Biaxially oriented polyester film roll

Abstract

The present invention aims to provide a polyester film roll with excellent printability and processability, having a very low antimony content, low impurities, excellent transparency, and heat resistance, while also being resistant to loosening of the film roll immediately after film formation and resistant to loosening of the film roll over time even when stored for a long period. To solve the above problem, the polyester film roll of the present invention is a film roll formed by winding a biaxially stretched polyester film having an antimony content of 10 ppm or less, a phosphorus content of 25 ppm or more and 75 ppm or less, and an average roughness of the film surface of 0.02 μm or more and 0.05 μm or less, and the biaxially stretched polyester film and the film roll are characterized by satisfying the following requirements (1) to (6). (1) Film roll winding length is 8,000 m or more and 80,000 m or less (2) Film roll width is 500 mm or more and 4000 mm or less (3) The average hardness of the outermost layer of the above film roll, when measured at intervals of 50 mm in the film width direction, is in the range of 500 or more and 700 or less. (4) When the hardness of the outermost layer of the above film roll is measured at intervals of 50 mm in the film width direction, the deviation of the hardness is 10% or more and 20% or less. (5) Film thickness is 5 µm or more and 40 µm or less (6) In the thickness non-uniformity in the film width direction on the surface layer of the film roll, the thickness pattern has a concave area, and in the concave area with the largest thickness difference (maximum concave area), the thickness non-uniformity of the maximum concave area calculated from the maximum thickness difference in the maximum concave area and the average film thickness is 10% or less.

Description

Technology Field

[0001] The present invention relates to a biaxially stretched polyester film roll with excellent hygiene properties, and more specifically, to a biaxially stretched polyester film roll that does not develop wrinkles or the like even after long-term storage following film formation, and does not cause problems during processing steps such as printing or bag manufacturing, making it suitable for use in food packaging bags or labels. Background Technology

[0002] Polyester resins, such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), which are thermoplastic resins with excellent heat resistance and mechanical properties, are used in a wide variety of fields including plastic films, electronics, energy, packaging materials, and automobiles. Among plastic films, biaxially stretched PET films are widely used in industrial and packaging fields because they offer an excellent balance of mechanical strength, heat resistance, dimensional stability, chemical resistance, optical properties, and cost.

[0003] In the field of industrial films, they can be used as functional films for flat panel displays (FPDs), such as liquid crystal displays and plasma displays, due to their excellent transparency. Additionally, PET films with hydrolytic resistance are also used as backsheet films for solar cells, and are used for various purposes as functional films and base films.

[0004] In the field of packaging films, they are utilized for food packaging and as gas barrier films. In particular, films with excellent gas barrier properties are used as packaging materials requiring airtightness for foods, pharmaceuticals, and electronic components, or as gas barrier materials, and demand has been rising recently. It is common practice to perform deposition processing using film rolls to impart barrier properties.

[0005] Recently, in order to improve productivity, the processing of deposited polyester films has been accelerating, and the film rolls used as substrates have been widened and lengthened. However, with the widening and lengthening of the rolls, problems have arisen such as deterioration of running performance, winding wrinkles, winding misalignment, and spiking wrinkles, which can cause localized staining or omission of the deposited film, resulting in deterioration of gas barrier properties, or wrinkles occurring during winding after deposition, leading to appearance defects and making the product unusable.

[0006] In addition, packaging bags are often discarded as waste, so thinning is required for environmental reasons. As the thickness decreases, rigidity is reduced, leading to defects in the appearance of the film roll during storage after slitting the film, which reveals problems. Consequently, troubles arise when printing or processing the film roll. In particular, there is a problem where the flatness is poor at locations where loosening occurs, and printing omissions occur at locations where loosening occurs in the width direction of the film roll, resulting in losses. The inventors have newly discovered that these problems, caused by loosening and changes in appearance due to storage, have become more pronounced due to thinning of the film and increased printing speed and multi-color printing. Consequently, it is difficult to apply to film rolls that have loosening within a range that was previously accepted without being a problem.

[0007] As a method to improve these problems, a film roll winding method has been proposed in which the surface pressure by the contact pressure roll is increased in the surface layer compared to the surface pressure in the winding core part (Patent Document 1). However, the aforementioned Patent Document 1 describes winding hardness, winding surface pressure, and winding tension to prevent misalignment between the surface layer wrinkles and the winding core wrinkles, but does not describe changes in the appearance of the film roll due to long-term storage.

[0008] In addition, since food packaging films come into direct contact with food, it is desirable for the polyester film to have minimal foreign substances from a hygiene perspective. Furthermore, because the antimony catalyst used in the process of producing (polymerizing) the polyester raw material has the potential to be carcinogenic, it is desirable for the polyester film to contain as little antimony as possible or not at all. Conventional examples include polyester raw materials that do not use antimony catalysts, as described in Patent Documents 2 and 3. However, methods for reducing film foreign substances and desired film characteristics are not described. Prior art literature

[0009] Japanese Patent Publication No. Sho 63-252853, Japanese Patent No. 3461175, Japanese Patent No. 3506236, Japanese Patent Publication No. 2001-151907 The problem to be solved

[0010] The objective of the present invention is to provide a biaxially stretched polyester film roll that has a very low antimony content, low impurities, excellent transparency, and heat resistance, and is not only unlikely to loosen immediately after film formation but also unlikely to loosen over time even when stored for a long period, thereby making it difficult to cause defects during printing processing. means of solving the problem

[0011] As a result of careful examination by the inventors, it was discovered that in a slitting process in which a polyester film having a desired surface roughness is slit from a master roll to an arbitrary width without using antimony to form a product roll, by controlling the winding tension after slitting and the contact pressure of the contact roll, the hardness of the roll can be kept within the above-mentioned range, and the film roll is less likely to become loose after long-term storage, and thus the present invention was completed.

[0012] The present invention is composed of the following components.

[0013] 1. A biaxially stretched polyester film roll formed by winding a film having an antimony content of 10 ppm or less, a phosphorus content of 25 ppm or more and 75 ppm or less, and an average roughness of the film surface of 0.02 μm or more and 0.05 μm or less, wherein the biaxially stretched polyester film and the film roll satisfy the following requirements (1) to (6).

[0014] (1) Film roll winding length is 8,000 m or more and 80,000 m or less

[0015] (2) Film roll width is 500 mm or more and 4000 mm or less

[0016] (3) The average hardness of the outermost layer of the above film roll, when measured at intervals of 50 mm in the film width direction, is in the range of 500 or more and 700 or less.

[0017] (4) When the hardness of the outermost layer of the above film roll is measured at intervals of 50 mm in the film width direction, the deviation of the hardness is 10% or more and 20% or less.

[0018] (5) Film thickness is 5 µm or more and 40 µm or less

[0019] (6) In the thickness non-uniformity in the film width direction on the surface layer of the film roll, the thickness pattern has a concave area, and in the concave area with the largest thickness difference (maximum concave area), the thickness non-uniformity of the maximum concave area calculated from the maximum thickness difference in the maximum concave area and the average film thickness is less than 10%

[0020] 2. A biaxially stretched polyester film roll as described in 1., wherein, regarding the thickness non-uniformity in the width direction of the film of each sample sampled at intervals of a winding length of 1000 m from the surface layer of the film roll, the thickness non-uniformity calculated from the maximum thickness difference at the maximum concave part and the average film thickness is 10% or less of the total sample.

[0021] 3. A biaxially stretched polyester film roll as described in either 1 or 2, wherein the absolute value of the difference in widthwise refractive index with the maximum thickness point at either end of the concave portion in the maximum concave portion is 0.010 or less.

[0022] 4. A biaxially stretched polyester film roll as described in any one of 1 to 3, characterized by having a defect count of 1 mm or more per 10,000 square meters of film of 1.0 or less.

[0023] 5. A biaxially stretched polyester film roll as described in any one of 1 to 4, wherein the coefficient of static friction and the coefficient of dynamic friction of the outer and inner surfaces of the film are both 0.1 or higher and 0.8 or lower.

[0024] 6. A biaxially stretched polyester film roll as described in any one of 1 to 5, characterized in that the film's intrinsic viscosity is 0.51 dL / g or higher and 0.70 dL / g or lower.

[0025] 7. A method for manufacturing a biaxially stretched polyester film roll as described in any one of 1 to 6, characterized by melt-extruding a raw polyester resin such that the difference between the intrinsic viscosity of the raw polyester resin and the intrinsic viscosity of the polyester film is 0.06 dL / g or less, then cooling and solidifying to obtain an unoriented film, then biaxially stretching the unoriented film, then performing a heat-setting treatment, then winding the biaxially stretched film as a master roll, and then slitting the master roll to wind it into a roll shape. Effects of the invention

[0026] According to the present invention, it is possible to provide a biaxially stretched polyester film roll that has a very low antimony content, low impurities, excellent transparency, and heat resistance, and is less prone to loosening of the film roll immediately after film formation, and is also less prone to loosening of the film roll over time even when stored for a long period, thereby making it less likely to cause defects during printing processing. Brief explanation of the drawing

[0027] FIG. 1 is a drawing showing the maximum concave portion in the thickness non-uniformity in the width direction of the film of the present invention. FIG. 2 is a drawing showing an example of a film transverse stretching (TD) process of the present invention. FIG. 3 is a diagram showing an example of a cooling process in the film transverse stretching (TD) process of the present invention. Specific details for implementing the invention

[0028] Embodiments of the present invention are described below. However, the present invention is not to be interpreted as being limited to embodiments including the following examples, and various modifications may naturally be made within the scope of achieving the purpose of the invention and without departing from the essence of the invention.

[0029] (Raw material polyester resin)

[0030] The biaxially stretched polyester film of the present invention comprises a polyethylene terephthalate-based resin as a component. Here, the polyethylene terephthalate-based resin contains an ethylene glycol-derived component and a terephthalic acid-derived component as main components. "Main components" means that terephthalic acid is 80 mol% or more of the total 100 mol% of the dicarboxylic acid components, and ethylene glycol is 80 mol% or more of the total 100 mol% of the glycol components.

[0031] Other dicarboxylic acid components and glycol components may be copolymerized as long as it does not impede the purpose of the present invention. The copolymerization amount of other dicarboxylic acid components and glycol components is preferably less than 20 mol% and 10 mol% or less, and particularly preferably 5 mol% or less, with respect to the total dicarboxylic acid components or the total glycol components.

[0032] Examples of other dicarboxylic acid components mentioned above include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, 4,4'-dicarboxybiphenyl, and 5-sodium sulfoisophthalic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,5-norbornene dicarboxylic acid, and tetrahydrophthalic acid, or aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, undecane dicarboxylic acid, dodecane dicarboxylic acid, octadecane dicarboxylic acid, fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, and dimer acid.

[0033] The other glycol components mentioned above include aliphatic glycols such as 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1,3-propanediol, 1,10-decanediol, dimethyloltricyclodecane, diethylene glycol, and triethylene glycol; ethylene oxide adducts or propylene oxide adducts of bisphenol A, bisphenol S, bisphenol C, bisphenol Z, bisphenol AP, and 4,4'-biphenol; alicyclic glycols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; polyethylene glycol, polypropylene glycol, etc. It is possible.

[0034] Any manufacturing method may be used as a polymerization method for such polyethylene terephthalate-based resins, such as a direct polymerization method in which terephthalic acid and ethylene glycol, and optionally other dicarboxylic acid components and glycol components are directly reacted, and an ester exchange method in which a dimethyl ester of terephthalic acid (including a methyl ester of an optional dicarboxylic acid) and ethylene glycol (including optionally other glycol components) are subjected to an ester exchange reaction followed by a polycondensation reaction.

[0035] As a polyester resin, it is also possible to use recycled resin made from recycled PET bottles or polyester resin containing biomass-derived monomer components.

[0036] As a component of the biaxially stretched polyester film of the present invention, other resins such as polyamide, polystyrene, polyolefin, and polyester other than those mentioned above may be included, but from the perspective of the mechanical properties and heat resistance of the biaxially stretched polyester film, the content of other resins is preferably 30 mass% or less, further 20 mass% or less, further 10 mass% or less, particularly 5 mass% or less, with respect to the total resin component of the polyester film, and most preferably 0 mass% (the total resin component constituting the polyester film is substantially a polyethylene terephthalate-based resin).

[0037] In addition, the intrinsic viscosity of the above polyethylene terephthalate-based resin is preferably in the range of 0.57 to 0.76 dL / g, more preferably 0.60 to 0.73 dL / g, and even more preferably 0.63 to 0.7 dL / g. If the intrinsic viscosity is lower than 0.57 dL / g, the film is prone to tearing (so-called breakage) during the production of the polyester film, and if it is higher than 0.76 dL / g, the increase in filter pressure becomes large, making high-precision filtration difficult, and thus making it difficult to extrude the resin through a filter.

[0038] In addition, the intrinsic viscosity of the resin of the polyester film is preferably in the range of 0.51 to 0.70 dL / g, more preferably 0.56 to 0.68 dL / g, and even more preferably 0.59 to 0.65 dL / g. If the intrinsic viscosity is lower than 0.51 dL / g, the polyester film is prone to tearing during processing steps such as printing, and if the intrinsic viscosity is higher than 0.76 dL / g, the effect of improving mechanical properties is prone to reaching a saturation state.

[0039] (Polymerization catalyst)

[0040] Next, the polymerization catalyst used to manufacture the raw polyester resin used in the present invention will be described. The polymerization catalyst used in the present invention is characterized by having the ability to promote esterification. In the present invention, it is preferable not to use polymerization catalysts of antimony compounds, such as antimony trioxide, which are conventionally used as described below, as much as possible. As such a polymerization catalyst, it is preferable to have a polymerization catalyst comprising one or more selected from aluminum compounds and one or more selected from phosphorus-based compounds.

[0041] When synthesizing the raw material polyester resin used in the present invention, known aluminum compounds may be used without limitation as the aluminum compound constituting the polymerization catalyst used.

[0042] Specifically, aluminum compounds include aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum chloride hydroxide, aluminum acetylacetonate, aluminum oxalate, and other organic aluminum compounds, as well as their partial hydrolysates. Among these, carboxylates, inorganic salts, and chelate compounds are preferred, and among these, aluminum acetate, basic aluminum acetate, aluminum lactate, aluminum chloride, aluminum hydroxide, aluminum chloride hydroxide, and aluminum acetylacetonate are more preferred, aluminum acetate, basic aluminum acetate, aluminum chloride, aluminum hydroxide, and aluminum chloride hydroxide are even more preferred, and aluminum acetate and basic aluminum acetate are most preferred.

[0043] The amount of aluminum compound used in the polymerization catalyst of the present invention is preferably 1 to 80 ppm with respect to the total mass of the polyester resin obtained as aluminum atoms, more preferably 2 to 60 ppm, even more preferably 3 to 50 ppm, particularly preferably 5 to 40 ppm, and most preferably 10 to 30 ppm.

[0044] If it falls below the above level, there is a possibility of poor catalyst activity, and if it exceeds the above level, there is a possibility of the formation of aluminum-based foreign substances.

[0045] Even if the aluminum compound is placed under a reduced pressure environment during polyester polymerization, almost 100% of the amount used remains, so the amount used can be considered as the amount remaining.

[0046] Phosphoric compounds used in polymerization catalysts are not particularly limited, but it is desirable to use phosphonic acid compounds or phosphinic acid compounds because they have a significant effect on improving catalytic activity, and among these, it is particularly desirable to use phosphonic acid compounds because they have a particularly significant effect on improving catalytic activity.

[0047] Among these phosphorus compounds, phosphorus compounds having a phenol group within the same molecule are preferred. While phosphorus compounds having a phenol structure are not particularly limited, it is preferable to use one or more compounds selected from the group consisting of phosphonic acid compounds and phosphinic acid compounds having a phenol group within the same molecule, as this significantly enhances catalytic activity. Among these, it is particularly preferable to use one or more phosphonic acid compounds having a phenol group within the same molecule, as this significantly enhances catalytic activity.

[0048] In addition, phosphorus compounds having a phenol group within the same molecule include compounds represented by the following general formulas (Chemical Formula 1) and (Chemical Formula 2).

[0049]

[0050]

[0051] (Among formulas (Chemical Formula 1) to (Chemical Formula 2), R 1 represents a hydrocarbon group having 1 to 50 carbon atoms including a phenolic portion, a substituent such as a hydroxyl group, a halogen group, an alkoxy group, or an amino group, and a hydrocarbon group having 1 to 50 carbon atoms including a phenolic portion. R 4 represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, or a hydrocarbon group having 1 to 50 carbon atoms comprising a substituent such as a hydroxyl group, a halogen group, an alkoxyl group, or an amino group. R 2 , R 3 Each represents independently hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, or a hydrocarbon group having 1 to 50 carbon atoms comprising a substituent such as a hydroxyl group or an alkoxyl group. However, the hydrocarbon group may include a branched structure, an alicyclic structure such as cyclohexyl, or an aromatic structure such as phenyl or naphthyl. R 2 and R 4 The ends of the ends may be connected.)

[0052] Examples of phosphorus compounds having a phenol group within the same molecule include p-hydroxyphenylphosphonic acid, p-hydroxyphenylphosphonic acid dimethyl, p-hydroxyphenylphosphonic acid diethyl, p-hydroxyphenylphosphonic acid diphenyl, bis(p-hydroxyphenyl)phosphonic acid, bis(p-hydroxyphenyl)phosphonic acid methyl, bis(p-hydroxyphenyl)phosphonic acid phenyl, p-hydroxyphenylphenylphosphonic acid, p-hydroxyphenylphenylphosphonic acid methyl, p-hydroxyphenylphenylphosphonic acid phenyl, p-hydroxyphenylphosphonic acid, p-hydroxyphenylphosphonic acid methyl, p-hydroxyphenylphosphonic acid phenyl, p-hydroxyphenylphosphonic acid, p-hydroxyphenylphosphonic acid methyl, p-hydroxyphenylphosphonic acid phenyl, etc. In addition, phosphorus compounds represented by the following general formula (Chemical Formula 3) may be cited.

[0053]

[0054] In formula (chemical formula 3), X1 and X2 each represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a metal with 1 or more valence.

[0055] In addition, X1 may have a metal with a valence of 2 or higher, and X2 may not exist. Furthermore, an anion corresponding to the excess valence of the metal may be placed in the phosphorus compound.

[0056] As metals, Li, Na, K, Ca, Mg, and Al are preferred.

[0057] By adding a phosphorus compound having a phenol group within the same molecule during the polymerization of the polyester, the catalytic activity of the aluminum compound is improved, and at the same time, the thermal stability of the polymerized copolymer polyester resin is also improved.

[0058] Among the above, the phosphorus compound preferred for use as a polycondensation catalyst is one or more phosphorus compounds selected from compounds represented by Chemical Formula 4 and Chemical Formula 5.

[0059]

[0060]

[0061] As a compound represented by the above chemical formula 4, Irganox 1222 (manufactured by BASF) is commercially available. In addition, as a compound represented by the chemical formula 5, Irganox 1425 (manufactured by BASF) is commercially available and can be used.

[0062] The amount of phosphorus compound used in the polymerization catalyst of the present invention is preferably 10 to 100 ppm with respect to the total mass of the raw material polyester resin obtained as phosphorus, more preferably 15 to 90 ppm, even more preferably 20 to 80 ppm, particularly preferably 25 to 70 ppm, and most preferably 30 to 60 ppm.

[0063] If an amount of phosphate remains exceeding the upper limit mentioned above, there is a possibility that it may reduce polymerization activity.

[0064] When phosphorus compounds are placed under a reduced pressure environment during polyester polymerization, approximately 10 to 30 percent of the amount used is removed from the system depending on the conditions. Therefore, in practice, it is necessary to determine the amount used after confirming the residual rate of phosphorus compounds in the polyester by conducting several trial experiments.

[0065] In addition, the heat resistance of the resin can be improved by using the above phosphorus compound. Although the cause is not clear, it is thought that the heat resistance of the copolymer polyester resin is improved by the hindered phenol portion of the phosphorus compound.

[0066] If the residual amount of the phosphorus compound is less than 10 ppm, the heat resistance improvement effect is weakened, and as a result, the heat resistance and color improvement effects of the copolymer polyester resin of the present invention may not be visible.

[0067] To further enhance catalytic activity without impairing the effects of the present invention, metal-containing polycondensation catalysts such as antimony compounds, titanium compounds, tin compounds, and germanium compounds may be used in combination. In that case, the antimony compound is preferably 10 ppm or less as antimony atoms relative to the mass of the copolymerized polyester resin obtained, the germanium compound is preferably 10 ppm or less as germanium atoms relative to the mass of the copolymerized polyester resin obtained, the titanium compound is preferably 3 ppm or less as titanium atoms relative to the mass of the copolymerized polyester resin obtained, and the tin compound is preferably 3 ppm or less as tin atoms relative to the mass of the polyester resin obtained. For the purposes of the present invention, it is preferable not to use these metal-containing polycondensation catalysts such as antimony compounds, titanium compounds, tin compounds, and germanium compounds as much as possible.

[0068] In the present invention, in addition to the aluminum compound, one or more selected from alkali metals, alkaline earth metals, and their compounds may be coexisted as a second metal-containing component. Coexisting such a second metal-containing component in the catalyst system enhances catalytic activity in addition to the effect of suppressing the formation of diethylene glycol, thereby obtaining a catalyst component with a higher reaction rate, which is effective for improving productivity. When alkali metals, alkaline earth metals, or their compounds are added in combination, the amount used (mol%) is preferably 1 × 10⁻⁶ with respect to the molar amount of the dicarboxylic acid component constituting the polyester resin. -5 ~0.01 mol%. Since almost 100% of the amount of alkali metals, alkaline earth metals, or their compounds remains even when placed under reduced pressure during polyester polymerization, the amount used can be considered as the amount of residue.

[0069] The polymerization catalyst of the present invention exhibits catalytic activity not only in polycondensation reactions but also in esterification and transesterification reactions. Transesterification reactions between alkyl esters of dicarboxylic acids, such as dimethyl terephthalate, and glycols, such as ethylene glycol, are typically carried out in the presence of transesterification catalysts such as zinc; however, it is also possible to use the catalyst of the present invention instead of these catalysts. Furthermore, the polymerization catalyst of the present invention exhibits catalytic activity in solid-state polymerization and solution polymerization as well as in melt polymerization.

[0070] The polyester polymerization catalyst used in the present invention may be added to the reaction system at any stage of the polymerization reaction. For example, it may be added to the reaction system at any stage before and during the esterification or transesterification reaction, immediately before the start of the polycondensation reaction, or at any stage during the polycondensation reaction. In particular, it is preferable to add the aluminum compound and phosphorus compound of the present invention immediately before the start of the polycondensation reaction.

[0071] (Preferable method for manufacturing a biaxially stretched polyester film)

[0072] The biaxially stretched polyester film of the present invention may have a laminated structure of one, two, three, or four or more layers. In the case of a structure of two or more layers, each layer is composed of a polyethylene terephthalate-based resin and inorganic particles as described above, and furthermore, a resin other than a polyethylene terephthalate-based resin, and it is preferable that the type or content of any one of the constituent components among adjacent layers be different.

[0073] In the case of a single-layer structure consisting of layer A, layer A in the present invention becomes the entire biaxially stretched polyester film.

[0074] In the case of a two-layer structure including layer A, layer A in the present invention becomes one or both layers. In the case of a three-layer structure, layer A in the present invention becomes one layer or two layers of both surface layers.

[0075] In particular, in the case of a three-layer structure, even if there are no inorganic particles in the inner layer, the surface roughness of the film can be controlled by controlling the amount of added particles in the surface layer alone, and the content of inorganic particles in the film can be reduced, which is desirable. This is because it also leads to an improvement in the issue of reduced fragrance retention caused by odor components escaping through voids formed at the boundary between the inorganic particles and the polyester resin.

[0076] In addition, within a range that does not adversely affect the characteristics of the film surface in the inner layer, it is easy to use recycled raw materials obtained by trimming the edge portion generated in the film-making process, or recycled raw materials from other film-making processes, by mixing them in a timely manner, which is advantageous in terms of cost.

[0077] As the above inorganic particles, for example, silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, etc., may be used. It is preferable that the average particle size of the inorganic particles be within the range of 0.05 to 3.0 μm when measured with a Coulter counter. The lower limit of the inorganic particle content in the film is preferably 0.01 wt%, more preferably 0.015 wt%, and even more preferably 0.02 wt%. If it is less than 0.01 wt%, the slipperiness may decrease. The upper limit is preferably 1 wt%, more preferably 0.2 wt%, and even more preferably 0.1 wt%. If it exceeds 1 wt%, transparency may decrease, so it is not very desirable.

[0078] As a method for incorporating inorganic particles into polyester, for example, inorganic particles are dispersed in the form of a slurry in a predetermined ratio in ethylene glycol, which is a diol component, and this ethylene glycol slurry is added at any stage before the completion of polyester polymerization.

[0079] Here, when adding particles, it is preferable to add, for example, a water sol or alcohol sol obtained during particle synthesis without drying it first, as this ensures good particle dispersibility and can suppress the occurrence of coarse protrusions.

[0080] In addition, a method of directly mixing the water slurry of particles with a predetermined polyester pellet and feeding it into a vent-type twin-screw kneading extruder to knead it into the polyester is also effective.

[0081] In the present invention, it is preferable to extrude the resin at a temperature of the extruder equal to or higher than the melting point of the resin plus 2°C and equal to or lower than the melting point of the resin plus 6°C. If the extrusion temperature is less than the melting point plus 2°C, the resin does not melt, so unmelted material is discharged, which is undesirable because it becomes a foreign substance. In addition, if the resin is extruded at a temperature higher than the melting point plus 6°C, the resin undergoes thermal degradation, which causes the generation of foreign substances, which is undesirable.

[0082] In addition, an unoriented film can be obtained by extruding the molten resin in the form of a sheet after extrusion through a T-die and then rapidly cooling it. Furthermore, as a method for rapidly cooling the molten resin, a method of obtaining a substantially unoriented resin sheet by casting the molten resin from the T-die onto a rotating drum and rapidly cooling and solidifying it can be suitably adopted.

[0083] Furthermore, sublimes of the molten resin (such as oligomers) are prone to adhering to the T-die. If these adhering materials detach, they stick to the unoriented sheet and become foreign substances on the film, which is undesirable. Therefore, it is advisable to attach an adhesive sheet to the T-die in advance to prevent sublimes from falling off, and to clean the cooling roll with a cleaner even during operation to prevent foreign substances from adhering to the unoriented sheet.

[0084] In addition, the obtained unoriented film is biaxially stretched, followed by heat-setting and heat-relaxation treatments. By appropriately combining film-forming conditions such as length and width-direction stretching conditions, heat-setting conditions, and heat-relaxation conditions as described below, desirable film characteristics described below can be achieved. These are explained in detail below.

[0085] The stretching method can be simultaneous biaxial stretching or sequential biaxial stretching, but sequential biaxial stretching is preferable because it has a faster film-forming speed and higher productivity. Below, we describe a sequential biaxial stretching method by longitudinal stretching followed by transverse stretching, in which longitudinal stretching is performed first and transverse stretching is performed next, but transverse stretching followed by longitudinal stretching in the reverse order is also acceptable.

[0086] For the lengthwise (longitudinal) direction (hereinafter abbreviated as MD), it is preferable to stretch at a temperature of (Tg+5) to (Tg+55)°C and a stretching ratio of 3 to 5 times for the purpose of reducing bowing. If the stretching temperature is higher than (Tg+55)°C or lower than 3 times, bowing is reduced, but the orientation in the lengthwise direction becomes insufficient, and the thickness non-uniformity in the lengthwise direction worsens, so it is not desirable. In addition, the flatness of the obtained biaxially stretched polyester film also worsens, so it is not desirable. On the other hand, if it is lower than (Tg+5)°C or higher than 5 times, shrinkage stress increases, and bowing increases, so it is not desirable.

[0087] In addition, regarding longitudinal stretching, in a method of multi-stage stretching between multiple rolls rather than single-stage stretching, the lengthwise stretching is performed gradually while controlling the stretching speed, so the difference in physical properties in the film width direction can be reduced. From the perspective of effectiveness, equipment, and cost, 2 to 5-stage stretching is preferred.

[0088] When stretching in the width (horizontal) direction (hereinafter abbreviated as TD), the unstretched film is introduced into a tenter device capable of heating by gripping both ends of the film with clips, and after heating the film to a predetermined temperature by hot air, the film is stretched in the width direction by widening the distance between the clips while conveying it in the length direction.

[0089] Furthermore, if the elongation temperature in the width direction is less than Tg + 5°C, it is undesirable as fracture is likely to occur during elongation. Also, if it is higher than Tg + 70°C, uniform elongation in the width direction becomes impossible, and since the thickness non-uniformity in the width direction increases, the variation in film roll hardness increases, which is undesirable. More preferably, it is Tg + 10°C or higher and Tg + 65°C or lower, and even more preferably, Tg + 15°C or higher and Tg + 60°C or lower.

[0090] Although there are no specific regulations regarding the elongation ratio in the width direction, it is desirable to have a ratio of 3 to 7. If the elongation ratio is less than 3, productivity deteriorates, and the lack of orientation in the width direction exacerbates thickness non-uniformity in the width direction, resulting in variations in the hardness of the film roll in the width direction, which is undesirable. Furthermore, if the elongation ratio exceeds 7, it is undesirable because it becomes prone to breakage during the stretching process.

[0091] The heat-setting temperature (heat treatment temperature) after TD stretching is preferably 230 to 255°C. If the heat-setting temperature is higher than 255°C, it is not desirable because the film melts and breaks as it approaches the melting point of the polyester resin. On the other hand, if it is lower than 230°C, the thermal shrinkage rate increases in both the length and width directions, which is not desirable because the thermal dimensional stability during deposition processing deteriorates.

[0092] In the heat relaxation process, the restraining force in the width direction decreases until the film shrinks due to heat relaxation, causing it to loosen due to its own weight or bulge due to the accompanying airflow; consequently, the film is in a state where it is highly prone to vertical fluctuation. For this reason, in this heat relaxation process, the change in the orientation angle and the difference in the inclination thermal shrinkage rate of the resulting biaxially stretched polyester film varies significantly depending on the film's transport condition. As a method to mitigate this, for example, the film can be kept parallel by appropriately adjusting the airflow speed ejected from the upper and lower nozzles. A thermal relaxation rate in the width direction of 4 to 8% is preferred. If the thermal relaxation rate is less than 4%, the thermal shrinkage rate in the width direction of the resulting biaxially stretched polyester film increases, which is undesirable because it impairs dimensional stability during deposition processing. Meanwhile, if the thermal relaxation rate is greater than 8%, an increase in bowing and loosening occurs, and since the thickness non-uniformity in the width direction increases, the variation in film roll hardness increases, which is undesirable.

[0093] In addition, oligomers are generated when a film that has undergone heat treatment within the TD is cooled. If oligomers adhere to the film, they become defects, which is undesirable as they cause printing omissions. Therefore, it is desirable to remove oligomers within the TD or by using adhesive rollers at the TD exit. As a specific example of removing oligomers, the method shown in Fig. 3 is preferred. If cooling air is blown onto the film alone, oligomers are generated, and the generated oligomers float within the zone and adhere to the film. Therefore, by installing a plenum duct that sucks in oligomers after blowing cooling air, the amount of oligomers floating within the zone is reduced, making it difficult for oligomers to adhere to the film.

[0094] The film produced by stretching using the above method is wound by a winder device to produce a master roll. Subsequently, a slitter is used to slit the film to a specified width and winding length, and the film is wound onto a winding core to obtain a biaxially stretched polyester film roll. As the winding core, typically a plastic core, metal core, or core tube of 3 inches, 6 inches, or 8 inches can be used. In addition, the preferred winding length and width of the film roll are as described above.

[0095] In addition, it is desirable to reduce loosening that occurs during slitting by adopting the following slit conditions.

[0096] As specific slit conditions, the slit is initiated with an initial tension of 70 to 160 N / m, preferably 80 to 150 N / m, and an initial surface pressure of 200 to 400 N / m, preferably 250 to 350 N / m. If the initial tension is higher than 160 N / m, it is undesirable because the uneven thickness of the concave portion is slightly stretched by the tension during slitting, causing looseness. Furthermore, if the initial tension is 70 N / m or less, the tension is insufficient when winding the film through the slit, resulting in an uneven cross-section of the film roll (so-called cross-sectional shift occurs), which is undesirable. Additionally, it is desirable to reduce the tension after the winding length reaches 500 m. Specifically, it is desirable to reduce the tension consistently in correlation with the winding length so that the tension at 300 m before the end of the slit is 50 to 80%, preferably 60 to 70%, of the initial tension. In addition, it is desirable to keep the surface pressure as constant as possible over the entire winding length. It is desirable for the initial surface pressure to be ±5% or less over the entire winding length, and more preferably, it is ±3% or less.

[0097] In general, for industrially produced film rolls, the film produced continuously is wound continuously. If the film production conditions are constant, the degree of thickness non-uniformity in the film width direction becomes almost constant over the entire winding length. However, slight variations occur over the entire winding length due to minute fluctuations in each process during film production. It is desirable that the thickness non-uniformity in the film width direction be controlled over the entire winding length. Whether the thickness non-uniformity is controlled over the entire winding length can be verified, for example, by taking samples from the film of the film roll at regular intervals along the winding length from the surface layer and measuring the thickness non-uniformity of each sample. In the film roll of the present invention, the thickness non-uniformity can be measured by taking a sample from the surface layer portion of the film roll and taking the measurement as a representative value for the film roll. In the present invention, as described in the examples to be described later, a sample is taken from a portion where the film is removed by 5 m from the surface layer of the film roll and measured to take the representative value. The suitable range for thickness non-uniformity in the film width direction (maximum concave portion and thickness non-uniformity in the width direction) in the film roll surface layer is as described above.

[0098] A preferred embodiment of the present invention is to take a sample and measure it every 1,000 m of winding length, and for the entire sample, the thickness non-uniformity (maximum concave portion and thickness non-uniformity in the width direction) is within a predetermined range. The suitable range for thickness non-uniformity in the film width direction (maximum concave portion and thickness non-uniformity in the width direction) over the entire length of the film roll is as described above.

[0099] (Composition and Characteristics of Biaxially Stretched Polyester Film)

[0100] The biaxially stretched polyester film of the present invention preferably has an antimony content of 10 ppm or less. Since antimony is a substance of concern regarding carcinogenicity, it is preferable that the amount be as low as possible; 5 ppm is preferable, and 0 ppm is more preferable. Although it is preferable that the antimony content of the raw resin used in the present invention be 0 ppm, it was set to 10 ppm or less due to the possibility of incorporation during production.

[0101] In the biaxially stretched polyester film of the present invention, it is preferable that the difference between the intrinsic viscosity of the polyester resin and the intrinsic viscosity of the polyester film is 0.06 dL / g or less. The difference in intrinsic viscosity serves as an indicator of the degree of degradation when melt-extruding the polyester resin. If it is higher than 0.06 dL / g, it is undesirable because the resin degrades within the extruder and becomes a cause of foreign substances. Furthermore, the difference in intrinsic viscosity is preferably 0 dL / g, but it is difficult to achieve 0 dL / g because it is substantially melted. It is preferable that it be 0.05 dL / g or less, and more preferable that it be 0.04 dL / g or less. In order to control the difference in intrinsic viscosity as described above, in the present invention, it is preferable to extrude the resin at a temperature of the extruder equal to the melting point of the resin + 2°C or higher and equal to the melting point of the resin + 6°C or lower. If the extrusion temperature is below the melting point + 2°C, the resin does not melt and unmelted material is discharged, which is undesirable as it becomes a foreign substance. Also, if extrusion is performed at a temperature higher than the melting point + 6°C, the resin deteriorates thermally and becomes a foreign substance, which is undesirable.

[0102] In the biaxially stretched polyester film of the present invention, it is preferable that the number of defects with a size of 1 mm or larger be one or less per 10,000 square meters. By reducing the number of defects with a size of 1 mm or larger per large area of ​​10,000 square meters to one or less in this way, printability becomes very good. If the number of defects caused by foreign substances is high, ink leakage occurs during printing, which is undesirable. The fewer the number of defects with a size of 1 mm or larger, the more desirable it is; 0.5 or less is more desirable; 0.3 or less is even more desirable; 0.1 or less is particularly desirable; and 0 is most desirable. In the present invention, the number was set to one or less because there is a possibility that foreign substances may be mixed in during unexpected troubles.

[0103] The calculated average roughness of the surface of the biaxially stretched polyester film of the present invention is preferably 0.02 μm or more and 0.05 μm or less. If it is less than 0.02 μm, blocking occurs where the film adheres within the film roll, and this is undesirable because a crack (the sound of the adhered film peeling off) occurs during unwinding, or the film breaks. In addition, if it exceeds 0.05 μm, it is undesirable because the deposition thin film is prone to omission during processing steps such as deposition, and the gas barrier performance deteriorates.

[0104] In addition, the thickness of the biaxially stretched polyester film of the present invention is preferably 5 μm or more and 40 μm or less. The upper limit of the film thickness is more preferably 35 μm or less, and even more preferably 30 μm or less. Since the thickness confirmed in the present invention was up to 5 μm, the lower limit of the thickness was set to 5 μm or more. Furthermore, since a thicker film tends to be preferable as it has greater rigidity and is less prone to loosening, a thicker film poses no problem, but it runs counter to environmental compliance when the thickness is thin. Additionally, since loosening is more likely to occur when the film is thin, a thin film thickness entails greater difficulties in the embodiment of the present invention.

[0105] In addition, it is preferable that the static friction coefficient and the dynamic friction coefficient between the film surfaces of the outer and inner winding surfaces of the biaxially stretched polyester film of the present invention are both 0.1 or higher and 0.8 or lower. If it is lower than 0.1, there is a possibility that excessive slippage may occur, causing misalignment of the cross-section. Also, if it is higher than 0.8, the amount of air incorporated during slitting increases, and it is undesirable because loosening or wrinkling is likely to occur due to air escaping from the concave part of the film roll. Preferably, it is 0.13 or higher and 0.77 or lower, and more preferably, it is 0.16 or higher and 0.74 or lower.

[0106] (Characteristics of biaxially stretched polyester film rolls)

[0107] The winding length of the biaxially stretched polyester film roll of the present invention is preferably 8,000 m or more and 80,000 m or less. In processing such as printing or deposition, a longer winding length reduces the frequency of changing the roll, thereby improving work efficiency. Preferably, it is 10,000 m or more, more preferably 12,000 m or more, and particularly preferably 14,000 m or more. There is no specific upper limit, and a longer winding length is preferred; however, since the inventors were only able to confirm winding lengths up to 80,000 m, the winding length of 80,000 m was set as the upper limit. Furthermore, as the winding length of the film roll increases, the surface area of ​​the film increases, and the opportunity for the defect of loosening to occur increases; therefore, in the state of the present invention, a long winding length of the film roll entails greater difficulties.

[0108] In addition, the width of the biaxially stretched polyester film roll of the present invention is preferably 500 mm or more and 4000 mm or less. There is no particular upper limit, and while a longer film roll width is desirable as it results in less loss during the printing process, the inventors set the width at 4000 mm as the upper limit because they were only able to confirm up to 4000 mm. Furthermore, as mentioned above, a wider film roll width is preferable because it increases efficiency in processing such as printing. The preferred width is 700 mm or more, more preferably 900 mm or more, and particularly preferably 1100 mm or more. Additionally, as the width of the film roll increases, the surface area of ​​the film increases, and the chance of the defect of loosening occurring increases; therefore, in the embodiment of the present invention, a longer film roll width entails greater difficulties.

[0109] In addition, regarding the thickness non-uniformity in the width direction of the film roll of the present invention, the thickness pattern has a concave portion, and at the concave portion with the largest thickness difference (maximum concave portion), it is preferable that the thickness non-uniformity of the maximum concave portion calculated by Equation 1 below from the maximum thickness difference at the maximum concave portion and the average film thickness is 10% or less (an example is shown in FIG. 1).

[0110] In addition, the term "concave portion" in the present invention refers to a portion of a thickness pattern that follows the pattern of peak-valve-peak, where, in the thickness non-uniformity in the film width direction measured using a continuous contact thickness gauge as described below, the point where the thickness decreases in both directions of the measurement direction is defined as the peak portion, and the point where the thickness increases in both directions of the measurement direction is defined as the valley portion. Furthermore, a film that does not have such a thickness pattern, that is, a film that does not have a concave portion, is not included in the present invention. In the case of two peak portions and one valley portion in the concave portion, the larger value of either of the thickness differences between the peak portions and the valley portions (or both values ​​if they are the same) is referred to as the maximum thickness difference in the concave portion.

[0111] If the thickness non-uniformity of the maximum concave area is higher than 10%, air is swept in and accumulates when the concave area is slit and wound into a film roll; subsequently, when the film roll is stored, air escape occurs, causing wrinkles and loosening, which is undesirable. Furthermore, since the thickness of the concave area is thinner than other locations in the width direction, it stretches in the length direction due to the tension when the concave area is slit and wound into a film roll. Consequently, the length of the concave area in the film roll becomes longer in the length direction than other locations in the width direction, causing that area to become loose. The inventors' investigation revealed that this becomes particularly pronounced when there is a large difference in thickness between the concave area and both ends thereof. The preferred thickness non-uniformity of the maximum concave area is 9% or less, and more preferably 8% or less. A lower thickness non-uniformity of the maximum concave area is preferable, and in the inventors' tests, 3% was found to be the lowest.

[0112] The thickness non-uniformity of the concave portion as described above must be measured using a continuous contact type thickness gauge as shown in the example below. For example, as shown in Patent Document 4, if thickness measurements are taken at intervals of 30 mm to 500 mm in the measurement direction, there is a possibility that the maximum thickness difference of the concave portion will be at an unmeasured location, making it difficult to determine the thickness difference in the accurate concave portion. In the present invention, thickness non-uniformity refers to that measured using a continuous contact type thickness gauge.

[0113] In addition, regarding the thickness non-uniformity in the width direction of each sample of the film sampled at intervals of 1000 m from the surface layer of the film roll of the biaxially stretched polyester film of the present invention, it is preferable that the thickness non-uniformity obtained from the maximum thickness difference at the maximum concave part and the average film thickness is 10% or less in the entire sample.

[0114] As described above, if the thickness non-uniformity of the maximum concave portion is higher than 10%, air is swept in and accumulates when the concave portion is slit and wound into a film roll. Subsequently, when the film roll is stored, air escape occurs, causing wrinkles and loosening, which is undesirable. Furthermore, since the concave portion is thinner than other locations in the width direction, it stretches in the length direction due to the tension during slitting. Consequently, the length of the concave portion in the film roll becomes longer in the length direction than other locations in the width direction, causing that portion to become loose. The inventors have found through their investigation that this becomes particularly pronounced when the thickness difference between the concave portion and its two ends (the thickness difference between the curved portion and the crest portion mentioned above) is large. For this reason, the thickness non-uniformity of the concave portion in the width direction of the roll is important. The preferred thickness non-uniformity of the concave portion is 9% or less, and more preferably 8% or less.

[0115] In addition, regarding the maximum concave portion in the widthwise thickness pattern of the polyester film roll of the present invention, it is preferable that the absolute value of the difference in widthwise refractive index between the maximum thickness portion at either end of the concave portion (the portion with the greater thickness among the two peaks) and the minimum thickness portion of the concave portion (the curved portion) is 0.01 or less. If the absolute value of the difference in widthwise refractive index between the maximum thickness portion at either end of the concave portion and the minimum thickness portion of the concave portion is higher than 0.01, the ease of elongation in the longitudinal direction differs between the minimum thickness portion and the maximum thickness portion of the concave portion, and a difference occurs in which the film roll is elongated in the longitudinal direction due to tension during slitting. As a result, the length in the longitudinal direction of the film roll increases, and the portion becomes loose. The preferred absolute value of the difference in widthwise refractive index is 0.008 or less, and more preferably 0.006 or less. The absolute value of the difference in refractive index in the width direction is preferably lower, and in the inventors' tests, 0.0003 was the lowest.

[0116] It is preferable that the average hardness of the outermost layer of the polyester film roll of the present invention, when measured at intervals of 50 mm in the film width direction, is in the range of 500 to 700, and the deviation of the hardness is 10% to 20%. The "outermost layer" of the film roll refers to the surface portion of the roll after unwinding the film from the roll and removing 5 m from the end in the longitudinal direction. In addition, the hardness is measured using a hardness tester, Parotester 2, manufactured by Proseo, Switzerland. If the winding hardness of the film roll surface layer is less than 500, it is undesirable because, for example, when the film roll is stored in a warehouse for half a year, air is swept in and escaped during slitting, causing the film roll to loosen. In addition, if the winding hardness of the film roll surface layer is higher than 700, it is undesirable because the film roll is wound tightly, and loosening occurs as the concave portions described above are compressed. The preferred winding hardness of the film roll surface layer is 530 or higher and 670 or lower, and more preferably 560 or higher and 640 or lower.

[0117] In addition, it is desirable that the deviation in hardness measured in the width direction of the film roll be 10% or more and 20% or less. If it is higher than 20%, for example, when the film roll is stored in a warehouse for half a year, the thickness non-uniformity in the width direction of the film is poor, or there is a difference in tension in the width direction in the slitting equipment, which is undesirable as it makes loosening after storage more likely. In addition, it is desirable that it be less than 10%, and since 10% was the lower limit in the present invention, it was set to 10%. The upper limit of the desirable deviation in winding hardness in the width direction is 19% or less, and more preferably 18% or less.

[0118] Examples

[0119] The present invention is described in more detail below by way of examples, but the present invention is not limited in any way to the aspects of these examples, and appropriate modifications are possible within the scope that does not deviate from the spirit of the present invention. The composition of raw materials used in the examples and comparative examples, the film stretching method in the examples and comparative examples, and the manufacturing conditions are each shown in the table.

[0120] In addition, the film evaluation method is as follows.

[0121] [Tg (glass transition point), Tm (melting point)]

[0122] Using a differential scanning calorimeter (manufactured by Seiko Electronics Co., Ltd., DSC220), 5 mg of unoriented film was placed in a sample pan, the lid of the pan was closed, and the temperature was raised from -40°C to 300°C at a heating rate of 10°C / minute under a nitrogen gas atmosphere to measure. Tg(°C) and Tm(°C) were determined based on JIS-K7121-1987.

[0123] [Extreme Viscosity (IV)]

[0124] 0.2 g of polyester was dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (weight ratio)) and measured using an Ostwald viscometer at 30°C. The unit is dL / g.

[0125] [Content of various atoms in polyester film]

[0126] Quantified using the method shown below.

[0127] (a) Antimony atom

[0128] 1 g of the sample was wet-decomposed with a mixture of sulfuric acid and hydrogen peroxide. Subsequently, sodium nitrite was added to decompose Sb atoms into Sb 5＋Brilliant Green was added to form a blue complex with Sb. After extracting this complex with toluene, the absorbance at a wavelength of 625 nm was measured using a spectrophotometer (manufactured by Shimadzu Corporation, UV-150-02), and the amount of Sb atoms in the sample was colorimetrically quantified from a calibration curve prepared in advance.

[0129] (b) Personnel

[0130] Phosphorus compounds were converted to orthophosphoric acid by dry incineration decomposition of 1 g of the sample in the presence of sodium carbonate, or by wet decomposition with a mixture of sulfuric acid, nitric acid, and perchloric acid, or a mixture of sulfuric acid and hydrogen peroxide. Subsequently, the molybdate was reacted in a 1 mol / L sulfuric acid solution to form phosphomolybdic acid, which was then reduced with hydrazine sulfate to produce heteropoly blue. The absorbance at a wavelength of 830 nm was measured using an absorbance spectrophotometer (manufactured by Shimadzu Corporation, UV-150-02), and the amount of phosphorus in the sample was quantified from a calibration curve prepared in advance.

[0131] (c) Aluminum atom

[0132] 0.1 g of the sample was dissolved in a 6 M hydrochloric acid solution and left for 1 day, then diluted with pure water to make a 1.2 M hydrochloric acid measurement solution. The prepared solution sample was analyzed by high-frequency plasma emission analysis.

[0133] [SRa of the film surface (calculated average roughness)]

[0134] The surface roughness of the film was measured using the following method.

[0135] · Device: Scanning confocal laser microscope (Olympus LEXT)

[0136] · Laser type: 405 nm semiconductor laser

[0137] · Objective lens: 50x

[0138] · Shooting Mode: High Precision

[0139] A confocal image of the measurement surface was captured using the above device and conditions.

[0140] Surface roughness analysis

[0141] · Measurement range: 256 µm (vertical) × 256 µm (horizontal)

[0142] · Analysis software: OLS4100

[0143] · No cutoff

[0144] Surface roughness analysis was performed under the above conditions, and the arithmetic mean roughness (SRa) was measured. The measurement was performed 10 times by changing the measurement location, and the average value was calculated. However, if a partial abnormality such as a scratch was clearly identified from the image, it was not included in the measurement value, and the measurement was repeated while avoiding the abnormal part.

[0145] [Non-uniform thickness in the width direction]

[0146] The roll was installed in the slitter. After that, 5 m was removed from the surface layer of the roll, the film roll was sampled in the width direction at full width and in the length direction at 40 mm, and the width direction thickness was measured continuously at 5 m / s using a continuous contact thickness gauge manufactured by Mikulon Measuring Instruments. The maximum thickness at the time of measurement was denoted as Tmax., the minimum thickness as Tmin., and the average thickness as Tave., and the thickness non-uniformity in the width direction of the film was calculated from the following equation (1).

[0147]

[0148] [Uneven thickness of the depression]

[0149] The continuous contact thickness in the width direction was calculated as described above, and the location with the maximum concave portion was identified as shown in FIG. 1. The thickness non-uniformity of the maximum concave portion was calculated from the equation (2) below. In addition, when the heights at both ends of the maximum concave portion were different, the higher value was selected and calculated.

[0150]

[0151] [Thickness non-uniformity of the maximum indentation in the roll width direction at the roll winding length]

[0152] The roll was installed in the slitter. After that, 5 m was removed from the surface layer of the roll, and the thickness non-uniformity of the maximum concave portion in the roll width direction was measured using the method described above. After the measurement, the roll was rewinded 1000 m through the slitter, and the thickness non-uniformity of the concave portion in the roll width direction was measured using the method described above. The measurement of the thickness non-uniformity of the maximum concave portion in the roll width direction was repeated by rewinding 1000 m.

[0153] [Difference in refractive index between the maximum concave area and the two ends of the maximum concave area]

[0154] The refractive index in the film width direction at the maximum concave area and the position where the thickness is higher at both ends of the maximum concave area was measured using an Abbe refractometer. Then, the difference was calculated from the equation (3) below and expressed as the absolute value.

[0155]

[0156] [Coefficient of Friction]

[0157] In accordance with JIS K-7125, the static and dynamic friction coefficients were determined when the front and back sides of the film were bonded under an environment of 23°C and 65%RH using a tensile testing machine (Tensilon manufactured by ORIENTEC). In addition, the weight of the upper film-wound sled (weight) was 1.5 kg, and the bottom surface area of ​​the thread was 63 mm in length × 63 mm in width. In addition, the tensile speed during friction measurement was 200 mm / min.

[0158] [Assessment of Loosening]

[0159] Samples were taken from the film roll, covering the entire width in the width direction and 4 m to 6 m in the length direction, and placed on a flat surface. At this time, if a strip-shaped area was visually identified along the length direction where the flatness was even slightly worse than other parts, it was deemed loose. The evaluation was performed as follows. In addition, the same evaluation was performed after storage for one year in a warehouse at a temperature of 23℃.

[0160] No loosening: ○

[0161] Looseness in 1 or more places: ×

[0162] [Evaluation of Winding Hardness]

[0163] Using the Swiss Proseoh Company's hardness tester Parotester 2, measurements were taken at intervals of 50 mm from the end in the roll width direction. The average value of the values ​​measured in the roll width direction was used as the measurement value. In addition, the deviation of hardness was calculated from Equation (4).

[0164]

[0165] Evaluation of wrinkles in film rolls

[0166] Immediately after production, and after storing the filmed polyester film rolls in a warehouse at a temperature of 23°C for one year, the wrinkles on the surface of the roll were visually evaluated according to the following criteria. A judgment of ○ or △ was considered acceptable.

[0167] ○: No wrinkles

[0168] △: There are slight wrinkles, but they disappear when a tension of about 20 N / m is applied to the withdrawn film.

[0169] ×: There are strong wrinkles, and the wrinkles do not disappear even when a tension of about 20 N / m is applied to the withdrawn film.

[0170] [Number of defects]

[0171] The obtained film roll was rewound using a rewinding machine. During rewinding, the number of defects was investigated using a defect detector (model F MAX MR) manufactured by FUTEC. Then, the number of defects with a size of 1 mm or more in either the vertical or horizontal direction was determined. From the total number of defects, the number of defects per 10,000 square meters was calculated using Equation (5).

[0172]

[0173] [print]

[0174] Immediately after production, and after storing the filmed polyester film roll in a warehouse at a temperature of 23°C for one year, the film roll was gravure printed at a speed of 300 m / min with a halftone of 5% using a gravure printing machine (manufactured by Higashitani Tetsukosho Co., Ltd.). The ink used was gravure printing ink (manufactured by Toyo Ink Co., Ltd.: product name Finestar R92 Black) mixed with a diluent (manufactured by Toyo Ink Co., Ltd.: product name SL302) in a ratio of 77:23. The obtained print sample was rewound using a rewinding machine. During rewinding, the number of print omissions was investigated using a defect detector (model F MAX MR) manufactured by FUTEC Co., Ltd. Then, the number of print omissions with a size of 1 mm or more in either the vertical or horizontal direction was calculated. From the total number of print omissions, the number of defects per 10,000 square meters was calculated by Equation (6).

[0175]

[0176] <Preparation of Polymerization Catalyst Solution>

[0177] (Ethylene glycol solution of phosphorus compounds)

[0178] In a flask equipped with a nitrogen inlet tube and a condenser, 2.0 liters of ethylene glycol were added at room temperature and atmospheric pressure, and 200 g of Irganox 1222 (manufactured by BASF), represented by Chemical Formula 4, was added as a phosphorus compound while stirring at 200 rpm under a nitrogen atmosphere. After adding an additional 2.0 liters of ethylene glycol, the jacket temperature setting was changed to 196°C and the temperature was raised; stirring was performed under reflux for 60 minutes starting from the point when the internal temperature reached 185°C or higher. Afterward, heating was stopped, the solution was immediately removed from the heat source, and the solution was cooled to 120°C or lower within 30 minutes while maintaining a nitrogen atmosphere.

[0179] (Ethylene glycol solution of aluminum compound)

[0180] 5.0 liters of pure water were added to a flask equipped with a cooling tube at room temperature and atmospheric pressure, and 200 g of basic aluminum acetate (hydroxyaluminum diacetate) was added as a slurry with pure water while stirring at 200 rpm. Additionally, pure water was added to make the total volume 10.0 liters, and the mixture was stirred for 12 hours at room temperature and atmospheric pressure. Afterward, the jacket temperature setting was changed to 100.5°C to raise the temperature, and stirring was performed under reflux for 3 hours starting from the point when the internal temperature reached 95°C or higher. Stirring was stopped, and the mixture was cooled to room temperature. If undissolved particles were observed at this time, the solution was filtered through a glass filter (3G) to obtain an aqueous solution of the aluminum compound.

[0181] Next, 2.0 liters of the aqueous solution of the aluminum compound and 2.0 liters of ethylene glycol were placed in a flask equipped with a distillation apparatus at room temperature and atmospheric pressure, and after stirring at 200 rpm for 30 minutes, a homogeneous water / ethylene glycol mixed solution was obtained. Subsequently, the jacket temperature setting was changed to 110°C and the temperature was raised, and water was distilled off from the solution. Heating was stopped when the amount of distilled water reached 2.0 liters, and the solution was cooled to room temperature to obtain an ethylene glycol solution of the aluminum compound.

[0182] In the following, "part" represents "part of mass".

[0183] 2,130 parts of terephthalic acid, 1,955 parts of ethylene glycol, and 0.7 parts of triethylamine were added to a reaction can equipped with a stirrer, a thermometer, and an outlet cooler. The temperature was gradually increased from 220°C to 250°C under a pressure of 0.35 MPa, and an esterification reaction was carried out while removing the effluent water from the system. Subsequently, the above polymerization catalyst solution was added such that the ethylene glycol solution of the phosphorus compound and the ethylene glycol mixed solution of the aluminum compound constituted 0.047 mol% as phosphorus atoms and 0.021 mol% as aluminum atoms relative to the dicarboxylic acid component of the polyester resin. Then, initial polymerization was carried out under reduced pressure up to 1.3 kPa over 1 hour while simultaneously raising the temperature to 270°C, and additionally, a subsequent polymerization was carried out at 0.13 kPa or less to obtain a polyester resin.

[0184] In addition, the polyesters used in the examples and comparative examples are as follows.

[0185] · Polyester 1: Polyethylene terephthalate (IV 0.73 dL / g)

[0186] · Polyester 2: Polyethylene terephthalate (IV 0.73 dL / g) prepared by adding SiO2 (spherical silica with an average particle size of 2 μm) as a lubricant at a ratio of 7,500 ppm relative to the polyester during the manufacture of the above Polyester 1.

[0187]

[0188] [Example 1]

[0189] The above-mentioned polyester 1 and polyester 2 were mixed in a weight ratio of 96:4 and fed into an extruder. Subsequently, the mixed resin was melted at 270°C, cooled to 260°C, extruded from a T-die, wound onto a rotating metal roll cooled to a surface temperature of 30°C, and rapidly cooled to obtain an unoriented film with a thickness of 220 μm. At this time, the take-up speed (rotation speed of the metal roll) of the unoriented film was approximately 80 m / min. The Tg of the unoriented film was 75°C and the Tm was 256°C. In addition, a laser cleaner was installed on the cooling metal roll to prevent the adhesion of foreign substances.

[0190] The obtained unoriented sheet was heated to 110°C and stretched in the longitudinal direction with a total stretching ratio of 4.5 times, with the first stage stretching by 1.5 times and the second stage stretching by 3 times. Subsequently, in a transverse stretching process (hereinafter referred to as a tenter), it was stretched in the width direction at a temperature of 130°C with the first stage stretching by 2 times and the second stage stretching by 2.3 times, with a total stretching ratio of 4.6 times (see Fig. 2). After stretching in the width direction by 4.6 times, it was heat-set at 243°C and subjected to 5% heat relaxation treatment in the width direction. The film after heat relaxation was cooled to 50°C or lower inside the tenter, and the oligomer was sucked across the entire width of the film in the width direction through the exhaust device shown in Fig. 3 at the exit of the tenter. Next, after cutting off both ends of the film after stretching, and then performing corona discharge treatment, the film was wound into a roll shape using a winder to produce a master roll of a biaxially stretched polyester film with a thickness of 12 μm, a width of 8 m, and a winding length of 85,000 m.

[0191] The above-mentioned biaxially stretched film was slit using a slitter to create sizes of 4,000 mm, 2,000 mm, and 1,000 mm in width, with a winding length of 80,000 m. Additionally, a 6-inch metal core was used.

[0192] As for the specific slit conditions, the slit was initiated with an initial tension of 150 N / m and an initial surface pressure of 330 N / m. As the winding length increased from 1,000 m to 79,000 m, the tension was reduced at a constant rate from 150 to 80 N / m. Additionally, the slit was performed so that the surface pressure remained constant at 330 N / m. The film formation process conditions and slit conditions are shown in Table 2.

[0193] Then, the characteristics of the obtained film were evaluated using the method described above. The evaluation results are shown in Tables 3 and 4. A film with the target characteristics was obtained, and the looseness was a good result. In addition, regarding looseness, in addition to the results in Table 3 (film roll surface layer), all samples at every 1000 m were evaluated, and the result was ○ (no looseness) for all samples of the three film rolls mentioned above.

[0194] [Example 2]

[0195] A biaxially stretched polyester film roll was obtained using the same method as in Example 1, except that polyester 1 and polyester 2 were mixed in a weight ratio of 94:6 and fed into an extruder. The film-forming process conditions and slit conditions are shown in Table 2, and the evaluation results are shown in Tables 3 and 4. The film was of good quality.

[0196] [Example 3]

[0197] A biaxially stretched polyester film roll was obtained using the same method as in Example 1, except that the film thickness was changed to 6 μm and the roll winding length was set to 30,000 m. The film formation process conditions and slit conditions are shown in Table 2, and the evaluation results are shown in Tables 3 and 4. The film was of good quality.

[0198] [Comparative Example 1]

[0199] As for the slitting conditions, the slitting was initiated with an initial tension of 120 N / m and an initial surface pressure of 280 N / m. As the winding length increased from 1,000 m to 79,000 m, the tension was reduced at a constant rate from 120 to 50 N / m. Additionally, the slitting was performed so that the surface pressure remained constant at 280 N / m. Except for the slitting conditions, the process was carried out under the same conditions as in Example 1. The film formation process conditions and slitting conditions are shown in Table 2, and the evaluation results are shown in Tables 3 and 4. Due to the low winding hardness, the appearance of the film roll and the loosening of the film after storage in the warehouse resulted in inferior performance. Furthermore, there was a high number of printing omissions after long-term storage.

[0200] [Comparative Example 2]

[0201] An unoriented sheet obtained by the same method as in Example 1 was heated to 110°C and stretched in the longitudinal direction with a total stretching ratio of 3 times, with the first stage stretching by 1.5 times and the second stage stretching by 2 times. Subsequently, in a transverse stretching process (hereinafter referred to as a tenter), the sheet was stretched in the width direction with a total stretching ratio of 4.6 times, with the first stage stretching by 2 times at a temperature of 140°C and the second stage stretching by 2.3 times at a temperature of 170°C. After stretching in the width direction by 4.6 times, the sheet was heat-set at 243°C and subjected to a 5% heat relaxation treatment in the width direction. The film after heat relaxation was cooled to 50°C or lower inside the tenter, and the oligomer was sucked in the width direction from the tenter exit using the exhaust device shown in Fig. 3. Subsequently, after trimming and removing the ends of the film following the stretching, a master roll of a biaxially stretched polyester film with a thickness of 12 μm, a width of 8 m, and a winding length of 35,000 m was produced by undergoing corona discharge treatment and winding it into a roll shape using a winder. As for the specific slit conditions, the slit was initiated with an initial tension of 150 N / m and an initial surface pressure of 330 N / m. The tension was reduced at a constant rate from 150 to 80 N / m as the winding length increased from 1,000 m to 29,000 m. Additionally, the slit was performed so that the surface pressure remained constant at 330 N / m to obtain a film roll with a winding length of 30,000 m. The film formation process conditions and slit conditions are shown in Table 2, and the evaluation results are shown in Tables 3 and 4.

[0202] The polyester film roll became of inferior quality due to poor thickness non-uniformity in the width direction, large variation in winding hardness, and poor appearance and looseness of the film roll.

[0203]

[0204]

[0205]

[0206] Industrial applicability

[0207] Since the biaxially stretched polyester film roll of the present invention has good looseness as described above, it can be suitably used in processing such as printing.

Claims

Claim 1 A biaxially stretched polyester film roll formed by winding a film having an antimony content of 10 ppm or less, a phosphorus content of 25 ppm or more and 75 ppm or less, and an average roughness of the film surface of 0.02 μm or more and 0.05 μm or less, wherein the biaxially stretched polyester film and the film roll satisfy the following requirements (1) to (6) and do not contain titanium. (1) Film roll winding length is 8,000 m or more and 80,000 m or less. (2) Film roll width is 500 mm or more and 4,000 mm or less. (3) The average hardness of the outermost surface layer of the film roll, when measured at intervals of 50 mm in the film width direction, is in the range of 500 or more and 700 or less. (4) The hardness deviation of the outermost surface layer of the film roll, when measured at intervals of 50 mm in the film width direction, is 10% or more and 20% or less. (5) Film thickness is 5 μm or more and 40 μm or less. (6) Regarding thickness non-uniformity in the film width direction on the surface layer of the film roll, the thickness pattern has a concave portion, and in the concave portion with the largest thickness difference (maximum concave portion), the thickness non-uniformity of the maximum concave portion calculated from the maximum thickness difference in the maximum concave portion and the average film thickness is less than 10%. Claim 2 A biaxially stretched polyester film roll according to claim 1, wherein, regarding the thickness non-uniformity in the width direction of the film of each sample sampled at intervals of a winding length of 1000 m from the surface layer of the film roll, the thickness non-uniformity calculated from the maximum thickness difference at the maximum concave part and the average film thickness is 10% or less of the total sample. Claim 3 A biaxially stretched polyester film roll according to claim 1, wherein the absolute value of the difference in widthwise refractive index with the maximum thickness point at either end of the concave portion in the maximum concave portion is 0.010 or less. Claim 4 A biaxially stretched polyester film roll according to claim 1, characterized in that the number of defects of 1 mm or more per 10,000 square meters of film is 1.0 or less. Claim 5 A biaxially stretched polyester film roll according to claim 1, wherein the coefficient of static friction and the coefficient of dynamic friction of the outer and inner surfaces of the film are both 0.1 or higher and 0.8 or lower. Claim 6 A biaxially stretched polyester film roll according to claim 1, characterized in that the film's intrinsic viscosity is 0.51 dL / g or higher and 0.70 dL / g or lower. Claim 7 A method for manufacturing a biaxially stretched polyester film roll as described in any one of claims 1 to 6, characterized by melt-extruding a raw polyester resin so that the difference between the intrinsic viscosity of the raw polyester resin and the intrinsic viscosity of the polyester film is 0.06 dL / g or less, then cooling and solidifying to obtain an unoriented film, then biaxially stretching the unoriented film, then performing a heat-setting treatment, then winding the biaxially stretched film as a master roll, and then slitting the master roll to wind it into a roll shape.

Images