JPH10330509A - Polyester film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-quality film reduced in surface defective streaks and nonuniformity in thickness by finely dispersing a copolyester having mesogen groups in the principal chain and a melt viscosity in a specified range in the mixture of a non-liquid-crystal polyester and particles in such a manner that the copolyester has a mean dispersed particle diameter in a specified range. SOLUTION: An example of the non-liquid-crystal polyester used is polyethylene terephthalate. The particles used preferably comprise inorganic particles (e.g. clay particles) having a mean diameter of 0.5-5 μm. The copolyester has a melt viscosity of 0.1-50 Pa.sec and a mean dispersed particle diameter of 0.001-5 μm. The mesogen groups preferably account for 15-90 wt.% of comonomers of the copolyester. It is desirable that the copolyester consists of structural units of formulas I to IV, wherein the molar fractions of units of formulas (I+II) and those of formula III respectively to units of formulas (I+II+III) are 15-90% and 85-10%, the molar ratio of units of formula I to those of formula II is (75:25) to (95:5), and the number of moles of units of formula IV is substantially equal to that of units of formulas II and III. In the formulas, R1 is of formula V and/or formula VI; and R2 is of formula VII, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality polyester film free from surface defects and minute surface irregularities, in particular, streak-like surface defects continuous in the longitudinal direction and thickness unevenness. The present invention relates to a glossy polyester film that can be suitably used for applications such as labeling and stamping.

[0002]

2. Description of the Related Art Eliminating surface defects of a polyester film, in particular, streak-like surface defects continuous in the longitudinal direction is important for improving productivity, yield, and quality. In particular, in applications requiring glossiness, streak-like surface defects immediately become quality defects, and thus greatly affect yield and productivity. Causes of the occurrence of the streak-like surface defects include scratches and deposits on the inside of the die, especially on the lip portion, and deposits on the lower surface of the die, particularly near the polymer outlet in the slit portion of the die. There is a method for improving the finishing accuracy of the polishing inside the base against the scratch inside the base. Also, for the deposit inside the base,
A method of blending an additive that makes it difficult for the polymer to adhere to the short tube or the base wall of the base, or the inside of the base is chrome-plated as represented in Japanese Patent Publication No. 5-33889 and Japanese Patent Publication No. 6-45914. There are ways to do that. Deposits on the lower surface of the base are caused by a phenomenon called die swell, in which the polymer itself swells immediately after the polymer comes out of the base.Therefore, measures such as raising the base temperature or widening the base slit gap have been taken. ing.

[0003]

However, even if the finishing accuracy of polishing the inside of the die is increased, the uneven surface defects in the uneven shape cannot be reduced, but the uneven surface defects in the convex and concave shapes cannot be eliminated. Further, even if the inside of the base is plated with chromium, the convex streak-like surface defect cannot be completely eliminated. In addition, there is a problem that increasing the die temperature or widening the slit gap deteriorates the thickness unevenness. Thus, it was not possible to eliminate all the irregular, convex, and concave streak-like surface defects at the same time. Further, if a streak-like surface defect occurs during the production, the production must be stopped and the base lip must be cleaned, so that the higher the frequency of occurrence of the streak-like surface defect, the lower the productivity.

That is, according to the present invention, the frequency of occurrence of uneven, convex, and concave streak-shaped surface defects, particularly the frequency of occurrence of convex streak-shaped surface defects, is greatly reduced as compared with the prior art, thereby improving productivity. And to provide a high-quality film with few surface defects.

[0005]

An object of the present invention is to provide a non-liquid crystalline polyester (A), particles (B) and a melt viscosity of 0.1.
In a composite consisting of a copolymerized polyester (C) having a mesogen group in the main chain at 1 to 50 Pa · s, the copolymerized polyester (C) having a mesogen group in the main chain is finely dispersed in the film, The average dispersion diameter is 0.001
５5 μm.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Representative non-liquid crystalline polyesters (A) used in the present invention include polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, and poly (ethylene terephthalate). Cyclohexanemethylene terephthalate, a copolymer thereof, and the like are used. Of course, polyesters having an ether component in the main chain, for example, copolymers of diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol and the like may be used. Further, the intrinsic viscosity of the non-liquid crystalline polyester is not particularly limited,
It is preferably 0.5 to 1.5.

The particles (B) used in the present invention include clay, mica, titanium oxide, calcium carbonate, kaolin,
Talc, wet silica, dry silica, calcium phosphate,
Inorganic particles such as aluminum oxide and zirconium oxide,
Organic particles containing acrylic acid, styrene, divinylbenzene and the like as constituent components, internal particles utilizing a catalyst at the time of polyester synthesis, and the like are used. The average particle size of the particles is not particularly limited, but the effect is larger when the particles are relatively large, such as 0.5 to 5 μm.

The addition amount of the particles (B) used in the present invention is 0.1.
The content is preferably 1 to 10% by weight, more preferably 0.2 to 10% by weight.
It is 8 wt%, more preferably 0.5 to 5 wt%. If the addition amount is less than 0.1 wt%, the effect of adding the particles is almost negligible, and the handleability tends to deteriorate, and if it exceeds 10 wt%, the surface of the film is liable to become rough, which is not preferable.

The copolymerized polyester (C) used in the present invention
Is a melt-moldable polyester having a mesogenic group (liquid crystalline structural unit) in the main chain. 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.

Examples of preferred copolymerized polyesters used in the present invention include copolymerized polyesters having the following structural units (I), (II), (III) and (IV):
At least one selected from copolymerized polyesters composed of structural units (I), (III) and (IV), and copolymerized polyesters composed of structural units (I), (II) and (IV). Can be

[0011]

Embedded image (However, R ₁ in the formula is

Embedded image And R ₂ is

Embedded image R ₃ 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 copolymerized polyester comprising the above structural units (I), (II) and (IV), R ₁ is

Embedded image And R ₂ is

Embedded image And at least one selected from the R ₃

Embedded image Those which are at least one kind selected from

In the case of a copolymerized polyester comprising the above structural units (I), (III) and (IV), R ₁ is

Embedded image And R ₃ is

Embedded image Is particularly preferred.

The structural units (I), (II) and (II)
In the case of the copolymerized polyester consisting of I) and (IV), R ₁ is

Embedded image And R ₂ is

Embedded image And R ₃ is

Embedded image Is particularly preferred.

The copolymerization amount of the above structural units (I), (II), (III) and (IV) is optional,
From the viewpoint of fine dispersion of the copolymerized polyester, the following copolymerization amount is preferable.

The structural units (I), (II) and (I)
In the case of the copolymerized polyester composed of V), the structural unit (I) is preferably 15 to 90 mol% of [(I) + (II)], more preferably 40 to 80 mol%. The structural unit (IV) is substantially equimolar to the structural unit (II).

In the case of a copolymerized polyester comprising the structural units (I), (III) and (IV), the structural unit (I) is 15 to 90 mol% of [(I) + (III)]. Is preferable, and 40 to 80 mol% is more preferable. The structural unit (IV) is substantially equimolar to the structural unit (III).

Further, the structural units (I), (II),
In the case of the copolymerized polyester composed of (III) and (IV), the molar fraction of [(I) + (II)] with respect to the structural unit [(I) + (II) + (III)] is 15 to 90. Mol%
Is preferable, and 40 to 80% is more preferable. Further, the molar fraction of (III) with respect to the structural unit [(I) + (II) + (III)] is preferably from 85 to 10 mol%, more preferably from 60 to 20 mol%. Further, the molar ratio of the structural units (I) / (II) is preferably from 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 copolymerized polyester, 3,3'-diphenyldicarboxylic acid, 2,2,
Aromatic dicarboxylic acids such as' -diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and dodecandioic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, chlorohydroquinone, methylhydroquinone, Aromatic diols such as 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, 4,4'-dihydroxybenzophenone, 1,4-butanediol,
1,6-hexanediol, neopentyl glycol,
Aliphatic, alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and m
-Hydroxybenzoic acid, aromatic hydroxycarboxylic acids such as 2,6-hydroxynaphthoic acid, and p-aminophenol, p-aminobenzoic acid, etc. are further copolymerized in a small proportion not to impair the object of the present invention. I can do it.

The copolyester (C) in the present invention
Is not particularly limited, and can be produced according to a known polyester polycondensation method.

For example, in the above-mentioned method for producing the preferably used copolymerized polyester (C), when the above structural unit (III) is not contained, the following (1) and (2), and when the structural unit (III) is contained, The following method (3) is preferable.

(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, the melt viscosity ratio (melt viscosity (non-liquid crystalline polyester) / melt viscosity (copolyester)) to the low-viscosity copolymer polyester (C), that is, the non-liquid crystalline polyester (A) is increased. Is preferred. This is because the suppression of shear heat generation in the extrusion step can be achieved more effectively than when the low-viscosity copolymerized polyester (C) is added to the non-liquid crystalline polyester (A). The melt viscosity ratio is preferably at least 5 or more, more preferably 10 or more, and particularly preferably 50 or more. Therefore, the copolymerized polyester (C)
Is preferably from 0.1 to 50 Pa · s under the conditions of 280 ° C. and a shear rate of 200 sec ⁻¹ , although it depends on the melt viscosity of the non-liquid crystalline polyester (A) used.
Preferably it is 0.3 to 10 Pa · sec, more preferably 0.5 to 3 Pa · sec. By adding an appropriate amount of such an ultra-low-viscosity copolymerized polyester to the non-liquid crystalline polyester, the copolymerized polyester is finely dispersed in the non-liquid crystalline polyester, the die swell becomes smaller, and there is no streak-like surface defect. A high quality film with little unevenness is obtained. The copolymerized polyester having such a low melt viscosity and particularly suitably used for achieving the object of the present invention is the above-mentioned structural unit (I), (I)
It is a copolymerized polyester consisting of (I), (III) and (IV). This copolymerized polyester is finely dispersed uniformly in the non-liquid crystalline polyester (A).

The polyester film of the present invention comprises a composite of a non-liquid crystalline polyester (A), particles (B) and a copolymerized polyester (C). The copolymerized polyester (C) is finely dispersed in the non-liquid crystalline polyester (A). Examples of the dispersion form include various forms called a skin core type, a sea-island type, and a multilayer fiber type. In the case of the present invention, it is particularly preferable that the copolymerized polyester (C) is finely dispersed in the non-liquid crystalline polyester (A) in a spherical, oblate and oval shape. Although not particularly limited, when the domains of the copolymerized polyester are oblate and oval, the aspect ratio (L / D) of the long axis to the uniaxial of the oblate and oval domains is preferably 2 to 50, It is more preferably 3 to 40, particularly preferably 5 to 30.

The average dispersion diameter of the copolymerized polyester (C) is from 0.001 to 5 μm, preferably from 0.0 to 5 μm.
It is 1 to 3 μm, and more preferably 0.1 to 1 μm. When the copolymerized polyester (C) is finely dispersed in the non-liquid crystalline polyester (A) at such a dispersion diameter, it is excellent in preventing thermal decomposition of the non-liquid crystalline polyester (A). This is preferable because it greatly reduces the die well ratio.

In general, the molten polymer extruded from the die has elasticity in the molten material, so that when it comes out of the die into the atmosphere, it swells, and the size of the molten resin extruded from the die is measured in the thickness direction of the die outlet (in the thickness direction). A phenomenon (die swell) that is larger than the lip gap is observed. In this case, the ratio of the lip gap (d1) of the die to the thickness (d2) of the extrudate is called a die swell ratio (d2 / d1), and it is known that the shear rate increases and the higher the molecular weight polymer, the larger the ratio. When the discharge rate is increased in order to increase the productivity, the shear rate in the die also increases, so that the die swell ratio increases. When the die swell ratio is large, the polymer easily adheres to the lower surface of the base lip, and the adhered polymer is thermally degraded, so that eyes and eyes are easily generated. This is undesirable because it causes surface defects of the film such as streak formation. However, by finely dispersing the copolymerized polyester (C) in the non-liquid crystalline polyester (A) as in the present invention, the apparent viscosity of the non-liquid crystalline polyester decreases, the die swell ratio decreases, and Occurrence of eyes and eyes due to the adhered polymer can be suppressed. If the polymer adheres to the lower surface of the base, it will cause a convex streak-shaped surface defect.Polymer adhered to the eyes, etc., can be easily removed by cleaning the lower surface of the base and the slit with a copper plate or the like. In order to perform the process, it is necessary to temporarily stop the film formation, so that the productivity of the film is reduced. According to the present invention, the die swell ratio is reduced, the adhesion of the polymer to the lower surface of the base is reduced, and the frequency of cleaning the base is reduced, so that not only the productivity is improved, but also a high-quality film having no streak-shaped surface defects is obtained. can get.

In order to finely disperse the copolymerized polyester (C) in the non-liquid crystalline polyester (A), it is desirable to increase the shear rate in an extruder. However, 500s
When a shear rate of ec ^-1 or more is applied, the shear heat is increased, so that the polymer is liable to be thermally decomposed, and as a result, it is liable to become an eye-like deposit on the lower surface of the mouthpiece, which causes a convex streak-like surface defect. Absent. In the present invention, the shear rate in the extruder is πDN / 60h [D = extruder cylinder diameter (cm), N = screw rotation speed (rpm),
h = screw metering section groove depth (cm)].

The thickness unevenness of the polyester film of the present invention is 1 to 15%, preferably 2 to 12%, and more preferably 3 to 10%. It is not a practical requirement that the thickness non-uniformity is less than 1%, and if it is more than 15%, the physical properties of the film greatly vary and pose a practical problem.

The amount of the copolyester (C) of the present invention is preferably in the range of 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, and most preferably 0.1 to 1% by weight. %. If the amount is less than 0.01% by weight, the effect of the copolymerized polyester (C) is difficult to exert, and if it exceeds 10% by weight, the basic properties of the film such as mechanical properties are liable to deteriorate, which is not preferable.

The polyester film of the present invention is particularly effective for applications such as stamping and labels, but is also useful for magnetic recording media, capacitors, electrical insulation, and the like.
It can also be used for packaging, ribbons and the like.

The polyester film of the present invention is prepared by melting a composite of a non-liquid crystalline polyester (A), particles (B) and a copolymerized polyester (C), extruding the molten polymer from a die, and then, if necessary. The film is produced by a method of stretching to form a film. At this time, it is preferable that at least a part of the surface of the die in contact with the molten polymer is a chrome-plated die. This makes it possible to produce the film for a long time in a state where the catalyst and additives in the polymer and the degraded polymer do not adhere to the surface of the die in contact with the molten polymer during the production of the film. Further, the surface roughness of the chromium plating film portion is preferably 1S or less, more preferably 0.6S or less, and further preferably in the range of 0.05 to 0.4S. 1S means that the Rmax value specified in the surface roughness measurement of JIS-B-0601 is 1 μm. The surface roughness can be measured using a commercially available surface roughness meter with a sample length of 1 to 10 mm and a cutoff of 0.1 to 1 mm. In the case where the sample is too large to fit on the surface roughness meter or the like, it is also possible to substitute for this by measuring a sample piece treated in the same manner as the sample.

The polyester film of the present invention may be an unstretched, uniaxially or biaxially stretched film, but a biaxially stretched film is preferred because it is superior in stability over time and balance of physical properties.

In the polyester film of the present invention, a compatibilizer, a plasticizer, a weathering agent, an antioxidant, etc., as long as the effects of the present invention are not impaired, other than the non-liquid crystalline polyester, the particles and the copolymerized polyester. Agents, heat stabilizers, antistatic agents, brighteners, coloring agents, conductive agents, and the like may be added.

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.

Next, a method for producing the polyester film of the present invention will be described, but the present invention is not limited to such an example.

Here, an example is shown in which polyethylene terephthalate is used as the non-liquid crystalline polyester (A), but the production conditions differ depending on the polymer used. According to a conventional method, bis-β-hydroxyethyl terephthalate (BHT) is obtained by esterifying terephthalic acid and ethylene glycol or transesterifying dimethyl terephthalate and ethylene glycol. Next, while transferring the BHT to the polymerization tank, the polymerization reaction is advanced by heating to 280 ° C. under vacuum. Here, a polyester having an intrinsic viscosity of about 0.65 is obtained. Using the obtained non-liquid crystalline polyester (A), a non-liquid crystalline polyester master chip containing high concentration particles (B) is prepared.

Next, a non-liquid crystalline polyester (A), a non-liquid crystalline polyester master chip containing high-concentration particles (B) and a copolymer polyester (C) chip are mixed.
After vacuum drying at 180 ° C. for 3 hours or more, it is supplied to an extruder heated to 280 ° C., filtered by a filter, and pressed into a sheet shape by a T-die having at least a part of the inner side in contact with the molten polymer, which is plated with chrome. put out. The non-liquid crystalline polyester (A) and the copolymerized polyester (C) may be mixed together as chips, but in order to enhance dispersibility,
It is also preferable that a non-liquid crystal polyester master chip containing a high concentration of copolymerized polyester is once prepared using a biaxial kneader or the like, and the chip is diluted with a non-liquid crystal polyester chip for use. At this time, if necessary, a laminated film of two or more layers may be formed by using two or more extruders, a pinol divided into two or more layers, or a die. Further, it is preferable to use various filters, for example, a sintered metal, a porous ceramic, a sand, a wire mesh, or the like to remove foreign matter. The sheet extruded from the T-die is adhered and solidified by electrostatic force on a drum cooled to a surface temperature of 25 ° C. to obtain a substantially amorphous cast film. The draft ratio at the time of extrusion from a die is preferably 2 to 200, more preferably 5 to 150, and most preferably 10 to 100. The amorphous film is heated by a group of heating rolls at 80 to 150 ° C., stretched in a longitudinal direction 2 to 4 times in one or two or more stages.
It cools with a 50 degreeC cooling roll group. Subsequently, while guiding to the tenter, holding both ends of the film with clips,
It is heated in a hot air atmosphere heated to 80 to 150 ° C. and stretched 2 to 6 times in the horizontal direction. Subsequently, 180
Heat set at a temperature of ~ 220C. The heat setting may be performed under tension, and it is also preferable to relax in the width direction in order to further improve the thermal dimensional stability. Further, if necessary, prior to heat setting, re-longitudinal stretching and / or re-lateral stretching can be performed.

[0043]

[Methods for measuring physical properties and evaluating effects]

(1) Average particle size of particles The polymer is removed from the film by a plasma low-temperature incineration method to expose the particles. The treatment conditions are selected so that the polymer is ashed but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM), and the particle image is processed with an image analyzer. The magnification of the SEM is appropriately selected from about 10 to 50 μm. The volume average diameter d is obtained from the particle diameter and its volume fraction by the following formula from 5000 particles or more at different observation points.

D = Σdi · NVi where di is the particle diameter and NVi is its volume fraction.

In the case where the particles are significantly damaged by the low-temperature plasma ashing treatment with organic particles or the like, the following method may be used.

The cross section of the film was examined with a transmission electron microscope (TE).
Observe at 3000 to 100,000 times using M). TEM
The thickness of the section is about 100 nm, the measurement is made at 500 places or more at different places, and the volume average diameter d is obtained from the above equation.

(2) Average Dispersion Diameter and Aspect Ratio of Copolymerized Polyester The polyester film is (A) a direction parallel to the flow direction and perpendicular to the film surface, (A) a direction parallel to the width direction and perpendicular to the film surface, C) The film is cut in a direction parallel to the film surface, and the cut surface is observed with a transmission electron microscope (TEM). (A) The thickness (la) of the domain of the copolymerized polyester (C) appearing on the cut surface in the thickness direction of the film
And the length in the flow direction (lb), the length in the thickness direction (lc) and the length in the width direction (ld) of the film of the domain of the copolyester (C) appearing on the cut surface in (a), and (c) )), The length in the flow direction (le) and the length in the width direction (l) of the domain of the copolyester (C) appearing on the cut surface.
f) was determined by direct observation or by micrograph. Note that these la, lb, lc, ld, le, and lf randomly use dispersed domains distributed on each cut plane, and
Of domains. The average dispersion diameter D of the copolymerized polyester was determined by (average value of la + average value of lc + average value of ld + average value of lf) / 4. The average length L of the domain was obtained by (average value of lb + average value of le) / 2, and the aspect ratio was L / D.

(3) Melt viscosity Using a high-low flow tester, 280 ° C., shear rate 2
The value at 00 seconds- ¹ was measured. The unit is represented by [Pa · sec].

(4) Surface roughness According to JIS-B-0601, using a contact-type surface roughness meter manufactured by Tokyo Seimitsu, measurement length 4 mm, cutoff 0.25 m
Rmax was measured in m.

(5) Streak-like surface defects SKD-61 was used as a base material as a base material, and a portion corresponding to a polymer flow path was subjected to two-step chrome plating (thickness of 200 μm).
m). The base is slit width 2mm, width 1
900 mm, a T-die die having a base material SKD-61 having an HR hardness of 40 degrees was attached to a 250 mm extruder, the die temperature was uniformly heated to 280 ° C. Then, the melt is extruded from the die and cooled by a casting drum while applying an electrostatic charge by a conventional method to obtain a cast film. Based on the time during which streak-like surface defects appear on the cast film, the state of occurrence of surface defects was classified as follows.

Time from discharge to appearance of streak-like surface defects Less than 1 day: × 1 day or more and less than 3 days: ○ 3 days or more: ◎

(6) A die having a die-swell ratio of 2.5 mmφ was attached to a 30 mm twin-screw extruder, and the temperature from the extruder to the die was heated to 280 ° C. The polymer was supplied to the extruder, heated and melted at 280 ° C., and the melt was extruded from the above die at a discharge rate of 7 kg / hr. The polymer discharged from the die was taken out of the die and cooled with water from a position of 10 mm at a speed of 1.2 times the speed of the polymer in the die to obtain a gut-shaped sample. The diameter of the obtained gut-shaped sample was measured at 100 points. The average value of the diameters of the 100 samples was taken as the diameter d2 of the obtained sample, and the ratio to the die diameter d1 was determined by the following equation to obtain the die swell ratio.

Die swell ratio = d2 / d1 The polymer velocity in the die was determined by the following equation.

Velocity in mouth [m / min] = Q / πr ² K Q: Discharge rate [g / hr] r: Radius of mouth [cm] K: Specific gravity of molten polymer [g / cm ³ ]

(7) Unevenness of film thickness (%) Film Thickness Tester KG6 manufactured by Anritsu Corporation
The thickness unevenness in the width direction of the film of the intermediate spool (width 4 m) after the biaxial stretching and heat treatment is continuously measured using 01A and an electronic micrometer K306. The film transport speed during the measurement was 3 m / min. From the maximum thickness value Tmax (μm) and minimum value Tmin (μm) at a length of 4 m, R = Tmax−Tmin is obtained. From R and the average thickness Tave (μm) of the 4 m length, the thickness unevenness (%) = (R / Tave) × 100.

(8) Intrinsic viscosity 25 ° C. at a concentration of 0.1 g / ml in orthochlorophenol
It is the value measured in. Since the copolymerized polyester did not dissolve in orthochlorophenol, the measurement was performed after removing the polymer by centrifugation.

[0057]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments.

Example 1 Using polyethylene terephthalate pellets having an intrinsic viscosity of 0.65, 10 parts of wet silica particles having an average particle size of 3 μm were prepared.
A wt% master chip was prepared. As the copolymerized polyester, copolymerized polyester A polycondensed from the following raw materials (melting point 208 ° C., liquid crystal onset temperature 190 ° C., melt viscosity 5
Pa · sec). A wet silica particle master chip was added so that 3% by weight of wet silica particles could be added to the polyethylene terephthalate, and 0.5% by weight of copolymerized polyester was added and mixed, and the mixture was supplied to an extruder.
It is melted at a temperature of 0 ° C, passed through a high-precision filter that cuts 95% of foreign matter to 80 µm or less, extruded with a T-die, and cooled and solidified on a casting drum with a surface temperature of 25 ° C using an electrostatic application method. Thus, an unstretched film in an amorphous state was obtained. This film is vertically stretched using a vertical stretching machine.
Stretched 3.4 times at 0 ° C., followed by a stenter at 90 ° C.
And then heat-treated at 210 ° C. for 2 seconds to obtain a polyethylene terephthalate film having a thickness of 50 μm. In this state, film formation was continuously performed for several days.
The properties of this film are as shown in Table 1, and no streak-like surface defects occurred on the film surface despite continuous long-term film formation. In addition, no deposits such as eyes and polymer degradation products were observed around the slit portion, which is the polymer outlet below the base.

[Material of Copolyester A] Hydroxybenzoic acid Copolymer molar ratio 42.5 4,4'-dihydroxybiphenyl 7.5 Ethylene glycol 50.0 Terephthalic acid 57.5

Examples 2 to 7 and Comparative Example 1 Polyester films were prepared in which the average particle size and the amount of particles added, the amount of the copolymerized polyester added and the melt viscosity were changed. Table 1 shows the properties of the obtained film. When the properties of the polyester film are within the scope of the present invention, the properties such as uneven thickness and streak-like surface defects are excellent. The surface defect was greatly inferior, resulting in a film having inferior surface characteristics, and the productivity was deteriorated.

Comparative Examples 2 and 3 Example 1 was repeated except that copolymer polyester B having a melt viscosity of 100 Pa · s and copolymer polyester C having a melt viscosity of 300 Pa · s were used as the copolymer polyester.
A biaxially oriented film was obtained in the same manner as described above. When the melt viscosity was out of the range of the present invention, a streak-like surface defect occurred in a short time after discharge.

[Copolymer Polyester B Raw Material] Hydroxybenzoic acid Copolymer molar ratio 80.5 4,4'-dihydroxybiphenyl 7.5 Ethylene glycol 12.5 Terephthalic acid 20.0

[Raw material of copolymerized polyester C] "VECTRA" B950 (manufactured by Polyplastics Co., Ltd.)

Examples 8 to 9 The copolyesters used were changed from the following materials to polycondensed copolyester B (copolyester B: melting point 265 ° C., liquid crystal onset temperature 240 ° C.), and only the melt viscosity was changed. A polyester film was formed in the same manner as in Example 1. The characteristics are good as shown in Table 1.

[Raw Material of Copolyester D] Hydroxybenzoic acid 72.5 4,4′-Dihydroxybiphenyl Copolymer molar ratio 7.5 Ethylene glycol 20.0 Terephthalic acid 27.5

[Table 1]

[0066]

The present invention relates to a non-liquid crystalline polyester (A)
And a particle (B), and a composite comprising a mesogen group-containing copolymerized polyester having a melt viscosity of 0.1 to 50 Pa · s as a film, and having uneven, convex, and concave streak-like surface defects. It is intended to provide a high quality polyester film with reduced thickness and uneven thickness. In particular, it can be used for magnetic recording media, capacitors, electrical insulation, packaging, ribbons, etc., including applications requiring gloss, such as labels and stamping.

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Claims (11)

[Claims] 1. A composite comprising a non-liquid crystalline polyester (A), particles (B) and a copolymerized polyester (C) containing a mesogen group in the main chain having a melt viscosity of 0.1 to 50 Pa · sec. A polyester film, wherein a copolymerized polyester (C) containing a mesogen group in the main chain is finely dispersed in the film, and the average dispersion diameter thereof is 0.001 to 5 μm. 2. The polyester film according to claim 1, wherein the particles (B) are inorganic particles. 3. The polyester film according to claim 1, wherein the particles (B) are inorganic particles having an average particle size of 0.5 to 5 μm. 4. A polyester film having a thickness unevenness of 15
% Or less, the polyester film according to any one of claims 1 to 3. 5. The content of the particles (B) is 0.1% by weight or more.
The amount is 10 wt%.
The polyester film according to any one of the above. 6. The polyester film according to claim 1, wherein the copolymerization amount of the mesogen group in the copolymerized polyester (C) is 15 to 90 mol%. 7. The polyester film according to claim 1, wherein the copolymerized polyester (C) is contained in the polyester film in an amount of 0.01 to 10% by weight. 8. A copolymerized polyester (C) comprising the following structural units (I), (III) and (IV), and a copolymerized polyester comprising the structural units (I), (II) and (IV): Polymerized polyester, (I), (II), (II
The polyester film according to any one of claims 1 to 7, wherein the polyester film is at least one selected from copolymerized polyesters comprising the structural units (I) and (IV). Embedded image (Where R ₁ in the formula is R ₂ 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) + (III
)] And the structural unit (IV) are substantially equimolar. ) 9. The non-liquid crystalline polyester (A) is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate and modified products thereof. The polyester film described in Crab. 10. A film for a stamping material, comprising the polyester film according to any one of claims 1 to 9. 11. A chromium-plated composite comprising a non-liquid crystalline polyester (A), particles (B) and a copolymerized polyester (C) containing a mesogen group in the main chain has an inner surface roughness of 1S or less. A method for producing a polyester film, which is melt-extruded by a die.