JP4604718B2 - Biaxially oriented laminated polyester film for optics - Google Patents

Description

  The present invention has excellent adhesion to the acrylic resin layer when the acrylic resin layer is laminated, interference spots are not conspicuous, and the haze increase is extremely small even in the heat treatment in the post-processing. The present invention relates to a biaxially oriented laminated polyester film (hereinafter sometimes simply referred to as an optical laminated polyester film).

  On the front surface of touch panels, computers, televisions, liquid crystal display devices, and other displays, decorative materials, etc., a base material made of transparent plastic film is laminated with a hard coat layer made of electron beam, ultraviolet light or thermosetting resin. Hard coat film is used. Moreover, as a transparent plastic film of a base material, a transparent biaxially oriented polyester film is generally used, and in order to improve the adhesion between the base material polyester film and the hard coat layer, the intermediate layer is in close contact. In many cases, a property modification layer is provided.

  The hard coat film is required to have temperature, humidity, light durability, transparency, chemical resistance, scratch resistance, antifouling property, and the like. Moreover, since a hard coat film is used for a display, a decoration material, etc., visibility and designability are requested | required. Therefore, in order to suppress glare and iris-like color caused by reflected light when viewed from an arbitrary angle, the antireflection of a multilayer structure in which a high refractive index layer and a low refractive index layer are laminated on top of the hard coat layer. It is common practice to provide a layer.

  However, in recent years, applications such as displays and decorative materials have been required to have a larger screen (larger area) and higher quality, and accordingly, there has been a demand for suppression of iris-like colors (interference fringes) particularly under fluorescent lamps. The level is getting higher. In addition, fluorescent lamps have become a three-wavelength type for daylight color reproducibility, and interference fringes are more likely to occur. Furthermore, there is an increasing demand for cost reduction by simplifying the antireflection layer. Therefore, it is demanded to suppress interference fringes as much as possible even with a hard coat film alone.

The iris color of the hard coat film (interference fringes) is the difference between the refractive index of the base polyester film (eg 1.62 for PET) and the refractive index of the hard coat layer (eg 1.49 for acrylic resin). It is thought to occur because of the large. In order to reduce the difference in refractive index and prevent the occurrence of interference fringes, a method for increasing the refractive index of the hard coat layer by adding metal oxide fine particles to the hard coat layer is disclosed (for example, (See Patent Document 1).
JP-A-7-151902

  However, the addition of metal oxide fine particles to the hard coat layer lowers the original functions of the hard coat layer, such as transparency, chemical resistance, scratch resistance, and antifouling properties. Further, when an antireflection layer is further provided on the hard coat layer, it is necessary to optimize the antireflection layer in accordance with the change in the refractive index of the hard coat layer.

In addition, as another method for suppressing interference fringes in the hard coat layer, an invention in which the width or area ratio of the interference fringes is specified by focusing on thickness spots of films and the like is disclosed (for example, Patent Documents 2 and 3). reference). Furthermore, paying attention to the back surface reflectance of the film itself, a method of laminating a hard coat having a specific hardness while suppressing the back surface reflectance is also disclosed (for example, see Patent Document 4).
JP 2001-71439 A JP 2002-241527 A JP 2002-210906 A

  However, in the methods described in Patent Documents 2 and 3, it is necessary to strictly control the thickness of each layer, which is problematic in terms of productivity. Moreover, in the method described in Patent Document 4, it is necessary to provide a coat layer having a specific refractive index and a specific thickness on the opposite surface of the hard coat layer of the hard coat film in order to reduce the back surface reflectance.

  Biaxially oriented polyester films are widely used as various optical films because of their excellent transparency, dimensional stability, and chemical resistance. In particular, a base film for a prism lens sheet, a base film for a touch panel, a base film for a diffusion plate, a base film for an AR (anti-reflection) film, an anti-crushing film for a CRT, and a plasma display panel used in a liquid crystal display device For applications such as a filter for a filter, excellent strength and dimensional stability are required, and therefore a relatively thick film of 100 μm or more is preferably used. The base film used for such an optical film is required to have excellent transparency and excellent adhesion to the acrylic resin and the base polyester film used during hard coat processing. It is desirable that the thermal stability is excellent, the haze increase is small, and the interference spots are not noticeable.

  However, in general, for example, when an adhesion modified layer and a hard coat layer are sequentially laminated on a biaxially oriented polyester film, the reflected light on the hard coat surface, the interface between the hard coat layer and the adhesion modified layer, and the adhesion modification. There is an interference spot caused by the optical path difference of the reflected light at the interface between the quality layer and the biaxially oriented polyester film, and the interference spot is larger as the difference in the refractive index between the adhesion modified layer and the base film is larger. The smoother the surface of the adhesion modified layer or the substrate film, the clearer it looks. Such interference spots tend to be particularly noticeable when the display is turned off, and this has been a factor that impairs display quality in plasma display panel filters, CRT anti-fracturing films, and the like. Further, even when used as a clear coat on the back surface of a diffusion plate for LCD, reduction of interference spots has been demanded.

  On the other hand, the base film generally contains inert inorganic particles and the like in order to improve the slipperiness (slidability). However, when these particles are included in the polyester film, the unevenness of the film surface not only provides easy lubrication but also makes the interference spots less noticeable, but on the other hand, the most important characteristic of the polyester film substrate for optics Tends to hinder transparency. That is, it has been extremely difficult to reduce interference spots while having high transparency.

Hard coat on one side of a biaxially stretched polyester film (product name: Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) in which a substrate film that does not contain substantial particles is laminated with an adhesion improving layer containing particles to improve display visibility. An optical laminated film in which a layer, a high refractive index antistatic layer, and a low refractive index layer are sequentially laminated has been proposed (see, for example, Patent Document 5). However, in the configuration described in Patent Document 5, although an improvement in the antireflection property is recognized, almost no improvement effect is observed for the interference spots.
JP 2002-267804 A

The reason is presumed as follows.
In general, the refractive index of the biaxially stretched polyester film by an Abbe refractometer is 1.49 to 1.50 in the film thickness direction, and 1.65 to 1.68 in the surface direction of the film. The reflectance of visible light, which is a plane wave, is greatly influenced by the refractive index in the surface direction of the latter. On the other hand, since the refractive index of the adhesion improving layer is generally 1.55 or less, the difference in refractive index between the surface direction of the base film and the adhesion improving layer is still large. Therefore, it is presumed that interference spots cannot be suppressed because the reflectance is large.

  Further, heating at 100 to 150 ° C. may be required in prism processing, hard coat processing, and diffusion layer forming processing. Furthermore, annealing treatment may be performed to improve thermal dimensional stability. However, the conventional optically easy-adhesive film based on the biaxially stretched polyethylene terephthalate that has undergone this process has a cyclic trimer, which is a typical low molecular weight substance contained in polyethylene terephthalate resin, on the film surface. There was a problem that precipitation occurred, resulting in an increase in haze and a white appearance defect. These have led to a reduction in the visibility and quality of the obtained product, and thus improvement has been strongly desired.

  Therefore, in order to prevent the cyclic trimer in the film from precipitating on the film surface, a method of using a polyester resin subjected to solid phase polymerization for both outer layers of a laminated polyester film having a three-layer laminated structure is proposed. (For example, see Patent Document 6). According to this method, the effect of suppressing the increase in the haze after the heat treatment is certainly present, but the effect of improving the interference spots is not recognized. In addition, when a polyester resin subjected to solid phase polymerization is used, there is also a problem that it tends to have a yellowish color tone, which is considered undesirable for optical applications.

  In the present invention, the haze increase suppression effect by heat treatment is due to the low crystallinity of the copolyester. This is presumably because of the effect of absorption by the copolyester layers laminated on both sides.

  In view of the above problems, the object of the present invention is excellent in transparency and adhesion in optical film applications that require an adhesion modified layer on at least one side, particularly from an ultraviolet curable or electron beam curable acrylic resin. When a cured product layer is provided by heat treatment, the increase in the haze of the film is extremely small, excellent in slipperiness, blocking resistance, dimensional stability, and high-quality biaxially oriented laminate for optical use with no noticeable interference spots. It is to provide a polyester film.

The biaxially oriented laminated polyester film for optical use that can solve the above-mentioned problems is as follows.
That is, the optically biaxially oriented laminated polyester film of the present invention is a polyester layer comprising a composition containing a polyester layer (A layer) containing substantially no particles and a copolymer polyester on both sides of the substrate. (B layer) was laminated, and further a laminated polyester film adhesion comprising modifying layer (C layer) provided a composition comprising an adhesion modified resin and particles of at least one surface of the layer B, the polyester The layer (A layer) is made of polyethylene terephthalate, and the copolymer polyester contained in the polyester layer (B layer) contains terephthalic acid or an ester-forming derivative thereof as an aromatic dicarboxylic acid component, and (a) ethylene glycol and a glycol component. (B) It is composed of a branched aliphatic glycol component or an alicyclic glycol, and has a surface direction refractive index ((Nx (longitudinal Direction refractive index) + Ny (width direction refractive index)) / 2) is 1.57 to 1.63, and has endothermic melting peaks at temperatures of (I) ° C., (II) ° C., and (III) ° C. The respective peak temperatures are measured by a differential scanning calorimeter (DSC) after heating from 30 ° C. to 300 ° C. at 5 ° C./min, and satisfy the following formulas (1), (2) and (3): And
200 <I ≦ II ≦ III < 259.3 (1)
8 <(III-II) <35 (2)
25 <(III-I) <58 (3)

In this case, it is preferable that the branched aliphatic glycol component is neopentyl glycol and the alicyclic glycol is 1,4-cyclohexanedimethanol.
Also. The copolymerized polyester is composed of ethylene glycol and neopentyl glycol as glycol components, and the neopentyl glycol is preferably 1 to 40 mol% based on the total glycol components.

  The biaxially oriented laminated polyester film for optical use preferably has a haze increase value of 1% or less after heating at 170 ° C. for 10 minutes.

  The biaxially oriented laminated polyester film for optics preferably has a total light transmittance of 90% or more and a haze of 1% or less.

  Moreover, it is preferable that the static friction coefficient μs of the optically biaxially oriented laminated polyester film is 1.0 or less.

  The biaxially oriented laminated polyester film for optics preferably has a heat shrinkage rate of 1.8% or less in the width direction and the longitudinal direction.

  Moreover, the hardened | cured material layer (D layer) which consists of an ultraviolet curable type or an electron beam curable acrylic resin is provided in the surface of C layer of the said biaxially-oriented laminated polyester film for optics, It is characterized by the above-mentioned.

  The melting peak at the temperature of (III) ° C. is mainly related to the homopolyester used for the A layer and the B layer, and the melting peak at the temperature of (II) ° C. is mainly used for the B layer. The present invention relates to a polymerized polyester or a mixture of the copolymerized polyester and the homopolyester described above. The melting peak at a temperature of (I) ° C. shows a thermal history that is considered to be melting of crystals stabilized by heat treatment in heat setting after stretching in the width direction.

  Moreover, in said Formula (2), it is the range of 8-35 degreeC. Further, it is more preferable that the lower limit is 10 ° C. and the upper limit is 30 ° C. When the above value is less than 8 ° C., the interference fringe reduction effect is poor, and when it is greater than 35 ° C., the elastic modulus of the B layer is extremely lowered, resulting in poor slipping and causing problems such as scratches and blocking. .

  In said Formula (3), it is the range of 25-58 degreeC. More preferably, the lower limit is 30 ° C., and the upper limit is 50 ° C. When the above value is less than 25 ° C., the elastic modulus of the B layer is extremely lowered, so that slippage is worsened, and problems such as scratches and blocking occur. On the other hand, when the temperature is higher than 58 ° C., the heat shrinkage rate at the time of heating increases, which causes a problem.

  The biaxially oriented laminated polyester film for optics of the present invention is a composition comprising a biaxially oriented polyester film (A layer) substantially free of particles as a base material and a specific copolymer polyester on both surfaces of the base material. The polyester layer (B layer) is laminated, and further, an adhesion modifying layer (C layer) made of a composition containing an adhesion modifying resin and particles is provided on at least one side of the B layer. In addition, when the cured product layer (D) made of an ultraviolet curable or electron beam curable acrylic resin is heat treated and laminated, the adhesiveness with the cured product layer (D) is excellent, There is an advantage that the haze increase is extremely small and interference spots are not noticeable.

Hereinafter, the biaxially oriented laminated polyester film for optics of the present invention will be described in detail.
The copolymer polyester used in the present invention is a base film material made of a copolymer polyester composed of an aromatic dicarboxylic acid component and a glycol component containing ethylene glycol and a branched aliphatic glycol and / or alicyclic glycol. Or 100% by mass.

  In the copolymerized polyester, the aromatic dicarboxylic acid component is mainly composed of terephthalic acid or an ester-forming derivative thereof. The amount of the terephthalic acid component with respect to the total dicarboxylic acid component is 70 mol% or more, preferably 85 mol% or more, particularly preferably. Is 95 mol% or more, and particularly preferably 100 mol%.

  Examples of the branched aliphatic glycol include neopentyl glycol, 1,2-propanediol, and 1,2-butanediol. Examples of the alicyclic glycol include 1,4-cyclohexanedimethanol and tricyclodecane dimethylol. Among these, neopentyl glycol and 1,4-cyclohexanedimethanol are particularly preferable, and are also preferable from the viewpoint of reducing interference spots when laminating a hard coat layer, which is a subject of the present invention, and reducing haze increase during post-processing. .

Furthermore, you may use together the following dicarboxylic acid component and / or glycol component as a copolymerization component in the said copolyester as needed, if necessary.
Other dicarboxylic acid components that can be used in combination with terephthalic acid or its ester-forming derivatives include (1) isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid Aromatic dicarboxylic acids such as acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic acid or their ester-forming derivatives, (2) oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid Aliphatic dicarboxylic acids such as fumaric acid and glutaric acid or ester-forming derivatives thereof; (3) alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid or ester-forming derivatives thereof; (4) p-oxybenzoic acid; Oxycarboxylic acids such as oxycaproic acid or their esters And forming derivatives.

  On the other hand, examples of other glycol components that can be used together with ethylene glycol and branched aliphatic glycol and / or alicyclic glycol include 1,3-propanediol, 1,4-butanediol, pentanediol, and hexane. Examples include aliphatic glycols such as diols, aromatic glycols such as bisphenol A and bisphenol S, and ethylene oxide adducts thereof, diethylene glycol, and triethylene glycol. Furthermore, if necessary, the copolymerized polyester may be further copolymerized with a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane.

  Examples of the catalyst used for producing the copolymer polyester include alkaline earth metal compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, titanium / silicon composite oxides, and germanium compounds. . Among these, an aluminum compound, an antimony compound, and a germanium compound are preferable from the viewpoint of catalytic activity. When manufacturing the said copolyester, you may add a phosphorus compound as a heat stabilizer. When using a heat stabilizer, phosphoric acid, phosphorous acid, etc. are preferable, for example.

  The copolyester preferably has an intrinsic viscosity of 0.50 dl / g or more, more preferably 0.55 dl / g or more, particularly preferably 0, from the viewpoint of mechanical strength and film formation stability. .60 dl / g or more. If the intrinsic viscosity is less than 0.50 dl / g, the film tends to break during film production, and the productivity tends to be lowered.

The copolymer polyester used in the present invention has, for example, ethylene glycol (EG) and neopentyl glycol (NPG) as main components as a glycol component. It is preferable that it is 40 mol%.
Furthermore, the composition ratio of NPG with respect to the total glycol component is more preferably 9 to 28 mol%, and further preferably 12 to 25 mol%. When the above composition ratio is less than 9 mol%, the interference fringe reduction effect is poor, and when it is higher than 28 mol%, the elastic modulus of the B layer is extremely lowered, resulting in poor slipping, and problems such as scratches and blocking. Arise.

  When the composition ratio of NPG is less than 1 mol%, when used as a laminated film of the present invention, the effect of reducing interference spots cannot be obtained. On the other hand, when the composition ratio of NPG exceeds 40 mol%, it is difficult to increase the degree of polymerization and it takes a long time to reach a predetermined intrinsic viscosity. Therefore, the color tone deteriorates due to the heat history during that period. Further, if the composition ratio of NPG is too high, the predetermined viscosity may not be reached. Furthermore, when a film is produced from the obtained copolyester, the film has an excessively high thermal shrinkage rate or a decrease in mechanical strength.

  In addition, an oxidation stabilizer, a UV absorber, and the like may be added as necessary when the polyethylene terephthalate resin and the copolyester used in the present invention are manufactured, as long as the object of the present invention is not hindered.

  Polyethylene terephthalate containing substantially no particles is used for the resin used for the B layer of the present invention and the resin blended as necessary with the A layer and the C layer. The phrase “substantially no particles are contained in the substrate film” means, for example, in the case of inorganic particles, a content that is below the detection limit when inorganic elements are quantified by fluorescent X-ray analysis. This is because contaminant components derived from foreign substances may be mixed without intentionally adding the particles to the adhesion modified layer.

  Moreover, the intrinsic viscosity of the resin pellet used for the polyester film of the present invention is preferably in the range of 0.45 to 0.75 dl / g. When the intrinsic viscosity is lower than 0.45 dl / g, breakage during film production tends to occur frequently, and the tear resistance tends to deteriorate. On the other hand, if the intrinsic viscosity is greater than 0.75 dl / g, the increase in the filtration pressure tends to be large and high-precision filtration tends to be difficult.

  Since the biaxially stretched polyester film used in the present invention is required to have excellent strength, dimensional stability and ease of handling, a film having a thickness of 50 μm or more, more preferably 100 μm or more is suitable.

  Although the thickness of A layer and C layer is not specifically limited, The sum total of the thickness of B layer laminated | stacked on both sides of A layer shall be 3 to 30% of the thickness of the whole film, Furthermore, it shall be 5 to 20% of range. preferable. When this value is less than 3%, the haze increase suppression effect by heat treatment is not sufficient, and a haze increase is accompanied. On the other hand, if this value is larger than 30%, the heat shrinkage rate is increased, which is not preferable. Furthermore, the difference in thickness between the B layers stacked on both sides of the A layer is preferably 2 μm or less. If it is 2 μm or more, good flatness cannot be obtained, and warping during heating becomes a problem. In this invention, in order to ensure high transparency, it is preferable not to contain the particle | grains for providing slipperiness in a film base material.

  Even if particles for the purpose of imparting slipperiness to the film base are not added, it is good if the adhesion modified layer laminated in-line is made slippery by containing fine particles with a uniform particle size. Therefore, it is not necessary to add particles to the polyester base film.

  In order to transfer the polyester raw material (pellet), it is usually carried out by air using a predetermined pipe. The air used at this time is preferably purified air using a HEPA filter in order to prevent dust contamination. As the HEPA filter, a filter having a performance of cutting 95% or more of dust having a nominal filtration accuracy of 0.5 μm or more is preferably used.

  The polyester polyester for the A layer and the C layer is mixed with the copolymerized polyester as necessary and polyethylene terephthalate pellets at a predetermined ratio, and the polyethylene terephthalate pellets for the B layer are dried and then fed to a known melt extruder. Then, it is extruded into a sheet form from a slit-shaped die and cooled and solidified on a casting roll to form an unstretched film.

In this case, it is preferable to perform high-precision filtration in order to remove foreign substances contained in the resin at any place where the molten resin is maintained at about 280 ° C. during melt extrusion.
The filter medium used for high-precision filtration of the molten resin is not particularly limited, but the filter medium of the stainless sintered body is excellent in removing aggregates and high melting point organic substances mainly composed of Si, Ti, Sb, Ge, and Cu. Therefore, it is preferable.

Furthermore, the filter particle size (initial filtration efficiency: 95%) of the filter medium is preferably 20 μm or less, particularly preferably 15 μm or less. When the filter particle size (initial filtration efficiency: 95%) of the filter medium exceeds 20 μm, foreign matters having a size of 20 μm or more cannot be sufficiently removed.
Productivity may be reduced by performing high-precision filtration of molten resin using a filter medium having a filter particle size (initial filtration efficiency: 95%) of 20 μm or less. However, a film with few protrusions due to coarse particles may be used. It is an important process in obtaining.

  More specifically, after drying the polyester raw material for each layer, it is supplied to a known melt laminating extruder, extruded from a slit-shaped die into a sheet, and cooled and solidified on a casting roll to produce an unstretched film. . That is, using two extruders, a three-layer manifold, or a merging block, film layers constituting each layer are laminated, two sheets are extruded from a die, and cooled with a casting roll to produce an unstretched film. In this case, it is preferable to perform high-precision filtration as described above in order to remove foreign substances contained in the resin at any location where the molten resin is maintained at about 280 ° C. during melt extrusion.

The obtained unstretched sheet is stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented PET film. In order to obtain the optically biaxially oriented laminated polyester film of the present invention, the refractive index ΔNx after uniaxial stretching is preferably 0.03 to 0.12, more preferably 0.05 to 0.08 or less. Note that ΔNx is a parameter represented by the following equation.
ΔNx = Nx− (Ny + Nz) / 2

  When the value of ΔNx is smaller than 0.04, the film thickness uniformity deteriorates. On the other hand, if it is larger than 0.12, the refractive index in the surface direction after biaxial stretching becomes large, and therefore interference fringes are conspicuously undesirable.

  Thereafter, an adhesion modifying layer is applied to at least one surface, and the edge of the film is further gripped with a clip, guided to a hot air zone heated to 80 to 180 ° C., dried, and 2.5 in the width direction. Stretch to ~ 5.0 times. Then, it guide | induces to the heat processing zone of 180-245 degreeC, and heat-processes for 1 to 60 seconds, and completes crystal orientation.

  The heat treatment zone temperature at this time is an important item that affects the interference fringe reduction effect. The temperature of the heat treatment zone is preferably the melting peak temperature (II) ° C. ± 20 ° C., preferably (II) ° C. ± 15 ° C. described in the claims of the present invention. By setting the heat treatment temperature to around the melting peak temperature (II) ° C. in this way, the homopolyester layer of the intermediate layer is crystallized, the elastic modulus is improved and the heat shrinkage property is lowered, so that stable film properties are obtained. In addition, since the outermost layer is exposed to a temperature close to the melting peak, crystal orientation proceeds in the direction of decay, the refractive index of the outermost layer is lowered, and interference fringes are reduced. That is, fundamental film characteristics are controlled by the intermediate layer, and optical characteristics such as interference fringes are controlled by the outermost layer.

When the temperature of the heat treatment zone is lower than (II) ° C.-20 ° C., the thermal shrinkage rate of the film itself increases and the interference fringe reduction effect is not sufficient. On the other hand, when the temperature is higher than (II) ° C. + 20 ° C., the orientation collapse of the outermost layer proceeds excessively, and the elastic modulus is extremely lowered, so that the slippage becomes worse, and problems such as scratches and blocking occur.

  Moreover, you may perform a 1-12% relaxation process in the width direction or a longitudinal direction as needed in this heat setting process process. The temperature during the relaxation treatment can be arbitrarily set in the range of 140 to 230 ° C., but is preferably 160 to 200 ° C. from the viewpoint of shrinkage characteristics and flatness maintenance of the film.

  The adhesion modifying layer can be applied by any known method. Examples include reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method and curtain coating method. These methods can be performed alone or in combination.

The step of applying the coating solution may be a normal coating step, that is, a step of applying to a base film that has been biaxially stretched and heat-fixed, but is preferably applied during the manufacturing process of the film. More preferably, it is applied to the substrate film before the crystal orientation is completed. The solid content concentration in the aqueous solution is usually 30% by mass or less, preferably 10% by mass or less. The aqueous coating solution is applied so that 0.01 to 5 g, preferably 0.2 to 4 g is adhered per 1 m ² of the running film. The film coated with the aqueous coating solution is guided to a tenter for stretching and heat setting, and heated there to form a stable film by a thermal crosslinking reaction, and becomes a polyester-based film. In order to obtain sufficient adhesion to the infrared absorption layer or hard coat layer, the coating amount at this time is 0.01 g / m ² or more per 1 m ^{2 of} film, and heat treatment at 100 ° C. for 1 minute or more is required. It is. The cleanliness when applying the coating liquid is preferably class 1000 or less in order to reduce the adhesion of dust.

As described above, the adhesion modified layer is laminated on the biaxially stretched polyester film for hard coat of the present invention. Examples of the resin for the adhesion modified layer include copolymer polyester resins, polyurethane resins, acrylic resins, styrene-maleic acid graft polyester resins, acrylic graft polyester resins, and the like, and at least one or more are used. It is preferable. Among these, a resin composed of a copolyester resin and a polyurethane resin, and a styrene-maleic acid graft polyester resin are particularly preferable because of excellent adhesion.
Regarding the adjustment of the coating solution used for forming the adhesion improving layer, an example of a coating solution comprising a copolymerized polyester resin and a polyurethane resin will be described below.

  The copolymerized polyester resin used in the adhesion modified layer of the present invention has a branched glycol component as a constituent component. Examples of the branched glycol component herein include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, and 2-methyl-2-butyl-1,3- Propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2 -Di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol And the like.

  The branched glycol component is contained in the total glycol component in a proportion of preferably 10 mol% or more, more preferably 20 mol% or more. As the glycol component other than the above compounds, ethylene glycol is most preferable. If it is a small amount, diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4 cyclohexanedimethanol or the like may be used.

  As the dicarboxylic acid component contained as a constituent component in the copolymer polyester resin, terephthalic acid and isophthalic acid are most preferable. If the amount is small, other dicarboxylic acids; diphenylcarboxylic acid and 2,6-naltalenedicarboxylic acid aromatic dicarboxylic acid may be added and copolymerized.

  In addition to the dicarboxylic acid component, 5-sulfoisophthalic acid is preferably used in the range of 1 to 10 mol% in order to impart water dispersibility. For example, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfo Examples include naphthalene isophthalic acid-2,7-dicarboxylic acid and 5- (4-sulfophenoxy) isophthalic acid and salts thereof.

  The polyurethane resin used in the adhesion modified layer of the present invention is, for example, a resin containing a block type isocyanate group, in which a terminal isocyanate group is blocked with a hydrophilic group (hereinafter referred to as a block), a heat-reactive water-soluble type Examples include urethane. Examples of the isocyanate group blocking agent include bisulfites and sulfonic acid group-containing phenols, alcohols, lactam oximes and active methylene compounds. The blocked isocyanate group makes the urethane prepolymer hydrophilic or water-soluble. When heat energy is applied to the resin during drying or heat setting during film production, the blocking agent is released from the isocyanate group, so the resin fixes a water-dispersible copolyester resin mixed in a self-crosslinked stitch. And reacts with the terminal groups of the resin. The resin under preparation of the coating solution is hydrophilic and has poor water resistance, but when the thermal reaction is completed by coating, drying and heat setting, the hydrophilic group of the urethane resin, that is, the blocking agent is released, so the water resistance is good. A coating film is obtained. Among the above blocking agents, bisulfites are most preferred as those that are suitable for heat treatment and heat treatment and are widely used industrially.

  The chemical composition of the urethane prepolymer used in the above resin is (1) an organic polyisocyanate having two or more active hydrogen atoms in the molecule, or a molecular weight having at least two active hydrogen atoms in the molecule. 200 to 20,000 compounds, (2) an organic polyisocyanate having two or more isocyanate groups in the molecule, or (3) a chain extender having at least two active hydrogen atoms in the molecule. The resulting compound has a terminal isocyanate group.

  The compound (1) generally known is a compound containing two or more hydroxyl groups, carboxyl groups, amino groups or mercapto groups in the terminal or molecule, and particularly preferred compounds include polyether polyols. And polyether ester polyols.

  As the polyether polyol, for example, a compound obtained by polymerizing ethylene oxide and alkylene oxides such as propylene oxide, styrene oxide and epichlorohydrin, or the like, or obtained by performing random polymerization, block polymerization or addition polymerization to a polyhydric alcohol. .

  Examples of the polyester polyol and the polyether ester polyol mainly include linear or branched compounds. Polyvalent saturated or unsaturated carboxylic acids such as succinic acid, adipic acid, phthalic acid and maleic anhydride, or the carboxylic acid anhydride, ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1 Condensation with polyvalent saturated and unsaturated alcohols such as 1,6-hexanediol and trimethylolpropane, polyalkylene ether glycols such as relatively low molecular weight polyethylene glycols and polypropylene glycols, or mixtures of these alcohols Can be obtained.

  Furthermore, polyesters obtained from lactones and hydroxy acids can be used as polyester polyols, and polyether esters obtained by adding ethylene oxide or propylene oxide to polyesters prepared in advance can also be used as polyether ester polyols. .

Examples of the organic polyisocyanate (2) include isomers of toluylene diisocyanate, aromatic diisocyanates such as 4,4-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4. -Alicyclic diisocyanates such as dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, or a single or a plurality of these compounds with trimethylolpropane and the like in advance. Examples include added polyisocyanates.

  Examples of the chain extender having at least two active hydrogens in (3) above include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,6-hexanediol, glycerin, trimethylolpropane, and Examples include polyhydric alcohols such as pentaerythritol, diamines such as ethylenediamine, hexamethylenediamine, and piperazine, amino alcohols such as monoethanolamine and diethanolamine, thiodiglycols such as thiodiethylene glycol, and water.

  In order to synthesize the urethane polymer of the above (3), it is usually 5 minutes to several times at a temperature of 150 ° C. or less, preferably 70 to 120 ° C., by a single-stage or multi-stage isocyanate polyaddition method using the chain extender. Let react for hours. The ratio of isocyanate groups to active hydrogen atoms can be freely selected as long as it is 1 or more, but it is necessary that free isocyanate groups remain in the obtained urethane prepolymer.

  Furthermore, the content of free isocyanate groups may be 10% by mass or less, but considering the stability of the urethane polymer aqueous solution after being blocked, it is preferably 7% by mass or less.

  The urethane prepolymer obtained is preferably blocked using bisulfite. Mix with aqueous bisulfite solution and allow reaction to proceed with good agitation for about 5 minutes to 1 hour. The reaction temperature is preferably 60 ° C. or lower. Thereafter, it is diluted with water to an appropriate concentration to obtain a heat-reactive water-soluble urethane composition. When the composition is used, it is prepared to have an appropriate concentration and viscosity. Usually, when heated to about 80 to 200 ° C., the bisulfite of the blocking agent is dissociated and the active isocyanate group is regenerated. A polyurethane polymer is produced by a polyaddition reaction that occurs within or between the molecules of the polymer, and has the property of causing addition to other functional groups.

As an example of the resin (B) containing a block-type isocyanate group described above, a trade name Elastron manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. is typically exemplified. Elastolone is a compound in which an isocyanate group is blocked with sodium bisulfite, and is water-soluble due to the presence of a carbamoylsulfonate group having strong hydrophilicity at the molecular end.
When the coating liquid is prepared by mixing the copolymerized polyester resin (A) containing a branched glycol component and the resin (B) containing a block type isocyanate group used in the present invention, the resin (A) and the resin The mass ratio of (B) is preferably (A) :( B) = 90: 10 to 10:90, more preferably (A) :( B) = 80: 20 to 20:80. If the ratio of the said resin (A) with respect to solid content mass is less than 10 mass%, the applicability | paintability to a base film is unsuitable, and the adhesiveness between a surface layer and this film will become inadequate. On the other hand, when it is less than 10% by mass, practical adhesion cannot be obtained in a UV curable hard coat.

  A catalyst may be added to the aqueous coating solution used in the present invention in order to promote the thermal crosslinking reaction, such as inorganic substances, salts, organic substances, alkaline substances, acidic substances and metal-containing organic compounds. These chemicals are used. Moreover, in order to adjust pH of aqueous solution, you may add an alkaline substance or an acidic substance.

  When applying the aqueous coating solution to the surface of the base film, a known anionic surfactant and nonionic surfactant are required to increase the wettability of the film and coat the coating solution uniformly. An amount can be added and used. As the solvent used in the coating solution, alcohols such as ethanol, isopropyl alcohol and benzyl alcohol may be mixed in addition to water until the ratio of the total coating solution is less than 50% by mass. Furthermore, if it is less than 10 mass%, you may mix in the range which can melt | dissolve organic solvents other than alcohol. However, the total of alcohols and other organic solvents in the coating solution is less than 50% by mass.

  If the addition amount of the organic solvent is less than 50% by mass, the drying property is improved at the time of coating and drying, and the appearance of the coating film is improved as compared with the case of using only water. If it exceeds 50% by mass, the evaporation rate of the solvent is high, the coating solution concentration changes during coating, the viscosity rises and the coating property is lowered, and there is a risk of causing poor appearance of the coating film, Furthermore, there is a risk of fire. The solution viscosity of the coating solution is preferably 1.0 PaS (Pascal Sec) or less. When the pressure is 1.0 PaS (Pascal Sec) or higher, streaky coating thickness spots are likely to occur.

  In the present invention, since a lubricant intended to impart easy lubricity is not added to the base film, it is preferable to add particles to the aqueous coating solution to form appropriate protrusions on the film surface. Examples of such particles include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide and other inorganic particles, crosslinked polymer particles, oxalic acid There may be mentioned organic particles such as calcium. Of these, silica is most suitable because it has a relatively close refractive index to that of the polyester resin and can easily provide high transparency.

  The average particle size of the particles added to the aqueous coating solution is usually 1.0 μm or less, preferably 0.5 μm or less, more preferably 0.1 μm or less. When the average particle diameter exceeds 1.0 μm, the film surface becomes rough and the transparency of the film tends to be lowered. The particle content contained in the coating liquid is usually 60% by mass or less, preferably 50% by mass or less, and more preferably 40% by mass or less after application and drying. Add as follows. When the particle content of the coating film exceeds 60% by mass, the adhesion of the film may be impaired.

  Two or more kinds of the above particles may be blended in the film, or the same kind of particles having different particle diameters may be blended. In any case, it is preferable that the average particle diameter of the whole particle and the total content satisfy the above-described range. When applying the coating solution, it is necessary to dispose a filter medium so that the coating solution is precisely filtered just before coating in order to remove coarse aggregates of particles in the coating solution.

  The filter medium for microfiltration of the coating solution used in the present invention needs to have a filtration particle size of 25 μm or less (initial filtration efficiency: 95%). When the particle size is 25 μm or more, coarse agglomerates cannot be removed sufficiently, and many coarse agglomerates that could not be removed spread the particles in the adhesion-modified layer when uniaxially stretched or biaxially stretched after coating, drying. It is recognized as an aggregate of 100 μm or more, and as a result, many optical defects are generated.

  The type of filter medium for microfiltration of the coating solution is not particularly limited as long as it has the above performance, and examples thereof include a filament type, a felt type, and a mesh type. The material of the filter medium for finely filtering the coating solution has the above-described performance and is not particularly limited as long as it does not adversely affect the coating solution, and examples thereof include stainless steel, polyethylene, polypropylene, and nylon.

  Various additives such as an antistatic agent, a pigment, an organic filler, and a lubricant may be mixed in the composition of the aqueous coating solution as long as the effect is not lost. Furthermore, since the coating solution is aqueous, other water-soluble resins, water-dispersible resins, emulsions, and the like may be added to the coating solution in order to improve performance as long as the contribution effect is not lost.

  The film direction refractive index [(Nx (longitudinal direction refractive index) + Ny (width direction refractive index) / 2)] of the film obtained as described above is in the range of 1.57 to 1.63. More preferably, it is .59 to 1.62. When this value is lower than 1.57 or higher than 1.62, the difference in refractive index from the hard coat increases, and reflection at the interface increases, so the interference fringes after applying the hard coat are tight. It becomes visible and becomes a problem. Moreover, in order to obtain this film refractive index, it can be achieved by film formation by the above method, but in particular, the composition ratio of the copolyester used in the B layer, the temperature at the first and second axes, the magnification, The heat treatment temperature in the heat setting zone, the treatment time, the temperature and the relaxation rate during the relaxation treatment are mainly contributing.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to these Examples.
In addition, the characteristic of the biaxially stretched polyester for hard coats of the present invention was measured according to the following method.

(1) Endothermic melting peak [melting point (Tm)]
Based on JIS K7121, the sample was measured in dry nitrogen using DSC6200 (Seiko Instruments Inc.), and melting peak temperatures I, II and III were measured. A polyester film sample piece (10 mg) was placed in an aluminum pan and heated at 30 ° C. to 300 ° C. at 20 ° C./min to output a DSC curve. The endothermic melting peak temperature was read in accordance with “How to obtain the melting temperature” described in JIS K7121.

(2) Measurement of total light transmittance The easily adhesive films for optics obtained in Examples and Comparative Examples were measured using a haze meter (Nippon Denshoku model TNDH2000).

(3) Measurement of haze value The easily adhesive films for optics obtained in Examples and Comparative Examples were measured using a haze meter (Nippon Denshoku model TNDH2000).
The haze increase value was determined from the difference in haze value before and after heat treatment (170 ° C. for 10 minutes).

(4) Interference fringe evaluation method A hard coat agent (Seika Beam EXF01 (B)) manufactured by Dainichi Seika Co., Ltd. is used on the easy-adhesion surface on the A layer side of the optical easy-adhesion films obtained in Examples and Comparative Examples. After removing the solvent by drying at 70 ° C. for 1 minute, a hard coat layer having a thickness of 3 μm was formed under the conditions of 200 mJ / cm ² , irradiation distance 15 cm, and traveling speed 5 m / min with a high-pressure mercury lamp. A coated film was obtained.

Next, a black glossy tape is attached to the opposite side of the hard coat layer for easy viewing, and the three-wavelength light from the hard coat layer side of the film (National Parrook, three-wavelength daylight white (F.L 15EX-N 15W)) Was observed, the intensity of the plaque was observed, and evaluated according to the following criteria.
○: Almost no interference spots can be confirmed Δ: Thin interference fringes are confirmed ×: Interference fringes are clearly observed

(5) Friction coefficient μs
Based on JIS-K 7125, the following conditions evaluated. Flat plate test piece: 130 mm in width and 250 mm in length, using the surface on the side in contact with the cooling roll after melt extrusion. Sled (table side) test piece: 120 mm wide and 120 mm long, using the opposite side of the flat plate test piece. Measurement atmosphere: 23 ° C., 50% RH, warpage mass: 200 gf, test speed: 150 mm / min.

(6) Adhesion evaluation method of hard coat layer A hard coat agent (Seika Beam EXF01 (B)) manufactured by Dainichi Seika Co., Ltd. is applied to the easy-adhesion surface on the A-layer side of the optical easy-adhesion films obtained in Examples and Comparative Examples. After coating with # 8 wire bar and drying at 70 ° C for 1 minute to remove the solvent, a hard coat layer with a thickness of 3 µm was formed with a high-pressure mercury lamp under the conditions of 200 mJ / cm ² , irradiation distance of 15 cm, and traveling speed of 5 m / min. did.
Adhesiveness of the obtained film was determined by a test method according to JIS-K5400 8.5.1. Specifically, 100 grid-like cuts that penetrated through the hard coat layer and the adhesion modifying layer and reached the base film were made using a cutter guide with a gap interval of 2 mm. Next, a cellophane adhesive tape (No. 405 manufactured by Nichiban Co., Ltd., width of 24 mm) was attached to the cut surface of the grid pattern, rubbed with an eraser to completely adhere, and then peeled off vertically to determine the adhesion from the following formula. It was. Adhesion (%) = (1-peeling area / evaluation area) × 100

(7) Film refractive index Thickness direction refractive index (Nz), width direction refractive index (Ny) and longitudinal direction refractive index (Nx)
Attaching a polarizing plate to an eyepiece using an Abbe refractometer 4T manufactured by Atago Co., Ltd., adjusting the direction of the polarizing plate and the direction of the film, respectively, the refractive index in the film thickness direction (Nz), the refractive index in the width direction (Ny) The refractive index (Nx) in the longitudinal direction was measured. Jodomethane was used as an intermediate solution. The refractive index in each direction was measured on both sides of the film with n = 3 for each sample, and the average value was taken as the refractive index in each direction.

Here, the width direction means a direction perpendicular to the roll unwinding direction, and the longitudinal direction means a direction parallel to the roll unwinding direction. The surface direction refractive index was determined as follows.
Refractive index in plane direction = (Nx + Ny) / 2

(8) Blocking resistance Two sample films cut to a width of 50 mm are stacked so that the surfaces are different, and after being treated at 60 ° C. × 80% RH for 20 hours under a load of 30 kg / cm ² , the coated surface Measure the peel strength between the surface and the non-coated surface and evaluate the blocking resistance as follows.
○: Peeling force ≦ 20 gf (good blocking resistance)
Δ: 20 gf <peeling force ≦ 50 gf (slightly poor blocking resistance)
×: 50 gf <Peeling force (Poor blocking resistance)

(9) Thermal contraction rate In the direction to be measured, the film is cut into a width of 10 mm and a length of 250 mm, marked at intervals of 200 mm, and a mark interval A is measured under a constant tension of 5 gf. Next, the film is placed in an oven in an atmosphere of 150 ° C., subjected to heat treatment at 150 ± 3 ° C. for 30 minutes under no load, and the interval B between the marks is measured under a constant tension of 5 gf. The thermal shrinkage rate was calculated from the following formula.
Thermal contraction rate (%) = (A−B) / A × 100

Example 1
(Production of copolymer polyester resin (a))
In a first esterification reaction vessel containing a reactant in advance, 100 mol% of high-purity terephthalic acid (TPA) as a dicarboxylic acid component, 70 mol% of ethylene glycol (EG) as a glycol component, and neopentyl glycol (NPG) ) And a slurry in which the molar ratio of all glycol components to the dicarboxylic acid component is 2.0 was continuously supplied as a produced polymer so that the production amount was 1 ton / hr. Furthermore, antimony trioxide was continuously supplied to the first esterification reaction can as an ethylene glycol solution of 12 g / L so that the Sb content was 0.025 mol% with respect to the produced polymer. While stirring at a pressure of 0.05 MPa, the reaction was carried out at about 250 ° C. for an average residence time of about 3 hours.

  This reaction product was transferred to a second esterification reaction can, and the reaction was carried out for about 1 hour as an average residence time at about 260 ° C. with stirring at a can internal pressure of 0.05 MPa. Next, this reaction product was transferred to a third esterification reaction can, and the reaction was carried out to a predetermined reactivity at about 260 ° C. with stirring at a can internal pressure of 0.05 MPa.

  The oligomer obtained at this time had an acid value of the end group of 380 eq / ton. To this oligomer, magnesium acetate tetrahydrate in an ethylene glycol solution of 50 g / L was used, and trimethyl phosphate was 65 g / L so that the Mg content (M) was 0.17 mol% with respect to the produced polymer. As an ethylene glycol solution, sodium acetate as a 10 g / L ethylene glycol solution so that the P content (P) is 0.079 mol% (M / P = 2.2; molar ratio) with respect to the produced polymer. Separately, cobalt acetate tetrahydrate as a 50 g / L ethylene glycol solution so that the Na content is 0.018 mol% with respect to the produced polymer, and 0.0035 mol% with respect to the produced polymer. Were continuously fed to the third esterification reaction can through the feed port.

  This esterification reaction product is continuously supplied to the first polycondensation reaction vessel, and is stirred at about 265 ° C. and 35 hPa for about 1 hour, and then stirred in the second polycondensation reaction vessel at about 270 ° C. and 5 hPa. The polycondensation was carried out for about 1 hour at about 280 ° C. and 0.5 to 1.5 hPa with stirring in the final polycondensation reaction vessel. After the polycondensation, it was passed through a tubular polymer filter with a leaf made of stainless steel long fibers having a removal rate of 95% or more and a filtration accuracy of 60 μm. Next, the molten resin was extracted in a strand form from the die, cooled with water in a water tank, and then cut into a chip shape to obtain a copolyester having an intrinsic viscosity (IV) of 0.74 dl / g.

(Copolymerized polyester b)
Copolymerized polyester resin having a glycol component containing alicyclic glycol and 30.5 mol% of 1,4-cyclohexanedimethanol (CHDM) and no inherent viscosity (IV) of 0.75 dl / g (Toyobo Co., Ltd.) Manufactured by FP301).

(Polyethylene terephthalate resin)
A polyethylene terephthalate resin (ME-553, manufactured by Toyobo Co., Ltd.) having an intrinsic viscosity (IV) not containing 0.62 dl / g particles was used.

(Adjustment of coating solution for adhesion modified layer formation)
A coating solution for forming an adhesion modified layer was prepared according to the following method. A reaction vessel was charged with 95 parts by weight of dimethyl terephthalate, 95 parts by weight of dimethyl isophthalate, 35 parts by weight of ethylene glycol, 145 parts by weight of neopentyl glycol, 0.1 part by weight of zinc acetate and 0.1 part by weight of antimony trioxide. The transesterification was carried out over 3 hours. Next, 6.0 parts by mass of 5-sodium isophthalic acid was added, an esterification reaction was performed at 240 ° C. over 1 hour, and then a polycondensation reaction was performed to obtain a polyester resin. 6.7 parts by mass of a 30% by mass aqueous dispersion of the obtained polyester resin, 20% by mass aqueous solution of a self-crosslinking polyurethane resin containing an isocyanate group blocked with sodium bisulfite (Daiichi Kogyo Seiyaku, trade name Elastron) 40 parts by mass of H-3), 0.5 parts by mass of elastolone catalyst (Cat 64), 47.8 parts by mass of water, and 5 parts by mass of isopropyl alcohol were mixed, and 1 anionic surfactant was further added. 5% by mass of spherical colloidal silica particles (manufactured by Nissan Chemical Industries, Snowtex OL) was added to prepare a coating solution.

(Manufacture of laminated film)
50 parts by mass of the copolyester resin pellet a as a raw material for the B layer and 50 parts by mass of polyethylene terephthalate resin pellets (ME-553 manufactured by Toyobo Co., Ltd.) containing no particles are blended and dried under reduced pressure at 50 ° C. for 6 hours ( After 1 Torr), polyethylene terephthalate pellets (ME-553, manufactured by Toyobo Co., Ltd.) containing no particles were dried in an extruder 1 (for layer B) at 135 ° C. for 6 hours under reduced pressure (1 Torr), and then the extruder 2 Each was supplied to (for layer A) and dissolved at 285 ° C. The two polymers were each filtered through a stainless steel sintered filter medium (nominal filtration accuracy: 10 μm particles were cut by 95%), laminated in a three-layer confluence block, extruded into a sheet form from the die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electric application casting method, and solidified by cooling to produce an unstretched film. The configuration along this time was B: A: B layer, and the discharge amount of each extruder was adjusted so that the lamination ratio of the thickness of each layer was 8: 84: 8.

  During the film formation, a stainless sintered filter medium having a filtration particle size (initial filtration efficiency: 95%) of 15 m was used as a filter medium for removing foreign substances from the molten resin. Next, this unstretched film was heated to 110 ° C. with a heated roll group and an infrared heater, and then, in the roll group with a difference in peripheral speed, the first stage was 1.95 times in the longitudinal direction and the second stage was 1. The film was stretched 64 times, a total of 3.2 times, to obtain a uniaxially oriented PET film. The refractive index ΔNx at this time was 0.062.

Thereafter, the coating solution for forming the adhesion modified layer was subjected to microfiltration with a felt type polypropylene filter medium having a filtration particle size (initial filtration efficiency: 95%) of 25 μm, applied on both sides by a reverse roll method, and dried. After coating, the end of the film is gripped with a clip, guided to a hot air zone heated to 150 ° C., and after drying, stretched 3.6 times in the width direction and set in a heat setting zone 1 set at 230 ° C. Heat-fixed for 5 seconds, then processed for 5 seconds in zone 2 set at 200 ° C., relaxed 3% in the width direction in this heat treatment process, and then led to the cooling zone to complete cooling, for optical use A biaxially stretched polyester film was obtained. The film thickness at this time was 100 μm, and the coating amount of the adhesion modified layer at this time was 0.01 g / m ² .

Example 2
In Example 1, 67 parts by mass of the copolyester resin pellet a as a raw material for the B layer and 33 parts by mass of polyethylene terephthalate resin pellets (ME-553, manufactured by Toyobo Co., Ltd.) containing no particles are stretched in the second axis. A biaxially oriented laminated polyester film for optics was obtained in the same manner except that the set temperature of the heat setting zone 1 was 225 ° C. in the process.

Example 3
In Example 1, 40 parts by mass of the copolyester resin pellet a as a raw material for the B layer and 60 parts by mass of polyethylene terephthalate resin pellets (ME-553, manufactured by Toyobo Co., Ltd.) containing no particles are stretched in the second axis. A biaxially oriented laminated polyester film for optics was obtained in the same manner except that the set temperature of the heat setting zone 1 was 245 ° C. in the process.

Example 4
In Example 1, a biaxially oriented laminated polyester film for optics was obtained in the same manner except that the set temperature of the heat setting zone 1 was 245 ° C. in the second-axis stretching step.

Example 5
In Example 4, a biaxially oriented laminated polyester film for optics was obtained in the same manner except that the setting temperature of the heat setting zone 1 was set to 215 ° C. in the second-axis stretching step.

Example 6
In Example 1, 50 parts by mass of the copolyester resin pellet a as a raw material for the B layer, 40 parts by mass of polyethylene terephthalate resin pellets (ME-553 manufactured by Toyobo Co., Ltd.) containing no particles, and an average particle size of 2 An optically biaxially oriented laminated polyester film was obtained in the same manner except that 10 parts by mass of polyethylene terephthalate resin pellets (RE-554, manufactured by Toyobo Co., Ltd.) containing 2000 ppm of silica particles of 5 μm were used.

Example 7
60 parts by mass of copolymerized polyester resin b (Toyobo Co., Ltd., FP301) and 40 parts by mass of polyethylene terephthalate resin pellets (ME-553, Toyobo Co., Ltd.) containing no particles are used as raw materials for the A layer and the C layer. A biaxially oriented laminated polyester film for optics was obtained in the same manner except that the set temperature of the heat setting zone 1 was set to 220 ° C. in the second axis stretching step.

Comparative Example 1
In Example 1, 100 parts by mass of polyethylene terephthalate resin pellets (ME-553, manufactured by Toyobo Co., Ltd.) containing no particles as the raw material for the B layer, except that the drying conditions were 135 ° C. for 6 hours under reduced pressure (1 Torr). A biaxially stretched polyester film for optics was obtained in the same manner.

Comparative Example 2
In Example 1, 27 parts by mass of the copolymer polyester resin pellet a as a raw material for the B layer and 73 parts by mass of polyethylene terephthalate resin pellets (ME-553, manufactured by Toyobo Co., Ltd.) containing no particles were used as the second axis. A biaxially oriented laminated polyester film for optics was obtained in the same manner except that the set temperature of the heat setting zone 1 was 245 ° C. in the stretching step.

Comparative Example 3
In Example 1, 100 parts by mass of the copolyester resin pellet a was used as the raw material for the B layer, and the temperature was set to 210 ° C. in the second axis stretching step. A biaxially oriented laminated polyester film was obtained.

Comparative Example 4
In Example 1, 40 parts by mass of the copolyester resin pellet a as a raw material for the B layer and 60 parts by mass of polyethylene terephthalate resin pellets (ME-553, manufactured by Toyobo Co., Ltd.) containing no particles were obtained. The stretched film was heated to 90 ° C. with a heated roll group and an infrared heater, and then stretched 3.6 times in a longitudinal direction with a roll group having a peripheral speed difference to obtain a uniaxially oriented PET film. . The refractive index ΔNx at this time was 0.115.

  Thereafter, the coating solution for forming the adhesion modified layer was subjected to microfiltration with a felt type polypropylene filter medium having a filtration particle size (initial filtration efficiency: 95%) of 25 μm, applied on both sides by a reverse roll method, and dried. After coating, the end of the film is gripped with a clip and guided to a hot air zone heated to 100 ° C. After drying, the film is stretched 4.2 times in the width direction and set in a heat setting zone 1 set at 210 ° C. The film was heat-set for 5 seconds, subjected to a relaxation treatment of 3% in the width direction in this heat treatment step, and immediately led to the cooling zone to complete the cooling to obtain a biaxially stretched polyester film for optics.

  Table 1 shows production conditions and physical properties of the films obtained in Examples 1 to 7 and Comparative Examples 1 to 4, and Table 2 shows physical properties and evaluation results.

  As described above, the optically biaxially oriented laminated polyester film of the present invention has been described based on a plurality of examples. However, the present invention is not limited to the configuration described in the above examples, and is described in each example. The configuration can be changed as appropriate within a range not departing from the gist, such as appropriately combining the configurations.

  The biaxially oriented laminated polyester film for optical use of the present invention has a very small increase in haze after heat treatment, is excellent in slipperiness, blocking resistance, dimensional stability and has no noticeable interference spots. It can be mounted on the front of display screens such as LCD), television and computer cathode ray tubes (CRT), plasma displays (PDP), etc. to suppress external light reflections, glare, iris colors, etc. It is suitable as a base material for various optical films such as an antireflection film having excellent properties.

It is an example of the DSC chart which shows the endothermic melting peak in the biaxially oriented laminated polyester film for optics of this invention.

Explanation of symbols

I: Endothermic melting peak
II: Endothermic melting peak
III: Endothermic melting peak

Claims (8)

A polyester layer (A layer) which does not substantially contain particles is used as a base material, and a polyester layer (B layer) made of a composition containing a copolymerized polyester is laminated on both surfaces of the base material. Further, at least one side of the B layer A laminated polyester film comprising an adhesion modifying layer (C layer) comprising a composition containing an adhesion modifying resin and particles,
The polyester layer (A layer) is made of polyethylene terephthalate,
The copolymerized polyester contained in the polyester layer (B layer) contains terephthalic acid or an ester-forming derivative thereof as an aromatic dicarboxylic acid component, and (a) ethylene glycol and (b) a branched aliphatic glycol component or fat as a glycol component. Composed of cyclic glycols,
The plane direction refractive index ((Nx (longitudinal direction refractive index) + Ny (width direction refractive index)) / 2) is 1.57 to 1.63,
And it has an endothermic melting peak at temperatures of (I) ° C, (II) ° C, and (III) ° C. Each peak temperature was heated from 30 ° C to 300 ° C at 5 ° C / min, and a differential scanning calorimeter (DSC ), And satisfies the following formulas (1), (2), and (3): a biaxially oriented laminated polyester film for optics.
200 <I ≦ II ≦ III < 259.3 (1)
8 <(III-II) <35 (2)
25 <(III-I) <58 (3) 2. The biaxially oriented laminated polyester film for optical use according to claim 1, wherein the branched aliphatic glycol component is neopentyl glycol and the alicyclic glycol is 1,4-cyclohexanedimethanol. The optical copolymer according to claim 1 or 2, wherein the copolymer polyester comprises ethylene glycol and neopentyl glycol as glycol components, and the neopentyl glycol is 1 to 40 mol% with respect to the total glycol components. Axial oriented laminated polyester film. The laminated polyester film according to claim 1, 2 or 3 optical biaxially oriented laminated polyester film, wherein the increase in value of the haze after heating at 170 ° C. 10 minutes is 1% or less. The laminated polyester film according to claim 1, optical biaxially oriented laminated polyester film of 3 or 4, wherein a total light transmittance of 90% or more, and a haze of 1% or less. Claim 1, 2, 3, 4 or 5 optical biaxially oriented laminated polyester film, wherein the static friction coefficient μs of the laminated polyester film is 1.0 or less. Claim 1, 2, 3, 4, 5 or optical biaxially oriented laminated polyester film according 6, wherein the width direction and the longitudinal thermal shrinkage of not more than 1.8%. A cured product layer (D layer) made of an ultraviolet curable or electron beam curable acrylic resin is provided on the surface of the layer C of the laminated polyester film according to claim 1, 2, 3, 4, 6 or 7. A biaxially oriented laminated polyester film for optical use.

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