TW202405067A - Ultraviolet absorbing polyester film, polarizer protective film, polarizing plate and image display device - Google Patents

Abstract

The present invention provides a polyester film which is characterized by comprising a layer that is formed of a biomass polyethylene terephthalate resin composition which contains a polyethylene terephthalate resin that uses a biomass resource as a starting material for at least one of ethylene glycol and terephthalic acid, and an ultraviolet absorbent that includes a cyclic imino ester-based ultraviolet absorbent.

Description

Ultraviolet absorbing polyester film and polarizer protective film, polarizing plate and image display device

The present invention relates to an ultraviolet absorbing polyester film, a polarizer protective film, a polarizing plate and an image display device. Specifically, it relates to an ultraviolet-absorbing polyester film using biomass-derived PET resin, a polarizer protective film with good visual visibility and few optical defects, and a polarizing plate and image display device using the same.

The polarizing plate used in a liquid crystal display device (LCD) is usually composed of a polarizer made of polyvinyl alcohol (PVA) or the like and dyed with iodine, sandwiched between two polarizer protective films. As for the polarizer protective film, triacetyl cellulose (TAC) film, PMMA film, and polyethylene terephthalate (PET) film are used. In particular, PET film has low moisture permeability and can greatly contribute to improving the durability of LCDs, and is widely used, mainly in large-scale displays.

When using PET film as a polarizer protective film, iridescent spots may occur. It is known that the iridescent color spots are caused by the retardation of the PET film and the emission spectrum of the backlight source. By combining a backlight source with a continuous luminescence spectrum and a PET film with specific hysteresis, the PET film can be used as a polarizer protective film.

On the other hand, such PET films are currently produced using resins produced by polycondensation of raw materials derived from fossil fuel resources. However, due to recent concerns about the depletion of fossil fuel resources or the increase in carbon dioxide in the atmosphere, the global Against the background of large-scale environmental problems, the world is seeking alternatives to the use of biological resources.

Examples of the production of ethylene glycol using biomass resources include producing ethanol from sugar cane, bagasse, carbohydrate-based crops, etc. through biological treatment methods, and further using ethylene oxide to produce ethylene glycol and diethylene glycol. Methods for mixtures of ethylene glycol and triethylene glycol, etc. In the production of terephthalic acid using biomass resources, for example, biomass resources such as wood chips are rapidly thermally decomposed by a catalyst to generate xylene, and then terephthalic acid can be generated through separation, purification and isomerization treatment. xylene, and is obtained by subjecting xylene to a liquid phase oxidation reaction.

The raw materials derived from biomass resources obtained in this way are subjected to distillation and purification to minimize impurities. However, it is known that in addition to the nitrogen contained in the biomass resources, there is also nitrogen derived from fermentation bacteria. Or impurities such as ammonia and metal cations are mixed in. Therefore, it is known that when polymers derived from biomass resources are used, foreign matter often occurs and resin deterioration easily occurs (for example, Patent Document 1). [Prior technical literature] [Patent Document]

Patent Document 1: Japanese Invention Patent No. 55729078

[Problem to be solved by the invention]

Terephthalic acid or ethylene glycol derived from biomass resources containing many impurities as mentioned above is usually further purified to reduce the amount of impurities before use, but it is known that even dicarboxylic acids that have undergone such purification can be used. In PET resins made from ethylene glycol or ethylene glycol, the amount of foreign matter present during the molding process is obviously higher when compared to PET resins derived from petroleum. Especially in the production of polarizer protective films, it becomes a big problem because it requires the management of very fine optical defects. Especially when a polyester film is used as a polarizer protective film, since ultraviolet absorbers are added to the PET resin, deterioration of the resin is easily accelerated. Especially when using PET resin derived from biomass resources, the impact is large.

The present invention was made to solve this problem, and its object is to provide a PET resin that uses raw materials derived from biomass resources, has excellent transparency, has few foreign matter, and has good visual visibility when used as a polarizer protective film. Ultraviolet absorbing polyester film with few optical defects, as well as polarizing plates and display devices. [Means used to solve problems]

The inventors of the present invention wanted to provide an ultraviolet-absorbing polyester film that has excellent transparency and few foreign matter even if a PET resin derived from biomass resources is used, and in particular, a polarizer protective film that has good visual visibility and few optical defects, and After careful review, we found that depending on the type of ultraviolet absorber, the deterioration of PET resin can be significantly suppressed. By combining this ultraviolet absorber with PET resin derived from biomass resources, a polarizer protective film with less foreign matter can be obtained.

That is, the present invention is as follows. Item 1: A polyester film characterized by containing a layer composed of a biopolyethylene terephthalate resin composition containing an ultraviolet absorber, the biopolyethylene terephthalate resin composition It contains: at least one of ethylene glycol and terephthalic acid, a polyethylene terephthalate resin using biomass resources as a raw material, and a cyclic imide ester-based ultraviolet absorber. Item 2: The polyester film described in Item 1 has an in-plane retardation of 3000 to 30000 nm. Item 3: The polyester film according to Item 1 or 2, in which the ratio of in-plane retardation to thickness direction retardation (Re/Rth) is 0.2 or more and 1.2 or less. Item 4: The polyester film according to any one of Items 1 to 3, wherein the polyester film has 3 including a first surface layer present on the first side, a second surface layer present on the opposite side, and an intermediate layer. The layer above the polyester resin layer, and only the middle layer is the aforementioned layer composed of a biopolyethylene terephthalate resin composition containing an ultraviolet absorber. Item 5: The polyester film according to any one of Items 1 to 4, the light transmittance at 380nm is less than 20%. Item 6: The polyester film according to any one of Items 1 to 4, in which the number of foreign objects with a long diameter of 50 μm or more is 3 to 2000/1000m ² . Item 7: The polyester film according to any one of Items 1 to 6, wherein the polyester film is composed of polyethylene terephthalate resin using biomass resources as raw materials and having a carboxyl terminal concentration of 50 eq/ton or less. . Item 8: The polyester film according to any one of Items 1 to 7, wherein the carboxyl terminal concentration of the polyethylene terephthalate resin constituting the polyester film is 100 eq/ton or less. Item 9: A laminated polyester film having a hard coating layer on at least one side of the polyester film according to any one of Items 1 to 8 Item 10: A polarizer protective film having any one of Items 1 to 8 The polyester film of the item is used as the base film. Item 11: The polarizer protective film according to Item 10, which has a hard coat layer. Item 12: A polarizing plate having the polarizer protective film according to Item 10 or 11 on at least one side of the polarizer. Item 13: An image display device having the polarizing plate according to Item 12. Item 14: The image display device described in Item 13 is a liquid crystal display device. Item 15: The image display device described in Item 13 is an organic EL display device. [Effects of the invention]

According to the present invention, even if a PET resin using raw materials derived from biomass resources is used, a polyester film with high transparency and few foreign matter can be obtained. In particular, a polarizer protective film with good visual visibility and few optical defects can be obtained. , and polarizing plates and image display devices. In this way, it is possible to solve environmental problems on a global scale such as concerns about the depletion of fossil fuel resources and the increase in carbon dioxide in the atmosphere.

[Form used to implement the invention]

The present invention is an ultraviolet-absorbing polyester film using polyethylene terephthalate resin derived from biomass resources (also referred to as "biopolyethylene terephthalate resin"). It is used as a polarizer protective film for the base film. Hereinafter, polyethylene terephthalate resin may be simply referred to as PET resin. In addition, polyethylene terephthalate resin derived from biomass resources may be called bioPET resin. Furthermore, in the present invention, the polarizer protective film may include a functional layer described below. In addition, a polyester film without a functional layer is called a polyester base film, but the polyester base film may include an easy-adhesion layer described below. When simply called polyester film, it means a polyester base film.

Bio-PET resin uses monomers from bio-resources (which are used as raw materials) for at least one of ethylene glycol and terephthalic acid. In particular, a PET resin using ethylene glycol derived from biomass resources is preferably 80% by mass or more of ethylene glycol, more preferably 90% by mass or more, and particularly preferably 100% by mass. Autogenous resources. Moreover, when using terephthalic acid derived from biomass resources, it is also preferable that it is 80 mass % or more of terephthalic acid, further preferably, it is 90 mass % or more, and it is especially preferable that 100 mass % is derived from biomass resources.

The polyester film can be a single layer or multiple layers. When it is multiple layers, it is preferable that at least one layer contains PET resin derived from biomass resources. Among the PET resins constituting the polyester film, the bio-PET resin is preferably 70 mass % or more, 80 mass % or more, 90 mass % or more, 95 mass % or more, and more preferably more than 95 mass %. The best is 96 mass% or more, the particularly good is 97 mass% or more, and the best is 100 mass%. Furthermore, relative to the total carbon of the PET resin constituting the polyester film, the content of carbon derived from biomass resources measured by radioactive carbon (C14) is preferably 14% or more, more preferably 16% or more, and still more preferably The best is more than 18%, the best is more than 19%, and the best is more than 19%. The carbon content derived from biomass resources has a theoretical upper limit of 20% when only ethylene glycol is derived from biomass resources. When terephthalic acid is also derived from biomass resources, the carbon content derived from biomass resources can exceed 20%. Since the higher one is better, the optimal value is 100%, but it can also be 95%. It may be 90% or less, 80% or less, or 70% or less.

Since carbon dioxide in the atmosphere contains C ¹⁴ at a certain ratio (105.5 pMC), it is known that the C ¹⁴ content in plants that grow by taking in carbon dioxide from the atmosphere, such as corn, is also about 105.5 pMC. Furthermore, it is also known that fossil fuels contain almost no C ¹⁴ . Therefore, the proportion of carbon derived from biomass resources can be calculated by measuring the proportion of C ¹⁴ contained in the total carbon atoms in the polyester. This biomass degree can be measured by radiocarbon (C ¹⁴ ) measurement shown in ASTM D6866-16 Method B (AMS), for example.

The polyester film preferably has an in-plane retardation of 2,500 to 30,000 nm. The lower limit of the in-plane retardation may be 3000 nm, a more preferable lower limit is 4500 nm, a further preferable lower limit is 5000 nm, a particularly preferable lower limit is 6000 nm, and an optimal lower limit is 7000 nm. When polyester film is used as a polarizer protective film, it can increase in-plane retardation, thereby reducing interference colors when viewed from an oblique direction and ensuring good visual visibility. Such a film with high in-plane hysteresis can be obtained by stretching only in the uniaxial direction, or even in the case of biaxial stretching, by making the stretching ratio in one direction larger than the stretching ratio in the orthogonal direction. Furthermore, when a polarizer protective film is used on the viewing side of an image display device and the reflectivity is lowered by providing an anti-reflection layer or the like, interference colors can be suppressed and visibility can be improved even if the in-plane retardation is low. The present invention can also be applied to polyester films with in-plane retardation less than 2500 nm, especially biaxially stretched polyester films.

A more preferable upper limit of in-plane retardation is 20,000 nm, a further preferable upper limit is 15,000 nm, a particularly preferable upper limit is 12,000 nm, and an optimal upper limit is 10,000 nm. Even if a polyester film with a higher in-plane hysteresis is used, not only is there no further improvement in visual visibility, but the thickness of the film also becomes considerably thicker, which reduces the workability as an industrial material. Not good.

In addition, the in-plane retardation can also be obtained by measuring the refractive index and thickness in the biaxial direction, or can be obtained by using a commercially available automatic birefringence measuring device KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.).

The polyester film preferably uses an ultraviolet absorber. In particular, the polarizer protective film aims to suppress the deterioration of optically functional dyes such as iodine dye in the polarizing plate, and it is preferable to use an ultraviolet absorber. Examples of ultraviolet absorbers include organic ultraviolet absorbers and inorganic ultraviolet absorbers. From the viewpoint of transparency, organic ultraviolet absorbers are preferred. Examples of organic ultraviolet absorbers include benzotriazole-based, benzophenone-based, cyclic imide ester-based ultraviolet absorbers, and combinations thereof. However, in the present invention, the cyclic imide ester-based ultraviolet absorber is The impact of PET resin degradation is minimal and preferable.

Examples of cyclic imide ester ultraviolet absorbers include 2,2'-(1,4-phenylene)bis(4H-3,1-benzo -4-one), 2-methyl-3,1-benzo -4-one, 2-butyl-3,1-benzo -4-one, 2-phenyl-3,1-benzo -4-keto etc. However, it is not particularly limited to these.

Most of the benzotriazole-based and benzophenone-based ultraviolet absorbers have an OH group at the terminal. The OH group reacts with the carbonyl group of the PET molecule in the melt extrusion step to cause hydrolysis and promote the generation of degraded products. Degraded substances are particularly likely to be generated in the stagnant portion of the resin. The degraded resin causes intermittently flowing out from the stagnant portion, thereby becoming a large amount of black foreign matter and conspicuously existing when the film is formed. In contrast, cyclic imide ester ultraviolet absorbers do not have an OH group at the terminal and are difficult to react with PET molecules. Although it seems that a part of the ultraviolet absorber decomposes during the melt extrusion step and generates carboxylic acid terminals, the reactivity to PET molecules is lower than that of other ultraviolet absorbers, and it is considered that it is difficult to produce degraded products. The present inventors have discovered that by using a cyclic imide ester-based ultraviolet absorber, the occurrence of black foreign matter caused by a deteriorated resin that easily occurs when a bio-PET resin is used to form a film can be suppressed. In addition, cyclic imide ester-based ultraviolet absorbers may contain anthranilic acids of the raw material or their decomposition products, side reactants, etc. as impurities, and these impurities may also promote the deterioration of the resin. The purity of the cyclic imide ester ultraviolet absorber is preferably 97.0 mass% or more, more preferably 98.0 mass% or more, further preferably 98.5 mass% or more, particularly preferably 99.0% or more, particularly preferably 99.5 mass% above. Purity can be determined by liquid chromatography.

In order to maintain a high biomass degree of the polyester film, a UV absorber is preferably added to the layer containing biomass PET resin. That is, at least one layer of the polyester film is preferably a layer composed of a bioPET resin composition containing an ultraviolet absorber and a PET resin derived from biomass resources. The polyester film may be composed of a single layer composed only of the bio-PET resin composition, but it is preferable that the polyester film is composed of at least three layers and composed of the bio-PET resin. The layers composed of objects are only in the middle layer. That is, in a polyester film having three or more layers, the layer of PET resin present on the first surface is the first surface layer, and the layer of PET resin present on the opposite surface is the second surface layer. When the surface layer and one or more layers existing between the two surface layers are used as the intermediate layer, it is preferable that the first surface layer and the second surface layer do not have an ultraviolet absorber, and only the intermediate layer has an ultraviolet absorber. A layer of bio-PET resin composition. At this time, the intermediate layer may be one or more layers. If at least one layer of the intermediate layer is a layer of a bio-PET resin composition containing an ultraviolet absorber, it is not necessary for all of the intermediate layers to have an ultraviolet absorber.

The light transmittance of the polyester film at a wavelength of 380nm should be less than 20%. The light transmittance of 380nm is preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. If the light transmittance is 20% or less, deterioration of the optically functional dye due to ultraviolet rays can be suppressed. In addition, the transmittance in the present invention is measured perpendicularly to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 model).

In order to reduce the transmittance of the polyester film at a wavelength of 380 nm to 20% or less, the ultraviolet absorber, concentration, and film thickness should be appropriately adjusted. The concentration is not particularly limited as long as the target transmittance is obtained, but the lower the concentration, the smaller the impact on the degradation of the PET resin, which is preferable. The content of the ultraviolet absorber in the bio-PET resin composition is preferably 3% by mass or less, more preferably 2% by mass or less, further preferably 1.5% by mass or less, and particularly preferably 1.2% by mass or less. The content of the ultraviolet absorber is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and further preferably 0.3 mass% or more.

In addition to the ultraviolet absorber, it is also preferred to contain various additives other than the catalyst within a range that does not impede the effects of the present invention. Examples of additives include inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light-resistant agents, flame retardants, thermal stabilizers, antioxidants, and anti-gelling agents. agents, surfactants, etc. In addition, in order to achieve high transparency, it is also preferred that the polyester film contains substantially no particles. The term “substantially does not contain particles”, for example, in the case of inorganic particles, means a content that is 50 ppm or less, preferably 10 ppm or less, and particularly preferably below the detection limit when inorganic elements are quantified by fluorescence X-ray analysis.

The polyester film preferably has a number of foreign objects with a major diameter of 50 μm or more present in the film that is 2,000 pieces/1,000 m ² or less. The major diameter refers to the largest distance between any two points when measuring the distance between any two points on the outer circumference of the cross-section of the foreign object. If the number of foreign matter is below the upper limit, the polarizer protective film will not suffer from optical defects. The number of foreign objects with a long diameter of 50 μm or more is more preferably 1000 objects/1000m ² or less, further preferably 500 objects/1000m ² or less, particularly preferably 100 objects/1000m ² or less, most preferably 50 objects/1000m ² or less . It is optimal to have zero foreign matter with a length of 50 μm or more, that is, no foreign matter. However, from the perspective of productivity, the lower limit of the number of foreign matter can be set to 3/1000m ² , and further it can be set to 5/1000m ² .

When the carboxyl terminal concentration of PET resin is high, it may react with the ultraviolet absorber and accelerate the deterioration of the resin. Therefore, the bio-PET resin used preferably has a carboxyl terminal concentration of 50 eq/ton or less, more preferably 45 eq/ton or less, and still more preferably 40 eq/ton or less. The concentration is preferably low, but from the viewpoint of productivity, it is preferably 10 eq/ton or more, more preferably 15 eq/ton or more, and further preferably 20 eq/ton. In addition, the carboxyl terminal concentration of the polyester can be measured by the titration method described below. When the layer containing the ultraviolet absorber also contains a PET resin derived from other than biomass resources, the preferable range of the carboxyl terminal concentration of the PET resin derived from other than biomass resources is also the same. The PET resin constituting the film preferably has a carboxyl terminal concentration of 100 eq/ton or less, more preferably 80 eq/ton or less, further preferably 75 eq/ton or less, particularly preferably 70 eq/ton or less, and most preferably 60 eq/ton or less. . Incidentally, the lower limit is the same as above.

If the intrinsic viscosity of the bio-PET resin becomes high, the shear heat generated in the melt-kneading step in the film production step will increase, and it may be easily decomposed and deteriorated. Therefore, the intrinsic viscosity is preferably 0.8 dL/g or less, more preferably 0.75 dL/g or less, and further preferably 0.72 dL/g or less. In terms of maintaining film formability and mechanical strength of the film, the lower limit of the intrinsic viscosity is preferably 0.5 dL/g or more, more preferably 0.55 dL/g or more. The same applies to the inherent viscosity range of PET resins derived from other than biomass resources. The polyester resin constituting the film preferably has an intrinsic viscosity of 0.78 dL/g or less, more preferably 0.75 dL/g or less, further preferably 0.72 dL/g or less, and particularly preferably 0.70 or less. Incidentally, the lower limit is the same as above.

Bio-PET resin is preferably produced using an antimony compound or an aluminum compound as a polymerization catalyst. Examples of antimony compounds include antimony trioxide, antimony pentoxide, antimony acetate, antimony glyoxylate, and the like, and antimony trioxide (Sb ₂ O ₃ ) is preferred. The content of antimony in the PET resin derived from biomass resources is preferably 80 mass ppm or more in terms of antimony element, more preferably 100 mass ppm or more, and further preferably 120 mass ppm or more. Moreover, the antimony content is preferably 330 mass ppm or less in terms of antimony element, more preferably 300 mass ppm or less, further preferably 270 mass ppm or less, particularly preferably 250 mass ppm or less, most preferably 220 mass ppm or less. Suitable catalysts using aluminum compounds include those shown in Japanese Patent Application Laid-Open No. 2001-026639 or Japanese Patent Application Laid-Open No. 2002-322255. The content of the aluminum compound in the bio-PET resin is preferably 5 mass ppm or more in terms of aluminum element, more preferably 7 mass ppm or more, further preferably 10 mass ppm or more, and particularly preferably 15 mass ppm or less. Moreover, the content of the aluminum compound is preferably 50 ppm by mass or less in terms of aluminum element, more preferably 40 ppm by mass or less, further preferably 30 ppm by mass or less, and particularly preferably 25 ppm by mass or less. Since the content of the antimony compound or the aluminum compound is within the above range, the bio-PET resin can be produced with good productivity, and decomposition and deterioration when melt-mixed with the ultraviolet absorber can be suppressed. The same applies to the type of catalyst and the content range of the catalyst for PET resin derived from other than biomass resources.

When the resin temperature of the film is high during the melt-kneading step in the film production process, the PET resin becomes easy to decompose and deteriorate. The maximum temperature reached by the resin in the melting and kneading step is preferably 295°C or lower, more preferably 290°C or lower, further preferably 288°C or lower. The maximum temperature reached by the resin is preferably 270°C or higher, more preferably 275°C or higher, further preferably 280°C or higher. In addition to the appropriate setting temperature of the barrel of the extruder, it is preferable to adjust the number of rotations, the screw configuration or the gap between the screw and the barrel, and adjust the resin so that the resin temperature does not exceed the above. filling rate, heat medium flow rate, etc.

Furthermore, it is preferable to minimize the amount of resin remaining in the path through which the molten resin passes. Specifically, in an extruder, it is preferable to minimize the height difference between screw elements, the height difference between each block of the barrel, and the height difference between each connecting part of the piping. Furthermore, it is preferable to create a design that reduces the retention of resin in piping, a filter housing, a filter element, a flow path of a metal port, etc., or to reduce the roughness of the inner walls thereof. In addition, foreign matter tends to increase at the beginning of film production or when the resin extrusion amount is increased. It is also preferable to temporarily increase the resin extrusion amount at such times and then lower it to a designated amount.

In addition, the method of blending the ultraviolet absorber into the PET resin can be a combination of well-known methods. However, for example, it can be produced by mixing the dried ultraviolet absorber and the polymer raw material using a kneading extruder in advance. The masterbatch is blended by a method such as mixing a specific masterbatch and polymer raw materials during film formation.

At this time, the ultraviolet absorber concentration of the masterbatch is preferably 5 to 30 mass %, more preferably 7 to 20 mass %, in order to uniformly disperse the ultraviolet absorber and economically blend it. Regarding the conditions for making the masterbatch, it is preferable to use a mixing extruder and extrusion at a temperature of 1 to 15 minutes, more preferably 2 to 10 minutes, above the melting point of the polyester raw material and below 290°C. When the temperature is above 290°C, the amount of ultraviolet absorber is greatly reduced, and the viscosity of the masterbatch may be greatly reduced due to decomposition of the PET resin. Furthermore, the temperature is preferably 270 to 285°C. When the extrusion temperature is 1 minute or less, uniform mixing of the ultraviolet absorber may become difficult. At this time, a stabilizer, a color tone adjuster, and an antistatic agent may be added as necessary.

It does not matter if the PET resin system contains other copolymerized components. These resins have excellent transparency, thermal properties, and mechanical properties, and can easily control hysteresis through drawing processing. However, since it contains a copolymerized component, the degree of crystallization decreases, making it difficult to obtain high retardation. One with a small copolymer component is the best since it is relatively easy to obtain a large hysteresis even if the thickness is thin. When the total acid component is regarded as 100 mol% and the total glycol component is regarded as 100 mol%, the total of other copolymer components, that is, acid components other than terephthalic acid and glycol components other than ethylene glycol The amount is preferably 10 mol% or less, more preferably 7 mol% or less, further preferably 5 mol% or less.

Furthermore, in order to improve the adhesion between the polyester film and the polarizer, corona treatment, coating treatment, flame treatment, etc. may also be performed.

In the present invention, in order to improve the adhesion with the polarizer, it is preferable that at least one side of the polyester film has an easy-adhesion resin containing at least one type of polyester resin, polyurethane resin or polyacrylic resin as the main component. layer. Here, the “main component” refers to a component of 50% by mass or more of the solid content constituting the easy-adhesion layer. The coating liquid used to form the easily adhesive layer of the present invention is preferably an aqueous coating containing at least one of a water-soluble or water-dispersible copolymerized polyester resin, an acrylic resin, and a polyurethane resin. liquid. Examples of such coating liquids include Japanese Invention Patent No. 3567927, Japanese Invention Patent No. 3589232, Japanese Invention Patent No. 3589233, Japanese Invention Patent No. 3900191, and Japanese Invention Patent No. 4150982. Water-soluble or water-dispersible copolymerized polyester resin solutions, acrylic resin solutions, polyurethane resin solutions, etc. disclosed in publications and the like.

The easily adhesive layer can be obtained by applying the coating liquid to one or both sides of a film before stretching or a longitudinal uniaxially stretched film, drying it at 100 to 150° C., and further stretching it in the transverse direction. The coating amount of the final easy-adhesive layer is preferably managed to be 0.05 to 0.20g/m ² . If the coating amount is 0.05 g/m ² or more, the adhesion to the polarizer will be good. On the other hand, if the coating amount is 0.20g/ ^m2 or less, the blocking resistance will be good. When the easy-adhesive layers are provided on both sides of the polyester film, the compositions of the easy-adhesive layers on both sides can be the same or different, and the coating amounts can be the same or different, and can be set independently within the above ranges.

In order to impart slipperiness to the easy-adhesion layer, it is preferable to add particles. The average particle diameter of the fine particles is preferably 2 μm or less from the viewpoint of preventing the particles from falling off from the coating layer. Examples of the particles contained in the easily adhesive layer include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, and hectorite. Inorganic particles such as zirconium oxide, tungsten oxide, lithium fluoride, and calcium fluoride, or organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and polysiloxane-based particles. These may be added to the easy-adhesion layer individually, or 2 or more types may be added in combination.

In addition, as a method of applying the coating liquid, a well-known method can be used. Examples include reverse roll coating, gravure coating, kiss coating, roller brushing, spray coating, air knife coating, wire bar coating, and tube doctoring. These methods can be performed alone or in combination.

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

The polyester film can be manufactured according to the general manufacturing method of PET film. For example, PET resin is melted and extruded into a sheet shape, and the formed unstretched sheet is stretched in the longitudinal direction in the direction of travel by utilizing the speed difference of the rollers at a temperature higher than the glass transition temperature, and then stretched by drawing. The web machine is extended in the transverse direction and heat treated.

It does not matter whether the polyester film is a uniaxially stretched film or a biaxially stretched film. However, when a biaxially stretched film is used as a polarizer protective film, iridescent stains will not be visible even when viewed from directly above the film surface. When viewed from an oblique direction, rainbow-like stains may be observed, so please be careful.

This phenomenon is because the biaxially stretched film is composed of refractive index ellipsoids with different refractive indexes in the longitudinal direction, width direction, and thickness direction. Depending on the direction of light penetration inside the film, there is a hysteresis that becomes zero (refractive index ellipse). The body looks like a perfect circle) exists in the direction. Therefore, when the liquid crystal display screen is viewed from a specific direction in the oblique direction, a point where hysteresis becomes zero may occur, and rainbow-shaped spots may appear concentrically around this point. Furthermore, if the angle from directly above the film surface (normal direction) to the position where the iridescent color spots are seen is regarded as θ, then this angle θ will be greater as the birefringence in the film surface is greater, and the iridescent color will be greater. The spots will become difficult to see. In a biaxially stretched film, the angle θ tends to become smaller, so a uniaxially stretched film is preferable because the iridescent stain becomes difficult to see.

However, a completely uniaxial (uniaxially symmetric) film is unfavorable because the mechanical strength in the direction orthogonal to the alignment direction is significantly reduced. The present invention preferably has biaxiality (biaxial symmetry) within a range in which iridescent color spots do not substantially occur, or in a range in which iridescent color spots do not occur in the viewing angle range required for the liquid crystal display screen. .

As a means of suppressing the occurrence of rainbow spots while maintaining the mechanical strength of the polyester film, it is preferable to control the ratio of the in-plane retardation to the thickness direction retardation (Rth) of the polyester film within a specific range. The thickness direction phase difference means the average phase difference obtained by multiplying the two birefringences ΔNxz and ΔNyz by the film thickness d when the film is viewed in cross section in the thickness direction. Since the smaller the difference between the in-plane retardation and the thickness direction retardation, the effect of birefringence caused by the observation angle increases isotropy, so the change in hysteresis caused by the observation angle becomes smaller. Therefore, it is considered that rainbow-like color spots due to the viewing angle are less likely to occur.

The ratio of in-plane retardation to thickness direction retardation (Re/Rth) of the polyester film is preferably 0.200 or more, more preferably 0.500 or more, and further preferably 0.600 or more. The greater the above-mentioned Re/Rth, the more isotropic the effect of birefringence, making it less likely that rainbow-like color spots due to the viewing angle will occur. Furthermore, for a completely uniaxial (uniaxially symmetric) film, Re/Rth becomes 2.0. However, as mentioned above, as the film approaches a completely uniaxial (uniaxially symmetric) film, the mechanical strength in the direction orthogonal to the alignment direction decreases significantly. Furthermore, as mentioned above, in the case of a biaxially stretched polyester film, Re/Rth can be less than 0.200.

Re/Rth of the polyester film is preferably 1.2 or less, more preferably 1.0 or less. In order to completely suppress the occurrence of rainbow-like color spots caused by the viewing angle, it is not necessary for Re/Rth to be 2.0, and 1.2 or less is sufficient. In addition, even if the above ratio is 1.0 or less, it is possible to sufficiently satisfy the viewing angle characteristics required for a liquid crystal display device (approximately 180 degrees left and right, and 120 degrees up and down).

If the film-making conditions of the polyester film are specifically described, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130°C, particularly preferably 90 to 120°C. Taking the aforementioned film with an in-plane retardation of 2500 nm to 30000 nm and a slow axis in the transverse direction as an example, the longitudinal stretching ratio is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times, and the horizontal stretching ratio is preferably It is 2.5 to 6.0 times, and the best one is 3.0 to 5.5 times. In the case of a film in which the slow axis is in the longitudinal direction, it is preferable to exchange the above-mentioned longitudinal and transverse ranges. In order to control hysteresis within the above range, it is preferable to control the ratio of the longitudinal stretch magnification and the transverse stretch magnification. If the difference between the vertical and horizontal stretch ratios is too small, it becomes difficult to increase the hysteresis, which is undesirable. In addition, setting a low extension temperature can also increase hysteresis, which is a better response. In the subsequent heat treatment, the treatment temperature is preferably 100 to 250°C, and particularly preferably 180 to 245°C.

In order to suppress the variation of hysteresis, it is preferable that the thickness variation of the film is small. Since the stretching temperature and stretching ratio have a great influence on the thickness unevenness of the film, it is also necessary to optimize the film production conditions from the perspective of thickness unevenness. In particular, if the longitudinal stretch ratio is reduced in order to increase hysteresis, the longitudinal thickness unevenness may worsen. Longitudinal thickness unevenness is particularly severe within a certain range of stretch magnification, so it is advisable to set film forming conditions outside this range.

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

As mentioned above, in order to control the hysteresis of the polyester film within a specific range, the stretching ratio, stretching temperature, and film thickness can be appropriately set. For example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film thickness, the easier it is to obtain high hysteresis. On the contrary, the lower the stretching ratio, the higher the stretching temperature, and the thinner the thickness of the film, the easier it is to obtain low hysteresis. However, if the thickness of the film is increased, the thickness direction phase difference tends to become larger. Therefore, the film thickness is preferably set appropriately within the range described below. In addition to hysteresis control, it is also necessary to set the final film forming conditions by taking into account the physical properties required for processing.

The thickness of the polyester film is arbitrary, but is preferably in the range of 15 to 300 μm, more preferably in the range of 20 to 200 μm. Even for films with a thickness less than 15 μm, retardation of more than 3000 nm can be obtained in principle. However, in this case, the anisotropy of the mechanical properties of the film will become significant, and cracks, damage, etc. will easily occur, and the practicality as an industrial material will be significantly reduced. The optimal lower limit of thickness is 25 μm. On the other hand, if the upper limit of the thickness of the polyester film exceeds 300 μm, the thickness of the polarizing plate becomes unfavorably too thick. From the viewpoint of practicality as a polarizer protective film and other various uses, the upper limit of the thickness is preferably 200 μm. The optimal upper limit of thickness is 100 μm.

Moreover, it is preferable that the polyester film has a multilayer structure of at least three layers and that an ultraviolet absorber is added to an intermediate layer of the film. A film with a three-layer structure containing an ultraviolet absorber in the middle layer can be produced specifically as follows. The polyester pellets for the outer layer are separated, and the masterbatch containing the ultraviolet absorber for the middle layer is mixed with the polyester pellets in a specific ratio. After drying, they are supplied to a well-known extruder for melt lamination. A sheet is extruded from a slit-shaped die and cooled and solidified on a casting roll to produce an unstretched film. That is, using two or more extruders, a three-layer manifold or a merging block (for example, a merging block having an angular merging part), the film layers constituting the two outer layers and the film layer constituting the middle layer are The three-layered sheets are laminated and extruded from the metal opening, and are cooled on a casting roller to produce an unstretched film. Furthermore, in the invention, in order to remove foreign matter contained in the raw material PET resin that causes optical defects, it is preferable to perform high-precision filtration during melt extrusion. The filter particle size of the filter material used for high-precision filtration of molten resin (initial filtration efficiency 95%) is preferably 15 μm or less from the viewpoint of ease of removing foreign matter.

It is also a preferred form to have a hard coat layer on at least one side of the polyester film. The hard coating pencil hardness is preferably H or higher, more preferably 2H or higher. The hard coat layer can be provided by applying a composition solution of a thermosetting resin or a radiation curing resin and hardening it, for example.

Examples of thermosetting resins include acrylic resins, urethane resins, phenol resins, urea-melamine resins, epoxy resins, unsaturated polyester resins, polysilicone resins, and combinations thereof. In the thermosetting resin composition, a hardener is added to the curable resin as necessary.

The radiation curable resin is preferably a compound having a radiation curable functional group. Examples of the radiation curable functional group include ethylenically unsaturated bond groups such as (meth)acrylyl, vinyl, and allyl. , epoxy group, oxetanyl group, etc. Among these, the ionizing radiation curable compound is preferably a compound having an ethylenically unsaturated bond group, more preferably a compound having two or more ethylenically unsaturated bond groups, and further more preferably, a compound having two or more ethylenically unsaturated bond groups. The polyfunctional (meth)acrylate compound of the above ethylenically unsaturated bond group. The polyfunctional (meth)acrylate compound may be a monomer, oligomer, or polymer.

Specific examples of these polyfunctional monomers include pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), and dipentaerythritol pentaacrylate (DPPA). )wait. In addition, in order to adjust the coating viscosity or hardness, a monofunctional monomer may be used together.

Examples of the polyfunctional oligomer include polyester (meth)acrylate, urethane (meth)acrylate, polyester-urethane (meth)acrylate, and polyether. (Meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, isocyanate (meth)acrylate, epoxy (meth)acrylate, etc.

Examples of the polyfunctional polymer include urethane (meth)acrylate, isocyanate (meth)acrylate, and polyester-urethane (meth)acrylate. , epoxy (meth)acrylate, etc. In order to achieve the hardness of the hard coat layer, it is preferable that the bifunctional or higher functional monomer is 50 mass % or more, and more preferably 70 mass % or more in the compound having a radiation curable functional group. Furthermore, in the compound having a radiation-curable functional group, the trifunctional or higher functional monomer is preferably 50 mass % or more, and more preferably 70 mass % or more. The above-mentioned compounds having a radiation curable functional group may be used alone or in combination of two or more types.

The thickness of the hard coat layer is preferably 0.1 to 100 μm, more preferably 1.0 to 20 μm, and further preferably 2.0 to 10 μm.

The refractive index of the hard coat layer is more preferably 1.45 to 1.70, further preferably 1.50 to 1.60. In addition, the refractive index of the hard coat layer is a value measured under the condition of a wavelength of 589 nm.

In order to adjust the refractive index of the hard coat layer, there are methods of adjusting the refractive index of the resin, and methods of adjusting the refractive index of the particles when adding particles. Regarding particles, examples of low refractive index particles include solid or hollow silica particles, magnesium fluoride particles, and the like. Examples of high refractive index particles include antimony pentoxide particles, zinc oxide particles, titanium oxide particles, cerium oxide particles, tin-doped indium oxide particles, antimony-doped tin oxide particles, and yttrium oxide particles. Zirconia particles, etc. The average particle diameter of the primary particles of these particles is preferably 5 to 200 nm, more preferably 8 to 100 nm, and further preferably 10 to 80 nm. The particles are more preferably surface-treated with a silane coupling agent, and particularly preferably surface-treated with a silane coupling agent having a (meth)acrylyl group.

The polyester film can have an anti-reflective layer, a low-reflective layer, an anti-glare layer, an anti-fouling layer, an anti-static layer, etc. These layers can be provided on the aforementioned hard coating layer, and the hard coating layer can be a layer with these functions, or can also constitute a part of these layers. Hereinafter, these layers including the hard coat layer may be called a functional layer, and a polyester film laminated with a functional layer may be called a laminated polyester film.

The low-reflective layer is a layer that has the function of providing a low-refractive index layer (low refractive index layer) on the surface of the base film to reduce the refractive index difference with air and thereby reduce the reflectivity. The description of the low refractive index layer is made in the following anti-reflection layer. The reflectivity of the laminated polyester film having a low-reflective layer, when measured from the low-reflective layer side, is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, and particularly preferably 2% or less. , the best is less than 1.5%. Furthermore, the reflectivity is preferably 0.2% or more.

The anti-reflective layer controls the thickness of the low refractive index layer so that the upper interface of the low refractive index layer (the interface between the low refractive index layer and the air) and the lower interface of the low refractive index (such as the interface between the base film and the low refractive index layer) ), the reflected light interferes with the layer that controls the reflection. In this case, the thickness of the low refractive index layer is preferably about the wavelength of visible light (400 to 700 mn)/(refractive index of the low refractive index layer × 4). It is also a better form to set up a high refractive index layer between the anti-reflective layer and the base film. It is also possible to set up two or more low-refractive index layers or high-refractive index layers to further improve the anti-reflective effect through multiple interference. .

The reflectivity of the laminated polyester film having an anti-reflection layer, when measured from the anti-reflection layer side, is preferably 2% or less, more preferably 1.5% or less, further preferably 1.2% or less, and particularly preferably 1% or less. . Furthermore, the reflectivity is preferably 0.1% or more.

The refractive index of the low refractive index layer is preferably 1.45 or less, more preferably 1.42 or less. Moreover, the refractive index of the low refractive index layer is preferably 1.20 or more, more preferably 1.25 or more. In addition, the refractive index of the low refractive index layer is a value measured under the condition of a wavelength of 589 nm.

The thickness of the low refractive index layer is not limited, but usually it can be set appropriately within the range of about 30 nm to 2 μm. Furthermore, if the purpose of further reducing the reflectance is to offset the reflection on the surface of the low refractive index layer and the interface reflection between the low refractive index layer and the layers inside it (base film, hard coat layer, etc.), the low refractive index layer The thickness is preferably 70-120nm, more preferably 75-110nm.

Preferable examples of the low refractive index layer include: (1) a layer composed of a resin composition containing a binder resin and low refractive index particles; (2) a layer composed of a fluororesin which is a low refractive index resin; (3) A layer composed of a fluororesin composition containing low refractive index particles, (4) a thin film of low refractive index materials such as silicon dioxide and magnesium fluoride, etc.

As the binder resin contained in the resin composition of (1), polyester, polyurethane, polyamide, polycarbonate, acrylic, etc. can be used without particular limitation. Among them, acrylic acid is preferred, and one obtained by polymerizing (crosslinking) a photopolymerizable compound by light irradiation is preferred. Examples of the low refractive index particles and photopolymerizable compounds are those described in the hard coat layer.

The content of the low refractive index particles in the low refractive index layer is preferably 10 to 250 parts by mass, more preferably 50 to 200 parts by mass, and further preferably 100 to 180 parts by mass based on 100 parts by mass of the binder resin.

As the fluorine-based resins of (2) and (3), a polymerizable compound containing a fluorine atom in the molecule or a polymer thereof can be used. The polymerizable compound is not particularly limited, but preferably has a curing reactive group such as a photopolymerizable functional group or a thermosetting polar group. Furthermore, a compound having both of these plural curing reactive groups may be used. In contrast to this polymerizable compound, the polymer does not substantially have the above-mentioned curing reactive group and the like.

(4) Thin films of low refractive index materials such as silicon dioxide and magnesium fluoride can be formed by dry processes such as evaporation, sputtering, and CVD. In addition, the sol-gel method using a silica compound is also a preferred method.

The refractive index of the high refractive index layer is preferably 1.55 to 1.85, more preferably 1.56 to 1.70. In addition, the refractive index of the high refractive index layer is a value measured under the condition of a wavelength of 589 nm.

The thickness of the high refractive index layer is preferably 30 to 200 nm, more preferably 50 to 180 nm. The high refractive index layer may be a plurality of layers, but it is preferably two or less layers, and more preferably a single layer. In the case of a plurality of layers, it is preferable that the total thickness of the plurality of layers is within the above range.

When there are two high refractive index layers, it is preferable to increase the refractive index of the high refractive index layer on the low refractive index layer side. Specifically, the refractive index of the high refractive index layer on the low refractive index layer side is preferably The refractive index of the other high refractive index layer is preferably 1.55 to 1.70.

The high refractive index layer is preferably composed of high refractive index particles and binder resin. Examples of high refractive index particles and resins include those described for the low refractive index layer. Alternatively, the film may be a thin film produced by a dry process of the metal compounds listed as high refractive particles.

Two or more types of high refractive index particles may be used in combination. In particular, in order to prevent aggregation, it is also preferable to add first high refractive index particles and second high refractive index particles having a smaller surface charge than the first high refractive index particles.

The content of the high refractive index particles is preferably 30 to 400 parts by mass with respect to 100 parts by mass of the resin, more preferably 50 to 200 parts by mass, and further preferably 80 to 150 parts by mass.

The high refractive index layer and the low refractive index layer can be formed by, for example, coating a resin composition containing a photopolymerizable compound on a base film, drying it, and then irradiating the coated resin composition with light such as ultraviolet rays. The photopolymerizable compound is polymerized (crosslinked) and formed.

(anti-glare layer) The anti-glare layer is a layer that is provided with concavities and convexities on the surface to cause diffuse reflection, thereby preventing external light from being reflected in the shape of the light source when it is reflected on the surface, or a layer that reduces glare.

The arithmetic mean roughness (Ra) of the uneven surface of the anti-glare layer is preferably 0.02 to 0.25 μm, more preferably 0.02 to 0.15 μm, and further preferably 0.02 to 0.12 μm.

The ten-point average roughness (Rzjis) of the surface of the anti-glare layer is preferably 0.15 to 2.00 μm, more preferably 0.20 to 1.20 μm, and further preferably 0.30 to 0.80 μm.

Ra and Rzjis are calculated from the roughness curve measured using a contact type roughness meter in accordance with JIS B0601-1994 or JIS B0601-2001.

Examples of methods for providing an anti-glare layer on a base film include the following methods. ・Coating anti-glare layer coating containing particles (fillers), etc. ・The resin for the anti-glare layer is hardened while in contact with the mold having an uneven structure ・Coat the anti-glare layer resin on a mold with a concave-convex structure and transfer it to the base film ・Coating that causes spindle decomposition during drying and film formation

The lower limit of the thickness of the anti-glare layer is preferably 0.1 μm, more preferably 0.5 μm. The upper limit of the thickness of the anti-glare layer is preferably 100 μm, more preferably 50 μm, and further preferably 20 μm.

The refractive index of the anti-glare layer is preferably 1.20 to 1.80, more preferably 1.40 to 1.70. When the refractive index of the anti-glare layer itself is reduced to pursue a low reflection effect, the refractive index of the anti-glare layer is preferably 1.20 to 1.45, more preferably 1.25 to 1.40. When a low refractive index layer described below is provided on the anti-glare layer, the refractive index of the anti-glare layer is preferably 1.50 to 1.80, more preferably 1.55 to 1.70. In addition, the refractive index of the anti-glare layer is a value measured under the condition of a wavelength of 589 nm.

The low refractive index layer may be provided with concavities and convexities to serve as an anti-glare low-reflective layer, or a low refractive index layer may be provided on the concavities and convexes to provide an anti-reflective function to serve as an anti-glare anti-reflective layer.

When forming a functional layer by coating, in addition to the particles or resin components constituting these layers, a coating composition containing a solvent and a polymerization initiator may be used if necessary. In the coating composition, dispersants, surfactants, antistatic agents, silane coupling agents, tackifiers, anti-coloration agents, colorants (pigments, dyes), defoaming agents, leveling agents, and flame retardants can be further added. Agents, UV absorbers, adhesion imparting agents, polymerization inhibitors, antioxidants, surface modifiers, slip agents, etc. In addition, for the purpose of improving fingerprint resistance, it is also preferable to add a well-known polysiloxane-based or fluorine-based antifouling agent.

The haze of the laminated polyester film is 2% or less, which is also a preferred form. The haze is more preferably 1.5% or less, further preferably 1.2% or less, and particularly preferably 1.0% or less. The haze is preferably 0.01% or more, more preferably 0.1% or more. By setting it within the above range, when the laminated polyester film is used as a polarizer protective film or the like, a highly transparent and clear image can be obtained. In order to bring the haze of the laminated polyester film into the above range, it is preferable to: reduce the particle size of the hard coat layer, etc.; fully disperse the particles and then filter to remove coarse particles; and select particles and resin in which the particles are less likely to agglomerate during drying. Combination; select a combination of resin and solvent that is not likely to roughen the surface during drying and adjust drying conditions.

In order to make the haze of the laminated polyester film fall into the said range, it is also preferable that the haze of the base film falls into the said range. Methods for bringing the haze of the base film into the above range include: reducing the amount of lubricant particles added to the base film; making the base film have a multilayer structure and adding lubricant particles only to the surface layer; A method in which lubricant particles are not added to the base film but lubricant particles are added to the easy-adhesion layer. Furthermore, by setting the added amount of the metal compound of the catalyst to the aforementioned range, the occurrence of foreign matter originating from the catalyst can be suppressed and an increase in haze can be suppressed.

Furthermore, in film production, the molten resin is extruded into a sheet shape on a cooling roll. However, if the cooling rate is slowed down, the haze of the film may become high. Especially when there are a lot of foreign matter or a large amount of catalyst, PET resin derived from biomass resources tends to crystallize easily. It is better to take countermeasures such as: lowering the temperature of the cooling roller; blowing cold air on the opposite side of the cooling roller to increase the cooling speed. The haze can be measured using a turbidity meter (NHD2000, manufactured by Nippon Denshoku Industries) in accordance with JIS-K7105.

In the present invention, the polyester film is preferably a long roll-shaped film wound on a core. The length of the long film is preferably not less than 500 m and not more than 20,000 m, more preferably not less than 1,000 m and not more than 10,000 m. The width is preferably from 300mm to 10,000mm, and more preferably from 500mm to 8,000mm. The same applies to laminated polyester films.

The polarizer has a structure in which a polarizer protective film is bonded to one side or both sides of the polarizer. Preferably, at least one of the polarizer protective films constituting the polarizer is a polyester film made of bio-PET resin. Among them, a polarizer protective film in which only one side of the polarizer is made of a biomass PET film is more preferred. On the other hand, the other surface of the polarizer may be a resin film without triacetyl cellulose, acrylic, polycyclic olefin, etc., a coating layer of a curable resin, or a composition of these films or coating layers. Furthermore, a layer with a phase difference can be provided on the other side of the polarizer to form a polarizing plate laminated with an optical compensation layer. Examples of the optical reinforcing layer include a coating layer formed by stretching a resin film such as triacetyl cellulose, acrylic acid, polycyclic olefin, or the like to impart a phase difference, or aligning a liquid crystal compound. Alternatively, the layer having a phase difference may be a λ/4 wavelength layer to form a circularly polarizing plate. Typical polarizers include stretched films made of PVA or the like dyed with iodine or a dichroic organic dye, but they may also be alignment films of liquid crystal compounds containing dichroic dyes, wire grid polarizers, etc.

The image display device is not particularly limited as long as it is a liquid crystal display device, an organic EL display device, a micro-LED display device, or the like that uses a polarizing plate. In the image display device, the polarizer protective film of the present invention is preferably arranged on the opposite side to the image display unit with the polarizer as a reference.

A liquid crystal display device is composed of at least a backlight source and a liquid crystal cell arranged between two polarizing plates. Furthermore, it may be suitably provided with other structures other than these, such as a color filter, a lens film, a diffusion sheet, an anti-reflection film, etc.

As for the structure of the backlight, it can be an edge light type using a light guide plate or a reflective plate as a component, or a direct type type. However, the liquid crystal display device preferably uses a white light source as the backlight source. Suitable white light sources include blue light using a compound semiconductor, or a white light emitting diode that emits white color by combining a light emitting diode and a phosphor that emits ultraviolet light. Combinations with phosphors include combinations with yellow phosphors to produce white light, combinations with green phosphors and red phosphors to produce white light, and the like. Examples of yellow phosphors include yttrium-aluminum-garnet-based yellow phosphors or yttrium-aluminum-garnet-based yellow phosphors. Examples of green phosphors include Eu-activated chlorosilicate phosphors, Eu-activated silicate phosphors, Eu-activated β-silica aluminum oxynitride (sialon) phosphors, and Eu-activated gallium sulfide Acid phosphors, rare earth aluminate phosphors, lanthanum silicon nitride phosphors, perovskite phosphors, etc. Examples of red phosphors include manganese ion-activated fluoride phosphors, Eu-activated calcium silicate phosphors, nitride phosphors, Eu-activated fluorine oxygen complex phosphorus (FOLP) phosphors, Perovskite phosphors, etc.

In addition, a white light source composed of a light source that emits excitation light and a light-emitting layer including quantum dots is also a preferred light source. As far as quantum dots are concerned, there are QDEF ^TM from Nanosys or Color IQ ^TM from QD Vision. A light-emitting layer composed of a combination of green quantum dots and the aforementioned red phosphor may be used, or a light-emitting sheet including a magenta diode and green quantum dots composed of the aforementioned blue diode and red phosphor may be used.

In organic EL display devices or micro-LED display devices, for the purpose of preventing reflection, a circular polarizing plate can be used on the visual recognition side of the image display device. [Example]

The following examples are given to illustrate the present invention in more detail. However, the present invention is not limited to the following examples and can be implemented with appropriate changes within the scope consistent with the spirit of the present invention. They are all included in the scope of the present invention. within the technical scope. In addition, the evaluation method of the physical properties in the following examples is as follows.

(1) In-plane hysteresis (Re) The so-called in-plane hysteresis is a parameter defined by the product of the anisotropy of the refractive index of the two orthogonal axes on the film (ΔNxy=∣Nx-Ny∣) and the film thickness d (nm) (ΔNxy×d). It is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) is determined by the following method. Using two pieces of polarizing plates, determine the alignment axis direction of the film, and cut out a 4cm × 2cm rectangle with the alignment axis directions orthogonal to serve as a sample for measurement. For this sample, the refractive index (Nx, Ny) of the two orthogonal axes and the refractive index (Nz) in the thickness direction were calculated using an Abbe refractometer (NAR-4T, manufactured by ATAGO, measuring wavelength 589 nm). The absolute value of the refractive index difference between the two axes (∣Nx-Ny|) is regarded as the refractive index anisotropy (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D manufactured by FEINPRUF), and the unit was converted into nm. The in-plane retardation (Re) is calculated from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the thickness d (nm) of the film.

(2) Thickness direction hysteresis (Rth) The so-called thickness direction hysteresis refers to the hysteresis obtained by multiplying the two birefringences ΔNxz (∣Nx-Nz∣) and ΔNyz (∣Ny-Nz∣) by the film thickness d when viewed from the film thickness direction cross-section. The average parameter. By the same method as the measurement of hysteresis, Nx, Ny, Nz and film thickness d (nm) were determined, the average value of (ΔNxz×d) and (ΔNyz×d) was calculated, and the thickness direction hysteresis (Rth) was calculated.

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

(4) Resin deterioration evaluation Place 9g of PET resin and 1g of ultraviolet absorber into the ampoule tube, heat at 290°C for 10 minutes under vacuum, and stir at 290°C for 10 minutes. Thereafter, the mixture was kept at a constant temperature for 2 hours while purging with nitrogen to obtain a masterbatch. The intrinsic viscosity of the PET resin before treatment and the intrinsic viscosity of the masterbatch after treatment are measured, and the degree of deterioration is evaluated from the difference (ΔIV) between the intrinsic viscosity before and after treatment.

(5)Carboxyl terminal concentration (AV) The film and raw material polyester resin were measured by the following method. Moreover, in the case of polyester resin, the fragments are directly used as samples, and in the case of polarizer protective film, the coating is used as a sample by cutting off the coating with a knife. i. Preparation of sample About 3g of the sample was freeze-pulverized, vacuum dried at 70°C for 24 hours, and then weighed in the range of 0.20±0.0005g using a balance. Let the mass at this time be W (g), add 10 ml of benzyl alcohol and the weighed sample into the test tube, immerse the test tube in a benzyl alcohol bath heated to 205°C, and stir the sample with a glass rod. Dissolve. Let the samples with dissolution times of 3 minutes, 5 minutes, and 7 minutes be designated A, B, and C respectively. Next, prepare a new test tube, add only benzyl alcohol, and process it with the same procedure. Let the samples at 3 minutes, 5 minutes, and 7 minutes be a, b, and c respectively. However, when inorganic fine particles are present in the sample, the value obtained by removing the mass of the inorganic fine particles becomes W (g). In addition, the content of the inorganic fine particles can be determined by dissolving the sample in a solvent, recovering the solid content by centrifugation, and measuring the mass. ii. Titration The titration was performed using a 0.04 mol/l potassium hydroxide solution (ethanol solution) with a previously known factor. Phenol red is used as the indicator, and the change from yellow-green to light red is regarded as the end point, and the titer (ml) of the potassium hydroxide solution is calculated. Let the titers of samples A, B, and C be XA, XB, and XC (ml), and let the titers of samples a, b, and c be Xa, Xb, and Xc (ml). iii. Calculation of carboxyl terminal concentration Using the titers XA, XB, and XC for each dissolution time, the titer V (ml) at the dissolution time of 0 minutes was determined by the least squares method. Similarly, using Xa, Xb, and Xc, the titer V0 (ml) is obtained. Next, the carboxyl terminal concentration was determined according to the following formula. Carboxyl terminal concentration (eq/ton)=[(V-V0)×0.04×NF×1000]/W NF: coefficient of 0.04mol/l potassium hydroxide solution

(6)Intrinsic viscosity (IV) Measure 0.20 g of the freeze-pulverized and dried sample obtained in the same manner as above for the carboxyl terminal concentration, and use 20 ml to mix 1,1,2,2-tetrachloroethane and p-chlorophenol at a ratio of 1:3 (mass ratio). The solvent was stirred at 100° C. for 60 minutes to completely dissolve, and then cooled to room temperature and passed through a glass filter to prepare a sample. Using an Ubbelohde viscometer (manufactured by Clutch Co., Ltd.) adjusted to 30°C, the falling time of the test material and solvent was measured, and the intrinsic viscosity [η] was calculated by the following formula. [η]=(-1+√(1+4K’ηSp))/2K’C ηSp=(τ-τ0)τ0 Here, [η]: Intrinsic viscosity (dl/g) ηSp: Specific viscosity (-) K’: Huggins constant (=0.33) C: Concentration (=1g/dl) τ: Sample falling time (sec) τ0: Solvent falling time (sec)

(7) The degree of biomass was measured by radiocarbon (C ¹⁴ ) as shown in ASTM D6866-16 Method B (AMS).

(8) Evaluation of the number of foreign matter in the film. Use a defect inspection machine (MaxEye. CORE/160C manufactured by FUTEC) to perform primary screening based on black and white judgment for scratches and internal foreign matter. Samples are taken from suitable places, and if they are foreign objects, the length and diameter are measured with a laser microscope. From the number of foreign objects with a long diameter of 50 μm or more to an area of 20 or more, calculate the number per 1000 m ² .

(9) Iridescent spot observation Paste the PET film made by the method described below on one side of the polarizer made of PVA and iodine in such a way that the absorption axis of the polarizer is perpendicular to the alignment main axis of the film, and paste the TAC film (Fuji Film) on the opposite side. (Co., Ltd., thickness 80μm), made into a polarizing plate. The polarizing plate on the viewing side of a liquid crystal display device using a white LED as a light source, which is composed of a light-emitting element that combines a blue light-emitting diode and a yttrium-aluminum-garnet-based yellow phosphor, is peeled off to display the The PET film on the light emitting side becomes the visual recognition side, and the polarizing plate is replaced by laminating the resulting polarizing plate so that the absorption axis of the polarizing plate becomes the same direction as the original polarizing plate. The liquid crystal display device produced was moved at an angle of about 50 degrees from the normal direction of the screen to an inclination direction of about 50 degrees from the long side to the short side of the screen, and visual observation was made to determine whether or not rainbow spots had occurred. , the judgment is made as follows. ◎: No rainbow spots occurred from any direction. ○: Very light iridescence or coloring is observed in some locations. △: Light iridescence or coloring is observed in some locations. ×: Rainbow spots or coloring are clearly observed in some directions.

(10)Content rate of metal elements in resin The polyester resin described below was weighed in a platinum crucible, carbonized in an electric furnace, and then ashed using a Monfoy furnace at 550° C. for 8 hours. The ashed sample was dissolved in 1.2 M hydrochloric acid. Sample solution. The prepared sample solution was measured under the following conditions, and the concentration of the antimony element in the polyester resin was determined by high-frequency inductively coupled plasma luminescence analysis. In addition, the concentration of aluminum element can be determined by the same method as above. Device: CIROS-120 manufactured by SPECTRO Corporation Plasma output: 1400W Plasma gas: 13.0L/min Auxiliary gas: 2.0L/min Nebulizer: Cross flow nebulizer Chamber: Cyclone Chamber Measurement wavelength: 167.078nm

(11)Haze In accordance with JIS-K7136, the haze of the film was measured using a turbidimeter (NHD2000, manufactured by Nippon Denshoku Industries).

(12)Reflectivity Using a spectrophotometer (UV-3150 manufactured by Shimadzu Corporation), the 5-degree reflectance at a wavelength of 550 nm was measured from the surface of the anti-reflection layer side (or low-reflection layer side). Furthermore, after applying black strange ink on the side opposite to the side of the polyester film with the anti-reflective layer (or low-reflective layer), stick the black polyvinyl chloride tape (Kyowa Co., Ltd. PVC Tape HF- 737 width 50mm) and measured.

Production Example 1 (Production of polyethylene terephthalate resin A) The esterification reaction tank was heated up, and when it reached 200°C, 86.4 parts by mass of petroleum-derived terephthalic acid and 64.6 parts by mass of petroleum-derived ethylene glycol were fed, while stirring, 0.017 parts by mass was fed. Antimony trioxide, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were used as catalysts. Then, the pressure was increased and the temperature was increased. After performing a pressure esterification reaction under the conditions of 0.34 MPa gauge pressure and 240° C., the esterification reaction tank was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, the temperature was raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Next, after 15 minutes, a high-pressure disperser was used to perform dispersion treatment. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction tank, and a polycondensation reaction was performed at 280° C. under reduced pressure.

After the polycondensation reaction is completed, filter it with a Naslon filter with a 95% cutoff diameter of 5 μm, extrude the strand form from the nozzle, and use cooling water that has been filtered in advance (pore size: 1 μm or less) to cool it. Solidify and cut into pellets. The obtained polyethylene terephthalate resin (A) has an inherent viscosity of 0.62dl/g, a carboxyl terminal concentration of 30eq/ton, an antimony element content in the resin of 135 ppm by mass, and substantially no inert particles and internal precipitation. particle. Hereinafter, polyethylene terephthalate resin A is simply referred to as PET (A).

Production Example 2 (Production of polyethylene terephthalate resin B) 10 parts by mass of a dried cyclic imide ester-containing ultraviolet absorber (2,2'-(1,4-phenylene) was mixed )bis(4H-3,1-benzo -4-one) (ultraviolet absorber a) and 90 parts by mass of particle-free PET (A) were kneaded and extruded to obtain polyterephthalic acid containing a cyclic imide ester-based ultraviolet absorber. Ethylene glycol resin (B). Hereinafter, polyethylene terephthalate resin B is simply referred to as PET (B). In the production of PET (B), the ultraviolet absorber is used with a purity of 99.5% or above, and the resin temperature in the mixing extruder does not exceed 285°C, and the mixing time is about 5 minutes.

Production Example 3 (Production of polyethylene terephthalate resin C) Except using biomass-derived ethylene glycol as ethylene glycol, the same method as Production Example 1 was used to obtain an intrinsic viscosity of 0.62 dl/g, a carboxyl terminal concentration of 35 eq/ton, and an antimony element content in the resin of 135 mass. ppm, polyethylene terephthalate resin (C) substantially free of inert particles and internal precipitated particles. Hereinafter, polyethylene terephthalate resin C is simply called PET (C). The biomass degree of the obtained PET(C) is over 19%.

Production Example 4 (Production of polyethylene terephthalate resin D) A polyethylene terephthalate resin (C) containing a cyclic imide ester-based ultraviolet absorber was obtained in the same manner as in Production Example 2 except that PET (C) was used. Hereinafter, polyethylene terephthalate resin D is simply referred to as PET (D).

Production Example 5 (Production of polyethylene terephthalate resin E) 10 parts by weight of a benzotriazole-based ultraviolet absorber (ultraviolet absorber b) 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1) as an ultraviolet absorber was mixed -Dimethylethyl)-4-methylphenol (ultraviolet absorber b) and 90 parts by weight of PET (C) were mixed using a kneading extruder to obtain a polymer containing a benzotriazole-based ultraviolet absorber. Ethylene phthalate resin (E). Hereinafter, polyethylene terephthalate resin E is simply referred to as PET (E).

Production Example 6 (Production of polyethylene terephthalate resin F) 10 parts by weight of a benzotriazole-based ultraviolet absorber 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]benzotriazole ( Ultraviolet absorber c) and 90 parts by weight of PET (C) were mixed and extruded using a kneading and extruder to obtain a polyethylene terephthalate resin (F) containing a benzotriazole-based ultraviolet absorber. Hereinafter, polyethylene terephthalate resin F is simply referred to as PET (F).

Manufacturing of adhesive modified coating liquid A water-dispersible copolymerized polyester resin containing a sulfonate metal base is prepared by carrying out transesterification reaction and polycondensation reaction by common methods, and its composition is 46 mol as the dicarboxylic acid component (relative to the total dicarboxylic acid component) % terephthalic acid, 46 mol% isophthalic acid and 8 mol% sodium 5-sulfonatoisophthalate, as 50 mol% of the diol component (relative to the total diol component) Ethylene glycol and 50 mol% neopentyl glycol. Next, after mixing 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, and 0.06 parts by mass of nonionic surfactant, heat and stir, and when reaching 77°C, add 5 parts by mass part of the water-dispersible sulfonate metal base-containing copolymerized polyester resin, and continue stirring until the lumps of the resin disappear. Then, the aqueous resin dispersion is cooled to normal temperature to obtain a uniform water dispersion with a solid content concentration of 5.0 mass%. copolymerized polyester resin liquid. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (Silysia 310 manufactured by Fuji SILYSIA Co., Ltd.) in 50 parts by mass of water, 99.46 parts by mass of the above water-dispersible copolymerized polyester resin liquid was dispersed 0.54 parts by mass of the aqueous dispersion of Silysia 310 was added, and 20 parts by mass of water was added while stirring to obtain an adhesively modified coating liquid.

Resin Deterioration Evaluation 1 Resin deterioration evaluation was performed using PET (A) resin pellets and ultraviolet absorber (a).

Resin Deterioration Evaluation 2 Resin deterioration evaluation was performed using PET (C) resin pellets and ultraviolet absorber (a).

Resin Deterioration Evaluation 3 Resin deterioration evaluation was performed using PET (C) resin pellets and ultraviolet absorber (b).

Resin Deterioration Evaluation 4 Resin deterioration evaluation was performed using PET (C) resin pellets and ultraviolet absorber (c).

[Table 1] PET resin UV absorber ⊿IV(dl/g) Rating 1 A a 0.16 Rating 2 C a 0.18 Rating 3 C b 0.28 Rating 4 C c 0.33

Table 1 shows the results of resin deterioration evaluation. Compared with evaluation 1, evaluation 2 series resin was slightly deteriorated. This is thought to be because the use of ethylene glycol derived from biomass resources increases impurities and promotes resin deterioration caused by ultraviolet absorbers. Furthermore, compared with Evaluation 2, Evaluation 3 and Evaluation 4 series resins were significantly deteriorated. This is considered to be because the ultraviolet absorber (b) and the ultraviolet absorber (c) containing an OH group at the terminal accelerate the deterioration of the PET resin.

Example 1 90 parts by mass of PET (C) resin pellets without particles and 10 parts by mass of PET (D) resin pellets containing ultraviolet absorber were dried under reduced pressure (1 Torr) at 135°C for 6 hours to serve as the base material The raw materials for the film middle layer are supplied to the extruder 2 (for the middle layer II), and the PET (A) is dried by a common method and supplied to the extruder 1 (for the outer layer I and the outer layer III) respectively, and dissolved. . The two types of polymers were filtered using stainless steel sintered filter media (nominal filtration accuracy: 95% retention of 10 μm particles), laminated in two types of three-layer combined blocks, extruded into thin sheets through metal openings, and then electrostatically applied In the casting method, the film is wound on a casting drum with a surface temperature of 30°C, and air at 20°C is blown from the opposite side to cool and solidify 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 became 10:80:10. The temperature of the resin in the extruder is adjusted not to exceed 285°C. Furthermore, the extruder is assembled in such a way that there is no level difference between the screw connection part, the barrel connection part, and the resin piping connection part. In addition, the filter housing should be designed with a design that is less likely to cause resin retention.

Next, apply the above-mentioned adhesively modified coating liquid on both sides of the unstretched PET film by the reverse roll method so that the coating amount after drying becomes 0.08g/ ^m2 , and then dry at 80°C for 20 seconds. .

The unstretched film on which the coating layer is formed is guided to a tenter stretching machine. While holding the end of the film with a clamp, it is guided to a hot air zone with a temperature of 125°C, and is extended to 4.0 times in the width direction. Next, the film was processed at a temperature of 225°C for 30 seconds while maintaining the width extended in the width direction, and further relaxed by 3% in the width direction to obtain a uniaxially aligned PET film with a film thickness of 50 μm.

Example 2 A uniaxially aligned 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 The unstretched film produced by the same method as Example 2 was heated to 105°C using a heated roller group and an infrared heater, and then stretched 1.5 times in the traveling direction using a roller group with a circumferential speed difference. The same method as Example 1 was used to extend the film 4.0 times in the width direction to obtain a biaxially aligned PET film with a film thickness of 50 μm.

Example 4 In the same method as Example 3, extend 2.0 times in the traveling direction and 4.0 times in the width direction to obtain a biaxially aligned PET film with a film thickness of about 50 μm.

Example 5 In the same method as Example 3, extend 3.3 times in the traveling direction and 4.0 times in the width direction to obtain a biaxially aligned PET film with a film thickness of 75 μm.

Example 6 In the same method as Example 3, extend 4.0 times in the traveling direction and 1.0 times in the width direction to obtain a uniaxially aligned PET film with a film thickness of 100 μm.

Example 7 In the same method as Example 3, extend 3.8 times in the traveling direction and 4.0 times in the width direction to obtain a biaxially aligned PET film with a film thickness of 50 μm.

Example 8 In the same method as Example 3, the film was extended 3.8 times in the traveling direction and 3.6 times in the width direction to obtain a uniaxially aligned PET film with a film thickness of 50 μm.

Comparative example 1 In the same manner as in Example 1, 90 parts by mass of particle-free PET (C) resin pellets and 10 parts by mass of PET (E) resin pellets containing an ultraviolet absorber were used as raw materials for the base film intermediate layer. particles to obtain a uniaxially aligned PET film with a film thickness of 50 μm.

Comparative example 2 In the same manner as in Example 2, 90 parts by mass of particle-free PET (C) resin pellets and 10 parts by mass of PET (F) resin pellets containing an ultraviolet absorber were used as raw materials for the base film intermediate layer. particles to obtain a uniaxially aligned PET film with a film thickness of 50 μm.

Table 2 below shows the evaluation results of the polyester films of Examples 1 to 8 and Comparative Examples 1 and 2. [Table 2] Thickness(μm) Travel direction extension magnification Width direction extension ratio Re(nm) Rth (nm) Re/Rth ratio Rainbow spot observation 380nm light transmittance (%) Number of foreign objects (pieces/1000m ² ) Film AV Film IV Haze Example 1 60 1.0 4.0 6240 7920 0.788 ◎ 7.0 50 47 0.59 0.7 Example 2 100 1.0 4.0 10300 13150 0.783 ◎ 1.0 93 47 0.59 0.8 Example 3 60 1.5 4.0 4680 8340 0.561 ○ 7.0 55 47 0.59 0.7 Example 4 60 2.0 4.0 3900 8850 0.441 ○ 7.0 43 47 0.59 0.7 Example 5 80 3.3 4.0 3840 13280 0.289 ○ 2.5 82 47 0.59 0.8 Example 6 100 4.0 1.0 16500 13250 1.245 ◎ 1.0 110 47 0.59 0.8 Example 7 60 3.6 3.8 1800 11280 0.160 × 7.0 55 47 0.59 0.7 Example 8 40 3.8 3.6 240 7760 0.031 △ 10.0 48 47 0.59 0.7 Comparative example 1 50 1.0 4.0 5200 6600 0.788 ◎ 8.5 1915 63 0.56 1 Comparative example 2 50 1.0 4.0 5200 6600 0.788 ◎ 8.5 3290 67 0.55 1

As shown in Table 2, in the films of Examples 1 to 8, films with a small number of foreign matter and high transparency were obtained. On the other hand, the films of Comparative Examples 1 and 2 had many foreign matter. The reason for this is considered to be that the ultraviolet absorber containing an OH group at the terminal accelerates the deterioration of the PET resin. In addition, thin films with an in-plane retardation of 3000 nm or more have good results in rainbow spot observation.

Example of manufacturing polarizer protective film with hard coat layer Example of manufacturing coating liquid for forming hard coat layer The following coating materials were mixed to prepare a coating liquid for forming a hard coat layer. Methyl ethyl ketone: 65.00 mass% Dipentaerythritol hexaacrylate: 27.20 mass% (A-DPH manufactured by Shin-Nakamura Chemical Co., Ltd.) Polyethylene diacrylate: 6.80% by mass (A-400 manufactured by Shin Nakamura Chemical Co., Ltd.) Photopolymerization initiator: 1.00 mass% (Irgacure 184 manufactured by CIBA Specialty Chemicals Co., Ltd.)

Production example of coating liquid for forming low refractive index layer 2,2,2-trifluoroethyl acrylate (45 parts by mass), perfluorooctylethyl acrylate (45 parts by mass), acrylic acid (10 parts by mass), and azoisobutyronitrile (1.5 parts by mass) were fed into the reaction vessel. parts by mass) and methyl ethyl ketone (200 parts by mass), and reacted at 80° C. for 7 hours in a nitrogen atmosphere to obtain a methyl ethyl ketone solution of a polymer with a weight average molecular weight of 20.000. The obtained polymer solution was diluted with methyl ethyl ketone to a solid content concentration of 5% by mass to obtain a fluoropolymer solution. The obtained fluoropolymer solution was mixed as follows to obtain a coating liquid for forming a low refractive index layer. ・Fluoropolymer solution: 44 parts by mass ・1,10-bis(2,3-epoxypropoxy)-2,2,3,3,4,4,5,5, 6,6,7,7,8,8,9,9 -Hexafluorodecane (Fluorite FE-16 manufactured by Kyeisha Chemical Co., Ltd.): 1 part by mass ・Triphenylphosphine: 0.1 parts by mass ・Methyl ethyl ketone: 19 parts by mass

Production example of coating liquid for forming high refractive index layer Feed 80 parts of methyl methacrylate, 20 parts of methacrylic acid, 1 part of azoisobutyronitrile, and 200 parts of isopropyl alcohol into the reaction vessel, and conduct the reaction at 80°C for 7 hours in a nitrogen atmosphere. An isopropyl alcohol solution of a polymer with a weight average molecular weight of 30,000 was obtained. The obtained polymer solution was further diluted with isopropyl alcohol to a solid content of 5% to obtain acrylic resin solution B. Next, the obtained acrylic resin solution was mixed with the following components to obtain a coating liquid for forming a high refractive index layer. ・Acrylic resin solution: 5 parts by mass ・Bisphenol A diglycidyl ether: 0.25 parts by mass ・Titanium oxide particles with an average particle diameter of 20 nm: 0.5 parts by mass ・Triphenylphosphine: 0.05 parts by mass ・Isopropyl alcohol: 14.25 parts by mass

Manufacturing example of surface processed film Example 9 The coating liquid for forming a hard coat layer was applied to one side of the polyester film obtained in Example 1, and dried at 70° C. for 1 minute to remove the solvent. Next, the film coated with the hard coat layer was irradiated with ultraviolet rays using a high-pressure mercury lamp to form a hard coat layer with a thickness of 5 μm, thereby obtaining a laminated polyester film having a hard coat layer. Furthermore, the coating liquid for forming a high refractive index layer obtained by the above method was applied to the hard coat layer and dried at 150° C. for 2 minutes to form a high refractive index layer with a film thickness of 0.1 μm. On this high refractive index layer, the coating liquid H for forming the low refractive index layer obtained by the above method was applied, and dried at 150° C. for 2 minutes to form a low refractive index layer with a film thickness of 0.1 μm, thereby obtaining a laminate with an antireflection layer. Polyester film.

Example 10 The coating liquid for forming the low refractive index layer obtained by the above method was applied to the hard coat surface of the polyester film laminated with the hard coat layer obtained above, and dried at 150° C. for 2 minutes to form a low refractive index layer with a film thickness of 2 μm. , to obtain a laminated polyester film with an anti-reflective layer.

Example 11 Except having used the polyester film as a base material as the polyester film of Example 7, it carried out similarly to Example 9, and obtained the laminated polyester film which has an antireflection layer.

Example 12 Except having used the polyester film as a base material as the polyester film of Example 8, it carried out similarly to Example 9, and obtained the laminated polyester film which has an antireflection layer.

Table 3 shows the evaluation results of the laminated polyester films of Examples 9 to 12. [table 3] Base film Functional layer Rainbow spot observation Haze(%) Reflectivity(%) Example 9 Example 1 Anti-reflective layer ◎ 0.7 1.0 Example 10 Example 1 Low reflective layer ◎ 0.7 1.9 Example 11 Example 7 Anti-reflective layer ○ 0.7 1.0 Example 12 Example 8 Anti-reflective layer ○ 0.7 1.0 [Possibility of industrial application]

According to the present invention, even if a PET resin using raw materials derived from biomass resources is used, a polyester film with high transparency and few foreign matter can be obtained, and a polarizer protective film with good visual visibility and few optical defects can be obtained. Polarizing plates, liquid crystal display devices. Furthermore, the polyester film of the present invention shows good ultraviolet absorption, and can be suitably used in surface protection films, scattering prevention films, windows, etc., for touch substrates, image display devices, etc., in addition to polarizer protective films. Laminating films and decorative films. This can contribute to solving global-scale environmental problems such as concerns about the depletion of fossil fuel resources and the increase in carbon dioxide in the atmosphere, and the possibility of industrial utilization is extremely high.

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Claims (15)

A polyester film characterized by containing a layer composed of a biomass polyethylene terephthalate resin composition containing an ultraviolet absorber, the biomass polyethylene terephthalate resin composition having: B At least one of glycol and terephthalic acid is a polyethylene terephthalate resin using biomass resources as a raw material, and a cyclic imide ester-based ultraviolet absorber. For example, the polyester film of claim 1 has an in-plane retardation of 3000 to 30000 nm. For example, the polyester film of claim 1 or 2 has a ratio of in-plane retardation to thickness direction retardation (Re/Rth) of 0.2 or more and 1.2 or less. The polyester film according to any one of claims 1 to 3, wherein the polyester film has three or more layers including a first surface layer present on the first side, a second surface layer present on the opposite side thereof, and an intermediate layer. A layer of polyester resin, and only the middle layer is a layer composed of a biopolyethylene terephthalate resin composition containing an ultraviolet absorber. For example, the polyester film according to any one of claims 1 to 4 has a light transmittance of 380nm of less than 20%. For example, in the polyester film according to any one of claims 1 to 4, the number of foreign objects with a long diameter of 50 μm or more is 3 to 2000/1000m ² . The polyester film according to any one of claims 1 to 6, wherein the polyester film is composed of polyethylene terephthalate resin using biomass resources as raw materials and having a carboxyl terminal concentration of 50 eq/ton or less. The polyester film according to any one of claims 1 to 7, wherein the carboxyl terminal concentration of the polyethylene terephthalate resin constituting the polyester film is 100 eq/ton or less. A laminated polyester film having a hard coat layer on at least one side of the polyester film according to any one of claims 1 to 8. A polarizer protective film, which uses the polyester film according to any one of claims 1 to 8 as a base film. The polarizer protective film of claim 10 has a hard coating layer. A polarizing plate having the polarizer protective film according to claim 10 or 11 on at least one side of the polarizer. An image display device having the polarizing plate of claim 12. The image display device of claim 13 is a liquid crystal display device. For example, the image display device of claim 13 is an organic EL display device.