KR102002798B1

KR102002798B1 - Polyester film and manufacturing process therefor

Info

Publication number: KR102002798B1
Application number: KR1020147019196A
Authority: KR
Inventors: 켄타 타카하시; 마사토 호리에; 타쿠지 히가시오지; 테츠야 마치다
Original assignee: 도레이 카부시키가이샤
Priority date: 2012-01-24
Filing date: 2013-01-16
Publication date: 2019-07-23
Also published as: JP5962648B2; JPWO2013111641A1; WO2013111641A1; KR20140116864A; TW201335259A; CN104053535B; TWI577721B; CN104053535A

Abstract

The present invention provides a polyester film which is suitable as a base film having small curl and excellent processability, which can reduce the dimensional change in various processes when used as a base film for a flexible device. The polyester film of the present invention is a polyester film obtained by using a polyester having a crystallization index (ΔTcg) of 10 ° C. or more and 60 ° C. or less. The polyester film has a surface orientation coefficient (fn) of 0.15 or more and 0.28 or less, ) Is 35% or less, and the heat shrinkage ratio in the film longitudinal direction and width direction at 180 ° C is 0% to 1.5%, respectively.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film,

The present invention relates to a biaxially oriented polyester film excellent in thermal dimensional stability particularly in a high temperature region. The biaxially oriented polyester film of the present invention can be preferably used for a substrate film for a flexible device. The biaxially oriented polyester film of the present invention may be used as a substrate film of organic electroluminescence (hereinafter sometimes abbreviated as EL) display, electronic paper, organic EL illumination, organic solar cell and dye sensitized solar cell It is possible to obtain a substrate film having small dimensional changes in various processes and having a small curl and excellent processability when used.

2. Description of the Related Art In recent years, various types of electrodevices have been used for applications requiring weight reduction, thin film formation, degree of freedom of shape, and the like. With respect to the flexibility of the electro-device, there is a method of using a plastic film in place of the glass used as a conventional substrate. However, the plastic film has a large thermal expansion coefficient and heat shrinkage, so that the thermal dimensional stability is poor, and curling easily occurs.

The biaxially oriented polyester film can be used for magnetic recording materials, packaging materials, electrical insulation materials, various photographic materials, graphic art materials or optical display materials And the like. However, it is necessary to improve the physical properties of the base film for a flexible device. To date, a method of blending another thermoplastic resin to polyester to improve the properties of the polyester film (Patent Document 1), a method of decreasing the thermal expansion coefficient by adding particles at a high concentration (Patent Document 2), a method of reducing heat shrinkage (Patent Document 3) is disclosed.

Japanese Patent Application Laid-Open No. 2003-101166 Japanese Patent Application Laid-Open No. 2004-35720 Japanese Unexamined Patent Application Publication No. 3-67627

However, in the method of blending the thermoplastic resin described in Patent Document 1, since the polyester is hardly aligned, the thermal expansion coefficient can not be sufficiently lowered. Further, in the method disclosed in Patent Document 2, when the particles are added at a high concentration, the stretchability is deteriorated and the coefficient of thermal expansion can not be sufficiently lowered. Further, the technique described in Patent Document 3 is aimed at reducing the heat shrinkage rate, and can not lower the coefficient of thermal expansion.

Thus, it is difficult to achieve both low-temperature expansion and low heat shrinkage.

It is an object of the present invention to provide a biaxially oriented polyester film which solves the above problems and is particularly excellent in thermal dimensional stability in a high temperature region. In particular, when used as a base film for a flexible device, And a curl is small, so that the biaxially oriented polyester film is excellent in processability.

The present invention aims at achieving the above object and has the following features.

(1) A polyester film comprising a polyester having a crystallization index (ΔTcg) of 10 ° C. or higher and 60 ° C. or lower, wherein the polyester film has a plane orientation coefficient fn of 0.15 or more and 0.28 or less and a crystallinity Xc (% And a heat shrinkage rate at 180 ° C in the film longitudinal direction and the transverse direction is 0% to 1.5%, respectively.

(2) The method according to (1)

(Fn / Xc) obtained by dividing the face orientation coefficient (fn) by the crystallinity (Xc) is 0.50 or more.

(3) In the item (1) or (2)

And the film haze value is 0 to 3%.

(4) The method according to any one of (1) to (3)

Wherein the polyester contains a crystal nucleating agent and the content of the crystal nucleating agent is 0.01 parts by mass or more and 2 parts by mass or less based on 100 parts by mass of the polyester.

(5) In any one of (1) to (4)

Wherein the polyester is a polyethylene terephthalate.

(6) A film for an organic EL substrate, characterized by using the polyester film according to any one of (1) to (5).

(7) A film for a flexible solar cell substrate, which comprises the polyester film according to any one of (1) to (5).

(8) In the present invention, the polyester resin is cooled and solidified while being melt-extruded to form an unstretched film, and then the unstretched film is biaxially stretched. Thereafter, the thermosetting temperature Ths (占 폚) (1) to (5), wherein the polyester resin is at least one kind of crystal nucleating agent (Ths-25) to (Ths-5) 占 폚, wherein the annealing is carried out at a temperature (Ths-25) to (Ths-5) ° C.

(Effects of the Invention)

According to the present invention, a polyester film excellent in thermal dimensional stability in a high-temperature region can be obtained. When used as a base film for a flexible device, it is possible to reduce the dimensional change in various processes, and in particular, a polyester film excellent in flatness with curl in the annealing process can be obtained.

It is important that the polyester film of the present invention has a crystallization index (hereinafter sometimes referred to as? Tcg) of 10 ° C or more and 60 ° C or less in order to satisfy the thermal dimensional stability in a high temperature region. When? Tcg is in the above range, the formation of microcrystals in the polyester film is promoted, and the thermal dimensional stability under high temperature is improved. In particular, the high temperature and heat shrinkage before the later-described relax annealing process (annealing process while relaxing) becomes small, and as a result, the flatness of the film in the relax annealing process becomes good. If? Tcg is less than 10 ° C, the crystallinity becomes excessively high, leading to deterioration of the stretchability, which may make film formation difficult. Further, when? Tcg is higher than 60 ° C, high-temperature heat shrinkage increases, and the thermal dimensional stability under high temperature is insufficient. The? Tcg is more preferably 30 to 50 占 폚. As a method of setting ΔTcg within the above range, it is preferable to use a polyester containing at least one type of nucleating agent in the polyester and adjusting the crystallization speed to be faster due to the effect of the nucleating agent. The crystal nucleating agent may be a transesterification catalyst or a compound used as a polymerization catalyst. For example, a method in which lithium acetate, magnesium acetate, potassium acetate, phosphorous acid, phosphonic acid, phosphinic acid or derivatives thereof, antimony oxide, and germanium oxide are present during ester exchange and polymerization are effective. A particularly preferable combination is magnesium acetate, phosphonic acid (or a derivative thereof) and antimony oxide, and examples of the phosphonic acid (or derivative thereof) include phenylphosphonic acid and dimethyl phenylphosphonate.

A method of improving the crystallization rate by adding a crystal nucleating agent other than the above compound to the polyester is also effective. The crystal nucleating agent may be selected from the group consisting of talc, aliphatic carboxylic acid amide, aliphatic carboxylic acid salt, aliphatic alcohol, aliphatic carboxylic acid ester, aliphatic / aromatic carboxylic acid hydrazide, sorbitol compound and organic phosphoric acid compound have. Among them, the polyester of the present invention is particularly preferable to contain at least one kind of crystal nucleating agent selected from an aliphatic carboxylic acid amide, an aliphatic carboxylic acid salt and a sorbitol compound. The content of the crystal nucleating agent is preferably 0.01 part by mass or more and 2 parts by mass or less, more preferably 0.1 part by mass or more and 2 parts by mass or less, based on 100 parts by mass of the polyester. When the content of the crystal nucleating agent is less than 0.01 parts by mass, the effect may not be sufficiently exhibited. If the content of the nucleating agent is more than 2 parts by mass, the transparency may be impaired.

Examples of the aliphatic carboxylic acid amide include aliphatic monocarboxylic acids such as lauric acid amide, palmitic acid amide, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, ricinoleic acid amide and hydroxystearic acid amide Oleic acid amide, N-oleyl stearic acid amide, N-stearyl oleic acid amide, N-stearyl stearic acid amide, N-stearyl erucic acid amide, N-substituted aliphatic monocarboxylic acid amides such as methylol stearic acid amide and methyl oleic acid amide, aliphatic amines such as methylenebisstearic acid amide, ethylenebislauric acid amide, ethylenebiscaric acid amide, ethylenebisoleic acid amide, ethylene bisstearate Acid amide, ethylenebis lauric acid amide, ethylene bisbehenic acid amide, ethylene bisisostearic acid amide, ethylene bis Hexamethylenebisstearic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisbehenic acid amide, hexamethylenebishydroxystearic acid amide, m-xylylenebisstearic acid, m-xylylenebisstearic acid amide, Amide, m-xylylene bis-12-hydroxystearic acid amide, N, N'-dioleyl sebacic acid amide, N, N'-dioleyl adipic acid amide, N Substituted N, N'-distearyl dicarboxylic acid amides such as N, N'-distearyl dicarboxylic acid amide, N, N'-distearyl dicarboxylic acid amide, Aliphatic carboxylic acid bisamides, N-butyl-N'-stearyl urea, N-propyl-N'-stearyl urea, N-stearyl- Aryl elements, xylylene bisstearyl elements, tolylene bisstearyl elements, hexamethylene Scan may be used stearyl urea, diphenylmethane-bis stearyl urea, diphenylmethane-bis-substituted N- d factors such us the current element. These may be one kind or a mixture of two or more kinds. Of these, aliphatic monocarboxylic acid amides, N-substituted aliphatic monocarboxylic acid amides and aliphatic biscarboxylic acid amides are preferably used, and in particular, palmitic acid amide, stearic acid amide, erucic acid amide, Amide, ricinoleic acid amide, hydroxystearic acid amide, N-oleyl palmitic acid amide, N-stearyl erucic acid amide, ethylene biscapric acid amide, ethylene bisoleic acid amide, ethylene bislauric acid amide, Erucic acid amide, m-xylylene bist stearic acid amide and m-xylylene bis-12-hydroxystearic acid amide are preferably used.

Specific examples of the aliphatic carboxylic acid salt include sodium acetate, potassium acetate, magnesium acetate, acetic acid salts such as calcium acetate, sodium laurate, potassium laurate, potassium hydrogen laurate, magnesium laurate, calcium laurate, Zinc laurate, lauric acid and the like, lithium myristate, sodium myristate, potassium hydrogen myristate, magnesium myristate, calcium myristate, zinc myristate and myristic acid Calcium palmitate, zinc palmitate, copper palmitate, lead palmitate, palmitic acid thallium, palmitic acid, palmitic acid and the like. Sodium oleate, calcium oleate, zinc oleate, lead oleate, thallium oleate, copper oleate, nickel oleate and the like, sodium stearate, sodium stearate, Stearic acid salts such as lithium stearate, magnesium stearate, calcium stearate, barium stearate, aluminum stearate, thallium stearate, lead stearate, nickel stearate, beryllium stearate, sodium isostearate, potassium isostearate , Isostearic acid salts such as magnesium isostearate, calcium isostearate, barium isostearate, aluminum isostearate, zinc isostearate and nickel isostearate, sodium behenate, potassium behenate, magnesium behenate, But are not limited to, behenic acid salts such as calcium bicarbonate, calcium bicarbonate, aluminum bicarbonate, aluminum behenate, zinc behenate and nickel behenate, sodium montanate, magnesium montanate, calcium montanate, barium montanate, montanate Zinc, and montanic acid salts such as montanic acid nickel. These may be one kind or a mixture of two or more kinds. Particularly, salts of stearic acid or salts of montanic acid are preferably used, and sodium stearate, potassium stearate, zinc stearate, barium stearate, sodium montanate and the like are preferably used.

Specific examples of the aliphatic alcohol include aliphatic monohydric alcohols such as pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, nonadecyl alcohol, eicosyl alcohol, ceryl alcohol and myristyl alcohol, 1,6- Aliphatic polyhydric alcohols such as 7-heptanediol, 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol, cyclopentane-1,2-diol, cyclohexane- Cyclic alcohols such as cyclohexane-1,4-diol and the like can be used. These may be one kind or a mixture of two or more kinds. Particularly, aliphatic monoalcohols are preferably used, and stearyl alcohol is particularly preferably used.

Specific examples of the aliphatic carboxylic acid ester include lauric acid cetyl ester, lauric acid phenacyl ester, myristic acid cetyl ester, myristic acid phenacyl ester, palmitic acid isopropylidene ester, palmitic acid dodecyl ester, Palmitic acid phenyl ester, palmitoyl peracyl ester, stearic acid cetyl ester, behenic acid ethyl ester, and the like can be used in combination with an ester such as trimellitic acid ester, trimellitic acid tetradodecyl ester, palmitic acid pentadecyl ester, palmitic acid octadecyl ester, palmitoic acid cetyl ester, Aliphatic monocarboxylic acid esters of aliphatic monocarboxylic acid esters, monolauric acid glycol, monopalmitic acid glycol, monoester of ethylene glycol such as monostearic acid glycol, dilauric acid glycol, dipalmitic acid glycol, distearic acid glycol and the like Diesters of ethylene glycol, monolauric acid glycerin ester, monomyristic acid glycerin esters Monoesters of glycerin such as monopalmitic acid glycerin ester and monostearic acid glycerin ester, diaryl glycerin ester, dimeric acid glycerin ester, dipalmitic acid glycerin ester and distearic acid glycerin ester. Esters, triesters of glycerin such as trilauric acid glycerin ester, trimyristic acid glycerin ester, tripalmitic acid glycerin ester, tristearic acid glycerin ester, palmit diol lane, palmit distearin, oleiodishearin and the like Etc. may be used. These may be one kind or a mixture of two or more kinds.

Specific examples of the aliphatic / aromatic carboxylic acid hydrazide include sebacic acid dibenzoic acid hydrazide and specific examples of the melamine compound include melamine cyanurate, melamine polyphosphate, and specific examples of the phenylphosphonic acid metal salt include phenylphosphonic acid zinc salt, calcium phenylphosphonate A salt of magnesium phosphate, a salt of magnesium phosphate of phenylphosphonic acid, or a salt of magnesium phosphate of magnesium phosphate of phenylphosphonic acid.

Examples of the sorbitol compound include 1,3-di (P-methylbenzylidene) sorbitol, 2,4-di (P-methylbenzylidene) sorbitol, 1,3-dibenzylidene sorbitol, 1,3-di (P-ethyl dibenzylidene) sorbitol, 2,4-di (P-ethyl dibenzylidene) sorbitol and the like.

Examples of the organic phosphoric acid compound include sodium bis (4-t-butylphenyl) phosphate, sodium 2,2'-methylenebis (4,6-di-t-butylphenyl) phosphate, cyclic organic phosphate ester basic multivalent metal salt, An alkali metal? -Diketonate, and an alkali metal? -Ketoacetic acid ester salt; and an organic carboxylic acid metal salt.

Above all, aliphatic carboxylic acid amide, aliphatic carboxylic acid salt and sorbitol compound are preferably used from the viewpoints of transparency and heat resistance.

It is important for the polyester film of the present invention that the plane orientation coefficient (fn) of the film is 0.15 or more and 0.28 or less. If the planar orientation coefficient fn is less than 0.15, the orientation property may deteriorate and sufficient low-temperature expansion may not be achieved. If the planar orientation coefficient fn exceeds 0.28, the film is excessively highly oriented, which may result in deterioration of film formability and difficulty in film formation. In the present invention, compatibility between low thermal expansion and low heat shrinkage is important. In order to achieve low thermal expansion, it is necessary to align the film, but orientation of the film is not preferable for reducing the heat shrinkage rate. Therefore, it is necessary to lower the heat shrinkage rate by adjusting? Tcg as described above. The plane orientation coefficient fn can be controlled by the film forming conditions, but the conditions of the heat treatment step and the draw ratio have a great influence. As the heat treatment temperature is increased, the thermal crystallization is promoted, so that the plane orientation coefficient fn tends to increase. In addition, since the in-plane orientation is increased by increasing the draw magnification, the plane orientation coefficient fn tends to increase. In particular, when the polyester is polyethylene terephthalate, the plane orientation coefficient fn is preferably 0.155 or more and 0.175 or less, more preferably 0.160 or more and 0.175 or less.

It is important that the polyester film of the present invention has a degree of crystallinity (Xc (%)) of 35% or less. If it is larger than 35%, crystals are grown, and orientation in the in-plane direction is lowered, so that sufficient low-temperature expansion can not be achieved. Particularly, the crystallinity (Xc (%)) is preferably 30% or less. The crystallinity (Xc (%)) greatly affects ΔTcg, the heat treatment process and the conditions of the relax annealing process. For example, the crystallization degree can be lowered by lowering the heat fixing temperature in the heat treatment process.

The polyester film of the present invention has a heat shrinkage ratio of 0 to 1.5%, more preferably 0 to 1.2%, still more preferably 0 to 1.0%, and particularly preferably 0 To 0.7%, and most preferably from 0 to 0.4%. If the heat shrinkage ratio in the longitudinal direction and the width direction at 180 ° C is within the above range, curling due to heat in various processes at the time of forming the device layer can be reduced, and the dimensional change becomes small, It is more preferable.

The heat shrinkage in the longitudinal direction and the width direction at 180 deg. C can be controlled by a predetermined film forming condition to be described later, but it is particularly preferable to control the conditions of the relax annealing step. The heat shrinkage rate of the film of the present invention becomes larger when the heat shrinkage rate of the film before the annealing process is larger. In order to reduce the heat shrinkage rate to 1.5% or less, the heat shrinkage rate of the film before the annealing process at 180 ° C is preferably 0 to 8.0%. If the film has a heat shrinkage rate of more than 8.0% at a temperature of 180 캜 before the annealing process, the heat shrinkage rate may be excessively large, so that the heat shrinkage rate may not be reduced to the range specified in the present invention even after the annealing process. In addition, since the thermal dimensional stability in the high temperature region is not sufficient, shrinkage increases in the relax annealing process, wrinkles, curvature, curl are generated, and planarity is sometimes deteriorated. The heat shrinkage ratio of the film before annealing is more preferably 0 to 7.0%, further preferably 0 to 5.0%. The heat shrinkage rate of the film before the annealing process is influenced by the stretching magnification and the heat treatment process. However, the heat shrinkage rate of the film before the relax annealing process can be reduced even when the ΔTcg is in the predetermined range, To 1.5%, and the flatness in the relax annealing process can be maintained.

The polyester film of the present invention preferably has a coefficient of thermal expansion of 0 to 25 ppm / ° C at a temperature of 50 to 150 ° C in both the longitudinal and transverse directions. When the coefficient of thermal expansion at the temperature of 50 to 150 캜 in the longitudinal direction and the width direction is within the above range, the dimensional change in the relax annealing process can be reduced and the planarity can be maintained. It is preferable because cracks due to peeling and deformation can be suppressed. The coefficient of thermal expansion at the temperature of 50 to 150 ° C in the longitudinal direction and the width direction is more preferably 0 to 22 ppm / ° C, and more preferably 0 to 18 ppm / ° C. The coefficient of thermal expansion is shown to be correlated with the plane orientation coefficient and the degree of crystallinity. The coefficient of thermal expansion of the present invention can be obtained by the film forming conditions to be described later. In particular, it can be obtained by controlling the drawing magnification and the heat treatment conditions.

The polyester used in the present invention is a polymer containing at least 80% by mass of a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid. The dicarboxylic acid is exemplified by terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, adipic acid and sebacic acid. The diol is ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol .

Specific examples of the polymer include polyolefin such as polymethylene terephthalate, polyethylene terephthalate, polypropylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate Phthalate, polyethylene-2,6-naphthalate, and the like can be used.

Of these, the polyesters may be either homopolymers or copolymers. In the case of copolymers, examples of the copolymerization component include diol components such as diethylene glycol, neopentyl glycol and polyalkylene glycol, adipic acid, sebacic acid, phthalic acid , Dicarboxylic acid components such as isophthalic acid and 2,6-naphthalenedicarboxylic acid, and hydroxycarboxylic acid components such as hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

In the case of the present invention, polyethylene terephthalate, polyethylene-2,6-naphthalate, and copolymers thereof are preferable, and blends of other polymers, or a composite such as a laminate may be used. In particular, a polyester containing as a main component polyethylene terephthalate (hereinafter, sometimes referred to as PET) is preferable in view of mechanical strength, heat resistance, chemical resistance, durability and the like. Therefore, PET is preferable for increasing the effect of the present invention. Various additives such as antioxidants, heat stabilizers, lubricants, antiblocking agents, antistatic agents, inorganic particles and organic particles may be added to the polyester. Of course, the film of the present invention may be a monolayer film, but other polymer layers such as polyester, polyamide, polyvinylidene chloride-based polymer and the like may be laminated. It is also possible to provide a surface-modified film by laying a coat layer of a resin such as polyurethane, polyacrylic, polyester, polyamide or the like on the surface of the film. The surface of the film may be subjected to surface activation treatment such as corona discharge treatment.

The polyester film of the present invention preferably has a value (fn / Xc) of 0.50 or more obtained by dividing the face orientation coefficient (fn) by the degree of crystallization (Xc). When the value (fn / Xc) obtained by dividing the planar orientation coefficient fn by the crystallinity Xc is in the above range, the coefficient of thermal expansion can be reduced and the thermal dimensional stability is improved. More preferably 0.55 or more. (Fn / Xc) of the present invention can be obtained by the film formation conditions to be described later, but it can be obtained particularly by controlling the drawing magnification, the heat treatment condition, and the annealing annealing temperature.

The polyester film of the present invention preferably has a film haze value of 0 to 5%. If the film haze value exceeds 5%, the transparency is low and the performance of the organic EL or thin film solar cell may not be sufficient. The film haze value is more preferably 0 to 3%, and still more preferably 0 to 1%. The film haze value may be increased by using a polyester having a high crystallization index (? Tcg). And can be controlled by the addition concentration or the average particle size of the added particles. When the average particle size of the added particles is 1 nm to 3000 nm, it is easy to set the film haze value in the above range, and it is preferable from the viewpoint of transparency of the film. More preferably 1 nm to 2000 nm, and further preferably 1 nm to 1500 nm. The particle concentration of the added particles is preferably 0.0 part by mass to 1.0 part by mass with respect to 100 parts by mass of the polyester. Two or more kinds of particles having different particle diameters may be mixed and used within the range of the particle diameter and the particle concentration.

The biaxially oriented polyester film of the present invention preferably has a variation in film haze value of 0.0 to 3.0% when heat treated at 180 占 폚 for 30 minutes. When the amount of change of the film haze value is within the above range, transparency can be maintained in the device layer forming process, which is preferable. When the amount of change in the film haze value exceeds 3.0%, transparency in the device layer formation process deteriorates, leading to deterioration of power generation efficiency and deterioration of light emission efficiency. The change amount of the film haze value is more preferably 0 to 1.5%. When a polyester film is subjected to a heat treatment at a high temperature, a low molecular weight component precipitates as an oligomer, so that the film haze value becomes large. The biaxially oriented polyester film of the present invention preferably uses a polyester resin from which an oligomer component has been removed as a raw material. As a method for producing a polyester resin from which an oligomer component has been removed, for example, the technique described in JP-A-2005-53968 can be adopted.

The polyester film of the present invention preferably has a film thickness of 25 to 150 mu m. If the thickness is less than 25 탆, the film may have a lowered stiffness, and may break when the film is made of an organic EL or a solar cell, and wrinkles tend to enter easily. When the thickness is more than 150 탆, the flexibility of the film is lost and the flexibility may be impaired. The film thickness is more preferably 75 to 125 占 퐉. The film thickness can be controlled by film forming conditions.

The film production method of the present invention will be described in detail. PET is described as a specific example, but is not limited thereto.

First, a PET resin to be used is prepared. PET is manufactured by any one of the following processes. (1) a process of obtaining a polymer by a polycondensation reaction using terephthalic acid and ethylene glycol as raw materials to obtain a low molecular weight PET or an oligomer by a direct esterification reaction and using the resulting antimony trioxide or a titanium compound as a catalyst, Or (2) a process for obtaining a polymer by a polycondensation reaction using dimethyl terephthalate and ethylene glycol as raw materials to obtain a low molecular weight compound through transesterification reaction and then using antimony trioxide or a titanium compound as a catalyst.

Here, although the esterification is carried out in the absence of a catalyst, the reaction proceeds, but in the transesterification reaction, a compound such as manganese, calcium, magnesium, zinc, lithium and titanium is generally used as a catalyst. In addition, a phosphorus compound may be added for the purpose of deactivation of the catalyst used in the reaction after the transesterification reaction is substantially completed.

In the case of promoting the crystallization of the PET film of the present invention, lithium acetate, magnesium acetate, potassium acetate, phosphorous acid, phosphonic acid, phosphinic acid or derivatives thereof, antimony oxide and germanium oxide are desirably present during transesterification and polymerization . When a crystal nucleating agent other than the above-mentioned compound is used, it is preferable to knead the PET and the PET resin in advance with PET using a vent type twin-screw kneading extruder and master pelletize in view of handleability and dispersibility. As a method of setting ΔTcg within a predetermined range, a method of controlling the content of the nucleating agent by mixing the PET pellets containing the nucleating agent produced by the above method with a PET resin substantially not containing the nucleating agent is preferably used.

In order to impart lubricity, abrasion resistance and scratch resistance to the surface of the PET film, inorganic particles or organic particles such as clay, mica, titanium oxide, calcium carbonate, carnion, talc, wet silica, dry silica, Inorganic particles such as silica, calcium phosphate, barium sulfate, alumina and zirconia, organic particles composed of acrylic acid, styrene resin, thermosetting resin, silicon and imide compound and the like and PET (So-called inner particles) or the like which are precipitated by the above-mentioned particles.

When inert particles are contained in PET which is a constituent component of the PET film of the present invention, it is preferable to disperse inert particles in ethylene glycol at a predetermined ratio in a slurry form, and to add ethylene glycol at the time of polymerization. When inert particles are added, for example, hydrosol or alcohol sol-like particles obtained at the time of synthesis of inert particles are added without being once dried, whereby the dispersibility of the particles is good. It is also effective to mix the water slurry of the inert particles directly with the PET pellets and knead them to PET using a vented twin-screw kneading extruder. As a method of controlling the content of the inert particles, a method of preparing master pellets of inert particles at a high concentration by the above method and diluting them with PET which does not substantially contain inert particles at the time of film formation is effective to control the content of inert particles .

Subsequently, the obtained pellets (crystal nucleating agent-containing PET pellets) and raw PET chips (PET resin chips not containing a nucleating agent) were dried under reduced pressure at 180 ° C for 3 hours or more, , To a desired film composition, and melt-extruded from a slit-shaped die and cooled and solidified on a casting roll to obtain an unstretched film. At this time, it is preferable to use filters made of various materials such as sintered metal, porous ceramics, sand, and wire mesh to remove foreign matter and altering polymer. In addition, a gear pump may be provided to improve the quantitative air gap as needed. When a film is laminated, two or more extruders and a manifold or a confluence block are used to melt laminate a plurality of other polymers. The intrinsic viscosity of the PET pellets containing the crystal nucleating agent and the PET resin chips not containing the crystal nucleating agent is preferably 0.5 to 1.5 dl / g such that the intrinsic viscosity of the polyester constituting the film is in a preferable range.

Also, as long as the effect of the present invention is not impaired, various additives such as a compatibilizer, a plasticizer, a lubricant, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a brightener, a colorant, a conductive agent, Flame retarding agents, pigments, dyes and the like may be added.

Subsequently, the sheet product thus formed is biaxially stretched. And stretched by two axes in the longitudinal direction and the width direction, and subjected to heat treatment.

Examples of the stretching method include a sequential biaxial stretching method such as stretching in the width direction after stretching in the longitudinal direction and a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously stretched by using a biaxial tenter or the like, And a method in which an axial stretching method and a simultaneous biaxial stretching method are combined. In order to control the thermal expansion coefficient and the heat shrinkage ratio within the range of the present invention, it is preferable that the heat treatment after the stretching process is carried out effectively without causing relaxation of the molecular chain orientation by excessive heat treatment.

(TD stretching) is performed by using a longitudinal stretching machine in which several rolls are disposed, stretching in the machine direction (MD stretching) by using the peripheral speed difference of the roll, and then transversely stretching by the stenter The drawing method will be described in more detail.

First, the MD film is stretched in an unstretched film. The stretching temperature is preferably in the range of (glass transition temperature (Tg) to (Tg + 40) ° C, more preferably in the range of (Tg + 5) to (Tg + 30) (Tg + 20) ° C, preferably 3.0 to 4.0 times, more preferably 3.2 to 4.0 times, and more preferably 3.5 to 4.0 times in the longitudinal direction (MD) It is preferable to conduct the stretching in the direction of the drawing and cooling in the group of cooling rolls at a temperature of 20 to 50 DEG C after stretching. In particular, if the stretching is carried out in the range of 3.2 to 4.0 times, the stretching orientation can be increased and the stretching can be effectively performed in the next step.

Then, stretching is performed in the width direction (TD) using a stenter. In the present invention, in the preheating step before the transverse stretching (TD stretching), a large number of microcrystals are formed to form a nodal point, which is a preferred embodiment from the viewpoint that the orientation can be effectively enhanced at the time of TD stretching and a predetermined thermal expansion coefficient can be obtained. The specific preheating temperature is preferably 90 占 폚 to 110 占 폚, and more preferably 95 占 폚 to 100 占 폚. The stretching temperature is preferably in the range of (preheating temperature -5) to (preheating temperature + 5) ° C, more preferably at the same temperature as the preheating temperature. The draw ratio is preferably 3.5 to 6.0 times, more preferably 4.0 to 6.0 times, still more preferably 4.5 to 6.0 times.

Subsequently, the stretched film is thermally fixed while being relaxed or relaxed in the width direction. The heat setting temperature (hereinafter sometimes abbreviated as Ths) is preferably 180 to 220 deg. C, more preferably 195 to 210 deg. C, and particularly preferably 200 to 210 deg. If Ths is less than 180 占 폚, the structure fixation is insufficient and fn increases, resulting in an increase in heat shrinkage and deterioration of film formability. When Ths exceeds 220 캜, the crystal growth is promoted, the in-plane orientation is relaxed, and the thermal expansion coefficient is sometimes deteriorated. The heat setting time is preferably in the range of 0.5 to 10 seconds. The relaxation rate (hereinafter, abbreviated as Rxhs) in the heat-setting treatment is preferably within three times the relaxation rate of the subsequent relaxed annealing process (hereinafter abbreviated as Rxa). The relaxation rate is the ratio of the width to the width after treatment based on the width before treatment. For example, when the relaxation rate is 2%, when the treatment transition is 100 mm, 2% of 2% Mm. If Rxhs for Rxa exceeds 3 times, the orientation relaxation proceeds excessively and the thermal expansion coefficient may be deteriorated. Rxhs is preferably 0 to 9%.

Thereafter, the film is cooled to a temperature of preferably 35 占 폚 or lower, more preferably 25 占 폚 or lower, and the film edge is removed and wound on the core. The biaxially stretched PET film wound to increase the thermal dimensional stability is preferably transported under tension at a constant temperature, and subjected to a relaxation annealing process to remove the deformation of the molecular structure and reduce the heat shrinkage rate. The annealing annealing temperature (hereinafter abbreviated as Ta) may preferably be lower than the heat setting temperature Ths and is preferably (Ths-25) to (Ths-5) -20) to (Ths-10) ° C, and particularly preferably (Ths-20) to (Ths-10) ° C and further preferably 195 ° C to 205 ° C. If Ta exceeds (Ths-5) 占 폚, the structure fixed by the heat fixing treatment tends to be relaxed again, so crystal growth is promoted and the in-plane orientation relaxes and the coefficient of thermal expansion tends to deteriorate. If Ta is less than (Ths-25) 占 폚, the removal of deformation of the molecular structure by annealing may be incomplete, and heat shrinkage may not be reduced. The relax annealing time is preferably 1 to 120 seconds, more preferably 5 to 90 seconds, and still more preferably 20 to 60 seconds. The relaxation rate (Rxa) in the relax annealing treatment is preferably 0.1 to 3%. If Rxa is less than 0.1%, the relaxation effect does not appear, the deformation of the molecular structure is not completely removed, and the heat shrinkage may not be reduced. If Rxa is more than 3%, the orientation relaxation proceeds excessively, and the thermal expansion coefficient may be deteriorated. Rxa can be set by the stretching tension and clip width of the relax annealing process. The film is annealed while being transported at a speed of 10 to 300 m / min to obtain the biaxially oriented PET film of the present invention.

In the present invention, the PET film or the PET film roll may be subjected to optional processing such as molding, surface treatment, lamination, coating, printing, embossing and etching as required.

After exhausting the inside of the chamber to 5 x 10 < ^-4 > Pa before discharging the plasma, for example, argon and oxygen are introduced into the chamber so that the pressure is 0.3 Pa (oxygen partial pressure is 3.7 mPa) , Power was applied at a power density of 2 W / cm 2 using indium oxide containing tin oxide (36% by mass, manufactured by SUMITOMO METAL MINING CO., LTD., Density 6.9 g / cm 3) A transparent conductive layer made of ITO of 250 nm is formed and an organic EL light emitting layer is formed, so that it can be used as an organic EL display substrate and an organic EL illumination substrate. And can be used as a flexible solar cell substrate by forming a power generation layer.

(Method of measuring physical properties and evaluation method of effect)

The method of measuring the characteristic value and the evaluation method of the effect in the present invention are as follows.

(1) Crystallization index (? Tcg (占 폚)), crystallinity (Xc (%))

Seiko Instruments Inc. as a differential scanning calorimeter according to JIS K7121-1987. (SSC / 5200) was used as a data analyzing apparatus, and 5 mg of a sample was sealed using an aluminum pan and a fan cover. The temperature was raised from 25 ° C to 300 ° C in a nitrogen atmosphere at a rate of 10 Lt; 0 > C / minute. Thereafter, quenching is performed using liquid nitrogen, and the temperature is raised again from 20 占 폚 to 300 占 폚 at a rate of 10 占 폚 / min in a nitrogen atmosphere.

The crystallization index (? Tcg) was calculated from the glass transition temperature (Tg) and the cold crystallization temperature (Tcc) in the second heating step using the following formula.

? Tcg = Tcc-Tg

The crystallinity Xc (%) was calculated from the following equation using the heat of fusion (ΔH _m ) and the amount of cold crystallization (ΔH _c ) in the first heating process.

Xc (%) = {(ΔH m -ΔH c) / ΔH m o} × 100

Here, ΔH _m ^o is the total crystallite heat of fusion, for example, 140.1 J / g for PET and 103.3 J / g for PEN (Wunderlich B "Thermal analysis of Polymeric Materials").

(2) Plane orientation coefficient (fn)

Was measured using the following measuring machine according to JIS-K7142 (2008). The sample was cut to a width of 25 mm and a length of 30 mm with a sample number of 3 and measured for the film length direction, the film width direction and the film thickness direction, and the average value was taken as the refractive index in each direction. Using the results, the surface orientation coefficient was calculated by the following formula. In the case where the longitudinal direction and the width direction of the film are unknown, the direction having the maximum refractive index in the film is regarded as the longitudinal direction, and the direction perpendicular to the longitudinal direction is regarded as the width direction. Further, the direction of the maximum refractive index in the film may be obtained by measuring the refractive index in all directions of the film by the Abbe's refractive index meter or may be obtained by determining the direction of the slow axis by a phase difference measuring apparatus (birefringence measuring apparatus) or the like.

· Apparatus: Abbe refractometer 4T (manufactured by ATAGO CO., LTD.)

· Light source: sodium D line

· Measuring temperature: 25 ℃

· Measuring humidity: 65% RH

Mount solution: methylene iodide (n _D ²⁰ = 1.74), sulfur iodide methylene (n _D ²⁰ = 1.74-1.78). When the refractive index was high and measurement was impossible using methylene iodide, measurement was carried out using sulfuric acid methylene iodide.

Plane orientation coefficient (fn)

fn = (nMD + nTD) / 2-nZD

nMD; The refractive index in the longitudinal direction of the film

nTD; The refractive index in the film width direction

nZD; Refractive index in film thickness direction.

(3) Thermal Expansion Coefficient

Measurement was made for each of the longitudinal and transverse directions of the film in accordance with JIS K7197 (1991) under the following conditions under the following conditions, and the average value was taken as the coefficient of thermal expansion in the longitudinal direction and the transverse direction.

· Measuring device: Seiko Instruments Inc. Production "TMA / SS6000"

Sample size: width 4 mm, length 20 mm

Temperature condition: Temperature was raised from 30 ° C to 175 ° C at 5 ° C / min and maintained for 10 minutes

· It is cooled down from 175 ℃ to 40 ℃ at 5 ℃ / min and maintained for 20 more minutes

· Load condition: 29.4mN schedule

Here, the temperature range of the thermal expansion coefficient measurement is from 150 캜 to 50 캜 at the time of temperature lowering. The thermal expansion coefficient was calculated from the following equation.

Thermal expansion coefficient [ppm / DEG C = 10 ⁶ x {(Dimension mm at 150 DEG C) - (Dimension mm at 50 DEG C) / 20 mm} / (150 DEG C -50 DEG C).

(4) Heat shrinkage at a temperature of 180 캜

The heat shrinkage percentage was measured by the following apparatus and conditions.

· Measuring equipment: universal projector

· Data size: Test length 200m × width 10mm

· Heat treatment apparatus: Gear oven

Heat treatment conditions: 180 占 폚, 30 minutes

· Load: 3g

· Calculation method

Before the heat treatment, a sample was drawn at intervals of 150 mm, and the distance between the marks after the heat treatment was measured. The heat shrinkage was calculated from the change in the distance between the marks before and after heating. The measurement was carried out by taking five samples in the longitudinal direction and the width direction of each film and evaluating the average value.

(5) Orientation parameter (fn / Xc)

The orientation parameter fn / Xc was obtained from the plane orientation factor fn and the degree of crystallinity Xc (%) obtained from the above formula by the following formula.

fn / Xc = fn / (Xc (%) / 100)

(6) Film haze value

A sample of 10 cm x 10 cm was cut out from the film and measured using a fully automatic Hayes computer HGM-2DP (manufactured by Suga Test Instruments Co., Ltd.) under the JIS K7105 (1985). This was repeated 10 times at random and the average value was taken as the film haze value.

(7) Stability of film formation

The film formability of the film was evaluated according to the following criteria. Evaluation D is rejected.

A: There is no occurrence of film tear, and stable film formation is possible.

B: Film tear is less likely to occur and stable film formation is possible.

C: Film tearing occurs a lot but can be formed.

D: Film tear is frequent and continuous film formation is difficult.

(Example)

Embodiments of the present invention will be described on the basis of embodiments.

(Reference Example 1)

194 parts by mass of dimethyl terephthalate and 124 parts by mass of ethylene glycol were charged into the transesterification reactor, and the contents were heated at a temperature of 140 캜 for dissolution. Thereafter, 0.1 part by mass of magnesium acetate tetrahydrate and 0.03 part by mass of antimony trioxide were added while stirring the contents, and the ester exchange reaction was carried out while distilling methanol at a temperature of 140 to 230 占 폚. Subsequently, 1 mass part (0.05 mass part as trimethyl phosphate) of a 5 mass% ethylene glycol solution of trimethyl phosphate was added. The addition of a solution of trimethyl ethylene glycol phosphate reduces the temperature of the reaction contents. Thus, stirring was continued until the temperature of the reaction contents returned to a temperature of 230 캜 while distilling the excess of ethylene glycol. After the temperature of the reaction contents in the transesterification reaction apparatus reached a temperature of 230 캜 in this manner, the reaction contents were transferred to the polymerization apparatus. After the transition, the reaction system was slowly heated from a temperature of 230 ° C to a temperature of 290 ° C, and the pressure was lowered to 0.1 ° C. The final temperature and time until reaching the final pressure were all 60 minutes. After the final temperature and the final pressure were reached, the reaction was carried out for 2 hours (polymerization was started for 3 hours). As a result, it was found that the stirring torque of the polymerization apparatus was lower than a predetermined value The value indicated by polyethylene terephthalate having an intrinsic viscosity of 0.65 was set to a predetermined value). Thus, the reaction system was purged with nitrogen to return to atmospheric pressure to stop the polycondensation reaction. The polycondensation reaction was stopped and discharged into cold water in the form of strands, and immediately cut to obtain PET pellets X of polyethylene terephthalate having an intrinsic viscosity of 0.65.

(Reference Example 2)

Except that 0.35 parts by mass of dimethylphenyl phosphonate (DPPO) was added as a crystal nucleating agent instead of trimethyl phosphate, and the transesterification reaction and the polymerization reaction were carried out in the same manner as in Reference Example 1 to adjust the crystallization rate Pellet Y was obtained.

(Reference Example 3)

The PET pellets obtained in Referential Example 1 and sodium montanate (manufactured by NITTO KASEI Co., Ltd.) as a crystal nucleating agent were mixed at a mass ratio of 90:10 and kneaded at 280 캜 using a vent type twin screw extruder to obtain sodium montanate To obtain a PET master pellet Z containing 10 parts by mass.

(Reference Example 4)

To a mixture of 100 parts by mass of dimethyl 2,6-naphthalenedicarboxylate and 60 parts by mass of ethylene glycol, 0.3 part by mass of manganese acetate · tetrahydrate salt was added and the ester exchange reaction was carried out while gradually raising the temperature from 150 ° C. to 240 ° C. I did. At the time when the reaction temperature reached 170 占 폚, 0.024 parts by mass of antimony trioxide was added. When the reaction temperature reached 220 캜, 0.042 part (corresponding to 2 mmol%) of 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt was added. Thereafter, the ester exchange reaction was carried out continuously, and 0.023 parts by mass of trimethyl phosphoric acid was added. Then, the reaction product is transferred to a polymerization apparatus, the temperature is raised to 290 ° C, and a polycondensation reaction is carried out under a high pressure of 30 Pa. While the stirring torque of the polymerization apparatus is a predetermined value (a specific value varies depending on the specifications of the polymerization apparatus, The value indicated by the polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.65 in the present polymerization apparatus was set to a predetermined value). Thus, the reaction system was purged with nitrogen, returned to atmospheric pressure to stop the polycondensation reaction, discharged into cold water in a strand shape, and immediately cut to obtain PEN pellets X having an intrinsic viscosity of 0.65.

(Reference Example 5)

PEN pellets obtained in Reference Example 4 and sodium montanate as a crystal nucleating agent were mixed at a mass ratio of 90:10 and kneaded at 280 ° C using a vent type twin screw extruder to obtain PEN master pellets Y containing 10 parts by mass of sodium montanate .

(Example 1)

90 parts by mass of the PET pellets X obtained in Reference Example 1 and 10 parts by mass of the PET pellets Y adjusted in the crystallization rate obtained in Reference Example 2 were mixed and decompressed at a temperature of 180 ° C for 3 hours and then heated to 280 ° C And introduced into a T-die under nitrogen atmosphere. Subsequently, the sheet was extruded into a sheet in a T-die compartment to form a molten single-layer sheet, and the sheet was cooled and solidified by electrostatic application onto a drum maintained at a surface temperature of 25 캜 to obtain an unstretched single-layer film. The glass transition temperature (Tg) of the unstretched single-layer film was measured to be 78 ° C.

Then, the obtained unstretched single-layer film was preheated in a heated roll group, and then subjected to 3.5-fold MD stretching at a temperature of 93 캜 and cooled in a roll group at a temperature of 25 캜 to obtain a uniaxially stretched film. The cold crystallization temperature of the obtained monoaxially stretched film was measured and found to be 90 ° C. Both ends of the obtained monoaxially stretched film were gripped by a clip while being guided to a preheating zone at a temperature of 95 DEG C in the tenter and successively heated in a heating zone at a temperature of 90 DEG C in a transverse direction (TD direction) The boat was extended. Subsequently, heat treatment was performed in a heat treatment zone in a tenter at 210 DEG C for 5 seconds as a heat fixing treatment, and further relaxation treatment was performed in the 2% width direction at the same temperature. Subsequently, the film was uniformly cooled to 25 占 폚, the film edge was removed, and the film was wound on a core to obtain a biaxially oriented film having a thickness of 100 占 퐉.

Then, the film was subjected to a relaxation annealing treatment at a relaxation rate of 1% at a temperature of 190 캜 for 30 seconds at a film speed of 30 m / min to obtain a polyester film.

As a result of evaluation of the obtained polyester film, as shown in Table 1, it was found that the polyester film had excellent thermal dimensional stability and film formability.

(Example 2)

A polyester film was obtained in the same manner as in Example 1 except that 98 parts by mass of the PET pellets X obtained in Reference Example 1 and 2 parts by mass of the PET pellets Y whose crystallization rates were adjusted in Reference Example 2 were mixed. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability and film formability.

(Example 3)

A polyester film was obtained in the same manner as in Example 1, except that 80 parts by mass of the PET pellets X obtained in Reference Example 1 and 20 parts by mass of the PET master pellets Z of sodium montanate obtained in Reference Example 3 were mixed. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability.

(Example 4)

Except that 95 parts by mass of the PET pellets X obtained in Reference Example 1 and 5 parts by mass of the PET master pellets Z of sodium montanate obtained in Reference Example 3 were changed to 3.0 times the MD stretching magnification and 4.2 times the TD stretching magnification A polyester film was obtained in the same manner as in Example 1. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability.

(Example 5)

Except that 95 parts by mass of the PET pellets X obtained in Reference Example 1 and 5 parts by mass of the PET master pellets Z of sodium montanate obtained in Reference Example 3 were changed to 3.2 times the MD stretching magnification and 4.2 times the TD stretching magnification A polyester film was obtained in the same manner as in Example 1. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability.

(Example 6)

Except that 80 parts by mass of the PET pellets X obtained in Reference Example 1 and 20 parts by mass of the PET master pellets Z of sodium montanate obtained in Reference Example 3 were changed to 3.2 times the MD stretching magnification and 4.2 times the TD stretching magnification A polyester film was obtained in the same manner as in Example 1. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability.

(Example 7)

Except that 98 parts by mass of the PET pellets X obtained in Reference Example 1 and 2 parts by mass of the PET pellets Y adjusted in the crystallization rate obtained in Reference Example 2 were mixed so that the MD stretching magnification was 3.0 times and the TD stretching magnification was 4.2 times A polyester film was obtained in the same manner as in Example 1. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability and film formability.

(Example 8)

A polyester film was obtained in the same manner as in Example 1 except that the heat fixing temperature Ths was changed to 190 캜 and the relaxed annealing temperature Ta was changed to 170 캜. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability.

(Example 9)

A polyester film was obtained in the same manner as in Example 1 except that the annealing temperature Ta was changed to 200 캜. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability and film formability.

(Example 10)

A polyester film was obtained in the same manner as in Example 1 except that 95 parts by mass of PEN pellets X obtained in Reference Example 4 and 5 parts by mass of PEN master pellets Y of sodium montanate obtained in Reference Example 5 were used. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability.

(Example 11)

A MD stretching ratio of 3.4 times, a TD stretching ratio of 3.7 times, a heat fixing temperature Ths of 215 占 폚 and a relax annealing temperature of 205 占 폚. The obtained polyester film was evaluated, and as a result, it was found that the polyester film had excellent thermal dimensional stability and film formability.

(Comparative Example 1)

A polyester film was obtained in the same manner as in Example 1 except that only the PET pellets X obtained in Reference Example 1 were used. As a result of evaluating the obtained polyester film, it was found that the heat shrinkage ratio was increased and the thermal dimensional stability was deteriorated.

(Comparative Example 2)

A polyester film was obtained in the same manner as in Example 1 except that only the PET pellets X obtained in Reference Example 1 were used and the MD stretching magnification was 3.0 times and the TD stretching magnification was 4.2 times. As a result of evaluating the obtained polyester film, it was found that the heat shrinkage ratio was increased and the thermal dimensional stability was deteriorated.

(Comparative Example 3)

A polyester film was obtained in the same manner as in Example 1 except that the relax annealing step was not performed as shown in Table 1. [ The obtained polyester film was evaluated, and as a result, it had a characteristic that heat shrinkage was large and thermal stability was deteriorated.

(Comparative Example 4)

A MD film was obtained in the same manner as in Example 1 except that the MD stretching magnification was 3.0 times and the TD stretching magnification was 3.35 times. As a result of evaluating the obtained polyester film, the thermal expansion coefficient was deteriorated and the thermal dimensional stability was deteriorated because the plane orientation coefficient was small.

(Comparative Example 5)

As shown in Table 1, 75 parts by mass of the PET pellets X obtained in Reference Example 1 and 25 parts by mass of the PET master pellets Z of sodium montanate obtained in Reference Example 3 were mixed, and the MD stretching magnification was 3.2 times and the TD stretching magnification was 4.2 times, and a polyester film was produced in the same manner as in Example 1, except that the annealing treatment was not performed. The crystallization index (? Tcg) was small and the film-forming stability deteriorated, making continuous film-forming difficult.

(Comparative Example 6)

A polyester film was obtained in the same manner as in Example 1 except that the heat fixing temperature Ths was changed to 175 캜 and the relaxed annealing temperature Ta was changed to 160 캜. The obtained polyester film was evaluated, and as a result, it had a characteristic that heat shrinkage was large and thermal stability was deteriorated.

(Comparative Example 7)

A polyester film was obtained in the same manner as in Example 1 except that the heat fixing temperature Ths was changed to 230 deg. C and the relaxed annealing temperature Ta was changed to 210 deg. As a result of evaluating the obtained polyester film, it was found that since the degree of crystallization was increased, the coefficient of thermal expansion deteriorated and the thermal dimensional stability deteriorated.

(Comparative Example 8)

A polyester film was obtained in the same manner as in Example 1 except that the annealing temperature Ta was changed to 180 캜. The obtained polyester film was evaluated, and as a result, it had a characteristic that heat shrinkage was large and thermal stability was deteriorated.

(Comparative Example 9)

A polyester film was obtained in the same manner as in Example 1 except that the annealing temperature Ta was changed to 210 캜. As a result of evaluating the obtained polyester film, it was found that since the degree of crystallization was increased, the coefficient of thermal expansion deteriorated and the thermal dimensional stability deteriorated.

(Comparative Example 10)

As shown in Table 1, 95 parts by mass of the PEN pellets X obtained in Reference Example 4 and 5 parts by mass of the PEN master pellet Y of sodium montanate obtained in Reference Example 5 were mixed so that the MD stretching magnification was 4.2 times and the TD stretching magnification was 4.2 A polyester film was obtained in the same manner as in Example 1, except that the annealing treatment was not performed. As a result of evaluating the obtained polyester film, the plane orientation coefficient fn was large and the film-forming stability deteriorated, making continuous film-forming difficult.

The polyester film of the present invention can be applied to a base film for a flexible device having excellent dimensional stability and curling property. Therefore, there is a possibility to be used for obtaining an organic EL display, an electronic paper, an organic EL lighting, an organic solar cell, and a dye-sensitized solar cell.

Claims

And a crystallinity (Xc (%)) of 35% or less, wherein the polyester film has a surface orientation coefficient (fn) of 0.15 or more and 0.28 or less, And a heat shrinkage rate at 180 캜 in the longitudinal direction and the transverse direction of the film are respectively more than 0% and 1.5% or less.

The method according to claim 1,
(Fn / Xc) obtained by dividing the face orientation coefficient (fn) by the crystallinity (Xc) is 0.50 or more.

3. The method according to claim 1 or 2,
And the film haze value is 0 to 3%.

3. The method according to claim 1 or 2,
Wherein the polyester contains a crystal nucleating agent and the content of the crystal nucleating agent is 0.01 parts by mass or more and 2 parts by mass or less based on 100 parts by mass of the polyester.

3. The method according to claim 1 or 2,
Wherein the polyester is a polyethylene terephthalate.

A film for an organic EL substrate, characterized by using the polyester film according to any one of claims 1 to 3.

A film for a flexible solar cell substrate, which comprises the polyester film according to claim 1 or 2.

The polyester resin is cooled and solidified while being melt-extruded to obtain an unstretched film, and then the unstretched film is biaxially stretched. Thereafter, heat fixing temperature Ths (占 폚) is heat set at 180 to 220 占 폚, The method for producing a polyester film according to claim 1 or 2, wherein the polyester resin contains at least one kind of nucleating agent and the annealing treatment is carried out at a temperature Ths-25) to (Ths-5) 占 폚.