JPH1044229A - Polyester film and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformity of thickness and to make processability good by a method wherein a substantially unoriented polyester film consisting of liq. crystal polyester and non-liq. crystal polyester is set in such a way that temp. coefficient of drawing stress satisfies a specified condition and it is at least uniaxially drawn. SOLUTION: A substantially unoriented polyester film consisting of liq. crystal polyester and non-liq. crystal polyester is set in such a way that temp. coefficient K of drawing stress satisfies an equation -0.35<=K<=0.1 (MPa/ deg.C) and it is at least uniaxially drawn. In addition, it is pref. that drawing is performed at a temp. of the glass transition temp. of the non-liq. crystal polyester +30 deg.C-+60 deg.C. In addition, it is pref. that fluctuation of thickness of at least uniaxially stretched polyester film is at most 5% and when wave shape of the fluctuation of thickness is Fourier-analysed, the ratio of sum of spectrum strength in the wave numbers of 1.00(1/m)-2.00(1/m) to the sum of spectrum strength of the whole wave number region is at most 0.15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyester film and a method for producing the same.

[0002]

2. Description of the Related Art Polyester films are widely used in various industrial fields such as magnetic recording media, electrical insulation, and packaging materials because of their excellent mechanical, thermal and electrical properties. I have. Among the non-liquid crystalline polyesters, polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate are particularly excellent in mechanical properties and thermal properties, and because polyethylene terephthalate is inexpensive, its application fields are wide. It has spread.

[0003] In producing a polyester film, thickness uniformity is one of important basic qualities. Polyester films are used for electrical insulation such as base films for magnetic recording media and capacitors, due to their excellent properties.
It is used in various applications such as OA applications such as printer ribbons, and heat-sensitive stencils which print by punching with heat. In these applications, high dimensional accuracy is required for the thickness of the film year by year. When the thickness unevenness is deteriorated, the physical property unevenness due to the film thickness is caused, which leads to deterioration in product quality. In addition, even if it is not directly related to the quality of the product, troubles when processing the film into a product and deterioration of the winding shape when winding in a roll shape, and eventually leading to deterioration of the quality of the processed product, which is preferable Absent.

[0004] In general, a method of forming a polyester film is to melt a polyester resin by an extruder, remove foreign matter through a filter or the like, and then remove the foreign matter.
The film is discharged from a die (die) having slits according to the shape of the film to be formed, and is continuously formed on a rotating roll (casting drum) through which a cooling medium is passed.
At this time, an electrostatic force is often applied in order to bring the polyester film into close contact with the casting drum. Further, in order to increase the strength of the film, the obtained cast film is generally stretched in the longitudinal direction and the width direction of the film.

The causes of thickness unevenness during film stretching are as follows: unevenness in roll temperature and uneven rotation during longitudinal (longitudinal) stretching, and uneven temperature in a tenter during transverse (width) stretching. And uneven wind speed.

In order to improve the thickness unevenness, in the longitudinal stretching step, Japanese Patent Application Laid-Open No. Sho 60-189422 proposes a method in which a film is adhered to a stretching roll by electrostatic force. Also, JP-A-54-56674 and JP-A-2-
No. 130125 proposes a method of improving thickness unevenness by performing longitudinal stretching in multiple stages.
However, at present it has not yet been fully resolved.

[0007]

As described above, there is a strong demand for improving the film thickness unevenness, and various improvement methods have been proposed for that purpose. However, the effect is still not enough, and the effect is not sufficient. Troubles due to the difference in thickness from the part are still present.

[0008] In order to solve such problems, the present invention reviews the stretching step in the film manufacturing process.
An object of the present invention is to provide a polyester film having a very uniform thickness and a method for producing the same.

[0009]

Means for Solving the Problems To solve the above-mentioned problems, the present inventors have studied the relationship between the thickness uniformity of a polyester film and the intrinsic viscosity, additives, longitudinal stretching temperature, and stretching stress-temperature curve of the polyester film. We studied diligently.
As a result, by stretching a polyester film containing a specific liquid crystalline polyester by a specific method, it is found that the thickness uniformity is excellent and the processability is good,
The present invention has been completed. That is, the present invention is characterized in that a substantially non-oriented polyester film composed of a liquid crystalline polyester and a non-liquid crystalline polyester is stretched at least uniaxially so that the temperature coefficient of stretching stress (K) satisfies the following expression. The main point is that this is a method for producing a polyester film.

-0.35 ≦ K ≦ 0.1 (MPa / ° C.)

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystalline polyester constituting the polyester film of the present invention is a polyester having a mesogen group in the main chain, which is melt-moldable and has liquid crystal forming properties. For example, polyesters forming an anisotropic molten phase composed of structural units selected from aromatic oxycarbonyl units, aromatic dioxy units, aromatic dicarbonyl units, alkylenedioxy units, alkylenedicarbonyl units, and the like.

Preferred examples of the liquid crystalline polyester used in the present invention include the following chemical formulas (I), (II) and (III):
And a liquid crystalline polyester comprising the structural units of (IV),
At least one selected from liquid crystalline polyesters composed of structural units (I), (III) and (IV), and liquid crystalline polyesters composed of structural units (I), (II) and (IV). Can be

[0013]

Embedded image (However, R1 in the formula is

Embedded image And R2 is

Wherein R3 represents one or more groups selected from

Embedded image Represents one or more groups selected from In the formula, X represents a hydrogen atom or a chlorine atom, and the structural unit [((II) + (II
I)] and the structural unit (IV) are substantially equimolar.

The structural unit (I) is a structural unit of a polyester formed from p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid, and the structural unit (II)
Is 4,4'-dihydroxybiphenyl, 3,3 ',
5,5′-tetramethyl-4,4′-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone,
Phenylhydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,2′-bis (4-hydroxyphenyl) propane and 4,4′-
A structural unit generated from an aromatic dihydroxy compound selected from dihydroxydiphenyl ether, a structural unit (III) is a structural unit generated from ethylene glycol, and a structural unit (IV) is terephthalic acid, isophthalic acid,
4,4'-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bis (phenoxy) ethane-
4,4'-dicarboxylic acid, 1,2-bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid and 4,
The structural units generated from aromatic dicarboxylic acids selected from 4'-diphenyl ether dicarboxylic acids are shown.

In the case of a liquid crystalline polyester comprising the above structural units (I), (II) and (IV), R1 is

Embedded image And R2 is

Embedded image R3 is at least one kind selected from

Embedded image Those which are at least one kind selected from

In the case of a liquid crystalline polyester comprising the above structural units (I), (III) and (IV), R1 is

Embedded image And R3 is

Embedded image Is particularly preferred.

The structural units (I), (II) and (II)
In the case of a liquid crystalline polyester comprising I) and (IV), R1 is

Embedded image And R2 is

Embedded image And R3 is

Embedded image Is particularly preferred.

The copolymerization amount of the above structural units (I), (II), (III) and (IV) is optional, but the following copolymerization amount is required in view of fluidity and compatibility with polyester. Is preferred.

The structural units (I), (II) and (I)
In the case of a liquid crystalline polyester composed of V), the structural unit (I) is preferably 15 to 90 mol%, more preferably 50 to 80 mol%, and more preferably 55 to 7 mol% of [(I) + (II)].
5 mol% is most preferred. The structural unit (IV) is substantially equimolar to the structural unit (II).

In the case of a liquid crystalline polyester comprising the structural units (I), (III) and (IV), the structural unit (I) is 30 to 95 mol% of [(I) + (III)]. Is preferable, and 40 to 80 mol% is more preferable.
~ 75 mol% is most preferred. The structural unit (IV) is substantially equimolar to the structural unit (III).

Further, the structural units (I), (II),
In the case of the liquid crystalline polyester comprising (III) and (IV), the molar ratio of [(I) + (II))] to the above structural unit [(I) + (II) + (III)] is 40 to 40. 85 mol% is preferable, and 60 to 80% is more preferable. Further, (III) to the structural unit [(I) + (II) + (III)]
Is preferably 60 to 15 mol%, and 40 to 20 mol%.
Molar% is more preferred. In addition, structural units (I) / (II)
Is preferably 75/25 to 95 from the viewpoint of fluidity.
/ 5, more preferably 78/22 to 93/7. The number of moles of the structural unit (IV) is the same as that of the structural unit [(II)
+ (III)].

The term "substantially" in the above description means that the number of the terminal groups of the polyester can be increased to either the carboxyl group terminal or the hydroxyl terminal group, if necessary. This is because the number of moles of the structural unit (IV) is not completely equal to the total number of moles of the structural unit [(II) + (III)].

In the polycondensation of the preferred liquid crystalline polyester, 3,3'-diphenyldicarboxylic acid, 2,2 ', besides the components constituting the structural units (I) to (IV),
-Aromatic dicarboxylic acids such as diphenyldicarboxylic acid,
Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and dodecanedioic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, chlorohydroquinone, methylhydroquinone, 4,4'-dihydroxydiphenylsulfone, 4,4 ' -Aromatic diols such as dihydroxydiphenyl sulfide, 4,4'-dihydroxybenzophenone, 1,4-butanediol, 1,
6-hexanediol, neopentyl glycol, 1,
Aliphatic and alicyclic diols such as 4-cyclohexanediol and 1,4-cyclohexanedimethanol and aromatic hydroxycarboxylic acids such as m-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid and p-aminophenol, p- Aminobenzoic acid and the like can be further copolymerized in a small proportion that does not impair the purpose of the present invention.

The method for producing the liquid crystalline polyester in the present invention is not particularly limited, and it can be produced according to a known polyester polycondensation method.

For example, in the above-mentioned method for producing a liquid crystalline polyester which is preferably used, the structural unit (III)
When the compound does not contain (1) and (2), the following (3) production method is preferable when the compound contains the structural unit (III).

(1) p-acetoxybenzoic acid and 4,
A method of producing from a diacylated aromatic dihydroxy compound such as 4'-diacetoxybiphenyl, 4,4'-diacetoxybenzene and an aromatic dicarboxylic acid such as terephthalic acid by a deacetic acid polycondensation reaction.

(2) p-hydroxybenzoic acid and 4,
A method of reacting an aromatic dihydroxy compound such as 4'-dihydroxybiphenyl and hydroquinone, and an aromatic dicarboxylic acid such as terephthalic acid with acetic anhydride to acylate a phenolic hydroxyl group, followed by a deacetic acid polycondensation reaction.

(3) Polyester polymers such as polyethylene terephthalate, oligomers or bis (β-
(Hydroxyethyl) terephthalate or the like, in the presence of bis (β-hydroxyethyl) ester of an aromatic dicarboxylic acid, by the method of (1) or (2).

Although these polycondensation reactions proceed without a catalyst, it is sometimes preferable to add a metal compound such as stannous acetate, tetrabutyl titanate, potassium acetate and sodium acetate, antimony trioxide and metallic magnesium. .

In the present invention, a low-viscosity liquid crystalline polyester, that is, a liquid crystalline polyester which increases the melt viscosity ratio (melt viscosity (non-liquid crystalline polyester) / melt viscosity (liquid crystalline polyester)) to the non-liquid crystalline polyester is preferable. . The reason for this is that the lower the viscosity of the non-liquid crystalline polyester, the better the liquid crystalline polyester is finely dispersed and the more uniform the thickness can be achieved.
This melt viscosity ratio needs to be at least 5 or more, preferably 10 or more, and particularly preferably 50 or more. Therefore, the melt viscosity of the liquid crystalline polyester depends on the melt viscosity of the non-liquid crystalline polyester used, but the melting point of the non-liquid crystalline polyester which is the matrix polymer + 1
Under conditions of 5 ° C. and a shear rate of 1000 sec −1, 200 [P
a · sec] or less. Having such a low melt viscosity, a liquid crystalline polyester that can be particularly preferably used to achieve the object of the present invention is:
A liquid crystalline polyester comprising the structural units (I), (II), (III) and (IV). This liquid crystalline polyester has a good dispersion state in the polyester film, and is particularly effective in achieving the thickness uniformity and processability within the scope of the present invention.

The amount of the liquid crystalline polyester in the polyester film of the present invention is not particularly limited.
0.1 to 40% by weight, preferably 0.5 to 20% by weight,
More preferably, the range is 1 to 10% by weight. If the addition amount is less than 0.1% by weight, it is difficult to obtain a film having good thickness unevenness. On the other hand, if it exceeds 40% by weight, the surface of the polyester film becomes very rough due to the liquid crystalline polyester, so that the thickness unevenness is reduced. It is not preferable because it becomes large.

The non-liquid crystalline polyester constituting the polyester film of the present invention includes aromatic dicarboxylic acids,
It is a polyester containing an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol as main components. Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid 4,4′-diphenyl ether dicarboxylic acid, 4,
4'-diphenylsulfonedicarboxylic acid and the like can be used, and particularly, terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid can be used. As the alicyclic dicarboxylic acid component, for example, cyclohexanedicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. One of these acid components may be used alone, or two or more thereof may be used in combination. Further, an oxyacid such as hydroxyethoxybenzoic acid may be partially copolymerized. Also,
As the diol component, for example, ethylene glycol,
1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2- Use of cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,4-cyclohexane dimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2′-bis (4′-β-hydroxyethoxyphenyl) propane, or the like Among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be preferably used, and particularly preferably, ethylene glycol and the like can be used. These diol components may be used alone or in combination of two or more. The non-liquid crystalline polyester includes other compounds such as a monofunctional compound such as trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, 2,4-dioxybenzoic acid, lauryl alcohol, and phenyl isocyanate. It may be copolymerized within a range that is linear in nature.

The method for producing a polyester film of the present invention comprises the steps of: forming a substantially non-oriented polyester film comprising a liquid crystalline polyester and a non-liquid crystalline polyester at least so that the temperature coefficient of stretching stress (K) satisfies the following expression. It is necessary to stretch uniaxially.

−0.35 ≦ K ≦ 0.1 (MPa / ° C.) Preferably, −0.25 ≦ K ≦ 0.05 (MPa / ° C.) More preferably, −0.15 ≦ K ≦ 0 (MPa / ° C) in the temperature range (K).

If the temperature coefficient (K) is smaller than -0.35, the dependence of the stretching tension on the stretching temperature becomes large, and the unevenness of the thickness becomes worse. When the temperature coefficient (K) is larger than 0.1, the stress increases as the stretching temperature increases, the crystallization of the film proceeds, and the stretchability of the film deteriorates. Therefore, the productivity and the control yield are deteriorated.

The method for producing the polyester film of the present invention is not particularly limited, but the glass transition temperature of the non-liquid crystalline polyester (hereinafter abbreviated as Tg) + 30 ° C. to Tg
It is preferred to stretch at a temperature of + 60 ° C. If the stretching temperature is less than Tg + 30 ° C., the temperature and roll unevenness of the roll greatly affects the film thickness, and the thickness unevenness of the film deteriorates. On the other hand, when the stretching temperature is higher than Tg + 60 ° C., the substantially non-oriented polyester film is crystallized, the stretchability is deteriorated, the film is frequently torn, and the control yield is deteriorated.

In recent applications, the polyester film of the present invention is not particularly limited, but is required to have at least a uniaxially stretched polyester film, since particularly high thickness uniformity is being demanded due to higher performance of hardware. The thickness unevenness is preferably 5% or less. It is more preferably at most 4%, more preferably at most 2%. If the thickness unevenness exceeds 5%, the difference in thickness between the thick portion and the thin portion of the film becomes too large, and the difference in physical properties is so large that the film cannot be used. For example, in applications such as heat-sensitive stencil paper and printer ribbons, the thickness unevenness causes uneven print density after printing, resulting in unclear finish. In addition, in applications such as electrical insulation and capacitors, dielectric breakdown may occur in a thin portion of the film, which may cause a failure of the device.

Although the polyester film of the present invention is not particularly limited, it is obtained by subjecting at least a uniaxially stretched polyester film to Fourier analysis of a waveform of uneven thickness.
It is preferable that the ratio Pw2 / PwT of the spectrum intensity sum Pw2 at the wavenumber of 1.00 (1 / m) or more and 2.00 (1 / m) or less to the spectrum intensity sum PwT in the entire wavenumber band is 0.15 or less. Wave number is 1.00
The thickness unevenness of (1 / m) or more and 2.00 (1 / m) or less,
It was found that it contributed to the generation of wrinkles during secondary processing. That is, the ratio Pw2 / P of the spectrum intensity sum Pw2 at the wavenumber of 1.00 (1 / m) or more and 2.00 (1 / m) or less to the spectrum intensity sum PwT in the entire wavenumber band.
If wT exceeds 0.15, troubles such as generation of wrinkles when the film is subjected to secondary processing increase.

Further, the polyester film of the present invention comprises
Although not particularly limited, at least a spectrum intensity sum Pw1 at a wavenumber of 0.15 (1 / m) or more and 0.45 (1 / m) or less when Fourier analysis is performed on the waveform of the thickness unevenness of the uniaxially stretched polyester film. Ratio Pw1 / Pw to the sum of spectrum intensities PwT in all wavenumber bands of
It is preferable that T is 0.2 or less. When a frequency analysis is performed on the waveform of the thickness unevenness, there is a correspondence such that a certain kind of trouble occurs when the thickness unevenness in a certain cycle is large. Here, when the waveform of the uneven thickness is analyzed by Fourier transform, the wave number is 0.15 (1 / m) or more and 0.45 (1
/ M) The ratio P of the sum of spectrum intensities Pw1 at wavenumbers equal to or less than the sum of spectrum intensities PwT in the entire wavenumber band
When w1 / PwT exceeds 0.2, troubles such as meandering and turbulence are caused when performing a processing such as coating on a film or a secondary processing such as a slit processing to a fixed width.

The polyester film of the present invention is not particularly limited, but the non-liquid crystalline polyester is preferably made of polyethylene terephthalate or polyethylene 2,6-naphthalenedicarboxylate. Trouble during secondary processing as described in the present invention is likely to occur when the film is transported at a high temperature, and is likely to occur when processing a very thin film having a thickness of 1 to 2 μm. Therefore, a polyester having high heat resistance and capable of forming an ultra-thin film has a high effect on the occurrence of meandering, turbulence and wrinkles. Among them, polyethylene-
2,6-Naphthalenedicarboxylate and polyethylene terephthalate are preferred. In particular, polyethylene terephthalate is inexpensive and therefore used in a wide variety of applications and is highly effective.

The polyester film of the present invention is not particularly limited, but preferably has an intrinsic viscosity [η] of 0.8 (d).
l / g) or more, more preferably 1 (dl / g) or more,
It is more preferably 1.2 (dl / g) or more. When the intrinsic viscosity [η] is less than 0.8 (dl / g), if the stretching temperature is equal to or higher than the glass transition temperature + 30 ° C., the temperature dependence of the stretching stress is large, and it is difficult to obtain a film having good thickness unevenness. It is to come.

The polyester film of the present invention is not particularly limited. In addition to the liquid crystalline polyester and the non-liquid crystalline polyester, polyethylene terephthalate (hereinafter abbreviated as PET) may be used as a compatibilizer between the liquid crystalline polyester and the non-liquid crystalline polyester. And PHB copolymer, polyethylene-2,6-naphthalenedicarboxylate (hereinafter referred to as PE
N) and a PHB copolymer, an epoxy-based compound, an oxadrine-based compound, or the like. PE
PET of T / PHB copolymer, PEN / PHB copolymer
The ratio between PEN and PEN is not particularly limited, but is preferably 50 mol% or more, more preferably 60 mol or more, from the viewpoint of compatibility. The content of the compatibilizer in the polyester film is not particularly limited, but is preferably 1 to 50% by weight of the content of the liquid crystalline polyester.

The non-liquid crystalline polyester used in the present invention may contain, if necessary, a flame retardant, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, an organic lubricant such as a pigment, a dye, a fatty acid ester, or a wax. Alternatively, an antifoaming agent such as polysiloxane can be blended. Also, clay, mica, titanium oxide, calcium carbonate, carion, talc,
Catalysts for blending inorganic particles such as wet or dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina and zirconia, organic particles containing acrylic acid, styrene, etc., and adding during non-liquid crystalline polyester polymerization reaction So-called internal particles, which are precipitated by the above method, can be contained, or a surfactant can be blended.

In the polyester film of the present invention, an oriented film uniaxially or biaxially stretched and heat-treated is preferable in terms of elastic modulus, heat resistance and the like.

The polyester film of the present invention may be a single film, but may be further provided with another polymer layer such as polyester,
Polyolefin, polyamide, polyvinylidene chloride, acrylic polymer, etc. may be laminated.

The thickness of the polyester film of the present invention is as follows:
Although not particularly limited, 0.5 to 500 μm is preferable.

The polyester film of the present invention is not particularly limited, but can be used for magnetic recording media, photographs, capacitors, discharge, packaging, drawing, ribbons, and the like.

Next, a preferred example of the method for producing a polyester film of the present invention will be described and described, but the present invention is not limited thereto.

A non-liquid crystalline polyester chip and a liquid crystalline polyester chip are charged into a vacuum dryer at predetermined ratios.
In order to suppress the hydrolysis, after sufficiently drying under reduced pressure at 180 ° C. for 10 hours, the mixture is fed to a melt extruder, and extruded while deaerated to suppress the decomposition of the non-liquid crystalline polyester and the liquid crystalline polyester. Draft ratio 5 to 100
Then, it is extruded into a sheet shape from a slit-shaped die and cooled and solidified on a casting roll to produce an unstretched film.

Before being charged into the vacuum dryer, the liquid crystalline polyester may be finely dispersed in the non-liquid crystalline polyester raw material. As a method of finely dispersing the liquid crystalline polyester in the non-liquid crystalline polyester raw material, first, a non-liquid crystalline polyester chip and a liquid crystalline polyester chip are mixed,
A method of melt-extrusion using a vented twin-screw kneading extruder or the like while performing nitrogen sealing and kneading the liquid crystalline polyester into the non-liquid crystalline polyester is preferably performed, and it is effective to perform the kneading a plurality of times. As the screw used at this time, a BM type screw is preferable from the viewpoint of kneading strength.

It is also preferable to reduce the dispersion diameter by pulverizing the liquid crystalline polyester chip before mixing it with the non-liquid crystalline polyester chip. For example, into a pulverizer, put an equal amount of liquid crystalline polyester chips and dry ice,
It is also effective to form a film by spinning at high speed, pulverizing, classifying, collecting a liquid crystalline polyester having a small dispersion diameter, mixing with a non-liquid crystalline polyester chip, and performing melt extrusion.

Next, the unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction and then in the width direction is performed first, the stretching in the longitudinal direction is divided into three or more stages, and the longitudinal stretching temperature is set from Tg + 30 ° C. to Tg + 6 of the non-liquid crystalline polyester.
0 ° C, total longitudinal stretching ratio 3-6 times, longitudinal stretching speed 5000
Perform in the range of 50,000% / min.

In general, the stretching stress-temperature curve of amorphous, unstretched, for example, polyethylene terephthalate, as shown in FIG. 2, shows that the stress is greatly reduced as the stretching temperature is increased. FIG. 2 shows the result of stretching an unstretched film (thickness: 180 μm) of polyethylene terephthalate by changing the stretching temperature.
It shows a drawing tension-temperature curve at a strain of 300%. From FIG. 2, it can be seen that the drawing stress has a large dependency on the drawing temperature, and the temperature coefficient (K) is smaller than −0.35 (MPa / ° C.). For this reason, since the difference in stretching stress due to the difference in stretching temperature is large, uneven thickness tends to occur during stretching.

However, as a result of intensive studies by the present inventors,
As shown in FIG. 1, the drawing stress-temperature curve of an amorphous unstretched polyester film composed of a non-liquid crystalline polyester and a liquid crystalline polyester shows a small decrease in stress even when the stretching temperature is increased. FIG. 1 shows a drawing stress-temperature curve at a strain of 300% when a noncrystalline non-stretched polyester film (thickness: 180 μm) composed of a non-liquid crystalline polyester and a liquid crystalline polyester was stretched while changing the stretching temperature. Things. It is understood that the temperature dependency of the stretching stress is small, and the temperature coefficient (K) is larger than -0.35 (MPa / ° C.). For this reason, even if the stretching temperature is different, the difference in stretching stress is small, so that thickness unevenness during stretching can be suppressed, and a film having excellent thickness uniformity can be obtained.

Next, stretching in the width direction is performed. The stretching in the width direction uses a tenter, the stretching temperature is 80 to 170 ° C., the stretching ratio in the width direction is 3 to 7 times, and the stretching speed in the width direction is 1000 to 200.
Perform in the range of 00% / min. Further, if necessary, re-longitudinal stretching and re-lateral stretching are performed. As the stretching conditions in that case, the stretching in the longitudinal direction is 90 to 180 ° C., and the stretching ratio is 1.1 to 2
The stretching is performed at a stretching temperature of 90 to 180 ° C in the width direction and at a stretching ratio of 1.1 to 2 times in the width direction.

Next, the biaxially oriented film is heat-treated and wound into a roll on a winder. In this case, the heat treatment temperature is 170 to 250 ° C. and the time is 0.5 to 60 seconds.

[Method for measuring physical properties and method for evaluating effects] The method for measuring characteristic values and the method for evaluating effects according to the present invention are as follows.

(1) Intrinsic viscosity [η] In orthochlorophenol at a concentration of 0.1 g / ml, 2
It was measured at 5 ° C. The unit is represented by dl / g. Since the liquid crystalline polyester does not dissolve in orthochlorophenol, the measurement was performed after removing the polymer by centrifugation.

(2) Glass transition temperature (Tg) A "robot" DSC-RDSC220 manufactured by Seiko Denshi Kogyo Co., Ltd. was used as a differential scanning calorimeter, and a disk station SSC / 5 manufactured by the company was used as a data analyzer.
Using 200, about 5 mg of the sample was melted and held on an aluminum saucer at 300 ° C. for 5 minutes, quenched and solidified with liquid nitrogen, and then heated from room temperature at a heating rate of 20 ° C./min. The temperature of the glass transition point observed at this time was defined as Tg.

(3) Unevenness of film thickness (%) Film Thickness Tester KG6 manufactured by Anritsu Corporation
Using 01A and an electronic micrometer K306C, the thickness of a film sampled 30 mm wide and 2 m long in one direction of the film is continuously measured. However, the thickness unevenness is measured in the direction in which the film is stretched first. The transport speed of the film was 3 m / min. Maximum thickness Tmax (μm) and minimum T for 2 m length
R = Tmax-Tmin was determined from min (μm), and the thickness unevenness (%) was determined from R and the average thickness Tave (μm) having a length of 2 m = (R / Tave) × 100.

(4) Fourier Analysis of Film Thickness Unevenness At the time of the above-mentioned thickness unevenness measurement, the output from the electronic micrometer was digitized through an analog / digital converter (A / D converter) and taken into a computer. At this time, the output voltage of the electronic micrometer and the A / D
If necessary, a preamplifier may be provided between the electronic micrometer and the A / D converter to optimize the input voltage of the converter. In the present invention, the output of an electronic micrometer is connected to an A / D converter ADX-98E and a dedicated trigger unit ADT-98E manufactured by Canopus Electronics Co., Ltd. via a self-made preamplifier, and a personal computer PC manufactured by NEC Corporation is connected. -9801
Data was imported to VM. The data acquisition software used was a self-made one. Data capture is 1
During the measurement of thickness unevenness of 0 m length, 20
Five points were sampled (because the transfer measurement was performed at 3 m / min, 0.195 sec × 205 × 3 m / min ÷ 60 sec / min =
At 1.99975 m, data on thickness unevenness of 1.99975 m was captured. Of course, it is not necessary to be limited to these devices, and there are many known devices having similar functions. The data thus fetched was subjected to a fast Fourier transform (FFT) process in the above-mentioned computer using self-made software. At this time, if the film forming time (second) converted from the film forming speed and the transport speed at the time of measurement is taken as the variable of the flow direction, the intensity distribution with respect to the frequency (Hz) is obtained by the FFT processing. Taking the film length (m) as a variable in the flow direction, an intensity distribution with respect to the wave number (1 / m) is obtained by FFT analysis.
For the FFT processing, for example, the Fourier transform theory is described in “Engineer's Mathematics I” first edition (Kyoritsu Shuppan Co., Ltd. Kyoritsu Zensho 516), and the FFT processing method is described in “Opto-Optics” first edition (Kyoritsu Shuppan Co., Ltd.). This is a known process such as a description. The captured data was subjected to Fourier transform processing as shown in the following Expression 1 to obtain a sum of spectrum intensities.

[0061]

(Equation 1) Here, assuming that the real part of Xn is an and the imaginary part is bn, the spectrum intensity sum Pwn can be expressed by the following equation (2).

[0062]

(Equation 2) On the other hand, the wave number for n is n / 1 from the measurement length of 10 m.
0 (1 / m), and the sum of the spectrum intensities from the wave numbers α to β is represented by the following Expression 3 where n corresponding to α and β is nα and nβ.

[0063]

(Equation 3) Then, the sum of all spectral intensities is 1 ≦ n ≦ (N / 2−
1), and the total spectrum intensity sum is expressed by the following equation (4).

[0064]

(Equation 4) (5) Stretching stress-temperature curve Using a biaxial stretching device manufactured by Toyo Seiki Seisaku-Sho, Ltd., the unstretched film sample was adjusted to 90 mm × 90 mm, and preheated in a predetermined temperature atmosphere for 20 seconds.
At 000% / min, the film was stretched in the other direction under one-way constraints, and the stress was measured by a strain gauge attached to a clip. However, the stretching stress is measured in the direction in which the stretching is performed first. The measurement was performed while keeping the strain of each sample constant (for example, the strain was set to 300%).

(6) Temperature coefficient (K) (MPa / ° C.) The slope was obtained from the stretching stress-temperature curve, for example, as follows (provided that the strain was 300%).

Temperature coefficient (K) = [(Tg of polyester)
+ 45 ° C. stretching stress) − (Tg of polyester + 15 ° C.)
Stretching stress)] / (45-15)

(7) Suitability of film processing The film wound up to a width of 500 mm was supplied from an unwinder to an oven processing apparatus manufactured by Inoue Metal Industry Co., Ltd. at a conveying speed of 20 m / min.
, And wound up in a length of 100 m. At this time, the end of the wound film is 1
“×” indicates that the projections were more than 0 mm and became irregular.
Those whose end protrusion is 5 mm or more and 10 mm or less,
A mark of less than 5 mm but wrinkles observed during processing was marked as “△”, and a mark with a protrusion at the end of less than 5 mm and no wrinkles observed during processing was marked as “○”.

(8) Average Dispersion Diameter (Fiber Diameter) of Liquid Crystalline Polyester, Aspect Ratio The film is immersed in liquid nitrogen and cooled sufficiently.
The film was cracked in the air, and its cross section was observed with a scanning electron microscope (SEM). The minor axis of the major axis / minor axis of the liquid crystalline polyester in the observed visual field was taken as the dispersion diameter, and the average was taken as the average dispersion diameter. The unit is expressed in μm. The ratio of the major axis / minor axis (dispersion diameter) of the liquid crystalline polyester was defined as the aspect ratio.

(9) Melt Viscosity Using a melt indexer, a value at a melt temperature of 280 ° C. and a shear rate of 1000 sec−1 was measured. The unit is Pa
Expressed as s.

(10) Draft ratio Die lip polymer flow rate / casting drum (C
D) Expressed by the upper film (polymer) flow rate.

[0071]

Next, embodiments of the present invention will be described based on examples.

Example 1 100 parts by weight of dimethyl terephthalate, 70 parts by weight of ethylene glycol, 0.002 parts by weight of lithium acetate, 0.06 parts by weight of magnesium acetate, and 0.1 part by weight of antimony trioxide.
After adding 03 parts by weight and subjecting it to a transesterification reaction according to a conventional method, 0.023 parts by weight of trimethyl phosphate was added. Thereafter, an ethylene glycol slurry of calcium carbonate having a particle size of about 0.6 μm and an ethylene glycol slurry of colloidal silica having a particle size of about 0.2 μm are added,
Then, the temperature was gradually increased and the pressure was reduced.
By conducting the polycondensation reaction at mHg or less, [η] =
A PET polymer having a diameter of about 2 mm and a height of about 3 mm was obtained as a PET polymer having 0.65, a calcium carbonate concentration of 0.01% by weight, and a colloidal silica concentration of 0.3% by weight.

After drying the obtained chips, preliminary crystallization was performed for 2 hours while stirring at 180 ° C. under reduced pressure of 1 mmHg or less. Thereafter, the temperature was further raised to 220 ° C., and the solid phase polymerization was continued for 50 hours to obtain a PET chip with [η] = 1.15.

The liquid crystalline polyester includes p-hydroxybenzoic acid (72.5 mol%), polyethylene terephthalate (20 mol%), 4,4′-dihydroxybiphenyl (7.5 mol%), and terephthalic acid (7.5 mol%). Mol%) (melting point: 260 ° C., liquid crystal onset temperature: 240 ° C., melt viscosity: 25 Pa · s).
Hereinafter, the liquid crystalline polyester is abbreviated as LCP.

After mixing 5 wt% of the LCP chip with the above PET chip, it was dried at 180 ° C. for 10 hours under reduced pressure (3 To
rr) and then fed to an extruder and degassed at 295 ° C.
Melted. This polymer is mixed with 30 μm or more
After filtration using a high-precision filter having a filtration accuracy of removing at a probability of 5%, a molten sheet is extruded from a T-die die at a draft ratio of 9 and casting at a surface temperature of 25 ° C. using an electrostatic application casting method. -It was wound around a drum and cooled and solidified to prepare an unstretched film ([η] = 1.05) containing 5% by weight of LCP. The discharge amount of the extruder was adjusted to adjust the total thickness.

The unstretched film was heated at a temperature of 125 ° C. (Tg
(+ 45 ° C.) and stretched 3.8 times in the longitudinal direction. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was stretched 3.8 times in the width direction at 105 ° C. using a tenter. This film is 225 under fixed length
Biaxially oriented PET with heat treatment at 7 ° C for 7 seconds
The film was wound with a winder. The average dispersion diameter of LCP in this film was 0.3 μm.

The properties of this biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Example 2 In the same manner as in Example 1, a PET chip ([η] =
0.95) and LCP chip, 3% by weight of LCP
An unstretched film ([η] = 0.85) was prepared.

The unstretched film was heated at a temperature of 116 ° C. (Tg
(+ 37 ° C.) and stretched 4.0 times in the longitudinal direction. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was stretched 3.9 times in the width direction at 103 ° C. using a tenter. This film is placed under a fixed length of 230
Biaxially oriented PE with a total thickness of 10 μm
A T film was obtained. The average dispersion diameter of LCP in this film was 0.5 μm.

The properties of the biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Example 3 In the same manner as in Example 1, a PET chip ([η] =
Using 1) and the LCP chip, an unstretched film ([η] = 0.9) containing 1% by weight of LCP was prepared. This unstretched film was stretched 3.8 times in the longitudinal direction at a temperature of 119 ° C. (Tg + 40 ° C.). This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was stretched 3.5 times in the width direction at 103 ° C. using a tenter. This film was heat-treated at 230 ° C. for 5 seconds under a constant length to obtain a biaxially oriented PET film having a total thickness of 10 μm.
The average dispersion diameter of LCP in this film was 0.4 μm.

The properties of this biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Example 4 In the same manner as in Example 1, an unstretched film ([η] = 1) containing 5% by weight of LCP was prepared using a PEN chip and an LCP chip.

The unstretched film was heated at a temperature of 162 ° C. (Tg
(+ 35 ° C.) and stretched 4.2 times in the longitudinal direction. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was stretched 4.5 times in the width direction at 155 ° C. using a tenter. This film is placed under a fixed length of 230
Biaxially oriented PE with a total thickness of 70 μm
An N film was obtained. The average dispersion diameter of LCP in this film was 0.5 μm.

The properties of this biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Example 5 As LCP, p-hydroxybenzoic acid (72.5 mol%), polyethylene terephthalate (20 mol%),
4,4′-dihydroxybiphenyl (7.5 mol%),
A liquid crystalline polyester chip composed of terephthalic acid (7.5 mol%) (melting point: 260 ° C., liquid crystal onset temperature: 240 ° C.,
A melt viscosity of 1.5 Pa · s) was used. Using a PET chip ([η] = 1.4) and an LCP chip, an unstretched film containing 0.5% by weight of LCP ([η] = 1.
I made 1).

This unstretched film was stretched in the same manner as in Example 1 to obtain a biaxially oriented PEN film having a total thickness of 7 μm. The average dispersion diameter of LCP in this film is 1
μm.

The properties of this biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Example 6 As LCP, p-hydroxybenzoic acid (42.5 mol%), polyethylene terephthalate (50 mol%),
4,4′-dihydroxybiphenyl (7.5 mol%),
Liquid crystalline polyester chip composed of terephthalic acid (7.5 mol%) (melting point 210 ° C., melt viscosity 18 Pa · s)
Was used. Using a PET chip ([η] = 1.2) and an LCP chip, an unstretched film ([η] = 0.95) containing 5% by weight of LCP was produced.

The unstretched film was stretched in the same manner as in Example 1 to obtain a biaxially oriented PEN film having a total thickness of 5 μm. The average dispersion diameter of LCP in this film was 0.3 μm.

The properties of the biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Example 7 As LCP, p-hydroxybenzoic acid (42.5 mol%), polyethylene terephthalate (50 mol%),
4,4′-dihydroxybiphenyl (7.5 mol%),
Liquid crystalline polyester chips composed of terephthalic acid (7.5 mol%) (melting point 210 ° C., melt viscosity 1.4 Pa ·
s) was used. PET chip ([η] = 1.3) and LC
Using a P chip, an unstretched film ([η] = 1.02) containing 1% by weight of LCP was prepared.

This unstretched film was stretched in the same manner as in Example 1 to obtain a biaxially oriented PEN film having a total thickness of 10 μm. The average dispersion diameter of LCP in this film was 0.2 μm.

The properties of this biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Example 8 As LCP, p-hydroxybenzoic acid (72.5 mol%), polyethylene-2,6-naphthalenedicarboxylate (20 mol%), 4,4'-dihydroxybiphenyl (7.5 mol%) %), Terephthalic acid (7.5 mol%)
A liquid crystalline polyester chip consisting of
a.s) was used. By using a PEN chip ([η] = 0.9) and an LCP chip, an unstretched film ([η] = 0.84) containing 3% by weight of LCP was produced.

The unstretched film was heated at a temperature of 171 ° C. (Tg
(+ 45 ° C.) and stretched 4.5 times in the longitudinal direction. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film was stretched 4.6 times in the width direction at 158 ° C. using a tenter. This film is placed under a fixed length of 230
Biaxially oriented PE with a total thickness of 10 μm
An N film was obtained. The average dispersion diameter of LCP in this film was 0.7 μm.

The properties of the biaxially oriented polyester film are as shown in Table 2, and were excellent in thickness uniformity and workability.

Comparative Example 1 An unstretched film ([η] = 1) was prepared by using 95% by weight of a PET chip ([η] = 1.4) and 5% by weight of a PET chip ([η] = 0.48). Had made.

In the same manner as in Example 1, this unstretched film was stretched 3.8 times in the longitudinal direction at 125 ° C. (Tg + 45 ° C.). This stretching is performed at the peripheral speed difference between two sets of rolls,
Performed in stages. This uniaxially stretched film was stretched 3.8 times in the width direction at 105 ° C. using a tenter. This film was heat-treated at 225 ° C. for 7 seconds under a constant length, and the thickness was 50 μm.
m biaxially oriented polyester film was obtained.

Comparative Example 2 A biaxially oriented polyester film was obtained in the same manner as in Comparative Example 1, except that the unstretched film was stretched at 95 ° C. (Tg + 15 ° C.).

Comparative Example 3 A biaxially oriented polyester film was obtained in the same manner as in Comparative Example 1, except that the unstretched film was stretched at 145 ° C. (Tg + 65 ° C.).

Comparative Example 4 In the same manner as in Example 1, an unstretched film ([η] = 1) containing 0.05% by weight of LCP was produced. This unstretched film was formed in the same manner as in Comparative Example 1 to obtain a biaxially oriented polyester film.

Comparative Example 5 An unstretched film ([η] = 0.65) was prepared using a PET chip ([η] = 0.7). A film was formed in the same manner as in Example 2 except that the unstretched film was stretched at 113 ° C. (Tg + 35 ° C.) to obtain a biaxially oriented polyester film.

Comparative Example 6 In the same manner as in Example 1, an unstretched film ([η] = 0.6) containing 45% by weight of LCP was prepared. Except for stretching this unstretched film at 118 ° C. (Tg + 40 ° C.), a film was formed in the same manner as in Example 1 to obtain a biaxially oriented polyester film.

Comparative Example 7 An unstretched film ([η] = 0.9) was prepared using a PEN chip ([η] = 1.2). This unstretched film was formed in the same manner as in Example 4 to obtain a biaxially oriented polyester film.

Comparative Example 8 The unstretched film used in Comparative Example 6 was heated at 142 ° C. (Tg +
Except for stretching at 15 ° C.), a film was formed in the same manner as in Example 4 to obtain a biaxially oriented polyester film.

[0107]

[Table 1]

[Table 2]

[0108]

According to the present invention, a substantially non-oriented polyester film composed of a liquid crystalline polyester and a non-liquid crystalline polyester is obtained. The temperature coefficient (K) of the stretching stress is -0.35≤K.
A film having excellent thickness uniformity and workability is produced by stretching at least uniaxially so as to satisfy ≦ 0.1 (MPa / ° C.).
Can be used for A applications.

[Brief description of the drawings]

FIG. 1 shows an unstretched polyethylene terephthalate film (having a thickness of 18) containing 5% by weight of a liquid crystalline polyester of the present invention.
FIG. 1 is a schematic diagram showing an example of a stretching stress-temperature curve (strain is 300%) of 0 μm).

FIG. 2 is a drawing stress-temperature curve of an unstretched film (thickness: 180 μm) of polyethylene terephthalate (having a strain of 30).
0%) is a schematic diagram showing an example.

Claims (11)

[Claims] 1. A substantially non-oriented polyester film comprising a liquid crystalline polyester and a non-liquid crystalline polyester is stretched at least uniaxially so that the temperature coefficient (K) of stretching stress satisfies the following expression. Of producing polyester film. −0.35 ≦ K ≦ 0.1 (MPa / ° C) 2. A substantially non-oriented polyester film comprising a liquid crystalline polyester and a non-liquid crystalline polyester, and a glass transition temperature of the non-liquid crystalline polyester + 30 ° C.
The method for producing a polyester film according to claim 1, wherein the film is stretched in a temperature range of from + to a glass transition temperature + 60 ° C. 3. A polyester film comprising a liquid crystal polyester and a non-liquid crystal polyester, wherein the non-oriented polyester film has a thickness unevenness of at least uniaxially stretched polyester film of 5% or less. 4. The spectrum intensity sum PwT in the entire wavenumber band of the spectrum intensity sum Pw2 at a wavenumber of 1.00 (1 / m) or more and 2.00 (1 / m) or less when a waveform of uneven thickness is subjected to Fourier transform. Pw2 / PwT with respect to
Is 0.15 or less, the polyester film according to claim 3. 5. A spectrum intensity sum PwT in the entire wavenumber band of a spectrum intensity sum Pw1 at a wavenumber of 0.15 (1 / m) or more and 0.45 (1 / m) or less when a waveform of uneven thickness is subjected to Fourier transform. Ratio Pw1 / PwT with respect to
The polyester film according to claim 3 or 4, wherein is not more than 0.2. 6. Pw1 / PwT of a polyester film
Is 0.2 or less, and Pw2 / PwT is 0.15
The polyester film according to any one of claims 3 to 5, wherein 7. A liquid crystalline polyester comprising structural units of the following chemical formulas (I), (III) and (IV), and a liquid crystalline polyester comprising structural units of (I), (II) and (IV) , (I), (II), (II
The polyester film according to any one of claims 3 to 6, wherein the polyester film is at least one selected from liquid crystalline polyesters comprising the structural units (I) and (IV). Embedded image (Where R1 in the formula is R2 represents one or more groups selected from Represents one or more groups selected from In the formula, X represents a hydrogen atom or a chlorine atom, and the structural unit [((II) + (II
I)] and the structural unit (IV) are substantially equimolar. ) 8. An intrinsic viscosity [η] of a polyester film.
Is 0.8 (dl / g) or more, the polyester film according to any one of claims 3 to 7. 9. The polyester film according to claim 3, comprising 0.1 to 40% by weight of a liquid crystalline polyester. 10. The polyester film according to claim 3, wherein the non-liquid crystalline polyester comprises polyethylene terephthalate or polyethylene 2,6-naphthalenedicarboxylate. 11. The polyester film according to claim 3, wherein the polyester film is a uniaxially or biaxially oriented film.