JP2017105985A - Polyester film for manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for manufacturing an optical film capable of being used as a substrate for achieving manufacturing of the optical film capable of drawing a laminate of a resin composition for optical film and a substrate in a rolled condition, less in generation of debris entrainment or scar, excellent in mold releasability and high in productivity.SOLUTION: There is provided a polyester film for manufacturing an optical film containing particles of 0.03 wt.% to 2.00 wt.% based on whole polyester resin composition constituting the polyester film, having stress at 10% elongation in a film MD direction at 150°C of 5 MPa to 30 MPa, liquid crystal size of a (100) surface obtained by an X ray diffraction measurement of 4.0 nm to 10.0 nm and crystal size uneveness calculated by the following method of 1.0 nm or less.SELECTED DRAWING: None

Description

  The present invention relates to a polyester film for producing an optical film.

  High contrast liquid crystal display devices (LCD) using birefringence are used in various screen display devices such as mobile phones, personal computers, and liquid crystal televisions. In the LCD, various optical films are used for the purpose of improving the brightness of the liquid crystal screen and improving the contrast. In recent years, LCDs have advanced in high definition, have a wide variety of uses, and have been demanded to improve optical compensation performance such as widening of the viewing angle. In order to improve viewing angle characteristics, various retardation films are used as optical films in LCDs. However, the conventional liquid crystal display device using the retardation film displays an image on the entire screen of the liquid crystal panel because the contrast ratio decreases in the oblique direction or the image color changes with the viewing angle. Has become a problem.

  In order to improve the viewing angle characteristics, an optical film having a higher retardation at longer wavelengths in the visible light region is used as the retardation film. As a method for producing such an optical film, a method of stretching a polymer film has been proposed. (Patent Document 1, Patent Document 2)

JP 2007-106848 A JP 2011-227429 A

  However, when the polymer film peeled off from the substrate as in Patent Document 1 is stretched, the polymer film is in direct contact with the roll or the air, so that foreign matter is entangled or scratched easily. There is. Moreover, in patent document 2, although the laminated body of a base material and a coating film is extended | stretched, extending | stretching was a batch process by a cut sheet size, and its productivity was bad.

  INDUSTRIAL APPLICABILITY The present invention can be used as a base material for realizing the production of a highly productive optical film that can reduce the occurrence of foreign matter and scratches, has excellent releasability, and can be stretched roll-to-roll. It aims at providing the polyester film for optical film manufacture.

  In order to solve the above-mentioned problems, the present invention is a polyester film comprising a polyester resin composition as a main constituent, and the amount of particles is 0.03% by weight with respect to the entire polyester resin composition constituting the polyester film. It is contained in an amount of 2.00% by weight or less, the stress at 10% elongation in the film MD direction at 150 ° C. is 5 MPa or more and 30 MPa or less, and the crystal size of the (100) plane determined by X-ray diffraction measurement is 4.0 nm. The main purpose is that the polyester film for optical film production has a crystal size unevenness of 10.0 nm or less and a (100) plane of 1.0 nm or less.

  According to the present invention, it is possible to stretch a laminate of a resin composition for an optical film and a substrate in a roll shape, the occurrence of foreign matter and scratches can be reduced, and a decrease in yield due to erroneous detection in inspection can be suppressed. The polyester film for optical film manufacture which can be used as a base material for manufacturing an optical film with small phase difference nonuniformity can be provided. In particular, the polyester film according to the present invention can be suitably used during the production of a retardation film.

  In the present invention, a polyester film for producing an optical film (hereinafter also simply referred to as a polyester film) is a resin composition for an optical film, which is obtained by applying a solution in which a resin composition for an optical film is dissolved to the surface of a substrate and drying it. A polyester used as a base material in an optical film manufacturing process in which an optical film is obtained by stretching the laminate at least in a uniaxial direction and finally peeling the base material from the laminate. It is a film. The polyester film for producing an optical film of the present invention can be suitably used as a substrate particularly in a retardation film producing process.

  The polyester constituting the polyester film of the present invention is a general term for polymer compounds in which main bonds in the main chain are ester bonds. The polyester resin can be usually obtained by polycondensation reaction of dicarboxylic acid or its derivative with glycol or its derivative. Further, the main constituent component of the polyester resin composition of the present invention means that the polyester resin composition is 60% by weight or more of the resin constituting the film.

  In the present invention, from the viewpoints of moldability, appearance, and economy, 60 mol% or more of the glycol units constituting the polyester are structural units derived from ethylene glycol, and 60 mol% or more of the dicarboxylic acid units are structures derived from terephthalic acid. Preferably it is a unit. Here, the dicarboxylic acid unit (structural unit) or the diol unit (structural unit) means a divalent organic group from which a portion to be removed by polycondensation has been removed. It is represented by

Dicarboxylic acid unit (structural unit): —CO—R—CO—
Diol unit (structural unit): —O—R′—O—
(Where R and R ′ are divalent organic groups)
In addition, when a trivalent or higher carboxylic acid or alcohol such as trimellitic acid unit or glycerin unit or a derivative thereof is included, the trivalent or higher carboxylic acid or alcohol unit (structural unit) is similarly obtained by polycondensation. The trivalent or higher valent organic group from which the part to be removed is removed is meant.

  Glycols or derivatives thereof that give polyester for use in the present invention include, in addition to ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, Aliphatic dihydroxy compounds such as 1,5-pentanediol, 1,6-hexanediol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, 1,4-cyclohexanedimethanol , Alicyclic dihydroxy compounds such as spiroglycol, aromatic dihydroxy compounds such as bisphenol A and bisphenol S, and derivatives thereof. Of these, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol are preferably used from the viewpoint of moldability and handleability.

  In addition to terephthalic acid, the dicarboxylic acid or derivative thereof that provides the polyester used in the present invention includes isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid. Acids, aromatic dicarboxylic acids such as 5-sodiumsulfone dicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid, etc. Alicyclic dicarboxylic acids, oxycarboxylic acids such as paraoxybenzoic acid, and derivatives thereof. Examples of dicarboxylic acid derivatives include dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl adipate, diethyl maleate, and dimethyl dimer. An esterified product can be mentioned. Among these, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and esterified products thereof are preferably used from the viewpoint of moldability and handleability.

  The resin constituting the polyester film of the present invention contains so-called internal particles that precipitate due to catalyst residues added during the polymerization reaction, and particles that are arbitrarily selected from external particles such as inorganic particles and organic particles. There is a need to. When particles are contained in the resin constituting the polyester film, it is possible to improve the slipperiness of the film and to improve the handleability during production. Moreover, in an optical film manufacturing use, the mold release property at the time of peeling the resin composition for optical films from a film becomes favorable by making a polyester film contain particle | grains. On the other hand, as will be described in detail later, when the particles are contained in the resin constituting the polyester film, unless the particles are uniformly dispersed, crystallization starting from the particles varies, resulting in uneven crystal size. Occurs, causing phase difference unevenness. The average particle size of the particles contained in the resin constituting the polyester film is preferably 0.01 to 8 μm, and more preferably 0.5 to 5 μm. If particles having an average particle diameter exceeding 8 μm are contained, defects may occur in the polyester film, which is not preferable. The particles are not particularly limited, but for example, inorganic particles such as silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, hydroxyapatite, styrene, silicone, acrylic acid, Organic particles or the like containing a component obtained by polymerizing methacrylic acid, ester, divinylbenzene or the like can be used. Among them, inorganic particles such as silica and alumina, organic particles composed of polymerized styrene, silicone, acrylic acid, methacrylic acid, ester, divinylbenzene, etc. are preferably used, particularly in optical film production applications. Silica is preferably used from the viewpoint of releasability. As the particles, two or more types of internal particles, inorganic particles, and organic particles may be used, or two or more types of internal particles, inorganic particles, and organic particles may be used in combination. Content of particle | grains needs to be the range of 0.03-2.00 weight% with respect to the whole resin composition which comprises a polyester film. More preferably, it is 0.03-1.00 weight%, More preferably, it is 0.03-0.50 weight%, Especially preferably, it is 0.05-0.30 weight%. When the content is less than 0.05% by weight, it is difficult to wind the film, and it is difficult to peel the optical film resin composition from the substrate. On the other hand, when the content exceeds 0.50% by weight, the appearance is deteriorated due to coarse protrusions and the film forming property is deteriorated. Moreover, the average particle diameter said here is a volume average particle diameter.

  In the polyester film of the present invention, the stress at 10% elongation in the film MD direction at 150 ° C. needs to be 5 MPa or more and 30 MPa or less. By making the stress at the time of 10% elongation in the film MD direction at 150 ° C. within the above range, when the polyester film is laminated with the resin composition for an optical film and then stretched at least in a uniaxial direction, the polyester film is used as a base material. Necessary stiffness and mechanical strength can be satisfied. If the stress at 10% elongation in the MD direction is less than 5 MPa, the stiffness of the polyester film may be insufficient and uneven retardation may occur. If the stress at 10% elongation in the MD direction is greater than 30 MPa, it may be difficult to stretch in the uniaxial direction after laminating the resin composition for an optical film, and necessary retardation characteristics may not be obtained.

  The stress at 10% elongation in the film MD direction at 150 ° C. means that a film sample cut into a rectangular shape having a test length of 50 mm is set in a thermostat set at 150 ° C. in advance, and after preheating for 90 seconds, 300 mm / The stress applied to the film when the sample is stretched 10% in the MD direction when a tensile test is performed at a strain rate of minutes is shown. The evaluation was performed by measuring the stress at 10% elongation in the MD direction at an arbitrary position of the film 5 times, and taking the average value as the stress at 10% elongation in the film MD direction at 150 ° C. In a cut film in which the TD direction and MD direction are not known, the main orientation axis direction is regarded as the TD direction, and the stress at 10% elongation in the MD direction is measured. From the viewpoint of stretchability after forming a laminate with the resin composition for optical films, the stress at 10% elongation in the film MD direction at 150 ° C. is more preferably 6 MPa or more and 20 MPa or less.

  In the polyester film of the present invention, there is no particular limitation on the method for setting the stress at 10% elongation in the MD direction of the film at 150 ° C. in the above range. For example, as a preferred configuration, a polyester resin constituting the polyester film is a glycol component. As a polyester resin containing 80 to 95 mol% of an ethylene glycol component, 5 to 20 mol% of at least one of a diethylene glycol component, a 1,4-cyclohexanedimethanol component and a neopentyl glycol component. The method, the method of adjusting the draw ratio of MD direction of a polyester film, etc. are mentioned. More preferably, the polyester resin constituting the polyester film is at least one of an ethylene glycol component of 85 mol% or more and 92 mol% or less, a diethylene glycol component, a 1,4-cyclohexanedimethanol component, or a neopentyl glycol component as a glycol component. It is preferable that 8 mol% or more and 15 mol% or less are contained, and 90 mol% or more is a terephthalic acid component as a dicarboxylic acid component. More preferably, 95 mol% or more of the dicarboxylic acid component is a terephthalic acid component.

  The polyester film of the present invention needs to have a (100) plane crystal size of 4.0 nm or more and 10.0 nm or less determined by a measurement method described later by X-ray diffraction measurement. By setting the crystal size of the (100) plane as described above, a solution in which the optical film resin composition is dissolved on the surface can be applied, dried, and then uniformly stretched in the stretching step. When the crystal size is less than 4.0 nm, the stretching stress at the time of stretching does not apply uniformly to the film, causing uneven retardation. On the other hand, when the crystal size is larger than 10.0 nm, unevenness in phase difference occurs due to local stress applied around the crystal. The crystal size of the (100) plane is preferably 5.0 nm or more and 9.0 nm or less.

  The method for setting the crystal size within the above range is not particularly limited, and examples thereof include a method of adjusting the heat treatment conditions of the film after biaxial stretching. By increasing the treatment temperature, orientation relaxation occurs and the crystal size tends to increase. From the viewpoint of film quality, the heat treatment temperature after biaxial stretching is preferably 200 ° C to 240 ° C, more preferably 210 ° C to 235 ° C, and most preferably 215 ° C to 230 ° C. The heat treatment temperature of the polyester film of the present invention is determined from the minute endothermic peak resulting from the thermal history in the DSC curve when measured at a temperature rising rate of 20 ° C./min in a differential scanning calorimeter (DSC) under a nitrogen atmosphere. It can be determined by measuring the minute endothermic peak temperature (Tmeta).

  Moreover, as preferable heat processing time, although it can set arbitrarily in 5 to 60 second, it is preferable to set it as 10 to 40 second from a viewpoint of a moldability, dimensional stability, a color tone, and productivity, and 15-30. Preferably it is seconds.

  Further, the polyester film of the present invention needs to have a (100) plane crystal size unevenness of 1.0 nm or less determined by a measurement method described later by X-ray diffraction measurement. By making the crystal size unevenness 1.0 nm or less, a solution in which the resin composition for an optical film is dissolved on the surface is applied, dried, and then stretched uniformly in a stretching process. More preferably, the crystal size unevenness is 0.8 nm or less. On the other hand, as the lower limit of the crystal size unevenness, if the crystal size unevenness is less than 0.01 nm, the stretching stress at the time of stretching may not be uniform in the film and may cause unevenness of the phase difference. Preferably there is.

  As a result of intensive studies by the present inventors, it has been clarified that the crystal size unevenness of the (100) plane is influenced by the degree of dispersion of particles contained in the polyester film (variation in the content concentration of particles).

  As for the polyester film containing particles, conventionally, a method of using a high concentration particle-containing master polyester raw material containing particles at a high concentration and a polyester raw material not containing particles for a melt extrusion film forming machine is well known. In this method, a polyester film having various particle concentrations can be produced simply by changing the distribution amount of the high concentration particle-containing master polyester raw material and the polyester raw material not containing particles to the melt extrusion film forming machine. It is used. However, in this method, when a high-concentration particle-containing master polyester raw material containing particles at a high concentration and a polyester raw material not containing particles are kneaded in a melt-extrusion film-forming machine, portions that are not sufficiently kneaded are generated, and the polyester film Minute variation occurs in the content of particles inside. In most applications where polyester films are used, this variation in fine particle content is not a practical problem. However, when it is used in a polyester film for producing an optical film, this variation in the fine particle content affects the generation of crystal size unevenness on the (100) plane, which affects the characteristics of the optical film, which is a problem. .

  Examples of the method for setting the crystal size unevenness within the above range include a method in which particles contained in a film are dispersed at a uniform concentration with very high accuracy. The method of dispersing the particles at a uniform concentration with very high accuracy is not limited to a specific method. For example, a biaxial kneader having a large L / D (for example, 20 or more, more preferably 40 or more) is used. A method of using a polyester resin and particles after kneading and then supplying to a melt film-forming machine, a method of supplying a master polyester raw material containing high concentration particles having a specific intrinsic viscosity, a polyester raw material not containing particles to a melt film-forming machine, etc. Can be mentioned. The method of using a high concentration particle-containing master polyester raw material having a specific intrinsic viscosity and a polyester raw material not containing particles for a melt film-forming machine will be described in detail later. By using the above method, the particles are uniformly dispersed in the film, and a film having a uniform crystal size (small crystal size unevenness) can be obtained.

  Moreover, it is preferable that the haze nonuniformity calculated | required by the method mentioned later of the polyester film of this invention is 0.01% or more and 0.70% or less. By setting the haze unevenness to 0.70% or less, a solution in which the resin composition for an optical film is dissolved on the surface is applied, dried, and then uniformly stretched in a stretching process. In addition, it is possible to suppress false detection in foreign matter inspection and application appearance inspection by automatic inspection with a defect detector and sampling terminal inspection, and an effect of improving yield can be obtained. More preferably, it is 0.50% or less, More preferably, it is 0.20% or less. On the other hand, as the lower limit of the haze unevenness, if the haze unevenness is less than 0.01%, the stretching stress at the time of stretching may not be uniform in the film and may cause the retardation unevenness. It is preferable that The method for setting the haze unevenness within the above range is not particularly limited, but in the same manner as the method for suppressing the crystal size unevenness, a high-concentration particle-containing master polyester raw material having a specific intrinsic viscosity, and a polyester raw material containing no particles are melt-casting machines. The method to use for is mentioned. Moreover, it is preferable that the thickness of the polyester film calculated | required by the method mentioned later of the polyester film of this invention is 25 micrometers or more and 125 micrometers or less. When the film thickness is smaller than 25 μm, the handling property of the film is lowered, which causes unevenness in retardation. On the other hand, if the thickness is larger than 125 μm, the thickness unevenness of the film becomes large, which causes unevenness of retardation. Preferably they are 40 micrometers or more and 100 micrometers or less.

  Moreover, it is preferable that the thickness nonuniformity of the polyester film calculated | required by the method mentioned later of the polyester film of this invention is 2 micrometers or less. If the thickness unevenness of the polyester film is larger than 2 μm, the thickness unevenness of the film is transferred to the thickness of the resin composition for an optical film and causes unevenness of retardation. Preferably, it is 1.8 μm or less. The method for adjusting the thickness unevenness to the above range is not particularly limited, but the ratio of longitudinal stretching is 2.5 times or more and 3.5 times or less. By setting it as the above, it is possible to implement uniform longitudinal stretching. If it is less than 2.5 times, unevenness in the longitudinal stretching occurs, and if it is more than 3.8 times, it causes deterioration of productivity due to film tearing. Preferably they are 2.7 times or more and 3.5 times or less.

The polyester film of the present invention preferably has a thickness unevenness of 2 μm or less after being stretched 10% in the MD direction under the following conditions. If the uneven thickness of the film is larger than 2 μm, the uneven thickness of the film may be transferred to the thickness of the resin composition for an optical film and cause uneven retardation. The method for setting the thickness unevenness after stretching in the MD direction to the above range is not particularly limited, but the above-described longitudinal stretching conditions may be 2.7 times or more and 3.5 times or less.
[MD direction 10% stretching conditions]
A polyester film was cut into an A4 size, and a sample cut into a rectangle with a length of 150 mm and a width of 10 mm was used as a measurement sample so that the MD direction was the length direction from the cut A4 size film. Using a tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.), the measurement film was set to a length between chucks of 50 mm (initial sample length), and the temperature was set to 150 ° C. and the humidity was 65% RH. After preheating for 60 seconds in a thermostatic layer, the film is pulled at a pulling speed of 300 mm / min and stretched 1.1 times.

  The polyester film of the present invention preferably has a crystal size unevenness of 1.0 nm or less after stretching in the MD direction. By setting the crystal size unevenness after stretching as described above, the stress at the time of peeling the resin composition for an optical film from the film becomes uniform, and the retardation unevenness can be suppressed. More preferably, the crystal size unevenness is 0.8 nm or less. In the polyester film of the present invention, examples of the method for setting the crystal size unevenness in the above range include a method of supplying a high concentration particle-containing master polyester raw material having a specific intrinsic viscosity and a polyester raw material not containing particles to a melt film forming machine. It is done.

Hereinafter, a method for supplying a high concentration particle-containing master polyester raw material having a specific intrinsic viscosity and a polyester raw material not containing particles to a melt film forming machine will be described. The method for producing a polyester film of the present invention uses a polyester raw material A, a polyester raw material B, a polyester raw material A obtained by melting and kneading the polyester raw material A, the polyester raw material B, and particles in a melt extrusion film forming machine. In the method for producing a polyester film, when the intrinsic viscosity of the polyester raw material A is IVa, the intrinsic viscosity of the polyester raw material B is IVb, and the intrinsic viscosity of the polyester raw material C is IVc, and the following formula (I), ( It is preferable to satisfy II).
IVc = (IVa × 0.4 + IVb × 0.4) ± 0.05 (I)
IVc <IVa <IVb (II)
By satisfying the above formulas (I) and (II), the particles, the polyester resin of the polyester raw material A, and the polyester resin of the polyester raw material B are uniformly dispersed in the film, so that a film having a uniform crystal size is obtained and retardation unevenness is obtained. Can be suppressed.
More preferably, the formula (I) satisfies the following formula (I ′): IVc = (IVa × 0.4 + IVb × 0.4) ± 0.04 (I ′)
In the method for producing a polyester film of the present invention, IVa is preferably 0.60 or more and 0.70 or less, and IVb is preferably 0.73 or more and 0.88 or less. By setting it as the said range, the polyester resin of the polyester raw material A and the polyester resin of the polyester raw material B are disperse | distributed uniformly in a film.

  The polyester film in the present invention can be produced by various conventionally known methods. Hereinafter, the example of the manufacturing method of the polyester film in this invention is demonstrated. A monolayer polyester film consisting of one layer will be described as an example of the polyester film, but the present invention is not construed as being limited to such an example.

  The method for producing a polyester film of the present invention will be described with examples, but the present invention is not construed as being limited to such examples. First, a polyethylene terephthalate resin (a) and a 1,4-cyclohexanedimethanol copolymerized polyethylene terephthalate resin (10% elongation stress at 150 ° C. in the film MD direction at 5% to 30 MPa are satisfied. b), a polyethylene terephthalate resin (a), a 1,4-cyclohexanedimethanol copolymerized polyethylene terephthalate resin (b), and a polyethylene compounded with particles, which are used for satisfying that the crystal size unevenness is 1.0 nm or less The terephthalate resin (c) is weighed at a predetermined ratio. Then, the mixed polyester resin is supplied to a vent type twin screw extruder and melt extruded. At this time, it is preferable to control the resin temperature to 265 ° C. to 295 ° C. under an atmosphere of flowing nitrogen in the extruder, with an oxygen concentration of 0.7% by volume or less. Next, foreign matter is removed and the amount of extrusion is leveled through a filter and a gear pump, and the sheet is discharged from the T die onto the cooling drum in a sheet form. At that time, an electrostatic application method in which the cooling drum and the resin are brought into close contact with each other by static electricity using an electrode applied with a high voltage, and the casting drum temperature is extruded from the glass transition point of the polyester resin to (glass transition point-20 ° C.). The sheet-like polymer is brought into close contact with the casting drum by a method of adhering the polymer or a combination of these methods, and is cooled and solidified to obtain an unstretched film. Among these casting methods, when using polyester, a method of applying an electrostatic force is preferably used from the viewpoint of productivity and flatness.

  Thereafter, this film is stretched at a roll length of 2.5 to 3.8 times with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented PET film. Thereafter, the end of the PET film is gripped with a clip and guided to a preheating zone of 80 to 130 ° C., and the solvent of the coating liquid is dried. After drying, the film is stretched 3.0 to 4.2 times in the width direction at a temperature of 100 to 160 ° C. Subsequently, the first stage heat treatment is conducted for 1 to 30 seconds, and then the second stage heat treatment is performed at a temperature higher than the first stage heat treatment temperature and in the range of 200 to 240 ° C. After ~ 30 seconds to complete crystal orientation. In this heating step (heat treatment step), 3 to 15% relaxation treatment may be performed in the width direction or the longitudinal direction as necessary.

(1) Composition of polyester resin A polyester resin and a film are dissolved in hexafluoroisopropanol (HFIP), and the content of each monomer residue component and by-product diethylene glycol is quantified using ¹ H-NMR and ¹³ C-NMR. In addition, about the polyester resin of a present Example, the composition was computed by calculation from the mixing ratio at the time of film manufacture.

(2) Intrinsic viscosity of the polyester resin The intrinsic viscosity of the polyester resin and the film was measured at 25 ° C. using an Ostwald viscometer after dissolving the polyester in orthochlorophenol. In the case of a laminated film, the intrinsic viscosity of each layer can be evaluated by scraping each layer of the film according to the laminated thickness.

(3) Minute endothermic peak temperature (Tmeta) before crystal melting
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., RDC220), measurement and analysis were performed in accordance with JIS K7121-1987 and JIS K7122-1987. Using 5 mg of a polyester film as a sample, a minute endothermic peak temperature appearing before the crystal melting peak when the temperature was raised from 25 ° C. to 300 ° C. at 20 ° C./min was read as Tmeta.

(4) Main orientation axis (TD) of the film
A sample is cut out with a size of 100 mm × 100 mm at an arbitrary point of the film, and a main orientation axis in the plane of the polyester film is obtained using a microwave molecular orientation meter MOA-2001A (frequency 4 GHz) manufactured by KS Systems (currently Oji Scientific Instruments). Was determined as the TD direction.

(5) Stress at 10% elongation in the film MD direction at 150 ° C. The film was cut into a rectangular shape having a length of 150 mm and a width of 10 mm so that the MD direction was the length direction. Using a tensile tester (Orientec Tensilon UCT-100), a tensile test was performed in the MD direction of the film with an initial tension chuck distance of 50 mm and a tensile speed of 300 mm / min. For the measurement, a film sample was set in a thermostat set at 150 ° C. in advance, and a tensile test was performed after 90 seconds of preheating. Read the load applied to the film when the sample is stretched 10% (when the distance between chucks is 55 mm), and divide by the cross-sectional area (film thickness x 10 mm) of the sample before the test. did. The evaluation was performed 5 times with the main orientation axis direction at an arbitrary position of the film as the TD direction, and the average value was defined as the stress at 10% elongation in the film MD direction at 150 ° C.

(6) Crystal size of (100) plane The crystal size of the (100) plane was determined by a reflection X-ray diffractometer (PW1728 manufactured by Philips) using the Scherrer equation. Here, the measured X-ray wavelength was 0.15418 nm (CuKα), and diffraction on the (100) plane was observed at a Bragg angle of about 25.8 °. The polyester film was cut into A4 size, measured at any five points in the cut sample, and the average value of the five times was taken as the crystal size.

(7) Unevenness of crystal size on (100) plane Among the five measurements measured in (6), the maximum value is Rcmax, the minimum value is Rcmin, and the crystal size obtained from the following formula (III) Unevenness Rc = Rcmax−Rcmin (III)
(8) Sample with crystal size unevenness film stretched 10% in MD direction cut to A4 size, and further cut from A4 size film into a rectangle 150 mm long and 10 mm wide so that the MD direction is the length direction It was. Using a tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.), the sample film was set so that the length between chucks was 50 mm (initial sample length). After preheating for 60 seconds in a constant temperature layer set to a temperature of 150 ° C. and a humidity of 65% RH, the sample was pulled at a pulling speed of 300 mm / min and stretched 1.1 times in the same manner as the method for measuring an unstretched sample. And measured. Using a measurement X-ray wavelength of 0.15418 nm (CuKα) for each arbitrary point of the portion sandwiched between five sample chucks obtained by stretching the sample film cut in the longitudinal direction 1.1 times, a Bragg angle of about 25 The crystal size of the (100) plane observed at .8 ° was determined using a Scherrer equation with a reflection X-ray diffractometer (PW1728 manufactured by Philips). Among the measurement results of 5 samples, the maximum value was Rcmax, the minimum value was Rcmin, and the crystal size unevenness at 10% elongation in the MD direction was determined by the above formula (III).

(9) Haze irregularity Using a turbidimeter “NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd., a method according to JIS “How to determine haze of transparent material” (K7136 2000 version) is carried out. The polyester film was cut into A4 size, measured at any five points in the cut sample, and the maximum value was determined as Hmax and the minimum value was determined as Hmin.
Haze irregularity = Hmax−Hmin (IV)
(10) The thickness film is cut into A4 size, and the thickness is measured by the micrometer method defined in JIS C2151 using the TESA Electronic Measuring Probe GT21 at any five points in the cut sample. The average value of the obtained values was taken as the film thickness.

(11) Thickness unevenness Among the five measurement values measured in (10), the maximum value is Rmmax, the minimum value is Rmmin, and the thickness unevenness Rm = Rmmax−Rmmin calculated from the following formula (IV): (IV)
(12) A sample in which an uneven thickness film at 10% in the MD direction is cut into an A4 size, and the film is further cut out into a rectangle having a length of 150 mm and a width of 10 mm from the A4 size film so that the MD direction is the length direction. did. Using a tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.), the sample film was set so that the length between chucks was 50 mm (initial sample length). After preheating for 60 seconds in a constant temperature layer set to a temperature of 150 ° C. and a humidity of 65% RH, the sample was pulled at a pulling speed of 300 mm / min and stretched 1.1 times in the same manner as the method for measuring an unstretched sample. And measured. Specified in JIS C2151 using a TESA electronic measuring probe GT21 for each arbitrary point of the portion sandwiched between five sample chucks obtained by stretching the sample film cut in the longitudinal direction 1.1 times. The thickness was measured by a micrometer method. Among the measurement results of 5 samples, the maximum value was Rmmax, and the minimum value was Rmmin, and the thickness unevenness at 10% elongation in the MD direction was determined by the above formula (IV).

(13) Molding workability Polyarylate / MEK dispersion was applied and dried on a 200 mm wide polyester film surface with a die coater. (Drying temperature: 150 ° C., unwinding tension: 200 N / m, winding tension: 100 N / m, drying time: 1 minute, polyarylate thickness after drying is 25 μm). Thereafter, the polyester film coated with polyarylate was put into a hot air oven and uniaxially stretched in the longitudinal direction (oven temperature: 150 ° C., width direction free). The stretchability (moldability) of the film was evaluated according to the following criteria.
A: The stretching tension was less than 1200 N / m, and 1.1-fold stretching was possible.
B: The film was stretched 1.1 times with a stretching tension of 1200 N / m or more and less than 1500 N / m.
C: The film could not be stretched 1.1 times even at a stretching tension of 1500 N / m.
B or higher was accepted.

(14) Uniformity in the width direction of the optical film The polyarylate-coated uniaxially stretched polyester film obtained in (13) was cut into a length of 300 mm. The polyarylate layer was peeled off, and the in-plane retardation was measured for any five points, and evaluated according to the following criteria. The retardation was measured using an automatic birefringence meter (KOBRA-21ADH) manufactured by Shin-Oji Scientific Instruments.
A: The difference between the maximum value and the minimum value of the retardation measured at 5 points was less than 10 nm.
B: The difference between the maximum value and the minimum value of the retardation measured at 5 points was 10 nm or more and less than 20 nm.
C: The difference between the maximum and minimum retardation values measured at 5 points was 20 nm or more.
B or higher was accepted.

(Manufacture of polyester)
The polyester resin used for film formation was prepared as follows.

(Polyester A)
Polyethylene terephthalate resin (intrinsic viscosity 0.65) in which the terephthalic acid component is 100 mol% as the dicarboxylic acid component and the ethylene glycol component is 100 mol% as the glycol component.

(Polyester B)
Cyclohexanedimethanol copolymerized polyester in which terephthalic acid component is 100 mol% as dicarboxylic acid component, ethyleneglycol component is 67 mol% as glycol component, and 33 mol% of 1,4-cyclohexanedimethanol component is copolymerized with glycol component (Intrinsic viscosity 0.84).

(Polyester C)
Using a twin-screw extruder, 70 parts by weight of polyester A and 30 parts by weight of polyester B are supplied to this extruder. At a cylinder temperature of 275 ° C. and a screw speed of 200 rpm, the resin is first extruded only with resin. After confirming that it is completely melted, agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight with respect to the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm and pelletized (inherent viscosity 0.60).

(Polyester D)
Using a twin-screw extruder, 70 parts by weight of polyester A and 30 parts by weight of polyester B are supplied to the extruder, and at a cylinder temperature of 282 ° C. and a screw speed of 210 rpm, the resin is first extruded only with resin. After confirming that it is completely melted, agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight with respect to the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm, and pelletized (intrinsic viscosity 0.56).

(Polyester E)
Using a twin screw extruder, 70 parts by weight of polyester A and 30 parts by weight of polyester B are supplied to this extruder, and at a cylinder temperature of 270 ° C. and a screw rotation speed of 180 rpm, the resin is first extruded only with resin. After confirming that it is completely melted, agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight with respect to the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm, and pelletized (inherent viscosity 0.63).

(Polyester F)
A neopentyl glycol copolymer polyethylene terephthalate resin (intrinsic viscosity 0.80) in which the terephthalic acid component is 100 mol% as the dicarboxylic acid component, the ethylene glycol component is 67 mol% and the neopentyl glycol component is 33 mol% as the glycol component.

(Polyester G)
Using a twin-screw extruder, 70 parts by weight of polyester A and 30% by weight of polyester F are supplied to this extruder. At a cylinder temperature of 275 ° C. and a screw speed of 200 rpm, the resin is first extruded and the resin is completely After confirming that it is melted, the agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight based on the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm, and pelletized (intrinsic viscosity 0.59).

(Polyester H)
A diethylene glycol copolymer polyethylene terephthalate resin (inherent viscosity 0.69) in which the terephthalic acid component is 100 mol% as the dicarboxylic acid component, the ethylene glycol component is 77 mol%, and the diethylene glycol component is 33 mol% as the glycol component.

(Polyester I)
Using a twin-screw extruder, 70 parts by weight of polyester A and 30 parts by weight of polyester H are supplied to this extruder. At a cylinder temperature of 275 ° C. and a screw speed of 200 rpm, the resin is first extruded only with resin. After confirming that it is completely melted, agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight with respect to the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm, and pelletized (inherent viscosity 0.58).

(Polyester J)
Polyethylene terephthalate resin containing 100% by mole of a terephthalic acid component as a dicarboxylic acid component, 100% by mole of an ethylene glycol component as a glycol component, and 0.3% by weight of aggregated silica particles having a number average particle diameter of 1.2 μm based on the total amount (Intrinsic viscosity 0.65).

(Polyester K)
Using a twin-screw extruder, 70 parts by weight of polyester A and 30 parts by weight of polyester B are supplied to the extruder, and at a cylinder temperature of 290 ° C. and a screw speed of 230 rpm, the resin is first extruded only with resin. After confirming that it is completely melted, agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight with respect to the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm, and pelletized (intrinsic viscosity 0.53).

(Polyester L)
Using a twin-screw extruder, 70 parts by weight of polyester A and 30 parts by weight of polyester B are supplied to the extruder, and at a cylinder temperature of 265 ° C. and a screw rotation speed of 170 rpm, the resin is first extruded only with resin. After confirming that it is completely melted, agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight with respect to the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm, and pelletized (inherent viscosity 0.65).

(Polyester M)
Using a twin-screw extruder, 70 parts by weight of polyester A and 30 parts by weight of polyester B are supplied to this extruder, and at a cylinder temperature of 270 ° C. and a screw speed of 310 rpm, the resin is first extruded only with resin. After confirming that it is completely melted, agglomerated silica particles having a number average particle diameter of 1.2 μm are added so as to be 1.0% by weight with respect to the total amount. The extruded gut was cooled in a cooling bath, cut into a length of 7 mm, and pelletized (inherent viscosity 0.50).

Example 1
The composition is as shown in the table, and the raw materials are respectively fed to a vented co-axial twin screw extruder having an oxygen concentration of 0.2% by volume and an L / D of 15, and the extruder cylinder temperature is melted at 277 ° C. The tube temperature was 277 ° C., the die temperature was 280 ° C., and the sheet was discharged from a T-die onto a cooling drum whose temperature was controlled at 25 ° C. At that time, a wire-like electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain an unstretched film. Next, before stretching in the longitudinal direction, the film temperature was raised with a heated roll, the longitudinal stretching ratio was stretched 3.1 times at a stretching temperature of 85 ° C., and immediately cooled with a metal roll controlled to 40 ° C.

  Next, the film was stretched 3.7 times in the width direction at a stretching first half temperature of 95 ° C., a stretching middle temperature of 105 ° C., and a stretching second half temperature of 140 ° C., and the first half heat treatment was performed at 220 ° C. in the tenter. The heat treatment was performed at 225 ° C. Thereafter, heat treatment was performed at a heat treatment latter half temperature of 180 ° C. while relaxing 3% in the width direction to obtain a biaxially oriented polyester film having a film thickness of 75 μm.

(Example 2)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the first half temperature of the heat treatment was 215 ° C. and the second half temperature of the heat treatment was 220 ° C.

(Example 3)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the heat treatment latter half temperature was 230 ° C.

Example 4
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 5)
A biaxially oriented polyester having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 6)
A biaxially oriented polyester having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 7)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 8)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film thickness was changed to 30 μm.

Example 9
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the thickness of the film was changed to 110 μm.

(Example 10)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 11)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 12)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 13)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Example 14)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that a bent simultaneous biaxial extruder having an L / D of 40 was used and the composition was changed as shown in the table.

(Example 15)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that a bent simultaneous biaxial extruder having an L / D of 40 was used and the composition was changed as shown in the table.

(Comparative Example 1)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Comparative Example 2)
The composition was changed as shown in the table, and a biaxially oriented polyester film having a thickness of 75 μm was obtained in the same manner as in Example 1 except that the first half temperature of the heat treatment was changed to 185 ° C. and the second half temperature of the heat treatment was changed to 190 ° C.

(Comparative Example 3)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Comparative Example 4)
The composition was changed as shown in the table, and a biaxially oriented polyester film having a thickness of 75 μm was obtained in the same manner as in Example 1 except that the first half temperature of the heat treatment was changed to 230 ° C. and the second half temperature of the heat treatment was changed to 245 ° C.

(Comparative Example 5)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Comparative Example 6)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

(Comparative Example 7)
A biaxially oriented polyester film having a film thickness of 75 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

The meanings of the abbreviations in the table are as follows.
CHDM: 1,4-cyclohexanedimethanol DEG: diethylene glycol NPG: neopentyl glycol

According to the present invention, it is possible to stretch a laminate of a resin composition for an optical film and a substrate in a roll shape, there is little occurrence of foreign matter and scratches, and it is possible to suppress a decrease in yield due to erroneous detection in inspection, and The polyester film for optical film manufacture which can be used as a base material for implement | achieving manufacture of the optical film excellent in moldability and high productivity can be provided.

Claims (6)

A polyester film comprising a polyester resin composition as a main constituent, and containing 0.03% by weight or more and 2.00% by weight or less of particles with respect to the entire polyester resin composition constituting the polyester film, 150 The stress at 10% elongation in the film MD direction at 5 ° C. is 5 MPa or more and 30 MPa or less, and the crystal size of the (100) plane determined by the following method by X-ray diffraction measurement is 4.0 nm or more and 10.0 nm or less, (100) A polyester film for producing an optical film having a crystal size variation of 1.0 nm or less.
[(100) plane crystal size, (100) plane crystal size unevenness measurement method]
The polyester film was cut into A4 size, and the crystal size of the (100) plane was determined at any 5 points in the cut sample using a Scherrer equation with a reflection X-ray diffractometer (PW1728 manufactured by Philips). The average value of the measured values is the crystal size of the (100) plane, and the difference between the maximum value and the minimum value of the five measured values is the uneven crystal size of the (100) plane. The polyester film for producing an optical film according to claim 1, wherein the haze unevenness is 0.01% or more and 0.70% or less.
[Method for measuring haze unevenness]
A polyester film was cut out to A4 size, and the turbidimeter “NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd. was used at any 5 points in the cut out sample, and JIS “How to determine haze of transparent material” (K7136 2000 edition) ) And the difference between the maximum value and the minimum value of the five measured values is defined as haze unevenness. The polyester film for producing an optical film according to claim 1 or 2, wherein the thickness of the polyester film obtained by the following method is 25 µm or more and 125 µm or less, and the thickness unevenness is 2 µm or less.
[Method for measuring thickness and unevenness of polyester film]
The polyester film was cut into A4 size, and at any 5 points in the cut sample, the micrometer method defined in JIS C2151 (2006) was used to measure the polyester film using (TESA Electronic Measuring Probe GT21). The thickness is measured, and the average value of the five measurement values is the thickness of the polyester film, and the difference between the maximum value and the minimum value of the five measurement values is the thickness unevenness. The thickness unevenness of the polyester film after stretching 10% in the MD direction under the following conditions is 2.0 µm or less, and the crystal size unevenness of the (100) plane is 1.0 nm or less. Polyester film for optical film production.
[MD direction 10% stretching conditions]
A polyester film was cut into an A4 size, and a sample cut into a rectangle with a length of 150 mm and a width of 10 mm was used as a measurement sample so that the MD direction was the length direction from the cut A4 size film. Using a tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.), the measurement sample was set so that the length between chucks was 50 mm (initial sample length), and the temperature was set to 150 ° C. and the humidity was 65% RH. After preheating for 60 seconds in a thermostatic layer, the film is pulled at a pulling speed of 300 mm / min and stretched 1.1 times. Stretching is performed with n = 5.
[Method for measuring thickness unevenness of polyester film after stretching in MD direction of 10%]
With respect to five measurement samples stretched by 10% in the MD direction, the micrometer method defined in JIS C2151 (2006) (Electronic measurement manufactured by TESA) was used at an arbitrary point between the chucks. The thickness of the polyester film is determined using the long probe GT21). The difference between the maximum value and the minimum value of the measurement values of the five measurement samples is the thickness unevenness of the polyester film after stretching in the MD direction by 10%.
[Measurement method of crystal size unevenness of polyester film after 10% stretching in MD direction]
With respect to five measurement samples stretched 10% in the MD direction, the crystal size of the (100) plane at any point in the portion sandwiched between chucks was measured by Scherrer using a reflection X-ray diffractometer (PW1728 manufactured by Philips). Obtained using an equation. The difference between the maximum value and the minimum value of the measurement values of the five measurement samples is defined as the crystal size unevenness of the (100) plane of the polyester film after 10% stretching in the MD direction. The polyester resin constituting the polyester film is an ethylene glycol component of 80 mol% to 95 mol% as a glycol component, a diethylene glycol component, a 1,3-propanediol component, a 1,4-butanediol component, and 1,4-cyclohexane. The polyester film for producing an optical film according to any one of claims 1 to 4, comprising at least one of a dimethanol component and a neopentyl glycol component in an amount of 5 mol% to 20 mol%. In a method for producing a polyester film by subjecting a polyester raw material A, a polyester raw material B, and a polyester raw material A obtained by melting and kneading the polyester raw material A, the polyester raw material B and particles to a melt extrusion film forming machine, When the intrinsic viscosity of the polyester raw material A is IVa, the intrinsic viscosity of the polyester raw material B is IVb, and the intrinsic viscosity of the polyester raw material C is IVc, the following formulas (I) and (II) are satisfied: Item 6. A method for producing a polyester film for producing an optical film according to any one of Items 1 to 5.
IVc = (IVa × 0.4 + IVb × 0.4) ± 0.05 (I)
IVc <IVa <IVb (II)