JP2014044390A - Liquid crystal display device, polarizing plate and polarizer protection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizer protection film suitable for a liquid crystal display device with excellent visibility.SOLUTION: In a polarizer protection film for a liquid crystal display device having a white light source with continuous emission spectra as a backlight light source, on at least one face of a polyester film with a retardation of 3000-30000 nm, a coating layer mainly composed of a urethane resin comprising an aliphatic polycarbonate polyol and a crosslinking agent is laminated.

Description

  The present invention relates to a liquid crystal display device, a polarizing plate, and a polarizer protective film. Specifically, the present invention relates to a liquid crystal display device having favorable visibility and suitable for thinning, and a polarizing plate and a polarizer protective film for the liquid crystal display device.

  A polarizing plate used in a liquid crystal display (LCD) usually has a configuration in which a polarizer in which iodine is dyed on polyvinyl alcohol (PVA) or the like is sandwiched between two polarizer protective films. As the film, a triacetyl cellulose (TAC) film is usually used. In recent years, with the thinning of LCDs, there has been a demand for thinner polarizing plates. However, if the thickness of the TAC film used as the protective film is reduced for this purpose, sufficient mechanical strength cannot be obtained, and the moisture permeability becomes high and the polarizer is likely to deteriorate. Further, TAC films are very expensive, and there is a strong demand for inexpensive alternative materials.

  Therefore, it has been proposed to use a polyester film instead of the TAC film so that the polarizing plate can be made thin so that high durability can be maintained even if the thickness is small as a polarizer protective film (Patent Documents 1 to 3). ).

JP 2002-116320 A JP 2004-219620 A JP 2004-205773 A

  The polyester film is superior to the TAC film in durability, but unlike the TAC film, the polyester film has birefringence. Therefore, when the polyester film is used as a polarizer protective film, there is a problem that the image quality is deteriorated due to optical distortion. That is, since the polyester film having birefringence has a predetermined optical anisotropy (retardation), when used as a polarizer protective film, a rainbow-like color spot is generated when observed from an oblique direction, and the image quality is deteriorated. . Therefore, in patent documents 1-3, the countermeasure which makes retardation small is made by using copolyester as polyester. However, even in that case, the iridescent color spots could not be completely eliminated.

  The present invention is to solve such a problem, and the object thereof is to cope with the thinning of the liquid crystal display device (that is, has sufficient mechanical strength) and is visually recognized by rainbow-like color spots. It is to provide a liquid crystal display device and a polarizer protective film that do not cause deterioration in properties. In addition, the present invention provides a polarizer protective film and a polarizing plate that have the above-mentioned properties and are excellent in adhesion to various functional layers such as a hard coat layer (particularly, adhesion under high-temperature and high-humidity conditions), and these. It is a further object to provide a liquid crystal display device.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have, as a main component, a urethane resin and a cross-linking agent, which are composed of aliphatic polycarbonate polyol, on a polyester film having a specific retardation. The present inventors have found that the above-mentioned problems can be solved by using a laminated film provided with a coating layer as a polarizer protective film and using it in combination with a specific backlight light source, thereby completing the present invention.

That is, a typical present invention is as follows.
Item 1.
A white light source having a continuous emission spectrum, in which a coating layer mainly composed of a urethane resin and a cross-linking agent containing aliphatic polycarbonate polyol as a main component is laminated on at least one surface of a polyester film having a retardation of 3000 to 30000 nm. A polarizer protective film for a liquid crystal display device using a light source as a backlight source.
Item 2.
Absorbance around 1460 cm ^-1 derived from an aliphatic polycarbonate component ratio of _{(A 1460)} and 1530 cm ^-1 near the absorbance derived from urethane component with _{(A 1530) (A 1460 /} A 1530) is 0.40 to 1.55 Item 2. The polarizer protective film according to Item 1.
Item 3.
Item 3. The polarizer protective film according to Item 1 or 2, wherein the crosslinking agent is at least one selected from the group consisting of a melamine crosslinking agent, an isocyanate crosslinking agent, a carbodiimide crosslinking agent, and an oxazoline crosslinking agent.
Item 4.
Item 4. The polarizer protective film according to any one of Items 1 to 3, wherein a mass ratio of the urethane resin and the crosslinking agent (urethane resin / crosslinking agent) is 1/9 to 9/1.
Item 5.
Item 5. The polarizer protective film according to any one of Items 1 to 4, wherein the ratio of the retardation of the polyester film to the retardation in the thickness direction (Re / Rth) is 0.2 or more.
Item 6.
Item 6. The polarizer protective film according to any one of Items 1 to 5, wherein the polyester film is composed of at least three layers and contains an ultraviolet absorber in a layer other than the outermost layer, and the light transmittance at 380 nm is 20% or less. .
Item 7.
One or more layers selected from the group consisting of a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, a low reflection antiglare layer, an antireflection antiglare layer and an antistatic layer are laminated on the coating layer. Furthermore, the polarizer protective film in any one of claim | item 1 -6.
Item 8.
The polarizing plate for liquid crystal display devices which makes the backlight light source the white light source which has the continuous emission spectrum by which the polarizer protective film in any one of claim | item 1 -7 was laminated | stacked on the at least one side of the polarizer.
Item 9
Item 9. The polarizing plate for a liquid crystal display device according to item 8, wherein the polarizer protective film is laminated on the polarizer via an ultraviolet curable, electron beam curable, or thermosetting adhesive.
Item 10.
Item 10. A liquid crystal display device, wherein the backlight source is a white light source having a continuous emission spectrum and has the polarizing plate according to Item 8 or 9.
Item 11.
Item 10. The liquid crystal display device according to item 10, wherein the polarizing plate disposed on the emission light side with respect to the liquid crystal is the polarizing plate according to item 8 or 9.
Item 12.
Item 12. The liquid crystal display device according to item 10 or 11, wherein the white light source having a continuous emission spectrum is a white LED.

  The liquid crystal display device, the polarizing plate and the polarizer protective film of the present invention have good visibility in which no noticeable rainbow-like color spots are observed at any viewing angle. Moreover, the polarizer protective film of this invention is excellent in adhesiveness (humidity heat resistance) under high temperature and high humidity with functional layers, such as various hard-coat layers. Therefore, the polarizer protective film of the present invention can maintain the initial adhesiveness for a long time because the adhesiveness with the hard coat layer hardly deteriorates over time even under high temperature and high humidity conditions. . In a preferred embodiment, the polarizer protective film of the present invention has a mechanical strength suitable for thinning.

  In general, the liquid crystal panel includes a rear module, a liquid crystal cell, and a front module in order from the backlight source side toward the image display side (viewing side or emission light side). The rear module and the front module are generally composed of a transparent substrate, a transparent conductive film formed on the liquid crystal cell side surface, and a polarizing plate disposed on the opposite side. Here, the polarizing plate is disposed on the backlight source side in the rear module, and is disposed on the image display side (viewing side or emission light side) in the front module.

  The liquid crystal display device of the present invention comprises at least a backlight source and a liquid crystal cell disposed between two polarizing plates. 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 backlight may be of an edge light type using a light guide plate or a reflection plate as a component, or a direct type, but a white light source having a continuous and broad emission spectrum should be used. Is preferred. Here, the continuous and broad emission spectrum means an emission spectrum in which there is no wavelength at which light intensity becomes zero in a wavelength region of at least 450 nm to 650 nm, preferably in a visible light region. Examples of such a white light source having a continuous and broad emission spectrum include a white light emitting diode (white LED). In the present invention, the white LED includes a phosphor type, that is, an element that emits white by combining a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor and a phosphor, or an organic light emitting diode (Organic light-emitting diode). diode: OLED). Examples of the phosphor include yttrium / aluminum / garnet yellow phosphor and terbium / aluminum / garnet yellow phosphor. Among white LEDs, white light-emitting diodes that consist of a light-emitting element that combines a blue light-emitting diode using a compound semiconductor and a yttrium / aluminum / garnet-based yellow phosphor have a continuous and broad emission spectrum and light emission efficiency. Therefore, it is suitable as the backlight light source of the present invention. By using a white LED or the like with lower power consumption as a light source, it is effective for energy saving.

  Fluorescent tubes such as cold cathode tubes and hot cathode tubes that have been widely used as backlight light sources conventionally have only a discontinuous emission spectrum whose emission spectrum has a peak at a specific wavelength. It is difficult to obtain the effects of the present invention.

  The polarizing plate has a configuration in which both sides of a polarizer in which iodine is dyed on PVA or the like are sandwiched between two polarizer protective films. In the present invention, at least one of the polarizer protective films constituting the polarizing plate is used. A polyester film having a specific range of retardation is used.

  The mechanism by which the occurrence of rainbow-like color spots is suppressed by the above aspect is considered as follows. When a polyester film having birefringence is disposed on one side of the polarizer, the linearly polarized light emitted from the polarizer is disturbed when passing through the polyester film. The transmitted light shows an interference color peculiar to retardation which is the product of birefringence and thickness of the polyester film. Therefore, if a discontinuous emission spectrum such as a cold cathode tube or a hot cathode tube is used as the light source, the transmitted light intensity varies depending on the wavelength, and a rainbow-like color spot is generated (see: 15th Micro Optical Conference Proceedings, No. 1 30-31).

  In contrast, white light emitting diodes usually have a continuous and broad emission spectrum in a wavelength region of at least 450 nm to 650 nm, preferably in the visible light region. And since the interference color spectrum by the transmitted light which permeate | transmitted the birefringent body becomes an envelope shape, it becomes possible to obtain the spectrum similar to the light emission spectrum of a light source by controlling the retardation of a polyester film. In this way, by making the emission spectrum of the light source similar to the envelope shape of the interference color spectrum by the transmitted light that has passed through the birefringent body, visibility is not noticeable without rainbow-like color spots. It is thought to improve.

  From the above principle, in the present invention, a white light emitting diode having a broad emission spectrum is used as a light source, so that the envelope shape of the spectrum of transmitted light can be approximated to the emission spectrum of the light source with only a relatively simple configuration, and as a result, liquid crystal It is thought that it is possible to suppress rainbow spots on the display.

(Polyester film: base film)
The polyester film used as the base film of the polarizer protective film of the present invention is preferably an oriented polyester film having a retardation of 3000 to 30000 nm. When the retardation is less than 3000 nm, when used as a polarizer protective film, it exhibits a strong interference color when observed from an oblique direction, so the envelope shape is different from the emission spectrum of the light source, and good visibility cannot be ensured. . The lower limit of the preferable retardation is 4500 nm or more, next preferably 5000 nm or more, more preferably 6000 nm or more, still more preferably 8000 nm or more, and still more preferably 10,000 nm or more.

  On the other hand, the upper limit of retardation is 30000 nm. Even if a polyester film having a retardation of more than that is used, it is not only possible to substantially improve the visibility, but also because the film thickness becomes considerably thick and the handling property as an industrial material is reduced, it is preferable. Absent.

  The retardation of the polyester film can be obtained by measuring the biaxial refractive index and thickness, or can be obtained by using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Scientific Instruments). . In this document, retardation means in-plane retardation.

  In the present invention, at least one of the polarizer protective films is a polarizer protective film having the specific retardation. The arrangement of the polarizer protective film having the specific retardation is not particularly limited, but the polarizer protective film on the incident light side of the polarizing plate arranged on the incident light side of the liquid crystal display device, or the polarized light arranged on the emission light side It is preferable that the polarizer protective film on the emission light side of the plate is a polarizer protective film made of a polyester film having the specific retardation. A particularly preferred embodiment is an embodiment in which the polarizer protective film on the exit light side of the polarizing plate disposed on the exit light side is a polyester film having the specific retardation. When the polyester film is disposed at a position other than the above, the polarization characteristics of the liquid crystal cell may be changed. Since it is not preferable to use the polymer film of the present invention at a place where polarization characteristics are required, it is preferably used as a protective film for a polarizing plate at such a specific position.

  The polarizing plate of the present invention has a structure in which both sides of a polarizer in which iodine is dyed on polyvinyl alcohol (PVA) or the like are sandwiched between two polarizer protective films, and any one of the polarizer protective films is specified above. It is a polarizing plate protective film which has this retardation. As the other polarizer protective film, it is preferable to use a film having no birefringence such as a TAC film, an acrylic film, and a norbornene-based film.

The polyester film can be obtained by condensing a dicarboxylic acid and a diol.
Examples of the dicarboxylic acid component that can be used for producing the polyester film include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1 , 5-Naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid , Hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyl Horse mackerel Phosphate, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecamethylene dicarboxylic acid and the like.

  Examples of the diol component that can be used for producing the polyester film include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1 , 3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, etc. Can be mentioned.

  Each of the dicarboxylic acid component and the diol component constituting the polyester film may be used alone or in combination of two or more. Specific polyester resins constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and preferably polyethylene terephthalate and polyethylene naphthalate. These resins are excellent in transparency and excellent in thermal and mechanical properties, and the retardation can be easily controlled by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence and a large retardation can be obtained relatively easily even if the film is thin.

  Moreover, in order to suppress deterioration of optical functional pigments such as iodine pigments, it is desirable that the protective film of the present invention has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. If the light transmittance is 20% or less, the optical functional dye can be prevented from being deteriorated by ultraviolet rays. In addition, the transmittance | permeability in this invention is measured by the perpendicular | vertical method with respect to the plane of a film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

  Setting the transmittance at a wavelength of 380 nm of the protective film of the present invention to 20% or less includes adding an ultraviolet absorber in the film, applying a coating solution containing the ultraviolet absorber to the film surface, and an ultraviolet absorber. This can be achieved by appropriately adjusting the type, concentration, and thickness of the film. The ultraviolet absorber used in the present invention is a known substance. Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable from the viewpoint of transparency.

  Examples of the organic ultraviolet absorber include benzotriazole, benzophenone, cyclic imino ester, and combinations thereof, but are not particularly limited as long as the absorbance is within the range defined by the present invention. However, from the viewpoint of durability, benzotoazole and cyclic imino ester are particularly preferable. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays having different wavelengths can be absorbed simultaneously, so that the ultraviolet absorption effect can be further improved. When the ultraviolet absorber is blended with the polyester film, the polyester film is preferably composed of three or more layers, and the ultraviolet absorber is blended with a layer other than the outermost layer (that is, the intermediate layer).

  Examples of the benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber, and acrylonitrile ultraviolet absorber include 2- [2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2,2 ′ -Dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2- (2′-Hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (5-chloro (2H) -benzotriazol-2-yl) -4-methyl-6- (tert-butyl) phenol, 2,2'-methylenebis (4- (1, 1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, etc. Examples of cyclic imino ester UV absorbers include 2,2 ′-(1,4-phenylene). ) Bis (4H-3,1-benzoxazinon-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, 2- Examples include phenyl-3,1-benzoxazin-4-one, but are not limited thereto.

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

(Coating layer)
The polarizer protective film of the present invention is formed with a coating layer mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component and a crosslinking agent. Here, the “main component” means that it is contained in an amount of 50% by mass or more, more preferably 70% by mass or more as the total solid component contained in the coating layer.

  When an optical functional layer or the like (for example, a hard coat layer) is laminated on the base polyester film, the functional layer and the coating layer are caused by shrinkage during curing of the photocurable resin constituting the functional layer and swelling during high-temperature and high-humidity treatment. Strong stress is generated between When this laminated film is placed under high temperature and high humidity, the coating layer deteriorates due to dissolution, swelling or hydrolysis by the solvent contained in the photocurable resin. As a result, it was considered that the above-mentioned stress could not be endured, the functional layer was peeled off, and the adhesion was lowered. Therefore, in order to maintain a high degree of adhesion under high temperature and high humidity, the coating layer should not only be firmly cross-linked or provided with hydrolysis resistance but also be flexible enough to withstand the above stress. Is considered desirable. However, simply having flexibility is problematic in terms of solvent resistance and strength. Therefore, it is most desirable to make these conflicting characteristics compatible.

In the present invention, the coating layer is mainly composed of a urethane resin having an aliphatic polycarbonate polyol as a constituent component and a cross-linking agent as a main component, and the coating layer is in the vicinity of 1460 cm ⁻¹ derived from an aliphatic polycarbonate component measured by infrared spectroscopy. The ratio (A ₁₄₆₀ / A ₁₅₃₀ ) of the absorbance (A ₁₄₆₀ ) and the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ derived from the urethane component is desirably 0.40 to 1.55. That is, the above-mentioned characteristics can be achieved by coexisting a predetermined amount of an aliphatic polycarbonate component having hydrolysis resistance and flexibility and a urethane component exhibiting toughness while providing solvent resistance with a crosslinking agent. Plan. Thereby, since the stress due to the shrinkage at the time of curing of the photocurable resin and the swelling due to the swelling at the time of high temperature and high humidity treatment can be relieved, it is possible to obtain good adhesion with various photocurable resins and the like. It is considered that the coating layer can be prevented from being degraded such as dissolution, swelling and hydrolysis due to the solvent and diluent monomer remaining in the coating layer even in a high temperature and high humidity environment.

Absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ is derived from the bending vibration specific to the CH bond of the methylene group contained in the aliphatic polycarbonate component. Therefore, the magnitude of the absorbance (A ₁₄₆₀ ) near 1460 cm ⁻¹ depends on the amount of the aliphatic polycarbonate polyol component constituting the urethane resin present in the coating layer. On the other hand, the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ is derived from the bending vibration specific to the N—H bond contained in the urethane component. Therefore, the magnitude of the absorbance (A ₁₅₃₀ ) near 1530 cm ⁻¹ depends on the amount of urethane components (number of urethane bonds) constituting the urethane resin present in the coating layer. Moreover, when using an isocyanate type crosslinking agent as a crosslinking agent, the magnitude | size of the light absorbency ( _A1530 ) vicinity of 1530cm < ^-1 > is the urethane component amount (urethane bond number) as the sum total of the urethane resin and crosslinking agent amount which exist in a coating layer. Depends on. Therefore, these absorbance ratios (A ₁₄₆₀ / A ₁₅₃₀ ) indicate that both components having different characteristics coexist in a specific ratio.
In the present invention, the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is preferably 0.4 to 1.55, but the lower limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is more preferably 0.45, Preferably it is 0.5. The upper limit of the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is more preferably 1.5, still more preferably 1.4, particularly preferably 1.30, and most preferably 1.2. When the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) is less than 0.4, there are too many hard urethane components, and the stress relaxation of the coating layer tends to decrease, so the heat and humidity resistance may decrease. Further, when the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) exceeds 1.55, there are too many aliphatic components of the flexible aliphatic polycarbonate, and the solvent resistance of the coating layer tends to be lowered, so that the heat and moisture resistance is increased. May decrease.

(Urethane resin)
The urethane resin constituting the coating layer contains at least a polyol component and a polyisocyanate component as constituent components, and further contains a chain extender as necessary. The urethane resin of the present invention is a polymer compound in which these constituent components are mainly copolymerized by urethane bonds. In this invention, it has an aliphatic polycarbonate polyol as a structural component of a urethane resin. Heat-and-moisture resistance can be improved by including a urethane resin containing an aliphatic polycarbonate as a constituent component in the coating layer of the present invention. The components of these urethane resins can be specified by nuclear magnetic resonance analysis or the like.

  The diol component, which is a constituent component of the urethane resin of the present invention, needs to contain an aliphatic polycarbonate polyol having excellent heat resistance and hydrolysis resistance. In the optical use of the present invention, it is preferable to use an aliphatic polycarbonate polyol from the viewpoint of preventing yellowing.

  Examples of the aliphatic polycarbonate polyol include aliphatic polycarbonate diols and aliphatic polycarbonate triols, and aliphatic polycarbonate diols can be preferably used. Examples of the aliphatic polycarbonate diol that is a constituent component of the urethane resin of the present invention include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl- 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexane Aliphatic polycarbonate diols obtained by reacting one or more diols such as dimethanol with carbonates such as dimethyl carbonate, diphenyl carbonate, ethylene carbonate, and phosgene. It is below.

The number average molecular weight of the aliphatic polycarbonate diol is preferably 1500 to 4000, and more preferably 2000 to 3000. When the number average molecular weight of the aliphatic polycarbonate diol is small, the ratio of the aliphatic polycarbonate component constituting the urethane resin is relatively small. Therefore, in order to make the ratio (A ₁₄₆₀ / A ₁₅₃₀ ) within the above range, it is preferable to control the number average molecular weight of the aliphatic polycarbonate diol within the above range. If the number average molecular weight of the aliphatic polycarbonate diol is large, the absorbance (A ₁₄₆₀ ) in the vicinity of 1460 cm ⁻¹ derived from the aliphatic polycarbonate component increases and the aliphatic component increases, so that the solvent resistance decreases. , The adhesion may be reduced. If the number average molecular weight of the aliphatic polycarbonate diol is small, a strong urethane component increases, and stress due to shrinkage or swelling of the photocurable resin or the like cannot be relieved, and adhesion may be lowered.

  Examples of the polyisocyanate that is a component of the urethane resin of the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis (isocyanatomethyl) cyclohexane. Such as alicyclic diisocyanates such as hexamethylene diisocyanate and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate; Isocyanates. When aromatic isocyanate is used, there is a problem of yellowing, which may not be preferable for optical use requiring high transparency. Moreover, since it becomes a hard coating film compared with an aliphatic type | system | group, it becomes impossible to relieve | moderate the stress by shrinkage | contraction and swelling of photocurable resin etc., and adhesiveness may fall.

The ratio (A ₁₄₆₀ / A ₁₅₃₀ ) can also be adjusted by a chain extender. Examples of the chain extender that can be used in the present invention include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol and 1,6-hexanediol, glycerin, trimethylolpropane, and pentaerythritol. Polyhydric alcohols, diamines such as ethylenediamine, hexamethylenediamine, and piperazine, amino alcohols such as monoethanolamine and diethanolamine, thiodiglycols such as thiodiethylene glycol, and water. However, when a chain extender having a short main chain is used, the absorbance (A ₁₅₃₀ ) in the vicinity of 1530 cm ⁻¹ derived from the urethane component increases, and the flexibility of the coating layer may decrease. Therefore, a chain extender having a long main chain is preferable. Moreover, the point which provides the softness | flexibility of an application layer has preferable the chain extender of the diol and the diamine whose length of carbon number of a main chain is 4-10. From these points, 1,4-butanediol, 1,6-hexanediol, hexamethylenediamine and the like are preferable as the chain extender used in the present invention.

  The coating layer is preferably provided by an in-line coating method described later using an aqueous coating solution. Therefore, it is desirable that the urethane resin of the present invention is water-soluble. The “water-soluble” means that it dissolves in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

  In order to impart water solubility to the urethane resin, a sulfonic acid (salt) group or a carboxylic acid (salt) group can be introduced (copolymerized) into the urethane molecular skeleton. Since the sulfonic acid (salt) group is strongly acidic and it may be difficult to maintain moisture resistance due to its hygroscopic performance, it is preferable to introduce a weakly acidic carboxylic acid (salt) group. Moreover, nonionic groups, such as a polyoxyalkylene group, can also be introduced.

  In order to introduce a carboxylic acid (salt) group into a urethane resin, for example, as a polyol component, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutanoic acid is introduced as a copolymer component to form a salt. Neutralize with an agent. Specific examples of the salt forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, tri-n-butylamine, N such as N-methylmorpholine and N-ethylmorpholine. -N-dialkylalkanolamines such as alkylmorpholines, N-dimethylethanolamine, N-diethylethanolamine and the like. These may be used alone or in combination of two or more.

  In order to impart water solubility, when a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component, the composition molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is the same as that of the urethane resin. When the total polyisocyanate component is 100 mol%, it is preferably 3 to 60 mol%, more preferably 5 to 40 mol%. If the composition molar ratio is less than 3 mol%, water dispersibility may be difficult. Moreover, when the said composition molar ratio exceeds 60 mol%, since water resistance falls, moist heat resistance may fall.

  The glass transition temperature of the urethane resin of the present invention is preferably less than 0 ° C, more preferably less than -5 ° C. When the glass transition temperature is less than 0 ° C., it is easy to achieve suitable flexibility from the viewpoint of stress relaxation of the coating layer.

  The urethane resin is preferably contained in an amount of 10% by mass to 90% by mass with respect to the crosslinking agent. In particular, when high adhesion is required, it is more preferably 20% by mass or more and 80% by mass or less. When the content of the urethane resin is large, the adhesiveness under high temperature and high humidity is lowered, and conversely, when the content is small, the initial adhesiveness is lowered.

  In order to improve the solvent resistance of the urethane resin, a self-crosslinking group may be introduced into the urethane resin itself in addition to the addition of a crosslinking agent. Thereby, the crosslinking degree of resin increases and solvent resistance improves. Although it does not specifically limit as a self-crosslinking group used for this invention, The comparatively stable silanol group can be used suitably also in aqueous | water-based coating liquid.

  A resin other than the urethane resin may be contained in order to improve adhesion. For example, a urethane resin, an acrylic resin, a polyester resin, or the like containing polyether or polyester as a constituent component can be used.

(Crosslinking agent)
It is preferable to include a crosslinking agent in the coating layer. By containing a crosslinking agent, it becomes possible to further improve the adhesion under high temperature and high humidity. As the cross-linking agent, those that react with a carboxylic acid group, a hydroxyl group, an amino group, etc. to form an amide bond, a urethane bond, or a urea bond are preferable because they are unlikely to be deteriorated by high-temperature and high-humidity treatment. An ester bond or an ether bond is not preferable because it may have hydrolyzability. Examples of the crosslinking agent suitably used in the present invention include melamine-based, isocyanate-based, carbodiimide-based, and oxazoline-based. Among these, an isocyanate type and a carbodiimide type are preferable from the viewpoint of stability over time of the coating solution and the effect of improving adhesion under high-temperature and high-humidity treatment. Furthermore, it is particularly preferable to use an isocyanate-based crosslinking agent from the viewpoint that the coating layer has appropriate flexibility and suitably imparts the stress relaxation action of the coating layer. Moreover, in order to promote a crosslinking reaction, a catalyst etc. are used suitably as needed.

  As content of a crosslinking agent, 10 mass% or more and 90 mass% or less are preferable with respect to urethane resin. More preferably, it is 20 mass% or more and 80 mass% or less. When the amount is small, the solvent resistance of the coating layer is reduced, and the adhesiveness under high temperature and high humidity is reduced.When the amount is large, the flexibility of the resin of the coating layer is reduced, and at room temperature and high temperature and high humidity. The adhesiveness of is reduced.

In the present invention, two kinds of crosslinking agents may be mixed in order to improve the coating film strength.
Moreover, in order to promote a crosslinking reaction, a catalyst etc. are used suitably as needed.

(Additive)
In the present invention, particles may be contained in the coating layer. Such particles include (1) silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, titanium dioxide, satin white, Inorganic particles such as aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrous halloysite, magnesium carbonate, magnesium hydroxide, (2) acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic Styrene / butadiene, polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, Phenol-based, diallyl phthalate, and organic particles of a polyester or the like.

  The particles preferably have an average particle size of 1 to 500 nm. Although an average particle diameter is not specifically limited, If it is 1-100 nm from the point which maintains the transparency of a film, it is preferable.

  The particles may contain two or more kinds of particles having different average particle diameters.

  The average particle size is measured by measuring the maximum diameter of 10 or more particles present in the cross section of the coating layer by photographing a cross section of the laminated film at a magnification of 120,000 using a transmission electron microscope (TEM). And can be obtained as an average value of them.

  As content of particle | grains, 0.5 mass% or more and 20 mass% or less are preferable. When the amount is small, sufficient blocking resistance cannot be obtained, and scratch resistance is deteriorated. When there is too much content of particle | grains, not only the transparency of an application layer will worsen but the coating-film intensity | strength will fall.

  The coating layer may contain a surfactant for the purpose of improving leveling properties during coating and defoaming the coating solution. The surfactant may be any of cationic, anionic and nonionic surfactants, but is preferably a silicon-based, acetylene glycol-based or fluorine-based surfactant. These surfactants are also preferably contained in a range that does not impair the adhesion to the optical functional layer, for example, in the range of 0.005 to 0.5% by mass in the coating solution.

  The polarizer protective film of the present invention preferably has a haze value of 2.5% or less, more preferably 2.0% or less, and further preferably 1.5% or less.

  In order to impart other functionality to the coating layer, various additives may be contained within a range that does not impair the adhesion with the sealing material. Examples of the additive include fluorescent dyes, fluorescent brighteners, plasticizers, ultraviolet absorbers, pigment dispersants, foam suppressors, antifoaming agents, preservatives, and antistatic agents.

  In the present invention, examples of the method for providing the coating layer on the polyester film include a method in which a coating solution containing a solvent, particles and a resin is applied to the polyester film and dried. Examples of the solvent include organic solvents such as toluene, water, and a mixed system of water and a water-soluble organic solvent. Preferably, water alone or a mixture of a water-soluble organic solvent and water is used from the viewpoint of environmental problems. preferable.

  At an arbitrary stage of the film manufacturing process, for example, a coating solution is applied to at least one surface of a polyester film such as a PET film to form the coating layer. The solid content concentration of the resin composition in the coating solution is preferably 2 to 35% by weight, particularly preferably 4 to 15% by weight.

  Any known method can be used as a method for applying the coating solution to the PET film. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, etc. It is done. These methods are applied alone or in combination.

  In the present invention, the coating layer is formed by coating the coating solution on an unstretched or uniaxially stretched PET film, drying it, stretching in at least a uniaxial direction, and then performing a heat treatment.

In the present invention, the finally obtained coating layer preferably has a thickness of 20 to 350 nm, and the coating amount after drying is preferably 0.02 to 0.5 g / m ² . When the coating amount of the coating layer is less than 0.02 g / m ² , the effect on adhesiveness is almost lost. On the other hand, when the coating amount exceeds 0.5 g / m ² , haze increases.

  On the coating layer, various functional layers such as various hard coat layers can be provided for the purpose of preventing reflection, suppressing glare, and suppressing scratches. As the functional layer, various types known in the technical field can be used, and the type is not particularly limited. As described above, the coating layer is excellent in adhesion to the functional layer and moisture and heat resistance.

  For example, in the formation of the hard coat layer, a known hard coat layer can be used, and is not particularly limited, but is polymerized by drying, heat, chemical reaction, or irradiation with any of electron beam, radiation, and ultraviolet rays. And / or a reactive resin compound can be used. Examples of such a curable resin include melamine-based, acrylic-based, silicon-based, and polyvinyl alcohol-based curable resins. However, in terms of obtaining high surface hardness or optical design, a photocurable acrylic curable resin is used. Resins are preferred. As such an acrylic curable resin, a polyfunctional (meth) acrylate monomer or an acrylate oligomer can be used. Examples of the acrylate oligomer include polyester acrylate, epoxy acrylate, urethane acrylate, Examples include ether acrylate, polybutadiene acrylate, and silicone acrylate. A coating composition for forming the optical functional layer can be obtained by mixing a reactive diluent, a photopolymerization initiator, a sensitizer and the like with these acrylic curable resins.

  The hard coat layer may have an anti-glare function (anti-glare function) that scatters external light. The antiglare function (antiglare function) can be obtained by forming irregularities on the surface of the hard coat layer. At this time, the haze of the film is preferably 2 to 50%, more preferably 2 to 40%, and particularly preferably 2 to 30%.

  The coating layer used in the present invention (a coating layer mainly composed of an aliphatic polycarbonate polyol and a urethane resin and a crosslinking agent) is not only a hard coat layer, but also an antiglare layer, an antireflection layer, and a low reflection layer. Excellent adhesion to functional layers such as a layer, a low-reflection anti-glare layer, an anti-reflection anti-glare layer, or an antistatic layer. This is because many of these layers are made of a curable resin that is polymerized and / or reacted by drying, heat, chemical reaction, or irradiation with electron beam, radiation, or ultraviolet light. From the viewpoint of preventing reflection from external light such as LCD and touch panel, it consists of a hard coat layer, anti-glare layer, anti-reflection layer, low reflection layer, low reflection anti-glare layer and anti-reflection anti-glare layer on the coating layer. Laminating one or more layers selected from the group is a preferred embodiment of the present invention. In addition, it is also a preferred embodiment of the present invention that an antistatic layer is laminated from the viewpoint of antistatic. Of the hard coat layer, antiglare layer, antireflection layer, low reflection layer, low reflection antiglare layer, antireflection antiglare layer and antistatic layer, only one type may be provided on the polyester film, You may laminate | stack combining 2 or more types as needed. For example, the antiglare layer and the antistatic layer may be laminated in order, or the antiglare layer may be provided with an antistatic function and the antiglare function and the antistatic function may be combined in one layer. . By providing these layers, an effect of reducing iridescent color spots caused by the polarizing plate can be expected. As the antiglare layer, antireflection layer, low reflection layer, low reflection antiglare layer, antireflection antiglare layer and antistatic layer, known ones can be used. The antistatic layer may be a layer containing a known antistatic agent or a layer containing a conductive polymer such as polythiophene, polypyrrole or polyaniline.

  Further, the polyester film of the present invention can be subjected to corona treatment, coating treatment, flame treatment and the like in order to improve the adhesion to the polarizer.

(Easily adhesive layer with polarizer)
The oriented polyester film which is the polarizer protective film of the present invention has a polyester resin, a polyurethane resin or a polyacrylic resin on the surface opposite to the surface on which the coating layer is provided in order to improve the adhesion to the polarizer. It is preferable to have an easy-adhesion layer containing at least one of the above as a main component. Here, the “main component” refers to a component that is 50% by mass or more of the solid components constituting the easy-adhesion layer. The coating solution used for forming the easy-adhesion layer is preferably an aqueous coating solution containing at least one of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin. Examples of these coating solutions include water-soluble or water-dispersible co-polymers disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Examples thereof include a polymerized polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.

  In addition to the above aspect, it is also preferable that a polarizer is laminated on the surface of the polarizer protective film of the present invention provided with the coating layer via an ultraviolet curable, electron beam curable, or thermosetting adhesive. It is. As described above, the coating layer of the polarizer protective film of the present invention is excellent in adhesiveness with a curable resin and excellent in adhesiveness with an adhesive such as an ultraviolet curable type, an electron beam curable type, and a thermosetting type. is there. As the ultraviolet curable adhesive, electron beam curable adhesive, and thermosetting adhesive, a conventionally known adhesive can be used for manufacturing a polarizing plate, and is not particularly limited. For example, curable resins disclosed in JP2011-219548, JP2011-186481, JP2011-175273, JP2011-127003, and the like can be used.

The easy-adhesion layer can be obtained by applying the coating solution on one or both sides of an unstretched or longitudinally uniaxially stretched film, drying at 100 to 150 ° C., and further stretching in the transverse direction. The final coating amount of the easy adhesion layer is preferably controlled to 0.05 to 0.20 g / m ² . If the coating amount is less than 0.05 g / m ² , the adhesion with the resulting polarizer may be insufficient. On the other hand, when the coating amount exceeds 0.20 g / m ² , blocking resistance may be lowered.

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

  Moreover, as a method for applying the coating solution, a known method can be used as in the case of the above-described coating layer. For example, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, etc. can be mentioned. Or it can carry out in combination.

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

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

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

  This phenomenon is that a biaxially stretched film is composed of refractive index ellipsoids having different refractive indexes in the running direction, width direction, and thickness direction, and the retardation becomes zero depending on the light transmission direction inside the film (refractive index ellipse). This is because there is a direction in which the body appears to be a perfect circle. Therefore, when the liquid crystal display screen is observed from a specific oblique direction, a point where the retardation becomes zero may be generated, and a rainbow-like color spot is generated concentrically around that point. When the angle from the position directly above the film surface (normal direction) to the position where the rainbow-like color spots are visible is θ, the angle θ increases as the birefringence in the film increases, and the rainbow-like color increases. Spots are difficult to see. The biaxially stretched film tends to reduce the angle θ, and therefore the uniaxially stretched film is more preferable because rainbow-like color spots are less visible.

  However, a perfect uniaxial (uniaxial symmetry) film is not preferable because the mechanical strength in the direction orthogonal to the orientation direction is significantly reduced. The present invention has biaxiality (biaxial symmetry) in a range that does not substantially cause rainbow-like color spots or a range that does not cause rainbow-like color spots in a viewing angle range required for a liquid crystal display screen. It is preferable.

  The present inventors specify the ratio of the retardation of the protective film (in-plane retardation) and the retardation in the thickness direction (Rth) as a means to suppress the occurrence of rainbow spots while maintaining the mechanical strength of the protective film. It was found that control was performed so as to be within the range. Thickness direction retardation means an average of retardation obtained by multiplying two birefringences ΔNxz and ΔNyz by film thickness d when the film is viewed from the cross section in the thickness direction. The smaller the difference between the in-plane retardation and the thickness direction retardation, the more isotropic the birefringence action due to the observation angle, and the smaller the change in retardation due to the observation angle. Therefore, it is considered that rainbow-like color spots due to the observation angle are less likely to occur.

  The ratio of the retardation of the polyester film of the present invention to the retardation in the thickness direction (Re / Rth) is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.6 or more. As the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is larger, the birefringence action is more isotropic, and the occurrence of iridescent color spots due to the observation angle is less likely to occur. In a complete uniaxial (uniaxial symmetry) film, the ratio of the retardation to the retardation in the thickness direction (Re / Rth) is 2. However, as described above, the mechanical strength in the direction orthogonal to the orientation direction is significantly lowered as the film approaches a complete uniaxial (uniaxial symmetry) film.

  On the other hand, the ratio of the retardation of the polyester film of the present invention to the retardation in the thickness direction (Re / Rth) is preferably 1.2 or less, more preferably 1 or less. In order to completely suppress the occurrence of rainbow-like color spots due to the observation angle, the ratio of retardation to thickness direction retardation (Re / Rth) does not have to be 2, and 1.2 or less is sufficient. Further, even when the ratio is 1 or less, it is possible to satisfy the viewing angle characteristics required for the liquid crystal display device (180 ° left and right, 120 ° up and down).

  Describing specifically the film forming conditions of the polyester film of the present invention, the longitudinal stretching temperature and the transverse stretching temperature are preferably from 80 to 130 ° C, particularly preferably from 90 to 120 ° C. The longitudinal draw ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. The transverse draw ratio is preferably 2.5 to 6.0 times, and particularly preferably 3.0 to 5.5 times. In order to control the retardation within the above range, it is preferable to control the ratio of the longitudinal draw ratio and the transverse draw ratio. If the difference between the vertical and horizontal draw ratios is too small, it is difficult to increase the retardation, which is not preferable. Also, setting the stretching temperature low is a preferable measure for increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably from 100 to 250 ° C, particularly preferably from 180 to 245 ° C.

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

The thickness unevenness of the film of the present invention is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, and 3.0% or less. It is particularly preferred. The thickness unevenness of the film can be measured by any means. For example, a tape-like sample (length 3 m) continuous in the film flow direction is collected, and an electronic micrometer (Millitron) manufactured by Seiko EM Co., Ltd. 1240) or the like is used to measure the thickness at 100 points at a pitch of 1 cm, and the maximum thickness (dmax), minimum value (dmin), and average value (d) are determined. %) Can be calculated.
Thickness unevenness (%) = ((dmax−dmin) / d) × 100

  As described above, the retardation of the film can be controlled within a specific range by appropriately setting the stretching ratio, the stretching temperature, and the film thickness. For example, it becomes easier to obtain a higher retardation as the stretching ratio between the longitudinal stretching and the lateral stretching is higher, the stretching temperature is lower, and the film is thicker. On the contrary, it becomes easier to obtain a lower retardation as the stretching ratio between the longitudinal stretching and the lateral stretching is lower, the stretching temperature is higher, and the film thickness is thinner. Moreover, the higher the stretching temperature and the lower the total stretching ratio, the easier it is to obtain a film having a lower ratio of retardation to thickness direction (Re / Rth). Conversely, the lower the stretching temperature and the higher the total stretching ratio, the easier it is to obtain a film with a higher ratio of retardation to thickness direction retardation (Re / Rth). The final film forming conditions must be set in consideration of the physical properties necessary for processing in addition to the retardation control.

  Although the thickness of the polyester film of this invention is arbitrary, the range of 15-300 micrometers is preferable, More preferably, it is the range of 15-200 micrometers. In principle, it is possible to obtain a retardation of 3000 nm or more even with a film having a thickness of less than 15 μm. However, in that case, the anisotropy of the mechanical properties of the film becomes remarkable, and it becomes easy to cause tearing, tearing, etc., and the practicality as an industrial material is remarkably lowered. A particularly preferable lower limit of the thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polarizer protective film exceeds 300 μm, the thickness of the polarizing plate becomes too thick, which is not preferable. From the viewpoint of practicality as a polarizer protective film, the upper limit of the thickness is preferably 200 μm. A particularly preferable upper limit of the thickness is 100 μm, which is about the same as a general TAC film. Polyethylene terephthalate is preferable as the polyester used as the film substrate in order to control the retardation within the range of the present invention even in the above thickness range.

  In addition, as a method of blending the ultraviolet absorber with the polyester film in the present invention, a known method can be used in combination. For example, a preliminarily kneaded extruder is used to blend the dried ultraviolet absorber and the polymer raw material. A master batch can be prepared and blended by, for example, a method of mixing the predetermined master batch and a polymer raw material during film formation. The added weight of the ultraviolet absorber added to the film is preferably 0.3 to 1.5%, more preferably 0.4 to 1.0%.

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

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

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

(1) Retardation (Re)
Retardation is a parameter defined by the product (ΔNxy × d) of the biaxial refractive index anisotropy (ΔNxy = | Nx−Ny |) and the film thickness d (nm) on the film. Yes, it is a scale showing optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using 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. With respect to 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 (| Nx−Ny |) of the refractive index difference between the axes 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).

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

(3) Light transmittance at a wavelength of 380 nm Using a spectrophotometer (manufactured by Hitachi, U-3500 type), the light transmittance in the wavelength region of 300 to 500 nm of each film is measured using the air layer as a standard, and the light beam at a wavelength of 380 nm. The transmittance was determined.

(4) Observation of rainbow spots A polyester film prepared by the method described later is attached to one side of a polarizer made of PVA and iodine so that the absorption axis of the polarizer and the orientation main axis of the film are perpendicular to each other, and TAC is attached to the opposite surface. A polarizing plate was prepared by attaching a film (manufactured by FUJIFILM Corporation, thickness 80 μm).
The obtained polarizing plate is made of polyester on the emission light side of a liquid crystal display device using a white LED composed of a light emitting element in which a blue light emitting diode and a yttrium / aluminum / garnet yellow phosphor are combined as a light source (Nichia Chemical, NSPW500CS). The film was installed so as to be on the viewing side (or the emission light side). This liquid crystal display device has a polarizing plate having two TAC films as polarizer protective films on the incident light side of the liquid crystal cell. Visual observation was performed from the front side and the oblique direction of the polarizing plate of the liquid crystal display device, and the presence or absence of the occurrence of iridescence was determined as follows. In Comparative Example 3, a backlight light source using a cold cathode tube as a light source instead of the white LED was used.
◎: No rainbow spots from any direction.
○: When observed from an oblique direction, a partly extremely thin rainbow can be observed.
X: When observing from an oblique direction, rainbow spots can be clearly observed.

(5) Tear strength The tear strength of each film was measured in accordance with JIS P-8116 using an Elmendorf tear tester manufactured by Toyo Seiki Seisakusho. The tearing direction was performed so as to be parallel to the orientation main axis direction of the film, and was determined as follows. In addition, the measurement of the orientation axis direction was measured with a molecular orientation meter (manufactured by Oji Scientific Instruments Co., Ltd., MOA-6004 type molecular orientation meter).
○: Tear strength is 50 mN or more ×: Tear strength is less than 50 mN

(6) Intrinsic viscosity Based on JISK7367-5, it measured at 30 degreeC, using the mixed solvent of a phenol (60 mass%) and 1,1,2,2-tetrachloroethane (40 mass%) as a solvent.

(7) Glass transition temperature Based on JIS K7121, the glass transition start temperature was calculated | required from the DSC curve using the differential scanning calorimeter (The Seiko Instruments Inc. make, DSC6200).

(8) Absorbance measurement by infrared spectroscopy About the obtained polarizer protective film, the coating layer of the side which apply | coated the coating liquid for coating layer formation was shaved off, and about 1 mg sample was extract | collected. A pressure was applied to the collected sample to prepare a coating layer sample piece (size: about 50 μm × about 50 μm) molded into a film having a thickness of about 1 μm. Further, a sample piece (blank sample piece) was prepared in the same manner as described above for a PET resin having the same quality as the base film as a blank sample.

  The prepared sample piece was placed on a KBr plate, and an infrared absorption spectrum was measured by a microscopic transmission method under the following conditions. The infrared spectrum of the coating layer was determined as the difference spectrum between the infrared spectrum obtained from the coating layer sample piece and the spectrum of the blank sample piece.

Absorbance around 1460 cm ^-1 derived from an aliphatic polycarbonate component _{(A 1460)} is 1460 and the value of the absorption peak height having an absorption maximum in the region of ± 10 cm ^-1, the absorbance in the vicinity of 1530 cm ^-1 derived from urethane component (A ₁₅₃₀ ) is the value of the absorption peak height having an absorption maximum in the region of 1530 ± 10 cm ⁻¹ . The baseline was a line connecting the hems on both sides of each maximum absorption peak. The absorbance ratio was determined from the obtained absorbance by the following formula.
(Absorbance ratio) = A ₁₄₆₀ / A ₁₅₃₀

(Measurement condition)
Apparatus: FT-IR analyzer SPECTRATECH IRμs / SIRM
Detector: MCT
Resolution: 4cm ^-1
Integration count: 128 times

(9) Adhesiveness 100 pieces reaching the base film through the hard coat layer using a cutter guide with a gap distance of 2 mm in the photocurable hard coat layer of the polarizer protective film having the obtained hard coat layer Make a grid of cuts. Next, a cellophane adhesive tape (manufactured by Nichiban Co., Ltd., No. 405; 24 mm width) was attached to the cut surface of the grid and rubbed with an eraser for complete adhesion. Then, after performing the work of peeling the cellophane adhesive tape vertically from the hard coat layer surface of the polarizer protective film 5 times, the number of squares peeled off from the hard coat layer surface of the polarizer protective film was visually counted, and the following formula Therefore, the adhesion between the hard coat layer and the substrate film was determined. In addition, what peeled partially among squares was also counted as the square which peeled, and was ranked according to the following references | standards.
Adhesiveness (%) = (1−number of peeled squares / 100) × 100
A: 100%, or material breakage of hard coat layer B: 99-90%
Δ: 89-70%
X: 69 to 0%

(10) Moisture and heat resistance The obtained polarizer protective film having a hard coat layer was boiled with water for 1 hour. Next, the laminated polyester film for optics was taken out, wiped off moisture, and immediately evaluated for adhesion. For the evaluation of adhesion, the adhesion between the hard coat layer and the polyester film was determined by the same method as in (9) above, and ranked according to the following criteria.
A: 100%, or material breakage of hard coat layer B: 99-90%
Δ: 89-70%
X: 69 to 0%

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

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

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

(Production Example 3-Preparation of coating solution for easily bonding layer formation with polarizer)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method, and as a dicarboxylic acid component (based on the total dicarboxylic acid component), 46 mol% terephthalic acid, 46 mol% isophthalic acid and sodium 5-sulfonatoisophthalate 8 A water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of mol%, glycol component (relative to the whole glycol component) of ethylene glycol 50 mol% and neopentyl glycol 50 mol% was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, 0.06 parts by mass of nonionic surfactant were mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal base-containing copolymer polyester resin and continuing to stir until the resin is no longer agglomerated, the resin water dispersion is cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A uniform water-dispersible copolymerized polyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silysia Co., Ltd.) in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolyester resin liquid was mixed with 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added with stirring to obtain an adhesive modified coating solution.

(Production Example 4-Polymerization of Urethane Resin A-1)
Urethane resin A-1 having an aliphatic polycarbonate polyol as a constituent component was prepared by the following procedure. In a four-necked flask equipped with a stirrer, Dimroth cooler, nitrogen inlet tube, silica gel drying tube, and thermometer, 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylolbutanoic acid, several 153.41 parts by mass of polyhexamethylene carbonate diol having an average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added and stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that had reached the predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin (A-1) having a solid content of 35%. The glass transition temperature of the polyurethane resin (A-1) containing the obtained aliphatic polycarbonate polyol as a constituent component was −30 ° C.

(Production Example 5-Polymerization of Urethane Resin A-2)
A urethane resin A-2 containing an aliphatic polycarbonate polyol as a constituent component was prepared by the following procedure. In a four-necked flask equipped with a stirrer, a Dimroth cooler, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 29.14 parts by mass of 4,4-diphenylmethane diisocyanate, 7.57 parts by mass of dimethylolbutanoic acid, several An average molecular weight of 3000 polyhexamethylene carbonate diol 173.29 parts by mass, dibutyltin dilaurate 0.03 parts by mass, and 84.00 parts by mass of acetone as a solvent were added, and the mixture was stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that had reached the predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 5.17 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring and adjusted to 25 ° C., while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin (A-2) having a solid content of 35%.

(Production Example 6-Polymerization of Urethane Resin A-3)
Urethane resin A-3 containing an aliphatic polycarbonate polyol as a constituent component was prepared by the following procedure. In a four-necked flask equipped with a stirrer, Dimroth cooler, nitrogen inlet tube, silica gel drying tube, and thermometer, 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 11.12 parts by mass of dimethylolbutanoic acid, hexane 1.97 parts by mass of diol, 143.40 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added, and 75 ° C. in a nitrogen atmosphere. The mixture was stirred for 3 hours to confirm that the reaction solution reached a predetermined amine equivalent. Next, after the temperature of this reaction liquid was lowered to 40 ° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, adjusted to 25 ° C., and stirred and mixed at 2O00 min ⁻¹ while adding a polyurethane prepolymer solution and dispersed in water. . Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble polyurethane resin (A-3) having a solid content of 35%.

(Production Example 7-Polymerization of Urethane Resin A-4)
A silanol group-containing urethane resin A-4 containing an aliphatic polycarbonate polyol as a constituent component was prepared by the following procedure. In a four-necked flask equipped with a stirrer, a Dimroth cooler, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 38.41 parts by mass of isophorone diisocyanate, 6.95 parts by mass of dimethylolpropanoic acid, and a number average molecular weight of 2000 Polyhexamethylene carbonate diol 158.999 parts by mass, dibutyltin dilaurate 0.03 parts by mass, and acetone 84.00 parts by mass as a solvent were added and stirred at 75 ° C. for 3 hours in a nitrogen atmosphere. It was confirmed that the equivalent amount was reached. Next, after cooling this reaction liquid to 40 degreeC, 4.37 mass parts of triethylamine was added, and the polyurethane prepolymer solution was obtained. Next, 3.84 parts by mass of γ- (aminoethyl) aminopropyltriethoxysilane, 1.80 parts by mass of 2-[(2-aminoethyl) amino] ethanol and 450 g of water were added, and the polyurethane prepolymer solution was dropped. And dispersed in water. Thereafter, a part of acetone and water was removed under reduced pressure to prepare a water-soluble silanol group-containing polyurethane resin (A-4) having a solid content of 30%.

(Production Example 8-Polymerization of Urethane Resin A-5)
A urethane resin A-5 containing an aliphatic polycarbonate polyol as a constituent component was prepared by the following procedure. A water-soluble polyurethane resin having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyhexamethylene carbonate diol having a number average molecular weight of 1000. (A-5) was obtained.

(Production Example 9-Polymerization of Urethane Resin A-6)
A urethane resin A-6 containing an aliphatic polycarbonate polyol as a constituent component was prepared by the following procedure. A water-soluble polyurethane resin having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyhexamethylene carbonate diol having a number average molecular weight of 5000. (A-6) was obtained.

(Production Example 10-Polymerization A-7 of Urethane Resin)
Polymerization A-7 of a urethane resin containing polyester polyol as a constituent component was prepared by the following procedure. The water-soluble polyurethane resin (A-) having a solid content of 35% was prepared in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 of the water-soluble polyurethane resin (A-1) was changed to a polyester diol having a number average molecular weight of 2000. 7) was obtained.

(Production Example 11-Polymerization A-8 of urethane resin)
Polymerization A-8 of a urethane resin having a polyether polyol as a constituent component was produced by the following procedure. A water-soluble polyurethane resin (A) having a solid content of 35% was obtained in the same manner except that the polyhexamethylene carbonate diol having a number average molecular weight of 2000 in the water-soluble polyurethane resin (A-1) was changed to a polyether diol having a number average molecular weight of 2000. -8) was obtained.

(Production Example 12-Polymerization of Block Polyisocyanate Crosslinking Agent)
100 parts by mass of a polyisocyanate compound having an isocyanurate structure using hexamethylene diisocyanate as a raw material (manufactured by Asahi Kasei Chemicals, Duranate TPA) in a flask equipped with a stirrer, a thermometer and a reflux condenser, 55 parts by mass of propylene glycol monomethyl ether acetate, 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) 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 (B) having a solid content of 75% by mass was obtained.

(Production Example 13-Polymerization of oxazoline-based crosslinking agent)
A mixture of 58 parts by mass of ion-exchanged water and 58 parts by mass of isopropanol as an aqueous medium in a flask equipped with a thermometer, a nitrogen gas introduction tube, a reflux condenser, a dropping funnel, and a stirrer, and a polymerization initiator (2, 2 4 parts by mass of '-azobis (2-amidinopropane) dihydrochloride) was added. On the other hand, in a dropping funnel, 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, methoxypolyethylene glycol acrylate (average number of moles of ethylene glycol added: 9 moles, Shin Nakamura Chemical) A mixture of 32 parts by mass and 32 parts by mass of methyl methacrylate was added, and the mixture was added dropwise at 70 ° C. for 1 hour in a nitrogen atmosphere. After completion of dropping, the reaction solution was stirred for 9 hours and cooled to obtain a water-soluble resin (C) having an oxazoline group with a solid content concentration of 40% by mass.

(Production Example 14—polymerization of carbodiimide-based crosslinking agent)
A flask equipped with a stirrer, thermometer and reflux condenser was charged with 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400), stirred at 120 ° C. for 1 hour, 26 parts by mass of 4′-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phospholene-1-oxide (2% by weight based on the total isocyanate) as a carbodiimidization catalyst were added, and 185 under a nitrogen stream. Stir at 5 ° C. for a further 5 hours. The infrared spectrum of the reaction solution was measured, and it was confirmed that absorption at a wavelength of 2200 to 2300 cm ⁻¹ disappeared. It stood to cool to 60 degreeC, 567 mass parts of ion-exchange water was added, and the carbodiimide water-soluble resin (D) of 40 mass% of solid content was obtained.

(Production Example 15-Preparation of coating solution A1 for forming a coating layer)
The following coating agent was mixed and the coating liquid for forming the coating layer excellent in adhesiveness with a hard-coat layer was created.
Water 55.62% by mass
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 11.29 mass%
Block polyisocyanate aqueous dispersion (B) 2.26% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(Production Example 16-Formation of hard coat layer)
The coating liquid for forming a hard coat layer (E) having the following composition was applied to the coating layer surface provided on the polyester film produced in each example described later using a # 10 wire bar and dried at 70 ° C. for 1 minute. The solvent was removed. Next, the film coated with the hard coat layer was irradiated with 300 mJ / cm ² ultraviolet rays using a high-pressure mercury lamp to obtain a polarizer protective film having a hard coat layer with a thickness of 5 μm.
Hard coat layer forming coating solution (E)
Methyl ethyl ketone 65.00% by mass
Dipentaerythritol hexaacrylate 27.20% by mass
(Shin-Nakamura Chemical A-DPH)
Polyethylene glycol diacrylate 6.80 mass%
(Shin-Nakamura Chemical A-400)
Photopolymerization initiator 1.00% by mass
(Irgacure 184 manufactured by Ciba Specialty Chemicals)

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

Next, a coating layer is applied to both surfaces of the unstretched PET film by a reverse roll method so that one surface is a coating solution for forming an adhesive layer with the polarizer and the other surface is a coating solution A1 for coating layer formation. It was applied and dried at 80 ° C. for 20 seconds. In addition, it adjusted so that the application quantity after the last (after extending | stretching) drying might be set to 0.15 g / m < ² >.

The unstretched film on which this coating layer was formed was guided to a tenter stretching machine, and the film was guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.0 times in the width direction.
Next, a polarizer that is a uniaxially oriented PET film having a film thickness of about 50 μm is processed by maintaining the width stretched in the width direction at a temperature of 225 ° C. for 30 seconds and further performing a relaxation treatment of 3% in the width direction. A protective film was obtained.

(Example 2)
A polarizer protective film, which is a uniaxially oriented PET film, was obtained in the same manner as in Example 1 except that the thickness of the unstretched film was changed to about 100 μm.

(Example 3)
An unstretched film produced by the same method as in Example 1 is heated to 105 ° C. using a heated roll group and an infrared heater, and then stretched 1.5 times in the running direction with a roll group having a difference in peripheral speed. After that, the film was stretched 4.0 times in the width direction in the same manner as in Example 1 to obtain a polarizer protective film which is a biaxially oriented PET film having a film thickness of about 50 μm.

Example 4
In the same manner as in Example 3, the film was stretched 2.0 times in the running direction and 4.0 times in the width direction to obtain a polarizer protective film which is a biaxially oriented PET film having a film thickness of about 50 μm.

(Example 5)
In the same manner as in Example 3, the film was stretched 3.3 times in the running direction and 4.0 times in the width direction to obtain a polarizer protective film which is a biaxially oriented PET film having a film thickness of about 75 μm.

(Example 6)
A polarizer protective film, which is a uniaxially oriented PET film having a film thickness of 50 μm, was obtained in the same manner as in Example 1 without using a PET resin (B) containing an ultraviolet absorber in the intermediate layer.
Although the resulting film was free from iridescent color spots, it has a high light transmittance of 380 nm, and there is a concern of deteriorating the optical functional dye.

(Example 7)
In the same manner as in Example 3, the film was stretched 4.0 times in the running direction and 1.0 times in the width direction to obtain a polarizer protective film which is a uniaxially oriented PET film having a film thickness of about 100 μm. The obtained film had Re of 3000 nm or more and good visibility, but the mechanical strength was slightly inferior.

(Example 8)
In the same manner as in Example 3, the film was stretched 3.5 times in the running direction and 3.7 times in the width direction to obtain a polarizer protective film which is a biaxially oriented PET film having a film thickness of about 250 μm. The obtained film had Re of 4500 nm or more, but the Re / Rth ratio was less than 0.2. Therefore, an extremely thin rainbow was observed in an oblique direction.

Example 9
In the same manner as in Example 1, the film was stretched 1.0 times in the running direction and 3.5 times in the width direction to obtain a polarizer protective film which is a uniaxially oriented PET film having a film thickness of about 75 μm.

(Example 10)
A polarizer protective film, which is a uniaxially oriented PET film having a thickness of about 275 μm, was obtained by using the same method as in Example 1 and changing the thickness of the unstretched film.

(Example 11)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the polyurethane resin (A-1) was changed to the polyurethane resin (A-5).

(Example 12)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-6).

(Example 13)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the coating solution A1 was changed to the following.
Water 53.91% by mass
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 14.51% by mass
Block polyisocyanate aqueous dispersion (B) 0.75% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(Example 14)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the coating liquid A1 was changed to the following.
Water 54.76% by mass
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 12.90 mass%
Block polyisocyanate aqueous dispersion (B) 1.51% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(Example 15)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the coating liquid A1 was changed to the following.
Water 57.35% by mass
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 8.06% by mass
Block polyisocyanate aqueous dispersion (B) 3.76% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(Example 16)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the coating liquid A1 was changed to the following.
59.92% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 3.23 mass%
Block polyisocyanate aqueous dispersion (B) 6.02 mass%
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(Example 17)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the coating liquid A1 was changed to the following.
60.79% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 1.61% by mass
Block polyisocyanate aqueous dispersion (B) 6.77% by mass
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(Example 18)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the polyurethane resin in the coating liquid A1 was changed to a polyurethane resin (A-2).

(Example 19)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the polyurethane resin in the coating solution A1 was changed to a polyurethane resin (A-3).

(Example 20)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the polyurethane resin in the coating solution A1 was changed to a silanol group-containing polyurethane resin (A-4).

(Example 21)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the block polyisocyanate aqueous dispersion (B) in the coating liquid A1 was changed to a water-soluble resin (C) having an oxazoline group.

(Example 22)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the blocked polyisocyanate aqueous dispersion (C) in the coating liquid A1 was changed to a carbodiimide water-soluble resin (D).

(Example 23)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the block polyisocyanate aqueous dispersion (B) was changed to imino / methylolmelamine (solid content concentration: 70% by mass).

(Example 24)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the coating liquid A1 was changed to the following.
62.82% by mass of water
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 5.64% by mass
Block polyisocyanate aqueous dispersion (B) 1.13% by mass
0.35% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.04% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.02% by mass
(Silicon, solid content concentration of 100% by mass)

(Example 25)
Observation of rainbow spots using an organic light-emitting diode (OLED) as the light source of the liquid crystal display device, and evaluation as an anti-glare layer with irregularities on the surface by adding particles to the hard coat layer of Production Example 16 Except for this, the procedure was the same as in Example 1.

(Comparative Example 1)
In the same manner as in Example 3, the film was stretched 3.6 times in the running direction and 4.0 times in the width direction to obtain a polarizer protective film which is a biaxially oriented PET film having a film thickness of about 38 μm. The obtained film had low retardation, and rainbow-like color spots were observed when observed from an oblique direction.

(Comparative Example 2)
A polarizer protective film, which is a uniaxially oriented PET film having a thickness of about 10 μm, was obtained by using the same method as in Example 1 and changing the thickness of the unstretched film. Since the obtained film was very easy to tear and there was no stiffness, it could not be used as a polarizer protective film. Moreover, the retardation was low and iridescent colored spots were observed.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that rainbow spots were observed using a cold cathode tube as the light source of the liquid crystal display device.

(Comparative Example 4)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-7).

(Comparative Example 5)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the polyurethane resin was changed to the polyurethane resin (A-8).

(Comparative Example 6)
A polarizer protective film having a coating layer was obtained in the same manner as in Example 1 except that the coating solution A1 was changed to the following.
Water 53.04 mass%
Isopropanol 30.00% by mass
Polyurethane resin (A-1) 16.13 mass%
Particles 0.71% by mass
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
0.07% by mass of particles
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

The results measured for the above Examples and Comparative Examples are shown in Table 1 below.

Claims (12)

A white light source having a continuous emission spectrum, in which a coating layer mainly composed of a urethane resin and a cross-linking agent containing aliphatic polycarbonate polyol as a main component is laminated on at least one surface of a polyester film having a retardation of 3000 to 30000 nm. A polarizer protective film for a liquid crystal display device using a light source as a backlight source. Absorbance around 1460 cm ^-1 derived from an aliphatic polycarbonate component ratio of _{(A 1460)} and 1530 cm ^-1 near the absorbance derived from urethane component with _{(A 1530) (A 1460 /} A 1530) is 0.40 to 1.55 The polarizer protective film according to claim 1, wherein The polarizer protective film according to claim 1 or 2, wherein the crosslinking agent is at least one selected from the group consisting of a melamine crosslinking agent, an isocyanate crosslinking agent, a carbodiimide crosslinking agent, and an oxazoline crosslinking agent. The polarizer protective film in any one of Claims 1-3 whose mass ratio (urethane resin / crosslinking agent) of a urethane resin and a crosslinking agent is 1 / 9-9 / 1. The polarizer protective film in any one of Claims 1-4 whose ratio (Re / Rth) of the retardation of a polyester film and thickness direction retardation is 0.2 or more. The polarizer protective film according to any one of claims 1 to 5, wherein the polyester film is composed of three or more layers, contains an ultraviolet absorber in a layer other than the outermost layer, and has a light transmittance of 380 nm of 20% or less. . One or more layers selected from the group consisting of a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, a low reflection antiglare layer, an antireflection antiglare layer and an antistatic layer are laminated on the coating layer. Moreover, the polarizer protective film in any one of Claims 1-6. The polarizing plate for liquid crystal display devices which makes the backlight light source the white light source which has the continuous emission spectrum by which the polarizer protective film in any one of Claims 1-7 was laminated | stacked on the at least one side of the polarizer. The polarizing plate for a liquid crystal display device according to claim 8, wherein the polarizer protective film is laminated on the polarizer via an ultraviolet curable, electron beam curable, or thermosetting adhesive. A liquid crystal display device comprising the polarizing plate according to claim 8 or 9, wherein the backlight light source is a white light source having a continuous emission spectrum. The liquid crystal display device according to claim 10, wherein the polarizing plate disposed on the emission light side with respect to the liquid crystal is the polarizing plate according to claim 8. The liquid crystal display device according to claim 10 or 11, wherein the white light source having the continuous emission spectrum is a white LED.