Liquid crystal display device and polarizing plate

Abstract

The present invention provides a liquid crystal display device having a light source that emits excitation light and a backlight source containing quantum dots, in which iridescence is suppressed even when a polyester film is used as the polarizer protective film. [Solution] A liquid crystal display device having a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates, wherein the backlight light source includes a light source that emits excitation light and quantum dots, and at least one of the polarizing plates has a polyester film laminated on at least one surface of the polarizer, the polyester film has retardation in the range of 1500 to 30000 nm, and an anti-reflective layer and / or a low-reflection layer laminated on at least one surface of the polyester film.

Description

[Technical Field]

[0001] This invention relates to a liquid crystal display device and a polarizing plate. More specifically, it relates to a liquid crystal display device and a polarizing plate in which the occurrence of rainbow-like color spots is reduced. [Background technology]

[0002] Polarizing plates used in liquid crystal displays (LCDs) typically have a structure in which a polarizer, made of polyvinyl alcohol (PVA) or similar material dyed with iodine, is sandwiched between two polarizer protective films. In most cases, triacetylcellulose (TAC) film is used as the polarizer protective film. In recent years, with the miniaturization of LCDs, there has been a demand for thinner polarizing plates. However, if the thickness of the TAC film used as the protective film is reduced to achieve sufficient mechanical strength and moisture permeability deteriorates. Furthermore, TAC film is very expensive, and polyester film has been proposed as a cheaper alternative material (Patent Documents 1-3), but it has the problem of exhibiting iridescent color flecks.

[0003] When a birefringent oriented polyester film is placed on one side of a polarizer, the polarization state of linearly polarized light emitted from the backlight unit or polarizer changes as it passes through the polyester film. The transmitted light exhibits interference colors characteristic of retardation, which is the product of the birefringence and thickness of the oriented polyester film. Therefore, when discontinuous emission spectra such as cold cathode tubes or hot cathode tubes are used as light sources, the transmitted light intensity differs depending on the wavelength, resulting in a rainbow-like color patch (see: Proceedings of the 15th Micro-Optical Conference, pp. 30-31).

[0004] As a means of solving the above problems, it has been proposed to use a white light source having a continuous and broad emission spectrum, such as a white light-emitting diode, as a backlight light source, and to use an oriented polyester film having a certain retardation as a polarizer protective film (Patent Document 4). White light-emitting diodes have a continuous and broad emission spectrum in the visible light region. Therefore, by focusing on the envelope linearity of the interference color spectrum due to transmitted light that has passed through a birefringent material, it has been proposed that by controlling the retardation of the oriented polyester film, a spectrum similar to the emission spectrum of the light source can be obtained, and iridescence can be suppressed.

[0005] By making the orientation direction of the oriented polyester film and the polarization direction of the polarizer perpendicular or parallel to each other, linearly polarized light emitted from the polarizer can pass through the oriented polyester film while maintaining its polarization state. Furthermore, by controlling the birefringence of the oriented polyester film to increase its uniaxial orientation, light incident from an oblique direction can also pass through while maintaining its polarization state. When the oriented polyester film is viewed from an oblique angle, a shift occurs in the direction of the principal orientation axis compared to when viewed from directly above. However, if the uniaxial orientation is high, the shift in the direction of the principal orientation axis when viewed from an oblique angle becomes smaller. Therefore, it is thought that the shift between the direction of linear polarization and the direction of the principal orientation axis becomes smaller, making it less likely for the polarization state to change. In this way, by controlling the emission spectrum of the light source, the orientation state of the birefringent, and the direction of the principal orientation axis, changes in the polarization state are suppressed, and visibility is significantly improved without the occurrence of rainbow-like color spots. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-116320 [Patent Document 2] Japanese Patent Publication No. 2004-219620 [Patent Document 3] Japanese Patent Publication No. 2004-205773 [Patent Document 4] WO2011 / 162198 [Overview of the project] [Problems that the invention aims to solve]

[0007] When industrially producing liquid crystal displays using polarizers with polyester film as a polarizer protective film, the direction of the polarizer's transmission axis and the phase advance axis of the polyester film are usually aligned perpendicular to each other. This is due to the following reasons: The polyvinyl alcohol film used as the polarizer is manufactured by uniaxial stretching in the longitudinal direction. Therefore, the polyvinyl alcohol film used as the polarizer is usually a film that is long in the stretching direction. On the other hand, the polyester film used as its protective film is manufactured by longitudinal stretching followed by transverse stretching, so the orientation principal axis of the polyester film is in the transverse direction. In other words, the orientation principal axis of the polyester film used as the polarizer protective film intersects approximately perpendicular to the longitudinal direction of the film. These films are usually laminated together so that their longitudinal directions are parallel to each other to manufacture a polarizer. In this case, the phase advance axis of the polyester film and the transmission axis of the polarizer are usually perpendicular to each other. However, we discovered a new problem: when the backlight source consists of a light source that emits excitation light and an emissive layer containing quantum dots, iridescence still occurs.

[0008] Due to the increasing demand for wider color gamuts in recent years, liquid crystal display devices have been developed that, in addition to white light sources utilizing quantum dot technology, have white light sources whose emission spectra exhibit clear relative emission intensity peaks in each of the R (red), G (green), and B (blue) wavelength regions. For example, liquid crystal display devices that support wide color gamuts have been developed using various types of light sources, such as phosphor-type white LED light sources using phosphors that have clear emission peaks in the R (red) and G (green) regions when excited by light, and blue LEDs, three-wavelength white LED light sources, and white LED light sources that combine red lasers. All of these white light sources have a narrower peak width at half maximum compared to conventional white light-emitting diodes using YAG-based yellow phosphors. We have discovered that when a retarded polyester film is used as a polarizer protective film, which is a component of the polarizer plate, these white light sources have the same problems as those in liquid crystal display devices that have a backlight light source consisting of a light source that emits excitation light and an emission layer containing quantum dots.

[0009] In other words, one of the objectives of the present invention is to provide a liquid crystal display device and a polarizer in which iridescence is suppressed even when a polyester film is used as a polarizer protective film, in a liquid crystal display device having a backlight source in which the full width at half maximum of each peak in the emission spectrum is relatively narrow, such as a backlight source that emits excitation light and a backlight source that includes quantum dots. [Means for solving the problem]

[0010] Representative examples of the present invention are as follows: Section 1. A liquid crystal display device having a backlight source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates, The aforementioned backlight light source includes a light source that emits excitation light and quantum dots, At least one of the polarizing plates has a polyester film laminated on at least one surface of the polarizer. The polyester film has retardation between 1500 and 30000 nm. An anti-reflective layer and / or a low-reflective layer are laminated on at least one surface of the polyester film. LCD display device. Section 2. A liquid crystal display device having a backlight source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates, The backlight light source emits light having peaks in its emission spectrum in the wavelength regions of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, with each peak having a full width at half maximum of 5 nm or more. At least one of the polarizing plates has a polyester film laminated on at least one surface of the polarizer. The polyester film has retardation between 1500 and 30000 nm. An anti-reflective layer and / or a low-reflective layer are laminated on at least one surface of the polyester film. LCD display device. Section 3. The liquid crystal display device according to item 2, wherein the backlight light source has peak tops of emission spectra in each wavelength region: 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 750 nm, and the full width at half maximum of each peak is 5 nm or more. Section 4. The liquid crystal display device according to any one of items 1 to 3, wherein the surface reflectance of the surface of the anti-reflective layer at a wavelength of 550 nm is 2.0% or less. Section 5. A polarizing plate in which a polyester film is laminated on at least one surface of the polarizer, The polyester film has retardation of 1500 to 30000 nm, and an anti-reflective layer and / or a low-reflective layer is laminated on at least one surface of the polyester film. A polarizing plate for a liquid crystal display device having a light source that emits excitation light and a backlight source containing quantum dots. Section 6. A polarizing plate in which a polyester film is laminated on at least one surface of a polarizer, wherein the polyester film has a retardation of 1500 or more and 30000 nm or less, and an antireflection layer and / or a low-reflection layer are laminated on at least one surface of the polyester film, A polarizing plate for a liquid crystal display device having a backlight source having an emission spectrum having peak tops in each of 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, and a half-value width of each peak being 5 nm or more. Item 7. The polarizing plate according to item 5 or 6, wherein the surface reflectance at a wavelength of 550 nm on the surface of the antireflection layer is 2.0% or less.

Advantages of the Invention

[0011] The liquid crystal display device and the polarizing plate of the present invention can ensure good visibility in which the generation of rainbow-colored spots is significantly suppressed at any viewing angle.

Brief Description of the Drawings

[0012] [Figure 1] An example showing a case where a plurality of peaks exist within a single wavelength region. [Figure 2] An example showing a case where a plurality of peaks exist within a single wavelength region. [Figure 3] An example showing a case where a plurality of peaks exist within a single wavelength region. [Figure 4] An example showing a case where a plurality of peaks exist within a single wavelength region.

Embodiments for Carrying Out the Invention

[0013] Generally, a liquid crystal display device has a rear module, a liquid crystal cell, and a front module, arranged in the order from the side where the backlight light source (also called the "backlight unit") is located to the side where the image is displayed (viewing side). The rear module and the front module generally consist of a transparent substrate, a transparent conductive film formed on its surface facing the liquid crystal cell, and a polarizing plate located on the opposite side. In other words, the polarizing plate is located on the side facing the backlight light source in the rear module, and on the side where the image is displayed (viewing side) in the front module.

[0014] The liquid crystal display device of the present invention comprises at least a backlight light source and a liquid crystal cell disposed between two polarizing plates. The backlight light source preferably has an emission spectrum in which peak tops are located in the wavelength regions of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and the full width at half maximum of each peak is 5 nm or more. The peak wavelengths of blue, green, and red as defined in 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 to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm correspond to the blue region, the green region, and the red region, respectively. An example of a light source having such an emission spectrum is a backlight light source that includes at least a light source emitting excitation light and quantum dots. Other examples include phosphor-type white LED light sources that combine a phosphor having emission peaks in the R (red) and G (green) regions respectively when excited by light with a blue LED, a three-wavelength white LED light source, and a white LED light source that combines a red laser. Examples of red phosphors include nitride-based phosphors with CaAlSiN3:Eu as the basic composition, sulfide-based phosphors with CaS:Eu as the basic composition, and silicate-based phosphors with Ca2SiO4:Eu as the basic composition. Examples of green phosphors include sialon-based phosphors with β-SiAlON:Eu as the basic composition, and silicate-based phosphors with (Ba,Sr)2SiO4:Eu as the basic composition.

[0015] A liquid crystal display device may have other components besides a backlight source, polarizer, and liquid crystal cell, such as a color filter, lens film, diffusion sheet, and anti-reflective film, as appropriate. A brightness-enhancing film may be provided between the light source-side polarizer and the backlight source. An example of a brightness-enhancing film is a reflective polarizer that transmits one linearly polarized light and reflects linearly polarized light perpendicular to it. As a reflective polarizer, for example, the DBEF (registered trademark) (Dual Brightness Enhancement Film) series brightness-enhancing film manufactured by Sumitomo 3M Limited is preferably used. Typically, the reflective polarizer is positioned so that its absorption axis is parallel to the absorption axis of the light source-side polarizer.

[0016] In a liquid crystal display device, it is preferable that at least one of the two polarizing plates arranged within the liquid crystal display device has a polyester film laminated on at least one side of a polarizer made of polyvinyl alcohol (PVA) or the like dyed with iodine. From the viewpoint of suppressing iridescent color spots, it is preferable that the polyester film has a specific retardation and that an anti-reflective layer and / or a low-reflective layer is laminated on at least one side thereof. The anti-reflective layer and / or low-reflective layer may be provided on the side of the polyester film opposite to the side on which the polarizer is laminated, or on the side on which the polarizer is laminated, or both. Preferably, it is preferable to provide the anti-reflective layer and / or low-reflective layer on the side of the polyester film opposite to the side on which the polarizer is laminated. When the anti-reflective layer and / or low-reflective layer is provided on the side of the polyester film on which the polarizer is laminated, the layer is made of polyester film It is preferable that the film be provided between the film and the polarizer. In addition, other layers (e.g., an easy-adhesion layer, a hard coat layer, an anti-glare layer, an anti-static layer, an anti-fouling layer, etc.) may be present between the anti-reflective layer and / or the low-reflective layer and the polyester film. From the viewpoint of further suppressing iridescent color spots, it is preferable that the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer be 1.53 or more and 1.62 or less. It is preferable that a film without birefringence, such as a TAC film, an acrylic film, and a norbornene-based film, is laminated on the other side of the polarizer (3-layer polarizer), but it is not necessarily required that a film be laminated on the other side of the polarizer (2-layer polarizer). When polyester films are used as protective films on both sides of the polarizer, it is preferable that the slow phase axes of both polyester films are substantially parallel to each other.

[0017] The polyester film may be laminated to the polarizer via any adhesive, or it may be laminated directly without an adhesive. The adhesive is not particularly limited and can be any adhesive. An adhesive can be used. For example, a water-based adhesive (i.e., an adhesive component dissolved in water or dispersed in water) can be used. For example, an adhesive containing a polyvinyl alcohol-based resin and / or a urethane resin as the main component can be used. To improve adhesion, an adhesive further containing isocyanate compounds and / or epoxy compounds can be used as needed. Another example is a photocurable adhesive. In one embodiment, a solvent-free ultraviolet-curable adhesive is preferred. Examples of photocurable resins include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

[0018] The backlight configuration can be either an edge-lit system using light guide plates and reflectors as components, or a direct-lit system. The backlight source is preferably a backlight source that emits excitation light and includes quantum dots, and has a emission spectrum with peak tops in each wavelength region: 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, with each peak having a full width at half maximum of 5 nm or more. For example, a layer containing many quantum dots can be provided and used as the backlight emission layer.

[0019] The application of quantum dot technology to LCDs is attracting attention due to the increasing demand for wider color gamuts in recent years. Conventional LEDs using white LEDs as backlight sources can only reproduce about 20% of the spectrum that the human eye can perceive. In contrast, when using a backlight source consisting of a light source that emits excitation light and a light-emitting layer containing quantum dots, it is said that it becomes possible to reproduce more than 60% of the spectrum that the human eye can perceive. One example of quantum dot technology that has been put into practical use is Nanosys' QDEF. TM or QD Vision's Per IQ TM These include:

[0020] A light-emitting layer containing quantum dots is constructed by incorporating quantum dots into a resin material such as polystyrene, and is a layer that emits light of each color on a pixel-by-pixel basis based on excitation light emitted from a light source. This light-emitting layer consists of, for example, a red light-emitting layer placed in a red pixel, a green light-emitting layer placed in a green pixel, and a blue light-emitting layer placed in a blue pixel. The quantum dots in these multiple color light-emitting layers generate light of different wavelengths (colors) based on the excitation light.

[0021] Examples of materials for such quantum dots include CdSe, CdS, ZnS:Mn, InN, InP, CuCl, CuBr, and Si, with particle sizes (size along one side) of these quantum dots being, for example, about 2 to 20 nm. Among the above quantum dot materials, InP is an example of a red-emitting material, CdSc is an example of a green-emitting material, and CdS is an example of a blue-emitting material. In such an emissive layer, It has been confirmed that the emission wavelength of quantum dots changes by altering their size (particle size) and material composition. These quantum dots are controlled in size and material, mixed with resin materials, and then applied to individual pixels for use. Furthermore, as the use of heavy metals such as cadmium is being restricted in many applications, cadmium-free quantum dots are being developed while maintaining the same brightness and stability as conventional ones.

[0022] Blue LEDs are used as the light source to emit excitation light, but laser light such as semiconductor lasers may also be used. When the excitation light emitted from the light source passes through the light-emitting layer, an emission spectrum is generated with peaks in the wavelength regions of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm. At this time, the narrower the full width at half maximum (FWHM) of the peaks in each wavelength region, the wider the color gamut. However, a narrower FWHM of the peaks reduces the luminous efficiency, so the shape of the emission spectrum is designed considering the balance between the required color gamut and luminous efficiency.

[0023] Light sources using quantum dots can be broadly categorized into two implementation methods, although they are not limited to the following. One is the on-edge method, in which quantum dots are mounted along the edge (side) of the backlight's light guide plate. Quantum dots, which are particles with a diameter of several n to tens of nanometers, are placed inside a glass tube with a diameter of several millimeters. The quantum dots are then sealed and placed between the blue LED and the light guide plate. Light from the blue LED shines onto the glass tube, and the blue light that collides with the quantum dots is converted into green and red light. The on-edge method has the advantage of being able to reduce the amount of quantum dots used even on large screens. Another method is the surface mount method, in which quantum dots are placed on top of the light guide plate. Quantum dots are dispersed in resin to form a sheet, and this quantum dot film is sealed by sandwiching it between two barrier films and then placed on the light guide plate. It is placed on top of the barrier film. The barrier film plays a role in suppressing the degradation of quantum dots by water and oxygen. The blue LED is placed on the edge (side) of the light guide plate, similar to the on-edge method. Light from the blue LED enters the light guide plate and becomes planar blue light, which irradiates the quantum dot film. There are two main advantages to the surface mount method. One is that the light from the blue LED passes through the light guide plate and hits the quantum dots. Therefore, the heat generated by the LEDs is less, making it easier to ensure reliability. Another point is, Because it is in film form, it is easy to use with a wide range of screen sizes, from small to large.

[0024] In the present invention, it is preferable that the backlight light source has peaks in its emission spectrum in the wavelength regions of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and that the full width at half maximum (FWHM) of each peak is 5 nm or more. The wavelength region of 400 nm to less than 495 nm is more preferably 430 nm to 470 nm. The wavelength region of 495 nm to less than 600 nm is more preferably 510 nm to 560 nm. The wavelength region of 600 nm to 780 nm is more preferably 600 nm to 750 nm, more preferably 630 nm to 700 nm, and even more preferably 630 nm to 680 nm. The preferred lower limit of the FWHM of each peak is 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. From the viewpoint of ensuring an appropriate color gamut, the upper limit of the full width at half maximum (FWHM) of each peak is preferably 140 nm or less, preferably 120 nm or less, preferably 100 nm or less, more preferably 80 nm or less, even more preferably 60 nm or less, and even more preferably 45 nm or less. Here, FWHM refers to the peak width (nm) at half the intensity of the peak intensity at the wavelength of the peak top. Any combination of the individual upper and lower limits of the wavelength range described herein is conceivable. Any combination of the individual upper and lower limits of the FWHM described herein is conceivable. Peak intensity is The emission spectrum of the backlight source can be measured using, for example, a Hamamatsu Photonics PMA-12 multi-channel spectrometer.

[0025] Multiple wavelengths in any of the following wavelength regions: 400nm to less than 495nm, 495nm to less than 600nm, or 600nm to 780nm If peaks exist, consider the following: If multiple peaks are independent peaks, it is preferable that the full width at half maximum (FWHM) of the peak with the highest peak intensity is within the above range. Furthermore, it is even more preferable that the FWHM of other peaks with an intensity of 70% or more of the highest peak intensity is also within the above range. For a single independent peak that has a shape in which multiple peaks overlap, if the FWHM of the peak with the highest peak intensity among the multiple peaks can be measured directly, that FWHM is used. Here, an independent peak is one that has an intensity region of half the peak intensity on both the short-wavelength and long-wavelength sides of the peak. That is, if multiple peaks overlap and each individual peak does not have an intensity region of half the peak intensity, the multiple peaks as a whole are considered as a single peak. For such a single peak with a shape in which multiple peaks overlap, the FWHM is defined as the width (nm) of the peak at half the intensity of the highest peak intensity among them. The point with the highest peak intensity among the multiple peaks is defined as the peak top. The full width at half maximum (FMAX) when multiple peaks exist within a single wavelength range is indicated by bidirectional arrows in Figures 1-4.

[0026] In Figure 1, peaks A and B each have points on the shorter and longer wavelength sides, respectively, where the peak intensity is half of the peak intensity. Therefore, peaks A and B are independent peaks. In the case of Figure 1, the width at half maximum can be evaluated by the width of the bidirectional arrow on peak A, which has the highest peak intensity.

[0027] In Figure 2, peak A has points on both its short-wavelength and long-wavelength sides where the peak intensity is 1 / 2, but peak B does not have a point on its long-wavelength side where the peak intensity is 1 / 2. Therefore, peaks A and B are considered together as a single independent peak. For an independent peak that has a shape in which multiple peaks overlap in this way, if the full width at half maximum (FWHM) of the peak with the highest peak intensity among the multiple peaks can be measured directly, that FWHM is taken as the FWHM of the independent peak. Therefore, in the case of Figure 2, the FWHM of the peak is the width of the double-headed arrow.

[0028] In Figure 3, there is no point on the shorter wavelength side of peak A where the peak intensity is half, Peak B does not have a point on its longer wavelength side where its peak intensity is half. Therefore, in Figure 3, as in Figure 2, peaks A and B are considered together as a single independent peak, and its full width at half maximum is the width indicated by the double-headed arrow.

[0029] In Figure 4, peak A has points on both its short-wavelength and long-wavelength sides where the peak intensity is 1 / 2, but peak B does not have a point on its long-wavelength side where the peak intensity is 1 / 2. Therefore, peaks A and B are considered together as a single independent peak. For a single independent peak that has a shape formed by the overlapping of multiple peaks, if the full width at half maximum (FWHM) of the peak with the highest peak intensity among the multiple peaks can be measured directly, that FWHM is used. Therefore, in the case of Figure 4, that FWHM is the width indicated by the double-headed arrow.

[0030] Figures 1-4 show examples in the wavelength range of 400 nm to less than 495 nm, but the same concept can be applied to other wavelength ranges as well.

[0031] Among multiple peaks, the peak with the highest peak intensity is designated as the peak top. Furthermore, it is preferable that the peaks with the highest peak intensity in the wavelength range of 400 nm to less than 495 nm, the wavelength range of 495 nm to less than 600 nm, or the wavelength range of 600 nm to 780 nm are independent of the peaks in other wavelength ranges. In particular, from the perspective of color vividness, it is preferable that there exists a region in the wavelength range between the peak with the highest peak intensity in the wavelength range of 495 nm to less than 600 nm and the peak with the highest peak intensity in the wavelength range of 600 nm to 780 nm where the intensity is 1 / 3 or less of the peak intensity of the peak with the highest peak intensity in the wavelength range of 600 nm to 780 nm.

[0032] The emission spectrum of the backlight source can be measured using a spectrometer such as the Hamamatsu Photonics PMA-12 multi-channel spectrometer.

[0033] As a result of diligent research, the present inventors have found that in a liquid crystal display device having a backlight source in which the full width at half maximum of each peak in the emission spectrum is relatively narrow, such as a light source that emits excitation light and a backlight source containing quantum dots, using a polyester film having an anti-reflective layer and / or a low-reflection layer and a specific retardation as a polarizer protective film provides a liquid crystal display device in which iridescence is suppressed and a polarizer plate useful for providing such a device. The mechanism by which the occurrence of iridescent color spots is suppressed in the above embodiment is thought to be as follows.

[0034] When an oriented polyester film is placed on one side of a polarizer, the polarization state of linearly polarized light emitted from the backlight unit or polarizer changes as it passes through the polyester film. One possible factor influencing this change in polarization state is the difference in refractive index at the interface between the air layer and the oriented polyester film, or the difference in refractive index at the interface between the polarizer and the oriented polyester film. When linearly polarized light incident on the oriented polyester film passes through each interface, a portion of the light is reflected due to the difference in refractive index between the interfaces. At this time, the polarization state of both the emitted and reflected light changes, which is thought to be one of the factors causing rainbow-like color spots. Therefore, by applying an anti-reflective or low-reflection layer to the surface of the oriented polyester film to reduce surface reflection, reflection at the interface between the air layer and the oriented polyester film is suppressed, thereby suppressing rainbow-like color spots.

[0035] As described above, by combining a backlight source with a relatively narrow half-width of each peak in the emission spectrum, such as a backlight source containing quantum dots that emits excitation light, with a polarizer using a polyester film as a polarizer protective film, it is possible to suppress rainbow-like color variations and achieve good visibility.

[0036] The polarizer preferably has a polarizer protective film made of polyester film laminated on at least one surface of the polarizer. The polyester film used for the polarizer protective film preferably has a retardation of 1500 to 30000 nm. A retardation within the above range tends to reduce iridescence more easily and is therefore preferable. The preferred lower limit of retardation is 3000 nm, the next preferred lower limit is 3500 nm, the more preferred lower limit is 4000 nm, the even more preferred lower limit is 6000 nm, and the even more preferred lower limit is 8000 nm. The preferred upper limit is 30000 nm, and polyester films with retardation above this limit tend to have considerably larger thicknesses, which tends to reduce their handling as industrial materials. In this document, retardation means in-plane retardation unless otherwise indicated.

[0037] Retardation can be determined by measuring the refractive index and thickness in two axes, or by using a commercially available automatic birefringence measuring device such as the KOBRA-21ADH (Oji Instruments Co., Ltd.). The refractive index can be determined using an Abbe refractometer (measurement wavelength 589 nm).

[0038] The ratio of the retardation in the thickness direction (Re / Rth) of a polyester film (Re: in-plane retardation) is preferably 0.2 or higher, preferably 0.3 or higher, preferably 0.4 or higher, preferably 0.5 or higher, more preferably 0.5 or higher, and even more preferably 0.6 or higher. The larger the ratio of the above retardation to the thickness direction retardation (Re / Rth), the more isotropic the effect of birefringence becomes, and the less likely it is that rainbow-like color spots will occur depending on the observation angle. In a perfectly uniaxial (uniaxially symmetric) film, the ratio of the above retardation to the thickness direction retardation (Re / Rth) is 2.0, therefore, The upper limit of the ratio of retardation in the vertical direction to retardation in the thickness direction (Re / Rth) is preferably 2.0. The phase difference in the thickness direction refers to the average of the phase differences obtained by multiplying the two birefringences ΔNxz and ΔNyz, respectively, by the film thickness d when the film is viewed from a cross-section in the thickness direction.

[0039] From the viewpoint of suppressing iridescent color variations, the NZ coefficient of the polyester film is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.8 or less, and even more preferably 1.6 or less. Since the NZ coefficient is 1.0 for a perfectly uniaxial (uniaxially symmetric) film, the lower limit of the NZ coefficient is 1.0. However, it should be noted that as the film approaches perfect uniaxiality (uniaxial symmetry), the mechanical strength in the direction perpendicular to the orientation direction tends to decrease significantly.

[0040] The NZ coefficient is expressed as |Ny-Nz| / |Ny-Nx|, where Ny is the refractive index in the direction of the slow phase axis, Nx is the refractive index in the direction perpendicular to the slow phase axis (refractive index in the direction of the fast phase axis), and Nz is the refractive index in the thickness direction. The orientation axis of the film is determined using a molecular orientation meter (MOA-6004 molecular orientation meter, manufactured by Oji Instruments Co., Ltd.), and the refractive index in the orientation axis direction and the direction perpendicular to it (Ny, Nx, where Ny>Nx), and the refractive index in the thickness direction (Nz) are determined using an Abbe refractometer (NAR-4T, manufactured by Atago, measurement wavelength 589nm). The NZ coefficient can then be calculated by substituting these values ​​into |Ny-Nz| / |Ny-Nx|.

[0041] Furthermore, from the viewpoint of suppressing iridescent color variations, the Ny-Nx value of the polyester film is preferably 0.05 or higher, more preferably 0.07 or higher, even more preferably 0.08 or higher, even more preferably 0.09 or higher, and most preferably 0.1 or higher. There is no particular upper limit, but in the case of polyethylene terephthalate-based films, an upper limit of about 1.5 is preferred.

[0042] In a more preferred embodiment of the present invention, it is preferable that the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer constituting the polarizer plate be in the range of 1.53 to 1.62. This makes it possible to suppress reflection at the interface between the polarizer and the polyester film and suppress rainbow-like color spots. If the refractive index exceeds 1.62, rainbow-like color spots may occur when observed from an oblique direction. The refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is preferably 1.61 or less, more preferably 1.60 or less, even more preferably 1.59 or less, and even more preferably 1.58 or less.

[0043] On the other hand, the lower limit of the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 1.53. If the refractive index is less than 1.53, the crystallization of the polyester film becomes insufficient, and properties obtained by stretching, such as dimensional stability, mechanical strength, and chemical resistance, become insufficient, which is undesirable. The refractive index is preferably 1.56 or higher, and more preferably 1.57 or higher. Any range can be assumed by combining the above-mentioned upper and lower limits of the refractive index.

[0044] To set the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer to a range of 1.53 to 1.62, it is preferable that the polarizer's transmission axis and the phase-advancing axis (perpendicular to the slow axis) of the polyester film are parallel. The polyester film can be adjusted to a low refractive index of approximately 1.53 to 1.62 in the direction of the phase-advancing axis, which is perpendicular to the slow axis, by stretching in the film-forming process described later. By making the phase-advancing axis of the polyester film parallel to the transmission axis of the polarizer, the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer can be set to 1.53 to 1.62. Here, parallel means that the angle between the transmission axis of the polarizer and the phase-advancing axis of the polarizer protective film is -15° to 15°, preferably -10° to 10°, more preferably -5° to 5°, even more preferably -3° to 3°, even more preferably -2° to 2°, and most preferably -1° to 1°. In a preferred embodiment, parallel means substantially parallel. Here, substantially parallel means that the transmission axis and the phase-advancing axis are parallel to the extent that they allow for the inevitable misalignment that occurs when the polarizer and the protective film are bonded together. The direction of the slow phase axis can be determined by measuring it with a molecular orientation meter (for example, the MOA-6004 molecular orientation meter manufactured by Oji Instruments Co., Ltd.).

[0045] In other words, the refractive index of the polyester film in the direction of the phase advance axis is preferably 1.53 or more and 1.62 or less. By laminating the films so that the transmission axis of the polarizer and the phase advance axis of the polyester film are approximately parallel, the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer can be set to 1.53 or more and 1.62 or less.

[0046] The polarizer protective film made of the polyester film described above can be used on polarizers on both the incident light side (light source side) and the outgoing light side (visibility side). For polarizers placed on the incident light side, the polarizer protective film made of the polyester film may be placed on the incident light side, on the liquid crystal cell side, or on both sides, starting from the polarizer, but it is preferable that it be placed at least on the incident light side. For polarizers placed on the outgoing light side, the polarizer protective film made of the polyester film may be placed on the liquid crystal side, on the outgoing light side, or on both sides, starting from the polarizer, but it is preferable that it be placed at least on the outgoing light side.

[0047] Polyester used in polyester films can be polyethylene terephthalate or polyethylene naphthalate, but may also contain other copolymer components. These resins have excellent transparency, as well as excellent thermal and mechanical properties, and retardation can be easily controlled by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence, and stretching the film can keep the refractive index in the phase-advancing axis (perpendicular to the phase-lagging axis) low, and a large retardation can be obtained relatively easily even with a thin film thickness.

[0048] Furthermore, in order to suppress the degradation of optically functional dyes such as iodine dyes, it is desirable that the polyester film has a light transmittance of 20% or less at a wavelength of 380 nm. A light transmittance of 15% or less at 380 nm is more preferable, 10% or less is even more preferable, and 5% or less is particularly preferable. If the light transmittance is 20% or less, the deterioration of optically functional dyes due to ultraviolet light can be suppressed. The transmittance is measured perpendicular to the plane of the film and can be measured using a spectrophotometer (for example, Hitachi U-3500).

[0049] To reduce the transmittance of the polyester film at a wavelength of 380 nm to 20% or less, it is desirable to appropriately adjust the type and concentration of the ultraviolet absorber and the thickness of the film. The ultraviolet absorbers used in this invention are known substances. Examples of ultraviolet absorbers include organic ultraviolet absorbers and inorganic ultraviolet absorbers, but organic ultraviolet absorbers are preferred from the viewpoint of transparency. Examples of organic ultraviolet absorbers include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and combinations thereof, but are not particularly limited as long as they fall within the absorbance range defined in this invention. However, from the viewpoint of durability, benzotriazole-based and cyclic iminoester-based are particularly preferred. When two or more ultraviolet absorbers are used in combination, ultraviolet light of different wavelengths can be absorbed simultaneously, thereby further improving the ultraviolet absorption effect.

[0050] Examples of benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and acrylonitrile-based UV absorbers include 2-[2'-hydroxy-5'-(methacryloyloxymethyl)phenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, and 2-[2' -Hydroxy-5'-(methacryloyloxypropyl)phenyl]-2H-benzotriazole, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,4-di-tert-butyl-6-(5-chlorobenzotriazole-2-yl)phenol, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(5-chloro(2H)-benzotriazole-2-yl)-4-methyl-6-(tert-butyl)pheno Examples include 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl)phenol. Examples of cyclic iminoester-based UV absorbers include 2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinone-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, and 2-phenyl-3,1-benzoxazin-4-one. However, the list is not limited to these.

[0051] Furthermore, in addition to the ultraviolet absorber, it is also preferable to include various additives other than catalysts, to the extent that they do not hinder the effects of the present invention. Examples of additives include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light-resistant agents, flame retardants, heat stabilizers, antioxidants, gelation inhibitors, and surfactants. In addition, in order to achieve high transparency, it is preferable that the polyester film is substantially free of particles. "Substantially free of particles" means, for example, in the case of inorganic particles, that the content is 50 ppm or less, preferably 10 ppm or less, and particularly preferably below the detection limit when inorganic elements are quantified by fluorescence X-ray analysis.

[0052] It is preferable to provide an anti-reflective layer and / or a low-reflective layer on at least one surface of the polyester film that serves as the polarizer protective film. The surface reflectance of the anti-reflective layer is preferably 2.0% or less. If it exceeds 2.0%, iridescent color spots become more visible. The surface reflectance of the anti-reflective layer is more preferably 1.6% or less, even more preferably 1.2% or less, and particularly preferably 1.0% or less. There is no particular lower limit to the surface reflectance of the anti-reflective layer, but for example, it is 0.01%. The reflectance can be measured by any method; for example, the light reflectance at a wavelength of 550 nm can be measured from the surface on the anti-reflective layer side using a spectrophotometer (Shimadzu Corporation, UV-3150).

[0053] The anti-reflective layer may be single-layer or multi-layer. In the case of a single layer, an anti-reflective effect can be obtained by forming a low-refractive-index layer made of a material with a lower refractive index than the polyester film so that its thickness is 1 / 4 wavelength of light or an odd multiple thereof. In the case of a multi-layer anti-reflective layer, an anti-reflective effect can be obtained by layering two or more layers of low-refractive-index and high-refractive-index alternately, and by appropriately controlling the thickness of each layer during lamination. Furthermore, if necessary, a hard coat layer can be laminated between the anti-reflective layers, and an anti-fouling layer can be formed on top of the hard coat layer.

[0054] One example of an anti-reflective layer is one that utilizes a moth-eye structure. A moth-eye structure is a surface-forming uneven structure with a pitch smaller than the wavelength. This structure makes it possible to change the abrupt and discontinuous change in refractive index at the boundary with air into a continuous and gradually changing change in refractive index. Therefore, by forming a moth-eye structure on the surface, light reflection on the film surface is reduced. The formation of an anti-reflective layer using a moth-eye structure can be carried out, for example, by referring to Japanese Patent Publication No. 2001-517319.

[0055] Methods for forming an anti-reflective layer include, for example, a dry coating method in which an anti-reflective layer is formed on the surface of a substrate (polyester film) by vapor deposition or sputtering; a wet coating method in which an anti-reflective coating solution is applied to the surface of the substrate and dried to form an anti-reflective layer; or a combined method that uses both of these methods. However, as long as the above characteristics are satisfied, it is not particularly limited.

[0056] A known low-reflectance layer can be used. For example, it can be formed by laminating at least one layer of a thin film of metal or oxide by vapor deposition or sputtering, or by coating with one or more layers of an organic thin film. Preferably, the low-reflectance layer is a single layer of organic thin film coated with a polyester film or a hard coat layer laminated on a polyester film, which has a lower refractive index than polyester film. The surface reflectance of the low-reflectance layer is preferably less than 5%, more preferably 4% or less, and even more preferably 3% or less. The lower limit is preferably around 0.8% to 1.0%.

[0057] The anti-reflective layer and / or low-reflective layer may also be provided with an anti-glare function. This further suppresses iridescence. Specifically, it may be a combination of an anti-reflective layer and an anti-glare layer, a combination of a low-reflection layer and an anti-glare layer, or a combination of an anti-reflective layer, a low-reflection layer and an anti-glare layer. Particularly preferred is a combination of a low-reflection layer and an anti-glare layer. As the anti-glare layer, a known anti-glare layer can be used. For example, from the viewpoint of suppressing surface reflection of the film, it is preferable to laminate an anti-glare layer onto a polyester film, and then laminate an anti-reflective layer or a low-reflection layer on top of the anti-glare layer.

[0058] When providing an anti-reflective or low-reflective layer, it is preferable that the polyester film has an easy-adhesion layer on its surface. In this case, from the viewpoint of suppressing interference due to reflected light, it is preferable to adjust the refractive index of the easy-adhesion layer to be near the geometric mean of the refractive index of the anti-reflective layer and the refractive index of the polyester film. The refractive index of the easy-adhesion layer can be adjusted using known methods, and can be easily adjusted, for example, by incorporating titanium, germanium, or other metal species into the binder resin.

[0059] Polyester films can also be subjected to corona treatment, coating treatment, and / or flame treatment, etc., to improve adhesion with polarizers.

[0060] In the present invention, in order to improve adhesion to the polarizer, it is preferable that at least one side of the film of the present invention has an easy-adhesion layer mainly composed of at least one of polyester resin, polyurethane resin, or polyacrylic resin. Here, "main component" refers to a component that accounts for 50% by mass or more of the solid components constituting the easy-adhesion layer. The coating liquid used to form the easy-adhesion layer of the present invention is preferably an aqueous coating liquid containing at least one of water-soluble or water-dispersible copolymer polyester resin, acrylic resin, and polyurethane resin. Examples of these coating liquids include water-soluble or water-dispersible copolymer polyester resin solutions, acrylic resin solutions, or polyurethane resin solutions disclosed in Japanese Patent Publication No. 3567927, Japanese Patent Publication No. 3589232, Japanese Patent Publication No. 3589233, Japanese Patent Publication No. 3900191, and Japanese Patent Publication No. 4150982, etc.

[0061] The easy-adhesion layer can be obtained by applying the coating solution to one or both sides of a uniaxially oriented film in the longitudinal direction, drying it at 100-150°C, and then stretching it in the transverse direction. The final amount of the easy-adhesion layer applied is 0.05-0.20 g / m². 2 It is preferable to manage the amount to 0.05 g / m². 2 If the amount is less than 0.20 g / m², the adhesion to the resulting polarizer may be insufficient. On the other hand, if the coating amount is 0.20 g / m², the adhesion to the polarizer may be insufficient. 2If this limit is exceeded, the blocking resistance may decrease. When an easy-adhesion layer is provided on both sides of the polyester film, the amount of easy-adhesion layer applied to both sides may be the same or different, and can be set independently within the above range.

[0062] It is preferable to add particles to the easy-adhesion layer to provide slipperiness. It is preferable to use particles with an average particle size of 2 μm or less. If the average particle size exceeds 2 μm, the particles tend to fall off the coating layer. Examples of particles to be included in the easy-adhesion layer include nitrate. Examples include inorganic particles such as tungsten, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride, as well as organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based materials. These may be added to the easy-adhesion layer individually or in combination of two or more types.

[0063] Furthermore, known methods can be used for applying the coating solution. Examples include the reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire bar coating method, and pipe doctor method, and these methods can be used individually or in combination.

[0064] The average particle size of the above particles is measured by the following method: A scanning electron microscope (SEM) is used to take a photograph of the particles, and the maximum diameter (distance between the two furthest points) of 300 to 500 particles is measured at a magnification such that the size of the smallest particle is 2 to 5 mm. The average value of these measurements is then taken as the average particle size.

[0065] Polyester films used as polarizer protective films can be manufactured according to general polyester film manufacturing methods. For example, one method involves melting polyester resin, extruding the unoriented polyester into a sheet, stretching it longitudinally using the speed difference of rolls at a temperature above the glass transition temperature, then stretching it transversely with a tenter, and finally heat-treating it.

[0066] The polyester film used in this invention may be either a uniaxially oriented film or a biaxially oriented film.

[0067] Specifically, the film-forming conditions for polyester film are as follows: The longitudinal stretching temperature and transverse stretching temperature are preferably 80 to 130°C, and particularly preferably 90 to 120°C. To orient the film so that the slow axis is in the TD direction, the longitudinal stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. The transverse stretching ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. To orient the film so that the slow axis is in the MD direction, the longitudinal stretching ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. The transverse stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times.

[0068] Setting a low stretching temperature is also a desirable approach for lowering the refractive index in the phase-advancing axis direction of the polyester film and increasing retardation. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250°C, and particularly preferably 180 to 245°C.

[0069] To suppress retardation fluctuations, it is preferable to have minimal film thickness variation. Since the stretching temperature and stretching ratio greatly affect film thickness variation, it is preferable to optimize the film formation conditions from the viewpoint of reducing thickness variation. In particular, lowering the longitudinal stretching ratio to increase retardation can result in larger longitudinal thickness variation. Since longitudinal thickness variation becomes very bad in a specific range of stretching ratios, it is desirable to set the film formation conditions outside of this range.

[0070] The thickness variation of the polyester film is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, and particularly preferably 3.0% or less. The thickness variation of the film can be measured as follows: A tape-shaped film sample (3m) is taken and measured using an electronic measuring tape manufactured by Seiko EM Co., Ltd. Using an ichromator, the Miltron 1240, the thickness was measured at 1 cm intervals for 100 points. From the measured values, the maximum (dmax), minimum (dmin), and average (d) thicknesses were determined, and the following formula was used. The thickness variation (%) is calculated. It is preferable to perform the measurement three times and calculate the average value. Thickness variation (%) = ((dmax - dmin) / d) × 100 As mentioned above, the retardation of polyester film can be controlled within a specific range by appropriately setting the stretching ratio, stretching temperature, and film thickness. For example, higher stretching ratios, lower stretching temperatures, and thicker films tend to yield higher retardation. Conversely, lower stretching ratios, higher stretching temperatures, and thinner films tend to yield lower retardation. However, increasing the film thickness tends to increase the phase difference in the thickness direction. Therefore, it is desirable to appropriately set the film thickness within the range described later. In addition to controlling retardation, it is also preferable to set the final film formation conditions considering the physical properties required for processing.

[0071] The thickness of the polyester film is arbitrary, but it is preferably in the range of 15 to 300 μm, and more preferably in the range of 15 to 200 μm. In principle, it is possible to obtain retardation of 1500 nm or more even with films thinner than 15 μm. However, in that case, the anisotropy of the mechanical properties of the film becomes significant, making it prone to tearing and ripping, and significantly reducing its practicality as an industrial material. The lower limit of a particularly preferred thickness is 25 μm. On the other hand, the upper limit of the thickness of the polarizer protective film is undesirable if it exceeds 300 μm, as this makes the polarizer plate too thick. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. The upper limit of a particularly preferred thickness is 100 μm, which is about the same as that of a general TAC film. In order to control retardation within the range of the present invention even within the above thickness range, polyethylene tarephthalate is preferred as the polyester used as the film substrate.

[0072] Furthermore, while a combination of known methods can be used to incorporate the ultraviolet absorber into the polyester film, for example, a masterbatch can be prepared by first blending the dried ultraviolet absorber with the polymer raw material using a kneading extruder, and then mixing the predetermined masterbatch with the polymer raw material during film formation.

[0073] At this time, the concentration of the UV absorber in the masterbatch is preferably 5 to 30% by mass to ensure uniform dispersion of the UV absorber and to allow for economical formulation. The conditions for preparing the masterbatch are preferably using a kneading extruder, with an extrusion temperature above the melting point of the polyester raw material and below 290°C for 1 to 15 minutes. Above 290°C, the amount of UV absorber decreases significantly, and the viscosity of the masterbatch also decreases considerably. Below 1 minute, uniform mixing of the UV absorber becomes difficult. At this time, stabilizers, color adjusters, and / or antistatic agents may be added as needed.

[0074] It is preferable to have a multilayer structure of at least three layers for the polyester film, and to add an ultraviolet absorber to the intermediate layer of the film. Specifically, a three-layer film containing an ultraviolet absorber in the intermediate layer can be manufactured as follows: Polyester pellets alone are used for the outer layer, and a masterbatch containing an ultraviolet absorber and polyester pellets are mixed in a predetermined ratio for the intermediate layer. After drying, the mixture is supplied to a known melt lamination extruder, extruded into a sheet from a slit-shaped die, and cooled and solidified on a casting roll to produce an unstretched film. That is, using two or more extruders and a three-layer manifold or confluence block (for example, a confluence block with a square confluence section), the film layers constituting both outer layers and the film layer constituting the intermediate layer are laminated, the three-layer sheet is extruded from a die, and cooled on a casting roll to produce an unstretched film. In this invention, it is preferable to perform high-precision filtration during melt extrusion in order to remove foreign matter contained in the raw polyester that causes optical defects. Filtration particle size of filter material used for high-precision filtration of molten resin (initial filtration efficiency 95%) The particle size is preferably 15 μm or less. If the filtration particle size of the filter media exceeds 15 μm, the removal of foreign matter larger than 20 μm tends to be insufficient. [Examples]

[0075] The present invention will be described more specifically below with reference to examples, but the present invention is not limited by the following examples, and can be implemented with appropriate modifications within the scope of the spirit of the invention, and all such modifications fall within the technical scope of the present invention. The method for evaluating the physical properties in the following examples is as follows.

[0076] (1) Refractive index of polyester film Using a molecular orientation meter (MOA-6004, manufactured by Oji Instruments Co., Ltd.), the slow phase axis direction of the film was determined. A 4cm x 2cm rectangle was cut out so that the slow phase axis direction was parallel to the longer side, and this was used as a sample for measurement. For this sample, the refractive index in two orthogonal axes (refractive index in the slow phase axis direction: Ny, fast phase axis direction (refractive index in the direction perpendicular to the slow phase axis direction): Nx) and the refractive index in the thickness direction (Nz) were determined using an Abbe refractometer (NAR-4T, manufactured by Atago, measurement wavelength 589nm).

[0077] (2) Retardation (Re) Retardation is a parameter defined by the product (△Nxy × d) of the anisotropy of the refractive indices of two orthogonal axes on a film (△Nxy = |Nx - Ny|) and the film thickness d (nm), and is a measure of optical isotropy and anisotropy. The anisotropy of the refractive indices of the two axes (△Nxy) was determined by the method in (1) above, and the absolute value of the difference in refractive indices of the two axes (|Nx - Ny|) was calculated as the refractive index anisotropy (△Nxy). The film thickness d (nm) was measured using an electric micrometer (Millitron 1245D, manufactured by FineLewf Co., Ltd.), and the unit was converted to nm. Retardation (Re) was determined from the product (△Nxy × d) of the refractive index anisotropy (△Nxy) and the film thickness d (nm).

[0078] (3) Thickness direction retardation (Rth) Thickness retardation is a parameter that represents the average retardation obtained by multiplying the two birefringences △Nxz (=|Nx-Nz|) and △Nyz (=|Ny-Nz|) as viewed from a cross-section in the thickness direction of the film by the film thickness d. Nx, Ny, Nz and the film thickness d (nm) were determined using the same method as for measuring retardation, and the thickness retardation (Rth) was determined by calculating the average value of (△Nxz×d) and (△Nyz×d).

[0079] (4) NZ coefficient The values ​​of Ny, Nx, and Nz obtained in (1) above were substituted into the equation (NZ = |Ny - Nz| / |Ny - Nx|) to find the value of the NZ coefficient.

[0080] (5) Measurement of the emission spectrum of the backlight source The liquid crystal display used in each example was a Sony BRAVIA KDL-40W920A (a liquid crystal display having a light source that emits excitation light and a backlight light source containing quantum dots). The emission spectrum of the backlight light source of this liquid crystal display was measured using a Hamamatsu Photonics PMA-12 multi-channel spectrometer. Emission spectra with peaks around 450 nm, 528 nm, and 630 nm were observed, with the full width at half maximum of 17 nm to 34 nm for each peak. The exposure time for spectrum measurement was 20 msec.

[0081] (6)Reflectance Using a spectrophotometer (Shimadzu Corporation, UV-3150), a 5-degree inverter at a wavelength of 550 nm was measured. The emissivity was measured from the surface on the anti-reflective layer side (or low-reflective layer side). For the measurement, black marker was applied to the side of the polyester film opposite to the side with the anti-reflective layer (or low-reflective layer), and then black vinyl tape (Kyowa Vinyl Tape HF-737, 50mm wide) was applied before measurement.

[0082] (7) Observation of rainbow spots The liquid crystal display devices obtained in each embodiment were visually observed in the dark from the front and oblique directions, and the presence or absence of iridescence was determined as follows. Here, oblique directions refer to a range of 30 to 60 degrees from the normal direction of the liquid crystal display device screen.

[0083] ○: No iridescence is observed. △: Slight iridescence is observed. ×: Iridescent spots are observed. ××: Significant iridescence is observed.

[0084] (Manufacturing Example 1 - Polyester A) The esterification reaction vessel was heated to 200°C, at which point 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged. While stirring, 0.017 parts by mass of antimony trioxide, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were charged as catalysts. Next, the mixture was heated under pressure and the esterification reaction was carried out at a gauge pressure of 0.34 MPa and 240°C. After that, the esterification reaction vessel was returned to atmospheric pressure and 0.014 parts by mass of phosphoric acid was added. Furthermore, the temperature was raised to 260°C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, the mixture was dispersed using a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction vessel and a polycondensation reaction was carried out under reduced pressure at 280°C.

[0085] After the polycondensation reaction was complete, the mixture was filtered through a Naslon filter with a 95% cut diameter of 5 μm. It was then extruded from a nozzle in strand form, cooled and solidified using pre-filtered cooling water (pore size: 1 μm or less), and cut into pellets. The resulting polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl / g and contained virtually no inert particles or internally precipitated particles. (Hereafter abbreviated as PET(A).)

[0086] (Manufacturing Example 2 - Polyester B) Ten parts by mass of a dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinon-4-one) and 90 parts by mass of particle-free PET(A) (with an intrinsic viscosity of 0.62 dl / g) were mixed, and polyethylene terephthalate resin (B) containing the ultraviolet absorber was obtained using a kneading extruder. (Hereafter, this will be abbreviated as PET(B).)

[0087] (Manufacturing Example 3 - Preparation of Adhesion Modifying Coating Solution) A water-dispersible sulfonic acid metal base-containing copolymer polyester resin was prepared by conventional transesterification and polycondensation reactions to obtain a water-dispersible sulfonic acid metal base-containing copolymer polyester resin with the following composition: dicarboxylic acid components (relative to the total dicarboxylic acid components) consisting of 46 mol% terephthalic acid, 46 mol% isophthalic acid, and 8 mol% sodium 5-sulfonaisophthalate; and glycol components (relative to the total glycol components) consisting of 50 mol% ethylene glycol and 50 mol% neopentyl glycol. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellsolve, and 0.06 parts by mass of a nonionic surfactant were mixed, and the mixture was heated and stirred until it reached 77°C. Then, 5 parts by mass of the above water-dispersible sulfonic acid metal base-containing copolymer polyester resin was added, and stirring continued until there were no more clumps of resin. After that, the resin aqueous dispersion was cooled to room temperature to obtain a uniform water-dispersible copolymer polyester resin liquid with a solid content concentration of 5.0% by mass. Furthermore, 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silicia Co., Ltd.) were dispersed in 50 parts by mass of water. Next, 0.54 parts by mass of an aqueous dispersion of Cylysia 310 was added to 99.46 parts by mass of the above-mentioned water-dispersible copolymer polyester resin liquid, and 20 parts by mass of water was added while stirring to obtain an adhesive-modifying coating solution.

[0088] (Manufacturing Example 4 - Preparation of High Refractive Index Coating Agent) 80 parts methyl methacrylate, 20 parts methacrylic acid, 1 part azoisobutyronitrile, and 200 parts isopropyl alcohol were charged into a reaction vessel and reacted at 80°C under a nitrogen atmosphere for 7 hours to obtain an isopropyl alcohol solution of a polymer with a weight-average molecular weight of 30,000. The obtained polymer solution was further diluted with isopropyl alcohol to a solid content of 5% to obtain acrylic resin solution B. Next, the obtained acrylic resin solution B was mixed with the following components to obtain a coating solution for forming a high refractive index layer.

[0089] • Acrylic resin solution B: 5 parts by mass • Bisphenol A diglycidyl ether 0.25 parts by mass • 0.5 parts by mass of titanium oxide particles with an average particle size of 20 nm • Triphenylphosphine 0.05 parts by mass Isopropyl alcohol 14.25 parts by mass

[0090] (Manufacturing Example 5 - Preparation of Low Refractive Index Coating Agent) 45 parts by mass of 2,2,2-trifluoroethyl acrylate, 45 parts by mass of perfluorooctyl ethyl acrylate, 10 parts by mass of acrylic acid, 1.5 parts by mass of azoisobutyronitrile, and 200 parts by mass of methyl ethyl ketone were charged into a reaction vessel and reacted at 80°C under a nitrogen atmosphere for 7 hours to obtain a methyl ethyl ketone solution of a polymer with a weight-average molecular weight of 20,000. The obtained polymer solution was diluted with methyl ethyl ketone to a solid content concentration of 5% by mass to obtain fluoropolymer solution C. The obtained fluoropolymer solution C was mixed as follows to obtain a coating solution for forming a low refractive index layer.

[0091] • Fluoropolymer solution C4 4 parts by mass • 1,10-bis(2,3-epoxypropoxy) - 2,2,3,3,4,4,5,5,6,6,7,7 , 8,8,9,9 - Hexadecafluorodecane (Kyoeisha Chemical Co., Ltd., Fluorite FE-16) 1 part by mass • Triphenylphosphine 0.1 parts by mass • Methyl ethyl ketone 19 parts by mass

[0092] (Manufacturing Example 6 - Preparation of Anti-Glare Coating Agent 1) A coating solution for forming an anti-glare layer was obtained by adding the solid components of the following to a mixed solvent of methyl ethyl ketone:1-butanol = 3:1 to a total of 35% by mass: unsaturated double bond-containing acrylic copolymer cyclomer P ACA-Z250 (manufactured by Daicel Chemical Industries, Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-20 (number average molecular weight 75,000) (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) (manufactured by Sekisui Chemical Co., Ltd.) (2 parts by mass), and Irgacure 184 (manufactured by BASF) (10 parts by mass).

[0093] (Manufacturing Example 7 - Preparation of Anti-Glare Coating Agent 2) Unsaturated double bond-containing acrylic copolymer cyclomer P ACA-Z250 (manufactured by Daicel Chemical Industries, Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-0.5 (number average molecular weight 25000) (manufactured by Eastman Chemical Corporation) (3 parts by mass), acrylic monomer AYARAD DPHA (manufactured by Nippon Kayaku Co., Ltd.) (49 parts by mass), acrylic-sty A coating solution for forming an anti-glare layer was obtained by adding the solid components of a lem copolymer (average particle size 4.0 μm) (manufactured by Sekisui Chemical Co., Ltd.) (4 parts by mass) and Irgacure 184 (manufactured by BASF) (10 parts by mass) to a mixed solvent of methyl ethyl ketone:1-butanol = 3:1 so that the total solid component content was 35% by mass.

[0094] (Manufacturing Example 8 - Preparation of Anti-Glare Coating Agent 3) A coating solution for forming an anti-glare layer was obtained by adding the solid components of the following to a mixed solvent of methyl ethyl ketone:1-butanol = 3:1 to a total of 35% by mass: unsaturated double bond-containing acrylic copolymer cyclomer P ACA-Z250 (manufactured by Daicel Chemical Industries, Ltd.) (49 parts by mass), cellulose acetate propionate CAP482-0.2 (number average molecular weight 15000) (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) (manufactured by Sekisui Chemical Co., Ltd.) (2 parts by mass), and Irgacure 184 (manufactured by BASF).

[0095] (Polarizer protective film 1) As raw materials for the intermediate layer of the base film, 90 parts by mass of particle-free PET(A) resin pellets and 10 parts by mass of PET(B) resin pellets containing an ultraviolet absorber were dried under reduced pressure (1 Torr) at 135°C for 6 hours, and then supplied to extruder 2 (for intermediate layer II). PET(A) was dried by a conventional method and supplied to extruder 1 (for outer layer I and outer layer III), respectively, and melted at 285°C. These two polymers were filtered using a stainless steel sintered filter medium (nominal filtration accuracy, 95% particle cut of 10 μm particles), laminated in a 2-layer 3-combination block, extruded into a sheet from a die, and then cooled and solidified using an electrostatic casting method on a casting drum with a surface temperature of 30°C to produce an unstretched film. At this time, the discharge rate of each extruder was adjusted so that the thickness ratio of layers I, II, and III was 10:80:10.

[0096] Next, using the reverse roll method, a coating amount of 0.08 g / m² was applied to both sides of the unstretched PET film after drying. 2 To achieve this, the above-mentioned adhesive modification coating solution was applied and then dried at 80°C for 20 seconds.

[0097] The unstretched film with this coating layer was guided into a tenter stretcher, and while holding the edges of the film with clips, it was guided into a hot air zone at a temperature of 125°C and stretched to 4.0 times its original width. Next, while maintaining the stretched width, it was treated at a temperature of 225°C for 10 seconds, and then a further relaxation treatment of 3.0% in the width direction was performed to obtain a uniaxially oriented PET film with a thickness of approximately 100 μm.

[0098] The high refractive index layer forming solution was applied to one coated surface of the uniaxially oriented PET film and dried at 150°C for 2 minutes to form a high refractive index layer with a thickness of 0.1 μm. The low refractive index layer forming solution obtained by the above method was applied on top of this high refractive index layer and dried at 150°C for 2 minutes to form a low refractive index layer with a thickness of 0.1 μm, thereby obtaining a polarizer protective film 1 with an anti-reflective layer laminated on top.

[0099] (Polarizer protective film 2) Polarizer protective film 2 was produced in the same manner as polarizer protective film 1, except that the line speed was changed to alter the thickness of the unstretched film, and a polarizer protective film 2 with an anti-reflective layer laminated on top was obtained, with a film thickness of approximately 80 μm.

[0100] (Polarizer protective film 3) Except for changing the line speed and altering the thickness of the unstretched film, the polarizer protective film 1 A polarizer protective film 3 with a film thickness of approximately 60 μm was obtained by forming a film in the same manner as before, with an anti-reflective layer laminated on top.

[0101] (Polarizer protective film 4) Except for changing the line speed to alter the thickness of the unstretched film, the polarizer protective film 4 was manufactured in the same manner as polarizer protective film 1, and a polarizer protective film 4 with an anti-reflective layer laminated on top was obtained, with a film thickness of approximately 40 μm.

[0102] (Polarizer protective film 5) An unstretched film, prepared in the same manner as polarizer protective film 1, was heated to 105°C using a heated roll group and an infrared heater. Then, it was stretched 3.3 times in the running direction using a roll group with different peripheral speeds. Finally, it was guided into a hot air zone at 130°C and stretched 4.0 times in the width direction to obtain polarizer protective film 5, with an anti-reflective layer laminated in the same manner as polarizer protective film 1, resulting in a film thickness of approximately 30 μm.

[0103] (Polarizer protective film 6) Except for not applying an anti-reflective layer, polarizer protective film 6 was manufactured using the same method as polarizer protective film 1, and a film thickness of approximately 100 μm was obtained.

[0104] (Polarizer protective film 7) Except for the absence of an anti-reflective layer, the polarizer protective film was prepared in the same manner as polarizer protective film 2. Anti-glare coating agent-1 was applied to one coated surface of the polarizer protective film so that the cured film thickness was 8 μm, and it was dried in an oven at 80°C for 60 seconds. Afterward, an ultraviolet irradiation device (Fusion UV Systems Japan, light source H bulb) was used to irradiate the film at a dose of 300 mJ / cm².2 The antiglare layer was laminated by irradiating with ultraviolet rays. Then, an antireflection layer was laminated on the antiglare layer in the same manner as the polarizer protection film 1 to obtain the polarizer protection film 7.

[0105] (Polarizer protection film 8) On one coated surface of the polarizer protection film produced in the same manner as the polarizer protection film 3, except that no antireflection layer was provided, an antiglare layer and an antireflection layer were laminated in the same manner as the polarizer protection film 7 to obtain the polarizer protection film 8.

[0106] (Polarizer protection film 9) On one coated surface of the polarizer protection film produced in the same manner as the polarizer protection film 4, except that no antireflection layer was provided, an antiglare layer coating agent - 2 was applied so that the film thickness after curing would be 8 μm, and it was 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 the antiglare layer. Then, an antireflection layer was laminated on the antiglare layer in the same manner as the polarizer protection film 1 to obtain the polarizer protection film 9.

[0107] (Polarizer protection film 10) On one coated surface of the polarizer protection film produced in the same manner as the polarizer protection film 5, except that no antireflection layer was provided, an antiglare layer was laminated in the same manner as the polarizer protection film 7 to obtain the polarizer protection film 10 (no antireflection layer was laminated).

[0108] (Polarizer protection film 11) On one coated surface of the polarizer protection film produced in the same manner as the polarizer protection film 1, except that no antireflection layer was provided, an antiglare layer coating agent - 3 was applied so that the film thickness after curing would be 8 μm, and it was dried in an oven at the same temperature for 60 seconds. Then, using an ultraviolet irradiation device (Fusion UV Systems Japan, light source H bulb), the irradiation dose was 300 mJ / cm 2A polarizer protective film 11 with an anti-glare layer was obtained by irradiating it with ultraviolet light.

[0109] (Polarizer protective film 12) Except for the absence of an anti-reflective layer, the polarizer protective film was prepared in the same manner as polarizer protective film 2. Anti-glare coating agent-1 was applied to one coated surface of the polarizer protective film so that the cured film thickness was 8 μm, and it was dried in an oven at 80°C for 60 seconds. Afterward, an ultraviolet irradiation device (Fusion UV Systems Japan, light source H bulb) was used to irradiate the film at a dose of 300 mJ / cm². 2 The anti-glare layer was laminated by irradiating it with ultraviolet light. Then, a low refractive index layer was laminated on top of the anti-glare layer in the same manner as in polarizer protective film 1. In this way, polarizer protective film 12 was obtained in which a low-reflection layer was laminated on top of the anti-glare layer.

[0110] A liquid crystal display device was created using polarizer protective films 1 to 12, as described later.

[0111] (Example 1) A polarizer protective film 1 was attached to one side of a polarizer made of PVA and iodine, such that the transmission axis of the polarizer and the phase advance axis of the film were perpendicular. A TAC film (manufactured by Fujifilm Corporation, 80 μm thick) was attached to the opposite side to create a polarizer plate 1. The polarizer was then laminated to the side of the polarizer protective film that did not have an anti-reflective layer to create the polarizer plate. A liquid crystal display device was created by replacing the polarizer plate on the viewing side of a SONY BRAVIA KDL-40W920A (a liquid crystal display device having a light source that emits excitation light and a backlight light source containing quantum dots) with the above polarizer plate 1, such that the polyester film was on the opposite side (distal) from the liquid crystal. The polarizer plate 1 was replaced so that the direction of the transmission axis of the polarizer plate was the same as the direction of the transmission axis of the original polarizer plate.

[0112] (Example 2) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 2.

[0113] (Example 3) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 3.

[0114] (Example 4) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 4.

[0115] (Example 5) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 4 was used instead of polarizer protective film 1, and it was attached so that its phase advance axis was parallel to the transmission axis of the polarizer.

[0116] (Example 6) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 7.

[0117] (Example 7) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 8.

[0118] (Example 8) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 9.

[0119] (Example 9) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 12.

[0120] (Comparative Example 1) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 5.

[0121] (Comparative Example 2) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 6.

[0122] (Comparative Example 3) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 10.

[0123] (Comparative Example 4) A liquid crystal display device was created in the same manner as in Example 1, except that polarizer protective film 1 was replaced with polarizer protective film 11.

[0124] The results of iridescence observation measurements for the liquid crystal displays obtained in each example are shown in Table 1 below.

[0125] [Table 1] [Industrial applicability]

[0126] The liquid crystal display device and polarizing plate of the present invention can ensure excellent visibility with significantly suppressed rainbow-like color spots at any angle, making a significant contribution to industry.

Claims

1. A liquid crystal display device having a backlight source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates, The backlight light source has peaks in its emission spectrum in the wavelength regions of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, respectively, and the full width at half maximum of each peak is 5 nm to 80 nm. In at least one of the polarizing plates, a polyester film is laminated on at least one surface of the polarizer. The polyester film has in-plane retardation between 1500 nm and 30000 nm, the ratio of in-plane retardation (Re) to retardation in the thickness direction (Rth) (Re / Rth) is between 0.6 and 2.0, and the NZ coefficient is 2.5 or less. An anti-glare layer is laminated on the surface of the polyester film opposite to the surface on which the polarizer is laminated, and an anti-reflective layer is laminated on top of the anti-glare layer. In a laminate comprising the polyester film, the anti-glare layer, and the anti-reflective layer, the surface reflectance at a wavelength of 550 nm, measured at an incident angle of 5 degrees from the surface of the laminate on the anti-reflective layer side, using a spectrophotometer with the surface opposite to the surface on the anti-reflective layer side of the laminate shielded with black light, is 2.0% or less. LCD display device.

2. A liquid crystal display device having a backlight source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates, The backlight light source has peaks in its emission spectrum in the wavelength regions of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, respectively, and the full width at half maximum of each peak is 5 nm to 80 nm. In at least one of the polarizing plates, a polyester film is laminated on at least one surface of the polarizer. The polyester film has in-plane retardation between 1500 nm and 30000 nm, the ratio of in-plane retardation (Re) to retardation in the thickness direction (Rth) (Re / Rth) is between 0.6 and 2.0, and the NZ coefficient is 2.5 or less. An anti-glare layer is laminated on the surface of the polyester film opposite to the surface on which the polarizer is laminated, and a low-reflection layer is laminated on top of the anti-glare layer. In a laminate comprising the polyester film, the anti-glare layer, and the low-reflection layer, the surface reflectance at a wavelength of 550 nm, measured at an incident angle of 5 degrees from the surface of the low-reflection layer side of the laminate using a spectrophotometer with the opposite side of the laminate shielded with black light, is less than 5%. LCD display device.

3. The liquid crystal display device according to claim 1 or 2, wherein the backlight light source includes a light source that emits excitation light and quantum dots.

4. The liquid crystal display device according to any one of claims 1 to 3, wherein the anti-glare layer comprises acrylic-styrene copolymer particles.

5. A polarizing plate in which a polarizer and a polyester film are laminated on at least one surface of the polarizer, The polyester film has in-plane retardation between 1500 nm and 30000 nm, the ratio of in-plane retardation (Re) to retardation in the thickness direction (Rth) (Re / Rth) is between 0.6 and 2.0, and the NZ coefficient is 2.5 or less. An anti-glare layer is laminated on the surface of the polyester film opposite to the surface on which the polarizer is laminated, and an anti-reflective layer is laminated on top of the anti-glare layer. In a laminate comprising the polyester film, the anti-glare layer, and the anti-reflective layer, the surface reflectance at a wavelength of 550 nm, measured at an incident angle of 5 degrees from the surface of the laminate on the anti-reflective layer side, using a spectrophotometer with the surface opposite to the surface on the anti-reflective layer side of the laminate shielded with black light, is 2.0% or less. Polarizing plate.

6. A polarizing plate in which a polarizer and a polyester film are laminated on at least one surface of the polarizer, The polyester film has in-plane retardation between 1500 nm and 30000 nm, the ratio of in-plane retardation (Re) to retardation in the thickness direction (Rth) (Re / Rth) is between 0.6 and 2.0, and the NZ coefficient is 2.5 or less. An anti-glare layer is laminated on the surface of the polyester film opposite to the surface on which the polarizer is laminated, and a low-reflection layer is laminated on top of the anti-glare layer. In a laminate comprising the polyester film, the anti-glare layer, and the low-reflection layer, the surface reflectance at a wavelength of 550 nm, measured at an incident angle of 5 degrees from the surface of the low-reflection layer side of the laminate using a spectrophotometer with the opposite side of the laminate shielded with black light, is less than 5%. Polarizing plate.

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