TWI760447B - Liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal display device, which is a liquid crystal display device having a backlight source including white light-emitting diodes, the white light-emitting diodes have a blue region (more than 400nm and less than 495nm), a green region (more than 495nm and Each wavelength region of less than 600nm) and red region (more than 600nm and less than 780nm) has a peak top of the emission spectrum, and the peak in the red region (more than 600nm and less than 780nm) has a narrower half-width (less than 5nm) emission spectrum; Even when a polyester film is used as a polarizer protective film, rainbow unevenness can be suppressed.

A liquid crystal display device, which is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers, characterized in that the backlight source is above 400nm and less than 495nm, 495nm A white light-emitting diode having an emission spectrum with a peak top of the emission spectrum in each wavelength region of not less than 600 nm and not more than 600 nm and not more than 780 nm; body; at least one polarizing plate among the polarizing plates, and a polyester film is laminated on at least one side of the polarizing lens; the polyester film has a retardation value of 1500 nm or more and 30000 nm or less; one of the polyester films Anti-reflection layer and/or low-reflection layer are laminated on the side surface; the polyester film laminated with anti-reflection layer and/or low-reflection layer, measured from the side where anti-reflection layer and/or low-reflection layer are laminated The reflection spectrum has a bottom wavelength in a wavelength region of 600 nm or more and 780 nm or less, and the reflectance at the bottom wavelength is 2% or less.

Description

Liquid crystal display device

The present invention relates to a polarizer protective film, a polarizer and a liquid crystal display device. In detail, it relates to a liquid crystal display device with improved rainbow spots.

Polarizers used for liquid crystal display devices (LCDs) are usually composed of two polarizer protective films sandwiched between two polarizer protective films, and a polarizer formed by dyeing iodine with polyvinyl alcohol (PVA), etc., is usually composed of triacetyl cellulose. (TAC) film as a polarizer protective film. In recent years, along with thinning of LCDs, thinning of polarizing plates has been gradually demanded. However, when the thickness of the TAC film used as a protective film is reduced due to this, sufficient mechanical strength cannot be obtained, and there is a problem that moisture permeability is deteriorated. In addition, TAC films are very expensive, and polyester films have been proposed as low-cost alternative materials (Patent Documents 1 to 3), but there is a problem of occurrence of rainbow spots.

When an oriented polyester film having birefringence is disposed on one side of the polarizer, the polarization state of linearly polarized light emitted from the backlight unit or the polarizer is changed when passing through the polyester film. The transmitted light exhibits an interference color peculiar to the product of the birefringence and the thickness of the oriented polyester film, that is, the retardation value. Therefore, 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 rainbow spots (see: Proceedings of the 15th Micro Optical Conference, 30th to 31 items).

As a means to solve the above problems, it has been proposed to use a white light source with a continuous and broad emission spectrum, such as a white light-emitting diode, as a backlight source, and further use an oriented polyester film with a certain hysteresis value as a polarizer protective film ( Patent Document 4). White light-emitting diodes have a continuous and broad emission spectrum in the visible light region. Therefore, if attention is paid to the envelope shape of the interference color spectrum generated by the transmitted light penetrating the birefringent, by controlling the retardation value of the alignment polyester film, a spectrum similar to the emission spectrum of the light source can be obtained. Can inhibit rainbow spots.

prior art literature Patent Literature

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

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

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

Patent Document 4 WO2011/162198

Due to the increasing demand for the expansion of the color gamut of liquid crystal display devices in recent years, a method using a white light emitting diode (eg, having a blue light emitting diode and at least K ₂ SiF ₆ : Mn ⁴⁺ as a phosphor) has been developed. A liquid crystal display device as a backlight source of a white light-emitting diode (such as a fluoride phosphor), the white light-emitting diode has a blue region (400nm or more and less than 495nm) and a green region (495nm or more and less than 600nm) Each wavelength region in the red region (600 nm or more and 780 nm or less) has a peak top of the emission spectrum, and in the red region (600 nm or more and 780 nm or less), the peak half-width is narrow (less than 5 nm).

In industrial production of a liquid crystal display device using a polarizer 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 because when the polyvinyl alcohol film of the polarizer is uniaxially stretched in the longitudinal direction to manufacture, the polyester film of the protective film is stretched in the longitudinal direction and then stretched in the transverse direction to manufacture, so the orientation axis direction of the polyester film becomes the transverse direction. When these elongated objects are bonded together to manufacture a polarizing plate, the fast axis of the polyester film and the transmission axis of the polarizer are usually perpendicular to each other. In this case, by using an oriented polyester film having a specific hysteresis value as the polyester film, and using, for example, a combination of blue light-emitting diodes and yttrium. aluminum. The light source with continuous and broad emission spectrum, represented by the white LED of the light-emitting element of the garnet-based yellow phosphor, is used as a backlight source. Although it can greatly improve the rainbow spot, it is used in the red region (more than 600nm and less than 780nm). In the case of a backlight source of a white light emitting diode having a light emission spectrum with a narrow (less than 5 nm) half-value width of the peak in ), it was found that a new problem such as occurrence of rainbow spots still exists.

That is, the subject of the present invention is to provide a liquid crystal display device having a backlight source including a white light emitting diode having a light source in the blue region (more than 400 nm and less than 495 nm), Each wavelength region of the green region (more than 495 nm and less than 600 nm) and the red region (more than 600 nm and less than 780 nm) has a peak top of the emission spectrum, and the half width of the peak in the red region (more than 600 nm and less than 780 nm) is narrow (less than 5nm); even in the case of using a polyester film as a polarizer protective film, rainbow spots can be suppressed.

Representative inventions are as follows.

Item 1. A liquid crystal display device, which is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers, characterized in that: the backlight source has a wavelength of 400 nm or more and less than 400 nm. 495nm, 495nm or more and less than 600nm, and 600nm or more and 780nm or less each wavelength region has the peak top of the emission spectrum, and the peak intensity of the highest peak in the wavelength region of 600nm or more and 780nm or less is less than 5nm. Light-emitting diodes; at least one polarizing plate among the polarizing plates, and a polyester film is laminated on at least one side of the polarizer; the polyester film has a hysteresis value of 1500 nm or more and 30000 nm or less; the polyester An anti-reflection layer and/or a low-reflection layer is laminated on one side of the film; the laminated polyester film with an anti-reflection layer and/or a low-reflection layer is laminated from the side where the anti-reflection layer and/or the low-reflection layer is laminated The measured reflection spectrum has a bottom wavelength in the wavelength region of 600 nm or more and 780 nm or less, and the reflectance at the bottom wavelength is 2% or less.

Item 2. The liquid crystal display device according to Item 1, wherein the light emission spectrum of the backlight light source has a half-value width of a peak with the highest peak intensity in a wavelength region of 400 nm or more and less than 495 nm, and a wavelength of 495 nm or more and less than 600 nm. The half-value width of the peak with the highest peak intensity in the region is 5 nm or more.

Item 3. A polarizer protective film comprising a polarizer protective film with an anti-reflection layer and/or a low-reflection layer laminated on one side of a polyester film, wherein the polyester film has a hysteresis of 1500 nm or more and 30000 nm or less Value; the polyester film with anti-reflection layer and/or low-reflection layer is laminated, the reflection spectrum measured from the side where anti-reflection layer and/or low-reflection layer is laminated has bottom wavelength in the wavelength region above 600nm and below 780nm , the reflectance at the bottom wavelength is less than 2%.

Item 4. A polarizing plate, wherein the polarizer protective film of item 3 is laminated on at least one side of the polarizer.

The liquid crystal display device, the polarizing plate and the polarizer protective film of the present invention can ensure good visibility in which the occurrence of rainbow spots is obviously suppressed at any viewing angle.

Form for carrying out the invention

Generally speaking, a liquid crystal display device is composed of a rear side module, a liquid crystal unit and a front side module in order from the backlight light source side to the display image side (visual recognition side). The rear-side module and the front-side module are generally composed of a transparent substrate, a transparent conductive film formed on the side surface of the liquid crystal cell, and a polarizer arranged on the opposite side thereof. Here, the polarizing plate is arranged on the backlight light source side in the rear side module, and is arranged on the display image side (visual recognition side) in the front side module.

The liquid crystal display device of the present invention includes at least a backlight light source and a liquid crystal cell disposed between two polarizers as constituent members.

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

Among the two polarizing plates arranged in the liquid crystal display device, at least one polarizing plate has a polyester film laminated on at least one surface of a polarizing mirror formed by dyeing iodine with polyvinyl alcohol (PVA) or the like. . In the present invention, from the viewpoint of suppressing rainbow spots, the polyester film has a specific hysteresis value, and an antireflection layer and/or a low reflection layer are laminated on at least one side of the polyester film. The anti-reflection layer and/or the low-reflection layer may be provided on the surface opposite to the surface of the polyester film laminated polarizer, or may be provided on the surface of the polyester film laminated polarizer, or both. Preferably, the anti-reflection layer and/or the low-reflection layer are provided on the surface opposite to the surface of the polyester film laminated polarizer. In addition, other layers (eg, an easy-bonding layer, a hard coat layer, an anti-glare layer, an antistatic layer, an antifouling layer, etc.) may also be present between the anti-reflection layer and/or the low-reflection layer and the polyester film. From the viewpoint of further suppressing rainbow spots, the refractive index of the polyester film in the direction parallel to the transmission axis of the polarizer is preferably 1.53 to 1.62. It is preferable to laminate on the other side of the polarizer a film (a polarizer composed of three layers), which is represented by a TAC film, an acrylic film and a norbornene film with virtually no birefringence (low hysteresis value), but It is not necessary to laminate a film (a polarizer composed of two layers) on the other side of the polarizer. In addition, when a polyester film is used as the protective film on both sides of the polarizer, the slow axes of the two polyester films are preferably slightly parallel to each other. Here, slightly parallel means that the angle formed by the two axes is -15°~15°, preferably -10°~10°, more preferably -5°~5°, still more preferably -3°~3° °, still more preferably -2° to 2°, still more preferably -1° to 1°.

As the polarizer, any polarizer (polarizing film) that can be used in this technical field can be appropriately selected and used. As a representative polarizer, a polyvinyl alcohol film or the like is exemplified by dyeing a dichroic material such as iodine, but the present invention is not limited to this, and a conventional polarizer or a polarizer that can be developed in the future can be appropriately selected and used.

A commercially available PVA film can be used, for example, "Kuraray Vinylon (Kuraray Co., Ltd.)", "Tohcello Vinylon (Tohcello Co., Ltd.)", "Nichigo Vinylon (Nippon Synthetic Chemical Co., Ltd.)", etc. can be used . As a dichroic material, iodine, a diazo compound, a polymethine dye, etc. are mentioned.

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

The structure of the backlight may be an edge type with a light guide plate or a reflector as a constituent member, or a direct type, but in the present invention, as the backlight source of the liquid crystal display device, it is preferable to include a white light emitting diode The backlight source, the white light emitting diode has a peak top of the emission spectrum in each wavelength region of 400 nm or more and less than 495 nm, 495 nm or more and less than 600 nm, and 600 nm or more and 750 nm or less, and any of the wavelength regions of 600 nm or more and 780 nm or less. The emission spectrum in which the half-value width of the peak with the highest peak intensity is less than 5 nm. The upper limit of the half-value width of the peak having the highest peak intensity in the wavelength region from 600 nm to 780 nm is preferably less than 5 nm, more preferably less than 4 nm, and even more preferably less than 3.5 nm. The lower limit is preferably 1 nm or more, more preferably 1.5 nm or more. If the half-value width of the peak is less than 5 nm, the color gamut of the liquid crystal display device is wide, which is preferable. In addition, the lower limit of the half-value width of the peak is not particularly set, but it can be set to 1 nm. If the peak half-width is less than 1 nm, there is a possibility that the luminous efficiency will deteriorate. The shape of the luminous spectrum can be designed from the balance of the required color gamut and luminous efficiency. In addition, here, the half-value width refers to the peak width (nm) at 1/2 intensity of the peak intensity among the wavelengths of the peak top.

The application of a backlight light source with "emission spectrum with the above-mentioned characteristics" to LCD has become a technology attracting attention due to the increasing demand for color gamut expansion in recent years. LEDs that use conventional white LEDs (for example, light-emitting elements that combine blue light-emitting diodes and yttrium-aluminum-garnet-based yellow phosphors) as backlight light sources can only reproduce what can be discerned by the human eye. about 20% of the spectrum. On the other hand, when a backlight light source having a light emission spectrum with the above-mentioned characteristics is used, it is said that more than 60% of colors can be reproduced.

The wavelength region of 400 nm or more and less than 495 nm is more preferably 430 nm or more and 470 nm or less. The wavelength region of 495 nm or more and less than 600 nm is more preferably 510 nm or more and 560 nm or less. The wavelength region of 600 nm or more and 780 nm or less is more preferably 600 nm or more and 700 nm or less, still more preferably 610 nm or more and 680 nm or less, and still more preferably 610 nm or more and 660 nm or less.

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

Specifically, as a white light source having "a light emission spectrum with the above-mentioned characteristics", for example, a fluorescent white light emitting diode, which is a combination of a blue light emitting diode and a phosphor, can be mentioned. Among the phosphors, red phosphors include, for example, fluoride phosphors (also referred to as "KSF") having a composition formula of K ₂ SiF ₆ : Mn ⁴⁺ and others. Mn ⁴⁺ activated fluoride complex phosphor is a phosphor with Mn ⁴⁺ as activator and fluoride complex salt of alkali metal, amine or alkaline earth metal as the main crystal. Among the fluoride complexes that form the main crystal, there are those whose coordination centers are trivalent metals (B, Al, Ga, In, Y, Sc, lanthanides), tetravalent metals (Si, Ge, Sn, Ti, Zr, Re, Hf) and pentavalent metals (V, P, Nb, Ta), the number of fluorine atoms coordinated around them is 5-7.

As a preferred example of the Mn ⁴⁺ -activated fluoride complex phosphor, there are: A ₂ [MF ₆ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs and NH ₄ ; M is one or more selected from Ge, Si, Sn, Ti and Zr), E[MF ₆ ]: Mn (E is one or more selected from Mg, Ca, Sr, Ba and Zn; M is selected from Ge, Si, One or more of Sn, Ti and 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 and NH ₄ ), A ₂ [MF ₅ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, and NH ₄ ; M is one or more selected from Al, Ga, and In), A ₃ [MF ₆ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs and NH ₄ ; M is one or more selected from Al, Ga and In), Zn ₂ [MF ₇ ]: Mn (M is selected from Al , one or more of Ga and In), A[In ₂ F ₇ ]: Mn (A is one or more selected from Li, Na, K, Rb, Cs, and NH ₄ ), and the like.

One of the preferred Mn ⁴⁺ activated fluoride complex phosphors is A ₂ MF ₆ : Mn (A is selected from Li, Na, K, One or more of Rb, Cs and NH ₄ ; M is one or more selected from Ge, Si, Sn, Ti and Zr). Among them, preferably, A is at least one selected from K (potassium) and Na (sodium), and M is Si (silicon) or Ti (titanium). Among them, A is K (the proportion of K in the total amount of A is more than 99 mol%), and M is Si. It is expected that Mn (manganese) in the activating element is 100%, but Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, Ti, Zr, Ge, Sn, Al, Ga, B, In, Cr, Fe, Co, Ni, Cu, Nb, Mo, Ru, Ag, Zn and Mg, etc. When M is Si, the ratio of Mn in the total of Si and Mn is desirably in the range of 0.5 mol % to 10 mol %. As other preferable Mn ⁴⁺ -activated fluoride complex phosphors, there can be mentioned the chemical formula A _{2+x My 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 the phosphor, particularly preferably a blue light-emitting diode and at least K ₂ SiF ₆ : The fluoride phosphor of Mn ⁴⁺ acts as a white light-emitting diode for the phosphor. For example, a white LED manufactured by Nichia Chemical Co., Ltd., that is, a commercial item such as NSSW306FT can be used.

In addition, as green phosphors among the phosphors, for example, sialon (SiAlON)-based phosphors based on β-SiAlON:Eu, etc., and (Ba,Sr) ₂ SiO ₄ : Eu and the like are silicate-based phosphors of basic composition, and others.

In addition, in the wavelength region of 400 nm or more and less than 495 nm, the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 780 nm or less, the presence of complex peaks can be considered as follows.

When the plural peaks are independent peaks, the half-value width of the peak with the highest peak intensity is preferably within the above-mentioned range. Furthermore, for other peaks having an intensity of 70% or more of the highest peak intensity, it is more preferable that the half-value width is also within the above-mentioned range.

Regarding an independent peak having a shape of overlapping of complex peaks, when the half-value width of the peak with the highest peak intensity among the complex peaks can be directly measured, its half-value width is used. Here, the independent peak refers to a region having an intensity equal to 1/2 of the peak intensity on both sides of the short-wavelength side and the long-wavelength side of the peak. That is, in the case where the complex peaks overlap and each peak does not have a region with an intensity equal to 1/2 of the peak intensity on both sides of each peak, the entire complex peak is regarded as one peak. For one peak having a shape of overlapping of complex peaks, the peak width (nm) in the intensity of 1/2 of the highest peak intensity is taken as the half-value width.

In addition, the point with the highest peak intensity among the complex peaks is regarded as the peak top.

In addition, the peak with the highest peak intensity among the wavelength regions of 400 nm or more and less than 495 nm, the wavelength region of 495 nm or more and less than 600 nm, or the wavelength region of 600 nm or more and 780 nm or less is preferably the peak of the other wavelength regions. independent relationship. In particular, from the viewpoint of clarity of color, it is preferable to be between "the peak with the highest peak intensity in the wavelength region of 495 nm or more and less than 600 nm" and "the peak with the highest peak intensity in the region of 600 nm or more and 780 nm or less". In the wavelength region between 600 nm and 780 nm, the intensity reaches 1/3 or less of the peak intensity of the peak having the highest peak intensity.

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

As a result of intensive research by the inventors of the present application, it has been found that when the above-mentioned backlight light source is provided, that is, 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 less than 780 nm) are included. In the liquid crystal display device of the backlight source of the white light emitting diode having a peak top of the emission spectrum in each wavelength region and a narrow half width of the peak in the red region (600 nm to 780 nm), as long as a specific hysteresis value is used , and a polyester film with a specific anti-reflection layer and/or a low-reflection layer laminated as a polarizer protective film has the effect of suppressing rainbow spots. Here, the polyester film on which the specific antireflection layer and/or the low reflection layer is laminated has a bottom wavelength of the reflection spectrum at 600 nm or more and 780 nm or less, and the reflectance at the bottom wavelength is 2% or less. In addition, the reflection spectrum is obtained by measuring the reflection spectrum from the side where the anti-reflection layer and/or the low-reflection layer is laminated with respect to the polyester film laminated with the anti-reflection layer and/or the low-reflection layer. The bottom wavelength of the reflection spectrum is the wavelength with the smallest reflectance in the reflection spectrum from 400nm to 780nm. The bottom wavelength of the reflection spectrum is preferably in the wavelength region of 600 nm or more and 780 nm or less, more preferably 600 nm or more and 700 nm or less, still more preferably 610 nm or more and 680 nm or less, and still more preferably 610 nm or more and 660 nm or less.

When the oriented polyester film is arranged on one side of the polarizer, the polarization state changes when linearly polarized light emitted from the backlight unit or the polarizer passes through the polyester film. One of the main reasons for the change of the polarization state is considered to be influenced by the refractive index difference between the interface between the air layer and the oriented polyester film, or the refractive index difference between the polarizer and the oriented polyester film. When linearly polarized light incident on the alignment polyester film passes through each interface, a part of the light is reflected due to the difference in refractive index between the interfaces.

The light incident on the alignment polyester film through the polarizer is linearly polarized light, which is considered to be in the state of linearly polarized light, and the transmittance has no dependence on the wavelength. Linearly polarized incident light becomes elliptically polarized or circularly polarized by passing through the alignment polyester film. The phase difference δ is represented by δ=2π×Re/λ (Re: retardation value, λ: wavelength), and the phase difference δ varies depending on the wavelength λ. That is, since the change period of linearly polarized light, elliptically polarized light, and circularly polarized light varies depending on the wavelength λ of light, it is considered that the polarization state when emitted from the aligned polyester film varies depending on the wavelength. When the oriented polyester film is emitted to the visual recognition side, the vertical S-polarized light component is more easily reflected than the parallel P-polarized light component with respect to the incident surface, and the difference (the difference between the P-polarized light component and the S-polarized light component) varies with There is a tendency to become larger from the visual recognition angle of the normal. Different wavelengths of light with different degrees of polarization have different effects on the S-polarized light that is easily reflected, so each transmittance changes when passing through the interface. When passing through the interface, the transmittance of the wavelength band with more S-polarized light components becomes lower, which is considered to be one of the main causes of rainbow spots. In particular, when there is a steep peak in the red region of 600 nm or more and 780 nm or less, the change in transmittance due to the wavelength is large, so that color irregularities are likely to occur. By thin-film interference, interface reflection at any wavelength can be suppressed. Therefore, it is considered that the transmittance of the red region can be improved by forming an anti-reflection layer and/or a low-reflection layer having a bottom wavelength in the red region (600 nm to 780 nm). That is, the reflection of the S-polarized light component is suppressed. In the steep red region, the transmittance of the S-polarized light component is increased, so that the transmittance of the light emitted from the alignment polyester film changes less with respect to the incident light passing through the polarizer, thereby suppressing rainbow spots.

As described above, in the present invention, in the present invention, each of the wavelength regions including 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) each has an emission spectrum. In the liquid crystal display device of the backlight source of the white light-emitting diode with a narrow peak at the peak and the peak in the red region (600 nm or more and 780 nm or less), even if a polarizing plate using a polyester film as a polarizer protective film is used , and no rainbow spots will occur, and it has good visual recognition.

In the polarizing plate of the present invention, a polarizer protective film comprising a polyester film is laminated on at least one side of the polarizer. The polyester film used for the polarizer protective film preferably has a retardation value of not less than 1500 nm and not more than 30000 nm. If the hysteresis value is within the above-mentioned range, rainbow unevenness tends to be more easily reduced, which is preferable. The preferred lower limit of the hysteresis value is 3000nm, the further preferred lower limit is 3500nm, the more preferred lower limit is 4000nm or 5000nm, the further preferred lower limit is 6000nm, and the further preferred lower limit is 8000nm. The preferable upper limit is 30,000 nm, and the polyester film having a hysteresis value higher than that has a relatively thick thickness, which tends to lower the usability as an industrial material. A more preferable upper limit is 15000 nm, still more preferably 12000 nm, and still more preferably 11000 nm.

In addition, the hysteresis value of the present invention can be obtained by measuring the refractive index and thickness in the biaxial direction, or can be obtained by using a commercially available automatic birefringence measuring apparatus such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.). In addition, the refractive index can be obtained by an Abbe refractometer (measurement wavelength: 589 nm).

The ratio (Re/Rth) of the hysteresis value (Re: in-plane hysteresis value) of the polyester film to the hysteresis value (Rth) in the thickness direction is preferably 0.2 or more, more preferably 0.5 or more, and even more preferably 0.6 or more. The larger the ratio (Re/Rth) of the retardation value to the retardation value in the thickness direction, the more the isotropy of the birefringence action increases, and the more likely it is that rainbow spots are less likely to occur depending on the viewing angle. In a completely uniaxial (uniaxially symmetric) film, the ratio of the retardation value to the thickness direction retardation value (Re/Rth) is 2.0, so the upper limit of the ratio of the retardation value to the thickness direction retardation value (Re/Rth) is preferably 2.0. In addition, the retardation in the thickness direction refers to the average of the retardation obtained by multiplying the two birefringences ΔNxz and ΔNyz by the film thickness d when the film is observed in a cross section in the thickness direction.

From the viewpoint of further suppressing rainbow spots, the NZ coefficient of the polyester film is preferably 2.5 or less, more preferably 2.0 or less, still more preferably 1.8 or less, still more preferably 1.6 or less. Next, since the NZ coefficient is 1.0 in a completely uniaxial (uniaxially symmetric) thin film, the lower limit of the NZ coefficient is 1.0. However, since the mechanical strength in the direction orthogonal to the alignment direction tends to decrease remarkably as the film approaches a complete uniaxiality (uniaxial symmetry), it is necessary to pay attention.

The NZ coefficient is represented by |Ny-Nz|/|Ny-Nx|, where Ny represents the refractive index in the slow axis direction, Nx represents the refractive index in the direction orthogonal to the slow axis (refractive index in the fast axis direction), Nz represents the refractive index in the thickness direction. The alignment axis of the thin film was determined using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments Co., Ltd.), and was determined by an Abbe refractometer (manufactured by ATAGO, NAR-4T, measurement wavelength: 589 nm). The biaxial refractive index (Ny, Nx, where Ny>Nx) and the refractive index (Nz) in the thickness direction are obtained in the direction of the alignment axis and the direction orthogonal thereto. The NZ coefficient can be obtained by substituting the value obtained in this way into |Ny-Nz|/|Ny-Nx|.

In addition, from the viewpoint of further suppressing rainbow spots, the Ny-Nx value of the polyester film is preferably 0.05 or more, more preferably 0.07 or more, still more preferably 0.08 or more, still more preferably 0.09 or more, and most preferably 0.1 above. The upper limit is not particularly limited, but in the case of a polyethylene terephthalate-based film, the upper limit is preferably about 1.5.

In this invention, as a more preferable aspect, it is preferable that the refractive index of a polyester film in the direction parallel to the transmission axis direction of the polarizer which comprises a polarizing plate is the range of 1.53 or more and 1.62 or less. Thereby, reflection in the interface of a polarizer and a polyester film can be suppressed, and rainbow unevenness can be suppressed. It is preferably 1.61 or less, more preferably 1.60 or less, still more preferably 1.59 or less, still more preferably 1.58 or less.

On the other hand, the lower limit value of the refractive index is preferably 1.53. When the refractive index is less than 1.53, the crystallization of the polyester film becomes insufficient, and the properties obtained by stretching such as dimensional stability, mechanical strength, chemical resistance, and the like may become insufficient, which is not preferable. Preferably it is 1.56 or more, More preferably, it is 1.57 or more.

In order to set the refractive index of the polyester film in the direction parallel to the transmission axis direction of the polarizer in the range of 1.53 or more and 1.62 or less, in the polarizer, the transmission axis of the polarizer and the fast axis of the polyester film (and the slow axis) are preferably axis perpendicular to the direction) is slightly parallel. The refractive index in the direction perpendicular to the slow axis in the polyester film, that is, in the fast axis direction, can be adjusted to a low value of about 1.53 to 1.62 by the stretching treatment in the following film forming step. By making the direction of the fast axis of the polyester film slightly parallel to the direction of the transmission axis of the polarizer, the refractive index of the polyester film in the direction parallel to the direction of the transmission axis of the polarizer can be set to 1.53 to 1.62. Here, slightly parallel means that the angle formed by the transmission axis of the polarizer and the fast axis of the polarizer protective film is -15°~15°, preferably -10°~10°, more preferably -5°~5° °, more preferably -3° to 3°, still more preferably -2° to 2°, and still more preferably -1° to 1°. In a preferred embodiment, slightly parallel means substantially parallel. Here, the term "substantially parallel" means that the transmission axis and the fast axis are parallel to the extent that when the polarizer and the protective film are bonded together, the transmission axis and the fast axis are allowed to unavoidably occur. The direction of the slow axis can be obtained by measuring with a molecular orientation meter (for example, MOA-6004 type molecular orientation meter manufactured by Oji Scientific Instruments Co., Ltd.).

That is, the refractive index in the fast axis direction of the polyester film is preferably 1.53 or more and 1.62 or less. The refractive index of the polyester film in the direction parallel to the transmission axis is 1.53 or more and 1.62 or less.

The polarizer protective film comprising a polyester film used in the present invention can be used for both polarizers on the incident light side (light source side) and on the light exit side (visual recognition side), but is preferably used at least on the light exit side ( The protective film of the polarizing plate on the visual recognition side).

Regarding the polarizing plate arranged on the light-emitting side, the polarizer protective film comprising the above-mentioned polyester film can be arranged on the liquid crystal side with the polarizer as a starting point, on the light-emitting side, or on both sides. It is preferable to arrange at least on the light-emitting side.

In the polarizing plate arranged on the incident light side, the polarizer protective film including the above-mentioned polyester film may be arranged on the incident light side with the polarizer as a starting point, on the liquid crystal cell side, or on both sides. , but preferably, it is disposed at least on the incident light side. In addition, the polarizer system arranged on the incident light side may be a polarizer protective film with substantially no birefringence (low hysteresis value), such as a triacetyl cellulose film, instead of a polarizer protective film containing a polyester film. .

As the polyester used for the polyester film, polyethylene terephthalate or polyethylene naphthalate may be used, but other copolymerization components may also be included. These resins are excellent in transparency, and are also excellent in thermal properties and mechanical properties, and the hysteresis value can be easily controlled by stretching. In particular, polyethylene terephthalate has a large intrinsic birefringence, and by extending the film, the refractive index in the fast axis (perpendicular to the slow axis direction) direction can be lowered, and the film can be easily obtained even if the thickness of the film is thin. Large hysteresis value, so it is the best material.

Moreover, in order to suppress deterioration of optical functional dyes, such as an iodine dye, it is desirable that the light transmittance of a polyester film in wavelength 380nm is 20 % or less. 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 deterioration of the optically functional dye due to ultraviolet rays can be suppressed. In addition, transmittance is measured in a direction perpendicular to the plane of the film, and can be measured using a spectrophotometer (eg, Hitachi Model U-3500).

In order to make the transmittance of the polyester film 20% or less at a wavelength of 380 nm, 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 one. As an ultraviolet absorber, an organic type ultraviolet absorber and an inorganic type ultraviolet absorber are mentioned, From a viewpoint of transparency, an organic type ultraviolet absorber is preferable. Examples of the organic ultraviolet absorber include benzotriazole-based, benzophenone-based, cyclic imidoester-based, etc., and combinations thereof, but are not particularly limited as long as they fall within the absorbance range specified in the present invention. . From the viewpoint of durability, benzotriazole-based and cyclic imidoester-based are particularly preferred. When two or more types of ultraviolet absorbers are used in combination, the ultraviolet absorption effect can be further improved because ultraviolet rays of respective wavelengths can be absorbed at the same time.

-4-酮)、2-甲基-3,1-苯并

-4-酮、2-丁基-3,1- 苯并

-4-酮、2-苯基-3,1-苯并

-4-酮等。然而，並非特別限定於此。 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 yl-6-(tert-butyl)phenol, 2,2'-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole- 2-yl)phenol, etc. As a cyclic imidoester-based ultraviolet absorber, for example: 2,2'-(1,4-phenylene)bis(4H-3,1-benzone)

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

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

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

-4-keto, etc. However, it is not particularly limited to this.

In addition to the ultraviolet absorber, various additives other than the catalyst are preferably contained within a range that does not hinder the effects of the present invention. Examples of additives include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, lightfast agents, flame retardants, thermal stabilizers, antioxidants, antigelling agents, Surfactant, etc. Moreover, in order to exhibit high transparency, it is also preferable that particles are not substantially contained in the polyester film. "Substantially free of particles" means, for example, in the case of inorganic particles, the content is 50 ppm or less, preferably 10 ppm or less, and particularly preferably less than the detection limit when quantifying inorganic elements by fluorescent X-ray analysis.

It is preferable to provide an anti-reflection layer and/or a low-reflection layer on the surface of one side of the polyester film used for the polarizer protective film of the present invention.

The reflection spectrum of the polyester film laminated with the antireflection layer and/or the low reflection layer is characterized by having a bottom wavelength in the wavelength region of 600 nm to 780 nm, and the reflectance at the bottom wavelength is 2% or less. The reflection spectrum is measured from the side where the anti-reflection layer and/or the low-reflection layer is laminated. The bottom wavelength of the reflection spectrum is the wavelength with the smallest reflectance in the reflection spectrum from 400nm to 780nm. The reflectance in the bottom wavelength of the anti-reflection layer and/or the low-reflection layer used in the present invention is preferably 2% or less. If it exceeds 2%, the rainbow spot is easily recognized visually, and it is not good. The reflectance is more preferably less than 2%, more preferably 1.6% or less, still more preferably 1.2% or less, and particularly preferably 1% or less. The lower limit of the reflectance is not particularly limited, but is, for example, 0.01%. The best reflectivity is 0%. In addition, in the case of laminating an antireflection layer, the upper limit of the reflectance is preferably less than 1%. When a low reflection layer is laminated, the upper limit of the reflectance is preferably 2% or less, more preferably less than 2%, and the lower limit is preferably about 1%.

The measurement of reflectance can be carried out by the method described in the following examples.

The anti-reflection layer can be a single layer or a multi-layer. In the case of a single layer, as long as the thickness of the refractive index layer containing a material with a refractive index lower than that of the polyester film is formed to be 1/4 wavelength of the light wavelength or its odd multiples, Anti-reflection effect can be obtained. In addition, when the antireflection layer is a multilayer, the antireflection effect can be obtained as long as two or more layers of the low-refractive index layer and the high-refractive index layer are alternately laminated and the thicknesses of the respective layers are appropriately controlled. In addition, a hard coat layer can also be laminated between the anti-reflection layers according to requirements, and an antifouling layer can be formed on the hard coat layer.

Other examples of the antireflection layer include those applying a moth-eye structure. The moth-eye structure is a concavo-convex structure with a pitch smaller than the wavelength formed on the surface, and by this structure, a sharp and discontinuous refractive index change at the interface with the air can be converted into a continuous and gradual refractive index change. Thereby, the reflection of light on the surface of the film is reduced due to the formation of a moth-eye structure on the surface. For example, Japanese Patent Application Laid-Open No. 2001-517319 can be referred to.

As a method for forming an anti-reflection film, there may be mentioned: a dry coating method in which an anti-reflection layer is formed on the surface of a substrate by evaporation or sputtering; an anti-reflection coating liquid is applied on the surface of the substrate and dried to form an anti-reflection coating layer wet coating method; or a combination of both methods. In the present invention, the composition of the antireflection layer and the method for forming the same are not particularly limited as long as the above-mentioned characteristics are satisfied.

As the low reflection layer, a conventionally known one can be used. For example, it can be formed by a method of depositing at least one or more layers of a metal or oxide thin film by a vapor deposition method or a sputtering method, a method of applying one or more layers of an organic thin film, and the like. As the low reflection layer, one coated with an organic film having a lower refractive index than a polyester film or a hard coat layer laminated on a polyester film can be preferably used.

If the bottom wavelength of the reflection spectrum of the anti-reflection layer and/or the low-reflection layer is to be 600 nm or more and 780 nm or less, for example, if the anti-reflection layer or the low-reflection layer is a single layer, it only needs to satisfy the formula of 2nd=λb/4. The thickness of the anti-reflection layer and the low-reflection layer can be adjusted in a manner. Here, n represents the refractive index of the antireflection layer or the refractive index of the low reflection layer, d represents the thickness of the antireflection layer or the thickness of the low reflection layer, and λb represents the bottom wavelength of the reflection spectrum.

In the case where the anti-reflection layer and the low-reflection layer are multilayered, the calculation can also be made as follows from the principle of thin-film interference. For example, it is composed of five layers (the first layer, the second layer, the third layer, the fourth layer, and the fifth layer; in the first layer, the incident medium layer ( In); and, in the fifth layer, there is an output medium layer (out) on the side opposite to the contact side with the fourth layer. For example, if the refractive index is n, the reflectivity is r, the thickness is d, and the refraction angle is When θ, wavelength is λ, and retardation is Δ, the reflectance of the lowermost layer (fifth layer) is expressed by the equation of thin-film interference as follows. Subscript numbers indicate layers. Also, consecutive subscript numbers of reflectance indicate reflectance between layers.

(5th floor)

_Δx is the phase difference when the refraction angle θx _is in a V-shape to and from the inside of the thin film of each layer x, and can be calculated by the formula of [Equation 2].

θ _x can be calculated by the formula of [Equation 3] by continuously using Snellen's law.

Generally, when calculating the reflection of a multilayer film, it can be calculated by adding the reflected light from the complex interface while considering the phase, so the reflectance of each layer can be obtained by the following formula.

(5th floor ~ 4th floor)

(5th floor ~ 3rd floor)

(5th floor ~ 2nd floor)

(5th floor ~ 1st floor)

The reflectance of the entire five layers can be obtained from the following equation.

The addition of the subscript numbers of the reflectances represents the total reflectance between the layers. The bottom wavelength can be designed in the target wavelength by adjusting the refractive index n or thickness d of each layer from the above formula.

In the emission spectrum of the backlight light source, the absolute value of the difference between λp and λb between the wavelength λp of the peak with the highest peak intensity in the wavelength range above 600nm and below 780nm and the bottom wavelength λb of the reflection spectrum should be 30nm or less. It is preferably 20 nm or less, more preferably 10 nm or less, and still more preferably 5 nm or less.

It is also possible to further impart an anti-glare function to the anti-reflection layer and/or the low-reflection layer. Thereby, rainbow unevenness can be further suppressed. That is, it may be a combination of an anti-reflection layer and an anti-glare layer, a combination of a low-reflection layer and an anti-glare layer, a combination of an anti-reflection layer and a low-reflection layer and an anti-glare layer. Particularly preferred is a combination of a low-reflection layer and an anti-glare layer. As the anti-glare layer, a conventionally known anti-glare layer can be used. For example, from the viewpoint of suppressing the surface reflection of the film, it is preferable to laminate an anti-glare layer on a polyester film, and then laminate an anti-reflection layer or a low-reflection layer.

When the anti-reflection layer or the low-reflection layer is provided, the polyester film preferably has an easy-bonding layer on its surface. In this case, from the viewpoint of suppressing interference caused by reflected light, it is preferable to adjust the refractive index of the easily bonding layer to be in the vicinity of the average product of the refractive index of the antireflection layer or the low-reflection layer and the refractive index of the polyester film. The refractive index of the easily bonded layer can be adjusted by conventional methods, for example, by including titanium, germanium or other metal species in the binder resin.

The polyester film may be subjected to corona treatment, coating treatment, flame treatment, or the like in order to have good adhesion to the polarizer.

In the present invention, in order to improve the adhesion to the polarizer, it is preferable that at least one side of the film of the present invention has at least one of polyester resin, polyurethane resin or polyacrylic resin as a main component the easy-to-bond layer. Here, the "main component" refers to a component of 50 mass % or more in the solid content constituting the easily bonded layer. The coating liquid for forming the easily adhesive layer of the present invention is preferably an aqueous coating liquid containing at least one of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin. Examples of such coating liquids include water-soluble ones disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Or water-dispersible copolymerized polyester resin solution, acrylic resin solution, polyurethane resin solution, etc.

The easy-bonding layer can be obtained by applying the coating solution to one or both sides of an unstretched film or a longitudinally uniaxially stretched film, drying at 100-150°C, and further extending in the lateral direction. The final coating amount of the easy-bonding layer is preferably controlled at 0.05 to 0.2 g/m ² . When the coating amount is less than 0.05 g/m ² , the adhesiveness with the obtained polarizer may become insufficient. On the other hand, when the coating amount exceeds 0.2 g/m ² , the blocking resistance may decrease. In the case of providing the easy-bonding layer on both sides of the polyester film, the coating amount of the easily-bonding layer on both sides may be the same or different, and may be independently set within the above ranges.

系、矽酮系等的有機聚合物系粒子等。該等可單獨添加至易接著層，亦可組合添加2種以上。 In order to impart slipperiness to the easy-bonding layer, it is preferable to add particles. It is preferable to use the particle|grains whose average particle diameter is 2 micrometers or less. When the average particle diameter of the particles exceeds 2 μm, the particles tend to fall off from the coating layer. Examples of particles contained in the easily bonding layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, lithium bentonite, zirconia, Inorganic particles of tungsten oxide, lithium fluoride, calcium fluoride, etc.; and styrene-based, acrylic-based, melamine-based, benzoguanidine

organic polymer-based particles such as silicone-based and silicone-based particles, etc. These may be added individually to the easily bonding layer, or may be added in combination of 2 or more types.

In addition, as a method of applying the coating liquid, a known method can be used. For example, a reverse roll coating method, a gravure coating method, a contact coating method, a roll brushing method, a spray coating method, an air knife coating method, a wire bar coating method, a pipe doctor method, etc., may be used alone or in combination. these methods.

In addition, the measurement of the average particle diameter of the above-mentioned particles was carried out by the following method. Take the image of the particles with a scanning electron microscope (SEM), measure the maximum diameter (the distance between the two farthest points) of 300 to 500 particles at a magnification of 2 to 5 mm for the size of one smallest particle, and average them. The value is regarded as the average particle size.

The polyester film used as the polarizer protective film can be produced according to the general production method of polyester film. For example, unoriented polyester formed by melting and extruding a polyester resin into a sheet shape, at a temperature above the glass transition temperature, is stretched in the longitudinal direction by the speed difference of the rollers, and then stretched in the transverse direction by a tenter. The method of stretching and heat treatment.

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, there is no film even when viewed from directly above the film surface. Rainbow spots are found, but when viewed from an oblique direction, rainbow spots are sometimes observed, so it is necessary to pay attention.

If the film forming conditions of the polyester film are specifically described, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130°C, and particularly preferably 90 to 120°C. In order to orient the film so that the slow axis is oriented in the TD direction, the longitudinal stretching ratio is preferably 1.0 to 3.5 times, and particularly preferably 1.0 to 3.0 times. In addition, the lateral stretching ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. In order to align the film so that the slow axis is in the MD direction, the longitudinal stretching ratio is preferably 2.5 times to 6.0 times, and particularly preferably 3.0 to 5.5 times. In addition, the lateral stretching ratio is preferably 1.0 times to 3.5 times, and particularly preferably 1.0 times to 3.0 times. In order to control the refractive index and hysteresis value in the fast axis direction of the polyester film within the above-mentioned ranges, it is preferable to control the ratio of the longitudinal stretching magnification and the transverse stretching magnification. In order to increase the hysteresis value, it is preferable to increase the difference between the vertical and horizontal stretch ratios. In addition, setting the stretching temperature low is also a preferable measure for reducing the refractive index in the fast axis direction of the polyester film and increasing the hysteresis value. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250°C, particularly preferably 180 to 245°C.

In order to suppress the fluctuation of the hysteresis value in the film, it is preferable that the thickness unevenness of the film is small. Since the stretching temperature and the stretching ratio greatly affect the thickness unevenness of the film, it is preferable to optimize the film forming conditions from the viewpoint of the thickness unevenness. In particular, when the longitudinal stretching ratio is lowered in order to increase the hysteresis value, the thickness unevenness in the longitudinal direction may worsen. Since the longitudinal thickness unevenness has a region where it is extremely deteriorated within a certain specific range of the draw ratio, it is desirable to set film forming conditions excluding this range.

The thickness variation of the polyester film is preferably 5% or less, more preferably 4.5% or less, still more preferably 4% or less, and particularly preferably 3% or less.

As described above, in order to control the hysteresis value 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, the thicker the film thickness, and the easier it is to obtain a high hysteresis value. Conversely, the lower the stretching ratio, the higher the stretching temperature, the thinner the film thickness, and the easier it is to obtain a low hysteresis value. However, when the thickness of the thin film is increased, the retardation in the thickness direction tends to increase. Therefore, it is desirable to appropriately set the film thickness within the following range. In addition to controlling the hysteresis value, it is also desirable to set the final film forming conditions in consideration of physical properties required for processing and the like.

The thickness of the polyester film is arbitrary, but is preferably in the range of 15 to 300 μm, more preferably in the range of 15 to 200 μm. In principle, a hysteresis value of 1500 nm or more can be obtained even for a thin film with a thickness of less than 15 μm. However, in this case, the anisotropy of the mechanical properties of the thin film becomes obvious, and splitting, breakage, etc. are likely to occur, and the practicality as an industrial material is remarkably reduced. The lower limit of the particularly preferred thickness is 25 μm. On the other hand, when the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. The upper limit of the particularly preferred thickness is 100 μm, which is about the same as a general TAC thin film. In order to also control the hysteresis value within the range of the present invention within the above thickness range, the polyester used as the film substrate is preferably polyethylene terephthalate.

In addition, as a method for blending the ultraviolet absorber into the polyester film, a conventional method can be used in combination. For example, a kneading extruder can be used in advance to mix the dried ultraviolet absorber and the polymer raw material to prepare The master batch is blended by a predetermined method of mixing the master batch with the polymer raw material at the time of film production.

At this time, in order to uniformly disperse the ultraviolet absorber and blend it economically, the concentration of the ultraviolet absorber in the master batch is preferably 5 to 30% by mass. As the conditions for preparing the master batch, it is preferable to use a kneading extruder, and extrude for 1 to 15 minutes at a temperature higher than the melting point of the polyester raw material and lower than or equal to 290°C. When the temperature is 290° C. or higher, the amount of the ultraviolet absorber is greatly reduced, and the viscosity of the master batch is greatly reduced. If the extrusion temperature is 1 minute or less, it will be difficult to uniformly mix the ultraviolet absorber. At this time, a stabilizer, a color tone adjuster, and an antistatic agent may also be added as required.

Moreover, it is preferable to make a polyester film into a multilayer structure of at least 3 layers or more, and to add an ultraviolet absorber to the intermediate layer of a film. The film of the three-layer structure in which the intermediate layer contains the ultraviolet absorber, specifically, can be produced in the following manner. The polyester pellets for the outer layer are separately supplied to a conventional extruder for fusion lamination, and the masterbatch containing the ultraviolet absorber for the intermediate layer and the polyester pellets are mixed at a predetermined ratio and dried, and then supplied to the extruder. In a conventional melt-lamination extruder, an unstretched film is produced by extruding from a slit-shaped die into a sheet shape, and cooling and solidifying it on a casting roll. That is, using two or more extruders, three-layer branch pipes or confluence sections (for example, a confluence section with a square confluence section), the film layers constituting the two outer layers and the film layers constituting the intermediate layer are laminated, A 3-layer sheet was extruded from a nozzle and cooled on a casting drum to make an unstretched film. Moreover, in this invention, in order to remove the foreign material contained in the raw material polyester which becomes the cause of an optical defect, it is preferable to perform high precision filtration at the time of melt extrusion. The filter particle size (initial filtration efficiency 95%) of the filter material used for high-precision filtration of molten resin is preferably 15 μm or less. When the filtration particle size of the filter medium exceeds 15 μm, the removal of foreign matters of 20 μm or more tends to become insufficient.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be implemented with appropriate modifications within the scope of the gist of the present invention, which are all included in the present invention. within the scope of the technology of the invention. In addition, evaluation methods of physical properties in the following examples are as follows.

(1) Refractive index of polyester film

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 was determined, and the film was cut out so that the slow axis direction was parallel to the long side of the measurement sample. A 2cm rectangle was used as a measurement sample. With respect to this sample, the refractive index of the two orthogonal axes (refractive index in the slow axis direction: Ny, fast axis (with slow axis direction: Ny), The refractive index in the direction orthogonal to the axis direction): Nx) and the refractive index in the thickness direction (Nz).

(2) Hysteresis value (Re)

The retardation value is a parameter defined by the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy=|Nx-Ny|) of the orthogonal biaxial axes on the film and the thickness d (nm) of the film (ΔNxy×d). Optical isotropy, anisotropy scale. The biaxial refractive index anisotropy (ΔNxy) was obtained 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 was determined, and the film was cut out so that the slow axis direction was parallel to the long side of the measurement sample. A 2cm rectangle is used as a measurement sample. For this sample, the refractive index of the orthogonal biaxial (refractive index in the slow axis direction: Ny, which is orthogonal to the slow axis direction) was obtained by an Abbe refractometer (manufactured by ATAGO, NAR-4T, measurement wavelength: 589 nm). The refractive index in the direction: Nx) and the refractive index in the thickness direction (Nz), and the absolute value (|Nx-Ny|) of the refractive index difference between the two axes was taken as the anisotropy of the refractive index (ΔNxy). The thickness d (nm) of the thin film was measured using an electric micrometer (manufactured by Feinpruf GmbH, Miitoron 1245D), and the unit was converted into nm. The retardation value (Re) was obtained from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the thickness d (nm) of the film.

(3) Hysteresis value in thickness direction (Rth)

The hysteresis value in the thickness direction is the hysteresis value obtained by multiplying the two birefringences △Nxz (=|Nx-Nz|) and △Nyz (=|Ny-Nz|) by the film thickness d respectively when viewed from the cross section of the film thickness direction the average parameters. Obtain Nx, Ny, Nz and film thickness d (nm) in the same way as measuring hysteresis value, and calculate the average value of (ΔNxz×d) and (ΔNyz×d) to obtain thickness direction hysteresis value (Rth) .

(4)NZ coefficient

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

(5) Measurement of the luminous spectrum of the backlight light source

As the liquid crystal display device used in each example, REGZA 43J10X manufactured by Toshiba Corporation was used. The luminescence spectrum of the backlight light source (white light emitting diode) of the liquid crystal display device was measured using a multi-channel spectroscope PMA-12 manufactured by Hamamatsu Photonics K.K., and as a result, luminescence spectra with peaks were observed around 450 nm, 535 nm and 630 nm. The half-value width of each peak top (the half-value width of the peak having the highest peak intensity in each wavelength region) is 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. In addition, although this light source has a complex peak in the wavelength region of 600 nm or more and 780 nm or less, the half-value width is evaluated by the peak in the vicinity of 630 nm where the peak intensity is the highest in this region. In addition, the exposure time at the time of measuring a spectrum was 20 msec.

(6) Measurement of reflection spectrum (evaluation of bottom wavelength and reflectance)

Cut out A4 size from the obtained polarizer protective film at any position, and evenly scratch the surface of the substrate opposite to the surface on which the low-reflection layer (or anti-reflection layer) is laminated with water-resistant sandpaper, and then apply BLACK. MAGIC INK (registered trademark) was then affixed with black tape (Nitto Denko vinyl tape No. 21 black) to prepare a sample in which the opposite side of the low-reflection layer (or anti-reflection layer) was non-reflective. Using a spectrophotometer UV-3150 manufactured by Shimadzu Corporation, the reflection spectrum of the low-reflection layer (or anti-reflection layer) of the fabricated sample was measured at 400-800 nm. The reflectance spectrum measurement conditions are based on the standard Al-evaporated mirror (Part No. 202-35988-05) attached to the specular reflection measuring device (Part No. 206-14064, manufactured by Shimadzu Corporation), and the full beam of 5 The angle of incidence of ° is implemented under the relative specular reflection. In addition, the measurement was performed under the conditions of sampling pitch: 1 nm, and opening size of the sample mask: 5 mmΦ. From the obtained reflection spectrum, the minimum value (minimum value) of the reflectance and the wavelength (bottom wavelength) at that time were obtained.

(Production Example 1 - Polyester A)

The temperature of the esterification reaction tank was raised, and when the temperature reached 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added, and 0.017 parts by mass of antimony trioxide, antimony trioxide as a catalyst, and 0.017 parts by mass were added while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine. Next, after pressurizing and raising the temperature, and performing pressurized esterification reaction under the conditions of a gauge pressure of 0.34 MPa and 240° C., the esterification reaction tank was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, the temperature was raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Next, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tank, and a polycondensation reaction was performed at 280° C. under reduced pressure.

After the completion of the polycondensation reaction, the filtration treatment is carried out with a filter made of naslon with a 95% cut-off diameter of 5 μm, and the strands are extruded from the nozzle, and the cooling water that has been previously filtered (pore size: 1 μm or less) is used. Allow to cool, solidify, and cut into granules. The intrinsic viscosity of the obtained polyethylene terephthalate resin (A) was 0.62 dl/g, and inactive particles and internally precipitated particles were not substantially contained. (hereinafter abbreviated as PET(A)).

(Production Example 2 - Polyester B)

-4-酮)及90質量份的不含粒子之PET(A)(固有黏度為0.62dl/g)混合，使用揉合擠製機，得到含有紫外線吸收劑的聚對苯二甲酸乙二酯樹脂(B)。(以下簡稱PET(B))。 10 parts by mass of the dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzone)

-4-keto) and 90 parts by mass of particle-free PET (A) (intrinsic viscosity: 0.62 dl/g), mixed with a kneading extruder to obtain a polyethylene terephthalate containing ultraviolet absorber Resin (B). (hereinafter referred to as PET(B)).

(Manufacturing Example 3 - Adjustment of Adhesion-Modifying Coating Liquid)

Carry out the transesterification reaction and the polycondensation reaction by the conventional method, and prepare the copolymerization polyester resin of water-dispersible sulfonic acid metal base, and its composition is: as the dicarboxylic acid component (relative to the whole dicarboxylic acid component) of 46 mol Ear % of terephthalic acid, 46 mol % of isophthalic acid and 8 mol % of sodium 5-sulfoisophthalic acid; 50 mol % as diol component (relative to the whole diol component) ethylene glycol and 50 mol% neopentyl glycol. Next, after mixing 51.4 parts by mass of water, 38 parts by mass of isopropanol, 5 parts by mass of n-butyl celusol, and 0.06 parts by mass of a nonionic surfactant, the mixture was heated and stirred until it reached 77°C. Add 5 parts by mass of the above-mentioned water-dispersible sulfonic acid metal base-containing co-polymerized polyester resin, continue stirring until there is no resin agglomeration, and then cool the resin aqueous dispersion to normal temperature to obtain a uniform solid content concentration of 5.0 mass %. Water-dispersible copolymerized polyester resin liquid. Further, after dispersing 3 parts by mass of aggregated silica particles (manufactured by FUJI SILYSIA Co., Ltd., SYLYSIA 310) in 50 parts by mass of water, 99.46 parts by mass of the above-mentioned water-dispersible copolymerized polyester resin liquid was used. 0.54 parts by mass of the aqueous dispersion of SYLYSIA 310 was added to the mixture, and 20 parts by mass of water was added while stirring to obtain an adhesive modified coating liquid.

(Production Example 4 - Adjustment of Low Reflection Layer Coating Liquid A)

As vinylidene fluoride-based polymer particles, 571.4 g of an aqueous dispersion (solid content of vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer (=72.1/14.9/13 (mol %)) particles Concentration 45.5 mass %) was put into a 2 L glass-made separate flask, 37.1 g of Newcol 707SF (manufactured by Nippon Emulsifier Co., Ltd.) as an emulsifier, and 59.3 g of water were added, and the aqueous dispersion was adjusted by mixing well.

Next, 208.1 g of methyl methacrylate, 44.9 g of n-butyl acrylate, and 7.0 g of acrylic acid were added to a 1 L glass flask to adjust a monomer solution.

The temperature inside the separable flask was raised to 80°C, and the total amount of the monomer solution was added to the aqueous dispersion of the vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer particles over 3 hours. In addition, simultaneously with the addition of the monomer solution, polymerization was performed while adding 41.1 g of 1 mass % of ammonium sulfate seven times every 30 minutes. After 5 hours from the start of polymerization, the reaction solution was cooled to room temperature to terminate the reaction, and an aqueous dispersion of acrylic-fluoro composite polymer particles was obtained. (Solid content concentration: 52.0 mass %) The mass ratio of the fluoropolymer part to the acrylic polymer part in the obtained acrylic-fluoro composite polymer particles was 50/50.

唑啉交聯劑WS-700(日本觸媒製EPOCROS製)、1.75質量份的膠質氧化矽粒子SNOWTEX ST-ZL(日產化學工業製)、0.30質量份的矽系界面活性劑並進行攪拌，得到低反射層塗布液A。 12.12 parts by mass of the acrylic-fluorine composite polymer particle aqueous dispersion, 61.47 parts by mass of water, 20.00 parts by mass of isopropanol, 2.80 parts by mass of

An oxazoline crosslinking agent WS-700 (manufactured by Nippon Shokubai Co., Ltd. EPOCROS), 1.75 parts by mass of colloidal silicon oxide particles SNOWTEX ST-ZL (manufactured by Nissan Chemical Industries, Ltd.), and 0.30 mass parts of a silicon-based surfactant were stirred to obtain Low reflection layer coating solution A.

(Production Example 5 - Adjustment of Low Reflection Layer Coating Liquid B)

As vinylidene fluoride-based polymer particles, 571.4 g of an aqueous dispersion (solid content of vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer (=72.1/14.9/13 (mol %)) particles Concentration 45.5 mass %) was put into a 2 L glass-made separate flask, 37.1 g of Newcol 707SF (manufactured by Nippon Emulsifier Co., Ltd.) as an emulsifier, and 59.3 g of water were added, and the aqueous dispersion was adjusted by mixing well.

Next, 208.1 g of methyl methacrylate, 44.9 g of n-butyl acrylate, and 7.0 g of acrylic acid were added to a 1 L glass flask to adjust a monomer solution.

The temperature inside the separable flask was raised to 80°C, and the total amount of the monomer solution was added to the aqueous dispersion of the vinylidene fluoride/tetrafluoroethylene/chlorotrifluoroethylene copolymer particles over 3 hours. In addition, simultaneously with the addition of the monomer solution, polymerization was performed while adding 41.1 g of 1 mass % of ammonium sulfate seven times every 30 minutes. After 5 hours from the start of polymerization, the reaction solution was cooled to room temperature to complete the reaction, and an aqueous dispersion (solid content concentration: 52.0 mass %) of acrylic-fluoro composite polymer particles was obtained. The mass ratio of the fluoropolymer moiety to the acrylic polymer moiety in the obtained acrylic-fluoro composite polymer particles was 50/50.

唑啉交聯劑WS-700(日本觸媒製EPOCROS製)、1.75質量份的膠質氧化矽粒子SNOWTEX ST-ZL(日產化學工業製)及0.30質量份的矽系界面活性劑並進行攪拌，得到低反射層塗布液B。 8.08 parts by mass of the acrylic-fluorine composite polymer particle aqueous dispersion, 61.47 parts by mass of water, 20.00 parts by mass of isopropanol, 8.40 parts by mass of

An oxazoline crosslinking agent WS-700 (manufactured by Nippon Shokubai Co., Ltd. EPOCROS), 1.75 parts by mass of colloidal silicon oxide particles SNOWTEX ST-ZL (manufactured by Nissan Chemical Industries, Ltd.), and 0.30 mass parts of a silicon-based surfactant were stirred to obtain Low reflection layer coating solution B.

(Polarizer Protective Film 1)

90 parts by mass of particle-free PET (A) resin particles as a raw material for the intermediate layer of the base film and 10 parts by mass of PET (B) resin particles containing an ultraviolet absorber were dried under reduced pressure at 135°C (1 Torr) After 6 hours, it was supplied to the extruder 2 (for the middle layer II layer), and the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, at 285. dissolve at °C. The two polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy of 10 μm particles with 95% retention), laminated in two types of three-layer confluence sections, extruded into sheets from a nozzle, and electrostatically applied. The casting method was wound around a casting drum having a surface temperature of 30° C. to cool and solidify, and an unstretched film was produced. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer might be 10:80:10.

Next, the low-reflection layer coating solution A of Production Example 4 was applied on the side of the unstretched PET film on which the low-reflection layer was formed by the reverse roll method, so that the coating weight after drying was 0.108 g/m ² , and the layer had a low The adhesive modified coating liquid of Production Example 3 was applied on the opposite side of the surface of the reflective layer so as to be 0.080 g/m ² , and then dried at 80° C. for 20 seconds.

The unstretched film on which the coating layer was formed was guided to a tenter stretching machine, and the end portion of the film was sandwiched by clips, and was guided to a hot-air zone with a temperature of 125° C., and stretched 4.0 times in the width direction. Next, while maintaining the width extended in the width direction, the temperature was 225° C. for 10 seconds, and further relaxation treatment was performed by 3.0% in the width direction to obtain a polarizer protective film 1 with a film thickness of about 100 μm.

The retardation value (Re) of the polarizer protective film 1 was 10300 nm, the retardation value (Rth) in the thickness direction was 12350 nm, Re/Rth was 0.834, and the NZ coefficient was 1.699.

In addition, in the reflection spectrum of the polarizer protective film 1, the bottom wavelength is 630 nm, and the reflectance at the wavelength of 630 nm is 1.71%.

(Polarizer protective film 2)

90 parts by mass of particle-free PET (A) resin particles as a raw material for the intermediate layer of the base film and 10 parts by mass of PET (B) resin particles containing an ultraviolet absorber were dried under reduced pressure at 135°C (1 Torr) After 6 hours, it was supplied to the extruder 2 (for the middle layer II layer), and the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, at 285. dissolve at °C. The two polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy of 10 μm particles with 95% retention), laminated in two types of three-layer confluence sections, extruded into sheets from a nozzle, and electrostatically applied. The casting method was wound around a casting drum having a surface temperature of 30° C. to cool and solidify, and an unstretched film was produced. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer might be 10:80:10.

Next, the coating solution B of Production Example 5 was applied on the side of the unstretched PET film on which the low-reflection layer was formed by the reverse roll method, so that the coating amount after drying was 0.09 g/m ² , and the low-reflection layer was laminated on the side of the unstretched PET film. The adhesive modified coating liquid of Production Example 3 was applied on the opposite side of the surface to be 0.08 g/m ² , and then dried at 80° C. for 20 seconds.

The unstretched film on which the coating layer was formed was guided to a tenter stretching machine, and the end portion of the film was sandwiched by clips, and was guided to a hot-air zone with a temperature of 125° C., and stretched 4.0 times in the width direction. Next, the stretched width in the width direction was maintained, the temperature was 225°C for 10 seconds, and the relaxation treatment was further performed by 3.0% in the width direction to obtain a polarizer protective film 2 with a film thickness of about 100 µm.

The retardation value (Re), the retardation value (Rth) in the thickness direction, the Re/Rth, and the NZ coefficient of the polarizer protective film 2 are the same as those of the polarizer protective film 1 . The bottom wavelength of the reflection spectrum of the polarizer protective film 2 is 550 nm, and the reflectance at the wavelength of 550 nm is 1.96%.

(Polarizer protective film 3)

90 parts by mass of particle-free PET (A) resin particles as a raw material for the intermediate layer of the base film and 10 parts by mass of PET (B) resin particles containing an ultraviolet absorber were dried under reduced pressure at 135°C (1 Torr) After 6 hours, it was supplied to the extruder 2 (for the middle layer II layer), and the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, at 285. dissolve at °C. The two polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy of 10 μm particles with 95% retention), laminated in two types of three-layer confluence sections, extruded into sheets from a nozzle, and electrostatically applied. The casting method was wound around a casting drum having a surface temperature of 30° C. to cool and solidify, and an unstretched film was produced. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer might be 10:80:10.

Next, the coating solution A of Production Example 4 was applied on the side of the unstretched PET film on which the low-reflection layer was formed by the reverse roll method, so that the coating amount after drying was 0.106 g/m ² , and the low-reflection layer was laminated on the side of the film. The adhesive modified coating liquid of Production Example 3 was applied on the opposite side of the surface to be 0.080 g/m ² , and then dried at 80° C. for 20 seconds.

The unstretched film on which the coating layer was formed was guided to a tenter stretching machine, and the end portion of the film was sandwiched by clips, and was guided to a hot-air zone with a temperature of 125° C., and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the temperature was 225° C. for 10 seconds, and a relaxation treatment of 3.0% was further performed in the width direction to obtain a polarizer protective film 3 with a film thickness of about 100 μm.

The retardation value (Re), the retardation value (Rth) in the thickness direction, the Re/Rth, and the NZ coefficient of the polarizer protective film 3 are the same as those of the polarizer protective film 1 . The bottom wavelength of the reflection spectrum of the polarizer protective film 3 is 615 nm, and the reflectance at the wavelength of 615 nm is 1.71%.

(Polarizer protective film 4)

90 parts by mass of particle-free PET (A) resin particles as a raw material for the intermediate layer of the base film and 10 parts by mass of PET (B) resin particles containing an ultraviolet absorber were dried under reduced pressure at 135°C (1 Torr) After 6 hours, it was supplied to the extruder 2 (for the middle layer II layer), and the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, at 285. dissolve at °C. The two polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy of 10 μm particles with 95% retention), laminated in two types of three-layer confluence sections, extruded into sheets from a nozzle, and electrostatically applied. The casting method was wound around a casting drum having a surface temperature of 30° C. to cool and solidify, and an unstretched film was produced. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer might be 10:80:10.

Next, the coating solution A of Production Example 4 was applied on the side of the unstretched PET film on which the low-reflection layer was formed by the reverse roll method, so that the coating amount after drying was 0.111 g/m ² , and the low-reflection layer was laminated on the side of the film. The adhesive modified coating liquid of Production Example 3 was applied on the opposite side of the surface to be 0.080 g/m ² , and then dried at 80° C. for 20 seconds.

The unstretched film on which the coating layer was formed was guided to a tenter stretching machine, and the end portion of the film was sandwiched by clips, and was guided to a hot-air zone with a temperature of 125° C., and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the temperature was 225° C. for 10 seconds, and further relaxation treatment was performed by 3.0% in the width direction to obtain a polarizer protective film 4 with a film thickness of about 100 μm.

The retardation value (Re), the retardation value (Rth) in the thickness direction, the Re/Rth, and the NZ coefficient of the polarizer protective film 4 are the same as those of the polarizer protective film 1 .

The bottom wavelength of the reflection spectrum of the polarizer protective film 4 is 645 nm, and the reflectance at the wavelength of 645 nm is 1.71%.

(Polarizer protective film 5)

90 parts by mass of particle-free PET (A) resin particles as a raw material for the intermediate layer of the base film and 10 parts by mass of PET (B) resin particles containing an ultraviolet absorber were dried under reduced pressure at 135°C (1 Torr) After 6 hours, it was supplied to the extruder 2 (for the middle layer II layer), and the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, at 285. dissolve at °C. The two polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy of 10 μm particles with 95% retention), laminated in two types of three-layer confluence sections, extruded into sheets from a nozzle, and electrostatically applied. The casting method was wound around a casting drum having a surface temperature of 30° C. to cool and solidify, and an unstretched film was produced. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer might be 10:80:10.

Next, the low-reflection layer coating solution B of Production Example 5 was applied on the side of the unstretched PET film on which the low-reflection layer was formed by the reverse roll method, so that the coating weight after drying was 0.10 g/m ² , and the layer had a low The adhesive modification coating liquid of Production Example 3 was applied on the opposite side of the surface of the reflective layer to be 0.08 g/m ² , and then dried at 80° C. for 20 seconds.

The unstretched film on which the coating layer was formed was guided to a tenter stretching machine, and the end portion of the film was sandwiched by clips, and was guided to a hot-air zone with a temperature of 125° C., and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the temperature was 225° C. for 10 seconds, and the relaxation treatment was further performed by 3.0% in the width direction to obtain a polarizer protective film 5 with a film thickness of about 100 μm.

The retardation value (Re) of the polarizer protective film 5 was 10300 nm, the retardation value (Rth) in the thickness direction was 12350 nm, Re/Rth was 0.834, and the NZ coefficient was 1.699.

In addition, the reflection spectrum of the polarizer protective film 5 has a bottom wavelength of 630 nm and a reflectance of 1.96% at a wavelength of 630 nm.

(Polarizer Protective Film 6)

90 parts by mass of particle-free PET (A) resin particles as a raw material for the intermediate layer of the base film and 10 parts by mass of PET (B) resin particles containing an ultraviolet absorber were dried under reduced pressure at 135°C (1 Torr) After 6 hours, it was supplied to the extruder 2 (for the middle layer II layer), and the PET (A) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I layer and the outer layer III), respectively, at 285. dissolve at °C. The two polymers were filtered with a stainless steel sintered filter material (nominal filtration accuracy of 10 μm particles with 95% retention), laminated in two types of three-layer confluence sections, extruded into sheets from a nozzle, and electrostatically applied. The casting method was wound around a casting drum having a surface temperature of 30° C. to cool and solidify, and an unstretched film was produced. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer might be 10:80:10.

Next, the adhesive modified coating liquid of Production Example 3 was coated on both sides of the unstretched PET film by the reverse roll method, so that the coating amount after drying on the low-reflection side was 0.10 g/m ² , and the opposite side of the low-reflection side was was 0.08 g/m ² , followed by drying at 80° C. for 20 seconds.

The unstretched film on which the coating layer was formed was guided to a tenter stretching machine, and the end portion of the film was sandwiched by clips, and was guided to a hot-air zone with a temperature of 125° C., and stretched 4.0 times in the width direction. Next, while maintaining the width extended in the width direction, the temperature was 225° C. for 10 seconds, and further relaxation treatment was performed by 3.0% in the width direction to obtain a polarizer protective film 6 with a film thickness of about 100 μm.

The retardation value (Re) of the polarizer protective film 6 , the retardation value (Rth) in the thickness direction, the Re/Rth, and the NZ coefficient are the same as those of the polarizer protective film 1 .

The bottom wavelength of the reflection spectrum of the polarizer protective film 6 is 600 nm, and the reflectance at the wavelength of 600 nm is 3.7%.

(Example 1)

In a manner that the transmission axis of the polarizer is perpendicular to the fast axis of the film, the polarizer protective film 1 is attached to one side of the polarizer containing PVA and iodine, and a TAC film (Fujifilm (stock) Company made, thickness 80μm), to make polarizing plate. In addition, a polarizer was laminated on the surface of the polarizer protective film on which the low reflection layer was not laminated to prepare a polarizing plate. The polarizing plate on the viewing side of REGZA 43J10X manufactured by Toshiba Corporation was replaced with the polarizing plate prepared above so that the polyester film and the liquid crystal were on the opposite side (remote position) to prepare a liquid crystal display device. Further, the replacement was performed so that the direction of the transmission axis of the polarizing plate was the same as the direction of the transmission axis of the polarizing plate before replacement.

(Comparative Example 1)

In Example 1, a liquid crystal display device was produced in the same manner except that the polarizer protective film 2 was used instead of the polarizer protective film 1 .

(Example 2)

In Example 1, a liquid crystal display device was produced in the same manner except that the polarizer protective film 3 was used instead of the polarizer protective film 1 .

(Example 3)

In Example 1, a liquid crystal display device was produced in the same manner except that the polarizer protective film 4 was used instead of the polarizer protective film 1 .

(Example 4)

In Example 1, a liquid crystal display device was produced in the same manner except that the polarizer protective film 5 was used instead of the polarizer protective film 1 .

(Comparative Example 2)

In Example 1, a liquid crystal display device was produced in the same manner except that the polarizer protective film 6 was used instead of the polarizer protective film 1 .

The liquid crystal display devices of Examples 1 to 4 and Comparative Examples 1 to 2 were placed side by side, and the screen was visually observed from the front and oblique directions in a dark place. As a result, the liquid crystal display device of Example 1 was the most capable of suppressing the occurrence of rainbow spots. The order of suppressing rainbow spots was Examples 2 and 3, Example 4, Comparative Example 1, and Comparative Example 2. Note that the rainbow spots referred to here are fog-like rainbow spots observed on the screen when the observer moves the head while viewing the film from an oblique direction (when observing while changing the angle with respect to the normal direction of the film).

In Examples 1 to 4 and Comparative Examples 1 to 2, the thickness of the polyester film was 100 μm, which was replaced by a film of 80 μm (the hysteresis value (Re) was 8080 nm, the hysteresis value (Rth) in the thickness direction was 9960 nm, and the Re /Rth is 0.811, NZ coefficient is 1.733), and the liquid crystal display devices of Examples 1' to 4' and Comparative Examples 1' to 2' were prepared. As a result, the visibility was confirmed to be the same as those of Examples 1 to 4 and Comparative Examples 1 to 1. 2 tendencies of the same order.

In addition, in Examples 1 to 4 and Comparative Examples 1 to 2, the thickness of the polyester film was 100 μm, which was replaced by a film of 60 μm (the hysteresis value (Re) was 6060 nm, and the hysteresis value (Rth) in the thickness direction was 7470 nm. , Re/Rth is 0.811, NZ coefficient is 1.733) to manufacture the liquid crystal display devices of Examples 1" to 4" and Comparative Examples 1" to 2", and the results are confirmed to be the same as those of Examples 1 to 4 and Comparative Examples regarding visibility. 1 to 2 tend to be in the same order.

Industrial Availability

The liquid crystal display device and the polarizing plate of the present invention can ensure good visual recognition, which can obviously suppress the occurrence of rainbow spots at any angle, which is extremely helpful to the industry.

Claims (8)

A liquid crystal display device, which is a liquid crystal display device having a backlight source, two polarizers, and a liquid crystal cell disposed between the two polarizers, characterized in that: the backlight source is above 400nm and less than 495nm, 495nm A white light source having an emission spectrum with a peak top of the emission spectrum in each wavelength region of not less than 600 nm and not more than 600 nm and not more than 780 nm, and the half-value width of the peak with the highest peak intensity in the wavelength region of not less than 600 nm and not more than 780 nm is less than 5 nm; At least one polarizer among the polarizers is laminated with a polyester film on at least one side of the polarizer; the polyester film has a retardation value of 1500 nm or more and 30000 nm or less; the surface of one side of the polyester film is The anti-reflection layer and/or the low-reflection layer are laminated; the polyester film with the anti-reflection layer and/or the low-reflection layer is laminated. The reflection spectrum measured from the side where the anti-reflection layer and/or the low-reflection layer is laminated is in The wavelength region of 600 nm or more and 780 nm or less has a bottom wavelength, and the reflectance at the bottom wavelength is 2% or less. The liquid crystal display device of claim 1, wherein the light emission spectrum of the backlight light source has a half-value width of a peak with the highest peak intensity in a wavelength region of 400 nm or more and less than 495 nm, and a peak value of 5 nm or more in a wavelength region of 495 nm or more and less than 600 nm. Among them, the half-value width of the peak with the highest peak intensity is 5 nm or more. The liquid crystal display device of claim 1 or 2, wherein the white light source comprises a fluoride phosphor. The liquid crystal display device of claim 1 or 2, wherein the white light source is a white light emitting diode. The liquid crystal display device of claim 1 or 2, wherein in the polarizer, the transmission axis of the polarizer is perpendicular to the fast axis of the polyester film. A polarizer protective film, which is a polarizer protective film with an anti-reflection layer and/or a low-reflection layer laminated on one side of a polyester film, characterized in that the polyester film has a hysteresis of more than 1500 nm and less than 30000 nm Value; the polyester film with anti-reflection layer and/or low-reflection layer is laminated, the reflection spectrum measured from the side where anti-reflection layer and/or low-reflection layer is laminated has bottom wavelength in the wavelength region above 600nm and below 780nm , the reflectance at the bottom wavelength is less than 2%. A polarizer, which is laminated on at least one side of a polarizer with the polarizer protective film of claim 6. The polarizing plate of claim 7, wherein the transmission axis of the polarizer is perpendicular to the fast axis of the polyester film.