JP2727831B2 - Biaxially stretched laminated polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched laminated polyester film in which running properties, surface flatness and scratches (hereinafter referred to as "scratch") are hardly generated even when the film is run at high speed.

[0002]

2. Description of the Related Art Polyester films represented by polyethylene terephthalate and polyethylene naphthalate have excellent mechanical properties, weather resistance, electrical insulation, and chemical resistance, and are widely used in magnetic tape films, capacitor films, photographic films, and the like. It's being used. In order to improve the handleability of these polyester films in the manufacturing process, as well as the slip properties and surface properties of the final product, a method of containing fine particles in the polyester and forming moderate irregularities on the film surface is usually used. I have.

As such a particulate-containing polyesters, (1) silicon oxide, titanium dioxide, calcium carbonate, talc, polyester compositions for the additional inclusion of inert granules child, such as clay, was added to (2) the synthesis of the polyester Polyester composition produced by a polycondensation reaction system with precipitated particles containing an alkali metal compound or an alkaline earth metal compound, and furthermore a phosphorus compound as a component, (3)
(1) and polyester for the additional inclusion of inert granules son of, (2)
There has been proposed a polyester composition in which a polyester containing precipitated particles is appropriately blended.

However, in order to achieve fine uniformity of the added particles in the composition (1), in the case of natural inorganic particles, it is necessary to go through steps such as pulverization and classification.
In the case of synthetic inorganic particles, the particle diameter tends to vary under the conditions at the time of synthesis, and it is necessary to perform dispersion, classification, and the like. Also, the case of adding such an inert granules child obtained in the polycondensation reaction system, easily aggregated particles each other, was always difficult to obtain a uniform particle size. Furthermore, since these inert granules child is not preferable affinity with polyester as a base material, after molding into a film, for example, when caused to travel as a magnetic recording tape, the inert granules child from the film removal It had a serious problem of easy release.

On the other hand, in the polyester composition obtained by precipitating the fine particles in a reaction system, the structure of the precipitated particles is similar to the structure of the polyester constituting the base material.
Although it has a good affinity for polyester, it has a drawback that the particle size of precipitated particles tends to vary due to slight fluctuations in the reaction system.

In order to improve the lubricity and surface properties of a film, Japanese Patent Publication No. 55-204 discloses a method as described above.
No. 96 discloses an example of a combination of inorganic particles having an average particle diameter of 1.0 to 10 μm and precipitated particles precipitated in a polyester reaction system. These methods were intended to simply control the film surface unevenness or prevent white powder generated when handling the film by combining particles with different characteristics, but nowadays, even more surface flatness is required. However, the method obtained by this method is not satisfactory.

In Japanese Patent Application Laid-Open No. Sho 59-204617, an alkali metal or an alkaline earth metal is used as a part of constituents in the presence of particulate matter having a specific surface area of 5 m ² / g or more during a polycondensation reaction. A method for precipitating particles and improving abrasion resistance is disclosed. By this method, it is possible to obtain a polyester containing finely precipitated particles to some extent, but the biaxially stretched polyester film using the polyester can be used at the time of recording when a manufacturing process, a processing process, or a product film is used as a magnetic tape. In addition, the film tends to be scratched at the time of recording reproduction.

In Japanese Patent Application Laid-Open No. 24823/1990,
There is disclosed an attempt to suppress the generation of scratches and abrasion powder when a film is formed from the polyester by using inactive particles precipitated in a polyester production process and inorganic particles having a Mohs hardness of 6 or more in combination. However, what is disclosed in the present patent application is simply the combined use of two or more types of particles, and the effect of improving the scratch resistance is insufficient. In a large amount.
When a large amount of the inorganic particles is contained, the thermal stability of the polyester is reduced, and the resulting film has a disadvantage that a gel-like foreign matter is easily generated.

In recent years, in particular, in magnetic tape applications, there has been a remarkable demand for higher recording density and high-speed running resistance. In addition to making the surface unevenness of the film uniform, improvement in the scratch resistance of the film at high-speed running has been required. Has been requested. However, in the polyester composition obtained by a conventionally known method, the added inert inorganic particles have insufficient affinity with the base polyester or the obtained film has insufficient uniformity of surface irregularities. In addition, the scratching property was unsatisfactory.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a biaxially stretched laminated polyester film which has good scratch resistance even at high speed running and excellent surface flatness. In the biaxially stretched laminated polyester film having a laminated structure of at least two layers or more, the outermost layer on at least one side of the film contains two types of inert particles having different ζ-potential values in pure water, so that the film surface Many fine protrusions can be generated,
As a result, it has been found that the film surface is excellent in flatness, that the friction characteristics during running can be improved, and that the scratch resistance can be significantly improved.

[0011]

An object of the present invention is to provide a laminated polyester film comprising (1) a main layer and a sublayer, and (2) a sublayer on at least one outer layer of the main layer. Are laminated, and (3) the polyester constituting the sub-layer contains at least two kinds of inert particles,
Two types of inert particles, relative to the polyester constituting the sublayer, non <br/> activity grains element which ζ- potential in pure water is a positive charge (A) 0.01 to 2 wt% , and aromatic carboxylates and alkali metal compound, at least one consists ζ- inert particles which potential is a negative charge (B) 0.01 to 2 wt% der alkaline earth metal compound
What, (4) addition can be accomplished by biaxially oriented laminated polyester film, wherein the thickness of the sublayer is 1/100 to 40/100 of the laminated film total thickness.

The inert particles in the present invention are particles substantially insoluble in polyester.

The ζ-potential in the present invention is a value obtained by adding inert particles to pure water to make a dilute slurry and measuring the diluted particles by a usual electrophoresis method. After evenly dispersing in it, PENKEM, L
The ζ-potential was measured using ASERZEE ™ Mode 1501 and indicated in mV. The concentration of the inert particles ζ- is not directly related to the potential, when dispersing the inert particles in pure water, normally, preferably in the concentration of 1~100ppm inert particles in the deionized water.

The aromatic polyester (hereinafter simply referred to as polyester) in the present invention is terephthalic acid, 2,6
-Naphthalenedicarboxylic acid, diphenyldicarboxylic acid,
A polyester obtained from an aromatic dicarboxylic acid component such as isophthalic acid and a glycol component such as ethylene glycol, butanediol, and cyclohexane dimethanol, specifically, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Can be. These polyesters may be homopolymers or copolymers. One or more of the above-mentioned dicarboxylic acid components and diol components may be used. Further, polyalkylene glycols such as polyethylene glycol and polybutylene glycol, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, 5-sodium sulfoisophthalic acid, and hydroxyethoxybenzoic acid can be used.

In the present invention, two types of inert particles contained in the sublayer side will be described. It is preferable that two types of inert particles having different ζ-potentials coexist before the completion of the polycondensation reaction of the polyester. . Polyester obtained by such a method is preferable because two types of particles having different ζ-potentials or composite particles can be obtained.

The inactive particles (A) having a positive ζ-potential in the present invention are those having a positive ζ-potential in the above-mentioned measuring method. In particular, if the ζ- potential is +30 mV or more, and further +50 mV or more, 以上
-It is easy to form a composite with inert particles charged with a negative potential, and when a film is formed, many fine protrusions are formed on the surface, and thus the surface flatness, the slipperiness, and the scratch resistance are excellent, which is preferable.

As the inert particles (A) having a positive charge of ζ-potential, magnesium oxide, calcium oxide,
Aluminum oxide, zirconium oxide, zinc oxide, etc.
And at least one of these composite oxides, barium oxide, and calcium carbonate. Among these compounds, aluminum oxide, zirconium oxide,
Magnesium oxide is particularly preferred because it particularly easily forms composite particles.

In the present invention, the inactive particles (A) having a positive charge of ζ-potential have an average primary particle diameter of 0.01.
It is preferably from 1.0 to 1.0 μm. The content is 0.01 to 2.0% by weight, more preferably 0.10 to 1.0% by weight, based on the polyester constituting the sublayer.
When the average primary particle diameter and the content of the inert particles (A) are in the above ranges, the inert particles themselves are less likely to aggregate and composite particles are easily generated, so that the surface flatness, slipperiness and scratch resistance are improved. This is preferred because the properties are improved.

In the present invention, the inactive particles (B) in which the ζ-electrode is negatively charged are defined as ζ-electrodes by the above-mentioned measurement method.
The potential exhibits a negative charge. In particular, ζ
-If the potential is -30 or less, the ζ- potential is liable to be compounded with the positively charged inert particles (A), and when formed into a film, many fine projections are generated on the surface, so that the surface is flat and smooth. And excellent scratch resistance.

Examples of the inert particles (B) having a negative charge of ζ-potential are aromatic dicarboxylates;
Examples of the inert particles include at least one of an alkali metal compound and an alkaline earth metal compound, and it is more preferable that a phosphorus compound is present. The content is 0.01 to 2% by weight based on the polyester constituting the sublayer.

In the present invention, the number of moles of the alkali metal compound (A) and the number of moles of the alkaline earth metal compound (M) contained in the inert particles (B) having a negative charge of ζ-potential, and the number of moles of the phosphorus compound Number (P) ratio, (M + 0.5
A) / P is preferably 0.5 to 5.0, since the particle size of the inert particles becomes uniform and fine.

As the alkali metal compound or alkaline earth metal compound, a glycol-soluble metal compound soluble in a polycondensation reaction system can be preferably used. Examples of such glycol-soluble alkali metal compounds and alkaline earth metal compounds include hydrides, alcoholates, halides, hydroxides, carbonates, carboxylate salts, and sulfate salts. Specifically, lithium acetate, lithium chloride,
Examples thereof include lithium hydroxide, sodium chloride, potassium acetate, calcium acetate, calcium chloride, calcium glycolate, and the like, and two or more kinds may be used.

The phosphorus compound may be trivalent or pentavalent. Specifically, phosphoric acid, phosphorous acid, or a methyl ester, an ethyl ester, a phenyl ester thereof, a half ester or a phosphonic acid thereof,
A group consisting of phosphinic acid or esters thereof is exemplified. It is particularly preferable to use a trivalent phosphorus compound and a pentavalent phosphorus compound in combination, since the composite particles are fine and uniform.

The composite particles according to the present invention can be obtained by mixing ζ in pure water.
-Inactive particles (A) whose potential is positively charged and ζ-
And inert particles (B) having a negative charge. By laminating the polyester film containing such composite particles on the polyester film constituting the main layer, many fine projections are generated on the film surface. As a result, the surface flatness is excellent, the friction characteristics during running can be improved, and the scratch resistance can be significantly improved.

In the present invention, the composite particles comprising the inactive particles (A) having a positively charged ζ-potential and the inactive particles (B) having a negatively charged ζ-potential have a positively charged ζ-potential. 30vol of inert particles (A)
Inactive particles whose ζ-potential minus charge is more than%
(B), and the average particle diameter of the composite particles is preferably 0.01 to 10 μm, and more preferably 0.1 to 10 μm.
5.0 μm is more preferable. The content of the composite particles is preferably 0.01 to 2.0% by weight, more preferably 0.1 to 2.0% by weight based on the polyester constituting the sublayer.
~ 1.0% by weight. When the average particle size and the content of the composite particles are in the above ranges, the surface flatness, the slipperiness and the scratch resistance of a biaxially stretched film are remarkably improved.

The composite particles to be contained in the polyester constituting the sub-layer of the present invention may be synthesized in a polyester polycondensation reaction system, or may be synthesized outside the polyester polycondensation reaction system and then be subjected to a polyester production step. In either case, two types of inert particles having different surface charges can coexist before the completion of the polyester polycondensation reaction. A polyester containing composite particles composed of active particles can be produced. The preferred coexistence time is a stage before the intrinsic viscosity of the polyester reaches 0.3.

The reason why the surface flatness, slipperiness and scratch resistance of the biaxially stretched film obtained by laminating the polyester containing such composite particles on the outer layer of the film is not clear is not clear. Is considered to have some action with the polyester constituting the sublayer.

[0028] In the present invention, the inert particles ζ- potential such as magnesium oxide is a positive charge (A) Cash
In addition , when inert particles having a negative charge of ζ-potential such as silicon dioxide, titanium oxide, talc, and kaolin are used, complex particles are formed with the inert particles (B) having negative charge of ζ-potential. Can not do. Further, when a polyester containing two kinds of inert particles having a negative charge of ζ-potential is used as a biaxially stretched film, the surface flatness, the slipperiness and the scratch resistance are not improved, and the average is merely averaged. The only difference is that dimple peaks formed by inert particles having different particle sizes are obtained. Also, ζ
-Even when inert particles having different potentials are used, it is difficult to form composite particles when coexisting after completion of the polyester polycondensation reaction.

A typical method for producing a polyester containing composite particles constituting a sublayer will be described with reference to polyethylene terephthalate as an example.

The terephthalic acid (hereinafter referred to as TPA) or a lower alkyl ester thereof and ethylene glycol (hereinafter referred to as EG) are subjected to an esterification reaction or a transesterification reaction to obtain bis- (β-hydroxyethyl) terephthalate and its low polymer. A coalescence (hereinafter referred to as BHT) is obtained. In the case of the esterification reaction method, an esterification catalyst may be added or no catalyst may be used. In the case of the transesterification method, a known transesterification catalyst such as an alkali metal compound, an alkaline earth metal compound, a zinc compound, and a manganese compound can be used.

After adding a phosphorus compound and inert particles (A) positively charged with a ζ-potential to the BHT thus obtained, polyethylene terephthalate (hereinafter referred to as PET ) is added in the presence of a polycondensation reaction catalyst. Get). The above-mentioned alkali metal compound and alkaline earth metal compound can be added again after the transesterification reaction is substantially completed. In this case, the inert particles (A) having a positive ζ-potential are charged. Is preferably present before the precipitation of particles containing at least one of an alkali metal compound and an alkaline earth metal compound and a phosphorus compound as a component is started. Further, the inert particles (A) charged positively with the ζ-potential are added with an alkali metal compound, an alkaline earth metal compound, and a phosphorus compound to be added after the esterification reaction or the transesterification reaction is completed. It is particularly preferred to have it exist before.

The method of adding the inert particles (A) charged positively with a ζ-potential to the reaction system is preferably in the form of a glycol slurry. In preparing the slurry, for example, a method proposed in JP-A-61-23623, a dispersion treatment by a wet medium method such as a known sand grinder, and a polycondensation reaction system after further performing a dispersion treatment such as ultrasonic waves. Is preferably added. In addition to these mechanical dispersion treatments, a treatment with a dispersant or a surface treatment agent can be performed, but treatment is preferably performed so as not to change the surface charge of the inert particles. Further, it can be added after subjecting to a classification treatment using a super decanter or the like.

As another method, an inert particle (B) comprising at least one of a BHT component, an alkali metal compound and an alkaline earth metal compound and a phosphorus compound is used.
After composite particles composed of inert particles (A) charged positively in potential are synthesized outside the polycondensation reaction in advance (hereinafter referred to as synthetic particles), and then reacted before the polycondensation reaction of PET is completed. A method of adding it into the system can be mentioned.

Next, an example of a method for obtaining synthetic particles will be described, but the method is not limited to this method. After adding an alkali metal compound, an alkaline earth metal compound, a phosphorus compound, and inert particles (A) positively charged with ζ-potential to BHT having a molar ratio of ethylene glycol of 20 to 200, 1.0-1 at 250 ° C
Let react for 0 hours to obtain a slurry of synthetic particles. At this time, the addition amounts of the alkali metal compound, the alkaline earth metal compound, the phosphorus compound and the inert particles (A) charged positively with the ζ-potential are each 0.01 to 2 with respect to 1 mol of the acid component. 0.0 mole is preferred. Next, the slurry of the synthetic particles is subjected to classification and dispersion treatment, and then added to the polyester polycondensation reaction system. Next, PET is obtained in the presence of a polycondensation reaction catalyst. As the polycondensation catalyst, known catalysts such as glycol-soluble antimony compounds, germanium compounds, and titanium compounds can be used.

The thus obtained polyester containing two types of inert particles having different ζ-potentials is laminated on at least one outer layer of the polyester constituting the main layer. More preferably, they are laminated on both sides.

The polyester constituting the main layer is not particularly limited, but the polyester containing substantially no particles, or even if the particles are contained, the amount of inert particles is determined by the amount of inert particles contained in the polyester constituting the sub-layer. The particles are preferably smaller than the amount of the active particles or finer than the average particle size of the inert particles contained in the polyester constituting the sublayer.

Such a biaxially stretched laminated film can be obtained, for example, by the following method.

After drying the polyester constituting the main layer and the polyester constituting the sub-layer, each is supplied to a known extruder for melt lamination, extruded into a sheet from a slit die, and cooled and solidified on a casting roll. To make an unstretched film. That is, two or more extruders, 2
The sheets are laminated using a manifold or a confluence block having more than one layer (for example, a confluence block having a square confluence part), extruding two or more layers of sheets from a die, and cooling with a casting roll to produce an unstretched film. In this case, a method of installing a static mixer and a gear pump in the polymer flow path is effective. Further, it is effective to lower the melting temperature of the extruder for extruding the polymer on the outermost layer portion side by 5 to 10 ° C. lower than that of the main layer portion side.

Next, this unstretched film is biaxially stretched,
Make it 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 total longitudinal stretching ratio is 3.5 to 6.5 times. The method is particularly preferred.

The stretching temperature in the longitudinal direction varies depending on the type of polyester, and cannot be unconditionally determined. However, it is generally effective to set the first stage at 50 to 130 ° C. and raise the temperature in the second and subsequent stages. The longitudinal stretching speed is 5,000 to 500
A range of 00% / min is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The stretch ratio is suitably in the range of 3.0 to 5.0 times. The stretching speed in the width direction is 1000 to 20000% / min, and the temperature is 80 to 160.
The range of ° C. is preferred. Next, this stretched film is heat-treated. In this case, the heat treatment temperature is preferably 170 to 220 ° C, particularly 180 to 200 ° C, and the time is preferably in the range of 0.2 to 20 seconds.

Here, the thickness of the polyester constituting the sub-layer is 1/100 to 40/1 of the total thickness of the composite film.
00 is preferable, and 2/100 to 20 / is more preferable.
100. When the lamination thickness is in the range of 1/100 to 40/100, the lamination thickness uniformity, film running property,
The uniformity of the projections and also the scratch resistance are improved.
Also, a single-phase film using only the polyester constituting the sub-layer is not preferable because the projection height becomes non-uniform.

Further, a polyester containing a high concentration of two or more types of inert particles having different ζ-potentials is blended with a polyester substantially free of inert particles, and a composition having a predetermined concentration is added to a sublayer. It can also be a side polyester.

Further, the polyester composition of the present invention includes:
In order to further improve the slipperiness of the obtained film, calcium carbonate, titanium oxide, kaolin, silicon dioxide and the like can be blended.

[0044]

The present invention will be described in detail with reference to the following examples. Parts in the examples are parts by weight. The measurement of each characteristic value was performed according to the following method.

A. Intrinsic viscosity of polymer Measured at 25 ° C. using o-chlorophenol as a solvent.

B. Average particle diameter of particles Before addition to the reaction system, the average particle diameter was measured using a scanning electron microscope in a diluted slurry state. The average particle diameter of the two types of particles in the polyester on the sublayer side of the biaxially stretched film was determined by using a scanning electron microscope after slicing the film to a thickness of 1 μm or less and then measuring the particles contained in the sublayer.

C. Particle Content in Sublayer-side Polyester 300 g of o-chlorophenol is added to 30 g of a sample obtained by scraping the sublayer polyester from the main layer polyester, and the polymer is dissolved at 100 ° C. for 1 hour with stirring.
Next, a rotor RP30 was equipped on a separation ultracentrifuge 40P manufactured by Hitachi, Ltd., and the lysis solution 30 was used per cell.
After injecting cc, gradually increase to 30,000 rpm. 3
The particle separation is terminated 60 minutes after reaching 000 rpm.
Next, the supernatant is removed and the separated particles are collected. After adding o-chlorophenol at room temperature to the collected particles and uniformly suspending, ultracentrifugation is performed. This operation is repeated until a melting peak corresponding to a polymer is no longer detected using a differential scanning calorimeter (DSC) on the separated particles described below. The separated particles thus obtained are heated at 120 ° C. for 1 hour.
After vacuum drying for 6 hours, the weight (W ₁ ) was measured. Thereafter, the value (W ₃ ) obtained by subtracting the content of the inorganic particles in the separated particles from the value (W ₂ ) measured by the atomic absorption method was defined as the content of the inert particles (B). The content of the inert particles (A) was determined by directly measuring the scraped sample by an atomic absorption method (W ₄ ), and the particle amount of the sublayer polyester was defined as W ₃ + W ₄ .

D. Thickness of laminated film A polyester having a known content of metal and phosphorus is prepared in several levels, and a metal element (M ⁺ ), a phosphorus element (P ⁺ ) and a carbon element are prepared using a secondary ion mass spectrometer (SIMS). Element (C ⁺ ) concentration ratio (M ⁺ / C), (P ⁺ / C ⁺ )
Ask for. Next, the concentration ratio (M ⁺ / C ⁺ ), (P ⁺ / C ⁺ ) from the polyester surface layer on the sublayer side in the depth direction of the film.
Is measured. From the determined concentration ratio, the concentration of the metal element or the phosphorus element at each depth can be known. The measurement depth was measured up to 50% of the total thickness of the film. The difference (M ⁺ / C ⁺ ) between the concentration ratios thus measured and (P ⁺ /
C ⁺ ) shows a high value in the surface layer of the film, but rapidly decreases as it approaches the main layer, and then stabilizes at a constant value. The two inflection points were connected by a straight line, and the distance from the value of 1/2 to the sublayer side surface layer was defined as the lamination thickness.

E. Evaluation of composite state of particles A laminated biaxially stretched film obtained by laminating polyester containing inactive particles (A) having a positive charge of ζ-potential and inactive particles (B) having negative charge of ζ-potential is obtained. . Separately,
Laminated biaxial which contains the same amount of the positively charged inert particles (A) alone as in the above laminated biaxially stretched film I without containing the negatively charged inert particles (B) having a negative potential. Obtain a stretched polyester film II. The polyester film I and the polyester film II are sliced to a thickness of 1 μm or less, and the number NI and NII of the inactive particles having a positive ζ-potential existing in the laminated portion (sublayer) are determined using a scanning electron microscope. Observe.
The compounding ratio is calculated by the following equation. Composite ratio (%) = (NII−NI) / NII × 100 The composite state of the particles was evaluated according to the following criteria. Composite rate 70% or more Class A Composite rate 30% or more and less than 70% Class B Composite rate less than 30% Class C Class A and Class B were used as composite particles.

F. Average Surface Roughness (Ra) Measured with a stylus type surface roughness meter at a cutoff of 0.08 mm and a measurement length of 4 mm according to the method specified in JIS B-0601, and expressed as Ra (nm). Ra20n
m or less was considered a pass.

G. Roughness parameter P10 Optical interference type three-dimensional surface shape analyzer (TOP manufactured by WYKO)
O-3D, the objective lens; 20-100 times, using a high-resolution camera used), to construct the film surface protrusion image on the image processing apparatus. In this surface projection image, the difference between the average of 10 points from the highest projection and the average of 10 points from the lowest dent was defined as P10 (nm). Such measurement was performed 20 times and the average value was obtained. The smaller the numerical value, the more uniform the protrusion.
50 nm or less was regarded as a pass.

H. Evaluation of Scratch Property The tape slit to 1/2 inch is repeatedly run using a high-speed tape running tester (running speed 8
00m / min, number of runs 5 passes). At this time, the scratches in the film were arbitrarily observed at 10 places in the width direction using a microscope, and the number of scratches per width was obtained. No scratches 1st grade 1 to 3 wounds 2nd grade 4 to 10 wounds 3rd grade 11 or more scratches 4th grade

I. Coefficient of friction Measured according to ASTM D-1894B using a slip tester, and the coefficient of static friction was used. The smaller the value, the better the slipperiness.

Reference Example 1 In a reaction system in which BHT obtained from EG / TPA (molar ratio: 1.15) was melted and stored at 250 ° C. in an esterification reactor,
A slurry obtained by kneading 86.5 parts of TPA and 37.1 parts of EG (EG / TPA, molar ratio: 1.15) was continuously supplied over 3.5 hours. The reaction system is 250 ° C from the start of the supply
, And an esterification reaction was performed, and the generated water was distilled off from the top of the rectification column. After the end of the slurry supply, the esterification reaction was continued for another 1.0 hour, and the reaction system became 97.8%
Of BHT was obtained.

Next, 104.8 parts of BHT (PET10
After transfer to the polycondensation reactor, a solution of 0.2 parts of lithium acetate and 10 parts of EG was added. After 10 minutes, a solution of 0.18 parts of trimethyl phosphate, 0.02 parts of phosphorous acid and 3 parts of ethylene glycol was added. After a further 10 minutes, a slurry of 0.1 part of calcium acetate, 0.03 part of antimony trioxide and 3 parts of ethylene glycol was added. Thereafter, a polycondensation reaction was carried out by a conventional method for 3.0 hours to obtain a polyester A containing 0.6% of inert particles (B) having an intrinsic viscosity of 0.615 and a ζ-potential of −60 mV.

Reference Examples 2 to 10 After the esterification reaction was completed in the same manner as in Reference Example 1,
A slurry obtained by diluting the inert particles (A) shown in Table 1 to 10% with ethylene glycol was added. After a lapse of 10 minutes, lithium acetate, trimethyl phosphate, phosphorous acid, calcium acetate, antimony trioxide, ethylene glycol and the like were added in the same manner as in Reference Example 1.

Thereafter, a polycondensation reaction was carried out in the same manner as in Reference Example 1 to obtain polyesters B to J. Inert particles
Table 1 shows the characteristics of (A) and (B) and the specific particle size of the polymer.

Reference Examples 11 and 12 To 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol, 0.06 part of magnesium acetate and 0.03 part of antimony trioxide were added, and a transesterification reaction was carried out by a conventional method to obtain a product. After adding 0.02 parts of trimethyl phosphate to the polycondensation reactor, the mixture was added to
The polycondensation reaction was performed for 0 hour to obtain a polyester K having an intrinsic viscosity of 0.615.

[0059] Substantially no inert particles were present in polyester K.

After the polyester K was transferred to a polycondensation reaction vessel, CaCO having an average particle diameter of 600 nm was used.
₃ A slurry obtained by diluting 1.0 part with ethylene glycol to 10% was added. Thereafter, a polycondensation reaction is carried out in the same manner as polyester K, and polyester L having an intrinsic viscosity of 0.610 is obtained.
I got

Reference Examples 13 to 16 A polycondensation reaction was carried out in exactly the same manner as in Reference Example 2, as shown in Table 1, except that the amounts of lithium acetate, calcium acetate and phosphorus compound were changed. The content of the inert particles (B) is 0.1% (polyester M);
5% (polyester N), 0.005% (polyester O) and 3.0% (polyester P) were obtained. Table 1 shows the characteristics of the inert particles (A) and (B) and the intrinsic viscosity of the polymer.

REFERENCE EXAMPLES 17-20 Polycondensation reaction was carried out in the same manner as in Reference Example 2, except that the amount of δ-type Al ₂ O ₃ was changed as shown in Table 1. , R, S and T were obtained. Table 1 shows the characteristics of the inert particles (A) and (B) and the intrinsic viscosity of the polymer.

REFERENCE EXAMPLE 21 Polyester U was prepared in exactly the same manner as in Reference Example 12, as shown in Table 1, except that 1.0% of δ-type Al 2 O 3 was added in place of CaCO 3 used in polyester L of Reference Example 12.
I got Table 1 shows the characteristics of the inert particles (A) and the intrinsic viscosity of the polymer.

[Table 1] Example 1 Polyester B of Reference Example 2 and Polyester K of Reference Example 11 were each dried under reduced pressure at 180 ° C. for 3 hours, and then supplied to an extruder and dissolved at 290 ° C.

After each of the polyesters was filtered with high precision, the polyester K was laminated on the main layer and the polyester B on both sides as sub-layers in a three-layer merging block having a rectangular laminated portion. After extruding into a sheet form from a tail-type die, it was wound around a casting drum having a surface temperature of 30 ° C. by using an electrostatic application casting method, and cooled and solidified to produce an unstretched film having a thickness of 160 μm.

The unstretched film was divided into three stages in the longitudinal direction, and 1.2 times at 123 ° C., 1.45 times at 126 ° C.,
Each was stretched 2.3 times at 14 ° C. This uniaxially stretched film is divided into two stages in the width direction using a
Stretched 3.7 times at 113 ° C and 1.2 times at 113 ° C.
Heat treatment was performed at 00 ° C. for 5 seconds to obtain a biaxially stretched laminated film having a thickness of 13 μm. The sublayer thickness of the biaxially stretched film was 1.0 μm (main layer thickness 11 μm). This film has Ra15, first class of scratch property, coefficient of friction of 1.
1, P ₁₀ 98, showing good results.

Examples 2 to 6 and Comparative Examples 1 to 4 In Example 1, instead of polyester B on the sublayer side,
A biaxially stretched laminated film having a thickness of 13 μm was obtained in the same manner as in Example 1 except that the polyesters shown in Table 2 were used. If ζ- potential of inert granules child is using each other as a negative charge to the sublayer polyester (Comparative Example 1
3), Ra, scratch resistance, and P10 are not preferred. Also, when polyester A containing only inactive particles having a negative charge of ζ-potential composed of an alkali metal compound and an alkaline earth metal compound is used as the polyester on the sublayer side (Comparative Example 4), Ra, Scratch property, P10
Is not preferred.

Examples 7 and 8 and Comparative Examples 5 and 6 The same procedures as in Example 1 were carried out except that the thickness of the sub-layer polyester B laminated on both sides of the main polyester K was changed as shown in Table 2. A biaxially stretched polyester film having a thickness of 13 μm was obtained in exactly the same manner. When the thickness of the sub-layer is less than the range of the present invention (Comparative Example 5),
The coefficient of friction is not preferable. On the other hand, if the sublayer thickness is beyond the scope of the present invention (Comparative Example 6), Ra is high, P ₁₀ is not preferable.

[0068]

[Table 2] Examples 11 and 12, Comparative Examples 7 and 8 Polyesters M, N , O and P were used as the sublayer side as shown in Table 2, and a biaxially stretched laminated polyester film was produced in the same manner as in Example 1. Obtained. When the content of the inert particles (B) is less than the range of the present invention (Comparative Example 7 ), both the scratch property and the coefficient of friction are not preferable.
On the other hand, when the value exceeds the range of the present invention (Comparative Example 8 ), Ra,
Both scratch property and P10 are not preferred.

Examples 13 and 14 and Comparative Examples 9 and 10 Polyesters Q, R, S and T were used as the sublayer side as shown in Table 3, and the biaxially stretched polyester was used in the same manner as in Example 1. A film was obtained. δ-type Al
When the added amount of 2 O3 is less than the range of the present invention (Comparative Example
9 ) and beyond the scope of the present invention (Comparative Example 10 ), Ra and scratch resistance and P10 are both unfavorable.

Example 15 The same procedure as in Example 1 was repeated, except that the composition obtained by mixing 80 parts of the polyester B of Reference Example 2 and 20 parts of the polyester L of Reference Example 12 was used as the sub-layer side polyester.
A 3 μm biaxially stretched laminated film was obtained. The film characteristics are Ra16, first class of scratch property, coefficient of friction 0.9, P
It was good film properties at ₁₀ 98.

Example 16 A biaxially stretched laminated film having a total thickness of 13 μm was obtained in the same manner as in Example 1, except that a composition in which 20 parts of polyester U and 80 parts of polyester A were blended was used as the polyester on the sublayer side. Was. Film properties Ra19, scratch resistance secondary friction coefficient 1.1, was P ₁₀ 140.

[0072]

[Table 3]

[0073]

The biaxially stretched laminated polyester film of the present invention containing the inactive particles (A) having a positively charged ζ-potential and the inactive particles (B) having a negatively charged ζ-potential is as follows. 1) Since the inert particles have excellent affinity with polyester, they are less likely to fall off from the film. (2) Since the protrusions are fine and uniform, the electromagnetic conversion characteristics when used as a film for magnetic recording media. to excellent, (3) for fine protrusions are numerous and less friction during processing or during use of the film, excellent in running properties,
(4) Scratch scars are unlikely to occur even when the film is run at high speed. (5) Since the particles are present only on the surface layer of the film, the projections are more uniform than when the particles are present on the entire film, and the production cost is higher. Can be reduced.

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Claims (2)

(57) [Claims] 1. A laminated polyester film comprising (1) a main layer and a sub-layer, (2) a sub-layer laminated on at least one outer layer of the main layer, and (3) a sub-layer contains at least two types of inert particles in the polyester constituting, the two types of inert particles, relative to the polyester constituting the sublayer, inertness ζ- potential in pure water is positive charge grain child (a) 0.01 to 2 wt%, and aromatic carboxylates and alkali metal compound, the inert particles in which at least one consists ζ- potential is a negative charge of an alkaline earth metal compound (B) 0.01 ~ 2
A weight percent, (4) Moreover, the biaxially oriented laminated polyester film, wherein the thickness of the sublayer is 1/100 to 40/100 of the laminated film total thickness. 2. A more 30 vol% of inert granules child (A) forms a composite particle with inert particles (B), and an average particle diameter of the composite particles at 0.01 to 10 [mu] m, yet the composite The content of the particles is 0.0% with respect to the polyester constituting the sub-layer.
The biaxially stretched laminated polyester film according to claim 1, wherein the content is 1 to 2.0% by weight.