyester film on the surface of the laminated polarizer, or both. It is preferable to provide an antireflection layer and/or a low reflection layer on the surface opposite to the surface of the laminated polarizer of the polyester film. When the anti-reflection layer and/or the low-reflection layer is provided on the surface of the laminated polarizer of the polyester film, the layer is preferably provided between the polyester film and the polarizer. In addition, other layers (eg, an easy-adhesion layer, a hard coat layer, an anti-glare layer, an antistatic layer, an antifouling layer, etc.) may be present between the anti-reflection layer and/or the low-reflection layer and the polyester film. From the viewpoint of further suppressing rainbow-like color irregularities, the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is preferably 1.53 or more and 1.62 or less. On the other side of the polarizer, it is preferable to laminate such as TAC film, acrylic film and

The olefin film is a representative film without birefringence (polarizing plate composed of three layers), but a laminated film (polarizing plate composed of two layers) is not necessarily required on the other side of the polarizer. Furthermore, when a polyester film is used as the protective film on both sides of the polarizer, the slow axes of the polyester films on both sides are preferably substantially parallel to each other.

The polyester film may be laminated on the polarizer via an arbitrary adhesive, or may be directly laminated without an adhesive. The adhesive is not particularly limited, and any one can be used. As an example, an aqueous adhesive (that is, an adhesive component dissolved in or dispersed in water) can be used. For example, an adhesive containing a polyvinyl alcohol-based resin and/or a urethane resin or the like as a main component can be used. In order to improve adhesiveness, an isocyanate-based compound and/or epoxy resin may be further blended as necessary. Adhesives for compounds, etc. Moreover, as another example, a photocurable adhesive can also be used. In one embodiment, a solvent-free UV-curable adhesive is preferred. As a photocurable resin, the mixture etc. of a photocurable epoxy resin and a photocationic polymerization initiator are mentioned, for example.

As the configuration of the backlight, an edge light method using a light guide plate, a reflector, or the like as a constituent member may be used, or a direct type method may be used. The backlight light source is a representative example of a backlight light source including a light source that emits excitation light and quantum dots, and preferably has a peak 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. top, a backlight source having an emission spectrum with a half-value width of each peak of 5 nm or more." Furthermore, quantum dots, for example, can be provided with a layer containing many quantum dots and used as a light-emitting layer for backlighting.

The application of quantum dot technology to LCD is a technology that has attracted attention from the perspective of the increasing requirements for color gamut expansion in recent years. In general LEDs that use white LEDs as backlight light sources, only about 20% of the color spectrum that can be recognized by human eyes can be reproduced. On the other hand, when a backlight light source composed of a light source that emits excitation light and a light-emitting layer of quantum dots is used, it is said that about 60% of the colors of the spectrum that can be recognized by the human eye can be reproduced. Practical quantum dot technologies include QDEF ^TM of Nanosys or Color IQ ^TM of QD Vision.

The light-emitting layer containing quantum dots is composed of quantum dots contained in a resin material such as polystyrene, for example, and emits light-emitting light of various colors on a pixel-by-pixel basis based on excitation light emitted from a light source. This light-emitting layer is composed of, for example, a red light-emitting layer arranged in a red pixel, a green light-emitting layer arranged in a green pixel, and a blue light-emitting layer arranged in a blue pixel. The light-emitting layer is constituted, and in the quantum dots of the light-emitting layers of these plural colors, based on the excitation light, light-emitting light rays of mutually different wavelengths (colors) are generated.

Examples of such quantum dot materials include CdSe, CdS, ZnS:Mn, InN, InP, CuCl, CuBr, Si, etc. The particle size (size in one side direction) of these quantum dots is, for example, 2 to 20 nm. about. Moreover, among the quantum dot materials mentioned above, InP is mentioned as a red light-emitting material, CdSe is mentioned as a green light-emitting material, for example, CdS etc. are mentioned as a blue light-emitting material, for example. In such a light-emitting layer, it was confirmed that the emission wavelength was changed by changing the size (particle diameter) of the quantum dots or the composition of the material. The size (particle size) and material of the quantum dots are controlled, mixed with a resin material, and used by color-separating coating for each pixel. In addition, since the use of heavy metals such as cadmium is regulated in many applications, development of cadmium-free quantum dots is also being carried out while maintaining the same brightness and stability as those of conventional ones.

As a light source for emitting excitation light, a blue LED can be used, but laser light such as a semiconductor laser can also be used. The excitation light from the light source passes through the light-emitting layer to generate emission spectra with peaks 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. In this case, the narrower the half-value width of the peaks in each wavelength region, the wider the color gamut, and the narrower the half-value width of the peaks, the lower the luminous efficiency. Therefore, the luminous spectrum is designed in consideration of the balance between the required color gamut and luminous efficiency. shape.

The light source system using quantum dots is not limited to the following, but there are roughly two installation methods. One is to install quantum dots on the edge along the end (side) of the light guide plate of the backlight. Particles with a diameter of several nanometers to tens of nanometers The quantum dots are placed in a glass tube with a diameter of several mm, which is sealed and placed between the blue LED and the light guide plate. When the light from the blue LED is irradiated to the glass tube, at this time, the blue light colliding with the quantum dots is converted into green light or red light. The edge-on-edge method has the advantage of reducing the amount of quantum dots used even in a large screen. The other is a surface mount method in which quantum dots are placed on a light guide plate. The quantum dots were dispersed in the resin, thinned, and the quantum dot film sandwiched and sealed by two barrier films was laid on a light guide plate. The barrier film plays a role in suppressing the degradation of quantum dots caused by water or oxygen. The blue LEDs are arranged on the end surface (side surface) of the light guide plate in the same manner as the edge-on-edge method. The light from the blue LED enters the light guide plate and becomes a planar blue light, which illuminates the quantum dot film. The advantages of the surface mounting method are roughly two. One is that the light from the blue LED collides with the quantum dots through the light guide plate, so the heat from the LED is less affected and reliability is easily ensured. The other system is in the form of a film, so it is easy to cope with a wide screen size from small to large.

In the present invention, the backlight light source preferably has a peak top of an emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 780 nm or less, and the half-value width of each peak is 5 nm or more. . The aforementioned wavelength region of 400 nm or more and 495 nm is more preferably 430 nm or more and 470 nm or less. The aforementioned wavelength region of 495 nm or more and less than 600 nm is more preferably 510 nm or more and 560 nm or less. The wavelength region of 600 nm or more and 780 nm or less is more preferably 600 nm or more and 750 nm or less, more preferably 630 nm or more and 700 nm or less, and even more preferably 630 nm or more and 680 nm or less. A preferable lower limit of the half-value width of each peak is 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more. from ensuring From the viewpoint of an appropriate color gamut, the upper limit of the half-value width of each peak is preferably 140 nm or less, more preferably 120 nm or less, more preferably 100 nm or less, particularly preferably 80 nm or less, particularly preferably 60 nm or less, ut Preferably it is 45 nm or less. In addition, the half-value width referred to here is the peak width (nm) when the peak intensity of the wavelength at the peak top is 1/2 intensity. The upper limit and the lower limit of each wavelength region described here assume any combination of them. The upper and lower limits of each half-value width described herein contemplate any combination of them. The peak intensity can be measured using, for example, a multi-channel spectroscope PMA-12 manufactured by Hamamatsu Photonics, etc., to measure the emission spectrum of the backlight light source.

In any wavelength range of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, or 600 nm or more and 780 nm or less, the existence of plural peaks is considered as follows. When the plurality of peaks are independent peaks, the half-value width of the peak with the highest peak intensity is preferably within the above range. Furthermore, for other peaks having an intensity of 70% or more of the highest peak intensity, it is also preferable that the half-value width is in the above-mentioned range. When it is possible to directly measure the half-value width of the peak with the highest peak intensity among the complex-numbered peaks for one independent peak in the shape having the overlapping peaks, the half-value width is used. Here, an independent peak is a region in which both the short wavelength side and the long wavelength side of the peak have an intensity that is 1/2 of the intensity of the peak. That is, when a plurality of peaks overlap and each peak does not have a region with an intensity equal to 1/2 of the peak intensity, the entirety of the plurality of peaks is regarded as one peak. One of the peaks in such a shape having a plurality of peaks overlapping in this way is regarded as the half width (nm) of the peak width (nm) of the intensity of 1/2 of the highest peak intensity. Among complex wave crests, make the crest stronger The highest point is regarded as the peak. In Figures 1 to 4, double-sided arrows indicate the half-value width when there are multiple peaks in a single wavelength region.

In FIG. 1, each of the peaks A and B has a peak as a starting point, and there are points that become 1/2 of the peak intensity on the short-wavelength side and the long-wavelength side. Therefore, peaks A and B are independent peaks. In the case of Fig. 1, the half-value width can be evaluated by the width of the double-sided arrow of the peak A having the highest peak intensity.

In Fig. 2, the peak A exists on the short wavelength side and the long wavelength side with 1/2 of the peak intensity, but the peak B has no point on the long wavelength side with 1/2 the peak intensity. . Therefore, the peak A and the peak B are aggregated and regarded as one independent peak. For an independent peak having such a shape of overlapping of multiple peaks, when the half width of the peak with the highest peak intensity among the complex peaks can be directly measured, the half width is regarded as the half width of the independent peak. Therefore, in the case of Fig. 2, the half width of the peak corresponds to the width of the double arrow.

In Fig. 3, the peak A does not have a point of 1/2 of the peak intensity on the short wavelength side, and the peak B has no point of 1/2 of the peak intensity on the long wavelength side. Therefore, in Fig. 3, as in the case of Fig. 2, the peaks A and B are aggregated and regarded as one independent peak, and the half-value width thereof is the width indicated by the double arrow.

In Fig. 4, the peak A exists on the short wavelength side and the long wavelength side with 1/2 of the peak intensity, but the peak B has no point on the long wavelength side with 1/2 the peak intensity. . Therefore, the peak A and the peak B are aggregated and regarded as one independent peak. For an independent peak with the shape of overlapping peaks of complex numbers, it is possible to directly determine the relationship between the peaks of the complex numbers. When the half-value width of the peak with the highest peak intensity is used, its half-value width is used. Therefore, in the case of Fig. 4, the half-value width is the width indicated by the double arrow.

FIGS. 1 to 4 show the wavelength region of 400 nm or more and less than 495 nm in the example, but the same consideration can be applied to other wavelength regions.

Among the multiple peaks, the peak with the highest peak intensity is regarded as the peak.

Furthermore, the peak having the highest peak intensity in the wavelength region of 400 nm or more and less than 495 nm, the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 780 nm or less is preferably independent of the peaks of other wavelength regions. Relationship. In particular, in the wavelength region between the peak having the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm and the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less, the intensity is in the wavelength region of 600 nm or more and 780 nm or less. It is preferable in terms of the vividness of the color to exist in an area less than 1/3 of the peak intensity of the peak having the highest peak intensity.

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

The inventors of the present invention have made intensive research and found that, such as a backlight source including a light source emitting excitation light and quantum dots, in a liquid crystal display device having a backlight source with a relatively narrow half-width of each peak of the emission spectrum, if a backlight source is used A polyester film with an anti-reflection layer and/or a low-reflection layer as a polarizer protective film and a specific retardation can provide a liquid crystal display device with suppressed rainbow spots and a polarizing plate useful for the provision. by the The mechanism for suppressing the occurrence of iridescent stains in this manner is judged as follows.

When the oriented polyester film is arranged on one side of the polarizer, the linearly polarized light emitted from the backlight unit or the polarizer passes through the polyester film, and the polarization state changes. One of the main reasons for the change of the polarization state is considered to be the influence of the refractive index difference at the interface between the air layer and the oriented polyester film, or the refractive index difference between the polarizer and the oriented polyester film. When the linearly polarized light incident on the alignment polyester film passes through each interface, a part of the light is reflected by the difference in refractive index between the interfaces. At this time, the polarization state of both the emitted light and the reflected light changes, and it is judged that this is one of the reasons for the occurrence of rainbow-like color spots. Therefore, by providing an anti-reflection layer or a low-reflection layer on the surface of the oriented polyester film to reduce surface reflection, it is judged that the reflection at the interface between the air layer and the oriented polyester film can be suppressed, and rainbow-like color spots can be suppressed.

As described above, by combining a backlight source with a relatively narrow half-width of each peak of the emission spectrum represented by a light source that emits excitation light and a backlight source of quantum dots, and a polarizer using a polyester film as a polarizer protective film When combined, rainbow-like discoloration can be suppressed and good visibility is obtained.

Preferably, a polarizer protective film made of polyester film is laminated on at least one side of the polarizer. The polyester film used for the polarizer protective film preferably has a retardation of 1500-30000 nm. If the hysteresis is in the above range, it is more likely to reduce rainbow unevenness, which is preferable. A preferred lower limit value of hysteresis is 3000nm, a more preferred lower limit value is 3500nm, a particularly preferred lower limit value is 4000nm, a particularly preferred lower limit value is 6000nm, and a particularly preferred lower limit value is 8000nm. The preferred upper limit is 30000nm, with The polyester film having the above hysteresis has a considerable thickness, and the handleability as an industrial material tends to decrease. In this specification, the so-called hysteresis means in-plane hysteresis unless otherwise specified.

In addition, the hysteresis system can be obtained by measuring the refractive index and thickness in the two-axis direction, and can also be obtained by using a commercially available automatic birefringence measuring apparatus such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.). In addition, the refractive index system can be calculated|required by Abbe's refractometer (measurement wavelength 589nm).

The ratio (Re/Rth) of the hysteresis (Re: in-plane hysteresis) of the polyester film to the hysteresis (Rth) in the thickness direction is preferably 0.2 or more, more preferably 0.3 or more, particularly preferably 0.4 or more, particularly preferably 0.5 More preferably, it is 0.5 or more, and particularly preferably 0.6 or more. The greater the ratio of the retardation to thickness direction retardation (Re/Rth), the more isotropic the effect of birefringence is, and the more difficult it is for rainbow-like color spots to occur depending on the viewing angle. In a completely uniaxial (uniaxially symmetric) film, the ratio of the retardation to thickness direction retardation (Re/Rth) is 2.0, so the upper limit of the ratio of retardation to thickness direction retardation (Re/Rth) is preferably 2.0. In addition, the retardation in the thickness direction means the average of the retardation obtained by multiplying each of the two birefringences ΔNxz and ΔNyz by the film thickness d when the film is viewed from a cross section in the thickness direction.

From the viewpoint of further suppressing rainbow-like color irregularities, the NZ coefficient of the polyester film is preferably 2.5 or less, more preferably 2.0 or less, still more preferably 1.8 or less, and even more preferably 1.6 or less. Furthermore, in a perfect uniaxial (uniaxially symmetric) thin film, since the NZ coefficient is 1.0, the lower limit of the NZ coefficient is 1.0. However, as the film approaches a fully uniaxial (one-axis symmetric) film, there is a significant reduction in mechanical strength due to the direction orthogonal to the alignment direction. tendencies and must be noted.

The NZ coefficient is represented by |Ny-Nz|/|Ny-Nx|, where Ny represents the refractive index in the direction of the slow axis, and Nx represents the refractive index in the direction orthogonal to the slow axis (the refractive index in the direction of the advancing axis). ), and Nz represents the refractive index in the thickness direction. The alignment axis of the film was obtained using a molecular alignment meter (MOA-6004 type molecular alignment meter, manufactured by Oji Scientific Instruments Co., Ltd.), and was determined by Abbe's refractometer (NAR-4T manufactured by ATAGO, measuring wavelength 589 nm). The refractive index (Ny, Nx, only Ny>Nx) of the two axes in the direction of the alignment axis and the direction orthogonal to it and the refractive index (Nz) in the thickness direction are obtained. The NZ coefficient is obtained by substituting the thus obtained value into |Ny-Nz|/|Ny-Nx|.

From the viewpoint of further 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, particularly preferably 0.08 or more, particularly preferably 0.09 or more, and most preferably 0.1 or more. The upper limit is not particularly specified, but in the case of a polyethylene terephthalate-based film, the upper limit is preferably about 1.5.

As a more preferable aspect of this invention, it is preferable to set the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer which comprises a polarizing plate in the range of 1.53 or more and 1.62 or less. Thereby, reflection at the interface between the polarizer and the polyester film can be suppressed, and rainbow-like color irregularities can be suppressed. When the refractive index exceeds 1.62, rainbow-like color unevenness occurs when viewed 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 even more preferably 1.58 or less.

On the other hand, the lower limit value 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 When it 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 unfavorable. The refractive index is preferably 1.56 or more, more preferably 1.57 or more. Arbitrary ranges combining each of the above-mentioned upper and lower limits of the refractive index are envisaged.

In order to set the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer in the range of 1.53 or more and 1.62 or less, the polarizer is preferably the transmission axis of the polarizer and the advancing axis of the polyester film ( The direction perpendicular to the retardation axis) is parallel. The refractive index of the polyester film in the direction of the advancing axis in the direction perpendicular to the slow axis can be reduced to about 1.53 to 1.62 by the stretching treatment in the film forming step described later. Since the direction of the advancing axis of the polyester film is parallel to the direction of the transmission axis of the polarizer, the refractive index of the polyester film in the direction parallel to the direction of the transmission axis of the polarizer can be set at 1.53~1.62. The so-called parallel here means that the angle formed by the transmission axis of the polarizer and the phase advance axis of the polarizer protective film is -15°~15°, preferably -10°~10°, more preferably - 5° to 5°, preferably -3° to 3°, particularly preferably -2° to 2°, and particularly preferably -1° to 1°. In a preferred embodiment, the so-called parallel is substantially parallel. The term "substantially parallel" here means that the transmission axis and the advance axis are parallel to the extent to allow the inevitable deviation when attaching the polarizer and the protective film. 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 Scientific Instruments Co., Ltd.).

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

The polarizer protective film made of the above polyester film can be used as a polarizing plate for both the incident light side (light source side) and the output light side (visual recognition side). In the polarizing plate arranged on the incident light side, the polarizer protective film system made of the above polyester film can be arranged on the incident light side, on the liquid crystal cell side, or on both sides, with the polarizer as a starting point. side, but preferably at least on the incident light side. Among the polarizers arranged on the light-emitting side, the polarizer protective film system made of the above polyester film can be arranged on the liquid crystal side with the polarizer as a starting point, on the light-emitting side, or on both sides. , but preferably at least on the light-emitting side.

As the polyester used for the polyester film, polyethylene terephthalate or polyethylene naphthalate may be used, but other copolymerization components may be included. These resin systems are excellent in transparency, and are also excellent in thermal and mechanical properties, and can easily control hysteresis by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence. By stretching the film, the refractive index in the direction of the advance axis (perpendicular to the slow axis direction) can be lowered, and even if the thickness of the film is thin, it is relatively A large hysteresis is easily obtained, so it is the most suitable material.

Moreover, in order to suppress the deterioration of optical functional dyes, such as an iodine dye, it is preferable that the light transmittance of a polyester film type|system|group system is 20% or less of wavelength 380nm. The light transmittance at 380 nm is preferably 15% or less, more preferably 10% or less, and particularly preferably 5% or less. If the said light transmittance is 20% or less, the deterioration by ultraviolet rays of an optical functional dye can be suppressed. Furthermore, the transmittance is measured in a direction perpendicular to the plane of the film , can be determined using a spectrophotometer (eg, Hitachi U-3500 model).

In order to make the transmittance of the polyester film at a wavelength of 380 nm to 20% or less, it is preferable to appropriately adjust the type and concentration of the ultraviolet absorber and the thickness of the film. The ultraviolet absorber used in this invention is a well-known thing. As an ultraviolet absorber, an organic type ultraviolet absorber and an inorganic type ultraviolet absorber are mentioned, From a viewpoint of transparency, an organic type ultraviolet absorber is preferable. Examples of the organic ultraviolet absorber include benzotriazole-based, diphenylketone-based, cyclic imide ester-based, and the like, and combinations thereof, but are not particularly limited as long as they are within the absorbance range defined in the present invention. However, from the viewpoint of durability, benzotriazole-based and cyclic imidoester-based are particularly preferred. When two or more types of ultraviolet absorbers are used in combination, the ultraviolet rays of the respective wavelengths can be absorbed at the same time, so that the ultraviolet absorption effect can be further improved.

-4- 酮)、2-甲基-3,1-苯并

-4-酮、2-丁基-3,1-苯并

-4-酮、2-苯基-3,1-苯并

-4-酮等。惟，不受此等所特別限定。 Examples of benzophenone-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'-dimethoxydiphenyl ketone, 2, 2',4,4'-tetrahydroxydiphenylketone, 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-(Tertiary-butyl)phenol, 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2- base) phenol, etc. As a cyclic imide ester type ultraviolet absorber, for example, 2,2'-(1,4-phenylene)bis(4H-3,1-benzoyl) can be mentioned

-4-keto), 2-methyl-3,1-benzo

-4-keto, 2-butyl-3,1-benzo

-4-keto, 2-phenyl-3,1-benzo

-4-keto, etc. However, it is not particularly limited by these.

Moreover, in addition to an ultraviolet absorber, it is also a preferable aspect which contains various additives other than a catalyst in the range which does not inhibit the effect of this invention. Examples of additives include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, lightfast agents, flame retardants, thermal stabilizers, antioxidants, and antigelling agents. agents, surfactants, etc. Moreover, in order to achieve high transparency, it is preferable that particle|grains are not substantially contained in a polyester film. The term "substantially free of particles" means that, for example, in the case of inorganic particles, the content of inorganic elements is 50 ppm or less, preferably 10 ppm or less, and particularly preferably the detection limit or less when the inorganic element is quantified by fluorescent X-ray analysis.

It is preferable to provide an antireflection layer and/or a low reflection layer on the surface of at least one side of the polyester film used as the polarizer protective film. The surface reflectance of the antireflection layer is preferably 2.0% or less. When it exceeds 2.0%, it becomes easy to visually recognize iridescent stains. The surface reflectance of the antireflection layer is more preferably 1.6% or less, particularly preferably 1.2% or less, and particularly preferably 1.0% or less. The lower limit of the surface reflectance of the antireflection layer is not particularly limited, and is, for example, 0.01%. The reflectance can be measured by any method. For example, the reflectance of light with a wavelength of 550 nm can be measured from the surface on the antireflection layer side using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3150).

The anti-reflection layer can be a single layer or a multi-layer. In the case of a single layer, as long as the thickness of the low refractive index layer made of a material with a lower refractive index than that of the polyester film is formed to be 1/4 wavelength or an odd multiple of the wavelength of light, the anti-reflection layer is formed. Anti-reflection available Effect. When the antireflection layer is a multilayer, the antireflection effect can be obtained by alternately forming two or more low-refractive-index layers and high-refractive-index layers, and by appropriately controlling the thickness of each layer and stacking the layers. In addition, if necessary, a hard coat layer may be laminated between the antireflection layers, and an antifouling layer may be formed on the hard coat layer.

As the antireflection layer, a moth-eye structure is used. The so-called moth-eye structure is a concavo-convex structure formed on the surface with a pitch smaller than the wavelength, and this structure can change the sharp and discontinuous refractive index change at the boundary with the air into a continuous and gradual refractive index. rate change. Therefore, by forming a moth-eye structure on the surface, light reflection on the surface of the film is reduced. The formation of the antireflection layer using the moth-eye structure can be carried out with reference to, for example, Japanese Patent Application Laid-Open No. 2001-517319.

As a method of forming the anti-reflection layer, for example, on the surface of the substrate (polyester film), a dry coating method of forming an anti-reflection layer by vapor deposition or sputtering can be used, and coating an anti-reflection layer on the surface of the substrate The coating liquid is a wet coating method in which the antireflection layer is formed by drying, or a combined method of using both of them. The composition of the antireflection layer and its formation method are not particularly limited as long as the above-mentioned properties are satisfied.

As the low-reflection layer, well-known ones can be used. For example, it can be formed by a method of depositing at least one metal or oxide thin film by a vapor deposition method or a sputtering method, or a method of coating one or more layers of an organic thin film. As the low reflection layer, a polyester film or a polyester film further coated with an organic film having a lower refractive index than that of a laminated hard coat layer or the like is preferably used. The surface reflectance of the low reflection layer is preferably less than 5%, more preferably 4% or less, and particularly preferably 3% or less. The lower limit is preferably about 0.8% to 1.0%.

In the anti-reflection layer and/or the low-reflection layer, anti-glare can also be provided function. Thereby, rainbow unevenness can be further suppressed. That is, a combination of an anti-reflection layer and an anti-glare layer, a combination of a low-reflection layer and an anti-glare layer, and a combination of an anti-reflection layer and a low-reflection layer and an anti-glare layer may be used. Particularly preferred is a combination of a low reflection layer and an anti-glare layer. As the anti-glare layer, a well-known anti-glare layer can be used. For example, from the viewpoint of suppressing the surface reflection of the film, after laminating the anti-glare layer on the polyester film, an anti-reflection layer or a low-reflection layer is preferably laminated on the anti-glare layer.

When the antireflection layer or the low reflection layer is provided, the polyester film preferably has an easily bonding layer on the surface thereof. In this case, from the viewpoint of suppressing interference caused by reflected light, it is preferable to adjust the refractive index of the easily bonding layer so that the refractive index of the antireflection layer and the refractive index of the polyester film are close to the geometric mean. . The adjustment of the refractive index of the easily bonding layer can be easily adjusted by a well-known method, for example, by including titanium, germanium, or other metal species in the binder resin.

The polyester film may be subjected to corona treatment, coating treatment, and/or flame treatment, etc. in order to improve the adhesion to the polarizer.

In the present invention, in order to improve the adhesion to the polarizer, it is preferable that at least one side of the film of the present invention has at least one type of polyester resin, polyurethane resin or polyacrylic resin as the film. The easy-bond layer of the main component. The "main component" as used herein refers to a component of 50% by mass or more in the solid content constituting the easily bonded layer. The coating liquid used for the formation of the easily adhesive layer of the present invention is preferably an aqueous coating liquid containing at least one of water-soluble or water-dispersible copolymerized polyester resins, acrylic resins, and polyurethane resins . Examples of such coating liquids include Japanese Patent No. 3567927, Japanese Patent No. Water-soluble or water-dispersible copolymerized polyester resin solutions, acrylic resin solutions, or polyamine based Formate resin solution, etc.

The easy-bonding layer can be obtained by applying the aforementioned coating solution on one or both sides of a longitudinally uniaxially stretched film, drying at 100-150°C, and extending in the lateral direction. The coating weight of the final easy-bonding layer is preferably managed at 0.05-0.20 g/m ² . When the coating amount is less than 0.05 g/m ² , the adhesiveness with the obtained polarizer may become insufficient. On the other hand, when the coating amount exceeds 0.20 g/m ² , the anti-blocking property may decrease. When the easy-bonding layers are provided on both sides of the polyester film, the coating amounts of the easily-bonding layers on both sides can be the same or different, and can be independently set within the above-mentioned ranges.

In the easily bonding layer, it is preferable to add particles in order to impart easy slipperiness. It is preferable to use the particle|grains whose average particle diameter of microparticles|fine-particles is 2 micrometers or less. When the average particle diameter of the particles exceeds 2 μm, the particles tend to fall off the coating layer. Examples of particles contained in the easily bonding layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, oxide Inorganic particles of zirconium, tungsten oxide, lithium fluoride, calcium fluoride, etc., or organic polymer particles of styrene-based, acrylic-based, melamine-based, benzoguanamine-based and polysiloxane-based, etc. These systems may be added individually to the easily bonding layer, or may be added in combination of two or more.

In addition, a well-known method can be used as a method of apply|coating a coating liquid. For example, a reverse roll coating method, a gravure coating method, a lip die coating method, a roll brush method, a spray coating method, an air knife coating method, and a wire bar coating method are mentioned. Cloth method and tube scraping method, etc. These methods can be carried out alone or in combination.

In addition, the measurement of the average particle diameter of the said particle|grains was performed by the following method. Take a picture of the particles with a scanning electron microscope (SEM), take the size of one smallest particle as a magnification of 2 to 5 mm, measure the maximum diameter (the distance between the two farthest points) of 300 to 500 particles, and average the values. as the average particle size.

The polyester film used as a polarizer protective film can be produced in accordance with a general polyester film production method. For example, the polyester resin is melted and extruded into a sheet shape, and the formed non-oriented polyester is stretched in the longitudinal direction at a temperature higher than the glass transition temperature using the speed difference of the rolls, and then stretched by a tenter. The machine is extended in the transverse direction, and the method of applying heat treatment.

The polyester film used in the present invention may be a uniaxially stretched film or a biaxially stretched film.

Specifically, the film forming conditions of the polyester film are described. The longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130°C, and particularly preferably 90 to 120°C. In order to align the film so that the retardation axis becomes the TD direction, the longitudinal stretching magnification is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. In addition, the lateral stretching ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. In order to align the film so that the slow axis becomes the MD direction, the longitudinal stretching ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. In addition, the lateral stretching ratio is preferably 1.0 times to 3.5 times, and particularly preferably 1.0 times to 3.0 times.

Setting a low stretching temperature also reduces the refractive index of the polyester film in the direction of the advancing axis, which is a better response in increasing the hysteresis. In the subsequent heat treatment, the treatment temperature is preferably 100~250°C, and particularly preferably 180°C. ~245°C.

In order to suppress fluctuations in hysteresis, the thickness unevenness of the thin film is preferably small. Since the stretching temperature and the stretching ratio have a great influence on the thickness unevenness of the film, it is also preferable to optimize the film forming conditions from the viewpoint of reducing the thickness unevenness. In particular, in order to increase the hysteresis, if the longitudinal stretching ratio is decreased, the thickness unevenness in the longitudinal direction becomes large. The thickness unevenness in the longitudinal direction is a region where the stretching ratio becomes very poor in a certain range of the stretching ratio, so it is preferable to set the film forming conditions outside this range.

The thickness unevenness of the polyester film is preferably 5.0% or less, more preferably 4.5% or less, particularly preferably 4.0% or less, and particularly preferably 3.0% or less. The thickness unevenness of the film can be measured as follows. A strip-shaped thin film sample (3 m) was collected, and the thickness was measured at 100 points at 1 cm intervals using an electronic micrometer Millitron 1240 manufactured by Seiko-Em Corporation. The maximum value (dmax), the minimum value (dmin), and the average value (d) of the thickness were obtained from the measured values, and the thickness unevenness (%) was calculated by the following formula. The measurement is preferably performed three times, and the average value thereof is obtained.

Uneven thickness (%)=((dmax-dmin)/d)×100

As described above, in order to control the hysteresis of the polyester film in a specific range, it can be performed by appropriately setting the stretching ratio, the stretching temperature, and the thickness of the film. For example, the higher the stretching ratio, the lower the stretching temperature, the thicker the film thickness, and the easier it is to obtain high hysteresis. Conversely, the lower the stretching ratio, the higher the stretching temperature, and the thinner the film thickness, the easier it is to obtain low hysteresis. However, when the thickness of the thin film is increased, the retardation in the thickness direction tends to increase. Therefore, the thickness of the film is desirably set in the range described later. In addition to the control of the hysteresis, the final film forming conditions must be set in consideration of physical properties 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, a hysteresis of 1500 nm or more can be obtained even in a thin film with a thickness of less than 15 μm. However, in this case, the anisotropy of the mechanical properties of the thin film becomes remarkable, and cracking, breakage, etc. tend to occur, and the practicality as an industrial material is remarkably reduced. A particularly preferred lower limit of thickness is 25 μm. On the other hand, when 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 unfavorable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. The upper limit of the particularly preferable thickness is 100 μm, which is about the same level as a general TAC film. In the above thickness range, in order to also control the hysteresis within the scope of the present invention, the polyester used as the film substrate is preferably polyethylene terephthalate.

In addition, as a method of blending the ultraviolet absorber in the polyester film, a well-known method can be used in combination, but a master can be prepared in advance by blending the dried ultraviolet absorber and the polymer raw material using a kneading extruder. When the film is formed, the specified method of mixing the master batch and the polymer raw material is formulated.

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

When the polyester film has a multilayer structure of at least three or more layers, it is preferable to add an ultraviolet absorber to the intermediate layer of the film. Specifically, the three-layer structure film containing the ultraviolet absorber in the intermediate layer can be produced as follows. The polyester pellets for the outer layer alone, the UV absorber-containing masterbatch for the intermediate layer, and the polyester pellets are mixed in a specified ratio, dried, and fed to a well-known melt-lamination extruder, and the slits are A sheet-like die is extruded, and cooled and solidified on a casting roll to produce an unstretched film. That is, using two or more extruders, three-layer manifolds, or merging blocks (for example, a junction block having a corner-shaped junction), the thin film layers constituting the two outer layers and the thin film layers constituting the intermediate layer are combined. It laminated|stacked, the sheet of three layers was extruded from a nozzle, and it cooled on a casting roll, and produced the unstretched film. Furthermore, in the present invention, in order to remove foreign matter contained in the raw material polyester that 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 material used for high-precision filtration of molten resin is preferably 15 μm or less. When the filtration particle size of the filter medium exceeds 15 μm, the removal of foreign matters of 20 μm or more is likely to be insufficient.

[Example]

Hereinafter, the present invention will be described in more detail with reference to the embodiments, but the present invention is not limited by the following embodiments, and can be implemented with appropriate modifications within the scope of the present invention, which are all included in the present invention. within the technical scope. In addition, the evaluation method of the physical property in the following Examples is as follows.

(1) Refractive index of polyester film

A molecular orientation meter (manufactured by Oji Scientific Instruments Co., Ltd., MOA-6004 Molecular Alignment Meter) to obtain the direction of the slow axis of the film, cut out a rectangle of 4 cm × 2 cm in such a way that the direction of the slow axis is parallel to the long side, and use it as a sample for measurement. For this sample, the refractive indices of two orthogonal axes (refractive index in the slow axis direction: Ny, advanced axis (with the The refractive index in the direction orthogonal to the slow axis direction): Nx) and the refractive index in the thickness direction (Nz).

(2) Hysteresis (Re)

The so-called hysteresis is a parameter defined by the product (ΔNxy×d) of the refractive index anisotropy of the orthogonal two axes on the film (ΔNxy=|Nx-Ny|) and the film thickness d (nm), It is a scale representing optical isotropy and anisotropy. The refractive index anisotropy (ΔNxy) of the two axes is obtained by the method of (1) above, and the absolute value of the difference between the refractive indices of the two axes (|Nx-Ny|) is regarded as the anisotropy of the refractive index. The opposite sex (ΔNxy) is calculated. The thickness d (nm) of the thin film was measured using an electric micrometer (manufactured by Feinpruf GmbH, Millitron 1245D), and the unit was converted into nm. The retardation (Re) was obtained from the product (ΔNxy×d) of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film.

(3) Thickness direction hysteresis (Rth)

The so-called thickness direction hysteresis means that the two birefringences ΔNxz (=|Nx-Nz|) and ΔNyz (=|Ny-Nz|) when viewed from a cross section in the thickness direction of the film are each multiplied by the film thickness d. The average parameter of the obtained hysteresis. By the same method as the measurement of hysteresis, Nx, Ny, Nz and film thickness d (nm) were obtained, and the average value of (ΔNxz×d) and (ΔNyz×d) was calculated, and the thickness direction hysteresis (Rth) was obtained. ).

(4)NZ coefficient

The value of the NZ coefficient is obtained by substituting the values of Ny, Nx, and Nz obtained in the above (1) into the formula (NZ=|Ny-Nz|/|Ny-Nx|).

(5) Determination of the emission spectrum of the backlight light source

In the liquid crystal display device used in each example, BRAVIA KDL-40W920A (a liquid crystal display device having a light source for emitting excitation light and a backlight source for quantum dots) manufactured by SONY was used. The luminescence spectrum of the backlight source of the liquid crystal display device was measured using a multi-channel spectroscope PMA-12 manufactured by Hamamatsu PHOTONICS, and the luminescence spectrum with peaks around 450nm, 528nm, and 630nm was observed, and the half-value width of each peak was 17nm~ 34nm. In addition, the exposure time at the time of spectrum measurement was 20 msec.

(6) Reflectivity

The 5-degree reflectance at a wavelength of 550 nm was measured from the surface on the antireflection layer side (or the low reflection layer side) using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3150). Furthermore, on the opposite side of the polyester film to the side where the anti-reflection layer (or low-reflection layer) is provided, after applying black strange ink, affix black vinyl tape (Konghe vinyl tape (stock) HF-737 width 50mm), and measured.

(7) Rainbow spot observation

The liquid crystal display device obtained in each Example was visually observed in a dark place from the front and oblique directions, and the presence or absence of rainbow spots was determined as follows. Here, the so-called oblique direction means a range of 30 degrees to 60 degrees from the normal line direction of the screen of the liquid crystal display device.

○: No rainbow spots are seen

△: Rainbow spots are slightly seen

×: Rainbow spots are seen

××: Rainbow spots are clearly seen

(Production Example 1 - Polyester A)

The temperature of the esterification reaction tank was raised, and when it reached 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added, and 0.017 parts by mass of antimony trioxide and 0.064 parts by mass as catalysts were added while stirring. of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine. Next, pressurized and heated up, and after performing pressurized esterification reaction under the conditions of a gauge pressure of 0.34 MPa and 240 degreeC, the esterification reaction tank was returned to normal pressure, and 0.014 mass part of phosphoric acid was added. In addition, it heated up to 260 degreeC over 15 minutes, and added 0.012 mass part of trimethyl phosphate. Next, 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 tank, and a polycondensation reaction was performed at 280° C. under reduced pressure.

After the completion of the polycondensation reaction, it was filtered with a Naslon filter with a 95% cut-off diameter of 5 μm, extruded from a nozzle into strands, and cooled using cooling water that had been filtered in advance (pore size: 1 μm or less). , cured, and cut into granules. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl/g, and the inert particles and the internally precipitated particles were substantially not contained. (hereinafter, abbreviated as PET(A)).

(Production Example 2 - Polyester B)

-4-酮)、90質量份的不含粒子之PET(A)(固有黏度為0.62dl/g)，使用混煉擠壓機，得到含紫外線吸收劑的聚對苯二甲酸乙二酯樹脂(B)。(以下，簡稱PET(B))。 Mix 10 parts by mass of the dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzone)

-4-ketone), 90 parts by mass of particle-free PET (A) (intrinsic viscosity: 0.62 dl/g), using a kneading extruder to obtain a polyethylene terephthalate resin containing an ultraviolet absorber (B). (hereinafter, abbreviated as PET(B)).

(Production Example 3 - Adjustment of Adhesive Modified Coating Liquid)

The transesterification reaction and the polycondensation reaction were carried out by common methods to prepare 46 mol% of terephthalic acid, 46 mol% of isophthalic acid, and 8 Aqueous dispersion composed of 5-mol% sodium 5-sulfonate isophthalate, 50mol% ethylene glycol and 50mol% neopentyl glycol as diol components (with respect to the total diol components) Copolymerized polyester resin containing sulfonic acid metal base. Next, after mixing 51.4 parts by mass of water, 38 parts by mass of isopropanol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant, the mixture was heated and stirred, and when it reached 77° C., 5 parts by mass was added. The above-mentioned water-dispersible sulfonic acid metal base-containing copolymerized polyester resin was continuously stirred until the agglomerates of the resin disappeared, and then the aqueous resin dispersion was cooled to room temperature to obtain a uniform water dispersion with a solid content concentration of 5.0% by mass. Copolymerized polyester resin liquid. Further, 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, 99.46 parts by mass of the above-mentioned water-dispersible copolymerized polyester resin liquid was used. 0.54 parts by mass of an aqueous dispersion of Silysia 310 was added to the mixture, and 20 parts by mass of water was added while stirring to obtain an adhesive modified coating liquid.

(Production Example 4 - Preparation of High Refractive Index Coating)

80 parts of methyl methacrylate, 20 parts of methacrylic acid, 1 part of azoisobutyronitrile, and 200 parts of isopropanol were added to the reaction vessel, and the reaction was carried out at 80° C. for 7 hours under a nitrogen atmosphere to obtain A solution of a polymer with a weight average molecular weight of 30,000 in isopropanol. Further, the obtained polymer solution was diluted with isopropanol until the solid content was 5%, and an acrylic resin solution B was obtained. Next, the obtained acrylic resin solution B was mixed with the following components, A coating liquid for forming a high refractive index layer was obtained.

(Production Example 5 - Preparation of Low Refractive Index Coating)

2,2,2-trifluoroethyl acrylate (45 parts by mass), perfluorooctyl ethyl acrylate (45 parts by mass), acrylic acid (10 parts by mass), azoisobutyronitrile (1.5 parts by mass), methyl methacrylate Methyl ethyl ketone (200 parts by mass) was put into the reaction vessel, and the reaction was carried out at 80° C. for 7 hours in 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 to a solid content concentration of 5 mass % with methyl ethyl ketone, and a fluoropolymer solution C was obtained. The obtained fluoropolymer solution C was mixed as follows to obtain a coating liquid for forming a low refractive index layer.

(Manufacturing example 6-Adjustment of anti-glare coating agent-1)

The unsaturated double bond-containing acrylic copolymer Cyclomer P ACA-Z250 (manufactured by DAICEL Chemical Industry Co., Ltd.) (49 parts by mass) and cellulose acetate propionate CAP482-20 (number average Molecular weight 75000) (EASTMAN Chemical Co., Ltd.) (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) (Sekisui The solid content of Irgacure 184 (manufactured by BASF Corporation) (2 parts by mass) and Irgacure 184 (manufactured by BASF) (10 parts by mass) was added to a mixed solvent of methyl ethyl ketone:1-butanol=3:1 to obtain anti-glare A coating liquid for layer formation.

(Manufacturing example 7-Adjustment of anti-glare coating agent-2)

The unsaturated double bond-containing acrylic copolymer Cyclomer P ACA-Z250 (manufactured by DAICEL Chemical Industry Co., Ltd.) (49 parts by mass) and cellulose acetate propionate CAP482-0.5 (number average molecular weight 25,000) were mixed so as to be 35% by mass. ) (manufactured by EASTMAN Chemical Co., Ltd.) (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) (Sekisui Chemical Industry Co., Ltd. The solid content of Irgacure 184 (manufactured by BASF) (4 parts by mass) and Irgacure 184 (manufactured by BASF) (10 parts by mass) was added to a mixed solvent of methyl ethyl ketone:1-butanol=3:1 to obtain an anti-glare layer formation coating liquid.

(Manufacturing example 8-Adjustment of anti-glare coating agent-3)

The unsaturated double bond-containing acrylic copolymer Cyclomer P ACA-Z250 (manufactured by DAICEL Chemical Industry Co., Ltd.) (49 parts by mass) and cellulose acetate propionate CAP482-0.2 (number average molecular weight 15,000) were mixed so as to be 35% by mass. ) (manufactured by EASTMAN Chemical Co., Ltd.) (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) (Sekisui Chemical Industry Co., Ltd. The solid content of Irgacure 184 (manufactured by BASF Co., Ltd.) (2 parts by mass) (10 parts by mass) was added to a mixed solvent of methyl ethyl ketone:1-butanol=3:1, A coating liquid for forming an antiglare layer was obtained.

(Polarizer Protective Film 1)

90 parts by mass of particle-free PET (A) resin particles and 10 parts by mass of PET (B) resin particles containing ultraviolet absorbent as raw materials for the intermediate layer of the base film were dried under reduced pressure (1 Torr) at 135° C. After 6 hours, it was supplied to the extruder 2 (for the middle layer II), and then the PET (A) was dried by a common method, and then supplied to the extruder 1 (for the outer layer I and the outer layer III), at 285 ° C. dissolve under. The two types of polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy of 10 μm particles was 95% intercepted), and the two types of three-layer confluence blocks were stacked, and extruded from a nozzle into sheets. In the electrostatic casting method, the film was wound on a casting drum with a surface temperature of 30°C, cooled and solidified, and an unstretched film was produced. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer would be 10:80:10.

Next, by the reverse roll method, on both sides of the unstretched PET film, the above-mentioned adhesive-improving coating liquid was applied so that the coating weight 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 the end portion of the film was grasped with a clip, and then guided to a hot air zone with a temperature of 125° C., and stretched 4.0 times in the width direction. Next, while maintaining the stretched width in the width direction, the temperature was 225° C. for 10 seconds, and further relaxation treatment was performed by 3.0% in the width direction to obtain a uniaxially stretched PET film with a film thickness of about 100 μm.

The above-mentioned coating liquid for forming a high refractive index layer was coated on the coating surface of one side of the uniaxially stretched PET film, and dried at 150° C. for 2 minutes. A high-refractive index layer with a thickness of 0.1 μm was formed. On the high-refractive index layer, the coating solution for forming a low-refractive-index layer obtained by the above method was applied, and dried at 150° C. for 2 minutes to form a low-refractive-index layer with a film thickness of 0.1 μm, thereby obtaining a layered anti-reflection layer. Polarizer protective film 1.

(Polarizer protective film 2)

Except for changing the line speed and changing the thickness of the unstretched film, a film was formed in the same manner as the polarizer protective film 1 to obtain a polarizer protective film 2 having an antireflection layer laminated with a film thickness of about 80 μm.

(Polarizer protective film 3)

Except for changing the line speed and changing the thickness of the unstretched film, a film was formed in the same manner as the polarizer protective film 1 to obtain a polarizer protective film 3 having an antireflection layer laminated with a film thickness of about 60 μm.

(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 and the thickness of the unstretched film was changed to obtain a polarizer protective film 4 having an antireflection layer laminated with a film thickness of about 40 μm.

(Polarizer protective film 5)

The 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 stretched 3.3 times in the traveling direction by a roll group with a peripheral speed difference Then, it was guided to a hot air zone with a temperature of 130° C., and extended 4.0 times in the width direction to obtain a polarizer protective film 5 having an antireflection layer laminated with a film thickness of about 30 μm in the same manner as the polarizer protective film 1 .

(Polarizer Protective Film 6)

Except that the anti-reflection layer is not provided, by combining with the polarizer protective film 1 The same method was used to obtain a polarizer protective film 6 with a film thickness of about 100 μm.

(Polarizer Protective Film 7)

Except that the antireflection layer was not provided, an antiglare layer coating was applied on the coating surface of one side of the polarizer protective film produced by the same method as the polarizer protective film 2 so that the film thickness after curing was 8 μm. Agent-1, dried in an oven at 80°C for 60 seconds. Then, using an ultraviolet irradiation device (Fusion UV Systems Japan, light source H bulb), ultraviolet rays were irradiated at an irradiation dose of 300 mJ/cm ² to laminate an anti-glare layer. Then, an antireflection layer was laminated on the antiglare layer by the same method as that of the polarizer protective film 1 to obtain a polarizer protective film 7 .

(Polarizer Protective Film 8)

An anti-glare layer and an anti-glare layer were laminated in the same manner as the polarizer protective film 7 on the coating surface of one side of the polarizer protective film produced by the same method as the polarizer protective film 3 except that the antireflection layer was not provided. The reflective layer was used to obtain a polarizer protective film 8 .

(Polarizer protective film 9)

Except that the antireflection layer was not provided, the antiglare layer coating was applied to the coating surface on one side of the polarizer protective film produced by the same method as the polarizer protective film 4 so that the film thickness after curing was 8 μm. Agent-2, dried in an oven at 80°C for 60 seconds. Then, using an ultraviolet irradiation device (Fusion UV Systems Japan, light source H bulb), ultraviolet rays were irradiated at an irradiation dose of 300 mJ/cm ² to laminate an anti-glare layer. Then, on the anti-glare layer, an anti-reflection layer was laminated in the same manner as the polarizer protective film 1 to obtain a polarizer protective film 9 .

(Polarizer protective film 10)

An anti-glare layer was laminated in the same manner as the polarizer protective film 7 on the coating surface of one side of the polarizer protective film produced by the same method as the polarizer protective film 5 except that the antireflection layer was not provided, to obtain Polarizer protective film 10 (the antireflection layer is not laminated).

(Polarizer protective film 11)

Except that the antireflection layer was not provided, an antiglare layer coating was applied to the coating surface on one side of the polarizer protective film produced by the same method as the polarizer protective film 1 so that the film thickness after curing was 8 μm. Agent-3, dried in an oven at 80°C for 60 seconds. Then, using an ultraviolet irradiation device (Fusion UV Systems Japan, light source H bulb), ultraviolet rays were irradiated with an irradiation dose of 300 mJ/cm ² to obtain a polarizer protective film 11 having an anti-glare layer laminated thereon.

(Polarizer protective film 12)

Except that the antireflection layer was not provided, an antiglare layer coating was applied on the coating surface of one side of the polarizer protective film produced by the same method as the polarizer protective film 2 so that the film thickness after curing was 8 μm. Agent-1, dried in an oven at 80°C for 60 seconds. Then, using an ultraviolet irradiation device (Fusion UV Systems Japan, light source H bulb), ultraviolet rays were irradiated at an irradiation dose of 300 mJ/cm ² to laminate an anti-glare layer. Then, on the anti-glare layer, a low-refractive index layer was laminated in the same manner as the polarizer protective film 1 . Thus, the polarizer protective film 12 in which the low reflection layer was laminated on the antiglare layer was obtained.

Using the polarizer protective films 1 to 12, a liquid crystal display device was produced as described later.

(Example 1)

On one side of the polarizer made of PVA and iodine, the polarizer protective film 1 is attached, and TAC is attached on the opposite side in such a way that the transmission axis of the polarizer and the advancing axis of the film are vertical. A film (manufactured by Fujifilm Co., Ltd., thickness 80 μm) was used as the polarizing plate 1 . Furthermore, a polarizer is laminated on the surface of the polarizer protective film on which the antireflection layer is not laminated to form a polarizing plate. BRAVIAKDL-40W920A (liquid crystal display device, which has a light source for emitting excitation light and a backlight source for quantum dots) made by SONY Co., Ltd., on the visual recognition side of the polarizing plate, with polyester film on the opposite side (remote position) to the liquid crystal. , replaced with the above-mentioned polarizing plate 1 to make a liquid crystal display device. Furthermore, the direction of the transmission axis of the polarizing plate 1 is replaced so that the direction of the transmission axis of the polarizing plate before replacement is the same.

(Example 2)

Except having replaced the polarizer protective film 1 with the polarizer protective film 2, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Example 3)

Except having replaced the polarizer protective film 1 with the polarizer protective film 3, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Example 4)

Except having replaced the polarizer protective film 1 with the polarizer protective film 4, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Example 5)

A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizer protective film 4 was used instead of the polarizer protective film 1, and the polarizer protective film 1 was attached so that its phase advance axis was parallel to the transmission axis of the polarizer.

(Example 6)

Except having replaced the polarizer protective film 1 with the polarizer protective film 7, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Example 7)

Except having replaced the polarizer protective film 1 with the polarizer protective film 8, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Example 8)

Except having replaced the polarizer protective film 1 with the polarizer protective film 9, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Example 9)

Except having replaced the polarizer protective film 1 with the polarizer protective film 12, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Comparative Example 1)

Except having replaced the polarizer protective film 1 with the polarizer protective film 5, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Comparative Example 2)

Except having replaced the polarizer protective film 1 with the polarizer protective film 6, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Comparative Example 3)

Except having replaced the polarizer protective film 1 with the polarizer protective film 10, it carried out similarly to Example 1, and produced the liquid crystal display device.

(Comparative Example 4)

Except having replaced the polarizer protective film 1 with the polarizer protective film 11, it carried out similarly to Example 1, and produced the liquid crystal display device.

For the liquid crystal display devices obtained in the respective examples, the results of measuring rainbow spots are shown in Table 1 below.

[Industrial Availability]

The liquid crystal display device and the polarizing plate of the present invention can ensure good visual recognition in which the occurrence of iridescent color spots is deliberately suppressed at any angle, which makes a great contribution to the industry.

Claims (23)

A liquid crystal display device, which is a liquid crystal display device with a backlight source, two polarizers and a liquid crystal cell disposed between the two polarizers, the backlight source includes a light source that emits excitation light and quantum dots, and the polarizer is At least one of the polarizers is formed by laminating a polyester film on at least one side of the polarizer in such a way that the transmission axis of the polarizer is perpendicular to the advancing axis of the polyester film, and the polyester film has 6000~ The hysteresis of 30000nm, the antireflection layer and/or the low reflection layer are laminated|stacked on at least one side surface of this polyester film. A liquid crystal display device, which is a liquid crystal display device with a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers, the backlight source is more than 400nm and less than 495nm, more than 495nm and less than 600nm, And each wavelength region above 600nm and below 780nm each has a peak top of the emission spectrum, and the half-value width of each peak is 5nm or more, and at least one of the polarizers in the polarizer is on at least one side of the polarizer. The film is formed by laminating the transmission axis of the polarizer perpendicular to the advancing axis of the polyester film. The polyester film has a hysteresis of 6000-30000 nm, and an anti-reflection layer is laminated on at least one side of the polyester film. layer and/or low reflection layer. A liquid crystal display device, which is a liquid crystal display device with a backlight source, two polarizers and a liquid crystal cell disposed between the two polarizers, the backlight source is above 400nm and less than 495nm, 495nm Above and below 600nm, and above 600nm and below 750nm, each has a peak top of the emission spectrum, the half-value width of each peak is 5nm or more, and at least one of the polarizing plates is connected to at least one of the polarizers. On the side, the polyester film is laminated in a way that the transmission axis of the polarizer is perpendicular to the advancing axis of the polyester film. The polyester film has a hysteresis of 6000-30000 nm. The upper build-up layer has an anti-reflection layer and/or a low-reflection layer. The liquid crystal display device according to any one of claims 1 to 3, wherein the surface reflectance of the surface of the anti-reflection layer at a wavelength of 550 nm is 2.0% or less. The liquid crystal display device according to any one of claims 1 to 3, wherein a ratio (Re/Rth) of the polyester film-based retardation (Re) to the thickness direction retardation (Rth) is 0.4 or more and 2.0 or less. The liquid crystal display device according to any one of claims 1 to 3, wherein there are other layers between the anti-reflection layer and/or the low-reflection layer and the polyester film. The liquid crystal display device according to any one of claims 1 to 3, wherein between the anti-reflection layer and/or the low-reflection layer and the polyester film, there is a hard coat layer. The liquid crystal display device according to any one of claims 1 to 3, wherein an anti-glare layer is provided between the anti-reflection layer and/or the low-reflection layer and the polyester film. The liquid crystal display device according to any one of claims 1 to 3, wherein the anti-reflection layer and/or the low-reflection layer are at least laminated on the polyester film layer on the opposite side of the polarizer. The liquid crystal display device according to any one of claims 1 to 3, wherein the polyester film has an easily adhesive layer on at least one side. The liquid crystal display device according to any one of claims 1 to 3, wherein the polyester film is laminated on the polarizer via an adhesive. The liquid crystal display device according to claim 2 or 3, wherein the upper limit of the half width of each peak is 120 nm or less. Application of a polarizing plate in a liquid crystal display device, the polarizing plate is formed by laminating polyester films on at least one side of a polarizer in such a way that the transmission axis of the polarizer is perpendicular to the advancing axis of the polyester film The polarizing plate, the polyester film has a retardation of 6000~30000nm, and the ratio (Re/Rth) of the retardation (Re) of the polyester film to the retardation (Rth) in the thickness direction (Re/Rth) is 0.4 or more and 2.0 or less. An anti-reflection layer and/or a low-reflection layer are laminated on one side, and the liquid crystal display device has a backlight source including a light source for emitting excitation light and quantum dots. Application of a polarizing plate in a liquid crystal display device, the polarizing plate is formed by laminating polyester films on at least one side of a polarizer in such a way that the transmission axis of the polarizer is perpendicular to the advancing axis of the polyester film The polarizing plate, the polyester film has a retardation of 6000~30000nm, and the ratio (Re/Rth) of the retardation (Re) of the polyester film to the retardation (Rth) in the thickness direction (Re/Rth) is 0.4 or more and 2.0 or less, An anti-reflection layer and/or a low-reflection layer are laminated on at least one side of the polyester film, and the liquid crystal display device has a backlight source with a range 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. Each of the wavelength regions has a peak top, and the half-value width of each peak is an emission spectrum of 5 nm or more. Application of a polarizing plate in a liquid crystal display device, the polarizing plate is formed by laminating polyester films on at least one side of a polarizer in such a way that the transmission axis of the polarizer is perpendicular to the advancing axis of the polyester film The polarizing plate, the polyester film has a retardation of 6000~30000nm, and the ratio (Re/Rth) of the retardation (Re) of the polyester film to the retardation (Rth) in the thickness direction (Re/Rth) is 0.4 or more and 2.0 or less. An anti-reflection layer and/or a low-reflection layer are laminated on one side, and the liquid crystal display device has a backlight source having a wavelength range 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 in each wavelength region. The peak top, the emission spectrum in which the half-value width of each peak is 5 nm or more. The use of the polarizing plate on a liquid crystal display device according to any one of claims 13 to 15, wherein the surface reflectance of the surface of the anti-reflection layer at a wavelength of 550 nm is below 2.0%. The use of the polarizing plate on a liquid crystal display device according to any one of claims 13 to 15, wherein there are other layers between the anti-reflection layer and/or the low-reflection layer and the polyester film. The use of the polarizing plate on a liquid crystal display device according to any one of claims 13 to 15, wherein between the anti-reflection layer and/or the low-reflection layer and the polyester film, there is a hard coat layer. The use of the polarizing plate on a liquid crystal display device according to any one of claims 13 to 15, wherein an anti-glare layer is provided between the anti-reflection layer and/or the low-reflection layer and the polyester film. The use of the polarizing plate in any one of claims 13 to 15 on a liquid crystal display device, wherein the anti-reflection layer and/or the low-reflection layer are laminated at least on the opposite side of the polyester film to the surface on which the polarizer is laminated on the face. The use of a polarizing plate on a liquid crystal display device according to any one of claims 13 to 15, wherein the polyester film has an easily adhesive layer on at least one side. The use of a polarizing plate on a liquid crystal display device according to any one of claims 13 to 15, wherein the polyester film is laminated on the polarizer via an adhesive. According to the use of the polarizing plate in claim 14 or 15 on a liquid crystal display device, the upper limit of the half width of each wave peak is 120 nm or less.

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