JP2017167331A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device suppressing occurrence of iridescent speckles even when a polyester film is used as a polarizer protective film that is a constituent member of a polarizing plate, in a liquid crystal display device having a white light emitting diode as a backlight light source which has such an emission spectrum that each wavelength region of R (red), G (green) and B (blue) has a peak top and that a half-value width of a peak with the highest peak intensity in the R (red) wavelength region is less than 5 nm.SOLUTION: The liquid crystal display device has a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates. The backlight light source is a white light emitting diode having such an emission spectrum that each wavelength region of from 400 nm to less than 495 nm, from 495 nm to less than 600 nm, and from 600 nm to 780 nm has a peak top of the emission spectrum and that a half-value width of a peak having the highest peak intensity in the wavelength region from 600 nm to 780 nm is less than 5 nm. At least one polarizing plate of the two polarizing plates has a polyester film laminated on at least one surface of a polarizer. The polyester film has an easy-adhesive layer on at least one surface thereof, in which a difference between a refractive index of the easy-adhesive layer and a refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 0.10 or less.SELECTED DRAWING: None

Description

  The present invention relates to a liquid crystal display device. Specifically, the present invention relates to a liquid crystal display device in which generation of rainbow-like color spots is improved.

  A polarizing plate used in a liquid crystal display device (LCD) is usually configured by sandwiching a polarizer obtained by dyeing iodine in polyvinyl alcohol (PVA) or the like between two polarizer protective films. In general, a triacetyl cellulose (TAC) film is used. In recent years, with the thinning 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 for this purpose, sufficient mechanical strength cannot be obtained and moisture permeability deteriorates. Moreover, although a TAC film is very expensive and a polyester film has been proposed as an inexpensive alternative material (Patent Documents 1 to 3), there is a problem that rainbow-like color spots are observed.

  When an oriented polyester film having birefringence is disposed on one side of the polarizer, the polarization state of the linearly polarized light emitted from the backlight unit or the polarizer changes when passing through the polyester film. The transmitted light shows an interference color peculiar to retardation which is a product of birefringence and thickness of the oriented polyester film. Therefore, if a discontinuous emission spectrum such as a cold cathode tube or a hot cathode tube is used as the light source, the transmitted light intensity varies depending on the wavelength, resulting in a rainbow-like color spot (see: Proceedings of the 15th Micro Optical Conference Proceedings, No. 1) 30-31).

  As means for solving the above problems, it is possible to use a white light source having a continuous and broad emission spectrum such as a white light emitting diode as a backlight light source, and further using an oriented polyester film having a certain retardation as a polarizer protective film. It has been proposed (Patent Document 4). White light emitting diodes have a continuous and broad emission spectrum in the visible light region. Therefore, focusing on the envelope shape of the interference color spectrum due to the transmitted light that has passed through the birefringent body, it becomes possible to obtain a spectrum similar to the emission spectrum of the light source by controlling the retardation of the oriented polyester film. It has become possible to suppress rainbow spots.

  In addition, by making the orientation direction of the oriented polyester film and the polarization direction of the polarizing plate orthogonal or parallel, the linearly polarized light emitted from the polarizer passes through the oriented polyester film while maintaining the polarization state. become. Further, by increasing the uniaxial orientation by controlling the birefringence of the oriented polyester film, light incident from an oblique direction also passes through while maintaining the polarization state. When the oriented polyester film is viewed from an oblique direction, a displacement occurs in the orientation main axis direction as compared to when viewed from directly above. However, when the uniaxial orientation is high, the displacement in the orientation principal axis direction when viewed from the oblique direction is reduced. For this reason, it is considered that the deviation between the direction of linearly polarized light and the direction of the main axis of orientation becomes small, and the change in polarization state is less likely to occur. In this way, by controlling the emission spectrum of the light source, the orientation state of the birefringent body, and the orientation main axis direction, the change in the polarization state is suppressed, and the visibility is significantly improved without causing rainbow-like color spots. It was thought to be.

JP 2002-116320 A JP 2004-219620 A JP 2004-205773 A WO2011 / 162198

  Due to the recent increase in color gamut demand for liquid crystal display devices, the emission spectrum peaks in each wavelength region of blue region (400 nm to less than 495 nm), green region (495 nm to less than 600 nm) and red region (600 nm to 780 nm or less). A liquid crystal display device using a white light emitting diode having a top and having a light emission spectrum having a relatively narrow half-width of a peak in a red region (600 nm or more and 780 nm or less) as a backlight light source has been developed.

  When industrially producing a liquid crystal display device using a polarizing plate using a polyester film as a polarizer protective film, the transmission axis of the polarizer and the fast axis direction of the polyester film are usually arranged to be perpendicular to each other. Is done. This is because the polyvinyl alcohol film that is a polarizer is manufactured by longitudinal uniaxial stretching, and the polyester film that is the protective film is manufactured by longitudinal stretching and then lateral stretching, so that the polyester film orientation This is because the main axis direction is the horizontal direction, and when these long objects are bonded together to produce a polarizing plate, the fast axis of the polyester film and the transmission axis of the polarizer are usually perpendicular. In this case, an oriented polyester film having a specific retardation is used as the polyester film, and, for example, a white LED composed of a light emitting element in which a blue light emitting diode and a yttrium / aluminum / garnet yellow phosphor are combined is used as a backlight light source. By using a light source having a continuous and broad emission spectrum, the rainbow-like color spot is greatly improved, but the half-width of the peak in the red region (600 nm to 780 nm or less) is relatively narrow (less than 5 nm). It has been found that there is still a new problem that rainbow spots still occur when using a backlight light source consisting of a white light emitting diode having a spectrum.

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

The representative present invention is as follows.
Item 1.
A liquid crystal display device having a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,
The backlight source has a peak top of the emission spectrum in each wavelength region of 400 nm to 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and has the highest peak intensity in the wavelength region of 600 nm to 780 nm. A white light-emitting diode having an emission spectrum with a peak half-width less than 5 nm,
At least one polarizing plate of the two polarizing plates is a polyester film laminated on at least one surface of a polarizer,
The polyester film has an easy adhesion layer on at least one surface,
The difference between the refractive index of the easy adhesion layer and the refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 0.10 or less.
Liquid crystal display device.
Item 2.
The emission spectrum of the backlight source is
The full width at half maximum of the peak with the highest peak intensity in the wavelength region of 400 nm or more and less than 495 nm is 5 nm or more,
Item 2. The liquid crystal display device according to item 1, wherein a half-width of a peak having the highest peak intensity in a wavelength region of 495 nm or more and less than 600 nm is 5 nm or more.
Item 3.
Item 3. The liquid crystal display device according to item 1 or 2, wherein the polyester film has a retardation of 1500 to 30000 nm.

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

(Liquid crystal display device)
In general, the liquid crystal display device includes a rear module, a liquid crystal cell, and a front module in order from the side facing the backlight light source toward the image display side (viewing side). The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface, and a polarizing plate disposed on the opposite side. Here, the polarizing plate is arranged on the side facing the backlight light source in the rear module, and is arranged on the side (viewing side) displaying the image in the front module. The configuration of the backlight may be an edge light method using a light guide plate or a reflection plate as a constituent member, or a direct type. In addition to the backlight source, the polarizing plate, and the liquid crystal cell, the liquid crystal display device may appropriately include other components such as a color filter, a lens film, a diffusion sheet, and an antireflection film. A brightness enhancement film may be provided between the light source side polarizing plate and the backlight light source. Examples of the brightness enhancement film include a reflective polarizing plate that transmits one linearly polarized light and reflects linearly polarized light orthogonal thereto. For example, a DBEF (registered trademark) (Dual Brightness Enhancement Film) series brightness enhancement film manufactured by Sumitomo 3M Limited is preferably used as the reflective polarizing plate. The reflective polarizing plate is usually arranged so that the absorption axis of the reflective polarizing plate and the absorption axis of the light source side polarizing plate are parallel to each other.

(Backlight light source)
The liquid crystal display device of the present invention comprises at least a backlight source and a liquid crystal cell disposed between two polarizing plates. The backlight light source has a peak top in each wavelength region of 400 nm or more, less than 495 nm, 495 nm or more, less than 600 nm, and 600 nm or more and 750 nm or less, and a white light source having an emission spectrum in which the half width of each peak is 5 nm or more preferable.

  The configuration of the backlight may be an edge light method using a light guide plate, a reflection plate, or the like, or a direct type, but in the present invention, as a backlight light source of a liquid crystal display device, 400 nm or more, less than 495 nm, 495 nm or more, less than 600 nm, and 600 nm or more and 780 nm or less, each having a peak top of the emission spectrum, and the half width of the peak with the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less A backlight light source consisting of a white light emitting diode having an emission spectrum of less than 5 nm is preferred. The upper limit of the full width at half maximum of the peak having the highest peak intensity in the wavelength region of 600 nm or more and 780 nm or less is preferably less than 5 nm, more preferably less than 4 nm, and still more preferably less than 3.5 nm. The lower limit is preferably 1 nm or more, and more preferably 1.5 nm or more. It is preferable that the half width of the peak is less than 5 nm because the color gamut of the liquid crystal display device is widened. Further, if the half width of the peak is less than 1 nm, the luminous efficiency may be deteriorated, which is not preferable. The shape of the emission spectrum is designed from the balance between the required color gamut and the luminous efficiency. Here, the half width is the peak width (nm) at half the intensity of the peak intensity at the peak top wavelength.

  The application of a backlight light source having an emission spectrum having the above-described characteristics to an LCD is a technology that has been attracting attention due to the recent increasing demand for color gamut expansion. Conventionally used white LEDs (for example, light-emitting elements that combine blue light-emitting diodes with yttrium, aluminum, and garnet yellow phosphors) as backlight light sources have a spectrum that can be recognized by the human eye. Only about 20% of colors can be reproduced. On the other hand, when a backlight light source having an emission spectrum having the above-described characteristics is used, it is said that it is possible to reproduce 60% or more of colors.

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

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

Specific examples of a white light source having an emission spectrum having the above-described characteristics include a phosphor type white light emitting diode in which a blue light emitting diode and a phosphor are combined. Examples of the red phosphor among the phosphors include a fluoride phosphor (also referred to as “KSF”) whose composition formula is K ₂ SiF ₆ : Mn ⁴⁺ , and others. The Mn ⁴⁺ activated fluoride complex phosphor is a phosphor having Mn ⁴⁺ as an activator, a fluoride complex salt of an alkali metal, amine, or alkaline earth metal as a base crystal. Fluoride complexes that form host crystals include those whose coordination center is a trivalent metal (B, Al, Ga, In, Y, Sc, lanthanoid), and tetravalent metal (Si, Ge, Sn, Ti, Zr, Re, Hf) and pentavalent metals (V, P, Nb, Ta), and the number of fluorine atoms coordinated around them is 5-7.

Preferable examples of the Mn ⁴⁺ activated fluoride complex phosphor include A ₂ [MF ₆ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, NH ₄ ; M is Ge, Si, One or more selected from Sn, Ti, Zr), E [MF ₆ ]: Mn (E is one or more selected from Mg, Ca, Sr, Ba, Zn; M is selected from Ge, Si, Sn, Ti, Zr) Ba _0.65 , Zr _0.35 F _2.70 : Mn, A ₃ [ZrF ₇ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, NH ₄ ) , A ₂ [MF ₅ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, NH ₄ ; M is one or more selected from Al, Ga, In), A ₃ [MF ₆ ] : Mn (A one is selected Li, Na, K, Rb, Cs, from NH ₄ Above; M is Al, Ga, one or more selected from _{In), Zn 2 [MF 7} ]: Mn (M is Al, Ga, one or more selected from _{In), A [In 2 F} 7]: Mn (A Is one or more selected from Li, Na, K, Rb, Cs, and NH ₄ ).

One of the preferable Mn ⁴⁺ activated fluoride complex phosphors is A ₂ MF ₆ : Mn (A is selected from Li, Na, K, Rb, Cs, NH ₄₎ whose base crystal is a hexafluoro complex salt of an alkali metal. One or more; M is one or more selected from Ge, Si, Sn, Ti, and Zr). Among them, A is preferably one or more selected from K (potassium) or Na (sodium), and M is Si (silicon) or Ti (titanium). Among them, particularly preferred are those in which A is K (the ratio of K in the total amount of A is 99 mol% or more) and M is Si. The activation element is preferably 100% Mn (manganese), but Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, in a range of less than 10 mol% with respect to the total amount of the activation element. Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn, Mg, and the like may be included. When M is Si, the ratio of Mn in the sum of Si and Mn is preferably in the range of 0.5 mol% to 10 mol%. Other preferred Mn ⁴⁺ activated fluoride complex phosphors have the chemical formula A _{2 + x} M _y Mn _z F _n (A is Na and K; M is Si and Al; −1 ≦ x ≦ 1 and 0.9 ≦ y + z ≦ 1) .1 and 0.001 ≦ z ≦ 0.4 and 5 ≦ n ≦ 7).

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

Among the phosphors, as the green phosphor, for example, a sialon phosphor having a basic composition of β-SiAlON: Eu or the like, or a silicate phosphor having a basic composition of (Ba, Sr) ₂ SiO ₄ : Eu or the like. Others are exemplified.

In the case where a plurality of peaks are present in any one of the wavelength region of 400 nm or more and less than 495 nm, the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 750 nm or less, the following is considered.
When a plurality of peaks are independent peaks, it is preferable that the half width of the peak with the highest peak intensity is in the above range. Furthermore, it is a more preferable aspect that the half-value width is similarly in the above range for other peaks having an intensity of 70% or more of the highest peak intensity. Here, the independent peak has an intensity region that is ½ of the peak intensity on both the short wavelength side and the long wavelength side of the peak. That is, when a plurality of peaks overlap and each peak does not have a region of intensity that is ½ of the peak intensity, the plurality of peaks are regarded as one peak as a whole. In such a peak having a shape in which a plurality of peaks are overlapped, the peak width (nm) at half the intensity of the highest peak intensity is set as the half width.
Of the plurality of peaks, the peak with the highest peak intensity is defined as the peak top.
Note that the peak having the highest peak intensity in the wavelength region of 400 nm or more and less than 495 nm, the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 750 nm or less is independent of the peaks of other wavelength regions. Is preferred. In particular, in the wavelength region between the peak having the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm, or the peak having the highest peak intensity in the region of 600 nm or more and 750 nm or less, the intensity is 600 nm or more and 750 nm or less. It is preferable in terms of color clarity that there is a region that is 1/3 of the peak intensity of the peak having the highest peak intensity in the wavelength region.

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

(Polarizer)
Of the two polarizing plates arranged in the liquid crystal display device, at least one polarizing plate has a polyester film laminated on at least one surface of a polarizer in which iodine is dyed on polyvinyl alcohol (PVA) or the like. It is. It is preferable that a film having no birefringence such as a TAC film, an acrylic film, or a norbornene-based film is laminated on the other surface of the polarizer (a polarizing plate having a three-layer structure). There is no need to laminate a film on the other side (two-layer polarizing plate). In addition, when a polyester film is used as a protective film on both sides of the polarizer, it is preferable that the slow axes of both polyester films are substantially parallel to each other.

  As a result of intensive studies, the present invention has a peak top 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 highest peak intensity in the wavelength region of 600 nm to 780 nm. In a liquid crystal display device using a white light emitting diode having an emission spectrum with a high peak half-value width of less than 5 nm as a backlight light source, even when a polarizing plate using a polyester film is used as a polarizer protective film, it is easy to use at least one side. If the difference between the refractive index of the easy-adhesive layer and the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is 0.10 or less using a polyester film having an adhesive layer, It was found that it can be suppressed. The mechanism for suppressing the occurrence of rainbow-like color spots according to the above aspect is considered as follows.

  When the oriented polyester film is disposed on one side of the polarizer, the polarization state of the linearly polarized light emitted from the backlight unit or the polarizer changes when passing through the polyester film. One of the factors that change the polarization state when linearly polarized light emitted from the backlight unit or polarizer passes through the oriented polyester film is the difference in refractive index at the interface between the easy-adhesive layer and the oriented polyester film. Found a possibility. When linearly polarized light incident from an oblique direction passes through each interface, a part of the light is reflected due to a difference in refractive index between the interfaces. At this time, since it is considered that the polarization state of the emitted light and the reflected light changes, it is considered that this is one of the factors that cause rainbow-like color spots. For this reason, by reducing the refractive index difference between the easy adhesion layer and the oriented polyester film in the polarization direction (transmission axis direction) of the incident linearly polarized light, reflection at each interface is suppressed, and rainbow-like color spots Is considered to be suppressed.

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

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

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

  The lamination method of the polyester film and the polarizer is not particularly limited, and the fast axis direction of the polyester film and the transmission axis direction of the polarizer are substantially parallel, or the slow axis direction of the polyester film and the transmission of the polarizer. An arrangement in which the axial direction is substantially parallel is preferable. The layers may be laminated with care so that the difference between the refractive index of the adhesive and the refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is within a preferred range.

  Here, the term “substantially parallel” means that the angle formed by the transmission axis of the polarizer and the fast axis (or slow axis) of the polarizer protective film is preferably −15 ° to 15 °, more preferably −10 °. 10 °, more preferably −5 ° to 5 °, even more preferably −3 ° to 3 °, even more preferably −2 ° to 2 °, and particularly preferably −1 ° to 1 °. In a preferred embodiment, substantially parallel is substantially parallel. Here, “substantially parallel” means that the transmission axis and the fast axis (or slow axis) are parallel to such an extent that a deviation inevitably caused when the polarizer and the protective film are bonded to each other is allowed. Means. 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 Scientific Instruments).

(Polyester film)
The polyester film used for the polarizer protective film preferably has a retardation of 1500 to 30000 nm. If the retardation is in the above range, it is preferable because rainbow spots tend to be reduced more easily. 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 still more preferred lower limit is 6000 nm, and the still more preferred lower limit is 8000 nm. A preferable upper limit is 30000 nm, and a polyester film having a retardation larger than this has a considerably large thickness and tends to deteriorate the handleability as an industrial material.

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

  The ratio (Re / Rth) of the retardation of the polyester film (Re: in-plane retardation) to the retardation in the thickness direction (Rth) is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.8. 6 or more. As the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is larger, the birefringence action is more isotropic, and the occurrence of rainbow-like color spots depending on the observation angle tends to be less likely to occur. In a complete uniaxial (uniaxial symmetry) film, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is 2.0. Therefore, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) The upper limit is preferably 2.0. The thickness direction retardation means an average of retardation obtained by multiplying two birefringences ΔNxz and ΔNyz by the film thickness d when the film is viewed from the cross section in the thickness direction.

The refractive index in the fast axis direction of the polyester film is preferably from 1.53 to 1.62. When 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. The upper limit of the refractive index in the fast axis direction of the polyester film is more preferably 1.61 or less, further preferably 1.60 or less, still more preferably 1.59 or less, and particularly preferably 1. 58 or less. The lower limit of the refractive index in the fast axis direction of the polyester film is more preferably 1.54 or more, further preferably 1.55 or more, still more preferably 1.56 or more, and particularly preferably 1. 57 or more.
The refractive index in the slow axis direction of the polyester film is preferably 1.67 or more and 1.75 or less. The upper limit of the refractive index in the slow axis direction of the polyester film is more preferably 1.74 or less, still more preferably 1.73 or less, still more preferably 1.72 or less, and particularly preferably 1. 71 or less. The lower limit of the refractive index of the slow axis of the polyester film is more preferably 1.68 or more. The refractive index can be easily adjusted by a stretching process in a film forming process described later.
The difference between the refractive index in the slow axis direction and the refractive index in the fast axis direction of the polyester film is preferably 0.05 or more, more preferably 0.07 or more, and further preferably 0.09 or more.

  The polarizer protective film made of the polyester film can be used for both the incident light side (light source side) and the outgoing light side (viewing side) polarizing plates. In the polarizing plate arranged on the incident light side, the polarizer protective film made of the polyester film is arranged on both sides, whether it is arranged on the incident light side starting from the polarizer or on the liquid crystal cell side. Although it may be arranged, it is preferably arranged at least on the incident light side. About the polarizing plate arranged on the outgoing light side, the polarizer protective film made of the above polyester film is arranged on both sides, whether it is arranged on the liquid crystal side starting from the polarizer or on the outgoing light side. It may be arranged, but it is preferable that it is arranged at least on the outgoing light side.

  Polyester used for the polyester film may be polyethylene terephthalate or polyethylene naphthalate, but may contain other copolymerization components. These resins are excellent in transparency and excellent in thermal and mechanical properties, and the retardation can be easily controlled by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence. By stretching the film, the refractive index in the fast axis direction (perpendicular to the slow axis direction) can be kept low, and it is relatively easy even if the film is thin. Therefore, it is the most suitable material.

  For the purpose of suppressing 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 particularly preferably 5% or less. If the light transmittance is 20% or less, the optical functional dye can be prevented from being deteriorated by ultraviolet rays. In addition, the transmittance | permeability is measured by the perpendicular | vertical method with respect to the plane of a film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

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

  Examples of the benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber, and acrylonitrile ultraviolet absorber 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′-me Tilphenyl) -5-chlorobenzotriazole, 2- (5-chloro (2H) -benzotriazol-2-yl) -4-methyl-6- (tert-butyl) phenol, 2,2′-methylenebis (4- ( 1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, etc. Examples of cyclic imino ester UV 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, Examples thereof include 2-phenyl-3,1-benzoxazin-4-one, but are not particularly limited thereto.

  Moreover, it is also a preferable aspect to contain various additives other than a catalyst in the range which does not prevent the effect of this invention other than an ultraviolet absorber. Examples of additives include inorganic particles, heat resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light proofing agents, flame retardants, thermal stabilizers, antioxidants, and antigelling agents. And surfactants. Moreover, in order to show high transparency, it is also preferable that a polyester film does not contain a particle | grain substantially. “Substantially free of particles” means, for example, in the case of inorganic particles, a content that is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less when inorganic elements are quantified by fluorescent X-ray analysis. means.

  On the surface of the polyester film that is a polarizer protective film used in the present invention, various functional layers, i.e., a hard coat layer, an antiglare layer, an antireflection layer, for the purpose of preventing reflection, suppressing glare, suppressing scratches, etc. It is also preferable to provide a low reflection layer or the like. When providing various functional layers, the polyester film preferably has an easy adhesion layer on the surface thereof.

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

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

As the easy adhesion layer, a conventionally known easy adhesion layer used for optical films can be used. It will not be specifically limited if the conditions of the refractive index difference with the polyester film mentioned above are satisfy | filled. Especially, it is preferable to have an easily bonding layer which has as a main component at least 1 type of a polyester resin, a polyurethane resin, a polyacryl resin, or a polyvinyl alcohol-type resin. Here, the “main component” refers to a component that is 50% by mass or more of the solid components constituting the easy-adhesion layer.
A conventionally known crosslinking agent can be added to these resins. The coating solution used for forming the easy-adhesion layer of the present invention is preferably an aqueous coating solution containing at least one of water-soluble or water-dispersible copolymerized polyester resins, acrylic resins, polyurethane resins, and polyvinyl alcohol resins. The polyester resin, polyurethane resin, acrylic resin, and polyvinyl alcohol resin may be used alone or in combination of two or more. For example, in order to improve adhesiveness with a polarizer, a combination of at least one selected from the group consisting of a polyester resin, a polyurethane resin, and an acrylic resin and a polyvinyl alcohol resin is preferable, and polyester is particularly preferable. A combination of a resin and a polyvinyl alcohol resin. Examples of these coating solutions include water-soluble or water-dispersible co-polymers disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Examples thereof include a polymerized polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.

  Examples of polyester resins include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyro Examples of glycol components such as merit acid, dimer acid, 5-sodium sulfoisophthalic acid include ethylene glycol, dimethylene glycol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,4 -Copolymers selected from butanediol, neopentyl glycol, xylene glycol, dimethylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) glycol, and the like. When these are used as a coating solution containing a water-based resin, it is preferable to copolymerize a compound containing a carboxylate group or a sulfonate group in order to facilitate water-solubilization and improve the adhesiveness of the polyester resin. Examples of the polyurethane resin include those composed of polyol, polyisocyanate, chain extender, crosslinking agent and the like. Examples of the polyol include a dehydration reaction between a dicarboxylic acid and a glycol containing a polyether such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polycaprolactone, and the like. Examples include polyesters to be produced, polycarbonates having carbonate bonds, acrylic polyols, and castor oil. Examples of the polyisocyanate include tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and isophorone diisocyanate. Examples of the chain extender or crosslinking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, triethylenetetramine, 4,4′-diaminodiphenylmethane, and 4,4′-diamino. Examples include dicyclohexylmethane and water. Examples of the acrylic resin include copolymers selected from methyl methacrylate, ethyl acrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, acrylamide, n-methylol acrylamide, glycidyl methacrylate, acrylic acid, and the like. When used as an aqueous resin coating solution, copolymerization with monomers having hydrophilic groups (acrylic acid, methacrylic acid, acrylamide, vinyl sulfonic acid and their salts, etc.) and emulsion polymerization with reactive emulsifiers and surfactants An acrylic resin prepared by a method such as suspension polymerization or soap-free polymerization can be used. Moreover, in order to improve applicability | paintability, the crosslinking agent etc. may contain. The cross-linking agent is not particularly limited as long as it is a compound that causes a cross-linking reaction. However, a methylolated or alkylolized urea, melamine, acrylamide, polyamide compound, epoxy compound, isocyanate compound, carbodiimide compound, oxazolyl. A coupling agent etc. can be illustrated.

Moreover, in order to adjust the refractive index of an easily bonding layer, high refractive index microparticles | fine-particles, a chelate compound, etc. can be added. As the high refractive index fine particles, for example, metal oxide fine particles having a refractive index of 1.60 to 2.80 can be suitably used. Specific examples of the metal oxide fine particles include titanium oxide (TiO ₂ , refractive index: 2.71), zirconium oxide (ZrO ₂ , refractive index: 2.10), tin oxide (SnO ₂ , refractive index). : 2.00), antimony tin oxide (ATO, refractive index: 1.75 to 1.95), cerium oxide (CeO _2, refractive index: 2.20), indium tin oxide (ITO, the refractive index: 1 .95 to 2.00), phosphorus tin compound (PTO, refractive index: 1.75 to 1.85), antimony oxide (Sb ₂ O ₅ , refractive index: 2.04), aluminum zinc oxide (AZO, refractive) Ratio: 1.90 to 2.00), niobium pentoxide (Nb ₂ O ₅ , refractive index: 2.33), gallium zinc oxide (GZO, refractive index: 1.90 to 2.00), tantalum oxide ( ta ₂ O _5: refractive index 2.16) and antimony Zinc (ZnSb ₂ O _6, refractive index: 1.90 to 2.00), or the like may enumerate. The average primary particle diameter of the high refractive index fine particles is not particularly limited, but is preferably 5 to 100 nm. The content of the high refractive index fine particles is not particularly limited, but may be adjusted so that the refractive index of the easy-adhesion layer becomes a target value. Examples of the chelate compound include a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, and a water-soluble zirconium compound. Examples of the water-soluble titanium chelate compound include isopropoxy (2-ethyl-1,3-hexanediolato) titanium, diisopropoxybis (acetylacetonato) titanium, diisopropoxybis (triethanolaminato). Examples thereof include titanium, di-n-butoxybis (triethanolaminato) titanium, hydroxybis (lactato) titanium, ammonium salt of hydroxybis (lactato) titanium, ammonium beloxocitrate ammonium salt, and the like. Examples of the water-soluble titanium acylate compound include oxotitanium bis (monoammonium oxalate). Examples of the water-soluble zirconium compound include zirconium tetraacetylacetonate and zirconium acetate.

In one embodiment, the refractive index of the easy adhesion layer is preferably 1.42-1.70. More preferably, it is 1.42-1.65, More preferably, it is 1.45-1.60, More preferably, it is 1.47-1.55, Especially preferably, it is 1.48-1.54.
When a functional layer (or polarizer) is further laminated on the polyester film easy-adhesive layer, the refractive index of the easy-adhesive layer is determined by the refractive index of the functional layer (or polarizer) and the refractive index of the polyester film (slow phase). It is preferable to adjust so that it is close to the geometric mean of the refractive index in the axial direction and the average value of the refractive index in the fast axis direction.
Furthermore, in the polarizing plate bonded so that the transmission axis of the polarizer and the slow axis of the polyester film are parallel, the refractive index of the easy-adhesion layer is different from the refractive index in the slow axis direction of the polyester film and the functional layer ( (Or polarizer) is more preferably in the vicinity of the geometric mean of the refractive index of the polarizer), and in the polarizing plate bonded so that the transmission axis of the polarizer and the fast axis of the polyester film are parallel, the refraction of the easily adhesive layer More preferably, the refractive index is the geometric mean of the refractive index in the fast axis direction of the polyester film and the refractive index of the functional layer (or polarizer). A known method can be used to adjust the refractive index of the easy-adhesion layer. For example, it is easy to adjust the copolymer component of the binder resin or to contain titanium, germanium, or other metal species in the binder resin. Can be adjusted.

  In the above-described embodiment, the refractive index of the functional layer (or the polarizer) ≦ the refractive index of the easy-adhesion layer ≦ the refractive index of the polyester film, and it is even more preferable that the refractive index difference between the layers is small. In a polarizing plate bonded so that the transmission axis of the polarizer and the slow axis of the polyester film are parallel, the refractive index of the functional layer (or the polarizer) ≦ the refractive index of the easy-adhesion layer ≦ the slow phase of the polyester film It is more preferable that the refractive index difference between the layers is small because of the relationship of the refractive index in the axial direction. For polarizing plates bonded so that the transmission axis of the polarizer and the phase advance axis of the polyester film are parallel, the refractive index of the functional layer (or the polarizer) ≦ the refractive index of the easy-adhesion layer ≦ the phase advance of the polyester film It is more preferable that the refractive index difference between the layers is small because of the relationship of the refractive index in the axial direction.

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

  The easy-adhesion layer can be obtained by applying the coating solution on one or both sides of a uniaxially stretched film or an unstretched film in the longitudinal direction, drying at 100 to 150 ° C., and further stretching in the transverse direction. The final thickness of the easy adhesion layer is preferably 3 nm or more and 200 nm or less, more preferably 50 nm or more and 150 nm or less, and still more preferably 80 nm or more and 130 nm or less. If the thickness is less than 3 nm, adhesion to the functional layer and the polarizer may be insufficient. On the other hand, if the thickness exceeds 200 nm, the blocking resistance may decrease. When providing an easily bonding layer on both surfaces of a polyester film, the application quantity of an easily bonding layer on both surfaces may be the same or different, and can be independently set within the above range.

  It is preferable to add particles to the easy-adhesion layer in order to impart easy slipperiness. It is preferable to use particles having an average particle size of 2 μm or less. When the average particle diameter of the particles exceeds 2 μm, the particles easily fall off from the coating layer. As particles to be included in the easy adhesion layer, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, Examples include inorganic particles such as calcium fluoride, and organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone. These may be added alone to the easy-adhesion layer, or may be added in combination of two or more.

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

  In addition, the measurement of the average particle diameter of said particle | grain is performed with the following method. Take a picture of the particles with a scanning electron microscope (SEM) and at a magnification such that the size of one smallest particle is 2-5 mm, the maximum diameter of 300-500 particles (between the two most distant points) Distance) is measured, and the average value is taken as the average particle diameter.

  The polyester film used as the polarizer protective film can be manufactured according to a general polyester film manufacturing method. For example, the polyester resin is melted and the non-oriented polyester extruded and formed into a sheet shape is stretched in the longitudinal direction by utilizing the speed difference of the roll at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction by a tenter. The method of performing heat processing is mentioned.

  The polyester film used in the present invention may be a uniaxially stretched film or a biaxially stretched film, but when the biaxially stretched film is used as a polarizer protective film, it is observed from directly above the film surface. However, rainbow-like color spots are not seen, but care must be taken because rainbow-like color spots may be observed when observed from an oblique direction.

The film forming conditions of the polyester film will be specifically described. The longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 135 ° C, more preferably 80 to 130 ° C, and particularly preferably 90 to 120 ° C. In order to orient the film so that the slow axis is in the TD direction, the longitudinal draw ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. The transverse draw ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. In order to orient the film so that the slow axis is in the MD direction, the longitudinal draw ratio is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times. Further, the transverse draw ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times.
In order to control the refractive index 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 draw ratio and the transverse draw ratio. If the difference between the longitudinal and lateral draw ratios is too small, the refractive index in the fast axis direction of the polyester film tends to exceed 1.62, and it is difficult to increase the retardation. In addition, setting the stretching temperature low is a preferable measure for increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably from 100 to 250 ° C, particularly preferably from 180 to 245 ° C.

  In order to suppress retardation fluctuation, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio greatly affect the thickness variation of the film, it is necessary to optimize the film forming conditions from the viewpoint of the thickness variation. In particular, if the longitudinal stretching ratio is lowered to increase the retardation, the longitudinal thickness unevenness may be deteriorated. Since there is a region where the vertical thickness unevenness becomes very bad in a specific range of the draw ratio, it is desirable to set the film forming conditions outside this range.

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

  As described above, in order to control the retardation of the polyester film within a specific range, the stretching ratio, the stretching temperature, and the thickness of the film can be appropriately set. For example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the higher the retardation. Conversely, the lower the stretching ratio, the higher the stretching temperature, and the thinner the film, the lower the retardation. However, when the thickness of the film is increased, the thickness direction retardation tends to increase. Therefore, it is desirable to set the film thickness appropriately within the range described below. In addition to controlling the retardation, it is necessary to set final film forming conditions in consideration of physical properties necessary for processing.

  Although the thickness of a polyester film is arbitrary, the range of 15-300 micrometers is preferable, More preferably, it is the range of 15-200 micrometers. Even in the case of a film having a thickness of less than 15 μm, it is possible in principle to obtain a retardation of 1500 nm or more. However, in that case, the anisotropy of the mechanical properties of the film becomes remarkable, and it becomes easy to cause tearing, tearing, etc., and the practicality as an industrial material is remarkably lowered. A particularly preferable lower limit of the thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. A particularly preferable upper limit of the thickness is 100 μm, which is about the same as a general TAC film. In order to control the retardation within the range of the present invention even in the above thickness range, the polyester used as the film substrate is preferably polyethylene terephthalate.

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

  At this time, the concentration of the UV absorber in the master batch is preferably 5 to 30% by mass in order to uniformly disperse the UV absorber and economically blend it. As a condition for producing the master batch, it is preferable to use a kneading extruder and to extrude it at a temperature not lower than the melting point of the polyester raw material and not higher than 290 ° C. for 1 to 15 minutes. Above 290 ° C, the weight loss of the UV absorber is large, and the viscosity of the master batch is greatly reduced. When the extrusion temperature is 1 minute or less, uniform mixing of the UV absorber becomes difficult. At this time, if necessary, a stabilizer, a color tone adjusting agent, and an antistatic agent may be added.

  Further, it is preferable that the polyester film has a multilayer structure of at least three layers and an ultraviolet absorber is added to the intermediate layer of the film. A film having a three-layer structure containing an ultraviolet absorber in the intermediate layer can be specifically produced as follows. Polyester pellets alone for the outer layer, master batches containing UV absorbers for the intermediate layer and polyester pellets are mixed at a predetermined ratio, dried, and then supplied to a known melt laminating extruder, which is slit-shaped. Extruded into a sheet form from a die 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 merging block (for example, a merging block having a square merging portion), a film layer constituting both outer layers and a film layer constituting an intermediate layer are laminated, An unstretched film is formed by extruding a three-layer sheet from the die and cooling with a casting roll. In the present invention, it is preferable to perform high-precision filtration during melt extrusion in order to remove foreign substances contained in the raw material polyester that cause optical defects. The filter particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. When the filter particle size of the filter medium exceeds 15 μm, removal of foreign matters of 20 μm or more tends to be insufficient.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention. In addition, the evaluation method of the physical property in the following examples is as follows.

(1) Refractive index of polyester film Using a molecular orientation meter (manufactured by Oji Scientific Instruments, MOA-6004 type molecular orientation meter), the slow axis direction of the film is obtained, and the slow axis direction is the long side of the sample for measurement. A 4 cm × 2 cm rectangle was cut out so as to be parallel to each other and used as a measurement sample. For this sample, the biaxial refractive index (the refractive index in the slow axis direction: Ny, the fast axis (the refractive index in the direction perpendicular to the slow axis direction): Nx), and the refractive index in the thickness direction ( Nz) was determined by an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm).

(2) Retardation (Re)
Retardation is a parameter defined by the product (ΔNxy × d) of the biaxial refractive index anisotropy (ΔNxy = | Nx−Ny |) and the film thickness d (nm) on the film. Yes, it is a scale showing optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments Co., Ltd.), the slow axis direction of the film is obtained, and 4 cm so that the slow axis direction is parallel to the long side of the measurement sample. A rectangle of × 2 cm was cut out and used as a measurement sample. For this sample, Abbe refracts the biaxial refractive index (the refractive index in the slow axis direction: Ny, the refractive index in the direction perpendicular to the slow axis direction: Nx), and the refractive index (Nz) in the thickness direction. The absolute value (| Nx−Ny |) of the biaxial refractive index difference was determined as a refractive index anisotropy (ΔNxy), which was obtained by a refractive index meter (NAGO-4T manufactured by Atago Co., Ltd., measurement wavelength 589 nm). The thickness d (nm) of the film was measured using an electric micrometer (manufactured by Fine Reef, Millitron 1245D), and the unit was converted to nm. Retardation (Re) was determined from the product (ΔNxy × d) of refractive index anisotropy (ΔNxy) and film thickness d (nm).

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

(4) Measurement of emission spectrum of backlight light source REGZA 43J10X manufactured by Toshiba was used for the liquid crystal display device used in each example. When the emission spectrum of the backlight source (white light emitting diode) of this liquid crystal display device was measured using a multi-channel spectrometer PMA-12 manufactured by Hamamatsu Photonics, an emission spectrum having peak tops in the vicinity of 450 nm, 535 nm, and 630 nm was observed. It was done. The half width of each peak top (the half width of the peak having the highest peak intensity in each wavelength region) was 17 nm for the peak at 450 nm, 45 nm for the peak at 535 nm, and 2 nm for the peak at 630 nm, respectively. This light source had a plurality of peaks in the wavelength region of 600 nm or more and 780 nm or less, and the half-value width was evaluated at a peak near 630 nm having the highest peak intensity in this region. Moreover, the exposure time in the spectrum measurement was 20 msec.

(5) Iridescent Observation The liquid crystal display device obtained in each example was visually observed in the dark from the front and oblique directions, and the presence or absence of the occurrence of irido was determined as follows.

○: Iridescent is not observed △: Iridescent is slightly observed ×: Iridescent is observed XX: Iridescent is remarkably observed

(6) Refractive index of easy-adhesion layer After apply | coating the adhesive property modification coating liquid to the glass plate, it solidified on the predetermined conditions and produced the coating film about several micrometers. The coating film was peeled from the glass plate, and the refractive index was measured with an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-1T SOLID, measurement wavelength 589 nm).

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

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

(Production Example 2-Polyester B)
10 parts by weight of a dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), PET (A) containing no particles (inherent viscosity Was 0.62 dl / g) and 90 parts by mass were mixed, and a polyethylene terephthalate resin (B) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter abbreviated as PET (B)).

(Production Example 3-Adjustment of Adhesiveness Modification Coating Solution)
A transesterification reaction and a polycondensation reaction are carried out by a conventional method, and as a dicarboxylic acid component (based on the whole dicarboxylic acid component) 46 mol% terephthalic acid, 46 mol% isophthalic acid and 8 mol% sodium 5-sulfonatoisophthalate, A water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of 50 mol% ethylene glycol and 50 mol% neopentyl glycol as a glycol component (based on 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, 0.06 parts by mass of nonionic surfactant were mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal base-containing copolymer polyester resin and continuing to stir until the resin is no longer agglomerated, the resin water dispersion is cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A uniform water-dispersible copolymerized polyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silysia Co., Ltd.) in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolyester resin solution was mixed with 99.46 parts by mass of the silicia 310. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added with stirring to obtain an adhesive modified coating solution. In addition, the refractive index of the easy-adhesion layer obtained using this easy-adhesion property modification coating liquid was 1.530.

(Polarizer protective film 1)
After drying 90 parts by mass of PET (A) resin pellets containing no particles as a raw material for the base film intermediate layer and 10 parts by mass of PET (B) resin pellets containing an ultraviolet absorber at 135 ° C. for 6 hours under reduced pressure (1 Torr) , And supplied to the extruder 2 (for the intermediate layer II layer). Also, the PET (A) was dried by an ordinary method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), and dissolved at 285 ° C. . After filtering these two kinds of polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles 95% cut), laminating them in a two-kind / three-layer confluence block, and extruding them into a sheet form from a die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and then cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Next, after applying the adhesive property-modifying coating solution on the both sides of this unstretched PET film by a reverse roll method so that the coating amount after drying was 0.08 g / m ² , the coating was dried at 80 ° C. for 20 seconds. .

  The unstretched film on which this coating layer was formed was guided to a tenter stretching machine, and the film was guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, it was treated at a temperature of 225 ° C. for 10 seconds, and further subjected to a 3.0% relaxation treatment in the width direction to obtain a uniaxially stretched PET film having a film thickness of about 100 μm. It was. Re of the obtained film was 10300 nm, Rth was 12350 nm, Re / Rth was 0.83, Nx = 1.588, Ny = 1.661.

(Polarizer protective film 2)
A film was formed in the same manner as the polarizer protective film 1 except that the thickness of the unstretched film was changed by changing the line speed, to obtain a uniaxially stretched PET film having a film thickness of about 80 μm. The obtained film had Re of 8080 nm, Rth of 9960 nm, Re / Rth of 0.81, Nx = 1.589, and Ny = 1.690.

(Polarizer protective film 3)
A film was formed in the same manner as the polarizer protective film 1 except that the thickness of the unstretched film was changed by changing the line speed to obtain a uniaxially stretched PET film having a film thickness of about 60 μm. Re of the obtained film was 6060 nm, Rth was 7470 nm, Re / Rth was 0.81, Nx = 1.589, and Ny = 1.690.

(Polarizer protective film 4)
A film was formed in the same manner as the polarizer protective film 1 except that the line speed was changed and the thickness of the unstretched film was changed to obtain a uniaxially stretched PET film having a film thickness of about 40 μm. Re of the obtained film was 4160 nm, Rth was 4920 nm, Re / Rth was 0.85, Nx = 1.487, Ny = 1.661.

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

(Polarizer protective film 6)
An unstretched film produced by the same method as that of the polarizer protective film 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then 2.0% in the traveling direction by a roll group having a difference in peripheral speed. After being double-stretched, it was introduced into a hot air zone at a temperature of 135 ° C. and stretched 4.0 times in the width direction, and a biaxially stretched PET film having a film thickness of about 100 μm was obtained in the same manner as the polarizer protective film 1. The obtained film had Re of 6400 nm, Rth of 14600 nm, Re / Rth of 0.44, Nx = 1.617, and Ny = 1.661.

(Polarizer protective film 7)
An unstretched film produced by the same method as that of the polarizer protective film 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then 2.8 in the traveling direction with a roll group having a difference in peripheral speed. After being double-stretched, it was introduced into a hot air zone at a temperature of 140 ° C. and stretched 4.0 times in the width direction, and a biaxially stretched PET film having a film thickness of about 100 μm was obtained in the same manner as the polarizer protective film 1. Re of the obtained film was 5400 nm, Rth was 15900 nm, Re / Rth was 0.34, Nx = 1.631, Ny = 1.485.

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

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

Example 1
A polarizer protective film 1 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and a TAC film (FUJIFILM Corporation) on the opposite side. Manufactured, with a thickness of 80 μm) to make a polarizing plate 1.
The polarizing plate on the viewing side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate 1 so that the polyester film was on the side opposite to the liquid crystal (distal), thereby producing a liquid crystal display device. In addition, it replaced so that the direction of the transmission axis of the polarizing plate 1 might become the same as the direction of the transmission axis of the polarizing plate before replacement.

(Example 2)
A polarizer protective film 2 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and a TAC film (Fuji Film Co., Ltd.) on the opposite side. Manufactured, with a thickness of 80 μm) to make a polarizing plate 2.
A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 2.

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

Example 4
A polarizer protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and a TAC film (Fuji Film Co., Ltd.) on the opposite side. Manufactured, with a thickness of 80 μm), and polarizing plate 3 was prepared.
The polarizing plate on the light source side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate 3 so that the polyester film was on the side opposite to the liquid crystal (distal), thereby producing a liquid crystal display device. In addition, it replaced so that the direction of the transmission axis of the polarizing plate 3 might become the same as the direction of the transmission axis of the polarizing plate before replacement.

(Example 5)
A polarizer protective film 3 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and a TAC film (Fuji Film Co., Ltd.) on the opposite side. Manufactured, with a thickness of 80 μm), and polarizing plate 3 was prepared.
A polarizing plate on the viewing side and the light source side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate 3 so that the polyester film was on the side opposite to the liquid crystal (distal), thereby producing a liquid crystal display device. In addition, it replaced so that the direction of the transmission axis of the polarizing plate 3 might become the same as the direction of the transmission axis of the polarizing plate before replacement.

(Example 6)
A polarizer protective film 4 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and a TAC film (FUJIFILM Corporation) Manufactured, with a thickness of 80 μm), and polarizing plate 4 was created.
A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 4.

(Example 7)
A polarizer protective film 5 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are parallel to each other, and a TAC film (Fuji Film Co., Ltd.) on the opposite side. Manufactured, with a thickness of 80 μm) to make a polarizing plate 5.
A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 5.

(Example 8)
A polarizer protective film 6 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the phase advance axis of the film are parallel to each other, and a TAC film (Fuji Film Co., Ltd.) on the opposite side. Manufactured, with a thickness of 80 μm) to make a polarizing plate 6.
A liquid crystal display device was produced in the same manner as in Example 1 except that the polarizing plate 1 was changed to the polarizing plate 6.

(Comparative Example 1)
A polarizer protective film 1 is attached to one side of a polarizer composed of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (Fuji Film Co., Ltd.) Manufactured, with a thickness of 80 μm), and a polarizing plate 7 was prepared.
The polarizing plate on the viewing side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate 7 so that the polyester film was on the side opposite to the liquid crystal (distal), thereby producing a liquid crystal display device. In addition, it replaced so that the direction of the transmission axis of the polarizing plate 7 might become the same as the direction of the transmission axis of the polarizing plate before replacement.

(Comparative Example 2)
A polarizer protective film 2 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (Fuji Film Co., Ltd.) Manufactured, with a thickness of 80 μm), and polarizing plate 8 was created.
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 8.

(Comparative Example 3)
A polarizer protective film 3 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (Fuji Film Co., Ltd.) Manufactured, with a thickness of 80 μm) to make a polarizing plate 9.
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 9.

(Comparative Example 4)
A polarizer protective film 3 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (Fuji Film Co., Ltd.) Manufactured, with a thickness of 80 μm) to make a polarizing plate 9.
The polarizing plate on the light source side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate 9 so that the polyester film was on the side opposite to the liquid crystal (distal), thereby producing a liquid crystal display device. In addition, it replaced so that the direction of the transmission axis of the polarizing plate 9 might become the same as the direction of the transmission axis of the polarizing plate before replacement.

(Comparative Example 5)
A polarizer protective film 3 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (Fuji Film Co., Ltd.) Manufactured, with a thickness of 80 μm) to make a polarizing plate 9.
A polarizing plate on the viewing side and the light source side of REGZA 43J10X manufactured by Toshiba Corp. was replaced with the polarizing plate 9 so that the polyester film was on the opposite side (distal) from the liquid crystal, thereby producing a liquid crystal display device. In addition, it replaced so that the direction of the transmission axis of the polarizing plate 9 might become the same as the direction of the transmission axis of the polarizing plate before replacement.

(Comparative Example 6)
A polarizer protective film 4 is attached to one side of a polarizer made of PVA and iodine so that the transmission axis of the polarizer and the fast axis of the film are perpendicular to each other, and a TAC film (Fuji Film Co., Ltd.) Manufactured and having a thickness of 80 μm) to make a polarizing plate 10.
A liquid crystal display device was produced in the same manner as in Comparative Example 1 except that the polarizing plate 7 was changed to the polarizing plate 10.

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

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

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

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

Claims (3)

A liquid crystal display device having a backlight light source, two polarizing plates, and a liquid crystal cell disposed between the two polarizing plates,
The backlight source has a peak top of the emission spectrum in each wavelength region of 400 nm to 495 nm, 495 nm to less than 600 nm, and 600 nm to 780 nm, and has the highest peak intensity in the wavelength region of 600 nm to 780 nm. A white light-emitting diode having an emission spectrum with a peak half-width less than 5 nm,
At least one polarizing plate of the two polarizing plates is a polyester film laminated on at least one surface of a polarizer,
The polyester film has an easy adhesion layer on at least one surface,
The difference between the refractive index of the easy adhesion layer and the refractive index of the polyester film in a direction parallel to the transmission axis of the polarizer is 0.10 or less.
Liquid crystal display device. The emission spectrum of the backlight source is
The full width at half maximum of the peak with the highest peak intensity in the wavelength region of 400 nm or more and less than 495 nm is 5 nm or more,
2. The liquid crystal display device according to claim 1, wherein a half-width of a peak having the highest peak intensity in a wavelength region of 495 nm or more and less than 600 nm is 5 nm or more. The liquid crystal display device according to claim 1, wherein the polyester film has a retardation of 1500 to 30000 nm.