KR102634613B1 - Liquid crystal display device and polarizing plate - Google Patents

Abstract

The present invention uses a polyester film as a polarizer protective film in a liquid crystal display device having a backlight light source with a relatively narrow half width of each peak of the emission spectrum, as represented by a light source emitting excitation light and a backlight light source containing quantum dots. Provided is a liquid crystal display device in which rainbow stains are suppressed even in cases where rainbow stains are suppressed.
The liquid crystal display device of the present invention is 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 emitting excitation light and a quantum dot, and the polarizing plate At least one of the polarizing plates is a polyester film laminated on at least one side of the polarizer, and the refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 1.53 to 1.62.

Description

Liquid crystal display device and polarizing plate}

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

Polarizers used in liquid crystal displays (LCDs) usually have a structure in which a polarizer dyed with iodine on polyvinyl alcohol (PVA) is sandwiched between two polarizer protective films. In most cases, the polarizer protective film is made of triacetylcellulose (TAC). Film is being used. Recently, along with the thinning of LCDs, there has been a demand for thinner polarizing plates. However, if the thickness of the TAC film used as a protective film is thinned for this purpose, sufficient mechanical strength is not obtained and moisture permeability deteriorates. In addition, the TAC film is very expensive, so polyester film has been proposed as an inexpensive alternative material (Patent Documents 1 to 3), but there is a problem in that rainbow-shaped color stains are observed.

When an oriented polyester film having birefringence is disposed on one side of a polarizer, the polarization state of linearly polarized light emitted from the backlight unit or the polarizer changes as it passes through the polyester film. The transmitted light exhibits a characteristic interference color due to retardation, which is the product of the birefringence and thickness of the oriented polyester film. For this reason, if a discontinuous emission spectrum such as a cold cathode tube or a hot cathode tube is used as a light source, the transmitted light intensity varies depending on the wavelength, resulting in a rainbow-shaped color stain (Reference: 15th Microoptics Conference Abstract, pages 30-31).

As a means of solving the above problem, it has been proposed to use a white light source with a continuous and wide emission spectrum, such as a white light emitting diode, as a backlight light source, and to use an oriented polyester film with a certain retardation as a polarizer protective film. There is (patent document 4). White light emitting diodes have a continuous and wide emission spectrum in the visible light region. Therefore, focusing on the parabolic shape of the interference color spectrum of the transmitted light passing through the 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 rainbow spots can be suppressed.

By making the orientation direction of the oriented polyester film and the polarization direction of the polarizer perpendicular to or parallel to each other, the linearly polarized light emitted from the polarizer passes through the oriented polyester film while maintaining its polarization state. In addition, by controlling the birefringence of the oriented polyester film to increase uniaxial orientation, light incident from an oblique direction also passes through while maintaining its polarization state. When an oriented polyester film is viewed obliquely, there is a deviation in the orientation main axis direction compared to when viewed from directly above, but if the uniaxial orientation is high, the deviation in the orientation main axis direction becomes small when viewed obliquely. For this reason, it is thought that the deviation between the direction of linear polarization and the main axis direction becomes small, making it difficult for changes in polarization state to occur. In this way, it was thought that by controlling the emission spectrum of the light source, the orientation state of the birefringent, and the main axis direction, changes in polarization state were suppressed, rainbow-shaped color spots did not occur, and visibility was significantly improved.

Japanese Patent Publication No. 2002-116320 Japanese Patent Publication No. 2004-219620 Japanese Patent Publication No. 2004-205773 International Publication WO 2011/162198

When a liquid crystal display device is industrially produced using a polarizing plate using a polyester film as a polarizer protective film, the directions of the transmission axis of the polarizer and the fast axis of the polyester film are usually arranged to be perpendicular to each other. This is due to the following circumstances. The polyvinyl alcohol film, which is a polarizer, is manufactured by longitudinal uniaxial stretching. Therefore, the polyvinyl alcohol film used as a polarizer is usually a long film in the stretching direction. Meanwhile, since the polyester film, which is the protective film, is manufactured by longitudinal stretching and then transverse stretching, the main axis direction of the polyester film is horizontal. That is, the main axis of orientation of the polyester film used as the polarizer protective film intersects the longitudinal direction of the film approximately perpendicularly. From the viewpoint of manufacturing efficiency, these films are usually bonded so that their longitudinal directions are parallel to each other to produce a polarizing plate. Then, the fast axis of the polyester film and the transmission axis of the polarizer are usually vertical. In this case, rainbow-shaped color spots are significantly improved by using an oriented polyester film with a specific retardation as the polyester film and using a light source with a continuous emission spectrum such as a white LED as a backlight light source. However, it was discovered that when the backlight light source consists of a light source that emits excitation light and a light-emitting layer containing quantum dots, a new problem exists in that rainbow spots still occur.

As the demand for color gamut expansion has recently increased, in addition to white light sources using quantum dot technology, the emission spectrum of white light sources has clear relative luminous intensity peaks in each wavelength range of R (red), G (green), and B (blue). Liquid crystal displays are being developed. For example, a combination of a phosphor-type white LED light source using a phosphor with clear emission peaks in the R (red) and G (green) regions due to excitation light and a blue LED, a 3-wavelength white LED light source, and a red laser. Liquid crystal displays capable of wide color gamut using various types of light sources, such as white LED light sources, are being developed. All of these white light sources have narrow peak half widths compared to light sources made of white light-emitting diodes using YAG-based yellow phosphors, which have been widely used in the past. These white light sources are used when a polyester film with retardation is used as a polarizer protective film, which is a structural member of a polarizer, and in the case of a liquid crystal display device having a backlight light source composed of a light source emitting the above-described excitation light and a light emitting layer containing quantum dots. It was discovered that the same problem exists.

That is, the object of the present invention is to provide a polyester film as a polarizer protective film in a liquid crystal display device having a backlight light source with a relatively narrow half width of each peak of the emission spectrum, as represented by a light source emitting excitation light and a backlight light source containing quantum dots. To provide a liquid crystal display device and a polarizing plate in which rainbow stains are suppressed even when using.

Representative examples of the present invention are as follows.

Paragraph 1.

A liquid crystal display device having a backlight light source, two polarizers, and a liquid crystal cell disposed between the two polarizers,

The backlight light source includes a light source that emits excitation light and quantum dots,

At least one of the polarizers is a polyester film laminated on at least one side of the polarizer, and the polyester film in a direction parallel to the transmission axis of the polarizer has a refractive index of 1.53 to 1.62.

Liquid crystal display device.

Paragraph 2.

A liquid crystal display device having a backlight light source, two polarizers, and a liquid crystal cell disposed between the two polarizers,

The backlight light source has a peak peak of the emission spectrum in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and emits light with a half width of each peak of 5 nm or more, ,

At least one of the polarizers is a polyester film laminated on at least one side of the polarizer, and the polyester film in a direction parallel to the transmission axis of the polarizer has a refractive index of 1.53 to 1.62.

Liquid crystal display device.

Paragraph 3.

The backlight light source has a peak peak of the emission spectrum in each wavelength region of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 750 nm, and emits light with a half width of each peak of 5 nm or more, The liquid crystal display device described in paragraph 2.

Paragraph 4.

The liquid crystal display device according to any one of items 1 to 3, wherein the difference between the refractive index in the transmission axis direction of the polarizer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 0.12 or less.

Clause 5.

A polarizing plate in which a polyester film is laminated on at least one side of the polarizer,

The refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 1.53 to 1.62,

A polarizer for a liquid crystal display device having a light source that emits excitation light and a backlight light source that includes quantum dots.

Clause 6.

A polarizing plate in which a polyester film is laminated on at least one side of the polarizer,

The refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 1.53 to 1.62,

A liquid crystal having a backlight light source that emits light with a peak width of each peak of 5 nm or more, with peak peaks of the emission spectrum in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm. Polarizer for display devices.

The liquid crystal display device and polarizing plate of the present invention can ensure good visibility with significantly suppressed occurrence of rainbow-shaped color stains at any observation angle.

Figure 1 is a diagram showing an example when multiple peaks exist within a single wavelength region.
Figure 2 is a diagram showing an example when multiple peaks exist within a single wavelength region.
Figure 3 is a diagram showing an example when multiple peaks exist within a single wavelength region.
Figure 4 is a diagram showing an example when multiple peaks exist within a single wavelength region.

Generally, a liquid crystal display device has a rear module, a liquid crystal cell, and a front module in the order from the side where the backlight light source (also called "backlight unit") is disposed to the side where the image is displayed (viewer side). The rear module and the front module generally consist of a transparent substrate, a transparent conductive film formed on the surface of the liquid crystal cell side, and a polarizing plate disposed on the opposite side. That is, the polarizer is disposed on the side facing the backlight light source in the rear module, and on the side where the image is displayed (viewer side) in the front module.

The liquid crystal display device of the present invention has at least a liquid crystal cell disposed between a backlight light source and two polarizing plates as a structural member. The backlight light source preferably has an emission spectrum with peak peaks in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and a half width of each peak of 5 nm or more. . It is known that the peak wavelengths of blue, green, and red defined in the CIE chromaticity diagram are 435.8 nm (blue), 546.1 nm (green), and 700 nm (red), respectively. Each wavelength region of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm corresponds to the blue region, green region, and red region, respectively. Light sources having the above-mentioned emission spectrum include a light source that emits excitation light and a backlight light source that includes at least quantum dots. In addition, a phosphor-type white LED light source that combines a blue LED and a phosphor with emission peaks in the R (red) and G (green) regions by excitation light, a 3-wavelength white LED light source, and a red laser are used. Examples include a white LED light source. Among the above phosphors, red phosphors include, for example, a nitride-based phosphor with a basic composition of CaAlSiN ₃ :Eu, a sulfide-based phosphor with a basic composition of CaS:Eu, etc., and a silicate-based phosphor with a basic composition of Ca ₂ SiO ₄ :Eu, etc. Examples include phosphors and the like. Among the above-mentioned phosphors, examples of green phosphors include sialon-based phosphors with a basic composition of β-SiAlON:Eu, and silicate-based phosphors with a basic composition of (Ba,Sr) ₂ SiO ₄ :Eu.

In addition to the backlight light source, polarizing plate, and liquid crystal cell, the liquid crystal display device may have other components, such as color filters, lens films, diffusion sheets, anti-reflection films, etc., as appropriate. A brightness enhancement film may be installed between the polarizer on the light source side and the backlight light source. Examples of the brightness enhancing film include a reflective polarizing plate that transmits linearly polarized light on one side and reflects linearly polarized light orthogonal to it. As a reflective polarizer, for example, a brightness enhancement film of the DBEF (registered trademark) (Dual Brightness Enhancement Film) series manufactured by Sumitomo 3M Corporation is suitably used. Additionally, the reflective polarizer is usually arranged so that the absorption axis of the reflective polarizer is parallel to the absorption axis of the polarizer on the light source side.

At least one of the two polarizers disposed in the liquid crystal display device is a polyester film laminated on at least one side of a polarizer made by dyeing iodine on polyvinyl alcohol (PVA) or the like. The refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is preferably 1.53 to 1.62. It is preferable that a film without birefringence, such as TAC film, acrylic film, and norbornene-based film, is laminated on the other side of the polarizer (polarizer with three-layer structure), but the film must be laminated on the other side of the polarizer. Not necessary (two-layer polarizer). Additionally, when polyester films are used as protective films on both sides of the polarizer, it is preferable that the slow axes of both polyester films are substantially parallel to each other.

The polyester film may be laminated on the polarizer via any adhesive, or may be laminated directly without using an adhesive. The adhesive is not particularly limited and any adhesive can be used. As an example, it is possible to use a water-based adhesive (i.e., adhesive components dissolved in water or dispersed in water). For example, it is possible to use an adhesive containing polyvinyl alcohol-based resin and/or urethane resin as a main component. To improve adhesion, it is also possible to use an adhesive additionally mixed with an isocyanate-based compound, epoxy compound, etc., if necessary. Additionally, as another example, it is also possible to use a photocurable adhesive. In one embodiment, a non-solvent type UV curing adhesive is preferred. Examples of the photocurable resin include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

The configuration of the backlight may be an edge light type using a light guide plate, a reflector, etc. as structural members, or a direct type type. The backlight light source is a light source emitting excitation light and a backlight light source containing quantum dots as a representative example, and has peaks in each wavelength range of "400 nm to 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm. A backlight light source having an emission spectrum that has a peak and a half width of each peak of 5 nm or more is preferable. In addition, it is possible to provide a layer containing a lot of quantum dots and use this as a light-emitting layer in a backlight, for example.

The application of quantum dot technology to LCDs is a technology that is attracting attention as the demand for color gamut expansion has recently increased. In the case of LEDs that use ordinary white LEDs as backlight light sources, they can only reproduce colors of about 20% of the spectrum that the human eye can perceive. In contrast, it is known that when a backlight light source consisting of a light source that emits excitation light and a light-emitting layer containing quantum dots is used, it is possible to reproduce more than 60% of the colors of the spectrum that the human eye can perceive. Quantum dot technologies that have been put into practical use include Nanosys' QDEF ^TM and QD Vision's Color IQ ^TM .

The light-emitting layer containing quantum dots is composed of quantum dots, for example, in a resin material such as polystyrene, and is a layer that emits light of each color on a 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 provided in the red pixel, a green light-emitting layer provided in the green pixel, and a blue light-emitting layer provided in the blue pixel, and the quantum dots in these multi-color light emitting layers are generated based on the excitation light. Generates luminous light of different wavelengths (colors).

Examples of materials for such quantum dots include CdSe, CdS, ZnS:Mn, InN, InP, CuCl, CuBr, and Si, and the particle size (size in one direction) of these quantum dots is, for example, about 2 to 20 nm. am. In addition, among the quantum dot materials, examples of the red emitting material include InP, examples of the green emitting material include CdSc, and examples of the blue emitting material include CdS. In the case of such a light emitting layer, it has been confirmed that the light emission wavelength changes by changing the size (particle diameter) of the quantum dots or the composition of the material. It is used by controlling the size (particle diameter) or material of the quantum dots, mixing them with a resin material, dividing them into pixels and applying them. Additionally, because the use of heavy metals such as cadmium in many applications is being regulated, quantum dots that are cadmium-free while maintaining the same brightness and stability as conventional ones are being developed.

A blue LED is used as a light source for emitting excitation light, but in some cases, laser light such as a semiconductor laser is used. As the excitation light from the light source passes through the light emitting layer, an emission spectrum with peaks in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm is generated. At this time, the narrower the half width of the peak in each wavelength region, the wider the color gamut, but since the narrower the half width of the peak is, the lower the luminous efficiency, the shape of the luminous spectrum is designed taking into account the balance between the required color gamut and luminous efficiency.

Light sources using quantum dots are not particularly limited, but there are two major mounting methods. One is the on-edge method, which mounts quantum dots along the cross-section (side) of the backlight light guide plate. Quantum dots, which are particles with a diameter of several n to tens of nanometers, are placed in a glass tube with a diameter of several millimeters, sealed, and placed between the blue LED and the light guide plate. Light from the blue LED is irradiated to the glass tube, and the blue light that collides with the quantum dots is converted into green light or red light. The on-edge method has the advantage of reducing the amount of quantum dots used even on large screens. The other is a surface mounting method that places quantum dots on a light guide plate. Quantum dots are dispersed in resin to form a sheet, sandwiched between two barrier films and sealed, and the quantum dot film is spread on the light guide plate. The barrier film plays a role in suppressing the deterioration of quantum dots due to water or oxygen. The blue LED is placed on the cross-section (side) of the light guide plate in the same way as 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 characteristics of the surface mounting method. First, because the light from the blue LED passes through the light guide plate and is irradiated to the quantum dots, the influence of heat from the LED is small, making it easy to secure reliability. Another thing is that because it is in a film shape, it is easy to respond to a wide range of screen sizes from small to large.

In the present invention, it is preferable that the backlight light source has a peak peak of the emission spectrum in each wavelength region of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and the half width of each peak is 5 nm or more. do. The wavelength range of 400 nm to 495 nm is more preferably 430 nm to 470 nm. The wavelength range of 495 nm to 600 nm is more preferably 510 nm to 560 nm. The wavelength range 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 lower limit of the half width of each peak is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more. From the viewpoint of securing an appropriate color gamut, the upper limit of the half width of each peak is preferably 140 nm or less, preferably 120 nm or less, preferably 100 nm or less, more preferably 80 nm or less, and still more preferably is 60 nm or less, and even more preferably is 45 nm or less. In addition, here, the half width refers to the width (nm) of the peak at 1/2 the intensity of the peak intensity at the wavelength of the peak peak. Any combination of the individual upper and lower limits of the wavelength range described here is assumed. The individual upper and lower limits of the half width described herein are assumed to be any combination thereof. The peak intensity can be measured using, for example, a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics.

The cases where multiple peaks exist in any one of the wavelength ranges between 400 nm and less than 495 nm, the wavelength range between 495 nm and less than 600 nm, or the wavelength range between 600 nm and 780 nm are considered as follows. . When a plurality of peaks are independent peaks, it is preferable that the half width of the peak with the highest peak intensity is within the above range. In addition, it is more preferable that the half width equally falls within the above range for other peaks having an intensity of 70% or more of the highest peak intensity. For one independent peak having an overlapping shape of multiple peaks, if the half width of the peak with the highest peak intensity among the multiple peaks can be measured as is, the half width of the peak is used. Here, an independent peak is one that has an intensity region that is 1/2 of the peak intensity on both the short-wavelength side and the long-wavelength side of the peak. That is, when multiple peaks overlap and each peak does not have an intensity region on both sides of the peak intensity that is 1/2 of the peak intensity, the multiple peaks are regarded as one peak as a whole. For one peak having a shape in which a plurality of such peaks overlap, the half width is the width (nm) of the peak at half the intensity of the highest peak intensity. Also, among a plurality of peaks, the point with the highest peak intensity is taken as the peak peak. The half maximum width when multiple peaks exist within a single wavelength region is indicated by a double-headed arrow in FIGS. 1 to 4.

In Figure 1, peaks A and B have points that are 1/2 of the peak intensity on the short-wavelength side and long-wavelength side, respectively, starting from the peak. Therefore, peaks A and B are independent peaks. In the case of Figure 1, the half width can be evaluated as the width of the double-headed arrow of peak A, which has the highest peak intensity.

In FIG. 2, peak A has a point that is 1/2 the peak intensity on the short wavelength side and the long wavelength side, but peak B does not have a point that is 1/2 the peak intensity on the long wavelength side. Therefore, peak A and peak B are combined and considered as one independent peak. In this way, for one independent peak having a shape in which multiple peaks overlap, if the half width of the peak with the highest peak intensity among the multiple peaks can be measured as is, the half width is set as the half width of the independent peak. Therefore, in the case of Figure 2, the half width of the peak is the width of the double-headed arrow.

In Figure 3, for peak A, there is no point on the short wavelength side where the peak intensity is 1/2, and for peak B, there is no point on the long wavelength side where the peak intensity is 1/2. Therefore, in Figure 3, as in the case of Figure 2, peak A and peak B are combined and regarded as one independent peak, and its half width is the width indicated by a double-headed arrow.

In Figure 4, peak A has a point that is 1/2 of the peak intensity on the short wavelength side and the long wavelength side, but peak B does not have a point that is 1/2 the peak intensity on the long wavelength side. Therefore, peak A and peak B are combined and considered as one independent peak. For one independent peak having an overlapping shape of multiple peaks, if the half width of the peak with the highest peak intensity among the multiple peaks can be measured as is, the half width of the peak is used. Therefore, in the case of Figure 4, the half width is the width indicated by a double-headed arrow.

Figures 1 to 4 illustrate the wavelength range of 400 nm or more and less than 495 nm, but the same idea applies to other wavelength ranges.

The peak with the highest peak intensity in each wavelength region of 400 nm to less than 495 nm, the wavelength region of 495 nm to less than 600 nm, and the wavelength region of 600 nm to 780 nm is different from the peaks in other wavelength regions. It is desirable to have an independent relationship with each other. In particular, in the wavelength range between the peak with the highest peak intensity in the wavelength range between 495 nm and less than 600 nm and the peak with the highest peak intensity in the wavelength range between 600 nm and 780 nm, the intensity is between 600 nm and 780 nm. In terms of color clarity, it is preferable that there be a region that is less than 1/3 of the peak intensity of the peak with the highest peak intensity in the following wavelength range.

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

As a result of intensive study, the present inventors have found that, as typified by the light source emitting the above-described excitation light and the backlight light source containing quantum dots, a liquid crystal display device having a backlight light source with a relatively narrow half width of each peak of the emission spectrum, polarizer protection It was found that even when a polarizing plate using a polyester film was used as a film, rainbow stains could be significantly suppressed if the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer constituting the polarizing plate was in the range of 1.53 to 1.62. did. The mechanism by which the occurrence of rainbow-shaped color stains is suppressed by the sun is thought to be as follows.

When an oriented polyester film is disposed on one side of a polarizer, the polarization state of linearly polarized light emitted from a backlight unit or a polarizer changes as it passes through the oriented polyester film. One of the factors causing the change in polarization state is the possibility that 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, may have an effect. When linearly polarized light incident on the oriented polyester film passes through each interface, part of the light is reflected due to the difference in refractive index at the interface. At this time, the polarization state of both the emitted light and the reflected light changes, and this is thought to be one of the factors causing rainbow-shaped color stains. For this reason, by reducing the refractive index difference between the air layer and the oriented polyester film in the polarization direction (transmission axis direction) of the incident linearly polarized light, and the refractive index difference between the polarizer and the oriented polyester film, reflection at each interface is suppressed, creating a rainbow-like shape. It is thought that color staining is suppressed. The refractive index difference between the air layer and the oriented polyester film in the polarization direction (transmission axis direction) of the incident linearly polarized light and the refractive index difference between the polarizer and the oriented polyester film are reduced by the oriented polyester film in the direction parallel to the transmission axis. This can be achieved by adjusting the refractive index to about 1.53 to 1.62.

As described above, a backlight light source with a relatively narrow half width of each peak of the emission spectrum, represented by a light source emitting excitation light and a backlight light source containing quantum dots, and a polarizer using an oriented polyester film as a polarizer protective film are combined to produce rainbow-shaped colors. It becomes possible to provide a liquid crystal display device with good visibility by suppressing stains.

In the polarizing plate of the present invention, a polarizer protective film made of a polyester film is laminated on at least one side of the polarizer. It is preferable that the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is low adjusted to be in the range of 1.53 or more and 1.62 or less. This makes it possible to suppress rainbow-shaped color spots by suppressing reflection at the interface between the air layer and the polyester film and at the interface between the polarizer and the polyester film. If the refractive index exceeds 1.62, rainbow-shaped color stains 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.

Meanwhile, the lower limit of the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is 1.53. If the refractive index is less than 1.53, crystallization of the polyester film becomes insufficient and properties obtained by stretching, such as dimensional stability, mechanical strength, and chemical resistance, become insufficient, which is not preferable. The refractive index is preferably 1.54 or more, more preferably 1.55 or more, even more preferably 1.56 or more, and even more preferably 1.57 or more. Any range combining the upper and lower limits of the above-mentioned refractive index is assumed.

To set the refractive index of the polyester film in the direction parallel to the direction of the transmission axis of the polarizer to a range of 1.53 to 1.62, the polarizer of the present invention must have the transmission axis of the polarizer and the fast axis (perpendicular to the slow axis) of the polyester film being parallel. It is desirable to do so. The refractive index of the polyester film in the fast axis direction (direction perpendicular to the slow axis) can be adjusted to the range of 1.53 to 1.62 by stretching in the film forming process described later. And by making the fast axis direction of the polyester film parallel to the transmission axis direction of the polarizer, it is possible to manufacture a polarizing plate in which the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer is 1.53 to 1.62. Here, parallel means that the angle formed by the transmission axis of the polarizer and the fast axis of the polarizer protective film is preferably -15° to 15°, more preferably -10° to 10°, and even more preferably -5° to 5°. °, more preferably -3° to 3°, even more preferably -2° to 2°, particularly preferably -1° to 1°. In one embodiment, parallel means substantially parallel. Here, substantially parallel means that the transmission axis and the fast axis are parallel to a degree that allows for misalignment that inevitably occurs when the polarizer and the protective film are put together. The direction of the slow axis can be determined by measuring with a molecular orientation meter (for example, MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.).

That is, the refractive index of the polyester film used in the present invention in the fast axis direction is preferably 1.53 or more and 1.62 or less, and by laminating the transmission axis of the polarizer and the fast axis of the polyester film to be approximately parallel, the polyester film is parallel to the transmission axis of the polarizer. It is possible to manufacture a polarizing plate in which the refractive index of the polyester film in each direction is 1.53 or more and 1.62 or less.

It is possible to use any polarizer (polarizing film) used in the technical field by appropriately selecting the polarizer. Representative polarizers include polyvinyl alcohol films dyed with dichroic materials such as iodine, but are not limited to this, and known or future developed polarizers can be appropriately selected and used.

Commercially available PVA films can be used, for example, “Kurare Vinylon (manufactured by Kuraray Co., Ltd.)”, “Dosello Vinylon (manufactured by Dosello Co., Ltd.)], and “Nichigo Vinylon (manufactured by Nippon Synthetic Chemicals Co., Ltd.)” (Manufactured by Co., Ltd.)], etc. can be used. Examples of dichroic materials include iodine, diazo compounds, and polymethine dye.

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

A more preferable aspect is that the difference between the refractive index in the direction of the transmission axis of the polarizer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 0.12 or less. The difference is more preferably 0.11 or less, more preferably 0.10 or less, more preferably 0.09 or less, even more preferably 0.08 or less, even more preferably 0.07 or less, particularly preferably 0.06 or less, most preferably 0.05 or less. It is as follows. A smaller refractive index difference is preferable because reflection at the polyester film interface can be suppressed and rainbow stains can be further suppressed. The lower limit of this difference is 0. The direction of the transmission axis of the polarizer can be determined using a known polarizing plate.

The polarizer is not particularly limited, but for example, it is possible to use a conventionally known polarizer such as polyvinyl alcohol (PVA) dyed with iodine. The refractive index of the polarizer in the direction of the transmission axis is preferably 1.41 to 1.56, more preferably 1.44 to 1.55, and even more preferably 1.47 to 1.54.

Additionally, the polyester film used in the polarizer protective film preferably has a retardation of 1,500 to 30,000 nm. When the retardation is in the above range, rainbow stains tend to be more easily reduced, so it is preferable. The lower limit of the preferable retardation is 3,000 nm, the next more preferable lower limit is 3,500 nm, the more preferable lower limit is 4,000 nm, the more preferable lower limit is 6,000 nm, and the still more preferable lower limit is 8,000 nm. The preferable upper limit is 30,000 nm, and in the case of polyester films with retardation above this, the thickness becomes considerably thick and the handleability as an industrial material tends to deteriorate. In this specification, retardation means in-plane retardation, except where specifically indicated.

Additionally, retardation can be obtained by measuring the refractive index and thickness in two axes, and it can also be obtained using a commercially available automatic birefringence measurement device called KOBRA-21ADH (Oji Measuring Instruments Co., Ltd.). Additionally, the refractive index can be determined using an Abbe refractometer (measurement wavelength 589 nm).

The ratio (Re/Rth) between the retardation (Re: in-plane retardation) of the polyester film and the retardation (Rth) in the thickness direction is preferably 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more. As the ratio (Re/Rth) between the retardation and the thickness direction retardation increases, the effect of birefringence increases isotropy, and rainbow-shaped color stains depending on the observation angle tend to be less likely to occur. In the case of a completely uniaxial (uniaxially symmetric) film, the ratio (Re/Rth) of the retardation and the thickness direction retardation is 2.0, so the ratio (Re/Rth) of the retardation and the thickness direction retardation is 2.0. The upper limit is preferably 2.0. In addition, the thickness direction retardation refers to the average of the retardation obtained by multiplying the two birefringences △Nxz and △Nyz by the film thickness d, respectively, when the film is viewed from the thickness direction cross section.

The polarizer protective film made of the polyester film can be used as a polarizing plate on both the incident light side (light source side) and the exit light side (viewer side). In the polarizing plate disposed on the incident light side, the polarizer protective film made of the polyester film may be disposed on the incident light side with the polarizer as the starting point, may be disposed on the liquid crystal cell side, or may be disposed on both sides, but may be disposed on the incident light side at least. It is preferable that it is placed on the side. Regarding the polarizing plate disposed on the emitted light side, the polarizer protective film made of the polyester film may be disposed on the liquid crystal side starting from the polarizer, may be disposed on the emitted light side, or may be disposed on both sides, but at least It is preferable that it is placed on the side of the emitted light.

The polyester used in the polyester film can be polyethylene terephthalate or polyethylene naphthalate, but may also contain other copolymerization components. These resins have excellent transparency and also have excellent thermal and mechanical properties, making it possible to easily control retardation by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence, so it is possible to suppress the refractive index in the direction of the fast axis (perpendicular to the slow axis) to a low level by stretching the film, and even if the film thickness is thin, large retardation can be obtained relatively easily. It is the optimal material.

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

In order to keep the transmittance of the polyester film at a wavelength of 380 nm below 20%, it is desirable to appropriately adjust the type and concentration of the ultraviolet absorber and the thickness of the film. The ultraviolet absorber used in the present invention is a known material. Examples of ultraviolet absorbers include organic ultraviolet absorbers and inorganic ultraviolet absorbers, but organic ultraviolet absorbers are preferred from the viewpoint of transparency. Organic ultraviolet absorbers include benzotriazole-based, benzophenone-based, cyclic iminoester-based, etc., and combinations thereof, but are not particularly limited as long as the absorbance is within the above-mentioned range. However, from the viewpoint of durability, benzotriazole series and cyclic iminoester series are particularly preferable. When two or more types of ultraviolet absorbers are used together, the ultraviolet ray absorption effect can be further improved because it is possible to simultaneously absorb ultraviolet rays of each wavelength.

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'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,4-di- tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2 -(5-chloro(2H)-benzotriazol-2-yl)-4-methyl-6-(tert-butyl)phenol, 2,2'-methylenebis(4-(1,1,3,3- Examples include tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol, etc. Examples of cyclic iminoester ultraviolet absorbers include 2,2'-(1,4-phenylene)bis. (4H-3,1-benzoxazinon-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, 2- Examples include phenyl-3,1-benzoxazin-4-one, but it is not particularly limited to these.

In addition to the ultraviolet absorber, it is also preferable to contain various additives other than the catalyst within a range that does not interfere with the effect 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, anti-light agents, flame retardants, heat stabilizers, antioxidants, gelling inhibitors, surfactants, etc. Additionally, in order to exhibit high transparency, it is also desirable not to substantially contain particles in the polyester film. “Substantially not containing particles” means, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescence X-ray analysis, it is 50 ppm or less, preferably 10 ppm or less, especially preferably less than the detection limit. It means the content.

It is also preferable to provide various functional layers, such as a hard coat layer, on the surface of the polyester film, which is the polarizer protective film used in the present invention, for the purpose of suppressing scratches. When installing various functional layers, it is desirable for the polyester film to have an easily adhesive layer on its surface. At this time, from the viewpoint of suppressing interference by reflected light, it is desirable to adjust the refractive index of the easily adhesive layer so that it is near the rising average of the refractive index of the functional layer and the refractive index of the polyester film. The refractive index of the easily adhesive layer can be adjusted using a known method, for example, by adding titanium, germanium, or other metals to the binder resin.

It is also possible to perform corona treatment, coating treatment, and/or flame treatment on the polyester film in order to improve adhesiveness with the polarizer.

In the present invention, in order to improve adhesion to a polarizer, it is preferable to have an easily adhesive layer containing as a main component at least one type of polyester resin, polyurethane resin, or polyacrylic resin on at least one side of the film of the present invention. Here, the “main component” refers to a component that is 50% by mass or more among the solid components constituting the easily adhesive layer. The coating liquid used to form 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 resin, acrylic resin, and polyurethane resin. These coating liquids include, for example, water-soluble or disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Examples include a water-dispersible copolyester resin solution, an acrylic resin solution, or a polyurethane resin solution.

The easily adhesive layer can be obtained by applying the coating liquid to one or both sides of a uniaxially stretched film in the longitudinal direction, drying it at 100-150°C, and further stretching it in the transverse direction. It is desirable to manage the final application amount of the easily adhesive layer at 0.05 to 0.20 g/m2. If the application amount is less than 0.05 g/m 2 , the adhesiveness with the polarizer obtained may become insufficient. On the other hand, if the application amount exceeds 0.20 g/m2, the blocking resistance may decrease. When providing an easily adhesive layer on both sides of a polyester film, the application amount of the easily adhesive layer on both sides may be the same or different, and can be set independently within the above range.

It is preferable to add particles to the easily adhesive layer in order to impart easy activity. It is desirable to use particles with an average particle diameter of 2 ㎛ or less. If the average particle diameter of the particles exceeds 2 μm, the particles tend to fall off from the coating layer. Particles contained in the easily adhesive layer include, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride. Inorganic particles such as these, and organic polymer-based particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles can be mentioned. These may be added to the easily adhesive layer individually, and it is also possible to add them in combination of 2 or more types.

Additionally, known methods can be used as a method of applying the coating liquid. Examples include the reverse roll coat method, gravure coat method, kiss coat method, roll brush method, spray coat method, air knife coat method, wire bar coat method, and pipe doctor method. These methods can be used alone It can be done by or in combination.

Additionally, the average particle diameter of the particles is measured by the following method. Photograph the particles with a scanning electron microscope (SEM), measure the maximum diameter (distance between the two furthest points) of 300 to 500 particles at a magnification such that the size of the smallest particle is 2 to 5 mm, and obtain the average value. is taken as the average particle diameter.

The polyester film used as a polarizer protective film can be manufactured according to a general polyester film manufacturing method. For example, non-oriented polyester, which is melted polyester resin and extruded into a sheet shape, is stretched in the longitudinal direction using the speed difference of the roll at a temperature above the glass transition temperature, and then stretched in the transverse direction with a tenter and heat treated. There are ways to do this.

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

To describe the film forming conditions of the polyester film in detail, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 135°C, more preferably 80 to 130°C, and particularly preferably 90 to 120°C. To orient the film so that the slow axis is in the TD direction, the longitudinal stretch ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. Additionally, 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 stretch ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. Additionally, the transverse stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times.

In order to control the refractive index or retardation in the fast axis direction of the polyester film within the above range, it is preferable to control the ratio of the longitudinal stretch ratio and the transverse stretch ratio. If the difference in the longitudinal and horizontal draw ratios is too small, the refractive index in the fast axis direction of the polyester film tends to exceed 1.62, and it is undesirable because it becomes difficult to increase retardation. Additionally, setting the stretching temperature low is a desirable response to increasing retardation. In continued heat treatment, the treatment temperature is preferably 100 to 250°C, and particularly preferably 180 to 245°C.

In order to suppress fluctuations in retardation, it is preferable that the thickness deviation of the film is small. Since stretching temperature and stretching ratio have a great influence on the thickness deviation of the film, it is desirable to optimize film forming conditions also from the viewpoint of reducing the thickness deviation. In particular, if the longitudinal stretching magnification is lowered to increase retardation, the vertical thickness deviation may increase. Since there are areas where the thickness deviation in the longitudinal direction becomes very worse in a certain range of the draw ratio, it is desirable to set the film forming conditions excluding this range.

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 especially preferably 3.0% or less. The thickness deviation of the film can be measured as follows. A tape-shaped film sample (3 m) is taken, and the thickness is measured at 100 points at a pitch of 1 cm using an electronic micrometer, Militron 1240, manufactured by Seiko EM Co., Ltd. The maximum value (dmax), minimum value (dmin), and average value (d) of the thickness are obtained from the measured values, and the thickness deviation (%) is calculated using the following formula. It is desirable to measure three times and obtain the average value.

Thickness deviation (%) = ((dmax-dmin)/d) × 100

As described above, in order to control the retardation of the polyester film to a specific range, it can be done by appropriately setting the stretching ratio, stretching temperature, and film thickness. For example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the easier it is to obtain high retardation. Conversely, the lower the stretching ratio, the higher the stretching temperature, and the thinner the film thickness, the easier it is to obtain low retardation. However, as the thickness of the film increases, the phase difference in the thickness direction tends to increase. For this reason, it is desired to appropriately set the film thickness within the range described later. Additionally, in addition to controlling retardation, it is desirable to set the final film forming conditions by taking into account the physical properties required for processing.

The thickness of the polyester film is arbitrary, but is preferably in the range of 15 to 300 ㎛, more preferably 15 to 200 ㎛. Even for films with a thickness of less than 15 μm, it is theoretically possible to obtain a retardation of 1,500 nm or more. However, in that case, the anisotropy of the mechanical properties of the film becomes significant, making it prone to tearing, cracking, etc., which significantly reduces its practicality as an industrial material. A particularly preferred lower limit of thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 ㎛, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. In particular, the upper limit of the preferred thickness is 100 μm, which is equivalent to that of a general TAC film. In order to control retardation within the range of the present invention even in the above thickness range, polyethylene terephthalate is suitable as the polyester used as the film base material.

As a method of mixing an ultraviolet absorber into a polyester film, a combination of known methods can be adopted. For example, a masterbatch is produced by blending a polymer raw material with an ultraviolet absorber that has been dried in advance using a kneading extruder, and the film It can be mixed by mixing the masterbatch and polymer raw materials at the time of film formation.

At this time, the concentration of the ultraviolet absorber in the masterbatch is preferably set to 5 to 30% by mass in order to uniformly disperse the ultraviolet absorber and to mix it economically. As conditions for producing the masterbatch, it is preferable to use a kneading extruder and to extrude for 1 to 15 minutes at a temperature above the melting point of the polyester raw material and below 290°C. Above 290°C, the loss of ultraviolet absorber is large and the viscosity of the masterbatch is also greatly reduced. At an extrusion temperature of 1 minute or less, uniform mixing of the ultraviolet absorber becomes difficult. At this time, stabilizers, color adjusters, and antistatic agents may be added as needed.

It is preferable to make the polyester film have a multi-layer structure of at least three layers and to add an ultraviolet absorber to the middle layer of the film. A film with a three-layer structure containing an ultraviolet absorber in the middle layer can be specifically produced as follows. Polyester pellets alone as the outer layer, and masterbatch containing an ultraviolet absorber and polyester pellets as the middle layer are mixed in a predetermined ratio, dried, and then supplied to a known extruder for melt lamination, and formed into a sheet through a slit-shaped die. It is extruded and cooled and solidified on a casting roll to make an unstretched film. That is, using two or more extruders, a three-layer manifold, or a confluence block (for example, a confluence block with a square confluence), the film layer constituting the outer layer and the film layer constituting the middle layer are stacked to form three layers from the spinneret. The sheet is extruded and cooled in a casting roll to make an unstretched film. In addition, in the present invention, it is desirable to perform high-precision filtration during melt extrusion to remove foreign substances contained in polyester, which is a raw material that causes optical defects. The filtration particle size of the filter medium used for high-precision filtration of molten resin (initial filtration efficiency 95%) is preferably 15 ㎛ or less. If the filtration particle size of the filter medium exceeds 15 μm, removal of foreign substances larger than 20 μm tends to become insufficient.

Example

The present invention will be described in more detail with reference to the Examples below, but the present invention is not limited by the Examples below, and may be implemented with appropriate changes within the scope appropriate to the spirit of the present invention, which include: All are included in the technical scope of the present invention. Additionally, the evaluation method of physical properties in the examples below is as follows.

(1) Refractive index of polyester film

Find the slow axis direction of the film using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.), and cut out a 4 cm x 2 cm rectangle for measurement so that the slow axis direction is parallel to the long side. It was used as a sample. The refractive index of the two axes orthogonal to this sample (refractive index in the slow axis direction: Ny, fast axis (refractive index in the direction perpendicular to the slow axis direction): Nx), and the refractive index in the thickness direction (Nz) were measured using an Abbe refractometer (Atago). Manufactured by NAR-4T, measurement wavelength 589 nm).

(2) Retardation (Re)

Retardation is a parameter defined as the product (△Nxy It is a measure. The biaxial refractive index anisotropy (△Nxy) was obtained by the method (1) above, and the absolute value of the biaxial refractive index difference (|Nx-Ny|) was calculated as the refractive index anisotropy (△Nxy). The thickness d (nm) of the film was measured using an electric micrometer (Militron 1245D, manufactured by Pineleup Co., Ltd.), and the unit was converted to nm. Retardation (Re) was determined from the product (ΔNxy×d) of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film.

(3) Thickness direction retardation (Rth)

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

(4) Measurement of the emission spectrum of the backlight light source

The liquid crystal display device used in each example was BRAVIA KDL-40W920A (a liquid crystal display device having a light source emitting excitation light and a backlight light source (on edge type) containing quantum dots) manufactured by SONY. As a result of measuring the emission spectrum of the backlight light source of this liquid crystal display device using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics, an emission spectrum with peaks around 450 nm, 528 nm, and 630 nm was observed, and the peaks of each peak were observed. The full width at half maximum was 17 nm to 34 nm. Additionally, the exposure time when measuring the spectrum was set to 20 msec.

(5) Observation of rainbow stains

The liquid crystal display devices obtained in each example were observed with the naked eye in the dark from the front and oblique directions, and the presence or absence of rainbow stains was determined as follows. Here, the tilt direction means a range of 30 to 60 degrees from the normal direction of the liquid crystal display screen.

○: Rainbow stains are not observed.

△: Slight rainbow stains observed

×: Rainbow stains observed

××: Rainbow stains are significantly observed.

(6) Refractive index of polarizer

The refractive index in the direction of the transmission axis of the polarizer was measured with an Abbe refractometer (manufactured by Atago, NAR-4T SOLID, measurement wavelength 589 nm).

(Production Example 1 - Polyester A)

The temperature of the esterification reaction tube 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 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 added as catalysts. did. Next, pressure was raised to increase the temperature and a pressure esterification reaction was performed under the conditions of a gauge pressure of 0.34 MPa and 240°C, and then the esterification reaction tube was returned to normal pressure and 0.014 parts by mass of phosphoric acid was added. Additionally, the temperature was raised to 260°C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Subsequently, 15 minutes later, dispersion treatment was performed using a high pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tube and polycondensation reaction was performed under reduced pressure at 280°C.

After the polycondensation reaction is completed, filtration is performed using a Naslon filter with a 95% cut diameter of 5 ㎛, extruded from a nozzle into a strand shape, and cooled and solidified using coolant that has been filtered in advance (pore diameter: 1 ㎛ or less). and cut into pellet shapes. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl/g, and it contained substantially no inert particles or internally precipitated particles (hereinafter abbreviated as PET(A)).

(Production Example 2-Polyester B)

10 parts by mass of dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinon-4-one), particle-free PET(A) (intrinsic viscosity 90 parts by mass (0.62 ㎗/g) were mixed, and polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained using a kneader extruder. (hereinafter abbreviated as PET (B)).

(Preparation Example 3 - Preparation of adhesive modified coating solution)

Transesterification reaction and polycondensation reaction were performed in a conventional manner to obtain 46 mol% terephthalic acid, 46 mol% isophthalic acid, and 8 mole sodium 5-sulfonatoisophthalate as dicarboxylic acid components (relative to the total dicarboxylic acid components). %, a water-dispersible sulfonic acid metal base-containing copolyester resin containing 50 mol% ethylene glycol and 50 mol% neopentyl glycol as the glycol component (relative to the entire glycol component) was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of a nonionic surfactant are mixed, heated and stirred, and when the temperature reaches 77° C., the water-dispersible sulfonic acid metal After adding 5 parts by mass of the base-containing copolyester resin and continuing to stir until the lumps of the resin disappeared, the aqueous resin dispersion was cooled to room temperature to obtain a uniform water-dispersible copolyester resin solution with a solid content concentration of 5.0 mass%. Additionally, 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, and then 0.54 parts by mass of the aqueous dispersion of Silysia 310 was added to 99.46 parts by mass of the water-dispersible copolyester resin solution. 20 parts by mass of water was added while stirring to obtain an adhesion-modifying coating liquid.

(polarizer)

A roll-shaped polyvinyl alcohol film with a thickness of 80 μm continuously dyed in an aqueous iodine solution was stretched 5 times in the conveyance direction and dried to obtain a long polarizer. The refractive index in the direction of the transmission axis of the polarizer was 1.51.

(Polarizer protective film 1)

As raw materials for the base film intermediate layer, 90 parts by mass of PET (A) resin pellets containing no particles and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber were dried under reduced pressure (1 Torr) at 135°C for 6 hours, and then dried in an extruder. 2 [for middle layer (II layer)], and PET (A) is dried by a conventional method and supplied to extruder 1 [for outer layer (I layer) and outer layer (III layer)] respectively and melted at 285°C. did. These two types of polymers are each filtered with a stainless steel sintered filter medium (nominal filtration accuracy: 95% cut of 10 ㎛ particles), stacked into two types of three-layer joined blocks, extruded from a spinneret into a sheet shape, and then electrostatically applied casting method is used. Then, it was wrapped around a casting drum with a surface temperature of 30°C and cooled to solidify to create an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio of layer I, layer II, and layer III was 10:80:10.

Next, the adhesion-modifying coating liquid was applied to both sides of the unstretched PET film by a reverse roll method so that the applied amount after drying was 0.08 g/m2, and then dried at 80°C for 20 seconds.

The unstretched film on which this application layer was formed was introduced into a tenter stretching machine, and while holding the end of the film with a clip, it was guided into a hot air zone at a temperature of 125°C and stretched 4.0 times in the width direction. Next, treatment was performed at a temperature of 225°C for 10 seconds while maintaining the stretched width in the width direction, and a 3.0% relaxation treatment was further performed in the width direction to obtain a uniaxially stretched PET film with a film thickness of approximately 100 μm. The obtained film had Re of 10,300 nm, Rth of 12,350 nm, Re/Rth of 0.83, Nx = 1.588, and Ny = 1.691.

(Polarizer protective film 2)

Except that the thickness of the unstretched film was changed by changing the line speed, it was formed in the same manner as for polarizer protective film 1 to obtain a uniaxially stretched PET film with a film thickness of about 80 μm. The obtained film had Re of 8,080 nm, Rth of 9,960 nm, Re/Rth of 0.81, Nx = 1.589, and Ny = 1.690.

(Polarizer protective film 3)

Except that the thickness of the unstretched film was changed by changing the line speed, it was formed in the same manner as the polarizer protective film 1 to obtain a uniaxially stretched PET film with a film thickness of about 60 μm. The obtained film had Re of 6,060 nm, Rth of 7,470 nm, Re/Rth of 0.81, Nx = 1.589, and Ny = 1.690.

(Polarizer protective film 4)

Except that the thickness of the unstretched film was changed by changing the line speed, it was formed in the same manner as for polarizer protective film 1 to obtain a uniaxially stretched PET film with a film thickness of about 40 μm. The obtained film had Re of 4,160 nm, Rth of 4,920 nm, Re/Rth of 0.85, Nx = 1.587, and Ny = 1.691.

(Polarizer protective film 5)

The unstretched film produced in the same manner as Polarizer Protective Film 1 is heated to 105℃ using a heated roll group and an infrared heater, and then stretched 1.5 times in the running direction in a roll group with a difference in peripheral speed, and then placed in a hot air zone with a temperature of 130℃. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film with a film thickness of about 100 ㎛ in the same manner as polarizer protective film 1. The obtained film had Re of 7,820 nm, Rth of 13,890 nm, Re/Rth of 0.56, Nx = 1.608, and Ny = 1.686.

(Polarizer protective film 6)

The unstretched film produced in the same manner as Polarizer Protective Film 1 is heated to 105°C using a heated roll group and an infrared heater, and then stretched 2.0 times in the running direction in a roll group with a difference in peripheral speed, and then placed in a hot air zone with a temperature of 135°C. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film with a film thickness of about 100 ㎛ in the same manner as polarizer protective film 1. The obtained film had Re of 6,400 nm, Rth of 14,600 nm, Re/Rth of 0.44, Nx = 1.617, and Ny = 1.681.

(Polarizer protective film 7)

The unstretched film produced in the same manner as Polarizer Protective Film 1 is heated to 105°C using a heated roll group and an infrared heater, and then stretched 2.8 times in the running direction in a roll group with a difference in peripheral speed, and then placed in a hot air zone with a temperature of 140°C. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film with a film thickness of about 100 ㎛ in the same manner as polarizer protective film 1. The obtained film had Re of 5,400 nm, Rth of 15,900 nm, Re/Rth of 0.34, Nx = 1.631, and Ny = 1.685.

(Polarizer protective film 8)

The unstretched film produced in the same manner as Polarizer Protective Film 1 is heated to 105°C using a heated roll group and an infrared heater, and then stretched 3.3 times in the running direction in a roll group with a difference in peripheral speed, and then placed in a hot air zone with a temperature of 140°C. and stretched 4.0 times in the width direction to obtain a biaxially stretched PET film with a film thickness of about 100 ㎛ in the same manner as polarizer protective film 1. The obtained film had Re of 4,800 nm, Rth of 16,700 nm, Re/Rth of 0.29, Nx = 1.640, and Ny = 1.688.

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

(Example 1)

Polarizer protective film 1 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 1 was produced.

The viewing side polarizer of BRAVIA KDL-40W920A (a liquid crystal display device having a light source emitting excitation light and a backlight light source containing quantum dots) manufactured by Sony Corporation is placed on the polarizer 1 so that the polyester film is opposite (far away) from the liquid crystal. A liquid crystal display device was produced by replacing with . In addition, the direction of the transmission axis of polarizer 1 was replaced so that it was the same as the direction of the transmission axis of the polarizer before replacement.

(Example 2)

Polarizer protective film 2 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 2 was produced.

A liquid crystal display device was manufactured in the same manner as in Example 1 except that polarizer 1 was replaced with polarizer 2.

(Example 3)

Polarizer protective film 3 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 3 was produced.

A liquid crystal display device was manufactured in the same manner as in Example 1 except that polarizer 1 was replaced with polarizer 3.

(Example 4)

Polarizer protective film 3 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 3 was produced.

The polarizer on the light source side of the BRAVIA KDL-40W920A manufactured by Sony (a liquid crystal display device having a light source emitting excitation light and a backlight light source containing quantum dots) is placed on the polarizer 3 so that the polyester film is opposite (far away) from the liquid crystal. A liquid crystal display device was manufactured by replacing with . In addition, the direction of the transmission axis of polarizer 3 was replaced so that it became the same as the direction of the transmission axis of the polarizer before replacement.

(Example 5)

Polarizer protective film 3 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 3 was produced.

Polarizers on the viewing side and the light source side of the BRAVIA KDL-40W920A manufactured by SONY (a liquid crystal display device having a light source emitting excitation light and a backlight light source containing quantum dots) are placed so that the polyester film is on the opposite side (far away) from the liquid crystal. A liquid crystal display device was manufactured by replacing the above polarizer 3. In addition, the direction of the transmission axis of polarizer 3 was replaced so that it became the same as the direction of the transmission axis of the polarizer before replacement.

(Example 6)

Polarizer protective film 4 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 4 was produced.

A liquid crystal display device was manufactured in the same manner as in Example 1 except that polarizer 1 was replaced with polarizer 4.

(Example 7)

Polarizer protective film 5 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 5 was produced.

A liquid crystal display device was manufactured in the same manner as in Example 1 except that polarizer 1 was replaced with polarizer 5.

(Example 8)

Polarizer protective film 6 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 6 was produced.

A liquid crystal display device was manufactured in the same manner as in Example 1 except that polarizer 1 was replaced with polarizer 6.

(Comparative Example 1)

Polarizer protective film 1 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 7 was produced.

The viewing side polarizer of BRAVIA KDL-40W920A (a liquid crystal display device having a light source emitting excitation light and a backlight light source containing quantum dots) manufactured by Sony Corporation is placed on the polarizer 7 so that the polyester film is opposite (far away) from the liquid crystal. A liquid crystal display device was produced by replacing with . Additionally, the direction of the transmission axis of polarizer 7 was replaced so that it became the same as the direction of the transmission axis of the polarizer before replacement.

(Comparative Example 2)

Polarizer protective film 2 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 8 was produced.

A liquid crystal display device was manufactured in the same manner as Comparative Example 1 except that polarizer 7 was replaced with polarizer 8.

(Comparative Example 3)

Polarizer protective film 3 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 9 was produced.

A liquid crystal display device was manufactured in the same manner as Comparative Example 1 except that polarizer 7 was replaced with polarizer 9.

(Comparative Example 4)

Polarizer protective film 3 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 9 was produced.

The polarizer on the light source side of BRAVIA KDL-40W920A (a liquid crystal display device having a light source emitting excitation light and a backlight light source containing quantum dots) manufactured by Sony Corporation is placed on the polarizer 9 so that the polyester film is opposite (far away) from the liquid crystal. A liquid crystal display device was produced by replacing with . Additionally, the direction of the transmission axis of polarizer 9 was replaced so that it became the same as the direction of the transmission axis of the polarizer before replacement.

(Comparative Example 5)

Polarizer protective film 3 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 9 was produced.

Polarizers on the viewing side and the light source side of the BRAVIA KDL-40W920A manufactured by SONY (a liquid crystal display device having a light source emitting excitation light and a backlight light source containing quantum dots) are placed so that the polyester film is on the opposite side (far away) from the liquid crystal. A liquid crystal display device was manufactured by replacing the above polarizer 9. Additionally, the direction of the transmission axis of polarizer 9 was replaced so that it became the same as the direction of the transmission axis of the polarizer before replacement.

(Comparative Example 6)

Polarizer protective film 4 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 10 was produced.

A liquid crystal display device was manufactured in the same manner as Comparative Example 1 except that polarizer 7 was replaced with polarizer 10.

(Comparative Example 7)

Polarizer protective film 7 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 11 was produced.

A liquid crystal display device was manufactured in the same manner as Comparative Example 1 except that polarizer 7 was replaced with polarizer 11.

(Comparative Example 8)

Polarizer protective film 8 is attached to one side of the polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel, and a TAC film (manufactured by Fuji Film Co., Ltd., thickness 80 ㎛) is attached to the opposite side. Polarizer 12 was manufactured.

A liquid crystal display device was manufactured in the same manner as Comparative Example 1 except that polarizer 7 was replaced with polarizer 12.

The results of measuring rainbow stains for the liquid crystal display devices obtained in each example are shown in Table 1 below.

The liquid crystal display device and polarizing plate of the present invention are capable of securing good visibility with significantly suppressed occurrence of rainbow-shaped color stains at any observation angle, and thus have very high industrial applicability.

Claims (11)

A liquid crystal display device having a backlight light source, two polarizers, and a liquid crystal cell disposed between the two polarizers,
The backlight light source includes a light source that emits excitation light and quantum dots,
At least one of the polarizers is a polyester film laminated on at least one side of the polarizer, and the polyester film has a refractive index of 1.53 to 1.62 in a direction parallel to the transmission axis of the polarizer,
The retardation of the polyester film is 7,820 nm or less.
Liquid crystal display device. A liquid crystal display device having a backlight light source, two polarizers, and a liquid crystal cell disposed between the two polarizers,
The backlight light source has a peak peak of the emission spectrum in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and the half width of each peak is 5 nm or more,
At least one of the polarizers is a polyester film laminated on at least one side of the polarizer, and the polyester film has a refractive index of 1.53 to 1.62 in a direction parallel to the transmission axis of the polarizer,
The retardation of the polyester film is 7,820 nm or less.
Liquid crystal display device. A liquid crystal display device having a backlight light source, two polarizers, and a liquid crystal cell disposed between the two polarizers,
The backlight light source has a peak peak of the emission spectrum in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 750 nm, and the half width of each peak is 5 nm or more,
At least one of the polarizers is a polyester film laminated on at least one side of the polarizer, and the polyester film has a refractive index of 1.53 to 1.62 in a direction parallel to the transmission axis of the polarizer,
The retardation of the polyester film is 7,820 nm or less.
Liquid crystal display device. According to any one of claims 1 to 3,
A liquid crystal display device wherein the difference between the refractive index in the direction of the transmission axis of the polarizer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 0.12 or less. According to any one of claims 1 to 3,
A liquid crystal display device wherein the polyester film has an easily adhesive layer on at least one side. According to any one of claims 1 to 3,
A liquid crystal display device in which the polyester film is laminated on the polarizer through an adhesive. delete A polarizing plate in which a polyester film is laminated on at least one side of the polarizer,
The refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 1.53 to 1.62,
The retardation of the polyester film is 7,820 nm or less,
A polarizer for a liquid crystal display device having a light source that emits excitation light and a backlight light source that includes quantum dots. A polarizing plate in which a polyester film is laminated on at least one side of the polarizer,
The refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 1.53 to 1.62,
The retardation of the polyester film is 7,820 nm or less,
A liquid crystal having a backlight light source in which the polarizer has a peak peak of the emission spectrum in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and the half width of each peak is 5 nm or more. Polarizer for display devices. A polarizing plate in which a polyester film is laminated on at least one side of the polarizer,
The refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 1.53 to 1.62,
The retardation of the polyester film is 7,820 nm or less,
A liquid crystal having a backlight light source wherein the polarizer has a peak peak of the emission spectrum in each wavelength range of 400 nm to less than 495 nm, 495 nm to less than 600 nm, and 600 nm to 750 nm, and the half width of each peak is 5 nm or more. Polarizer for display devices. According to any one of claims 8 to 10,
A polarizing plate wherein the difference between the refractive index in the transmission axis direction of the polarizer and the refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 0.12 or less.