JP2015224267A - Polyester film, method for producing polyester film, polarizing plate, image display device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a polyester film capable of suppressing generation of iridescent irregularity and improving display quality of a liquid crystal display device when incorporated into a liquid crystal display device; a method for producing a polyester film; a polarizing plate; an image display device; and a liquid crystal display device.SOLUTION: There is provided a polyester film which comprises a polyester and is obtained by uniaxially stretching in the film width direction, wherein the retardation Re in the in-plane direction is 4000 to 20000 nm, the sub-peak melting temperature (Tsm) is 130 to 190°C, the aspect ratio of the length in the film width direction to the direction orthogonal to the film width direction is 2 or more, the length in the film width direction is 10 μm or more and the number of concave or convex shapes having a concave or convex step of 0.1 μm or more is 0.3 pieces/mor less.

Description

  The present invention relates to a polyester film, a method for producing a polyester film, a polarizing plate, an image display device, and a liquid crystal display device.

  Image display devices such as liquid crystal display (LCD), plasma display (PDP), electroluminescence display (OELD or IELD), field emission display (FED), touch panel, and electronic paper have a polarizing plate on the display screen side of the image display panel. Has been placed.

The polarizing plate is formed of a polarizer containing polyvinyl alcohol and a protective film bonded to both sides of the polarizer, and the protective film has a deterioration in image quality due to optical distortion (rainbow unevenness; in other words, the protective film is obliquely oriented. Conventionally, cellulose ester films having small optical anisotropy (Re value: retardation value in the in-plane direction) have been mainly used to prevent rainbow-like color spots when observed from above.
In recent years, a polyester film having birefringence (high optical distortion) is controlled by controlling the reflectance of the surface (see Patent Document 1) or by stretching it in a uniaxial direction to increase the Re value than usual. It has been practiced to make the unevenness difficult to see (see Patent Document 2).

JP 2009-14886 A International Publication WO2012 / 157663

On the other hand, there is a trend toward higher definition and / or larger area as a trend of image display devices on the market.
However, when the high-re polyester film described in Patent Document 2 is used as a protective film for a polarizing plate when the image display device has a high definition and / or a large area, the present inventors have a problem in display quality. It became clear by their examination. In particular, in the image display apparatus of 4K2K (the number of pixels means a high resolution image of around 4000 × 2000 pixels) that will become the mainstream in the future, display quality is improved when a polyester film is used as a protective film for a polarizing plate. Necessary.

  The present invention aims to solve the above problems. Specifically, the problem to be solved by the present invention is to provide a polyester film capable of suppressing the occurrence of rainbow unevenness and improving the display quality of the liquid crystal display device when incorporated in the liquid crystal display device. .

As a result of intensive studies by the present inventors, in an image display device such as a high-definition and / or large-area liquid crystal display device, the aspect ratio of the length in the film width direction to the direction perpendicular to the film width direction is 2 or more. Yes (long in the width direction of the film), the length in the width direction of the film is 10 μm or more, and the concave or convex shape in which the convex part or the concave step is 0.1 μm or more is visually recognized as a defect in the polarizing plate state. Control of the number of concave or convex shapes per unit area extending in the width direction of the film is insufficient at the level at which there was no problem with conventional low-definition or small-area image display devices. Experiments have revealed that it is necessary to reduce the number to less than (eg, 0.3 / m ² or less).

  In addition, since the polyester film having Re of several hundreds of nanometers that cannot solve the rainbow unevenness that has been known so far is usually stretched in the biaxial direction, It was also found that there was no problem of deterioration of display quality due to the convex shape, the concave extending in the film width direction or the defect due to the convex shape. That is, the problem of deterioration in display quality that occurs when the image display device has a higher definition and / or a larger area occurs for the first time when a polyester film such as PET having a high Re is used to eliminate rainbow unevenness. This is a new problem that has not been known so far. This problem is particularly a problem with 4K2K image display devices.

As a result of intensive studies conducted by the present inventors under such circumstances, the polyester film is uniaxially stretched in the film width direction, and the retardation Re in the in-plane direction is 4000 to 20000 nm. If the sub-peak temperature Tsm is 130 to 190 ° C. and the number of concave or convex shapes extending in the specific film width direction is 0.3 / m ² or less, the occurrence of rainbow unevenness can be suppressed, and a liquid crystal display device can be used. It was found that a polyester film that can improve the display quality of the liquid crystal display device when incorporated can be provided.
The present invention, which is a specific means for achieving the above object, is as follows.

[1] A polyester film containing polyester and uniaxially stretched in the film width direction,
In-plane retardation Re is 4000 to 20000 nm,
The melting sub-peak temperature Tsm is 130-190 ° C.,
The aspect ratio of the length in the film width direction to the direction perpendicular to the film width direction is 2 or more, the length in the film width direction is 10 μm or more, and the convex or concave step is 0.1 μm or more. A polyester film having a shape of 0.3 pieces / m ² or less.
[2] The polyester film according to [1] preferably has a concave or convex shape of 0.1 pieces / m ² or less.
[3] The polyester film according to [1] or [2] preferably has an average value of a concave or convex convex part or concave step of 0.1 μm or less.
[4] The polyester film according to any one of [1] to [3] is preferably obtained by polymerizing polyester using a catalyst containing a titanium atom.
[5] In the polyester film according to any one of [1] to [4], the amount of the ultraviolet absorber is preferably 0.1% by mass or less based on the polyester.
[6] The polyester film according to any one of [1] to [5] preferably has a common logarithm logSR of the surface resistivity SR of at least one surface of the polyester film of 10 or less; The unit of the surface resistivity SR is Ω / sq.
[7] The polyester film according to any one of [1] to [6] is preferably used for a polarizing plate protective film.
[8] A polarizing plate comprising a polarizer and the polyester film according to any one of [1] to [7].
[9] The polarizing plate according to [8] further has a cellulose acylate film,
It is preferable that a polyester film is laminated on one surface of the polarizer and a cellulose acylate film is laminated on the other surface.
[10] In the polarizing plate according to [8] or [9], it is preferable that a polyester film is laminated with a polarizer via an ultraviolet curable adhesive.
[11] The polyester film according to any one of [1] to [7] or the polarizing plate according to any one of [8] to [10], wherein the number of pixels is 3000 or more in width, and An image display device having a length of 1500 or more.
[12] a liquid crystal cell;
The polyester film according to any one of [1] to [7] or any one of [8] to [10] disposed on at least one surface of the backlight side and the front side of the liquid crystal cell. A polarizing plate of
A liquid crystal display device in which the number of pixels is 3000 or more in the horizontal direction and 1500 or more in the vertical direction.
[13] The liquid crystal display device according to [12] preferably has, as a polyester film, a polyester film in which the amount of the ultraviolet absorber is 0.1% by mass or less based on the polyester, on the backlight side of the liquid crystal cell. .
[14] a melting step of melting polyester with an extruder;
A filtration step of filtering the melted polyester through a filter equipped with a filter;
A film forming step of extruding the filtered polyester into a sheet form from a die and forming an unstretched polyester film by cooling and solidifying by adhering it onto the cooling drum;
A step of stretching the unstretched polyester film while holding it with a clip in a tenter-type stretching device having a clip that runs along a pair of rails installed on both sides of the film conveyance path;
Including a heat setting step of heating the polyester film after transverse stretching to the maximum temperature in the tenter,
The manufacturing method of the polyester film whose opening of the filter installed in a filtration process is 8 micrometers or less.
[15] The method for producing a polyester film according to [14] includes three or more sets of filtration devices in the filtration step,
The filter aperture Xμm installed in the first set of filtration devices, counted from the upstream side of the filtration process, the filter aperture Yμm installed in the second set of filtration devices, and the third set of filtration devices It is preferable that the aperture Z μm of the formed filter satisfies the following formula A.
Formula A ... Z≤X <Y
[16] In the method for producing a polyester film according to [14] or [15], the extruder used in the melting step is a twin-screw extruder,
The temperature of the polyester extruded from the die is preferably 280 ° C. or higher and 320 ° C. or lower.
[17] The method for producing a polyester film according to any one of [14] to [16] uses an electrostatic application electrode when the polyester is brought into close contact with the cooling drum in the film forming step.
The temperature of the polyester when in close contact with the cooling drum is 280 ° C. or higher,
The distance between the electrostatic application electrode and the point where the polyester adheres to the cooling drum is 15 mm or less,
The applied voltage of the electrostatic application electrode is preferably 9 kV or more.
[18] In the method for producing a polyester film according to any one of [14] to [17], the unstretched polyester film is peeled from the cooling drum to the entrance of the tenter-type stretching device. A transport roll is installed,
It is preferable that 50% or more of the transport rolls in contact with the unstretched polyester film are drive-type transport rolls.
[19] The method for producing a polyester film according to any one of [14] to [18] further includes a step of applying a coating solution to the unstretched polyester film,
The coating method of the coating liquid is bar coating,
It is preferable to use a rolling bar for the bar coat.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester film which can suppress generation | occurrence | production of a rainbow nonuniformity and can improve the display quality of a liquid crystal display device when it incorporates in a liquid crystal display device can be provided.

It is the schematic which shows the cross section of an example of the polarizing plate of this invention.

The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
Moreover, although mentioned later in detail, a polyester film is normally obtained by conveying using a roll etc. and extending | stretching. At this time, the film conveyance direction is also referred to as MD (Machine Direction) direction. Moreover, the conveyance direction of a film is also called the longitudinal direction of a film. The film transport direction is also called the longitudinal direction, stretching in the film transport direction is called longitudinal stretching, and contraction in the film transport direction is also called longitudinal shrinkage.
The film width direction is a direction orthogonal to the longitudinal direction. In the film manufactured while transporting the film, the film width direction is also referred to as a direction orthogonal to the film transport direction, that is, a TD (Transverse Direction) direction. The direction orthogonal to the film transport direction is also referred to as the transverse direction, and stretching in the direction orthogonal to the film transport direction is also referred to as lateral stretching.

[Polyester film]
The polyester film of the present invention is a polyester film containing polyester and stretched in the film uniaxial width direction, having an in-plane retardation Re of 4000 to 20000 nm, and a melting subpeak temperature Tsm of 140 to 220 ° C. And the aspect ratio of the length in the film width direction with respect to the direction perpendicular to the film width direction is 2 or more, the length in the film width direction is 10 μm or more, and the convex or concave step is 0.1 μm or more. Or convex shape is 0.3 piece / m < ² > or less.
In the present specification, the aspect ratio of the length in the film width direction to the direction perpendicular to the film width direction is 2 or more, the length in the film width direction is 10 μm or more, and the convex or concave step is 0. A concave or convex shape that is 1 μm or more may be referred to as “a concave or convex shape extending in the film width direction”.
With such a configuration, the polyester film of the present invention can suppress the occurrence of rainbow unevenness and can improve the display quality of the liquid crystal display device when incorporated in the liquid crystal display device. Although not bound by any theory, when the retardation Re in the in-plane direction is 4000 to 20000 nm, the generation of rainbow unevenness can be suppressed by a mechanism similar to that of International Publication WO2012 / 157663.
Further, since the concave or convex shape extending in the film width direction is 0.3 pieces / m ² or less, the polyester film of the present invention has a high definition and / or a large area such as 4K2K. The concave or convex shape extending in the film width direction is difficult to be visually recognized as a defect even when incorporated in the film, and the display quality can be improved.
Moreover, when the melting sub-peak temperature Tsm is 140 to 220 ° C., the thermal dimensional change (150 ° C., 30 minutes) is improved and rainbow unevenness can be suppressed.

<Optical properties of polyester film>
The polyester film of the present invention is a polyester film formed by uniaxial stretching in the film width direction.
The in-plane retardation Re (retardation value) of the polyester film of the present invention which is a stretched polyester film is 4000 to 20000 nm, more preferably 5000 nm to 15000 nm. By setting Re to 4000 nm or more, rainbow unevenness (colored) from the front tends to be inconspicuous. In addition, the retardation Re in the in-plane direction of the stretched polyester film is represented by the following formula (1).

Re = (na−nb) × d (1)
Here, na is the refractive index in the in-plane slow axis direction of the polyester film, nb is the in-plane fast axis direction (direction perpendicular to the in-plane slow axis direction) of the polyester film, and d Is the thickness of the polyester film.

The retardation Rth in the thickness direction of the polyester film is preferably 4000 to 20000 nm, more preferably 5000 to 15000 nm, and particularly preferably 6000 to 15000 nm.
The retardation in the thickness direction means two birefringences ΔNxz (= | Nx−Nz |) and ΔNyz (= | Ny−Nz |) when viewed from the cross section in the film thickness direction, respectively, and the film thickness d. This is a parameter indicating the average retardation obtained. Nx, Ny, Nz and film thickness d (nm) are obtained by the same method as the measurement of retardation Re, and the average value of (ΔNxz × d) and (ΔNyz × d) is calculated to obtain a letter in the thickness direction. The foundation (Rth) can be determined.

<Physical properties of polyester film>
The polyester film of the present invention has a melting subpeak temperature (Tsm) of the polyester film of 140 to 220 ° C, preferably 150 ° C or higher and lower than 220 ° C, more preferably 150 ° C or higher and lower than 210 ° C, and further preferably 150 ° C. Less than 200 ° C. When the melting sub-peak temperature is 140 ° C. or higher, the thermal dimensional change (150 ° C., 30 minutes) is improved, the thermal dimensional change (150 ° C., 30 minutes) is improved, and rainbow unevenness can be suppressed. Further, when a coating layer such as a hard coat layer is provided on the polyester film, if the melting sub-peak temperature is 140 ° C. or higher, the hard coat layer is hardly cracked. On the other hand, when the melting subpeak temperature is 220 ° C. or lower, in the polarizing plate of the present invention described later, the deviation between the maximum elastic modulus at the end in the film width direction and the stretching direction of the polarizer can be reduced.
Although there is no restriction | limiting in particular in order to obtain the polyester film which satisfies the conditions of this melting subpeak temperature, For example, it can obtain by manufacturing a film on the extending | stretching conditions shown to the manufacturing method of the below-mentioned polyester film.

In the polyester film of the present invention, the aspect ratio of the length in the film width direction to the direction perpendicular to the film width direction is 2 or more, the length in the film width direction is 10 μm or more, and the convex or concave step is 0. A concave or convex shape of 1 μm or more, that is, a concave or convex shape extending in the film width direction is 0.1 piece / m ² or less. The concave or convex shape extending in the film width direction is preferably 0.2 pieces / m ² or less, and more preferably 0.3 pieces / m ² or less.
The upper limit value of the aspect ratio of the concave or convex shape extending in the film width direction (the aspect ratio of the length in the film width direction to the direction orthogonal to the film width direction) is not particularly limited, but is preferably, for example, 10 or less. More preferably, it is 5 or less.
The average length of the concave or convex film width direction extending in the film width direction is preferably 50 μm or less, more preferably 30 μm or less, and particularly preferably 10 μm or less.
The average value of the concave or convex convex portion or concave step (height) extending in the film width direction is preferably 0.1 μm or less, and particularly preferably 0.08 μm or less.

In the polyester film of the present invention, the common logarithm logSR of the surface resistivity SR of at least one surface of the polyester film is preferably 14 or less, more preferably 10 or less; provided that the unit of the surface resistivity SR Is Ω / sq.
Although there is no restriction | limiting in particular as a method of controlling logSR of the polyester film of this invention, For example, the method of adding an antistatic agent to the below-mentioned easily bonding layer can be mentioned, As this antistatic agent, the below-mentioned 4th is mentioned. A quaternary ammonium salt is preferred.

  The thickness of the polyester film is preferably 20 to 100 μm, and more preferably 30 to 70 μm. When the thickness of the polyester film is 20 μm or more, it tends to be handled easily, and when the thickness is 100 μm or less, there is a merit of thinning.

The polyester film of the present invention is uniaxially stretched in the film width direction. The polyester film formed by uniaxial stretching in the film width direction is preferably uniaxially oriented, and by confirming that it is uniaxially oriented, confirm that it is uniaxially stretched in the film width direction. Can do.
Moreover, it can confirm that it is the polyester film orientated uniaxially because the refractive index of a longitudinal direction is 1.590 or less. The refractive index in the longitudinal direction of the polyester film is more preferably 1.585 or less, and further preferably 1.580 or less. The degree of crystallinity of the polyester film is preferably 5% or more, more preferably 20% or more, and further preferably 30% or more.
The crystallinity can be calculated from the density of the film. That is, the density X (g / cm ³⁾ of the film density at a crystallinity of ^{0% Y = 1.335g / cm 3} , using density Z = 1.501g / cm ³ at 100% crystalline below The crystallinity (%) can be derived from the calculation formula.
Crystallinity = {Z × (XY)} / {X × (ZY)} × 100
The density can be measured according to JIS K7112.

<Layer structure of polyester film, surface treatment>
The polyester film of the present invention is preferably used for a polarizing plate protective film, in other words, used as a protective film for a polarizer.
The polyester film of the present invention preferably contains polyester and contains polyester as a main component (a component of 50% by mass or more of the polyester film). The polyester film of the present invention may be a monolayer film containing polyester or a multilayer film having a layer containing polyester. Further, the polyester film of the present invention may be a single layer film containing polyester as a main component or a multilayer film having a layer containing polyester as a main component.
Further, the polyester film of the present invention may be a single layer film or a multilayer film that has been subjected to surface treatment on both sides or one side. It may be surface modification by electron beam irradiation or the like, or may be thin film formation by coating or vapor deposition of polymer or metal.

<Material of polyester film>
(polyester)
The mass ratio of the polyester to the whole polyester film is usually 50 mass% or more, preferably 70 mass% or more, more preferably 90 mass% or more.
Examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate, and 1,4-cyclohexanedimethylene terephthalate, and two or more of them may be used as necessary. . Of these, polyethylene terephthalate is preferably used.

  Polyethylene terephthalate is a polyester having a structural unit derived from terephthalic acid as a dicarboxylic acid component and a structural unit derived from ethylene glycol as a diol component, and 80 mol% or more of all repeating units are preferably ethylene terephthalate. The structural unit derived from other copolymerization components may be included. Other copolymer components include isophthalic acid, p-β-oxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl, 4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid , Dicarboxylic acid components such as sebacic acid, 5-sodium sulfoisophthalic acid, 1,4-dicarboxycyclohexane, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, bisphenol A ethylene oxide adduct, polyethylene glycol And diol components such as polypropylene glycol and polytetramethylene glycol. These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. It is also possible to use an oxycarboxylic acid such as p-oxybenzoic acid in combination with the carboxylic acid component or diol component. As another copolymer component, a dicarboxylic acid component and / or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used. Polyethylene terephthalate can be produced by a direct polymerization method in which terephthalic acid and ethylene glycol and, if necessary, other dicarboxylic acid and / or other diol are directly reacted, dimethyl ester of terephthalic acid and ethylene glycol, and necessary Depending on the above, any production method such as a so-called transesterification method in which a dimethyl ester of another dicarboxylic acid and / or another diol is transesterified can be applied.

-Catalyst-
For the polymerization of polyester, Sb, Ge, Ti, Al-based catalysts are used, preferably Sb, Ti, Al-based catalysts, and more preferably Ti-based catalysts.
That is, the polyester film of the present invention is preferably obtained by polymerizing polyester using a catalyst containing a titanium atom.
By using the Ti-based catalyst, it is possible to obtain a polyester film that can improve the display quality of the liquid crystal display device when incorporated in the liquid crystal display device, compared to the case of using another catalyst (for example, Sb-based). This is presumed to be due to the following reasons.
Since the Ti-based catalyst has high catalytic activity, the required amount of addition is small. Further, since the reaction is performed under reduction, foreign matter precipitation as titanium oxide hardly occurs. Therefore, the reason why the display quality of the liquid crystal display device can be improved is that there are few foreign matters due to the catalyst and the defect failure is unlikely to occur.

・ Ti catalyst:
As the Ti-based catalyst, those described in JP-A-2013-47317 [0063] to [0090] can be used, and the contents described in this publication are incorporated herein. Among them, as the Ti catalyst, tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate Titanium alkoxide such as tetrabenzyl titanate, titanium oxide obtained by hydrolysis of titanium alkoxide, titanium-silicon or zirconium composite oxide obtained by hydrolysis of a mixture of titanium alkoxide and silicon alkoxide or zirconium alkoxide, titanium acetate, Titanium oxalate, potassium potassium oxalate, sodium oxalate, potassium titanate, sodium titanate, titanate-aluminum hydroxide mixture, titanium chloride, titanium chloride-salt Aluminum mixture, titanium acetylacetonate, an organic chelate titanium complex having an organic acid as a ligand, and the like are preferably used.
Although there is no restriction | limiting in particular as a method of superposing | polymerizing a polyester resin using the said Ti type catalyst, Specifically, it can superpose | polymerize according to [0063]-[0111] of Unexamined-Japanese-Patent No. 2013-47317.
The amount of Ti-based catalyst is preferably 1 to 50 ppm, more preferably 2 to 30 ppm, and still more preferably 3 to 15 ppm as the amount of Ti element with respect to the mass of the polyester.

・ Al catalyst:
As the Al-based catalyst, those described in [0013] to [0148] of WO2011 / 040161 ([0021] to [0123] of US2012 / 0183761) can be used with reference to these publications. The contents described are incorporated herein.
Although there is no restriction | limiting in particular as a method of superposing | polymerizing a polyester resin using the said Al type catalyst, Specifically, [0091]-[0094] of WO2012 / 008488 ([0144]-of US2013 / 0112271- [0153]) can be used to polymerize according to these publications, the contents of which are incorporated herein.
Such Al-based catalysts include, for example, [0052] to [0054], [0099] to [0104] of JP2012-122051 ([0045] to [0047], [0091] of WO2012 / 029725. To [0096]) can be prepared according to these publications, and the contents described in these publications are incorporated herein. The amount of the Al-based catalyst is preferably 3 to 80 ppm, more preferably 5 to 60 ppm, and still more preferably 5 to 40 ppm as the amount of Al element with respect to the mass of the polyester resin.

・ Sb catalyst:
As the Sb-based catalyst, those described in [0050], [0052] to [0054] of JP 2012-41519 A can be used.
Although there is no restriction | limiting in particular as a method of superposing | polymerizing a polyester resin using the said Sb type catalyst, Specifically, it can superpose | polymerize according to [0086]-[0087] of WO2012 / 157762.

(Other compounds in polyester)
The polyester film may be blended with known additives as necessary. Examples thereof include ultraviolet absorbers, particles, lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, and light resistance. Agents, impact modifiers, lubricants, dyes, pigments and the like. However, when using a polyester film as a polarizing plate protective film, since transparency is generally required, it is preferable to keep the additive amount to a minimum.

-UV absorber-
In the polyester film, an ultraviolet absorber can be contained in order to prevent the liquid crystal of the liquid crystal display from being deteriorated by ultraviolet rays (sunlight or the like) from the outside environment. The ultraviolet absorber is not particularly limited as long as it is a compound having ultraviolet absorbing ability and can withstand the heat applied in the production process of the polyester film.
When the polyester film of the present invention is used on the backlight side of the liquid crystal cell, an ultraviolet absorber is not necessary because external light does not enter the polyester film directly.

  As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a benzotriazole type, a cyclic imino ester type, a benzophenone type etc. are mentioned. From the viewpoint of durability, benzotriazole and cyclic imino ester are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

  Examples of the benzotriazole-based ultraviolet absorbers include, but are not limited to, 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'- Hydroxy-5 '-(methacryloyloxyhexyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-tert-butyl-5'-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2 -[2'-hydroxy-5'-tert-butyl-3 '-(methacryl Yloxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2′-hydroxy-5 ′ -(Methacryloyloxyethyl) phenyl] -5-methoxy-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-cyano-2H-benzotriazole, 2- [2 '-Hydroxy-5'-(methacryloyloxyethyl) phenyl] -5-tert-butyl-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-nitro-2H -Benzotriazole and the like.

  Moreover, as a commercial item, a benzotriazole type | system | group ultraviolet absorber can be mentioned, for example, It can be used as it is disperse | distributed to water as it is, using an emulsifier as needed. In addition, New Coat UVA-204W (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.), SE-2538E (trade name, manufactured by Taisei Fine Chemical Co., Ltd.) and the like can be exemplified as water-based benzotriazole ultraviolet absorbers.

  Examples of the cyclic imino ester-based ultraviolet absorber include, but are not limited to, 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazine-4, for example. -One, 2-phenyl-3,1-benzoxazin-4-one, 2- (1- or 2-naphthyl) -3,1-benzoxazin-4-one, 2- (4-biphenyl) -3, 1-benzoxazin-4-one, 2-p-nitrophenyl-3,1-benzoxazin-4-one, 2-m-nitrophenyl-3,1-benzoxazin-4-one, 2-p-benzoyl Phenyl-3,1-benzoxazin-4-one, 2-p-methoxyphenyl-3,1-benzoxazin-4-one, 2-o-methoxyphenyl-3,1-benzoxazin-4-one, -Cyclohexyl-3,1-benzoxazin-4-one, 2-p- (or m-) phthalimidophenyl-3,1-benzoxazin-4-one, N-phenyl-4- (3,1-benzoxazine -4-On-2-yl) phthalimide, N-benzoyl-4- (3,1-benzoxazin-4-one-2-yl) aniline, N-benzoyl-N-methyl-4- (3,1- Benzoxazin-4-one-2-yl) aniline, 2- (p- (N-methylcarbonyl) phenyl) -3,1-benzoxazin-4-one, 2,2′-bis (3,1-benzo Oxazin-4-one), 2,2′-ethylenebis (3,1-benzoxazin-4-one), 2,2′-tetramethylenebis (3,1-benzoxazin-4-one), 2, 2'-Decame Renbis (3,1-benzoxazin-4-one, 2,2 '-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] [In addition, 2,2'-p- Phenylenebis (3,1-benzoxazin-4-one)], 2,2′-m-phenylenebis (3,1-benzoxazin-4-one), 2,2 ′-(4,4 ′) -Diphenylene) bis (3,1-benzoxazin-4-one), 2,2 '-(2,6- or 1,5-naphthylene) bis (3,1-benzoxazin-4-one), 2, 2 '-(2-methyl-p-phenylene) bis (3,1-benzoxazin-4-one), 2,2'-(2-nitro-p-phenylene) bis (3,1-benzoxazine-4 -One), 2,2 '-(2-chloro-p-phenylene) bis (3 , 1-benzoxazin-4-one), 2,2 ′-(1,4-cyclohexylene) bis (3,1-benzoxazin-4-one), 1,3,5-tri (3,1- Benzoxazin-4-on-2-yl) benzene, 1,3,5-tri (3,1-benzoxazin-4-on-2-yl) naphthalene, 2,4,6-tri (3,1- Benzoxazin-4-one-2-yl) naphthalene, 2,8-dimethyl-4H, 6H-benzo (1,2-d; 5,4-d ′) bis (1,3) -oxazine-4,6 -Dione, 2,7-dimethyl-4H, 9H-benzo (1,2-d; 4,5-d ') bis (1,3) -oxazine-4,9-dione, 2,8-diphenyl-4H , 8H-Benzo (1,2-d; 5,4-d ′) bis (1,3) -oxazine-4,6-dio 2,7-diphenyl-4H, 9H-benzo (1,2-d; 4,5-d ′) bis (1,3) -oxazine-4,6-dione, 6,6′-bis (2- Methyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2-ethyl-4H, 3,1-benzoxazin-4-one), 6,6′-bis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-methylenebis (2- Phenyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-ethylenebis ( 2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′- Tylene bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-butylene bis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′- Oxybis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-oxybis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6′- Sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6′-sulfonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 6,6 '-Carbonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,6'-carbonylbis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7 , 7'-methylenebis (2 -Methyl-4H, 3,1-benzoxazin-4-one), 7,7'-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one), 7,7'-bis (2 -Methyl-4H, 3,1-benzoxazin-4-one), 7,7'-ethylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7'-oxybis ( 2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-sulfonylbis (2-methyl-4H, 3,1-benzoxazin-4-one), 7,7′-carbonyl Bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-bis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′- Bis (2-phenyl-4H, 3,1-benzoxazine-4 ON, 6,7′-methylenebis (2-methyl-4H, 3,1-benzoxazin-4-one), 6,7′-methylenebis (2-phenyl-4H, 3,1-benzoxazin-4-one) ) And the like.

  Among the above compounds, when considering the color tone, a benzoxazinone-based compound which is difficult to be yellowed is preferably used. As an example thereof, a compound represented by the following general formula (1) is more preferably used. It is done.

General formula (1)

In the general formula (1), R represents a divalent aromatic hydrocarbon group, and X ¹ and X ² are each independently selected from hydrogen or the following functional group group, but are not necessarily limited thereto. Absent.

  Functional group: alkyl group, aryl group, heteroaryl group, halogen, alkoxyl group, aryloxy group, hydroxyl group, carboxyl group, ester group, nitro group.

  Among the compounds represented by the general formula (1), 2,2 ′-(1,4-phenylene) bis [4H-3,1-benzoxazin-4-one] is particularly preferable in the present invention.

The amount of the ultraviolet absorber to be contained in the polyester film is usually 10.0% by mass or less, preferably 3.0% by mass or less based on the polyester. In the case where 10.0% by mass or less of the ultraviolet absorber is contained, the surface functionality is improved such that the ultraviolet absorber hardly bleeds out on the surface and the adhesiveness does not deteriorate. When using the polyester film of this invention as a protective film of the polarizing plate of the front side of a liquid crystal display device, it is preferable from a light-resistant viewpoint that a polyester film contains a ultraviolet absorber.
On the other hand, it was found that the volatile substance may increase during film formation by adding an ultraviolet absorber, and that the volatile substance is involved in the concave or convex shape extending in the film width direction, that is, the increase in defects.
From the viewpoint of suppressing the number of concave or convex shapes extending in the film width direction, the amount of the ultraviolet absorber is preferably 0.1% by mass or less with respect to the polyester, and more preferably does not contain the ultraviolet absorber. preferable. In particular, when the polyester film of the present invention is used as a protective film for a polarizing plate on the rear side of a liquid crystal display device, it is possible to reduce the ultraviolet absorber in the polyester film as much as possible. From the viewpoint of suppressing the number of

  Further, in the case of a polyester film having a multilayer structure, a film having at least a three-layer structure is preferable, and the ultraviolet absorber is preferably blended in the intermediate layer. By blending an ultraviolet absorber in the intermediate layer, this compound can be prevented from bleeding out to the film surface, and as a result, characteristics such as film adhesion can be maintained.

  If the polyester film prevents the deterioration of the liquid crystal due to ultraviolet rays, as a guide, the light transmittance of the polyester film at a wavelength of 380 nm is preferably 15% or less, more preferably 10% or less, and still more preferably. 5% or less.

-Particles-
The polyester film is preferably blended with particles mainly for the purpose of imparting easy slipping and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, it is also possible to use precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the polyester film manufacturing process.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.1-2 micrometers. If the average particle size is less than 0.01 μm, sufficient slipperiness cannot be imparted, or the particles may aggregate, resulting in insufficient dispersibility, which may reduce the transparency of the polyester film. . On the other hand, when the thickness exceeds 3 μm, the surface roughness of the polyester film becomes too rough, and a problem may occur when a functional layer such as a prism layer or a light diffusion layer is formed in a subsequent process.

  Furthermore, the particle content in the polyester film is usually in the range of 0.001 to 5 mass%, preferably 0.005 to 3 mass%. When the particle content is less than 0.001% by mass, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by mass, the transparency of the polyester film is insufficient. There are cases.

  The method for adding particles to the polyester film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  Moreover, in order to provide a haze to a polyester film, you may mix | blend an inorganic particle or an organic particle with a polyester film. As inorganic particles, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, zinc oxide and other inorganic particles, and these inorganic particles are surface treated with fatty acids and the like. What has been applied can be cited as a representative one. The organic particles include melamine beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), methyl methacrylate / styrene copolymer resin beads (refractive index 1.50 to 1.59). ), Polycarbonate beads (refractive index 1.55), polyethylene beads (refractive index 1.53), polyvinyl chloride beads (refractive index 1.46), silicone resin beads (refractive index 1.46) and the like are used. be able to.

<Hard coat layer>
The hard coat layer is provided on the surface of the polyester film in order to impart physical strength.

The polarizing plate of the present invention preferably has a hard coat layer formed by coating.
The hard coat layer is preferably formed using a composition for a hard coat layer containing an ionizing radiation curable resin which is a resin curable by ultraviolet rays and a photopolymerization initiator.

(resin)
Examples of the ionizing radiation curable resin include a compound having one or more unsaturated bonds such as a compound having an acrylate functional group, and the polarizing plate of the present invention has an acrylate hard coat layer. It is preferable from the viewpoint of improving the adhesion between the polyester film as the protective film for the polarizer and the hard coat layer laminated on the polyester film after wet heat aging. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include polymethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like, and ethylene oxide ( A polyfunctional compound modified with EEO), or a reaction product of the polyfunctional compound and (meth) acrylate (for example, poly (meth) acrylate ester of polyhydric alcohol). It is possible. In the present specification, “(meth) acrylate” refers to methacrylate and acrylate.

  In addition to the above compounds, polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyds having a relatively low molecular weight (number average molecular weight of 300 to 80,000, preferably 400 to 5000) having an unsaturated double bond. Resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, and the like can also be used as the ionizing radiation curable resin. The resin in this case includes all dimers, oligomers, and polymers other than monomers.

Preferred compounds as the acrylate include compounds having 3 or more unsaturated bonds. When such a compound is used, the crosslink density of the hard coat layer to be formed can be increased, and the coating hardness can be improved.
Specifically, in the present invention, pentaerythritol triacrylate, pentaerythritol tetraacrylate, polyester polyfunctional acrylate oligomer (3 to 15 functional), urethane polyfunctional acrylate oligomer (3 to 15 functional) and the like are used in appropriate combination. Is preferred.

  The ionizing radiation curable resin is used in combination with a solvent-drying resin (a thermoplastic resin or the like, which is a resin that forms a film only by drying the solvent added to adjust the solid content during coating). You can also. By using a solvent-drying resin in combination, coating defects on the coated surface can be effectively prevented. The solvent-drying resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and a thermoplastic resin can be generally used.

  The thermoplastic resin is not particularly limited. For example, a styrene resin, a (meth) acrylic resin, a vinyl acetate resin, a vinyl ether resin, a halogen-containing resin, an alicyclic olefin resin, a polycarbonate resin, or a polyester resin. Examples thereof include resins, polyamide-based resins, cellulose derivatives, silicone-based resins, rubbers, and elastomers. The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoints of film forming properties, transparency, and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

Moreover, the said composition for hard-coat layers may contain the thermosetting resin.
The thermosetting resin is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation Examples thereof include resins, silicon resins, polysiloxane resins, and the like.

(Photopolymerization initiator)
The photopolymerization initiator is not particularly limited, and known ones can be used. For example, specific examples of the photopolymerization initiator include acetophenones, benzophenones, Michler benzoylbenzoate, α-amylo. Examples include oxime esters, thioxanthones, propiophenones, benzyls, benzoins, and acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

  As the photopolymerization initiator, when the ionizing radiation curable resin is a resin system having a radical polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. may be used alone or in combination. It is preferable to use it. When the ionizing radiation curable resin is a resin system having a cationic polymerizable functional group, the photopolymerization initiator may be an aromatic diazonium salt, aromatic sulfonium salt, aromatic iodonium salt, metallocene compound, benzoin sulfone. It is preferable to use acid esters alone or as a mixture.

  As the photopolymerization initiator, in the case of an ionizing radiation curable resin having a radical polymerizable unsaturated group, 1-hydroxy-cyclohexyl-phenyl-ketone is compatible with the ionizing radiation curable resin, and yellowing is also caused. It is preferable for the reason that there are few.

  The content of the photopolymerization initiator in the hard coat layer composition is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the ionizing radiation curable resin. If it is less than 1 part by mass, the hardness of the hard coat layer in the optical laminate of the first invention may not be in the above-described range, and if it exceeds 10 parts by mass, up to the deep part of the coated film. This is because the ionizing radiation does not reach and internal curing is not promoted, and there is a risk that the pencil hardness of 3H or higher on the surface of the target hard coat layer may not be obtained.

  The minimum with more preferable content of the said photoinitiator is 2 mass parts, and a more preferable upper limit is 8 mass parts. When the content of the photopolymerization initiator is in this range, a hardness distribution does not occur in the film thickness direction, and uniform hardness is likely to occur.

(particle)
The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).

(Characteristics of hard coat layer)
The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.

  The hardness of the hard coat layer is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K-5400. Alternatively, the scratch resistance of the docoat layer is preferably as the wear amount of the test piece provided with the hard coat layer before and after the test is smaller in the Taber test according to JIS K-5400.

<Easily adhesive layer>
(Hard coat layer side easy adhesion layer)
The hard coat layer side easy-adhesion layer in the present invention has improved adhesion to various surface functional layers, and when used as a protective film on the front side of the front side polarizing plate, for example, the front side of a polyester film A hard coat layer, an antiglare layer, or the like can be effectively formed on the side opposite to the side where the polarizing film is bonded.

-Resin-
In the polarizing plate of the present invention, the hard coat layer side easy-adhesion layer contains at least one selected from polyester resin, acrylic resin and urethane resin, and is laminated on a polyester film and a polyester film as a protective film for a polarizer. From the viewpoint of improving the adhesion of the coat layer with time after wet heat, it is preferable.
Moreover, it is more preferable that the hard-coat layer side easily bonding layer contains 2 or more types chosen from a polyester resin, an acrylic resin, and a urethane resin.

(1) Polyester resin The polyester resin used for the hard-coat layer side easily bonding layer in this invention consists of the following polyvalent carboxylic acid and a polyvalent hydroxy compound as main structural components, for example. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6 -Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, 4-sodium sulfoisophthalic acid, 4-potassium sulfoisophthalic acid , 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride , Pyromellitic anhydride, phthalic anhydride, p -Hydroxybenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. Examples of the polyvalent hydroxy compound include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 , 3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p -Xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, Methylol - trimethylolpropane, sodium dimethylol ethyl sulfonate, potassium dimethylol ethyl sulfonate, or the like can be used potassium dimethylolpropionic acid. One or more compounds may be appropriately selected from these compounds, and a polyester resin may be synthesized by a conventional polycondensation reaction.

(1 ') Aliphatic polyester for hard coat layer side easy-adhesion layer As polyester for hard coat layer side easy adhesion layer, it is a polyester film as a protective film of a polarizer to use aliphatic polyester among the above-mentioned polyester resins. From the viewpoint of improving the adhesion between the hard coat layer laminated on the polyester film and the time after wet heat and the light resistance of the adhesion of the hard coat layer, alicyclic polyester is more preferred. The alicyclic polyester is composed of an alicyclic dicarboxylic acid as a main dicarboxylic acid component and an alicyclic diol as a main diol component.

(1′-1) Alicyclic dicarboxylic acid The alicyclic polyester is composed of an alicyclic dicarboxylic acid as a main dicarboxylic acid component. Here, the main dicarboxylic acid component means 80 mol% or more, preferably 90 mol% or more per total dicarboxylic acid component. Within this range, an easy-adhesion layer excellent in both heat resistance can be obtained.

  The alicyclic dicarboxylic acid is one in which two carboxyl groups are bonded to the alicyclic structure. Specifically, for example, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid 2,6-decahydronaphthalenedicarboxylic acid and 2,7-decahydronaphthalenedicarboxylic acid. Among these, 1,4-cyclohexanedicarboxylic acid is preferable because the molding temperature of the obtained polyester is close to the molding temperature of the conventional polyester and is easily available industrially. 1,4-Cyclohexanedicarboxylic acid has a trans form and a cis form as isomers, but the ratio of the trans form of 1,4-cyclohexanedicarboxylic acid to the cis form is preferably 80 from the viewpoint of heat resistance of the obtained polyester. / 20 to 100/0, more preferably 85/15 to 100/0, and particularly preferably 90/10 to 100/0.

  In addition to the alicyclic carboxylic acid, the alicyclic polyester may contain an aromatic dicarboxylic acid and / or an aliphatic dicarboxylic acid at a ratio of 20 mol% or less per total dicarboxylic acid component.

  Specific examples of the aromatic dicarboxylic acid include terephthalic acid, phthalic acid, isophthalic acid, phenylenedioxycarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, and 4,4′-diphenyl. Examples thereof include ketone dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and 2,6-naphthalenedicarboxylic acid. Specific examples of the aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, and dodecadicarboxylic acid.

(1′-2) Diol Component The alicyclic polyester is composed of an alicyclic diol as a main diol component. Here, the main diol component means 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, particularly preferably 97 mol% or more, based on the total diol component. Within this range, an easy-adhesion layer excellent in both transparency and heat resistance can be obtained.

  As the alicyclic diol, an alicyclic structure in which two hydroxyl groups are bonded, and an alicyclic diol in which two hydroxyl groups are bonded to a 5-membered or 6-membered ring is preferable. When the alicyclic diol is a 5-membered or 6-membered alicyclic diol, the heat resistance of the resulting polyester can be improved.

  Examples of the 5-membered alicyclic diol include 1,2-cyclopentanedimethanol, 1,3-cyclopentanedimethanol, bis (hydroxymethyl) tricyclo, and [5.2.1.0] decane. be able to.

  Examples of the 6-membered alicyclic diol include 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, Mention may be made of 6-membered ring diols such as 1,4-cyclohexanedimethanol and 2,2-bis (4-hydroxycyclohexyl) -propane.

  Among these alicyclic diols, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol are preferable, and 1,4-cyclohexanedimethanol is particularly preferable. 1,4-Cyclohexanedimethanol is highly reactive because the methylol group is in the para position, it is easy to obtain a polyester with a high polymerization degree, a polyester with a high glass transition temperature is obtained, and it is an industrial product and is available. This is because there is an advantage that it is easy. 1,4-Cyclohexanedimethanol has a trans isomer and a cis isomer, and a molar ratio of the trans isomer to the cis isomer is preferably in the range of 60/40 to 100/0.

  Examples of the diol component other than the alicyclic diol constituting the alicyclic polyester include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol.

  In the alicyclic polyester, it is preferable that 80 mol% or more of the dicarboxylic acid component is occupied by the alicyclic dicarboxylic acid and 80 mol% or more of the diol component is occupied by the alicyclic diol. The alicyclic dicarboxylic acid of the alicyclic polyester is preferably cyclohexane dicarboxylic acid, and the alicyclic diol is preferably cyclohexane dimethanol. The most preferred alicyclic polyester is an alicyclic polyester in which 80 mol% or more of the dicarboxylic acid component is occupied by cyclohexanedicarboxylic acid and 80 mol% or more of the diol component is occupied by cyclohexanedimethanol.

(2) Acrylic resin The acrylic resin used for the hard coat layer side easy-adhesion layer in the present invention is a polymerizable monomer having a carbon-carbon double bond, as typified by an acrylic or methacrylic monomer. It is the polymer which becomes. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing compounds such as meth) acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, vinyl propionate Various vinyl esters such as: Various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; Phosphorus-containing vinyl monomers; Various such as vinyl chloride and biridene chloride And various conjugated dienes such as butadiene.

(3) Urethane resin As the urethane resin used for the hard coat layer side easy-adhesion layer in the present invention, various urethane resins described in the polarizer-side easy adhesive layer described later can be used.

  In the present invention, the total content of the polyester resin, acrylic resin, and urethane resin in the hard coat layer side easy-adhesion layer is usually 10% by mass or more, preferably 30 to 95% by mass, and more preferably 40 to 95%. It is the range of mass%. When the amount is less than 10% by mass, sufficient adhesion to a hard coat layer or a surface functional layer such as an antiglare layer described later may not be obtained.

(4) Other binder polymers In the present invention, the hard coat layer-side easy-adhesion layer can be used in combination with a binder polymer other than polyester resin, acrylic resin or urethane resin in order to improve the coating surface state and transparency. It is.

  Specific examples of the binder polymer include polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like.

-Crosslinking agent-
Furthermore, in the hard coat layer side easy-adhesion layer, a crosslinking agent can be used in combination as long as the gist of the present invention is not impaired. By using a cross-linking agent, the easy-adhesion layer becomes stronger, so that the moisture and heat resistance and the scratch resistance may be further improved. Examples of the crosslinking agent include melamine compounds, epoxy compounds, oxazoline compounds, isocyanate compounds, carbodiimide compounds, and the like. These cross-linking agents may be used alone or in combination of two or more. Furthermore, when consideration is given to application to in-line coating, it is preferable to have water solubility or water dispersibility.

-Particles-
The hard coat layer side easy-adhesion layer may contain particles for the purpose of improving the blocking property and slipperiness of the easy-adhesion layer, such as inorganic particles such as silica, alumina, metal oxide, or crosslinked polymer particles. Organic particles such as

-Material for adjusting the refractive index-
Furthermore, when a clear surface functional layer such as a hard coat layer is formed in the hard coat layer side easy-adhesion layer, a material that adjusts the refractive index is used in order to reduce interference unevenness due to external light. It is also possible. Specifically, the material for adjusting the refractive index is a high refractive index material in the present invention. Examples of the high refractive index material include metal compounds, aromatic-containing organic compounds, sulfur atoms, bromine atoms and the like.

  Examples of the metal compound include titanium oxide, zinc oxide, tin oxide, antimony oxide, yttrium oxide, zirconium oxide, indium oxide, cerium oxide, ATO (antimony / tin oxide), and ITO (indium / tin oxide). Aluminum such as metal oxide, aluminum acetylacetonate, hydroxyaluminum diacetate, dihydroxyaluminum acetate; tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, titanium acetylacetate Nato, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine Titanium such as iron acetate and titanium ethyl acetoacetate; Iron such as iron acetylacetonate and iron acetate; Cobalt such as cobalt acetylacetonate; Copper acetate, copper acetate monohydrate, copper acetate multihydrate, copper acetyl Coppers such as acetonate; zincs such as zinc acetate, zinc acetate dihydrate, zinc acetylacetonate hydrate; zirconium acetate, zirconium normal propylate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetate Examples thereof include organic compounds having a metal element such as zirconium and zirconium compounds such as narate and zirconium bisacetylacetonate. These may be used alone or in combination of two or more.

Among the metal compounds described above, in the polarizing plate of the present invention, it is preferable that the hard coat layer-side easy-adhesion layer contains rutile-type titanium oxide fine particles described later.
Among the organic compounds having the metal element, an organic compound having a titanium element or a zirconium element is preferable in terms of particularly good coatability and transparency, and more preferably water-soluble when considering application to in-line coating. Titanium chelate compounds, water-soluble zirconium chelate compounds and the like are preferably used.

  Examples of aromatic-containing organic compounds include compounds having a high proportion of benzene rings such as condensed polycyclic aromatic compounds, bisphenol A compounds, biphenyl compounds, and fluorene compounds, which can be exemplified by naphthalene rings and anthracene rings. Examples thereof include compounds, ultraviolet absorber-containing compounds such as benzophenone and benzotriazole, and various heteroaromatic ring compounds. These may be used alone or in combination of two or more. An aromatic compound is effective because it can be incorporated into a polyester resin, an acrylic resin, or a urethane resin contained in the hard coat layer side easy-adhesion layer. Among these, polyester resins can easily use many aromatic compounds because of their structures. Among the aromatic compounds, naphthalene rings and bisphenol A compounds are useful because they can efficiently increase the refractive index of the easily adhesive layer. A melamine compound that can be used as a crosslinking agent is a compound having a high ratio of heteroaromatic rings, and is also a compound effective for increasing the refractive index.

In the polarizing plate of the present invention, the hard coat layer-side easy-adhesion layer contains rutile-type titanium oxide fine particles as described above, and a hard coat layer laminated on a polyester film as a polarizer protective film and a polyester film From the viewpoints of improving the adhesiveness of the film after wet heat and improving the light resistance of the adhesiveness of the hard coat layer.
In the present invention, the crystal system of the titanium oxide fine particles is preferably a rutile type. When the titanium oxide fine particles are of a crystal system other than the rutile type, such as an anatase type, the light resistance against external light is deteriorated. The crystal system of titanium oxide is measured using an X-ray diffractometer. When the titanium oxide fine particles are composed of a plurality of crystal systems, the case where the rutile type peak intensity ratio exceeds 50%, preferably 60%, is regarded as the rutile type titanium oxide fine particles.

  The content of the rutile-type titanium oxide fine particles in the easy adhesion layer is, for example, 0.5 to 75% by mass, preferably 0.5 to 55% by mass, more preferably 1 to 50 per 100% by mass of the total mass of the easy adhesion layer. % By mass. When the content of the titanium oxide fine particles exceeds 75% by mass, the cohesive force of the coating layer decreases and the adhesiveness deteriorates, which is not preferable, and when it is less than 0.5% by mass, the refractive index of the easy-adhesive layer decreases, When a hard coat layer is formed thereon, interference unevenness appears and becomes unfavorable.

  The average primary particle diameter of the rutile-type titanium oxide fine particles is preferably 4 to 25 nm, more preferably 5 to 25 nm. If the average primary particle diameter exceeds 25 nm, optical scattering occurs and the transparency of the easy-adhesion layer is unfavorable. On the other hand, if the average primary particle diameter is less than 4 nm, the aggregation of fine particles increases and the secondary particle diameter increases, resulting in optical scattering. Occurs, and the transparency of the easy-adhesion layer deteriorates, which is not preferable. In addition, the average primary particle diameter of the fine particles in the present invention is the number average primary particle diameter.

As rutile type titanium oxide fine particles, those having a refractive index of preferably 1.70 to 3.00, more preferably 1.90 to 2.80 are used. If the refractive index is less than 1.70, the volume fraction of the fine particles with respect to the polymer binder is increased, the cohesive force of the easy-adhesion layer is lowered, and it is not preferable. It is difficult and undesirable to use industrially.
The rutile-type titanium oxide fine particles are preferably used as an aqueous dispersion in order to reduce environmental burden and handle easily during application.

(Easily adhesive layer on the polarizer side)
The polarizer-side easy-adhesion layer in the present invention is a layer for improving adhesiveness with various functional layers, for example, adhesiveness with various adhesives used for laminating a polarizer and a polyester film. Can be used to improve.

  In order to improve the adhesion between the polyester film and the adhesive layer, the present inventors have examined compounds such as urethane resin and polyvinyl alcohol. As a result of further investigations, it has been found that the adhesiveness is relatively improved in the easy-adhesion layer using a combination of urethane resin and polyvinyl alcohol. On the other hand, as a result of various studies of the crosslinking agent, it was also found that the adhesiveness is relatively improved by combining the oxazoline compound and polyvinyl alcohol or the oxazoline compound and urethane resin and devising the composition ratio. . By combining these results and using urethane resin, polyvinyl alcohol, and oxazoline compound together, surprisingly, the adhesiveness was drastically improved and succeeded in forming an easy-adhesive layer that can be used for polarizer protection. did.

  The urethane resin contained in the polarizer-side easy-adhesion layer in the present invention is a polymer compound having a urethane resin in the molecule. Usually, urethane resin is prepared by reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

  Polycarbonate polyols are obtained from a polyhydric alcohol and a carbonate compound by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be mentioned. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of polycarbonate polyols obtained from these reactions include poly (1,6-hexylene) carbonate, poly (3- And methyl-1,5-pentylene) carbonate.

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, etc.).

  Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, and the like.

  Among the above polyols, polycarbonate polyols are more preferably used in order to improve the adhesiveness with various adhesive layers.

  Examples of the polyisocyanate compound used for obtaining the urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methanzi Cyanate, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

  A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with an isocyanate group. Alternatively, a chain extender having two amino groups can be mainly used.

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. And glycols such as glycols. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexane Alicyclic diamines, and the like of.

  The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into a skeleton of a urethane resin to form an ionomer is preferable because it is excellent in the storage stability of the liquid and the water resistance, transparency, and adhesion of the easily adhesive layer obtained. Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance and the like of the easy-adhesive layer obtained in addition to excellent stability in a liquid state before coating.

  Polyvinyl alcohol contained in the polarizer-side easy-adhesion layer in the present invention has a polyvinyl alcohol moiety, including, for example, modified compounds partially acetalized or butyralized with respect to polyvinyl alcohol, Conventionally known polyvinyl alcohol can be used. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably 300 to 40,000. When the degree of polymerization is less than 100, the water resistance of the easy-adhesion layer may be lowered. Further, the saponification degree of polyvinyl alcohol is not particularly limited, but a polyvinyl acetate saponified product in a range of 70 mol% or more, preferably in the range of 70 to 99.9 mol% is practically used.

  The oxazoline compound contained in the polarizer-side easy-adhesion layer in the present invention is a compound having an oxazoline group in the molecule. In particular, a polymer containing an oxazoline group is preferable, and it can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  Moreover, improvement in coating film strength and improvement in wet heat resistance can be expected when the number of hydrophilic groups such as polyalkylene glycol components is small and the amount of oxazoline groups is large.

  Content of the compound derived from the urethane resin which occupies for a polarizer side easily bonding layer is 10-80 mass% normally, Preferably it is 15-75 mass%, More preferably, it is 20-50 mass%. When the amount of the urethane resin is out of the above range, sufficient adhesion between the polyester film and the adhesive layer may not be obtained.

  Content of the compound derived from the polyvinyl alcohol which occupies for a polarizer side easily bonding layer is 10-80 mass% normally, Preferably it is 15-60 mass%, More preferably, it is 20-50 mass%. When the amount is less than 10% by mass, the adhesiveness with the adhesive layer may not be sufficient due to a small amount of the polyvinyl alcohol component. When the amount exceeds 80% by mass, the other component is small, and thus the adhesion with the polyester film may be insufficient. Sexuality may not be sufficient.

  The content of the compound derived from the oxazoline compound in the polarizer-side easy-adhesion layer is usually 10 to 80% by mass, preferably 15 to 60% by mass, and more preferably 20 to 40% by mass. When the amount is less than 10% by mass, the easy-adhesion layer becomes brittle due to a small amount of the crosslinking component, and the heat-and-moisture resistance may be reduced. Adhesion and adhesiveness with the adhesive layer may not be sufficient.

  In the polarizer-side easy-adhesion layer, a binder polymer other than a polyester resin or polyvinyl alcohol can be used in combination in order to improve the coating surface state and transparency.

  In the present invention, the “binder polymer” is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). It is defined as a polymer compound of 1000 or more and having a film-forming property.

  Specific examples of the binder polymer include polyester resin, acrylic resin, polyvinyl (polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like.

  Furthermore, a crosslinking agent other than the oxazoline compound can be used in combination in the polarizer-side easy-adhesion layer as long as the gist of the present invention is not impaired. Various known resins can be used as the crosslinking agent, and examples thereof include melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and the like.

  A melamine compound is a compound having a melamine skeleton in the compound. For example, an alkylolated melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and a mixture thereof can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  As an epoxy compound, the compound containing an epoxy group in a molecule | numerator, its prepolymer, and hardened | cured material are mentioned, for example. Examples include condensates of epichlorohydrin with hydroxyl groups and amino groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A, and polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. is there. Examples of the polyepoxy compound include sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylol. Examples of the propane polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether. Ether, polypropylene glycol diglycidyl ether, Ritetramethylene glycol diglycidyl ether and monoepoxy compounds include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N ′,-tetraglycidyl-m. -Xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like.

  As an isocyanate compound, it refers to a compound having an isocyanate group in the molecule, specifically, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tolylene diisocyanate, Examples include block bodies and derivatives.

  Among these crosslinking agents, in particular, by using an epoxy compound in combination, the easy-adhesion layer is strengthened, and an improvement in adhesion and wet heat resistance can be expected. These cross-linking agents preferably have water solubility or water dispersibility in consideration of application to in-line coating.

  Further, the polarizer-side easy-adhesion layer may contain particles for the purpose of improving the blocking property and slipperiness of the easy-adhesion layer, such as inorganic particles such as silica, alumina, metal oxide, or crosslinked polymer particles. Organic particles, and the like.

(Other additives used for easy adhesion layers)
Furthermore, in the range not impairing the gist of the present invention, the polarizer-side easy-adhesion layer and the hard coat layer-side easy-adhesion layer may be provided with an antifoaming agent, a coating property improver, a thickener, an organic lubricant, An inhibitor, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment and the like may be contained.
In particular, the antistatic agent has an effect of suppressing adhesion of foreign substances in the environment due to charging of the film to the film, and is effective in reducing foreign substances. As the antistatic agent, a general quaternary ammonium salt, PEDOT or the like can be used.
As the quaternary ammonium salt, those described in JP-A-2005-89569, [0010] can be used, and the contents described in these publications are incorporated herein.
As the quaternary ammonium salt, a commercially available product may be used, and for example, Enacol, manufactured by Lion Corporation can be preferably used.

  In addition, the coating composition for an easy-adhesion layer used in the present invention may contain a surfactant, a crosslinking agent, a dispersant, a thickener, a film forming aid, an antiblocking agent, and the like as necessary.

  Analysis of various components in the easy-adhesion layer can be performed by surface analysis such as TOF-SIMS.

(Manufacturing method of easy adhesion layer)
When providing an easy-adhesion layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or water dispersion, and a coating solution adjusted to a solid content concentration of about 0.1 to 50% by mass is applied onto the polyester film. It is preferable to produce a polyester film as described above. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  The film thickness of the hard coat layer side easy adhesion layer of the polyester film in the present invention is usually in the range of 0.002 to 1.0 μm, more preferably 0.02 to 0.5 μm, and further preferably 0.03 to 0.2 μm. It is. If the film thickness is less than 0.002 μm, sufficient adhesion may not be obtained, and if it exceeds 1.0 μm, the appearance, transparency, and film blocking properties may be deteriorated.

  The film thickness of the polarizer-side easy-adhesion layer of the polyester film in the present invention is usually in the range of 0.002 to 1.0 μm, more preferably 0.03 to 0.5 μm, and still more preferably 0.04 to 0.2 μm. is there. If the film thickness is less than 0.002 μm, sufficient adhesion may not be obtained, and if it exceeds 1.0 μm, the appearance, transparency, and film blocking properties may be deteriorated.

In the present invention, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating and the like can be used as a method of providing an easy adhesion layer on the polyester film. As for the coating method, there is a description example in “Coating method” published by Yoji Harasaki in 1979. The easy adhesion layer may be applied by the method described in [0062] to [0070] of WO2012 / 157762.
Among these, a bar coat is preferable, and using a rolling bar for the bar coat makes the film less susceptible to scratches when the coating solution is applied than when using a wire bar or the like, and in the subsequent transverse stretching step The generation of a concave or convex shape extending in the film width direction can be suppressed, and as a result, it is preferable from the viewpoint of improving the display quality of the liquid crystal display device when incorporated in the liquid crystal display device. That is, the method for producing a polyester film of the present invention described later further includes a step of applying a coating solution to an unstretched polyester film, the coating method of the coating solution is a bar coat, and a rolling bar is used for the bar coat. Is preferred.
Although there is no restriction | limiting in particular as a rolling bar, The thing as described in [0054]-[0060] of Unexamined-Japanese-Patent No. 2008-264757 can be used, and the content described in this gazette is integrated in this specification. It is.

  In the present invention, the drying and curing conditions for forming the easy-adhesion layer on the polyester film are not particularly limited. For example, when the easy-adhesion layer is provided by off-line coating, it is usually 3 at 80 to 200 ° C. The heat treatment may be performed for ˜40 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when an easy-adhesion layer is provided by in-line coating, it is usually preferable to perform heat treatment at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

[Production method of polyester film]
The method for producing a polyester film of the present invention includes a melting step of melting polyester with an extruder, a filtration step of filtering the melted polyester through a filtration device provided with a filter, and filtering the filtered polyester from a die into a sheet form. A film forming step of forming an unstretched polyester film by extruding and solidifying on a cooling drum to form an unstretched polyester film, and unstretched polyester film along a pair of rails installed on both sides of the film conveyance path Installed in the filtration process, including a process of transverse stretching while gripping with a clip in a tenter-type stretching device with a traveling clip, and a heat setting process of heating the polyester film after transverse stretching to the maximum temperature in the tenter The opening of the filter is 8 μm or less.
With such a configuration, the polyester film of the present invention can be produced. Although not bound by any theory, if the opening of the filter installed in the filtration process in which the melted polyester is filtered through a filtration device provided with a filter is 8 μm or less, foreign matter can be sufficiently removed. It is possible to suppress the occurrence of concave or convex shapes extending in the film width direction in the subsequent transverse stretching step. As a result, the number of the concave or convex unit areas extending in the film width direction of the obtained polyester film can be controlled to be equal to or less than the upper limit value defined in the present invention.
In order to impart the above properties to the polyester film, it is preferably produced by the following method.

<Melting process>
The method for producing a polyester film of the present invention includes a melting step of melting polyester with an extruder.
It is preferable to dry the polyester resin or the polyester resin and additive masterbatch produced by the above-described masterbatch method to a moisture content of 200 ppm or less and then introduce them into a uniaxial (uniaxial) or biaxial extruder and melt them. At this time, in order to suppress degradation of the polyester, it is also preferable to melt in nitrogen or vacuum. Detailed conditions can be carried out according to these publications with the aid of Patent Nos. 4926661 [0051] to [0052] (US2013 / 0100378 [0085] to [0086]), and are described in these publications. The contents are incorporated herein.

  In the method for producing a polyester film of the present invention, the extruder used in the melting step is a twin screw extruder, which reduces the remaining melt of the raw material polyester and suppresses the generation of foreign matter, and the film width in the subsequent transverse stretching step The generation of a concave or convex shape extending in the direction can be suppressed, and as a result, it is preferable from the viewpoint of improving the display quality of the liquid crystal display device when incorporated in the liquid crystal display device.

  Furthermore, it is also preferable to use a gear pump in order to increase the delivery accuracy of the molten resin (melt).

<Filtration process>
The manufacturing method of the polyester film of this invention includes the filtration process which filters the melted polyester through the filtration apparatus with which the filter was installed, and the opening of the filter installed in the filtration process is 8 micrometers or less.
Only one set of filtration devices having such a filter having an opening range may be installed in the filtration process, or two or more sets may be installed.

In the method for producing a polyester film of the present invention, there are three or more sets of filtration devices in the filtration step, and the opening size X μm of the filter installed in the first set of filtration devices counted from the upstream side of the filtration step, and the second set It is preferable that the opening Y μm of the filter installed in the filtration device of No. 1 and the opening Z μm of the filter installed in the third set of filtration device satisfy the following formula A.
Formula A ... Z≤X <Y

<Film forming process>
The method for producing a polyester film of the present invention includes a film forming step of forming an unstretched polyester film by extruding the filtered polyester into a sheet form from a die and bringing the filtered polyester into close contact with a cooling drum to cool and solidify.

When the melted (and kneaded) and filtered polyester (melt containing polyester) is extruded from a die into a sheet, it may be extruded as a single layer or as a multilayer. In the case of extruding in multiple layers, for example, a layer containing an ultraviolet absorber and a layer not containing an ultraviolet absorber may be laminated. More preferably, a three-layer structure including an ultraviolet absorber as an inner layer suppresses deterioration of a polarizer due to ultraviolet rays. The bleed-out of the ultraviolet absorber can be suppressed, which is preferable.
When the polyester film is produced by being extruded in multiple layers, the preferred inner layer thickness (ratio to the total layer) of the resulting polyester film is preferably 50% or more and 95% or less, more preferably 60% or more and 90% or less, Preferably they are 70% or more and 85% or less. Such lamination can be performed by using a feed block die or a multi-manifold die.

  According to [0059] of JP2009-269301A, a polyester (melt containing polyester) extruded from a die into a sheet is extruded onto a cooling drum (casting drum), cooled and solidified, and an unstretched polyester film (raw fabric) Is preferred.

In the method for producing a polyester film of the present invention, the temperature of the polyester extruded from the die is preferably 280 ° C. or higher and 320 ° C. or lower, and more preferably 285 ° C. or higher and 310 ° C. or lower. The temperature of the polyester extruded from the die in the melting step is 280 ° C. or more, which reduces the remaining melt of the raw material polyester and suppresses the generation of foreign matter, and the concave or convex extending in the film width direction in the subsequent transverse stretching step. The generation of the shape can be suppressed, and as a result, it is preferable from the viewpoint of improving the display quality of the liquid crystal display device when incorporated in the liquid crystal display device. The temperature of the polyester extruded from the die in the melting step is 320 ° C. or less, which reduces the degradation of the polyester and suppresses the generation of foreign matter, and has a concave or convex shape extending in the film width direction in the subsequent transverse stretching step. Occurrence can be suppressed, and as a result, it is preferable from the viewpoint of improving the display quality of the liquid crystal display device when incorporated in the liquid crystal display device.
The temperature of the polyester extruded from the die can be measured in a non-contact manner with a radiation thermometer (manufactured by Hayashi Denko, model number: RT61-2, used at an emissivity of 0.95).

  In the method for producing a polyester film of the present invention, in the film forming step, the electrostatic application electrode is used when the polyester is closely attached to the cooling drum. In the subsequent lateral stretching step, it is possible to suppress the occurrence of concave or convex shapes extending in the film width direction, and as a result, the display quality of the liquid crystal display device can be improved when incorporated in a liquid crystal display device. From the viewpoint of improvement, it is preferable.

In the polyester film production method of the present invention, when the polyester temperature is 280 ° C. or higher when the polyester film is in close contact with the cooling drum (the point where the molten polyester extruded from the die first comes into contact with the cooling drum), From the viewpoint of improving the display quality of the liquid crystal display device when incorporated in a liquid crystal display device, because electrical conductivity increases, it can be strongly adhered to the cooling drum by electrostatic application, and the film surface roughness can be suppressed. preferable.
The temperature of the polyester when closely contacting the cooling drum can be measured in a non-contact manner with a radiation thermometer (manufactured by Hayashi Denko, model number: RT61-2, used at an emissivity of 0.95).

In the method for producing a polyester film of the present invention, the distance between the electrostatic application electrode and the point where the polyester adheres to the cooling drum is 15 mm or less. In the subsequent lateral stretching step, it is possible to suppress the occurrence of concave or convex shapes extending in the film width direction, and as a result, the display quality of the liquid crystal display device can be improved when incorporated in a liquid crystal display device. From the viewpoint of improvement, it is preferable. The distance between the electrostatic application electrode and the point at which the polyester is in close contact with the cooling drum is preferably 14 mm or less, and more preferably 13 mm or less.
The distance between the electrostatic application electrode and the point at which the polyester is in close contact with the cooling drum means the following two linear distances. That is, it is the linear distance between the point where the polyester just lands on the cooling drum and the center point of the electrostatic application electrode.

In the method for producing a polyester film of the present invention, it is possible that the applied voltage of the electrostatic application electrode is 9 kV or more so that the polyester can be strongly adhered onto the cooling drum so that the film surface shape is not roughened. Generation | occurrence | production of the concave or convex shape extended in the film width direction in the extending | stretching process can be suppressed, As a result, it is preferable from a viewpoint which can improve the display quality of a liquid crystal display device, when incorporating in a liquid crystal display device. The applied voltage of the electrostatic application electrode is preferably 9.5 kV or more, and more preferably 10 kV or more.
The applied voltage of the electrostatic application electrode can be freely controlled by setting an arbitrary value.

  The method for producing a polyester film of the present invention is such that a transport roll is installed between the point at which the unstretched polyester film is peeled off from the cooling drum and the entrance of the tenter-type stretching device, and is in contact with the unstretched polyester film. 50% or more of the rolls are driven transport rolls, and the film is less likely to be scratched than when a high ratio of non-driven free rolls is used, and extends in the film width direction in the subsequent transverse stretching process. Occurrence of concave or convex shapes can be suppressed, and as a result, it is preferable from the viewpoint of improving the display quality of the liquid crystal display device when incorporated in the liquid crystal display device. More preferably, 70% or more of the transport roll in contact with the unstretched polyester film is a drive-type transport roll, and 80% or more of the transport roll in contact with the unstretched polyester film is a drive-type transport roll. Is particularly preferred.

<The process of apply | coating a coating liquid>
It is preferable that the manufacturing method of the polyester film of this invention further includes the process of apply | coating a coating liquid to an unstretched polyester film. It is preferable that the process of apply | coating a coating liquid is a process of apply | coating the coating liquid for forming an easily bonding layer. In the step of applying the coating solution, the coating method is preferably bar coating, and it is preferable to use a rolling bar for the bar coating. The preferable aspect of the process of apply | coating a coating liquid is the same as the preferable aspect of the method of providing an easily bonding layer in the polyester film of this invention.

<Step of transverse stretching>
The method for producing a polyester film according to the present invention comprises a tenter-type stretching device having a clip that travels along a pair of rails installed on both sides of a film transporting path for an unstretched polyester film while holding it with a clip. A step of stretching.

  There is no restriction | limiting in particular as a tenter type extending | stretching apparatus which has a clip which drive | works along a pair of rail installed in the both sides of a film conveyance path. A pair of endless rails is usually used as the pair of rails. In addition, a clip is synonymous with a holding member.

The unstretched polyester film is preferably stretched transversely at a temperature of Tg to (Tg + 60) ° C. of the polyester film, preferably 3 to 10 times, more preferably 3 to 7 times in the width direction. The polyester film is preferably uniaxially stretched in the width direction from the viewpoint of greatly expressing the in-plane retardation Re. The glass transition temperature of the film is expressed as Tg.
Specifically, the stretching temperature in the transverse stretching step is preferably 70 ° C or higher and 170 ° C or lower, more preferably 80 ° C or higher and 140 ° C or lower, and further preferably 90 ° C or higher and 120 ° C or lower. The stretching temperature here refers to an average temperature from the start to the end of stretching.

As temperature control means for heating or cooling the polyester film in preheating, transverse stretching, heat setting, thermal relaxation, and cooling before transverse stretching, hot or cold air is blown on the polyester film, or the polyester film is heated to a temperature. Examples include contacting the surface of a controllable metal plate or passing the vicinity of the metal plate.
In addition, although the upper limit of the width | variety after extending | stretching a polyester film does not have a restriction | limiting in particular, For example, it can be set as 6 m or less in width.

<Heat setting process>
The manufacturing method of the polyester film of this invention includes the heat setting process of heating the polyester film after carrying out horizontal stretching to the highest temperature in a tenter.
It is preferable to perform heat treatment (referred to herein as heat setting) at 140 ° C. or higher and 220 ° C. or lower for 1 to 60 seconds. The heat setting temperature is more preferably 150 ° C. or higher and 220 ° C. or lower, and particularly preferably 150 ° C. or higher and lower than 220 ° C.
When the heat setting temperature is 150 ° C. or more and less than 220 ° C., the deviation in the orientation direction of the polyester is reduced and the thermal dimensional change is also reduced.

When an unstretched polyester film is stretched in the width direction and heat-set, a bowing phenomenon that deforms in a bow shape in the film longitudinal direction occurs. Due to this bowing phenomenon, the stretched polyester film is displaced in the alignment direction between the central portion and the end portion in the width direction.
Although the bowing phenomenon is remarkable in a polyester film having a width of 1.4 m or more after stretching, the polyester film of the present invention has a thermal dimensional change by controlling the melting sub-peak temperature within the above-mentioned value range. It is suppressed.

<Relaxation treatment>
Furthermore, it is preferable to perform reheat treatment (referred to as relaxation treatment) while shrinking 0-20% in the longitudinal direction and / or width direction at a temperature 0-20 ° C. lower than the heat setting temperature, and shrinking 0-20% in the width direction. However, it is more preferable to perform the reheat treatment. In this method, since the film is less likely to come into contact with the roll, minute scratches and the like are less likely to occur on the film surface than in the method described above, which is advantageous for application to optical applications.

<Recovery of film, slit, winding>
After the heat setting step or an optional relaxation treatment, the film is trimmed, slit, and thickened as necessary and wound for collection.
In the method for producing a polyester film of the present invention, the film width after opening from the clip is preferably 0.8 to 6 m from the viewpoint of efficiently securing the film product width and preventing the apparatus size from becoming excessive, and 1 to 5 m. Is more preferable, and it is especially preferable that it is 1-4 m. An optical film requiring accuracy is usually formed with a thickness of less than 3 m, but in the present invention, it is preferable to form a film with the above-mentioned width.
In addition, the film formed into a wide film may be slit to preferably 2 or more, 6 or less, more preferably 2 or more and 5 or less, and still more preferably 3 or more and 4 or less, and then wound.
In addition, when trimming the edge part of a film by arbitrary width, or when slitting in arbitrary numbers after film forming, the film width after trimming or slit corresponds to the film width of the polyester film of this invention.

Moreover, after slitting, it is preferable to process the thickness at both ends (providing knurling).
The winding is preferably performed at a diameter of not less than 1000 m and not more than 10,000 m on a winding core having a diameter of 70 mm or more and 600 mm or less. Winding tension per cross-sectional area of the film is preferably 3~30kgf / cm ^2, more preferably 5~25kgf / cm ^2, more preferably from 7~20kgf / cm ^2. The thickness of the wound film is the same as [0049] of Japanese Patent No. 4926661. It is also preferable to bond a masking film before winding.

[Polarizer]
The polarizing plate of the present invention includes a polarizer and the polyester film of the present invention.
The polarizing plate of the present invention preferably has an arbitrary protective film, a polyester film is laminated on one surface of the polarizer, and an arbitrary protective film is laminated on the other surface. The polarizing plate of the present invention further has a cellulose acylate film, more preferably a polyester film is laminated on one surface of the polarizer, and a cellulose acylate film is laminated on the other surface.
The polarizing plate of the present invention is disposed on the protective film, the polarizer disposed on the protective film and containing polyvinyl alcohol, the polyester film of the present invention disposed on the polarizer, and the polyester film of the present invention. It is preferable to have a hard coat layer side easy-adhesion layer and a hard coat layer disposed on the hard coat layer side easy-adhesion layer.

<Configuration>
First, the structure of the polarizing plate of this invention is demonstrated based on drawing.
The polarizing plate of the present invention shown in FIG. 1 includes a polarizer 1 containing polyvinyl alcohol, a polyester film 2 laminated on one side of the polarizer 1, and a hard coat layer side easy placed on the polyester film 2. The hard coat layer 4 is provided on the adhesive layer 3b and the hard coat layer side easy adhesive layer 3b.
In the polarizing plate of the present invention, it is preferable that a polarizer-side easy-adhesion layer 3 a is disposed between the polarizer 1 and the polyester film 2, that is, the polyester film 2 is disposed on the polarizer 1 on the polarizer side. It is preferable to laminate via the easy adhesion layer 3a.
Further, the polarizing plate of the present invention is a protective film 10 or optical layer laminated on another surface of the polarizer 1 opposite to the surface on which the polyester film 2 is laminated via another easy adhesion layer (not shown). A compensation film (not shown) may be provided.

  The polarizing plate of the present invention is preferably strip-shaped. In the present specification, a belt-like shape is almost synonymous with a long shape, that is, a continuous film of several thousand meters. The polarizing plate of the present invention has an effect of obtaining a polarizing plate that can be continuously produced at a high speed and has a stable quality by being strip-shaped.

  Hereinafter, a preferable aspect is demonstrated about each member which comprises the polarizing plate of this invention, those manufacturing methods, etc.

In the polarizing plate of the present invention, the angle formed by the maximum direction of the elastic modulus in the plane of the polyester film and the absorption axis direction of the polyvinyl alcohol polarizer (generally the same as the stretching direction) is at the end and center in the width direction of the polyester film. Within 90 ° ± 25 °, distortion due to the angle between the orientation direction of the polyester film and the stretching direction of the polarizer is suppressed by the polyester film, and after wet heat aging with the hard coat layer formed on the polyester film It is preferable from the viewpoint that it becomes possible to obtain the adhesiveness.
The angle formed between the maximum in-plane elastic modulus direction of the polyester film and the absorption axis direction of the polarizer is more preferably 90 ° ± 20 °, and particularly preferably 90 ° ± 5 °.

<Polarizer>
The polarizer used in the polarizing plate of the present invention preferably contains polyvinyl alcohol and is made of polyvinyl alcohol. Although there is no restriction | limiting in particular as a manufacturing method of a polarizer, Usually, the process of uniaxially stretching a polyvinyl alcohol-type resin film by a well-known method, and dyeing a polyvinyl alcohol-type resin film with a dichroic dye, It is manufactured through a step of adsorbing water, a step of treating a polyvinyl alcohol resin film adsorbed with a dichroic dye with an aqueous boric acid solution, and a step of washing with water after the treatment with an aqueous boric acid solution.

<Adhesive>
When using a polyester film as a protective film for a polarizer in a polarizing plate, generally, the polarizer is bonded to the polarizer-side easy-adhesion layer side via an adhesive for adhering the polarizer.
As the adhesive, conventionally known ones can be used, for example, acrylic compounds such as polyvinyl alcohol, polyvinyl butyral and polybutyl acrylate, and epoxy having an alicyclic epoxy group exemplified by glycidyl group and epoxycyclohexane. System compounds and the like.

The adhesive may be an ultraviolet curable adhesive (UV adhesive), or may be a method described in Japanese Patent Application Laid-Open No. 2014-66955 or Japanese Patent Application Laid-Open No. 2014-56040.
As the UV adhesive, the contents described in [0214] to [0301] of JP 2014-66955 A can be used, and the contents described in this gazette are incorporated in the present specification.

[Image display device]
The image display device of the present invention includes the polyester film of the present invention or the polarizing plate of the present invention, and has a number of pixels of 3000 or more in width and 1500 or more in length.
Examples of the image display device include a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (OELD or IELD), a field emission display (FED), a touch panel, and electronic paper. These image display devices preferably include the polarizing plate of the present invention on the display screen side of the image display panel.

[Liquid Crystal Display]
The liquid crystal display device of the present invention has a liquid crystal cell and the polyester film of the present invention or the polarizing plate of the present invention disposed on at least one surface of the backlight side and the front side of the liquid crystal cell. 3000 or more and 1500 or more in the vertical direction.
The liquid crystal display device of the present invention preferably includes the polarizing plate of the present invention and a liquid crystal display element. Here, the liquid crystal display element is typically a liquid crystal panel that includes a liquid crystal cell in which liquid crystal is sealed between upper and lower substrates and displays an image by changing a liquid crystal arrangement state by applying a voltage. The polarizing plate of the present invention can be applied to various known displays such as a display panel, a CRT display, and an organic EL display.
In the liquid crystal display device, when the polarizing plate of the present invention has a hard coat layer, the polarizing plate of the present invention is preferably arranged on the viewer side with respect to the liquid crystal display element with the hard coat layer side facing outside. The polyester film may be directly bonded to the surface of the liquid crystal display element. When the liquid crystal panel is used as a liquid crystal display element, for example, as described above, the polyester film is bonded to the surface of the liquid crystal panel via a polarizer. You can also. Thus, when the polarizing plate of the present invention having a polyester film is applied to a liquid crystal display element, the polyester film and the hard coat layer are excellent in adhesion durability after wet heat aging, and a conventional protective film is used. The strength of the liquid crystal display element is reinforced more than the case, and the warpage of the liquid crystal display element can be prevented.

  In the liquid crystal display device of the present invention, it is preferable that the number of pixels is 3000 or more in the horizontal direction and 1500 or more in the vertical direction, 3840 or more in the horizontal direction called 4K2K, and 2160 or more in the vertical direction. As a recent trend, an increase in size and / or a higher definition is progressing. A liquid crystal panel having a size of 46 inches or more, a resolution of 4840 pixels, a horizontal size of 3840 or more, and a vertical number of 2160 or more is becoming common. In this 4K2K TV, the viewing distance recommended by TV manufacturers is 1.5 times the screen height, and the viewing distance recommended by conventional TV manufacturers is 3 times the screen height. The visibility of defects is increasing.

From the viewpoint of improving the display quality, the liquid crystal display device of the present invention has a polyester film on the backlight side of the liquid crystal cell in which the amount of the ultraviolet absorber is 0.1% by mass or less with respect to the polyester as the polyester film. ,preferable. More preferably, the polyester film used on the backlight side does not contain an ultraviolet absorber.
On the other hand, the liquid crystal display device of the present invention preferably has a polyester film containing a UV absorber as a polyester film on the front side of the liquid crystal cell from the viewpoint of improving light resistance. The preferable range of the content of the ultraviolet absorber in the polyester film used on the front side is the same as the preferable range of the content of the ultraviolet absorber in the polyester film of the present invention.

  As a method for bonding the polarizing plate to an image display device such as a liquid crystal display device, a known method can be used. In addition, a roll-to-panel manufacturing method can be used, which is preferable for improving productivity and yield. The roll-to-panel manufacturing method is described in JP2011-48381, JP2009-175653, JP4628488, JP4729647, WO2012 / 014602, WO2012 / 014571, and the like. It is not limited.

In an image display device such as a liquid crystal display device, a light source having a continuous emission spectrum is preferably used as the light source.
This is because it becomes easy to eliminate rainbow unevenness as described in [0019] to [0020] of WO2011 / 162198.
As a light source used in the image display device, the one described in [0013] of WO2011 / 162198 is used. On the other hand, the light source described in [0014] to [0015] of WO2011 / 162198 is not a continuous light source and is not preferable.
When the image display device is a liquid crystal display device, the configuration described in [0011] to [0012] of WO2011 / 162198 can be used for the liquid crystal display device (LCD).
The liquid crystal display device using the polyester film of the present invention and / or the polarizing plate of the present invention is preferably one using a white light source having a continuous emission spectrum, whereby a discontinuous (bright line) light source is used. Rainbow unevenness can be reduced more effectively. This is due to the same reason as described above, with the reason described in [0015] to [0027] of Patent No. 4888853 ([0029] to [0041] of US2012 / 0229732). The contents described in these publications are incorporated herein.

  Here, the iridescent color spots are caused by the retardation of the polyester film having a high retardation and the emission spectrum of the backlight light source. Conventionally, a fluorescent tube such as a cold cathode tube or a hot cathode tube is used as a backlight source of a liquid crystal display device. The spectral distribution of a fluorescent lamp such as a cold cathode tube or a hot cathode tube shows an emission spectrum having a plurality of peaks, and these discontinuous emission spectra are combined to obtain a white light source. When light passes through a film having a high retardation, the transmitted light intensity varies depending on the wavelength. For this reason, when the backlight light source has a discontinuous emission spectrum, only a specific wavelength is strongly transmitted, and a rainbow-like color spot is generated.

  When the image display device is a liquid crystal display device, it is preferable to include a backlight light source and a liquid crystal cell disposed between two polarizing plates as constituent members. Moreover, you may have suitably other structures other than these, for example, a color filter, a lens film, a diffusion sheet, an antireflection film etc. suitably.

The configuration of the backlight may be an edge light method using a light guide plate, a reflection plate, or the like, or a direct type, but in the present invention, white is used as the backlight light source of the liquid crystal display device. It is preferable to use a light emitting diode (white LED) from the viewpoint of improving rainbow unevenness. In the present invention, the white LED is an element that emits white by combining a phosphor with a phosphor system, that is, a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor. Examples of the phosphor include yttrium / aluminum / garnet yellow phosphor and terbium / aluminum / garnet yellow phosphor. In particular, white light-emitting diodes, which are composed of light-emitting elements that combine blue light-emitting diodes using compound semiconductors with yttrium, aluminum, and garnet-based yellow phosphors, have a continuous and broad emission spectrum and are also efficient in light emission. Since it is excellent, it is suitable as a backlight light source of the image display device of the present invention. Here, the continuous emission spectrum means that there is no wavelength at which the light intensity becomes zero at least in the visible light region. Further, since the white LED with low power consumption can be widely used according to the present invention, an effect of energy saving can be achieved.
The mechanism by which the occurrence of rainbow-like color spots is suppressed by the above embodiment is described in International Publication No. WO2011 / 162198, and the contents of this publication are incorporated in the present invention.

In addition, the image display device according to the present invention preferably includes a light source unit having at least blue, green, and red emission peaks as a backlight light source, and a liquid crystal cell having polarizing plates on both sides.
The emission spectrum of the light source unit has at least blue, green and red emission peaks, the full width at half maximum of the green and red emission peaks is 20 nm or more, and at least one minimum value L1 is present between wavelengths 460 nm to 520 nm. Having at least one maximum value L2 between wavelengths 520 nm and 560 nm, having at least one minimum value L3 between wavelengths 560 nm and 620 nm, and the values of L1 and L3 being less than 35% of L2 Preferably there is.
The full width at half maximum of the green and red emission peaks is preferably 20 nm or more and 60 nm or less. Of the green emission peak and the red emission peak of the light source unit, the full width at half maximum W of the smaller full width at half maximum is 50 nm or less. It is preferable that it is 20 nm or more and 40 nm or less. It is preferable that the full width at half maximum is small because the color reproducibility of the liquid crystal display device can be improved. Moreover, it is preferable for the full width at half maximum to be 20 nm or more because rainbow unevenness can be prevented from occurring by using the first protective film having Re of 5000 nm or more.
The values of L1 and L3 are more preferably less than 20% of L2, and most preferably less than 10%. It is preferable that the values of L1 and L3 are smaller than the value of L2, because light emission of blue, green, and red is separated and the color reproducibility of the liquid crystal display device can be improved.
The light source unit may include a blue light emitting diode, a green light emitting diode, and a red light emitting diode, but from the viewpoint of cost reduction, the blue light emitting diode or the ultraviolet light emitting diode and the blue light emitting diode or the ultraviolet light emitting diode are used. It is preferable to have at least a phosphor capable of emitting light when excited by light. When using a blue light emitting diode, it is preferable to have a phosphor that emits green light and a phosphor that emits red light. When an ultraviolet light emitting diode is used, a phosphor that emits blue light, It is preferable to have a phosphor that emits green light and a phosphor that emits red light.
The aforementioned phosphor may be enclosed in a blue light emitting diode or an ultraviolet light emitting diode, but in order to prevent deterioration of the phosphor due to heat, the phosphor is enclosed in a glass tube, Or it is preferable to arrange | position so that light emission of a ultraviolet-ray light-emitting diode may hit, or to arrange | position the film containing a fluorescent substance inside a light source unit.
The phosphor preferably includes quantum dots, at least one of which is a nanometer-sized semiconductor particle. The quantum dot phosphor is preferable because it can reduce the full width at half maximum of the emission peak and can improve the color reproducibility of the liquid crystal display device.

  In general, since a light source including quantum dots has high luminous efficiency, heat generation from the backlight unit can be suppressed as compared with a backlight unit using a white LED or a cold cathode fluorescent lamp (CCFL). Therefore, after the liquid crystal display device is stored in a high-temperature and high-humidity environment, an increase in temperature when it is turned on can be suppressed, and warpage of the liquid crystal cell and display unevenness can be further reduced.

  The emission spectrum of the light source unit can be measured using a spectroradiometer “SR-3” manufactured by Topcon Techno House Co., Ltd.

  An emission spectrum of a general cold cathode fluorescent lamp (CCFL) will be described. Blue, green, and red have sharp emission peaks, so blue, green, and red light emission are separated, and the color reproducibility of liquid crystal display devices using CCFLs is generally higher than that of liquid crystal displays using white LEDs. Also excellent. On the other hand, since the full width at half maximum of the green and red light emission peaks is as small as about 2 nm or less, when a film having high Re is used as the first protective film, rainbow unevenness is visually recognized.

  The emission spectrum of a general white LED will be described. A white LED is usually manufactured by enclosing an organic phosphor that emits yellow or green and red light inside a blue light emitting diode. In this case, the full width at half maximum of the green and red emission peaks is 20 nm or more. Therefore, in general, in a liquid crystal display device using a white LED, when a film having a high Re is used as the first protective film, rainbow unevenness occurs. It is suppressed. On the other hand, since there is no minimum value between wavelengths 460 nm and 520 nm and between wavelengths 560 nm and 620 nm, or the minimum value is larger than the maximum value L2 between wavelengths 520 nm and 560 nm, blue, green, and Separation of red light emission is insufficient and color reproducibility is poor.

  An emission spectrum of a light source using the quantum dot phosphor will be described. A light source using a quantum dot phosphor generally has a full width at half maximum of green and red emission peaks of 20 nm or more, has at least one minimum value L1 between wavelengths of 460 nm and 520 nm, and has a wavelength of 520 nm to 520 nm. Since it has at least one maximum value L2 between 560 nm, at least one minimum value L3 between wavelengths 560 nm and 620 nm, and the values of L1 and L3 are less than 35% of L2, It can be suitably used as a light source unit of an image display device.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
<Synthesis of raw material polyester>
(Raw material polyester 1)
As shown below, by directly reacting terephthalic acid and ethylene glycol to distill off water, esterify, and then use a direct esterification method in which polycondensation is performed under reduced pressure, raw polyester 1 ( Sb catalyst system PET) was obtained.

(1) Esterification reaction In a first esterification reaction tank, 4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol are mixed for 90 minutes to form a slurry, and continuously at a flow rate of 3800 kg / h. It supplied to the 1st esterification reaction tank. Further, an ethylene glycol solution of antimony trioxide was continuously supplied, and the reaction was carried out at a temperature in the reaction vessel of 250 ° C. with stirring and an average residence time of about 4.3 hours. At this time, antimony trioxide was continuously added so that the amount of Sb added was 150 ppm in terms of element.

  This reaction product was transferred to a second esterification reaction vessel, and reacted with stirring at a temperature in the reaction vessel of 250 ° C. and an average residence time of 1.2 hours. To the second esterification reaction tank, an ethylene glycol solution of magnesium acetate and an ethylene glycol solution of trimethyl phosphate are continuously supplied so that the added amount of Mg and the added amount of P are 65 ppm and 35 ppm in terms of element, respectively. did.

(2) the polycondensation reaction above-obtained esterification reaction product supplied to the first polycondensation reaction vessel continuously stirring, the reaction temperature 270 ° C., the reaction vessel pressure 20 torr (2.67 × 10 ^{- 3} MPa) and polycondensation with an average residence time of about 1.8 hours.

Further, the mixture was transferred to the second double condensation reaction tank, and while stirring in this reaction tank, the reaction tank temperature was 276 ° C., the reaction tank pressure was 5 torr (6.67 × 10 ⁻⁴ MPa), and the residence time was about 1.2 hours. The reaction (polycondensation) was performed under the conditions.

Subsequently, it was further transferred to the third triple condensation reaction tank. In this reaction tank, the reaction tank temperature was 278 ° C., the reaction tank pressure was 1.5 torr (2.0 × 10 ⁻⁴ MPa), and the residence time was 1.5 hours. The reaction product (polyethylene terephthalate (PET)) was obtained by reaction (polycondensation) under the following conditions.

  Next, the obtained reaction product was discharged into cold water in a strand form and immediately cut to prepare polyester pellets (cross section: major axis: about 4 mm, minor axis: about 2 mm, length: about 3 mm).

  The obtained polymer had IV = 0.63. This polymer was designated as raw material polyester 1 (hereinafter abbreviated as PET1).

(Raw material polyester 2)
10 parts by weight of the dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazin-4-one), 90 parts by weight of PET1 (IV = 0.63) The mixture was mixed and pelletized in the same manner as the production of PET1 using a kneading extruder to obtain a raw material polyester 2 containing an ultraviolet absorber (hereinafter abbreviated as PET2).

(Raw material polyester 3)
1 part by weight of the dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazin-4-one), 99 parts by weight of PET1 (IV = 0.63) The mixture was mixed and pelletized using a kneading extruder in the same manner as the production of PET 1 to obtain a raw material polyester 3 containing an ultraviolet absorber (hereinafter abbreviated as PET 3).

<Manufacture of polyester film>
(Film forming process)
After 90 parts by mass of raw material polyester 1 (PET1) and 10 parts by mass of raw material polyester 2 (PET2) containing an ultraviolet absorber are dried to a water content of 20 ppm or less, the hopper 1 of a uniaxial kneading extruder 1 having a diameter of 50 mm is used. The melt was added to the extruder 1 at 300 ° C. (intermediate layer II layer).
Moreover, after drying PET1 to a water content of 20 ppm or less, it was put into a hopper 2 of a uniaxial kneading extruder 2 with a diameter of 30 mm and melted at 300 ° C. with the extruder 2 (outer layer I layer, outer layer III layer).
These two kinds of polymer melts are passed through one set of filtration devices each having a gear pump and a filter (opening 8 μm, that is, a pore diameter of 8 μm), and then from the extruder 1 in a two-type three-layer merge block. The extruded polymer was laminated on the intermediate layer (II layer) so that the polymer extruded from the extruder 2 became the outer layer (I layer and III layer), and extruded from a 120 mm wide die into a sheet.
The molten resin was extruded from the die under conditions of pressure fluctuation of 1% and molten resin temperature distribution of 2%. Specifically, the back pressure was increased by 1% with respect to the average pressure in the barrel of the extruder, and the piping temperature of the extruder was heated at a temperature 2% higher than the average temperature in the barrel of the extruder.
The molten resin extruded from the die was extruded onto a cooling cast drum set at a temperature of 25 ° C., and was brought into close contact with the cooling cast drum using an electrostatic application method. The resin temperature during extrusion was 300 ° C. The resin temperature when closely contacting the cooling drum was 277 ° C. It peeled using the peeling roll arrange | positioned facing the cooling cast drum, and the unstretched polyester film 1 was obtained. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of the I layer, the II layer, and the III layer was 10:80:10.

(Formation of easy adhesion layer)
(1) Formation of hard coat layer side easy-adhesion layer The following compounds were mixed in the following ratio to prepare coating liquid H1 for hard coat layer-side easy adhesive layer.

・ Coating liquid H1 for hard coat layer side easy adhesion layer
Polyester resin: (IC) 60 parts by mass Acrylic resin: (II) 25 parts by mass Melamine compound: (VIB) 10 parts by mass Particles: (VII) 5 parts by mass Details of the compounds used are shown below.
・ Polyester resin: (IC)
A sulfonic acid aqueous dispersion monomer composition of a polyester resin copolymerized with a monomer having the following composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4- Butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)

・ Acrylic resin: (II)
Aqueous dispersion of acrylic resin polymerized with monomers of the following composition Ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (mass%) emulsion polymer ( Emulsifier: Anionic surfactant)
-Urethane resin: (IIIB)
400 parts by weight of a polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 10.4 parts by weight of neopentyl glycol, 58.4 parts by weight of isophorone diisocyanate, 74.3 parts by weight of dimethylol butanoic acid. An aqueous dispersion of urethane resin obtained by neutralizing a prepolymer consisting of parts by mass with triethylamine and extending the chain with isophoronediamine.
Melamine compound: (VIB) hexamethoxymethylmelamine Particles: (VII) Silica sol having an average particle size of 65 nm

(2) Formation of polarizer-side easy-adhesion layer The following compounds were mixed in the following ratio to prepare a coating liquid P1 for a polarizer-side easy-adhesion layer.

(2-1) Synthesis of copolymer polyester resin (A-1) Dimethyl terephthalate 194.2 parts by mass Dimethyl isophthalate 184.5 parts by mass Dimethyl-5-sodium sulfoisophthalate 14.8 parts by mass Diethylene glycol 233.5 parts by mass Ethylene glycol 136.6 parts by mass Tetra-n-butyl titanate 0.2 parts by mass The above compound was charged, and a transesterification reaction was performed at a temperature of 160 ° C to 220 ° C over 4 hours. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 30 Pa to obtain a copolymerized polyester resin (A-1).

(2-2) Production of polyester aqueous dispersion (Aw-1) Copolyester resin (A-1) 30 parts by mass Ethylene glycol n-butyl ether 15 parts by mass Dissolved. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution while stirring. After the addition, the solution was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (Aw-1) having a solid content of 30% by mass.

(2-3) Preparation of aqueous polyvinyl alcohol solution (Bw-1) 90 parts by mass of water was added, and while stirring, polyvinyl alcohol resin (manufactured by Kuraray) having a saponification degree of 88% and a polymerization degree of 500 (B-1) 10 masses Part was added gradually. After the addition, the solution was heated to 95 ° C. while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature with stirring to prepare a polyvinyl alcohol aqueous solution (Bw-1) having a solid content of 10% by mass.

Polyisocyanate compound having isocyanurate structure made from hexamethylene diisocyanate (Duranate TPA manufactured by Asahi Kasei Chemicals)
100 parts by mass Propylene glycol monomethyl ether acetate 55 parts by mass Polyethylene glycol monomethyl ether (average molecular weight 750) 30 parts by mass The above compound was charged and held at 70 ° C. for 4 hours in a nitrogen atmosphere. Thereafter, the reaction solution temperature was lowered to 50 ° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured to confirm that the absorption of the isocyanate group had disappeared, and a block polyisocyanate aqueous dispersion (C-1) having a solid content of 75% by mass was obtained.

The following coating agent was mixed and the coating liquid P1 for polarizer side easily bonding layers from which the mass ratio of polyester-type resin (A-1) / polyvinyl alcohol-type resin (B-1) becomes 70/30 was produced.
Water 40.61 mass%
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 11.67 mass%
Polyvinyl alcohol aqueous solution (Bw-1) 15.00 mass%
Block isocyanate-based crosslinking agent (C-1) 0.67% by mass
Particles (silica sol with an average particle diameter of 100 nm, solid content concentration 40% by mass)
1.25% by mass
Catalyst (organotin-based compound solid concentration 14% by mass) 0.3% by mass
Surfactant (silicon-based, solid content concentration 10% by mass) 0.5% by mass

(3) Application of easy-adhesion layer to both surfaces of polyester film In the bar coating method using a wire bar, the following coating liquid H1 for the hard coat layer-side easy-adhesion layer is applied to one side of the unstretched polyester film 1 The coating liquid P1 for the polarizer-side easy-adhesion layer was applied to the surface using a wire bar while adjusting the coating amount after drying so that both surfaces were 0.12 g / m ² .

(Horizontal stretching process)
-Preheating section-
The preheating temperature was 90 ° C., and the mixture was heated to a temperature at which stretching was possible.

-Extension part-
The unstretched polyester film 1 coated and preheated with an easy-adhesion layer is guided to a tenter (transverse stretching machine), and the ends of the film are gripped with clips, while the TD direction (film width direction, The film was transversely stretched under the following conditions in the transverse direction) to obtain a film having a width of 5 m.
"conditions"
-Transverse stretching temperature: 90 ° C
・ Horizontal stretch ratio: 4.3 times

-Heat fixing part-
Next, a heat setting treatment was performed while controlling the film surface temperature of the polyester film within the following range.
<Condition>
・ Heat setting temperature: 180 ℃
・ Heat setting time: 15 seconds

-Thermal relaxation part-
The polyester film after heat setting was heated to the following temperature to relax the film.
-Thermal relaxation temperature: 170 ° C
-Thermal relaxation rate: TD direction (film width direction, lateral direction) 2%

-Cooling section-
Next, the polyester film after heat relaxation was cooled at a cooling temperature of 50 ° C.

-Film collection and film division-
After cooling, the polyester film 1 was divided into 1.4 m widths in the width direction, and the chuck portion was trimmed. Then, after extruding (knurling) at a width of 10 mm on both ends of each divided roll, it was wound up 2000 m at a tension of 18 kg / m. As described above, three rolls of a uniaxially stretched polyester film 1 having a strip shape (long shape) having a thickness of 100 μm and a width of 1.4 m were produced.

(Formation by applying a hard coat layer)
Thereafter, the surface of the polyester film 1 coated with the coating liquid H1 for the hard-coat layer-side easy-adhesion layer was coated and dried with a mixed coating liquid (acrylic-1) having the following composition so that the dry film thickness was 5 μm. A hard coat layer was formed by curing by irradiating with ultraviolet rays.
Dipentaerythritol hexaacrylate 85 parts by mass 2-hydroxy-3-phenoxypropyl acrylate 15 parts by mass photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals)
5 parts by weight methyl ethyl ketone 200 parts by weight

<Strip (long) polarizing plate processing>
A commercially available cellulose acetate film (WVBZ, manufactured by Fuji Film Co., Ltd.) was prepared as a polarizing plate protective film, continuously passed through a 1.5 N aqueous sodium hydroxide solution, and immersed at 55 ° C. for 2 minutes. It wash | cleaned in the room temperature water-washing tub, and neutralized using 0.1 N sulfuric acid at 30 degreeC. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. In this way, the surface of a commercially available cellulose acetate film was saponified.
Subsequently, a roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in the conveying direction in an aqueous iodine solution and dried to obtain a polarizer having a thickness of 20 μm.
Polarizer side of strip-like (long) uniaxially stretched polyester film sample 1 using the 3% aqueous solution of polyvinyl alcohol (Kuraray Polarizer-117H) as an adhesive and any surface of the saponified cellulose acetate film described above. The surface on which the coating liquid P1 for the easy adhesion layer is applied is the polarizer side, and two films are bonded together by roll-to-roll with the polarizer in between, and both sides of the polarizer are protected by a film (long) A polarizing plate was obtained.

<Manufacture of liquid crystal display devices>
Using the manufactured polarizing plate, the polarizing plate of a commercially available liquid crystal TV was replaced as described below.
Ten 4K2K VA mode liquid crystal cells 1 (Toshiba 65-inch 65Z8X, number of pixels 2160 in length, 3840 in width) were prepared, the upper and lower polarizing plates were peeled off, and the polarizing plate of Example 1 produced was a liquid crystal cell. I stuck it to the side. The crossed nicols were arranged so that the transmission axis of the upper polarizing plate was in the vertical direction and the transmission axis of the lower polarizing plate was in the horizontal direction.
The obtained liquid crystal display device was used as the liquid crystal display device of Example 1.

[Examples 2 to 13 and Comparative Examples 1 and 2]
The production conditions of the liquid crystal display devices of other examples and comparative examples, the structures of the polyester films used for the front and back side polarizing plates on the front and back of the liquid crystal cell, etc. are shown in Table 1 or Table 2 below. Details are described below.

  In Example 2, instead of the liquid crystal cell 1, a 4K2K VA mode liquid crystal cell 2 (55 inches 55XS5 manufactured by Toshiba, the number of pixels is 2160 in length and 3840 in width) was used.

  Films 1 to 11 used in Examples 3 to 12 and Comparative Example 1 were produced by the following methods, respectively.

  In the production of film 1, in the production of film 1, the filtration device for passing the melted polyester is changed from one set of filtration device having a filter opening of 8 μm to three sets of filtration device, and the first set is counted from the upstream side of the filtration process. Film 1 except that the filter aperture installed in the filtration device is 5 μm, the filter aperture installed in the second set of filtration devices is 8 μm, and the filter aperture installed in the third set of filtration devices is 4 μm. It produced similarly.

  In the production of film 1, instead of synthesizing antimony trioxide using PET resin as a synthesis catalyst in the production of film 1, a Ti catalyst (sodium titanate with composition formula, Ti addition amount is 10 ppm in terms of element) The film 1 was prepared in the same manner as the film 1 except that it was synthesized.

  The film 4 was produced in the same manner as the film 1 except that in the production of the film 1, PET1 containing no UV absorber was used instead of PET2 as a material for the intermediate layer (II layer).

  The film 5 is a film except that in the production of the film 1, a quaternary ammonium salt (Enazicol CNS, manufactured by Lion Corporation) is further added in an amount of 10.0% by mass with respect to the solid content of the polyester. 1 was produced.

  The film 6 was produced in the same manner as the film 1 except that the uniaxial kneading extruder was changed to a biaxial kneading extruder in the production of the film 1.

  The film 7 is manufactured by changing the distance between the electrostatic application electrode and the point where the polyester resin adheres to the cooling drum from 17 mm to 13 mm, changing the electrostatic application voltage from 8.5 kV to 10 kV, and cooling the film 1. It was produced in the same manner as Film 1 except that the resin temperature when closely contacting on the drum was changed from 277 ° C. to 280 ° C. or higher.

  The film 8 is different from the production of the film 1 except that 20% (4 of 20) of the transport roll group is driven, and 90% (18 of 20) of the transport roll group is driven. Was prepared in the same manner as film 1.

  The film 9 was produced in the same manner as the film 1 except that, in the production of the film 1, an application bar used for applying an easy-adhesion layer to the unstretched polyester film 1 was changed from a wire bar to a rolled bar.

  In the production of film 1, the filtration device for passing the melted polyester is changed from one set of filtration device with a filter opening of 8 μm to three sets of filtration device in the production of film 1, and the first set of filtration counted from the upstream side of the filtration process The filter aperture installed in the device is 5 μm, the filter aperture installed in the second set of filtration devices is 8 μm, the filter aperture installed in the third set of filtration devices is 4 μm, and PET resin is a Ti catalyst. The film 1 was changed from a single-screw kneading extruder to a twin-screw kneading extruder, and the distance from the point where the polyester resin was in close contact with the cooling drum was changed from 17 mm to 13 mm, and the electrostatic applied voltage was changed from 8.5 kV to 10 kV. Then, the resin temperature when closely contacting the cooling drum is changed from 277 ° C. to 280 ° C. or more, and 20% of the transport roll of the film 1 (in 20 90% (18 out of 20) are changed to drive-type transport rolls, while quaternary ammonium salt (Enazicol CNS, manufactured by Lion Co., Ltd.) is applied to coating liquid P1. ) Was added in an amount of 10.0% by mass with respect to the solid content of the polyester, and was produced in the same manner as the film 1 except that a rolling bar was used as the coating bar.

  The film 11 has one filter (aperture, that is, a pore diameter of 10 μm) instead of one set of filtration device having a filter (aperture 8 μm) as a filtration device for passing molten polyester in the production of the film 1. It produced similarly to the film 1 except having used 1 set of filtration apparatuses. In Example 1 of [0105] of International Publication WO2012-157663, a filter having a filtration accuracy of 10 μm (aperture 10 μm) is used as the filter medium.

  The film 12 was produced in the same manner except that the raw material polyester 3 was used instead of the raw material polyester 2 in the production of the film 1.

  In the production of the film 11, the film 13 is stretched 3.2 times at 90 ° C. with respect to the conveying direction before stretching in the width direction, and then stretched 4 times in the width direction at 145 ° C., and 220 ° C. at the heat setting part. A biaxially stretched film was prepared in the same manner except that it was heat-treated.

[Example 14]
In the following, adhesion to the polarizer was performed using a UV adhesive instead of the above PVA glue.
Details are shown below.

According to the following method, a coating liquid 1 for forming an adhesive layer, which is a cationic polymerization type actinic ray curable adhesive liquid, was prepared. After the following components were mixed, defoaming was performed to prepare a coating solution 1 for forming an adhesive layer.
・ 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate
: 45 parts by mass · Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries): 40 parts by mass · 1,4-butanediol diglycidyl ether: 15 parts by mass · triarylsulfonium hexafluorophosphate: 2.3 Parts by mass, 9,10-dibutoxyanthracene: 0.1 parts by mass, 1,4-diethoxynaphthalene: 2.0 parts by mass

A polarizing plate was produced according to the following method.
The prepared adhesive layer-forming coating solution 1 was applied onto the film 1 with a bar coater so that the film thickness after curing was 2.0 μm to form an actinic ray curable resin layer. The prepared polyvinyl alcohol-iodine polarizer was bonded to the obtained actinic ray curable resin layer.
Next, using the WVBZ (retardation film), the prepared adhesive layer forming coating solution 1 is coated with a bar coater so that the film thickness after curing is 2.0 μm, and the actinic ray curable resin layer Formed.
A polarizer bonded to one side of the film 1 is bonded to the actinic ray curable resin layer, and film 1 / active ray curable resin layer / polarizer / active ray curable resin layer / WVBZ is laminated. The resulting laminate was obtained. In that case, it bonded in the strip | belt state so that the slow axis of WVBZ and the absorption axis of a polarizer may become mutually orthogonal.
UV irradiation is performed from the WVBZ surface side of this laminate using an ultraviolet irradiation device (the lamp uses a D bulb manufactured by Fusion UV Systems) so that the integrated light quantity becomes 750 mJ / cm ^2, and actinic ray curing is performed. The mold resin layer was cured to produce the polarizing plate of Example 14. This polarizing plate was used on the front side and the backlight side of the liquid crystal cell as shown in Table 2 below.

[Example 15]
In Example 14, films 3 and 4 were used instead of film 1 as shown in Table 2 below. The backlight side polarizing plate was irradiated with UV from both surfaces of WVBZ and film 4 during UV exposure. Since both sides could be irradiated, irradiation time and adhesiveness with a polarizer improved. Otherwise, a liquid crystal display device was produced in the same manner.

[Examples 16 and 17]
The film 14 was produced in the same manner as the production of the film 1 except that the coating liquid P1 for the polarizer-side easy-adhesion layer was not applied.
The film 15 was produced in the same manner as the production of the film 1 except that the surface thereof was subjected to corona discharge treatment (corona discharge treatment condition: ² KJ / m ² ) before applying the adhesive layer forming coating solution 1. .
Other than that was carried out similarly to Example 14, and produced the liquid crystal display device by the structure shown in Table 2 below.

[Characteristics of polyester film, evaluation of liquid crystal display]
Characteristic evaluation of the polyester film used for the polarizing plate of each Example and Comparative Example, and evaluation of the polarizing plate and liquid crystal display device of each Example and Comparative Example were performed by the following methods.
The obtained results are shown in Table 1 or 2.

<Confirmation of concave or convex shape extending in the film width direction>
Each of the prepared film samples is visually and observed with a 20-fold stereo microscope, the aspect ratio is 2 or more, the length in the film width direction is 10 μm or more, and the convex or concave step is 0.1 μm or more. Or for convex shapes (concave or convex shape extending in the film width direction), the number per unit area of concave or convex shapes extending in the film width direction, aspect ratio of concave or convex shapes extending in the film width direction (film width) The average value of the length in the direction of the film / the average value of the length in the film longitudinal direction), and the average value (size) of the length in the film width direction of the concave or convex shape extending in the film width direction were evaluated.
Furthermore, the (height) of the concave or convex convex portion or concave step extending in the film width direction was measured by the following method.
The height of the step of the concave portion or the convex portion was measured with respect to each linear concave portion or convex portion using an optical interference microscope (non-contact surface shape measuring device VertScan, manufactured by Ryoka System Co., Ltd.).
Note that the average value of the length in the film width direction of the concave or convex shape extending in the film width direction, the average value of the length in the film longitudinal direction, and the average value of the convex or concave step are all aspect ratios of 2 or more. The average in 1 m ² of a concave or convex shape (concave or convex shape extending in the film width direction) having a length in the film width direction of 10 μm or more and a convex or concave step of 0.1 μm or more. Asked.

<Re>
The retardation in the in-plane direction is the product (ΔNxy × d) of the biaxial refractive index anisotropy (ΔNxy = | Nx−Ny |) on the film and the film thickness d (nm). It is a defined parameter and is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using two polarizing plates, the orientation axis direction of the film was determined, and a 4 cm × 2 cm rectangle was cut out so that the orientation axis directions were perpendicular to each other, and used as a measurement sample. For this sample, the biaxial refractive index (Nx, Ny) perpendicular to each other and the refractive index (Nz) in the thickness direction were determined by an Abbe refractometer (NAGO-4T, measurement wavelength 589 nm, manufactured by Atago Co., Ltd.). The absolute value of the refractive index difference (| Nx−Ny |) was defined as the refractive index anisotropy (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (manufactured by Fine Reef, Millitron 1245D), and the unit was converted to nm. Retardation (Re) was determined from the product (ΔNxy × d) of refractive index anisotropy (ΔNxy) and film thickness d (nm).

<Melting sub-peak temperature (Tsm)>
Using DSC220 manufactured by Seiko Denshi Kogyo Co., Ltd., a DSC curve is drawn at a rate of temperature increase of 20 ° C./min using a polyester film sample amount of 10 mg. (Tsm).

<Common logarithm of surface resistivity SR (log SR)>
Using a super insulation resistance / microammeter TR8601 (manufactured by Advantest Co., Ltd.), the surface resistivity SR (unit is Ω / sq) was measured.

<Evaluation of rainbow unevenness>
Using a continuous light source (white LED) from one side, light was incident, and visually observed through polarized sunglasses from the opposite side, and the rainbow unevenness was evaluated by the ease of visual recognition of the rainbow unevenness.
Note that the rainbow unevenness was evaluated from both the normal direction of the polarizing plate and the oblique direction (45 ° from the normal line).
A: Rainbow unevenness is not visible B: Rainbow unevenness is visible

<Display quality: Confirmation by sensory evaluation>
The quality (defects) when the produced liquid crystal display devices of Examples and Comparative Examples were displayed under normal temperature and humidity conditions was observed.
Each of the 10 liquid crystal display devices was evaluated by having ten observers point the display quality sensuously. If the average of less than 1 out of 10 is found to be defective when displaying black or white, S,
1 or more than 10 out of 10 A,
B in the case of 1.5 to 3 of 10
In case of 3 or more out of 10 or more than 4
As evaluated. Practically, S, A or B evaluation is required, S or A evaluation is preferable, and S evaluation is more preferable.

From the above Tables 1 and 2, it was found that the polyester film of the present invention can suppress the occurrence of rainbow unevenness and can improve the display quality of the liquid crystal display device when incorporated in the liquid crystal display device.
On the other hand, from Comparative Example 1, as in Example 1 of [0105] of International Publication No. WO2012-157663, a film 11 produced by making the aperture of a filter through which molten polyester passes larger than the range specified in the present invention. Was found to be a polyester film in which the number per unit area of concave or convex shapes extending in the film width direction exceeded the upper limit of the range defined in the present invention. Further, such a polyester film (film 11) in which the number per unit area of the concave or convex shape extending in the film width direction exceeds the upper limit value of the range defined in the present invention is liquid crystal when incorporated in a liquid crystal display device. It was found that the display quality of the display device was inferior.

  In addition, rather than the liquid crystal display device of Example 5 using the film 4 to which the ultraviolet absorber is not added as the protective film for the front side polarizing plate, the film 1 to which the ultraviolet absorber is added as the protective film for the front side polarizing plate. Polarizer performance when the liquid crystal display device according to any one of Examples 1 to 4 and 6 to 12 using any one of 3 and 5 to 10 is irradiated with ultraviolet rays from the front-side polarizing plate It was found that the light resistance was good and the light resistance was good.

DESCRIPTION OF SYMBOLS 1 Polarizer 2 Polyester film 3a Polarizer side easy-adhesion layer 3b Hard coat layer side easy-adhesion layer 4 Hard coat layer 10 Protective film

Claims (19)

A polyester film containing polyester and uniaxially stretched in the film width direction,
In-plane retardation Re is 4000 to 20000 nm,
The melting sub-peak temperature Tsm is 130-190 ° C.,
The aspect ratio of the length in the film width direction to the direction perpendicular to the film width direction is 2 or more, the length in the film width direction is 10 μm or more, and the convex or concave step is 0.1 μm or more. A polyester film having a shape of 0.3 pieces / m ² or less. The polyester film according to claim 1, wherein the concave or convex shape is 0.1 piece / m ² or less.   The polyester film according to claim 1 or 2, wherein an average value of the concave or convex convex portions or concave steps is 0.1 µm or less.   The polyester film according to any one of claims 1 to 3, wherein the polyester is polymerized using a catalyst containing a titanium atom.   The polyester film according to claim 1, wherein the amount of the ultraviolet absorber is 0.1% by mass or less based on the polyester. The polyester film according to any one of claims 1 to 5, wherein a common logarithm logSR of the surface resistivity SR of at least one surface of the polyester film is 10 or less.
However, the unit of the surface resistivity SR is Ω / sq.   It is a polarizing plate protective film use, The polyester film as described in any one of Claims 1-6.   A polarizing plate comprising a polarizer and the polyester film according to claim 1. Furthermore, it has a cellulose acylate film,
The polarizing plate according to claim 8, wherein the polyester film is laminated on one surface of the polarizer and the cellulose acylate film is laminated on the other surface.   The polarizing plate according to claim 8 or 9, wherein the polyester film is laminated with the polarizer via an ultraviolet curable adhesive.   An image display comprising the polyester film according to any one of claims 1 to 7 or the polarizing plate according to any one of claims 8 to 10, wherein the number of pixels is 3000 or more in the horizontal direction and 1500 or more in the vertical direction. apparatus. A liquid crystal cell;
The polyester film according to any one of claims 1 to 7 or the polarizing plate according to any one of claims 8 to 10 disposed on at least one surface of a backlight side and a front side of the liquid crystal cell. And
A liquid crystal display device in which the number of pixels is 3000 or more in the horizontal direction and 1500 or more in the vertical direction.   The liquid crystal display device according to claim 12, wherein the polyester film has a polyester film having an ultraviolet absorber amount of 0.1% by mass or less with respect to the polyester on the backlight side of the liquid crystal cell. A melting step of melting polyester with an extruder;
A filtration step of filtering the melted polyester through a filtration device provided with a filter;
Extruding the filtered polyester into a sheet form from a die, a film forming step of forming an unstretched polyester film by cooling and solidifying by adhering onto a cooling drum,
In the tenter type stretching device having a clip that travels along a pair of rails installed on both sides of the film conveyance path, the unstretched polyester film is horizontally stretched while being gripped by the clip; and
Including a heat setting step of heating the polyester film after the transverse stretching to the maximum temperature in the tenter,
The manufacturing method of the polyester film whose aperture of the filter installed in the said filtration process is 8 micrometers or less. In the filtration step, there are three or more sets of filtration devices,
The filter opening Xμm installed in the first set of filtration devices, counted from the upstream side of the filtration process, the filter opening Yμm installed in the second set of filtration devices, and the third set of filtration devices The method for producing a polyester film according to claim 14, wherein the aperture Z μm of the formed filter satisfies the following formula A:
Formula A ... Z≤X <Y The extruder used in the melting step is a twin screw extruder;
The method for producing a polyester film according to claim 14 or 15, wherein a temperature of the polyester extruded from the die is 280 ° C or higher and 320 ° C or lower. In the film forming step, an electrostatic application electrode is used when the polyester is in close contact with the cooling drum,
The temperature of the polyester when in close contact with the cooling drum is 280 ° C. or higher,
The distance between the electrostatic application electrode and the point where the polyester is in close contact with the cooling drum is 15 mm or less,
The method for producing a polyester film according to any one of claims 14 to 16, wherein an applied voltage of the electrostatic application electrode is 9 kV or more. From the point where the unstretched polyester film is peeled off from the cooling drum, a transport roll is installed between the tenter-type stretching device and the entrance.
The manufacturing method of the polyester film as described in any one of Claims 14-17 in which 50% or more of the said conveyance roll which contacts the said unstretched polyester film is a drive-type conveyance roll. A step of applying a coating solution to the unstretched polyester film;
The coating method of the coating solution is bar coating,
The manufacturing method of the polyester film as described in any one of Claims 14-18 using a rolling bar for the said bar coat.

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