WO2010119751A1

WO2010119751A1 - Biaxially-oriented polyester film for use in laminating curable resin

Info

Publication number: WO2010119751A1
Application number: PCT/JP2010/054947
Authority: WO
Inventors: 通久上野; 純平中尾上; 浩一村田; 勝文熊野
Original assignee: 東洋紡績株式会社
Priority date: 2009-04-13
Filing date: 2010-03-23
Publication date: 2010-10-21
Also published as: TW201041744A; TWI393636B

Abstract

A biaxially-oriented polyester film for use in laminating a curable resin, the film comprising a polyethylene terephthalate resin and satisfying the requirements (1) to (3): (1) the thickness of the film is from 30 to 500 μm; (2) the plane orientation degree (ΔP) of the film is from 0.150 to 0.180; and (3) the ratio of the axial surface orientation degree between the front surface and the back surface of the film is from 0.80 to 0.98. When the thickness is 500 μm or less, potential warpage, which counteracts the curing and shrinking of a curable resin, is easy to occur, and when the thickness is 30 μm or more, the film can maintain flatness as a base material film. When the ratio of the axial surface orientation degree between the front surface and the back surface of the film is 0.98 or less, potential warpage, which can counteract when a curable resin is laminated, can occur, and when the ratio is 0.80 or more, the film can maintain flatness. When ΔP is 0.150 or more, the film can maintain firmness as a film which can withstand the curing and shrinking of a curable resin, and when ΔP is 0.180 or less, potential warpage, which counteracts the curing and shrinking of a curable resin, is easy to occur, and a laminate can have a favorable surface accuracy.

Description

Biaxially stretched polyester film for curable resin lamination

The present invention provides a biaxially stretched polyester film suitable for a substrate film on which a curable resin is laminated. Specifically, the present invention relates to a biaxially stretched polyester film suitable for a base film of a curable resin laminate having excellent planarity.

A biaxially stretched polyester film made of polyethylene terephthalate resin is used as a base film for various laminates because of its excellent transparency, dimensional stability, and chemical resistance. In particular, a relatively thick film is used for applications such as a base film for laminating a curable resin, because excellent strength and dimensional stability are required.

Examples of such a curable resin include a thermosetting resin that undergoes a curing reaction by drying, heat, and a chemical reaction, and an ionizing radiation curable resin that undergoes a curing reaction by irradiation with electron beams, radiation, ultraviolet rays, and the like. As the curable resin, an acrylate resin, a melamine resin, an acrylic resin, a silicon resin, or the like is used.

Examples of the curable resin laminate as described above include a reflective plate, a diffusion sheet, a lens sheet, and a solar cell protective sheet used in hard coat films and liquid crystal display devices (Patent Document 1, etc.). In such a field, high surface accuracy is required due to sophistication of optical design. However, by providing a layer made of a curable resin as described above, curable shrinkage occurs, so that there is a problem that warpage occurs on the laminated surface side of the curable resin.

Therefore, the following proposals have been made as a method for reducing the occurrence of warpage due to the curable shrinkage of the curable resin. (1) Use a special resin mold that can reduce warpage (Patent Document 2), (2) Use a special curable resin that hardly warps (Patent Document 3), (3) Suppress warpage Such a special support is provided (Patent Document 4).

In addition, in the laminate used for the optical member, a functional layer containing various pigments may be provided in order to develop an optical function. For example, PDP uses near-infrared cut layers containing near-infrared absorbers such as diimonium compounds and fluorine-containing phthalocyanine compounds, LCD uses PVA layers containing iodine dyes, electronic paper uses dye layers containing color inks, dye-sensitized solar Examples of the battery include a photoelectric excitation compound. These laminates may be exposed to sunlight for a long period of time like outdoor displays and solar cells, and functional dyes are generally decomposed by ultraviolet rays contained in solar rays, resulting in poor weather resistance and long-term performance. There was also a drop by use. For this reason, the polyester film which provided the ultraviolet absorptivity by kneading a ultraviolet absorber in a base film is proposed (patent documents 5 and 6).

JP 2003-188394 A JP 2008-221643 A JP 2008-281614 A JP 2009-48152 A JP 2007-149600 A JP 2007-146015 A

The above method has a certain result in reducing the warpage of the curable resin laminate. However, in Patent Document 3 and Patent Document 4, there is a problem that the selection of the curable resin and the layer configuration of the laminate are restricted, and in Patent Document 2, there is a problem that the structure of the curable resin layer is restricted. . Therefore, in order to obtain higher productivity, it has been required to reduce warpage while having the conventional curable resin and layer structure.

The above-described problem can be achieved by the following solution means.
A first aspect of the present invention is a biaxially stretched polyester film made of a polyethylene terephthalate resin, which is a biaxially stretched polyester film for curable resin lamination that satisfies the following requirements (1) to (3).
(1) Thickness is 30 to 500 μm (2) Plane orientation degree ΔP is 0.150 to 0.180 (3) Surface axis orientation degree Y _max or Y _min Is 0.80 to 0.98. Here, the ratio between the front and back of the surface axis orientation Y _max and Y _min is obtained as follows.
(Ratio between front and back surface axis orientation)
For film samples, determine the absorbance _{A 1340} and the absorbance _{A 1410} in the vicinity of a wavelength 1410 cm ^-1 in the vicinity of wavelength 1340 cm ^-1 by the polarization ATR method, determining the ratio Y represented by the following formula. Starting from the first measured point, the film sample is rotated in-plane every 10 ° and measured in the same manner in the range of 0 ° to 170 °. The maximum value and the minimum value among the obtained 18 points are defined as surface axis orientation degrees Y _max and Y _min . The surface axis orientation degrees Y _max and Y _min are measured on the front and back sides of the film sample, and the ratio between the front and back sides of the surface axis orientation degrees Y _max and Y _min is determined using the larger value of the front and back sides as the denominator.
Y = A ₁₃₄₀ / A ₁₄₁₀
2nd invention is the said biaxially stretched polyester film for curable resin lamination | stacking which consists of a 3 layer structure in which the said biaxially stretched polyester film has an intermediate | middle layer containing a ultraviolet absorber.
A third invention is a biaxially stretched polyester film for curable resin lamination having a coating layer having a coating layer on at least one surface of the biaxially stretched polyester film for curable resin lamination, wherein the coating layer is a copolyester. A biaxially stretched polyester film for laminating a curable resin with a coating layer, comprising at least one of a resin, an acrylic resin and a polyurethane resin as a main component.
A fourth invention is a curable resin laminate having a curable resin layer using the biaxially stretched polyester film for curable resin lamination as a base film.
5th invention is a curable resin laminated body which has a curable resin layer by using the said biaxially stretched polyester film for curable resin lamination | stacking with a coating layer as a base film.

The biaxially stretched polyester film for laminating a curable resin of the present invention has good flatness when used as a base film of a curable resin laminate. Therefore, it is suitable for applications requiring high surface accuracy such as a reflection plate, a diffusion sheet, and a lens sheet used in hard coat films and liquid crystal display devices. Further, as a preferred embodiment, even when materials having different shrinkage properties or shrinkage properties are laminated or bonded, the planarity of the entire laminate is good.

As a result of intensive studies on maintaining the surface accuracy of the curable resin laminate, the present inventor has provided a specific orientation difference on the front and back of the biaxially stretched polyester film as the base material, so that the base film is curable. It has been found that good surface accuracy can be maintained as a resin laminate. That is, the present invention is a biaxially stretched polyester film in which the ratio of the degree of surface axis orientation on the front and back of the film is in a specific range.

By providing an orientation difference between the front and back of the film, a mechanism that maintains good surface accuracy when the curable resin is laminated is considered as follows.
In producing the curable resin laminate, the curable resin composition is applied and laminated on the base film, and then the curable resin is cured by irradiation with ionizing radiation such as heat or ultraviolet rays. Curing shrinkage occurs in the curable resin due to the progress of the curing reaction, and a force is generated to shrink in the surface direction on the curable resin laminate surface side. Under the present circumstances, it can antagonize the force which arises on one side by having an orientation difference in the front and back of a base film. In addition, when the base film is heated by irradiation with ionizing radiation such as heat or ultraviolet rays, shrinkage of the front and back shrinks due to the orientation difference between the front and back of the film, and a force that warps the film occurs. This antagonizes the force action caused by the shrinkage of the curable resin and the front and back, so that good surface accuracy is maintained as the curable resin laminate.

The film of the present invention comprises a polyethylene terephthalate resin, and the orientation difference between the front and back surfaces of the film can be specified by the front / back ratio of the surface axis orientation degree Y _max or Y _min . Here, the ratio between the front and back of the surface axis orientation Y _max and Y _min is obtained as follows.

For film samples, determine the absorbance _{A 1340} and the absorbance _{A 1410} in the vicinity of a wavelength 1410 cm ^-1 in the vicinity of wavelength 1340 cm ^-1 by the polarization ATR method, determining the ratio Y represented by the following formula. Starting from the first measured point, the film sample is rotated in-plane every 10 ° and measured in the same manner in the range of 0 ° to 170 °. The maximum value and the minimum value among the obtained 18 points are defined as surface axis orientation degrees Y _max and Y _min . The surface axis orientation degrees Y _max and Y _min are measured on the front and back sides of the film sample, and the ratio between the front and back sides of the surface axis orientation degrees Y _max and Y _min is determined using the larger value of the front and back sides as the denominator.
Y = A ₁₃₄₀ / A ₁₄₁₀

Here, the absorbance A ₁₃₄₀ near the wavelength of ₁₃₄₀ cm ⁻¹ is derived from the longitudinal vibration of CH ₂ contained in the ethylene glycol unit of the polyethylene terephthalate molecular chain. This indicates the presence of the trans position of the CH ₂ unit in the polyethylene molecular chain, and the intensity of such a signal quantitatively indicates the concentration of the trans isomer, that is, the state of the strength of orientation due to stretching of the polyester molecule. Is. On the other hand, the absorbance A _{1410 in the} vicinity of the wavelength of ₁₄₁₀ cm ⁻¹ is derived from the C = C in-plane bending vibration included in the benzene ring structure in the polyethylene molecular chain. This is used to normalize the absorption intensity in the vicinity of a wavelength of 1340 cm ⁻¹ as a reference band because the absorption intensity at in-plane rotation is constant regardless of the orientation of polyethylene terephthalate. Since each absorption is measured by the ATR method with polarized light by a polarizer, the strength of orientation of the polyethylene terephthalate near the film surface in a specific direction is determined by the ratio Y obtained by normalizing the absorbance A ₁₃₄₀ to the absorbance A _1410. It can be expressed quantitatively.

The ratio Y is measured by rotating the film sample in-plane, and the maximum value and the minimum value among the obtained values are defined as the surface axis orientation degrees Y _max and Y _min . Usually, the directions in which Y _max and Y _min are obtained substantially coincide with the stretching axis direction of the film sample. This is because when the film is stretched biaxially, it exhibits an elliptical orientation behavior with the two machine axis directions of the stretched longitudinal direction and the transverse direction as axes. As a result, two orthogonal machine axis directions are defined, which are substantially the same as the directions in which the surface axis orientation degrees Y _max and Y _min are obtained.

In the film of the present invention, the front / back ratio of at least one of the degree of surface axis orientation Y _max or Y _min obtained as described above is 0.80 to 0.98. If the front / back ratio of any one of the surface axis orientations is 0.98 or less, a potential warp that can antagonize when the curable resin is laminated may occur. Moreover, if the ratio of the front and back of any one of the said surface axis orientation degrees is 0.80 or more, the planarity suitable for workability as a base film can be hold | maintained. 0.97 is preferable, 0.96 is more preferable, 0.96 is further more preferable, 0.95 is further more preferable, and 0.94 is still more preferable. 0.82 is preferable, 0.83 is more preferable, 0.83 is more preferable, 0.85 is further more preferable, and 0.86 is further more preferable.

As described above, since the film of the present invention has an orientation difference between the front and back surfaces, it can maintain good surface accuracy as a curable resin laminate, and further, by having a specific degree of surface orientation and thickness, It has favorable flatness as a substrate film while having an orientation difference of. Thereby, the workability is also excellent in terms of workability.

The film of the present invention resists curing shrinkage due to the curable resin, and further maintains the flatness as a substrate film while having a difference in orientation between the front and back surfaces, the film thickness is more preferably 30 to 500 μm. Is 50 to 500 μm. If the thickness of the film is 500 μm or less, the specific orientation difference tends to cause a potential warpage that antagonizes the curing shrinkage of the curable resin, and the surface accuracy of the laminate is improved against the effective shrinkage of the curable resin. Can be good. Moreover, if the thickness of a film is 30 micrometers or more, More preferably, it is 50 micrometers or more, The planarity as a base film can be maintained, having a specific orientation degree. In addition, when providing a temperature difference on the front and back of the film during the production of the film to be described later to give a difference in orientation between the front and back, the thicker the film, the easier it is to provide a temperature difference between the front and back of the film. It is preferable in providing. The upper limit of the thickness of the film of the present invention is preferably 450 μm, more preferably 400 μm, and still more preferably 370 μm. The lower limit of the thickness of the film of the present invention is more preferably 75 μm, still more preferably 80 μm, and still more preferably 100 μm.

Further, in order to suitably provide a difference in orientation between the front and back of the film, it is preferable to control the thickness of the film within the certain range. For example, as described below, when providing a difference in the amount of heat on the front and back of the film by providing a difference in the amount of heat on the front and back of the film, considering the heat transferability inside the film, the larger the thickness of the film, It is easy to maintain the difference. Therefore, the thickness of the film is preferably equal to or more than the above lower limit because it is easy to provide an orientation difference between the front and back of the film.

The film of the present invention has a plane orientation degree ΔP of 0.150 to 0.180. By setting the above-mentioned plane orientation degree ΔP of the film in such a range, the waist strength (strength) as a film that can resist the curing shrinkage of the curable resin in the case where there is an orientation difference between the front and back in the above range. Can be held. Here, the plane orientation degree ΔP is obtained by the following equation.
ΔP = (nx + ny) / 2−nz
Here, nx, ny, and nz represent the refractive index in the longitudinal direction, the refractive index in the width direction, and the refractive index in the thickness direction, respectively. Since the longitudinal direction and the width direction are the same as or substantially the same as the directions in which Y _min and Y _max are obtained as described above, it is possible to specify the longitudinal direction and the width direction based on these directions.

The degree of plane orientation ΔP indicates the orientation strength of the entire film surface. When the degree of plane orientation ΔP is 0.150 or more, the waist strength (strength) as a film that can resist the curing shrinkage of the curable resin can be maintained in the case where the orientation difference between the front and back surfaces is in the above range. . Further, if the degree of plane orientation ΔP is 0.180 or less, a specific warpage tends to cause a potential warpage that antagonizes the curing shrinkage of the curable resin, and the laminate is resisted against the effective shrinkage of the curable resin. The surface accuracy of the body can be improved. The upper limit of the degree of plane orientation ΔP of the present invention is preferably 0.178, more preferably 0.176, still more preferably 0.175, and still more preferably 0.173. Further, the lower limit of the degree of plane orientation ΔP of the present invention is preferably 0.153, more preferably 0.155, still more preferably 0.158, still more preferably 0.160, and particularly preferably 0.163. In addition, in the case of providing an orientation difference between the front and back of the film in an in-line film manufacturing process as described later, it may be difficult to provide an orientation if the degree of plane orientation ΔP of the film is too small, and conversely, it may be difficult to provide an orientation difference that is too large. is there. Therefore, it is preferable to provide the degree of plane orientation ΔP of the film in the predetermined range in order to suitably provide an orientation difference between the front and back of the film.

The film of the present invention preferably has good flatness as a base film. Here, the planarity of the substrate film can be evaluated as follows. A rectangular film sample of 300 mm in the longitudinal direction and 210 mm in the width direction perpendicular thereto is cut out from the film, and the film sample is allowed to stand for 30 minutes or more in a room controlled at a temperature of 23 ± 2 ° C. and a humidity of 65 ± 5%. Then, the height of warping of the four corners of the film is measured in the vertical direction with reference to the stationary surface. Under the present circumstances, it is preferable that the maximum value of the height of the curvature of four corners of the film of this invention is below film thickness.

The maximum value of the warp height is preferably not more than the film thickness, more preferably not more than 90% of the film thickness, still more preferably not more than 80%, and particularly preferably not more than 50%. . When the maximum value of the warp is equal to or less than the film thickness, there is little distortion in flatness during processing of the film such as application of a curable resin, and the processing characteristics are excellent.

The film of the present invention is made of polyethylene terephthalate resin. Here, the polyethylene terephthalate-based resin contains ethylene glycol and terephthalic acid as main components. Other dicarboxylic acid components and glycol components may be copolymerized as long as the object of the present invention is not impaired. Examples of other dicarboxylic acid components include isophthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-dicarboxybenzophenone, bis- (4-carboxyphenylethane), adipine Examples include acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1,4-dicarboxylic acid and the like. Examples of the other glycol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, bisphenol A and other ethylene oxide adducts, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. In addition, oxycarboxylic acid components such as p-oxybenzoic acid can also be used.

As a polymerization method of such polyethylene terephthalate (hereinafter simply referred to as PET), a direct polymerization method in which terephthalic acid and ethylene glycol and, if necessary, other dicarboxylic acid component and diol component are directly reacted, and dimethyl terephthalate are used. Any production method such as a transesterification method in which an ester (including a methyl ester of another dicarboxylic acid as necessary) and ethylene glycol (including another diol component as necessary) are transesterified can be used. .

The film of the present invention may be a single layer or a film having a multilayer structure of two or more layers. In the case of having two or more layers, it is desirable that the resins constituting the film front and back layers (both outermost layers) are the same from the viewpoint of planarity as a base film. Here, the same type of resin refers to a polyethylene terephthalate resin having the same or substantially the same intrinsic viscosity and / or melting point. When the intrinsic viscosity and / or melting point of the PET constituting the outermost layer is the same or substantially the same, even if it has a multilayer structure of two or more layers, good flatness can be obtained as a base film. Here, the intrinsic viscosities being substantially the same mean that the difference between the intrinsic viscosities measured by the following measuring method is 0.1 g / dl or less, preferably 0.05 g / dl or less. Moreover, the melting points being substantially the same means that the difference between the melting points of the outermost layers measured by the following measurement method is 3 ° C. or less, preferably 2 ° C. or less.

Intrinsic viscosity is based on JIS K 7367-5 after drying a ground PET sample, and a mixed solvent of phenol (60% by mass) and 1,1,2,2-tetrachloroethane (40% by mass) is used as a solvent. Measure at 30 ° C.

The melting point is obtained using a differential scanning calorimeter, and the melting peak temperature (Tpm) defined in JIS-K7121-1987, item 9/1 is defined as the melting point.

Moreover, fine particles can be added to the film of the present invention as necessary. Examples of the fine particles added at that time include known inorganic fine particles and organic fine particles. Furthermore, in the resin forming the film, various additives as necessary, for example, waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducing agents, heat stabilizers, coloring pigments, An anti-coloring agent, an ultraviolet absorber and the like can be added.

For example, when light resistance is imparted to the film, an ultraviolet absorber can be added to the film. In this case, it is also preferable to provide a layer having a three-layer structure as a film and containing an ultraviolet absorber as an intermediate layer. By containing an ultraviolet absorber in the intermediate layer, bleeding out of the additive can be suitably prevented, and deterioration of the adhesion of the curable resin due to bleeding out of the additive can be suppressed.

The UV absorber used here is a known substance. Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable from the viewpoint of transparency. Examples of the organic ultraviolet absorber include benzotoazole, benzophenone, cyclic imino ester, and combinations thereof, but are not particularly limited as long as the absorbance is within the range defined by the present invention. However, from the viewpoint of durability, benzotoazole and cyclic imino ester are particularly preferable. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays having different wavelengths can be absorbed simultaneously, so that the ultraviolet absorption effect can be further improved.

Examples of benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, and acrylonitrile ultraviolet absorbers include 2- [2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2 ′.
-Hydroxy-5 '-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2,2'-dihydroxy- 4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2- ( 2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (5-chloro (2H) -benzotriazol-2-yl) -4-methyl-6- ( tert-butyl) phenol, 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H -Benzotriazol-2-yl) phenol, etc. Examples of cyclic imino ester UV absorbers include 2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinone-4- ON), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, 2-phenyl-3,1-benzoxazin-4-one, etc. However, the present invention is not limited to these.

As a method of blending the ultraviolet absorber into the film, known methods can be used in combination. For example, the ultraviolet absorber dried in advance using a kneading extruder and the polyester raw material as exemplified above are used. A master batch can be prepared by blending and blended by, for example, a method of mixing a predetermined master batch and a polyester raw material during film formation. At this time, the concentration of the UV absorber in the master batch is preferably 5 to 30% by mass in order to uniformly disperse the UV absorber and economically blend it.

The film of the present invention preferably has a transmittance of 20% or less at a wavelength of 380 nm. In particular, when used as a display member such as a PDP filter or a polarizing plate protective film, or as a base material for a solar cell protective film, the transmittance at 380 nm is preferably 15% or less, and more preferably 5% or less. When the transmittance is 20% or less, alteration of the optical functional dye such as a near-infrared absorbing dye, iodine dye, or electroexcitation compound contained in the optical functional layer due to ultraviolet rays can be suppressed. In order to reduce the transmittance of the film at a wavelength of 380 nm to 20% or less, the concentration of the ultraviolet absorber and the thickness of the base film are appropriately adjusted. The transmittance in the present invention is measured by a method perpendicular to the plane of the adhesive modified base film optical laminated film, and is measured using a spectrophotometer (for example, Hitachi U-3500 type). be able to.

In addition, it is preferable to add fine particles to the polyethylene terephthalate resin in the present invention to improve the workability (slidability) of the film. Any fine particles can be selected. For example, calcium carbonate, calcium phosphate, amorphous silica, spherical silica, crystalline glass filler, kaolin, talc, titanium dioxide, alumina, silica-alumina composite oxide particles, barium sulfate, fluoride. Inorganic particles such as calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica, crosslinked polystyrene particles, crosslinked acrylic resin particles, crosslinked methyl methacrylate particles, benzoguanamine / formaldehyde condensate particles, melamine / formaldehyde condensate particles, Examples thereof include heat-resistant polymer fine particles such as polytetrafluoroethylene particles. In particular, from the viewpoint of transparency, silica particles, particularly amorphous silica, having a refractive index relatively close to that of the resin component are suitable.

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

As a method of blending the above particles with the polyethylene terephthalate resin, for example, it can be added at any stage of producing the polyethylene terephthalate resin, but preferably at the esterification stage or after completion of the transesterification reaction, polycondensation It may be added as a slurry dispersed in ethylene glycol or the like at the stage before the start of the reaction to proceed the polycondensation reaction. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyethylene terephthalate resin raw material, or a dried particle and a polyethylene terephthalate system using a kneading extruder It can be performed by a method of blending with a resin raw material.

Further, when the film of the present invention is used as an optical application member such as a diffusion sheet or a lens sheet, high transparency is required. In order to obtain such high transparency, it is preferable that the polyester constituting the film does not substantially contain particles. Here, “substantially contain no particles” means, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescent X-ray analysis, it is 50 ppm or less, preferably 10 ppm or less, particularly preferably the detection limit or less. Means content.

As a preferred embodiment of the present invention, in order to obtain good transparency and stable workability (especially surface friction characteristics), a film having a multilayer structure and using a polyester layer containing fine particles only in the outermost layer is used. You can also. Such a base film has a multilayer structure (a / b / a) in which outermost layers (a layer) containing inert particles are laminated on both sides of a central layer (b layer) by a coextrusion method. It is preferable to use a polyester film. The layers constituting the outermost layer on the front and back may be the same or different, but in order to maintain the flatness of the base film, the polyester resin on the outermost layer on the front and back should have the same configuration. Is desirable.

The average particle size of the fine particles contained in the outermost layer is preferably 1 to 10 μm, more preferably 1.5 to 7 μm, still more preferably 2 to 5 μm. If the average particle diameter of the fine particles is 1.0 μm or more, it is preferable because the surface can be provided with a concavo-convex structure suitable for providing easy slipping. On the other hand, if the average particle diameter of the fine particles is 10 μm or less, it is preferable because high transparency is maintained. The content of inert particles in the outermost layer is desirably 0.005 to 0.1% by mass, preferably 0.008 to 0.07%, and more preferably 0.01 to 0%. .05%. If the content of the fine particles is 0.005% by mass or more, it is preferable because a concavo-convex structure suitable for imparting slipperiness can be imparted to the outermost layer surface. On the other hand, if the content of fine particles is 0.1% by mass or less, it is preferable because high transparency is maintained.

According to any of the above embodiments, the film of the present invention can exhibit high transparency and can be suitably used for optical applications. The haze of the film of the present invention and the film with a coating layer described below is preferably 3.0% or less as a whole, more preferably 2.0% or less, and 1.5% or less. Further preferred. Furthermore, it is preferable that the total light transmittance of a film and the film with a coating layer mentioned later is 85% or more, More preferably, it is 88% or more. When the haze or total light transmittance is in the above range, high luminance can be obtained even when used as a display member. The haze and total light transmittance can be measured using a turbidimeter according to JIS-K7105.

Furthermore, the film of the present invention can be subjected to corona treatment, coating treatment, flame treatment or the like in order to improve the adhesion of the film surface when the curable resin is laminated.

In the present invention, in order to improve the adhesion with the curable resin, at least one surface of the film of the present invention has a coating layer mainly composed of at least one of polyester resin, polyurethane resin or polyacrylic resin. Is preferred. Here, the “main component” refers to a component that is 50% by mass or more of the solid components constituting the coating layer. The coating solution used for forming the coating layer of the present invention is preferably an aqueous coating solution containing at least one of water-soluble or water-dispersible copolymerized polyester resin, acrylic resin and polyurethane resin. Examples of these coating solutions include water-soluble or water-dispersible co-polymers disclosed in Japanese Patent No. 3567927, Japanese Patent No. 3589232, Japanese Patent No. 3589233, Japanese Patent No. 3900191, and Japanese Patent No. 4150982. Examples thereof include a polymerized polyester resin solution, an acrylic resin solution, and a polyurethane resin solution.

The coating layer can be obtained by applying the coating liquid on one or both sides of a uniaxially stretched film in the longitudinal direction, drying at 100 to 150 ° C., and stretching in the transverse direction. The final coating amount of the coating layer is preferably controlled to 0.05 to 0.20 g / m ² . If the coating amount is less than 0.05 g / m ² , adhesion with the resulting curable resin may be insufficient. On the other hand, when the coating amount exceeds 0.20 g / m ² , blocking resistance may be lowered. When coating layers are provided on both sides of the polyester film, the coating amounts of the coating layers on both sides may be the same or different, and can be independently set within the above range.

It is preferable to add particles to the coating layer in order to impart easy slipperiness. It is preferable to use particles having an average particle size of 2 μm or less. When the average particle diameter of the particles exceeds 2 μm, the particles easily fall off from the coating layer. Examples of the particles to be contained in the coating layer include the same particles as those described above.

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

Although the coating layer can be provided on any surface of the film of the present invention, it is preferable to provide the surface of the surface axial orientation degree Y _max or Y _min whichever is smaller. This is because providing a curable resin layer on a surface with a low degree of orientation tends to easily maintain antagonism between the front and the back due to the mechanical strength retention due to the orientation difference between the front and back, or the occurrence of a potential warp due to heating.

In the present invention, in order to make the ratio of the degree of surface axial orientation of the front and back of the film within the above specified range, a method of relaxing the surface orientation by applying heat treatment in-line or offline after production, Examples thereof include a method in which thermal energy is applied to at least one surface to relax the surface orientation, and a method in which the surface orientation is relaxed by applying a volatile organic solvent to the one surface. In the present invention, the film of the present invention can be suitably obtained by positively providing a difference in molecular orientation between the front and back of the film by providing a difference in the amount of heat applied between the front and back in the film production process. More specifically, for example, the following methods (1) to (3) are preferable as a method of providing a difference in heat addition between the front and back sides in the film production process. By associating these means alone or with each other, it is possible to obtain the film of the present invention that can resist the curing shrinkage of the curable resin even though the substrate film is flat.

(1) Temperature difference between front and back of unstretched sheet In the production of the film of the present invention, a molten resin is first extruded from a die, and rapidly cooled and solidified by winding on a cooled casting drum to obtain an unstretched sheet. Since the unstretched sheet is cooled from the sheet surface, the cooling efficiency differs between the surface in contact with the casting drum and the opposite surface, and a temperature difference occurs between the front and back of the unstretched sheet.

In the present invention, when the second cooling roll (separating roll) following the casting drum is separated, the surface temperature difference between the front and back of the unstretched sheet is preferably 3 ° C. or higher and 33 ° C. or lower. The surface temperature difference between the front and back of the sheet at the outlet of the second cooling roll is more preferably 5 ° C or higher, further preferably 8 ° C or higher, and particularly preferably 10 ° C or higher. The surface temperature difference between the front and back of the sheet is more preferably 30 ° C. or less, further preferably 28 ° C. or less, and particularly preferably 25 ° C. or less. When the said temperature difference exceeds 30 degreeC, the planarity as a base film may worsen.

As a method for controlling the surface temperature difference between the front and back of the unstretched sheet within the above range, it is desirable to appropriately control the cooling time and the temperature of the cooling roll. Further, the surface temperature difference between the front and back sides of the sheet can be controlled by cooling the back surface using cooling air or by cooling the back surface with the second cooling roll early by reducing the diameter of the casting drum. Furthermore, since the time required for cooling depends on the thickness of the sheet, the speed of the cooling roll, etc., it is preferable to appropriately adjust the temperature of the cooling air, the cooling range, the temperature of the second cooling roll, and the like.

(2) Temperature difference between front and back in longitudinal stretching In order to obtain the film of the present invention, it is desirable to provide a temperature difference between the front and back of the film in the longitudinal stretching step and change the degree of molecular orientation on the front and back of the film. When a temperature difference between the front and back of the film is provided in the longitudinal stretching step, orientation distortion remains on the side having a lower surface temperature than on the side having a higher surface temperature, and an orientation difference due to stretching tends to occur. During longitudinal stretching in the production of the film of the present invention, in order to provide a temperature difference between the front and back, roll temperature setting on the front and back, non-contact infrared irradiation, heating with high-speed heating air, etc. Heating or cooling means can be used.

Further, the longitudinal stretching may be performed in a single step or multiple steps, but it is preferably performed in two or more steps in order to suitably provide a difference in orientation between the front and back sides. When longitudinal stretching is performed in two or more stages, stretching with a temperature difference can be further performed in a state where the stretching orientation has progressed, and it becomes easy to provide a difference in orientation between the front and back surfaces. For this reason, the difference in the amount of heat to be applied in the two stages rather than the one stage can be reduced, which is more preferable for maintaining flatness as a film base material. In this case, it is more preferable that the film is once cooled and then once cooled and then subjected to longitudinal stretching with a temperature difference between the front and back surfaces in order to effectively provide an orientation difference.

Specifically, when longitudinal stretching is performed using a heating means such as an infrared heater between rolls having a circumferential speed difference, the temperature difference between the front and back of the film can be changed by changing the amount of heating or cooling of the front and back. Is preferably adjusted to be 0.3 ° C. or higher and 5 ° C. or lower. If the temperature difference between the front and back sides is 5 ° C. or less, the planarity can be suitably maintained as a base film. (In addition, the temperature of the film front and back in the longitudinal stretching step refers to two other than the center obtained by dividing the film into three in the thickness direction. Specifically, it can be obtained by heat transfer calculation.)

In the stretching process, when a difference in orientation is provided by providing a temperature difference between the front and back of the film, a higher stretching deformation rate is suitable. Therefore, in providing the front and back orientation difference, the longitudinal stretching process is more suitable than the lateral stretching process as described above. However, it is possible to provide a temperature difference in the vertical direction in the transverse stretching process and to provide a difference in orientation between the front and back of the film.

(3) Temperature difference between upper and lower heat setting temperature In the present invention, in the heat setting step of heat setting the film after biaxial stretching, the temperature of the front and back of the film is a temperature of 0.1 ° C. or more and 0.5 ° C. or less. It is preferable to provide a difference. This is to substantially change the shrinkage ratio between the front and back surfaces by providing a difference in the degree of heat treatment between the front and back surfaces. In order to provide a temperature difference between the front and back sides in the heat setting step, for example, it is possible to change the temperature up and down through the film of the heat setting device or / and to provide a wind speed difference. In order to provide the above temperature difference between the front and back of the film, the temperature difference between the upper and lower sides of the heat setting device is preferably 3 ° C. or higher and 30 ° C. or lower. If the temperature is less than 3 ° C., the difference in wind speed between the upper and lower sides in the fixing device increases to give a temperature difference of the film, and a distortion force acts on the film. On the other hand, if the temperature is higher than 30 ° C., the air balance is liable to be lost due to the difference in density between the air above and below the film.

Other than the method described in detail above, it is also possible to use other methods such as passing a heating roll for performing single-side heat treatment during film formation, or heating the opposite surface of the single-side cooling by infrared heating or hot air heating. Further, in the in-line manufacturing process, it is possible to provide a difference in orientation between the front and back surfaces by a method of stretching in the longitudinal direction while providing aberration on the front and back surfaces along a roll having a high curvature. In any case, as long as the orientation difference between the front and back of the film is controlled within a specific range of the present application, the manufacturing method is not specified.

In the film of the present invention, in order to control the degree of plane orientation ΔP within the above range, it is preferable to appropriately set the draw ratio and the heat setting treatment temperature. That is, in order to reduce the plane orientation coefficient, the stretching temperature for longitudinal stretching or lateral stretching may be set high, the stretching ratio may be set low, or the heat treatment temperature may be set high.

When performing longitudinal-lateral stretching, the average film temperature (average of the front and back temperatures) is 80 to 125 ° C for longitudinal stretching and 80 to 180 ° C for horizontal stretching, while the stretching ratio is adjusted in both the longitudinal, lateral, and both directions. It is preferable to adjust to 2.5 times to 4.5 times, more preferably to 3.0 times to 4.2 times, and more preferably to 3.2 times to 4.1 times. Further preferred. It is preferable to adjust to. If the longitudinal stretch ratio is 4.5 times or less, a potential warp is likely to occur, and the front / back antagonism with curing shrinkage can be suitably controlled. Moreover, if a draw ratio is 2.5 times or more, it will be easy to show the waist strength which can maintain the planarity as a base film.

In the present invention, the heat setting treatment is performed following the transverse stretching step. The temperature in the heat setting treatment step is preferably 180 ° C. or higher and 240 ° C. or lower. If the temperature of the heat setting treatment is less than 180 ° C., the absolute value of the heat shrinkage rate is increased, which is not preferable. On the other hand, if the temperature of the heat setting treatment exceeds 240 ° C., the film tends to become opaque and the frequency of breakage increases, which is not preferable.

で It is effective to control the heat shrinkage rate, especially the heat shrinkage rate in the width direction, by narrowing the guide rail of the gripping tool by the heat fixing treatment and then performing the relaxation treatment. The temperature for the relaxation treatment can be selected in the range from the heat setting treatment temperature to the glass transition temperature Tg of the polyethylene terephthalate resin film, but is preferably (heat setting treatment temperature) -10 ° C. to Tg + 10 ° C. The width relaxation rate is preferably 1 to 6%. If it is less than 1%, the effect is small, and if it exceeds 6%, the flatness of the film is deteriorated.

The present invention is suitable for laminating a resin composition having shrinkage with curing. A curable resin laminate is obtained by applying and laminating the resin composition to the film of the present invention, and irradiating with ionizing radiation such as drying, heat, chemical reaction, or ultraviolet rays to cure the curable resin. In the present invention, the curable resin refers to a resin compound that is polymerized and / or reacted by irradiation with any of drying, heat, chemical reaction, electron beam, radiation, and ultraviolet light. Examples of the curable resin used in the present invention include melamine-based, acrylic-based, silicon-based, and polyvinyl alcohol-based curable resins, and acrylate-based curable resins are preferable in terms of obtaining high surface hardness or optical design. Examples of the curable resin composition containing an acrylate-based curable resin include a composition containing urethane (meth) acrylate oligomer, epoxy (meth) acrylate oligomer, reaction diluent, photopolymerization initiator, and sensitizer. It is done.

Examples of urethane (meth) acrylate oligomers include polyols such as ethylene glycol, 1,4 butanediol, neopentyl glycol, polycaprolactone polyol, polyester polyol, polycarbonate diol, polytetramethylene glycol, hexamethylene diisocyanate, isophorone diisocyanate, It can be obtained by reacting with organic polyisocyanates such as tolylene diisocyanate and xylene isocyanate. However, it is not particularly limited.

Examples of the epoxy (meth) acrylate oligomer include epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, terminal glycidyl ether of bisphenol A type propylene oxide adduct, and fluorene epoxy resin. It can be obtained by reacting with (meth) acrylic acid. However, it is not particularly limited to these

Such a curable resin forms a crosslinked structure by a curing reaction, and cure shrinkage occurs. By using the base film of the present invention, high surface accuracy can be maintained as a laminate even when curing shrinkage occurs due to the curable resin. Although the curable resin used in the present invention can be arbitrarily selected, it is preferably used by appropriately adjusting the curing shrinkage rate from 1 to 20%, more preferably 2 to 18%, and further preferably 3 to 15%. Can do. For example, when using a curable shrinkable resin composition in which a plurality of curable resin compounds having different numbers of functional groups are mixed, the cure shrinkage rate can be controlled by adjusting the mixing ratio. Here, the curing shrinkage rate can be obtained by the following equation. Here, the specific gravity can be measured according to JIS-K-6833.
(Curing shrinkage) = [{(specific gravity before cured product) − (specific gravity before curing)} / (specific gravity before curing)] × 100

The layer thickness of the curable resin layer in the laminate of the present invention is not particularly limited, but is preferably 1 to 300 μm, more preferably 2 to 200 μm, still more preferably 2 to 150 μm, and still more preferably 3 to 100 μm. It can be used by appropriately adjusting from the range.

When a curing reaction is caused by irradiation with ionizing radiation, a light source such as a chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, an electrodeless UV lamp, a visible light halogen lamp, a xenon lamp, or sunlight can be used. . The atmosphere during irradiation with ionizing radiation may be air or an inert gas such as nitrogen or argon. The irradiation energy is, for example, such that the integrated energy in the wavelength range of 200 to 600 nm, preferably 320 to 390 nm is, for example, 0.01 to 10 J / cm ² , preferably 0.4 to 8 J / cm ^2. It is appropriate to do. Furthermore, curing the laminate is suitable for imparting an antagonistic force due to the potential warpage of the film of the present invention.

The structure of the curable resin layer of the laminate is not particularly limited, but may have, for example, the structure exemplified below. Those having a substantially uniform layer thickness such as a hard coat layer or antireflection layer, those having a mountain-shaped prism at a specific pitch interval such as a prism lens, and those having an irregular convex structure such as a micro lens , One provided with unevenness by embossing, etc., one having particles such as a diffusion layer, having a surface uneven structure or internal cavity structure, and one having a sea island structure with a plurality of resins. In these cases, it is preferable that the maximum thickness of the curable resin layer (for example, a lens apex in the case of a prism lens) is within the range of the layer thickness.

The curable resin laminate of the present invention has good flatness. Here, the planarity of the curable resin laminate can be evaluated as follows. A rectangular sample of 300 mm in the longitudinal direction and 210 mm in the width direction perpendicular thereto is cut out from the curable resin laminate, and the sample is allowed to stand for 30 minutes or more in a room controlled at a temperature of 23 ± 2 ° C. and a humidity of 65 ± 5%. . Then, the height of warping of the four corners of the film is measured in the vertical direction with reference to the stationary surface. Under the present circumstances, it is preferable that the height of the curvature of four corners is 0.5 mm or less.

The film of the present invention has good flatness as a base film, and can maintain high surface accuracy as a curable resin laminate. Further, as a preferred embodiment, even when materials having different shrinkage properties or shrinkage properties are laminated or bonded, the planarity of the entire laminate is good. Therefore, the film of the present invention includes, for example, various optical films such as a lens film, a diffusion film, a hard coat film, and an NIR film, a touch panel, ITO, a solar cell protective film, a solar cell back sheet, a polarizing plate protective film, and a polarized light. It is suitable as a base film for laminates such as a child protective film, organic EL, and electronic paper. Further, it is also suitable as a base film for use as a building material for applying and laminating a curable coating agent, a recording material using a curable resin ink or the like, a use for a laminate member using two or more films bonded together.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples. In addition, the evaluation method used in each Example and the comparative example is demonstrated below.

(1) Intrinsic viscosity Based on JIS K 7367-5, a mixed solvent of phenol (60% by mass) and 1,1,2,2-tetrachloroethane (40% by mass) was used as a solvent and measured at 30 ° C.

(2) Melting point The melting point is determined using a DSC 6220 type differential scanning calorimeter manufactured by SII Nano Technology. In a nitrogen atmosphere, the resin sample was heated and melted at 300 ° C. for 5 minutes, then rapidly cooled with liquid nitrogen, and 10 mg of the pulverized resin sample was heated at a rate of 20 ° C./min, and differential thermal analysis was performed. The amount of heat of crystal melting was defined as the melting peak temperature (Tpm) defined in JIS-K7121-1987, Section 9.1.

(3) Film thickness The film thickness is about 20 mm in the direction perpendicular to the longitudinal direction of the film sample cut to 210 mm in the longitudinal direction by 300 mm in the longitudinal direction using an electronic micrometer MILLITRON (Seiko Precision Machinery Sales). The measurement is performed 10 times at the position and the average value is obtained.

(4) Haze and total light transmittance The haze (cloudiness value) and total light transmittance of a film sample were measured using an NDH-300A turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd. Measured according to “Method”. As a result of the measurement, those having a haze of 3% or less were evaluated as ◯, and those having a haze exceeding 3% were evaluated as ×. Moreover, about the total light transmittance, the thing of 90% or more was set as (circle), and the thing below 90% was set as x.

(5) Plane orientation coefficient (ΔP)
According to JIS K 7142-1996 5.1 (Method A), the refractive index in the film longitudinal direction (nx), the refractive index in the width direction (ny), and the refractive index in the thickness direction (nz) using an Abbe refractometer with the sodium D line as the light source ) And the plane orientation coefficient (ΔP) was calculated by the following formula.
ΔP = (nx + ny) / 2−nz

(6) Degree of surface axis orientation Based on infrared absorption spectrum analysis in a single reflection of the polarized ATR method. The measuring surface of the sample film was set to single-reflection ATR accessory, after measuring the spectrum of the single reflection, absorption A at absorbance _{A 1340} and the wavelength 1410 cm ^-1 in the vicinity of a wavelength of 1340 cm ^-1 after optimizing the baseline ₁₄₁₀ is digitized. Based on the obtained measured value, the ratio Y represented by the following formula is obtained. The film sample is rotated in-plane every 10 ° with the initial measurement position as a base point, and the measurement is similarly performed in the range of 0 ° to 170 °.
Y = A ₁₃₄₀ / A ₁₄₁₀
Of the 18 alignment parameters, the maximum value is Y _max , the minimum value is Y _min , and Y _max / Y _min is the surface axis orientation degree. The surface axis orientation degrees Y _max and Y _min were measured on the front and back sides of the film sample, and the ratio between the front and back sides of the surface axis orientation degrees Y _max and Y _min was determined with the larger of the front and back sides as the denominator. The front / back ratio of the degree of orientation of the surface axis shown in the table indicates the smaller of the ratios determined by either Y _max or Y _min .
The measuring equipment and conditions are as follows.
Spectrometer: FTS-60A / 896 (BioRad
FTIR manufactured by DIGILAB)
Attached equipment: High-sensitivity, single-reflection diamond horizontal ATR device (SPECAC)
Light source: high brightness new ceramic detector: MCT (HgCdTe)
Resolution: 4cm ^-1
Integration count: 64 times IRE: Ge
Incident angle: 45 °
Polarizer: Wire grid, Polarization theory Detection depth: About 0.7 μm (at 1000 cm ⁻¹ )
For baseline, the baseline line connecting two bottom peak lying between 1380 ~ 1300 cm ^-1 for absorbance _{A 1340,} two bottom peak lying between 1350 ~ 1450 cm ^-1 for absorbance _{A 1410} The top peak height is obtained and measured using the line connecting the lines as the base line. Note that the infrared absorption band containing material and coating the coexisting materials, if overlaps the absorption band in the absorption band, or 1410 cm ^-1 in 1340 cm ^-1, by using the difference spectrum method, a method of calculating the intensity ratio Is adopted.

(7) Flatness of film 1
Fifty samples of 300 mm in the longitudinal direction and 210 mm in the width direction are collected from the film. This sample is placed on a horizontal glass plate (thickness 5 mm) in a room controlled at a temperature of 23 ± 2 ° C. and a humidity of 65 ± 5%, and the heights of the four corners of the film sample (vertical direction from the horizontal plane) Is measured using a microscope (trade name: VH-6300, manufactured by Keyence Corporation). When the heights of the four corners are “0” or the cross section appears to be M-shaped, the warpage is measured with the opposite surface facing up. Displays the maximum height of the four corners measured for all samples.

(8) Flatness 2 of curable resin laminate
One of the following resin compositions was applied to the surface having the smaller degree of surface axis orientation by using an applicator so as to have the following layer thickness. Using a high pressure mercury lamp with a lamp emission length of 50 cm and 160 W / cm as a light source, the resin composition was irradiated with ultraviolet rays having an irradiation amount of 1 J / cm ² (measuring instrument: manufactured by Oak Manufacturing Co., Ltd., UV-350). Was cured. Five samples cut from the curable resin laminate thus obtained to a size of 300 mm in the longitudinal direction and 210 mm in the width direction were collected. Placed on a horizontal glass plate (thickness 5 mm) with the resin composition side up, and the height of the four corners of the laminate sample in a room controlled at a temperature of 23 ± 2 ° C. and a humidity of 65 ± 5% (Height in the vertical direction from the horizontal plane) is measured using a microscope (trade name: VH-6300, manufactured by Keyence Corporation). The average height of the four corners measured in all samples is displayed.

(Curing resin composition A)
M-315 (manufactured by Toa Gosei Co., Ltd.) 100 parts by weight nonabutylene glycol dimethacrylate (PBOM) 100 parts by weight urethane acrylate (U-2PHA) (manufactured by Shin-Nakamura Chemical Co., Ltd.) 40 parts by weight Irgacure 184 (manufactured by Ciba Specialty Chemicals) ) 3 parts by mass The curing shrinkage percentage of the curable resin composition B by the following measurement method was 8.0%. The curable resin composition B was applied and laminated so that the laminated thickness after curing was 30 μm.

(Curable resin composition B)
Dipentaerythritol hexaacrylate (DPHA) 100 parts by mass Methyl ethyl ketone 100 parts by mass Toluene 100 parts by mass Irgacure 184 (manufactured by Ciba Specialty Chemicals) 4 parts by mass The curing shrinkage of curable resin composition B by the following measurement method is 11. It was 5%. The curable resin composition B was applied and laminated so that the laminated thickness after curing was 10 μm.

(9) Curing Shrinkage The specific gravity before and after curing of the hard coat layers obtained in Examples and Comparative Examples was measured. The specific gravity is measured according to JIS-K-6833. The cure shrinkage was measured by the following formula.
(Curing shrinkage) = [{(specific gravity before cured product) − (specific gravity before curing)} / (specific gravity before curing)] × 100

(10) Light transmittance at a wavelength of 380 nm Using a spectrophotometer (manufactured by Hitachi, U-3500 type), the light transmittance in a wavelength region of 300 to 500 nm is measured using an air layer as a standard, and the transmittance at a wavelength of 380 nm is obtained. Asked.

[Example 1]
(Preparation of coating solution)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method, and as a dicarboxylic acid component (based on the total dicarboxylic acid component) 46 mol% terephthalic acid, 46 mol% isophthalic acid and 8 mol% sodium 5-sulfonatoisophthalate, A water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of 50 mol% ethylene glycol and 50 mol% neopentyl glycol as a glycol component (based on the entire glycol component) was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, 0.06 parts by mass of a nonionic surfactant were mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal base-containing copolymer polyester resin and continuing to stir until the resin is no longer agglomerated, the resin water dispersion is cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A uniform water-dispersible copolymerized polyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silysia Co., Ltd.) in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolyester resin solution was mixed with 99.46 parts by mass of the silicia 310. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added with stirring to obtain a coating solution.

(Film production)
As a raw material polymer, polyethylene terephthalate (PET) resin pellets (melting point: 256 ° C.) containing no particles and having an intrinsic viscosity of 0.62 dl / g were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours. Next, the dried PET resin pellets were supplied to an extruder, melted and extruded into a sheet at about 285 ° C., and rapidly cooled and solidified on a metal roll maintained at a surface temperature of 22 ° C. to obtain an unstretched sheet.

After heating the film temperature of the obtained unstretched sheet with a heated roll group, an infrared heater (first infrared ray) provided between the nip rolls between the first nip roll and the second nip roll arranged in front and back. While being heated by a heater, the film was stretched 2.77 times in the longitudinal direction (longitudinal direction) (first longitudinal stretching). At this time, in the first infrared heater, assuming that the infrared output on the front side was 100%, the infrared output on the back side was 90%. Here, the rear second nip roll was cooled.

Thereafter, while the film after the longitudinal stretching is heated by the infrared heater (second infrared heater) provided between the second nip roll and the third nip roll disposed immediately thereafter, the longitudinal direction ( The film was stretched 1.17 times in the longitudinal direction (second-stage longitudinal stretching). Further, the film was stretched 1.08 times in the longitudinal direction (longitudinal direction) while being heated by an infrared heater (third infrared heater) provided between the nip rolls between the third nip roll and the fourth nip roll disposed immediately thereafter. (Third-stage longitudinal stretching). In the second and third infrared heaters, assuming that the infrared output on the front side is 100%, the infrared output on the back side is 95%. It should be noted that the relationship between the output of the infrared heater and the surface temperature is measured in advance with a model machine, and the temperature difference on the film surface is adjusted while adjusting the average temperature of the film to 100 ° C. according to the above settings. The first stage was adjusted to 2 ° C., the second stage to 3 ° C., and the third stage to 3 ° C.

The coating solution was applied to both sides of the obtained uniaxially stretched polyester film so that the final coating layer thickness was 0.08 g / m ^2, and then dried at 135 ° C.

The coated film was guided to a tenter and subjected to transverse stretching of 4 times at 135 ° C. Thereafter, a heat setting treatment was performed at 233 ° C., and a transverse relaxation treatment of 2.2% was performed at 225 ° C. This obtained the 125-micrometer-thick polyester film for laminated | stacking cured resin with a coating layer. Furthermore, a curable resin laminate was produced using the curable resin composition A. The properties of the obtained film and laminate are shown in Table 1.

[Example 2]
Adjust the take-up speed of the unstretched sheet to change the thickness of the unstretched sheet, and longitudinal stretching is 2.53 times in the first stage, 1.17 times in the second stage, and 1.08 times in the third stage. Except having changed the magnification, it carried out like Example 1 and obtained the polyester film for laminated | stacking cured resin with a coating layer with a thickness of 125 micrometers. The properties of the obtained film and laminate are shown in Table 1.

[Example 3]
The thickness of the unstretched sheet was changed by adjusting the take-up speed of the unstretched sheet, and the longitudinal stretching was changed to a two-stage stretching of 2.6 times in the first stage and 1.27 times in the second stage. % Was performed in the same manner as in Example 1 except that a temperature difference between the front and back sides was provided as shown in Table 1 to obtain a 188 μm thick cured resin laminated polyester film with a coating layer. The properties of the obtained film and laminate are shown in Table 1.

[Example 4]
Adjust the take-up speed of the unstretched sheet to change the thickness of the unstretched sheet, and carry out in the same manner as in Example 3 except that a temperature difference between the front and back sides is provided as shown in Table 1. A polyester film for resin lamination was obtained. The properties of the obtained film and laminate are shown in Table 1.

[Example 5]
When producing a laminated body using the film obtained in Example 4, the film and the laminated body were obtained similarly to Example 4 except having used curable resin composition B. The properties of the obtained film and laminate are shown in Table 1.

[Example 6]
A polyethylene terephthalate (PET) resin pellet A containing no inert particles and having an intrinsic viscosity of 0.62 dl / g was dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours. Subsequently, the dried PET pellets were supplied to the A layer extruder (1). As a raw material for the B layer, the above-described resin pellet A and resin pellet B having an intrinsic viscosity of 0.62 dl / g containing 1500 ppm of irregular-shaped massive silica particles having an average particle size of 2.3 μm are mixed at a ratio of 80:20. Then, it was dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours. Next, the dried PET pellets were supplied to the B layer extruder (2). After the polymer supplied to the extruder is melted at 285 ° C., each is filtered with a filter medium having a filtration particle size (initial filtration efficiency of 95%) of 15 μm, and laminated so as to be B layer / A layer / B layer, After adjusting the discharge rate of the extruder so that the lamination ratio becomes 5/90/5, co-extrusion from the T die at 285 ° C in layers, adjusting the take-up speed of the unstretched sheet and changing the thickness of the unstretched sheet And rapidly solidified on a metal roll maintained at a surface temperature of 22 ° C. to obtain an unstretched sheet. A polyester film for curable resin lamination with a coating layer having a thickness of 300 μm was obtained in the same manner as in Example 1 except that the obtained unstretched sheet was used. The properties of the obtained film and laminate are shown in Table 1.

[Example 7]
The unstretched film obtained in the same manner as in Example 1 was heated only on the surface by an infrared heater provided immediately before the first nip roll, and a temperature difference between the front and back of the film as shown in Table 1 was provided. Thereafter, a curable resin-laminated film with a coating layer was obtained in the same manner as in Example 1 except that the film was longitudinally stretched. The properties of the obtained film and laminate are shown in Table 1.

[Example 8]
The unstretched film obtained in the same manner as in Example 4 was heated only at the surface by high-speed heated air provided immediately before the first nip roll, and a temperature difference between the front and back of the film as shown in Table 1 was provided. Thereafter, a curable resin-laminated film with a coating layer was obtained in the same manner as in Example 4 except that the film was longitudinally stretched. The properties of the obtained film and laminate are shown in Table 1.

[Example 9]
Adjusting the take-up speed of the unstretched sheet and changing the thickness of the unstretched sheet, the longitudinal stretching is 3.00 times in the first stage, 1.17 times in the second stage, and 1.08 times in the third stage. Except having changed the magnification, it carried out like Example 1 and obtained the polyester film for laminated | stacking cured resin with a coating layer with a thickness of 125 micrometers. The properties of the obtained film and laminate are shown in Table 1.

[Example 10]
Adjust the take-up speed of the unstretched sheet to change the thickness of the unstretched sheet, and carry out in the same manner as in Example 1 except that a temperature difference between the front and back sides is provided as shown in Table 1. A polyester film for resin lamination was obtained. The properties of the obtained film and laminate are shown in Table 1.

[Example 11]
Implemented except changing the thickness of the unstretched sheet by adjusting the take-up speed of the unstretched sheet, changing the longitudinal stretching to 3.5-fold stretching in the first stage, and providing a temperature difference between the front and back as shown in Table 1. It carried out like Example 4 and obtained the polyester film for hardening resin lamination with a coating layer of thickness 250 micrometers. The properties of the obtained film and laminate are shown in Table 1.

[Comparative Example 1]
Example obtained after obtaining an unstretched sheet in the same manner as in Example 1 and then adjusting the output of the infrared heaters in the first and second stages of the longitudinal stretching so that there was no difference in output between the front and back sides. In the same manner as in Example 1, a curable resin laminating film with a coating layer was obtained. The properties of the obtained film and laminate are shown in Table 1.

[Comparative Example 2]
Adjust the take-up speed of the unstretched sheet to change the thickness of the unstretched sheet, and carry out in the same manner as in Example 3 except that a temperature difference between the front and back sides is provided as shown in Table 1. A polyester film for resin lamination was obtained. The properties of the obtained film and laminate are shown in Table 1.

[Comparative Example 3]
Adjust the take-up speed of the unstretched sheet to change the thickness of the unstretched sheet, and longitudinal stretching is 2.37 times in the first stage, 1.17 times in the second stage, and 1.08 times in the third stage. A coating layer having a thickness of 125 μm was carried out in the same manner as in Example 1 except that the magnification was changed, the average stretching temperature of the film during longitudinal stretching was changed to 115 ° C., and the lateral stretching was stretched 4 times at 140 ° C. A polyester film for laminating cured resin was obtained. The properties of the obtained film and laminate are shown in Table 1.

[Comparative Example 4]
As a raw material for the C layer, polyethylene terephthalate (PET) resin pellets C containing no inert particles and having an intrinsic viscosity of 0.58 dl / g were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours. Subsequently, the dried PET pellets were supplied to the C layer extruder (1). As a raw material for the D layer, resin pellets D containing no inert particles and having an intrinsic viscosity of 0.62 dl / g were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours. Subsequently, the dried PET pellets were supplied to the D layer extruder (2). After the polymer supplied to the extruder is melted at 285 ° C., each is filtered through a filter medium having a filtration particle size (initial filtration efficiency of 95%) of 15 μm and laminated so as to be a C layer / D layer. After adjusting the discharge rate of the extruder so as to be 30/70, co-extrusion from a T die to a layer at 285 ° C., adjusting the take-up speed of the unstretched sheet, changing the thickness of the unstretched sheet, and a surface temperature of 22 It was rapidly cooled and solidified on a metal roll kept at ° C. to obtain an unstretched sheet. A polyester film for laminating a cured resin with a coating layer having a thickness of 125 μm was obtained in the same manner as in Comparative Example 1 except that the obtained unstretched sheet was used. The properties of the obtained film and laminate are shown in Table 1.

[Example 12]
(Preparation of coating solution)
A transesterification reaction and a polycondensation reaction were carried out by a conventional method, and as a dicarboxylic acid component (based on the total dicarboxylic acid component) 46 mol% terephthalic acid, 46 mol% isophthalic acid and 8 mol% sodium 5-sulfonatoisophthalate, A water-dispersible sulfonic acid metal base-containing copolymer polyester resin having a composition of 50 mol% ethylene glycol and 50 mol% neopentyl glycol as a glycol component (based on the entire glycol component) was prepared. Next, 51.4 parts by mass of water, 38 parts by mass of isopropyl alcohol, 5 parts by mass of n-butyl cellosolve, 0.06 parts by mass of a nonionic surfactant were mixed and then heated and stirred. After adding 5 parts by mass of a water-dispersible sulfonic acid metal base-containing copolymer polyester resin and continuing to stir until the resin is no longer agglomerated, the resin water dispersion is cooled to room temperature to obtain a solid content concentration of 5.0% by mass. A uniform water-dispersible copolymerized polyester resin liquid was obtained. Furthermore, after dispersing 3 parts by mass of aggregated silica particles (Silicia 310, manufactured by Fuji Silysia Co., Ltd.) in 50 parts by mass of water, 99.46 parts by mass of the water-dispersible copolyester resin solution was mixed with 99.46 parts by mass of the silicia 310. 0.54 parts by mass of the aqueous dispersion was added, and 20 parts by mass of water was added with stirring to obtain a coating solution.

(Film production)
10 parts by weight of a dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), PET resin pellets containing no particles (with intrinsic viscosity 0.62 dl / g) 90 parts by weight were mixed, and an ultraviolet absorbent-containing masterbatch (A) was prepared using a kneading extruder, and the extrusion temperature at this time was 285 ° C.

As a raw material for the film intermediate layer, 90 parts by weight of PET resin pellets having an intrinsic viscosity of 0.62 dl / g not containing particles and 10 parts of an ultraviolet absorber-containing master batch (A) were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours. Thereafter, polyethylene terephthalate pellets (inherent viscosity: 0.62 dl / g) containing no particles were supplied to the extruder (for the outermost layer) in an extruder (for the intermediate layer) and dissolved at 285 ° C. These two polymers are each filtered through a filter material of stainless steel sintered body (nominal filtration accuracy 10 μm particle 95% cut), laminated in a three-layer confluence block, extruded into a sheet form from the die, and then electrostatically applied. The film was wound around a casting drum having a surface temperature of 22 ° C. using a casting method and solidified by cooling to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the thickness ratio was 5: 90: 5.

The coated film was guided to a tenter and subjected to transverse stretching of 4 times at 135 ° C. Thereafter, a heat setting treatment was performed at 233 ° C., and a transverse relaxation treatment of 2.2% was performed at 225 ° C. This obtained the 125-micrometer-thick polyester film for laminated | stacking cured resin with a coating layer. Furthermore, a curable resin laminate was produced using the curable resin composition A. The properties of the obtained film and laminate are shown in Table 2.

[Example 13]
Adjust the take-up speed of the unstretched sheet to change the thickness of the unstretched sheet, and longitudinal stretching is 2.53 times in the first stage, 1.17 times in the second stage, and 1.08 times in the third stage. Except having changed the magnification, it carried out similarly to Example 12, and obtained the polyester film for cured resin lamination | stacking with a coating layer of thickness 125 micrometers. The properties of the obtained film and laminate are shown in Table 2.

[Example 14]
The thickness of the unstretched sheet was changed by adjusting the take-up speed of the unstretched sheet, and the longitudinal stretching was changed to a two-stage stretching of 2.6 times in the first stage and 1.27 times in the second stage. % Was performed in the same manner as in Example 12 except that a temperature difference between the front and back sides was provided as shown in Table 2 to obtain a 188 μm thick cured resin laminated polyester film with a coating layer. The properties of the obtained film and laminate are shown in Table 2.

[Example 15]
The thickness of the unstretched sheet was changed by adjusting the take-up speed of the unstretched sheet, and the same procedure as in Example 14 was performed except that a temperature difference between the front and back sides was provided as shown in Table 2. Curing with a 250 μm thick coating layer A polyester film for resin lamination was obtained. The properties of the obtained film and laminate are shown in Table 2.

[Example 16]
When producing a laminated body using the film obtained in Example 15, the film and the laminated body were obtained similarly to Example 15 except having used the curable resin composition B. The properties of the obtained film and laminate are shown in Table 2.

[Example 17]
The unstretched film obtained in the same manner as in Example 12 was heated only on the surface by an infrared heater provided immediately before the first nip roll, and a temperature difference between the front and back of the film as shown in Table 2 was provided. Thereafter, a curable resin-laminated film with a coating layer was obtained in the same manner as in Example 12 except that the film was longitudinally stretched. The properties of the obtained film and laminate are shown in Table 2.

[Example 18]
The unstretched film obtained in the same manner as in Example 15 was heated only at the surface by high-speed heated air provided immediately before the first nip roll, and a temperature difference between the front and back of the film as shown in Table 2 was provided. Thereafter, a curable resin-laminated film with a coating layer was obtained in the same manner as in Example 15 except that the film was longitudinally stretched. The properties of the obtained film and laminate are shown in Table 2.

[Example 19]
As a raw material for the intermediate layer of the film, 80 parts by weight of PET resin pellets having an intrinsic viscosity of 0.62 dl / g not containing particles and 6 parts of an ultraviolet absorber-containing masterbatch (A), the thickness ratio is 5: 90: 5 A curable resin-laminated film with a coating layer was obtained in the same manner as in Example 12 except that it was not changed. The properties of the obtained film and laminate are shown in Table 2.

[Example 20]
2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol (manufactured by Asahi Denka Co., Ltd., LA31) 10 parts by weight and 90 parts by weight of PET resin pellets (inherent viscosity 0.62 dl / g) containing no particles were mixed, and an ultraviolet absorbent-containing master batch (B) was prepared using a kneading extruder. The extrusion temperature at this time was 285 ° C.

As a raw material for the base film intermediate layer, 90 parts by weight of PET resin pellets having an intrinsic viscosity of 0.62 dl / g containing no particles and 10 parts of a UV-absorbing masterbatch (B) were vacuum-dried at 135 ° C. for 6 hours (1 Torr Then, polyethylene terephthalate pellets (inherent viscosity: 0.62 dl / g) containing no particles were supplied to the extruder (for the outermost layer), respectively, and melted at 285 ° C. in the extruder (for the intermediate layer). A curable resin-laminated film with a coating layer was obtained in the same manner as in Example 12 except that these two polymers were used. The properties of the obtained film and laminate are shown in Table 2.

[Comparative Example 3]
Example: Except for obtaining an unstretched sheet in the same manner as in Example 12, and adjusting the output of the first and second infrared heaters in the longitudinal stretching to perform longitudinal stretching so that there is no difference between the front and back outputs. In the same manner as in No. 12, a curable resin-laminated film with a coating layer was obtained. The properties of the obtained film and laminate are shown in Table 2.

[Comparative Example 4]
Adjust the take-up speed of the unstretched sheet to change the thickness of the unstretched sheet, and longitudinal stretching is 2.37 times in the first stage, 1.17 times in the second stage, and 1.08 times in the third stage. A coating layer having a thickness of 125 μm was carried out in the same manner as in Example 12 except that the magnification was changed, the average stretching temperature of the film during longitudinal stretching was changed to 115 ° C., and the lateral stretching was stretched 4 times at 140 ° C. A polyester film for laminating cured resin was obtained. The properties of the obtained film and laminate are shown in Table 2.

The polyethylene terephthalate resin film of the present invention is excellent in flatness and suitable as a base film for a laminate. For example, various optical films such as lens film, diffusion film, hard coat film, NIR film, touch panel, ITO, protective film for solar cell, back sheet for solar cell, polarizing plate protective film, polarizer protective film, etc. Suitable as a base film. Further, it is also suitable as a base film for use as a building material for applying and laminating a curable coating agent, a recording material using a curable resin ink or the like, a use for a laminate member using two or more films bonded together.

Claims

A biaxially stretched polyester film made of polyethylene terephthalate resin,
A biaxially stretched polyester film for laminating a curable resin that satisfies the following requirements (1) to (3).
(1) Thickness is 30 to 500 μm (2) Plane orientation degree ΔP is 0.150 to 0.180 (3) Surface axis orientation degree Y max or Y min determined by the following method The front-to-back ratio is 0.80 to 0.98 (surface-axis orientation degree front-to-back ratio)
For film samples, determine the absorbance A 1340 and the absorbance A 1410 in the vicinity of a wavelength 1410 cm -1 in the vicinity of wavelength 1340 cm -1 by the polarization ATR method, determining the ratio Y represented by the following formula. Starting from the first measured point, the film sample is rotated in-plane every 10 ° and measured in the same manner in the range of 0 ° to 170 °. The maximum value and the minimum value among the obtained 18 points are defined as surface axis orientation degrees Y max and Y min . The surface axis orientation degrees Y max and Y min are measured on the front and back sides of the film sample, and the ratio between the front and back sides of the surface axis orientation degrees Y max and Y min is determined using the larger value of the front and back sides as the denominator.
Y = A 1340 / A 1410
The biaxially stretched polyester film for curable resin lamination according to claim 1, wherein the biaxially stretched polyester film has a three-layer structure having an intermediate layer containing an ultraviolet absorber.
A biaxially stretched polyester film for curable resin lamination with a coating layer having a coating layer on at least one side of the biaxially stretched polyester film for curable resin lamination according to claim 1 or 2,
The coating layer is mainly composed of at least one of a copolyester resin, an acrylic resin, and a polyurethane resin.
Biaxially stretched polyester film for curable resin lamination with a coating layer.
A curable resin laminate having a curable resin layer using the biaxially stretched polyester film for curable resin lamination according to claim 1 or 2 as a base film.
A curable resin laminate having a curable resin layer using the biaxially stretched polyester film for curable resin laminate with a coating layer according to claim 3 as a base film.